Study on extraction lithium from brine with high magnesium using ionic liquid/metal salt extraction system
The optimal extraction system was determined to be 1-octyl-3-methylimidazole hexafluorophosphate([C8mim]PF6)/sodium hexafluorophosphate(NaPF6)/tributyl phosphate(TBP)by studying the effects of different metal salt co-extraction reagent,and different extraction systems on the extraction efficiency of lithium and magnesium,and the cation loss rate of ionic liquid.The effects of[C8mim]PF6 concentration,NaPF6 concentration and phase ratio on the extraction effi-ciency of lithium and magnesium,and the cation loss rate of ionic liquid in[C8mim]PF6/NaPF6/TBP/extraction system were investigated,it was concluded that[C8mim]PF6 concentration was 0.2 mol/L,NaPF6 concentration was 0.2 mol/L,and phase ratio was 2.5.Under the optimum extraction conditions,the single stage extraction efficiency of lithium was 80.5%,the single stage extraction efficiency of magnesium was 6.5%,and the cation loss rate of ionic liquid was 2.6%.The optimum concentration of hydrochloric acid for stripping was 1 mol/L,and the stripping phase ratio was 2.5.Under the optimum strip-ping conditions,the stripping efficiency of lithium and magnesium was 95.2%and 99.0%,respectively.[C8mim]PF6/NaPF6/TBP extraction system could efficiently extract lithium,and reduce the cation loss rate of ionic liquid.It could be used as a reference for the development of a new ionic liquid/metal salt extraction system for extracting lithium from brine with high magnesium lithium ratio.
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