Theoretical Foundations of Chemical Engineering最新文献

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 chemical composition of a sample of anorthosite from the Kotozero deposit (Karelia, Russia) was determined by inductively coupled plasma atomic emission spectroscopy. The mineral composition of the sample was calculated by physicochemical modeling and confirmed by X-ray powder diffraction analysis. Methods for using this rock were proposed.

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.

The synthesis of a new adsorbent based on Tebinbulok vermiculite modified with Apis mellifera chitosan for cleaning textile wastewater from indigo dye is described, and a technology for organovermiculite and modified vermiculite with hydrochloric acid is developed.

The studied object is a more than hundred-year-old ceramic material taken from a distillery in the village of Rozhdestveno, Samara oblast. The elemental chemical composition of the studied material shows an increased carbon content (C = 9.48 wt %), which is indicative of the introduction of fuel into the raw brick. The pressing of fuel into the raw brick allows one to carry out the firing process without fuel losses, since the chemical reaction of carbon with oxygen, steam, carbon dioxide, and clay oxides occurs intensively at temperatures of 800°C and above, while a reducing medium is formed inside the product, which helps to increase the mechanical strength of the baked shard. In addition, CO burns out on the surface of the material, which intensifies the baking. The diffusion of oxygen into the bulk of the product promotes carbon burnout and accelerates baking. Clay minerals do not melt when heated to 1000°C, but the increased content of alkali oxides (R₂O = 3.78 wt %) promotes the formation of mixtures with a melting point of 950°C. The liquid phase, even in small quantities, plays a very important role in increasing the sintering of the shard, effectively gluing the mineral particles of the ceramic mass into a single entity. The increased contents of the oxides of calcium (CaO = 9.42 wt %), magnesium (MgO = 2.875 wt %), and aluminum (Al₂O₃ = 18.45 wt %) in the test sample contribute to the formation of anorthite and diopside, which increase the strength of the products.