Vol 90, No 8 (2017)

Application of the Redlich–Kister polynomial with varied number of parameters for describing the concentration dependence of thermodynamic systems of liquid metallic systems with a strong interaction between their components is considered for the example of the lead–tellurium system. Particular attention is given to the range of dilute solutions of tellurium in liquid lead.

Powdered nanocrystalline europium orthoferrite was synthesized by the glycine-nitrate combustion method, and specific features of its formation were studied in relation to the redox composition of the starting reaction mixture. The products of glycine-nitrate combustion were characterized by X-ray fluorescence microanalysis, X-ray diffraction analysis, scanning electron microscopy, and helium pycnometry. It was found that, depending on the glycine-nitrate ratio, EuFeO₃ nanopowders with average crystallite size of 28 ± 3 to 46 ± 5 nm can be obtained. The crystallites form under the given conditions porous micrometer-size agglomerates with developed surface. Their morphology and characteristic size vary with the redox composition of the reaction mixture.

Results of a study of the electrodeposition of thin cadmium sulfide films from a sulfite electrolyte and its degradation in the course of electrolysis are presented. The factors determining the degradation rate of the electrolyte are revealed. The supposed mechanism of reactions resulting in that CdS is formed is described.

Kinetics and selectivity of oxidation of dyes (Methyl Orange and Chrome Dark Blue) on a lead dioxide (Pb/PbO₂) anode at various current densities, substrate concentrations, and pH values with the use of various active oxygen species was studied. It was shown that the electrochemical oxidation of dyes on the Pb/PbO₂ anode occurs rather effectively under the chosen conditions. The mineralization efficiency in 5 h was 51 to 89.5 and 93 to 100% for, respectively, Methyl Orange and Chrome Dark Blue, depending on the electrolysis conditions.

Sorption concentration of platinum(II, IV) and palladium(II) from freshly prepared and aged two-yearold hydrochloric acid solutions by a series of anion exchangers with different functional groups and of different physical structure of Purolite and CYBBER grades was studied. The high sorption ability of the ion exchangers in relation to the extracted chlorocomplexes of noble metals is shown. It was demonstrated that palladium(II) from all tested ion exchangers can be completely desorbed with thiourea solutions acidified with hydrochloric acid, while complete desorption of platinum is achieved only from Purolite S 985 anion exchanger of the complexforming type and Purolite A 111 weak base anion exchanger.

Possibility of the electroflotation separation and extraction of cerium(II, IV), copper(II), and iron(II, III) from aqueous solutions is demonstrated. The optimal pH value and the concentration ratio of ions of the metals being separated, at which their electroflotation separation and extraction from aqueous solutions is the most efficient, was determined. It was shown that the electroflotation method is promising for selective separation and extraction of metal ions with various hydrate-formation pH values from aqueous solutions.

A study of specific features of the growth, composition, and content of natural gas hydrates formed in a water-in-oil emulsion demonstrated that the process in which hydrates are formed in a water-oil emulsion occurs in stages and depends on the saturation of hydrate growth zones with the hydrate-forming gas via diffusion of natural-gas components across the oil phase. Hydrates enriched in methane are formed in water-oil emulsions, compared with the hydrates grown from distilled water, which is accounted for by the difference in solubility between natural-gas components in oil and water, and also by the presence of a surfactant layer on the surface of emulsified water drops. With increasing fraction of water in an emulsion, the content of hydrates decreases, and the mass of a hydrate being formed is independent of the composition of the water-oil emulsion.

Results are presented of a study of the liquid product formed in pyrolysis of automobile tires and fractions of this product. The diesel fraction of the pyrolytic liquid fuel was hydrodesulfided on a polymetallic catalyst. The results of the hydrodesulfidation in a flow-through laboratory installation in the temperature range 320–380°C at a hydrogen delivery rate of 6 L h^–1 are shown. The experiment was performed during 1 h with preliminary activation in a flow of hydrogen for 2 h and raw material delivery rate of 4–16 mL h^–1 on a polymetallic Al–Ni–V–Mo catalyst supported by γ-Al₂O₃. It was found that the degree of purification grows by 14% as the delivery rate is lowered from 16 to 8 mL h^–1, and by 27% upon its decrease to 4 mL h^–1. With temperature varied at the optimal raw material delivery rate of 4 mL h^–1, the degree of purification also changes: the minimum degree of purification is observed at 320°C. The degree of purification grows by 7% as the process temperature is raised by 20°, and by 28% upon its increase by 40°.

The yield and properties of solid and liquid products of hydrothermal treatment of organic waste were determined with cheese, meat, and apples as an example. The solid products of hydrothermal treatment of cheese and apples have higher carbon content, lower oxygen content, and, correspondingly, higher heat of combustion compared to the initial biomass, which allows these products to be considered as a promising solid biofuel. The oils obtained in experiments with cheese and meat also have higher carbon content and higher heat of combustion compared to the initial substances, which allows these products to be considered as a promising liquid biofuel.

Ceramic-forming compounds based on polycarbosilane and polyorganosilazanes modified with atoms of refractory metals (Ti and Zr) were studied. The curing and pyrolysis of the compounds in an inert medium and the thermal oxidation resistance of ceramic pyrolysis residues were examined by synchronous thermal analysis and extraction. A ceramic matrix composite material was prepared from the compounds studied and a carbon reinforcing filler, and the physicochemical properties and thermal oxidation resistance of this material were evaluated.

Magnetically recoverable cobalt doping Fe₃O₄/TiO₂ magnetic nanocomposites with an acceptable core–shell structure were prepared via a sol-gel process at low calcination temperature. The crystalline size and structure, morphology, and magnetic properties of resulting particles have been characterized by X-ray diffraction (XRD), fourier transform infrared (FT-IR), FT-Raman, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). Metoprolol tartrate (MET) as a pharmaceutical pollutant was used to observe the photocatalytic degradation ability of the magnetically recoverable particles. The process of degradation under UV irradiation at controlled temperature was studied and the remaining concentrations of MET as a contaminant were measured by UV-Vis spectrometer at λ = 229 nm. This ability remained 95.76% after three times of repetitive use at the same conditions. Various parameters such as reaction temperature, pH, and speed of stirring of the aqueous solution had an effect on the rate of degradation. The amount of cobalt dopant and nanocomposites are also effective on the rate of degradation. Coupling of electrical current with photocatalytic process has proven to be effective in the degradation of MET aqueous solution clearly.

Three new poly(arylene ether nitrile ketone)s (PENKs), special engineering plastics, with different molecular structure were prepared. The obtained PENKs were characterized by FTIR spectroscopy. The thermodynamic and heat resistance behavior of PENKs were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. It was noticed that the glass transition temperature (T_g) and initial decomposition temperature (T_i) of the PENKs were higher than 160 and 480°C, respectively. The main reason was due to their molecular structure, in which the stronger intermolecular forces improved the heat resistance. Moreover, the crystallinity of PENKs decreased with increasing the nitrile group (–CN) content, which indicated that the regularity of molecular chain decreased. The dielectric property indicated that the dielectric constant (K) of PENKs increased with–CN content because of its strong polarity. Meanwhile, the T_g of PENKs was higher than traditional poly(ether–ketone) (PEK) and poly(ether–ether–ketone) (PEEK). It was important that the solubility of PENKs was well improved. Besides, the tensile strength of PENKs was higher than that of common poly(arylene ether nitrile) (PEN).

Al/Bi₂O₃ nanothermites were prepared via a self-assembly method using poly-4-vinylpyridine and surface modification of particles by a kind of binder oleic acid respectively. The structures, morphology, and energetic properties were characterized. The pressure discharge properties were studied by a closed bomb. The peak pressures and pressurization rates of Al/Bi₂O₃/P4VP and Al/Bi₂O₃/OA were 5590 kPa, 13.976 GPa s^–1 and 4858 kPa, 12.146 GPa s^–1, respectively, better than those of Al/Bi₂O₃ prepared by normal ultrasonic method (4559 kPa, 11.397 GPa s^–1 ). However, the decreased ignition delay time for self-assembled method and the increased one for modifying with oleic acid suggested different mechanism in accelerating the reaction of Al/Bi₂O₃. Moreover, the effect of mass fraction of oleic acid on nanothermite reaction was demonstrated.

The strength and resistance of epoxide (ED20 + polyethylenepolyamine)–micronanoiron (R10 or R20) composite systems, which are of interest for machine-building, instrument-making, and aerospace industry, were studied. Introduction of micronanoiron into the epoxy resin allows preparation of iron–epoxy composites without significant changes in the adhesion to steel and in the bending modulus, with only a slight (10–15%) decrease in the compression strength. Filling does not affect the heat resistance of the components (thermal gravimetric analysis) and enhances the flame resistance. The morphology of the composites is characterized by aggregative, relatively uniform distribution of iron particles in the resin. The compression strength increases after heating to 250°С (in contrast to the unfilled polymer). On the other hand, filling slightly weakens the resistance of iron–epoxy composites to aggressive media (with acetone–ethyl acetate mixture and 25% HNO₃ as examples). Surface modification of iron particles with acrylic varnish in some cases enhanced both the swelling resistance (with 10% modified R10 iron in contact with water and 25% HNO₃ as example) and the strength characteristics (with the bending modulus and compression strength after heating to 250°С as example).

The effect that polyfluorinated alcohols immobilized on montmorillonite support exert on structuralmorphological characteristics and combustibility of polymer composites was studied with 1,1,9-trihydroperfluoro- 1-nonanol as example. The relationship between the flame resistance of this heterochain polymer and its morphology was revealed by X-ray diffraction analysis, electron microscopy, DSC, and Fourier IR spectroscopy. This relationship is associated with the reorganization of the crystal and molecular structure under the influence of fluorinated organoclay, ensuring increased degree of crystallinity and redistribution of the fractions of α- and γ-crystalline forms in the polymorphic composition of polycaprolactam, making its supramolecular structure more perfect, and favoring preparation of a fluorinated material of decreased combustibility.

Modification of cellulose-containing materials (wood veneer, paper) with solutions of radiationsynthesized tetrafluoroethylene telomers was studied. Treatment with a solution of tetrafluoroethylene telomers enhances the ultimate strength, chemical resistance, and flame resistance of the materials and decreases the yield of extractable substances in treatment with organic solvents.