Vol 89, No 9 (2016)

Acid-base and sorption properties of spherically granulated material based on hydrated titanium dioxide were studied. It was shown that the sorption capacity of the ion exchanger is due both to the structure (cross-linking density of gels and, consequently, their porosity) and to the number of active acid centers. The kinetic specific features of the sorption of cations were considered and it was found that the sorption kinetics is limited by the intraparticle diffusion. It was shown that the sorbent can be used to purify low-salt technological solutions of liquid radioactive wastes.

Chelate complex cerium [Ce(BA)₃)] and europium [Eu(BA)₃] benzoyl acetonates were synthesized. According to IR spectroscopic data and elemental analyses, the composition of the complexes is described by the empirical formulas M(BA)₃·2H₂O. Sorbents based on a mesoporous silica gel modified with cerium and europium benzoyl acetonates were obtained. The nitrogen porosimetry demonstrated that, as the complexes are deposited onto the surface of the starting support, the specific surface area and the pore volume become smaller. The polarity of the sorbents Chromaton N-AW + SiO₂ + M(BA)₃ with respect to all classes of test compounds decreases in the order Ce^III > Eu^III. According to the data obtained for the capacity factors, the sorbent modified with cerium benzoyl acetonate selectively separates alcohols, and Chromaton N-AW + SiO₂ with deposited chelates Eu(BA)₃ shows the best separating capacity for alkanes and alcohols. It was shown that the sorbents can be used in practice for separating gaseous mixtures of light hydrocarbons.

Conditions were determined in which an active anodic dissolution of tungsten is observed in a borongluconate electrolyte used to obtain Co–W coatings (pH ~6.5) and the nature of critical currents of transition to the passivation was found, which makes it possible to use the tungsten anode as a soluble electrode. The anodic dissolution of tungsten occurs under these conditions with a current efficiency of 90–100%, which, in contrast to the case of a graphite anode, does not lead to an additional oxidation of the electrolyte components and polymerization in solution; in combination with the decrease in the concentration of tungstate ions, this reduces the electrolyte performance. It was shown that the use of a soluble tungsten anode in obtaining nanocrystalline cobalt–tungsten coating can improve the electrolyte performance due to the rise in the current efficiency of electrodeposition and to the increase in the microhardness of the coatings in comparison with the case of an insoluble graphite anode.

A procedure for treatment of simulated wastewater solutions to remove Cu²⁺, Ni²⁺, and SCN⁻ ions using various combinations of aluminum and iron electrodes in the electro- and peroxyelectrocoagulation processes was studied. The influence exerted by the current density, pH of solution, and concentrations of impurities and hydrogen peroxide on the efficiency of removal of these ions was analyzed. Electrocoagulation using aluminum anode does not lead to a significant decrease in the thiocyanate concentration. In the peroxyelectrocoagulation process, the efficiency of removal of SCN− ions increases with an increase in the [H₂O₂]: [SCN⁻] ratio. The electrocoagulation efficiency with the Fe/Fe electrode pair reaches 87% for SCN⁻ and 99.5% for Cu²⁺ and Ni²⁺ at a current density of 20 mA cm^–2 and electrolysis time of 20 min.

The kinetics of thermal degradation of low-density polyethylene was studied by TGA and DSC at heating rates from 0.5 to 40 deg min^–1. Causes of significant discrepancies in the published effective kinetic constants of the overall reaction of thermal degradation of the polymers, determined using different experimental methods and different data treatment procedures, were analyzed. The possibility of using random break model as an alternative approach to describing polymer thermal degradation curves obtained by thermal analysis methods was demonstrated by the example of polyethylene.

A novel technology for preparing nanocomposites on the basis of ultra-high-molecular-mass polyethylene and nanoparticles of inorganic compounds (SiO₂, Al₂O₃, ZrO₂, AlN, Si₃N₄) was developed and tested. The technology consists in liquid-phase compounding of nanocomposite components under the continuous action of ultrasonic vibrations. The developed technology ensures dispersion of nanopaticle agglomerates in a liquid medium, efficient mixing of components of the powder blend, and uniform distribution of nanoparticles in the polymer matrix. The nanocomposites obtained exhibit increased levels of strength and elasticity.

Modification of polyvinyl alcohol with monomethylolurea and 4,5-dihydroxyimidazolidin-2-one was performed in a wide temperature interval (40–80°С). Irrespective of the initial conditions, modification with the monofunctional agent yielded a non-cross-linked polyfunctional product, which was subsequently used for developing compounds for various purposes. The kinetics of the modifier grafting to the polymer was studied, which is important for controlling the process and choosing its optimum conditions.

The influence of the ratio of acrylamide, acrylonitrile, and 2-acrylamido-2-methylpropanesulfonic acid monomeric units in the terpolymer on its molecular-mass characteristics was studied. The influence of the copolymer composition on its resistance to the action of CaCl₂ was determined. The capability of the synthesized terpolymers to reduce the hydrodynamic resistance to a liquid flow was evaluated with a laboratory capillary turbulent rheometer. The hydrodynamic resistance reduction effect depends on the molecular-mass characteristics of the terpolymers.

Effect of surface water shear stress on the performance of an inhibitor film used in the carbon steel pipelines for oil and gas product transportation is studied. Experiments were conducted in laboratory by electrochemical impedance spectroscopy (EIS). EIS that was carried out under various rotation rates, different temperature, and immersion time was taken to investigate the behavior of a corrosion inhibitor and the destruction process. Typical EIS spectral changes were acquired during the film destruction processes, and this means that EIS is an effective method for evaluating inhibitor performance and monitoring the film layers’ behavior. Experimental results show that the film layers become more porous with increase in rotation rates and temperature. Therefore, the performance of this corrosion inhibitor decreased resulting from surface shear stress and bubble impact. In addition, scanning electron microscopy (SEM) was also taken to help confirm the inhibitor film structure under different conditions.

The adsorption of the 2,3,7,8-tetrachlorodibenzodioxin (TCDD) molecule on the B₁₂N₁₂ nanocage (B₁₂N₁₂-NC) was studied by M06-2X/6-31++G** method. There are three sites for TCDD adsorption on B₁₂N₁₂-NC. The B–B atom pair in six-membered rings (B_(6MR)–B_(6MR)) of B₁₂N₁₂-NC is the preferable adsorption site. When TCDD approaches the B₁₂N₁₂ nanocage, electronic exchange between them occurs, and TCDD is converted to 3,4-dichlorophenol, 3-chloroprop-2-en-1-ol, and 1-chloroprop-1-ene. The HOMO/LUMO energy, energy gaps (E_g), thermodynamic properties, and structural deformation are calculated by DFT methods. The lowest value of E_g (3.796 eV) was obtained for TS-3 (the first transition state of conversion of intermediate 3,4-dichlorophenol to 3-chloroprop-2-en-1-ol and 1-chloroprop-1-ene). The Gibbs free energy and heat of reactions are negative; therefore, these reactions are favorable and spontaneous and make B₁₂N₁₂-NC suitable as nanosensor for TCDD detection and reduction.

The photocatalytic degradation of phenazopyridine (PhP) as a model contaminant from pharmaceutical compounds was studied using batch-recirculated photoreactor packed with immobilized TiO₂–P25 nanoparticles on glass beads. The effects of operational parameters (irradiation time, initial concentration of PhP, volume of solution, and volumetric flow rate) were evaluated by the response surface methodology (RSM). The proposed model of the RSM is a second order mathematical model. According to the results of ANOVA, initial concentration of PhP, volumetric flow rate, irradiation time, volume of solution, mutual effects of initial concentration of PhP × irradiation time, irradiation time × volume of solution and quadratic effects of initial concentration of PhP, and volume of solution are significant model parameters. The optimization process by RSM offers the following optimal conditions: PhP concentration 24 mg L^–1, liquid volumetric flow rate 230 mL min^–1, irradiation time 30 min, and volume of solution 300 mL. Under these conditions, the proposed removal percent of RSM is 90.28% which have good correspondence with experimental removal percent (87.36%).

The possibility of electrochemical preparation of metal–polymer nanocomposites and coatings on pure iron and steel electrode by combining the electrochemical initiated (co)polymerization of 1-vinyl-1,2,4-triazole and crotonaldehyde with the cathodic deposition of the metals was examined. The structure and composition of the synthesized films were determined by IR spectroscopy, X-ray diffraction, elemental analysis, and thermal gravimetric analysis. Silver nanoparticles were found to be uniformly distributed throughout the polymer matrix.