Integration of selectrodialysis and selectrodialysis with bipolar membrane to salt lake treatment for the production of lithium hydroxide

Abstract

Extracting lithium from salt lakes and preparing lithium hydroxide could provide important commodities for the economic development in future. In this work, a complete system was divided into two steps of selectrodialysis (SED) and selectrodialysis with bipolar membrane (BMSED) to treat salt lakes for the production of lithium hydroxide. The effects of the applied current density, the commercial monovalent selective cation-exchange membranes (CIMS and CSO), the monovalent selective anion-exchange membranes (ACS and ASV) and the voltage drop in the SED process were investigated, respectively. The experimental results indicated that under the current density of 12 mA/cm2 can effectively avoid membrane scaling. The separation performance for Mg2+ and Ca2+ by using CIMS/ACS membrane stack was demonstrated to be superior to CSO/ASV membrane stack. Additionally, the SED stack had proven to be feasible for concentrating lithium and removing divalent ions simultaneously. In BMSED process, the purpose was to combine the monovalent selective ion-exchange membrane with bipolar membrane (FBM) inside the membrane stack to remove divalent ions and simultaneously produced LiOH. The results showed that the concentration of LiOH and current efficiency were optimized at the current density of 6 mA/cm2. Furthermore, different cation-exchange membranes (CIMS, CSO and CMX) and anion-exchange membranes (ACS, ASV and AMX) were used to evaluate the BMSED process. Compared to the FBM/ASV/CSO/FBM membrane stack and FBM/AMX/CMX/FBM membrane stack, FBM/ACS/CIMS/FBM membrane stack exhibited superior current efficiency and separation performance for Mg2+ and Ca2+.