Efficient degradation of chloroquine via pyrite-modified electro-Fenton yielding •OH and O2•-

Abstract

In the face of the mass production and consumption of chloroquine (CLQ), the presence of CLQ has posed a significant threat to the water environment and living organisms due to its bio-accumulative and persistent nature. In this work, a heterogeneous electro-Fenton system using a pyrite-modified carbon felt as the cathode (EF-FeS₂-CF) was constructed to remove CLQ. EF-FeS₂-CF was found to achieve 92.4 ± 0.1% removal of 5 mg/L CLQ after 30 min at 20 mA and exhibited an outstanding catalytic performance for CLQ removal in wide ranges of operating conditions, excellent recyclability with low iron leaching (>90% 30-min CLQ removal efficiency for all five cyclic experiments which led to only an accumulative Fe loss of <0.3%) and remarkable application potential in different aqueous environments without any pH adjustment. Both O₂^•- and ^•OH were found to greatly contribute to CLQ degradation while the latter played a major role (>50% CLQ removal). To describe CLQ degradation towards complete mineralization in EF-FeS₂-CF, three CLQ degradation paths were proposed based on the main degradation intermediates identified with generally lower ecotoxicities. Such an EF-FeS₂-CF system therefore presents promising application potential to treat CLQ-laden waters.