Home – Home – Jornals – Chemistry for Sustainable Development 2022 number 4

Results of geochemical investigation of drainage waters discharging from the mining objects (dumps, quarries, tailings) of the Orlovskoe tantalum deposit (Transbaikal Territory) are presented. It is determined that the drainage waters from the dumps of overburden rocks and from blast holes are acid and weakly acid, and highly mineralized (TDS up to 4232 mg/L). With respect to the chemical composition, these waters are mainly of sulphate type, with anomalously high concentrations of aluminium, fluorine, chalco- and siderophilic elements. The waters of the tailing storage facility are neutral and weakly alkaline, with increased tungsten and arsenic concentrations. Thermodynamic calculations of the major forms of element migration in drainage waters show that simple cationic forms dominate for most metals, while the second prevailing forms are sulphate and fluoride complexes. The average concentrations of Mn, Al, Be, Zn, Fe, Li, Со, Ni, Cu, W, F^- and SO₄^2- are determined to be substantially higher than the maximum permissible concentrations for water objects for fishery, household, drinking and amenity water usage, which is connected both with the composition of the ores and host rocks of this deposit, and with technogenic activities.

In this study, the conditions for the precipitation of aluminium hydroxide from sodium aluminate solutions obtained from the alkaline solution of raw alunite ore by hydrogen peroxide, an eco-friendly reagent, are studied. Factors influencing the precipitation by H₂O₂ and aluminium hydroxide from diluted aluminate solutions (concentrations of hydrogen peroxide and alkali, volume ratios of hydrogen peroxide and aluminate solution, temperature, time, caustic modulus) are investigated and found under optimal conditions (initial concentration of hydrogen peroxide >15 %; temperature 20-40 °C, V_H2O2/V_sol = (5-20) : 20 mL, alkali concentration 42.33 g/L (according to Na₂O)) precipitation of ~95 % of aluminium in aluminate solution is achieved. The recovery of alkali (sodium hydroxide) after the precipitation of aluminium hydroxide by H₂O₂, its return to the leaching of alunite has been studied, and several difficulties have been eliminated in the precipitation of aluminium hydroxide by other methods. The characteristics of the obtained samples are confirmed by means of XRD, SEM/EDS analysis.

Comparative analysis of the macro and trace element composition of fruit, leaves and stems of the plants was carried out with respect to the content of mineral nutrition elements in the soils in the natural population of the Altai subspecies of blue honeysuckle (Lonicera caerulea subsp. altaica) in the local zone where disjunctive geological structures are concentrated in the valley of the Kyzyl-Yaryk river (the Altai Mountains, the North Chuya Ridge). Substantial variations of the total content of macro and trace elements Ca, Al, K, Na, Sr, P, Mn, Ba, B, Zn, Cu, Cr and Ni, the mobile forms of Ca, Sr, Fe, Mn, Cu, Cr, Ni, Co, Na in the soils and soil acidity (pH 4.5-6.7) were revealed at the regions differing from each other in the volume activity of radon emission field (262-1162 Bq/m³). Micropopulations of L. caerulea subsp. altaica at these regions differed from each other in the level of accumulation of Сu, K, P, Na, Mo, Cr, P, Sr, Si in plant organs, and in the physiologically essential ratios Cu/Zn, Fe/Mn and K/Ca. An increase in the Cu/Zn ratio in plant organs had a significant effect on a decrease in fruit size, number of seeds in fruit, their germination capacity, and an increase in the seed germination power. The seed germination power is also in significant positive correlation with the level of Ca, Mg, Cr, Cu, Sr, Pb accumulation in leaves and stems, and with the Fe/Cu ratio. The content of K in fruit is in significant negative correlation with seed germination power.

The problem of utilization of sludge from the storage facilities of the Baikal Pulp and Paper Mill (BPPM) for the purpose of improving the environmental situation in the Baikal region is considered. Geographical and seismic characteristics of the territory where this object of environmental danger is located are described. The factors threatening Lake Baikal are highlighted. Qualitative and quantitative characteristics of sludge-lignin contained in sludge storage facilities are presented. During the recent years, all the numerous attempts to utilize sludge-lignin invariably ended in failure. Transportation of waste to other temporary settling tanks located at a distance from Lake Baikal also would not solve the problem and can only worsen the current situation due to the large volume of accumulated waste and the permanent flow of rain and snowmelt water into the settling tanks. A retrospective review of the technical, technological and organizational measures taken by the administrative and engineering personnel of the BPPM and aimed at economically affordable and environmentally friendly disposal of sludge waste from sedimentation tanks was carried out. The analysis of patent, scientific and technical data bases made it possible to select a number of documents concerning the reactivity of lignins in the sulphate production of cellulose. The information is found that the dry sludge-lignin product of BPPM had been in demand by oil and gas exploration enterprises throughout Siberia for several years (1980-90s) as a cheap substitute for water-soluble cellulose esters, starch, xanthan resins and other components for washing liquids during the construction of deep oil and gas wells. Ways of utilization of the sludge-lignin component of the BPPM sedimentation tanks are proposed.

The effect of the mixtures of ethers and alcohols on the performance characteristics of motor petrol is investigated. The objects of investigation are industrially available domestic oxygenates: methyl tert -butyl ether (MTBE) and isobutyl alcohol (IBA). Investigation of the effect of the ratio of these oxygenates in the two-component mixture on the change in antiknock activity of petrol revealed a synergistic effect in the octane number within the range of the concentrations of MTBE (20 to 80 wt. %) and IBA (80 to 20 wt. %). Involvement of this two-component mixture in petrol provides an increase in the octane number. The optimal ratio of oxygenates is determined (MTBE/IBA = 50 : 50 wt. %), which provides, along with the manifestation of the synergistic effect in octane number (an increase by 7.9 units), a more uniform distribution of octane numbers over fractions and stability of performance characteristics during transportation and storage of commercial fuel. Resulting from the discovered synergism of oxygenates MTBE and IBA, a new additive to motor petrol is developed. In order to enhance and expand the range of action of the new additive based on the two-component mixture of MTBE and IBA, a formulation involving monomethylaniline (MMA) and anti-corrosion additive DCI-11 is developed. At the same time, the amount of MMA involved in motor petrol compounding did not exceed the sensitivity of the method. In comparison with the additive based on the two-component mixture, the use of the additive with an extended range of action made it possible to enhance the anti-knock characteristics (at the level of 1 octane unit, depending on the ratio) and anticorrosive properties (degree of corrosion 0 points) of petrol.

The effect of natural surfactants (SA) on the efficiency of the polymer additive against the formation of deposits in high-paraffin oil with increased content of resin-asphaltene components is investigated. It is demonstrated that the addition of the polymer to oil, either individually or with natural SA, causes a decrease in the amount of the formed deposits. It is determined that the maximal inhibiting ability is exhibited by the composition containing the polymer and 0.03 wt. % naphthenic acids (SA). Natural SA, either alone or together with the polymer, when added to oil, cause a decrease in the size of associates of paraffin hydrocarbons and their aggregates in the oily fraction of the oil deposits under investigation.

As an alternative to mercury release by cementation on metallic aluminum, for the purpose of improving the purity of commercial selenium, we investigated the processes of selective sorption of mercury ions from the technological solutions of selenous acid onto styrene-divinylbenzene Lewatit MP 68 resin. The isotherms of mercury ion sorption are obtained, the main quantitative parameters and limiting stages of the process are assessed. It is established that for a low degree of resin filling with the sorbate (with the equilibrium concentration of mercury ions in solution ≤0.4 mmol/dm³) and for the sorbent - sorbate type interaction, the distribution coefficient decreases initially, and then increases while the sorption ability increases and the structures of sorbate - sorbate type are formed. The degree of mercury extraction from solution (β) is inversely proportional to the equilibrium concentration of mercury ions in the solution ( С_eq) and is described by the linear equation: β = -133.5 С_eq + 99.81. Experimental data processing shows the simultaneous occurrence of the stages of external (film) and internal (gel) diffusion, which is evidence in favour of mixed diffusion sorption mode. The rate constants of external diffusion are approximately three times larger than the rate constants of internal diffusion. It is shown that the kinetic equations of pseudo-first and pseudo-second order models provide satisfactory description of experimental data, and that the difference between determination coefficients is not large ( R_i² > 0.98). The values of thermodynamic functions of mercury sorption within the temperature range 298-333 K were determined: -Δ G = 2.35-2.99 kJ/mol, Δ H = 3.1 kJ/mol, Δ S = 18 J/(mol•K). The practical significance of the revealed sorption parameter (dynamic exchange capacity of Lewatit MP resin is 68-269 g/dm³, specific volume of solution for resin saturation in the dynamic mode is 3800, element content in saturated resin is, %: Hg ~26.0, Se <1.0) is due to their involvement in designing the industrial installation.

A new method of purification of rough sphene concentrate from phosphorus impurities has been developed, based on its treatment with low-concentrated solutions of orthophosphoric or sulphuric acids in the presence of sulphocationite. It is shown that this method provides effective purification of sphene concentrate and makes it possible to increase the efficiency of the technology through significant reduction of the consumption of acids, elimination of the formation of liquid waste, and due to the possibility of using aluminium, which is formed during the decomposition of nepheline contained in the initial concentrate.

A new cyclopropane-containing optically transparent copolymer has been obtained by radical copolymerization of 4-(2-carboxycyclopropyl)styrene (CCPS) with acrylonitrile (AN), and its characterization was carried out. The structural peculiarities of the obtained polymer and the basic regularities of the studied process are investigated, the useful properties of the obtained compound are revealed, and the possible areas of its practical use are considered. It is established by means of turbidimetric analysis that the obtained polymer products are true copolymers, and not a mixture of two homopolymers. It is shown that copolymerization reactions proceed with opening of the double bond of the vinyl group in CCPS and AN. Copolymerization constants are measured ( r ₁ = 0.7 and r₂ = 0.15), Q-e Alfrey-Price parameters ( Q ₁ = 0.267, е₁ = -0.30) and microstructures of the copolymer are determined. During radical copolymerization, CCPS shows higher activity in comparison with AN. It is revealed from the microstructural parameters of the copolymer of CCPS with AN that the minimal blocking occurs in the range of M₁ / M₂ ~ (50 : 50)-(25 : 75), where M₁, M₂ are the fractions of CCPS and AN, respectively, mol. %. It is revealed that the radical copolymerization of CCPS with AN in the bulk allows obtaining the polymer with high purity in comparison with copolymerization of the monomers in the benzene solution. For obtaining the copolymer with the highest light transmission, comonomer ratio CCPS/AN should be 75 : 25 mol. %. The physical-mechanical, thermophysical, optical properties of the obtained copolymer are determined. In comparison with polystyrene and the copolymer of styrene with AN, the synthesized new copolymer possesses higher heat resistance, tensile strength and water absorption. It is established that the synthesized copolymer samples are characterized by good light transmission (87 %) and optical transparency ( n_D²⁰ = 1.5898). The copolymer of CCPS with AN possesses higher light transmission and refraction index than the copolymer of styrene with AN. The change rate of the light transmission index of copolymer of CCPS with AN depending on the composition of the synthesized polymer is investigated.

Coke formation process is studied by the example of SARA fractions - saturated (S) and aromatic (A) hydrocarbons, resins (R) and asphaltenes (A) - naphthenic and methane crude oils by means of thermogravimetry. The studied oil samples are characterized as heavy, high-sulphur, high-resin and contain large amounts of asphaltenes. They differ from each other in the content of resins, asphaltenes, sulphur, and in the yields of fractions with the initial boiling point (IBP) 360 ^оC. Thermogravimetric analysis was carried out heating the samples from 25 to 650 C at a rate of 10 C/min in argon. It is demonstrated that the yield of coke-like condensation products (coke) depends on the composition and structure of SARA fractions. During thermal analysis, the yield of coke is lower from the fractions of saturated and aromatic hydrocarbons and resins of naphthenic oil than from similar fractions of methane oil. The amount of solid products formed during thermal analysis of asphaltenes from naphthenic oil is larger than for asphaltenes of methane oil. Experimental and calculation data on coke yield from thermal analysis of model mixtures are presented. It is determined that coke formation during thermal analysis of model mixtures is not a direct function of the additive contribution from each of the components of the mixture.

Application of activated carbon (AC) obtained from cotton wastes (bolls, stems, and roots) for phenol adsorption from water, or wastewater dephenolization, is presented. The kinetics of phenol adsorption by carbon adsorbents were studied using UV/Vis spectrophotometer. The porosity of the formed ACs ranged from 1.952 to 2.339 cm³/g, the volume of macropores was from 1.79 to 2.09 cm³/g, while the commercial sample BAU-A showed 1.920 and 1.320 cm³/g, respectively. The highest phenol adsorption rate, 32.49-52.80 mg/(g•min), was observed for contact time up to 5 min on carbon adsorbents obtained from cotton waste. The adsorption equilibrium was achieved within 5 min after the contact, which is shorter than the analogous commercial adsorbents (7-12 min). Sufficiently high phenol adsorption activity of AC from cotton stems, roots and bolls is revealed. Therefore, the use of AC from cotton wastes as adsorbents for the treatment of industrial wastewater to remove organic and other impurities can be recommended for environmental remediation applications.

An urgent direction of the fuel and energy industry is the development of methods for vegetable oil and hydrocarbon co-processing in order to produce low-freezing and environmentally friendly components for diesel fuel. Zeolites of different structures and modifications are becoming increasingly popular as catalysts for these processes. Processing of the straight-run diesel fuel and a mixture of diesel fuel with 10 vol. % sunflower oil has been carried out over a zeolite catalyst of ZSM-5 type at a pressure of 0.35 MPa, feed rate 0.5 h^-1 and two different temperature points: 375 and 475 °C. Regularities of temperature effect and the influence of sunflower oil involvement into processing over zeolite catalyst on the composition and properties of the products are determined. These regularities are shown to depend on process temperature. It is established that the products of diesel fuel co-processing with sunflower oil over the zeolite catalyst at 375 °C correspond in their low-temperature characteristics to the Arctic grade of commercial diesel fuel, and at 475 °C - to the winder grade of commercial diesel fuel. It is demonstrated that the products of processing over the zeolite catalyst are promising components of low-freezing fuel. The results provide evidence that co-processing of diesel fraction and sunflower oil over the zeolite catalyst is promising for obtaining low-freezing components of engine fuel. The involvement of sunflower oil will expand the feedstock pool for fuel production.

Microcystin-producing culture of benthic cyanobacterium Tychonema sp. BBK16 isolated from biofilm fouling of the coastal zone of Lake Baikal is described for the first time. The pink colour of the trichomes and the developed keritomy of the cells indicate belonging to the genus Tychonema . Investigation of the morphology and the fragment of the 16S RNA gene showed the uniqueness of this type of cyanobacteria, the closest relative of the new species being the rheophilic cyanobacterium Tychonema sp. K27 from the karstwater stream. At the phylogenetic tree, together they form a separate clade of benthic attached forms. It is determined that the Baikal strain of Tychonema sp. BBK16 produces microcystin LR and does not synthesize anatoxin, which distinguishes it from the previously described species. This ability was revealed in vitro on media with Baikal bottled water and with wastewater from sewage treatment plant of Vydrino settlement. The addition of purified wastewater to the medium enhances the metabolism of cyanobacteria and results in an increase in the concentration of microcystin LR to 320 μg/g of dry weight. Assimilation of the additional amount of biogenic and organic substances by cyanobacteria has a stimulating effect on their metabolism. Analyzing the emergence of cyanobacteria of Tychonema genus in Lake Baikal, we assume that these bacteria undergo mass development in places of excess intake of nutrients, in particular those of organic origin.

Nanostructured composite material is obtained on the basis of multiwall carbon nanotubes filled with the products of thermal decomposition of cobalt complexes with disodium salt of ethylenediaminetetraacetic acid (Trilon B) - CoH₂Y. The performed characterization of the composite shows that the content of cobalt in it is consistent with that assigned during the synthesis, and sodium chloride obtained as a by-product is almost completely removed by washing. The consistent results of cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance measurements reveal a noticeable increase in the electrical capacity of the carbon matrix in the region of low scanning rates with the introduction of a filler (up to 1.8 times at a rate of 10 mV/s), which is associated with the occurrence of relatively inertial electrode Red-Ox processes like CoO ↔ CoO _х (OH) _у ↔ Со₂О₃ ↔ Со₃О₄ under these conditions. At high potential scanning rates, the introduction of small amounts of filler (less than 5%) has practically no effect on charge accumulation. With an increase in filler content, a symbate decrease in the capacity is observed, which is likely associated with an increasing blocking of the nanotube surface and a decrease in the capacity due to the formation of an electric double layer, while the Red-Ox reactions with the participation of the filler do not occur under these conditions due to relatively low rates. The results of impedance and galvanostatic measurements are consistent with this model.