Activated peracetic acid by Mn3O4 for sulfamethoxazole degradation: A novel heterogeneous advanced oxidation process

In this study, a novel peracetic acid (PAA)-based advanced oxidation process using Mn 3 O 4 as a catalyst was proposed. A thorough sulfamethoxazole (SMX) removal could be achieved within 12 min in Mn 3 O 4 /PAA system at neutral pH. The characterization results of fresh and used Mn 3 O 4 suggested that ≡Mn(II), ≡Mn(III) and ≡Mn(IV) on Mn 3 O 4 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., CH 3 C(O)O • and CH 3 C(O)OO • ) were verified to be the dominant reactive species responsible for SMX degradation in Mn 3 O 4 /PAA system by radical scavenging experiments. The neutral condition was the most favorable pH for SMX removal in Mn 3 O 4 /PAA system and the increase of PAA or Mn 3 O 4 dosage could enhance SMX degradation. Presence of HCO 3 − and natural organic matter (NOM) could inhibit SMX degradation, while Cl − , NO 3 − and SO 4 2− had a negligible effect on SMX removal. The thorough SMX removal in successive experiments and characterization results of used Mn 3 O 4 suggested the good reusability and stability of Mn 3 O 4 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 Mn 3 O 4 /PAA system.