Waste Acid Recovery Utilizing Monovalent Cation Permselective Membranes through Selective Electrodialysis

Abstract

Selective electrodialysis (SED) has surfaced as a highly promising membrane separation technique in the realm of acid recovery owing to its ability to effectively separate monovalent ions through the utilization of a potential difference. However, the current SED process is limited by conventional commercial monovalent cation permselective membranes (MCPMs). This study systematically investigates the use of an independently developed MCPM in the SED process for acid recovery. Various factors such as current density, volume ratio, initial ion concentration, and waste acid systems are considered. The independently developed MCPM offers several advantages over the commercial monovalent selective cation-exchange membrane (CIMS), including higher recovered acid concentration, better ion flux ratio, improved acid recovery efficiency, increased recovered acid purity, and higher current efficiency. The SED process with the MCPM achieves a recovered acid of 95.9% and a concentration of 2.3 mol·L–1 in the HCl/FeCl2 system, when a current density of 20 mA·cm–2 and a volume ratio of 1:2 are applied. Similarly, in the H2SO4/FeSO4 system, a purity of over 99% and a concentration of 2.1 mol·L–1 can be achieved in the recovered acid. This study thoroughly examines the impact of operation conditions on acid recovery performance in the SED process. The independently developed MCPM demonstrates outstanding acid recovery performance, highlighting its potential for future commercial utilization.