Fine Chemical Technologies

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Vol 13, No 6 (2018)
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5-27 477
One of the harmful factors of the interaction of microorganisms with the technosphere is the formation of biofilms on the surface of various products. Steady colonies of bacteria ensure a stable contamination of the handling medium of the product, and their release is a cause of biodestructive processes in materials. In many cases, single or even regular antimicrobial treatment does not lead to complete suppression of colony formation. Therefore, today the most demanded methods of preventing biofilms formation involve the creation of materials that are resistant to colonization by bacteria. Since bacteria cells directly interact with the surface of the material, it is the surface that should have antibacterial properties. In the review, various methods of preventing the formation of biofilms by the example of polymeric materials are considered. The main attention is paid to the methods of creating antibacterial surfaces, which in various ways prevent the formation of biofilms. In accordance with the world practice, all antibacterial surfaces are divided into four types: releasing, contact-active, repelling and self-polishing. The advantages and disadvantages of each type of antibacterial surfaces, their existing limitations in use and prospects for further development are noted. Information on the compatibility of individual types of surfaces is also noted in the literature.
28-34 319
A new hydrophobizator - tetra(ethoxy)di(octyl)disiloxane (TEDODS) - was synthesized in an ethanol solution at boiling point for 6 hours and characterized by NMR and IR spectroscopy. New hydrophobic coatings based on this compound were obtained under mild conditions by direct chemical modification of the surfaces of the cellulose materials (textile of different composition). The formation of a modified layer on the materials surface occurs due to the interaction of the ethoxy groups of the modifier and the hydroxyl groups of cellulose followed by heat treatment to fix it on the materials surface. The optimal conditions for obtaining the coatings were determined: 8% TEDODS weight gain with maximum hydrophobicity, with a wetting angle of 135°. The properties of the modified cellulose materials were studied (hydrophobicity, moisture absorption, etc.). The efficiency of using tetraethoxydioctyldisiloxane as a hydrophobizator when the content from 1% and a relatively small thickness of the coating of 2 microns was shown. It was found that hydrophobic coatings on the surface of cellulosic materials have little effect on moisture absorption and breathability of the original tissue.
35-41 374
Currently, halogen-free cable compositions are becoming increasingly common in the manufacture of cable compositions. The concept of halogen-free or “zero halogen” becomes a symbol of fire resistance, low-smoke characteristics, low toxicity of volatile products of combustion, the absence of the toxic, corrosive and irritating gas - hydrogen chloride - and other hydrogen halides in the volatile products. More and more manufacturers of cable products are beginning to pay increasing attention to the problems of processing, toxicity and fire safety. It should be noted that the requirements for improving the fire safety of cable products are constantly becoming tougher, since the main problem of most of these polymeric materials is their flammability, high smoke generation and high flame spread rate. In this regard, there is a burning question to increase these characteristics and bring them to the level of compounds based on PVC. The main way to increase the flame-retardant characteristics of halogenfree cable compositions is to introduce mineral fire retardants into these compositions. The study of the composition and packaging of these mineral fillers-flame retardants makes it possible to increase the level of flame-retardant characteristics of halogen-free cable compositions. The paper presents the results of studies on the thermal stability of cable compositions based on PE + EVA mixtures containing magnesium hydroxide crystalline hydrate as a filler-flame retardant. It is shown that cable compositions containing magnesium hydroxide crystal hydrate are characterized by higher heat resistance and thermal stability (~ 2-fold) compared to a polymeric matrix based on PE + SEVA. This allows to process them at high temperatures (more than 200°C) by extrusion and pressure casting.


42-51 319
The literature data on the composition and structure of rare-earth borate compounds of the huntite family with the general composition LnM3(BO3)4, where Ln3+ = Y, La = Lu and M3+ = Al, Fe, Cr, Ga, Sc as well as a number of solid solutions with М3+ = Sc are systematized. The difference between the real compositions of crystals and the compositions of the initial mixture, the most characteristic of rare-earth scandium borates, is shown. The significant role of the composition in the manifestation of the compounds symmetry is established. The necessity of determining the crystals symmetry only on single-crystals with detailed analysis of diffraction reflections is proved. Morphotropic series were selected depending on changes in the ionic radii of Ln and M. Attention is paid to the peculiarity of the structural behavior of Cr3+ ions. It was revealed that the formation of solid solutions and internal solid solutions is most likely for rare-earth scandium borates. The implementation of polytypic modifications for LnM3(BO3)4, where M3+ = Al, Cr, and polymorphs for a number of Ln ions with M3+ = Fe, the existence of which is not excluded for M3+ = Sc, is demonstrated. Crystal-chemical effects observed for huntite-like crystals (morphotropy, isomorphism, polymorphism, polytypy; internal solid solutions; phase order-disorder phase transitions of different nature) with specific features of scandium borates are presented. The realization of polymorphism and polytypism for compounds of the huntite family confirms the crystal-chemical situation, according to which hightemperature polymorphic modifications should form more symmetrical compounds, but it is not typical of polytypic modifications.
52-59 349
The primary objective of the study was to test the possibility of cesium-137 transmutation into a stable barium isotope in contact with an aerobic syntrophic association (SA - a conglomerate of several thousands of different species of bacteria, protozoa and fungi living in symbiosis with each other) together with a set of macro- and microelements. The study was performed sequentially on two different SA. In the course of the work, the transmutation of cesium-137 into stable barium with the use of SA was not experimentally revealed, but the phenomenon of cesium-137 biosorption by both SA was detected to different degrees. In the course of the experiment the possibility of cesium-137 sorption by SA from the solution in the pH range of 7.7 - 8.6 was shown. In the process of the work, the time dependence of cesium-137 distribution in the liquid phase and the phase of SA was determined. The time dependence of the sorption capacity of the syntrophic association was revealed. With further continuation of the study, it is possible to obtain a mixture of SA capable of selectively extracting and concentrating prescribed radionuclides from the liquid phase.The result of this work may be the development of a technology for processing and conditioning low-level liquid radioactive waste (RW) by transferring the bulk of radioisotopes in the phase of SA (the so-called "nanosorbent of biological origin"), with multiple volume reduction.The cost of such a technology compared to existing technologies using synthetic sorbents should be several times less due to the cheapness of the SA and the reagents required for it. Besides, the new technology is more environmentally friendly. The process of biotechnologyoxidation of sulfide ores and concentrates based on the activity of chemolitotrophic bacteria that translate insoluble metal sulfides into soluble metal sulfates can serve as analogue for hardware design of RW purification technology using nanosorbent of biological origin.
60-68 318
The interaction of CuCl and 2-(phenyl-4-chlorophenylacetyl)indandione-1,3 (HL, C23H15ClO3) in a mixed organic solvent (CH3CN, C5H5N, EtOH) gave a solvated crystal complex of copper(II) of composition [Cu(C2H5OH)(L)2]•C2H5OH (I). The isolated compound was investigated by X-ray and IR spectroscopy methods. Lattice parameters of (I): space gr. P21/c, a = 14.982(1), b = 14.558(1), с = 20.608(2) Å; β= 105.176(2)°; Z = 4 (Z′=1). It is established that the structural units in the crystal structure of the obtained compounds are the neutral square-planar coordination spheres of Cu(II) with cis-oriented deprotonated indandionate ligands L. The spheres are located in the space pairwise. One molecule of EtOH is included in the internal sphere of the complex, and the second is a bridge that unites the coordination centers due to the hydrogen bonds between the hydrogen atom of the hydroxo group of the coordinated alcohol and the O-atom of the keto group of the adjacent bis-chelate. This results in a dimer structure. At the same time, in addition to ethanol, molecules of other co-solvents (CH3CN, C5H5N) do not participate in complex formation and do not form solvates. It was found that a copper(II) complex is formed from copper(I) chloride. When using copper(I) iodide as a starting compound in ethanol in the presence of pyridine the formation of the chelate with the deprotonated ligand HL is not observed.
69-78 260
The article is devoted to the substantiation of the proposed technological scheme of electrochemical processing of rhenium-containing heat-resistant alloy ZhS32-VI of composition (mass %): Re - 4.0; Co - 9.3; W - 8.6; Y - 0.005; Lа - 0.005; Al - 6.0; Cr - 5.0; Tа - 4.0; Nb - 1.6; Mо - 1.1; С - 0.16; B - 0.15; Cе - 0.025, Ni - 60.05 to obtain nickel-containing cathode deposits. The results of studying the composition, surface morphology and granulometric analysis of cathodic precipitates obtained during the electrochemical processing of the spent heat-resistant alloy ZhS32-VI with the use of acid electrolytes are presented. Anodic dissolution of ZhS32-VI was performed in the galvanostatic mode. The effect of the electrolyte composition on the process parameters (current yield, distribution of alloy components between the electrolysis products, particle size distribution of the cathode product), electrochemical processing of this alloy were established. It is shown that depending on the nature of the electrolyte, cathode deposits of different chemical and phase composition can be obtained. They differ in the size and morphology of the surface. It has been established that the value of the cathode precipitate grains obtained in acid electrolytes is almost the same: 99% of the cathode precipitate grains are in the range from 0.04 to 0.60 μm. The main difference is a slight increase in the amount of fine fraction when sulphosalicylic acid is added to the electrolyte. All the cathodic deposits obtained have a dendritic structure, the development of which depends on the nature of the electrolyte, the precipitates obtained with the use of a nitrate electrolyte having the most developed structure and the smallest particle size.


79-88 308
The article reports the development of a technological scheme for isoamyl acetate preparation on the basis of kinetic data, vapor-liquid and liquid-liquid equilibrium data. A review of isoamyl acetate production methods was made. At present most of the methods are based on esterification reaction, which takes place in the presence of homogenous and heterogeneous catalysts. Heterogeneous catalysis is preferred because of absence the catalyst separation problem. In the first part of the work vapor-liquid and liquid-liquid equilibrium simulation was made. NRTL and UNIQUAC models were used to calculate phase equilibrium of a quaternary reaction mixture. It was proved by comparison of deviations of the calculated temperature and vapor mole fractions from the experimental values that NRTL is the best model for the considered mixture phase equilibrium calculations. This model was used in further calculations of distillation and liquid-liquid splitting. The choice of the technological scheme is based on the use of the principle of both distillation and liquid phase separation and the recycling of substances in the system. The difficulty in isolating pure isoamyl acetate as a product is due to the presence of four binary azeotropes and two triple ones in the system. When developing and selecting a technological scheme, the possibility of obtaining maximum conversions of the reactants was taken into account. Besides, when designing and calculating the scheme, an assumption was made about infinite separating ability of separation distillation columns. To check operating efficiency of the scheme in real conditions, a verification calculation was made to determine the minimum and working reactor volume. The minimum and working reactor volume calculation was based on the Langmuir-Hinshelwood-Hougen-Watson model for the kinetics of the esterification reaction. The selection of constructive and operating parameters of the scheme, at which high quality of isoamyl acetate is achieved, was made.


89-96 223
A mathematical theory is developed for constructing integral transformations in a partially bounded region with a radial heat flow - a massive body bounded from the inside by a cylindrical cavity. Constructed: an integral transformation, the image of the operator on the right side of the equation of unsteady heat conduction, the inversion formula for the image of the desired function. The proposed approach favorably differs from the classical theory of differential equations of mathematical physics for the construction of generalized integral transformations based on the eigenfunctions of the corresponding singular Sturm-Liouville problems. The developed method is based on the operational solution of the initial boundary problems of unsteady heat conduction with an initial function of a general form L2(r0,∞) belonging to the r > r0 region and homogeneous boundary conditions and is associated with the calculation of the Riemann-Mellin contour integrals from images containing various combinations of modified Bessel functions. At the same time, for the above-mentioned region, the method of Green's functions was developed by constructing integral representations of analytical solutions of the first, second and third boundary value problems through inhomogeneities in the initial formulation of the problem (boundary conditions, source function in the initial equation). Mathematical models for finding the corresponding Green's functions are formulated, and functional relations of all three Green functions included in the presented integral formula are written out with the help of the developed theory of integral transformations. The functional relations constructed in the article can be used when considering numerous special cases of practical thermal physics. The specific possible applications of the presented results in many areas of science and technology are given.

ISSN 2410-6593 (Print)
ISSN 2686-7575 (Online)