Selective photocatalytic degradation of azodyes in NiO/Ag3VO4 suspension

BACKGROUND: This work deals with the development of an active heterogeneous catalyst for selective organic synthesis under both visible light and UV irradiation to utilize efficiently solar light. Very few studies have been reported on the selective photooxidation performance of multimetal oxide materials under visible light irradiation. The photocatalytic degradation of azodyes was investigated systematically in aqueous NiO/Ag3VO4 dispersion under visible light irradiation. RESULTS: The catalyst NiO/Ag3VO4 showed high activity and selectivity for the photodegradation of the nonbiodegradable azodyes acid red B, reactive brilliant red X-3B, and acid orange 7. From total organic carbon (TOC), Fourier transform infrared spectroscopy (FTIR), and gas chromatography/mass spectroscopy analyses, the tested azodyes were selectively oxidized into aromatic and aliphatic acids without any decrease of TOC. The high photooxidation selectivity also applied to UV light irradiation. Electron spin resonance and radical scavenger studies suggest that the anionic superoxide radical O2−• was the predominant active species in the photocatalytic reaction. CONCLUSION: The selectivity of NiO/Ag3VO4 for the oxidation of azodyes was not affected by the energy of light (UV and visible light). This approach allows effective controlled oxidation but avoids undesirable mineralization into CO2 and H2O. c © 2010 Society of Chemical Industry