Prepatation Of SrTiO₃/CeO₂ Photocatalyst And Its Activity In The Degradation Of Azo Dyes

The preparation of SrTiO₃/CeO₂ composite and its activity in the photocatalysis of azo dyes were investigated, which showed that SrTiO₃/CeO₂ can be a candidate photocatalyst.The photocatalytic degradation of C.I. Direct Red 23 (4BS) in aqueous solutions under UV irradiation was investigated with SrTiO₃/CeO₃ composite as the catalyst. The SrTiO₃/CeO₂ powders had more photocatalytic activity for decolorization of 4BS than that of pure SrTiO₃ powder under UV irradiation. The effects of catalytic dose, pH value, initial concentration of dye, irradiation intensity as well as scavenger KI were ascertained, and the conditions for maximum degradation were determined. Under the irradiation of a 250 W mercury lamp, the best catalytic dose was 1.5 g/L and the best pH was 12.0. Light intensity exhibited a significant positive effect on the efficiency of decolorization, whereas the initial dye concentration showed a significant negative effect. Under the conditions of a catalytic dose of 1.5 g/L, pH of 12.0, initial dye concentration of 100 mg/L, light intensity of 250 W, air flow rate of 0.15 m³/h, the complete decolorization, as determined by UV-visible analysis, was achieved in 60 min, corresponding to a reduction in COD of 69% after 240 min reaction. A tentative degradation pathway based on the sensitization mechanism of photocatalysis is proposed.The photocatalytic degradation mechanism of C.I. Reactive Black 5 (RB5) has been investigated in an aqueous suspension of SrTiO₃/CeO₃ composite under the optimum conditions. The adsorption peaks at wavelengths of 600, 312 and 254 nm were identified as the chromophore structure, the naphthalene and benzene components of RB5, respectively. Little influence of iodide ion, terf-butyl alcohol, fluoride ion or persulfate ion as h_vb⁺,·OH or e_cb^- scavengers on the decolorization proved that the decolorization of RB5 primarily proceeded by photolysis and/or O₂·^- in the bulk solution. After the decolorization, the process could shift progressively from the bulk solution to the surface of the catalysts and cleavage of the naphthalene and benzene rings was mainly attributed to the h_vb⁺ pathway and·OH_ads reactions, which was further verified by the effect of scavengers.