Home – Home – Jornals – Chemistry for Sustainable Development 2023 number 1

The article reports the geochemical characterization of soils, vegetation, and groundwater of the recultivated spoils of three coal deposits. Recultivation was carried out 30-40 years ago, and then the spoils were left for self-overgrowth without any additional measures. A common pattern for all sites is the presence of carbonaceous particles, their oxidation leads to an increase in temperature in the spoil rocks. The sum of biologically active temperatures exceeds the values for natural soils of undisturbed areas. Technogenic landscapes are characterized by a smaller share of moisture-loving forest and pratal species, compared to the reference areas. Hydrogeochemical anomalies practically do not go beyond the flooded borrow excavations of spoils. Reclamation by applying a fertile soil layer provides minimization of the negative effects associated with an increase in the temperature of spoil soils and accelerates the remediation of regional plant communities.

Results of the field studies of mercury emission from the cyanation waste dump in the oxidation zone of the Novo-Ursk pyrite polymetallic deposit (Ursk settlement, the Kemerovo Region) are presented. Mercury content in the surface atmospheric layer above the dump surface is determined to vary within the range of 20-3600 ng/m³, while the diurnal average maximum permissible concentration (MPC_d) is 300 ng/m³, thus this value is exceeded in some sites by a factor of 12. The regional background above the dump surface is exceeded by a factor of 570 on average. Comparison between the morning and evening measurement results shows that mercury concentration increases in the evening. This is due to the active emission of mercury under the action of solar radiation and heating of the dump surface. Numerical models of mercury propagation are constructed using the methods of mathematical modelling. According to the model built up on the basis of the maximal measured concentrations, the whole territory of Ursk settlement is within the zone of very high mercury vapour concentrations. Calculation over the averaged concentrations shows that the safe level is achieved at a distance of 600 m from the dump, but within the boundaries of the settlement. The obtained results provide evidence of the danger of mercury action on the population of the settlement and pose the goal of more detailed investigation of air composition over old gold mining waste storage facilities.

Currently there is no agreement among the researchers worldwide about the mechanism of MFI-type zeolites deactivation due to coke accumulation in the areas of coke localization. This problem does not allow answering the question about the stability of these zeolites and their resistance to the reversible deactivation by coke. Our research provides the solution to this problem using physical and chemical methods: the electron paramagnetic resonance, X-ray photoelectron spectroscopy, thermal analysis and catalytic method of methanol conversion into hydrocarbons. We show that the key mechanism of coke formation is carbenium mechanism. Deactivation of zeolites occurs mainly due to the coke accumulation on the external surface of crystals of MFI-type zeolites. The contribution of “hydrocarbon pool” mechanism is negligibly small compared to the contribution of the carbenium mechanism of olefin formation by the dehydration reaction. This understanding allows increasing the stability of MFI type zeolites to coke formation by removing the acidic centres from the external surface of the crystals.

The effect of high-temperature treatment (900 ^oC) of N339 carbon black in the presence of carbon dioxide, followed by low-temperature treatment (-5 ^oC) in a mixture of oxygen with ozone, on its properties was studied. As a result of complex oxidative action, a carbon material is formed with textural properties that are several times higher than the levels of values characteristic of the original carbon black. The oxygen content in the final material can vary from 19 to 35 wt. %, which suggests that it is promising for use as a high-performance pigment.

The conditions for the formation of Pickering emulsions in the crude oil-water system were studied using cellulose nanocrystals with partially acylated surface as a stabilizer. Biodegradation of the obtained emulsions by natural microorganisms was investigated depending on the ratio of components in the emulsion. The formation of stable emulsions was evaluated depending on the nanocellulose concentration. At a low content of cellulose nanocrystals, the stability of the emulsion is achieved only with an increase in the concentration of the background electrolyte. Oil dispersing in water allows conserving the contact between the air and water phases, which promotes efficient biodegradation of oil due to an increase in the area of contact between oil microdrops and water. According to chromatographic analysis, the residual content of hydrocarbons in the emulsion is 20-25 % after incubation with an inoculant of microorganisms for 30 days. This method enhances the stability of oil dispersion, which promotes an increase in the rate of its biodegradation on various water surfaces.

Extraction processing of pine needles ( Pinus sylvestris Ledeb.) allows obtaining the products that are used to manufacture the goods in medical, food, perfumery and cosmetics, and other branches of industry. At the same time, the post-extraction residue of needles (PERN), being a specific lignocellulose raw material, has not yet found proper (effective) use for obtaining innovative products. Using the method of thermogravimetry in a nitrogen atmosphere (TG/DTG), a number of thermal decomposition patterns of PERN have been established. Based on the results of TG/DTG, the kinetics of PERN pyrolysis was analyzed, the thermodynamic parameters Δ H , Δ G and Δ S were calculated. The average values of Δ H , Δ G and Δ S are 246.3, 160.3 kJ/mol and 135.7 J/(mol · K), respectively. According to the method of the fourth derivative of DTG contour proposed by us, a detailed “fractionality” of mass loss during heating of PERN under the conditions of thermogravimetric test has been established. The values of the apparent rate constant are calculated, indicating the multistage (I-V) process of thermal decomposition. By means of analytical flash pyrolysis of PERN, 66 pyrolysis products were identified. Among them, 35 compounds were identified that are not found in pine bark and wood pyrolyzates and can be in demand in organic synthesis, in the production of technical and food products, perfumes, medical products, etc . The obtained results are basic for designing the manufacture of technical products with increased added value and scaling of heat treatment technologies and pyrolysis of similar plant raw materials.

In order to develop a technology for the chemical processing of methane from the coal industry into valuable products, conditions for the reactions of combined steam/carbon dioxide and autothermal reforming of methane were optimized. The effects of temperature (600-900 °C), volumetric feed rate (50-400 mL/min), contact time (0.04-0.45 s) and the molar ratio of components (O₂/CH₄ = 0.25-1.0, CO₂/H₂O = 0.5-2.0) of the reaction mixture on the conversion rates of initial reagents (CH₄, CO₂, O₂) and the yield of target reaction products (H₂, CO) were studied. It has been shown that the use of combined reforming allows regulating the H₂/CO molar ratio within a wide range (4.1-0.9). Optimal process conditions have been established to ensure the complete conversion of methane and the maximum yield of useful products for the effective utilization of methane-air mixtures in coal production with the generation of a hydrogen-containing gas.

The composition and transformation dynamics of saturated hydrocarbon biomarkers in the coal of the Sergeevo deposit were studied using gas chromatography and gas chromatography - mass spectrometry. Depending on biomarker parameters in the studied section, the layers of allochthonous, autochthonous and mixed origin were identified, differing from each other in the nature and conditions of plant biomass accumulation. Allochthonous coals, enriched with bitumoids and genetically related to terragenic biomaterial, were formed in an oxidative environment. The transition to autochthonous and mixed coals was accompanied by an increase in the contribution from aquagene biomarkers and repeated changes in the facies conditions of sedimentation. Autochthonous coals are distinguished by an abnormal content of higher alkanes and a non-standard distribution of isoprenoid hydrocarbons.

Vanadium precipitation in the form of ammonium metavanadate and polyvanadate from alunite processing solutions is studied. The degree of precipitation of vanadium-containing sediment is determined, depending on solution pH, the initial concentration of vanadium(V) oxide and ammonium sulphate, temperature, and contact time. The results show that ammonium metavanadate (NH₄VO₃) precipitates from the solution at room temperature at pH 8, and when the ammonium metavanadate solution is heated to 90 °C and then acidified to pH 2 and stirred, ammonium polyvanadate (NH₄)₂V₆O₁₆ precipitates. The obtained products were characterized by X-ray phase analysis, infrared spectroscopy, and scanning electron microscopy.

The influence of various technological additives on the plastic and rheometric properties of a rubber mixture is investigated, physical-mechanical and performance characteristics of rubber based on a combination of SKN 4055 nitrile butadiene caoutchouc and Therban 3406 hydrogenated nitrile butadiene caoutchouc are assessed. The rubber mixture included SKN 4055 and Therban 3406, curing agent Luperox F-40P, antioxidant Diaphene FP, fillers: burnt magnesia, carbon black T 900 and P 514, oligoester acrylates TGM-3, MGF-9, and other ingredients. We used Z-50, Z-60, Struktol WB-222, Kvalistrol A-100, B-70 and B-70-20 as technological additives. The rubber mixture was made on laboratory rolls LB 320 160/160, then vulcanized at 150 °C for 60 min and thermostated at 160 °C for 3 h. Studies of the plastic and rheometric properties of the rubber compound, the physical and mechanical properties of vulcanizates were carried out in accordance with the standards existing for rubber industry. The study of thermo-aggressive resistance of vulcanizates was carried out by determining the change in their physical-mechanical parameters after 1 day exposure to air and standard liquid SZhR-1 at a temperature of 150 °C. It is found that the introduction of technological additives leads to improvement in the distribution of ingredients, as well as in the plastoelastic and rheometric properties of the rubber mixture. Rubber containing Kvalistrol B-70-20 has increased physical and mechanical properties, exhibiting the least changes after exposure to aggressive media.

Results of the studies of municipal sewage sludge (MSS) oxidation during pumping a water-oxygen fluid through its bed under uniform (1.5 K/min) temperature ( T ) rise up to 733 K are presented. The temperature dependences of the yield of volatile and liquid products, as well as data on the content of mineral components in the ash residue and water collected at the reactor outlet are obtained. It follows from the temporal dependences of the reactor wall temperature, the power of the ohmic heaters, and the degree of carbon burn-up that the major part of MSS organic matter is oxidized at T < 602 K. According to the data of IR spectroscopy and ultimate analysis, an increase in the oxidation duration and temperature leads to a decrease in the content of hydroxyl and amide groups and an increase in the proportion of aromatic compounds in liquid products. The volatile products obtained at T > 673 K contain only inorganic substances - CO₂, CO, N₂, and NH₃. It is revealed that the major part of nitrogen in the form of NH₄⁺ ions passes into the aqueous phase, while the elements Si, Ca, Al, Fe, P, S, K, Na, and Mg are concentrated in the ash residue.

The article presents a geochemical interpretation of data on the physicochemical properties and individual composition of oils and condensates from the Bovanenkovo and East-Bovanenkovo fields (the distribution of light hydrocarbons (HC) C₃-C₈, n -alkanes, acyclic isoprenanes, steranes, terpanes, arenes). The main purpose of this study is the identification of the main sources of HC fluids, as well as geological and geochemical processes that have affected their composition and the formation of deposits. It is shown that the formation of naphthides from both fields occurred in several stages with the participation of the organic matter (OM) varying in genotype, in particular due to the widespread processes of secondary migration and reformation of primary deposits. Oils and condensates from the Jurassic deposits of the Bovanenkovo field were established to have a genetic relationship with the terrestrial OM of the Lower and Middle Jurassic strata, which was a source of both liquid and gaseous hydrocarbons and subsequently formed these oil and gas accumulations. It is assumed that the naphthides of the Neocomian part of the section are derivatives of the aquatic OM in the Bazhenov formation. These gas-condensate deposits during their formation were differently enriched with light components generated by the terrestrial OM of the Lower and Middle Jurassic strata. The effect of biodegradation processes on the composition of condensates of the Aptian and Albian-Cenomanian deposits was recorded. Their formation is considered having occurred due to the carbonaceous OM of the Cretaceous strata, which served as a source of primary “immature” condensates with terrestrial composition, which were mixed with secondary-migration HC fluids generated by: the aquatic OM of the Bazhenov formation in the case of gas condensates of the Aptian deposits; terrestrial OM of the Lower and Middle Jurassic strata in the case of the pools of the Albian-Cenomanian reservoir. In addition, the naphthides formed with the participation of aquatic OM are observed to be confined to the East-Bovanenkovo field and the southeastern part of the Bovanenkovo field.

In connection with depleting light oil reserves, oil fields with an increased content of paraffin hydrocarbons and resinous-asphaltene components characterized by high density, viscosity and pour point values are increasingly being put into operation. Their extraction is accompanied by the formation of asphalt-resin-paraffin deposits on the walls of technological equipment and, as a result, leads to additional material expenses associated with increased wear of equipment. The influence of the magnetic field on the structural, rheological and energy characteristics of two kinds of oil, differing from each other in composition, and their emulsions (10 wt. % water) was studied. After magnetic treatment, the component composition of the studied oil-containing systems changes. The effect of the magnetic field on low-paraffin, highly resinous oil is accompanied by an increase in viscosity within the whole temperature range. The viscosity of high-paraffin oil changes only slightly after processing, however, a decrease in the pour point is observed.

The content of 25 chemical elements was determined quantitatively, by means of mass spectrometry and atomic emission with inductively coupled plasma, in natural spring sources, as well as in water from central utility and drinking water supply systems and secondary water purification systems (household filters) for the purpose of exploring the safety of drinkable water for the population of some districts of the Magadan Region. Conformity of chemical element concentrations to the standard quality requirements for drinkable water was determined. The study confirms that water is safe for human consumption with respect to the accumulation of conventionally essential and toxic chemical elements. However, water tests showed poor saturation with physiologically useful elements at all sampling sites in the towns and settlements of the Magadan Region.