Photocatalytic degradation of methyl orange by titanium dioxide-decatungstate nanocomposite films supported on glass slides

Photocatalytic nanocomposite films of titanium dioxide (TiO2)/polyoxometalate, decatungstate (Na4W10O32, abb. W10O32) were prepared via electrostatic layer-by-layer self-assembly method. Atomic force microscopy (AFM) observations and X-ray photoelectron spectroscopy (XPS) analyses show that the positive TiO2 nanoparticles and W10O32 polyanions were successfully incorporated into multilayer nanocomposite films. The photocatalytic activities of these multilayer films were tested via the degradation of methyl orange (MO) aqueous solution under UV irradiation. The influence of operational parameters including bilayer number of films, initial dye concentration, and electron acceptor such as hydrogen peroxide were checked to obtain the optimum conditions of MO photocatalytic degradation. The experimental results show that the degradation rate of MO decreases with an increase of initial dye concentration. The addition of hydrogen peroxide with concentration over the range 2.5–20 mM evidently improves the decolorization rate by inhibiting the electron–hole recombination and producing an abundance of OH radicals. The kinetics of MO oxidation process was determined to be first-order reaction according to the Langmiur–Hinshelwood kinetics model at different H2O2 concentrations. Our results could provide valuable information for large-scale treatment of dye-bearing wastewaters.