Vol 91, No 9 (2018)

Papers dealing with chemical modification of the surface of noble metal nanoparticles and their use in analytical and bioanalytical chemistry, pharmacology, etc., are analyzed. Grafting of a layer of preset chemical composition on the nanoparticle surface allows preparation of functional materials combining the properties of the metal core (surface plasmon resonance, enhancement of fluorescence and nonelastic scattering) and shell (selective interaction with components of the surrounding medium). Combination of these properties opens wide prospects for using the modified nanoparticles in various branches of science and engineering, primary in chemical and biochemical analysis, and also in pharmacology.

Electrochemical oxidation for degradation of industrial dye Methyl Orange in aqueous sulfate solutions with various electrocatalytic materials: boron-doped diamond electrode and electrode based on titanium and ruthenium oxides. The influence exerted by the main working parameters of electrolysis (current density, concentration of Methyl Orange, pH) on the discoloration efficiency and on the chemical oxygen demand (COD) was examined. It was shown that an increase in the current density and a decrease in the pollutant concentration improve the process efficiency. However, this leads to an increase in the specific electric energy consumption per unit mass of COD. It was found that the boron-doped diamond electrode is a more efficient electrocatalytic material, compared with electrode based on titanium and ruthenium oxides. At low concentrations of Methyl Orange (<50 mg L^–1), there exists the possibility in principle of using the electrode based on titanium and ruthenium oxides not only for discoloration, but also for making lower the COD level.

UV spectroscopy and cyclic voltammetry were used to examine the thermochemical and electrochemical stabilities of liquid sulfolane-based electrolyte systems for lithium and lithium-ion batteries. It was found that solutions of lithium salts in sulfolane are stable in prolonged keeping at 100°C. The thermochemical stability of lithium salt solutions in sulfolane changes in the order LiBF₄ > LiClO₄ ≈ LiN(CF₃SO₂)₂ > LiCF₃SO₃. It was shown that the electrochemical stability of lithium salt solutions in sulfolane is in the range from 5.5 to 5.9 V (relative to Li/Li⁺) and prolonged action of high temperatures (100°C) does not yield electrochemically active thermal destruction products.

Impedance spectroscopy, chronovoltammetry, chronopotentiometry, scanning electron microscopy, and atomic-force microscopy were used to examine the corrosion behavior in acid and alkaline media and the morphology of nickel coatings electrodeposited from acetate, tartrate, and isobutyrate electrolytes at a temperature of 20–25°C. Models describing the nickel corrosion processes in H₂SO₄ and NaOH solutions were suggested. It was found that nickel coatings formed from isobutyrate electrolytes have the highest corrosion resistance.

Physicomechanical behavior of cross-linked segmented polyester urethane ureas with poly(tetramethylene oxide) segments of varied molecular mass, plasticized with di-(2-ethylhexyl) cebacate, was considered. Data on how the structure of flexible and rigid segments affects the physicomechanical properties of the plasticized material, including those at low temperatures, are presented. Ways were determined for obtaining the optimal hybrid structure of the polymers under study for developing materials with enhanced frost resistance.

Aromatic hydrocarbons, epichlorohydrin, and polyethyleneimine were used to synthesize polyfunctional anion exchangers. IR spectroscopy and elemental analysis were used to examine their composition and structure. The method of classical polarography was employed to examine the process of extraction of lead ions and determine the dependences of the sorption of lead(II) ions in the static mode on the solution acidity, concentration of metal ions, and duration of contact between ion exchangers and a Pb(NO₃)₂ solution. It was found that the ion exchangers possess high sorption properties for lead ions.

Information on the volume of production of biodiesel and crude glycerol from it is analyzed. The possibility of using crude glycerol as a feedstock for preparing solketal is demonstrated. The specific features of the solketal synthesis from crude glycerol and of separation of the reaction products are described. A catalytic process is suggested for selective decomposition of solketal to glycerol to obtain purified glycerol of any required concentration up to 99.8 wt %. A flowsheet is suggested for processing of crude glycerol to obtain solketal and subsequently converting it to obtain pure glycerol.

The biodiesel was obtained from used vegetable oil (UVO) and animal waste oil (AWO) by the two stages transesterification reaction. Also chemical and technical properties of feed and products were determined. Conditions of transesterification reaction for each of the oil samples were determined as a result of several sets of experiments. The suitable conditions of transesterification reaction were the following. Hereto a molar ratio of oil: methanol: catalyst was 1: 6: 1/40, for 30 min, at temperature of 600°C. To obtain biodiesel directly by the one stage transesterification, in case of using UVO sample, when the acidity number of feed oil had to less than 3 mg KOH/g. The biodiesel from UVO and AWO was prepared by mixing 5, 10, 20% of volume in the summer and winter diesel fuel. However, the product from mixture of UVO and winter diesel fuel met the technique requirements both of winter and summer diesel fuel, but the product from mixture of AWO and summer diesel fuel did not satisfy technical requirements of diesel fuel.

A \(\rm{SO_4^{2-}}\)/MCM-41 superacid catalyst was prepared by impregnation and characterized by various methods. A novel procedure for oxidative desulfurization of simulated light fuel oil using K₂FeO₄ over \(\rm{SO_4^{2-}}\)/MCM-41 was developed. Fourier transform infrared spectroscopy (FTIR) and low-angle X-ray diffractometry (XRD) show that the material synthesized by the precipitation-sol-hydrothermal method is mobil composition of matter no. 41 (MCM-41). Thermogravimetry/differential thermal analysis (TG-DTA) shows that when the calcination temperature is higher than 300°.

ZnSe films up to 2300 nm thick on glass-ceramic supports were prepared by chemical bath deposition in the ZnCl₂–Na₂EDTA–NaOH–NH₂OH·HCl system using sodium selenosulfate as a chalcogenizer. The reflections observed in the X-ray diffraction patterns correspond to the ZnSe (stilleite) phase of cubic (space group F\(\overline 4 \)3m) structure with a = 5.610 ± 0.002 Å. As shown by electron-microscopic examination, ZnSe films consist of globular formations tightly adjoining to each other with the mean size of 250–400 nm depending on the deposition conditions. Elemental EDX analysis shows that the films contain, on the average, 43.68 at. % Zn, 30.50 at. % Se, and 25.82 at. % O, with the oxygen concentration somewhat decreasing at a depth of 30 nm. The internal mechanical compression stresses caused by the difference in the thermal expansion coefficients of the ZnSe film and glass-ceramic support were calculated; these stresses depend on the film thickness and at ~1040 nm reach–30.62 kN m^–2. The results obtained make it possible to exclude film discontinuities, which can appear with increasing film thickness in preparation of precursor layers, and to choose the optimum support material.

Adsorption of cesium (Cs⁺), strontium (Sr²⁺), and europium (Eu³⁺) onto stannic silico vanadate as ion exchange material, and the effects of experimental conditions on adsorption were considered. The material were characterized by X-ray diffractometer system (XRD), scanning electron microscopy (SEM), X-ray fluorescence spectrometry (XRF), infrared (IR), and thermal analysis (TGA and DTA). The selectivity coefficients for different cations determined by mixed solution method were found to be less than unity. The thermodynamic parameters such as ΔG*, ΔS*, and ΔH* have also been calculated for the adsorption of Cs⁺, Sr²⁺, and Eu³⁺ onto stanic silicovanadate, showing that the overall adsorption process is spontaneous and endothermic.