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The parameters for arsenic removal from Dashkesan ore enrichment tailings, which contain cobaltine (CoAsS), erythrite (Co₃(AsO₄)₂⋅8H₂O) and arsenopyrite (FeAsS), by combustion method with soda (Na₂CO₃) have been investigated. The processing method consists of two stages: 1) tailing/soda/coal mixture (molar ratio 1 : 1 : 0.2) was combusted at temperature 750 °C and time (1-3 h), 2) the combusted material was dissolved at 90 °C for 1 h in water with a phase ratio of S/L = 1 : 5. It was shown that the amount of As₂O₃ decreased from 5.47-6.19 to 0.52-0.71 wt%. The change of arsenic-containing phases in raw materials and processed products were studied by XRD, SEM/EDS and DTA/TG analysis methods. As the results of XRD analysis, the following arsenic-containing phases have been found in the combusted material obtained at 750 °C: sodium arsenate (Na₃AsO₄), sodium oxoarsenate (Na₅AsO₅) and scorodite (FeAsO₄⋅2H₂O). The residue obtained after dissolution is enriched with cobalt (CoO - 4.43 %) and can be considered as initial raw material for cobalt extraction.

The chemical composition of the fluff of Scheuchzer’s cottongrass (Eriophrum scheuchzeri Hoppe) is investigated, and its practical applicability as an alternative to cotton-containing plant raw material for the production of cellulose ethers and esters on its basis is assessed. It is shown that the fluffiness of the cottongrass seeds is 40.5 %, the average length of cellulose fibre is 10-25 mm, the mass fraction of hard-to-hydrolyse polysaccharides is 59.0±0.6 %, cellulose - 40.5±0.7 %, lignin - 25.8±0.3 %, water-soluble substances - 14.5±0.5 %, extractive fat-soluble substances (oil content) - 14.3±0.3 %, ash content - 5.0±0.6 % of the fluff mass. The degree of cellulose polymerisation is 1510 units, the mass fraction of α-cellulose is 84±1 %. In the composition of ash substances, there was no accumulation of noticeable amounts of heavy metals. The composition of ash substances is mainly represented by, rel%: potassium oxides (44.5), the compounds of phosphorus (18.7), silicon (15.2), calcium (9.6), magnesium (4.5), sulphur (3.1), and chlorine (1.53). Based on the conducted studies, a preliminary conclusion was made about the potential suitability of this kind of plant raw material for economical use.

A brief characterisation of helium is presented, the global reserves of this chemical element are analysed, and the structure of its consumption and production dynamics on the global market are considered. The increasing production and consumption of commercial helium, as well as the high industrial potential of helium products at the territory of Russia, necessitate the development of a set of technological solutions to improve helium extraction, its storage and processing. An analysis of membrane gas separation applications is presented, along with a comparative evaluation of this method against the traditional cryogenic distillation technology. The membrane unit is characterised by energy efficiency, compactness, simplicity of technological maintenance and process control, and does not require significant capital or operational costs. The types of filter cartridges used and the main technological schemes for producing helium in the gas industry are reviewed. Depending on the intended use plan for the helium products at the Markovskoye natural gas and condensate field (the Irkutsk Region), the use of combined technology (two-stage membrane separation with and without recycle, with additional fine purification units for helium concentrate) is proposed. The economic efficiency and commercial value of the proposed technological solution are substantiated.

Over the two recent decades, ionic liquids have become a focus of intensive research in the field of green chemistry. One of the recently developed application areas for ionic liquids is their use in agrochemistry as regulators and stimulators of plant growth, promoting an increase in crop yields and improvement of crop. In this review, research results in the area of using ionic liquids as herbicides, fungicides, antimicrobial agents, detergents, plant immunity inducers enhancing resistivity against phytopathogens, and plant growth stimulators. The advantages and disadvantages of ionic liquids in comparison with commercial products are described. The achievements and outlooks for the application of ionic liquids in agriculture are described, along with the possibilities to use them as multifunctional biologically active substances.

The features of the molecular and supramolecular structure of brown and bituminous coals at different metamorphisms stages have been determined using a complex of methods: IR spectroscopy, X-ray diffraction, the kinetics of swelling in solvents, and sorption of molecular iodine. The relations of the supramolecular structure of coals with the indicators of molecular composition are established, the evolution of coal structure in the series of metamorphism, the mechanisms of transport of solvent molecules into the volume of the organic mass of various coals are considered.

The regularities of ethoxylation of benzoic acid derivatives during interaction with polyethylene glycol through mechanochemical solid-phase synthesis in a vibrating apparatus have been studied. The conditions for carrying out mechanochemical reactions to increase the conversion degree of initial reagents into reaction products are analysed. The products of ethoxylation are characterized by IR spectroscopy, acid-base potentiometric titration, tensiometry, and dilatational rheology. It has been established that the degree of starting reagents conversion into ethoxylation products depends on the nature of the substituent and its position in the benzene ring. The degree of conversion into reaction products is higher for ortho-substituted derivatives of benzoic acid. It is shown that the salts of ethoxylated derivatives of benzoic acid exhibit pronounced surfactant properties at the air - solution interface.

A mesoporous carbon sorbent modified with sulphosalicylic acid by adsorption from aqueous solutions has been synthesized. The optimal modification parameters were selected: the ratio, concentration, the duration of impregnation and heat treatment stages, and pH. The physicochemical properties of the samples have been studied: textural characteristics, qualitative and quantitative composition of surface functional groups, the amount of applied modifier, adsorption and desorption properties. The adsorption characteristics of the studied samples with respect to organic dyes methylene blue and methanyl yellow are determined. It has been established that during desorption for 48 h, ~68 and ~82% of the initial concentration of sulphosalicylic acid applied to the sample pass into the aqueous solution, modelling the intestinal medium and into ethanol, respectively. In this case, a decrease in the pH of the initial solutions by 6 units is observed. High antibacterial properties of the modified carbon sorbent towards Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae have been established in vitro .

The breadth of the use of activated carbons (AC) in many areas of economy, ecology and defense of the country is shown. The unique physicochemical characteristics of AC are denoted, and their modern determination is presented. It is established that the Russian Federation is currently lagging far behind industrialised countries in the output of AC production. Attention is paid to the coals of Kuzbass as a raw material for the large-tonnage production of AC. Various technologies for manufacturing active coals on this basis are considered.

The paper presents the results of applying the methodology of chemical fingerprinting to survey the territories of industrial and natural objects, environmental accidents and objects of accumulated environmental damage in various regions of Siberia, including the Arctic zone of Russia. The data obtained by GC/MS using the capabilities of targeted and survey ecological analysis are presented. Polycyclic aromatic hydrocarbons, polychlorinated biphenyls, various classes of hydrocarbons, including relict oil biomarkers, chloro- and methylphenols, Cl-, N-, S-, O-organic compounds of various classes were considered as pollutants. The most important tools of chemical fingerprinting are considered, and it is shown that the use of a set of data on marker compounds of various types, diagnostic ratios of characteristic compounds, multi-vector chromatographic profiling of characteristic compounds ("fingerprints") makes it possible to establish the origin of pollution sources with a high degree of probability.

2-Methyl-9H-selenoxanthen-9-one (selenoxanthone) 1 was obtained by the reaction of bis-(2-carboxyphenyl)diselenide with toluene in concentrated sulphuric acid. It is demonstrated by means of cyclic voltammetry, EPR spectroscopy and quantum chemical DFT calculations that the electrochemical reduction (ECR) of selenoxanthone 1 in acetonitrile is a one-electron reversible process with the formation of a long-lived radical anion having a similar type of the highest occupied molecular orbital (HOMO) to the radical anions of the thioxanthone series. The ECR potential of selenoxanthone 1 is found to be less negative than the corresponding ECR potential of its related 2-methyl-9H-thioxanthen-9-one, which indicates an increase in the adiabatic electron affinity of selenoxanthone 1 compared to its sulphur-containing analogue. This fact confirms the general nature of the phenomenon of an increase in the adiabatic electron affinity of heterocyclic compounds when a heteroatom is replaced by a heavier one within group VIa of the periodic system of elements.