Papers by Keyword: Kaolin

Abstract: The ceramic industry is one of the most important productive chains of the State of Pará, generating both money and employment. Kaolin has many industrial applications and new uses are constantly surveyed. Although the extraction and processing of kaolin contribute to the economy growth, the activity also provokes serious environmental issues. Being aware of the environmental problem caused by the inadequate decomposition of kaolin residues from the beneficiation process of these minerals, which pollute and attack the environment, this paper aims the chemical, physical and mineralogical characterization of the kaolin residue from the post-treatment disposal provided by CADAM S/A company. The main oxides in the residues were SiO₂ and Al₂O₃. In the X-ray diffraction analysis it was verified that the kaolin residue is basically formed by kaolinite and quartz, in the particle size analysis it was observed that the medium size of the particle was of 1,77 μm.

Abstract: Class C fly ash is widely used as a geopolymer raw material. It contains high calcium oxide and iron oxide resulting in a fast setting property. The influence of using kaolin and metakaolin replaced class C fly ash in geopolymer processing were investigated in term of compressive strength and setting time. Kaolin and metakaolin which calcined at different temperature of 600°C and 700°C replaced Class C fly ash between 0 to 50 wt. %. The geopolymers were prepared at constant KOH concentration as 6.0 M, K₂SiO₃/KOH ratio as 1.0, solid/liquid ratio as 1.5 and 7 days of curing. The compressive strength is obviously increased when fly ash was replaced with both kinds of metakaolin, although, it is inclined to decrease when replaced by kaolin. The compressive strength is increased up to 13% and 47% with the replacement by 50 wt. % of metakaolin calcined at 600°C and 700°C, respectively. On the other hand, the replacement by 50 wt. % of kaolin give the initial setting time prolonging from about 6 min to 80 min. However, the initial setting time of metakaolin calcined at 600°C and 700°C replacement is also improved to about 37 min and 20 min, respectively. These results from their difference of amorphous phase and reactivity of the replacement materials. XRD analysis reveals the combination phases of amorphous geopolymer gel that is the broad hump centered at 28 – 30° 2θ, and products from the reaction such as calcium oxide, arcanite, calcium silicate hydrate, quartz and muscovite which the two latter are from unreacted metakaolin. They are confirmed by FT-IT result and microstructure evaluation by SEM. Therefore, the partially replacement of fly ash with kaolin and metakaolin in fly ash-based geopolymer production are affected to the compressive strength and resulted to modify the setting time.

Abstract: Zeolite A from natural kaolin have been successfully synthesized via calcination and hydrothermal. However, these techniques have one drawback since, the impurities in kaolin such as muscovite and quartz in the kaolin structure, which depend on temperature and alkaline activation. This work was separated into two steps, first step was used calcination technique, and second step was used hydrothermal technique. Reaction of temperature in the first step was studied the influence of temperature from 500°C to 800°C for 3 hours. In this step, kaolin transformed to metakaolin and remain the impurities. Next, reaction of alkaline activation in second step was studied about the influence of NaOH. The concentration of NaOH in hydrothermal was varied from 1M to 4M and mixed with metakaolin at 90°C for 72 hours. X-ray Diffraction Spectroscopy (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were used for characterization. The solid products were formed to zeolite A at 1M NaOH hydrothermal with 500°C to 800°C calcination and it can be seemed good of euhedral structure at 700°C

Abstract: The purpose of this work was to investigate the phenomenon of microbial iron reduction in industrial minerals and materials. These materials are generally not pure, often associated with impurities usually in the form of Fe³⁺. In all cases, the presence of iron affects the colour and the physical properties of the mineral and therefore lowers their industrial value and limits their application. In this study bentonite, kaolin and quartz sand sample were used for the experiments and compared in effectiveness of iron dissolution. The experimental results showed that after 30 days of bioleaching process, bacteria are able to remove 9.29% of Fe occurring in the kaolin sample (K-I) in amorphous form of oxyhydroxides and approximately 12% of Fe from the bentonite sample (B-JP) also in amorphous form of oxyhydroxides. In the quartz sand sample C3-15D, the concentration of Fe decreased by 15% after 15 days of bioleaching process and in the sample C3-30D after 30 days of bioleaching process by 24.7%.

Abstract: Generally, Saman tree is a plant in the Fabaceae. (Leguminosae) subfamily Minosoideae in a large tree. There are many branches with small leaves, pink flowers with a seed pod of pink flesh..Therefore, branch and leaves of Saman tree were left and considered as unwanted materials. They were destroyed via the waste combustion process. Then, the Saman tree ash was become residues. In order to protect the environment and to increase the valuable of the bottom ash from Saman tree, the Saman tree ash glaze in Ratchaburi potteries was performed using triaxial diagram. The clay in this stoneware was chosen from Ratchaburi Province. After that, the glazing formula was then created. The gas kiln was selected. The temperature of reduction fire for glazing was 1,250 degree Celsius. The fifteen testing formula were tested by the variation of Saman tree ash, soda feldspar, and kaolin. The suitable ratio among of glaze formula Saman tree ash : soda feldspar : kaolin was Saman tree ash 5:3:2, respectively. The Stoneware prototypes were shaped as tea set by the throwing method. The results showed that the glaze of all products was glossy with light-green colour. This developed glazing process was well performed in the Ratchaburi pottery industries. In addition, the mixing between Saman tree ash and metal oxides are under investigation to create a variety of color shades.

Abstract: The paper investigates the peculiarities of the chemical and mineralogical compositions of semi-flint kaolins and their behavior under heating up to 1500 °C. It was found that the sintering process of kaolin clay raw materials depends on the temperature of their preliminary calcining, method of milling after the thermal treatment and application of mineralizing additives. In the case of Borovichy kaolin, preliminary calcining at 850 °C and 980 °C and its subsequent milling increase the material strength after sintering calcining at the temperature of 1400–1450 °C at the expense of uniform sintering and the formation of a homogeneous microstructure of sintered material.

Abstract: Small pellets with differing mullite contents were prepared by a conventional ball-milling and dry-powder pressing technique, followed by firing at temperature of 1300°C and 1600°C for four hours. Kaolin processing waste and high purity aluminum hydroxide were used as starting materials. The sintered samples were examined using X-ray diffraction to determine the weight percent of each identified phase. The results showed that the percentage of mullite in kaolin processing waste can be increased by introducing additional aluminum hydroxide. It was found that sintered samples yielded best results when derived from both types of kaolin processing waste with 40wt% of aluminum hydroxide and a firing temperature of 1600°C.

Abstract: In the present study, mullite powders were prepared from fired Ranong kaolin powder at high temperatures. Differential thermal analyses and X-ray diffraction (XRD) technique were used to understand kaolin–mullite reaction sequence and phase formation of the starting material after a heat treatment, respectively. It was found that phase of mullite started to occure at ∼1000 °C. Microstrural study by a scanning microscope, indicated that there was a change in microsture after the heat treatment, i.e. grain shape changed from equiaxed to needle grains shape . The AC conductivity decreased with decreasing the sintering temperature and 1500 °C ceramic presented a very high frequency stabilty of conductivity, suggesting that this martial can be used as an electrical insulator for wide frequency range.

Abstract: The conventional technique to synthesizes zeolite A from kaolin is calcination. However, this technique has one drawback since, the impurities in kaolin, such as muscovite and quartz, remain. Therefore, the hydrothermal process without calcination is used to synthesize high purity zeolite A. Hydrothermal synthesis without calcination can be separated into two steps, namely first and second hydrothermal steps. Alkaline activation reaction in the first hydrothermal step was used to study the effect of NaOH concentration ranging from 4M, 6M, 8M, 10M to 12M at 200°C for 3 hours. In this step, sodium aluminosilicate (cancrinite and nepheline hydrate) was produced and then dissolved in HCl. After filtration, the impurity was removed, and adjusted for neutral pH of 7 to form amorphous aluminosilicate gel. For the second hydrothermal step, amorphous gel was mixed with NaOH (1-4M) to form zeolite A at 90°C for 3 days. The x-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were used for characterization.

Abstract: Kaolin is a white clay, formed by hydrated aluminum silicates, which has several industrial applications. Since it is associated to impurities and presents considerable contents of contaminant elements that interfere in its performance and in its applications, kaolin must pass through a beneficiation process in order to meet the market's demands. The purpose of this work is to study the use of a hydrocyclone in the beneficiation of primary kaolins from Província Pegmatítica da Borborema. The samples were characterized by cation-exchange capacity (CEC), granulometric analysis by laser diffraction (GA), chemical composition by X-ray fluorescence (EDX), X-ray diffraction (DRX), differential thermal analysis (DTA) and thermogravimetric analysis (TG). The purification process did not show good results for kaolin in ABNT 200 mesh in the attempt to obtain colloidal kaolin. On the other hand, it presented very promising results for the beneficiation of raw kaolin, proving the feasibility of the application of this technology to the granulometric classification of this mineral, being an alternative route for the processes adopted in the regional kaolin beneficiation plants, which use washing and sieving.