Comparison of EDBM stacks and influence of different experimental conditions on LiOH production

Electrodialysis with bipolar membranes (EDBM) is a promising route for LiOH production from Li 2 SO 4 solutions, but its applicability depends strongly on membrane selectivity and process operation. In this study, four stack configurations combining two bipolar membranes with either blocking or non-blocking monopolar membranes were evaluated for LiOH production. Electrical tests confirmed stable performance and showed that the monopolar membrane type affected stack performance more strongly than the bipolar membrane type. Undesired H⁺ transport was the main limitation, reducing lithium recovery and efficiency under unfavourable conditions. The operating mode was therefore investigated by controlling first the acid concentration and then the acid and base concentrations simultaneously. Reducing the concentration gradients across the stack markedly improved all key performance parameters. The best results were obtained with the blocking monopolar configuration under simultaneous acid–base control, reaching a lithium yield of 98.2%, LiOH purity of 98.1 wt.%, and specific energy consumption of 2.89 kWh kg –1 LiOH; acid-dilution mode reached purities up to 99.0 wt.%. At an acid concentration of 0.25 mol L –1 , non-blocking configurations also became highly effective, exceeding 90% yield and 97 wt.% purity. Efficient EDBM LiOH production thus requires both a suitable configuration and strict gradient control.