Home – Home – Jornals – Chemistry for Sustainable Development 2025 number 4

The results of studies on the synthesis of anionic substances based on a mixture of higher carboxylic acids isolated from linseed oil as well as individual linolenic acid (C18:3) are presented. Potassium, sodium and calcium salts were obtained based on synthesised sulphonic acids at a ratio of 1 : 2 : 1 at room temperature. The synthesised compounds are characterised by the necessary physicochemical, surface-active and anticorrosive functional properties. It is shown that the maximum surface activity is observed in the sodium salt of sulphated linolenic acid (the surface tension at the kerosene-water interface decreases from 42.4 to 4.1 mN/m). This fact indicates the surface activity of the compound the molecules of which are diphilic and include a large hydrocarbon fragment. The maximum efficiency of the compounds in protecting against carbon dioxide corrosion is 98.7 % at a concentration of sodium salt obtained from linolenic acid 100 ppm. As a result of the conducted studies, it was established that based on polyunsaturated fatty acids contained in linseed oil as well as individual linolenic acid, the synthesised surfactants are effective inhibitors of corrosion of low-carbon steels when protecting against carbon dioxide corrosion in mineralised environments at elevated temperatures.

The effect of the concentration of lanthanum introduced into high-silica TsVN zeolite (the zeolite with HZSM-5 structure of MFI type) in methanol conversion into С₂-С₄ olefins and p-xylene has been investigated. Lanthanum-modified zeolite catalysts with La content 1.0-5.0 wt% were characterised by X-ray diffraction, low-temperature nitrogen adsorption, and temperature-programmed ammonia desorption. It has been shown that an increase in lanthanum content in the catalyst causes a decrease in specific surface area, total pore volume and mean pore diameter. As a result of La interaction with acidic OH groups of zeolite, the strength and amount of strong Brønsted acid sites decrease, while new stronger Lewis acid sites are formed. It has been determined that the yield of С₂-С₄ olefins and selectivity to p-xylene depend on the ratio of acid sites of different types, the volume and mean diameter of pores in zeolite, which are controlled by lanthanum content variation. The maximum yield of С₂-С₄ olefins (33.7 wt%) from methanol at 400 °C is achieved over the catalyst modified with 5.0 wt% lanthanum. The maximum yield of xylenes (21.7-22.6 wt%) with p-xylene selectivity equal to 71.6-79.3 % is achieved over the catalyst modified with 3.0-4.0 wt% lanthanum.

Studies of CO₂ sorption by composite sorbents based on the active component (branched polyethylenimine) dispersed using a porous support have been carried out. Composite materials with a branched polyethylenimine content of 40 wt% were synthesised on the basis of four porous supports of different chemical nature, including two polymer materials, silica gel and aluminium oxide. The sorption properties of the obtained composite sorbents were studied in the process simulating the removal of CO₂ from biogas (CO₂ concentration in the gas mixture was in the range from 15 to 50 vol%). Based on the results of the sorption experiments, the values of the dynamic sorption capacity and enthalpy of CO₂ sorption were determined for the materials. It is shown that the sorption properties of composite sorbents are mainly determined by the choice of a porous support. The analysis of thermal energy consumption for the regeneration of composite sorbents within the adsorption cycle was carried out, on the basis of which the promising materials for the extraction of CO₂ from biogas were selected.

Results of the studies on surface cleaning of the end-of-life R-Fe-B (R = Nd, Pr, Tb, Dy) system magnets by chemical etching to involve them in recycling are presented. The material for experiments included magnets that were disassembled from the end-of-life hard disk drives for personal computers. The choice of these parts was conditioned by their low cost, easy disassembling, and small size. Disassembled magnets were demagnetized at 623 K and medium vacuum through 4 h. Sandblasting with slag abrasives supplied at a pressure of 300 kPa was carried out to remove the electrodeposit coating from their surface. A specimen was prepared on the cleaned surface, which was subjected to oxidation under natural conditions. The effect of acid type (nitric, hydrochloric, sulphuric) and acid solution concentration on the efficiency of etching the oxidised surface and on the behaviour of rare-earth and doping elements during chemical etching was investigated. The morphology of specimen surface and oxygen content were analysed by scanning electron microscopy. It has been found that chemical etching with 0.5-1.0 wt% sulphuric acid solution for 1 min leads to a decrease in oxygen content from 3.1±0.2 to (2.2±0.2)-(2.4±0.1) wt% on the surface of the major stoichiometric phase of the alloy, as well as to etching the phases enriched with rare-earth metals off the surface and to the formation of pores on their place.

The influence of phthalic anhydride concentration in the reaction mixture on the composition and colloidal stability of the products of catalytic acylation of petroleum tar in the presence of AlCl₃ has been assessed. Tar from the West Siberian oil and the products of its interaction with phthalic anhydride were used as the objects of investigation. The analysis of changes in the composition, structure and aggregation stability of tar and its components was carried out using liquid adsorption chromatography, IR spectroscopy, and visible spectrophotometry. The dynamics of asphaltene aggregate growth was estimated by the dynamic light scattering method. It has been found that at phthalic anhydride concentration of 25 % per tar mass, about 7 wt% of resins lose the ability to dissolve in n-alkanes and are converted into asphaltenes due to the incorporation of carboxybenzoyl radical into their molecular structure, which is confirmed by the results of IR spectroscopy. The process of tar acylation increases its colloidal stability by 20-30 %, depending on the ratio of reagents.

A highly dispersed palladium catalyst supported on nitrogen-doped carbon nanotubes was studied in CO₂ hydrogenation to formic acid in the liquid phase at temperatures of 100-150 °C and high pressure. It has been shown that an increase in the catalyst loading (from 1.6 to 4.0 g/L), total pressure (from 20 to 40 atm) and P_H2/P_CO2 ratio (from 1 : 1 to 2 : 1) in the reactor allows increasing the yield of formic acid by over 5 times. At 150 °C, the maximum formic acid yield (27.6 g/g_Pd) with a selectivity of 98 % was obtained. The presence of a lot of single palladium atoms in the catalyst, in addition to its nanoparticles 1.5 nm in size, was determined to have a positive effect on the course of CO₂ hydrogenation, as in the case of formic acid decomposition. On the basis of the high efficiency of this catalytic system in the reaction of formic acid decomposition to produce pure hydrogen, a conclusion was made about its potential for use in the cycle of chemical storage of hydrogen based on CO₂.

Survival, possibility and efficiency of using the bacterial strain of Pseudomonas extremorientalis PhS1 in the combined application in different doses with a chemical seed dresser have been studied for the first time in laboratory and field experiments. In has been established in laboratory experiments that seed dresser Oplot does not cause a decrease in the number of bacteria for 24 h. Phytoexamination of the seeds of spring wheat using the filter roll paper method showed a substantial decrease in the total infection of seeds in all variants in comparison with the reference: the application of chemical preparation caused a decrease in germ length and an increase in the amount of roots; the treatment with both the fungicide and bacteria partially eliminated the retarded effect of the pesticide. In the field experiment, the efficiency of pre-sowing seed treatment with the bacteria, chemical dresser and their mixture was determined: the incidence of root rot on plants during the growing season decreased significantly compared to the control, and the fungicide contributed to an increase in the height and dry mass of plants from the middle of vegetation. Application of both bacteria and the dresser promoted the accumulation of nitrogen in the plants; the use of the fungicide alone caused a decrease in the amount of phosphorus. Analysis of crop structure revealed an increase in plant height and ear length, the number of spikelets and grains per ear, biological yield for either 100 or 50 % dose of the application of chemical preparation by 105 and 59 %, respectively. Seed bacterisation promoted improvement of crop structure but to a smaller extent than the complex treatment, and also caused an increase in crop yield by 14 %. Analysis of grain quality showed that all the methods of pre-sowing treatment of spring wheat seeds provided a statistically significant increase of protein, gluten content, and vitreousness.

Promising adsorbents that normalize the content of copper(II) and zinc ions in the human body may be food products that contain pectin or a sufficient amount of fibres. Within the framework of this study, dependences of the value of copper(II) and zinc ion adsorption by the food products of plant origin (potatoes, carrots, radish, pumpkin, cauliflower, broccoli, vegetable marrow, bananas, plums, apples) were analysed (in the range of metal ion molar concentrations 1.25-5 mmol/L) depending on a number of parameters: temperature (20, 100 °C), acidity (pH 2.0, 6.5), adsorption time (20-60 min). It has been found that the value of adsorption of zinc and copper(II) ions by food products is on average 1.2 times larger after heat treatment than without it. However, with an increase in adsorption time (from 20 to 60 min), the amount of ions adsorbed by food products without their preliminary heat treatment increases by a factor of 1.9 on average, while after heat treatment - by a factor of 1.3. With an increase in the acidity of the medium (pH decrease from 6.5 to 2.0), the value of zinc ion adsorption decreases by a factor of 1.9, and copper(II) ions - by a factor of 1.2 on average. To determine the dependence of adsorption value on time and on concentration, several regression models were statistically constructed: linear, quadratic, cubic, power, logarithmic, hyperbolic, common exponential, and natural exponential. The results were compared with each other by correlation, average approximation error and selected graphical relationships that can be used to calculate the required amount of vegetables and fruits when adjusting nutrition in order to normalize zinc ions in the human body. Based on the comparison of regression models by correlation and average approximation error, the dependences providing the best proximate description of zinc ion adsorption at the studied parameters have been chosen. These dependences can be used to calculate the necessary amounts of legumes and fruits to correct nutrition for the purpose of bringing zinc ion content in human organism to the normal level.

MgFeGa-layered triple hydroxides (MgFeGa-LTH) were synthesized by co-precipitation method. On the basis of molded polyurethane (PU), the composites (PU)/MgFeGa-LTH were prepared, the effect of particle size of MgFeGa-LTH on flame retardancy and mechanical characteristics of composites was investigated. It has been determined that the introduction of MgFeGa-LTH particles 3.5 μm in size results in a more substantial improvement of fireproof and mechanical characteristics of the composites than the introduction of particles 0.06 μm in size.

The properties of hymatomelanic acids extracted with lower alcohols (methanol, ethanol, n-propanol) from native (unmodified) and ethoxylated humic acids were studied. Humic and hymatomelanic acids were characterized by IR and UV spectroscopy, and the aqueous solutions of their sodium salts were characterized by acid-base potentiometric titration, tensiometry, and dilatational rheology. It has been established that lower alcohols facilitate the extraction of native and ethoxylated hymatomelanic acids, which differ in structure and properties. Ethoxylation products have been found in hymatomelanic acids and in the residues of humic compounds after alcohol extraction. The aqueous solutions of sodium salts of humic, hymatomelanic acids and their ethoxylated forms exhibit pronounced surface-active properties at the interface with air.

A bilayer Zr_0.85Y_0.15O_2-δ /Ce_0.9Gd_0.1O_2-δ (YSZ/GDC) solid oxide fuel cell electrolyte was first formed on a microtubular NiO/YSZ anode by the reactive magnetron sputtering method. The composite material La₂NiO_4+δ -Ce_0.8Sm_0.2O_2-δ (LNO-SDC) was used as the cathode and characterised using the X-ray diffraction method. The current-voltage characteristics of a microtubular solid oxide fuel cell (MT SOFC) with anode-supporting design featuring a two-layer thin-film YSZ/GDC electrolyte and an air LNO-SDC electrode were measured. The microstructure of a single fuel cell after electrochemical measurements was investigated using scanning electron microscopy (SEM). A comparison with literature data on MT SOFCs that have similar functional layers was made.

The effect of ZnCl₂ on the composition of pyrolysis liquid and the solid pyrolysis product, as well as on the electrochemical properties of the carbonisate obtained during pyrolysis of fir bark was studied. It has been found that destruction starts in the mixture of fir bark with ZnCl₂ at lower temperatures and with lower rates of mass loss than the destruction of fir bark without ZnCl₂, and leads to the formation of a highly porous ZnO/C composite with the specific surface area of up to 770 m²/g. Current-voltage measurements of the samples have shown that the ZnO/C composite has a specific capacitance of 394 F/g, which allows using it for making supercapacitors. The charge accumulation dynamics was revealed to be significantly dependent on the potential scanning rate, and specific capacitance noticeably decreases with its increase. Ion accumulation is assumed to proceed over the surface accessible for ions, and the accessible surface area decreases with an increase in scanning rate because of diffusion-related limitations. The composition of the pyrolysis liquid from initial fir bark and a mixture of fir bark with ZnCl₂ was determined using gas chromatography with mass spectrometric detection, which showed a more complex composition of the pyrolysate for the former case, with a high content of phenol and guaiacol homologues, carboxylic acids and their esters. When using a mixture of fir bark with ZnCl₂, the pyrolysis liquid contains mainly carboxylic acids, predominantly hexa- and heptadecanoic acids, while the homologues of phenol and guaiacol are almost completely absent. It is assumed that ZnCl₂ as a catalyst of Lewis acid type promotes the formation of carbonium ions and the synthesis of more stable high-molecular products.

Increased demand for aluminium around the world is promoting interest in developing alternative technologies for producing aluminium oxide (alumina) from non-bauxite sources, especially from clay. The sulphuric acid decomposition of kaolin clay of the Chovdar deposit (Azerbaijan) has been investigated with the aim of aluminium recovery using the aqueous solution of sulphuric acid as a leaching agent. Before leaching, kaolin clay was calcined at a temperature of 700-750 °C for 2 h. This process involves dehydration of kaolinite, which is the main mineralogical phase of kaolin, and its transformation into metakaolin, an amorphous Al-Si structure from which aluminium is readily leached. The optimal conditions for iron oxide and aluminium oxide leaching by sulphuric acid have been determined, and the degree of recovery was determined for these metals. It has been revealed that kaolin clay leaching to extract aluminium and iron oxides is achieved using kaolin clay samples calcined under the above-mentioned conditions, by treating them with 40 % sulphuric acid for 120 min at a temperature of 95 °C. The degree of Аl₂О₃ and Fе₂O₃ extraction under these conditions is 95.6 and 85.2 %, respectively.

Laser ignition of brown coal samples (rank 2B, Kaychaksky open pit) with rectangular 1-10 ms pulses of the quasi-continuous ytterbium laser YLR-150/1500-QCW-MM-AC (1070 nm, 1.6 kW) has been investigated before and after coal demineralisation. Coal demineralisation is demonstrated to cause an increase in the energy density necessary for ignition.

The mechanism of atmospheric organic aerosol formation in the interaction of the aldehydes emitted by plants with typical urban air pollutants has been investigated. The kinetics of aerosol formation in the aldehyde vapour was studied under laboratory conditions, and the effect of ozone and nitrogen oxides on the rate and mechanism of condensable product formation was determined. The chemical nature of the terminal groups of a growing organic chain was determined to change in the presence of increased ozone concentration. The effect of biogenic aldehydes on the reduction of polluted urban air toxicity was assessed. The field measurements were carried out, revealing the role of vegetation in the reduction of toxic action of anthropogenic air pollutants.