Opportunities of desalination concentrates for lithium recovery: optimal separation by synergic solvents

Abstract

Lithium, highly demanded for its use in the battery industry, among other applications, has become a vulnerable commodity due to shortages in traditional sources. Although it is found in low concentration in SWRO brines, this waste represents a new source of this raw material. Based on previous studies in which Li+ extractions > 95 % were achieved, the optimal separation conditions of lithium from SWRO concentrates by solvent extraction with DBM•TOPO and FDOD•TOPO have been obtained for the first time. To this end, response surface methodology (RSM) with a three-level central composite design (CCD) has been applied. Three process variables, extractant concentration, basicity of the aqueous phase, and molar ratio between extractants, were evaluated using statistical parameters and second-order regression models. The optimized variables achieved maximum predicted extraction values of 99.7 % for DBM•TOPO and 100 % for FDOD•TOPO, not found yet in the open literature. Notably, for FDOD•TOPO system the needed pH for extraction is reduced, and both systems require a DBM:TOPO and FDOD:TOPO less than 1, a crucial consideration in terms of cost. This study opens new opportunities for lithium supply through desalination concentrates recovery.