Papers by Keyword: Kaoline

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Authors: Takayoshi Nakano, M. Kamitani, Mamoru Senna
Authors: Mohammad Pazouki, M.R. Hosseini, M. Ranjbar, F. Ghavipanjeh
Abstract: In this work, bioleaching of iron from a kaolin sample was carried out using two different strains of Aspergillus niger, and the effects of strain type, pulp density, and addition time of clay on the iron removal were investigated using a full factorial design. It is concluded that strain type has the most significant effect on the iron removal. Also, the highest removal extent was 42.8% that was achieved by using the strain isolated from pistachio shell at the pulp density of 20 g/l, when the clay was added at the beginning of the experiments. The results showed that for the experiments in which the clay was added in the first day of cultivation, the average organic acids concentration (citric acid: 5.6 g/l, and oxalic acid: 4.54 g/l) were higher in comparison to those experiments in which the clay was added in the third day (citric acid: 5.25 g/l, and oxalic acid: 2.87).
Authors: Iveta Štyriaková, Michal Lovás
Abstract: Bioleaching is technology applicable to iron extraction from low-grade non-metallic raw materials. Bioleaching of quartz sands and feldspars involves the action of heterotrophic bacteria. Impurities include fine – grained limonite, goethite, hematite or mica were removed by the reductive dissolution of Fe3+ in linked with the silicate mineral destruction. Heterotrophic bacteria produced organic acids that are able to solubilize Fe oxide and silicates but require organic carbon as a source of energy. Molasses is a relatively inexpensive carbon source used for various industrial fermentations and contains also other nutrients that accounted for the enhancement of iron dissolution in this study. The admixture of pigments in molasses coloured the samples, but the discoloration could be removed by the addition of NaClO following the bioleaching step. The feasibility of the bioleaching treatment has to be tested specifically to each type of silicate raw materials. The Fe content in the quartz sands and feldspar samples by the biological leaching decreased as much as 60% and by subsequent using of electromagnetic separation of feldspars, the decrease of Fe content in 74% was achieved. However, the application of magnetic separation of quartz sands after bioleaching resulted in total iron removal of 93 % and in such combined way prepared product contained 0.024 % of Fe2O3. Achieved results on iron removal point to the fact that combination of leaching and magnetic separation enables to obtain product usable in glass and ceramic industry.
Authors: S. Papargyri, D.N. Tsipas, A. Botis, X. Spiliotis, A. Papargyris
Abstract: Although structural kaolin based ceramics are attractive and useful materials, having good mechanical characteristics, low density, good corrosion and high temperature resistance, their use is restricted by their brittle behaviour. In order to improve their properties and mainly strength, toughness and high temperature performance, fibre composite ceramics have been developed. In the present work a series of kaolin-short random dispersed Grafil carbon fibre composites were produced and sintered in an inert atmosphere of Argon at 1000oC and 1300oC and characterised using various techniques. XRD analysis of the kaolin matrix at 1000oC showed that the crystalline phases were decomposed without the formation of mullite a fact which also reconfirmed by SEM examination. However at 1300oC mullite formation was well evidenced. XRD analysis of the fibres in “as received” showed that they have graphite structure which was also retained, as SEM examination revealed, after sintering. Examination of the Grafil fibres showed that they were quite uniform in length and diameter and retained their integrity after sintering at the examined temperatures. Examination the fractured composite surfaces showed only a weak bond between fibres and matrix and at the pull out areas the fibres were replicated in the matrix.
Authors: T. Plachký, J. Křesťan, M. Korenko, Zoltán Lenčéš, Pavol Šajgalík
Abstract: β-sialons prepared from pyrophyllite resp. kaoline were used for investigation of corrosion resistance in aluminium, NaF-AlF3 and NaCl-KCl mixture. The results were compared with β-sialon of similar composition, prepared from commercial powders. The differences in corrosion process of β-sialon prepared from natural hydrosilicates and synthetic powders are discussed.
Authors: Bülent Eker, Ayşegül Akdogan Eker
Abstract: The important effect of yoghurt on people's health caused increasing of many technological works and researches not only in our country but also all over the world.The environment in which yoghurt kept, may cause many sort of germs and contamination paths by the effects of some factors which are fairly similar to its own structure. These factors change the shelf-life of yoghurt and finally cause spoilage in yoghurt. In this context, it is known that the scientific works in this area which are aiming to minimize this spoilage effect, focus on the yogurt structure and packaging of yoghurt. The aim of this paper is to improve a smart polymer material which interacts with serum and changes color of the package by considering serum occurring within the shelf-life of yoghurt. PP based material will be used with the biological agencies like “kaoline” and “talc” and implemented mainly or superficial, the color change will be arised if the serum's PH increases. In practice, everyone can see the color changes with the window which will be placed on the label and the window will include the cautions according to the color levels.
Authors: Min Ling Gao, Xiao Jun Ma, Fei Lian, Wen Hua Song, Kai Zhang
Abstract: The aim of this study was to investigate the effect of temperature on adsorption behavior of di-n-butyl phthalate (DBP) in kaoline and montmorillonite. Adsorption isotherms experiments were conducted at 288, 298 and 308 K, respectively. Results showed that adsorption capacity decreased and adsorption intensity enhanced with temperature increased in both minerals. Adsorption amount was larger in montmorillonite than in kaoline. Thermodynamic data indicated the process was a spontaneous and exothermal process and the dominant affection was physical adsorption.
Authors: Adem Demir, F. Caliskan
Abstract: In this study, the production of β-Si6-zAlzOzN8-z (z =3) powders by the carbothermal reduction and nitridation of kaolin (Al2O3.2SiO2.2H2O) of Turkish origin (Can-Canakkale) was carried out with different processing parameters. It was found that the morphology of the produced SiAlON powder was mixture of irregular and whisker like grains. Therefore this morphology is suitable for liquid metal infiltration since the powders are already high porous. The kaolin powder containing stoichiometric rate carbon black and 30 % charcoal were pressed and reacted under nitrogen flow (2 lt/min) between 1400-1475°C for 4 h. After a carbothermal reduction and nitridation (CRN) process, porous β- SiAlON ceramic was produced from natural kaolin. Residual carbon and charcoal in the produced ß-SiAlON ceramic were fired at 1000°C giving extra porosity. The porous ß-SiAlON ceramics were sintered under N2 atmosphere at 1550°C for 2 h to make preform for infiltration process. SEM image analyses were carried out to determine preform and pore morphology and XRD analysis were performed for phase transformation.
Authors: Nan Chun Chen, Dong Chen
Abstract: Natural and raw high-silica kaolins are firstly processed into fine kaolin powders with oxidation-reduction bleaching method before mixed with Al2O3 powders and then baked to produce mullite composite oxides at temperature between 1050-1150°C. The mullite composite oxides are further made into composite mullite nanocrystals by using open-system hydrothermal crystallization method under normal pressure. Analysis of the final products show that the mullite nanocrystals are texturally homogenous at an average size around 80-100 nm and have high thermal stability.
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