Direct lithium extraction from natural brines with co-valorization of boron, magnesium and sodium by combining solvent extraction and electrodialysis operations

Abstract

Continental brines are the main source of lithium which could significantly contribute to meet lithium demand for electric mobility. Traditional, lithium production from brines generates huge amounts of solid waste encompassing the other brines components, which should be co-valorized together with lithium. This paper focuses on a novel approach to directly extract lithium from continental brines by combining solvent extraction with electrodialysis. The extraction solvent containing 2 mol L-1 2-butyloctan-1-ol diluted in kerosene and exhibited 90% extraction efficiency of boron. This extraction solvent allowed to produce high-grade borax (Na2B4O7•2H2O) with purity=99% by crystallization. These operations were followed by a three-stage process combining electrodialysis and precipitation operations. In the first electrodialysis stage, the abatement of divalent cations was produced, leading to the production of magnesium hydroxide (Mg(OH)2, purity=71.2%). Both the boron depleted brine and a native brine were processed by electrodialysis, and results shown that a reduced amount of electric charge, and hence electric energy were required for successful abatement of divalent species. The second electrodialysis stage produced sodium carbonate (Na2CO3, purity=99.99%). While, the final stage is a similar setup to the second stage, and leads to production of high purity lithium carbonate (Li2CO3, purity=99.9%). At the end of the process, the total dissolved solid (TDS) of the brine were decreased by 99.8%. This low salinity effluent could potentially be recycled in the process and employed for irrigation purposes.