Towards a higher level of circularity in lithium brine mining: CO₂ absorption in concentrated brines

Abstract

The transition to sustainable lithium production from brines requires innovations that address chemical consumption, water use, and carbon emissions. This work proposes a novel six-stage treatment of real, highly saline lithium-rich brine to simultaneously recover lithium carbonate (Li2CO3), co-produce sodium carbonate (Na2CO3), and achieve permanent CO2 storage through mineralization. The strategy integrates five electrochemical steps—employing an anion exchange membrane—with one chemical CO₂ absorption step. Electrolysis initially raises brine pH to eliminate divalent cations without chemical additives. Subsequent CO2 sparging in alkaline brines induces Li2CO3 and later Na2CO3 precipitation. Results demonstrate 78% Li⁺ recovery as impure Li2CO3 and 71.8% Na⁺ recovery as Na2CO3. Notably, 231.7 g of CO2 per litre of initial brine were absorbed, of which 215.6 g were permanently stored in solid carbonates. The process minimizes chemical inputs, reduces reliance on remote chemical delivery, and leverages high brine salinity to enhance CO₂ capture kinetics and electrochemical efficiency. Though not optimized for energy consumption, this proof-of-concept study reveals a circular approach to lithium extraction, integrating critical material recovery with climate-relevant carbon capture. Future improvements could enable direct air capture integration and Li2CO3 purification. This study introduces an industrially relevant pathway to reduce the environmental impact of lithium brine mining by turning waste brine constituents into valuable, stable products while closing the carbon cycle through mineralization.

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