Home – Home – Jornals – Chemistry for Sustainable Development 2012 number 4

A brief review is presented concerning the methods for producing synthetic and composite polymer materials those can decompose under the influence of environmental factors. The advantage of these materials is demonstrated in comparison with the “classical” industrially produced petroleum-based polymers. Main ways and means are indicated to impart the biodegradable properties to polymeric materials.

Different models of defect ordering in strongly nonstoichiometric perovskite-like oxides based on strontium ferrites/cobaltites Sr(Co_0.8Fe_0.2)O_3–δ, (Sr_0.7La_0.3)(Co_0.5Al_0.3Fe_0.2)O_3–δ, (Sr_0.7Сa_0.3)(Co_0.5Al_0.3Fe_0.2)O_3–δ, Sr(Co_0.75Nb_0.05Fe_0.2)O_3–δ, Sr(Co_0.7Nb_0.1Fe_0.2)O_3–δ and Sr(Fe_0.95Mo_0.05)O_3–δ (2.5 < (3–δ) < 2.7) are considered. Diffraction patterns of a number of samples differing in cation composition and degree of nonstoichiometry exhibit intensive reflections that are characteristic of the perovskite structural type with weak wider superstructural peaks. It is demonstrated by means of computer modelling of X-ray scattering on the crystals with different defects that such a diffraction pattern can correspond to three models of ordering of the oxygen vacancies: the formation of a homogeneous structure with the ordered state of oxygen vacancies (structural elements of the low-symmetry phase) and the formation of nano-heterogeneous systems (brownmillerite ABO_2.5 + perovskite ABO₃) of two types. In the first case, the components of the system have lamellar shape and interchange in one direction (a unidimensional disorder). In the second case we speak of the structure of brownmillerite domains turned with respect to each other at an angle of 90°, with different methods of redistribution of the perovskite component – at interfaces or in the form of separate domains. It is demonstrated with the help of two-dimensional diffraction of X-rays that this texture is observed not only at the nano-level but also for the samples with microdomains.

Results of the investigation of aerosol in the region of Seversk (Tomsk Region) performed in 2010 using mass spectrometry and atomic emission with inductively coupled plasma are presented. With the help of GIS methods, geochemical indicators of technogenic aerosol of the Siberian Chemical Combine were revealed, and the basic aureoles of their distribution were determined. Comparative analysis of the results and the data published previously is presented.

Total heavy metal content in the soil in the region of the storage of wastes from pyrometallurgical works (Belovo Zinc Plant) was investigated. It was established that the high level of zinc and copper pollution is conserved also after the plant stops its operation. The maximal pollution was detected in the direct vicinity of clinker mound; it exceeds the background values for zinc by a factor of 60. At a distance of 300 m pollution decreases (17-fold excess over the background value) but it can be followed even at a distance of 5 km from the Belovo Zinc Plant (5-fold level). The fraction of mobile forms of a number of elements extracted through stepwise leaching was determined. For the soil with the heaviest pollution (рН of water extract 5.58), the fraction of mobile zinc forms exceeds the MPC by a factor of 66, copper by a factor of 2, manganese is below the normal value, mobile forms of nickel were not detected. Thus obtained row depicts the geoecological condition of soil in the region of waste storage of the Belovo Zinc Plant.

Physicochemical state of YBa₂Cu₃O_{6 + δ} powder subjected to mechanochemical treatment was studied by means of thermogravimetry, X-ray diffraction, iodometry and X-ray photoelectron spectroscopy. It is demonstrated that the indicated treatment causes broadening of the range of variation for oxygen parameter (δ) and an increase in the chemical activity of yttrium/barium cuprate above the limit that can be attributed to a decrease in particle size. The discovered features are due to increased non-equilibrium character of activated YBa₂Cu₃O_{6 + δ}, including uncharacteristic combination of the oxidation numbers of copper and oxygen ions interacting with each other (Cu³⁺, O^–).

Kinetic characteristics and mechanism of silver dissolution in the course of leaching the gold-silver alloy by nitric acid solutions in the presence of ammonium nitrate under a pressure of gas phase reaction products were investigated by means of the method of rotating disk. Parameters were revealed for the process occurring in the external diffusion, kinetic and transition zones. Factors have been found those determine the dissolution rate of the metallic silver.

A new approach is presented with respect to solving the problem of the complex processing of a low-grade manganese-containing raw material, based on deep reductive melting with the separation of metal and silicate parts of the melt and the amorphization of the latter by via cooling in a thermal shock mode. As the result of these processes, a XRD amorphous foamed silicate with wide application potentialities is formed as well as ferromanganese silicon segregation is observed.

The effect of nanocomposite obtained by means of solid-phase mechanochemical synthesis from non-fruit parts of buckthorn (buckthorn-based serotonin powder, BBSP) on the immunophysiological status of dwarf hamsters during autumn decrease of photoperiod was studied. It was shown that the addition of BBSP to food in curds has no effect on the amount of curds ate by the animals, does not eliminate the basic morphological changes developed in the animals under the conditions of decreasing daylight hours, does not affect the degree of ecdysis. At the same time, the addition of BBSP promotes reliable decrease in body mass, and increase in the spontaneous activity of the animals during the first four weeks of the experiment, conservation of the summer type of thermoregulation (high energy consumption for the compensation of the action of cold, and prevalence of chemical thermogenesis) and an increase in the humoral immune response to the introduction of sheep erythrocytes.

An effect of inhibitory additive on the kinetics of sediment formation in highly paraffinic oil was investigated. It has been demonstrated that the maximum rate of sediment formation occurs within the first minutes of the process. The inhibitory additive promotes greatly decreasing to a considerable extent the rate of sediment formation in the oil due to the retention of solid paraffin hydrocarbons in the bulk. An influence of the inhibitory additive upon the group composition of sediments and the composition of paraffinic hydrocarbons was investigated.

A novel technology has been developed for conditioning cold mineralized groundwater inherent in the northern Tyumen Region, Russia. The technology involves the use of three chemicals such as hydrogen peroxide, potassium permanganate and sodium hydroxide to provide purifying the water from iron, manganese, hydrogen sulphide and silicon up to the standards of drinking water, as well as the stabilization treatment of water. Rationale for choosing the type of reagent for stabilization treatment and the results of testing the technology are presented.

A catalytic process of the oxygen-driven oxidation of aspen wood and enzymatic lignin as a waste of processing aspen wood into biobutanol was investigated in a static reactor using a rotating magnetic stirrer in an alkaline medium. The effect of temperature and of a mode of alkali feeding into reactor on the yield of syringaldehyde and vanillin was studied. It has been established that the fermentation lignin is close to the native lignin being much more efficient as compared with lignosulphonates for using as a feedstock for the preparation of vanillin and syringaldehyde.  Separation is experimentally realized concerning the stages of lignin oxidation by oxygen, on the one hand, and the retro-aldol cleavage of oxidation products into vanillin and syringaldehyde, on the other hand.

Using the mechanochemical method during 30 min in the planetary mill, we synthesized the samples of hydroxyapatite (HAP) modified with silicate ions in the amount of 0.1, 0.2, 0.4 and 0.8 molar fractions of the ion in HAP at the given molar ratio Са/(Р + Si) = 1.67. As a result of activation in the air medium, hydroxyapatite with the average crystallite size of ~20 nm was formed. The mechanochemically sy6nthesized samples contain carbonate ion substituting the phosphate ion, with the formation of carbonatehydroxyapatite of B type; its amount decreases with an increase in the amount of silicate introduced. Modification of hydroxyapatite with silicate ions is a competing reaction for phosphate substitution with carbonate. Depending on the ratio of silicate to carbonate amounts in hydroxyapatite structure, the mechanism of substitution changes. In the case of predominance of the carbonate ion in apatite, the composition corresponds to the general formula Сa_{10 - (x - y)/2}(PO₄)_{6 - (y + x)}(SiO₄)_y(CO₃)_x(OH)₂ (х > у). In the case of the equal number of substituents (х = у) silicate-substituted hydroxyapatite has the stoichiometric composition with the general formula Ca₁₀(PO₄)_{6 - (y + x)}(SiO₄)_у(CO₃)_х(OH)₂. In the case of predominance of silicate ion (х < у), charge compensation occurs due to the formation of vacancies in the positions of (ОН)^- groups: Ca₁₀(PO₄)_{6 - (y + x)}(SiO₄)_у(CO₃)_х(OH)_{2 - у}. After annealing the samples, the silicate group occupies the positions of phosphate ion in hydroxyapatite structure with the formation of vacancies in the positions of (ОН)^- group; the composition is described by the general formula Са₁₀(PO₄)_{6 - x}(SiO₄)_x(OH)_{2 - x х}.

An influence of the synthesis conditions upon the direction of o-cresol alkylation conditions with camphene in the presence of sulphated zirconia was investigated. There were O- and C-alkylation products obtained with a different structure of terpene substituent. It is demonstrated that the presence of sulphated zirconia results in the formation of 4-isobornylphenol, 4-isocamphylphenol and para-alkylated phenol with the methyl groups at positions 1, 4, 7 in the terpene moiety. The catalysis with sulphated zirconia allows obtaining para-alkylated 2-methylphenol with the isobornyl structure of terpene substituent, with a yield of 58 %.

An influence of the molecular structure of hydrocarbons and halogenated derivatives thereof upon the acute toxicity was studied with the use of a 2D simplex representation of the molecular structure and partial least squares technique. Adequate QSAR models were obtained, wherefrom structural fragments have been revealed those could cause the toxicity level to increase. With the help of QSAR models a relative influence of some physicochemical factors upon the acute toxicity was assessed.