Home – Home – Jornals – Chemistry for Sustainable Development 2026 number 3

A comparative analysis of the composition of low-molecular nitrogenous bases (NBs) in high-sulphur natural asphaltite and liquid products of its conversion in supercritical water (SCW) at 400  C and 30 MPa with and without the presence of aluminium and zinc additives was carried out for the first time. Based on the results of analysis of NB extracts by gas chromatography - mass spectrometry, the trends have been revealed in the changes of structural-group and molecular composition of various NB types due to changes of the conditions of SCW-conversion of asphaltite. It has been discovered that the homologous series of basic aromatic nitrogen-containing compounds containing from two to five aromatic rings are present in all the studied NB extracts from conversion products. The addition of aluminium and zinc promotes the formation of additional amounts of non-substituted structures or the structures containing smaller total number of carbon atoms in alkyl substituents, as well as pentacyclic azabenzopyrenes, dibenzoacridines and tricyclic phenylquinolines. A change in the relative content or appearance of the above-listed NBs in SCW conversion products points to the presence of such nitrogen- and nitrogen-sulphur-containing structural fragments in the resin-asphaltene components of natural asphaltite.

Sulphur dioxide (SO₂) is one of the main atmospheric pollutants emitted from sulphide-containing ore processing and fossil fuel combustion. Efficient utilisation of SO₂ is a significant task both from the environmental perspective and within the framework of industrial technologies improvement. Investigation of the autocatalytic action of sulphide phases formed on the surface of X18H9T(10T) steel on SO₂ reduction using gaseous reducing agents has been carried out. Taking into account literature data, it has been concluded that during the reduction process, mainly iron sulphides (pyrrhotine (Fe_1-xS) and pyrite (FeS₂)) are formed on the surface of steel, as well as, to a lesser extent, sulphides of nickel (NiS) and chromium (Cr₂S₃). Sulphide phases formed under the action of reaction medium have been revealed to provide high catalytic activity and synergism in SO₂ reduction. In the presence of iron, nickel and chromium, more active reducing agent, hydrogen sulphide (H₂S) is formed, which, in turn, amplifies the synergistic effect and intensifies the catalytic process. It has been determined that the addition of Cr and Ni (up to 5 wt% of each element) to iron sulphide phases provides an increase in catalytic activity. These modified sulphides exhibit efficiency not lower than that of the sulphides formed on the surface of X18H9T(10T) steel, despite the higher content of Cr (about 18 wt%) and Ni (about 9 wt%) in the steel itself. A distinguishing feature of the process is in catalyst formation directly during reduction process, which ensures continuous renewal of its activity without the necessity of additional regeneration. The potential for using metal alloys as carriers for self-generated catalysts for sulphur dioxide utilisation is demonstrated.

Paralytic neurotoxins (saxitoxins) produced by cyanobacteria have been found in Lake Baikal and the reservoirs of the Angara cascade of hydropower plants. These neurotoxins are dangerous for humans and animals. The concentration of paralytic toxins was determined to be 0.2-182.6 μg/L, exceeding the limits recommended by the World Health Organisation. Cyanobacterium Dolichospermum lemmermannii was highly abundant in Lake Baikal and reservoirs of the region, its mass development causing localised surface blooms. Cyanobacterial cultures isolated from Lake Baikal were identified as D. lemmermannii. Saxitoxin biosynthesis gene sequences were detected in samples from the studied water bodies and in cultured strains; they had high similarity to each other and belonged to the single species - D. lemmermannii. This is the first report of the ability of D. lemmermannii to synthesise paralytic shellfish toxins. Four toxin variants were identified in the plankton of Lake Baikal and reservoirs: saxitoxin and neosaxitoxin containing carbamoyl groups, as well as decarbamoyl derivatives of goniatoxins. It is shown that in the ancient oligotrophic Lake Baikal and the Angara River reservoirs, there is a source of occurrence and spread of harmful algal blooms due to the presence of toxin-producing cyanobacteria. Under favourable hydrophysical and hydrochemical conditions, and influenced by climatic and anthropogenic factors, the frequency and prevalence of toxic cyanobacterial blooms in the aquatic ecosystems of the Baikal region, as globally, exhibit an increasing trend. This underscores the need for further research and implementation of significant efforts aimed at monitoring cyanotoxins and toxic bacterial species, as well as at understanding the mechanisms underlying the initiation and proliferation of cyanobacterial blooms.

The analytical and methodological problems that arise during the preparation of samples for determining the gold content in rocks are described, and possible solutions are suggested. It is determined that the accuracy of the results depends on the method of preliminary decomposition, which should be chosen taking into account the complex composition of the material under study. Decomposition methods are tested on standard samples of rocks with different mineralogical compositions, in particular, the effect of the acid ratio in aqua regia on the efficiency of gold extraction is studied. Special attention is given to atomic absorption analysis as a promising method for determining gold concentration. Treatment of the samples with reverse aqua regia (HСl/HNO₃ = 1 : 3) allowed for the most complete extraction of gold. It is shown that gold extraction increases from 62 to 95 % on average with an increase in the relative concentration of nitric acid and a decrease in the concentration of hydrochloric acid.

The features of the composition of carbon and heteroatomic functional groups on the surface of carbonification series coals, oxygen and nitrogen distribution over the surface and volume have been characterised by X-ray photoelectron spectroscopy. It has been established that oxygen in brown coals is almost equally represented on the surface and in volume. The surface of hard coals is enriched in oxygen-containing groups, and their concentration in coking coals significantly exceeds the volume concentration. Carbon is present on the surface mainly in polycondensed aromatic (graphite-like) structures. Their proportion and degree of uniformity increase with carbonification. The oxidised forms of carbon are present on the surface mainly in the form of phenolic and ether groups. Heteroatomic nitrogen-containing groups are represented by aromatic, mainly five-membered pyrrole, to a lesser extent six-membered pyridine structures. It is shown that as carbonification degree increases, the five-membered cycles in coals are transformed into six-membered cycles.

Platinum-containing catalysts for n-butane isomerisation based on sulphated zirconium and aluminium oxides differing by synthesis conditions were investigated. It has been demonstrated that the method of mixing initial reagents, temperature, and pH for the precipitation of precursors affect the textural properties of the supports. Precipitation in an alkaline medium at 15 °C with controlled pH (10-12) yields fine crystalline zirconium dioxide with developed specific surface area and a dominant mesoporous structure. It has been determined that, regardless of synthesis conditions, introducing 9.0 wt% sulphate groups suppresses crystallisation of the monoclinic phase and promotes the formation of the tetragonal modification of crystalline ZrO₂ after calcining the hydroxide precursor at 710 °C. It has been established that the optimal reaction conditions (H₂/n-butane = 0.1, pressure 1.5 MPa, temperature 160-200 °C) enable achieving a high yield of the target product, isobutene (up to 44 wt%), and avoiding excessive formation of side products.

A quantitative assessment and identification of organochlorine compounds present in the oil directed for processing was performed, and an effective method for their extraction was proposed. It is shown that feeding an aqueous alkaline solution for mixing with processed oil before it enters the electrical desalting unit at the maximum admissible temperature in the electrical dehydrators (135 ° C) allows reducing the content of organochlorine compounds from 6 to 1 ppm.

The volatile part of molecular resource of the plants belonging to Dracocephalum genus (dragonhead) of Lamiaceae family growing at the territory of Dagestan has been investigated. The subject of investigation was the component composition of essential oil in the above-ground part of Dracocephalum multicaule collected in three locations of the Akhty District (Dagestan, Russia). The yield of essential oil obtained by hydrodistillation from the dried plant raw material using a Ginsberg apparatus ranged from 0.7 to 1.2 %, recalculated for the dry weight. Analysis by gas chromatography in combination with mass spectrometry has revealed the presence of over 40 compounds, accounting for up to 99.4 % of the total amount of oil. The compounds dominating among monoterpenes were γ-terpinene, p-cymene, α-pinene, 1,8-cineole; among sesquiterpenes - germacrene D, spathulenol, allo-aromadendrene and α-humulene. It has been found that, while the component composition of the studied samples is the same, there is a significant variability in the concentrations of individual compounds.

A comparison of the time series of concentrations of substances predominantly of anthropogenic origin polluting the groundwater of several large territories of the Moscow urban agglomeration in aquifers located at a depth from 3 to 50 m has been performed. It has been found that not all controlled indicators tend to decrease steadily with an increase in depth, the observed changes of parameters are often insignificant, and the concentration of petroleum products, for example, increases by several times when passing to deeper horizons. This makes the notion of deep-lying water as a strategic resource ensuring the sustainable development of a city unreasonable. To identify the sources from which impurities enter deeply located horizons, the causal relationships between the chemical analytical data for groundwaters were analysed using correlation and variance analyses. To measure the similarity of these series, the dynamic time scale transformation (DTW) algorithm was applied because the time series of data for different horizons experience shifts that change over time, so that their rhythms may differ. A significant similarity in the time series of water pollutant concentrations in different aquifers has been established. On this basis, it is concluded that the rock layers separating the aquifers in the territories under consideration are permeable, which provides the possibility of the vertical migration of pollutants to deeper bedded groundwaters. This conclusion is not cancelled by relatively large DTW distances found in some cases, meaning that some additional decrease in water quality is possible due to mass transfer of impurities between neighbouring geological provinces. Based on the results of the work, it is recommended to expand the programme of hydrogeochemical monitoring of pollution over the districts of Moscow in combination with the formation of a currently missing reliable profile of groundwater composition, in particular in relatively deep aquifers.

The results of studying methane hydrate formation processes using swollen gel particles synthesised from the copolymers of acrylamide and acrylic acid with varying degrees of cross-linking are presented. The effect of chemical composition of gel particles and their structural-morphological characteristics on the hydrate formation kinetics and efficiency of water conversion to methane hydrate is investigated. Experimental studies were conducted in specialised autoclave installations under strictly controlled thermobaric conditions: initial pressure at 20 °C was 9.5 MPa with subsequent temperature reduction to 1 °C to ensure thermodynamic conditions for hydrate stability. It has been established that gel particles containing predominantly acrylamide fragments exhibit low activity in initiating hydrate formation and do not contribute to the formation of significant amounts of hydrate. In contrast, particles with reduced cross-linking degree and increased content of acrylic acid functional groups demonstrate intense hydrate formation with almost no induction period. The quantitative analysis of hydrate formation products in the case of samples with a high content of acrylic acid fragments has demonstrated high efficiency of water conversion into methane hydrate reaching 42-67 %. Introduction of a kinetic promoter based on castor oil (COS-3MS) into the mixture of gel-forming agents allowed for an additional increase in the degree of water conversion to hydrate up to 58 %. Visual observations revealed a characteristic hydrate growth mechanism: the process is initiated on the surface of gel particles, and then the crystals propagate into the gel volume through diffusive and capillary transport of the aqueous phase. The obtained results convincingly demonstrate the high potential for the practical application of gel systems for intensifying hydrate formation processes and creating innovative technologies for efficient storage and transportation of natural gas in the hydrate form.

The kinetics of lactic acid polycondensation in the dispersions of liquid-gas type is investigated. The dispersions were obtained by depositing drops of lactic acid spray or applying an ensemble of millimetre-sized drops from a capillary onto a glass substrate. The average droplet diameter for the fine and coarse-dispersed samples differed by more than an order of magnitude. The dynamics of changes in the amount of lactic acid in washouts from the substrate were analysed using anion chromatography. It has been confirmed that polylactide is formed during dispersion at room temperature and atmospheric pressure without the use of a catalyst. The reaction rate is directly related to the diameter of droplets in the dispersion. It has been shown that an increase in temperature from 20 to 40 °C causes an increase in lactic acid conversion by a factor of 1.5.

The influence of glycerol and boric acid on the rheological properties of aqueous solutions of polyvinyl alcohol (PVA) and starch, as well as on the elastic and thermophysical properties of cryogels prepared from them, was studied. It has been shown that all solutions exhibit non-Newtonian properties. The addition of 0.5 wt% boric acid caused an increase in the dynamic viscosity of PVA solution by a factor of 1.5-2.3, and starch solution by a factor of 0.8-1.1; the addition of 0.25 wt% boric acid with 10 wt% glycerol as a plasticiser caused a 1.6-2.4 times increase in the viscosity of PVA solution, and the viscosity of starch solution increased by a factor of 0.9-1.3. The addition of 20 wt% plasticiser (glycerol) had a maximum effect and caused an increase in the dynamic viscosity of PVA solution by a factor of 1.8-2.6, and starch solution by a factor of 1.1-1.5. It has been determined that the elastic modulus of cryogels increases with the addition of glycerol and boric acid into the polymer solution (PVA, starch or their mixture). The elastic modulus of cryogels has been determined to depend primarily on the proportion of each polymer in the mixture, and then on glycerol concentration, increasing by a factor of 2.6-12 in its presence. During destruction in water, the mass loss by compositions based on starch was 45-70 % within 20 days. For the mixed compositions with two polymers, the weight loss within 30 days varied within the range of 40-65 %. The presence of glycerol suppressed the destruction of samples with high PVA content (weight loss 24-28 %) and stimulated the decomposition of cryogels with high starch content (weight loss up to 83-87 %). Microstructural studies of films based on PVA and starch with glycerol before and after biodegradation showed the colonisation of surfaces by microbial cells, the appearance of irregularities, cracks and cavities.

The data on the concentrations of phenolic compounds, photosynthetic pigments, pectin substances and triterpenoid saponins in the leaves of Chlorophytum сomosum Thunb. Jacques are presented, the antioxidant and antiviral activity of the extracts of this plant species is assessed. High concentrations of chlorophyll a and b (434.67 and 245.11 mg/100 g, respectively), tannins (82.34 mg/g), catechins (0.73 mg/g), hydroxycinnamic acids (36.67 mg/g), saponins (64.53 mg/g), carotenoids (75.70 mg/100 g) and pectin substances are detected in the leaves of this plant species. The total content of phenolic compounds and flavonols was termed as insignificant. The water-ethanol extracts of the leaves exhibited antiradical activity in the reaction with the stable free radical 2,2-diphenyl-1-picrylhydrazyl. The antiviral activity of the aqueous extract was detected with respect to the avian virus A/chicken/ Kurgan/05/2005 (H5N1).

A new synthetic approach has been developed on the structure modification of bioactive furanolabdanoid phlomisoic acid methyl ester by introducing 1,3,4-oxadiazolylcarbonyl fragment at position 16 of the carbon framework. The key steps of the synthesis are the preparation of (2-(2-(aryloyl/hetaryloyl)hydrazinyl)-2-oxoacetyl)furans and their subsequent heterocyclisation proceeding under the action of dehydrating agents. The cytotoxic properties of the obtained compounds were evaluated with MTT test against three human cancer cell lines. It has been shown that introduction of (5-(pyridin-4-yl)-1,3,4-oxadiazol-1-yl)methanone motif on the furan ring of the starting labdanoid significantly increases the cytotoxic action.