Efficient degradation of bisphenol A by the UV-enhanced nano zero-valent iron-activated hydrogen peroxide advanced oxidation system

Abstract

Bisphenol A (BPA) in a water environment has hazardous and is difficult to degrade under natural conditions. In this study, the UV-nZVI-H2O2 system was constructed to efficiently degrade BPA. The results show that the removal rate and mineralization rate of BPA were 85.03 % and 21.31 %, respectively, under the conditions of initial pH = 3, UV = 10 W, [nZVI] = 0.05 g/L, [H2O2] = 0.06 mmol/L, [BPA] = 40 mg/L and t = 60 min. This is mainly attributed to the synergistic effect among UV, nZVI and H2O2. The dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO•, and the yield of HO• was up to 333.81 μmol/L, which was much higher than that of other systems in the controlled experiment. In addition, the system can efficiently remove a variety of aromatic and refractory organic matter (e.g., ibuprofen (IBU) and ciprofloxacin (CIP)). The reaction intermediates were identified, and it was speculated that the possible degradation pathways of BPA were mainly HO• attack on the electron-rich benzene ring in the BPA molecule and attack on the C–C bond connected between isopropyl and the benzene ring. The possible degradation pathways of IBU include decarboxylation, hydroxylation addition and single bond breaking. The possible degradation pathway of CIP is the loop opening of the piperazine ring and quinolone ring of CIP after continuous oxidation of HO•. The reaction mechanism of this system is a homogeneous and heterogeneous Fenton reaction and adsorption and precipitation of BPA by iron-based oxides.