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Vol. 6 Issue 2

Archives Journal Chemical Bulletin Vol. 6 Issue 2

Adsorption of kappa-carrageenan on the surface of chitosan and its sulfuric acid salt and stabilization of chitosan-sulfate nanoparticles by it

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 5-18 p.
Abstract
Objectives: to investigate the adsorption of k-carrageenan on the surface of chitosan at pH 7.4 and chitosan treated with dilute sulfuric acid solution (pH 2.5-2.7). To develop a method for obtaining the sol of the chitosan sulfate salt - chitosan sulfate (CX) and to investigate its stability in time depending on the use of various acids as precursors, and its increase with the addition of different concentrations of k–carrageenan.
Methods. To determine the viscosity of polymer solutions, their molecular weight and to study the adsorption of k-carrageenan on CX, the method of capillary viscometry was used. The assessment of the stability of the zones over time was carried out photometrically.
Results. The adsorption of k-carrageenan on chitosan and CX has been studied: experimental isotherms of k-carrageenan adsorption have been constructed.on the surfaces of chitosan and CX, the constants of the Langmuir equation are calculated and complete theoretical adsorption isotherms are constructed using them. A method for obtaining a CX hydrosol with a positive particle charge has been developed. The stability of CX sols in time both without additives and with additives of k-carrageenan in time has been studied.
Conclusions. The adsorption of k-carrageenan on chitosan and CX is monomolecular. The adsorption equilibrium constant is greater with the adsorption of k-carrageenan on the surface of CX, and the maximum adsorption value is greater with the adsorption on the surface of chitosan. Of the acids used as precursors, the sol obtained using citric acid has the greatest stability. With an additional additive to the sols of the protective colloid - k-carrageenan to sols obtained using hydrochloric acid and citric acid, the sol obtained with the use of hydrochloric acid and carrageenan additives in the range of 0.04-0.06% has the greatest aggregate stability.
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Energy-efficient nanocomposite membrane-electrode blocks for chemical current sources

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 19-28 p.
Abstract
Electrode materials based on platinum metal nanoparticles are widely used to create alternative energy sources with high specific characteristics. Industrial carbon-containing carriers and perfluorinated proton exchange membranes of the Nafion type are used as matrices for the fuel cell electrodes formation. In this work, new effective polymer-carbon catalysts modified with platinum nanoparticles have been synthesized. Physicochemical and functional characteristics of nanocomposites have been studied by electron microscopy, X-ray phase analysis, small-angle X-ray scattering and cyclic voltammetry. Increased catalytic activity and stability of the formed electrodes in hydrogen-oxygen fuel cells had been found. The test results of hydrogen-air fuel cells in model operating conditions had been obtained. The current density maximum parameters of the membrane-electrode assemblies had been found for nanocomposites formed on multi-walled carbon nanotubes with a solubilization coefficient of ω equal to 1.5 and a platinum content of 0.35 mg/cm2. The creation of new membrane-electrode assemblies helps to reduce the cost of chemical current sources, as well as increase their energy efficiency.
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Using the spectrophotometric method to evaluate the properties of complex compounds of iron (III), copper (II) and magnesium with organic ligands

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 29-37 p.
Abstract
In this paper, we propose a spectrophotometric method for assessing the effect of organic ligands on the oxidizing properties of complexing agents (iron (III), copper (II)) and on the heterogeneous equilibrium in the magnesium-hydrophosphate system. An analysis of experimental data shows that glutamic acid at a concentration in solution from 50 to 250 mg/l does not affect the reduction of iron (III), however, the interaction of copper (II) with glutamic acid reduces the ability of Cu2+ to reduce by 9% and 39% at concentration in solution from 50 to 100 mg/l, respectively. The greatest complexing interaction with magnesium, in the "magnesium-hydrophosphate" system, was shown by proton pump inhibitors: rabeprazole and pantoprazole, and the smallest - esomeprazole and omeprazole.
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Structural and morphological characteristics of layered hydroaluminosilicates activated by solutions of alkali metal chlorides

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 38-49 p.
Abstract
This study presents the results of a comparative investigation into the chemical and mineralogical compositions, as well as the structural-morphological characteristics of enriched and modified forms of clay, which contains layered hydroaluminosilicate – montmorillonite – as its main mineral phase. Impurity minerals in the clay raw material include kaolinite, low-temperature trigonal quartz, calcite, and illite, whose presence is confirmed by transmission electron microscopy and infrared Fourier spectrometry. Activation of the enriched rock was performed by treating it with solutions of alkali metal chlorides – lithium, potassium, and sodium chlorides. It is shown that the original form of the clay does not contain Na2O and Li2O oxides. However, through the salt treatment of the enriched hydroaluminosilicate rock, products with a content of lithium, sodium, and potassium oxides were obtained, amounting to 1.96%, 3.98%, and 6.28% by mass, respectively. It is established that the treatment with potassium chloride solution has the most significant influence on the structural-morphological characteristics of montmorillonite clay. Specifically, the sample treated with KCl solution exhibits an increased tendency towards particle aggregation and the formation of relatively large, spherical grains. It is also shown that the activated product mentioned above is almost entirely devoid of the mineral phase known as calcite. Meanwhile, the impact of LiCl and NaCl salt solutions on the enriched clay raw material hardly alters the microstructure of the resulting products.
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