The corrosion–electrochemical behavior of nickel and nickel–molybdenum coatings electrodeposited from electrolytes based on deep eutectic solvents (DES) in a 3% NaCl aqueous solution was examined. The coatings were deposited from eutectic mixtures of choline chloride with ethylene glycol (ethaline) and urea (reline) at different current densities; for comparison, nickel coatings prepared using a conventional aqueous sulfate–chloride nickel-plating electrolyte were also studied. The corrosion characteristics were determined by potentiodynamic polarization with subsequent Tafel analysis to calculate the corrosion current density, corrosion potential, and polarization resistance. It was shown that coatings deposited from DES-based electrolytes exhibit higher corrosion resistance than those obtained from the aqueous electrolyte. The incorporation of molybdenum into the deposit was found to decrease the corrosion current density and increase the polarization resistance, while an increase in the Mo content in the alloy leads to further improvement in the anticorrosion properties of the coatings. It was also shown that, at similar molybdenum contents, coatings deposited from the reline-based electrolyte exhibit higher corrosion resistance than those obtained from ethaline, which is associated with the higher carbon and oxygen contents in such coatings and the formation of an additional barrier layer on the surface.

The use of ultra-high frequency (UHF) ultrasound (10–25 MHz) in sonoluminescence spectroscopy was studied. Methods for determining impurities in highly concentrated solutions were developed and used to determine the main substance content in natural brines and solutions of CsCl (400 and 600 g/dm3) and LiCl (400 g/dm3). The simultaneous use of UHF and low-frequency (LF) ultrasound (18–23 kHz) for the sonoluminescence determination of potassium, lithium, calcium, and magnesium in NaCl brines was studied. When using the simultaneous action of UHF and LF ultrasound, the lower limit of determination of KCl, LiCl, CaCl2, and MgCl2 in brines decreases fivefold (0.10 g/dm3) compared with the separate use of UHF or LF ultrasound. The optimal parameters are as follows: UHF: frequency of 20–22 MHz and intensity of 20 W/cm2; LF: frequency of 19–22 kHz and intensity of 1.3–1.5 W/cm2.

The temperature dependences of the solubility of 4,7-dioxo-7-phenylheptanoic acid in organic solvents, in particular methyl acetate, ethyl acetate, acetonitrile, acetone, n-propanol, isopropanol, n-butanol and isobutanol, in the temperature range of 272–295 K were experimentally investigated. Based on the results obtained, the enthalpy (solH) and entropy (solS) of dissolution were determined. The enthalpy and entropy of melting of this acid were calculated using the method of differential thermal analysis. The thermodynamic parameters were reduced to the standard temperature of 298.15 K, and the enthalpies and entropies of mixing of the components at this temperature were also calculated. Based on the thermodynamic parameters of mixing, a compensation effect was revealed, and the nature of the interaction between the solvent and the solute was investigated.

Water pollution from industrial waste, particularly dye contaminants such as methyl green, is a major problem. One promising approach involves using kaolin clay and its composite with palmitic acid. The materials were characterized using X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The adsorption efficiencies of kaolin clay and its compounds for methyl green were 86% and 97%, respectively, indicating that the modification improved the adsorption performance of the clay.

The degree of connectivity of the spatial structural network of boron, silicate, and boron-silicate glass, depending on the chemical composition, is proposed to be estimated using the values of the relative fraction of free volume in their structure. These values are calculated using developed formulas as a function of the molar volume of the glass and the content of B2O3, SiO2, and Li2O oxides in the glass. For glassy substances in the oxide systems Li2O–B2O3, Li2O–SiO2, and Li2O–B2O3–SiO2, the dependence of the calculated values of the relative fraction of free volume in their structure on their chemical composition was established, as well as a strong correlation between the amount of free volume in experimental glassy substances and the values of their properties. This provides reason to believe that the proposed formulas are sufficiently justified and suitable for the quantitative assessment of the degree of connectivity of the spatial structural network of boron, silicate, or boron-silicate glassed. The differences in the values of the coefficient of linear thermal expansion and glass transition temperature for glassy boric anhydride, in comparison with quartz glass, are due to a significantly higher content of free volume in its structure than in glassy SiO2. In this regard, the addition of Li2O to the composition of boron glass in an amount of up to approximately 37 mol.% contributes to a decrease in the proportion of free volume in the glass structure and a corresponding increase in the degree of connectivity of its anionic network, as well as the formation of [BO4]5– tetrahedra. In contrast, an increase in the Li2O content in the glass composition above approximately 37 mol.% leads to an increase in the proportion of free volume in the glass structure and a decrease in the degree of connectivity of its anionic network.

The study investigates the influence of solid-state polycondensation (SSP) conditions on the change in intrinsic viscosity (IV) of recycled poly(ethylene terephthalate) (PET) processed via a bottle-to-bottle technology. Experimental work was carried out within the temperature range of 110–1600C while varying the duration of SSP. It was found that during SSP at 110–1300C, the intrinsic viscosity of PET-BTB increased by 23–34%, whereas the melt flow index (MFI) decreased by up to 54%, indicating a nonlinear relationship between IV and MFI. A mathematical model was proposed to predict IV as a function of temperature, SSP duration, and MFI value. Validation of the model revealed a deviation not exceeding 6%, which confirms its high practical reliability. The proposed approach enables a reduction in the scope of experimental work required for optimizing SSP conditions of recycled PET and assessing its recyclability toward products with the desired level of physical and mechanical properties.

The relevance and potential of modifying calcium silicophosphate glasses with components such as Li2O, MgO, SrO, ZnO, Ga2O3, Nb2O3, CeO2, and SnO2 have been analyzed with the aim of developing biocompatible glass-ceramic materials with adjustable resorption rates for the replacement of bone tissue areas under different loading conditions. An evaluation of the degradation behavior in model solutions was conducted depending on the content of crystalline phases and the residual glass matrix in vitro, as well as the relationship between surface structure and the potential for apatite-like layer formation in vivo. It has been established that the modification of calcium silicophosphate glass-ceramic materials containing 45–55 vol.% hydroxyapatite and 10–15 vol.% lithium disilicate, with additives of MgO+ZnO+SrO in total concentrations of 2–6 mass%, SnO2+CeO2 at 0.5–1 mass%, and Nb2O3+Ga2O3 at 0.02–0.1 mass%, provides a resorption behavior characterized by a mass gain of 1–2% in simulated body fluid (SBF), and a Ca:P ratio of 1.0–1.67 on the surface. The resulting surface roughness (Ra2.2–4.0 m) and surface free energy (SFE73.45–77.51 mJ/m2) create favorable conditions for the formation of an apatite-like layer in vitro within 30 days. Based on these findings, the feasibility of implementing novel types of biocompatible bone implants and coatings using the developed bioactive modified glass-ceramic materials has been demonstrated.

Gold nanoparticles were synthesized by reducing hydrogen tetrachloroaurate(III) trihydrate (HAuCl43H2O) using plant waste (banana peel) extracts obtained using a deep eutectic solvent (DES) based on choline chloride. It was demonstrated that the plant waste (banana peel) extract obtained by DES allows the synthesis of spherical gold nanoparticles (Au NPs), characterized by a maximum plasmon resonance absorption peak at approximately =540–560 nm, with an average nanoparticle size range of 31–68 nm with a zeta potential value of –33 to –36 mV, depending on the initial concentration of the precursor stabilizer used in the synthesis process. Choline chloride-based DES was used as a new alternative to conventional solvents for ultrasonic extraction of active substances from plant waste, in particular banana peel. Low-temperature eutectic solvents based on choline chloride were compared with glycerol and lactic acid in a ratio of 1:3 and water 10–30%. It was found that choline chloride and glycerol in a ratio of 1:3 with a water content of 30% are highly effective for the extraction of flavonoid compounds from plant waste (banana peel). The influence of extraction parameters, namely sample-to-solvent ratio and extraction time, on the content of extracted flavonoids and antioxidant activity of the extract was studied using the methods of determining antioxidant activity by ferric ion reduction (FRAP) and the ABTS test (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid). It was established that the extracted flavonoid content using DES is 222–521 mg/100 g. It was established that the sample-to-solvent ratio (1:45–1:80) and the extraction time of 10–30 min allow obtaining the antioxidant activity value of banana peel extracts, determined by the FRAP and ABTS methods: 20–60 mmol/l and 15–35 mmol/l. The gold nanoparticles obtained using DES extracts of banana peel showed higher antibacterial activity against E. coli compared to the DES extract of banana peel and non-sterilized gold nanoparticles.

A study was conducted on the catalytic activity of various glass layers formed using different technologies and prepared from colloidal solutions of the manganese–aluminum–silicon oxide (MAS) system on the surface of mullite–silica in the reaction of converting carbon monoxide (CO) to carbon dioxide (CO2). A dependence was established between the structural and chemical state of the surface of secondary carriers created by technological influences and their catalytic and energetic properties. Mullite–silica exhibited practically no catalytic activity, indicating the absence or low propensity of active sites on its surface to conduct reactions. The application of a single amorphous layer onto the mullite–silica significantly increases the degree of CO conversion, indicating the presence of active sites on the new reaction surface. The maximum reactivity and the highest activation energy value were shown by the amorphous surface structure formed by two layers, obtained under conditions of rapid firing. The profilograms of such a surface indicated that this firing mode promotes the formation of a larger number of high-energy reactive centers. Modifying the surface of mullite–silica with an amorphous glass composition allows targeted control of its catalytic activity. It has been shown that not only the amount of glass but also the method of its application and thermal treatment have a significant influence, which must be taken into account when developing catalytic neutralizers based on ceramic carriers.

Interaction in the systems "sulfur(IV) oxide–2-hydroxypropylamine (MiPA)–water" and "sulfur(IV) oxide–MiPA–paraform–water" leads to the formation of 2-hydroxypropylammonium sulfite [CH3CH(OH)CH2NH3]2SO3 (I) and N-(2-hydroxypropyl)aminomethanesulfonic acid CH3CH(OH)CH2N+H2CH2SO3– (II), respectively. These compounds, upon independent recrystallization from aqueous solution, are transformed into 2-hydroxypropylammonium sulfate [CH3CH(OH)CH2NH3]2SO4 (III) as a result of hydrolytic transformations. The obtained products were characterized by the methods of elemental and X-ray structural analysis, IR, Raman, 1H and 13C NMR spectroscopy, and mass spectrometry. Compound III crystallizes in triclinic class (space group P-1, a=9.0753(8) Å, b=10.3038(7) Å, c=13.6845(14) Å, =99.491(7)0, =94.712(8)0, =90.119(7)0, V=1257.7(2) Å3, Z=4). The IR spectrum of salt I shows the valence vibrations of (SO) sulfite anion (1 and 3), represented by bands at 912 and 954 cm–1, respectively. The vibration s (2) of SO32– ion is observed in the IR spectrum as relatively intense bands at 610 and 621 cm–1. In the IR spectrum of compound II, the vibrations as(SO2) appear as a doublet at 1234 and 1208 cm–1; s(SO2) is represented by a multiplet of lines in the 1180–1030 cm–1 region. Upon attempted recrystallization from aqueous solution, the ammonium sulfite salt MiPA (I) undergoes hydrolytic sulfoxidation, converting into the corresponding sulfate III. Similarly, the N-alkylated AMSA derivative II is oxidized via a hydrolytic redox process to sulfate III as well.