Applying a novel advanced oxidation process of activated peracetic acid by CoFe₂O₄ to efficiently degrade sulfamethoxazole

In this study, peracetic acid (PAA) is successfully activated by cobalt ferrite (CoFe₂O₄/PAA) to remove sulfamethoxazole (SMX). Increasing either PAA (25–200 μM) or CoFe₂O₄ (25–200 mg/L) dose accelerated SMX degradation in the CoFe₂O₄/PAA system, and the best removal of SMX (87.3%) was acquired with 200 μM PAA and 0.1 g/L CoFe₂O₄ at neutral condition. Addition of humic acid or HCO₃^– inhibited SMX removal, whereas Cl^– had little impact. The redox cycle of ≡Co³⁺/≡Co²⁺ on the CoFe₂O₄ surface dominated PAA activation to produce organic radicals (R-O^•) including CH₃C(O)O^• and CH₃C(O)OO^• accounting for SMX degradation. Based on the density functional theory (DFT) calculation and identified oxidation products, SMX transformation pathway was proposed to be initiated by electron transfer reaction with R-O^•. The insignificant variation of acute toxicity, the fine CoFe₂O₄ stability and the good removal of some other micro-organic pollutants suggested the potential applicability of the CoFe₂O₄/PAA system in degrading micro-organic pollutants.