Study on Efficient Operating Conditions for Bipolar Membrane Electrodialysis Using Different Ion Species and Anion-Exchange Membranes

To investigate efficient operating conditions for bipolar membrane electrodialysis (BMED), a comparison of current efficiency (CE) and power intensity (PI) was conducted using different anion-exchange membranes (AEMs) and salt solutions (NaCl and Na2SO4) as feed solutions in BMED. The results indicated that CE was higher and PI was lower for a commercial proton-blocking AEM (ACM) than for a standard AEM (ASE) when NaCl was used. This is because ASE has a higher water content than ACM, leading to greater H+ permeability, which reduces CE. Conversely, when Na2SO4 was used, ASE exhibited higher CE and lower cell voltage (CV) than ACM, resulting in lower PI for ASE. This is attributable to the fact that, with Na2SO4, the effect of CV was more significant than H+ permeability. These findings suggest that efficient operation can be achieved by selecting the appropriate combination of AEMs and salt solutions.