Lithium Extraction with a Synergistic System of Dioctyl Phthalate and Tributyl Phosphate in Kerosene and FeCl3

Abstract

Innovative applications of dioctyl phthalate (DOP) as a synergist for the extraction of lithium chloride from saturated MgCl2 solutions were investigated using tributyl phosphate (TBP) as the extractant and FeCl3 as the co-extractant. The effects of solvent concentration, HCl concentration, phase ratio, Fe/Li molar ratio, and other factors on Li extraction were analyzed. The preliminary results demonstrated that a single-stage Li extraction efficiency of >90% was obtained with a low TBP concentration of 40% (V/V) and 20% (V/V) DOP without phase separation problems. A Li extraction efficiency of 99.5% was obtained via a three-stage simulation of countercurrent extraction. A study on the mechanism revealed that TBP and DOP molecules associated with the Fe-Li complex through hydrogen bonding. Compared with the traditional TBP–kerosene system, the proposed system prevented the formation of the third phase and significantly reduced the TBP concentration, resulting in less severe causticity to the equipment and reduced aqueous loss of TBP during the extraction process.