Russian Journal of Physical Chemistry A最新文献

The interaction of magnetic materials R₂Fe₁₇ (R = Gd, Dy, Lu) with hydrogen at 473 and 523 K and hydrogen pressure up to 5 MPa was studied by the Calvet calorimetry method. The dependences P = f(C) and ∆H = f(C) were obtained (P is the equilibrium pressure of hydrogen, ∆H is the enthalpy of absorption/desorption, C is the concentration of hydrogen in an intermetallic compound (IMC), C = H/IMC). It has been established that the enthalpy values of the reaction of hydrogen with IMC change with changes in the process temperature, the concentration of hydrogen in the metal matrix, as well as during the transition from one compound to another. The graphs of the dependence ∆H = f(C) show two sections where the enthalpy values are constant. It is assumed that the observed changes in the thermodynamic parameters of the process are related to the filling order of octahedral interstices 9e and tetrahedral interstices 18g, and the filling process of octahedral interstices 9e occurs in two stages with different energy characteristics.

The effects of the initial composition of the system, nature of the solvent, rare earth salt, and temperature on the formation of self-assembled structures in the dynamic interfacial layer of a heterogeneous liquid system were studied. It is shown that by means of self-assembly at the liquid/liquid interface it is possible to create a material which, when transferred to a glass plate, forms surfaces with different microreliefs, characterized by different wettabilities. The presence of a bianion and polymer solvation by the insertion reaction were confirmed by IR spectroscopy.

When predicting retention indices using deep learning, there is typically no way to assess the reliability of predictions for specific molecules. The present study demonstrates, using stationary phases based on polyethylene glycol and NIST 17 database, that predictions are generally more accurate when the training dataset includes molecules structurally similar to the compound for which prediction is made. The Tanimoto similarity of “molecular fingerprints” ECFP is the most suitable algorithm for this task among the four algorithms considered. For several transformation products of unsymmetrical dimethylhydrazine whose structures were established using such predictions, the predictions were shown to be unreliable.

Adsorption complexes of vancomycin with detonation nanodiamonds having positive and negative surface charges were obtained. The kinetics of vancomycin adsorption on nanodiamonds is described by a pseudo-second-order equation with similar parameters for both types of nanodiamonds. The kinetics of vancomycin–nanodiamond complexation is described by a pseudo-first-order equation. Using radioactive tracers and IR spectroscopy, it was found that some part of vancomycin is tightly bound to the nanodiamond surface and is not removed during washing. The amount of the tightly bound substance was three times greater for complexes with negative nanodiamonds. However, the retention strength of vancomycin on positive nanodiamonds was higher, and its content changed little during desorption over 10 days. Both types of complexes exhibit identical antimicrobial properties against Staphylococcus aureus. The data obtained support the hypothesis that hydrogen bonding with water molecules plays a key role in the adsorption and retention of vancomycin on the surface of nanodiamonds.

Quantum-chemical methods B3LYP and M06 are used to study the interaction between N,O‑dimethylcarbamate and the monomer and dimer of methylamine as a model for the production of polyureas. A one-stage mechanism of interaction and a two-stage route with the formation of an intermediate containing a tetracoordinated carbon atom are both considered. The latter path is unlikely, since the formation of the intermediate is characterized by low values of the equilibrium constants. Kinetically and thermodynamically reactions with the participation of the methylamine dimer are more preferable. The kinetic preference for reactions with the participation of the methylamine dimer is due to its enhanced donor and acid-base properties, relative to the monomer. The thermodynamic preference for reactions with the methylamine dimer is due to the greater entropy of transformation, relative to the reaction with the monomer.

The catalytic properties of Cu–Zn catalysts are investigated on such commercial supports as Al₂O₃, SiO₂, ZrO₂(La), TiO₂, ZnO, and activated carbon in the reaction of CO₂ hydrogenation with the production of methanol. CuZn/Al₂O₃ catalyst displays the highest conversion of CO₂. The highest selectivities toward methanol (99 and 97.5%) are observed for CuZn/ZrO₂(La) and CuZn/SiO₂ catalysts, respectively, while high values of selectivity toward CH₃OH (90–95%) are achieved in the 175–275°C range of temperatures. The highest methanol productivity is 547 g/(kg_kat h) on catalyst CuZn/ZrO₂(La). The synthesized catalysts are studied via low-temperature nitrogen adsorption, X-ray diffraction, and SEM-EDX.

A PET-UiO-66 sample of metal-organic framework UiO-66 (Zr₆O₄(OH)₄bdc, bdc = benzene-1,4-dicarboxylate/terephthalate), a promising adsorbent of persistent organic pollutants from aqueous media, is prepared using an original procedure assisted by MW activation of the reaction mass under atmospheric pressure following a one-step approach in the nontraditional “green” solvent triethylene glycol. The PET-UiO-66 material is synthesized using polymer waste (polyethylene terephthalate (PET)) as an organic linker (terephthalic or benzene-1,4-dicarboxylic acid, H₂bdc) to create the framework. Its adsorption activity is studied for the first time in the adsorption removal of the food dye tartrazine (Е-102) from aqueous media. It is established that the kinetics of adsorption is obeyed to a pseudo-second order, and its thermodynamics fits the Langmuir model.

Cyclic voltammetry and gravimetry are used to study the behavior of a smooth gold electrode in a medium of bridged 1,2,4-trioxalane in acetonitrile. It is found that the peroxide bond in the molecule of bridged 1,2,4-trioxalane is reduced on the surface of the electrode during the cathodic process, with the subsequent formation of a diketone fragment. The formation of colloidal gold particles is detected during anodic oxidation.

This work aims to develop a CuCr₂O₄ nanoparticle at 850°C in air, and WO₃ nanoparticles by one-step hydrothermal method. The novel CuCr₂O₄/WO₃ hetero-system is successfully used for the photoreduction of Cr(VI) (30 mg/l) under sunlight. Both materials are characterized by the structural, physical and electrochemical techniques. The energy of the spinel gap (CuCr₂O₄)(E_g = 1.78 eV) is determined by diffuse reflectance and corresponds to the solar spectrum. Capacitance measurements indicate p-type conduction with a flat band potential of 0.62V_SCE. For WO₃: a direct gap (E_g = 2.90 eV) with n-type behavior with an electron density (N_D = 5.4 × 10¹⁶ cm^–3) and a flat band potential of 0.25V_SCE. Optimization of the experimental conditions of chromate photoreduction at pH ~4 (adipic acid = 5 × 10^–1 mol /L, CuCr₂O₄/WO₃ (1/1) and a dose of 1mg/L) led to a conversion of 92% of 30 mg/L of Cr (IV) in Cr(III) within 180 min under sunlight. The photocatalytic performance is due to the synergy of the p–n hetero-system whose electrons generated in the conduction band of CuCr₂O₄ excited by solar light are injected into CB-WO₃). The role of adipic acid is essential; it improves the reduction of Cr(VI) under solar irradiation. The photoreduction kinetics follows a pseudo-first order model with a constant rate of 5.51 × 10^–3 min^–1.

In the treatment process of sulfur-containing wastewater from oil fields, sulfides and metal salts are used to generate precipitation to remove sulfides from oil and gas field wastewater. As an excellent precipitant, soluble sulfate is necessary to be investigated in depth for its dissolution and crystallization in aqueous solution, which can provide theoretical guidance for the optimization of the oilfield water treatment process. In this paper, the result of the stable solid-liquid equilibria in the ternary system sodium sulfate–zinc sulfate–water at 323 K and 0.1 MPa were presented based on the method of isothermal dissolution equilibrium. In the experiment, saturated liquid phase and humid residue composition for a series of synthetic brine were determined. At the same time, the corresponding equilibrium solid phases were identified by using the X-ray powder diffraction combined with Schreinemakers’ method. Since the foundation of phase diagram theory concerning water salt system, the phase diagram of the system was constructed. The result show that the ternary system Na₂SO₄−ZnSO₄−H₂O at 323 K is considered to be the double salt type owing to the existence of double salt Na₂SO₄⋅ZnSO₄⋅4H₂O. And the phase diagram of the ternary system Na₂SO₄−ZnSO₄−H₂O at 323 K includes two invariant points, three univariant solubility curves and three solid crystalline phase regions corresponding to Na₂SO₄, Na₂SO₄⋅ZnSO₄⋅4H₂O, and ZnSO₄⋅6H₂O. The Pitzer equation was selected to calculate the solubility data in the ternary system Na₂SO₄−ZnSO₄−H₂O at 323 K. The solubility modeling approach achieved a very good agreement with experimental solubility data at 323.15 K. The experimental densities of the equilibrium solutions were determined by the density bottle method, and the theoretical densities of each saturated solution were calculated based on the Laliberte model. The results show that the theoretical densities are basically in agreement with the experimental densities, and the model can reasonably predict the densities of this ternary system.