Enhanced photocatalytic degradation of methyl red and thymol blue using titania-alumina-zinc ferrite nanocomposite

Nanocomposite of magnetically separable, TiO(2)-ZnFe(2)O(4) with an intermediate layer of alumina has been synthesized by a multistep wet chemical process. UV-vis absorption spectra show a red shift of the absorption edges for the composite systems compared to single phase TiO(2). Magnetic measurements indicate that the ZnFe(2)O(4) is ferromagnetic at room temperature with low coercivity when the applied field is low, typical of soft magnetic materials. After TiO(2) and alumina coatings, the samples show similar magnetic behaviour. Photocatalytic activity studies for methyl red and thymol blue degradation indicate an enhanced activity for the composites when the alumina interlayer is present between TiO(2) and ZnFe(2)O(4). When Pd is used as a co-catalyst in TiO(2)-ZnFe(2)O(4), an enhanced activity is observed, which is comparable to that of TiO(2)-Al(2)O(3)-ZnFe(2)O(4). The present study leads to a new result that an insulating interlayer like alumina can enhance the photocatalytic activity of TiO(2) coated ferrites as much as that of a noble metal co-catalyst like Pd. The enhanced photocatalytic activity of TiO(2)-Al(2)O(3)-ZnFe(2)O(4) is attributed to the decrease in the migration of photogenerated charge carriers to zinc ferrite layer and due to the increased adsorption of the reactants on the surface of TiO(2)-Al(2)O(3)-ZnFe(2)O(4). (C) 2011 Elsevier B.V. All rights reserved.