TBP-MNPK combinations: a promising approach for selective Lithium extraction from high Mg/Li ratio liquids

To address the third-phase formation and high-acidity stripping corrosion of the traditional TBP-FeCl₃ system for Li extraction from high Mg/Li ratio salt-lake brines, this study developed a TBP-MNPK-kerosene-FeCl₃ system using 2-heptanone (MNPK) as a modifier. MNPK eliminated third-phase formation and enabled complete phase separation within 50s. Under optimal conditions (20  vol % kerosene, 40  vol % TBP), Li extraction efficiency reached 85.4 % with a Li/Mg separation factor of 315. After water scrubbing and 3 mol/L HCl stripping, the stripping solution had 5.46 g/L Li (3.12-fold enrichment) and Li/Mg ratio of 11.38. This system provides an efficient, industrial-feasible Li extraction solution.