Selective extraction of lithium from alkaline brine using HBTA-TOPO synergistic extraction system

Innovative application of Synergistic extraction system benzoyltrifluoroacetone(HBTA) and tri-n-octyl phosphine oxide(TOPO) for the extraction of lithium from alkaline brine were investigated. The extraction efficiencies of this extraction system were measured as a function of various extraction parameters, including pH value of aqueous phase, extraction temperature, and composition of organic phase. The extraction complex was determined by slope analysis method, which indicated that HBTA, TOPO and lithium formed a 2:1:1 complex. With this system, separation factor between lithium and sodium could be over 2100 by two stages countercurrent extraction according to McCabe Thiele diagram, and lithium extraction could be 95%. Co-extracted or restrained sodium in organic phase could be fully scrubbed by 0.5 M HCl at O/A = 10:1 and equilibrium pH = 4.68. Lithium reserved in organic phase was stripped completely into aqueous phase using 2.5 M HCl at O/A = 10:1 subsequently. Blank organic after stripping was regenerated by 2 M NaOH at R = 70% for next extraction circle. Stability test of organic phase was conducted with five-stage extraction process containing two stages extraction, single stage scrubbing, stripping and regeneration. Lithium yield reached 95.5% with high purity through the process, neither emulsification nor third phase was found during whole process.