English English

2025

Archives Journal Chemical Bulletin Vol. 8

Adsorption of methylene blue by activated pyrolysis products of sunflower seed husks

https://doi.org/10.58224/2619-0575-2025-8-3-1
, ,
Abstract
In the context of the global environmental crisis caused by the rapid growth of industrial and household waste, the search for effective methods of their recycling is becoming a key task of sustainable development. Traditional disposal methods, such as burial or incineration, not only require significant resources, but also lead to atmospheric pollution with negatively biologically active gases. In this context, pyrolysis of carbon-containing waste represents a promising alternative combining environmental safety and economic feasibility. Unlike combustion, pyrolysis takes place in an environment with a limited oxygen content, which minimizes CO and CO2 emissions, and also allows for the production of valuable secondary products — pyrolysis gases, liquid and solid carbon materials. The latter are suitable for use as adsorbents. Activation of pyrolysis products by chemical reagents (alkalis, acids, or steam) is used to increase the adsorption capacity, which significantly increases their porosity and adsorption capacity. In this work, the adsorption properties of sunflower husk pyrolysis products activated with an aqueous 2 M solution of potassium hydroxide (KL-21(A)), sunflower husk pyrolysis products combined with bentonite clay (KL-21(A)) and pyrolysis products of crushed worn car tires (KR-21(A)) were determined. Their effectiveness in terms of adsorption of methylene blue (MG), a model cationic dye widely used in assessing the absorption capacity of adsorbents, has been studied by spectrophotometric method. Kinetic dependences of adsorption have been established, and the maximum adsorption capacities of experimental materials have been determined depending on MG concentration. The results of experimental studies allow us to conclude that the activation of pyrolysis products of crop and communal waste with potassium hydroxide improves the adsorption characteristics of the developed material.
Objectives: to identify the adsorption properties of pyrolysis products of sunflower seed husk KL-21(A) activated with an aqueous 2 M solution of potassium hydroxide, pyrolysis products of sunflower seed husk combined with bentonite clay KL-21(A) and pyrolysis products of worn-out automobile tires KR-21(A).
Methods. A Nabi MicroDigital spectrophotometer (South Korea), laboratory instruments and reagents were used to study the adsorption properties by the spectrophotometric method.
Results. Graphical dependences of the absorption capacity on the duration and rate of adsorption are revealed, and adsorption isotherms are constructed and analyzed.
Conclusions. An adsorption-active material based on pyrolysis products of sunflower seed husks and pyrolysis products of worn-out automobile tires was obtained. The adsorption capacity of CL-21(A) samples was 474 mg/g, CLG-21(A) – 131 mg/g, and KR-21(A) – 351 mg/g. The obtained isotherms are determined by the Langmuir model.
It was found that the adsorption equilibrium occurs after 6 hours in KL-21(A) and a day later in KL-21(A) and KR-21(A).
It was found that the highest rate of adsorption is characteristic of the KL-21(A) sample and amounted to 0.00094 mmol/min or 0.300 mg/min in the first 15 minutes of exposure.
PDF

Colloidal protection of magnetite hydrosols with polysaccharides

https://doi.org/10.58224/2619-0575-2025-8-3-2
, ,
Abstract
This article investigates the stabilization of aqueous dispersions of magnetic Fe₃O₄ nanoparticles using polysaccharide stabilizers. The effect of electrolyte coagulants and polysaccharide stabilizers on the stability of magnetite hydrosols and their stability at physiological pH with and without the addition of polysaccharides is stud-ied. The results demonstrate the effectiveness of nonionic polysaccharides, such as hydroxypropyl methylcellulose and hydroxyethylcellulose, in stabilizing magnetic nanoparticles from electrolyte coagulation and over time, which is important for their application in medicine.
Objectives. To obtain and characterize magnetite hydrosols and to study their stabilization with polysaccharides over time and with the addition of non-indifferent and indifferent electrolytes.
Methods. Hydrosol coagulation was studied photometrically. The size of hydrosol nanoparticles was determined using dynamic light scattering.
Results. Nonionic polysaccharides, such as hydroxyethyl cellulose and hydroxypropyl methylcellulose, are promising for stabilizing aqueous dispersions (hydrosols) of Fe3O4 magnetic nanoparticles.
Conclusions. The coagulation threshold of magnetite hydrosol with a non-differentiated electrolyte, sodium hy-droxide, is 20,5 times lower than the coagulation threshold of magnetite hydrosol with an indifferent electrolyte, sodium chloride. Hydroxyethyl cellulose and hydroxypropyl methylcellulose exhibited the greatest protection of magnetite hydrosol from coagulation with sodium chloride. Hydroxypropyl methylcellulose exhibited the greatest protection of magnetite hydrosol from coagulation with sodium hydroxide. Sols containing hydroxypropyl methyl-cellulose exhibit the greatest stability over time at pH 7.4 (the pH of blood), created by the addition of a phosphate-buffered saline mixture.
PDF

Adsorption of Acetone on HNO3-Treated AG-3 Activated Carbon: Performance and Kinetic Study

https://doi.org/10.58224/2619-0575-2025-8-2-1
Abstract
The study focuses on enhancing the adsorption of acetone, a prevalent oxygenated volatile organic compound (VOC), using HNO3-modified AG-3 activated carbon (AC) to mitigate its environmental and health impacts. It aims to optimize HNO3 modification of AG-3 AC, targeting enhanced acetone adsorption capacity and improved kinetics.
Methods: In this work, commercial AG-3 was treated with 2 M, 4, M and 6 M HNO3 solutions through reflux heating at 100 °C, followed by washing and drying. Adsorption experiments were conducted using gravimetric analysis at 25 °C and 1 atm, with kinetic data fitted to pseudo-first-order, pseudo-second-order, Elovich, and Mor-ris-Weber models. The modified ACs were evaluated for their specific adsorption capacities and time-dependent adsorption behaviors.
Results: Results showed that HNO3 treatment enhanced acetone adsorption, with the 2 M HNO3-treated AC (HAC-2) exhibited the highest capacity of 0.2951 g/g, a 15 % improvement over unmodified AG-3 (0.2570). Kinetic studies revealed that the pseudo-second-order kinetic model best described the adsorption process, indicating chemisorption as the primary mechanism. As concentration of HNO3 increased (4 M and 6 M), it led to reduced adsorption capacity compared to HAC-2, suggesting excessive oxidation may damage the carbon structure.
Conclusions: The study concludes that the optimal HNO3 concentration for enhancing acetone adsorption on G-3 AC lies around 2 M. This approach highlights the potential of HNO3-modified AG-3 as an effective adsorbent for acetone remediation in adsorption application.
PDF

A set of possible approximative methods for efficiently recalculating the contribution of coulomb integrals to the elements of the single-electron hamiltonian at SCF iterations to dramatically speed up extremely resource-intensive DFT calculations of giant biomolecules

https://doi.org/10.58224/2619-0575-2025-8-3-3
Abstract
The investigation aims to identify potential approximative methodologies for expediting repeated calculations of Coulomb integral contributions to single-electron Hamiltonian elements during self-consistent field (SCF) iterations, thereby dramatically accelerating computationally intensive density functional theory (DFT) analyses of massive biomolecular structures. The research addressed several challenges: a) evaluating semi-empirical approaches for quantum chemical examination of enormous molecular systems; b) exploring how numerous distant molecular fragments could facilitate faster computation of Coulomb interaction contributions; c) examining contemporary approaches to fixed-geometry single-point molecular calculations; d) developing innovative methodologies for accelerated Coulomb integral contribution computation in DFT analyses of substantial bi-omolecular entities.
We present a novel suite of approximation techniques designed to substantially expedite calculations of Cou-lomb integral contributions to one-electron Hamiltonian elements in conventional DFT methodologies during SCF iterations-typically the rate-limiting phase of these essential yet computationally demanding calculations for exten-sive biomolecular systems, including thousands of docking complexes comprising thousands of atoms.
Our integrated approach features rapid and precise approximation of contribution modifications across innu-merable 4-center Coulomb integrals between successive SCF iterations through auxiliary density function-mediated transformation into linear combinations of 3-center integrals, subsequently converted to combinations of 2-center integrals. Contribution variations from non-multipole short-range components of these 2-center integrals are swiftly determined by modifying pre-computed spline contributions based on inter-atomic separations. The re-maining multipole-based long-range contributions undergo rapid computation for expansive molecular systems using a fast multipole method (FMM) framework, which strategically partitions extensive spatial domains into hi-erarchical regions (a technique originally pioneered for galactic dynamics simulations).
Each SCF iteration employs sophisticated screening to identify exclusively non-negligible integral combina-tions, particularly accounting for the progressively diminishing density matrix increments characteristic of con-verging SCF processes. The framework accommodates the unique characteristics of specific massive molecular systems or extensive collections thereof, such as thousands of docking arrangements between substantial protein structures and diverse small organic ligand molecules.
All bimolecular components-including approximations of two-center basis function overlaps via linear combi-nations of single-center auxiliary density functions-undergo efficient computation utilizing specialized database-stored inter-nuclear distance splines. For novel basis sets, the reference database can be promptly augmented through decomposition into universal exponential components with corresponding database enrichment.
PDF

Synthesis of sulfur-containing precursor of targeted lipoconjugates

https://doi.org/10.58224/2619-0575-2025-8-3-4
, ,
Abstract
Objectives: To search for and develop a method for synthesizing sulfur-containing lipids based on 1,2-di-O-tetradecyl-rac-glycerol.
Methods. Separation and purification of the obtained compounds were accomplished by column chromatography on silica gel and extraction. A combination of physicochemical analytical methods, including NMR-spectroscopy and mass-spectrometry, was used to confirm the structures of the obtained compounds.
Results. A new method for synthesizing sulfur-containing precursors for targeted lipoconjugates has been developed. 1,2-di-O-tetradecyl-rac-glycerol with a tetraethylene glycol spacer was used as the hydrophobic domain. Divinyl sulfone was attached to the terminal amino group under basic conditions. However, proton signals from the dioxothiomorphonyl group were detected in the NMR spectra of the resulting compound, confirming the cyclization of the vinylsulfone group with primary amines. This problem can be solved by replacing divinyl sulfone with its analog with an ethylene glycol spacer, bis-vinylsulfone, and alkylating the primary amino group of the tetraethylene glycol spacer, since the formation of the dioxothiomorphonyl group is excluded from secondary amines.
Conclusions. The interaction of divinyl sulfone with the primary amino group of a tetraethyleneglycol-containing lipid based on 1,2-di-O-tetradecyl-rac-glycerol was investigated. The resulting addition reaction product was further used to create CL and study the delivery of NA to target cells. The search for optimal synthesis conditions for producing vinyl sulfone-containing precursors of the targeted lipoconjugates will also continue.
PDF

Bentonite from the Nalchik deposit and the possibilities of its use as a cationic adsorbent

https://doi.org/10.58224/2619-0575-2025-8-2-2
, , , ,
Abstract
Chemical, mineralogical, granulometric and structural-morphological characteristics of bentonite clays of the Nalchik deposit have been established. The elemental composition contains B (trace amounts), Al, Si, K, Ca, Ti, Fe. It has been revealed that the mineralogical composition of the studied clay is complex of montmorillonite, clinoptilolite and low-temperature trigonal quartz. The montmorillonite content is 53.0 ± 1.1 wt.%. The maximum particle size is 198.7-210.1 μm, the proportion of such particles is 0.69 wt.%. The minimum particle size is 0.6-0.9 μm, the proportion of such particles is 1.22 wt.%. According to the results of differential thermal analysis, 4 endoeffects were recorded, the total mass loss on sample calcination was 16.5%, taking into account the loss of free water - 9.5 wt.%. The adsorption characteristics of the analyzed bentonite were studied using “model” pollutants – nickel (II) cations and methylene blue dye. It was found that the adsorption isotherm of nickel (II) ions belongs to class L type 3, and the adsorption isotherm of methylene blue belongs to class L type 2 according to the Gils classification. The results of the study showed that bentonite clay from the Nalchik deposit is capable of purifying wastewater to the maximum permissible concentration of cationic pollutants.
Objectives: to investigate the material composition and adsorption properties of bentonite clay from the Nalchik deposit.
Methods. To determine the elemental, phase and granulometric composition, the following equipment was used: transmission electron microscope JEM-2100 (Jeol, Japan), diffractometer Ultima IV (Rigaku, Japan), combined analyzer TG/DTG/DTA SDT Q600 (TA Instruments, Inc., USA), particle size analyzer Microtrac S3500 (USA), as well as laboratory instruments and reagents.
Results. The mineralogical composition of the clay sample from the Nalchik deposit was established; the mass content of montmorillonite was determined. The granulometric composition was studied. The adsorption processes of the clay sample in relation to the organic dye methylene blue and nickel (II) ions were investigated.
Conclusions. The mineralogical composition of the clay sample from the Nalchik deposit was determined: montmorillonite, clinoptilolite and low-temperature trigonal quartz. The montmorillonite content is 53.0 ± 1.1 wt.%. The maximum particle size of the fraction in the studied clay sample is 198.7-210.1 μm, the proportion of such particles is 0.69 wt.%. The minimum particle size of the fraction is 0.6-0.9 μm, the proportion of particles is 1.22 wt.%. The adsorption processes of the clay sample in relation to the organic dye methylene blue and nickel (II) ions were studied. It was shown that the clay of the Nalchik deposit is capable of purifying wastewater from the specified cationic pollutants to the regulatory requirements.
PDF

Aluminum oxide for liquid filters

https://doi.org/10.58224/2619-0575-2025-8-2-3
, , , ,
Abstract
Liquid filtration is an important process in many high-tech and critical manufacturing sectors. Traditional filter materials have a number of limitations. Anodic aluminum oxide stands out due to its unique highly ordered nanoporous structure, high thermal and chemical resistance, and the possibility of surface functionalization. The main areas of successful use of nanoporous aluminum oxide filters are pharmaceuticals and biotechnology, microelectronics, food industry, as well as other specialized environmental and industrial tasks. A comprehensive evaluation of 100 nm alumina liquid filters and comparison with alternative filtration technologies has shown their undeniable advantages in high temperature and aggressive chemical environments. However, significant challeng-es remain, primarily related to cost, contamination, potential fragility, and the need to further improve the long-term stability of some alumina phases or under extremely harsh operating conditions.
PDF

Prospects for the development and analysis of raw materials for bioethanol production

https://doi.org/10.58224/2619-0575-2025-8-2-4
,
Abstract
Objectives: the purpose of the work is to consider bioethanol as a promising renewable fuel, analyze its production technology, raw material base, technological generations, as well as the structure of the global market and its environmental role.
The methods consist in analyzing the historical development of technology. A review of the raw material base (sugar-containing, starch-containing, lignocellulose materials) and an analysis of global experience (Brazil, USA, EU) and the potential of Russia. The article highlights the history of bioethanol development, starting with the first developments of Henry Ford and ending with modern trends and technologies. The factors contributing to the growing interest in bioethanol production technology are analyzed. The different generations of bioethanol (first, second, third and fourth) are considered in detail. Special attention is paid to the overview of the global bioethanol market, its current state and growth forecasts due to strict environmental regulations and the increased use of bio-fuels in the transportation industry.
Results. The data on different generations of bioethanol, their advantages and disadvantages are systematized. A comparative analysis of the effectiveness of different types of raw materials (yield, ethanol yield) is presented. An assessment of Russia's prospects in the development of the bioethanol industry is given against the background of international experience. The article discusses the raw material base and technologies for the production of first-generation bioethanol from sugar cane, corn, wheat, and sugar beet. In addition, promising areas of technology for the production of bioethanol of the second and third generations are being considered. Where lignocellulose raw materials such as wood waste, straw waste, and fast-growing energy crops are used as raw materials. Special at-tention is paid to comparing the effectiveness of different types of raw materials: sugar-containing crops (sugar beet, cane), starch-containing (cereals, potatoes) and lignocellulose waste (straw, wood, miscanthus). The ecologi-cal role of bioethanol and its importance for energy security are emphasized.
Conclusions. Sugar-containing raw materials demonstrate high efficiency, but their use is limited by seasonality and competition with the food industry. Starch-containing cultures provide stable ethanol yield, but require addi-tional hydrolysis steps. Lignocellulose raw materials are the most promising direction for second—generation bio-ethanol. It solves the problem of waste disposal and does not compete with food resources, but requires more so-phisticated processing technologies. The market leaders are Brazil (cane ethanol), the USA (corn), and the EU (lignocellulose technologies). Their success is linked to government support and environmental regulations. Russia also has significant raw material potential for the development of this industry. The article is based on current re-search and contains comparative characteristics of raw materials, which makes it useful for specialists in the field of bioenergy, agriculture and ecology.
PDF

Thermal decomposition of low-density polyethylene: kinetic study using TGA and DTG data

https://doi.org/10.58224/2619-0575-2025-8-1-1
Abstract
Pyrolysis of low-density polyethylene (LDPE) waste is considered as a highly efficient and promising recycling method. The aim of this work is to investigate the pyrolysis kinetics using three model-free methods (Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS)) and two model-fitting methods (Arrhenius and Coates-Redfern). Thermogravimetric (TGA) and differential thermogravimetric (DTG) thermograms at 5, 10, 20 and 40 K min−1 showed a linear curve, which implies the first-order reactions. The kinetic parameter values (E_A and A) of LDPE were calculated at different conversions by three model-free methods, and the average values of activation energies obtained were in good agreement and ranged from 190.23 to 191.89 kJ/mol. These kinetic parameters were additionally calculated at different heating rates using the Arrhenius and Coates-Redfern methods.
PDF

The Review of corrosion protection by nanotubes TiO2 and BTA/TiO2 nanotubes dispersed in Epoxy and proposed method for preparation of anti-corrosion coating from this material assisted by ultrasound

https://doi.org/10.58224/2619-0575-2025-8-1-2
,
Abstract
This review presents the corrosion resistance of epoxy coatings containing TiO2 nanotubes and BTA (benzotriazole)-modified TiO2 nanotubes. The purpose of the study is to examine how effectively these materials protect against corrosion on metal surfaces in various environments. The synthesis of TiO2 nanotubes and BTA/TiO2 nanotubes in epoxy coatings offers a promising approach to significantly enhance corrosion resistance while also opening considerable potential for applications in industries requiring high durability and material protection.
PDF