A Study on the Treatment of Sodium Sulfate Waste Solution by Constant Current Control Bipolar Membrane Electrodialysis

As environmental pollution has intensified, the importance of recycling spent lithium-ion batteries (LIBs) has significantly increased. Valuable metals contained in LIBs are typically recovered through processes such as leaching, precipitation, and solvent extraction. However, these recycling processes require large amounts of sulfuric acid and caustic soda, resulting in the generation of significant volumes of Na2SO4 waste solution. In order to solve this problem, recent research has focused on using bipolar membrane electrodialysis (BMED) technology to split Na2SO4 and simultaneously recover H2SO4 and NaOH. This study investigated the process of recovering H2SO4 and NaOH from Na2SO4 solution using BMED in a threecompartment cell under constant current conditions. The study evaluated the effects of current density, initial Na2SO4 concentration, and initial H2SO4 and NaOH concentrations. Recovery of H2SO4 and NaOH, current efficiency, energy consumption, and process time were analyzed to determine optimal conditions. Under optimal conditions (1.30 M Na2SO4 solution at 360 A/m²), the recovery of H2SO4 and NaOH were 77.35% and 75.18%, respectively. Energy consumption was 1.43 kWh/kg, with current efficiencies for the acid and base of 51.1% and 49.7%, respectively.