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The paper presents the results of characterization and study of adsorption-photocatalytic properties of commercial and synthesized-by-hydrothermal method TiO2 and TiO2-SnO2 nanocomposites. Hydrothermal synthesis of TiO2-based nanocomposites was performed in two ways: single-stage and two-stage methods. Characterization was carried out by XRD, X-ray fluorescence method, XPS, EPR, PL, and low-temperature adsorption-desorption of nitrogen, which showed that TiO2-SnO2 nanostructured composites were obtained with tin(IV) oxide content of 10 wt.% and had acidic surface and different porous structures. Besides, modification of a commercial sample with tin(IV) oxide led to a slight decrease in the specific surface area, while modification of a synthesized-by-hydrothermal method TiO2 sample led to an increase. It was found that sorption properties of the obtained nanocomposites and pure TiO2 are better towards anionic dyes. Photocatalytic activity, on the contrary, is higher towards cationic dyes, which is consistent with additional studies on the destruction of these dyes. It was established that in terms of photocatalytic activity, TiO2-SnO2 nanocomposites are more promising than solid solutions, and modification of TiO2 with tin(IV) oxide, in general, leads to improvement of its photocatalytic activity.

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The photocatalytic and physicochemical properties of titanium (IV) oxide modified by yttrium and niobium oxides were studied. It is shown that modification is a powerful way to increase the efficiency of catalysts' photocatalytic properties and improve the photocatalytic process as a whole. Commercial and laboratory-synthesized titanium (IV) oxides were used as catalysts for modification. Modification of titanium (IV) oxide powders in an amount of 1 wt. % by appropriate modifiers was performed by the hydrothermal method, after which they were characterized by diffraction and X-ray fluorescence methods. The structural characteristics of modified and non-modified titanium (IV) oxide samples by the method of low-temperature nitrogen adsorption-desorption have been studied. A slight increase in the specific surface area was found: from 61 m2/g to 70 m2/g for the commercial sample and from 172 m2/g to 180 m2/g for the synthesized one in this work. Similar dependencies are observed when studying the optical properties by the spectrophotometric method. Determination of surface properties (surface acidity) of modified and non-modified photocatalysts based on TiO2 showed different effects of modifiers on TiO2 acidity: in the modification by yttrium oxide, the acidity decreases, and in the case of niobium oxide – increases. Studies of photocatalytic and sorption activities with respect to dyes of different nature are not the same – the photocatalytic activity after modification increases, the sorption capacity with the cationic dye decreases, anionic – increases. Additional studies on dye destruction are in full accordance with photocatalytic and sorption experiments.

Storage of red mud, because of its large quantity and specific compounds, causes a lot of problems. Thereby, development of complex technology utilization of wastes (red mud) is the most economically and environmentally attractive way to solve the problem of red mud accumulation and obtaining of highly efficient purification reagents from secondary raw materials.The purpose of this work is synthesis and verification of efficacy of adsorption reagents that were obtained by using "red mud" in technologies of wastewater treatment from compounds of organic origin.The proposed sorption reagent derived from activated "red mud" and activated carbon brand F300 revealed sufficient sorption efficiency at wastewater treatment from the dye "Active brilliant blue KX". At the the initial concentration of dye 10, 30, 50 mg/l dye extraction to 84-100% in following conditions was achieved: рН medium 4 -4,3, dose of sorbent 12 g/l, asdorption duration 150 min.Conducted research revealed that synthesized sorbent based on activated "red mud" and activated carbon (where activated carbon functionates as carrier) has potential for use in water treatment to remove organic dyes.