High efficiency extraction of lithium from the high magnesium brine by P248 with FeCl3 co-extractant

Tributyl phosphate (TBP), as a typical extractant for lithium recovery from high magnesium brine in salt lakes, it is not widely employed in industries for its insufficient chemical stability and considerable water solubility. Therefore, there is an urgent need to develop an alternative extraction system for lithium separation from high magnesium bine. In this study, a novel extractant di(2-ethylhexyl) phenyl phosphonate (P248), possessing lower dissolution loss and better stability comparing to TBP, was applied to recover lithium from high magnesium brine, along with kerosene serving as the diluent and FeCl3 acting as the co-extractant. The extraction complex formula Li(P248)3FeCl4 was determined by FT-IR spectra, Raman spectroscopy and slope method. The extraction conditions were optimized and a nine-stage cascade extraction process was conducted. The process involved two stages of extraction, one stage of scrubbing, four stages of stripping and two stages of regeneration, and each section of the operation condition was optimized. High extraction efficiency were achieved with a total lithium extraction efficiency of 99.02 %, the magnesium lithium separation factor (beta Mg/Li) can reach 20988 and the concentration of Li+ and Mg2+ in the stripping solution could reach 37.81 g/L and 0.31 g/L respectively. No prior studies have systematically evaluated the combination of P248 with FeCl3 for lithium extraction from high magnesium brines. This study will provide a stable, efficient, and environmentally friendly neutral phosphonate system, laying the foundation for the future development of lithium recovery extractants suitable for high magnesium brines.