Vol 59, No 1 (2025)

Protective coating with microtubular structure was formed by plasma electrolytic oxidation on aluminum alloy AMg3 (Al–Mg system) in tartrate-fluoride electrolyte. This protective layer was additionally modified using azole group corrosion inhibitors (1,2,4-triazole, benzotriazole) and polymer (polyvinylidene fluoride). The morphology, composition, corrosion mechanism and protective properties of the formed coatings were studied.

At present, there is a growing interest in the study of possible applications of plasma discharge water treatment technology in various industrial fields. The equipment considered in this work is based on the combined effect on water of plasma discharge and cavitation in flowing mode. The optimal design of the installation was determined. Many authors note the possibility of regulating the growth and development of plants of various crops as one of the promising applications of this technology. Previously, physicochemical processes occurring in water during plasma discharge treatment have been investigated, and the formation of reactive oxygen species (ROS), including hydrogen peroxide, in treated water has been noted. ROSs are actively involved in regulation of plant growth and development. Adjustment of the power of electric pulses supplied to the reactor of the plant allows controlling the generation of hydrogen peroxide. The aim of the work was to determine the most effective mode of water treatment to regulate the growth of lettuce variety “Tuscan” of the genus Lettuce of the Aster family (Lactuca sativa L.). When watering lettuce with water treated in the most effective mode, the dry weight of lettuce increased more than 2 times, and the ascorbic acid content increased by 40%.

The pattern of diffusion front propagation in pure agarose hydrogels as well as with the addition of graphene oxide was compared by the methods of moving boundaries and optical sensing, and the mass-transfer properties of the gel systems were measured. It was found that graphene oxide has high surface activity, becomes part of the mesh structure of the gel, increasing its porosity and thus aÿecting the diÿusion rate and eåciency. In addition, graphene oxide contributes to the ordering of the gel structure or reduces light scattering within the gel. The combination of hydrogels with graphene oxide enables the creation of systems with controllable optical properties, which in turn opens up new opportunities for improving 3D-bioprinting technologies. Based on the random walk method, a numerical model is proposed that is well suited to describe the structures of hydrogels with graphene oxide. This model will help to determine the quality of materials in 3D-bioprinting technologies in terms of nutrient delivery eåciency for living microorganisms located inside the gel. The comparison of experimental data and numerical modeling demonstrated a good agreement between them.

Ethane dehydrogenation is one of the most important processes for ethylene production. The main regularities of this process have been studied in a membrane reactor with an industrial alumina-chromium catalyst and a Pd-6%Ru palladium alloy foil. The working part of the reactor consists of two cylindrical chambers separated by a membrane partition. The upper chamber is vacuumed and the lower chamber is kept at atmospheric pressure. It is known that hydrogen additives at the inlet prevent the formation of carbon deposits on the catalyst, so in this work the effect of these additives on the process was investigated. With uniform feedstock supply (ethane and hydrogen) along the outer perimeter of the lower chamber, the problem is reduced to finding the fluxes of ethane, ethylene, hydrogen and methane from the solution of a system of nonlinear ordinary differential equations. The temperature interval 600 K < T < 1000 K at small values of hydrogen and ethane flux ratios at the inlet is considered. The conditions under which hydrogen yield and ethane conversion reach 100% at maximum flux H2 through the membrane are found. Calculations are compared with experimental data.

In the development of methods for the efficient extraction and concentration of rare earth elements (REE), as well as for the removal of impurities of related metals, the solubility of salts, in particular sulfates, often used in hydrometallurgy as intermediates, is of great importance. In this work, the precipitation of complex potassium scandium sulfate KSc(SO₄)₂, whose crystals are elongated hexagonal prisms 5–10 μm wide and 20–50 μm long, was proposed for the extraction of scandium from sulfate solutions. The absence of crystallization water and the presence of a reversible phase transition around 447°C are shown by DTA method. The solubility of KSc(SO₄)₂ in water at 25°C was 0.28±0.01 wt.% Sc. A decrease in the solubility of KSc(SO₄)₂ was achieved by increasing the concentration of sulfuric acid (H₂SO₄) over 3–4 mol/L. Additional introduction of 0.5 mol/L K₂SO₄ reduces the solubility of scandium as a complex compound by an order of magnitude and increases the efficiency of scandium extraction from sulfate solutions. Experimental results on the solubility of KSc(SO₄)₂ are described by the change in the ionic strength of the solution in the presence of homonymous ions (K⁺ and HSO₄^–). The degree of scandium extraction from sulfate solutions with the addition of 0.5 mol/L K₂SO₄ is more than 99%. The principal technological scheme of scandium extraction from red slimes with crystallization of KSc(SO₄)₂ is proposed. The results will be useful for the development of methods of metal separation at sulfuric acid processing of raw materials and expansion of methods for obtaining concentrates and pure metal oxides, as well as for studying the behavior of REE compounds close in properties.

This paper proposes a method for optimizing a two-stream heat exchange system, taking into account the technical limitations imposed by the heat exchange equipment and cost-effectiveness of the reconstruction project. Optimization of the heat exchanger network is performed taking into account the need for industrial safety expertise in case the design temperatures for the heat exchangers are exceeded by the process flows. This method was applied to optimize energy consumption at a real hydrocracking unit. Two types of heat exchangers were considered – shell-and-tube and plate heat exchangers for possible increase of heat exchange surface area in the existing heat recovery system. For shell-and-tube heat exchangers, the minimum present value of the reconstruction project is observed when the heat exchange surface is increased by 500 m², which corresponds to the installation of a two-section heat exchanger. It allows to reduce specific consumption of hot utilities by 51%, and cold utilities – by 31%. However, the simple payback period of such a project is ~ 1.5 years. At the same time for plate heat exchangers the minimum annual costs are observed when the heat exchange surface is increased by 400 m². The cost of such a modernization project is 18% less than for shell-and-tube heat exchangers, and the reduction of specific consumption of hot and cold utilities is 66% and 40%, respectively.