Voprosy khimii i khimicheskoi tekhnologii (Issues of Chemistry and Chemical Technology)

6-16

Authors: A.R. Gaidai, P.V. Vakuliuk, I.M. Furtat, T.V. Murlanova, N.I. Kunytsya, V.A. Tertykh, R.B. Kozakevych, A.H. Grebeniuk, A.A. Golub

This work deals with the preparation of nanocomposites based on pyrogenic silicon matrix modified with ornidazole. The physical, chemical and functional properties of the synthesized nanocomposites were characterized. 13С and 1Н nuclear magnetic resonance and UV spectroscopies were used to study the composition of the prepared nanocomposites (i.e. ornidasils). The presence of ornidazole on the silica surface was proved using elemental analysis, liquid chromatography and high resolution mass spectrometry. Sorption kinetics of active substance and sorption capabilities of ornidasils towards pathogens and proteins was investigated. The PM3 method of quantum chemistry showed that the formation of adsorption complexes on the highly dispersed silica surface occurs due to the hydrogen bonds between the surface groups of silanol and the nitro groups of ornidazole; the water excess will gradually wash away the molecules of ornidazole adsorbed on the surface of silica. The release of ornidazole in the model solution was about 77% of the active compound after 20 min of desorption and further concentration of ornidazole in the solution was maintained at a stable level due to the gradual release of the drug which was experimentally confirmed. The expansion of antimicrobial effect of ornidazole in the nanocomposites for the gram-positive and gram-negative test cultures was established as compared with the initial active compound.

22-29

Authors: M. Litynska, N. Tolstopalova, I. Astrelin, N. Petrus

High arsenic content is typical of natural waters of many countries, including Ukraine. Concentration of arsenic in drinking water, which is higher than 10 g/L, causes a lot of undesirable consequences (hyperkeratosis, cancer, different diseases). It is necessary to develop new methods of arsenic removal and improve the existing ones. Iron-containing adsorbents are ones of the most usable for water treatment in case of pollution by arsenic. Both natural water and wastewaters have complicated mineral composition. That is why the study of influence of other ions is a topical issue. The paper reports the influence of anions (chlorides, sulfates and hydrocarbonates), cations (sodium and calcium) and pH on the arsenate adsorption on the synthesized goethite, hematite and ferrihydrite. The influence of chlorides is ambiguous and an increase of arsenate adsorption efficiency occurs in case of iron (III) oxide and hydroxide. Sulfates and hydrocarbonates significantly impede removal of arsenate for all investigated iron-containing sorbents. The effect of chlorides and sulfates does not practically change in the pH range of model water of 6 to 8, while the presence of hydrocarbonates dramatically deteriorates the process with increasing pH. One can conclude from these data that high concentrations of sulfates and hydrocarbonates are undesirable in waters which are purified from arsenic compounds by iron-containing adsorbents.

35-45

Authors: N.V. Nikolenko, Yu.V. Kalashnikov, A.O. Kostyniuk, A.Yu. Poloz, E.V. Aksenenko

The adsorption of a number of organic acids and bases from aqueous and methanol solutions was studied under static conditions at room temperature. It was shown that the organic compounds are adsorbed on Fe(III) and Mo(VI) oxides and Fe(III) molybdate due to the formation of the surface hydrogen bonds. The possibility of the adsorption by means of a donor-acceptor interaction of the organic compounds with the surface cations Fe3+ was not detected. It was shown that the adsorption energies of organic bases are linearly correlated with the effective charge of nitrogen atoms and their adsorbability changes in the following range: Fe2O3>MoO3>Fe2(MoO4)3. An explanation of these correlations was proposed based on the concept of the domination of electrostatic interactions. Heterogeneous-catalytic oxidation of methanol and formaldehyde was proposed to consider assuming two forms of adsorption of their molecules: via binding of oxygen atoms with Lewis acid sites, or via the interaction of carbon and hydrogen atoms of the C–H bonds with Lewis basic centers of a catalyst. It was concluded that the selectivity of the iron molybdate catalyst in the partial oxidation of methanol can be caused by low adsorbability of intermediate products of the methanol oxidation reaction on the catalyst surface.

53-58

Authors: Y.A. Titov, N.M. Belyavina, M.S. Slobodyanik, V.V. Chumak, O.I. Nakonechna

By using X-ray powder diffraction method, it was determined that scandium atoms in SrNdScO4 slab perovskite-like structure are substituted according to SrNdSc1–хInxO4 type if 0x0.85. A further increase in a degree of substitution of scandium atoms for indium ones in the single-slab SrNdSc1–хInxO4 scandatoindates (x>0.85) results in destruction of a slab structure and formation of a second phase with CaFe2O4 structure type, which quantitative content increases up to ca. 100% at х=1. Orthorhombic crystal structure (Pbca space group) of SrNdSc1–хInxO4 phases with a substitution degree of scandium atoms equal to 0.25, 0.5 and 0.7 was determined by the Rietveld procedure. The base of SrNdSc1–хInxO4 slab peroskite-like structure consists of two-dimensional perovskite-like blocks of one slab of distorted InO6 octahedra joined by vertices. There are no direct (Sc,In)–O–(Sc,In) bonds between the octahedra of adjacent blocks. There is a layer of (Sr,Nd)O9 polyhedra between adjacent blocks, while the –O2–(Sr,Nd)–O2 interblock bonds provide a junction of the perovskite-like blocks. Comparison of structure features of SrNdScO4 scandate and SrNdSc1-xInxO4 phases showed that the isovalent substitution of the scandium atoms for bigger indium atoms in the single-slab SrNdSc1–xInxO4 structure leads to a consistent increase in the deformation degree of (Sr,Nd)О9 interblock polyhedra, the average (Sc, In)– O distance in (Sc,In)O6 octahedra and their inclination to each other, as well as to a significant increase in the length of the (Sr,Nd)–O2 interlock bond (from 0.226(1) nm at x=0 to 0.238(1) nm at x=0.3–0.7). An increase in the distance between the perovskite-like blocks weakens their bonding strength, while an increase in the deformation degree of (Sr,Nd)O9 interblock polyhedra and the inclination of (Sc,In)O6 adjacent octahedra increases the structure tension. The total effect of these factors leads to the destabilization and destruction of the slab perovskite-like structure and causes both the limited range of SrNdSc1–xInxO4 solid solutions with a slab perovskite-like structure (0x0.85) and makes impossible the formation and existence of SrNdInO4 indate with this structure type.

67-73

Authors: А.I. Yanchak, Yu.I. Slyvka, V.V. Kinzhybalo, T.J. Bednarchuk, M.G. Mys'kiv

By means of alternating current electrochemical synthesis with wire copper electrodes in methanolic solutions of corresponding ligands and copper(II) halide salts, two novel copper(I) -complexes [Cu2(dau)Cl1.58Br0.42] (I) and [Cu2(dapa)Cl1.74Br0.26] (II) (where dau and dapa are 1,3-diallylurea and 1,3-diallylparabanate, respectively) were prepared in well-shaped crystalline form and studied with X-ray diffraction method. Compound I crystallizes in orthorhombic crystal system, space group P212121: a=8.047(3) Å, b=8.154(3) Å, c=16.533(5) Å, V=1085.8(76) Å3, Z=4. Compound II crystalizes in monoclinic crystal system, space group I2/a: a=6.420(3) Å, b=8.088(3) Å, c=49.020(9) Å, =90.92(3), V=2545.03(16) Å3, Z=8. Both structures contain two crystallographically independent copper(I) ions with one half in trigonal planar coordination environment and the other half in trigonal pyramidal one. Both compounds are built of parallel copper halide polymeric chains of one type in I and two types in II, cross-linked by organic ligand molecules to produce 3D-polymer bulk in I and 2D-layered structure in II. In compound I, 1,3-diallylurea is both - and -bonded to copper(I) halide chains (by means of two allylic C=C bonds and carbonyl O atom), whereas 1,3-diallylparabanate is a solely -donor ligand in compound II. The structure of II is noteworthy due to the combination of two different chain types that have been previously observed only separately in copper(I) halide coordination compounds.

83-97

Authors: A.V. Slyuzar, Z.O. Znak, Ya.A. Kalymon, R.L. Bukliv

The main methods of purification and processing of hydrogen sulfide-containing gases are reviewed. The methods are classified as non-conversion and conversion ones, according to the nature of physical-chemical and chemical transformations of hydrogen sulfide in these processes. The adsorption, absorption, chemisorption and membrane processes are non-conversion methods. The catalytic solid- and liquid-phase, biological, plasma- and electrochemical processes are conversion methods. Their main advantages and disadvantages of these methods are discussed. The processes that are widely used in industry, especially those used in Ukrainian industry, are described in detail. It is noted that the use of known and traditional methods, which are widely-distributed in industry to purify high debit gases, is economically ineffective for the purification of hydrogen sulfide-containing gases from low debit sources. It is shown that the lack of appropriate gas purification technologies causes the pollution of the environment by harmful gas emissions, the inefficient use of these gases and the necessity of using additional stages of neutralization of generated wastes. A conclusion is drawn about the necessity of wider implementation of the newest methods that would minimize pollution of the environment by sulfur-containing compounds and make these processes cheaper as result of full utilization of hydrogen sulfide and the production of valuable marketable products, hydrogen and fine-dispersed or polymeric sulfur.

109-115

Authors: M.F. Buller, V.A. Robotko

The paper reports the long-term influence (more than 3 years) of water in a liquid and vaporous state on the main properties of double-base propellants. It was established that either a quick increase or a loss of weight due to the moisture migration occurs originally during the experiment (up to 200 days), depending on the relative humidity of an ambient air and the initial content of moisture in a propellant. Subsequently (more than 200 days), a continuous weight loss of the samples was observed that is explained by the removal of volatile components (i.e. liquid plasticizers) from a propellant. Using the obtained experimental data, the diffusion coefficients of moisture and propellant volatile components were calculated. Diffusion coefficients of volatile components do not depend on the humidity of an ambient air. The effects of atmospheric moisture during the experiment on the combustion heat and density of double-base propellants were analyzed. The process of migration of double-base propellant components into a surrounding aqueous medium was investigated in the course of a long-term exposure (more than 2 years). On the basis of the performed study, diffusion coefficients of nitroglycerine, dinitrotoluene and centralite-ІІ into water were calculated. Migration of double-base propellant components into water occurs from a thin external layer of the propellant element and is determined by the low solubility of the components of double-base propellants.

123-131

Authors: A. Kityk, V. Protsenko, V. Pavlik, M. Boča

High-temperature corrosion of stainless steels AISI 316 and AISI 304 in a molten "solar salt" used as a heat transfer fluid in concentrating solar power (60 wt.% NaNO3 and 40 wt.% KNO3) was investigated at the temperature of 550C. It was shown that the corrosion rate is influenced by the composition of stainless steel and the presence of impurities NaCl in the solar salt. With an increase in the content of sodium chloride impurity in the solar salt, the corrosion rate of both stainless steels increases. The corrosion resistance to the destruction of stainless steels AISI 316 and AISI 304 is provided by the formation of (Cr,Fe)2O3 oxide film on the surface of the samples. Thus AISI 304 stainless steel with chromium content of ca. 20% shows higher corrosion resistance in the solar salt than AISI 316 stainless steel with lower chromium content (ca. 18%). It is known that AISI 304 stainless steel additionally contains molybdenum and a higher content of nickel. The presence of these transition metals in the composition of stainless steel also affects the formation of a protective oxide film that prevents further corrosion damage of steel samples.

139-144

Authors: L.Ya. Parashchuk, V.V. Kochubey, L.I. Odosiy, S.V. Korolko

The effect of the cement type, from which engineering protective constructions are produced, on the value of the linear absorption coefficient of radiation flow has been investigated. The chemical and mineralogical composition of cement for the protective concrete was selected so that hydrated new-formations with the highest possible content of chemically bound water can be formed when hardened. The differential thermal analysis was conducted using a derivatograph Q-1500 D of Paulic-Paulic-Erdey system. Based on the obtained data, the quantitative composition of hydration products of cements under study was determined. A change in radiation intensity (in becquerel) was experimentally measured after passing through the concrete samples based on the Portland cement PC II/A-S 400 and the expansive Portland limestone cement PLC-5. Using the law of the weakening of a narrow monoenergetic beam of -quanta after passing through a substance, a linear absorption coefficient was calculated for the concrete samples of different composition. By means of special mechanical and physicochemical methods, the relationships between the processes of structure formation and the protective characteristics of the samples have been established. It was shown that hydrated compounds formed in the course of hydration of a cement constituent allow increasing the linear absorption coefficient together with raising the level of protection.

151-157

Authors: O.V. Savvova, A.F. Lyahovskiy, N.K. Blinova, G.K. Voronov, S.A. Ryabinina, V.L. Topchyi

The paper reports promising directions of development of glass-ceramic materials using in the military sector of industry for the production of protective armor plates which are exploited under the conditions of high-speed mechanical stressing and action of electromagnetic waves. The main types and areas of application of protective glass-ceramic materials with high radio-transparency and armor protection capacity are analyzed. The purpose of this work was to develop the components of impact-resistant glass-ceramic materials and obtain competitive radio-transparent light armor structures. The compositions of glass-ceramic materials based on lithium disilicate, -spodumene or mullite (80 vol.%) were chosen, these materials being prepared under the conditions of low temperature thermal treatment and characterized by high mechanical properties. The influence of chemical composition, structure of glass-ceramic materials and current frequency on the change of their electrical properties has been established. The developed glass-ceramic materials show improved mechanical properties and radio-transparency in a wide range of frequencies which allows using them as protective structures for radio equipment.

166-175

Authors: О.S. Khomenko, N.M. Sribniak, S.O. Hretsai, I.F. Teliushchenko, V.D. Ivchenko, V.V. Dushyn

The work was aimed at improving the production technology of porous ceramic blocks and improving their operational properties. It was established that the introduction of a complex of burning additives, which contains the wastes of pulp and paper industry, ash from thermal power-station and sawdust, into the composition of ceramic mass allows intensifying the processes of drying of semi-finished products and firing of finished products. The specified additives burn out at different temperatures during burning process and emit heat, which promotes reducing fuel consumption and allows saving energy. When the additives burn out, a porous structure of products is formed which leads to the improvement of their thermal insulation capacity. It is important that the selected complex of additives ensures an increase in the mechanical strength of the products by almost 4–4.5 times as compared with the products of the base composition. The rational amounts of additive components (relative to 100 wt.% ceramic mass) are as follows (wt.%): 10 sawdust, 5 wastes of pulp and paper industry, and 8 ash. The main properties of porous blocks are as follows: the density of 814 kg m–3, the water absorption of 13.7%, the mechanical compressive strength of to 9.2 MPa, and the thermal conductivity of 0.29 W (m C)–1.

181-185

Authors: M.D. Koshel'

This communication is devoted to the memory of outstanding Ukrainian electrochemist Professor O.S. Ksenzhek. The communication describes the main stages of the life and research activities of Prof. O.S. Ksenzhek.