Home – Home – Jornals – Chemistry for Sustainable Development 2017 number 4

Polymeric guanidine derivatives occupy a special place among antimicrobial compounds. Guanidines are well soluble in water, have a wide spectrum of antimicrobial action and durable effects, nontoxic, and also meet modern medical requirements. Due to the high reactivity of guanidine to interact with various functional groups, we manage to carry out a number of new chemical modifications that allow obtaining new biologically active low and high molecular mass compounds. The present paper presents preparation of water-soluble guanidine derivatives of pectin and carboxymethyl cellulose bound between each other with the amine bond. A process for the preparation of guanidine derivatives of pectin and carboxymethyl cellulose consists of the following stages: periodate oxidation of polysaccharides, the condensation reaction of guanidine with oxidized pectin and carboxymethyl cellulose, –C=N bond reduction. The structure and composition of the resulting compounds were studied by IR spectroscopy, X-ray structural and elemental analysis (by nitrogen content). It was determined that the maximum number of guanidine groups in the resulting products was contained during the interaction of dialdehyde derivatives of pectin and carboxymethyl cellulose with guanidine in a 1.0 : 2.3 molar ratio. Antimicrobial activity of resulting guanidine derivatives of pectin and carboxymethyl cellulose against Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella, Escherichia coli and Streptococcus faecalis was explored. It was found that bacteriostatic effect began to increase with an increase in the concentration of the obtained compounds. The paper gives acute toxicity studies results on guanidine derivatives of pectin and carboxymethyl cellulose, upon the results of which they can be referred to class IV slightly toxic substances.

The paper studied the effect of conditions of oxidative treatment of comminuted rubber with nitrogen (I) oxide (the so-called ketonization) obtained by mechanical grinding of truck and passenger tires on the main characteristics of the resulting regenerate samples. As established, treatment of comminuted rubber with the initial amount of nitrogen (I) oxide of 2 mol for 1 h or 1 mol for 6 h at the process temperature of 230 °С ensured obtaining the regenerate with the optimum ratio of oligo- and macromolecules containing statistically distributed С=О groups. The reactive oligomeric component formed in the technical synthesis process provides the regenerate with the level of rheological properties required for the use in the content of elastomeric compositions. The presence of functional groups in the oligomer and polymer components of pilot regenerate samples leads to a decrease in the induction period of vulcanisation, which is driven by the acceleration of the formation process of a benzthiazolyl radical arising during decomposition of a vulcanisation accelerator and by the involvement of free sulphur that enters into regenerate composition into the vulcanisation process. The found character of the influence of pilot regenerates on structurisation processes of carbon-chain polymers allows carrying out the optimisation of the content of compositions in which it is planned to use the regenerate, and also adjusting technological modes for vulcanisation of rubber mixtures. As demonstrated in the carried out comparative study of strength-elastic properties of the pilot and industrial regenerate samples, vulcanisates based on trial regenerate samples had high conditional tensile strengths at 200 % elongation. The resulting effect of an increase in strength is reached due to a more homogeneous distribution of the applied load and realisation of orientational phenomena in a low-modulus elastomeric matrix.

The contents of di-n-butyl phthalate (DBP) and di (2-ethylhexyl) phthalate (DEHP) were assessed in the Lake Baikal pelagic zone. The spatial heterogeneity of the distribution of phthalates in the upper and deep water levels for all basins of Lake Baikal was determined from 0.06 to 3.1 µg/dm³ of DBP and from 0.03 to 1.4 µg/dm³ of DEHP, seasonal variability of the total concentrations of phthalates in the pelagic zone of the lake being up to 10 times. Background stations of the reference section in three lake basins were proposed as reference areas for monitoring, and the average concentrations of phthalates in the upper aqueous layer (5–200 m) were proposed to assess the present content of phthalates in the water of the lake. The contents of DBP and DEHP in Lake Baikal Water over the period 2015–2016 were 0.35–0.89 and 0.06–0.32 µg/dm³, respectively, and do not exceed the MPC for water bodies specified in Russia. A simultaneous change in DBP concentration in the upper water layer of the pelagic zone of the southern lake basin and in its coastal area as pollution indicator was noted. Phthalates were determined by liquid-liquid extraction of analytes into n-hexane, direct analysis of extracts using chromatography-mass spectrometry in selective detection mode (m/z 149 and 153) and measurements by the internal standard method using di-n-octylphthalate-3,4,5,6-d₄ as a surrogate standard. Secondary pollution of water and extracts with laboratory phthalates was regarded as the systematic error that was assessed by the value of reagent blanks and subtracted from analysis results. The total error was assessed using the values of 25 and 20 % for DBP and DEHP, respectively.

The paper studied joint transformations of vacuum gas oils characterised by the group composition with various vegetable oils under catalytic cracking conditions. It was determined that the distribution of target cracking products depended not only on the carbon component of mixed raw materials but also on the fatty acid composition of vegetable oils. The greater was the number of C=C double bonds in the composition of triglycerides of vegetable oil, the more pronounced promoting effect it had for vacuum cracking of gas oil, as established. This was related to the progression of hydrogen transfer reactions. Olefins that act as hydrogen acceptors were formed during cracking of initial glycerides, and paraffins and naphthenes in vacuum gas oils were donors. Herewith, an increase in the contents of mono- and polyaromatic hydrocarbons was noted in the composition of liquid products. Additionally, it was found that the higher was the content of unsaturated fatty acids in the composition of glycerides of vegetable oils, the higher was the yield of target cracking products (light olefins, gasoline). It was demonstrated that a high content of aromatic hydrocarbons in the composition of vacuum gas oil during the transformation of mixed raw materials resulted in a decrease in the yield of target cracking products with a simultaneous increase in the yield of liquid products and coke. This is related to the fact that aromatic hydrocarbons were poorly subjected to transformations and concentrated in highly-boiling fractions, with the result that an increase in the yields of light and heavy gas oils was observed. Additionally, heavy aromatic hydrocarbons actively took part in condensation reactions with the formation of polyaromatic compounds and coke, as evidenced by the increased formation of coke deposits on catalysts.

The paper carried out X-ray phase analysis of arsenic sludge, whereby the following compounds were detected: (CaSO₄) • 2H₂O, Cu(OH)₂, Ni(OH)₂, Fe(OH)₃, Ca(OH)₂, and Zn(OH)₂. The presence of arsenic (III) as calcium metaarsenite (Ca(AsO₂)₂) was also determined. Options for extraction of non-ferrous metals from multicomponent hydroxide raw materials containing significant amounts of arsenic were considered. Solutions of sulphuric acid, ammonium salts, oxyethylidenediphosphonic (OEDP), ethylenediaminotetraacetic acid (EDTA), alkaline metal tartrates were explored as reagent solvents. The values for the logarithms of the stability constants of copper (II), nickel (II), and calcium (II) complexes with appropriate ligands were presented. According to experimental data, the use of substances that ensure the copper and nickel extraction as complexes while maintaining pH > 5 allows for almost complete elimination of arsenic dissolution. It was experimentally proven that ammoniacal leaching and leaching in solutions of EDTA salts did not lead to arsenic contamination of the filtrate ensuring copper and nickel extraction from sludges. The use of EDTA and its salts also simplified technology and equipment selection for further solution processing. The findings led to the conclusion that the use of EDTA solutions at leaching of sludges of neutralising industrial solutions was promising.

The paper studies low-temperature (77 K) radiolysis of various modifications of silica, such as macroporous glass (MPG) with a pore diameter of 2000 and 1500 Å, regular sodium glass, and fused quartz by the electron paramagnetic resonance (EPR) method. Paramagnetic centres in various modifications of SiO₂ may vary significantly, depending on origin, the presence of impurities, treatment conditions, and radiation activation of samples, as demonstrated. Hole centres in oxygen and silicon atoms and electron centres in silicon atoms and alkaline metal ions are the main paramagnetic centres in γ-irradiated SiO₂; their contribution in glasses and quartz is 90–95 and ~70 %, respectively. The number of radical centres in all silicas (H^•, Si^•, >Si^•–H) does not exceed 3–4 %. The radiation yield of atomic hydrogen G_H = 0.02–0.4 per 100 eV. Spectra of НО₂^• radicals and SiO₂^• macroradicals are recorded during heating of irradiated samples in the oxygen atmosphere. According to the data of quantum chemical calculations, the doublet with the splitting α^H = 12.5 mT registered during heating of irradiated MPG and quartz belongs to formyl radicals that are formed from the self-hydrogenation reaction of natural impurities of CO in silicas. The doublet with α^H ≈ 1.0 mT, g = 2.002 is referred to hole centres –Si⁺(OH)H in the surface silicon atoms containing hydroxyl groups and the H atom.

The paper studied some regularities of extraction of dihydroxybenzenes (DHB) using toluene organic solutions of amine and phosphine oxides with the purpose of extraction concentration and determination of trace amounts in aqueous solutions. Distribution coefficients of DHB between toluene solutions of organic oxides and water versus the position of OH group in the molecule and the donor ability of oxides were determined. Pyrocatechin has higher extraction characteristics than resorcin and hydroquinone. The maximum distribution coefficients of DHB were reached, which provided their 95–97 % extraction from aqueous media at 50-fold concentration and single extraction. A method for determination of trace amounts of DHB (10^–7–10^–5 mol/dm³) in water samples with pre-concentration with toluene solutions of trioctylphosphine and trioctylamine oxides (0.5–0.7 mol/dm₃) followed by voltammetric detection in extract with a glassy carbon electrode (GCE) against acetonitrile and a solution of sodium perchlorate in isopropyl alcohol was developed. The current-voltage curves reflecting the kinetics of oxidation of analytes in a disk GCE at voltammetric detection of DHB in the organic phase were obtained. Calibration curve method was used for quantitative voltammetric determination of each isomer in individual solutions or binary mixtures of catechol, resorcin, and hydroquinone, resorcin, and also total DHB (in terms of pyrocatechin) in an extract. The level of reliable determination of DHB concentrations is 0.5–1 MPC; relative error does not exceed 5 %. A method for total determination of DHB, and also each isomer in individual samples or binary mixtures of pyrocatechin and resorcin, and hydroquinone and resorcin is recommended for use in analytical laboratories for monitoring the quality of natural and treated waste water.

The paper studied an opportunity of obtaining bismuth formates from solid basic bismuth nitrate by its interaction with formic acid solutions of different concentrations at process temperatures of (22±1) and (55±2) °С. Interaction products of bismuth oxohydroxonitrate having the composition Bi₆О₄(ОН)₄(NO₃)₆ • H₂O with formic acid solutions were studied by X-ray phase analysis (XPA), thermogravimetry (TG), electron microscopy, IR spectroscopy, and chemical analysis. It was found that solubility isotherms had two branches driven by the formation of bismuth formates with the composition BiOCOOH and Bi(COOH)₃ and proceeded via a maximum at bismuth concentrations in solutions of 31 and 23 g/L at 22 and 55 °C, respectively. An opportunity to obtain bismuth oxide formate was demonstrated through treatment of bismuth (III) formate with water at the mass ratio of water to bismuth formate of 10. Bismuth oxide formate is spherical particles with a size of about 6 µm comprising of smaller crystals, and middle-sized bismuth is needles crystallised as druses with a size of about 100 µm. It was demonstrated that thermal decomposition of basic bismuth formate in air allowed obtaining tetragonal (β) bismuth oxide. It was found that thermal decomposition of a mixture of bismuth oxide formate and oxohydroxynitrate (~50 %) proceeded in several steps, began at 200 °С and completed at 560 °С with the formation of monoclinic (β) bismuth oxide. It was demonstrated that thermal decomposition of a mixture of bismuth oxonitrate/oxoformiate was a promising synthesis method of basic bismuth oxonitrate with the composition Bi₅O₆(NO₃)₂OH or Bi₅O₇NO₃.

The paper examines a facile and efficient method for dehydration of sludge from chemical water treatment of the Surgut Thermal Power Plant using a water-soluble powdered high molecular mass polymer i.e. the sodium salt of carboxymethyl cellulose (Na-CMC), as an additive. The integral mass loss and volume loss of samples vary within 70–80 % for 10–15 days when using this method. The optimum amount of the introduced binder is 3–5 % of the mass of the initial sample to obtain dense smooth shaped samples, as established. The data of morphology, structure, phase composition, and particle size in the initial and final products, and also in waste dehydration process are given. Changes in the waste surface during the interaction with Na-CMC accompanied by the formation of hydroaluminate, hydrosulphoaluminate, and hydrosulphoalumoferrite particles with a size of less than 300 nm were recorded. The particles generate a primary alumoferrite frame of a hardening system of coagulation and crystallization structures, as established in a more detailed study. During dehydration and binding processes, it is suggested to dispose of the dry product in the construction industry as an additive for manufacturing cements, foam blocks, foam concretes, in mortars or producing plasters due to the formation of the space frame of iron (III) and aluminium hydroxides. The presence of small amounts of Na-CMC binder will make a positive contribution since it is introduced to reduce setting time when manufacturing construction materials. The results offer prospects for solving environmental issues related to liberating overfilled sludge pits of the thermal power station.

A method for the selective removal of indium from solutions (sol.) of acid leaching of Waelz zinc oxide (0.02–0.1 g/dm³ In) was proposed. It is an alternative technique for extraction. Adsorption over modified montmorillonite that is the Меtоsol reagent (reag.) in dynamic mode allows maximally implementing the reagent exchange capacity with the optimum cycle of sorption/desorption operations. Adsorption of iron (II) and zinc ions in static mode was detected. It is driven by the formation of intermolecular bonds with the developed surface of modified aluminosilicate. The formation of a stationary front of indium ion sorption from a polycomponent solution over the Меtоsol mineral sorbent due to predominant adsorption of In³⁺ compared to Fe²⁺ and Zn²⁺ was found in dynamic mode. The latter cations are replaced by In³⁺ ions that form chelates with ionogenic groups of di(2-ethylhexyl)phosphoric acid. Output curves of sorption of In ions at unit load V_sol/V_reag = 1–2.7 h^–1 and temperatures of 298–328 K are mainly S-shaped. The inflection point is shifted to the low-value range of the specific volume of the past solution (V_sol/V_reag), which indicates slowing down the ion diffusion rate in sorbent. Indium ions passing into the filtrate comes much earlier (V_sol(1)/V_sol = 3.33–0.66), the width of the chromatographic front (ΔV_sol /V_reag = 12.1–12.35) increases, the full dynamic exchange capacity (FDEC = 0.572–0.237 µmol-eq/g) and the utilization rate of the resin bed are decreased with increasing the linear rate (ω_0.5) of the transmission of the eluent through a column in the range 4.78 to 12.74 cm/h. The width of the chromatographic front (ΔV_sol /V_reag = 12.1–10.24) decreases; the full dynamic exchange capacity (FDEC = 0.572–1.293 mol-eq/g) and the utilization rate of the resin bed (η = 0.226–0.256) are increased, which testifies monitoring the process of sorption of indium by mixed diffusion. The Меtоsol reagent allows selectively extracting indium from production solutions in dynamic mode.

Mechanochemical synthesis of sodium thiosulphate pentahydrate (Na₂S₂O₃•5H₂O) was carried out for the first time in a planetary ball mill by mechanical activation of a suspension of sodium sulphate (Na₂SO₃) and sulphur (S). The degree of Na₂SO₃ + S = Na₂S₂O₃ reaction in suspension solution at soft and short mechanical activation conditions is almost 95 %, as established by methods of iodometric titration, X-ray phase and thermal analysis.

An increase in the octane number of straight-run fractions of normal hydrocarbons С₅–С₆ up to 92 points by research octane number (RON) through their catalytic isomerisation appears to be an effective solution of the critical applied task of changing the structure of the domestic gasoline pool. Isomerisates have a high octane number and do not contain hazardous sulphur compounds, aromatic hydrocarbons and particularly, benzene. Herewith, selection of the optimum technology for isomerisation of light gasoline fractions considering a peculiarity of a specific refinery is an important scientific and technical issue. Additionally, a number of complex multiple-factor tasks, such as ensuring of a specified quality and quantity of raw materials, maintaining the optimum activity of the used catalysts, and also providing the optimum operation modes for each complex block considering energy and resource efficiency in manufacturing might arise. To describe nonstationary catalytic processes of catalytic processing of light alkanes the mathematical modelling method is used. This paper assesses the operating efficiency of catalysts for isomerisation of light gasoline fractions based on Pt/SO₄^2–/ZrO₂ and Pt/Cl^–/Al₂O₃ using the mathematical modelling method for nonstationary catalytic processing of hydrocarbon raw materials. Catalysts based on sulphated zirconium oxide retain high activities and stabilities during the entire operating cycle, while catalytic systems based on chlorinated alumina are deactivated faster. Isomerisation process scheme with the recycle of unreacted C₅ and C₆ hydrocarbons involves significant capital and operating costs, however, its use will allow increasing the RON of isomerisates in 10–12 points.

The paper justifies factors and causes of hard washability of finely disseminated copper-nickel ore, the main of which are incomplete and insufficiently selective expansion of sulphide and rock-forming mineral aggregates due to low mechanical interactions in ball mills, with the result that a large number of non-ferrous and precious metals pass to concentration production wastes adding to technogenic accumulations. Technological possibilities of high-energy and high-velocity impact grinding in a disintegrator, wherein increased destructive effects lead to an increase in expansion of aggregates, were explored. The opportunity to control energy and free kick speed allows carrying out the destruction mainly along the boundaries of mineral intergrowths and reducing the amount of the fine fraction slurry in grinding products. However, an increase in the disintegration rate to 7200 rpm did not result in obtaining flotation size products –0.071+0.02 mm, and a substantial part of ore remains in the larger, difficult-to-float condition. With a view to optimising opening of mineral associations by granulometric composition, the principle of stage grinding that allows consistently in the regimes of increasing energy effects regrinding larger ore fractions and liberating minerals from genetic associations with increased strength was proposed. This methodological approach allowed in the optimum rate mode destructing sulphide minerals and obtaining during flotation separation concentrates with increased content of non-ferrous metals, which offers opportunities for improvement of metallurgical methods for processing concentrates. More high-energy destruction allows liberating residual amounts of sulphides in rock associations and transferring into reject materials to 50 % of ore rocks. It is noteworthy that herewith, a large number of nickel compounds found in aggregates with rock formations are released, which is of great importance for increasing nickel extraction into concentrates. The carried-out research demonstrates that high-energy grinding is an advanced method for selective destruction of aggregates and mineral liberation in finely impregnated ores prior to concentration processes.

The paper demonstrates an opportunity to determine the elemental composition of the combustible mass of plant biomass, peat, and fossil coal based on technical analysis findings followed by the assessment of the low heat value of solid fuel. This approach may be useful with the absence of elemental analysis findings and the lower heat of combustion of solid fuel. The content of carbon as the main element that forms the structure of solid fuel may be assessed via the yield of volatile matter, as demonstrated in the first case. Empirical dependencies of H_at/C_at and O_at/C_at ratios on carbon content in solid fuel, against which the low heat value of solid fuel with a sulphur content of no more than 2 % is calculated, are defined. Herewith, the deviation from the literature data did not exceed 10 %. The second option examines an opportunity to determine H_at/C_at and O_at/C_at ratios via the yield of volatile matter. The low heat values of solid fuels with sulphur contents of no more than 2 % were calculated on the basis of the resulting empirical dependencies; herewith, the deviation from the known values does not exceed 6 %. The use of the resulting empirical dependencies to define the low heat values of solid fuels with a sulphur content of 2.1–8.4 % in some cases, gives an increase in deviations from the literature data within 12–14 %.