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.

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.

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 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 kinetics of the processes of simultaneous reduction of Cr(VI) and degradation of phenol during the treatment of their aqueous solutions with different initial concentrations using an atmosphericpressure air direct-current discharge have been studied. The solution served as the discharge cathode. It has been shown that the discharge treatment leads to a decrease in the concentration of both Cr(VI) and phenol. Phenol additives accelerate the Cr(VI) reduction process and make it irreversible. The phenol degradation and Cr(VI) reduction kinetics are described well (R2 > 0.99) by the pseudo-first-order rate equation in phenol and Cr(VI) concentrations, respectively. The apparent rate constants of the processes have been determined, the energy efficiency of the processes has been evaluated, and possible mechanisms of the proceeding reactions have been discussed.

A new method is proposed for the synthesis of powdered zinc oxide with the use of a plasma–solution system. The chemical and phase compositions and the morphology of the synthesized powders have been determined. It has been found that the calcination of powders obtained in the plasma–solution system leads to the formation of ZnO.