Activated peracetic acid by MnO for sulfamethoxazole degradation: A novel heterogeneous advanced oxidation process.

In this study, a novel peracetic acid (PAA)-based advanced oxidation process using MnO as a catalyst was proposed. A thorough sulfamethoxazole (SMX) removal could be achieved within 12 min in MnO/PAA system at neutral pH. The characterization results of fresh and used MnO suggested that ≡Mn(II), ≡Mn(III) and ≡Mn(IV) on MnO were the Mn species for PAA activation, constituting the redox cycles of ≡Mn(II)/≡Mn(III) and ≡Mn(III)/≡Mn(IV) simultaneously. Organic radicals (i.e., CHC(O)O and CHC(O)OO) were verified to be the dominant reactive species responsible for SMX degradation in MnO/PAA system by radical scavenging experiments. The neutral condition was the most favorable pH for SMX removal in MnO/PAA system and the increase of PAA or MnO dosage could enhance SMX degradation. Presence of HCO and natural organic matter (NOM) could inhibit SMX degradation, while Cl, NO and SO had a negligible effect on SMX removal. The thorough SMX removal in successive experiments and characterization results of used MnO suggested the good reusability and stability of MnO for PAA activation. Based on six detected transformation products of SMX, hydroxylation, nitration, bond cleavage and coupling reaction were proposed to be its degradation pathways in MnO/PAA system.