Efficient degradation of organic dyes by titanium dioxide–silicotungstic acid nanocomposite films: Influence of inorganic salts and surfactants

Photocatalytic nanocomposite films (TiO2/SiW12)n (TiO2 = titanium dioxide, SiW12 = H4SiW12O40) were fabricated via an electrostatic layer-by-layer (LbL) self-assembly method, which is a rapid and simple experimental fabrication process. UV–vis absorption spectra, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were performed to characterize the LbL assembly process, surface morphology, and elemental composition of (TiO2/SiW12)n multilayer films. The influence of bilayers number of (TiO2/SiW12)n composite films on the efficient removal of methyl orange (MO) was studied. In order to determine the feasibility of the film catalysts for dye pollutants degradation, we chose three types of colorful dyes including azoic, fluorescent, and sulfonic. Photodegradation rate of MO is significantly suppressed by inorganic salts including sodium chloride and sodium sulphate due to the aggregation or association of ionic dye in water. The presence of nonionic polyoxyethylene dodecyl ether (C12E23) accelerates the MO degradation. However, a marked inhibition of anionic sodium dodecylsulfate (SDS) on MO degradation is found at different SDS concentrations. It is expected that the fabricated photocatalytic nanocomposite films could have substantial applications in textile industries or wastewater purification.