Effects of cell configuration and bipolar membrane on preparation of LiOH through bipolar membrane electrodialysis from salt lake brine

Bipolar membrane electrodialysis (BMED) is a promising process to prepare LiOH from the salt lake brine. Revealing the effects of the cell configuration and property of bipolar membrane (BM) on the mass transfer and current efficiency of BMED is crucial to promote its industrial application. Herein, two-compartment (C-B) and three-compartment (A-C-B), and three types of BMs (FBM, BP-1, and TWBP1) were systematically studied. Results show that three-compartment is superior to two-compartment, as the latter could restrain electromigration of Li+, enable recombination of H+ and OH–, and lead to lower current efficiency. Among three BMs, TWBP1 has highest current efficiency, while BP-1 can prepare LiOH solution with least impurity ions. To reveal the influencing mechanism of the BMs' properties on the electromigration of Li+ and co-ions leakage, CVC curves and chronopotentiograms were detailly investigated. Results show that the higher energy consumption of BP-1 may be attributed to its highest specific resistivity, while its better co-ions selectivity is beneficial to prepare acid/base solutions with lesser impurities, indicating that effects of the specific resistivity and selectivity of BMs on BMED process for producing LiOH from salt lake brine is an important "trade-off" relationship needing to be balanced to realize the higher current efficiency and higher quality products.