Extraction of lithium from magnesium-rich solution using a new ionic liquid extraction system

A new extraction system, tetraoctylammonium bis(trifluoromethylsulfonyl)imide (N8888NTf2)/tri-n-butyl phosphate (TBP)/sodium perchlorate (NaClO4), is proposed for extracting lithium (Li) from magnesium (Mg)-rich solution. This system can increase the Li+ extraction efficiency compared with TBP/NaClO4 system and decrease the stripping acidity compared with TBP/bis(trifluoromethylsulfonyl)imide lithium (LiNTf2) system. Cation loss of ionic liquid can also be avoided in the extraction process. Under optimal conditions, the Li+ extraction efficiency reaches 82.3% and the Li+/Mg2+ separation factor reaches 254. The Li+ stripping efficiency reaches about 100% when 0.5 mol·L−1 HCl is used as stripping agent. The extraction mechanism of N8888NTf2/TBP/NaClO4 system is proposed based on experimental results and verified by Fourier transform infrared spectroscopy (FT-IR), slope analysis, and simulation calculation using Gaussian software. N8888NTf2/TBP/NaClO4 system is highly stable over seven extraction cycles. This new extraction system has a great potential for selective extracting Li+ from Mg2+ rich brine.