Photocatalytic heterogeneous oxidation of azo dyes by hydrogen peroxide on the example of Congo red

Abstract

The kinetics of photocatalytic heterogeneous oxidation of azo dyes has been studied using Congo red as an example. It was found that the use of V2O5 as a photocatalyst at 5·10-2 mol/dm3 concentration leads to the oxidation of the dye by 95% when exposed to light in the visible frequency range and by 80% when exposed to light in the ultraviolet frequency range for 30 minutes. The spectrum of Congo red in the presence of V2O5 recorded in the wavelength range of 190-900 nm and the chromato-mass spectrum, taken after 4 hours of irradiation with light in the visible frequency range indicate the complete mineralization of the dye to carbon dioxide and water. Based on the analysis of spectroscopic data, mass spectrometry and available literature data, a mechanism of azo dye oxidation has been proposed.