The paper demonstrates the possibility of using a dielectric barrier discharge for the deposition of polymer organosilicate films on the surface of glass substrates. A planar barrier discharge of atmospheric pressure was excited in a flow reactor in an atmosphere of (Bis(trimethylsilyl)amine at a fixed flow rate. Helium as the carrier gas was used. The carrier gas and working fluid flow rates were fixed at 45 ml/s and 0.2 ml/s, respectively. The frequency of the dielectric barrier discharge was 50 Hz, the average discharge current was 3 mA at a total power put into the discharge of 24 VA. The deposition time varied in the range of 30-1200 s. It was shown that under the conditions studied, the discharge has a filamentous form. The study of the surface morphology and elemental composition of the deposited film was carried out using scanning electron microscopy and energy-dispersive spectroscopy. Surface wettability was determined by the contact angle method and the method of photofixation of drops. The elemental composition of the deposited coatings indicates the formation of an organosilicon film. The contact angle method for polar (distilled water) and non-polar (diiodomethane, glycerol) liquids showed that the wettability of the deposited coatings is higher than that of the original substrate. Additionally, the effect of storage time of deposited coatings (under normal conditions) on their properties was studied. It was found that the storage effect does not have a significant effect on the wettability of the films.

We propose a 0-D model describing processes in a system comprising an atmospheric pressure DC discharge and aqueous nickel nitrate solution. The model is represented as two coupled subsystems: plasma and solution. Characteristics of the discharge plasma have been determined by jointly solving the Boltzmann equation for electrons; equations of vibrational kinetics for the ground states of N2, O2, NO, H2, and H2O molecules; and equations of chemical kinetics (328 reactions, 34 components). In doing so, use was made of experimentally determined reduced electric field strength and vibrational and gas temperatures. The kinetics of the processes in the solution included 121 reactions and 34 components. The calculation results agree with experimental data on the vibrational temperatures of N2(X) molecules, the kinetics of the decrease in Ni2+ concentration, and the variation in solution pH. We have determined the degree of Ni2+ conversion and the energy yield of conversion and identified the mechanisms that determine the concentration of the major solution components.

The paper presents a novel method for obtaining cobalt ferrites with a spinel type structure under the action of a nonequilibrium atmospheric pressure gas-discharge plasma in air on a mixture of solid iron and cobalt hydroxonitrates. The data of energy dispersive X-ray spectroscopy and X-ray phase analysis showed that the synthesized powders have a complex phase and chemical composition, which depends on the Fe:Co molar ratio in the initial salts. The best result in terms of yield of cobalt ferrite is obtained with Fe:Co = 2:1. The resulting material contains 86 wt ∼ 490 Oe. The saturation magnetization was ∼ 52 emu/g, and the remnant magnetization was ∼ 22 emu/g.

The production of nanosized oxide materials is an important practical problem. This is due to the fact that many of these substances are intensively used as catalysts, microelectronic devices, medical applications, etc. Among the various methods for their production, methods based on the use of gas-discharge plasma are the least studied. But these methods, compared to others, have a number of significant advantages. Among them, the main ones are high process rates and the absence of additional reagents. Therefore, in this work the regularities of the processes of formation of insoluble compounds under the action of a direct current discharge of atmospheric pressure in air on aqueous solutions of cobalt (II) nitrate have been studied. The solutions served as the cathode and anode of the discharge. The discharge was excited by applying a high voltage to two pointed titanium electrodes placed above the liquid anode and liquid cathode in the H-shaped cell. The range of discharge currents was (20-80) mA, and the range of concentrations was (20-60) mmol l-1. It was discovered that when a discharge acts on a liquid anode, a colloidal solution is formed in it, the destruction of which leads to the formation of precipitates. Based on measurements of the kinetics of consumption of Co2+ ions (spectrophotometric method) and the power inputted in the discharge, the rates of this process, effective rate constants, as well as the degree of conversion of Co2+ ions and energy yields of conversion were determined. These parameters depended on the discharge current and the initial concentration of the solution. The values of the constants were similar to(0.2-6) x 10-1 s-1, the energy yields were similar to(0.2-0.5) ions per 100 eV, and the degrees of conversion were similar to(0.1-0.5). The resulting powders were analyzed by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS). The sizes of the powder aggregates were estimated from the results of scanning electron microscopy (SEM), transmission electron microscope (TEM) and Scherrer's relation. It turned out that the resulting precipitates were a mixture of amorphous Co2+ and Co3+ hydroxides. Their calcination in air led, depending on the temperature, to the formation of predominantly cubic either CoO or Co3O4. The size of the aggregates of the calcined samples was similar to 500 nm. The specific surface area of the powders, determined by the Brunauer-Emmett-Teller (BET) method, was similar to 53 m2 g-1. The average pore volume and their size was similar to 17 cm3 g-1 and similar to 240 & Aring;. The advantages of the proposed method over other methods are high process rates (process time similar to 10 min) and the absence of any additional reagents.

The kinetics of decomposition of ibuprofen in its aqueous solution by the action of atmospheric-pressure direct-current discharge in ambient air has been studied. The treated solution served as both the cathode and the anode of the discharge system. Degradation rates and effective degradation rate constants have been determined. Based on these data, the energy yields and degrees of destruction were calculated for various discharge powers (discharge currents). Discharges in a liquid cathode and anode differ little in the energy yields of degradation. But the rates and rate constants of degradation in the liquid cathode are higher than in the liquid anode. Therefore, the complete destruction of ibuprofen in the liquid cathode is achieved within shorter discharge times. A comparison is made of the destruction efficiencies for the cases of solution treatment using glow, dielectric barrier, and pulsed corona discharges.

The kinetics of decomposition of paracetamol in its aqueous solution under the action of a direct current discharge at atmospheric pressure in the ambient air has been studied. The range of studied concentrations of paracetamol was 7-37 mg/l (0.046-0.25 mmol/l). The discharge currents varied from 20 to 50 mA. The decomposition kinetics was determined in the time range of 0-600 s. The concentration of paracetamol was measured spectrophotometrically by absorption at a wavelength of 242 nm (maximum of the absorption band of paracetamol). The solutions were processed for cases when the solution was a liquid cathode and a liquid anode. It is shown that the kinetics of decomposition is described by a formal first-order kinetic equation with respect to the concen-tration of paracetamol. Formal decomposition rate constants were determined, which depended both on the initial concentration of the solution and on the discharge current. The constants increased with an increase in the discharge current and decreased with an increase in the initial concentration. Typical values of the rate constants were in the range of similar to(8 & BULL;10(-2)-8 & BULL;10(-3)) s(-1), and the degree of decomposition reached 100% for some parameters. At a fixed time of plasma exposure, the degree of decomposition was the greater, the lower the initial concentration and the greater the discharge current. Other things being equal, the rate constants of decomposition, the rate and degree of decomposition in the solution that served as the cathode, were higher than the solution that served as the anode. Based on these measurements, the energy characteristics of the decomposition process were calculated. The energy yields of decomposition lie in the range of similar to(0.05-0.019) of decomposed paracetamol molecules per 100 eV of input energy. Despite the higher rates and degrees of decomposition in a discharge with a liquid cathode, due to the difference in the parameters of the discharges, the energy efficiency in a discharge with a liquid anode is higher.

A new method for obtaining ultrafine particles of cobalt ferrites is proposed. This synthesis is a two-step process: the first step is the synthesis of ultrafine particles from aqueous solutions of nitrates under the action of non-equilibrium low-temperature plasma. The second stage is high-temperature treatment of the resulting powders. The action of plasma on solutions of iron and cobalt nitrates leads to the formation of a colloidal suspension at the plasma-solution interface in the liquid anode. The kinetics of co-precipitation from solutions under the action of plasma has been studied. It is shown that the process of formation is complex, includes several stages. The rate of formation of particles directly depends on the concentration of iron nitrate in the initial mixture. An increase in the discharge current leads to an increase in the rate of particle formation. The obtained substances were studied immediately after the plasma-solution interaction, after centrifugation, and after high-temperature treatment. X-ray diffraction analysis showed that the resulting ultrafine particles are a mixture of hydroxonitrites and hydroxides of cobalt and iron. The data of thermogravimetric analysis confirm the data of X-ray diffraction analysis. The surface morphology was studied using a scanning electron microscope; the resulting powders have a well-developed surface. The resulting particles are characterized by two sizes, 92 nm and 1.46 μm. The magnetic characteristics of the particles were studied using a vibrating magnetometer at room temperature with a maximum applied field of up to 30 kOe. The coercive force of the obtained particles was 210 Oe. The saturation magnetization (MS) obtained at room temperature was found to be 65 emu/g and remanent magnetization (Mr) was 22 emu/g.

The kinetics of the formation of hydrogen peroxide (H 2 O 2 ), nitrite ( NO_2^ - ) and nitrate ions ( NO_3^ - ), pH changes in an aqueous liquid anode under the action of a direct current discharge of atmospheric pressure in air were studied. To describe the obtained results and analyze them, a 0-D model of the discharge system was used, which consisted of two submodels. One of them described the discharge, and the other—the solution. The sub-model of the discharge in air was based on the self-consistent solution of the Boltzmann equation, the equations of vibrational kinetics for the ground states of N 2 , O 2 , H 2 , H 2 O, NO molecules, and the equations of chemical kinetics. The electric field strengths, gas and vibrational temperatures required for these calculations were measured experimentally. Based on these calculations, the fluxes of various species arriving at the surface of the solution from the plasma were determined. Solution reactions included 28 components and 119 reactions between them. The results of calculations of the concentrations of NO_2^ - , NO_3^ - , and pH agree with the experiment within the limits of the latter’s accuracy. The data obtained for both calculations and experiments are compared with those previously obtained for a discharge with a liquid cathode at the same discharge parameters. It was found that the concentration of H 2 O 2 in the liquid cathode is two orders of magnitude higher, and the concentration of NO_2^ - ions is two orders of magnitude lower than in the liquid anode. And the concentrations of NO_3^ - ions are close. The action of the discharge on the liquid anode leads to higher pH values compared to the liquid cathode. The differences in concentrations are due to the fact that in a liquid cathode, an essential role in the initiation of chemical reactions is played by the bombardment of the solution surface by positive ions accelerated in the cathode voltage drop. In a liquid anode, this factor is absent. But the reactions associated with electrons coming from the gas phase, which are solvated in solution, become significant. The data obtained explain the different chemical activity of anodic and cathodic solutions in relation to the reduction of some strong inorganic oxidants and the preparation of insoluble metal hydroxo compounds.

The article provides an overview of the results of research of the purification processes of gas and solution media from organic (tetrachloromethane, 1,4-dichlorobenzene and 2,4-di-chlorophenol, etc.) and inorganic (Cr(VI), Mn(VII), Cu2+, Fe2+3+, Zn2+, Cd2+, Ni2+, etc.) substances, as well as the synthesis of oxide materials based on the above metals under the action of a dielectric barrier discharge (DBD) and atmospheric pressure DC discharge. The work was carried out in joint research conducted at the Departments of Industrial Ecology and Microelectronic Devices and Materials of the ISUCT over the past 10 years. As a result of the research, the kinetic regularities of decomposition of the above organic substances were revealed, i.e. the rate and effective rate constants of the decomposition reactions and their dependences on the DBR parameters (power, gas and solution flow rates) were determined. On the basis of these data, the energy efficiency of decomposition processes was found. The main decomposition products and their dependence on the discharge parameters are determined. Probable mechanisms of the ongoing processes were proposed. It is shown that the action of a direct current discharge on aqueous solutions leads to the reduction of Cr(VI) and Mn(VII) in the composition of Cr2O72- and MnO4- to Cr3+ and Mn2+ ions. When the same discharge acts on solutions of salts containing Cu2+, Fe2+3+, Zn2+, Cd2+, Ni2+ ions, the formation of colloidal solutions of hydroxo compounds of these ions is observed. The sizes of resulting particles, their phase and chemical composition were determined by DLS, SEM, EDX, TGA, XRD, DSC methods. It is shown that the calcination of the obtained particles leads to the formation of crystalline oxides of the corresponding metals. Thus, the action of the discharge ensures the purification of aqueous solutions from heavy metals with the formation of oxide materials of the nanoscale range, which have semiconductor and catalytic properties. For citation: Guschin A.A., Grinevich V.I., Kvitkova E.Yu., Gusev G.I., Shutov D.A., Ivanov A.N., Manukyan A.S., Rybkin V.V. Gas discharges as a tool for cleaning gas and solution mediums and synthesis of inorganic materials. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 7. P. 120-131. DOI: 10.6060/ivkkt.20236607. 6835j.

In this paper, we consider the preparation of some double oxides of transition metals, namely (ZnO)0.92 (CdO)0.08, NiOCuO, NiOCo2O, CoFe2O4, NiFe2O4, ZnFe2O4. The synthesis of bimetallic oxide compounds occurred in two stages. First, plasma-solution synthesis of ultrafine particles from solutions of a mixture of nitrates under the action of a DC glow discharge. The second was the high-temperature treatment of the resulting hydroxonitrates and hydroxides. The kinetics of the formation of the solid phase in the solution had an induction period associated with the accumulation of active particles in the solution under the action of the plasma and the change in the intensity of the light transmitted through the solution during the plasma treatment has an exponential decreasing character. The characteristic times of solid phase formation obtained from these dependences decrease with increasing discharge current. As a result of hydrolysis-like processes, hydroxides and hydroxonitrates of the corresponding metals were formed in the solution. This was confirmed by the XRD and EDS data. According to the data of a SEM and DLS, the particles obtained were characterized by two sizes: one was about 100 nm and the other was about 1.5 μm.

The paper describes the formation of a solid phase in aqueous solutions of potassium permanganate under the action of a direct current discharge in air above the liquid phase at atmospheric pressure. The discharge current was 40 mA (the total input power was 6 W). The discharge was ignited in the system without contact of the electrodes with the liquid phase. Assumptions were made about considerable difference between the mechanisms of reactions induced by the discharge and reactions that take place in solutions of transition metal salts under the same conditions. The obtained solid product was investigated by X-ray diffraction analysis and thermogravimetric analysis and by scanning electron microscopy.

In this work, the process of formation of insoluble zinc and cadmium compounds, initiated by the action of a direct current discharge of atmospheric pressure in air on an aqueous solution of zinc and cadmium nitrates, has been investigated. It was found that when the solution is the anode, the action of the discharge leads to the formation of a colloidal solution of zinc and cadmium hydroxynitrates and hydroxides of white color. The kinetics of the formation of colloidal particles was investigated by the turbidimetric method. It turned out that the rate of formation increases with an increase in the discharge current from 30 to 70 mA. At concentrations of zinc and cadmium nitrates 50 mmol/l the rate constant of the process increases from 1.3.10(-3) to 12.10(-3) s(-1). When this solution is destroyed a precipitate of the corresponding compounds is formed. X-ray analysis showed that the precipitate particles have a crystalline structure. The sediment particles, as shown by SEM, have a spheroidal shape with a characteristic size of about 1 mu m. Thermal decomposition of the resulting precipitate proceeds in several stages and ends at a temperature of similar to 300 degrees C. As a result of calcination, a mixture of crystalline zinc and cadmium oxides is formed According to EDX data, at a molar ratio of 1:1 of zinc and cadmium in the initial solution, the obtained solid particles contain 8 mol.% cadmium and 92% zinc.

The solution of the fundamental problem of the physicochemical interaction of plasma with solutions of transition metal salts has practical applications in the field of creating new materials and purifying water from heavy metal ions. Plasma-solution synthesis has established itself as a simple and effective method for obtaining ultrafine materials with new properties. The formation of precipitation under the action of atmospheric pressure glow discharge on an iron and cobalt nitrates solution, which was the anode, was studied. It turned out that the rate of formation increases with an increase in the discharge current from 30 to 70 mA. In the course of work, the concentrations of nitrates were varied. The concentrations were chosen in such a way that the final product was stoichiometric Fe2O3·CoO. The result of the study of kinetic regularities indicates that the sedimentation of the solid phase from nitrate solutions occurs in two stages. The first is the precipitation of particles containing iron anions; the second capture is the precipitation of cobalt-containing particles.

The kinetics of the formation of hydrogen peroxide, nitrate and nitrite ions and the pH of the solution, which served as the cathode, were studied under the action of a direct current discharge at atmospheric pressure in air. A 0D kinetic model has been developed that describes the reactions occurring in solution. The model includes 28 components, 119 reactions between them, as well as fluxes of particles coming to the surface of the solution from the discharge. The particle fluxes were determined from the 0D model of a discharge in air based on the self-consistent solution of the Boltzmann equation, the equations of vibrational kinetics for the ground states of N 2 , O 2 , H 2 O, NO molecules, and the equations of chemical kinetics. The proposed model is semi-empirical, since it includes not only known experimental kinetic data, but also some assumptions that were made to match the calculation results with experiment. An analysis of the experimental data and calculations by the model showed that the main factors initiating reactions in solution are the bombardment of the surface by a flux of positive ions accelerated in the cathode potential drop and the flux of NO molecules from the discharge. Ion bombardment leads to the formation of hydrogen peroxide, during the decomposition of which OH radicals are formed, the subsequent reactions of which determine the composition of the particles of the solution. The source of nitrogen-containing particles is the flux of NO molecules from the discharge. Data are given on the kinetics of the concentrations of the main particles of the solution and the analysis of the mechanisms of the processes of their formation and decay. The results of calculations of the concentrations of H 2 O 2 , NO 2 − , NO 3 − , and pH agree with the experiment within the limits of the latter’s accuracy.

In this paper we present the results on the synthesis of nickel-containing particles from solutions of nickel nitrate under the action of a DC glow discharge at atmospheric pressure in air. The interaction of the plasma with the solution leads to the formation of a colloidal suspension in the anode part of the cell, followed by the formation of agglomerates and precipitation to the bottom of the cell. The composition and surface structure of the resulting powders were studied using scanning electron microscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction analysis, X-ray energy -dis-persive spectroscopy, and thermogravimetric analysis. According to the results of dynamic light scattering, particles in solution have two characteristic sizes of the order of 73.5 nm and 1.2 mu m. Images obtained on a scanning electron microscope showed that the resulting powders have a well -developed granular structure. X-ray phase analysis of the obtained samples showed the presence of clearly defined reflections, which indicate the crystallinity of the structure of the synthesized powder. Decoding showed that it is beta-type nickel hydroxide. The elemental composition of the sur-face obtained using X-ray energy-dispersive spectroscopy showed the presence of nitrogen in the sample. Therefore, the powders have a complex composition and are a mixture of hydroxide and hydroxonitrate with a ratio of 0.8 Ni(OH)2 : 0.2 Ni(OH)NO3. Thermogravimetric analysis confirms the data obtained using X-ray energy dispersive spectroscopy. High-temperature treatment of the obtained powders leads to the formation of beta-type nickel oxide. The specific surface area (Ssp) was calculated using the Brunauer-Emmett-Teller method from the adsorption branch in the range of relative pressures of 0.05-0.20; the total pore volume (Vp) and pore size distribution were calcu-lated from the desorption branch in the range of 0.40-0.99.

The formation of precipitation under the action of a direct current atmospheric pressure discharge in air on a copper (II) nitrate solution was investigated. The discharge was excited by applying a high voltage to two pointed titanium electrodes placed above the liquid anode and liquid cathode in the H-shaped cell. The one of the advantages of such design is the absence of the contact of the electrodes and liquid phase that can affect on the precipitation composition. The studies were carried out at initial concentrations of 0.005 and 0.1 mol·L−1 of Cu(NO3)2 and discharge currents from 30 to 70 mA. Under the discharge action of the discharge, the formation of colloidal solutions occurs only in the anode part of the discharge. Turbidimetry kinetic measurements showed that the process includes two stages. In the first stage (slow), insoluble copper compounds are formed, the coagulation of which and an increase in concentration leads to the second stage (fast). When the precipitate is calcined, crystalline monoclinic CuO is formed. The size of the aggregates of the sediment particles was less than 1 μm. It is assumed that the process is initiated by solvated electrons generated in the anodic part of the discharge. Their reactions with water molecules lead to the formation of hydroxide ions. These ions, reacting with copper ions, lead to the formation of their insoluble hydroxo compounds.

The process of formation of insoluble iron compounds, initiated by the action of a direct current discharge of atmospheric pressure in air on an aqueous solution of iron (III) sulfate, has been investigated. It was found that when the solution is the anode, the action of the discharge leads to the formation of a colloidal solution of iron hydroxosulfates and iron hydroxide. The colloidal solution, as shown by the DLS method, consists of two fractions 47 nm (73%) and 950 nm in size. The kinetics of the formation of colloidal particles was investigated by the turbodimetric method. It turned out that the rate of formation increases with an increase in the discharge current from 30 to 70 mA. At concentrations of iron (III) sulfate 5 mmol/l the rate constant of the process increases from 7.10(-3) to 2.2.10(-2) s(-1). When this solution is destroyed, a precipitate of the corresponding compounds is formed. X-ray analysis showed that the precipitate is amorphous. The resulting precipitate, as shown by SEM, has a dense structure. The particle size is 100 nm on average. As a result of calcining the precipitate, as shown by X-ray analysis and EDX, it turns into crystalline iron (III) oxide of the trigonal system (hematite). The resulting oxide powder has a developed surface, with a particle size of less than 50 nm on average.

The paper proposes a new method for the synthesis of powders containing transition metals using a plasma-solution system. The reactor was an H-shaped glass cell, the two parts of which were separated by a cellophane membrane. A discharge consisting of two discharges - with a liquid cathode and a liquid anode - a high voltage is applied to titanium electrodes located above the surface of the solution. Aqueous solutions of zinc, iron, cadmium, cobalt, nickel, and copper nitrates were used as the liquid phase. Under the action of the discharge on the liquid anode, in the region of contact of the discharge with the solution the formation of a colloidal suspension was observed. The kinetics of the process of synthesis of solid-phase particles in solution under the action of a discharge have been studied. The chemical composition and morphology of the formed solid phase have been established. The mechanisms of chemical reactions occurring in the solution under the action of plasma, and the mechanisms of formation of transition metal oxides in the process of calcining the synthesized powders have been proposed.

The results of experimental study of the electrical and physical parameter of the gas discharge in air under the solutions of the two types of surfactants are given. The discharge was ignited between metal needle anode and liquid cathode. As the cathode the solutions of anionic surfactant C12H25SO4Na (SLS) and cationic surfactant C12H46ClN, (AOTC) were used. In the concentration range of 5·10-3-10 g/L and discharge current range of 20-100 mA the phenomenology of discharge was studied, the current densities and inputted power, cathode voltage drops, vibrational temperatures of N2(C3Πu), gas temperatures were obtained and reduced electric field strength was calculated. It was show that increase of the SLS concentration leads to the change in the discharge color due to transfer of Na atoms from liquid to the gas phase. In the same time there are no any new emission lines or band for the AOTC solutions were obtained. It was established that for cationic surfactants the cathode voltage drop is lower than for anionic surfactant. The gas temperatures and vibrational temperatures don’t depend on solution type. Reduced electric field is in the range of 10-15 Td and the increase of the concentration leads to decrease of the E/N. The increase of the discharge current results in the growth of reduced electric field.