Facile synthesis of hexamine–silicotungstic acid hybrid and its photocatalytic activity toward degradation of dyes

A new organic hybrid of silicotungstic acid was prepared by means of an easily available, very cheap, and non-toxic amine via a facile precipitation method. Characterization of hybrid was carried out by elemental analyses, Fourier transform infrared spectroscopy, powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Dye adsorption and photocatalytic properties of the prepared water-insoluble hybrid were examined by studying the decolorization of model dyes such as methylene blue and methyl, orange and their mixture solutions under ultraviolet, visible, and sunlight irradiation. The effect of different factors containing the initial concentration, pH, catalyst dosage, H2O2 dosage, and salt adding was investigated on the decolorization of dyes. The results showed that the hybrid is a good heterogeneous photocatalyst in the degradation of methylene blue, methyl orange and their mixture and can be recovered and reused. The methylene blue is removed via combination of adsorption and photocatalytic degradation under ultraviolet, visible, and sunlight through direct oxidation by hybrid. The methyl orange is removed via ultraviolet and solar photocatalytic degradation through indirect oxidation by ·OH radicals. While the visible light is not able to degrade methyl orange solution alone in the presence of hybrid, it degrades the methyl orange mixed with methylene blue solution.