Home – Home – Jornals – Chemistry for Sustainable Development 2020 number 5

The species of Rheum L. genus (rhubarb) have long attracted the attention of researchers as possible sources of drugs for various purposes. Mostly the underground organs of plants were studied since the main attention was paid to a group of substances specific to the species of this genus - anthraquinones and anthrons that exhibited multiple biological activity. Insufficient attention was given to the study of aboveground organs, while flowers and leaves are a valuable source of flavonoids, an equally important group of biologically active substances. Rhubarb growing both in nature and in culture in the forest-steppe region of West Siberia is characterized by a high content of flavonoids. It was found that during the period of mass flowering of wild plants from the regions of Siberia, the content of flavonoids varies within the limits for Rheum compactum 3.87-10.06 % (in flowers), 1.17-5.16 % (in leaves), for Rheum undulatum (syn. R. rhabarbarum ) 5.04-9.62 % (in flowers), 2.00-7.57 % (in leaves) per the mass of absolutely dry raw materials. In culture, R. compactum and R. undulatum retain their ability to synthesize flavonoids. Their content in the flowers of R. compactum reaches 7.68 %, in the leaves - 4.27 %, in R. undulatum , respectively, 9.43 and 4.95 %. For 10 individual R. undulatum plants , the flavonoid content is in the range 3.53-9.43 % (flowers) and 2.25-4.95 % (leaves), the variation coefficients are 35 and 24 %, respectively, which is a favourable factor for the selection of highly productive rhubarb forms. When introduced into the Novosibirsk region, all 15 tested rhubarb species, regardless of the origin of the seeds, showed the ability to synthesize a large number of flavonoids, especially in flowers, which indicates that its cultivation on an industrial scale is promising. The representatives of the Rhapontica and Palmata sections are particularly responsive to cultural conditions.

For the first time, nanocomposites based on non-ozonized and ozonized multi-walled carbon nanotubes (MWCNT) were obtained, with the outer and channel surfaces covered with nanosized crystallites of PtFe and PtCo bimetallic systems. The character of electrode Red-Ox processes taking place in a potential window from -1 to +1 V was established; electrochemical (energy storage) properties of nanocomposites in asymmetric two-electrode model cells of supercapacitors was studied. It was established that with an increase in the content of bimetallic phase up to 5 mass % in the composites, the electrode capacitance increases by a factor of 1.3-1.5 in comparison with initial nanotubes, which is explained by the formation of a pseudo-capacitive component due to the high-rate electrode Red-Ox processes involving intermetallic PtM.

Boron carbide powders were ground in a planetary ball mill, and the mixtures of various size fractions were compacted by uniaxial dry pressing. A green density of 75% of the theoretical was achieved. Upon infiltrating B₄C framework with molten silicon, a non-porous composite is formed with a density of 2.45-2.55 g/cm³ and hardness of 22-27 GPa. As a result of the introduction of 1-5 % MWCNT (multi-walled carbon nanotubes), the green density of the compacts decreases, however, the strength of the infiltrated material increases significantly. The effect is due to the formation of platelike SiC crystals as a result of the interaction of nanotubes with silicon.

Begonia grandis is a unique representative of the genus Begonia inhabiting the temperate zone. The mechanisms of adaptation of this plant to low temperatures, in particular under the influence of physiologically active substances, are of great interest. The effects of the product of straw processing, ecotol, on the dynamics of the parameters of physiological state of Begonia grandis plants introduced in West Siberia (Novosibirsk), in a greenhouse and at an open ground were studied during air temperature drops at the end of the growing season. The concentrations of chlorophylls a and b , carotenoids, anthocyanins, flavones (luteolin, orientin) and flavonols (quercetin, kaempferol, hyperoside, isoquercitrin, and astragalin) were determined, and the ratios chlorophyll a / b , chlorophyll ( a + b )/carotenoids, chlorophyll ( a + b )/anthocyanins) in the leaves were calculated. With a decrease in the diurnal temperature to 10 ^oC and a short-term drop to negative temperatures, the open-ground plants treated with ecotol retained a higher proportion of the leaves (59.9% of their initial number) compared to the control ones (5.8 %), and the concentrations of chlorophyll and antioxidants (carotenoids, anthocyanins, isoquercitrin) in them was more significant (up to 3.1, 1.2, 12.8 and 11.2 mg/g, respectively) than in the leaves of control plants (up to 1.4; 0.5; 1.8 and 7.0 mg/g). The properties of ecotol as a complex stimulator of plant resistance were confirmed. Under low-temperature stress, it provided a higher physiological state of B. grandis plants during their transition to dormancy.

The review of the results of scientific research in the field of obtaining and studying the properties of hydroxybenzoic acids and their esters is presented. The main representatives of this class of organic compounds, in particular, o - and p -hydroxybenzoic acids and their alkyl and cycloalkyl esters are considered. It is known that p -hydroxybenzoic acid is present in many organisms and acts as an intermediate in the biosynthesis of a number of other compounds. Its esters are used as preservatives in the cosmetic, pharmaceutical and food industries. It occurs in nature both in the free form and in the form of derivatives. Salicylic acid has a bactericidal effect, its salts and esters are often used in medicine and veterinary medicine as drugs. It is reported that these compounds have high antimicrobial and antifungal activity against various microorganisms and fungi. The representatives of hydroxybenzoic acid esters are widely used in medical practice as bacteriostats. The main methods for the synthesis of hydroxybenzoic acids and their derivatives, in particular esters, salts and nitrogen-containing derivatives, are shown. It was stressed that o - and p -hydroxybenzoic acid esters are usually obtained from phenol in two stages according to the classical scheme: carboxylation of phenol with the introduction of a COOH group, and subsequent esterification with alcohols under the conditions of acid catalysis. The results of the author's own research are presented, in particular, the addition reactions of benzoic acid to polycycloolefin hydrocarbons were carried out, and the corresponding esters were obtained in a high yield. The influence of various reaction parameters on the yield of the target product was studied.

Graphene membranes were manufactured for the purpose of developing efficient materials for the membrane technologies of water freshening. Investigation of the nature of their functional groups was carried out by means of IR spectroscopy. Graphene membranes were obtained using two methods: 1) vacuum filtration; 2) immersion precipitation. Graphene materials used in the study were graphene oxide (a commercial sample) and graphene (a laboratory sample obtained by means of stepwise carbonization of rice husks). The data of the FTIR spectra of diffuse reflection (DRIFT) from membranes manufactured using graphene point to the low defect content in its single-layer graphite structure, while membranes based on graphene oxide contain not only graphene layers but also amorphous carbon with sp ³-hybridized atoms and oxygen-containing functional groups (mainly carboxylic and phenolic). The tests of the membranes were carried out with respect to the efficiency of filtration of salt-containing solutions (NaCl, KCl, MgCl₂, CaSO₄ и MgSO₄) and salt removal. Analysis of desalinated solutions by means of atomic absorption flame emission spectrophotometry showed that purification efficiency was 74-80 % for membranes obtained by means of vacuum filtration.

This work deals with the study of the problem of soil contamination with heavy metals in a large city. The content of mobile forms of heavy metals was determined in the soils of the industrial zone in the Kirovskiy region of Novosibirsk at the territory affected by the metallurgical enterprise - Novosibirsk tin plant. Chemical analysis was performed by means of inductively coupled plasma mass spectrometry and atomic absorption. It is shown that the maximum permissible concentrations (MPC) of the following heavy metals are exceeded in the samples under analysis: Cr, Ni, Zn, Pb, Cu. With an increase in the distance from the plant, the content of heavy metals decreases, but the permissible concentrations are exceeded even in the area of natural parkland. To calculate the accumulation of the mobile forms of heavy metals in the soil of the industrial zone near the plant, the MPC value for As was accepted to be equal to the maximum permissible excess (MPE). The sequence of accumulation of the mobile forms of heavy metals in the soil of industrial zone near the plant was formed according to the calculated concentration coefficients: Cr < Ni < Zn < Pb < Cu < As. The category of soil contamination is characterized according to the total pollution index as dangerous.

Complications in the technological processes of hydrocarbon transport (an increase in viscosity, the loss of fluidity, the formation of asphalt-resin-paraffin deposits on the surface of the equipment) arising with a decrease in the temperature of the feed stream cause an increase in energy consumption and reduce the efficiency of petroleum transportation. During the recent decade, the physical methods and their combinations with chemical methods allowing a substantial improvement of the structural-mechanical characteristics of problematic oil have been under active development. One of these methods is ultrasonic treatment. The effect of ultrasonic treatment and the addition of petroleum resins on the viscosity, temperature and energy-related parameters of a 6 mass % solution of petroleum paraffin in decane (PP-d) simulating a high-paraffin petroleum system was investigated. Ultrasonic treatment (field frequency 22 kHz, intensity 18 W/cm², duration 10 min) of the PP-d solution stimulates the crystallization of the molecules of petroleum paraffin after the treatment, which causes an increase in viscosity, pour point temperature and the amount of paraffin deposits. The introduction of benzene and benzene-alcohol resins extracted from highly resinous petroleum into the PP-d solution suppresses the crystallization of petroleum paraffin molecules thus promoting a decrease in viscosity and temperature characteristics, the activation energy of viscous flow, the specific fracture energy of the disperse system, the amount of paraffin deposits, changes in the shape and structure of petroleum paraffin crystals. It is demonstrated that alcohol-benzene resins containing a larger amount of heteroatomic functional groups and longer alkyl substituents in aromatic and naphthene cycles are the best depressants of viscosity and pour point. The formation of deposits in the solution under investigation is stronger inhibited by benzene resins containing a larger amount of aromatic structures.

Results of the quantitative chemical analysis of waters in the lakes of the Onon-Borzya, Ingoda, Torey and Ivano-Arakhley limnic systems in Eastern Transbaikalia are systematized and analyzed. The content of humic acids in the waters under investigation was determined to vary within a broad range. Statistical interrelations between the determined concentrations of humic acids and the major physicochemical parameters of the medium were established. An increase in the concentrations of humic acids and fulvic acids is observed with an increase in pH, total dissolved solids (TDS), chemical oxygen demand, the content of carbonate, sulphate, nitrate ions, sodium and total phosphorus, while a decrease is observed with an increase in the redox potential (Eh). Taking into account the chemical composition of waters, thermodynamic calculations were carried out using MINTEQ software, and the major migration forms of humic acids were determined. It was revealed that humic and fulvic acids are present in lake water mainly in the anion and molecular forms, and in compounds with calcium and magnesium ions. The application of the Stockholm Humic Model (SHM) in thermodynamic calculations allowed us to establish the formation of the complexes of humic acids of different denticity with other metals, however, their content is insignificant for each element separately in comparison with the other forms of migration of the organic matter. Definite dependencies were demonstrated between migration forms and the characteristics of the environment. Molecular and anion forms of humic acids exhibit multidirectional correlations with TDS and pH. An increase in Eh of the system leads to inverse correlations with the molecular and anion forms in comparison with рН and TDS. It is stressed that all the established dependencies are interrelated with the properties of humic acids and their compounds with metals, mineralization and humification of organic substances, the formation of secondary minerals, and the types of studied waters.

XII All-Russian Scientific and Practical Conference "Education and Science for Sustainable Development" dedicated to the Decade of actions to achieve the goals of sustainable development was held on April 21-23, 2020, at the D. Mendeleev University of Chemical Technology of Russia. Due to the difficult conditions caused by the present pandemic of coronavirus, the conference was held in on-line format for the first time during the recent 12 years. More than 150 persons representing 15 organizations from many regions of the Russian Federation participated in the conference. The representatives of all levels from Bachelor, Master and Post-Graduate students to worldwide known scientists were among the participants. The scope of reports provides evidence of an increase in the positive effect of various areas of chemistry on sustainable development and proves the priorities of green chemistry.