Abstract:In order to find out properties and mechanism of mixed lithium extraction system from brine, influences of O/A and n(Fe3+/Li+) (mole ratio) on extraction system of 40%TBP-20%BA-40% 200# sulfonated kerosene were discussed. The single-stage extraction rate of lithium and magnesium is 87.34% and 3.89% respectively under the optimum conditions of O/A=1.5 and n(Fe3+/Li+)=1.5. These parameters were beneficial to subsequent multistage extraction test and further industrial design. Co-extraction phenomenon of Fe3+, Cl-, and Li+ in LiFeCl4 formed delocalized π-bond was analyzed by means of chlorine bridge theory. Combination between Li+ coordination water molecule and P=O, C=O polar functional group in TBP and BA was speculated as hydrogen bonding association by 1H-NMH spectra of organic phases before/after extraction. Modified electrostatic model was proposed according to ion-pair extraction theory. Competitive relationship among Li+, Mg2+ and other undesired impurities was discussed.