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KINETICS OF DISSOLUTION OF CR(OH)3 AND AL(OH)3 IN SULFURIC ACID

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 54-60 p.
Abstract
This work is a continuation of studies related to the kinetics of dissolution of oxides and hydroxides of aluminum (III) and chromium (III). Earlier studies have shown that oxides and hydroxides of these metals are better soluble in sulfuric acid than in hydrochloric, nitric, oxalic and phosphoric. This article presents experimental studies on the effect of sulfuric acid concentration on the rate of heterogeneous reaction of chromium (III) and aluminum (III) hydroxides. It is established that the rate of dissolution of hydroxides increases with increasing concentration of sulfuric acid. Moreover, the rate of transition of aluminum (III) ions from hydroxide is higher than the rate of transition of chromium (III) ions, under the same conditions. To calculate the main kinetic parameters, a model of a chain mechanism was selected. The dissolution simulation was carried out using the mathematical computer program MathCad. The need for real models is associated with the need to optimize ore leaching technologies, regulate the physico-chemical processes of oxide dissolution, scale etching and removal of deposits from thermal power equipment. Experimental studies have made it possible to determine that the rate of dissolution is limited by the formation and subsequent transition of surface compounds of the form: into an electrolyte solution. Such studies will help to create a generalized mechanism for the heterogeneous process of dissolution of aluminum and chromium oxides in acidic media.
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SYNTHESIS OF POLYMERIC MATERIALS BASED ON AROMATIC POLYESTER MATERIALS BY HIGH-TEMPERATURE POLYCONDENSATION

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 61-73 p.
Abstract
As part of solving the problem of creating recipes for the synthesis of domestic superconstruction polymers, work was carried out on the synthesis of aromatic polyester materials with a complex of valuable performance characteristics. It has been established that it is possible to improve the economic performance of the PCM synthesis process based on aromatic polyesters by replacing the traditional 4,4'-difluorobenzophenone monomer with a chlorine-containing functional analog, which makes it possible to synthesize new materials with a cost up to 6 times lower than known competitors. The paper studies the features and determines the optimal conditions for the synthesis of new aromatic polyester materials: oligoetherketones and polyetherketones, polyimides and polyeth-erimides, to create binders for the impregnation of glass and carbon reinforcing fillers. It is described that the syn-thesis of polyimides (PI) was carried out by a two-stage method: obtaining a polyamic acid (PAA) and obtaining an insoluble diversified polymer. It has been established that by replacing the expensive dihalide, it is possible to a large extent to reduce the cost of synthesized polymers, increase their yield and manufacturability. A complex of physicochemical studies by various methods has been carried out, the structure of the synthesized polymers has been established, it has been determined that new polyester materials based on poly(aryleneetherketones) and pol-yetherimides are superior in their basic physicochemical and operational properties to industrial analogous poly-ester superstructural materials.
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FORMATION AND RESEARCH OF BIMETALLIC ELECTRODE MATERIALS ON POLYMER-CARBON CARRIER MATRICES FOR ENERGY POWER SOURCES

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 74-82 p.
Abstract
Fuel cells are promising devices for direct conversion of chemical energy into electrical energy from the point of view of efficiency and low emission of pollutants. The main component of fuel cells is a solid polymer electrolyte. Membranes made of perfluorinated sulfonated copolymers of the Nafion type with different content of sulfogroups satisfy most of the application conditions, because they have a sufficiently high degree of proton conductivity, stability in electrolyte solutions and high mechanical strength. The principal disadvantage of such membranes is their relatively low ion selectivity and a decrease in mechanical strength at temperatures above 100oC. To improve the characteristics of the membrane, various modification methods are used, including various additives and metal nanoparticles. The main obstacle to the widespread large-scale use of fuel cells is their cost, in which the main part is the cost of electrocatalysts based on platinum metals. Therefore, the development of effective electrode materials with a reduced content of platinum metals is an urgent task. In this work, bimetallic platinum-ruthenium nanoparticles were synthesized on combined carrier matrices consisting of a Nafion polymer membrane and carbon nanotubes. The sizes of Pt-Ru nanoparticles were compared with varying the molar ratio of wa-ter:surfactant from 1.5 to 8. It was found that the minimum size is characteristic of nanoparticles obtained with a maximum platinum content in nanoparticles (7:1) and the degree of solubilization ω = 1.5. It was found that in the methanol oxidation reaction, electrode materials based on bimetallic Pt-Ru nanoparticles (7:1) demonstrate the greatest catalytic activity when the catalyst is loaded 0.2 mg/cm2 on polymer substrates with the addition of multi-walled carbon nanotubes at a temperature of 60oC.
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THE JOINT INFLUENCE OF SUCCAROSE AND HIGHLY DISPERSED CALCIUM HYDROSILICATES ON THE STRENGTH DEVELOPMENT KINETICS OF CEMENT CONCRETE

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 83-94 p.
Abstract
Сement hydration accelerator (highly dispersed calcium hydrosilicates) and hydration retarder (sucrose) are components of calcium silicate dispersion (CSD). Their joint influence on the processes of setting and hardening of cement composites is considered. The content of 10% CSD in the composition of the composite binder (CB) leads to a shift of the thermal maximum on the thermokinetic curve by a day. At the same time, at the late stages of hydration (>70 hours), the heat release rate remains consistently high, it is 2-3 times higher than the heat release rate of the control sample. The setting kinetics of CB pastes depends on the content of CSD in its composition and is of an extreme nature. The effectiveness of CSD in the composition of CB was evaluated on the example of ordinary heavy concrete (B25) with the replacement of cement with CSD. The results of assessing the change in the strength of concrete at CB are supplemented with calculated strength indicators in the future up to 1800 days hardening. The expected compressive strength of concrete samples on a composite binder is 1.8 times higher than the strength of the control sample.
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STUDY OF THE EFFECT OF ANIONS ON THE DISSOLUTION RATE OF CO2O3 AND CR(OH)3

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 95-100 p.
Abstract
Сhromium compounds are widely used in industry, therefore, studies related to the study of the process of dissolution of oxides in various environments, including aggressive ones, are relevant. Currently, a huge amount of experimental material has been accumulated on the dissolution of metal oxides and hydroxides. Despite this, the effect of anions on the dissolution rate of these compounds has not yet been sufficiently studied, models have not been developed and generalized dissolution mechanisms have not been found. This article presents experimental studies on the effect of nitrate and sulfate ions on the dissolution rate of chromium (III) oxide and hydroxide. It was found that chromium (III) oxide and hydroxide dissolve better in sulfuric acid in the presence of nitrate ions than sulfate ions. Moreover, chromium (III) hydroxide dissolves better in acids with the addition of anions than chromium (III) oxide. Based on the data obtained, using the equation of the chain mechanism (the Barton-Stransky model), we found the functional dependence of the specific rate of dissolution on the concentration of anions in an acidic medium. With the help of the mathematical computer program MathCad, models of the dissolution of chromium oxide phases were selected. A scheme of the mechanism of the heterogeneous process of dissolution of chromium oxide and hydroxide in acidic media was proposed.
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PURIFICATION OF OIL-CONTAINING WASTE WATER FROM HERMETIA ILLUCENS FLY LARVAE LIPID CONCENTRATE PRODUCTION

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 5-16 p.
Abstract
The work is devoted to the study of the possibility of waste water from the lipid concentrate (oil) obtained on the basis of the larvae of the Black Soldier fly (Hermetia Illucens) production treatment. Treatment of oily wastewater is not an easy task due to the specific properties and condition of the oils contained in such wastewater. Typically, wastewater containing fats and oils has a high chemical oxygen demand (COD), biological oxygen demand (BOD), large amounts of suspended solids, oils, fats, phosphates and sulfates. Various physicochemical methods are used to treat such wastewater. However, the search for inexpensive effective materials for the oils extraction from aqueous media is an actual task.
For cleaning, we used the crushed fruits of the Sycamore tree – a deciduous tree widespread in the southern strip of the Russian Federation. Model emulsions containing "Black Soldier" larvae oil were subjected to cleaning. The influence on the purification efficiency of such factors as the dose of the sycamore fruit (SF) added biomass, the SF interaction duration with the emulsion, and the pH of the medium was investigated. It was found that high purification efficiency is achieved at the SF dose of 1 g per 10 cm3; pH = 4; the duration of the contact is at least 10 minutes.
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INVESTIGATION OF PHOTOPROTECTIVE PROPERTIES OF TROXERUTIN, FERULIC ACID, AQUEOUS EXTRACTS OF LEMON BALM (MELISSA OFFICINALIS), AND PEPPERMINT (MENTHA PIPERITA) BY UV SPECTROSCOPY

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 17-28 p.
Abstract
Both natural and ingredients created in laboratories are used as photoprotective agents in cosmetic products. This paper presents the results of a study of photoprotective properties of aqueous extracts of lemon balm (Melissa officinalis) and peppermint (Mentha piperita), aqueous solutions of troxerutin and ferulic acid by UV spectroscopy. The work objective was to evaluate photoprotective qualities of these substances, for which such indicators calculated from UV spectra as sun protection factor – SPFin vitro, the critical wavelength – λcrit and the ratio of the areas under the absorption spectrum curve in the ranges 320-400 nm and 290-320 nm – UV-A/UV-B. The stability of the studied objects to the action of UV radiation was also checked. During the work carried out, it was found that the aqueous extracts of lemon balm and peppermint have particular photoprotective properties. At the same time, the extract obtained from lemon balm and purified from ballast substances showed the highest value of SPFin vitro. However, with prolonged UV irradiation simulating sunlight, the absorption properties of plant extracts decrease. Troxerutin absorbs UV rays mainly in the wavelength range of 320-400 nm, is resistant in aqueous solutions to UV radiation, air oxygen, and can be used as a UV-B filter in cosmetic compositions. Ferulic acid absorbs UV radiation mainly in the wavelength range of 280-320 nm, but under the influence of ultraviolet, the absorption properties of this substance change significantly. A change in the nature of the UV spectrum of ferulic acid is also observed under the influence of air oxygen.
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ESTIMATION OF UNCERTAINTY OF GRADING SAMPLES FOR X-RAY FLUORESCENT DETERMINATION OF RHENIUM CONTENT

 29-38 p.
Abstract
For the development and metrological certification of the procedure for measuring the mass fractions of rhenium in metallurgical samples by the extraction-X-ray fluorescence method, solid-phase samples-emitters were prepared to construct a calibration characteristic. The article evaluates the values of the expanded uncertainty of the emitter samples using the Bayesian approach. The sources of uncertainties associated with the preparation of the standard solution, the preparation of the extractant, the extraction process and the measurement of the analytical signal intensity were identified: the error of a volumetric flask and a pipette; the error in measuring the time and temperature of extraction, the error in the expansion of the volume of the flask at the stage of preparation of solutions, the error in the scales when measuring the mass of the extractant and when measuring the weight of the weighed portion of ammonium perrhenate, the error in measuring the optical density on an X-ray fluorescence spectrometer for the prepared emitter samples, repeatability of the results when measuring the analytical signal - emitters, linearity of the calibration characteristics. A quantitative assessment of each source of uncertainty was made, the contribution to the value of expanded uncertainty of all stages of the process was estimated. It was found that the greatest contribution to the value of the total uncertainty is made by the error associated with the error at the stage of preparation of the extractant and the stage of extraction concentration and extraction of the analyte from the liquid phase to the solid. An equation for calculating the total standard uncertainty is derived. The results obtained can be used in the metrological substantiation of the procedure for performing measurements of the ex-traction-X-ray fluorescence determination of the rhenium content in metallurgical samples.
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INFLUENCE OF PROBIOTICS IN THE COMPOSITION OF FEED SUBSTRATE ON THE AMINO ACID PROFILE OF HERMETIA ILLUCENS LARVES

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 39-47 p.
Abstract
The use of probiotics Bacillus subtilis B-8130 and Bacillus licheniformis B-4162 as part of the feed mixture in the cultivation of larvae of the black soldier fly Hermetia illucens influenced the features of the amino acid profile of the larvae. The greatest impact was caused by B. licheniformis B-4162, which caused a statistically significant decrease in the level of 10 of the 18 essential amino acids, including the sulfur-containing amino acids cystine and methionine. B subtilis B-8130 demonstrated an unreliable tendency to decrease the total amino acid content, but statistically significantly reduced the cystine content compared to the control.
The revealed changes in the amino acid content in the larvae occurred against the background of an increase in their mass compared to the control larva. It is assumed that the decrease in the level of amino acids is associated with their expenditure on the formation of glucose and metabolic energy in a more intensively developing larva on a feed mixture with a probiotic.
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NICKEL IONS ADSORPTION BY THERMOMODIFIED FALLEN LEAVES OF CHESTNUT

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 48-59 p.
Abstract
In recent years, the attention of researchers has been attracted by industrial and agricultural waste, which can be used as sorption materials. A special group is made up of lignocellulose-containing components of woody biomass (leaves, bark, needles, fruits, etc.) and wood processing products (sawdust, shavings, chips, etc.). Advantages of using the latter as reagents for wastewater treatment include simple technique, small processing, good adsorption capacity, selective adsorption of heavy metal ions, low cost, free availability and easy regeneration. Trees foliage attracts attention аmong the components of the woody biomass, it has a large specific surface area and falls annually under the conditions of the Russian Federation, which facilitates its collection and use.
Nickel ions are one of the most toxic pollutants that enter water bodies with industrial wastewater. The infor-mation on the nickel compounds toxic effect on living organisms is briefly presented. In this work, we studied the sorption properties of chestnut fallen leaves (CFL) in relation to nickel ions. The sorption capacity maximum value of the thermally modified CFL at a temperature of 250° C (CFL250) is 1.3 mmol / g for nickel ions. By processing the obtained isotherm within the framework of the Langmuir, Freundlich, BET, Dubinin-Radushkevich sorption models, it was found that the adsorption process is most accurately described by the Langmuir model (R2 = 0.9912). The calculated Gibbs energy is equal to -7.86 kJ / mol, it indicates the occurrence of spontaneous physical adsorption of Ni2 + ions on the CFL250 surface.
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