ДОСЛІДЖЕННЯ КІНЕТИКИ ТЕРМІЧНОГО РОЗКЛАДАННЯ РИСОВОГО ЛУШПИННЯ ПІСЛЯ ВИДАЛЕННЯ ЛІГНІНУ

The study addresses the problem of using recycled materials for the production of a wide range of diverse products; in this context, the paper investigates the extractin of amorphous silicon (IV) dioxide from rice waste, i.e. rice husk, which differs in its chemical composition from all other cereal crops by a high content of silicon dioxide. Amorphous silicon (IV) oxide is widely used in electronics, medicine, food industry, cosmetology, paintwork materials manufacturing, and other industries. Amorphous silicon(IV) oxide has to meet various requirements, the main ones being amorphous structure, degree of purification, and particle size. A derivatographic method of analysis is used to study the non-isothermal kinetics of rice husk residue thermal decomposition. According to the results of derivatographic, chemical, and phase analyzes, a method for amorphous silicon (IV) oxide extraction by thermal decomposition of rice husk after the lignin removal has been proposed. The values of relative activation energies and the pre-exponential factors of the reactions have been calculated. A mathematical model characterized by a system consisting of three first order differential equations and four algebraic equations has been designed. Through the use of the proposed model, the time response characteristics of the process have been studied.В рамках решения проблемы использования вторичного сырья для производства широкого спектра разнообразных продуктов, рассматривается выделение аморфного диоксида кремния из отходов рисового производства – рисовой шелухи, которая отличается по своему химическому составу от всех других злаковых культур большим содержанием диоксида кремния. Аморфный диоксид кремния имеет широкий спектр применения в электронике, медицине, пищевой промышленности, косметологии, при производстве лаков и красок, а также в других отраслях промышленности. К аморфному диоксиду кремния предъявляются различные требования, но основными являются аморфная структура, степень очистки и размер частиц. Для изучения неизотермической кинетики термического разложения остатка рисовой шелухи применяли дериватографический метод анализа. По результатам дериватографического, химического и фазового анализов предложен механизм процесса выделения аморфного диоксида кремния путем термического разложения рисовой шелухи после удаления лигнина. Рассчитаны значения условных энергий активации и предэкспоненциальных множителей реакций. Построена математическая модель, которая описывается системой, состоящей из трех дифференциальных уравнений первого порядка и четырех алгебраических. С ее помощью изучены временные характеристики процесса.У рамках вирішення проблеми використання вторинної сировини для виробництва широкого спектру різноманітних продуктів, розглядається виділення аморфного силіцій (IV) оксиду з відходів рисового виробництва – рисового лушпиння, яка відрізняється за своїм хімічним складом від усіх інших злакових культур великим вмістом діоксиду кремнію. Аморфний силіцій (IV) оксид має широкий спектр застосування в електроніці, медицині, харчовій промисловості, косметології, при виробництві лаків і фарб, а також в інших галузях промисловості. До аморфному діоксиду кремнію пред'являються різні вимоги, але основними є аморфна структура, ступінь очищення та розмір частинок. Для вивчення неізотермічної кінетики термічного розкладання залишку рисового лушпиння застосовували дериватографічний метод аналізу. За результатами дериватографічного, хімічного і фазового аналізів запропоновано механізм процесу виділення аморфного силіцій (IV) оксиду шляхом термічного розкладання рисового лушпиння після видалення лігніну. Розраховані значення умовних енергій активації і предекспоненціальних множників реакцій. Побудовано математичну модель, яка описується системою, що складається з трьох диференціальних рівнянь першого порядку і чотирьох алгебраїчних. З її допомогою вивчені тимчасові характеристики процесу

Study of the Anticorrosion Effect of Polymer Phosphates on Steel at Elevated Temperatures

Technological greases based on polyphosphates of alkali metals have great prospects for application at high-temperature machining of steel. An important task is to study the anti-corrosive effect of polyphosphates on steel at elevated temperatures. Temperature ranges, in which phase transformations of metaphosphate and sodium tripolyphosphate, as well as interaction with iron oxide, occur, were established using a thermogravimetric method. Composition of products of interaction between metaphosphate and sodium tripolyphosphate and scale is determined employing an X-ray phase analysis. It was established that in the region of temperatures of hot steel deformation the iron oxides, contained in scale, are dissolved in molten metaphosphate and sodium tripolyphosphate. As a result of interaction between sodium metaphosphate and iron oxide, the mixed polyphosphates Na3Fe2(PO4)3 and Na9Fe2(P3O10)3 are formed. It is shown that sodium tripolyphosphate almost does not participate in the interaction with the iron oxide of scale. Comparison of the results of corrosion test of the steel surface, treated in the presence of a polyphosphate lubrication and sodium chloride, testifies to the high anti-corrosive effect of polyphosphates. Thus, the time before the emergence of first signs of corrosion in the presence of polyphosphates increased fourfold, while the degree of corrosion damage was reduced by 40 times. It was established that at the deformation treatment of steel at a temperature of 800 °C in the presence of a polyphosphate lubricant, corrosion resistance is due to the formation of a barrier film at the steel surface, consisting of mixed polymer phosphates

Studying the Kinetics of Extraction Treatment of Rice Husk When Obtaining Silicon Carbide

Silicon carbide is characterized by a wide range of beneficial electrophysical, anti-corrosion, and strength properties. A promising raw material for the synthesis of silicon carbide is the waste of rice production, which includes compounds of silicon and carbon-containing organic substances. The cheapness and availability of such raw materials necessitate the development of technologies to obtain silicon carbide from it. An important direction in silicon carbide synthesis technology is to obtain a high purity product. To remove impurities from rice husks, it is necessary to carry out its pre-extraction treatment. It has been established that the extraction treatment of rice husks with acid solution makes it possible to clean the raw materials from metal compounds and the excess amount of carbon-containing components. To remove impurities of metal compounds and the excess amount of carbon-containing compounds from rice husks, it has been proposed to perform the extraction with an aqueous solution of the mixture of 10 % sulfur and 15 % acetic acids. We have derived the time dependences of the degree of extraction of cellulose from rice husks. Two temporal sections of the process have been identified. It is shown that the extraction of cellulose from rice husks obeys a pseudo first-order reaction. We have calculated the constants of speed and activation energy in the course of extraction for the two time sections of the process. The activation energy of extraction over a first period is 10.75 kJ/mol; over a second period, the activation energy value is 26.10 kJ/mol. It has been established that an increase in the extraction temperature from 20 to 100 °C leads to a two-fold improvement in the process efficiency. It is shown that silicon carbide, synthesized from rice husk after its extraction treatment, is a pure crystalline material whose particles' size is from 1 to 20 micrometer

Development of A New Suspension Electrolyte Based on Methane-sulphonic Acid for the Electrodeposition of Cu–TiO2 Composites

Electrodeposition of composite coatings based on copper is a promising direction in the creation of advanced materials for multifunctional purposes. An important area of composites application is to use them in the treatment systems for gas emissions and wastewater. It is advisable to use semiconductor oxide materials, in particular titanium dioxide, as the photocatalysts in the photo destruction of organic pollutants of wastewater. The structural features of wastewater treatment equipment require that titanium dioxide particles should be fixed in a rigid matrix. Resolving the task of fixing photosensitive elements at the surface of a certain configuration implies the electrodeposition of coatings by composites, in particular Cu–TiO2. An important factor affecting the functional characteristics of composites and their manufacturing technology is the nature of the electrolyte. It has been shown that the electrodeposition of Cu–TiO2 composites from methane-sulfonate electrolytes makes it possible to reduce the coagulation of the dispersed phase and to obtain coatings with a high content of titanium dioxide from a suspension solution containing no more than 4 g/l of TiO2. It was established that the content of the dispersed phase in the composite made at a current density of 2 A/dm2 and the concentration of titanium dioxide in the electrolyte at the level of 4 g/l is 1.3 % by weight, which is twice as much as when using a sulfate electrolyte. It has been shown that the increase in the content of the dispersed phase in the coatings from 0.1 to 1.3 % by weight is accompanied by an increase in the degree of photo destruction of the colorant from 6 to 15.5 %. The micro-hardness of coatings increases, in this case, by 30 %. The proposed electrolyte to make the Cu–TiO2 composites is an important contribution to the development of the synthesis of wear-resistant high-performance photocatalysts for treating wastewater from organic pollutant

Research Into Effect of Propionic and Acrylic Acids on the Electrodeposition of Nickel

Nickel coatings are widely used in machine-building, electronics, automotive and aerospace industries. High requirements for environmental safety and operational performance of contemporary processes of electrochemical nickel plating predetermine the search for the new electrolytes. Electrolytes based on carboxylic acids are characterized by high buffer properties, ecological safety, and enhanced values of limiting current. Heuristic approach when fabricating comprehensive electrolytes, based on empirical data, does not make it possible to conduct predictable optimization of the formulations of nickel plating electrolytes. Solving this problem seems possible when using a quantum-chemical simulation. In this work, we performed quantum-chemical calculations for the propionate and acrylate complexes of nickel. It was established that coordination numbers of the propionate and acrylate complexes of nickel are equal to five and six, respectively. It is shown that electroreduction of the propionate nickel complex proceeds with the formation of an intermediate particle. The negative charge of this particle is localized on the intrasphere molecules of water. This may lead to the electroreduction of the latter and to an increase in the pH of a near-electrode layer. In the intermediate particle of the acrylate complex, localization of the charge occurs on the vinyl fragment of acrylate-ion. Electrochemical reaction of reduction of the coordinated water molecules in such a particle is not energetically favorable. It was established that the isolation of nickel from the acrylate complex proceeds with lower kinetic difficulties than from the propionate complex. An assumption was made that fewer insoluble hydroxide nickel compounds, which block the cathode surface, form in the acrylate electrolyte.Such an assumption is based on the fact that given close buffer properties of acids, electroreduction of the acrylate complexes does not imply the involvement of coordinated water molecules in the electrode process. The results obtained are very valuable for selecting the nature of carboxylic acid as a component for the complex nickel plating electrolyt