Activation of persulfate by magnetite: Implications for the degradation of low concentration sulfamethoxazole

Abstract

Abstract Sulfamethoxazole (SMX) was widely detected in the effluent of sewage treatment plants and water environment. In this study, SMX with low concentration was effectively degraded by magnetite-activated persulfate (PS) system. The process mainly involved the sulphate radical (SO4 −) and hydroxyl radicals (HO ), formed from PS activated by Fe(II) and Fe(III) in Fe3O4. The second-order reaction rate constants for the reaction between SMX and HO /SO4 − were estimated. The SMX degradation rate decreased as the solution pH increased from pH 3.5–10.5 and the pH dependency of SMX degradation rate was closely related to the speciation of Fe2+. HO , SO4 − and O2 − were involved during PS activation. The effects of chloride were investigated. SMX degradation efficiency was significantly decreased due to the trapping of SO4 − by Cl− at pH 4.0, while it had no effect by Cl− at pH 10.5 due to the formation of HO . The potential recyclability of Fe3O4 was measured and it could be reused at least 4 times. The findings may have promising implications in the application of Fe3O4 on a new technology for the treatment of micro-contaminated waters and soils, especially the application of natural magnetite.