Abstract:

Solvent extraction was considered to be a importing technique for lithium extraction from the salt lake brine.The ionic liquid system containing tributyl phosphate（TBP） and 1-butyl-3-methylimidazolium bistrifluoromethylsulfonimide salt（[C₄mim][NTf₂]） was used to extract lithium ions from salt lake brine with a high Mg/Li ratio.The scrubbing and stripping processes from the loaded organic phase were also studied.In the extraction experiment,under the condition of a volume ratio of TBP to[C₄mim][NTf₂] of 9∶1 and a phase ratio （O/A） of 2∶1,the separation factor βLi/Na,βLi/K and βLi/Mg were 94.70,148.85 and 131.81,respectively.In the scrubbing experiment,the effect of the types and concentration of scrubbing agent,phase ratio and scrubbing times on scrubbing efficiencies were investigated systematically.The results showed that the mixed solution of lithium chloride and hydrochloric acid was an effective scrubbing agent for removing impurity ions from the loaded organic phase.Optimal extraction conditions of the scrubbing process included 4 mol/L LiCl and 0.5 mol/L HCl in scrubbing agent,phase ratio（O/A） of 5∶1 and the scrubbing times of two times.In the stripping experiment,the loaded organic phase was stripped by 1.0 mol/L HCl and the single-stage stripping rate reached 97.81% at the phase ratio（O/A） of 1/1.This study showed that the new ionic liquid system had a good application prospect for extracting lithium from salt lake brine with a high Mg/Li ratio.

Key words: ionic liquid, salt lake brine, lithium, scrubbing