Theoretical Foundations of Chemical Engineering最新文献

The work studied the UV–visible transparency of oxide films of ZrO₂, CuO, TiO₂, Y₂O₃, ZnO, and NiO of various thicknesses on quartz glass, which were obtained by the extraction–pyrolytic method at a pyrolysis temperature of 500°C and a crystallization temperature of 700°C. The results of studying the optical properties of the produced samples showed the possibility of obtaining coatings that provide both a decrease and an increase in transparency in various regions of the UV radiation.

Abstract—Aerobic oxidation of organosulfur compounds of petroleum origin by atmospheric oxygen was performed using a heterogeneous catalyst in the form of Fe₃O₄ nanoparticles. By studying the oxidation of model mixtures (a solution of dibenzothiophene in decalin), the following conditions for the complete oxidation of dibenzothiophene were selected: catalyst weight, 1 mg; temperature 130°C; and time, 180 min. The catalyst remains active throughout five oxidation cycles. Physicochemical studies showed that the phase composition and structure of the catalyst persist after the regeneration stage.

The extraction of molybdenum from a multicomponent nitric acid productive solution with various values of the redox potential using extractant CYANEX®600 (Solvay company) and diluent Elixore 205 (Total company) is studied. Extraction curves are constructed and the process of molybdenum extraction from nitrate leaching solutions is simulated using the Minchem software package from Solvay. The number of extraction stages necessary to achieve an extraction efficiency of more than 95% is selected, which is found to be equal to two stages with phase ratios (Org/Aq) of 1.5 : 1 and 1 : 1 for an extractant concentration of 25%. It is established that the degree of extraction of molybdenum at the extraction stages with reduced values of the redox potential of the productive solution increases from 68.64 to 97.36%.

A brief review was made of literature data on the extraction of carboxylic acids with binary extractants and hydrophobic bifunctional ionic liquids. It was noted that the carboxylic acids in systems with these extractants are distributed mainly by ion pairing and hydrogen bonding. An important advantage of these extraction systems is the ability to effectively recover carboxylic acids from dilute aqueous solutions. An analysis of literature data showed the promise of using binary extractants and hydrophobic bifunctional ionic liquids for the recovery and separation of carboxylic acids.

Using the method of solid-phase reaction of AlCl₃·6H₂O and MgCl₂·6H₂O with (NH₄)₂CO₃ at room temperature, a Mg–Al layered hydroxide with composition Mg₄Al₂(OH)₁₂CO₃·3.85H₂O with the structure of hydrotalcite is obtained. The results of determining the effect of rehydration conditions on the structural and surface properties of layered reduced double hydroxides (LDHs) of magnesium and aluminum are described. It is shown that the samples obtained by reduction of thermally treated initial Mg–Al LDH for 2 h (regardless of the pH of the medium) have specific surface-area parameters (both total area and outer surface area) that are not different from those of the initial LDH sample, and their specific pore volume increases by a factor of 1.3–1.5 (from 0.121 to 0.159–0.183 cm³/g). It is established that the pH of the isoionic point of the rehydrated Mg–Al LDH samples depends only slightly on the rehydration conditions and equals 9.7 ± 9%, which suggests a high sorption capacity of both synthesized and rehydrated Mg–Al LDH samples with respect to nonferrous metal ions.

A biocompatible protective coating is formed by plasma electrolytic oxidation (PEO) on the bioresorbable Mg–0.8Ca magnesium alloy. The electrochemical properties and bioresorption mechanism are established for the material, suggesting a model for the process of biodegradation in the alloy with a hydroxyapatite-containing PEO coating in the cultivation medium of mammalian cells.

The structural features of halide varieties in an analogous series of double compounds of aluminum and lithium are studied. The possibility of transition of a bromine-containing version of the double compound of aluminum and bromine into a lithium concentrate is shown. Methods are found for preparing a lithium concentrate without bromine admixture. After bromine is industrially removed, the resulting lithium concentrate is used to obtain the following lithium products: lithium carbonate and lithium hydroxide monohydrate. In an integrated scheme, magnesium hydroxide after separating bromine and lithium products is precipitated to produce a calcium chloride solution.

Abstract—The chemical compounds formed during the dissolution of the products of gas-phase conversion of the Tokem-308 cationite (analog of KU-2x8) in an HNO₃(vapor)–air atmosphere, obtained by vaporization of 12 M HNO₃, in H₂O and 0.045 and 0.5 M NaOH solutions were studied. Ozonation of the alkaline solutions of the products was studied for utilization of the latter. The sequence of procedures including gas-phase treatment in the HNO₃(vapor)–air atmosphere and dissolution in NaOH followed by ozonation makes it possible to obtain alkaline solutions almost without any toxic aromatic impurities, due to which the solutions are suitable for safe disposal.

Replacing gas-mask filters based on the workers’ subjective assessment of the smell of gas in the mask has proven to be unreliable and is not practiced in developed countries. To prevent acute poisoning and chronic occupational diseases, it is necessary to determine the service life of filters and replace them on a schedule. Lifetime sensors (ESLI) have not become widespread.