Recovery of lithium from alkaline brine by solvent extraction with β-diketone

Lithium recovery from alkaline brines by counter-current method using beta-diketone was investigated. By comparing effect of different co-extractants and diluents on lithium extraction, HBTA-TOPO-kerosene system was determined as the extraction system. In extraction process, 0.4 mol/L HBTA and 0.3 mol/L TOPO in kerosene performed as extractant and three theoretical stages were required to reach 95% extraction according to McCabe Thiele diagram. 1 mol/L HCl and 3 mol/L HCl solution were used as scrubbing agent and stripping agent respectively. In regeneration stage, 2 mol/L NaOH was used as regeneration agent to remove free acid entrained in organic phase and exchange H+ of hydroxyl. Bench experiments indicated that the respective number of extraction, scrubbing, stripping and regeneration were 3, 1, 2 and 1 stage. A 7-stage extraction process was conducted in a mixer-settler for 30 h to reach stable state, average extraction rate of lithium was 96% and lithium concentration in stripping solution was 15 g/L. Concentration of impurity ions in stripping liquor was < 1 g/L. No third phase or emulsification was observed during the operation. In summary, HBTA-TOPO-kerosene extraction system was verified an effective method to recovery lithium from alkaline brine.