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Coupling of Li–Fe: Li Isotope Fractionation during Sorption onto Fe-Oxides | ACS Earth and Space Chemistry
Coupling of Li–Fe: Li Isotope Fractionation during Sorption onto Fe-Oxides
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Coupling of Li–Fe: Li Isotope Fractionation during Sorption onto Fe-Oxides
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ACS Earth and Space Chemistry

Cite this: ACS Earth Space Chem. 2025, 9, 1, 49–63
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https://doi.org/10.1021/acsearthspacechem.4c00205
Published November 25, 2024

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Abstract

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Chemical weathering processes play a key role in regulating the global climate over geological time scales. Lithium (Li) isotope compositions have proven to be a robust proxy for tracing weathering processes that produce secondary minerals, such as clays and oxides, with a focus often placed on Li adsorption to, or incorporation into, clay minerals. In addition, the interaction between Li and Fe-oxides has long been assumed and discussed based on field observations, but experimental constraints on this process are lacking. Here, we investigated the geochemical behavior of Li during its sorption onto individual Fe-oxides, including goethite, hematite, wüstite, and magnetite. With a point of zero charge at ∼7.7, poorly crystallized goethite nanoparticles take up ∼20% of dissolved Li over a pH range from ∼4 to ∼10, rising to ∼90% at pH ∼12. In contrast, the sorption of dissolved Li is insignificant for well-crystallized Fe-oxides (hematite, wüstite, magnetite, and goethite). This Li uptake by poorly crystallized goethite is likely attributed to dissolution and reprecipitation reactions at poorly crystalline goethite surfaces. The goethite particles preferentially take up light 6Li isotopes, resulting in an isotope fractionation of Δ7Lioxide-fluid ∼ −16.7 to −20.1‰. Overall, our study provides valuable data to better understand the processes occurring in highly weathered soil and sediment profiles that are rich in Fe-oxides, such as laterites. This research also emphasizes the significance of chemistry at mineral surfaces during mineral–water interactions and illuminates the mechanisms of large-scale Li extraction for future applications.

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This paper published ASAP on November 25, 2024 with an incomplete author list. The list was updated to add Josephina J.P.A. Mulders, and the revised paper was reposted on December 12, 2024.

1. Introduction

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The complex interactions among the lithosphere, atmosphere, hydrosphere, and biosphere at the Earth’s surface play a crucial role in shaping landscapes, in facilitating the transfer of matter from the continents to the oceans, and in regulating long-term climate via the consumption of atmospheric carbon dioxide through silicate weathering. (1,2) Using lithium (Li) isotopes to investigate and quantify water–rock interactions has been shown to be a robust approach due to (1) an enrichment of Li in secondary phases such as clays; (2) significant Li isotope fractionation due to the large relative mass difference between the two isotopes (7Li and 6Li); and (3) little involvement of Li in biological processes. (3−8)
In the past three decades, there have been major advances in our understanding of Li isotope geochemistry, which has received considerable attention due to its applications for water–rock interactions and weathering studies. During water–rock interactions, the lighter 6Li is preferentially retained in solid secondary materials, causing an enrichment of heavy 7Li in the fluid phase. (9−12) Therefore, Li isotope compositions in geological materials (expressed as δ7Li values, in permille relative to the 7Li/6Li ratio in the standard reference material L-SVEC: δ7Li (‰) = ((7Li/6Li)/(7Li/6Li)L-SVEC – 1) × 1000) can be used to investigate chemical weathering histories, (5,13−23) seawater-composition evolution, (4,24−26) and authigenic clay formation. (26−28)
A number of experimental approaches have been used to constrain Li isotope fractionation during water–rock interactions under both high-temperature (29−33) and low-temperature (9−12,34−37) conditions. In general, these studies demonstrate that (1) there is little Li isotope fractionation associated with mineral dissolution processes; (2) Li isotope fractionation takes place during the formation of secondary phases; and (3) Li isotope fractionation is inversely related to temperature, with less fractionation at high temperatures.
Despite these significant advancements in Li isotope geochemistry, a few key scientific questions remain under-addressed. In particular, how Li behaves during interactions between Fe-(oxyhydr)oxides and solutions requires further investigation. (38) Iron oxide minerals are the dominant constituents of laterite and lateritic soils, which represent the products of prolonged and/or intense weathering processes. (39,40) Observations on such deposits show a more complex relationship between Li behavior (Li concentrations and δ7Li values) and Fe-oxide-rich materials compared to the Li behavior in systems dominated by silicates. For example, in a laterite profile from Deccan, India, Kısakürek et al. (41) observed a distinct difference in Li behavior between a paleo-watertable sample with highly elevated Fe contents, which had low Li concentrations and low δ7Li values, and other samples from the same depth profile with lower Fe contents that were characterized by a negative relationship between Li concentrations and Li isotopes. The authors attributed the former observation to a weathering signal and the latter observation to an external dust endmember mixing with the laterite materials. In laterite soil profiles from Yunnan, China, Ji et al. (42) reported a negative correlation between Si isotopes and Li isotopes and a positive relationship between Li isotopes and Fe3+/Fe2+ ratios. These observations are intriguing because they also differ from findings for phyllosilicate-rich materials, in which Si isotopes and Li isotopes are positively correlated. (28,43) In addition, the correlation between δ7Li values and Fe3+/Fe2+ ratios in the laterite seemingly implies that redox conditions may play a role in setting Li isotope signatures in oxides, even though Li has only one valence state. Unfortunately, in these studies, no oxides were separated from the bulk soils for analysis. Therefore, the observed relationships between Li and Fe content remain empirical, and the mechanisms driving the coupling between Li and Fe are unclear.
In non-laterite profiles, Fe-oxides have also been proposed to modify fluid Li geochemistry. (21,44,45) For example, in Iceland, ferrihydrite is one of the most common secondary phases formed during the weathering of basalts and is found even in young soils, where interesting relationships between the Fe content and the δ7Li values of both solids and solutions have also been observed. (46,47) On the one hand, it has been suggested that the formation and presence of ferrihydrite could potentially fractionate Li isotopes and generate high δ7Li values in the fluids. (46) However, no correlation is observed between the abundance of ferrihydrite and the δ7Li signature in Icelandic soils. (47)
How Li interacts with Fe-oxides remains insufficiently addressed due to a lack of experimental investigations. For example, experimental work has shown that different Li isotope fractionations can be associated with Li uptake by the various locations (octahedral site, outer-sphere complex, etc.) of clay minerals. (9,10) In contrast, it is unclear if similar mechanisms are in operation during the interaction between Li and Fe-oxides, and the literature presents contradictory suggestions for the association of Li with Fe-oxides during water–rock interactions. (48,49) On the one hand, studies of suspended sediments from Greenland and a catchment observatory in Shale Hills (Pennsylvania, USA) assumed that a significant amount of Li may be taken up by Fe-(oxyhydr)oxides (44,48) and suggested an associated isotope fractionation of ∼−20‰. (48) On the other hand, the Li geochemistry of marine ferromanganese deposits (49) implies that little seawater Li is adsorbed onto the surface of goethite or amorphous FeOOH, which hold a slightly positive charge at seawater pH values.
To date, only one study has directly investigated the effect of Fe-oxides on fluid Li geochemistry. A single experiment conducted by Pistiner and Henderson (34) has shown that a moderate proportion of dissolved Li (32%) can be taken up by ferrihydrite after 24 h, generating a change in fluid δ7Li values of 1.6‰. The associated Li isotope fractionation (Δ7Lisolid–fluid = δ7Lisolid – δ7Lifluid = ∼−3.5‰) is significantly smaller than the fractionation observed during clay formation, which typically ranges from −16 to −22‰, (9−12,50,51) but is close to some fractionations observed for Li adsorption onto exchangeable outer-sphere sites of clay minerals (Δ7Li ∼ 0‰). (9,10,34) In contrast, indirect approaches based on oxide leaching methods suggest a larger Li isotope fractionation by Fe-oxides, ranging from −16 to −27‰, (52) but such leaching methods suffer from potential contamination by other secondary phases because no chemical reagent has absolute selectivity.
Most previous experimental studies of Li isotope fractionation during weathering have focused on Al-rich secondary minerals, such as gibbsite and phyllosilicates. Compared to these minerals, Fe-oxides such as goethite and hematite have no interlayers because Fe-oxide structures are usually close-packed. (53,54) Gibbsite or clay minerals are therefore not suitable as analogues for understanding interactions of Li with Fe-oxides. In contrast to the suggestion that little Li is adsorbed by goethite mineral surfaces, (49) experimental studies (55−57) have used magic angle spinning nuclear magnetic resonance (MAS NMR) to demonstrate that Li can be adsorbed by goethite under pH conditions ranging from 4 to 11. The NMR characterization also suggests that the Li binding sites are different under different pH conditions. (55,57) Given that goethite has a point of zero charge (PZC) value of 8.3 ± 0.9, (55,58) it is intriguing that Li+ can be adsorbed onto goethite surfaces even in acidic environments where the surface should hold a positive charge.
The contrasting observations of Li behavior in Fe-rich geological materials and a lack of experimental work warrant new studies investigating the interaction between Li and Fe-rich minerals such as oxides. Here, we focus on the interaction between dissolved Li+ in aqueous solutions and a range of Fe-oxide minerals (goethite, hematite, wüstite, and magnetite) at pH values between 2 and 12. Through sorption experiments, we address how much Li is taken up by these Fe-oxides across a wide range of initial pH, assess the uptake mechanisms, and determine the Li isotope fractionation associated with sorption.

2. Materials and Methods

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2.1. Materials

Six samples, including four different Fe-oxides, were employed in this study. Two goethite (FeOOH) and two hematite (Fe2O3) samples were used to represent fully oxidized Fe-oxides, whereas the mixed valence and less oxidized Fe-oxides were represented by magnetite (Fe3O4) and wüstite (FeO). The Fe-oxides were either synthesized (two goethite and one hematite sample) or commercially available (magnetite, wüstite, and one hematite sample). The Fe3O4 powder used as magnetite was iron (II, III) oxide (Aldrich 99.99%, Lot# MKBP9789 V). Iron(II) oxide was used as wüstite (Aldrich 99.9%, Lot# STBF3726 V). Iron(III) oxide powder (Aldrich ≥ 99%, Lot# MKBS6874 V) was used as a hematite sample. The samples synthesized on site (two goethite and one hematite sample) were produced in the laboratory following methods described by Cornell and Schwertmann. (53) Hematite was prepared at high temperature by heating a 0.002 M HCl solution containing 0.02 M FeCl3 for 10 days at 98 °C. Goethite samples were synthesized at both low and high temperatures. Low-temperature goethite synthesis was achieved by bubbling air through a mixture of 110 mL 1 M NaHCO3 and 1 L 0.05 M FeCl2·4H2O solutions for 48 h at room temperature (∼21 °C). High-temperature goethite was synthesized by adding 180 mL 5 M KOH solution into 100 mL 1 M Fe(NO3)3, diluting to 2 L, heating at 70 °C for 60 h, washing with double-deionized water, and finally drying at 50 °C. To distinguish the two hematite samples, hematite synthesized in our laboratory is referred to as hematitesyn, and hematite from a commercial source is referred to as hematitecom. To distinguish the goethite synthesized using different methods, the goethite produced at low temperature is referred to as goethiteLT, and the goethite synthesized at high temperature is referred to as goethiteHT. The synthesized Fe-oxides were washed repeatedly with double-deionized water and freeze-dried. The specific surface area (SSA) of the oxide powders, as determined by nitrogen adsorption using the Brunauer–Emmet–Teller (BET) method at Utrecht University (UU), ranged widely from 0.137 to 146 m2/g (Table 1).
Table 1. Specific Surface Areas (SSA) of Fe-Oxides
oxide sampledescriptionSSA (m2/g)
goethiteLTsynthesized at ∼21 °C145.824 ± 1.196
goethiteHTsynthesized at 70 °C28.292 ± 0.198
hematitesynsynthesized at 98 °C15.547 ± 0.198
hematitecomAldrich3.110 ± 0.233
magnetiteAldrich7.265 ± 0.039
wüstiteAldrich0.137 ± 0.059

2.2. Experiments

Two sets of sorption experiments were performed in the Geolab at UU. The first set of experiments (Experiment 1) investigated the effect of pH on the interaction between dissolved Li and various Fe-oxide particles. The second set of experiments (Experiment 2) studied Li uptake by Fe-oxide particles (goethiteLT) as a function of time. In all of the experiments, a 0.1 M NaCl solution was used as the fluid matrix to minimize potential complex reactions between Fe-oxide particles and other dissolved ions.
In the Experiment 1 series, stock solution was prepared by diluting concentrated LiCl solution, which is made by dissolving LiCl (Carl Roth > 99%, Lot#212309558) in double-deionized water, using 0.1 M NaCl to obtain a Li concentration of ∼175 μM. Then, five substock solutions were prepared by adjusting the pH of each solution using either 0.1 M HCl or 0.1 M NaOH to reach the desired pH values of 1.98, 4.01, 5.96, 8.01, and 11.98. Before the experiment, the Fe-oxide particles (Table 1) were first preconditioned with a 0.1 M NaCl solution, recollected through centrifugation, and freeze-dried. Then, 10 mL of substock solution was added to approximately 0.2 g of Fe-oxide particles in 15 mL polypropylene centrifuge tubes, except for the hematitecom experiments in which less than 0.1 g of particles were used. In the subexperiments that used commercially obtained oxides, trace amounts of Li at the level of μg/g may have been present as impurities. However, their impact on the experiment is considered insignificant due to the high Li background concentration (∼175 μM) of the initial solution. The interaction experiments between fluid and Fe-oxide lasted for 30 days, with the suspension manually shaken twice a week and left at room temperature. Then, the samples were centrifuged at 4000 rpm to separate the aqueous solution from the solid Fe-oxides. An aliquot of the sample solutions (∼2 mL) was collected and filtered with 0.2 μm pore-size syringe filters for Li isotope and chemical analyses, and the remaining solution volumes were used for pH measurements.
In the Experiment 2 series, 2.494 g of goethiteLT particles were allowed to interact with 80 mL of mixed LiCl-NaCl solution. The solution initially had a pH of 12.03, a LiCl concentration of 36 μM, and a NaCl concentration of 0.1 M. The reaction was performed in a precleaned 100 mL borosilicate bottle, which was stirred with a magnetic stir bar at a room temperature of 21 ± 1 °C. The well-mixed solution was sampled after 1, 2, 4, 8, 16, 32, and 70 days of interaction. At each sampling point, 2 mL of sample mixtures containing both the reacting fluid and solids were pipetted and filtered using a 0.2 μm syringe filter.
Finally, a series of desorption experiments (Experiment 3) were conducted. At the end of Experiment 1, the Fe-oxide particles were carefully rinsed with double-distilled water and ethanol, filtered at 0.2 μm, and freeze-dried. Selected samples were allowed to react with extraction agents to investigate the desorption capacity of adsorbed Li. Two different agents were used to examine the effect of the pH on the extraction. For one experiment, ∼0.01 g reacted Fe-oxide particles were extracted using 2 mL of 1 M NH4Cl solution at a pH of 4.84. In a separate experiment, ∼0.05 g of Fe-oxide particles were extracted using 3 mL of 1 M NH4OAc at a pH of 7.26. The extraction experiments were conducted in 15 mL polypropylene centrifuge tubes, and the samples were shaken for 24 h, with the extracted solutions collected by centrifugation at 4000 rpm and filtration at 0.2 μm. In all of our experiments, no unforeseen or unusually high safety risks were identified.

2.3. Fluid Chemical and Isotopic Analyses

Measurements of Li concentrations were conducted in the Geolab at UU for high-concentration samples ([Li] > 144 μM or 1 μg/mL) and at Institute de Physique du Globe de Paris (France) for samples with lower Li concentrations ([Li] < 144 μM or 1 μg/mL). All samples were redissolved in 0.7 M HNO3. High-concentration samples were measured by inductively coupled plasma mass spectrometry (ICP-MS, NeXION 2000P) and were calibrated using a set of standards with concentrations ranging from 0 to 10.8 μM (or 75 ng/mL). The detection limit ranged from 0.14–1.44 μM (or 1–10 ng/mL), depending on operational conditions. Low-concentration samples were measured by inductively coupled plasma quadrupole mass spectrometry (ICP-Q-MS, Agilent 7900) and were calibrated using a set of standards with concentrations ranging from 0.14 to 28.81 μM (or 1–200 ng/mL). Independent standard solutions with concentrations of 10–100 ng/mL were prepared in-house by diluting certified quality control standards (QCP-QCS-1 and IV-28, Inorganic Ventures) and measured to determine analytical accuracy. Analytical uncertainties for measurements at both laboratories were below 10%. Several samples were measured in both laboratories and had concentration differences that were within 2%. Sodium contents were measured by inductively coupled plasma optical emission spectroscopy (ICP-OES, PerkinElmer Avio 500) in the Geolab at UU with an analytical uncertainty better than 10%.
A double-step separation protocol using AG50W X-12 200–400 mesh cation exchange resin and elution with 0.2 M HCl (11) was followed to purify Li from the sample matrix prior to Li isotope measurements of the aqueous solutions. (46,52,59) The Li isotope composition of the purified samples was measured at the LOGIC laboratories at University College London (United Kingdom) using a Nu Plasma 3 multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) coupled to a CETAC Aridus III desolvating nebulizer system. An IRMM-016 solution was used as the bracketing standard to correct for instrumental mass fractionation. Atlantic seawater and blanks were processed together with the experimental samples to check the quality of the Li purification and Li isotope measurement. The IRMM-016 standard had an intensity of ∼17 pA for a 1 ng/mL solution (∼1.7 V/ppb), the background solution (2% HNO3 v/v) had an intensity less than 0.02 pA, and the total procedural blank had a signal of 0.09 pA, registering a negligible effect (<0.2% of total Li) on the Li isotope measurements. Two Atlantic seawater samples were measured, with δ7Li values (30.9 ± 0.5 and 30.7 ± 0.1‰) in good agreement with previously reported seawater values. (11,60) Measurement uncertainties are, in general, better than 0.5‰ (2 s.d), and the long-term external error, based on seawater analyzed over a period of several years, is ±0.4‰ (2 s.d., n = 52). (46)

2.4. Characterization of Fe-Oxide Particles

All of the Fe-oxide particles were characterized in the Geolab at UU using a Bruker-AXS D8 ADVANCE X-ray diffractometer (XRD) DAVINCI design with a LYNXEYE XE-T detector (with 192 measuring points) and a θ/θ goniometer. The accuracy was 0.01° 2θ. In brief, ∼1 g of the bulk sample was loaded and scanned from 3 to 80 2θ (°) using Cu Kα X-ray radiation, and ∼0.1 g of samples recovered from the experiment was scanned from 5 to 80 2θ (°). Solid samples were also characterized by attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy. Raman spectra were acquired on a WITEC Alpha 300 system equipped with a 532 nm laser and a grating of 600 grooves/mm. Spectra were acquired for 30 seconds to provide sufficient signal to noise ratios. The ATR-FTIR measurements were performed using a Thermo Fisher Scientific Nicolet 6700 instrument equipped with a GladiATR monolithic diamond crystal ATR accessory. Selected goethite samples were analyzed at the Electron Microscope Centre at UU using a Zeiss Gemini 450 scanning electron microscope (SEM) and a Thermo Fisher Talos F200X (scanning) transmission electron microscope ((S)TEM) to examine the main morphological features and nanostructures of the goethite particles.

3. Results

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The XRD patterns and ATR-FTIR absorbances of the Fe-oxides used for this study are displayed in Figures S1 and S2. Notably, goethiteHT exhibits a higher crystallinity than goethiteLT, as indicated by the smaller width at half-height of the XRD and ATR-FTIR bands for goethiteHT. Imaging by SEM further demonstrates the differences between goethiteLT and goethiteHT (Figure 1a,b). The goethiteHT grains display a well-defined mineral morphology, with clear facets and smooth mineral surfaces (Figure 1b). The grain lengths were >1 μm, and widths generally ranged from ∼100 to ∼200 nm. Less defined surficial features were observed in the goethiteLT particles (Figure 1a). These particles are significantly smaller than those synthesized at high temperatures (goethiteHT particles), and their characteristics can only be observed under TEM, which has a higher spatial resolution. The goethiteLT particles had grain lengths varying from ∼50 to ∼70 nm and widths ranging from 5 to 10 nm (Figure 2a,b).

Figure 1

Figure 1. SEM characterization of (a) goethiteLT and (b) goethiteHT particles. Inset graphs show XRD results (Figure S1).

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Figure 2

Figure 2. Solid characterization of goethiteLT particles using transmission electron microscopy (TEM) and high-resolution TEM (HRTEM): (a) unreacted goethiteLT particles; (b) particles from (a) observed under HRTEM; (c) goethiteLT particles interacted with a solution of pH ∼ 12; and (d) particles from panel (c) observed under HRTEM.

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In the Experiment 1 series, with the exception of the goethiteLT experiments, no significant Li uptake by Fe-oxides was observed across the pHi (i denotes initial) range from 2 to 10 (Figure 3). Although an ∼10% decrease in fluid Li content was observed for the experiments at pHi ∼ 12, this difference is within the margin of uncertainty and therefore not significant. In the experiments where goethiteLT was the sorbing substrate, ∼25% Li was removed from the fluid phase when pHi was between 4 and 10, and ∼90% Li was removed at pHi ∼ 12 (Figure 3 and Table 2).

Figure 3

Figure 3. Lithium sorption onto Fe-oxides at various initial pH values: (a) changes of fluid Li content in percentage under different initial pH conditions with various Fe-oxides from Experiment 1; and (b) δ7Li signatures in fluids at the end of sorption from selected samples, with the initial δ7Li signature of the LiCl stock solution marked by the dashed lines (12.8 ± 0.4‰).

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Table 2. Experiment 1: Li Sorption by Fe-Oxide Powders (Goethite, Hematite, Magnetite, and Wüstite) at Various pH Conditions
samplemass of oxides (g)pHipHf[Li]i (μmol/L)a[Li]f (μmol/L)a[Na]i (mmol/L)a[Na]f (mmol/L)aexpected initial surface charge based on PZCbfinal δ7Li in solution2 s.d.
goethiteLT synthesized at 21 °C
GX20.19892.014.15180.70180.07108.01115.31   
GX40.19244.067.68185.55141.41107.02110.47+16.60.4
GX60.19695.987.68181.38139.35108.85110.50+13.70.9
GX80.19738.037.67183.03139.25108.35111.73–16.90.7
GX100.191410.017.64185.94141.06106.43112.36–16.80.3
GX120.194311.989.72188.1821.12117.46116.82 28.10.5
goethiteHT synthesized at 70 °C
GN20.20712.012.09180.70180.63108.01108.10   
GN40.20504.066.73185.55178.96107.02109.28+  
GN60.20345.986.92181.38188.75108.85110.80+  
GN80.20488.036.99183.03180.38108.35110.43–  
GN100.207010.017.21185.94185.80106.43110.97–  
GN120.199511.9811.91188.18174.68117.46119.47 12.10.3
synthesized hematitesyn
HX20.20772.011.96180.70179.68108.01104.77   
HX40.22524.063.78185.55184.52107.02110.74–  
HX60.19955.984.06181.38178.59108.85108.39–  
HX80.20048.034.21183.03181.64108.35108.69–  
HX100.200510.014.14185.94177.99106.43105.65–  
HX120.201311.9811.85188.18166.12117.46114.99 12.90.8
commercially available hematitecom
HN20.03782.011.97180.70171.73108.01110.23   
HN40.04724.064.33185.55181.75107.02107.47   
HN60.09915.986.07181.38185.55108.85107.53+  
HN80.08968.036.32183.03179.98108.35109.48–  
HN100.033410.016.96185.94183.76106.43107.19–  
HN120.049311.9812.03188.18182.51117.46115.50   
commercially available magnetite
M20.19202.012.13180.70184.15108.01106.30   
M40.10124.066.85185.55182.84107.02107.12+  
M60.19935.987.03181.38174.80108.85112.07+  
M80.19818.037.06183.03185.44108.35114.24–  
M100.216610.017.47185.94189.69106.43110.81–  
M120.197711.9811.95188.18166.59117.46117.74 13.50.6
commercially available wüstite
W20.19882.013.91180.70179.94108.01110.27   
W40.22704.0610.08185.55182.42107.02103.57+  
W60.19925.9810.26181.38179.17108.85107.39+  
W80.17298.0310.14183.03179.38108.35108.66+  
W100.175210.0110.15185.94178.53106.43109.03+  
W120.187611.9811.92188.18170.80117.46122.40 13.41.0
a

Analytical uncertainty is ±10%.

b

PZC is reflected in the pHf when this is consistent within 1 pH unit and across several initial pH conditions. Under these conditions, it is expected that charge neutrality is achieved via interaction with solution ions only; therefore, the expected initial charge is not given for the highest and lowest pH experiments, which deviate in their final pH.

A “buffer” effect was observed in the experiments based on the difference between pHi and pHf (f denotes final) when the pHi was between 4 and 10. In these cases, pHf reached very similar values when the same phase was used despite the different initial pH values (Figure 4): 7.67 ± 0.02 for goethiteLT experiments, 6.96 ± 0.17 for goethiteHT, 4.05 ± 0.16 for hematitesyn, 5.92 ± 0.97 for hematitecom, 7.10 ± 0.23 for magnetite, and 10.15 ± 0.06 for wüstite. The experiments conducted at pHi of ∼2 and ∼12 did not follow this trend and instead remained at a similar pH throughout the experiment, except for the experiments with goethiteLT where the pH was shifted by ∼2 units toward neutral in both experiments. A similar shift was observed for wüstite in the experiment at pHi ∼ 2 but not at pHi ∼ 12.

Figure 4

Figure 4. Variations in fluid pH at the beginning (pHi) and the end (pHf) of the Li-sorption experiments.

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As most of the experiments showed a similar behavior in their pHf and minimal to no Li uptake, only selected samples were analyzed for their δ7Li signatures, including samples from the goethiteLT experiments and samples from the most alkaline experiments for all Fe-oxide types (pHi ∼ 12). For the goethiteLT experiments, all of the solutions were either slightly or significantly enriched in the heavy Li isotope 7Li compared to their initial LiCl-NaCl solution, which had a δ7Li value of 12.8 ± 0.4‰ (Figure 3b). The solutions from the goethiteLT experiments conducted at pH ranging from 4 to 10 resulted in a similar pHf (∼7.6) and degree of Li sorption (∼25%) and also had relatively similar δ7Li signatures (16.0 ± 1.3‰). The experiment with the highest uptake at pHi ∼ 12 had the highest δ7Li value of 28.1 ± 0.5‰. In contrast, the experiments conducted at pHi ∼ 12 with the other Fe-oxides all produced δ7Li values that were within the error of their initial LiCl-NaCl solution value (Figure 3b).
In the Experiment 2 series, fluid Li was rapidly taken up by goethiteLT, with the dissolved Li content decreasing from ∼36 to ∼3 μM within 1 day, after which the concentration of Li in solution remained stable (Table 3, Figure 5). The fluid samples from Experiment 2 were also analyzed for their δ7Li signatures, revealing a consistent enrichment of 7Li in solution during fluid interaction with goethiteLT. Compared to the initial LiCl-NaCl solution (δ7Li = 12.8‰ ± 0.4), the final solutions of the goethiteLT subexperiments had δ7Li signatures that varied from 29.7 to 32.6‰. This change in the Li isotope composition directly corresponds to the rapid removal of Li from the solution and the change in the pH within the first day of this experiment (Table 3).

Figure 5

Figure 5. Lithium sorption and isotope fractionation by goethiteLT at pHi ∼ 12 from Experiment 2. Changes in fluid Li content are represented in %.

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Table 3. Experiment 2: Li Sorption through Time by GoethiteLT Powders with a Starting pH of 12
sampleelapsed time (days)[Li] (μmol/kg)aδ7Li in solution2 s.d.pH[Na] (mmol/kg)a
LiCl-NaCl solution 36.212.80.412.03116.22
D112.832.10.49.73113.56
D222.632.11.0 111.54
D442.232.60.9 115.61
D882.232.10.69.68113.03
D16161.931.80.9 116.95
D30301.931.30.2 115.29
D70702.129.70.99.59114.63
a

Analytical uncertainty is ±10%.

Selected samples of solid goethiteLT recovered from Experiments 1 and 2 were characterized by TEM, ATR-FTIR, XRD, and Raman spectroscopy. No significant difference was observed in the mineral morphology between the reacted and unreacted goethiteLT particles (e.g., Figure 2c,d cf. Figure 2a,b). Shifts of ATR-FTIR absorbance were observed between the unreacted goethiteLT particles and the goethiteLT particles recovered from the sorption experiments. At ca. 630 cm–1, the band positions of reacted goethiteLT particles from Experiments 1 and 2 are shifted to lower wavenumbers compared to those of unreacted goethiteLT particles (Figure S3). For comparison, the peak positions of unreacted goethiteHT particles were also analyzed, and they showed the same bands, but the band close to 630 cm–1 was found to occur at a higher wavenumber than determined for the goethiteLT particles (Figure S3). Minor differences were observed in the XRD patterns (Figure S4) and Raman spectra (Figure S5) between the reacted and unreacted goethiteLT powders.
In the Experiment 3 series, Li taken up by goethiteLT during the Experiment 1 series was extracted from the reacted goethiteLT particles. When NH4OAc was used to extract the Li, less than 3% was released back into solution, whereas significant amounts (50–82%) of Li were liberated when NH4Cl was used as the extracting agent (Table 4).
Table 4. Experiment 3: Li Desorption by Extracting with NH4Cl and NH4OAc
samplemass (g)Li adsorbed from Exp 1 (ng)a[Li] in extraction solution (μg/kg)fraction extracted (%)
Li extraction with 2 mL NH4Cl (pH = 4.84)
GX40.0090143.33 ± 75.6859.08 ± 5.9182.44 ± 44.30
GX120.0075447.59 ± 50.71113.10 ± 11.3150.54 ± 7.64
Li extraction with 3 mL NH4OAc (pH = 7.26)
GX40.0595916.60 ± 493.964.20 ± 0.421.37 ± 0.75
GX120.04902924.26 ± 331.4624.99 ± 2.502.56 ± 0.37
a

Li adsorbed from Experiment 1 is calculated as ([Li]i – [Li]f) × 10 mL × 6.941 g/mol × sample mass (used in Experiment 3)/sample mass (used in Experiment 1); [Li]i, [Li]f, and mass used in Experiment 1 are from Table 2.

4. Discussion

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4.1. Lithium Sorption onto Fe-(Oxyhydr)oxides

In all of the experiments conducted between pH values of 4 and 10, there is a buffering effect of the Fe-oxide on the pH of the solution (Figure 4). This feature has been described previously in the literature for Fe-oxides, including goethite, (61) hematite, (62) and magnetite. (63) The attainment of a consistent pHf across a range of pHi values reflects the electrostatic interaction of negatively or positively charged ions within the solution at the sample surface to achieve charge neutrality. In previous experiments, the pHf value has been demonstrated to reflect the point of zero charge for a material under the chemical conditions of the solution. (61−63) Therefore, we expect that our systems have attained charge neutrality by the end of the experiments. This scenario means that there is no overall attractive force expected to occur in the experiments between the surface of the mineral and the ions in the fluid at equilibrium.
However, when the pHi was above the pHf, and hence the surface was negatively charged (Table 2), the uptake of positively charged ions, such as Li+ or Na+, at the mineral surface could be expected to have occurred during the equilibration process. (61,63) Based on the changing pH observed in Experiment 2 (Table 3) and previous studies, (61,63) such a process can be expected to have occurred quickly, within the first 24 h of the experiments. However, no changes in the Na+ or Li+ concentrations in solution that would reflect attractive forces based on the expected mineral surface charge and PZC were observed with any of the Fe-oxides, except for goethiteLT (Table 2). The goethiteLT samples showed an overall Li uptake over the entire pH range studied (Figure 3a), where the uptake does not correlate with the expected cation exclusion effects in the experiments conducted at pHi values of ∼4 and ∼6, which should have a positively charged surface based on the PZC of this sample at pH 7.67. This finding is consistent with previous experiments, which have shown that positively charged ions only very weakly interact with negatively charged Fe-oxide surfaces in the form of an outer-sphere complex, (64) and hence we conclude that the observed Li uptake by goethiteLT is not driven by outer-sphere electrostatic adsorption.
A lack of inner-sphere adsorption complexes has previously been demonstrated for Li+ on magnetite (63) and hematite (65) using potentiometric methods, even at solution Li concentrations above those expected in the natural environment or used here. However, this lack of direct interaction between Li+ and Fe-oxide surfaces is contradicted by more recent NMR studies focusing on goethite nanoparticles. (55,57) Here, evidence for direct interactions involving Fe–O–Li (inner-sphere complexation) on nanoparticulate goethite synthesized at room temperature was observed after sample drying at pH values above the measured PZC. Direct interaction between the solid phase and Li+ in solution was also present in our experiments with goethiteLT. In contrast to the study of Nielsen et al., (55) our goethiteLT experiments demonstrated Li loss from the solution across the entire pH range. This finding corresponds with an increase in the PZC of 0.71 pH units from that of goethiteHT to that of goethiteLT (Figure 4). Given that no evidence for an additional phase was observed in SEM, TEM, or XRD analyses, the Li uptake by the solid and the change in the PZC imply that a chemical change may have occurred to the goethite surface during the experiments. This chemical change to the goethiteLT is supported by the ATR-FTIR absorbance shift (Figure S3) at peak positions that correspond to the symmetric Fe–O stretching band (ca. 630 cm–1). (66) Decreases in goethite crystallinities result in a shift toward lower wavenumbers of this band. (66) Among the analyzed goethite samples, the frequencies of this band decrease in an order from goethiteHT particles with the highest frequencies (634.2 cm–1) to unreacted goethiteLT particles (629.5 cm–1) and finally to reacted goethiteLT particles with the lowest frequencies (∼610–618 cm–1). This finding suggests that chemical changes of the goethiteLT particles occurred during the sorption experiments. At mineral surfaces, a typical cation uptake reaction can involve dissolution and reprecipitation, which is driven by the neoformation of the solid phase. (67) Hence, our observations could be explained by the reprecipitation at active sites on the poorly crystalline goethiteLT surface. Unfortunately, it is not clear from the Nielsen et al. study (55) whether any pH changes were observed during their experiments. Therefore, we cannot presently evaluate whether the minerals in their system behaved in a similar manner, but their observations of apparent inner-sphere complexes at the surface could potentially reflect the neoformation of a solid phase, with Li occupying sites other than the OH-site within the goethite channels.
The extraction test in Experiment 3 demonstrated that only minimal Li+ could be extracted from the goethiteLT at near-neutral pH values, whereas there was significant extraction in an acidic environment (Table 4). A mineral phase is expected to have minimal solubility close to its PZC, (63) so the goethiteLT sample is expected to have a minimal solubility at pH values close to 7.67. The restricted extraction of Li from the samples using NH4OAc reflects this feature, as this solution has a pH of 7.26, and only a very small fraction of adsorbed Li was released (∼1.4% for goethiteLT reacted at pH ∼ 4, and ∼2.4% for goethiteLT reacted at pH ∼ 12). In contrast, during the extraction in an acidic environment with NH4Cl (pH of 4.84), a significant portion of the originally adsorbed Li was extracted, with release of 82.4% of the Li adsorbed on goethiteLT reacted at pH ∼ 4, and 50.5% of the Li adsorbed on goethiteLT reacted at pH ∼ 12. We note that during the goethiteLT particle recovery through rinsing and filtration, some adsorbed Li may have been removed by rinsing with water. (28) Therefore, these results may provide only a lower limit on the extraction capacity.

4.2. Lithium Sorption onto Poorly Crystalline GoethiteLT Particles and Associated Li Isotope Fractionation

In the Experiment 1 series, the fluid pHf values imply different systematic behavior under the tested pH range, as discussed in Section 4.1. In general, pHf tends to deviate from pHi to reach the PZC when pHi ranges from 4 to 10, whereas at pHi of 2 or 12, the reacted solutions have pHf values close to pHi. Therefore, the Fe-oxides likely underwent different reactions, such as dissolution at pH ∼ 2 and possible reprecipitation at pH ∼ 12. This variation could also have resulted in different interactions between fluid Li and reacted Fe-oxides. Lithium uptake was only observed with goethiteLT, and indeed, this Li uptake was controlled by pHi: at pH ∼ 2, the system likely prefers goethiteLT dissolution, and no Li uptake was observed, whereas at higher pHi values from 4 to 12, Li uptake became significant. Furthermore, the Li uptake capacity of goethiteLT varied with pH, with only ∼25% Li adsorbed for pHi ranges from 4 to 10, increasing to ∼90% uptake of Li at pHi ∼ 12 in both Experiments 1 and 2, whereas the changes in solution Na content were minor (Tables 2 and 3). Hence, the mechanisms driving the Li uptake may have varied, as suggested by differences in pHf (Figure 4) and by previous NMR studies. (55,57)
We suggest that the uptake of Li by goethiteLT can be attributed to Li incorporation on poorly crystalline goethiteLT surfaces through dissolution and reprecipitation at active sites and that two different neoformations of solid phases, for instance, two different materials, may occur at pHi from 4 to 10 and at pHi ∼ 12. Our Li sorption results are in agreement with previously reported Li adsorption behavior traced by 6Li MAS NMR spectra. (55) That study showed an elevated Li adsorption capacity of goethite with increasing pH and suggested that adsorbed Li can be located in different inner-sphere sites. Interestingly, in the NMR characterization, a 6Li peak was detected in their goethite particles (with particle size smaller than goethiteLT used in the current study) when reacted with dissolved Li at pHi ∼ 4, which is much lower than the PZC of goethite. Nielsen et al. (55) suggested that the presence of Li in the goethite particles could be due to (i) a pH change during the experiment or (ii) Li precipitation during the goethite recovery at the end of the adsorption experiment (isolation and drying). (55) At pH > PZC, NMR results suggest that Li can be bound to a bidentate edge site associated with two FeOH groups, or at high pH a pocket site associated with a deprotonated Fe3OH group and FeOH group. (57)
Because we monitored the changes of Li concentration in the fluid, our experimental data demonstrate that Li sorption indeed takes place when the initial solution pH is significantly lower than the PZC (e.g., pH ∼ 4). In addition, the reacting fluids showed an increase in pH from 4.06 to 7.68 at the end of the experiment. If the Li uptake was driven by electrostatic forces, positively charged Li cations would not be taken up under pH conditions lower than those of the PZC. Therefore, our observations support the assumption that Li uptake is caused by a fluid-goethite reaction via neoformation.
We also note that the solubility of goethite varies with pH, with higher solubilities at both acid (pH < 6) and alkaline (pH > 10) conditions. (68−70) Furthermore, we note that the goethiteLT grain surfaces are not well defined, which is indicated by their roughness (Figure 2). A possible mechanism during fluid-goethiteLT interactions could be provoked by the partial dissolution of FeOOH at defect-containing goethite surfaces, thus containing active sites. (71) Various aqueous Fe species could be formed, such as Fe(OH)2+ in acidic pH or Fe(OH)4– at alkaline conditions. (68−70) The reprecipitation or readsorption of this temporarily dissolved Fe back onto the goethite surface could essentially form new molecules, which take up cations such as Li from the ambient solution. A first-order observation can be made from our results that the Li sorption capacity is related to the SSA (Tables 1 and 2), which can be explained by the higher population of active sites in poorly crystalline particles, which in turn would result in both a larger SSA and greater potential for reprecipitation reactions.
Geochemical modeling using PHREEQC (72) suggests the potential formation of hematite throughout the pH range used in Experiment 1, and fluid chemistry modeling using HSC Chemistry software (version 9) suggests the possible presence of LiFe5O8 under alkaline conditions (Figure S6). We note that the modeled results may not be fully indicative because the actual solubility of goethiteLT surficial materials is unknown, and the precipitated phases are likely amorphous and, therefore, not available in the PHREEQC database. For the fluid chemistry modeling, we have opted to use a fluid system with relatively high Fe and Li contents to maximize the potential formation of Li-carrying Fe-oxides. In spite of the limitations, the modeled results support the formation of a new oxide phase incorporating Li and Fe preferentially under alkaline conditions, as suggested by Experiments 1 and 2. Our extraction results (Experiment 3) can therefore be explained by a higher solubility of this neoformed solid phase in an acidic environment.
In the experiments with goethiteLT, the Li uptake was accompanied by Li isotope fractionation, with light 6Li preferentially taken up by the solid phase. The Li isotope fractionation in the fluid system follows the isotope mass balance
δ7Lii×[Li]i×M=δ7Lif×[Li]f×M+δ7Liads×|[Li]i−[Li]f|×M
(1)
where M is the fluid mass and δ7Liads is the Li isotope signature of the adsorbed Li on the goethiteLT particles, which can be calculated because values for all of the other terms in eq 1 are available in Tables 2 and 3. Direct measurements of δ7Liads values are not possible due to the challenge associated with isolating the Li taken up by goethite nanoparticles from the Li in the reacting fluids. The Li isotope fractionation during Li uptake by Fe-oxides can then be calculated as
Δ7Lioxide−fluid=δ7Liads−δ7Lif
(2)
and the associated Li isotope fractionation factor (α) can be determined based on the processes driving the fractionation. Here, there are two possibilities: either (i) equilibrium fractionation, if the neoformed Li-containing phase forming via surface reactions is in a continuous chemical equilibrium with the fluid, or (ii) Rayleigh fractionation, if the Li precipitated in the newly formed solid phase removes Li from the fluid via fractional distillation.
Under circumstance (i), α can be calculated as
δ7Lit=δ7Lii−1000×ln(α)×F
(3)
where t denotes the time of sampling and F is the fraction of Li taken up by the solid phase, which is calculated as
F=1−[Li]t/[Li]i
(4)
On the other hand, under circumstance (ii), the α value can be estimated from
δ7Lit=δ7Lii+1000×(α−1)×ln(1−F)
(5)
In Experiment 1, although the Li uptake mechanisms by goethiteLT may differ between pH conditions (e.g., pHi 4–10 vs pHi ∼ 12), the calculated Δ7Lioxide-fluid values of samples with different pHi values indicate only minor deviations in the isotope fractionation (Table S1). The Li isotope fractionation associated with Li sorption by goethiteLT nanoparticles averages Δ7Lioxide-fluid = −16.7 ± 0.5‰. We excluded a single data point from the experiment performed at a pHi of 5.98 (Table 3), the Li isotope fractionation of which is insignificant. The reasons for this difference are unclear but may potentially be an analytical artifact, such as ineffective isolation of the reacting fluids from the goethite nanoparticles or poor instrumental performance for this sample. The associated fractionation factor in the scenario of equilibrium fractionation is α = 0.9834 ± 0.0005 (n = 4) (Figure 6a). In the scenario of Rayleigh fractionation, two α values were determined (Table S1): Li sorption by goethiteLT at pH values ranging from 4 to 10 has a similar fractionation factor of α = 0.9855 ± 0.0004 (n = 3), whereas at pH ∼ 12, the value becomes 0.9930 (Figure 6b).

Figure 6

Figure 6. Estimation of Li isotope fractionation factors for (a) Experiment 1 in the scenario of equilibrium fractionation; (b) Experiment 1 in the scenario of Rayleigh fractionation; (c) Experiment 2 in the scenario of equilibrium fractionation; and (d) Experiment 2 in the scenario of Rayleigh fractionation.

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In Experiment 2, the average fractionation and the fractionation factor were estimated between each sampling point and the initial solution, as the experiment quickly reached dynamic equilibrium in terms of Li concentration (Δ[Li] ∼ 0) in less than 1 day (Figure 5). A fractionation of Δ7Lioxide-fluid = −20.1 ± 1.0‰ (n = 7) was observed (Table S1). In the case of equilibrium fractionation, the associated fractionation factor is α = 0.9801 (Figure 6c), which is slightly different from the α value (0.9829) calculated in Experiment 1 under the same pH conditions. In the case of Rayleigh fractionation, α = 0.9933 (Figure 6d), and this value is close to the one from Experiment 1 under the same scenario (α = 0.9930; Figure 6b).
A difference of ∼3‰ in Δ7Lioxide-fluid (i.e., ∼−17‰ vs ∼−20‰) is observed between the results obtained from Experiments 1 and 2, which essentially leads to the small difference in the Li isotope fractionation factors calculated in the scenario of equilibrium fractionation. With the current data set, we are unable to determine the cause of this difference. However, there were some differences in the design of these two experiments, which could potentially account for such a difference: (1) in Experiment 1, the goethiteLT particles were equilibrated with 0.1 M NaCl before interacting with the mixed NaCl-LiCl solutions at various pH values, whereas in Experiment 2, the goethiteLT particles were not pretreated with a NaCl solution and were directly mixed with NaCl-LiCl at pH ∼ 12; (2) in Experiment 1, all of the samples were manually shaken with the Fe-oxide particles settled at the bottom of the centrifuge tube, whereas the sample in Experiment 2 was rigorously stirred, which ensured the sample mixture remained well mixed; and (3) different initial Li concentrations were used, with [Li]i = 175 μM in Experiment 1 and [Li]i = 36 μM in Experiment 2.
Because Na is typically considered mobile and is not taken up by secondary phases, (47,73,74) as also observed in our experiments (Tables 2 and 3), the evolution of the Li/Na ratio in the fluid reflects the Li uptake by the oxides and varies accordingly with fluid δ7Li values. The coevolution of δ7Li values and Li/Na ratios in Experiment 2 is compared between the measured data (Table 3) and the modeled results calculated with eqs 3–5 for equilibrium fractionation and Rayleigh fractionation scenarios (Figure S7). The two scenarios remain unresolvable for Experiment 2 with the current data set.
In Experiment 1, under the scenario of equilibrium fractionation, similar fractionation factors are obtained from the subexperiments of goethiteLT at pH values of 4–12 (Figure 6a). This feature could be explained by reprecipitation through Ostwald ripening, which dissolves smaller particles, possibly at surface defects, and reprecipitates solid phases. (75) In this case, Li uptake through reprecipitation during the interaction between fluid Li and goethiteLT has similar α values at different pHi values (Figure 6a), even though the neoformed phase may be different, and the fractionation factors are comparable to those obtained from Li interactions with poorly crystalline kaolinite. (12) On the other hand, in the scenario of Rayleigh fractionation, the two different α values determined with different pHi values (4–10 vs 12) suggest two different isotope fractionation factors, which could be attributed to different solid chemistry during reprecipitation at moderate pHi values (4–10) and high pHi ∼ 12. This latter scenario would agree with the findings of the NMR investigations that the Li sorption on goethite varies as a function of pH. (55,57) Although we cannot completely determine which fractionation process dominates the Li uptake by goethiteLT with our data set, Rayleigh fractionation is favored because in this scenario (Figure 6b), two different α values, which suggest two different types of reactions, are respectively associated with pHi values of 4–10 and pHi ∼ 12. This scenario would be consistent with the observations of different Li uptake in the pH range from 4 to 10 compared to pH ∼ 12, as shown by the pHf (Figure 4), Li uptake capacity (Figure 3), and NMR results. (57) Also, in this case, the results of the goethiteLT experiments conducted at pHi ∼ 12 in both Experiment 1 and 2 are consistent with each other, giving almost identical fractionation factors (Figure 6b,d).
Furthermore, we note that the calculated fractionation factor may be at the higher limits of the true value, as the goethiteLT particles have sizes (<100 nm; Figure 2) that are smaller than the pore size of the filter (0.2 μm), such that centrifugation at 4000 rpm may not be totally efficient at completely isolating the nanoparticles from the fluid. Hence, the fluid chemistry could be partly distorted toward lower δ7Li values (but also higher [Li]) by a potential mixture toward any isotopically light goethiteLT remaining in the analyzed solution. In addition, the magnitude of Li isotope fractionation observed in our experiments (−17 and −20‰) is significantly greater than that derived from the only previous experimental study that examined Li isotope fractionation during interactions with Fe-oxides (−3.5‰ for ferrihydrite, calculated using eqs 1 and 2). (34) Finally, our results are comparable to the estimated values from acid-reductive leaching methods (−17 to −28‰), (52) which implies that carefully operated leaching methods supported by measurements of trace element ratios in the leachates could be a valid approach to target the composition of Fe-oxide phases in natural samples.
In summary, dissolved Li can be taken up by poorly crystalline goethiteLT particles over a wide range of pH values from 4 to 12. This Li uptake is associated with a Li isotope fractionation of Δ7Lioxide-fluid ∼ −17 to −20‰. Previous studies suggested that the Li adsorption is due to adsorption at inner-sphere sites at pH values greater than the PZC of goethite, (55,57) and we further suggest that Li sorption through the dissolution–reprecipitation of active sites may also be an important process, especially under conditions where pH < 8, and should be investigated by future studies.

4.3. Mineral Crystalline State as an Often-Overlooked Factor Affecting Mineral–Water Interactions

An important finding from our study is that a given mineral can show distinctive geochemical behavior when in different crystalline states. Specifically, poorly crystalline goethiteLT can take up ∼90% of dissolved Li with a fractionation Δ7Lioxide-fluid ∼ −20‰ in an alkaline solution at pH ∼ 12, whereas highly crystalline geothiteHT particles are not reactive with dissolved Li at pH ∼ 12 or over a wide range of pH conditions. To date, in the isotope geochemistry community, most fluid–rock interaction studies focus on the effect of mineralogy. Here, we argue that mineral crystallinity can also play an important role. It is well known that Fe-oxide minerals display various crystallinity states and can be relatively quickly recrystallized. (53,68,76,77) In natural systems, it is therefore to be expected that well-aged, and hence more crystalline, Fe-oxides would not actively react with fluid Li. For aluminosilicate clays, this phenomenon of crystallinity affecting water–rock interaction has also been observed for Li adsorption onto laboratory-synthesized smectite. (10) Specifically, Vigier et al. (10) reported that hectorite synthesized at lower temperatures has a greater capacity for Li adsorption due to the presence of more crystal defects, in agreement with the geochemical behavior of Li observed in the present study. Additionally, the previously reported observation of the preferential release of 6Li during the dissolution of poorly crystalline kaolinite at low pH values (12) can be further explained by the dissolution of octahedral structures at active sites.
Therefore, in both the case of clay minerals and Fe-oxides, the effect of the crystalline state needs to be considered, and here, we raise two related concerns. First, in experimental studies of water–rock interactions, mineralogy has often been addressed, whereas mineral crystallinity has rarely been examined. Therefore, directly applying sorption coefficients or isotope fractionation factors obtained from experimental studies to natural settings may introduce biases. Future studies should further investigate this under-addressed issue, potentially by studying secondary phases in both poorly crystallized and well-crystallized secondary phases, as well as studying amorphous phases. Second, mineral crystalline states vary between natural field areas. In kinetically limited weathering regimes (typically characterized by high physical erosion rates), particles have short residence times, so minerals tend to be less crystalline than in supply-limited weathering regimes (typically characterized by low physical erosion rates), where particle residence times are long. For example, goethite particles from Iceland, an example of a kinetically limited setting, are nanocrystalline, (78) whereas goethite particles observed in laterite profiles from the Congo Basin, a typical supply limited environment, are well crystallized and can have lengths greater than 10 μm. (79) According to our experimental results, these goethite particles exhibit different geochemical characteristics. Therefore, not only is it important to analyze the mineralogy using XRD techniques, but complementary observations of sample particles using electron-sourced imaging techniques (such as SEM and TEM) would greatly improve our knowledge of the coupled geochemical and mineralogical behavior, with implications for Li isotope characteristics in natural environments.

5. Implications and Conclusions

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Our study provides new experimental constraints on the fundamental behavior of Li and Li isotopes during their interaction with Fe-oxides. First, we show that Li can be taken up by poorly crystalline goethite nanoparticles, resulting in Li isotope fractionation Δ7Lioxide-fluid ranging from −17 to −20‰. The fractionation factor calculated from our experiments is important for improving our understanding of highly weathered soil profiles such as laterites, as well as in subsurface water–rock interactions where Fe-oxide formation can be common. (15,21,38,48,80,81) Second, we show that the Li uptake by goethite is controlled by both the fluid pH and the goethite crystallinity. Poorly crystalline goethite can take up ∼90% dissolved Li at pH ∼ 12, likely through reprecipitation reactions occurring at active sites, and a significant fraction of the Li uptake could be released with extraction under lower pH conditions. In contrast, Li adsorption by outer-sphere complexation at the surfaces of well-crystalline Fe-oxides appears to be insignificant.
These results have two significant implications. To an extent, the Li uptake and Li isotope fractionation associated with neoformation at mineral surfaces could be at least partially responsible for Li isotope signals observed in floodplains. (4,73) For example, when poorly crystalline materials formed in upper catchment areas are transported and deposited in lower floodplains, water–rock interactions with these materials can further modify the fluid Li chemistry through adsorption, incorporation, and isotope fractionation. Similarly, at the land–sea interface, where seawater generally has higher pH values than river waters, the interaction of poorly crystalline detrital materials with seawater could occur during sediment transport into the mixing zone or during sea-level rise over longer time scales. (82) These effects could potentially be considered by re-examining observations made in estuaries. (16,83,84) Furthermore, our results point to the potential of poorly crystalline goethite for efficient large-scale industrial extraction of Li, which warrants further investigation because Li is in high demand for the energy transition. (85)
Finally, we demonstrate that constraining sorption behavior during water–rock interactions requires the effects of mineral crystallinity to be evaluated. Hence, we suggest that (1) a better understanding of crystal nucleation, growth, and defect recrystallization should be an important target for future studies; and (2) future studies should prioritize further characterization of nanoparticles in combination with quantification of fluid chemistry with suitable methods.

Data Availability

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For the purpose of open access, the author has applied a “Creative Commons Attribution (CC BY) license” to any author accepted manuscript version arising. The original XRD, ATR-FTIR, and Raman results are freely available at Utrecht University Yoda data repository: 10.24416/UU01-MYX8OZ

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsearthspacechem.4c00205.

  • Solid characterization of Fe-oxide particles used in the sorption experiments (XRD, ATR-FTIR, and Raman); thermodynamic calculations of fluid chemistry; and calculation of Li isotope fractionation during sorption onto poorly crystalline goethite (PDF)

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Author Information

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  • Corresponding Author
  • Authors
    • David J. Wilson - LOGIC, Department of Earth Sciences, University College London, WC1E 6BS London, U.K.
    • Maartje F. Hamers - Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, The Netherlands
    • Philip A. E. Pogge von Strandmann - MIGHTY, Institute for Geosciences, Johannes Gutenberg University Mainz, D-55128 Mainz, Germany
    • Josephina J. P. A. Mulders - Evides Water, Schaardijk 150, 3063 NH Rotterdam, The Netherlands
    • Oliver Plümper - Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, The Netherlands;  Orcidhttps://orcid.org/0000-0001-9726-0885
    • Helen E. King - Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, The Netherlands;  Orcidhttps://orcid.org/0000-0002-1825-782X
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This research was fully funded by the Dutch Research Council funding OCENW.M20.156. The authors sincerely thank P. Burkel for his assistance in conducting the Li concentration measurements at IPGP. The authors appreciate S. Turner for scientific discussion and N. Kopacz for sample preparation. The authors also thank A. van Leeuwen-Tolboom for her assistance in performing XRD analysis, C. Mulder and H. de Waard for their help in measuring Li and Na concentrations, and other colleagues from Geolab at Utrecht University for their help in this project. P.A.E.P.vS. is funded by ERC grant 682760. D.J.W. is funded by a NERC independent research fellowship (NE/T011440/1).

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    Pogge von Strandmann, P. A. E.; Kasemann, S. A.; Wimpenny, J. B. Lithium and Lithium Isotopes in Earth’s Surface Cycles. Elements 2020, 16 (4), 253– 258,  DOI: 10.2138/gselements.16.4.253
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    Pogge von Strandmann, P. A. E.; Henderson, G. M. The Li Isotope Response to Mountain Uplift. Geology 2015, 43 (1), 67– 70,  DOI: 10.1130/G36162.1
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    Dellinger, M.; Bouchez, J.; Gaillardet, J.; Faure, L.; Moureau, J. Tracing Weathering Regimes Using the Lithium Isotope Composition of Detrital Sediments. Geology 2017, 45 (5), 411– 414,  DOI: 10.1130/G38671.1
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    Dellinger, M.; Gaillardet, J.; Bouchez, J.; Calmels, D.; Galy, V.; Hilton, R. G.; Louvat, P.; France-Lanord, C. Lithium Isotopes in Large Rivers Reveal the Cannibalistic Nature of Modern Continental Weathering and Erosion. Earth Planet. Sci. Lett. 2014, 401, 359– 372,  DOI: 10.1016/j.epsl.2014.05.061
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    Penniston-Dorland, S.; Liu, X.-M.; Rudnick, R. L. Lithium Isotope Geochemistry. Rev. Mineral. Geochem. 2017, 82 (1), 165– 217,  DOI: 10.2138/rmg.2017.82.6
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    Tomascak, P. B.; Magna, T.; Dohmen, R. Advances in Lithium Isotope Geochemistry; Springer International Publishing: Switzerland, 2016.
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    Hindshaw, R. S.; Tosca, R.; Goût, T. L.; Farnan, I.; Tosca, N. J.; Tipper, E. T. Experimental Constraints on Li Isotope Fractionation during Clay Formation. Geochim. Cosmochim. Acta 2019, 250, 219– 237,  DOI: 10.1016/j.gca.2019.02.015
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    Experimental constraints on Li isotope fractionation during clay formation
    Hindshaw, Ruth S.; Tosca, Rebecca; Gout, Thomas L.; Farnan, Ian; Tosca, Nicholas J.; Tipper, Edward T.
    Geochimica et Cosmochimica Acta (2019), 250 (), 219-237CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    Knowledge of the lithium (Li) isotope fractionation factor during clay mineral formation is a key parameter for Earth system models. This study refines our understanding of isotope fractionation during clay formation with essential implications for the interpretation of field data and the global geochem. cycle of Li. We synthesized Mg-rich layer silicates (stevensite and saponite) at temps. relevant for Earth surface processes. The resultant solids were characterized by X-ray diffraction (XRD) and Fourier-transform IR spectroscopy (FT-IR) to confirm the mineralogy and crystallinity of the product. Bulk solid samples were treated with ammonium chloride to remove exchangeable Li in order to distinguish the Li isotopic fractionation between these sites and structural (octahedral) sites. Bulk solids, residual solids and exchangeable solns. were all enriched in 6Li compared to the initial soln. On av., the exchangeable solns. had δ7Li values 7‰ lower than the initial soln. The av. difference between the residual solid and initial soln. δ7Li values (Δ7Liresidue-solution) for the synthesized layer silicates was -16.6 ± 1.7‰ at 20 °C, in agreement with modeling studies, extrapolations from high temp. exptl. data and field observations. Three bonding environments were identified from 7Li-NMR spectra which were present in both bulk and residual solid 7Li-NMR spectra, implying that some exchangeable Li remains after treatment with ammonium chloride. The 7Li-NMR peaks were assigned to octahedral, outer-sphere (interlayer and adsorbed) and pseudo-hexagonal (ditrigonal cavity) Li. By combining the 7Li-NMR data with mass balance constraints we calcd. a fractionation factor, based on a Monte Carlo min. misfit method, for each bonding environment. The calcd. values are -21.5 ± 1.1‰, -0.2 ± 1.9‰ and 15.0 ± 12.3‰ for octahedral, outer-sphere and pseudo-hexagonal sites resp. (errors 1σ). The bulk fractionation factor (Δ7Libulk-solution) is dependent on the chem. of the initial soln. The higher the Na concn. in the initial soln. the lower the bulk δ7Li value. We suggest this is due to Na outcompeting Li for interlayer sites and as interlayer Li has a high δ7Li value relative to octahedral Li, increased Na serves to lower the bulk δ7Li value. Three expts. conducted at higher pH exhibited lower δ7Li values in the residual solid. This could either be a kinetic effect, resulting from the higher reaction rate at high pH, or an equil. effect resulting from reduced Li incorporation in the residual solid and/or a change in Li speciation in soln. This study highlights the power of 7Li-NMR in exptl. studies of clay synthesis to target site specific Li isotope fractionation factors which can then be used to provide much needed constraints on field processes.
  10. 10
    Vigier, N.; Decarreau, A.; Millot, R.; Carignan, J.; Petit, S.; France-Lanord, C. Quantifying Li Isotope Fractionation during Smectite Formation and Implications for the Li Cycle. Geochim. Cosmochim. Acta 2008, 72 (3), 780– 792,  DOI: 10.1016/j.gca.2007.11.011
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    Pogge von Strandmann, P. A. E.; Fraser, W. T.; Hammond, S. J.; Tarbuck, G.; Wood, I. G.; Oelkers, E. H.; Murphy, M. J. Experimental Determination of Li Isotope Behaviour during Basalt Weathering. Chem. Geol. 2019, 517, 34– 43,  DOI: 10.1016/j.chemgeo.2019.04.020
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    11
    Experimental determination of Li isotope behaviour during basalt weathering
    Pogge von Strandmann, Philip A. E.; Fraser, Wesley T.; Hammond, Samantha J.; Tarbuck, Gary; Wood, Ian G.; Oelkers, Eric H.; Murphy, Melissa J.
    Chemical Geology (2019), 517 (), 34-43CODEN: CHGEAD; ISSN:0009-2541. (Elsevier B.V.)
    Silicate weathering is the primary control of atm. CO2 concns. on multiple timescales. However, tracing this process has proven difficult. Lithium isotopes are a promising tracer of silicate weathering. This study has reacted basalt sand with natural river water for ∼9 mo in closed expts., in order to examine the behavior of Li isotopes during weathering. Aq. Li concns. decrease by a factor of ∼10 with time, and δ7Li increases by ∼19‰, implying that Li is being taken up into secondary phases that prefer 6Li. Mass balance using various selective leaches of the exchangeable and secondary mineral fractions suggest that ∼12-16% of Li is adsorbed, and the remainder is removed into neoformed secondary minerals. The exchangeable fractionation factors have a Δ7Liexch-soln = -11.6 to -11.9‰, while the secondary minerals impose Δ7Lisecmin-soln = -22.5 to -23.9‰. Overall the expt. can be modelled with a Rayleigh fractionation factor of α = 0.991, similar to that found for natural basaltic rivers. The mobility of Li relative to the carbon-cycle-crit. cations of Ca and Mg changes with time, but rapidly evolves within one month to remarkably similar mobilities amongst these three elements. This evolution shows a linear relationship with δ7Li (largely due to a co-variation between aq. [Li] and δ7Li), suggesting that Li isotopes have the potential to be used as a tracer of Ca and Mg mobility during basaltic weathering, and ultimately CO2 drawdown.
  12. 12
    Zhang, X. Y.; Saldi, G. D.; Schott, J.; Bouchez, J.; Kuessner, M.; Montouillout, V.; Henehan, M.; Gaillardet, J. Experimental Constraints on Li Isotope Fractionation during the Interaction between Kaolinite and Seawater. Geochim. Cosmochim. Acta 2021, 292, 333– 347,  DOI: 10.1016/j.gca.2020.09.029
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    Experimental constraints on Li isotope fractionation during the interaction between kaolinite and seawater
    Zhang, Xu; Saldi, Giuseppe D.; Schott, Jacques; Bouchez, Julien; Kuessner, Marie; Montouillout, Valerie; Henehan, Michael; Gaillardet, Jerome
    Geochimica et Cosmochimica Acta (2021), 292 (), 333-347CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    In this study, to better understand the factors controlling the concn. and isotope compn. of lithium (Li) in the ocean, we investigated the behavior of Li during interaction of kaolinite with artificial seawater. Dissoln. of kaolinite in Li-free seawater at acidic conditions (exp. 1) results in a strong preferential release of light Li isotopes, with Δ7Liaq-kaol ~ -19‰, likely reflecting both the preferential breaking of 6Li-O bonds over 7Li-O bonds and the release of Li from the isotopically lighter AlO6 octahedral sites. Sorption expts. on kaolinite (exp. 2) revealed a partition coeff. between kaolinite and fluid of up to 28, and an isotopic fractionation of -24‰. Thermodn. calcn. indicates authigenic smectites formed from the dissoln. of kaolinite in seawater at pH 8.4 (exp. 3). The formation of authigenic phase strongly removed Li from the soln. (with a partition coeff. between the solid and the fluid equal to 89) and led to an increase of ca. 25‰ in seawater δ7Li. This fractionation can be described by a Rayleigh fractionation model at the early stage of the expt. during rapid clay pptn., followed, at longer reaction time, by equil. isotope fractionation during the much slower removal of aq. Li via co-pptn. and adsorption. Both processes are consistent with a fractionation factor between the solid and the aq. soln. of ~ -20‰. These expts. have implications for interpreting the Li isotopic compn. of both continental and marine waters. For instance, the preferential release of 6Li obsd. during kaolinite far-from-equil. dissoln. could explain the transient enrichments in 6Li obsd. in soil profiles. With regard to the evolution of seawater δ7Li over geol. time scales, our exptl. results suggest that detrital material discharged by rivers to the ocean and ensuing "reverse chem. weathering" have the potential to strongly impact the isotopic signature of the ocean through the neoformation of clay minerals.
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    Huh, Y.; Chan, L.-H.; Zhang, L.; Edmond, J. M. Lithium and Its Isotopes in Major World Rivers: Implications for Weathering and the Oceanic Budget. Geochim. Cosmochim. Acta 1998, 62 (12), 2039– 2051,  DOI: 10.1016/S0016-7037(98)00126-4
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    Rudnick, R. L.; Tomascak, P. B.; Njo, H. B.; Gardner, L. R. Extreme Lithium Isotopic Fractionation during Continental Weathering Revealed in Saprolites from South Carolina. Chem. Geol. 2004, 212 (1), 45– 57,  DOI: 10.1016/j.chemgeo.2004.08.008
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    Henchiri, S.; Gaillardet, J.; Dellinger, M.; Bouchez, J.; Spencer, R. G. M. Riverine Dissolved Lithium Isotopic Signatures in Low-Relief Central Africa and Their Link to Weathering Regimes. Geophys. Res. Lett. 2016, 43 (9), 4391– 4399,  DOI: 10.1002/2016GL067711
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    Pogge von Strandmann, P. A. E.; James, R. H.; van Calsteren, P.; Gíslason, S. R.; Burton, K. W. Lithium, Magnesium and Uranium Isotope Behaviour in the Estuarine Environment of Basaltic Islands. Earth Planet. Sci. Lett. 2008, 274 (3–4), 462– 471,  DOI: 10.1016/j.epsl.2008.07.041
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    Pogge von Strandmann, P. A. E.; Desrochers, A.; Murphy, M.; Finlay, A. J.; Selby, D.; Lenton, T. M. Global Climate Stabilisation by Chemical Weathering during the Hirnantian Glaciation Geochem. Perspect. Lett. 2017, 3 230 237 DOI: 10.7185/geochemlet.1726 .
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    Wimpenny, J.; Gíslason, S. R.; James, R. H.; Gannoun, A.; Pogge Von Strandmann, P. A. E.; Burton, K. W. The Behaviour of Li and Mg Isotopes during Primary Phase Dissolution and Secondary Mineral Formation in Basalt. Geochim. Cosmochim. Acta 2010, 74 (18), 5259– 5279,  DOI: 10.1016/j.gca.2010.06.028
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    Song, Y.; Zhang, X.; Bouchez, J.; Chetelat, B.; Gaillardet, J.; Chen, J.; Zhang, T.; Cai, H.; Yuan, W.; Wang, Z. Deciphering the Signatures of Weathering and Erosion Processes and the Effects of River Management on Li Isotopes in the Subtropical Pearl River Basin. Geochim. Cosmochim. Acta 2021, 313, 340– 358,  DOI: 10.1016/j.gca.2021.08.015
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    Bastian, L.; Revel, M.; Bayon, G.; Dufour, A.; Vigier, N. Abrupt Response of Chemical Weathering to Late Quaternary Hydroclimate Changes in Northeast Africa. Sci. Rep. 2017, 7, 44231,  DOI: 10.1038/srep44231
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    Lemarchand, E.; Chabaux, F.; Vigier, N.; Millot, R.; Pierret, M.-C. Lithium Isotope Systematics in a Forested Granitic Catchment (Strengbach, Vosges Mountains, France). Geochim. Cosmochim. Acta 2010, 74, 4612– 4628,  DOI: 10.1016/j.gca.2010.04.057
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    Zhang, X.; Bajard, M.; Bouchez, J.; Sabatier, P.; Poulenard, J.; Arnaud, F.; Crouzet, C.; Kuessner, M.; Dellinger, M.; Gaillardet, J. Evolution of the Alpine Critical Zone since the Last Glacial Period Using Li Isotopes from Lake Sediments. Earth Planet. Sci. Lett. 2023, 624, 118463  DOI: 10.1016/J.EPSL.2023.118463
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    Cai, D.; Henehan, M. J.; Uhlig, D.; von Blanckenburg, F. Lithium Isotopes in Water and Regolith in a Deep Weathering Profile Reveal Imbalances in Critical Zone Fluxes. Geochim. Cosmochim. Acta 2024, 369, 213– 226,  DOI: 10.1016/j.gca.2024.01.012
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    Hathorne, E. C.; James, R. H. Temporal Record of Lithium in Seawater: A Tracer for Silicate Weathering?. Earth Planet. Sci. Lett. 2006, 246 (3–4), 393– 406,  DOI: 10.1016/j.epsl.2006.04.020
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    Misra, S.; Froelich, P. N. Lithium Isotope History of Cenozoic Seawater: Changes in Silicate Weathering and Reverse Weathering. Science 2012, 335, 818– 823,  DOI: 10.1126/science.1214697
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    Lithium Isotope History of Cenozoic Seawater: Changes in Silicate Weathering and Reverse Weathering
    Misra, Sambuddha; Froelich, Philip N.
    Science (Washington, DC, United States) (2012), 335 (6070), 818-823CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Weathering of uplifted continental rocks consumes carbon dioxide and transports cations to the oceans, thereby playing a crit. role in controlling both seawater chem. and climate. However, there are few archives of seawater chem. change that reveal shifts in global tectonic forces connecting Earth ocean-climate processes. The authors present a 68-Myr record of lithium isotopes in seawater (δ7LiSW) reconstructed from planktonic foraminifera. From the Paleocene (60 Myr ago) to the present, δ7LiSW rose by 9‰, requiring large changes in continental weathering and seafloor reverse weathering that are consistent with increased tectonic uplift, more rapid continental denudation, increasingly incongruent continental weathering (lower chem. weathering intensity), and more rapid CO2 drawdown. A 5‰ drop in δ7LiSW across the Cretaceous-Paleogene boundary cannot be produced by an impactor or by Deccan trap volcanism, suggesting large-scale continental denudation.
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    Li, G.; West, A. J. Evolution of Cenozoic Seawater Lithium Isotopes: Coupling of Global Denudation Regime and Shifting Seawater Sinks. Earth Planet. Sci. Lett. 2014, 401, 284– 293,  DOI: 10.1016/j.epsl.2014.06.011
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    Evolution of Cenozoic seawater lithium isotopes: Coupling of global denudation regime and shifting seawater sinks
    Li, Gaojun; West, A. Joshua
    Earth and Planetary Science Letters (2014), 401 (), 284-293CODEN: EPSLA2; ISSN:0012-821X. (Elsevier B.V.)
    The Li isotopic record of seawater shows a dramatic increase of ∼ 9‰ over the past ∼ 60 million years. Here we use a model to explore what may have caused this change. We focus particularly on considering how changes in the "reverse weathering" sinks that remove Li from seawater can contribute to explain the obsd. increase. Our interpretation is based on dividing the oceanic sink, which preferentially removes light Li, into two components: (i) removal into marine authigenic clays in sediments at low temps., with assocd. high fractionation factors, and (ii) removal into altered oceanic basalt at higher temps. and resulting lower fractionation factors. We suggest that increases in the flux of degraded continental material delivered to the oceans over the past 60 Ma could have increased removal of Li into sedimentary authigenic clays vs. altered basalt. Because altered basalt is assocd. with a smaller isotopic fractionation, an increasing portion of the lower temp. (authigenic clay-assocd.) sink could contribute to the rise of the seawater Li isotope value. This effect would moderate the extent to which the isotopic value of continental inputs must have changed in order to explain the seawater record over the Cenozoic. Nonetheless, unless the magnitude of fractionation during removal differs significantly from current understanding, substantial change in the δ7Li of inputs from continental weathering must have occurred. Our modeling suggests that dissolved riverine fluxes in the early Eocene were characterized by δ7Li of ∼0 to + 13‰, with best ests. of 6.6-12.6‰; these values imply increases over the past 60 Myrs of between 10 and 24‰, and we view a ∼ 13‰ increase as a likely scenario. These changes would have been accompanied by increases in both the dissolved Li flux from continental weathering and the removal flux from seawater into marine authigenic clays. Increases in δ7Li of continental input are consistent with a change in the global denudation regime as a result of increasing continental erosion rate through the Cenozoic. Changes in denudation may have meant increasing climate sensitivity of weathering over time but do not require globally supply-limited and thus entirely climate-insensitive weathering in the early Cenozoic.
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    Andrews, E.; Pogge von Strandmann, P. A. E.; Fantle, M. S. Exploring the Importance of Authigenic Clay Formation in the Global Li Cycle. Geochim. Cosmochim. Acta 2020, 289, 47– 68,  DOI: 10.1016/j.gca.2020.08.018
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    Exploring the importance of authigenic clay formation in the global Li cycle
    Andrews, Elizabeth; Pogge von Strandmann, Philip A. E.; Fantle, Matthew S.
    Geochimica et Cosmochimica Acta (2020), 289 (), 47-68CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    Lithium isotopic (δ7Li) and elemental concns. of pore fluids and carbonates from IODP Site U1338 Hole A (eastern equatorial Pacific Ocean) suggest that clay authigenesis (i.e., in situ pptn.) is a significant sink for Li in carbonate-rich sedimentary sections. Systematic variations in pore fluid δ7Li with depth in the section suggest that clay authigenesis can (i) strongly decrease pore fluid Li concns. with depth and (ii) fractionate Li isotopically to a considerable degree (Δ ~ 5-21‰ relative to seawater). We hypothesize that clay authigenesis in carbonate-rich sections occurs due to the presence of reactive biogenic silica, and reactive transport modeling supports the contention that the pore fluid δ7Li depth profile at Site U1338 is best explained by faster authigenesis at depth. The significance of clay authigenesis in carbonate-rich sediments is two-fold: if global in scale, (i) it can generate sizeable output fluxes in the global Li cycle, and (ii) the evolution of the sedimentary system over time can markedly impact the isotopic compn. of the global Li output flux. We compile ODP and IODP pore fluid Li data from 267 sites; of these, 207 have Li pore fluid concn. gradients in the upper 50-100 m that indicate the sites as diffusive sinks of Li. We then est. that clay authigenesis in carbonate-rich sediments could reasonably generate a Li output flux on the order of ~ 1.2·1010 moles/yr, which is comparable to the gross input fluxes in the modern Li cycle. A series of reactive transport simulations illustrate how clay authigenesis might impact the isotopic compn. of the output flux of Li from the global ocean. The suggestion is that applying a const. fractionation factor from the global ocean over time is likely incorrect, and that secular changes in the δ7Li of the output flux will be driven by rates of authigenesis, burial rates, and the depth extent of authigenesis in the sedimentary section. Utilizing a time-dependent, depositional diagenetic model, the δ7Li values of bulk carbonate are shown to be a consequence not of recrystn. alone, but recrystn. in the presence of clay authigenesis. Further, our model results are used to illustrate how carbonate δ7Li may be used to constrain the temporal evolution of clay authigenesis in the sedimentary section. Ultimately, this work suggests that the Li isotopic compn. of bulk carbonates can be altered diagenetically. However, such alteration is not a detriment, but provides useful information on those diagenetic processes in the sedimentary column that impact the global Li cycle. Thus, Li isotopes in bulk carbonates have the potential to elucidate diagenetic controls on the global Li cycle over long time scales.
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    Zhang, X.; Gaillardet, J.; Barrier, L.; Bouchez, J. Li and Si Isotopes Reveal Authigenic Clay Formation in a Palaeo-Delta. Earth Planet. Sci. Lett. 2022, 578, 117339  DOI: 10.1016/j.epsl.2021.117339
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    Quantifying chemical weathering intensity and trace element release from two contrasting basalt profiles, Deccan Traps, India
    Babechuk, M. G.; Widdowson, M.; Kamber, B. S.
    Chemical Geology (2014), 363 (), 56-75CODEN: CHGEAD; ISSN:0009-2541. (Elsevier B.V.)
    Weathering profiles developed on basalt substrate contain information relevant to climate, atm. compn. and evolution, nutrient release into the hydrosphere, and understanding Martian regolith. In this study, the chem. compns. of two profiles developed on Deccan Trap basalt are examd. One is sub-Recent and has only progressed to a moderate degree of alteration (Chhindwara profile), whereas the other is ancient (Paleocene) and the degree of alteration is extreme (Bidar laterite). In an attempt to better quantify the chem. changes during incipient to intermediate weathering of mafic substrates, a new index is proposed: the mafic index of alteration (MIA). Similar to the chem. index of alteration (CIA), the MIA quantifies the net loss of the mobile major elements (Ca, Mg, Na, K ± Fe) relative to the immobile major elements (Al ± Fe). The redox-dependent weathering behavior of Fe is factored into two sep. arrangements of the MIA that apply to oxidative [MIA(O)] or reduced [MIA(R)] weathering. The MIA can be visualized in a variety of ternary diagrams in the Al-Fe-Mg-Ca-Na-K system. To chem. quantify the stages of advanced to extreme weathering, at which the MIA and CIA are ineffective, the SiO2 to (Al2O3 + Fe2O3) mass ratio, based on the established Si-Al-Fe (SAF) 'laterite' ternary diagram, is used; we propose that this ratio be referred to as the 'index of lateritisation' (IOL). Major element chem. variations, as expressed by weathering indexes, are used to relate the extent of weathering with the behavior of trace elements (alkali, alk. earth, rare earth, and Nb) in the profiles. During the early stages of basalt weathering, the mobile trace elements (Sr, Be, Li) are anti-correlated with the chem. weathering indexes and thus released during these stages. By contrast, the monovalent elements (K, Rb, Cs, Tl), excluding Na and Li, appear to be assocd. with the pedogenetic clay minerals. Of these elements, those with the most similar ionic radii are closely related in their weathering behavior. Fractionation of the REE (Sm/Nd, Eu/Eu*, Ce/Ce*) is evident during weathering of the basalt. The loss of Eu is linked with that of Sr, Ca, and Na and thus assocd. with plagioclase dissoln. during the stages of incipient to intermediate weathering. The fractionation of Sm/Nd suggests that basaltic weathering products may not always preserve their parent rock ratio and, consequently, their Nd isotope compn. over time. Finally, weathering in the sub-Recent profile is shown to have progressed across two lava flows, whose morphol. initially controlled the extent of weathering. Certain compositional variations in the original flows (e.g., immobile element ratios) are preserved through the effects of chem. weathering and have the potential to influence mass balance calcns. across the entire profile.
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    Kısakürek, B.; Widdowson, M.; James, R. H. Behaviour of Li Isotopes during Continental Weathering: The Bidar Laterite Profile, India. Chem. Geol. 2004, 212 (1–2), 27– 44,  DOI: 10.1016/j.chemgeo.2004.08.027
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    Ji, H.; Chang, C.; Beckford, H. O.; Song, C.; Blake, R. E. New Perspectives on Lateritic Weathering Process over Karst Area – Geochemistry and Si-Li Isotopic Evidence. Catena 2021, 198, 105022  DOI: 10.1016/j.catena.2020.105022
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    Pogge von Strandmann, P. A. E.; Frings, P. J.; Murphy, M. J. Lithium Isotope Behaviour during Weathering in the Ganges Alluvial Plain. Geochim. Cosmochim. Acta 2017, 198, 17– 31,  DOI: 10.1016/j.gca.2016.11.017
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    Wimpenny, J.; James, R. H.; Burton, K. W.; Gannoun, A.; Mokadem, F.; Gíslason, S. R. Glacial Effects on Weathering Processes: New Insights from the Elemental and Lithium Isotopic Composition of West Greenland Rivers. Earth Planet. Sci. Lett. 2010, 290 (3), 427– 437,  DOI: 10.1016/j.epsl.2009.12.042
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    Millot, R.; Vigier, N.; Gaillardet, J. Behaviour of Lithium and Its Isotopes during Weathering in the Mackenzie Basin, Canada. Geochim. Cosmochim. Acta 2010, 74, 3897– 3912,  DOI: 10.1016/j.gca.2010.04.025
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    Pogge von Strandmann, P. A. E.; Cosford, L. R.; Liu, C.-Y.; Liu, X.; Krause, A. J.; Wilson, D. J.; He, X.; McCoy-West, A. J.; Gislason, S. R.; Burton, K. W. Assessing Hydrological Controls on the Lithium Isotope Weathering Tracer. Chem. Geol. 2023, 642, 121801  DOI: 10.1016/j.chemgeo.2023.121801
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    Pogge von Strandmann, P. A. E.; Burton, K. W.; Opfergelt, S.; Genson, B.; Guicharnaud, R. A.; Gislason, S. R. The Lithium Isotope Response to the Variable Weathering of Soils in Iceland. Geochim. Cosmochim. Acta 2021, 313, 55– 73,  DOI: 10.1016/j.gca.2021.08.020
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    Steinhoefel, G.; Brantley, S. L.; Fantle, M. S. Lithium Isotopic Fractionation during Weathering and Erosion of Shale. Geochim. Cosmochim. Acta 2021, 295, 155– 177,  DOI: 10.1016/j.gca.2020.12.006
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    Lithium isotopic fractionation during weathering and erosion of shale
    Steinhoefel, Grit; Brantley, Susan L.; Fantle, Matthew S.
    Geochimica et Cosmochimica Acta (2021), 295 (), 155-177CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    Clay weathering in shales is an important component of the global Li budget because Li is mobilized from Li-rich clay minerals and shale represents about one quarter of the exposed rocks on Earth. We investigate Li isotopes and concns. to explore implications and mechanisms of Li isotopic fractionation in Shale Hills, a first-order catchment developed entirely on shale in a temperate climate in the Appalachian Mountains, northeastern USA. The Li isotopic compns. (δ7Li) of aq. Li in stream water and groundwater vary between 14.5 and 40.0‰. This range is more than half that obsd. in rivers globally. The δ7Li of aq. Li increases with increasing Li retention in secondary minerals, which is simulated using a box model that considers pore fluid advection to be the dominant transport process, silicate dissoln. to be the source of Li to the pore fluid, and uptake of Li by kaolinite, Fe-oxides, and interlayer sites of clays to be the sinks. The simulations suggest that only those deep groundwaters with δ7Li values of ~ 15‰ are explainable as steady state values; those fluids with δ7Li values > 18‰, esp. near-surface waters, can only be explained as time-dependent, transient signals in an evolving system. Lithium is highly retained in the residual solid phase during chem. weathering; however, bulk soils (0.5 ± 1.2‰ (1 SD)) and stream sediments (0.3‰) have similar, or higher, δ7Li values compared to av. bedrock (-2.0‰). This is attributed to preferential removal of clay particles from soils. Soil clays are isotopically depleted in 7Li (δ7Li values down to -5.2‰) compared to parental material, and δ7Li values correlate with soil Li concn., soil pH, and availability of exchangeable sites for Li as a function of landscape position (valley floor vs. ridge top). The strong depletion of Li and clay minerals in soils compared to bedrock is attributed at least partly to loss of Li through export of fine-grained clay particles in subsurface water flow. This process might be enhanced as the upper weathering zone of this catchment is highly fractured due to former periglacial conditions. The Li isotopic compn. of vegetation is similar to soil clay and both are distinct from mobile catchment water (soil pore water, stream and groundwater). Extrapolating from this catchment means that subsurface particle loss from shales could be significant today and in the past, affecting isotopic signatures of soils and water. For example, clay transformations together with removal of clay particles before re-dissoln. support weathering conditions that lead to a low aq. Li flux but to high δ7Li values in water.
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    Chan, L.-H. H.; Hein, J. R. Lithium Contents and Isotopic Compositions of Ferromanganese Deposits from the Global Ocean. Deep Sea Res., Part II 2007, 54 (11), 1147– 1162,  DOI: 10.1016/j.dsr2.2007.04.003
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    Taylor, T. I.; Urey, H. C. Fractionation of the Lithium and Potassium Isotopes by Chemical Exchange with Zeolites. J. Chem. Phys. 1938, 6 (8), 429– 438,  DOI: 10.1063/1.1750288
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    Wimpenny, J.; Colla, C. A.; Yu, P.; Yin, Q.-Z.; Rustad, J. R.; Casey, W. H. Lithium Isotope Fractionation during Uptake by Gibbsite. Geochim. Cosmochim. Acta 2015, 168, 133– 150,  DOI: 10.1016/j.gca.2015.07.011
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    Lithium isotope fractionation during uptake by gibbsite
    Wimpenny, Josh; Colla, Christopher A.; Yu, Ping; Yin, Qing-Zhu; Rustad, James R.; Casey, William H.
    Geochimica et Cosmochimica Acta (2015), 168 (), 133-150CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    The intercalation of lithium from soln. into the six-membered μ2-oxo rings on the basal planes of gibbsite is well-constrained chem. The product is a lithiated layered-double hydroxide solid that forms via in situ phase change. The reaction has well established kinetics and is assocd. with a distinct swelling of the gibbsite as counter ions enter the interlayer to balance the charge of lithiation. Lithium reacts to fill a fixed and well identifiable crystallog. site and has no solvation waters. The lithium-isotope data shows that 6Li is favored during this intercalation and that the solid-soln. fractionation depends on temp., electrolyte concn. and counter ion identity (whether Cl-, NO-3 or ClO-4). We find that the amt. of isotopic fractionation between solid and soln. (ΔLisolid-solution) varies with the amt. of lithium taken up into the gibbsite structure, which itself depends upon the extent of conversion and also varies with electrolyte concn. and in the counter ion in the order: ClO-4 < NO-3 < Cl-. Higher electrolyte concns. cause more rapid expansion of the gibbsite interlayer and some counter ions, such as Cl-, are more easily taken up than others, probably because they ease diffusion. The relationship between lithium loading and ΔLisolid-solution indicates two stages: (1) uptake into the crystallog. sites that favors light lithium, in parallel with adsorption of solvated cations, and (2) continued uptake of solvated cations after all available octahedral vacancies are filled; this second stage has no isotopic preference. The two-step reaction progress is supported by solid-state NMR spectra that clearly resolve a second reservoir of lithium in addn. to the expected layered double-hydroxide phase.
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    Liu, C.-Y.; Pogge von Strandmann, P. A. E.; Tarbuck, G.; Wilson, D. J. Experimental Investigation of Oxide Leaching Methods for Li Isotopes. Geostand. Geoanal. Res. 2022, 46 (3), 493– 518,  DOI: 10.1111/ggr.12441
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    Cornell, R. M.; Schwertmann, U. The Iron Oxides: Structure, Properties, Reactions, Occurrences and Uses; Wiley Online Library; Wiley, 2003.
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    Schwertmann, U.; Cornell, R. M. Iron Oxides in the Laboratory: Preparation and Characterization; John Wiley & Sons, 2008.
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    Nielsen, U. G.; Paik, Y.; Julmis, K.; Schoonen, M. A. A.; Reeder, R. J.; Grey, C. P. Investigating Sorption on Iron–Oxyhydroxide Soil Minerals by Solid-State NMR Spectroscopy: A 6Li MAS NMR Study of Adsorption and Absorption on Goethite. J. Phys. Chem. B 2005, 109 (39), 18310– 18315,  DOI: 10.1021/jp051433x
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    Investigating Sorption on Iron-Oxyhydroxide Soil Minerals by Solid-State NMR Spectroscopy: A 6Li MAS NMR Study of Adsorption and Absorption on Goethite
    Nielsen, Ulla Gro; Paik, Younkee; Julmis, Keinia; Schoonen, Martin A. A.; Reeder, Richard J.; Grey, Clare P.
    Journal of Physical Chemistry B (2005), 109 (39), 18310-18315CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
    High-resoln. 2H MAS NMR spectra can be obtained for nanocryst. particles of goethite (α-FeOOH, particle size ≈ 4-10 nm) at room temp., facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, the system representing an ideal model system for NMR studies. 6Li resonances with large hyperfine shifts (approx. 145 ppm) were obsd. above the goethite point of zero charge, providing clear evidence for the presence of Li-O-Fe connectivities, and thus the formation of an inner sphere Li+ complex on the goethite surface. Even larger Li hyperfine shifts (289 ppm) were obsd. for Li+-exchanged goethite, which contains lithium ions in the tunnels of the goethite structure, confirming the Li assignment of the 145 ppm Li resonance to the surface sites.
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    Kim, J.; Grey, C. P. 2H and 7Li Solid-State MAS NMR Study of Local Environments and Lithium Adsorption on the Iron(III) Oxyhydroxide, Akaganeite (β-FeOOH). Chem. Mater. 2010, 22 (19), 5453– 5462,  DOI: 10.1021/cm100816h
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    2H and 7Li Solid-State MAS NMR Study of Local Environments and Lithium Adsorption on the Iron(III) Oxyhydroxide, Akaganeite (β-FeOOH)
    Kim, Jongsik; Grey, Clare P.
    Chemistry of Materials (2010), 22 (19), 5453-5462CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    2H and 7Li MAS NMR spectroscopy have been applied to characterize the surface and bulk hydroxyl groups and Li+ sorption on the iron oxyhydroxide akaganeite (β-FeOOH), a common soil mineral with a large surface area and uptake capacity for toxic cations and anions. The formation of both inner and outer-sphere complexes on the surface of akaganeite was confirmed, the former giving rise to 7Li NMR signals with large 7Li hyperfine shifts. The concns. of these complexes was detd. as a function of pH and possible Li+ binding modes and sites are proposed based on their 7Li hyperfine shifts. The binding is compared with those of the other FeOOH polymorphs, goethite and lepidocrocite. The modes of binding are similar to those of goethite, except that sites at the entrances to the tunnels become available for binding, particularly for nanosized akaganeite particles.
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    Kim, J.; Nielsen, U. G.; Grey, C. P. Local Environments and Lithium Adsorption on the Iron Oxyhydroxides Lepidocrocite (γ-FeOOH) and Goethite (α-FeOOH): A 2H and 7Li Solid-State MAS NMR Study. J. Am. Chem. Soc. 2008, 130 (4), 1285– 1295,  DOI: 10.1021/ja0761028
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    Local Environments and Lithium Adsorption on the Iron Oxyhydroxides Lepidocrocite (γ-FeOOH) and Goethite (α-FeOOH): A 2H and 7Li Solid-State MAS NMR Study
    Kim, Jongsik; Nielsen, Ulla Gro; Grey, Clare P.
    Journal of the American Chemical Society (2008), 130 (4), 1285-1295CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    2H and 7Li MAS NMR spectroscopy techniques were applied to study the local surface and bulk environments of iron oxyhydroxide lepidocrocite (γ-FeOOH). 2H variable-temp. (VT) MAS NMR expts. were performed, showing the presence of short-range, strong antiferromagnetic correlations, even at temps. above the Neel temp., TN, 77 K. The formation of a Li+ inner-sphere complex on the surface of lepidocrocite was confirmed by the observation of a signal with a large 7Li hyperfine shift in the 7Li MAS NMR spectrum. The effect of pH and relative humidity (RH) on the concns. of Li+ inner- and outer-sphere complexes was then explored, the concn. of the inner sphere complex increasing rapidly above the point of zero charge and with decreasing RH. Possible local environments of the adsorbed Li+ were identified by comparison with other layer-structured iron oxides such as γ-LiFeO2 and o-LiFeO2. Li+ positions of Li+-sorbed and exchanged goethite were reanalyzed on the basis of the correlations between Li hyperfine shifts and Li local structures, and two different binding sites were proposed, the second binding site only becoming available at higher pH.
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    Kosmulski, M.; Durand-Vidal, S.; Maczka, E.; Rosenholm, J. B. Morphology of Synthetic Goethite Particles. J. Colloid Interface Sci. 2004, 271 (2), 261– 269,  DOI: 10.1016/j.jcis.2003.10.032
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    Morphology of synthetic goethite particles
    Kosmulski, Marek; Durand-Vidal, Serge; Maczka, Edward; Rosenholm, Jarl B.
    Journal of Colloid and Interface Science (2004), 271 (2), 261-269CODEN: JCISA5; ISSN:0021-9797. (Elsevier Science)
    The sp. surface area of synthetic goethite depends on the prepn.: the Fe(III):OH ratio, the rate of base titrn. of Fe salt, and the temp. and time of crystn. The crystals also have different morphologies as detd. by SEM or TEM. C coating is used to improve the quality of SEM images of nonconducting specimens. Needle-like goethite particles become substantially thicker in the course of std. carbon coating, and the length-to-width ratio obtained for carbon-coated particles is lower than that for the original goethite particles. The morphol. of the goethite particles was also studied by tapping mode AFM.
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    Pogge von Strandmann, P. A. E.; Renforth, P.; West, A. J.; Murphy, M. J.; Luu, T. H.; Henderson, G. M. The Lithium and Magnesium Isotope Signature of Olivine Dissolution in Soil Experiments. Chem. Geol. 2021, 560, 120008  DOI: 10.1016/j.chemgeo.2020.120008
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    The lithium and magnesium isotope signature of olivine dissolution in soil experiments
    Pogge von Strandmann, Philip A. E.; Renforth, Phil; West, A. Joshua; Murphy, Melissa J.; Luu, Tu-Han; Henderson, Gideon M.
    Chemical Geology (2021), 560 (), 120008CODEN: CHGEAD; ISSN:0009-2541. (Elsevier B.V.)
    This study presents lithium and magnesium isotope ratios of soils and their drainage waters from a well-characterized weathering expt. with two soil cores, one with olivine added to the surface layer, and the other a control core. The exptl. design mimics olivine addn. to soils for CO2 sequestration and/or crop fertilization, as well as natural surface addn. of reactive minerals such as during volcanic deposition. More generally, this study presents an opportunity to better understand how isotopic fractionation records weathering processes. At the start of the expt., waters draining both cores have similar Mg isotope compn. to the soil exchangeable pool. The compn. in the two cores evolve in different directions as olivine dissoln. progresses. Mass balance calcns. show that the water δ26Mg value is controlled by congruent dissoln. of carbonate and silicates (the latter in the olivine core only), plus an isotopically fractionated exchangeable pool. For Li, waters exiting the base of the cores initially have the same isotope compn., but then diverge as olivine dissoln. progresses. For both Mg and Li, the transport down-core is significantly retarded and fractionated by exchange with the exchangeable pool. This observation has implications for the monitoring of enhanced weathering using trace elements or isotopes, because dissoln. rates and fluxes will be underestimated during the time when the exchangeable pool evolves towards a new equil.
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    Kuessner, M. L.; Gourgiotis, A.; Manhès, G.; Bouchez, J.; Zhang, X.; Gaillardet, J. Automated Analyte Separation by Ion Chromatography Using a Cobot Applied to Geological Reference Materials for Li Isotope Composition. Geostand. Geoanal. Res. 2020, 44, 57– 67,  DOI: 10.1111/ggr.12295
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    Automated Analyte Separation by Ion Chromatography Using a Cobot Applied to Geological Reference Materials for Li Isotope Composition
    Kuessner, Marie L.; Gourgiotis, Alkiviadis; Manhes, Gerard; Bouchez, Julien; Zhang, Xu; Gaillardet, Jerome
    Geostandards and Geoanalytical Research (2020), 44 (1), 57-67CODEN: GGREA3; ISSN:1639-4488. (Wiley-Blackwell)
    We present an automated ion chromatog. sepn. method using a robotic pipetting arm, termed ChemCobOne, to reduce sample sepn. time. Its performance was tested for lithium isotope sepn. in geol. ref. materials using a single-step sepn. with HCl (0.2 mol l-1) and a 2 mL resin vol. This refined lithium purifn. method does not forfeit precision, accuracy or purity compared with manual sample processing. In addn., a δ7Li value for NASS-6 of 30.99 ± 0.50‰ (2s) (95% CI = 0.14‰, n = 44) was detd. and the first δ7Li values for the granite rock ref. material GS-N (-0.57 ± 0.25‰ (2s), 95% CI = 0.15‰, n = 15), and for the soil ref. material NIST SRM 2709a (-0.37 ± 0.67‰ (2s), 95% CI = 0.15‰, n = 63) are proposed.
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    Cristiano, E.; Hu, Y.-J.; Sigfried, M.; Kaplan, D.; Nitsche, H. A Comparison of Point of Zero Charge Measurement Methodology. Clays Clay Miner. 2011, 59 (2), 107– 115,  DOI: 10.1346/CCMN.2011.0590201
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    A comparison of point of zero charge measurement methodology
    Cristiano, Elena; Hu, Yung-Jin; Siegfried, Matthew; Kaplan, Daniel; Nitsche, Heino
    Clays and Clay Minerals (2011), 59 (2), 107-115CODEN: CLCMAB; ISSN:0009-8604. (Clay Minerals Society)
    Contaminant-transport modeling requires information about the charge of subsurface particle surfaces. Because values are commonly reused many times in a single simulation, small errors can be magnified greatly. Goethite (α-FeOOH) and pyrolusite (β-MnO2) are ubiquitous mineral phases that are esp. contaminant reactive. The objective of the present study was to measure and compare the point of zero charge (PZC) using different methods. The pyrolusite PZC was measured with three methods: mass titrn. (MT) (PZC = 5.9 ± 0.1), powder addn. (PA) (PZC = 5.98 ± 0.08), and isoelec. point, IEP (PZC = 4.4 ± 0.1). The IEP measurement was in agreement with literature values. However, MT and PA resulted in a statistically larger PZC than the IEP measurement. The surface area of pyrolusite, 2.2 m2g-1, was too small to permit PZC detn. by the potentiometric titrn. (PT) method. Goethite PZC values were measured using MT (7.5 ± 0.1), PT (7.46 ± 0.09), and PA (7.20 ± 0.08). The present work presents the first reported instance where MT and PA have been applied to measure the point of zero charge of either pyrolusite or goethite. The results illustrate the importance of using multiple, complementary techniques to measure PZC values accurately.
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    The point of zero charge (pHzpc) of natural magnetite [1309-38-2] and its adsorptive properties with regard to alkali metal ions are reported. The pHzpc of freshly ground, untreated magnetite is 6.5, decreasing, after treatment with HCl, to the value of pH 3.8. This discrepancy might be explained as a consequence of possible structure changes on the magnetite surface. Adsorption properties of magnetite with respect to Li3+, Na+ and K+ ions in the concn. and pH ranges varying from 0.1 to 1.0 mol.cm3 and 6.5 to 10, resp., were examd. For the chloride media, the adsorption sequence obtained is Na+ > K+ > Li+. The study concerns with magnetite corrosion product removal from PWR.
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    Diakonov, I. I.; Schott, J.; Martin, F.; Harrichourry, J. C.; Escalier, J. Iron(III) Solubility and Speciation in Aqueous Solutions. Experimental Study and Modelling: Part 1. Hematite Solubility from 60 to 300 °C in NaOH–NaCl Solutions and Thermodynamic Properties of Fe(OH)4–(Aq). Geochim. Cosmochim. Acta 1999, 63 (15), 2247– 2261,  DOI: 10.1016/S0016-7037(99)00070-8
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  1. Wenxian Gou, Wei Li, Zhengrong Wang, Dong-Xing Guan, Bo Xia, Yi Huang. Sorption-induced metal isotope fractionation: Two decades of advances in methodologies, mechanisms, and kinetics. Earth-Science Reviews 2025, 269 , 105186. https://doi.org/10.1016/j.earscirev.2025.105186
  2. Chengfan Yang, Jiacheng Peng, Junjie Guo, Qiang Hao, Jinniu Chen, Shouye Yang. Lithium isotope fractionation in the mid-lower Changjiang basin: Insights from riverine geochemistry and the role of authigenic oxyhydroxides. Geochimica et Cosmochimica Acta 2025, 407 , 121-132. https://doi.org/10.1016/j.gca.2025.09.007
  3. Philip A.E. Pogge von Strandmann, Xiaoqing He, Ying Zhou, David J. Wilson. Comparing open versus closed system weathering experiments using lithium isotopes. Applied Geochemistry 2025, 189 , 106458. https://doi.org/10.1016/j.apgeochem.2025.106458
  4. Venkata Sailaja Pappala, Carli A. Arendt, Xiao‐Ming Liu. Elemental and Li Isotopic Investigation of a Proglacial River System: Insights to Modern Chemical Weathering Processes. Journal of Geophysical Research: Earth Surface 2025, 130 (4) https://doi.org/10.1029/2024JF007856
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  • Abstract

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    Figure 1

    Figure 1. SEM characterization of (a) goethiteLT and (b) goethiteHT particles. Inset graphs show XRD results (Figure S1).

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    Figure 2

    Figure 2. Solid characterization of goethiteLT particles using transmission electron microscopy (TEM) and high-resolution TEM (HRTEM): (a) unreacted goethiteLT particles; (b) particles from (a) observed under HRTEM; (c) goethiteLT particles interacted with a solution of pH ∼ 12; and (d) particles from panel (c) observed under HRTEM.

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    Figure 3

    Figure 3. Lithium sorption onto Fe-oxides at various initial pH values: (a) changes of fluid Li content in percentage under different initial pH conditions with various Fe-oxides from Experiment 1; and (b) δ7Li signatures in fluids at the end of sorption from selected samples, with the initial δ7Li signature of the LiCl stock solution marked by the dashed lines (12.8 ± 0.4‰).

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    Figure 4

    Figure 4. Variations in fluid pH at the beginning (pHi) and the end (pHf) of the Li-sorption experiments.

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    Figure 5

    Figure 5. Lithium sorption and isotope fractionation by goethiteLT at pHi ∼ 12 from Experiment 2. Changes in fluid Li content are represented in %.

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    Figure 6

    Figure 6. Estimation of Li isotope fractionation factors for (a) Experiment 1 in the scenario of equilibrium fractionation; (b) Experiment 1 in the scenario of Rayleigh fractionation; (c) Experiment 2 in the scenario of equilibrium fractionation; and (d) Experiment 2 in the scenario of Rayleigh fractionation.

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  • References

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      A computer model has been constructed that considers the effects on the CO2 level of the atm., and the Ca, Mg, and HCO3 levels of the ocean, of the following processes: weathering on the continents of calcite [13397-26-7], dolomite [16389-88-1], and Ca- and Mg-contg. silicates; biogenic pptn. and removal of CaCO3 from the ocean; removal of Mg from the ocean via volcanic-seawater reaction; and the metamorphic-magmatic decarbonation of calcite and dolomite (and resulting CO2 degassing) as a consequence of plate subduction. Assuming steady state, values for fluxes to and from the atm. and oceans are first derived for the modern ocean-atm. system. Then the consequences of perturbing steady state are examd. by deriving rate expressions for all transfer reactions. These rate expressions are constructed so as to reflect changes over the past 100 Myr. The CO2 content of the atm. is highly sensitive to changes in seafloor spreading rate and continental land area, and, to a much lesser extent, to changes in the relative masses of calcite and dolomite. Plate tectonics, as it affects both metamorphic-magmatic decarbonation and changes in continental land area, is a major control of world climate.
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      Experimental constraints on Li isotope fractionation during clay formation
      Hindshaw, Ruth S.; Tosca, Rebecca; Gout, Thomas L.; Farnan, Ian; Tosca, Nicholas J.; Tipper, Edward T.
      Geochimica et Cosmochimica Acta (2019), 250 (), 219-237CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      Knowledge of the lithium (Li) isotope fractionation factor during clay mineral formation is a key parameter for Earth system models. This study refines our understanding of isotope fractionation during clay formation with essential implications for the interpretation of field data and the global geochem. cycle of Li. We synthesized Mg-rich layer silicates (stevensite and saponite) at temps. relevant for Earth surface processes. The resultant solids were characterized by X-ray diffraction (XRD) and Fourier-transform IR spectroscopy (FT-IR) to confirm the mineralogy and crystallinity of the product. Bulk solid samples were treated with ammonium chloride to remove exchangeable Li in order to distinguish the Li isotopic fractionation between these sites and structural (octahedral) sites. Bulk solids, residual solids and exchangeable solns. were all enriched in 6Li compared to the initial soln. On av., the exchangeable solns. had δ7Li values 7‰ lower than the initial soln. The av. difference between the residual solid and initial soln. δ7Li values (Δ7Liresidue-solution) for the synthesized layer silicates was -16.6 ± 1.7‰ at 20 °C, in agreement with modeling studies, extrapolations from high temp. exptl. data and field observations. Three bonding environments were identified from 7Li-NMR spectra which were present in both bulk and residual solid 7Li-NMR spectra, implying that some exchangeable Li remains after treatment with ammonium chloride. The 7Li-NMR peaks were assigned to octahedral, outer-sphere (interlayer and adsorbed) and pseudo-hexagonal (ditrigonal cavity) Li. By combining the 7Li-NMR data with mass balance constraints we calcd. a fractionation factor, based on a Monte Carlo min. misfit method, for each bonding environment. The calcd. values are -21.5 ± 1.1‰, -0.2 ± 1.9‰ and 15.0 ± 12.3‰ for octahedral, outer-sphere and pseudo-hexagonal sites resp. (errors 1σ). The bulk fractionation factor (Δ7Libulk-solution) is dependent on the chem. of the initial soln. The higher the Na concn. in the initial soln. the lower the bulk δ7Li value. We suggest this is due to Na outcompeting Li for interlayer sites and as interlayer Li has a high δ7Li value relative to octahedral Li, increased Na serves to lower the bulk δ7Li value. Three expts. conducted at higher pH exhibited lower δ7Li values in the residual solid. This could either be a kinetic effect, resulting from the higher reaction rate at high pH, or an equil. effect resulting from reduced Li incorporation in the residual solid and/or a change in Li speciation in soln. This study highlights the power of 7Li-NMR in exptl. studies of clay synthesis to target site specific Li isotope fractionation factors which can then be used to provide much needed constraints on field processes.
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      Silicate weathering is the primary control of atm. CO2 concns. on multiple timescales. However, tracing this process has proven difficult. Lithium isotopes are a promising tracer of silicate weathering. This study has reacted basalt sand with natural river water for ∼9 mo in closed expts., in order to examine the behavior of Li isotopes during weathering. Aq. Li concns. decrease by a factor of ∼10 with time, and δ7Li increases by ∼19‰, implying that Li is being taken up into secondary phases that prefer 6Li. Mass balance using various selective leaches of the exchangeable and secondary mineral fractions suggest that ∼12-16% of Li is adsorbed, and the remainder is removed into neoformed secondary minerals. The exchangeable fractionation factors have a Δ7Liexch-soln = -11.6 to -11.9‰, while the secondary minerals impose Δ7Lisecmin-soln = -22.5 to -23.9‰. Overall the expt. can be modelled with a Rayleigh fractionation factor of α = 0.991, similar to that found for natural basaltic rivers. The mobility of Li relative to the carbon-cycle-crit. cations of Ca and Mg changes with time, but rapidly evolves within one month to remarkably similar mobilities amongst these three elements. This evolution shows a linear relationship with δ7Li (largely due to a co-variation between aq. [Li] and δ7Li), suggesting that Li isotopes have the potential to be used as a tracer of Ca and Mg mobility during basaltic weathering, and ultimately CO2 drawdown.
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      Zhang, X. Y.; Saldi, G. D.; Schott, J.; Bouchez, J.; Kuessner, M.; Montouillout, V.; Henehan, M.; Gaillardet, J. Experimental Constraints on Li Isotope Fractionation during the Interaction between Kaolinite and Seawater. Geochim. Cosmochim. Acta 2021, 292, 333– 347,  DOI: 10.1016/j.gca.2020.09.029
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      Experimental constraints on Li isotope fractionation during the interaction between kaolinite and seawater
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      In this study, to better understand the factors controlling the concn. and isotope compn. of lithium (Li) in the ocean, we investigated the behavior of Li during interaction of kaolinite with artificial seawater. Dissoln. of kaolinite in Li-free seawater at acidic conditions (exp. 1) results in a strong preferential release of light Li isotopes, with Δ7Liaq-kaol ~ -19‰, likely reflecting both the preferential breaking of 6Li-O bonds over 7Li-O bonds and the release of Li from the isotopically lighter AlO6 octahedral sites. Sorption expts. on kaolinite (exp. 2) revealed a partition coeff. between kaolinite and fluid of up to 28, and an isotopic fractionation of -24‰. Thermodn. calcn. indicates authigenic smectites formed from the dissoln. of kaolinite in seawater at pH 8.4 (exp. 3). The formation of authigenic phase strongly removed Li from the soln. (with a partition coeff. between the solid and the fluid equal to 89) and led to an increase of ca. 25‰ in seawater δ7Li. This fractionation can be described by a Rayleigh fractionation model at the early stage of the expt. during rapid clay pptn., followed, at longer reaction time, by equil. isotope fractionation during the much slower removal of aq. Li via co-pptn. and adsorption. Both processes are consistent with a fractionation factor between the solid and the aq. soln. of ~ -20‰. These expts. have implications for interpreting the Li isotopic compn. of both continental and marine waters. For instance, the preferential release of 6Li obsd. during kaolinite far-from-equil. dissoln. could explain the transient enrichments in 6Li obsd. in soil profiles. With regard to the evolution of seawater δ7Li over geol. time scales, our exptl. results suggest that detrital material discharged by rivers to the ocean and ensuing "reverse chem. weathering" have the potential to strongly impact the isotopic signature of the ocean through the neoformation of clay minerals.
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      There is no corresponding record for this reference.
    18. 18
      Wimpenny, J.; Gíslason, S. R.; James, R. H.; Gannoun, A.; Pogge Von Strandmann, P. A. E.; Burton, K. W. The Behaviour of Li and Mg Isotopes during Primary Phase Dissolution and Secondary Mineral Formation in Basalt. Geochim. Cosmochim. Acta 2010, 74 (18), 5259– 5279,  DOI: 10.1016/j.gca.2010.06.028
      There is no corresponding record for this reference.
    19. 19
      Song, Y.; Zhang, X.; Bouchez, J.; Chetelat, B.; Gaillardet, J.; Chen, J.; Zhang, T.; Cai, H.; Yuan, W.; Wang, Z. Deciphering the Signatures of Weathering and Erosion Processes and the Effects of River Management on Li Isotopes in the Subtropical Pearl River Basin. Geochim. Cosmochim. Acta 2021, 313, 340– 358,  DOI: 10.1016/j.gca.2021.08.015
      There is no corresponding record for this reference.
    20. 20
      Bastian, L.; Revel, M.; Bayon, G.; Dufour, A.; Vigier, N. Abrupt Response of Chemical Weathering to Late Quaternary Hydroclimate Changes in Northeast Africa. Sci. Rep. 2017, 7, 44231,  DOI: 10.1038/srep44231
      There is no corresponding record for this reference.
    21. 21
      Lemarchand, E.; Chabaux, F.; Vigier, N.; Millot, R.; Pierret, M.-C. Lithium Isotope Systematics in a Forested Granitic Catchment (Strengbach, Vosges Mountains, France). Geochim. Cosmochim. Acta 2010, 74, 4612– 4628,  DOI: 10.1016/j.gca.2010.04.057
      There is no corresponding record for this reference.
    22. 22
      Zhang, X.; Bajard, M.; Bouchez, J.; Sabatier, P.; Poulenard, J.; Arnaud, F.; Crouzet, C.; Kuessner, M.; Dellinger, M.; Gaillardet, J. Evolution of the Alpine Critical Zone since the Last Glacial Period Using Li Isotopes from Lake Sediments. Earth Planet. Sci. Lett. 2023, 624, 118463  DOI: 10.1016/J.EPSL.2023.118463
      There is no corresponding record for this reference.
    23. 23
      Cai, D.; Henehan, M. J.; Uhlig, D.; von Blanckenburg, F. Lithium Isotopes in Water and Regolith in a Deep Weathering Profile Reveal Imbalances in Critical Zone Fluxes. Geochim. Cosmochim. Acta 2024, 369, 213– 226,  DOI: 10.1016/j.gca.2024.01.012
      There is no corresponding record for this reference.
    24. 24
      Hathorne, E. C.; James, R. H. Temporal Record of Lithium in Seawater: A Tracer for Silicate Weathering?. Earth Planet. Sci. Lett. 2006, 246 (3–4), 393– 406,  DOI: 10.1016/j.epsl.2006.04.020
      There is no corresponding record for this reference.
    25. 25
      Misra, S.; Froelich, P. N. Lithium Isotope History of Cenozoic Seawater: Changes in Silicate Weathering and Reverse Weathering. Science 2012, 335, 818– 823,  DOI: 10.1126/science.1214697
      25
      Lithium Isotope History of Cenozoic Seawater: Changes in Silicate Weathering and Reverse Weathering
      Misra, Sambuddha; Froelich, Philip N.
      Science (Washington, DC, United States) (2012), 335 (6070), 818-823CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Weathering of uplifted continental rocks consumes carbon dioxide and transports cations to the oceans, thereby playing a crit. role in controlling both seawater chem. and climate. However, there are few archives of seawater chem. change that reveal shifts in global tectonic forces connecting Earth ocean-climate processes. The authors present a 68-Myr record of lithium isotopes in seawater (δ7LiSW) reconstructed from planktonic foraminifera. From the Paleocene (60 Myr ago) to the present, δ7LiSW rose by 9‰, requiring large changes in continental weathering and seafloor reverse weathering that are consistent with increased tectonic uplift, more rapid continental denudation, increasingly incongruent continental weathering (lower chem. weathering intensity), and more rapid CO2 drawdown. A 5‰ drop in δ7LiSW across the Cretaceous-Paleogene boundary cannot be produced by an impactor or by Deccan trap volcanism, suggesting large-scale continental denudation.
    26. 26
      Li, G.; West, A. J. Evolution of Cenozoic Seawater Lithium Isotopes: Coupling of Global Denudation Regime and Shifting Seawater Sinks. Earth Planet. Sci. Lett. 2014, 401, 284– 293,  DOI: 10.1016/j.epsl.2014.06.011
      26
      Evolution of Cenozoic seawater lithium isotopes: Coupling of global denudation regime and shifting seawater sinks
      Li, Gaojun; West, A. Joshua
      Earth and Planetary Science Letters (2014), 401 (), 284-293CODEN: EPSLA2; ISSN:0012-821X. (Elsevier B.V.)
      The Li isotopic record of seawater shows a dramatic increase of ∼ 9‰ over the past ∼ 60 million years. Here we use a model to explore what may have caused this change. We focus particularly on considering how changes in the "reverse weathering" sinks that remove Li from seawater can contribute to explain the obsd. increase. Our interpretation is based on dividing the oceanic sink, which preferentially removes light Li, into two components: (i) removal into marine authigenic clays in sediments at low temps., with assocd. high fractionation factors, and (ii) removal into altered oceanic basalt at higher temps. and resulting lower fractionation factors. We suggest that increases in the flux of degraded continental material delivered to the oceans over the past 60 Ma could have increased removal of Li into sedimentary authigenic clays vs. altered basalt. Because altered basalt is assocd. with a smaller isotopic fractionation, an increasing portion of the lower temp. (authigenic clay-assocd.) sink could contribute to the rise of the seawater Li isotope value. This effect would moderate the extent to which the isotopic value of continental inputs must have changed in order to explain the seawater record over the Cenozoic. Nonetheless, unless the magnitude of fractionation during removal differs significantly from current understanding, substantial change in the δ7Li of inputs from continental weathering must have occurred. Our modeling suggests that dissolved riverine fluxes in the early Eocene were characterized by δ7Li of ∼0 to + 13‰, with best ests. of 6.6-12.6‰; these values imply increases over the past 60 Myrs of between 10 and 24‰, and we view a ∼ 13‰ increase as a likely scenario. These changes would have been accompanied by increases in both the dissolved Li flux from continental weathering and the removal flux from seawater into marine authigenic clays. Increases in δ7Li of continental input are consistent with a change in the global denudation regime as a result of increasing continental erosion rate through the Cenozoic. Changes in denudation may have meant increasing climate sensitivity of weathering over time but do not require globally supply-limited and thus entirely climate-insensitive weathering in the early Cenozoic.
    27. 27
      Andrews, E.; Pogge von Strandmann, P. A. E.; Fantle, M. S. Exploring the Importance of Authigenic Clay Formation in the Global Li Cycle. Geochim. Cosmochim. Acta 2020, 289, 47– 68,  DOI: 10.1016/j.gca.2020.08.018
      27
      Exploring the importance of authigenic clay formation in the global Li cycle
      Andrews, Elizabeth; Pogge von Strandmann, Philip A. E.; Fantle, Matthew S.
      Geochimica et Cosmochimica Acta (2020), 289 (), 47-68CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      Lithium isotopic (δ7Li) and elemental concns. of pore fluids and carbonates from IODP Site U1338 Hole A (eastern equatorial Pacific Ocean) suggest that clay authigenesis (i.e., in situ pptn.) is a significant sink for Li in carbonate-rich sedimentary sections. Systematic variations in pore fluid δ7Li with depth in the section suggest that clay authigenesis can (i) strongly decrease pore fluid Li concns. with depth and (ii) fractionate Li isotopically to a considerable degree (Δ ~ 5-21‰ relative to seawater). We hypothesize that clay authigenesis in carbonate-rich sections occurs due to the presence of reactive biogenic silica, and reactive transport modeling supports the contention that the pore fluid δ7Li depth profile at Site U1338 is best explained by faster authigenesis at depth. The significance of clay authigenesis in carbonate-rich sediments is two-fold: if global in scale, (i) it can generate sizeable output fluxes in the global Li cycle, and (ii) the evolution of the sedimentary system over time can markedly impact the isotopic compn. of the global Li output flux. We compile ODP and IODP pore fluid Li data from 267 sites; of these, 207 have Li pore fluid concn. gradients in the upper 50-100 m that indicate the sites as diffusive sinks of Li. We then est. that clay authigenesis in carbonate-rich sediments could reasonably generate a Li output flux on the order of ~ 1.2·1010 moles/yr, which is comparable to the gross input fluxes in the modern Li cycle. A series of reactive transport simulations illustrate how clay authigenesis might impact the isotopic compn. of the output flux of Li from the global ocean. The suggestion is that applying a const. fractionation factor from the global ocean over time is likely incorrect, and that secular changes in the δ7Li of the output flux will be driven by rates of authigenesis, burial rates, and the depth extent of authigenesis in the sedimentary section. Utilizing a time-dependent, depositional diagenetic model, the δ7Li values of bulk carbonate are shown to be a consequence not of recrystn. alone, but recrystn. in the presence of clay authigenesis. Further, our model results are used to illustrate how carbonate δ7Li may be used to constrain the temporal evolution of clay authigenesis in the sedimentary section. Ultimately, this work suggests that the Li isotopic compn. of bulk carbonates can be altered diagenetically. However, such alteration is not a detriment, but provides useful information on those diagenetic processes in the sedimentary column that impact the global Li cycle. Thus, Li isotopes in bulk carbonates have the potential to elucidate diagenetic controls on the global Li cycle over long time scales.
    28. 28
      Zhang, X.; Gaillardet, J.; Barrier, L.; Bouchez, J. Li and Si Isotopes Reveal Authigenic Clay Formation in a Palaeo-Delta. Earth Planet. Sci. Lett. 2022, 578, 117339  DOI: 10.1016/j.epsl.2021.117339
      There is no corresponding record for this reference.
    29. 29
      James, R. H.; Allen, D. E.; Seyfried, W. E. An Experimental Study of Alteration of Oceanic Crust and Terrigenous Sediments at Moderate Temperatures (51 to 350 C): Insights as to Chemical Processes in near-Shore Ridge-Flank Hydrothermal Systems. Geochim. Cosmochim. Acta 2003, 67 (4), 681– 691,  DOI: 10.1016/S0016-7037(02)01113-4
      There is no corresponding record for this reference.
    30. 30
      Berger, G.; Schott, J.; Guy, C. Behavior of Li, Rb and Cs during Basalt Glass and Olivine Dissolution and Chlorite, Smectite and Zeolite Precipitation from Seawater: Experimental Investigations and Modelization between 50 and 300 C. Chem. Geol. 1988, 71 (4), 297– 312,  DOI: 10.1016/0009-2541(88)90056-3
      There is no corresponding record for this reference.
    31. 31
      Berger, G.; Schott, J.; Loubet, M. Fundamental Processes Controlling the First Stage of Alteration of a Basalt Glass by Seawater: An Experimental Study between 200 and 320 C. Earth Planet. Sci. Lett. 1987, 84 (4), 431– 445,  DOI: 10.1016/0012-821X(87)90008-2
      There is no corresponding record for this reference.
    32. 32
      Seyfried, W. E.; Janecky, D. R.; Mottl, M. J. Alteration of the Oceanic Crust: Implications for Geochemical Cycles of Lithium and Boron. Geochim. Cosmochim. Acta 1984, 48 (3), 557– 569,  DOI: 10.1016/0016-7037(84)90284-9
      There is no corresponding record for this reference.
    33. 33
      Millot, R.; Scaillet, B.; Sanjuan, B. Lithium Isotopes in Island Arc Geothermal Systems: Guadeloupe, Martinique (French West Indies) and Experimental Approach. Geochim. Cosmochim. Acta 2010, 74 (6), 1852– 1871,  DOI: 10.1016/j.gca.2009.12.007
      There is no corresponding record for this reference.
    34. 34
      Pistiner, J. S.; Henderson, G. M. Lithium-Isotope Fractionation during Continental Weathering Processes. Earth Planet. Sci. Lett. 2003, 214 (1), 327– 339,  DOI: 10.1016/S0012-821X(03)00348-0
      There is no corresponding record for this reference.
    35. 35
      Verney-Carron, A.; Vigier, N.; Millot, R. Experimental Determination of the Role of Diffusion on Li Isotope Fractionation during Basaltic Glass Weathering. Geochim. Cosmochim. Acta 2011, 75 (12), 3452– 3468,  DOI: 10.1016/j.gca.2011.03.019
      There is no corresponding record for this reference.
    36. 36
      Zhang, L.; Chan, L.-H.; Gieskes, J. M. Lithium Isotope Geochemistry of Pore Waters from Ocean Drilling Program Sites 918 and 919, Irminger Basin. Geochim. Cosmochim. Acta 1998, 62 (14), 2437– 2450,  DOI: 10.1016/S0016-7037(98)00178-1
      There is no corresponding record for this reference.
    37. 37
      Pogge von Strandmann, P. A. E.; Liu, X.; Liu, C.-Y.; Wilson, D. J.; Hammond, S. J.; Tarbuck, G.; Aristilde, L.; Krause, A. J.; Fraser, W. T. Lithium Isotope Behaviour during Basalt Weathering Experiments Amended with Organic Acids. Geochim. Cosmochim. Acta 2022, 328, 37– 57,  DOI: 10.1016/j.gca.2022.04.032
      There is no corresponding record for this reference.
    38. 38
      Chapela Lara, M.; Buss, H. L.; Henehan, M. J.; Schuessler, J. A.; McDowell, W. H. Secondary Minerals Drive Extreme Lithium Isotope Fractionation During Tropical Weathering. J. Geophys. Res.: Earth Surf. 2022, 127 (2), e2021JF006366  DOI: 10.1029/2021JF006366
      There is no corresponding record for this reference.
    39. 39
      Schellmann, W. A New Definition of Laterite. Memoirs Geol. Survey India 1986, 120, 1– 7
      There is no corresponding record for this reference.
    40. 40
      Babechuk, M. G.; Widdowson, M.; Kamber, B. S. Quantifying Chemical Weathering Intensity and Trace Element Release from Two Contrasting Basalt Profiles, Deccan Traps, India. Chem. Geol. 2014, 363, 56– 75,  DOI: 10.1016/j.chemgeo.2013.10.027
      40
      Quantifying chemical weathering intensity and trace element release from two contrasting basalt profiles, Deccan Traps, India
      Babechuk, M. G.; Widdowson, M.; Kamber, B. S.
      Chemical Geology (2014), 363 (), 56-75CODEN: CHGEAD; ISSN:0009-2541. (Elsevier B.V.)
      Weathering profiles developed on basalt substrate contain information relevant to climate, atm. compn. and evolution, nutrient release into the hydrosphere, and understanding Martian regolith. In this study, the chem. compns. of two profiles developed on Deccan Trap basalt are examd. One is sub-Recent and has only progressed to a moderate degree of alteration (Chhindwara profile), whereas the other is ancient (Paleocene) and the degree of alteration is extreme (Bidar laterite). In an attempt to better quantify the chem. changes during incipient to intermediate weathering of mafic substrates, a new index is proposed: the mafic index of alteration (MIA). Similar to the chem. index of alteration (CIA), the MIA quantifies the net loss of the mobile major elements (Ca, Mg, Na, K ± Fe) relative to the immobile major elements (Al ± Fe). The redox-dependent weathering behavior of Fe is factored into two sep. arrangements of the MIA that apply to oxidative [MIA(O)] or reduced [MIA(R)] weathering. The MIA can be visualized in a variety of ternary diagrams in the Al-Fe-Mg-Ca-Na-K system. To chem. quantify the stages of advanced to extreme weathering, at which the MIA and CIA are ineffective, the SiO2 to (Al2O3 + Fe2O3) mass ratio, based on the established Si-Al-Fe (SAF) 'laterite' ternary diagram, is used; we propose that this ratio be referred to as the 'index of lateritisation' (IOL). Major element chem. variations, as expressed by weathering indexes, are used to relate the extent of weathering with the behavior of trace elements (alkali, alk. earth, rare earth, and Nb) in the profiles. During the early stages of basalt weathering, the mobile trace elements (Sr, Be, Li) are anti-correlated with the chem. weathering indexes and thus released during these stages. By contrast, the monovalent elements (K, Rb, Cs, Tl), excluding Na and Li, appear to be assocd. with the pedogenetic clay minerals. Of these elements, those with the most similar ionic radii are closely related in their weathering behavior. Fractionation of the REE (Sm/Nd, Eu/Eu*, Ce/Ce*) is evident during weathering of the basalt. The loss of Eu is linked with that of Sr, Ca, and Na and thus assocd. with plagioclase dissoln. during the stages of incipient to intermediate weathering. The fractionation of Sm/Nd suggests that basaltic weathering products may not always preserve their parent rock ratio and, consequently, their Nd isotope compn. over time. Finally, weathering in the sub-Recent profile is shown to have progressed across two lava flows, whose morphol. initially controlled the extent of weathering. Certain compositional variations in the original flows (e.g., immobile element ratios) are preserved through the effects of chem. weathering and have the potential to influence mass balance calcns. across the entire profile.
    41. 41
      Kısakürek, B.; Widdowson, M.; James, R. H. Behaviour of Li Isotopes during Continental Weathering: The Bidar Laterite Profile, India. Chem. Geol. 2004, 212 (1–2), 27– 44,  DOI: 10.1016/j.chemgeo.2004.08.027
      There is no corresponding record for this reference.
    42. 42
      Ji, H.; Chang, C.; Beckford, H. O.; Song, C.; Blake, R. E. New Perspectives on Lateritic Weathering Process over Karst Area – Geochemistry and Si-Li Isotopic Evidence. Catena 2021, 198, 105022  DOI: 10.1016/j.catena.2020.105022
      There is no corresponding record for this reference.
    43. 43
      Pogge von Strandmann, P. A. E.; Frings, P. J.; Murphy, M. J. Lithium Isotope Behaviour during Weathering in the Ganges Alluvial Plain. Geochim. Cosmochim. Acta 2017, 198, 17– 31,  DOI: 10.1016/j.gca.2016.11.017
      There is no corresponding record for this reference.
    44. 44
      Wimpenny, J.; James, R. H.; Burton, K. W.; Gannoun, A.; Mokadem, F.; Gíslason, S. R. Glacial Effects on Weathering Processes: New Insights from the Elemental and Lithium Isotopic Composition of West Greenland Rivers. Earth Planet. Sci. Lett. 2010, 290 (3), 427– 437,  DOI: 10.1016/j.epsl.2009.12.042
      There is no corresponding record for this reference.
    45. 45
      Millot, R.; Vigier, N.; Gaillardet, J. Behaviour of Lithium and Its Isotopes during Weathering in the Mackenzie Basin, Canada. Geochim. Cosmochim. Acta 2010, 74, 3897– 3912,  DOI: 10.1016/j.gca.2010.04.025
      There is no corresponding record for this reference.
    46. 46
      Pogge von Strandmann, P. A. E.; Cosford, L. R.; Liu, C.-Y.; Liu, X.; Krause, A. J.; Wilson, D. J.; He, X.; McCoy-West, A. J.; Gislason, S. R.; Burton, K. W. Assessing Hydrological Controls on the Lithium Isotope Weathering Tracer. Chem. Geol. 2023, 642, 121801  DOI: 10.1016/j.chemgeo.2023.121801
      There is no corresponding record for this reference.
    47. 47
      Pogge von Strandmann, P. A. E.; Burton, K. W.; Opfergelt, S.; Genson, B.; Guicharnaud, R. A.; Gislason, S. R. The Lithium Isotope Response to the Variable Weathering of Soils in Iceland. Geochim. Cosmochim. Acta 2021, 313, 55– 73,  DOI: 10.1016/j.gca.2021.08.020
      There is no corresponding record for this reference.
    48. 48
      Steinhoefel, G.; Brantley, S. L.; Fantle, M. S. Lithium Isotopic Fractionation during Weathering and Erosion of Shale. Geochim. Cosmochim. Acta 2021, 295, 155– 177,  DOI: 10.1016/j.gca.2020.12.006
      48
      Lithium isotopic fractionation during weathering and erosion of shale
      Steinhoefel, Grit; Brantley, Susan L.; Fantle, Matthew S.
      Geochimica et Cosmochimica Acta (2021), 295 (), 155-177CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      Clay weathering in shales is an important component of the global Li budget because Li is mobilized from Li-rich clay minerals and shale represents about one quarter of the exposed rocks on Earth. We investigate Li isotopes and concns. to explore implications and mechanisms of Li isotopic fractionation in Shale Hills, a first-order catchment developed entirely on shale in a temperate climate in the Appalachian Mountains, northeastern USA. The Li isotopic compns. (δ7Li) of aq. Li in stream water and groundwater vary between 14.5 and 40.0‰. This range is more than half that obsd. in rivers globally. The δ7Li of aq. Li increases with increasing Li retention in secondary minerals, which is simulated using a box model that considers pore fluid advection to be the dominant transport process, silicate dissoln. to be the source of Li to the pore fluid, and uptake of Li by kaolinite, Fe-oxides, and interlayer sites of clays to be the sinks. The simulations suggest that only those deep groundwaters with δ7Li values of ~ 15‰ are explainable as steady state values; those fluids with δ7Li values > 18‰, esp. near-surface waters, can only be explained as time-dependent, transient signals in an evolving system. Lithium is highly retained in the residual solid phase during chem. weathering; however, bulk soils (0.5 ± 1.2‰ (1 SD)) and stream sediments (0.3‰) have similar, or higher, δ7Li values compared to av. bedrock (-2.0‰). This is attributed to preferential removal of clay particles from soils. Soil clays are isotopically depleted in 7Li (δ7Li values down to -5.2‰) compared to parental material, and δ7Li values correlate with soil Li concn., soil pH, and availability of exchangeable sites for Li as a function of landscape position (valley floor vs. ridge top). The strong depletion of Li and clay minerals in soils compared to bedrock is attributed at least partly to loss of Li through export of fine-grained clay particles in subsurface water flow. This process might be enhanced as the upper weathering zone of this catchment is highly fractured due to former periglacial conditions. The Li isotopic compn. of vegetation is similar to soil clay and both are distinct from mobile catchment water (soil pore water, stream and groundwater). Extrapolating from this catchment means that subsurface particle loss from shales could be significant today and in the past, affecting isotopic signatures of soils and water. For example, clay transformations together with removal of clay particles before re-dissoln. support weathering conditions that lead to a low aq. Li flux but to high δ7Li values in water.
    49. 49
      Chan, L.-H. H.; Hein, J. R. Lithium Contents and Isotopic Compositions of Ferromanganese Deposits from the Global Ocean. Deep Sea Res., Part II 2007, 54 (11), 1147– 1162,  DOI: 10.1016/j.dsr2.2007.04.003
      There is no corresponding record for this reference.
    50. 50
      Taylor, T. I.; Urey, H. C. Fractionation of the Lithium and Potassium Isotopes by Chemical Exchange with Zeolites. J. Chem. Phys. 1938, 6 (8), 429– 438,  DOI: 10.1063/1.1750288
      There is no corresponding record for this reference.
    51. 51
      Wimpenny, J.; Colla, C. A.; Yu, P.; Yin, Q.-Z.; Rustad, J. R.; Casey, W. H. Lithium Isotope Fractionation during Uptake by Gibbsite. Geochim. Cosmochim. Acta 2015, 168, 133– 150,  DOI: 10.1016/j.gca.2015.07.011
      51
      Lithium isotope fractionation during uptake by gibbsite
      Wimpenny, Josh; Colla, Christopher A.; Yu, Ping; Yin, Qing-Zhu; Rustad, James R.; Casey, William H.
      Geochimica et Cosmochimica Acta (2015), 168 (), 133-150CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      The intercalation of lithium from soln. into the six-membered μ2-oxo rings on the basal planes of gibbsite is well-constrained chem. The product is a lithiated layered-double hydroxide solid that forms via in situ phase change. The reaction has well established kinetics and is assocd. with a distinct swelling of the gibbsite as counter ions enter the interlayer to balance the charge of lithiation. Lithium reacts to fill a fixed and well identifiable crystallog. site and has no solvation waters. The lithium-isotope data shows that 6Li is favored during this intercalation and that the solid-soln. fractionation depends on temp., electrolyte concn. and counter ion identity (whether Cl-, NO-3 or ClO-4). We find that the amt. of isotopic fractionation between solid and soln. (ΔLisolid-solution) varies with the amt. of lithium taken up into the gibbsite structure, which itself depends upon the extent of conversion and also varies with electrolyte concn. and in the counter ion in the order: ClO-4 < NO-3 < Cl-. Higher electrolyte concns. cause more rapid expansion of the gibbsite interlayer and some counter ions, such as Cl-, are more easily taken up than others, probably because they ease diffusion. The relationship between lithium loading and ΔLisolid-solution indicates two stages: (1) uptake into the crystallog. sites that favors light lithium, in parallel with adsorption of solvated cations, and (2) continued uptake of solvated cations after all available octahedral vacancies are filled; this second stage has no isotopic preference. The two-step reaction progress is supported by solid-state NMR spectra that clearly resolve a second reservoir of lithium in addn. to the expected layered double-hydroxide phase.
    52. 52
      Liu, C.-Y.; Pogge von Strandmann, P. A. E.; Tarbuck, G.; Wilson, D. J. Experimental Investigation of Oxide Leaching Methods for Li Isotopes. Geostand. Geoanal. Res. 2022, 46 (3), 493– 518,  DOI: 10.1111/ggr.12441
      There is no corresponding record for this reference.
    53. 53
      Cornell, R. M.; Schwertmann, U. The Iron Oxides: Structure, Properties, Reactions, Occurrences and Uses; Wiley Online Library; Wiley, 2003.
      There is no corresponding record for this reference.
    54. 54
      Schwertmann, U.; Cornell, R. M. Iron Oxides in the Laboratory: Preparation and Characterization; John Wiley & Sons, 2008.
      There is no corresponding record for this reference.
    55. 55
      Nielsen, U. G.; Paik, Y.; Julmis, K.; Schoonen, M. A. A.; Reeder, R. J.; Grey, C. P. Investigating Sorption on Iron–Oxyhydroxide Soil Minerals by Solid-State NMR Spectroscopy: A 6Li MAS NMR Study of Adsorption and Absorption on Goethite. J. Phys. Chem. B 2005, 109 (39), 18310– 18315,  DOI: 10.1021/jp051433x
      55
      Investigating Sorption on Iron-Oxyhydroxide Soil Minerals by Solid-State NMR Spectroscopy: A 6Li MAS NMR Study of Adsorption and Absorption on Goethite
      Nielsen, Ulla Gro; Paik, Younkee; Julmis, Keinia; Schoonen, Martin A. A.; Reeder, Richard J.; Grey, Clare P.
      Journal of Physical Chemistry B (2005), 109 (39), 18310-18315CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
      High-resoln. 2H MAS NMR spectra can be obtained for nanocryst. particles of goethite (α-FeOOH, particle size ≈ 4-10 nm) at room temp., facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, the system representing an ideal model system for NMR studies. 6Li resonances with large hyperfine shifts (approx. 145 ppm) were obsd. above the goethite point of zero charge, providing clear evidence for the presence of Li-O-Fe connectivities, and thus the formation of an inner sphere Li+ complex on the goethite surface. Even larger Li hyperfine shifts (289 ppm) were obsd. for Li+-exchanged goethite, which contains lithium ions in the tunnels of the goethite structure, confirming the Li assignment of the 145 ppm Li resonance to the surface sites.
    56. 56
      Kim, J.; Grey, C. P. 2H and 7Li Solid-State MAS NMR Study of Local Environments and Lithium Adsorption on the Iron(III) Oxyhydroxide, Akaganeite (β-FeOOH). Chem. Mater. 2010, 22 (19), 5453– 5462,  DOI: 10.1021/cm100816h
      56
      2H and 7Li Solid-State MAS NMR Study of Local Environments and Lithium Adsorption on the Iron(III) Oxyhydroxide, Akaganeite (β-FeOOH)
      Kim, Jongsik; Grey, Clare P.
      Chemistry of Materials (2010), 22 (19), 5453-5462CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      2H and 7Li MAS NMR spectroscopy have been applied to characterize the surface and bulk hydroxyl groups and Li+ sorption on the iron oxyhydroxide akaganeite (β-FeOOH), a common soil mineral with a large surface area and uptake capacity for toxic cations and anions. The formation of both inner and outer-sphere complexes on the surface of akaganeite was confirmed, the former giving rise to 7Li NMR signals with large 7Li hyperfine shifts. The concns. of these complexes was detd. as a function of pH and possible Li+ binding modes and sites are proposed based on their 7Li hyperfine shifts. The binding is compared with those of the other FeOOH polymorphs, goethite and lepidocrocite. The modes of binding are similar to those of goethite, except that sites at the entrances to the tunnels become available for binding, particularly for nanosized akaganeite particles.
    57. 57
      Kim, J.; Nielsen, U. G.; Grey, C. P. Local Environments and Lithium Adsorption on the Iron Oxyhydroxides Lepidocrocite (γ-FeOOH) and Goethite (α-FeOOH): A 2H and 7Li Solid-State MAS NMR Study. J. Am. Chem. Soc. 2008, 130 (4), 1285– 1295,  DOI: 10.1021/ja0761028
      57
      Local Environments and Lithium Adsorption on the Iron Oxyhydroxides Lepidocrocite (γ-FeOOH) and Goethite (α-FeOOH): A 2H and 7Li Solid-State MAS NMR Study
      Kim, Jongsik; Nielsen, Ulla Gro; Grey, Clare P.
      Journal of the American Chemical Society (2008), 130 (4), 1285-1295CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      2H and 7Li MAS NMR spectroscopy techniques were applied to study the local surface and bulk environments of iron oxyhydroxide lepidocrocite (γ-FeOOH). 2H variable-temp. (VT) MAS NMR expts. were performed, showing the presence of short-range, strong antiferromagnetic correlations, even at temps. above the Neel temp., TN, 77 K. The formation of a Li+ inner-sphere complex on the surface of lepidocrocite was confirmed by the observation of a signal with a large 7Li hyperfine shift in the 7Li MAS NMR spectrum. The effect of pH and relative humidity (RH) on the concns. of Li+ inner- and outer-sphere complexes was then explored, the concn. of the inner sphere complex increasing rapidly above the point of zero charge and with decreasing RH. Possible local environments of the adsorbed Li+ were identified by comparison with other layer-structured iron oxides such as γ-LiFeO2 and o-LiFeO2. Li+ positions of Li+-sorbed and exchanged goethite were reanalyzed on the basis of the correlations between Li hyperfine shifts and Li local structures, and two different binding sites were proposed, the second binding site only becoming available at higher pH.
    58. 58
      Kosmulski, M.; Durand-Vidal, S.; Maczka, E.; Rosenholm, J. B. Morphology of Synthetic Goethite Particles. J. Colloid Interface Sci. 2004, 271 (2), 261– 269,  DOI: 10.1016/j.jcis.2003.10.032
      58
      Morphology of synthetic goethite particles
      Kosmulski, Marek; Durand-Vidal, Serge; Maczka, Edward; Rosenholm, Jarl B.
      Journal of Colloid and Interface Science (2004), 271 (2), 261-269CODEN: JCISA5; ISSN:0021-9797. (Elsevier Science)
      The sp. surface area of synthetic goethite depends on the prepn.: the Fe(III):OH ratio, the rate of base titrn. of Fe salt, and the temp. and time of crystn. The crystals also have different morphologies as detd. by SEM or TEM. C coating is used to improve the quality of SEM images of nonconducting specimens. Needle-like goethite particles become substantially thicker in the course of std. carbon coating, and the length-to-width ratio obtained for carbon-coated particles is lower than that for the original goethite particles. The morphol. of the goethite particles was also studied by tapping mode AFM.
    59. 59
      Pogge von Strandmann, P. A. E.; Renforth, P.; West, A. J.; Murphy, M. J.; Luu, T. H.; Henderson, G. M. The Lithium and Magnesium Isotope Signature of Olivine Dissolution in Soil Experiments. Chem. Geol. 2021, 560, 120008  DOI: 10.1016/j.chemgeo.2020.120008
      59
      The lithium and magnesium isotope signature of olivine dissolution in soil experiments
      Pogge von Strandmann, Philip A. E.; Renforth, Phil; West, A. Joshua; Murphy, Melissa J.; Luu, Tu-Han; Henderson, Gideon M.
      Chemical Geology (2021), 560 (), 120008CODEN: CHGEAD; ISSN:0009-2541. (Elsevier B.V.)
      This study presents lithium and magnesium isotope ratios of soils and their drainage waters from a well-characterized weathering expt. with two soil cores, one with olivine added to the surface layer, and the other a control core. The exptl. design mimics olivine addn. to soils for CO2 sequestration and/or crop fertilization, as well as natural surface addn. of reactive minerals such as during volcanic deposition. More generally, this study presents an opportunity to better understand how isotopic fractionation records weathering processes. At the start of the expt., waters draining both cores have similar Mg isotope compn. to the soil exchangeable pool. The compn. in the two cores evolve in different directions as olivine dissoln. progresses. Mass balance calcns. show that the water δ26Mg value is controlled by congruent dissoln. of carbonate and silicates (the latter in the olivine core only), plus an isotopically fractionated exchangeable pool. For Li, waters exiting the base of the cores initially have the same isotope compn., but then diverge as olivine dissoln. progresses. For both Mg and Li, the transport down-core is significantly retarded and fractionated by exchange with the exchangeable pool. This observation has implications for the monitoring of enhanced weathering using trace elements or isotopes, because dissoln. rates and fluxes will be underestimated during the time when the exchangeable pool evolves towards a new equil.
    60. 60
      Kuessner, M. L.; Gourgiotis, A.; Manhès, G.; Bouchez, J.; Zhang, X.; Gaillardet, J. Automated Analyte Separation by Ion Chromatography Using a Cobot Applied to Geological Reference Materials for Li Isotope Composition. Geostand. Geoanal. Res. 2020, 44, 57– 67,  DOI: 10.1111/ggr.12295
      60
      Automated Analyte Separation by Ion Chromatography Using a Cobot Applied to Geological Reference Materials for Li Isotope Composition
      Kuessner, Marie L.; Gourgiotis, Alkiviadis; Manhes, Gerard; Bouchez, Julien; Zhang, Xu; Gaillardet, Jerome
      Geostandards and Geoanalytical Research (2020), 44 (1), 57-67CODEN: GGREA3; ISSN:1639-4488. (Wiley-Blackwell)
      We present an automated ion chromatog. sepn. method using a robotic pipetting arm, termed ChemCobOne, to reduce sample sepn. time. Its performance was tested for lithium isotope sepn. in geol. ref. materials using a single-step sepn. with HCl (0.2 mol l-1) and a 2 mL resin vol. This refined lithium purifn. method does not forfeit precision, accuracy or purity compared with manual sample processing. In addn., a δ7Li value for NASS-6 of 30.99 ± 0.50‰ (2s) (95% CI = 0.14‰, n = 44) was detd. and the first δ7Li values for the granite rock ref. material GS-N (-0.57 ± 0.25‰ (2s), 95% CI = 0.15‰, n = 15), and for the soil ref. material NIST SRM 2709a (-0.37 ± 0.67‰ (2s), 95% CI = 0.15‰, n = 63) are proposed.
    61. 61
      Cristiano, E.; Hu, Y.-J.; Sigfried, M.; Kaplan, D.; Nitsche, H. A Comparison of Point of Zero Charge Measurement Methodology. Clays Clay Miner. 2011, 59 (2), 107– 115,  DOI: 10.1346/CCMN.2011.0590201
      61
      A comparison of point of zero charge measurement methodology
      Cristiano, Elena; Hu, Yung-Jin; Siegfried, Matthew; Kaplan, Daniel; Nitsche, Heino
      Clays and Clay Minerals (2011), 59 (2), 107-115CODEN: CLCMAB; ISSN:0009-8604. (Clay Minerals Society)
      Contaminant-transport modeling requires information about the charge of subsurface particle surfaces. Because values are commonly reused many times in a single simulation, small errors can be magnified greatly. Goethite (α-FeOOH) and pyrolusite (β-MnO2) are ubiquitous mineral phases that are esp. contaminant reactive. The objective of the present study was to measure and compare the point of zero charge (PZC) using different methods. The pyrolusite PZC was measured with three methods: mass titrn. (MT) (PZC = 5.9 ± 0.1), powder addn. (PA) (PZC = 5.98 ± 0.08), and isoelec. point, IEP (PZC = 4.4 ± 0.1). The IEP measurement was in agreement with literature values. However, MT and PA resulted in a statistically larger PZC than the IEP measurement. The surface area of pyrolusite, 2.2 m2g-1, was too small to permit PZC detn. by the potentiometric titrn. (PT) method. Goethite PZC values were measured using MT (7.5 ± 0.1), PT (7.46 ± 0.09), and PA (7.20 ± 0.08). The present work presents the first reported instance where MT and PA have been applied to measure the point of zero charge of either pyrolusite or goethite. The results illustrate the importance of using multiple, complementary techniques to measure PZC values accurately.
    62. 62
      Čerović, L.; Fédoroff, M.; Jaubertie, A.; Lefèvre, G. Deposition of Hematite from Flowing Suspensions onto Aluminum and Polypropylene Pipe Walls. Mater. Manuf. Processes 2009, 24 (10–11), 1090– 1095,  DOI: 10.1080/10426910903022296
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      Milonjić, S. K.; Kopečni, M. M.; Ilić, Z. E. The Point of Zero Charge and Adsorption Properties of Natural Magnetite. J. Radioanal. Chem. 1983, 78 (1), 15– 24,  DOI: 10.1007/BF02519745
      63
      The point of zero charge and adsorption properties of natural magnetite
      Milonjic, S. K.; Kopecni, M. M.; Ilic, Z. E.
      Journal of Radioanalytical Chemistry (1983), 78 (1), 15-24CODEN: JRACBN; ISSN:0022-4081.
      The point of zero charge (pHzpc) of natural magnetite [1309-38-2] and its adsorptive properties with regard to alkali metal ions are reported. The pHzpc of freshly ground, untreated magnetite is 6.5, decreasing, after treatment with HCl, to the value of pH 3.8. This discrepancy might be explained as a consequence of possible structure changes on the magnetite surface. Adsorption properties of magnetite with respect to Li3+, Na+ and K+ ions in the concn. and pH ranges varying from 0.1 to 1.0 mol.cm3 and 6.5 to 10, resp., were examd. For the chloride media, the adsorption sequence obtained is Na+ > K+ > Li+. The study concerns with magnetite corrosion product removal from PWR.
    64. 64
      Rundberg, R. S.; Albinsson, Y.; Vannerberg, K. Sodium adsorption onto goethite as a function of pH and ionic strength. Radiochimca Acta 1994, 66–67 (Supplement), 333– 340,  DOI: 10.1524/ract.1994.6667.special-issue.333
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      Breeuwsma, A.; Lyklema, J. Interfacial Electrochemistry of Haematite (α-Fe2O3). Discuss. Faraday Soc. 1971, 52 (0), 324– 333,  DOI: 10.1039/DF9715200324
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      Cornell, R. M.; Schwertmann, U. Characterization. Iron Oxides 2003, 139– 183,  DOI: 10.1002/3527602097.ch7
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      Regalbuto, J. R. Electrostatic Adsorption. Synth. Solid Catal. 2009, 33– 58,  DOI: 10.1002/9783527626854.ch3
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      Furcas, F. E.; Lothenbach, B.; Mundra, S.; Borca, C. N.; Albert, C. C.; Isgor, O. B.; Huthwelker, T.; Angst, U. M. Transformation of 2-Line Ferrihydrite to Goethite at Alkaline PH. Environ. Sci. Technol. 2023, 57 (42), 16097– 16108,  DOI: 10.1021/acs.est.3c05260
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      Schwertmann, U. Solubility and Dissolution of Iron Oxides. Plant Soil 1991, 130 (1), 1– 25,  DOI: 10.1007/BF00011851
      69
      Solubility and dissolution of iron oxides
      Schwertmann, U.
      Plant and Soil (1991), 130 (1-2), 1-25CODEN: PLSOA2; ISSN:0032-079X.
      A review with 63 refs. Topics discussed include: what are some iron oxides; soly. of Fe (III) oxides, including soil Fe oxides, Al-for-Fe substitution, and Fe (III, II) oxides; and dissoln. of Fe (III) oxides as regards dissoln. mechanisms, factors and kinetics of dissoln., complexation, redn., and solid-phase variables.
    70. 70
      Diakonov, I. I.; Schott, J.; Martin, F.; Harrichourry, J. C.; Escalier, J. Iron(III) Solubility and Speciation in Aqueous Solutions. Experimental Study and Modelling: Part 1. Hematite Solubility from 60 to 300 °C in NaOH–NaCl Solutions and Thermodynamic Properties of Fe(OH)4–(Aq). Geochim. Cosmochim. Acta 1999, 63 (15), 2247– 2261,  DOI: 10.1016/S0016-7037(99)00070-8
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      Samson, S. D.; Eggleston, C. M. Nonsteady-State Dissolution of Goethite and Hematite in Response to PH Jumps: The Role of Adsorbed Fe (III). Water–Rock Interactions, Ore Deposits, and Environmental Geochemistry: A Tribute to David A. Crerar 2002, 7, 61– 73
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      Parkhurst, D. L.; Appelo, C. A. J. User’s Guide to PHREEQC (Version 2): A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations; US Geological Survey, 1999.
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      Dellinger, M.; Gaillardet, J.; Bouchez, J.; Calmels, D.; Louvat, P.; Dosseto, A.; Gorge, C.; Alanoca, L.; Maurice, L. Riverine Li Isotope Fractionation in the Amazon River Basin Controlled by the Weathering Regimes. Geochim. Cosmochim. Acta 2015, 164, 71– 93,  DOI: 10.1016/j.gca.2015.04.042
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      Gaillardet, J.; Viers, J.; Dupré, B. Trace Elements in River Waters. Treatise Geochem. 2003, 5, 605
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      Li, W.; Beard, B. L.; Johnson, C. M. Exchange and Fractionation of Mg Isotopes between Epsomite and Saturated MgSO4 Solution. Geochim. Cosmochim. Acta 2011, 75 (7), 1814– 1828,  DOI: 10.1016/j.gca.2011.01.023
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      Kühnel, R. A.; Roorda, H. J.; Steensma, J. J. The Crystallinity of Minerals─A New Variable in Pedogenetic Processes: A Study of Goethite and Associated Silicates in Laterites. Clays Clay Miner. 1975, 23 (5), 349– 354,  DOI: 10.1346/CCMN.1975.0230503
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      Burleson, D. J.; Penn, R. L. Two-Step Growth of Goethite from Ferrihydrite. Langmuir 2006, 22 (1), 402– 409,  DOI: 10.1021/la051883g
      77
      Two-Step Growth of Goethite from Ferrihydrite
      Burleson, David J.; Penn, R. Lee
      Langmuir (2006), 22 (1), 402-409CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      Goethite (α-FeOOH) is an antiferromagnetic Fe oxyhydroxide that is often synthesized by pptn. from homogeneous, aq. soln. followed by aging. This paper addresses goethite growth by phase transformation of six-line ferrihydrite (Fe5HO8.4H2O) nanoparticles to goethite followed by oriented aggregation of the goethite primary particles. Data tracking goethite nanocrystal growth as a function of pH, temp., and time is presented. In general, goethite growth by oriented aggregation is faster at higher pH and at higher temp. even as growth by coarsening becomes increasingly important as pH increases. Particle size measurements demonstrate that the primary nanoparticles grow by Ostwald ripening even as they are being consumed by oriented aggregation. Finally, the use of a microwave anneal step in the prepn. of the precursor six-line ferrihydrite nanoparticles substantially improves the homogeneity of the final goethite product. Final goethite nanoparticles are unaggregated, acicular crystals in the tens of nanometers size range. These particles may be ideal for mineral liq. crystal and magnetic-recording media applications.
    78. 78
      ThomasArrigo, L. K.; Notini, L.; Shuster, J.; Nydegger, T.; Vontobel, S.; Fischer, S.; Kappler, A.; Kretzschmar, R. Mineral Characterization and Composition of Fe-Rich Flocs from Wetlands of Iceland: Implications for Fe, C and Trace Element Export. Sci. Total Environ. 2022, 816, 151567  DOI: 10.1016/j.scitotenv.2021.151567
      78
      Mineral characterization and composition of Fe-rich flocs from wetlands of Iceland: Implications for Fe, C and trace element export
      ThomasArrigo, Laurel K.; Notini, Luiza; Shuster, Jeremiah; Nydegger, Tabea; Vontobel, Sophie; Fischer, Stefan; Kappler, Andreas; Kretzschmar, Ruben
      Science of the Total Environment (2022), 816 (), 151567CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
      In freshwater wetlands, redox interfaces characterized by circumneutral pH, steep gradients in O2, and a continual supply of Fe(II) form ecol. niches favorable to microaerophilic iron(II) oxidizing bacteria (FeOB) and the formation of flocs; assocns. of (a)biotic mineral phases, microorganisms, and (microbially-derived) org. matter. On the volcanic island of Iceland, wetlands are replenished with Fe-rich surface-, ground- and springwater. Combined with extensive drainage of lowland wetlands, which forms artificial redox gradients, accumulations of bright orange (a)biotically-derived Fe-rich flocs are common features of Icelandic wetlands. These loosely consolidated flocs are easily mobilized, and, considering the proximity of Icelands lowland wetlands to the coast, are likely to contribute to the suspended sediment load transported to coastal waters. To date, however, little is known regarding (Fe) mineral and elemental compn. of the flocs. In this study, flocs from wetlands (n = 16) across Iceland were analyzed using X-ray diffraction and spectroscopic techniques (X-ray absorption and 57Fe Mossbauer) combined with chem. extns. and (electron) microscopy to comprehensively characterize floc mineral, elemental, and structural compn. All flocs were rich in Fe (229-414 mg/g), and floc Fe minerals comprised primarily ferrihydrite and nano-cryst. lepidocrocite, with a single floc sample contg. nano-cryst. goethite. Floc mineralogy also included Fe in clay minerals and appreciable poorly-cryst. aluminosilicates, most likely allophane and/or imogolite. Microscopy images revealed that floc (bio)orgs. largely comprised mineral encrusted microbially-derived components (i.e. sheaths, stalks, and EPS) indicative of common FeOB Leptothrix spp. and Gallionella spp. Trace element contents in the flocs were in the low μg/g range, however nearly all trace elements were extd. with hydroxylamine hydrochloride. This finding suggests that the (a)biotic reductive dissoln. of floc Fe minerals, plausibly driven by exposure to the varied geochem. conditions of coastal waters following floc mobilization, could lead to the release of assocd. trace elements. Thus, the flocs should be considered vectors for transport of Fe, org. carbon, and trace elements from Icelandic wetlands to coastal waters.
    79. 79
      Stoops, G.; Marcelino, V. Lateritic and Bauxitic Materials. Interpret. Micromorphol. Features Soils Regoliths 2010, 329– 350,  DOI: 10.1016/B978-0-444-53156-8.00015-5
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      Anovitz, L. M.; Cheshire, M. C.; Hermann, R. P.; Gu, X.; Sheets, J. M.; Brantley, S. L.; Cole, D. R.; Ilton, E. S.; Mildner, D. F. R.; Gagnon, C.; Allard, L. F.; Littrell, K. C. Oxidation and Associated Pore Structure Modification during Experimental Alteration of Granite. Geochim. Cosmochim. Acta 2021, 292, 532– 556,  DOI: 10.1016/j.gca.2020.08.016
      80
      Oxidation and associated pore structure modification during experimental alteration of granite
      Anovitz, Lawrence M.; Cheshire, Michael C.; Hermann, Raphael P.; Gu, Xin; Sheets, Julia M.; Brantley, Susan L.; Cole, David R.; Ilton, Eugene S.; Mildner, David F. R.; Gagnon, Cedric; Allard, Lawrence F.; Littrell, Kenneth C.
      Geochimica et Cosmochimica Acta (2021), 292 (), 532-556CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      Weathering plays a crucial role in a no. of environmental processes, and the microstructure and evolution of multi-scale pore space is a critically important factor in weathering. In igneous rocks the infiltration of meteoric water into initially relatively dry material can initiate disaggregation, increasing porosity and surface area, and allowing further disaggregation and weathering. These processes, in turn, allow biota to colonize the rock, further enhancing the weathering rate. In some rocks this may be driven by primary mineral oxidn. One such mineral, biotite, has been repeatedly mentioned as a cause of cracking during oxidn. However, the scale-dependence of the processes by which this occurs are poorly understood. We cannot, therefore, accurately extrapolate lab. reaction rates to the field in predictive numerical models.In order to better understand the effects of oxidn. and test the hypothesis that fracture and disaggregation are initiated by swelling of oxidizing biotites, we reacted granite cores in a selenic acid-rich aq. soln. at 200 °C for up to 438 days. Elevated temps. and selenic acid were used to provide relatively fast reaction rates and highly oxidizing conditions in sealed reaction vessels. These expts. were analyzed using a combination of imaging, X-ray diffraction, M.ovrddot.ossbauer spectroscopy, and small- and ultra-small angle neutron scattering to interrogate porosity and microfracture formation. The exptl. results show little observable biotite swelling, but significantly more observable fractures and growth of iron oxides and/or clays along grain boundaries. Pyrite disappeared from the reacted sample. Significant increases in porosity were also obsd. at the sample rim, likely assocd. with feldspar alteration. Fractures and transport were obsd. throughout the core, suggesting that stresses due to crystn. pressures caused by the growing iron phases may be the initiating factors in granite weathering, possibly followed by biotite swelling after sufficient permeability is achieved.
    81. 81
      Sanchez-Roa, C.; Saldi, G. D.; Mitchell, T. M.; Iacoviello, F.; Bailey, J.; Shearing, P. R.; Oelkers, E. H.; Meredith, P. G.; Jones, A. P.; Striolo, A. The Role of Fluid Chemistry on Permeability Evolution in Granite: Applications to Natural and Anthropogenic Systems. Earth Planet. Sci. Lett. 2020, 553, 116641  DOI: 10.1016/j.epsl.2020.116641
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      Zhang, X. Sedimentary Recycling and Chemical Weathering: A Silicon and Lithium Isotopes Perspective; Institut de Physique du Globe de Paris, 2018.
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      Yang, C.; Yang, S.; Vigier, N. Li Isotopic Variations of Particulate Non-Silicate Phases during Estuarine Water Mixing. Geochim. Cosmochim. Acta 2023, 354, 229– 239,  DOI: 10.1016/j.gca.2023.06.020
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      Liu, C.-Y.; Wilson, D. J.; Hathorne, E. C.; Xu, A.; Pogge von Strandmann, P. A. E. The Influence of River-Derived Particles on Estuarine and Marine Elemental Cycles: Evidence from Lithium Isotopes. Geochim. Cosmochim. Acta 2023, 361, 183– 199,  DOI: 10.1016/j.gca.2023.08.015
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      European Commission. Report from the Commission to the European Parliament and the Council Progress on Competitiveness of Clean Energy Technologies; Brussels 2023 https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:52023DC0652. (accessed June 8, 2024).
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    • Solid characterization of Fe-oxide particles used in the sorption experiments (XRD, ATR-FTIR, and Raman); thermodynamic calculations of fluid chemistry; and calculation of Li isotope fractionation during sorption onto poorly crystalline goethite (PDF)


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