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

Abstract

Abstract Cu-Fe-O nanoparticles (CFO NPs), synthesized with zero-valent iron (ZVI) and Cu(NO3)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 O3 alone at the initial pH of 5.70. The generation of hydroxyl radicals ( OH), methyl radicals ( CH3) and superoxide radicals (O2 −) 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/O3 system. The underlying mechanisms were probably initiated by a chain reaction: initiated O3 reaction with Cu(I)/ Fe(II) OH to form OH and O2 −, accelerated reaction between Cu(II)/ Fe(III) and the in situ generated O2 − with a relatively high reaction constant, redox reaction between Cu(I) and Fe(III), OH oxidizing reaction with DMP to produce CH3. In addition, different degradation pathways of DMP were proposed based on the intermediates in the presence of CH3. This study sheds new light on the specific radical chain reaction mechanisms of catalytic ozonation.