MnO2-PI⁎ and IO3•-mediated degradation of bisphenol A in the manganese oxide-supported catalyst-activated periodate system.

In this study, manganese oxide-supported catalysts (MnO x @SiO 2 ) were synthesized by co-precipitation with a subsequent high-temperature calcination and employed to activate periodate (PI) for the degradation of bisphenol A (BPA). The MnO x @SiO 2 –500 system exhibits optimum PI activation performance with an associated 96.0 % BPA degradation efficiency outperforming MnO x . The MnO x @SiO 2 –500/PI system was subjected to comprehensive analysis, including electrochemical tests, quenching experiments, electron spin resonance (ESR), methyl phenyl sulfoxide (PMSO) probe experiments, Mn ion leaching detection, UV–vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results revealed that BPA degradation is promoted by a MnO 2 -PI ⁎ complex via homogeneous activation in solution and iodate radicals (IO 3 • ) involving heterogeneous activation. In the case of the homogeneous activation, Mn(II) undergoes a two-electron transfer to form MnO 2 , which is complexed with PI to generate MnO 2 -PI ⁎ . In the heterogeneous activation, Mn 3 O 4 on the surface of MnO x @SiO 2 –500 activates PI to produce IO 3 • . Based on high-performance liquid chromatography-mass spectrometry (HPLC-MS) and density functional theory (DFT) calculations, three possible BPA degradation pathways are proposed. In pathways I and II, the active species attack C atoms on the two BPA benzene rings to initiate hydroxylation and oxidation. In pathway III, the attack generates a C C bond, yielding multiple degradation intermediates bearing a benzene ring. In addition, the acute and chronic toxicities of by-products with respect to aquatic organisms are predicted using the ECOSAR software. The majority of degradation intermediates exhibit lower toxicity than the starting BPA. This study provides a green and efficient strategy for BPA removal in wastewater treatment.