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2024

Archives Journal Chemical Bulletin Vol. 7

Removal of harmful gases from the air stream using carbon sorbents based on plant waste of the Republic of the Union of Myanmar

https://doi.org/10.58224/2619-0575-2024-7-4-118-130
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 118-130 p.
Abstract
Objectives: in this work, we evaluated the ability of the adsorbent of gas-vapor activated carbon obtained from the shells of macadamia nuts of one of the enterprises in Myanmar as an agent of the recovery technology using the example of the extraction of n-butanol vapors from their mixtures with air (AVM).
Methods. The object of the study was pre-dried macadamia nuts, which were crushed, heat treated at 650-700°C for 60 minutes in pyrolysis, followed by water vapor at a temperature rise of 15 °C/min without thermal ex-posure, the specific consumption of water vapor was 5 g per 1 g of the resulting activated carbon. The obtained sorbents were analyzed for the sorption properties of C6H6, CCL4 and H2O vapour. Their total volume was deter-mined, their porous structure was estimated by the volume of pores of various sizes, the absorption of iodine and methylene blue from aqueous solutions. Their ability to remove harmful gases during adsorption of n-butanol at different relative pressures was characterized and their adsorption kinetics and isotherms were studied.
Results. It is shown that the values of the coefficients obtained from the kinetic equation a = A(1-e-B·τ) of the obtained active carbons are preliminarily performed in their pores with butanol. According to the values of A and B, these sorbents are actively absorbed by harmful gases from the vapor-air mixture. For comparison, the article presents the quality indicators of active carbons of the CS (coconut shell) and PS (plum seed) brand made frоm a number of agricultural wastes of Myanmar.
Conclusions. The studies allow us to state quite satisfactory absorption properties of the obtained new activated carbon from the shell of macadamia nuts, in the studied process of extracting n-butanol vapors from their mixtures with air, which indicates the probable competitiveness of this adsorbent in solving the problems of purification from vapors of organic substances of emissions of high concentrations, provided that its production is organized in the conditions of Myanmar.
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A set of possible approximative methods for effectively accounting for the contribution of Coulomb integrals to dramatically accelerate the calculations of DFT giant biomolecules: reduction to fast-computable short-range two-center splines plus FMM long-range Coulomb

https://doi.org/10.58224/2619-0575-2024-7-3-49-63
 49-63 p.
Abstract
A set of approximative methods is proposed to radically accelerate the calculation of the contribution of Coulomb integrals in the calculations of DFT giant biomolecules - the limiting stage of such relevant but extremely resource-intensive calculations, including calculations of thousands of docking complexes of thousands of atoms. The proposed complex includes, through a quick and accurate approximation of the contribution of a huge number of 4-center Coulomb integrals through a linear combination of 3-center integrals, and then through a combination of 2-center integrals. The non-multi-complete short-range components of these 2-center integrals are very quickly considered pre-prepared splines from the center-to-center distances. The remaining long-range multipole contributions are quickly calculated for giant molecules in the FMM style (splitting a huge space into regions and subdomains, was originally developed for the dynamics of galaxies). Calculations are saved as much as possible everywhere due to pre-selected combinations of integrals. All two-center components (including the approximation of two-center overlaps of basic functions through linear combinations of single-center auxiliary density functions) are quickly calculated due to splines from internuclear distances from a specially prepared database. For new bases, the database is easily and quickly replenished by decomposing the new basis into a set of universal ex-ponents and a database with them.
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Electrochemical production of manganese dioxide from sulfuric acid electrolyte

https://doi.org/10.58224/2619-0575-2024-7-3-64-77
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 64-77 p.
Abstract
This paper investigates the process of electrochemical production of manganese dioxide from a 10% sulfuric acid electrolyte leaching the active mass of spent manganese-zinc chemical power sources. The relevance of the topic is due to the wide application of MnO2 in modern industry and the need to develop efficient methods for obtaining it from secondary raw materials. The aim of the study was to examine the influence of electrolyte temperature and ultrasonic treatment on the properties and sizes of the obtained manganese dioxide particles. The experimental methodology included electrolysis in a three-electrode cell with temperature variation from 30°C to 90°C and current density of 3-5 A/dm2. Ultrasonic treatment of the electrolyte was carried out at a frequency of 20 kHz. The obtained MnO2 samples were studied using scanning electron microscopy and X-ray energy-dispersive analysis. The results showed that increasing the electrolyte temperature leads to an increase in the size of manganese dioxide particles from 0.2 to 5-10 microns. The introduction of ultrasound allows obtaining highly dispersed MnO2 with crystallite sizes of less than 50 nm. The maximum current yield (92%) is achieved at 60°C and a current density of 5 A/dm2. The practical significance of the work is associated with the possibility of obtaining nanostructured manganese dioxide with improved electrochemical characteristics from spent raw materials. Further research will be aimed at optimizing the parameters of electrolysis and ultrasonic treatment to control the morphology and properties of MnO2.
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Kinetics and mechanism of adsorption of methylene blue dye by crushed sunflower biomass

https://doi.org/10.58224/2619-0575-2024-7-3-78-92
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 78 – 92 p.
Abstract
Objectives: to study the kinetics and mechanism of dye adsorption by cellulose raw materials. Methods. As a sorbent, waste from crop production was used – ground sunflower stalks, initial and modified with 10% NaOH alkali, with a particle size from 1 to 2 mm. Methylene blue dye was selected as an adsorbate by preliminary tests. Adsorption isotherms were constructed to determine the maximum sorption capacity. Kinetic models of sorption of the pseudo-first and pseudo-second order are constructed. In order to determine the mechanism of the process, thermodynamic constants were determined: sorption energy (E), Gibbs energy (ΔG) and Bio coefficient (Bi).
Results. The maximum sorption capacity of the crushed biomass of sunflower stalks in relation to the dye is 0.52 mmol/g for the alkali-modified material, which is 48% higher than the initial content (0.35 mmol/g). Thus, the SP(NaOH) material showed improved sorption properties, and it was selected for further kinetic studies. The sorp-tion energy is 5.82 kJ/mol, which may indicate physical adsorption. The Gibbs energy is -6.3742 kJ/mol, less than zero, which indicates the spontaneity of this process. The adsorption equilibrium for the MG dye occurs after 120 minutes, the kinetic curve has a smooth character. The Bio coefficient is 1.812, therefore, the adsorption process is limited by mixed diffusion.
Conclusions. The analysis of the data obtained made it possible to determine the Bio coefficient reflecting the course of MG adsorption by a mixed–diffusion mechanism over the entire time range of adsorption. This indicates the complex character of the MG adsorption process and confirms the importance of taking into account various factors influencing this process when developing methods for cleaning aquatic environments from organic pollu-tants.
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Investigation of the processing of fossil coals from the Kalewa and Tigyit deposits as raw materials for the production of activated by steam-gas activation

https://doi.org/10.58224/2619-0575-2024-7-3-93-101
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 93-101 p.
Abstract
Objectives: the article reveals the results of research on the technical indicators of the target products of the processes of steam-gas activation of fossil coals of the Tigyit and Kalewa deposits (Tigyit/Kalewa, Myanmar).
Methods. In order to assess the suitability of fossil coals from the Tigyit and Kalewa deposits for the production of granular activated carbons, the results of their petrographic analysis in the form of maceral composition and arbitrary vitrinite reflection indicators are characterized, indicating the potential possibility of their use to solve this problem, based on data from thermographic tests performed in a protective atmosphere, the rational limits of thermal effects on this raw material are estimated during pyrolysis.
Results. The results of steam-gas activation of the named fossil coals are presented, indicating the possibility of obtaining activated carbons with structurally acceptable adsorption properties for practical use, it is concluded that it is necessary to improve the processes of the named steam activation in order to optimize them.
Conclusions. Thus, the described results indicate the fundamental possibility of obtaining on the basis of fossil coals of the Kalewa and Tigyit deposits by the characterized reception of sufficiently high quality activated car-bons.
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Extraction of sodium hydroxide from cotton processing facilities

https://doi.org/10.58224/2619-0575-2024-7-3-102-108
 102-108 p.
Abstract
The process of extracting technological contaminants from textile materials is considered as a mass transfer process, for the intensification of which pulsed exposure to an ultrasonic field is chosen.
A lightweight fabric was selected for the study in order to eliminate the influence of surface density and fabric thickness on the kinetics of the process. The results of an experimental study of the kinetics of the extraction of so-dium hydroxide during washing after mercerization of a light standard cotton fabric are presented. The studies were carried out in laboratory conditions on a model installation with a different washing bath module without intensification and with the use of ultrasonic exposure as an intensifier. At the same time, the optimal distance from the ultrasound source to the washed tissue was determined based on previous studies. Exposure to ultrasound sig-nificantly reduces the duration of the process, especially at the initial stage. Equations for approximating the kinet-ics curves of sodium hydroxide extraction from cotton fabric without intensification and with intensification by ul-trasonic action are obtained, and their parameters are determined. The correlation of calculated and experimental data is acceptable for approximate kinetic calculations. The obtained equations can be practically used in engi-neering practice for a preliminary assessment of the duration of the process of extrusion-washing of cotton fabrics belonging to the group of light cotton fabrics from alkali in various modules of the washing bath.
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Improving the energy efficiency of the drying process of fibre materials

https://doi.org/10.58224/2619-0575-2024-7-3-109-119
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 109-119 p.
Abstract
In the modern textile industry, one of the most energy-consuming and widespread processes is drying, to which fibers, yarns and fabrics are subjected after various operations (impregnation, extraction, dyeing, etc.). A complex heat and mass transfer drying process is carried out at sufficiently high temperatures and is energy-consuming. To reduce the overall energy consumption in textile production, it is necessary to carry out preliminary dehydration of materials before drying, for example, in centrifuges, intensification of drying by physical fields, etc. Modern industrial drying plants for textile materials provide sufficiently fast and uniform drying, increasing the overall efficiency of this stage of production of finished textile products. Energy-efficient solutions for the drying process can reduce the negative impact of the process on the environment. Industrial drying of textile materials is carried out in convective or contact dryers using thermal energy. In convective dryers, the drying agent is air. In contact dryers, water vapor is used to heat the drums. The article discusses important areas of improvement of the technological process and equipment designed for drying fibrous materials. These include: the introduction of me-chanical pre-drying dewatering; the choice of hybrid systems in drum dryers; utilization of condensate and steam in drum dryers; insulation of end panels and the abolition of intermediate drying in drum cylindrical dryers; con-trol of moisture content of the material to prevent drying of the fabric; reduction of dryer downtime by planning the supply of batches of fabric; the use of multiple drying of fabric in drum dryers. The improvement of the drying pro-cess of textile materials is possible with the use of an ultrasonic field, infrared radiation and other intensification methods while ensuring timely maintenance of drying equipment, programmable temperature changes during the drying process.
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Improving the impact resistance of a polymer composite material based on epoxy prepreg through the addition of nonwoven material based on polyamide 12

https://doi.org/10.58224/2619-0575-2024-7-3-120-136
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 120-136 p.
Abstract
The effect of introducing nonwoven material based on polyamide PA 12-E on the mechanical properties of polymer composite materials based on the epoxy autoclave prepreg T107 was investigated. The presence of the nonwoven material slightly lowers the glass transition temperature to 171 ℃, which does not affect the feasibility of using the material up to the maximum operating temperature of 120 ℃. Electron microscopy studies of the composite's cross-sections revealed uniform distribution of the thermoplastic phase between the layers of carbon fabric as well as high adhesion of polyamide to the epoxy matrix. It was demonstrated that introducing nonwoven material does not lead to a reduction in the mechanical properties of the composites. The main advantage of composites based on nonwoven material is their enhanced resistance to impact loads. Under a free impact with energy of 6.67 J per 1 mm of the specimen, a through penetration with fiber destruction was observed in the sample without the nonwoven material, while for the sample with nonwoven material, the damage was characterized by delamination without fiber damage. The compressive strength after impact increased from 257 to 326 MPa with the introduction of nonwoven material. As a result, the proposed modification of commercial prepreg could expand the range of applications for the material and improve safety, particularly in aircraft structures.
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Optimization of the flow part of the microfluidic channel

https://doi.org/10.58224/2619-0575-2024-7-2-4-12
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 4-12 p.
Abstract
In this paper, the features of microfluidic channel optimization are considered. The microfluidic channel is a key component of the microreactor, its shape and features of the hydrodynamic regime directly affect the successful course of chemical reactions carried out in it. The microfluidic industry regulates processes occurring in small volumes of liquids – on the order of a nano liter or less. It is applicable to various fields such as microelectronics, pharmaceuticals, specialty chemicals, etc. The Comsol Multiphysics computational modeling program was used as an optimization tool. It is based on the finite element method, which allows you to accurately model the problems of the hydrodynamic profile. In this article, the simplest form of a microchannel is considered – a 0.75 mm circular channel with a mixing cell. The mathematical modeling of the process is given, the optimality criterion adequate for the task is determined. As one of the components of this criterion, diodicity was used – a criterion that determines the ability to pass a stream in the forward direction, provided there is a reverse flow. As a result of this work, the most optimal shape of the microreactor channel satisfying the required process conditions was identified, the main hydrodynamic parameters were obtained and the dependence of the diode on the criterion used was determined.
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The influence of hydrogen injection together with methane on changes in the physicochemical properties of sandstone

https://doi.org/10.58224/2619-0575-2024-7-3-137-145
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 137-145 p.
Abstract
The scientific basis of hydrogen storage in the environment, the causes and mechanisms of its interaction with other natural gases and fluid-containing media are poorly developed. Therefore, it is important to conduct a set of studies aimed at clarifying the main factors of its storage in UGS facilities together with methane. Changes in the physico-chemical properties of a sandstone sample after prolonged exposure to a hydrogen-methane mixture have been studied using infrared spectroscopy (IR), nuclear magnetic resonance (NMR), X-ray fluorescence analysis, and velocity measurement of longitudinal and transverse sound waves. Changes in the composition of the rock are confirmed by differences in the IR, NMR, and transformation spectra of the mineral component of sandstone, which is largely due to the crystallization processes of substances dissolved in adsorbed water. The results of these studies can be used in the planning and operation of underground gas storage facilities in regions where large-scale hydrogen production and storage will be organized.
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