Hydroxylamine-induced activation of permanganate for enhanced oxidation of sulfamethoxazole: Mechanism and products

Recently, many reagents have been introduced to accelerate the formation of highly reactive intermediate Mn species from permanganate (KMnO 4 ), thereby improving the oxidation activity of KMnO 4 towards pollutants. However, most studies have mainly focused on sulfur-containing reducing agents (e.g., bisulfite and sodium sulfite), with little attention paid to nitrogen-containing reducing agents. This study found that hydroxylamine (HA) and hydroxylamine derivatives (HAs) can facilitate KMnO 4 in pollutant removal. Taking sulfamethoxazole (SMX) as a target contaminant, the effect of pH, SMX concentration, KMnO 4 and HA dosages, and the molar ratio of HA and KMnO 4 on the degradation of SMX in the KMnO 4 /HA process was systematically investigated. Quenching experiments and probe analysis revealed MnO 2 -catalyzed KMnO 4 oxidation, Mn(III) and reactive nitrogen species as the primary active species responsible for SMX oxidation in the KMnO 4 /HA system. Proposed transformation pathways of SMX in the KMnO 4 /HA system mainly involve hydroxylation and cleavage reactions. The KMnO 4 /HA system was more conducive to selective oxidation of SMX, 2,4-dichlorophenol, and several other pollutants, but reluctant to bisphenol S (BPS). Overall, this study proposed an effective system for eliminating pollutants, while providing mechanistic insight into HA-driven KMnO 4 activation for environmental remediation.