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.