Properties Of Individual Substances Research Articles

Расчет равновесного состава сложных термодинамических систем с использованием языка Julia и библиотеки Ipopt

The article considers the possibility of using the Ipopt optimization package for the calculating the phase and equilibrium compositions of a multicomponent heterogeneous thermodynamic system. Two functions are presented for calculating the equilibrium composition and properties of complex thermodynamic systems, written in the Julia programming language. These functions are the key ones in the program integrated with the IVTANTERMO database on thermodynamic properties of individual substances and used for conducting test calculations. The test calculations showed that Ipopt package allows determining the phase and chemical compositions of simple and complex thermodynamic systems with a fairly high speed. Using the JuMP modeling language significantly simplifies the preparation of the initial data for the Ipopt package, therefore the functions presented in this article are very compact. It is shown how the Ipopt package can be used when the temperature of the thermodynamic system is unknown. The approach proposed in this work is applicable both for analyzing the equilibrium of individual chemical reactions and for calculating the equilibrium composition of complex chemically reacting systems. The simplicity of the proposed functions allows their easy integrating into application programs, embedding them into more complex applications, using them in combination with more complex models (real gas, nonideal solutions, constrained equilibria), and, if necessary, modifying them. It should be noted that the versatility of the JuMP modeling language makes it possible to replace the Ipopt package with another one without significant modification of the program text

Разработка антиоксидантного комплекса для использования в продуктах с эмульсионной основой

Исследованы антиоксидантные свойства индивидуальных веществ и их смесей, таких как α-токоферол, кверцетин, β-ситостерин, ретинил пальмитат для создания антиоксидантного комплекса, стабилизирующего эмульсионные системы. Для определения антиоксидантной активности оценивали способность индивидуальных соединений и их смесей тормозить реакции термического окисления метилового эфира олеиновой кислоты. Показано, что усиление антиоксидантных свойств бинарной смеси витаминов наблюдается при увеличении концентрации α-токоферола и уменьшении концентрации ретинил пальмитата. Установлен эффект взаимного подавления антиоксидантных свойств смеси ретинил пальмитата с β-ситостерином. Доказано, что значение антиоксидантной активности реакционной смеси, включающей кверцетин в сочетании с витаминами или β-ситостерином, обладает аддитивными свойствами. Для смеси, состоящей из 4-х компонентов: α-токоферол, кверцетин, β-ситостерин, ретинил пальмитат, характерно увеличение антиоксидантных свойств в 2,5 раза при минимальных концентрациях, а при максимальных концентрациях в 1,5 раза. Установлено, что все исследуемые природные соединения обладали антипероксидной активностью, при этом наиболее высокий уровень отмечен у кверцетина, далее у ретинил пальмитата, β-ситостерина и α-токоферола. Показано, что смесь природных антиоксидантов обладала антипероксидной активностью в 1,5 раза выше, чем у кверцетина. На основе полученного уравнения регрессии, адекватно описывающего процесс, реализована программа оптимизации, позволившая сформировать антиоксидантный комплекс, включающий ретинил пальмитат, α-токоферол, β-ситостерин и кверцетин в оптимальных соотношениях. Показано, что антиоксидантная активность комплекса в 1,7 раза превосходила результат этого показателя в смеси, состоящей из 4-х изучаемых компонентов. Разработанный антиоксидантный комплекс рекомендован для использования в составе продуктов с эмульсионной основой

Photodecomposition of pharmaceuticals and personal care products using P25 modified with Ag nanoparticles in the presence of natural organic matter

The presence of pharmaceuticals and personal care products (PPCPs) in water remains a concern due to their potential threat to environmental and human health. Advanced oxidation processes (AOPs) have been receiving attention in water treatment studies to remove PPCPs. However, most studies have been focused on pure water containing a limited number of substances. In this study, the photocatalytic efficiency of commercially available titanium dioxide nanoparticles (P25) and P25 modified by silver nanoparticles (Ag-P25) were compared for their ability to degrade 23 target PPCPs (2 μg L‐1) in realistic water matrices containing natural organic matter (Suwanee River NOM, 6.12 mg L-1). The experiments were completed under ultraviolet-light emitting diode (UV-LED) illumination at 365 and 405 nm wavelengths, with the latter representing visible light exposure. Under 365 nm UV-LED treatment, 99% of the PPCPs were removed using both P25 and Ag-P25 photocatalysts within 180 min of the treatment duration. The number of PPCPs removed dropped to 57% and 53% for P25 and Ag-P25 respectively under the 405 nm UV-LED irradiation. Dissolved organic carbon (DOC) and UV absorbance at 254 nm (UV254) measured at the end of the experiment indicated that the aromatic fraction of NOM was preferentially removed from the water matrix. Also, Ag-P25 was more effective in DOC removal than P25. The relationships of removal rate constants with physico-chemical properties of the substances were also determined. The molecular weight and charge were strongly associated with removal, with the former and the latter being positively and negatively correlated with the rate constants. The results of this work indicate that Ag-P25 is a promising photocatalyst to degrade persistent substances such as PPCPs and NOM even if they are present in a complex water matrix. The properties of individual substances can also be employed as an indication of their removal using this technology.

Thermodynamic Analysis of the Oxidation of Radioactive Graphite in the CuO–NaCl–KCl–Na2CO3–K2CO3 Melt in Water Vapor

Graphite is widely used in the atomic industry and nuclear power engineering. In the next 10–15 years, the resource of most blocks in the uranium–graphite reactors in Russia will be exhausted with allowance for the elongation of the service life, as follows from the results of repair-and-renewal operations. High-activity graphite can be processed by flameless oxidation in molten salts. The purpose of this work is to study the behavior of radionuclides during the flameless oxidation of radioactive graphite in the CuO–NaCl–KCl–Na2CO3–K2CO3 melt in water vapor using a thermodynamic simulation and the Terra software package. A thermodynamic simulation is an effective and unique method used to investigate diverse high-temperature processes of thermal decomposition, reduction, and synthesis. The calculation is performed using a reference datable of the properties of individual substances. Graphite burns up at 573 K. The condensed compounds of cesium, chlorine, and uranium evaporate at 1673 K. An increase in the temperature to 1973 K leads to the vapor pressure of the condensed compounds of beryllium, calcium, and strontium. The condensed oxide of europium(III) and the condensed oxide of plutonium(IV) transform into a vapor state at 2173 K. The condensed oxide of nickel transforms into a vapor state at 2473 K. A further increase in the temperature to 2773 K leads to the transformation of the condensed oxide of americium(III) into a vapor state. Only a vapor–gas phase is present in the isolated system in the temperature range from 2773 to 3273 K.

Thermodynamic Analysis of the Oxidation of Radioactive Graphite in a Multicomponent Melt in an Inert Atmosphere

Graphite occupies a specific place among the entire mass of accumulated radioactive wastes. The problem of reclamation of spent graphite has not yet been solved in the world. The behavior of radioactive graphite in the multicomponent CuO–NaCl–KCl–Na2CO3–K2CO3 melt in an argon atmosphere in the temperature range 373–3273 K is studied by thermodynamic simulation with the Terra software package, which is intended for calculating the phase compositions and the thermodynamic and transport properties of arbitrary systems. The calculation was performed using a database on the properties of individual substances. At 1273 K, graphite burns to form carbon monoxide and carbon dioxide. The condensed compounds of cesium, chlorine, and uranium evaporate at 1573 K. An increase in the system temperature to 1873 K leads to the vapor pressure of condensed nickel. Condensed strontium oxide transforms into a vaporized state at 2273 K. The condensed compounds of plutonium, calcium, and europium transforms into a vaporized state at 2373 K. Condensed beryllium oxide evaporates at 2473 K. A further increase in the temperature to 2673 K leads to the evaporation of condensed americium(III) oxide. Only a vapor–gas phase is present in the isolated system in the temperature range 2673–3273 K.

Thermodynamic Modeling of Plasmochemical Process of Synthesis of Dispersed Metal Oxides

Nowadays plasmochemical synthesis is one of the widespread methods of producing powders that allows finely dispersed materials with required structure and uniform distribution of components to be synthesized. To develop a reliable and effective plasmochemical reactor, a comprehensive study of the processes proceeding in it is required, and as a consequence, their thermodynamic modeling is necessary. Thermodynamic calculation of the equilibrium structure of cerium and yttrium nitrate decomposition products in plasma is complicated by the fact that the gas phase is multicomponent, and various processes with formation of atoms and radicals can proceed in plasma; in addition, the processes of restoration of originally formed ions proceed at high temperatures in plasma. In this regard, thermodynamic modeling by computer programs is often used to determine the composition of components and the system properties. The universal program TERRA intended for calculation of multicomponent heterogeneous systems [1] was used for thermodynamic analysis of plasmochemical process of producing cerium and yttrium oxides. The program TERRA of thermodynamic calculations is based on the principle of maximum entropy for isolated thermodynamic systems in equilibrium state. It possesses its own base of thermodynamic properties of individual substances. The base is constantly updated and refined. Nowadays the thermodynamic functions for 3500 individual substances at temperatures in the range 300–6000 K are contained in the databank.

A Study of Polymers. III. Technique of Mechanical Tests of Vulcanizates of Rubber and Plastics

Abstract 1. From the point of view of mechanical properties, the special attributes of highly polymeric substances, including rubber vulcanizates, are clearly defined by their reversible highly elastic deformation as a function of time. The time required for attaining this deformation within a given interval of time varies practically from zero to infinity. 2. Disregard of the temperature and time relation of deformation of highly polymeric substances leads to erroneous conclusions regarding their industrial working properties, and is the cause of the unsatisfactory results obtained by conventional methods of investigation. 3. The effect of increased degree of vulcanization on the mechanical properties of rubber is manifest in a decrease in complete elastic deformation and shift of the temperature-apparent modulus (inverse to the deformation in a given time) curve toward higher temperatures. 4. Conventional ideas of the plastic (irreversible) and elastic deformation of solid materials, when applied to highly polymeric substances without concern for the laws governing their deformation, lead to erroneous conclusions regarding the existence of specific properties of individual substances, e.g., ebonite and synthetic resins, and mistaken hypotheses regarding structural changes during their deformation. In the present communication, this is illustrated by studies of various investigators. 5. Conventional methods of studying thermal stability and brittleness, as well as other methods of testing, of highly polymeric substances frequently do not make it possible to evaluate the actual technical utility of materials within intervals of temperature encountered in service and they should be critically reëxamined with regard to the relations between deformation and reversibility, time and temperature.

The kinetic theory of fluids

The kinetic theory is applied to the properties of real fluids by including the effect of molecular attraction. The observed properties of individual substances are calculated directly by pure dynamics from the attraction of their ultimate particles, thermal agitation and volume only, without the introduction of any arbitrary factors. The mutual attraction of the molecules of real substances increases their mean square velocity. Maxwell's law is modified by the introduction of a parameter λ which multiplies the most probable speed of the molecules, λ being the ratio of the most probable speed in a real fluid to that in an ideal gas. Other necessary consequences of molecular attraction are that all real gases and liquids are associated; there is at every interface an adsorbed layer which modifies the average effect of the transfer of momentum in collision, and there is a change of energy, due to variation of λ, in passing from one medium into another. These effects have been calculated. In order to apply the results, a law of force must be adopted. Edser's inverse-eighth-power law is found to hold. The method is applicable to all the physical properties of fluids and is applied, by way of example, to the equation of state of a gas and the vapour pressure and viscosity of a liquid with satisfactory results. The new theory explains the observed decrease of viscosity of liquids with temperature, without which no theory can be accepted.