Towards environmentally friendly wastewater treatment photocatalytic degradation of reactive Blue-19 under visible light.

The presence of noble metals such gold have been reported to activate the photocatalytic performance of TiO₂ in the visible light. It is important because pristine TiO₂ alone can only be activated by UV light which comprises only 8% of the irradiation reaching Earth. To degrade pollutants discharge by the textile industries in waste water by light is essential for clean environment. One of primary aims of this thesis is to test the hypothesis that augmenting standard TiO₂ photocatalysts with Au nanoclusters could show performance of a catalyst under blue light. For this, the photocatalytic activity of several Au₉ clusters based on Titanium dioxide (P-25-TiO₂) materials were evaluated by using photo degradation of an industrial dye Reactive Blue 19 (RB-19) as a model reaction. Three different loadings (0.17, 0.34 and 0.5 wt%) of (Au) gold nanoclusters Au₉(PPh₃)₈(NO₃)₃ were deposited on pristine P-25 TiO₂ and sulfuric acid washed P-25 TiO₂ as heterogeneous photocatalysts under UV and blue light. Post treatment was done to remove the ligands characterised by TEM, XPS. 30 mg of each catalyst was sonicated and dispersed in 100 ml of 0.08 g/L of RB-19 and subjected to UV and blue light. It was found that the effect of Au₉ increased the photo catalytic degradation under blue irradiation (78%) while the only pristine P-25 was totally inactive in that wavelength. Interestingly, not only the rate of degradation increased but also the percentage degradation increased when acid washed P-25 TiO₂ used as catalyst. Au9 with ligands clusters were loaded on acid washed P-25, the highest degradation was observed under the blue light with the 0.5 wt% highest percentage of loading during the study. While the degradation was lowered down in the case of, with respect to same loadings, Au₉ as made or calcined clusters when deposited on the support pristine P-25 TiO₂. It is infer that SO₄²⁻ on TiO₂ has 26% degradation under blue light