Kinetic Monte Carlo simulation of the growth of CdSe nanocrystals

This article is devoted to modeling the kinetics of colloidal crystallization of cadmium selenide (CdSe) nanoparticles (NPs). The kinetic equation is modified, considering the contributions of the reaction rate constants of individual stages. It includes the reaction rate constants, thermodynamic and calculated parameters, and physical properties. There is used modified kinetic model based on the crystallization equation. There are considered the contributions of adsorption, desorption, and migration of nucleated particles at different times. Modified model assumes that, upon crystallization of NPs CdSe, monomer units depend on the frequency of attachment and detachment transitions of the monomer–CdSe complex. In this case, the transformation of the precursor into a monomer, the formation of an effective monomer and nucleation pass into the growth stage of (NC CdSe) nanocrystals with a seeded mass. In the process, the resulting nanocluster will continue to grow due to early maturation, aging, and subsequent growth into larger NC CdSe. The Kinetic Monte Carlo method (KMC) is used to approximate the model of the nucleation–growth of NC considering different contributions to the reaction rate constants. The modified model with the use of KMC allows to describe the dependences of the kinetic rate constants on the average radius of nanoparticles as a function of time, concentration, and distribution of NC CdSe at a given time. There are described conditions for the formation of NPs CdSe with an evolutionary distribution function of NC CdSe in size space. The results of modeling the kinetics of colloidal crystallization of CdSe can be used to control nucleation rate and growth of NPs CdSe, as well as similar systems in the formation of high-quality NC.

Methods of determination and extractants used in the isolation of platinum (review)

There is carried out a systematic review of the literature on methods for determining platinum (IV) ions and extractants used for their extraction in the article. The article considers chemical, physical, and physico-chemical methods of determination. Also, the authors of the article focused on selective and sensitive spectroscopic methods. There are considered several groups of such reagents and extractants as organophosphorus (tributyl phosphate, di-2-ethylhexylphosphoric acid) diphenylthiourea, high-molecular aliphatic alcohols, organic sulfides isolated from high-sulfur oils, binary extractants based on oxygen-containing and sulfur-containing acids, as well as secondary (R_2 〖NН〗_2А), tertiary (R_3NНA) amines, diamines, and quaternary ammonium bases (R_4NA). They were used for the extraction of platinum from multicomponent objects. Practically common to all the extractants used (chloroform, diethyl ether, carbon tetrachloride, etc.) are their rather high solubility in water, toxicity, volatility, fire hazard. Therefore, it is of fundamental importance to select such extraction systems that combine the effectiveness of organic reagents and the use of such extractants that would eliminate the disadvantages of liquid organic solvents. As such extractants, so-called low-melting organic substances can be used, which do not dissolve in water, are non-toxic, fire-safe, have a high extraction capacity, selectivity, and sensitivity to low content of elements. Therefore, it is fundamentally important to select such extraction systems, which would combine the efficiency of organic reagents and the use of such extractants that eliminate the disadvantages of liquid organic solvents. As such extractants can be used so-called fusible organic substances, which are insoluble in water, non-toxic, fire-safe, have a high extraction capacity, selectivity, sensitivity to low element content.

Methodology for measuring the mass concentration of germanium in technological products of lead, zinc, and copper production of the UK MC KAZZINC LLP

Germanium is an indispensable high-tech element in many modern industries due to the unique semiconductor properties of its crystals. Subsequently, there were discovered other interesting properties of germanium and its compounds, which contributed to a significant expansion of its industrial use. At present, there are developed few methods for the determination of germanium in various raw materials that could find practical application. The article presents a method for measuring the concentration of germanium in technological products of lead, zinc, and copper industries using the latest technological equipment-an atomic emission spectrometer with inductively coupled plasma Spectro CirosCCD with Smart Analyzer Vision software in solutions obtained after decomposition of samples with a mixture of concentrated nitric and hydrofluoric acids, followed by the addition of dilute sulfuric acid at a wavelength of 209.43 nm. The range of analyte contents is 10-4-10-3% by mass, the accuracy of the analysis method is ± Δ0.0011-0.0012% by mass, and the extended uncertainty of the analysis results is U (CGe) 0.0011-0.013% by mass.

Geography of the presidential elections in Poland in 2020

The elections for the president of Poland in 2020 took place during a difficult period of the pandemic. Additionally, by the decision of the National Electoral Commission, they were postponed from May 10 to June 28. The incumbent president Andrzej Duda won the election, defeating his opponent Rafał Trzaskowski with a majority of around 420,000 in the second round. votes. The study aims to indicate the geographical differentiation of the results of two candidates and the spatial changes in the results in the first and second rounds of elections. In the first round, A. Duda won in thirteen regions (voivodeships) of Poland, in the second only in six, in eastern and south-eastern Poland. However, the big difference in the winning regions (15-20%) allowed him to win the final. R. Trzaskowski won in ten regions (voivodeships), but his advantage was small (5-10%).

Methods of coating a three-dimensional structure with polymer electrolytes for lithium-ion batteries

The paper considers various methods of conformal coating the three-dimensional structure of Ni foam with polymers as electrolytes in lithium-ion batteries. Polymethylmethacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and polyethylene oxide (PEO) were chosen as polymer electrolytes because of their good ionic conductivity and mechanical stability. Conformal coating was performed using two methods: drop coating, dip coating. The polymer-coated three-dimensional Ni foams were characterized by field-emission scanning electron microscopy (FE-SEM) to determine the more conformal coating method and testing the ionic conductivity of polymers. From this research, it could be concluded that the dip coating method allows a more conformal coating of the three-dimensional Ni foam structure and the polymers obtained by this method have a good value of ionic conductivity.

Proposal for the synthesis of organic fertilizer from poultry litter using the intensive composting method

The current practice on local poultry farms is that the manure from the poultry farms is hardly ever recycled, resulting in soil, water, and air pollution in the vicinity of the factory. One of such poultry farms is located directly in the zone of the Aktobe city near residential areas, which leads to pollution of soil, water, and air nearby to the territory and worsening living conditions of the city residents. The stench is a constant problem in these places. Therefore, there is urgent need for environmentally and economically sustainable technologies. The creation of effective fertilizers based on the poultry litter may be the most appropriate solution. On the one hand it would solve the problem of the difficult ecological condition of areas with poultry farms. On the other hand, it would solve the problem of a catastrophic decrease in the fertility of soils used in agriculture. As a result of the analysis of existing techniques for processing poultry manure, the authors propose a method of intensive composting of poultry litter by pumping air for the organic and organic-chemical fertilizers production. The method implements the processes of drying, disinfection, aerobic fermentation, and granulation of enriched poultry litter.

Technogenic systems of Pavlodar region

Technogenesis is a process of environmental transformation under the influence of various types of technical human activity. Technogenesis - this transformation of the earth's crust occurs during the extraction and processing of mineral resources, engineering and geological activities. One of the technogenically transformed areas is the Pavlodar region of Kazakhstan. This scientific article presents the main sources of technogenic impact in the Pavlodar region. The research gives a description of the two main technogenic systems. There have been determined the main chemical contaminants of the components of the natural environment. The authors have calculated using modern methods of GIS technologies, the area of sludge collectors. The article describes a promising method for solving such non-trivial problems as identifying the spatial distribution of ecological risk zones, or the spatial display of the concentration distribution of pollutants. The article gives a description of the main industrial facilities of the Pavlodar region, the number of emissions, and also characterizes the climatic factors of the study area.

The current state of surface waters in the Ilek River basin within the Aktobe region

The article is devoted to the study of the Ilek River basin. The article gives a physical and geographical description of the basin territory. The article considers the hydrological regime of the Ilek River and its tributaries as a result of expeditionary observations in 2018-2019. The article presents results of chemical analyzes of surface water samples from key observation sites located along the perimeter of the river (study area). After two years of fact-finding, a surface water geodatabase was created to integrate data with published literature, for forecasting and modelling geo-environmental zoning. There are also described the main sources of pollution in the Ilek River, and factors in the formation of anthropogenic geosystems. The scientific article also describes the main sources of pollution of the Ilek River, lists the factors of the formation of anthropogenic geosystems.

Catalysts for methane conversion process

The article describes current trends in the catalytic processing of natural gas such as partial and deep, also steam oxidation of methane and methane decomposition. Kazakhstan is rich in large energy resources. Therefore, it is important to create new gas chemical technologies that will allow gas resources to produce valuable chemical products. Currently, processes based on these reactions have not been introduced into production. There are highlighted catalyst systems for each reaction that provides good performance. The oxide catalysts based on metals of variable valency are effective in all processes. In the future, it is important to increase the activity of these catalysts. The catalysts were prepared by impregnating the carrier capillary (γ-Al2O3) by incipient wetness and subsequently dried at 2000C (2 h) and calcination at 5000C for three hours. In this article, a catalyst based on nickel-zirconium (3%NiО-2%ZrО2) is active in the partial oxidation of methane to obtain synthesis gas. On this catalyst, the reaction products are H2 - 60.5 vol.%, CO - 30.5 vol.%. On a 3%NiО-7%Со2О3-0,5%Сe2O3 catalyst in the reaction of DRY conversion methane 95.6% and the yield of hydrogen and carbon monoxide is 47.0 and 45.9 vol%, respectively. 29.6% methane is converted even at low temperatures (350°C) on catalyst 3%NiО-2%СеО2/γ-Al2O3 modified with cerium oxide in the reaction of deep oxidation of methane. Iron-based catalysts for the reaction of decomposition of methane to hydrogen gas are effective. On 5 wt.% Fe/ɣ-Al2O3 catalyst at 700°C of reaction of methane conversion was 2%, with an increase in the reaction temperature to 850°C, the methane conversion reached 13%, and the hydrogen yield is increased to 5.8 vol.%.

Physical and chemical properties of natural clay deposits

The problem of creating and using sorption materials is relevant for the practice of modern chemistry, biotechnology, medicine and agriculture. Knowledge of the physical and chemical laws of the processes of carbonation, activation, as well as sorption and desorption is of particular importance in the case of nanostructured carbon sorbent for highly effective treatment of water contaminated with pesticides, as well as for reducing the concentration of cytokines in the blood of patients with sepsis. It is of great practical importance to obtain adsorbents using a carbon sorbent to significantly reduce the concentrations of heavy substances, which is very important for the Western regions of Kazakhstan. Thus, it is currently relevant to develop such sorbents that would have high mechanical strength and withstand high fluid pressure during operation, have a large capacity and high wear resistance, allowing them to work for a year or more. Based on the above, the goal of our research is to create new modified carbon sorbents for industrial use for wastewater treatment.