Enhancement in Sulfamethoxazole Degradation via Efficient Heterogeneous Activation of Peracetic Acid by FeS

Peracetic acid (PAA) has attracted increasing attention in wastewater decontamination for yielding reactive oxygen species (ROS). In this study, mackinawite (FeS) was synthesized and applied as the heterogeneous catalyst for PAA activation. Using sulfamethoxazole (SMX) as the target pollutant, the influences of FeS dosage, PAA dosage and initial pH values on SMX degradation by the FeS/PAA process were investigated. Under optimal conditions, SMX could be completely removed within 5 min with the apparent first-order rate constant (kobs) of 7.71 × 10−4 s−1. Electron spin resonance spectroscopy (ESR) analysis and radical scavenging experiments were modulated to detect the active species. During the activation process of PAA, various active components were evidenced to be hydroxyl radicals (HO•), singlet oxygen (1O2), superoxide radicals (O2•−) and organic radicals (R-O•, e.g., CH3C(O)O• and CH3C(O)OO•), whereas HO• and R-O• were demonstrated as the dominant active species responsible for SMX abatement. Both dissolved Fe(II) ions and active sites on the surface of FeS were proven to be activators for PAA, and SMX abatement was highly promoted as a result. Furthermore, the acidic pH displayed superior efficiency in SMX decomposition compared with alkaline and neutral conditions. Five degradation pathways of SMX were put forward and the toxicity of byproducts was further evaluated. Overall, this study provided an efficient and environmentally friendly PAA activation approach using FeS, which might broaden its applicability in the remediation of micropollutants.