This work investigates the impact of doping bismuth photocatalysts based on the SrO-Bi2O3 system with rare-earth elements (La and Ce) as coatings. The authors have developed a method to create photocatalytic coatings on a silicate carrier, which enables the doping of coatings during their formation. The study shows that this method is effective for doping coatings. The addition of 1 to 5% La or Ce controls the light absorption efficiency of the materials in the visible region of the spectrum as well as their hydrolytic stability. The effect of dopants on the efficiency of coatings in the photocatalytic degradation of methylene blue, formic acid, ethylene glycol, and nitrite ions was investigated, and the effect of La and Ce on the structure of the resulting materials was demonstrated. It was found that the optimum content of the doping element Ce is 3%, at. which increases the degradation of pollutants from 1.7 to 15.7 times.

This work is devoted to the study of water purification from organic pollutants using new environmentally safe photocatalysts capable of using solar insolation to oxidize organic pollutants. Most methods of creating photocatalysts allow obtaining them only in powder form, which limits their application in water treatment plants. In this regard, photocatalysts formed as coatings on the carrier surface may be more promising. This work contributes to solving the problem of developing a technologically concise and economical method of creating bismuth photocatalytic coatings with biological indifference and high light absorption efficiency (LAE) of solar irradiation. The developed cleaning material is a structurally organized system consisting of a ceramic carrier on which a photocatalytic coating is formed. The coating was formed by soaking the silicate carrier in a bismuth precursor solution (BPS) followed by drying and oxidative pyrolysis. The highest catalytic activity and LAE (58.3-60.3%) were observed for the materials obtained at 10-15% wt. bismuth in BPS. The highest hydrolytic stability was observed at 25% wt. bismuth in BPS. Strontium bismuthate SrBi7.65O13 was the dominant phase in the coating composition for the samples with the highest activity and LAE. Increasing the content of another photocatalytically active phase Bi4Si3O12 resulted in the LAE decreasing to 51.9%, providing greater hydrolytic stability of the material. The proposed method allows for flexibly controlling the properties of the obtained photocatalytic coatings, thus making possible to directionally create different types of materials to be applied in the field of wastewater treatment.

A study was carried out to obtain effective photocatalytic coatings on a ceramic silicate carrier. The analysis of the characteristics of silicate materials, such as: ceramic carrier "Biopur"; porous glass carrier "Siporax"; glass-ceramic carrier (sitall) "Biopur forte" produced by the company "SERA", Germany, was made. According to X-ray phase analysis data, it was shown that the “Biopur” ceramic support is formed by magnesium aluminosilicates of the composition MgAl2Si3O10 and MgAl2Si4O12. The porous material “Siporax” is X-ray amorphous. The silicate material “Biopur forte” does not have a pronounced amorphous component in its structure and can be assigned to the class of sitall with a high SiO2 content and a low content of alkali and alkaline earth metal cations in the structure. A method for impregnating a ceramic support with a solution of a bismuth photo-catalyst precursor, a specially developed composition of a complex of bismuth with sorbitol, is considered. An effective concentration of a solution of a complex of bismuth with sorbitol in ethanol equal to 10% was found. By low-temperature pyrolysis at , photo-catalytically active coatings of strontium bismuthates were obtained on each of the considered types of ceramic supports. The highest photocatalytic activity was detected in the coating deposited on a ceramic carrier with a glass structure – “Biopur forte”. A study of the photocatalytic activity of coatings, based on strontium bismuthate, depending on the multiplicity of coating on a “Biopur forte” ceramic carrier, was made. The effective number of layers of the photocatalytic coating on a “Biopur forte” ceramic carrier is determined, which corresponds to the highest rate of decrease in the optical density of a model organic pollutant upon irradiation with visible light in the spectrum.

The paper shows the possibility of application of photocatalytic water treatment method as applied to model effluents of car repair plants containing ethylene glycol. The influence of functional components of automobile coolants on total efficiency of photooxidation was considered. It has been revealed that the presence of organic dyes in automobile coolants with absorption areas coinciding with the absorption areas of photocatalysts reduces the overall efficiency of photooxidation processes.

In this work, we studied the effect of doping with d metals (Me: Mn, Fe, Cu) on the photocatalytic activity and optical properties of the hetero-structured, bismuth-containing Sr1-xMexBi4O7 / (BiO)2CO3 photo-catalyst, where x = 0.01–0.05. The stages of oxidative pyrolysis of precursor organometallic complexes with sorbitol by differential scanning calorimetry have been studied. The first stage of oxidative destruction is induced by the influence of nitrate-ion and terminates at temperatures below . The second stage of pyrolysis is associated with a further thermal degradation of sorbitol to pyrolytic carbon in the temperature range 113 - . The third stage 287–462°C is associated with the combustion of the formed pyrolytic carbon. The final stage of pyrolysis occurs in the temperature range of 462-with the formation of the target synthesis products. It has been established that Cu is the most effective dopant. In contrast to other metals, doping with copper results in the formation of a solid solution in the CuO-SrBi4O7 system. Compared to the initial SrBi4O7, as a result of doping Cu in an amount of 5 at. % the largest change in the band gap from 2.77 to 2.62 eV is achieved. The efficiency of photo-catalysis (estimated by the half-conversion of methylene blue) of the Cu0.05Sr0.95Bi4O7 / (BiO) 2CO3 composition turned out to be 2.3 times higher than the initial - undoped catalyst; and 3.1 times higher than in the non-catalytic process.

Strontium-bismuth containing photocatalytic active coatings on a silicate carrier using sorbite-nitrate pyrolytic synthesis were obtained. The effect of strontium-bismuth molar ratio in the precursor mixture on the phase composition, boundaries of the visible light absorption region and photocatalytic activity of the coatings obtained were studied. The best photocatalytic activity is achieved by coatings obtained from the precursor mixture at Sr:Bi molar ratio of (1:3) and (1:4) in the experiment with a model organic pollutant - methylene blue (MB). The obtained photocatalytically active coatings on silicate carrier (Sr: Bi-1:4) were tested in a water purification unit (WPU) at different rotation speeds. The effective range of rotation of samples without loss of photocatalytic properties at photo-oxidation of MB (15-35 rpm) was established. (c) 2021 Elsevier B.V. All rights reserved.

This work is devoted to the study of the content of mineral forms of nitrogen in the water of small rivers in Khabarovsk and its surroundings, represented by the Bolshekhekhtsirsky Nature Reserve, during the winter low water of 2017-2021, which lasts from December to February.The dynamics of quantitative distribution of ammonium, nitrite, and nitrate nitrogen in relation to different groups of watercourses were considered.The correlation analysis enabled to reveal the probable reasons for such correlations of their content.

This work is devoted to the study of new bioindifferent photocatalysts that use the energy of solar radiation to purify water from organic pollutants. Photocatalytic materials were obtained by a previously developed low-temperature pyrolytic synthesis. Varying the bismuth content in the percursor mixture within 15-30 %, allows controlling the phase formation of the bismuth and strontium silicate phases. The samples obtained at 25 % bismuth in the precursor mixture (in terms of Bi2O3 %, wt.) show the highest photocatalytic activity with Bi12SiO2, Bi4Si3O12 formed in the catalyst composition. Photocatalytic activity of coatings with the predominance of bismuth silicates is inferior to coatings with the predominance of strontium bismuthates, but their greater hydrolytic stability is observed.

The photocatalytic activity of heterostructural α-Bi 2 O 3 /Bi compositions obtained by low-temperature pyrolysis of bismuth complexes with sorbite has been investigated. The efficiency of catalysts has been estimated based on the decomposition rate of methylene blue under illumination by visible light. The obtained catalysts are characterized by different contents of metallic Bi and different degrees of imperfection of the α-Bi 2 O 3 lattice, which was obtained by changing the amount of sorbite in the composition of the precursor organomineral bismuth complex and varying the synthesis temperature. It is established that isothermal annealing of the α-Bi 2 O 3 /Bi compositions in air in the range of 400–600°C leads to relaxation of defects and an increase in the α-Bi 2 O 3 lattice volume. An increase in the annealing temperature to 550°C is accompanied by a rise in the α-Bi 2 O 3 /Bi catalytic activity. However, the heterostructure degrades at higher temperatures as a result of metallic bismuth oxidation, while the catalytic activity decreases.

This investigation reveals the possibility of effective photocatalytic purification of aqueous solutions of organic pollutants in an experimental unit with an automatically cleaned photocatalytic coating. The automatic cleaning process is realizing by friction of rotating cylindrical photocatalytic coating carriers against a replaceable brush module. Based on data on phase analysis and sorption activity, an optimal silicate carrier was selected for further formation of a continuous coating with high photocatalytic activity on its surface. The effect of its multiple applications (1–4) and temperature (500 °C and 700 °C) on the formation, phase composition, morphology and photocatalytic properties of the coating was studied. It is shown that the highest photocatalytic activity of the coating is achieved with a double application and annealing temperature of 500 °C. Phase analysis and electron microscopy data indicate that with the above synthesis parameters, a continuous coating consisting of a strontium bismuthate phase in strontium to bismuth ratio close to 1:5 is formed. In an experimental wastewater purification unit equipped with samples of the coating that had the highest photocatalytic activity, the efficiency of photo-oxidation of real organic pollutants of wastewater was assessed by bio-testing with Lemna minor as a biological object. Comparative assessment of the efficiency of toxic impact reduction was carried out for two types of organic pollutants: (1) single-stage oxidizing; (2) having photo-oxidation intermediates. For both types of organic pollutants, the effectiveness of the photocatalytic material in reducing the toxic impact on the biological site has been demonstrated.

Приведены результаты автоматизированных измерений каталитической активности висмутовых покрытий в ходе реакции фоторазложения водного раствора модельного загрязнителя.Измерения проведены с помощью разработанной установки, в которой объединены фотореакционные и измерительные ячейки.Эффективность фотокаталитических покрытий -нанопорошков висмутата стронция, нанесенных на керамический носитель в один, четыре и семь слоев, оценивалась по скорости уменьшения концентрации органического красителяметиленового синего -после продолжительного облучения видимым и ультрафиолетовым светом.Показано, что фотокаталитическая активность покрытий на основе висмутатов стронция зависит от кратности их нанесения на

Представлены результаты изучения свойств фотокаталитически активной композиции SrBi 4-у O 7-z / ½у(BiO) 2 СО 3 , где y=1,2…1,7, полученной пиролитическим синтезом из органических прекурсорных комплексов стронция и висмута с сорбитом.Установлено, что синтезированные порошковые материалы поглощают свет видимого диапазона вплоть до 500 нм за счет наличия узкозонного полупроводника SrBi 4 O 7 .Присутствие широкозонного полупроводника (BiO) 2 СО 3 обеспечивает эффективное разделение электронно-дырочных пар.Спектры диффузного отражения композиций имеют отличия от аналогичных спектров механической смеси данных полупроводниковых фаз того же состава, что позволяет предполагать гетероструктурное строение полупроводниковой системы.Каталитические частицы, синтезированные при температуре 500 °С и содержащие 73 мас.% SrBi 4-у O 7-z и 27 мас.% (BiO) 2 СО 3 , обладают наибольшей активностью при фоторазложении метилена синего.Показана возможность управления оптическими свойствами и фотокаталитической активностью композиции за счет совместного формирования фазы висмутата

This paper presents the results pertaining to studying the properties of the photocatalytically active composition of strontium bismuthate SrBi2.70O5.05, SrBi2.90O5.35, and SrBi3.25O5.88 and bismuth carbonate (BiO)2CO3 in molar ratios 1/0.67, 1/0.56, and 1/0.37, respectively. These compositions are obtained through pyrolytic synthesis from organic precursor complexes of strontium and bismuth with sorbitol. It has been established that the synthesised powder materials absorb the light of the visible range up to 500 nm owing to the presence of a narrow-gap semiconductor strontium bismuthate. The presence of a wide-band semiconductor (BiO)2CO3 ensures an effective separation of electron-hole pairs. The diffuse reflection spectra (DRS) of compositions differ from the analogous spectra of a mechanical mixture of these semiconductor phases with the same composition, which allows one to assume the heterostructural structure of the semiconductor system. The same heterostructure is confirmed by the results of mapping. Catalytic particles that are synthesised at a temperature of 500°C containing 27 mass% (BiO)2CO3 (corresponding to SrBi2.9O5.35/(BiO)2CO3 = 1/0.56) have the greatest activity with respect to the photodecomposition of methylene blue (MB). The possibility of controlling the optical properties and photocatalytic activity of the composition is depicted due to the joint formation of the strontium bismuthate phase and the bismuth carbonate phase.

The quantum-mechanical approach (the density functional theory and the pseudopotential method) is used to study the friction in the aluminum-aluminum, aluminum-tungsten, and tungsten-tungsten nanopairs on the atomic level in the presence of external pressure. Nanopairs were constructed from crystalline nanoslabs and crystalline nanorods of rectangular cross section. The nanoslabs had infinite periodic structures in the X and Y directions; the nanorods were periodic in the Y direction. The process of friction was studied by reducing a rod and a slab to an equilibrium contact with subsequent step-by-step shift of the rod relative to the slab along the X direction. The rod was located above the slab (in the Z direction). The total energy of the system was calculated on each step. The friction force was calculated as a ratio of the change in the total energy to the value of the rod shift step. The pressure force was applied to the rod in the Z direction. The coefficient of friction was calculated as a ratio of the friction force to the pressure force. Observation of the behavior of atoms showed that for all the nanopairs studied the process of friction is accompanied by the processes of deformation and destruction. Both components of a nanopair are subjected to deformation, whereas destruction is observed only in the nanorods. Aluminum rods are subject to the maximum deformations and destructions in both aluminum-aluminum and aluminum-tungsten pairs. The tungsten rods are not destroyed; deformations in them and in tungsten slabs are minimal. The friction coefficients in the aluminum-aluminum pairs decrease with increasing pressure, and they increase in the aluminum-tungsten and tungsten-tungsten pairs.