Synthesis of Colloidal Silver Using Lignosulfonates

Colloidal silver solutions can be used as catalysts for carrying out various chemical transformations of organic substances and solving the problems of disposal of toxic compounds, as well as antibacterial agents for combating pathogenic microflora, in the manufacture of lubricants and light-absorbing materials, coatings, sensors, conductive pastes, and high-performance electrode materials. The research purpose is to study the synthesis of colloidal silver using a solution of technical lignosulfonates (LST) as a stabilizer. Colloidal silver was synthesized as a result of the reduction-oxidation (redox) reaction of Ag(I) cations with glucose at 100 °C in the presence of lignosulfonates. The reaction was carried out in an alkaline medium, which is provided by the addition of ammonia water. Electronic spectroscopy was used to control the synthesis of colloidal silver. After the reaction, the solution turned dark brown and an intense absorption band with a maximum at 400 nm appeared on the electron spectra. The effects of reagent consumption and synthesis duration were studied. It was found that the optimal reagent consumption in the colloidal silver synthesis is as follows: 2.5–5 g glucose / g Ag, 0.3–1 g LST / g Ag, and 3–5 g NH3 / g Ag. The synthesis duration is 2–5 min. The resulting colloidal silver solution is stable for several months. Partial stratification without precipitation is observed during the solution storage. It is shown experimentally that the stratification is followed by a redistribution of colloidal silver particles. Electron spectroscopy confirmed the absence of colloidal silver particles in the upper layer. The reaction kinetics has been studied in experiments carried out under thermostatically controlled conditions at temperatures from 50 to 100 °C. The kinetic dependence is described by a first-order equation at the initial stage of the reaction, the duration of which depends on the temperature. The duration of the active part of the kinetic curves is 15–90 % of the total reaction time. The logarithm of the rate constant on the active section was proved to depend linearly on the reverse thermodynamic temperature (pair correlation coefficient is 0.9887). The activation energy was 47 kJ/mol. For citation: Plakhin V.A., Khabarov Yu.G., Veshnyakov V.A. Synthesis of Colloidal Silver Using Lignosulfonates. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 184–195. DOI: 10.37482/0536-1036-2021-6-184-195

Research of drying kinetics of prepared wheat flour

Introduction. Processing of grain raw material with influence on starch or albumens by application of heat treatment creates the variety of functional properties of a product and is perspective in the modern terms vital functions of man. Research methods and methods. The flour obtained from wheat of the Ascanian wheat and from wheat of the soft varieties: Sophia ("sweet wheat"), Blond (soft) and Chornobrova (enriched with micro- and macronutrients) were used in the study. Thermal modification of flour samples was carried out in a convective manner. The control sample for determining the quality indicators is obtained in industrial conditions, extruded wheat flour produced by LLC "AS groups, LTD". Research results. The obtained kinetic dependence shows the gradual loss of moisture standards with different speed which accordingly influences on duration of drying. The moisture content of the drying agent most affects the intensity at the initial stage of the constant drying rate. With an increase in the moisture content of the coolant, the period of constant drying increases and the amount of evaporated moisture increases during this period. With the subsequent removal of moisture from raw materials, the degree of influence of this parameter on the intensity decreases. The nature of the drying curves is the same and the recommended process for obtaining modified flour is the process duration of 300 minutes or 5 hours. It was determined microscopically, that the samples of dried wheat flour have a purpose and are partially destroyed by starch granules and amorphization of biocomposite materials. Based on the data on the kinetics of drying flour samples, the kinetic coefficients and values of the critical moisture content for drying wheat flour were calculated, which is 1.18-1.30 %. It was determined that for the sensorial indicators the obtained samples have indicators characteristic of the varietal characteristics of wheat, from which the flour was taken. In terms of physical and chemical parameters, the modified wheat flour samples are not inferior to the well-known industrial sample of extruded flour. Conclusions. Use of flour, obtained from the wheat with different correlation of amilose and amylopectin, positively influences on a technological process and allows to extend the assortment of modified starch products, and accordingly, food products. Kinetics of the convective drying standards of the flour is investigated. Researches showed that a it is physically modified flour obtained from the different sorts of the soft wheat is not inferior in quality to the extruded wheat flour.

APPLICATION FOR CALCULATING THE PARAMETERS OF A GAS SENSOR FROM THE EXPERIMENTAL KINETIC DEPENDENCE OF RESPONSE

The elements of the structure and user interface of a specialized application for processing experimental data and calculating the parameters of gas sensors, based on the concept of using various software, packages and media are presented that are most effective at each stage. The application provides such service functions as data entry using Excel spreadsheet program; calculations in the mathematical package "Mathcad"; test item examples of using computational algorithms and providing the necessary textual information from internal sources and the Internet.

Регистрация терагерцового излучения с помощью наноструктур карбида кремния

The response to external terahertz (THz) radiation from the silicon carbide nanostructures prepared by the method of substitution of atoms on silicon is investigated. The kinetic dependence of the longitudinal voltage is recorded at room temperature by varying the drain-source current in the device structure performed in a Hall geometry. In the frameworks of proposed model based on the quantum Faraday effect the incident radiation results in the appearance of a generated current in the edge channels with a change in the number of magnetic flux quanta and in the appearance of features in the kinetic dependence of the longitudinal voltage. The generation of intrinsic terahertz radiation inside the silicon carbide nanostructures is also revealed by the electrically-detected electron paramagnetic resonance (EDEPR) measured the longitudinal voltage as a function of the magnetic field value.

ИССЛЕДОВАНИЕ ЗАКОНОМЕРНОСТЕЙ СОРБЦИИ НЕКОТОРЫХ МЕТАЛЛОВ ГЛАУКОНИТОМ

The imperfection of industrial wastewater treatment technologies has led to the fact that a huge amount of inorganic ecotoxicants of various salts of heavy metals gets into water bodies. The extraction of a valuable component from industrial solutions seems to be economically and environmentally justified for enterprises in Republic of Armenia. Therefore, one of the directions of greening the industrial technologies is the use of local wastewater treatment plants to remove the heavy metal ions when discharging wastewater into water bodies. Most often, for these purposes, the sorption method of purification is used using various sorbents based on a wide variety of mineral raw materials. The search for ion exchangers of high capacity, selectivity, and low cost is of great importance, since ion exchange has taken an important place among the main methods of wastewater treatment. It is known from literature that the natural mineral glauconite, due to its structure and physicochemical properties, has the ability to extract heavy metals from water bodies. The presence of glauconite from the Garni deposit of RA predetermines its use, and the surface modification makes it possible to use it in water treatment. The results of kinetic studies of sorption of nickel and zinc ions under static conditions on a composite glauconite sorbent by constructing concentration isotherms are presented. The static capacities on the sorbent for zinc and nickel cations are determined. The kinetic dependence of the adsorption of zinc and nickel cations on the studied sorbent is investigated to determine the time of arrival of the equilibrium state. The limiting stage of the sorption process is determined by establishing the mechanism of interaction of the metal cation with the active center of the adsorbent. From the data obtained, it is found that the linear dependence of At/Amax indicates that the adsorption process at this stage is limited by gel external mass transfer, and the subsequent deviation - by the enhancement of the effect of external diffusion on the adsoption rate.

Mechanism of Ion-Diffusion Solid-Phase Reduction of Iron Oxides of Technogenic Origin in the Presence of the Liquid Phase and without it

The processes of iron oxides’ reduction have a complex physicochemical mechanism, with the participation of solid, liquid, and gaseous substances. The article discusses the existing models for the reduction of iron oxides and provides data on the thermodynamic possibility of carrying out the reactions of their reduction through the solid and gas phases. Experimental data on the reduction of iron from industrial scale, obtained by the DSC (differential scanning calorimetry) method, show the kinetic dependence of the rate and completeness of recovery on external factors: pressing pressure during sample preparation and the reagents’ composition. The pressing pressure, under conditions of iron ions’ solid-phase diffusion, has the significant effect by increasing the reagents’ contact area. Under conditions of iron ions’ comprehensive diffusion, the pressing pressure does not affect the reduction processes rate. The introduction of 10 mass.% flux into the raw mixture composition leads to a partially liquid-phase diffusion of iron ions and weakens the effect of the pressing pressure in this process. An ion diffusion-catalytic mechanism is proposed to describe the observed effects during the reduction of iron oxide of technogenic origin.

Investigation of the Mechanism of Sulfur Dioxide Adsorption from Gas Emissions of Sodium Bisulfite Production

It is proposed to purify industrial gas emissions from sulfur dioxide by the adsorption method. Waste from the power industry - sludge from the chemical water treatment of Kazan CHPP-1 - was used as an adsorption material. Its chemical composition is presented. Experimental studies of a new sorption material based on energy waste for gas purification from sulfur dioxide have been carried out. The kinetic dependence and isotherm of the adsorption process are obtained. The mechanism of the process of adsorption of sulfur dioxide by sorption material at different temperatures has been studied. The Gibbs free energy, differential heat, and activation energy of adsorption are determined. The economic and environmental impact of modernization of procedure for cleaning gas emissions from sulfur dioxide in sodium bisulfite production at JSC “Chemical factory named after L.Ya. Karpov” was measured.

Modified sludge-based purification of flue gases produced by thermal power plants

This paper proposes an adsorption-based method of removing sulfur dioxide from the flue gases produced by the thermal power plant. A power plant waste – chemical water treatment sludge available at Kazan CHPP-1 – was used as an adsorption material. Presented here is the chemical composition of the chemical water treatment sludge for a modified sorption material to be designed therefrom. The new sorp-tion material was trial tested for removal of sulfur dioxide from gases. This resulted in kinetic dependence and adsorption isotherm. The test results were then used to design the adsorber. The economic and envi-ronmental effect of using the chemical water treatment sludge as the sorption material was calculated.

Complex Extraction of Metals in an Aqueous Two-Phase System Based on Poly(Ethylene Oxide) 1500 and Sodium Nitrate

This article presents an ecologically safe aqueous two-phase system based on poly(ethylene oxide) with a molecular weight of 1500, designed for complex extraction of Ni(II), Co(II), Fe(III), Mn(II), Zn(II), Cu(II), and Al(III) from nitrate solutions. A kinetic dependence has been investigated for a distribution ratio for the metals examined. The influence of pH-values, temperature, initial metal concentration, and nitric acid content have on the extraction of a wide range of metals in the heterogeneous poly(ethylene oxide) 1500-NaNO3-H2O system has been discovered. As a result, the complex extraction of metals (EMe > 60%) was achieved in one step of extraction without introducing additional chemicals into the system.

KINETIC AND STRUCTURAL CHARACTERISTICS OF ULTRAFILTRATIONAL MEMBRANES AT SEPARATION OF SOLUTIONS CONTAINING SODIUM LAURYLSULPHATE

In work the generalized analysis of literary data on a research of relative permeability ratio of various types of porous organic and inorganic membranes was submitted. Application of a method of X-ray analysis of samples of the semipermeable ultrafiltrational membranes on a diffractometer of DRON-3 and a specific output flow on a flat-chamber ultrafiltration unit is shown. In materials of work the pilot and theoretical studies on isokinetic zones and structural characteristics of polymeric semipermeable membranes in the course of ultrafiltrational separation of the technological solutions containing the anionic and fissile surface substances are conducted. It is experimentally confirmed that kinetic curves on a specific output flow have two isokinetic zones. The first zone, the stage of the ultrafiltration process, proceeds quickly, lasts only a few minutes - 7.8 min and 13.05 min, the second zone is slower with duration of about 30 min and 60 min for ultrafiltration cellulose acetate membranes of the UAM-100 and UAM-50 series, respectively. The revealed isokinetic zones differ in characteristic times, which differ by orders of magnitude, and, as a result, the final kinetic dependence has an exponential form. The comparative analysis of roentgenograms allows to note coincidence of angles of diffraction, but significant redistribution of intensity of reflexes in air-dried and working sapless in the range of scattering angles 2θ from 8°-35°. The obtained experimental data and their comparison with literary, indicate the same set of the diffraction reflexes at corners 2θ = 17°; 22°; 25° for both samples of membranes that corresponds to the crystal reflexes of membranes created from polyamide fibers (nylon).