Environmental impact of direct lithium extraction from brines

Abstract

Evaporitic technology for lithium mining from brines has been questioned for its intensive water use, protracted duration and exclusive application to continental brines. In this Review, we analyse the environmental impacts of evaporitic and alternative technologies, collectively known as direct lithium extraction (DLE), for lithium mining, focusing on requirements for fresh water, chemicals, energy consumption and waste generation, including spent brines. DLE technologies aim to tackle the environmental and techno-economic shortcomings of current practice by avoiding brine evaporation. A selection of DLE technologies has achieved Li + recovery above 95%, Li + /Mg 2+ separation above 100, and zero chemical approaches. Conversely, only 30% of DLE test experiments were performed on real brines, and thus the effect of multivalent ions or large Na + /Li + concentration differences on performance indicators is often not evaluated. Some DLE technologies involve brine pH changes or brine heating up to 80 o C for improved Li + recovery, which require energy, fresh water and chemicals that must be considered during environmental impact assessments. Future research should focus on performing tests on real brines and achieving competitiveness in several performance indicators simultaneously. The environmental impact of DLE should be assessed from brine pumping to the production of the pure solid lithium product. Sections Lithium mining from continental brinesAs of 2022, worldwide, there are eight full-scale active facilities that produce lithium compounds from continental brines 9 and more are likely to become active before 2030 (Fig. 1a). The evaporitic technology (Fig. 1b) is currently in use at seven of those facilities 18,19 . Brines are Key points• Fresh water consumption of direct lithium extraction (DLE) needs to be urgently quantified. Many DLE technologies might require larger freshwater volumes than current evaporative practices, compromising their applicability in arid locations.• Environmental monitoring guidelines have been drafted with evaporitic technology in mind, but they should also be applied to the implementation of any DLE technology, which still consumes brine, uses fresh water and produces residues, the latter two hopefully at considerably lower volumes.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author selfarchiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Sustainable Lithium Recovery from Hypersaline Salt-Lakes by Selective Electrodialysis: Transport and Thermodynamics

“…Based on experiments with dilute binary cation solutions, selectivity enhancements in Li + /Mg 2+ separations with multilayered or polyelectrolyte ion-exchange membranes are well documented in the literature. ,,,− As stressed in recent reviews on salt-lake lithium extraction, however, over 95% of prior work disregards the deleterious impacts from competing ions and the high feed salinity that is representative of salt-lake brines. ,, Our experiments reveal that when binary cation solutions are utilized in place of salt-lake brines, the apparent Li + /Mg 2+ selectivity may be overestimated by a factor of 2.5 and that the specific energy consumption may be underpredicted by a factor of 54.8. In lithium extraction applications, the feed solution is typically acid pretreated to a pH of 3 or lower, to mitigate carbonate and phosphate scaling risks; ,, a majority of the charged moieties in commercial IEMs are based on weak organic acids, and the repercussions of the acidic conditions on the IEM’s selectivity remain unanswered. , Further, in hypersaline conditions, the performance of electrodialysis is bounded by a steep trade-off between counterion selectivity and thermodynamic efficiency, which appears to be governed by the current density.…”

“…4,31,32,43−45 As stressed in recent reviews on salt-lake lithium extraction, however, over 95% of prior work disregards the deleterious impacts from competing ions and the high feed salinity that is representative of salt-lake brines. 1,4,19 Our experiments reveal that when binary cation solutions are utilized in place of salt-lake brines, the apparent Li + /Mg 2+ selectivity may be overestimated by a factor of 2.5 and that the specific energy consumption may be underpredicted by a factor of 54.8. In lithium extraction applications, the feed solution is typically acid pretreated to a pH of 3 or lower, to mitigate carbonate and phosphate scaling risks; 5,19,46 a majority of the charged moieties in commercial IEMs are based on weak organic acids, and the repercussions of the acidic conditions on the IEM's selectivity remain unanswered.…”

“…4,45 As stressed in a recent review on salt-lake lithium extraction, fewer than 5% of the membrane literature considered the impact of competing cations and the high feed salinities that are representative of salt-lakes. 1 Further, to the best of the authors' knowledge, the influence of the strong acidity of post-treated brines on the IEM's selectivity is nuanced and has yet to be fully explained. 79,80 To address these knowledge gaps, we conduct experiments with multicomponent acid-treated brine and quantify their impacts on ion selectivity with our computational frameworks.…”

“…The demand for battery-grade lithium is expected to intensify by 40-fold, driven by the meteoric expansion of the electric vehicle market, which will increase from several thousands of vehicles in 2010 to over 142 million by 2030. − Over 89 million tons of lithium exist naturally in solid minerals (e.g., spodomene, laponite) and in continental and geothermal salt-lakes. , State-of-the-art evaporative technologies for salt-lake lithium harvesting, however, consume up to 800 m 3 of freshwater per ton of Li 2 CO 3 , aggravating water scarcity in some of the most arid regions of the world while exacerbating aquifer pollution and wetland destruction from its reliance on evaporation ponds. ,− Lithium production is further bottlenecked by the protracted concentration cycles of evaporation ponds, which contribute to a price-inelastic supply that is unresponsive to market demand. ,, …”

“…Further, by avoiding brine evaporation altogether, DLE can be viable for dilute lithium sources . The high Mg 2+ concentrations in salt-lake brines, however, attenuate the extraction effectiveness of DLE, as a result of the comparable solubility products and ionic radii of Li + and Mg 2+ . ,, DLE methods to isolate Li from a Na-rich mixture typically require the Li + /Mg 2+ ratio of the brine to be greater than approximately 4 to minimize chemical usage for precipitation and/or solvent recovery. , To enhance the selectivity and the atomic efficiency of DLE, the salt-lake brine can be pretreated with membrane processes like nanofiltration (NF) − or electrodialysis (ED) − to eliminate multivalent cations. The prospect of ED for lithium concentration from salt-lakes is particularly promising because of its successful commercial history in salt production from hypersaline brines. , …”