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Vol. 8 Issue 3

Archives Journal Chemical Bulletin Vol. 8 Issue 3

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

https://doi.org/10.58224/2619-0575-2025-8-3-1
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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.
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Colloidal protection of magnetite hydrosols with polysaccharides

https://doi.org/10.58224/2619-0575-2025-8-3-2
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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.
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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.
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Synthesis of sulfur-containing precursor of targeted lipoconjugates

https://doi.org/10.58224/2619-0575-2025-8-3-4
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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.
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