Removal of p-Nitrophenol in high-salinity wastewater by chlorine-mediated electrochemical advanced oxidation

Chlorine-mediated electrochemical advanced oxidation (EAO-Cl) process, which converted Cl - into highly oxidizing active chlorine species under electricity, exhibits exceptional performance in wastewater pollutants removal. In this study, degradation of p -Nitrophenol (PNP) through EAO-Cl was investigated with RuO 2 /Ti foam as anode and Ti foam as cathode. Under high salinity (342 mM NaCl) condition, 95.4 % of PNP with initial concentration of 20 mg/L was removed within 120 min. The reaction kinetics constant was 0.0265 min −1 , which increased nearly 14 times compared to that of in low salinity (25 mM NaCl). ESR and quenching experiments were employed to identify the in-situ generated reactive chlorine species and evaluate their relative contributions to the degradation process. It was found that chlorine radicals (·Cl) was the dominant oxidants and contributed 60.0 % to PNP degradation. The reaction mechanisms and PNP degradation pathways mediated by chlorine species were further elucidated. Long-term continuous reactor operation revealed that PNP was near-completely removed in single-pass mode with energy consumption of 5.22 kWh/m 3 . This study proposed a novel “waste to treat waste” approach for contaminant removal in high-salinity wastewater by in situ conversion of unwanted chloride ions into useful reactive chlorine species, simultaneously enabling pollutant degradation and resource utilization from inherent wastewater salinity.