AbstractThe practical implementation of new highly efficient methods of liquid–liquid chromatography requires preliminary mathematical modeling for the conditions of the separation process being developed, including its equipment design. In this work, two approaches to the mathematical description of the processes of liquid–liquid chromatography are theoretically analyzed, one of which is based on solving the material-balance equations of a model of a cascade of equilibrium steps, and the other of which uses the Gaussian distribution to describe the outlet concentration profiles of the components of the mixture being separated. It is shown that, if the number of equilibrium steps (characterizing the efficiency of the chromatographic system) is N ≥ 50, then the separation processes can be mathematically modeled using the simpler dependences obtained from the Gaussian distribution. For the conditions when the efficiency of the chromatographic system is N < 50, dependences are obtained using the model of equilibrium steps for mathematical modeling of the processes of separation by various methods of liquid–liquid chromatography.

Abstract—The article theoretically substantiates the ability of ultrasonic vibrations to dehydrate capillary-porous materials due to the dispersion of moisture from the capillaries and pores of the material under the action of shock waves formed by cavitation bubbles. A phenomenological model is presented based on the analysis of the slow growth of a distorted cylindrical cavitation bubble, taking into account the influence of the cylindrical capillary walls limiting its oscillations. The optimal range (150–170 dB) of ultrasonic pressure levels is revealed, at which the mechanism of cavitation moisture dispersion is realized. It is established that the optimal conditions for the action of ultrasonic vibrations on a dried material are realized when the dimensions or thicknesses of the layer of the dried material correspond to the length of ultrasonic vibrations in air.

AbstractPhenol is a vicious contaminant due to its high toxicity and potential for accumulating in the environment. This ubiquitous organic pollutant gets introduced to the surface water through the effluents of various industries such as industrial coal conversion, fertilizers, petroleum refineries, coke oven plants, pharmaceutical, dye processing, etc. Since presence of even a smaller concentration of phenolic compounds is a serious threat to the living organisms, elimination of this hazardous material from the waste water prior to its discharge is utmost necessary. To mitigate this challenge, numerous techniques have been employed till date, of which, adsorption method has emerged as a promising processing candidate. The method has gained tremendous attention due to the use of natural adsorbents (or biosorbent) specifically derived from the agricultural or household residues. The wide availability, low cost, environmental friendliness and excellent biodegradability of the biosorbent not only enhances the efficacy but also dictates the simplicity and versatility of this technique. The current research deals with the actively removal of phenol concentration from real coke wastewater using activated carbon extracted from banana peel waste as an adsorbent. The maximum phenol removal efficiency from coke wastewater was achieved by batch study with varying parameters at 100 min equilibrium contact time, pH: 7, and adsorbent dosage 0.5 g/30 mL. The parameters such as the adsorbent dose (A: 0.1–1 g), pH (B: 2–10), and temperature (C: 25–50°C) were optimized and statistically analyzed by using Box Behnken design (BBD). The use of activated banana peel biosorbent resulted to achieve maximum phenol removal efficiency of 89.22%. The detailed characterization of biosorbent was corroborated by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and the surface area were analyzed by Brunauer–Emmett Teller (BET). The adsorption data were analyzed and fitted well with the Temkin adsorption isotherm and pseudo-second-order kinetic model. The thermodynamic study indicates that the phenol adsorption on to banana peel biosorbent was an endothermic and physio-sorption process.

AbstractA chromatographic method for determining the mass fraction of organochlorine compounds in oil and its refined products has been developed. An inert gas is bubbled through a container filled with the analyzed liquid; the flow of the inert gas containing vapors of organochlorine compounds is divided into two parallel flows in the chromatograph; one of the two flows is separated with a capillary chromatographic column, while the other, with a polycapillary chromatographic column, both at a constant temperature. The organochlorine compounds are detected with a single electron-capture detector connected to each of the two flows in accordance with the release time of a definite organochlorine compound. The developed method allows automated measurements of mass fraction of organochlorine compounds in oil and its refined products using flow gas chromatographs of explosion-proof design; the analysis time decreases, and the losses due to contamination of feedstock with organochlorine compounds at oil refineries and oil transportation enterprises are reduced.

AbstractPyrolysis is considered as a promising direction in the processing of plastic waste for energy production and as a clean technology that meets energy security objectives. The main products obtained in the pyrolysis process are gas, liquid (condensable pyrolysis fuel), and coal (solid component). The influence of the process temperature and catalysts on the yield of pyrolysis fractions is analyzed. This study indicates that it is important not only to solve the problem of plastic waste, but also to develop fuels based on the pyrolysis of plastics.

AbstractThe energy efficiency of using nonadiabatic distillation in the process of extractive distillation of an acetone–chloroform–n-butanol mixture with dimethylformamide as an entrainer is evaluated. Two options for organizing heat integration are considered: (1) between the regeneration column of the entrainer and the extractive column; and (2) between the regeneration column, the extractive column, and the chloroform-recovery column. It is shown that the use of nonadiabatic distillation schemes makes it possible to decrease the energy consumption by 7.4–12.7% during heat integration between the extractive distillation and dimethylformamide regeneration columns; in the case of heat integration of all columns of the scheme, energy consumptions is reduced by up to 20% compared to the original scheme.

AbstractOrganoclays as a nanocomposite filler in nanocomposite polymer materials improves the physico-chemical properties of polymeric materials. They are better combined with polymer and form layered polymer nanocomposite. This ratio is about 2–5% total material mass. Synthesizing nanocomposites and analysis by XRD and IR spectroscopy shows that crystalline structure and hydrophobicity of polymer nanocomposite well formed.

AbstractThe low-temperature chemical vapor deposition was used to coat zeolitic imidazolate framework-8 crystals onto the selective layer of polysulfone membrane to obtain a composite membrane. The chemical vapor deposition was performed by a reaction between zinc and 2-Methyl-1H-imidazole vapor at room conditions. The physical and chemical properties of the obtained composite membrane were characterized using material analysis methods. The effects of feed pressure and age of the membranes on CO2 and CH4 permeation were investigated. The results showed that the prevailing cracks were decreased in the composite membrane containing zeolitic imidazolate framework-8 nano-crystals. The molecular sieving effect of zeolitic imidazolate framework-8 caused the increase of the CO2/CH4 selectivity of the composite membrane up to 31%. The age of membranes and the feed pressure made slight drops in CO2 and CH4 permeation and less than 4% enhancement in the ideal CO2/CH4 selectivity. The results showed that the low-temperature and room-pressure chemical vapor deposition is useful for enhancing the CO2/CH4 selectivity of polymeric membranes.

AbstractThe porous structure of acetylene black samples obtained by decomposition of acetylene at various pressures in a constant-volume tube reactor and subsequent heat treatment in an inert medium at temperatures of 200, 400, 600, 800, 1000, 1200, and 1400°C has been studied. Nitrogen adsorption isotherms at 77 K were obtained by the low-temperature adsorption method, and the textural characteristics of carbon black were calculated from them. It was found that at a pressure increased from 2.5 to 5 bar during the decomposition of pure acetylene, the surface area of acetylene black did not change and amounted to 88 and 83 m2/g (according to BET), respectively. As a result of heat treatment in the inert medium, the specific surface area obtained at 2.5 bar decreased relative to that of the starting carbon black not subjected to heat treatment. The average pore radius determined by the Barrett–Joyner–Halenda (BJH) method did not change at different temperatures and pressures and amounted to 1.62 nm. A scanning electron microscopy study shows that the average particle size decreased from 53 to 40 nm at increased initial pressure of acetylene. Based on the results, it can be concluded that subsequent heat treatment does not lead to an appreciable change in the particle shape and size, nor in the overall structure of the carbon black surface. A thermogravimetric analysis (TGA) of the original carbon black sample in an inert medium was performed. It shows that the mass of carbon black increased by 4% when the sample was heated to 400°C, did not change on heating from 400 to 1150°C, and decreased by 1% on heating from 1150 to 1400°C.

AbstractAn earlier-developed procedure for calculating the molar volumes of electrolytes Vs0 is used for a comparative analysis. The molar volumes Vs0 are determined for four electrolytes NH4Cl, NaBr, KBr, and KI based on the published data, and the errors of these values are estimated. Comparison of the obtained values of Vs0 and the earlier-found [1] similar values for various cations and anions is performed. It is shown that there is no correlation between Vs0 and the values of the ionic radii.

AbstractThermochemical recovery of the heat of automotive internal combustion engine (ICE) exhaust gas saves fuel and reduces harmful emissions. Two designs of thermochemical heat recovery in propane-fueled ICEs are numerically analyzed. In both designs, a mixture of 10–20% of the initial propane with part of the ICE exhaust gas is subjected to catalytic reforming, and then the hydrogen-containing reforming products together with propane are added to the combustion chamber. In the first design, the reforming is carried out in an adiabatic reactor; and in the second, in a tubular one. In the analysis, the fraction of the exhaust gas recycle is varied within the range 0.1–0.5 and the temperature in the range 470–690°С. The second design is shown to be more efficient; it ensures an increase in the chemical enthalpy of the fuel mixture by 1.9–3.6% at a hydrogen mass fraction of 0.3–0.9%. For the operating conditions of an ICE with an effective power of 30 kW, the characteristics of an adiabatic reformer and a tubular reformer with a Ni/Cr2O3/Al2O3 catalyst are calculated.

Abstract—The influence of the temperature–time parameters and the composition of the reaction system on the kinetics of the acetalization reaction during the preparation of polyvinyl formal foam from aqueous solutions of polyvinyl alcohol is studied. The mechanism of the acetalization reaction and the equations are provided to describe the transformation of polyvinyl alcohol into polyvinyl formal in the presence of formaldehyde and acid catalysts of the homogeneous and heterogeneous reaction regions. We show that the degree of conversion by the acetalization reaction remains almost unchanged (0.85–0.87) with increase in concentration of polyvinyl alcohol, but the time to reach the maximum conversion increases by a factor of ~2.5 (from 11 to 26 min). The optimal concentrations of formaldehyde and sulfuric acid (catalyst) for the kinetics of the acetylation of polyvinyl alcohol in aqueous solution are found: the concentration of formaldehyde \(C_{a}^{0}\) is 3.3 mol/L and that of sulfuric acid \(C_{{{{{\text{H}}}_{{\text{2}}}}{\text{S}}{{{\text{O}}}_{{\text{4}}}}}}^{0}\) is 3.5 mol/L. An increase in temperature leads to an increase in the rate of the acetalization reaction and a decrease in the time for the synthesis of polyvinyl formal from aqueous solutions of polyvinyl alcohol. We show that it is inexpedient to increase the synthesis temperature higher than 50°C. The optimal temperature to obtain polyvinyl formal from aqueous solutions of polyvinyl alcohol is considered as ~40–45°С. The data obtained prove that the acetalization reaction is completed within the time that provides the stability of the foam from aqueous solution of polyvinyl alcohol (at least 20–30 min).

AbstractIn the present work, we performed using global and local indices of conceptual DFT, a study of the oxidation reaction of CO on hetero-fullerenes C59X (X = B, Si, P and S). Our calculations, show: firstly, that the thermodynamic stability of these nanosystems, reflected by the calculation of the formation energies, depends considerably on the nature of the doping atom X. at the second, we have found that the C59Si with the highest electrophilic character, a high polarity translated by the greatest value of Δω, the smallest energy gap and the lowest adsorption energy, is the appropriate choice for the chemisorptionof theO2 and therefore it is the favored surface for the oxidation of CO. Finally, the key step of the LH mechanism, which is the chemisorptionof the O2 molecule on the catalyst surface, was well illustrated using local indices derived from the conceptual DFT. In this study step, we have shown that the most favored electrophilic-nucleophilic interaction will preferentially take place between an oxygen atom in the O2 molecule and Si in C59Si. This interaction leads to the chemisorption of an oxygen atom on the surface of the C59Si nanocatalyst.

AbstractAn algorithm is proposed to process experimental data to determine the thermophysical properties (specific heat capacity and thermal conductivity) of phosphorites by solving the inverse-coefficient heat-conduction problem, which reduces to programmable heating complicated by thermally activated endothermic reactions of dissociation of carbonates and control of the internal thermal state of a system with distributed parameters. Consideration is made of the problem of mathematical and computer modeling of a system for processing experimental data and generalizing the main dependences of the thermophysical properties in the operating temperature range of thermal-engineering equipment for the heat treatment of ore raw materials and the actual chemical-composition range of phosphorites. This problem is solved by solving the inverse-coefficient heat-conduction problem. The control parameters are thermal conductivity and specific heat capacity, which are the coefficients in the heat equation for a plate. The optimality criterion is the smallest deviation of the temperature distribution in the plate thickness obtained in a computational experiment from a given distribution. The optimization problem is solved by the sliding-tolerance method with optimization by the deformable-polyhedron method. The article presents the results obtained in computational experiments modeling phosphate raw materials. The obtained numerical results agree well with the results of physical experiments, which confirms the adequacy of our developed mathematical and computer models and the proposed algorithm for solving the inverse-coefficient heat-conduction problem.

AbstractThe vapor–liquid equilibrium of the tetrahydrofuran–acetonitrile system, the equimolar tetrahydrofuran–acetonitrile–chloroform mixture is experimentally studied. The effect of various amounts of dimethyl sulfoxide on the relative volatilities of the components at 101.32 kPa is investigated. The extractive distillation flowsheets of the tetrahydrofuran–acetonitrile–chloroform mixture with dimethyl sulfoxide are calculated.

AbstractThe need for alternative renewable fuels for conventional fossil fuels is to neutralize the increases in energy demand and decrease serious emissions. Vegetable oil-based biodiesel is a promising replacement and alternative. This study produces biodiesel from a low-cost and unexplored feedstock, Raphanus sativus (R. sativus) oil. The biodiesel produced from this source is subjected to engine performance and emission characteristics. A nano-additive (nano-Al2O3) is used in this study to enhance the performance and reduces the emission while using biodiesel. The parameters affecting the characteristics are fuel blend ratio, additive dosage, load conditions and fuel inlet conditions, which are optimized using the Taguchi statistical method and analysis of variance table. From the main effect plot of signal to noise ratio, it is clear that the biodiesel blend ratio of B20 along with 60 ppm nano-Al2O3, injection timing of 27° before top dead center and 220 bar pressure gives greater brake thermal efficiency with decreased brake specific fuel consumption and exhaust gas temperature on preferred full load condition. Whereas for reduced emissions of CO, CO2, NOx and HC, it requires B20 along with 60 ppm nano-Al2O3, 23° before top dead center injection timing and 180 bar pressure.

Abstract—The results of studying the processes of electrochemical oxidation–reduction of bismuth in aqueous solutions of potassium chloride by the method of taking potentiodynamic polarization curves are presented. The influence of the concentration and temperature of the electrolyte and the sweep rate on the electrochemical behavior of bismuth is studied. The features of the influence of the electrolyte composition on the formation of bismuth oxychloride are studied. The optimal parameters of electrolysis for the production of bismuth oxychloride are revealed.

Phase equilibria in sections of the calcium-nitrate–glycerol–water system at temperatures from 0 to –47°C are studied by visual polythermal analysis. The ratio of calcium nitrate and glycerol in the sections varies from 3 : 1 to 1 : 3. It is found that all nitrate–glycerol compositions are characterized by good ice-melting capacity and form low-temperature eutectics. These compositions are promising for the development of new anti-icing agents on their basis.

The efficiency of the extraction–pyrolytic method and its combination with the plasma–electrolytic oxidation method for obtaining thin-film coatings of various functional purposes (protective, luminescent, magnetic, catalytic, and biomedical) is demonstrated. The methods make it possible to form functional layers of complex composition and successfully create multilayered compositions on substrates of various natures.

AbstractThe possibility of using technogenic titanium-containing waste from the enrichment of apatite–nepheline ores to obtain import-substituting functional products, in particular fillers for temperature-controllable sealing agents used in advanced branches of technology (shipbuilding, aircraft, and rocket manufacturing), is examined. The method developed is based on the different solubility of the mineral components contained in the waste in hydrochloric acid medium, which makes it possible to separate titanite from apatite and nepheline by sequential processing at the first stage and to separate the titanosilicate precipitate from titanite (a precursor to obtain a filler) at the second stage. It is shown that the neutralization of the hydrochloric acid effluents formed after the first stage of treatment with ammonia water at pH 7–12 provides almost complete precipitation of the aluminum and calcium in them as hydrophosphate amorphous phases and of the silicon as silica. The phase composition of the precipitate obtained remains almost unchanged during its heat treatment (T = 500°C). There is only a decrease in the specific surface area of the particles, which indicates the compaction of its structure. It is recommended to use the sediment thus obtained as an additive to increase the strength of concrete.