Vol 97, No 8 (2023)

Selecting standard and reference states for a thermodynamic description of the non-exchange sorption of substances by ion exchangers is considered a stoichiometric process. It is shown that it is best to choose different reference states for free and sorption centers associated with the absorbed substance, since this allows calculations of the thermodynamic constants and energy characteristics of sorption. Results from calculating thermodynamic characteristics of sorption are presented and discussed for systems with the participation of amino acids (glycine and phenylalanine).

This paper presents the results of a study of the KFe0.33W1.67O6 system. The compound was obtained by a solid-phase synthesis method at a temperature of 1073 K. The structural, morphological, and spectroscopic properties of KFe0.33W1.67O6 were characterized using XRD, SEM-EDS. The compound crystallizes in a cubic lattice with the space group Fd–3m (227). The obtained lattice parameter a = 10.3697 (3) Å. The phase transitions of KFe0.33W1.67O6 were determined by low-temperature and high-temperature X-ray diffraction. The temperature dependence of heat capacity of KFe0.33W1.67O6 has been measured for the first time in the range from 5 to 638 K by precision adiabatic vacuum calorimetry and differential scanning calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity C∘p∘(T), enthalpy H°(T) − H°(0), entropy S°(T) − S°(0), and Gibbs function G°(T) − H°(0), for the range from T → 0 to 630 K.

A study is performed of the electrocatalytic activity of substituted pyridine salts (N-hydro-, N‑methyl-, and N-phenyl-2,4,6-triphenylpyridinium perchlorates) in the electroreduction of carbon dioxide to carbon monoxide. The effect the natures of the substituent and the H+ source have on the efficiency of the process is determined. The main reasons for the occurrence of the electrocatalytic process are identified, and the values of TOF (catalyst speed) and TON (number of revolutions of the catalyst) are calculated. It is shown that the values of TOF and TON fall as the pK of the acid rises.

The solubility diagram of the ternary system NdCl3–PrCl3–H2O has been studied by the method of isothermal saturation in ampules at 25°C. In the system NdCl3–PrCl3–H2O, isovalent substitution solid solutions with the miscibility gap (PrCl3)x(NdCl3)1 – x·6H2O and (PrCl3)x(NdCl3)1 – x·7H2O have been crystallized. In the system, there is one non-invariant eutonic type point, corresponding to the saturation of the solution by two solid phases.

The H2O–3-amino-1-propanol (3AP) system at 300 K was studied by molecular dynamics, graph theory, and Delaunay simplex methods. All the molecules were shown to be bound into a three-dimensional network of hydrogen bonds over the entire range of concentrations in the system. The characteristics of the networks and their concentration dependences were determined. The frequency at which the environment of molecules changes is discussed. The results were compared with those for mixed networks in aqueous solutions of 1,3-propanediol and monoethanolamine.

This review considers the well-known results of rheological studies, first of all, the viscosity and flow curves of various dispersed and polymer systems. The existing explanations of the causes of non-Newtonian flow are presented. Various rheological models are described, in which a change in viscosity is associated with a change in the structure of a substance. The new structural rheological model proposed by us is a generalization of the Casson and Cross rheological models. Its scope includes various structured systems: suspensions, emulsions, polymer solutions and melts, micellar solutions, and liquid crystals. Our attention was focused on the features of the stationary shear flow of non-Newtonian systems.

A dynamic model of the transfer and molecular sorption processes inside a sorption column is considered, based on the acid retardation of a gel anion exchanger. A three-layer model of a space filled with a solution is used to describe the process of keeping solution components inside nanosized pores in a multicomponent system. Allowance is made for the heterogeneity of the concentrations of molecules in the pores of the sorbent, caused by the forces acting on polar molecules from the sorption centers. The model allows calculation of changes in the concentrations of components over time inside the sorption column and, based on output concentration curves obtained experimentally, to determine characteristics of the process of holding molecules inside nanosized pores. Results from modeling are compared to experimental data on the purification of industrial extractive phosphoric acid.

The elution curves were modeled at a constant relative length of the adsorbent bed, but at different values of the b constant involving the kinetic and adsorption constants and the mobile phase velocity. The symmetry coefficients were calculated. They were revealed to be independent of the b constant at selected heights and have a functional dependence on the relative adsorbent bed length. A regularity in the formation of the symmetry of the elution curves in linear adsorption dynamics was established.

It is shown that the column dead time determined from the retention of uracil is longer than the one determined from the retention of homologs—lutein diesters—for C16 reversed phases on three columns with sorbents with different pore diameters (80, 110, and 160 Å). This finding confirms the familiar assumption that the sorbate molecules 10% larger than the pore diameter can cause problems with the retention of the sorbate. It is found for smaller molecules (of alkyl benzoates) that the dead time determined from the retention of uracil is less than the one determined from the retention of the homologs on the same stationary phases, confirming that the main cause of the observed effect is the size factor.

The mechanism and products of the photoreaction of 2-isopropyl-9,10-anthraquinone (1) with ethanol have been established. An analysis of the signals of chemical nuclear polarization (CNP) showed that during the formation of CNP, only the mechanism of singlet-triplet transitions in radical pairs takes place without the participation of a triplet mechanism. In the study of the phase of multiplet and integral effects, the elementary acts of photoreaction were determined, and the structure of the anthrasemiquinone radical participating in the reaction was established.

An experimental study is performed of the mechanism of sulfur dioxide–hydrogen interaction (4Н2 + 2SО2 → S2 + 4H2О) at temperatures of 623, 673, 723, and 773 K and a pressure of 198 Torr. The mechanism is analyzed via mathematical modeling. It is found to be a chain reaction of hydrogen oxidation with sulfur dioxide, which results in the formation of molecular sulfur (S2). The process is characterized by negative Gibbs free energy ΔG723 = −49.950 kcal/mol. The potential energy surface of the (HOSO + HOSO) system is studied by various means of quantum chemistry, and the thermodynamic parameters of the НОSO + НОSO → SO + SO2 + Н2О reaction are determined. A new mechanism of the reaction, supplemented by elementary acts, is discussed. Good agreement is found between energies of activation determined experimentally and calculated using data from our numerical kinetic analysis.

The reaction of hydrogen oxidation with sulfur dioxide in the region of self-ignition (T = 470–510°C and R < 200 Torr) is accompanied by the formation of elemental sulfur in an explosive mode. Kinetic calculations made with the SENKIN:CHEMKIN II program are used to analyze observed flashes of light from the explosive process, based on a mathematical model describing the oxidation of hydrogen with sulfur dioxide. Characteristics of the oxidation of hydrogen with sulfur dioxide in the region of a low-temperature chain explosion are revealed.

A study is performed of the effect native and polymeric β-cyclodextrins have on the solubility and membrane permeability of baricitinib, a new generation immunomodulator. It is found that native and polymeric β-cyclodextrins exhibit the same solubilizing effect in relation to baricitinib, while their effect on the membrane permeability of the drug differs. The increased solubility of baricitinib is due to the formation of inclusion complexes that have the same stability but are enthalpy-entropy stabilized in native β-cyclodextrin and enthalpy stabilized in polymeric β-cyclodextrin. The effect cyclodextrins on baricitinib’s coefficients of permeability of through a model membrane is discussed in terms of complexation, changes in the viscosity of the medium, and the state of the water boundary layer near the membrane’s surface.