Vol 97, No 12 (2023)

The electrical conductivity of a number of tetraalkylammonium ionic liquids with tetrafluoroborate anion has been studied in acetone in the temperature range 298–313 K. Based on the obtained conductometric data for the compounds under study, the Lee–Wheaton method has been used to calculate the ion association constants (Ka), limiting molar electrical conductivities (λ0), and Gibbs association energy (ΔG0) in solutions. From the temperature dependence of equivalent electrical conductivity, the values of association enthalpy (ΔH0) and entropy (ΔS0) have been calculated. For all studied compounds, the Walden–Pisarzhevsky product has been calculated. Conclusions are drawn about the influence of the structure of the studied ionic liquids on the thermodynamic parameters of association in acetone solutions.

A study is performed of the self-diffusion of tritium and fluorine atoms, and the change in the structure of molten FLiBe upon raising the temperature of the system from 873 to 1073 K. The interaction between neutrons and both lithium and beryllium in molten-salt reactors (MSR) using FLiBe as a fuel salt results in the formation of large amounts of tritium. Tritium, which easily penetrates metallic structural materials at high temperatures, is a radionuclide hazard. Predictive models for the behavior of tritium in a molten fluoride salt must therefore be developed to solve the problem of MSR safety. The emergence of tritium in the system increases the average energy of interatomic bonds upon raising the temperature and concentration of tritium in the system. A rise in temperature is also accompanied by fluorine atoms creating a closer short-range order in the environment of tritium atoms. This is expressed in the formation of a high first peak of radial distribution function gT-F(r), an increase in the number of probable geometric neighbors, which is shown by Voronoi polyhedra, and fluorine atoms giving priority to fourth-order rotational symmetry in the environment of tritium atoms.

The kinetic regularities of degradation of the azo dye methyl orange (MO) in photoinitiated oxidizing systems have been studied using a xenon lamp (UV–Vis) as a source of quasi-solar radiation. According to the efficiency and rate of dye destruction, the considered oxidizing systems can be arranged in the following series: {UV–Vis} < {UV–Vis/S2O2-8} < {S2O2-8/Fe0} < {UV–Vis/S2O2-8/Fe0} < {UV–Vis/S2O2-8/Fe2+}. It has been established that in photoinitiated Fenton-like oxidizing systems there is not only complete conversion of MO but also its deep mineralization in aqueous solution; a decrease in the content of total organic carbon reaches 60%. In this case, the specific catalytic activity of iron ions in the combined system {UV–Vis/S2O2-8/Fe0} is much higher than in {UV–Vis/S2O2-8/Fe2+}. Using inhibitors of radical reactions, it has been proved that in the combined system {UV–Vis/S2O2-8/Fe0} both hydroxyl and sulfate anion radicals take part in oxidative degradation. An inhibitory influence of anions (bicarbonates, chlorides, nitrates, and sulfates) and natural dissolved organic matter (Suwanee River 2R101N) on the process of mineralization of total organic carbon during oxidative destruction of MO in the combined system {UV–Vis/S2O
/Fe0} has been found.

Quantum-chemical calculations of the structure of the molecular forms of glycine and glycylglycine and conjugate ionic forms have been performed. Our own and published data on the thermodynamic characteristics of the reactions of acid–base interactions of glycine and glycylglycine in aqueous organic solutions are summarized, and the influence of the composition of mixed solvents on the acid dissociation constant of the amide group in the copper(II) peptide complex is considered.

The behavior of copper ion-exchange composites with metal particles of various sizes and contents in the electroreduction of oxygen dissolved in water have been studied. The primary size effect is significant for samples with low metal capacity: the smaller the metal particle size, the higher the process rate. At the same time, for samples with high metal capacity, the process occurs at approximately the same rate on copper particles obtained using different reducing agents due to the comparable size. A secondary size effect is observed due to the collective interaction of metal particles. The size effect was taken into account along with the effect of the content of metal particles using the proposed nanosized complex, which represents the ratio of capacity and size. At the level of electronic conductivity percolation, the nanosized complex reaches the limiting value corresponding to the highest degree of development of the reaction surface, which makes it possible to increase the current to the maximum current capacity. The reduction of oxygen occurs along several routes: electroreduction on copper particles, mainly on the surface of nanocomposite grains; and autocatalytic chemical reaction with electroregenerated metal nanoparticles in the nanocomposite grains. The electroreduction of oxygen generally reaches an intense steady-state mode.

Water-insoluble photosensitizing (PS) systems active in the generation of singlet 1O2 oxygen are obtained by immobilizing fluorinated tetraphenylporphyrin (FTPP) from a solution in acetone on films of polyelectrolyte complexes based on sodium alginate (SA) and chitosan (CT), and on solid water-insoluble gels of alginate and chitosan. The obtained polymer PS systems are used to establish the intensity of the photoluminescence of singlet oxygen in D2O and the activity of the photocatalytic oxidation of tryptophan in water. It is shown that the photocatalytic activity in the tryptophan oxidation of fluorinated tetraphenylporphyrin immobilized on a SA–CT polyelectrolyte complex and alginate solid gel is higher than that of FTPP immobilized on chitosan solid gel. Spectral-luminescent properties of polysaccharide–FTPP systems and the surface structure of carriers are studied via atomic force microscopy to determine the mechanism of the increase in porphyrin activity when it is fixed on alginate-containing carriers. It is suggested that aspects of the supramolecular structure of solid gels are responsible for the increase in the photocatalytic activity of FTPP upon immobilization on alginate-containing polysaccharide systems.

Chromatography and mass spectrometry have been used to study the effect of shungite composition on its reaction with 1,1-dimethylhydrazine and its oxidative transformation products. Compounds contained in aqueous solutions of 1,1-dimethylhydrazine before and after its contact with shungite, as well as on the surface of shungite with different ratios of organic and inorganic components, have been analyzed qualitatively and quantitatively depending on the contact time. It has been found that the composition of shungite affects the products of its reaction with 1,1-dimethylhydrazine.

The behavior of surface-active substances (surfactants) is studied using the examples of lignosulfonate (LS) and sodium dodecyl sulfate (SDS) in aqueous and nitric acid media as promising additives for the nitric acid leaching of refractory ore concentrates. The effect the temperature (15–70°С) and concentrations of the surfactant (Csurfactant = 0.02–200 g/dm3) and nitric acid (CHNO3 = 0.1–10 g/dm3) have on the surface tension, critical concentration of micelles (CMC), electrical conductivity, pH, and optical density of solutions is established. The critical association of concentration is determined for lignosulfonate: CLS ~ 0.13–0.14 mol/dm3. An increase in the surface activity of lignosulfonate is noted upon raising the temperature of and adding nitric acid to an LS–H2O system. The established effects (a drop in σl–g) are explained by an increase in the coefficient of diffusion of LS macromolecules and a change in the intensity of the associative-dissociative processes of counterions and the LS polyanion. The positive effect nitric acid has on the surface activity of SDS is noted and found to reduce surface tension at the liquid–gas interface and CMCs. Associative processes in SDS–HNO3 systems are also confirmed by measuring the optical density of the considered systems.

Results are presented from studying the effect barium additives (0.01–1.0 wt %) as a structure modifier have on the anodic behavior of lead babbit BBa (PbSb15Sn10Ba) in a NaCl electrolyte medium. The studies are performed using the potentiostatic technique in the potentiodynamic mode with a potential sweep rate of 2 mV/s. It is shown that the free corrosion potential of alloys shifts to the positive side over time and acquires a positive value upon an increase in the concentration of the modifier (barium) in the lead babbit. Adding barium to lead babbit BBa (PbSb15Sn10Ba) raises its corrosion resistance by 20–25%. An increase in the rate of the corrosion of alloys is noted, regardless of their composition and the concentration of NaCl in a solution. It is shown that raising the concentration of chloride ions in a NaCl electrolyte lowers the potentials of the free corrosion, repassivation, and pitting of alloys.

The kinetic regularities of photochemical oxidation of stable complex cyanides (hexacyanoferrates) with persulfate (oxidizing system {UV/S2O
}) and hydrogen peroxide (oxidizing system {UV/H2O2}) under the influence of quasi-monochromatic UVC radiation from a KrCl excilamp (222 nm) have been studied. According to the efficiency and rate of the destruction of the target compound, the oxidizing systems under study can be arranged in the following series: {UV/S2O2-8} > {UV/H2O2} > {UV}. The effective destruction of hexacyanoferrates at micromolar concentrations (≤47 μM) to nontoxic and biodegradable compounds in the combined {UV/S2O2-8} system is due to the high oxidizing ability of reactive oxygen species formed as a result of persulfate photolysis.

The photochemical reduction of water with cadmium sulfide suspensions containing mixtures of sodium sulfite and formic and acetic acid solutions has been studied by electromotive force measurements and gasometry. The sulfite ions are oxidized on the anode in the sulfite–acetate suspensions; the sulfite ions and formic acid, in the sulfite–formate solutions. Hydrogen peroxide was found among the products of the photochemical reaction; it is involved in the oxidation of the radicals of sulfite ions and molecular sulfur of CdS particles and prevents the reduction of water.

A study is performed of the micromycete biocorrosion of electrical copper M1E and fiberglass FR4 with copper coating, which are used in the production of printed circuit boards. The structure of the surfaces of corroded samples is studied via optical and electron microscopy. Energy dispersive X-ray spectroscopy is used to perform a qualitative and semi-quantitative analysis of chemical elements present in the composition of corrosion products after exposing samples to a bed of micromycetes. An X-ray phase analysis of the products of copper biocorrosion is performed. It is established that microorganisms adhere to the metal surface at the initial stage of micromycetic corrosion, and colonies of them develop. It is suggested that reactive oxygen species (superoxide anion-radical and hydrogen peroxide) participate in the biocorrosion of copper and the functioning of the zerovalent copper–hydrogen peroxide system, triggering a cascade of reactions that result in the destructive oxidation of copper. The role of biofilms of the microscopic fungal colony as the main factor in the mycological corrosion of copper is explained.