Enhanced mineralization of dimethyl phthalate by heterogeneous ozonation over nanostructured Cu-Fe-O surfaces: Synergistic effect and radical chain reactions

Cu-Fe-O nanoparticles (CFO NPs), synthesized with zero-valent iron (ZVI) and Cu(NO 3 ) 2 as the metal precursors, were used to enhance ozonation to degrade dimethyl phthalate (DMP). Great DMP degradation and mineralization rates were achieved in a wide range of the initial pH values (3–9); the amount of OH in catalytic ozonation was much higher than that of O 3 alone at the initial pH of 5.70. The generation of hydroxyl radicals ( OH), methyl radicals ( CH 3 ) and superoxide radicals (O 2 − ) were identified and OH mainly contributed to DMP removal. The potential of Fe(III)/ Fe(II) and Cu(II)/ Cu(I) cycles have largely been overlooked, which was found to be the key for producing more OH in CFO/O 3 system. The underlying mechanisms were probably initiated by a chain reaction: initiated O 3 reaction with Cu(I)/ Fe(II) OH to form OH and O 2 − , accelerated reaction between Cu(II)/ Fe(III) and the in situ generated O 2 − with a relatively high reaction constant, redox reaction between Cu(I) and Fe(III), OH oxidizing reaction with DMP to produce CH 3 . In addition, different degradation pathways of DMP were proposed based on the intermediates in the presence of CH 3 . This study sheds new light on the specific radical chain reaction mechanisms of catalytic ozonation.