Selective separation of lithium from synthetic brine using a solid extractant containing oxybenzophenone derivative and tributyl phosphate

This case study introduces the solid extractant (TVEX) based on 2-oxy-4-(C 7 -C 9 -alkyl)oxybenzophenone (AOOBP) and a synergistic mixture of AOOBP and tributyl phosphate (TBP) for selective extraction of lithium from model solution in batch mode. A direct relationship was established between the content of divinyl benzene (DVB) in TVEX and lithium uptake. The optimal content of DVB in the TVEX-AOOBP/TBP matrix is 25 wt.%, which provides the maximum capacity for lithium 21.94 mg/g. At optimal pH 9.5 (pOH ≈4.5) the equilibrium requires ∼4 h of contacting, whereas separation factors of Li/K, Li/Na, Li/Mg and Li/Ca reach 13, 15, 35 and 37, respectively. Elution with 1M HCl provides recovery of 96% of adsorbed lithium so that the regenerated TVEX could be used during 12 cycles of sorption-desorption. The results of this study indicate the remarkable efficiency of the TVEX-AOOBP/TBP in simulated brine and encourage its usage for the extraction of lithium from natural sources. • First TVEX with AOOBP/TBP for selective Li + extraction from brine. • Optimal 25 wt.% DVB gives 21.94 mg/g capacity and α(Li/Mg) = 35.5. • Synergistic AOOBP/TBP effect and 96% elution with 1 M HCl over 12 cycles. • Rapid equilibrium (4 h) and high stability without organic diluents. • Proof-of-concept for sustainable lithium recovery from salt lakes.