Degradation of phenylarsonic acid in phenylarsenic chemical warfare agents by Fe-modified CNT electroactive filter activating peroxymonosulfate: Performance and mechanism

Phenylarsonic acid (PAA) is a major organic arsenic contaminant in abandoned arsenic-based chemical weapons areas, and poses threats to the water environment due to potential arsenic pollution; However, relevant remediation methods are lacking. In this study, a Fe-modified carbon nanotube (CNT) electroactive filter was developed for peroxymonosulfate (PMS) activation towards PAA decontamination. The developed system can realise synchronous adsorption and oxidation of PAA (85.6%) with PMS (1.5 mM) under electric field assistance (-1 V). Radicals (SO4•– and HO•) and non-radicals (1O2) contributed to PAA degradation and the formation of As (V). The preferable PAA degradation efficiency stemmed from facilitated Fe (II)/Fe (III) redox cycles with applied electric field assistance. Secondary inorganic arsenic could also be immobilised as Fe-O-As bonds on the Fe-modified CNT filter. Additionally, PAA degradation pathways were proposed based on density functional theory (DFT) and intermediate identification. The system efficacy was also evaluated by regulating the critical operational parameters (applied voltage, flow rate, PMS concentration, pH and co-existing anions) and using complicated matrices (tap water and lake water). Our findings provide a new solution for PAA remediation and simultaneous immobilisation of secondary inorganic arsenic by combining membrane, PMS activation and electrochemical methods.