Separation Of Magnesium From Brine By Extraction And The Electrochemical Property Of Extraction System

In order to realize the separation of lithium and magnesium in salt lake brine with high Mg/Li ratio,the combination of solvent extraction with electrodeposition technique was proposed in this work.The extraction of lithium and the electrochemical properties of the extracting system were studied in detail.The phase equilibrium of the quaternary system(P204+MIBK+[P4446][NTf2]+H2O)was subsequently investigated.An eco-friendly,economical and efficient method for the separation of lithium and magnesium from brine was finally obtained,by which it provides an important foundation for the high-value utilization of lithium and magnesium resources in brine.Main conclusions are summarized as follows:(1)A novel extraction system(P204+MIBK+[P4446][NTf2])for magnesium separation from salt lake brine with high Mg/Li ratio was established,and relevant technological parameters including extraction time,saponification rate,the composition of organic phase,pH of brine,and phase ratio R(O/A)were investigated.The single-stage extraction rate of Mg2+reached to 80.51%at the optimized conditions of 40%P204+55%MIBK+5%[P4446][NTf2],phase ratio R(O/A)=7.5,70%saponification rate,pH?5.0,extraction and standing time of 10 min.(2)The variations of conductivity in the extraction system(P204+MIBK+[P4446][NTf2])with the percentage of each component were carried out.The results showed that the increase of P204 content could not improve the conductivity of the system.On the contrary,the increase of MIBK and[P4446][NTf2]could significantly improve it.When the volume fraction of P204,MIBK and[P4446][NTf2]were 20%,72%and 8%,respectively,the maximum conductivity of 1658 ?S·cm-1 was obtained.It was found that the conductivity of the extraction system increased with the increase of MIBK percentage at(298.15 and 353.15)K.When the mass percentage of MIBK was less than 50%,it increased slowly.While when the percentage of MIBK reached to 50%,the conductivity increased sharply and reached the maximum value at 75%MIBK.When MIBK is less than 45%,the conductivity of the system did not change with temperature.However,when MIBK is more than 45%,it decreased with the increase pf temperature.(3)The phase equilibrium behaviors of the quasi-ternary system(P204+MIBK+[P4446][NTf2]+H2O)were studied by visual method at room temperature.Based on the experimental results,the phase diagram of the emulsified region was plotted.It was found in the system of(Mi+[P4446][NTf2]+H2O)that when the mass ratio of[P4446][NTf2]and H2O was 1:1 and the mass percentage of M1 reached to 18.52%,an emulsification phenomenon was observed,but it disappeared when the mass percentage of M1 reached to 60.5 8%.In the system of(M2+[P4446][NTf2]+H2O),when the mass ratio of[P4446][NTf2]and H20 was 1:1 and the mass percentage of M2 reached to 14.42%,the emulsification phenomenon began,while it disappeared when the mass percentage of M2 reached to 35.53%.The emulsion in the quasi ternary system(P204+MIBK+[P4446][NTf2]+H2O)was determined to be O/W model by the dyeing method,and the oil evolution rate decreased with the decrease of P204 content in the system.