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 reme-diation 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 center dot- and HO center dot) 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 the-ory (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.