An efficient Fe2+ assisted UV/electrogenerated-chlorine process for carbamazepine degradation: The role of Fe(IV)

Abstract

To improve the performance and solve the restrictions of UV/chlorine process (e.g., the narrow pH application range and high disinfection by-products (DBPs) formation), a Fe2+ assisted advanced oxidation process with electrochemically generated chlorine (UV/E-Cl/Fe2+) was proposed for carbamazepine (CBZ) degradation, which eliminated CBZ (5 mg/L) within 4 min under the optimal conditions. Compared with UV/electro-generated chlorine (UV/E-Cl) and anodic oxidation-chlorination/Fe2+ (AO-Cl/Fe2+) processes, the apparent first-order kinetics constant in UV/E-Cl/Fe2+ increased by 2.56 and 3.18 times respectively, and the energy consumption was lower (1.15 kWh/m3-log). Simultaneously, the pH application range could be expanded to 9, and DBPs formed in this process were 17.1% less than those in UV/E-Cl. Through quenching tests, electron paramagnetic resonance (EPR) experiments, measurement of •OH concentration, quantification of methyl phenyl sulfoxide (PMSO) and benzosulfone (PMSO2) and processes comparison, possible CBZ degradation pathways and mechanism of UV/E-Cl/Fe2+ were proposed, in which Fe(IV) played the dominant role in the early stage, while the production of radicals (i.e., •OH and Cl•) was enhanced with the increase of chlorine generation, accelerating the CBZ removal. Furthermore, this process demonstrated wide application prospect in treating various contaminants and real wastewaters. In conclusion, this study offers an effective and energy-efficient method for organic pollutants degradation.