The mechanism of degradation of bisphenol A using the magnetically separable CuFe2O4/peroxymonosulfate heterogeneous oxidation process

The removal of bisphenol A (BPA) in aqueous solution by an oxidation process involving peroxymonosulfate (PMS) activated by CuFe2O4 magnetic nanoparticles (MNPs) is reported herein. The effects of PMS concentration, CuFe2O4 dosage, initial pH, initial BPA concentration, catalyst addition mode, and anions (Cl-, F-, ClO4- and H2PO4-) on BPA degradation were investigated. Results indicate that nearly complete removal of BPA (50 mg/L) within 60 min and 84.0% TOC removal in 120 min could be achieved at neutral pH by using 0.6 g/L CuFe2O4 MNPs and 0.3 g/L PMS. The generation of reactive radicals (mainly hydroxyl radicals) was confirmed using electron paramagnetic resonance (EPR). Possible mechanisms on the radical generation from CuFe2O4/PMS system are proposed based on the results of radical identification tests and XPS analysis. The lack of inhibition of the reaction by free radical scavengers such as methanol and tert-butyl alcohol suggests that these species may not be generated in the bulk solution, and methylene blue probe experiments confirm that this process does not involve free radical generation. Surface-bound, rather than free radicals generated by a surface catalyzed-redox cycle involving both Fe(III) and Cu(II), are postulated to be responsible for the mineralization of bisphenol A. (C) 2016 Elsevier B.V. All rights reserved.