Mechanism of chlorine-mediated electrochemical remediation system for contaminated Cl-Na type coastal groundwater

Groundwater is a critical component of water resources and plays a fundamental role in maintaining ecological stability and supporting economic development. Industrial activities constitute a major source of groundwater contamination. Controlling groundwater pollution in industrial production facilities has become a key priority in environmental management. In this study, we present a high-performance ex situ electrochemical remediation system designed to treat contaminated saline (Cl–Na type) groundwater from an operational coastal chemical park. The system, optimized with a Ti/RuO 2 –IrO 2 anode and Ni cathode, achieved complete removal of ammonium nitrogen (100%) and converted 79% of total nitrogen to harmless N 2 within 45 min at a current density of 5.0 mA cm −2 . Energy consumption was as low as 1.2 kWh·m −3 . Remediation efficacy was primarily driven by in situ–generated reactive chlorine species (RCS) (e.g., Cl•, Cl 2 • - , ClO•), whose formation was significantly enhanced by the presence of bicarbonate (HCO 3 − ). Notably, the system exhibited superior removal efficiency for persistent humic acid–like dissolved organic matter (DOM) compared with biodegradable protein-like DOM, resulting in a 71% reduction in overall fluorescence intensity. The system maintained robust performance across different real groundwater samples (energy consumption: 1.2-2.1 kWh·m −3 ) and demonstrated excellent electrode stability. These results demonstrate that the technology is an economically viable and effective approach for on-site remediation of contaminated groundwater in challenging coastal industrial environments.