Проанализированы результаты исследований по изменению при термообработке химического состава и структуры модифицированного гидроксида титана. Показано, что при нагревании во всех случаях сначала образуется анатаз, который при повышении температуры или/и продолжительности термообработки переходит в рутил. Температура начала перехода анатаз - рутил зависит от вида модифицирующего компонента. Переход происходит не скачком при определенной температуре, а постепенно в широком интервале температур, при этом одновременно могут существовать оба соединения. При постоянной температуре доля рутила возрастает с увеличением продолжительности термообработки. На основании проведенных исследований заключено, что в присутствии модифицирующих компонентов образцы диоксида титана представляют собой широкие классы нестехиометрических соединений с разной кристаллической структурой и переход анатаз - рутил не является полиморфным превращением I рода, а является следствием протекания различных химических процессов, включающих выделение анионных и/или катионных примесей в газовую или твердую фазу. The results of studies on changes in the chemical composition and structure of doped titanium hydroxide during thermal treatment are analysed. It is shown that anatase is formed at first under heating in all cases, and with further increase in temperature or in the duration of thermal treatment it is transformed into rutile. The temperature of the start of anatase-rutile transition depends on the type of doping component. The transition proceeds not abruptly at a certain temperature but gradually over a wide temperature range, while both compounds can exist simultaneously. At a constant temperature, the proportion of rutile increases with an increase in the duration of thermal treatment. It is concluded on the basis of the conducted studies that the samples of titanium dioxide in the presence of doping components represent the broad classes of non-stoichiometric compounds with different crystal structures, and the transition of anatase to rutile is not a polymorphic transformation of the 1st kind but it is a consequence of various chemical processes involving the release of anionic and/or cationic impurities into the gas or solid phases

The results of studies on changes in the chemical composition and structure of doped titanium hydroxide during thermal treatment are analysed. It is shown that anatase is formed at first under heating in all cases, and with further increase in temperature or in the duration of thermal treatment it is transformed into rutile. The temperature of the start of anatase-rutile transition depends on the type of doping component. The transition proceeds not abruptly at a certain temperature but gradually over a wide temperature range, while both compounds can exist simultaneously. At a constant temperature, the proportion of rutile increases with an increase in the duration of thermal treatment. It is concluded on the basis of the conducted studies that the samples of titanium dioxide in the presence of doping components represent the broad classes of non-stoichiometric compounds with different crystal structures, and the transition of anatase to rutile is not a polymorphic transformation of the 1st kind but it is a consequence of various chemical processes involving the release of anionic and/or cationic impurities into the gas or solid phases.

The results of studying of the nitric acid and NaOH + KOH alkalis’ mixture recovery from concentrated solutions in filter-press-type electrodialyzers with anion-exchange, cation-exchange, and bipolar membranes are presented. The necessity of the technological solutions preliminary purification from calcium and boron compounds was established, in order to obtain crystalline boric acid (H3BO3) and gypsum (CaSO4·2H2O). The possibility of obtaining, from purified concentrated salt solutions, acids and alkalis with a concentration of ~300–600 g/L suitable for reuse is shown. This can be provided only by the electrodialysis with anion- and cation-exchange membranes, while electrodialysis with bipolar membranes is complicated by noticeable contamination of both acidic and alkaline solutions with salts.

We have synthesized oxide composites based on tungsten-modified titanium dioxide and investigated specific features of their formation and their physicochemical, adsorptive, and photocatalytic properties. The results demonstrate that tungsten modification of TiO2 makes it possible to obtain nanopowders (7.2 to 96.7 nm in particle size) with a free specific surface area from 6.4 to 215 m(2)/g. The synthesized composites have been shown to have considerably higher adsorption capacity and photocatalytic activity (PCA) in comparison to unmodified TiO2 with the same thermal history and Degussa P-25 commercially available titanium dioxide. The materials in which tungsten is incorporated into the crystal lattice of anatase, without tungsten in the form of an individual phase, offer the highest PCA. The electrical conductivity of the composites has been shown to correlate with their PCA.

We have synthesized oxide composites based on TiO 2 modified with aliovalent cations, W 6+ , Co 3+ , Cu 2+ , and Fe 3+ , in the range 5–30 wt %. Its deviation from stoichiometry is increased by active generation of Ti 3+ cations during vacuum calcination at temperatures from 500 to 800°C. The photocatalytic activity (PCA) of the composites for dye degradation reactions under illumination with visible light exceeds that of analogous samples calcined in air. The PCA of the synthesized materials is an intricate function of their composition and structure. The highest PCA, which considerably exceeds the PCA of TiO 2 of similar origin and that of the commercially available Degussa P-25 TiO 2 , is offered by the optimal compositions of the W- and Cu-modified samples for ferroin and methylene blue degradation and the Co- and Fe-modified samples for aniline degradation.

The aim of the work is the continuation of the development of a new efficient hydrochemical technology for the processing of apatite concentrate, which makes it possible to produce phosphoric acid with a reduced content of impurities as a product, to use all the valuable components of apatite concentrate. The dependence of the efficiency of decomposition of apatite concentrate with a phosphate acid solution at a temperature of 20 and 50 °C in the presence of sulfate cationite КУ-2-8чС in Na+- and K+ - forms was studied. The influence of the decomposition conditions (expense and form of sorbent, the ratio of liquid: solid, the interaction temperature) on the degree of decomposition of the concentrate, the completeness of absorption by the sorbent of the metallic cations of the concentrate, the content of impurities in the resulting phosphate-acid solution, and the composition of undissolved residues are studied. The possibility of achieving a high degree of decomposition of the concentrate (up to 99.5 %) is established. High sorption efficiency of calcium and strontium (up to 90.2 and 93.4 % respectively) is shown. The sorption of REE of the cerium group was better than the REE of the middle and yttrium groups. Increasing the temperature from 20 to 50 °C reduced REE sorption by 14-170%. Aluminum, thorium and uranium were the most difficult to sorb. It has been found that effective purification of phosphoric acid from the impurity of fluorine is achieved directly in the process of decomposition. The efficiency of purification from fluorine when using a sorbent in the K+ - form is greater than when using a sorbent in the Na+- form. It is shown that the obtained acid can be purified from sodium or potassium by the electrodialysis method in a two-chamber electrodialyzer equipped with a cation exchange membrane. It is found that before electrodialysis, preliminary purification of the phosphate solution from calcium, which is obtained during the decomposition of apatite concentrate, is necessary. To this purpose, an additional purification of the phosphoric acid solution by sulphocathionite sorption has been investigated. The lower sorption from the phosphoric acid solution of Al, Ti, Fe, Th, and U is explained by the formation of stable anionic complexes or undissociated molecules by these elements. The developed technology for the production of phosphoric acid from the apatite concentrate does not require the use of sulfuric acid, has a number of other advantages. The content of impurities in the resulting phosphoric acid is much less than in the extraction phosphoric acid produced by the sulfuric acid processing of apatite concentrate.

The paper describes distillation of hydrofluoric acid from model and process acid fluoride-sulphate solutions. Conditions for the most complete distillation of hydrofluoric acid from fluoride-sulphate solutions were determined and proposed. Fluorosulphonic acid is formed in large amounts, as shown for model solutions containing hydrofluoric and sulphuric acids. Herewith, with increasing the concentration of acids, their interaction degree rises and fluorosulphonic acid is formed, as demonstrated. An increase in the heating temperature of the mixture leads to a substantial increase in acidity due to HSO3F content decrease. The larger the concentration of acids (especially, sulphuric) is, the higher heating temperatures are required to decompose HSO3F, as established. The formation of fluorosulphonic acid may have a significant effect on HF distillation degree, as shown. The energetic and economic cost in the processing of 1 m(3) of process acid fluoride-sulphate solution is calculated with an account of the initial concentration of HF of 78 g/L. Considering sulphuric acid regeneration and having excluded lime content for its neutralization, energy costs for processing of this solution do not exceed 4500 RUB. The findings explain high solubility of lanthanide fluorides compared to their dissolution in monobasic acids, as noted in a series of papers. Our earlier observations of decreasing the concentration of fluorine determinable by potentiometric titration relatively to initially introduced one at pH correction by using sulphuric acid, unlike that with nitric or hydrochloric ones were also explained.

The effect of the conditions of ammonolysis of mesoporous magnesiothermic tantalum powders with the specific surface area of 56–63 m 2 g –1 on phase composition and specific surface area of the products is studied in the temperature range of 400–900°C. The ammonolysis products are shown to be X-ray amorphous at 400–600°C. At the heating rate of 20 K/min, the nitrogen content in these products is 5.4–7.3% and the specific surface area is 42–35 m 2 g –1 , while at heating rate of 8 K/min these parameters are 2.4–5.4% and 56–49 m 2 g –1 , respectively. The crystalline phase of tantalum oxynitride TaON is formed at a temperature of 700°C and above. The resulting materials exhibit a high photocatalytic activity in the reactions of ferroin and methylene blue degradation under irradiation with visible light (λ ≥ 420 nm).

We have studied the phase transitions, morphology, and photocatalytic activity of titanium(IV) oxide–cerium(IV) oxide materials at Ce doping levels from 1 to 20 wt % and heat-treatment temperatures from 80 to 1150°C. The highest photocatalytic activity under illumination in the spectral range λ ≥ 670 nm is offered by mesoporous X-ray amorphous and multiphase (X-ray amorphous phase + anatase + rutile + CeO2) nanomaterials, whereas the two-phase materials (rutile + CeO2) have the lowest photocatalytic activity.

The phase formation, texture, and photocatalytic activity of synthesized oxide nanocomposites of titanium(IV) and cobalt(II) have been studied in relation to the cobalt content and temperature of heat treatment. The high photocatalytic activity of optimum compositions has been recorded within the spectral range of visible light with λ ≥ 670 nm.

Composites based on titanium(IV) and nickel(II) oxides have been synthesized and investigated in a wide composition range: 0.5–60 wt % Ni. We have analyzed the effect of synthesis conditions on the phase composition and texture of the composites, some of which contain mesopores, consist of nanoparticles, and offer photocatalytic activity in the visible range.

We have established conditions for the preparation of multiphase composites based on titanium(IV) and copper(II) oxides in a wide composition range and examined correlations between the phase composition, texture, and preparation conditions of the composites. Some of them have a mesoporous structure, consist of nanoparticles, and exhibit photocatalytic activity under illumination in the visible range.