Theoretical Foundations of Chemical Engineering最新文献

Abtract—The possibility was shown of using a thin-film rotary apparatus for the preparation of dry precursor salts in the form of ammonium uranyl nitrate and uranyl formate containing up to 5 wt % low-background plutonium. Dioxide powders obtained after the thermal decomposition and reduction of the salts are represented by a solid solution (U_0.95Pu_0.05)O₂ in both cases. Based on the analysis of the amounts of secondary radioactive waste (RAW), specific surface areas of powders, and particle shapes, it was decided to continue elaboration of the process using highly active uranium-plutonium solutions and formic acid.

A comparative analysis was made of the effect of high-density polyethylene (HDPE) and ultra-high-molecular-weight polyethylene (UHMWPE) on the vulcanization characteristics of rubber mixtures and the physicomechanical properties of vulcanizates based on BNKS-18AMN nitrile butadiene rubber. It was shown that the introduction of 10 pts wt HDPE has a reinforcing effect, but reduces the degree of crosslinking of vulcanizates and abrasion resistance. In comparison with HDPE, the introduction of 10 pts wt UHMWPE does not have a reinforcing effect, but on the contrary leads to a decrease in physicomechanical properties in tension, but at the same time increases the wear resistance and frost resistance of the samples.

Abstract—Information is provided on the synthesis of mono-azo compounds with 60–97% yields by the azo coupling reaction of 2-methylresorcinol with aryldiazonium salts of various structures. The synthesized mono-azo compounds are tested as acid and disperse dyes for dyeing of textile materials made of polycaproamide fibers. The results of research of color fastness to washing, sweat, and light show good operational properties of coloring. Conclusions on the dependence of color fastness on the structure of the studied azo compounds are made.

The effect of Tb³⁺ and Bi³⁺ sensitizing ions on the spectral luminescent characteristics of the Eu³⁺ activating ion in lanthanum ortho- and metaborates is studied. The compounds are studied by X-ray diffraction and luminescent spectroscopy. The doping of La_{1 – x}Eu_хBO₃ and La_{1 – x}Eu_х(BO₂)₃ (х = 0.025; 0.05; 0.075; 0.10) with ions Tb³⁺ and Tb³⁺ in combination with Bi₃ is found to enlarge the range of luminescence in the visible region. Moreover, due to energy transfer from Bi³⁺ to Eu³⁺ in lanthanum orthoborates, the integral luminescence intensity (λ_ex ~ 615 nm) grows by ~25% as compared to the samples free from Bi³⁺ (optimal Bi³⁺ concentration is 5 mol %).

A method for processing perlite with a 20% caustic soda solution at a temperature of 108°C was developed. The work was aimed at studying the processing of perlite at low temperatures, without autoclaving, without sintering, and with the extraction of a significant amount of useful components: aluminum oxide and silicon oxide with the production of sodium metasilicate nanohydrate, aluminosilicates of various metals, and crystalline SiO₂.

A method for synthesizing magnetic polymer microspheres with carboxyl groups on the surface is proposed. In an aqueous medium, magnetic microspheres form stable colloidal dispersions with an average hydrodynamic particle diameter of 110–170 nm and a negative surface charge. When dispersed in an aqueous–organic mixture, the microspheres remain resistant to aggregation. Microspheres can be extracted from the dispersion using an external magnetic field. Magnetic microspheres can be used as supports for heterogeneous catalysts operating in organic media.

The results of studies on the inhibition of uncontrolled side reactions during the synthesis of epoxyacrylate oligomer from epoxydiane resin ED-20 and acrylic acid are presented. The factors governing the esterification of ED-20 with acrylic acid were studied. The efficiency of using p-methoxyphenol as an inhibitor of side reactions during the synthesis of epoxyacrylate oligomer was examined, and its optimum amount was determined.

The behavior of actinium-227 and actinium-228 in the life cycle of monazite processing is considered. The recommended system for separation of actinium-227 and actinium-228 is 90–100% TBP–300–350 g/dm³ of Ln(NO₃)₃–0.1–0.5 mol/dm³ of HNO₃. The process is combined: actinium-227 and actinium-228 are removed simultaneously with purification from rare earth impurities, iron, aluminum, calcium, and phosphate ions occurs. If monazite does not contain uranium, it is recommended to hold the rare earth concentrate (solution or carbonates) after separation of thorium for 1–2 days. A process flow chart for separation of the sum of REEs isolated from monazite is proposed, with production of didymium, lanthanum–cerium concentrate, and yttrium REE concentrate.

The dissolution of quartz during the hydrometallurgical desilication of silica–titanium concentrates from Pizhemskoe field (Komi Republic) was studied. The concentrate desilication occurs in the CaO–SiO₂–Na₂O–H₂O system due to the binding of silica into calcium silicate hydrate, in particular, into CaO·SiO₂·nH₂O. The main factors (temperature, duration, CaO : SiO₂ ratio, NaOH content) governing the extent of concentrate desilication and crystallization of wollastonite from calcium silicate hydrates resulting from the reaction were determined.