Russian Journal of Physical Chemistry A最新文献

The results of the kinetics study of the isotope exchange reaction between water and chloroform, one of the methods for obtaining deuterochloroform, used as a solvent for nuclear magnetic resonance spectroscopy, are presented. It is shown that increasing the temperature from 298 to 323 K leads to an increase in the observed rate constant by almost an order of magnitude. The results of the study of the reaction kinetics depending on the concentration of the catalyst, alkali, are presented. Thus, increasing the concentration of alkali from 0.05 to 0.1 M leads to a 4-fold acceleration of the reaction. It is shown that the reaction rate does not depend on the alkali cation. The paper also presents the definitions of the separation coefficient of the studied system in the temperature range of 298–323 K: the heavy isotope, deuterium, is concentrated in the organic phase, and the value of the single separation effect decreases from 1.062 ± 0.015 to 1.034 ± 0.011.

Photocatalytic technology, renowned for its green, economical, and highly efficient characteristics, has garnered significant attention in the fields of wastewater treatment and environmental remediation. In this study, Ba_0.7Sr_0.3TiO₃ was synthesized via the solid-state method, and g-C₃N₄ was incorporated to construct a g-C₃N₄/Ba_0.7Sr_0.3TiO₃ multiphase composite with enhanced photocatalytic performance. The photocatalytic efficiency of the composite catalysts with varying mass fractions was evaluated for the degradation of tetracycline hydrochloride. The g-C₃N₄/Ba_0.7Sr_0.3TiO₃ composite was characterized using XRD, SEM, UV–Vis, and PL techniques to analyze its crystal structure, microstructure, and optical properties. The results demonstrated that the composite with 5% g-C₃N₄ mass fraction exhibited the highest photocatalytic activity, achieving a tetracycline hydrochloride degradation rate of 86% within 120 min, compared to 67% for pure Ba_0.7Sr_0.3TiO₃. These findings indicate that the incorporation of g-C₃N₄ effectively reduces the band gap of the composite, increases carrier concentration, and significantly enhances photocatalytic performance. This study highlights the potential of g-C₃N₄/Ba_0.7Sr_0.3TiO₃ as a promising material for photocatalytic applications in environmental remediation.

The structural, electronic and nonlinear optical (NLO) properties of BN-substituted graphdiyne (BNGDY) with the doping of Li₃NM (M = Li, Na, and K) alkalides are systematically studied using density-functional theory calculations, in order to disclose the effect of the alkalides on molecular optical properties. The results show that the Li₃NM alkalides can stably adsorb on the surface of six planar BNGDY structures, of which the structures with small substitution ratios of BN-pairs on diacetylenic linkages exhibit strong chemical stabilities. Moreover, the Li₃NM alkalides have the slightly increased charge transfer with alkali metals from Li to K, and that is a decreasing trend with increasing BN substitution ratios (A → F) on GDY. More interestingly, the successive introduction of the alkalides on BN-substituted graphdiyne can effectively modulate the electronic properties and nonlinear optical responses of the systems. Importantly, the BNGDY structure (D) with the doping of Li₃NLi on triangular hole possesses the excellent nonlinear optical performance with much larger first hyperpolarizability values (e.g., 1.890 × 10⁶ a.u.), which can be further understood by the analysis of the first hyperpolarizability density and the two-level model from the excitation energy calculations. This study will inevitably provide an excellent strategy for designing the next generation high-performance NLO materials.

The influence of the pore size of a nanoporous material and the rate of change in the internal volume of the nanoporous material–nonwetting liquid system on the filling pressure of the nonwetting liquid (distilled water) of hydrophobized nanoporous materials with pore sizes of 9 nm (Fluka 100 C8), 5 nm (Fluka 60 C8 PF), and 2 nm (MCM-41-C1) at rates of change in the volume of the nanoporous material–nonwetting liquid system of 2.7 × 10^–4, 2.7 ×10^–3, and 2.7×10^–2 cm³/s was studied. It was shown that decreasing the pore size increases the characteristic pore filling pressures, which follows from the classical theory of capillarity. It was also found that increasing the rate of change in the internal volume of the nanoporous material–nonwetting liquid system leads to an increase in filling pressures for all systems with an increase in the rate from 2.7 × 10^–4 up to 2.7 × 10^–3 cm³/s, but further increase in rate to 2.7 × 10^–2 cm³/s leads to an increase in filling pressures only for MCM-41-C1, while for other systems this increase is within the measurement error. Based on the results obtained, it can be concluded that there is a transition from a quasi-static to a quasi-dynamic filling mode. It is also possible to assume the existence of a critical pore size that determines condition for the growth of filling pressure with an increase in the rate of change in the internal volume of the system.

The process of reprocessed uranium enrichment according to a double-cascade scheme using an inert carrier gas to purify the regenerate from the isotope ²³²U is considered. Using the quasi-ideal cascade model, numerical studies of the influence of various process parameters on the distribution of key isotopes and the integral characteristics of the system were carried out. The limits of the possible purification effect, determined by the proportion of carrier gas in the feed of the second cascade while maintaining external enrichment conditions, are estimated. It is shown that an increase in the proportion of carrier gas in the second cascade feed leads to an increase in the isotope ²³⁶U content in the final product, which entails a significant (more than 1%) increase in ²³⁵U enrichment. In addition, the efficiency of the cascade scheme in terms of purification from ²³²U is largely determined by the choice of the operating mode of individual separation devices.

It was experimentally established that an increase in the temperature in the range of 20–90°C improves the parameters of Lu/Yb chromatographic separation on the Dowex 50WX8 cation exchanger with the α-HIBA eluent (0.125 M, pH 4.3). An increase in the temperature leads to a decrease in the height of the equivalent theoretical plate (HETP) from 7.7 to 0.6 mm for Yb and from 1.1 to 0.3 mm for Lu, to an increase in resolution between peaks from 0.6 to 1.7, and a change in Yb peak asymmetry from 2.1 to 0.4. The temperature dependences of the retention volumes are well described by the Van’t Hoff equation (R² = 0.99). The observed 1.8-fold peak broadening for Yb and 2.4-fold for Lu is accompanied by a decrease in the maximum yield in fractions from 14.4 to 5.5% for Lu and from 5 to 3% for Yb.

The processes of electrodeposition of tin–nickel alloys on 08kp steel from oxalate–ammonium electrolytes and the physicochemical properties of the coatings were investigated. It is shown that the electrodeposition proceeds with high polarization, in contrast to the process of deposition of tin–nickel alloys from a chloride–fluoride electrolyte. The highest corrosion rate (26 μA/cm²) corresponds to a sample with a coating obtained from the chloride–fluoride electrolyte. Low corrosion rate is observed for coatings of tin–nickel alloys with a low nickel content deposited from oxalate–ammonium electrolytes with the addition of the OS-20 preparation (1.2–5 μA/cm²). The influence of the ratio of alloy components on the chemical composition and microstructure of the coatings is demonstrated.

The authors present results from studying of the distribution of the activity of different products of thoron decay according to the size of aerosol particles in the nanometer range under conditions of long-term storage. Instrumental, methodological, and metrological features of studying the state of radioactive aerosol particles are considered.

The thermal stability of polymers based on oligoester(meth)acrylates (OCM-2, PEGDM-n (n = 210, 550, 750), PETA) as a function of the nature of the monomer, quinone concentration in the photoinitiating system, monomer conversion, and radical polymerization method is studied by thermogravimetric analysis. Of the studied polymers, polyPETA synthesized by sequential photo- and heat-curing exhibits the highest thermal stability. The other polymers have comparable thermal stability. It is shown that the polymer degradation temperature increases with an increase in monomer conversion and elongation of the polyethylene glycol linker. The effective activation energies for thermal degradation processes are calculated by the Friedman and Vyazovkin methods.

A lignosulfonate (LS) sample was modified by introducing zinc and iron(III) cations in it (ion exchange sorption). Associative and dissociative transformations of modified LSs in an aqueous environment were studied. The effects of the concentration (0.01–0.32 g/dm³) and nature of the counterion (Na⁺, H⁺, Zn²⁺, Fe³⁺) in LS on the variation of pH, specific and molar electric conductivity, size of LS associates, and their polydispersity, as well as the surface tension at the liquid–gas boundary, were revealed. Using the nanoprecipitation method, modified LS nanopowders with particle sizes of 40–250 nm were obtained. It is shown that the nature of the LS cation introduced in the polymer matrix has almost no effect on the morphology and size of the isolated nanostructures. The encapsulating effect of the obtained nanoassociates of modified LSs relative to the hydrophobic dye cerasine red was evaluated. It was found that the encapsulation efficiency increases with the growth of LS concentration and the charge introduced in the LS cation and amounts to 60–70%.