Vol 91, No 6 (2017)

The temperature dependences of the viscosity of microheterogeneous metal melts are analyzed in terms of the Frenkel–Eyring theory. Using viscometric experimental data, the sizes of dispersed particles in metal melts whose components undergo eutectic and monotectic interactions are numerically estimated.

Mixing enthalpies of alloys in the Cu–La system are measured using isoperibolic calorimetry method over the ranges 0 < x_La < 0.185 at 1400–1430 K and 0.659 < x_La < 1 at 1370 K. They have moderate exothermic values over the whole concentration range and agree with literature data. Activities of the components, enthalpies and entropies of formation of intermetallics in this system, and its phase diagram are optimized using an ideal associated solution (IAS) model, and agree with most literature data. The updated thermodynamic properties can be used in further investigation of multicomponent systems based on the binary Cu–La.

NaLaX, NaX + Co, and NaPdX catalysts are synthesized by modification of NaX zeolite with transition metals (La, Co, Pd). The activity of the prepared materials in catalytic ethanol oxidation is studied in the temperature range of 423–723 K. It is shown that NaPdX and NaX + Co accelerate the reactions of partial and complete oxidation of ethanol as the temperature rises. NaLaX accelerates both intramolecular and intermolecular dehydration of alcohol. It is shown that the NaPdX (1.0% Pd) sample has the highest activity in the complete oxidation of alcohol with the formation of CO₂.

Dynamical synchronous modes in a network of four nearly identical chemical oscillators unidirectionally coupled via inhibitory pulse coupling with time delay τ (when a spike in one oscillator inhibits the next oscillator in the circle after time delay τ), are obtained experimentally. The Belousov–Zhabotinsky reaction is used as a chemical oscillator. The existence of four main modes is confirmed experimentally: in-phase (IP) oscillations; an anti-phase (AP) mode, in which any two neighboring oscillators have a phase shift equal to half of global period T; a walk mode (W), in which oscillators produce consecutive spikes in the direction of the connection with a phase shift between neighboring oscillators equal to T/4; and a walk-reverse mode (WR), when the oscillators produce consecutive spikes (with phase shift T/4), but in the direction opposite the connections (the mode opposite to the W mode). In addition to the main modes, OS modes in which at least one of the four oscillators is suppressed, and “2+1+1” modes in which two neighboring oscillators produce spikes simultaneously and the phases of the third and the fourth oscillators are shifted by T/3 and 2T/3, respectively, are found. It is shown that the modes found experimentally correspond to those found in simulations.

Enthalpies of complex formation for glycine (HL^±) with Ce³⁺ and Er³⁺ ions at 298.15 K and the value of the ionic strength of 0.5 (KNO₃) are determined by calorimetric means using two independent procedures. Thermodynamic characteristics of the reactions of formation for complexes of glycine with Ce³⁺ and Er³⁺ ions at various [metal]: [ligand] molar ratios are calculated.

Liquid density, viscosity, ultrasonic velocity and refractive index values have been reported for the binary system of propiophenone and benzyl acetate at temperatures 303.15–313.15 K for the whole compositions. Equations have been developed for the effect of temperature and concentration on viscosity, ultrasonic velocity and refractive index. The nature of molecular interaction has been concluded from the excess properties as well as from the newly developed equations.

The solubilities of the sulfonamide—sulfamethoxazole in methanol, ethanol, 1-propanol, 2-propanol, and chloroform have been determined at 293.15–323.15 K by a static equilibrium method. The experimental results can be approximated with Apelblat equation. The positive enthalpy Δ_solH and entropy Δ_solS for each system revealed that sulfamethoxazole dissolution in each solvent is an entropy-driven process.

A correlation between the lifetimes of hydrogen bonds and the thermodynamic characteristics of their formation and breaking, and the experimental relaxation times of dielectric spectra and the energy characteristics of relaxation processes, is observed via molecular dynamics (MD) simulation of the rearranging of the network structure of 1,2-ethanediol. The MD torsional frequency of the transition of gauche conformer tGg′ at 224.1 cm₋₁ and the experimental frequency of the band maximum of torsional vibrations at 230 cm₋₁ in the infrared spectrum correlate with the oscillation frequency of molecules at 240 cm₋₁ inside clusters in the Dissado–Hill (DH) model. The MD and DH models indicate a predominantly parallel alignment of the electric dipole moments of conformers tGg′ in the three-dimensional network of hydrogen bonds of the liquid 1,2-ethanediol phase.

The magnetic properties of a binuclear copper(II) complex {Cu₂(μ₂-O₂CCH₃)₄}(OCNH₂CH₃)₂ have been investigated on the basis of density functional theory with the broken symmetry (BS) approach. The magnetic coupling constant J values for the investigated complex have been calculated by different methods (HF, m06, PBE, B3LYP, B3PW91, B3P86, BLYP, BPW91, BP86) and basis sets (TZVP, TZV, 6-31G, 6-31++G) for the metal centers, and SVP basis set for the other atoms. The best calculated J value is‒142.6 cm⁻¹, which is in the excellent agreement with the experimental value (J = −101 ± 2 cm⁻¹). By investigating the spin density distribution from the magnetic centers to the atoms of ligands and the singly occupied molecular orbitals (SOMOs) of the Cu(II) ions at the low spin group states, we found that there is a spin delocalization between the Cu(II) ions and acetate ligands.

The interaction between porous spherical nanocluster polyoxometalate and water-soluble nonionic polymers (polyvinyl alcohol and polyethylene glycol) in the compositions of film is studied via calorimetry. The concentration dependences of the enthalpies of these processes are obtained using calculations based on the thermodynamic cycle.

Features of the reduction of graphene from graphene oxide in media containing hydrazine hydrate, ethylene glycol, and hydrogen are studied. X-ray energy dispersive spectroscopy, Raman spectroscopy, and scanning electron microscopy data indicate that this process proceeds through the high-temperature annealing of graphene oxide in a hydrogen environment.

The strain energy in nanocomposites based on porous anodic aluminum oxide and filamentary nanoparticles of Cu, Ag, and Au is simulated numerically. The results allow us to estimate the contribution from mechanical stresses produced upon heating, due to differences between the thermal coefficients of the linear expansion of elements of heterogeneity upon a change in the melting point of spatially confined metallic filamentary nanoparticles. The dependence of the energy of deformation on the structural parameter associated with the concentrations of Cu, Ag, and Au fibers in the considered nanocomposite systems is studied. It is found that at temperatures close to 1000°C, the contribution from mechanical stresses to the change in melting point, quantitatively expressed by the studied energy characteristic, is negligible in comparison to the contribution from the surface.

Adsorption of a broad range of humic substances (HS) of different origins and fractional compositions on a macroporous weakly basic anion-exchange resin is studied. It is found that the nature of the HS has a substantial effect on both the efficiency of sorption and the mechanism of interaction with the adsorbent. The dependence of the determined thermodynamic parameters of sorption on the HS origin, composition, and structure is shown for a broad range of HS. It is concluded that the results can be used to predict the sorption properties of weakly basic anion-exchange resins with respect to HS of known origin and structural group composition.

Features of the adsorption of phosphatidylcholine (PCh) by inorganic silicon-containing materials with various degrees of order (MCM-41, MMC-1, and silica gel) from solutions in hexane under equilibrium conditions in the temperature range of 283–323 K are considered. It is found that the adsorption of the phospholipid within the C_e = (0.6–4.0) × 10^–4 mmol/dm³ range of concentrations on the investigated materials is characterized by monomolecular absorption. Differential thermodynamic characteristics (ΔG, ΔH, and ΔS) of the sorption of PCh by silicon-containing materials with various degrees of order in the temperature range of 283–323 K are considered. An increase in the affinity of silicon-containing materials toward the phospholipid upon an increase in the temperature of the sorption process is observed.

A method for performing a single act of separation of the components contained in a liquid solution of optical isomers in a reversible process is proposed. Mechanisms that allow the reversible separation of mixture components at least in theory are discussed.

Preoxidation process is usually needed in the treatment of arsenic containing water because arsenite (i.e., As(III)) is less easily to be removed by adsorption. Nano-scale titanium dioxide (TiO2) is an efficient photocatalyst for arsenite oxidation. In this study, a series of photocatalysts of un-doped, single-doped and co-doped flower-like TiO₂ were successfully prepared by template method using Fe(NO₃)₃ · 9H₂O, ammonium ceric nitrate and tetrabutyl titanate (Ti(OC₄H₉)₄) as precursors and glucan as template. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and N₂ adsorption-desorption measurement were employed to characterize the morphology, crystal structure and surface structure of the samples. The photoabsorbance of the obtained catalysts was measured by UV–Vis absorption spectroscopy, and the photocatalytic activities of the prepared samples under UV light were estimated by measuring the oxidation rate of As(III) in an aqueous solution. The characterizations indicated that the prepared photocatalysts had flowerlike structures, consisted of anatase phase and possessed high surface area of ca. 160 m²/g. It was shown that the Fe, Ce co-doped flower-like TiO₂ could be used as an effective catalyst in photocatalytic oxidation reactions. The synergistic effect of Fe and Ce co-doping played an important role in improving the photocatalytic activity. In addition, the possibility of cyclic usage of the co-doped flower-like TiO₂ was also confirmed, the photocatalytic activity of flower-like TiO₂ remained 88% of that of the fresh sample after being used four times.

Analysis of the adsorption isotherms by virtue of experimentally obtained data of anti-tumorous compound mitoxantrone and ethidium bromide binding with DNA has been carried out. The obtained data showed that throughout the comparatively simple linear isotherm, the more precise values of the binding constant K and number of nucleotides n, per binding site were received. Based on the values of K, those for the enthalpy changes at complex-formation of these ligands with DNA were obtained.

Concentrations of particles in acid–base equilibria in aqueous and nonaqueous solutions of electrolytes are calculated on the basis of logarithmic charts, activity coefficients, and equilibrium constants.

The fluorescence of pure tryptophan and tryptophan residues in albumin is studied at an excitation wavelength of 288 nm. The range of wavelength registration is 280–380 nm. A broad fluorescence band at 350–355 nm and an elastic scattering line at 288 nm are observed in the spectrum measured at 90° relative to the primary beam. The fluorescence of pure tryptophan and tryptophan in albumin is greatly reduced under the impact of the plasma radiation of a spark discharge, while the elastic scattering peak remains unchanged within the limits of error. A comparison of the elastic scattering and fluorescence indicates that tryptophan loses its inherent property to fluoresce under an external influence. The structure of the other tryptophan levels remains unchanged.