Application of Electrodialysis for Concentration and Desalination of Monovalent Salts

Abstract

This study investigates electrodialysis (ED) performance for desalination and concentration of monovalent salts (NaCl, NH4Cl, KCl, and NaNO3) at varying mass concentrations. Systematic comparisons of current efficiency (η), energy consumption, water loss, desalination rate ηsalt, and other key parameters reveal salt-specific behaviors and process determinants. Experimental results show distinct performance hierarchies across operational phases. In the 1% desalination phase, KCl achieved optimal performance with 95.3% salt removal, a dilute η of 99.96%, a production capacity (Q) of 54.95 L/(h·m2), and a unit energy consumption (Eu) of 3.24 kWh/t. This performance outshone that of NaCl (ηsalt = 95.2%) and NaNO3 (ηsalt = 89.5%), with NH4Cl showing the lowest value (80.6%) in this phase. This trend inversely correlated with cation hydration energies. On the other hand, in the 3% concentration phase, NH4Cl demonstrated superior performance with a concentrate η of 83.49%, a flux of 35.71 L/(h·m2), and the lowest Eu (5.30 kWh/t), despite a lower concentration factor (5.33) than NaNO3 (6.48). These findings highlight that KCl is ideal for energy-efficient brine treatment (<3% salinity), while NH4Cl is better suited to high-purity recovery. Although NaNO3 has a high Eu during concentration, it is favorable for applications where minimizing energy usage is critical.