Elevated temperatures persisted for an anomalously protracted interval following pulsed volcanic carbon release associated with the end-Permian mass extinction, deviating from the expected timescale of climate recovery following a carbon injection event. Here, we present evidence for enhanced reverse weathering-a CO2 source-following the end-Permian mass extinction based on the lithium isotopic composition of marine shales and cherts. We find that the average lithium isotopic composition of Lower Triassic marine shales is significantly elevated relative to that of all other previously measured Phanerozoic marine shales. Notably, the record generated here conflicts with carbonate-based interpretations of the lithium isotopic composition of Early Triassic seawater, forcing a re-evaluation of the existing framework used to interpret lithium isotopes in sedimentary archives. Using a stochastic forward lithium cycle model, we demonstrate that elevated reverse weathering is required to reproduce the lithium isotopic values and trends observed in Lower Triassic marine shales and cherts. Collectively, this work provides direct geochemical evidence for enhanced reverse weathering in the aftermath of Earth\'s most severe mass extinction.

In terms of isotopic technologies, it is essential to be able to produce materials with an enriched isotopic abundance (i.e., a compound isotopic labelled with 2H, 13C, 6Li, 18O or 37Cl), which is one that differs from natural abundance. The isotopic-labelled compounds can be used to study different natural processes (like compounds labelled with 2H, 13C, or 18O), or they can be used to produce other isotopes as in the case of 6Li, which can be used to produce 3H, or to produce LiH that acts like a protection shield against fast neutrons. At the same time, 7Li isotope can be used as a pH controller in nuclear reactors. The COLEX process, which is currently the only technology available to produce 6Li at industrial scale, has environmental drawbacks due to generation of Hg waste and vapours. Therefore, there is a need for new eco-friendly technologies for separation of 6Li. The separation factor of 6Li/7Li with chemical extraction methods in two liquid phases using crown ethers is comparable to that of COLEX method, but has the disadvantages of low distribution coefficient of Li and the loss of crown ethers during the extraction. Electrochemical separation of lithium isotopes through the difference in migration rates between 6Li and 7Li is one of the green and promising alternatives for the separation of lithium isotopes, but this methodology requires complicated experimental setup and optimisation. Displacement chromatography methods like ion exchange in different experimental configurations have been also applied to enrich 6Li with promising results. Besides separation methods, there is also a need for development of new analysis methods (ICP-MS, MC-ICP-MS, TIMS) for reliable determination of Li isotope ratios upon enrichment. Considering all the above-mentioned facts, this paper will try to emphasize the current trends in separation techniques of lithium isotopes by exposing all the chemical separation and spectrometric analysis methods, and highlighting their advantages and disadvantages.

Lithium has been used as a treatment for bipolar disorder for over half a century, but there has thus far been no clinical differentiation made between the two naturally occurring stable isotopes (6Li and 7Li). While the natural lithium salts commonly used in treatments are composed of a mixture of these two stable isotopes (approximately 7.59% 6Li and 92.41% 7Li), some preliminary research indicates the above two stable isotopes of lithium may have differential effects on rat behaviour and neurophysiology. Here, we evaluate whether lithium isotopes may have distinct effects on HT22 neuronal cell viability, GSK-3-β phosphorylation in HT22 cells, and GSK-3-β kinase activity. We report no significant difference in lithium isotope toxicity on HT22 cells, nor in GSK-3-β phosphorylation, nor in GSK-3-β kinase activity between the two isotopes of lithium.

Sub-anesthetic doses of ketamine produce an increase in rodent ambulation that is attenuated by co-administration of naturally-occurring lithium (LiN), the drug most commonly employed in the treatment of bipolar illness. As a consequence, ketamine-induced hyperactivity has been proposed as an animal model of manic behavior. The current study employed a modified version of this model to compare the potency of LiN to that of each of its two stable isotopes - lithium-6 (Li-6) and lithium-7 (Li-7). Since Li-7 constitutes 92.4% of the parent compound it was hypothesized to produce comparable behavioral effects to that of LiN. The current study was devised to determine whether Li-6 might be more, less, or equally effective at tempering hyperactivity relative to Li-7 or to LiN in an animal model of manic behavior. Male rats were maintained on a restricted but high-incentive diet containing a daily dose of 2.0 mEq/kg of lithium (LiN), Li-6 or Li-7 for 30 days. A control group consumed a diet infused with sodium chloride (NaCl) in place of lithium to control for the salty taste of the food. On day 30, baseline testing revealed no differences in the locomotor behavior among the four treatment groups. Animals then continued their Li/NaCl diets for an additional 11 days during which every subject received a single IP injection of either ketamine (25 mg/kg) or 0.9% physiological saline. On the final four days of this regimen, locomotor activity was assessed during 60 min sessions each beginning immediately after ketamine injection. While all three lithium groups produced comparable decreases in ketamine-induced hyperactivity on the first trial, by the fourth trial Li-6 animals exhibited significantly greater and more prolonged reductions in hyperactivity compared to either Li-7 and Li. These results suggest that Li-6 may be more effective at treating mania than its parent compound.

Water-rock interactions in aquifer systems are a key control on water quality but remain poorly understood. Lithium (Li) isotopes are useful for understanding water-rock interactions, but there are few data available for groundwater aquifers. Here we present a Li isotope dataset for rainfall and groundwater samples from a carbonate island aquifer system: Rottnest Island, Western Australia. This dataset was complemented by strontium (Sr) isotope and major and trace element data for groundwaters, and leaching experiments on bedrock samples. The δ7Li values and 87Sr/86Sr ratios of fresh groundwaters ranged from +23 to +36‰ and 0.709167 to 0.709198, respectively. Mass balance calculations indicated that silicate weathering supplied ~60 and 70% of dissolved Li and Sr in fresh groundwaters, respectively, with the remainder provided by atmospheric input, and carbonate weathering; for major cations, the majority of calcium and sodium (Na) are supplied by carbonate weathering and atmospheric input, respectively. The estimated low proportion of Sr produced by carbonate weathering was surprising in a carbonate aquifer, and the 87Sr/86Sr data indicated that the silicate Sr source had low Rb/Sr and 87Sr/86Sr ratios. There was an increase in the maximum δ7Li values in fresh groundwaters (+36‰) relative to the maximum value in rainfall and seawater (ca. +31‰). As clay minerals are undersaturated in fresh groundwaters, this increase may be explained by Li isotope fractionation associated with ion-exchange reactions on clays and iron(oxy)hydroxides. In the more saline groundwaters, the minimum δ7Li values decreased with depth to +14.5‰, suggesting increased silicate mineral dissolution in the deeper aquifer. These results reveal the importance of water-rock interactions in a coastal carbonate aquifer, and demonstrate the usefulness of Li isotopes for tracing weathering reactions in an environmental setting where traditional weathering tracers, such as sodium and Sr isotopes, are less appropriate.

Adsorptive membrane-based chromatography can provide the high separation efficiency common to column chromatography but at a lower working pressure. Herein, a novel membrane chromatography system for lithium isotope adsorptive separation is reported. It uses polysulfone-graft-4\'-aminobenzo-15-crown-5-ether (PSf-g-AB15C5) porous membranes (0.52 mmol/g of immobilization crown ether, average pore size of 62.7 nm, porosity of 80.4%) as a stationary phase packed in a chromatography column (Ø 25 × 100 mm). Furthermore, a four-stage tandem membrane chromatography system was designed to enhance lithium isotope separation performance. The partial eluate from the former column was used as the feed solution for the next stage. Results show that the flow rate of the eluent could reach 18 mL/h owing to the lower internal diffusion resistance of membranes. Meanwhile, adsorption isotherms and adsorption kinetics show that Li+ adsorption was an exothermic and spontaneous process. The surface diffusion, multilayer adsorption and ion-pore electrostatic interaction between Li+ and the crown ether groups on the membranes played a key role in the separation of 7Li+ and 6Li+ by membrane chromatography. The separation factor obtained from the single-stage membrane chromatography was up to 1.0232. The abundances of 7Li+ and 6Li+ gradually increased with an increase in the elution stages. The relative abundances of 7Li+ and 6Li+ obtained from the four-stage tandem membrane chromatography increased by 0.26% (from 92.40 to 92.66%) and 0.2% (from 7.60 to 7.80%), respectively. In conclusion, our current research opens a new avenue for the simultaneous enrichment of 7Li+ and 6Li+ during lithium isotope adsorptive separation.