Solar-light-assisted photo-degradation of azo dyes using some transition metal oxides

Abstract

Nano size SnO2 and CeO2 doped compounds were prepared by co-precipitation precursor method. SnO2 is diamagnetic in nature and shows semiconductor behaviour. SnO2 has band gap of 3.5 eV, which help in preventing the electron-hole recombination. It is found that azo dye Auramine O can be degraded efficiently using SnO2 semiconductor photo-catalyst with solar light. CeO2 has low photo-catalytic activity for the degradation of Naphthol Blur Black. Increase in photo-catalytic activity was noticed by incorporation of Mn in CeO2 lattice. This is mainly due to the increase of the redox couple Ce4+ - Ce3+ and improvement of the band gap energy. The mechanism involves the formation of OH. radicals which are active oxidizing agents for the degradation of dyes. Also oxygen prevents the recombination of electron-hole pairs hence increasing the reaction rate. The dye degrades to a colourless solution after irradiation.