Tailoring anion exchange membranes for palladium recovery from industrial solutions using electrodialysis

Limited natural reserves and extensive use of palladium across various industries make it urgent to implement efficient recovery strategies. Despite its unique advantages, the use of ion exchange membranes in electrodialysis to recover palladium species from diverse sources remains unexplored. This study focuses on tailoring anion exchange membranes (AEMs) for the recovery of palladium tetrachloride ([PdCl4]2−) from industrial hydrochloric acid-based solutions (pH below 1) in electrodialysis, aiming to overcome limitations associated with conventional separation methods. The properites and performances of the AEMs were optimized by brominating poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) polymers and the subsequent quaternization using tertiary amines of varying chain lengths to form quaternary ammonium bases, promoting their ion association with [PdCl4]2−. The AEM matrix optimization also involves adjusting polymer concentration, which affects the charge density, hydrophilicity, polymer network density, and microstructure of the membrane, thereby influencing the palladium recovery efficiency. A remarkable [PdCl4]2− recovery rate of exceeding 90 % was achieved using the tailored AEMs after a 4-hour electrodialysis process.