Bipolar membrane electrodialysis: A promising paradigm for caustic soda production

Abstract

AbstractCurrently, a supply‐demand imbalance between NaOH and Cl2 in the chlor‐alkali process places a great burden on the environment. Bipolar membrane electrodialysis (BMED) is a competitive technology to produce acid and base due to its water splitting characteristics. To determine the competitiveness of NaOH production between BMED and the chlor‐alkali method, BMED was evaluated at various current densities with different NaCl concentrations. Results show that NaOH energy consumption in BMED is less than that of the chlor‐alkali method at a moderate salt concentration (<9 wt.%). Interestingly, the stack voltage suddenly increases during the later stage of BMED. It is speculated that the high osmotic pressure surrounding bipolar membranes restrains water transport into the interfacial layer. In addition, economic assessment indicates that BMED has less impact on global warming than the chlor‐alkali process. Overall, the BMED technique is a promising paradigm for base production in an economical and sustainable manner.