Electrodialysis Treatment of Nitrate‐Contaminated Groundwater Using Modified Cation‐Exchange Membranes

Nitrate contamination in drinking water remains a significant concern for the scientific community, particularly in agricultural regions where concentrations often exceed regulatory limits. In this context, selective electrodialysis offers a promising alternative by enabling targeted removal of nitrates while preserving useful hardness ions. In this study, commercially available anion and cation exchange membranes were evaluated for their ion removal and energy consumption performance to select the optimal cation exchange membrane (CEM) for reducing divalent ion depletion using polyethyleneimine (PEI) crosslinked with glutaraldehyde (GA). A systematic investigation of key modification parameters was followed, including casting with PEI of different molecular weights, rinsing after casting, GA concentration, crosslinking time, and different pH values. The resulting membranes were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and cyclic voltammetry (CV), and their performance was tested in treating nitrate‐contaminated groundwater. The optimal modification pathway demonstrated reduced divalent‐ion depletion, achieving maximum nitrate removal (99%) and low energy consumption (0.43 kWh/m 3 ). Stability and regeneration experiments showed a partial and temporary recovery of divalent‐ion retention, with the strongest improvement observed after acidic regeneration. Post‐operation SEM and EDS analyses revealed a Mg‐rich surface deposition, suggesting that it might contribute to performance deterioration.