Integration of electrodialysis and Donnan dialysis for the selective separation of ammonium from high-salinity wastewater

Abstract In this study, a novel method, concentration electrodialysis (CED), was developed by combining conventional electrodialysis (ED) and Donnan dialysis (DD) effectively and selectively to separate NH4+-N from high-salinity wastewater. A high initial concentration of Na+ was provided in the cathode compartment to impede its competitive migration with NH4+. After optimization, the CED process removed up to 89.1% of NH4+-N from simulated high-salinity wastewater with an energy consumption of 0.51 × 10-3 KWh·mol-1. The initial brine concentration was the limiting factor for the removal percentage and rate. The maximum removal percentage was 13.3% and 32.3% higher than those of conventional ED and DD, respectively. CED shortened the time required to achieve the same final removal percentages achieved by conventional ED and DD by 14 h and 10 h, respectively. In addition, the current efficiency of CED was increased by 1.84 times greater than that of conventional ED, while reduced 50.48% of energy consumption. Moreover, the Na+ concentrations in the cathode and wastewater compartments both remained relatively constant, indicating that there was no need to add additional Na+ during the experimental process, which was beneficial for prolonging the experiment and reducing cost. Finally, the performance of CED in removing NH4+-N from actual maricultural wastewater further supported its potential for application in the future.