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

Abstract

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.