In the present work

a typical room temperature ionic liquids (RTILs)

1-octyl-3-methyl-imidazolium hexafluorophosphate ([C8mim][PF6])

was used as an alternative solvent to study liquid/liquid extraction of lithium from salt lake brine. In this system

the ionic liquids and tributyl phosphate (TBP) were used as extraction medium and extractant respectively. The effects of solution pH value

phase ratio and other factors on lithium extraction efficiency had been investigated. The preliminary experimental results had demonstrated that

compared with using conventional extraction system

the extraction efficiency had been increased greatly in this ionic liquid system. Optimal extraction conditions of this system include the ratio of TBP/ILs at 9/1(vol)

O/A at 2:1 and unadjusted pH. Under the optimal conditions

the single extraction efficiency of lithium ion and magnesium ion were 80.64% and 5.30%

respectively. And total extraction efficiency of 99.42% was obtained by triple-stage countercurrent extraction. The single stripping rate of lithium ion and magnesium ion were 98.78% and 99.15%

respectively

at 80℃ when the A/O phase ratio was 2. The Mg/Li ratio was 3.03 in the aqueous phase after stripping

which have dropped 93.41% when compared with the initial value. To evaluate the potential use of RTILs to replace traditional volatile organic compounds (VOCs) in liquid/liquid extraction of lithium

the extractions of lithium ion with VOCs and ionic liquid were compared. Compared with using conventional extraction system

the extraction efficiency had been increased greatly in this ionic liquid system. In addition

the equipment corrosion and the environmental pollution had been avoided in this new extraction system. The extraction mechanism was deduced based on the ultraviolet-visible(UV) absorption. Cation exchange was proposed to be the mechanism of extraction followed in ionic liquid. So the ionic liquid was not only regarded as the solvent but also the co-extraction reagent to some extent. Preliminary results indicated that the ionic liquids had the potential to replace traditional volatile organic solvents in liquid/liquid extraction of metal ions.