scholarly journals Optimisation of conditions for deacetylation of chitin-containing raw materials

2021 ◽  
Vol 15 (3) ◽  
Author(s):  
O. Pavlova ◽  
M. Trusova

The paper describes the differences between chitosan and chitin, and reviews works by foreign scientists on obtaining chitosan from various raw materials. Methods of modifying chitosan and obtaining combined sorbents have been analysed. It has been studied whether chitosan is applicable in the technology of wines and alcoholic beverages as a sorbent. The purpose of the study was determining the optimal conditions of the deacetylation stage to obtain chitosan with the best sorption properties from Aspergillus niger biomass. A three-factor experiment has been carried out. It involved obtaining 27 samples of chitosan using sequential four-step acid-base hydrolysis under various conditions of the deacetylation stage. The deacetylation process was optimised under alkaline conditions depending on the alkali concentration, processing temperature, and exposure. For each of the samples obtained, the adsorption activity, specific surface area, and distribution coefficient in the sorbent–sorbate system have been determined. The degrees of deacetylation of all chitosan samples have been determined by potentiometric titration. The study has resulted in determining the optimal conditions for the deacetylation stage: processing temperature 110–130°C, sodium hydroxide concentration 27–36 g/dm3, exposure 45 to 65 minutes. The sample deacetylated at the temperature 120 °C, alkali concentration 30 g/dm3, and exposure 45 minutes has shown the best adsorption activity values: the adsorption activity for methyl orange 347.96 mg/g, the specific surface area of the sorbent samples 0.52·105 m2/g, the distribution coefficient in the sorbent–sorbate system 3.29·10-3 ml/g. This sample had the highest degree of deacetylation, 43.6%. The sample has been analysed using IR spectroscopy, and its main characteristic frequencies have been studied. It has been concluded that the sample obtained was equivalent to the reference chitosan

Author(s):  
Т.В. САВЕНКОВА ◽  
М.А. ТАЛЕЙСНИК ◽  
Н.А. ЩЕРБАКОВА ◽  
С.Ю. МИСТЕНЕВА ◽  
И.И. МИЗИНЧИКОВА

Описаны и теоретически обоснованы разработанные технологические приемы производства мучных кондитерских изделий при сохранении влаги на всех стадиях производства. В рамках исследования решали следующие задачи: увеличение удельной поверхности частиц дисперсной фазы эмульсии за счет моделирования рецептурного состава; дезагрегирование муки, повышение равномерности распределения дисперсионной среды (эмульсии) с образованием оболочек вокруг максимально возможного количества частиц муки различных фракций. Объектом для моделирования рецептурного состава было сахарное печенье. Установлено, что замена рецептурных компонентов с повышенной влажностью на сырье с высоким содержанием сухих веществ позволяет высвободить влагу и использовать новые виды сырья с повышенными нативными свойствами. Предложенные приемы подготовки сырьевых компонентов: снижение вязкости солодового экстракта, используемого для снижения количества сахара-песка, осмотическое набухание яичного порошка, пластикация жира со стабилизацией его структуры лецитином, инверсия сахарозы в условиях совмещения гидродинамического и акустического кавитационных воздействий при получении инвертного сиропа – обеспечивают благоприятные условия получения эмульсии с повышенной удельной поверхностью. Отличительной особенностью предлагаемой технологии является получение эмульсии в две стадии: приготовление суспензии без жира и собственно получение эмульсии. Раздельная подача сахара в два приема: 40–60% его рецептурного количества вносится на стадии приготовления суспензии, оставшаяся часть – при приготовлении эмульсии – и кавитационная обработка суспензии при температуре 36–38°С и частоте колебаний волновода 24 кГц позволяют повысить частичную концентрацию частиц сахара в 8–12 раз. При приготовлении эмульсии пластицированный жир и лецитин предварительно смешивают с оставшейся частью сахара-песка, а затем с суспензией. Дезагрегированную путем аэрации муку и эмульсию одновременно и параллельно подают в месильную машину для достижения их заданного соотношения до начала процесса тестообразования. Разработанный комплекс технологических приемов позволил создать технологический поток производства сахарного печенья с улучшенными показателями качества – намокаемостью до 230% (по классической технологии 180–200%), сниженной на 20% плотностью, повышенными пористостью и рассыпчатостью и сохраняющего до 92% влажности, что на 18% выше, чем в изделиях, полученных по классической технологии. The developed technological techniques for the production of flour confectionery products while maintaining moisture at all stages of production are described and theoretically justified. The following tasks were solved in the framework of the study: increasing the specific surface area of the particles of the dispersed phase of the emulsion by modeling the recipe composition; disaggregating flour, increasing the uniformity of the distribution of the dispersion medium (emulsion) with the formation of shells around the maximum possible number of flour particles of various fractions. The object for modeling the formulation composition was sugar cookies. It is established that the replacement of prescription components with high humidity with raw materials with a high content of dry substances allows you to release moisture and use new types of raw materials with increased native properties. The proposed methods of preparation of raw materials: reducing the viscosity of malt extract used to reduce the amount of granulated sugar, osmotic swelling of egg powder, fat plasticization with the stabilization of its structure with lecithin, sucrose inversion under conditions of combining hydrodynamic and acoustic cavitation effects in the production of invert syrup – provide favorable conditions for obtaining an emulsion with an increased specific surface area. The production of an emulsion in two stages is a distinctive feature of the proposed technology: the preparation of a suspension without fat and the actual production of the emulsion. Separate supply of sugar in two steps: 40–60% of its prescription amount is introduced at the stage of preparation of the suspension, the remaining part – during the preparation of the emulsion – and cavitation treatment of the suspension at a temperature of 36–38°С and the waveguide oscillation frequency of 24 kHz, it is possible to increase the partial concentration of sugar particles by 8–12 times. When preparing the emulsion, the plasticized fat and lecithin are pre-mixed with the remaining part of the granulated sugar, and then with the suspension. The aeration-disaggregated flour and emulsion are fed simultaneously and in parallel to the kneading machine to achieve their desired ratio before the dough-forming process begins. The developed complex of technological techniques allowed to create a technological flow for the production of sugar cookies with improved quality indicators – wetting up to 230% (according to the classical technology 180–200%), reduced density by 20%, increased porosity and friability, and preserving up to 92% humidity, which is 18% higher than in products obtained by the classical technology.


2016 ◽  
Vol 18 (2) ◽  
pp. 141 ◽  
Author(s):  
A.A. Atchabarova ◽  
R.R. Tokpayev ◽  
A.T. Kabulov ◽  
S.V. Nechipurenko ◽  
R.A. Nurmanova ◽  
...  

<p>Electrode materials were prepared from activated carbonizates of walnut shell, apricot pits and shungite rock from “Bakyrchik” deposit, East Kazakhstan. Physicochemical characteristics of the obtained samples were studied by the Brunauer-Emett-Taylor method, scanning electron microscopy, Raman spectroscopy and other methods. Electrochemical properties of the obtained materials were studied by the method of cyclic voltammetry. It was found that the samples have an amorphous structure. Samples based on plant raw materials after hydrothermal carbonization at 240 °С during 24 h, have more homogeneous and developed surface. Specific surface area of carbon containing materials based on apricot pits is 1300 m<sup>2</sup>/g, for those on the based on mineral raw material, it is 153 m<sup>2</sup>/g. It was shown that materials after hydrothermal carbonization can be used for catalytic purposes and electrodes after thermal carbonization for analytical and electrocatalytic purposes. Electrode obtained by HTC have electrocatalytic activity. CSC 240 has high background current (slope i/Е is 43 mА V<sup>–1</sup> cm<sup>–2</sup>), low potential of the hydrogen electroreduction (more positive by ~ 0.5 V than samples based on plant raw materials). The reaction of DA determination is more pronounced on the electrodes obtained by HTC 240 °C, 24 h, due to the nature, carbon structure and high specific surface area of obtained samples.</p>


2011 ◽  
Vol 356-360 ◽  
pp. 1900-1908 ◽  
Author(s):  
Juliana De Carvalho Izidoro ◽  
Denise Alves Fungaro ◽  
Shao Bin Wang

A Brazilian fly ash sample (CM1) was used to synthesize zeolites by hydrothermal treatment. Products and raw materials were characterized in terms of real density (Helium Pycnometry), specific surface area (BET method), morphological analysis (SEM), chemical composition (XRF) and mineralogical composition (XRD). The zeolites (ZM1) from fly ash were used for metal ion removal from water. Results indicated that hydroxy-sodalite zeolite could be synthesized from fly ash sample. The zeolite presented higher specific surface area and lower SiO2/Al2O3ratio than the ash precursor. The adsorption showed that cadmium is more preferentially adsorbed on ZM1 than zinc. The adsorption equilibrium time for both Zn2+and Cd2+was 20 hours in a batch process. The adsorption isotherms were better fitted by the Langmuir model and the highest percentages of removal using ZM1 were obtained at pH 6 and 5 and doses of 15 and 18 g L-1for Zn2+and Cd2+, respectively. Thermodynamic studies indicated that adsorption of Zn2+and Cd2+by ZM1 was a spontaneous, endothermic process and presented an increase of disorder at the interface solid/solution.


2010 ◽  
Vol 636-637 ◽  
pp. 124-129 ◽  
Author(s):  
D.G. Pinto ◽  
Abílio P. Silva ◽  
A.M. Segadaes ◽  
T.C. Devezas

Alumina, with high melting point (2050°C), high hardness and mechanical strength, and excellent abrasion resistance, is one of the most common raw materials used in self-flow refractory castables (SFRC) for monolithic linings and is commercially available in various fine to coarse size classes. However, the performance of the refractory lining depends not only on the properties of its ingredients but also on its easy installation (good flowability). The aim of this work was to evaluate the relationship between the flowability index (FI) of fresh castable and the specific surface area (SSA) of its particles, which is mostly determined by the finer particles content. The results obtained showed that, by controlling the proportion between matrix and aggregate, it is possible to control the SSA of the refractory castable and find a mathematical relationship between the specific surface area and the minimum flowability index required to obtain a self-flow refractory castable. It is, thus, possible to optimize the refractory castable size composition and obtain an estimate for FI as a function of SSA. Using a minimum 45 wt.% matrix content in the castable mixture, a SSA value above 2.215 m2/g is obtained, which leads to FI ≥ 80%, the recommended value for self-flow.


2019 ◽  
Vol 956 ◽  
pp. 294-304
Author(s):  
Guo Jun Ke ◽  
Hong Jun Tan ◽  
Peng Fei Yang ◽  
Pin Yu Zou

Using magnesium nitrate, nickel nitrate and aluminum nitrate as raw materials and urea as precipitant, magnesium nickel aluminum ternary hydrotalcites with large specific surface area were prepared by hydrothermal method. The prepared samples were characterized by SEM、XRD、BET and EDS etc., respectively. The adsorption properties of MgNiAl-LDHs, MgAl-LDHs and their calcined products (MgNiAl-LDOs, MgAl-LDOs) for chloride ions in solution were investigated. The results show that MgNiAl-LDHs are cubic with rod-like structure, with a specific surface area of 197.62 m2/g, which is much larger than that of MgAl-LDHs (102.82 m2/g). Under the same adsorption conditions, the saturated adsorption capacities of MgNiAl-LDHs and MgAl-LDHs for chloride ions are 130.06mg/g and 110.02 mg/g respectively. MgNiAl-LDOs showed better adsorption ability for chloride ions. By simulating the adsorption data, the results show that the adsorption kinetics and the adsorption isotherm are in accordance with the quasi-second-order kinetic model and the Langmuir isotherm model, respectively.


2016 ◽  
Vol 718 ◽  
pp. 100-104 ◽  
Author(s):  
Pichaya Nitnithiphrut ◽  
Rangsinee Pimsri ◽  
Varinrumpai Seithtanabutara

Para-wood residue was impregnated in 40% wt. of H3PO4 solution for 24 h before carbonization under different temperatures and times. The response surface methodology (RSM) based on Box-Behnken was applied to optimize the operating conditions in producing activated carbon with high specific surface area. The effects of three variables; impregnation ratio, carbonising temperature and time on the specific surface of activated carbons were investigated. The proposed model was almost in accordance with the experimental case with correlation efficient and of 0.9653 and 0.9029, respectively. The optimal conditions were found to be 6%wt. of impregnation ratio and carbonization at 400°C for 67.27 min. The predicted surface area of produced activated carbon under these optimal conditions determined by RSM was 1069.30 m2/g. Experimental validation at these conditions was observed of 978.95 m2/g which closely agreed with the predicted value. This obtained activated carbon structure composed of mesopores and micropores with the average pore diameter of 21.71°A. This study indicated the RSM based on Box-Behnken design was the effectively method to optimize the operating condition and maximize the specific surface area of produced activated carbons.


2012 ◽  
Vol 600 ◽  
pp. 178-181 ◽  
Author(s):  
Kun Wang ◽  
Qiao Wen Yang ◽  
Chuan Liu ◽  
Hui Zhao ◽  
Gan Chen ◽  
...  

Coke fines and semi-cokes have high ash content, low specific surface area and pore volume. In order to increase the properties of the sample and make the activated composite materials, it must be deashed and activated. In this research, the deashing experiment of the raw materials by different concentration of HNO3 and KOH was tested, then the material was activated in high temperature steam. From the FTIR test, we can acquire the content of the surface functional groups, such as carboxyl and hydroxyl. The specific surface area, pore size, volume of the material were determinated by using the N2 isothermal adsorption. From the experiments of acid and alkali treatment, we can conclude that the optimal technological condition of the material: the concentration 20% of alkali and acid treatment processing. The ash content is decreased to 8%. The acid functional groups increased rapidly after HNO3 treatment. The activated coke fines have mainly mesopores and its proportion of microspore is low. The specific surface area of the activated material reached 80m2/g and increased about 5 times than that of raw materials.


2021 ◽  
Author(s):  
Yong Ai ◽  
Na Yin ◽  
Yanquan Ouyang ◽  
Yuanxin Xu ◽  
Pengfei Yang

Abstract In order to make full use of waste as raw materials to prepare low-cost zeolite, develop green chemical industry and achieve the purpose of treating waste with waste. High-purity zeolite X was prepared by the alkaline fusion hydrothermal method (AFH) using waste basalt powder as raw material, and was used as an adsorbent to investigate the adsorption performance for uranium-containing wastewater. The structure, morphology, specific surface area, chemical composition, chemical bonds, characteristic functional groups and chemical states of surface elements of the samples were characterized by XRD, SEM, BET, EDS, FT-IR and XPS. zeolite X with high crystallinity and rich hydroxyl/carboxyl groups was successfully synthesized by the AFH method, and its specific surface area was as high as 623.4 m2·g-1. When the adsorption time (t) is 720 min, the adsorption temperature (T) is 30 ℃, the initial uranium (VI) concentration is (C0) 35 mg/L, pH is 6.0, and the adsorbent dosage (m) is 5/35 mg/mL, the equilibriu adsorption capacity of zeolite X for uranyl ions is 228.4 mg·g-1. Thermodynamic results show that the adsorption process of uranyl ions by zeolite X is spontaneous and exothermic. Freundlich isotherms and quasi-second-order models are suitable to describe the adsorption process of uranyl ions by zeolite X. XPS analysis results show that -OH and -COOH play an important role in the adsorption process. At the same time, there is ion exchange between UO22+ and zeolite during the adsorption process.


2020 ◽  
pp. 17-24
Author(s):  
Dmitriy Aleksandrovich Yelatontsev ◽  
Elena Vladimirovna Ivanyuk

The paper presents the of influence peroxide ammonium, alkali, nitric acid, organosolvent and "aqueous ammonia soaking" (AAS) delignification methods on the degree of removal of lignin from non-wood lignocellulosic waste walnut shell Juglans Regia L. and apricot seed Prunus Armeniaca L. It is shown that the maximum degree of delignification (94%) is achieved when processing raw materials with 42 wt% HNO3 and 20 wt% NaOH; the minimum is at peroxide-ammonia treatment (80%). We found that the greatest specific surface area (202 m2∙g-1) provided by the application 42 wt% HNO3, and a maximum iodine number (32 mg∙g-1) when using 25 wt% NH4OH. Delignification significantly increases the specific surface area (5 m2∙g-1 to 120–200 m2∙g-1) iodine number (6.35 mg∙g-1 to 25 to 32 mg∙g-1) of biomass, however, at 45–55% reduced exchange capacity of the material. The obtained cellulose intermediates having acceptable physical and chemical characteristics can be used for further preparation of available sorbents or ion exchange materials. In accordance with the principles of "green chemistry", it is proposed to dispose the spent delignification solutions from AAS and nitric acid methods in liquid nitrogen fertilizers producing.


2021 ◽  
Vol 43 ◽  
pp. e51699
Author(s):  
Thiago Melanda Mendes ◽  
Wellington Longuini Repette

For a controlled particle size distribution, nano-silica was added to three different cements. The chemical and mineralogical compositions of the cements were characterized by fluorescence and X-ray diffraction. The granulometric distributions of cements and nano-silicas were obtained by laser granulometry and dynamic lightning scattering. The specific surface area of the raw materials was determined by gas adsorption. The effect of nano-silica and type of cement on rheological behavior was evaluated by rotational rheometry. The mechanical performance was investigated through the compression strength. The microstructural analysis was performed by scanning electron microscopy. The water demand and the consumption of dispersant increases according to the nano-silica content. The reduction in the inter-particle separation, and the agglomeration of nano-silica led to an increase in the viscosity of the suspension. The mechanical performance was directly affected by the specific surface area of the cements. Microstructural analysis showed that nano-silica changed from a layered adsorbed structure, to a porous or agglomerated structure.


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