Home – Home – Jornals – Chemistry for Sustainable Development 2018 number 1

The results of experimental studies aimed at determining methane formation mechanisms in the aerobic plant phyllosphere and the contribution of vegetation to global methane emission are reviewed and summarized. Until recently, methane formation and emission by biogenic sources had been associated exclusively with activities of methanogenic archaea growing under anaerobic conditions of water bodies and streams, swamps, rice fields, dumps, and the gastrointestinal tract of animals and termites. However, as demonstrated by modern data, methane formation is also possible via not only the microbial route, in the aerobic plant phyllosphere. Although the mechanism of anaerobic methane formation in plants is not clearly identified, the interconnection between the observed liberation of methane by plants and UV radiation impact and other physiological stresses (temperature change and plant physical trauma) recorded on the example of numerous experimental works demonstrates that this is a general process occurring in the presence of oxygen. It is considered that during UV radiation impact and other physiological stresses on plants, chemical reactions with the formation of oxygen active species start and consequently, some amount of methane is liberated from methoxyl groups of plant pectins (and according to some data, also from plant cellulose and lignin) as part of cell dissolution process. Using very diverse approaches, it is estimated that the most probable range of total methane emission by vegetation is 20-60 Tg/yr. Herewith, the fraction of foliar methane emission related to ultraviolet irradiation of pectin does not exceed 5% of global methane emission by vegetation, ~60% of which falls on tropical latitudes.

The effect of surfactants on the rate of the target reaction of tellurium precipitate from alkaline tellurium solutions and the side reaction of further reduction to ditelluride anions, and also current efficiency and morphology of cathode tellurium precipitates is examined on a graphite electrode pre-coated with tellurium sludges by the voltammetry method. Sodium lignosulphonate and polyvinyl alcohol have a weak effect on the rates of both cathode reactions and therefore on morphology of tellurium precipitates, as demonstrated. Tetrabutyl ammonium hydroxide additive inhibits both reactions but simultaneously worsens the quality of cathode precipitate: there generated a powdery sludge that is partly poured out from the substrate and is almost completely rinsed away upon water washing. The most efficient additive to obtain dense tellurium precipitates is OP-10 wetting agent. It substantially inhibits tellurium deposition and suppresses the side reaction of its dissolution in the virtually important range of potentials until the maximum current. At the same time, OP-10 significantly improves precipitate morphology and ensures obtaining fine-crystalline dense cathode tellurium precipitates.

The paper presents results of comparative study of composition and structure of nitrogen-containing resin bases of heavy oil from the Usinsk field before and after thermal effects at 450 ^oС for 30 min. Different molecular mass nitrogen-containing bases are isolated using sedimentation methods with hydrogen chloride and sulphuric-acid extraction from initial and thermolised resins. High molecular mass compounds comprise the bulk of bases in both cases, however, their fraction in thermolysed resins is substantially lower. Thermally transformed bases have lower masses compared to the initial ones. Structural group analysis and gas chromatographic mass spectrometry techniques examine the composition of the isolated compounds. Middle molecules of nitrogen-containing resin bases of both types consist of polycyclic rings that include aromatic and saturated cycles with different alkyl frames, as demonstrated. Average species of thermolysed resin compounds are more aromatic due to a decrease in the fraction of naphthene and alkyl fragments. In the composition of bases of initial and thermolysed resins, there are alkyl derivatives of quinoline, benzoquinoline, dibenzoquinoline, and azapyrene, the maximum of the distribution of which falls at alkylbenzoquinolines. The fraction of alkylquinolines is elevated among azaarenes of thermolysed resins. A higher fraction of structures with a lower number of carbon atoms in alkyl substituents is typical for all types of bases of thermolysed resins. It may be assumed that the identified compounds would enter into the composition of distillate fractions during thermal processing of heavy hydrocarbon raw materials. This is necessary to consider in solving issues related to preparation of high-quality fuels and lubricants based thereon.

The results of the study of chemical and phase compositions, IR spectroscopy analysis, morphology, specific surface area, pH of aqueous extract, and magnetic susceptibility of vermiculite samples from the Koksharovsky deposit of Primorsky Krai (the mineral, concentrate, and intumesced product) are presented. Comparative analysis of samples of vermiculite from Koksharovsky and Kovdor deposits of different origins was carried out.

Properties of anticorrosive coatings based on water-dispersive copolymers pigmented with manganese species were studied. It was found that the inclusion of the synthesized pigments into the composition of coatings elevated their ability to suppress underfilm steel corrosion. The compositions of anticorrosive primers that exceeded industrial analogues according to the efficiency of protective action were proposed.

Efficient nanocontainers based on noncovalent electrostatic complexes, such as sulfonated calix(4)resorcinol - cationic surfactants (CR - CS) with regulated solubilization and catalytic activity, were developed. Mono-, di-, and tetra-quaternized derivatives of 1,4-diazabicyclo(2.2.2)octane were used as CS. Reaction kinetics for hydrolysis of esters of acids of phosphorus, namely, 4-nitrophenyl-O-ethyl chloromethyl phosphonate, in the presence of CR - CS mixed compositions was studied by UV spectroscopy method during variation in the number of cationic centres of CS and addition of a hydrophobic dye (Orange-OT). Reaction parameters (the specific reaction rate in the micellar phase, substrate binding constant with aggregates, and the critical micelle concentration) attest to the fact that CR - mono-cationic surfactant system has the maximum catalytic activity.

The effect of heavy high molecular mass components of crude oil (asphaltenes, resins, and aromatic hydrocarbons) on its aggregative stability was studied on the example of heavy oils from the Usinsk field. The componential composition of oil samples was determined by precipitation and chromatography methods. Different spectral characteristics in the visible region that allow operatively comparing the resistance of crude oil against precipitation of asphaltenes were determined by the method of electron spectroscopy. For this purpose, dynamic curves of a change in the optical density were removed in solvent/precipitator (toluene/hexane) system and light absorption (C₅₀₀) and colour (Cc) coefficients were computed. The stability of crude oil was determined by not only the ratio of resin and asphaltene components, as demonstrated. Oil aggregative stability versus the degree of condensation and a network of aromatic compounds was revealed using colour coefficient.

Complex comparative analysis of some modifiers based on refractory ceramic particles was carried out. Compositions based on nanodispersed tungsten and titanium carbides were obtained by a combined method (self-propagating high-temperature synthesis in combination with mechanochemical treatment). In experiments on intra-mould modification of grey cast iron and 110G13L steel, they demonstrated the maximum efficiency compared to other studied modifiers: within ceramic phase concentrations of 0.013-0.2 %, for gray cast iron, an increase in tensile strength was to 20 %, in hardness - to 13 %, in wear resistance - to 69 %, in corrosion resistance - 2.6 times; for steel, an increase in temporary tear resistance reached 18.0 %, in relative elongation - to 40 %, grain size reduction - by 6.8 times. As demonstrated during modification of grey cast iron by additives containing nanodispersed ceramic phases, not only the concentrations and composition of modifiers but also various process parameters (the design, the volume of the mold, the method of introduction of modifiers, etc. ) should be taken into account.

A colorimetric sensor based on a transparent polymethacrylate matrix modified with diphenylcarbazone was developed with a view to spectrophotometric determination of Hg(II) in various objects. The effect of pH of a solution of diphenylcarbazone on its immobilization into a polymer matrix was studied. The maximum value of the analytical signal was reached near 520 nm and remained almost unchanged in the 3-11 рН range, as established. During the study of complexation of diphenylcarbazone immobilized into a matrix with mercury(II) ions, there were found optimum conditions for determination of Hg²:^: рН 2.5-4 and duration of the interaction of mercury with diphenylcarbazone (with violet complex formation) of no more than 15 min. Mercury content was determined spectrophotometrically in the 1-25 µg/dm³ range by measuring absorption of light near 540 nm. The developed procedure of express analysis of mercury(II) was tested during studying organomercury granosan pesticide by indirect electrooxidation.

Decomposition and formation conditions of carbon dioxide hydrate were experimentally determined in porous matrix. As the latter, samples of γ, θ, and α phases of alumina with different porous structure, pore size distribution, and specific surface area were selected. The resulting deviation values of decomposition temperature from the equilibrium curve were compared with a possible diameter of hydrate species computed on the ground of the Gibbs-Thomson equations and known data about the porous structure of the used samples. Comparative analysis of the results of this work and earlier studies of hydrate formation processes in natural coals revealed qualitative differences.

The paper notes a crucial role of personal protective equipment (PPE) of skin integument during work with hazardous substances and liquidation of emergency at industry and transport enterprises. Earlier, two- and three-layer materials were used in the country and abroad to manufacture PPE of the isolating type. Currently, the leading companies manufacturing these means overseas for emergency PPE developed new four- and five-layer materials. These suits are present in the Russian market of PPE, however, their cost is quite high. For the first time in the country, the KazKhimNII JSC developed innovative multilayer LTL-1-2 material and its elastomer-based analogues. The universality of protective properties is due to selection of elastomers with different properties, specially developed formulations, and preparation method of composite materials. By protective properties, new isolating matters are not inferior to the best foreign materials of the highest level of protection. The developed innovative multilayer materials are designed to manufacture multifunctional isolating suits for personnel of industrial enterprises, objects of the Roscosmos State Corporation, and emergency response teams.

Research was carried out into the development of a lite protective flame-resistant rubberized material with a set of protective properties against aggressive media (acids and alkalis), gaseous highly toxic substances (chlorine and ammonia), solvents, and oils. The effect of the composition of rubbers on their protective properties was studied. Rubbers with improved protective properties were prepared on the basis of chlorosulphonated polyethylene combined with chloroprene rubber. A substantial impact of the nature of cross bonds and the type of vulcanizing agent on resistance of rubbers to aggressive media was determined. A series of antipyrenes with a total content of 60 pts. wt. were developed. They ensure preparation of self-extinguishing rubber upon preservation of residual durability. A protective lite material with the low surface density and good protecting properties compared to analogues was prepared on the ground of the data obtained.

Research into the development of siloxane rubbers with increased thermal and fire resistance was carried out. Rubber nanocomposites based on SKTB-1 siloxane rubber that were filled with aluminium trihydrate were obtained using domestic and foreign manufacture organobentonites. It was found that the introduction of organobentonites into siloxane rubbers filled with Al(OH)₃ contributed to an increase in their thermal and fire resistance. Fire-resistant and heat-protective materials, and also preparation technology of tissues by glue spreading using IBO 3320 and Siltex spreading machines were developed according to the results of experiments using glass, silica, and aramid fabrics as a reinforcing frame. Tests of the resulting materials were carried out and areas of application of protective clothing based thereon were proposed.

Properties of industrial copolymers were determined and the optimum ratios of monomers to obtain similar acrylic polymers were found. The effect of the composition of monomers on characteristic viscosity and relative hardness of acrylic copolymers based on methyl methacrylate and butyl methacrylate was studied. The optimum conditions for synthesis of acrylic copolymer with required properties were defined. Spray plastic with good performance properties was developed.

By the example of four types of soils of Udmurtia, sorption process by them of arsenic and chromium ions in extremely toxic forms is considered. Langmuir and Freundlich isotherms are constructed based on acquired experimental data and constants pointing to weak adsorption power of soils of the Non-Black Earth Zone in relation to these anions are determined. High solubility of arsenic and chromium species against weak sorption capacity of soils determines environmental risks of active migration of As(III) and Cr(VI) anions along soil profile. Their mobility should be taken into account during environmental monitoring.

A new approach towards determination of structure and composition of fragments coupled via a C--O bond in ethers and esters of petroleum and natural bitumen oils is developed. It is based on the use of the known chemical reaction of selective cleavage of ether/ester bridges in petroleum oil components using BBr₃. Unlike the known approach involving the stage for reduction of products of chemical modification of oils with lithium aluminium hydride, it is proposed to analyse the composition of the resulting organic bromides by the GC-MS method. Mono- and dibromo derivatives of C₁₃-C₂₂ alkyltrimethylbenzenes are identified in chemical modification products on an example of natural bitumen oils from the Ashalchinsk field (Tatarstan). Unlike С₁₈-С₂₂ compounds, С₁₃-С₁₇ homologues are not detected in initial oils, therefore they are entirely coupled to other fragments of complex high molecular mass formations by one or two ester-ether bridges. Furthermore, as established during analysis of GC/MS results, there are ions corresponding to monobromides of characteristic fragment ions of n -alkanes, and also to mono- and dibromides of characteristic molecular ions of naphthalene, phenanthrene, dibenzothiophene, and their homologues. Hence, in complex high molecular mass formations of the studied oils, some of the listed compounds are linked via one or two ether/ester bridges.