Electrodialysis processes with bipolar membranes for simultaneous RO brine treatment and acid-base production

Abstract

Reverse osmosis (RO) desalination brine poses serious environmental concerns because of high salinity and the presence of contaminants. Addressing these issues requires advanced, and sustainable technologies for effective treatment. This study presents an innovative method for fabricating high-performance cation exchange membranes (CEMs) and bipolar membranes (BPMs) aimed at treating RO desalination brine using electrodialysis with bipolar membranes (EDBM), while simultaneously generating useful acids and bases. The CEM was developed by blending polyvinyl alcohol (PVA) with carboxymethyl cellulose (CMC) and was incorporated into a BPM structure with a chitosan-based Anion Exchange Layer (AEL). A comprehensive characterization, including SEM, FTIR, Ion Exchange Capacity (IEC), swelling degree, water uptake, and mechanical strength, confirmed significant material enhancements. A pre-treatment of the membranes with ferric chloride (FeCl<inf>3</inf>) before sulfonation using sulfuric acid boosted the IEC from 0.317 to 0.53 meq/g, outperforming commercial Nafion-117. The system achieved a salt rejection rate of 55.2 %, with acid and base concentrations rising by factors of 19.2 and 9.04, respectively. It also exhibited a low voltage drop of 2.16 V at 90 mA/cm², superior to previously reported BPM-1 (3.45 V) and BPM-60 (2.73 V). These results highlight the membrane's enhanced energy efficiency, scalability, and potential as a cost-effective solution for sustainable brine management.