Enhanced self-catalytic degradation of CuEDTA in the presence of H2O2/UV: Evidence and importance of Cu-peroxide as a photo-active intermediate

• A enhanced self-catalytic effect was observed for CuEDTA–H2O2/UV system.
• CuO2 was found to be a favorable photo-active intermediate.
• Photolysis of CuO2 could effectively speed up the transform of Cu(II)-to-Cu(I).

A new insight into the degradation of CuEDTA with UV/H2O2 was performed. It was found that the degradation was an UV-enhanced self-catalytic process with two main stages. The first was the induction stage in which cupric ions were produced in CuEDTA degradation with UV photolysis or/and H2O2 oxidation. The second was the photo-catalytic degradation stage in which CuEDTA was oxidized by UV-enhanced cupric ion-based Fenton process. The degradation efficiency reached as high as 82.2% during 18 min, being 37.4 times higher than the efficiency sum of single H2O2 oxidation and single UV photolysis. The enhancement effect can be contributed to the synergetic interaction between H2O2, cupric ion and UV, specially, to the excellent photo-activity of copper-peroxide intermediates. One of them was identified to be CuO2 by analysis of its CE-C4D electropherograms, UV–vis adsorption spectra, FT-IR spectra, Raman spectra, especially XPS spectra. The enhancement mechanism was experimentally confirmed to be due to the acceleration of Cu(II)-to-Cu(I) transform by the photolysis of copper-peroxide intermediates, leading to the increasing CuEDTA degradation.

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