THE PHYSICOCHEMICAL AND PHOTOCATALYTIC PROPERTIES OF SNO2–TIO2 COMPOSITES
Abstract
The issue of safe drinking water is a highly pressing concern today. The textile industry is one of the key sources of pollution, particularly due to the absence or insufficient effectiveness of treatment facilities. Dyes, which are also used in other industries, enter the soil via wastewater and inhibit the growth of flora. Among the various methods of water treatment, photocatalytic treatment is gaining popularity, characterised by its environmental friendliness and high efficiency, particularly at low dye concentrations. The most common photocatalysts are those based on metal oxides such as TiO2, ZnO, SnO2 and others, which are capable of effectively decomposing organic pollutants, particularly dyes, under ultraviolet radiation. The aim of this work is to investigate the physicochemical and photocatalytic properties of SnO2 and TiO2-based nanocomposites synthesised by the hydrothermal method, as well as their individual phases, and to determine the effectiveness of their use for dye removal. X-ray phase analysis revealed that, under hydrothermal synthesis conditions, a single composite is formed at a SnO2 to TiO2 ratio of 1 to 4. X-ray diffraction analysis showed that all photocatalyst samples have crystal sizes ranging from 36 to 122 Å. Analysis of the structural and adsorption properties indicates a reduction in the surface area of mesoporous photocatalysts due to an increase in pore diameter as a result of high-temperature treatment. Based on the UV diffuse reflection spectra obtained, the optical width of the band gap was calculated for all photocatalyst samples; for composite catalyst formulations, this value is smaller than for their individual phases. The determination of the adsorption properties of the catalysts indicates low adsorption activity towards methylene blue for all samples, whilst the determination of photocatalytic activity indicates that all photocatalysts are photoactive; among these, the single SnO2-TiO2 composite proved to be the most effective, due to the presence of both a solid solution crystallised in the rutile phase and an anatase phase within it.