Treatment of a Nigerian Kaolin ore for Improved Industrial Application (original) (raw)
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Bleaching of a Nigerian Kaolin by Oxalic Acid Leaching
2015
The level of improvement of whiteness of Egbeda (Nigeria) kaolin ore by oxalic acid leaching was investigated. The effects of acid concentration, reaction temperature and particle size on the extent of the ore dissolution were examined. The results of the leaching investigation on the improvement of the ore whiteness assessment were found to increase with increasing acid concentration, reaction temperature and decreasing particle size. At optimal leaching (0.5 mol L -1 H 2 C 2 O 4 , 85°C, 120 minutes) with moderate stirring, the dissolution reached 79.9 %, when total iron removal was achieved as evidenced from the EDXRF and EDS analyses. The dissolution curves were analyzed and found to conform to the surface chemical reaction, and the calculated activation energy of 41.34 kJ mol -1 supported the proposed model. These results are also corroborated by the output of the Post-Hoc test by Duncan Univariate Anova Analysis using SPSS 7.1. Finally, oxalic acid proved to be effective for tr...
Kinetics Study of Iron Leaching from Kaolinitic Clay Using Oxalic Acid
European Scientific Journal, 2015
The kinetics study of iron leaching from kaolin clay from the County of Agua Blanca (Mexico) was carried out using solutions of oxalic acid for iron dissolution. The effects of acid concentration and temperature were studied to determinate kinetics parameters during iron leaching in oxalic acid media. It was found that iron dissolution rate increased with increasing of concentration and temperature, respectively. Leaching results showed that iron dissolution from the kaolin clay could be due to a chemical reaction control. The energy of activation calculated in this work was of 50.32 kJ • mol-1 , for the interval of temperatures from 273 to 333 K; which is characteristic of a process controlled by chemical reaction. According to the results shown above, iron removal is possible, and this can improve the economic value for this kind of kaolin clay, being possible its use in the ceramic and paper industries as raw material of high quality.
Clay Minerals
This study reports a leaching process along with a novel physical pretreatment technique to remove iron impurities from kaolin using oxalic acid. A detailed examination of the physical properties of the minerals confirmed that almost none of the leaching-resistant iron oxides, specifically hematite, was completely interlocked with the clay minerals. Accordingly, a pre-agitating technique followed by high-pressure washing of the sample on a 600 μm sieve were applied. In this method, by discarding up to 20% of the raw material, >54% of the total iron content of the raw kaolin was removed, and the iron content was reduced from 9.75% in the initial sample to <6.00% in the passing fraction. Application of this pretreatment method rendered the leaching process successful at 97°C using 0.3 M oxalic acid solutions for 1 h under atmospheric pressure. Compared to the leaching of the raw material without pretreatment, which consumed at least 0.5 M oxalic acid over a minimum period of 2 h...
Dissolution Kinetics and Leaching of Ca, Mg, Na and Zn from Kaolin Mineral ore in Hydrochloric Acid
Research Journal of Chemistry and Environment, 2018
This study presents a detailed leaching and dissolution kinetics of a kaolin mineral ore sample in hydrochloric acid media. The ash and moisture contents, pH, elemental composition, morphology, functional group compositions, crystallographic and mineralogical analyses of the kaolin samples were carried out. The effects of HCl concentration, process temperature and leaching time on the dissolution rate were investigated. The characterization of the kaolin sample revealed a thick spongy-like morphology and the presence of Ca, Zn, Mg, Na, Si and O elements. Experimental results showed that the leaching order of the metals is Mg> Na> Ca > Zn. The dissolution of the metals from kaolin increased with increasing temperature and leaching time but decreased with increasing HCl concentration. Approximately 81.2% kaolin of particle size 125 mm was successfully leached at optimum conditions of 0.5 M HCl, contact time of 25 min and at 100 o C. The apparent rate constants for the chemically controlled reaction(kr) and diffusion-controlled reaction (kd) are 0.0163 min-1 and 0.0061 min-1 respectively. The kinetic data analysis showed that the dissolution mechanism followed the diffusion controlled shrinking core model with the surface diffusion reaction as the rate controlling step.
Journal of Advances in Science and Engineering, 2022
Kaolin clay is a type of clay made primarily of the mineral kaolinite, which can be found all over the world. It's likewise referred to as white clay or China clay. Kaolin is called after the Kao-ling Hill in China, which has been mining this clay for hundreds of years. Kaolinite is presently mined in several nations, including China, the United States, Brazil, Pakistan, Bulgaria, and others. It grows best on soils created by the weathering of rocks in hot, humid settings like rain forests [1]. This clay is white or pink and is made up of delicate, microscopic crystals of minerals like silica, quartz, and feldspar. Kaolin is a versatile industrial mineral that is employed in a wide range of applications. The main mineral in kaolin is kaolinite, which has the chemical formula A12O3•2SiO2•2H2O [2, 3]. The kaolin layer comprises a single alumina
Mining, Metallurgy & Exploration, 2019
The increasing demand for pure aluminum and aluminum compounds of industrial quality from kaolinite ore cannot be overemphasized. Nigeria is one of the African countries endowed with abundant solid mineral resources that have not been sufficiently exploited to assist its indigenous industries. A wide array of applications of pure aluminum and its compounds are available, such as paper filling, refractories, adsorbent, catalysis, and paint additives. In this study, the upgrading of a Nigerian biotite-rich kaolinite ore by a hydrometallurgical route was investigated in oxalic acid media. During leaching studies, the effects of parameters including reaction temperature, lixiviant concentration and particle size on the extent of ore dissolution were examined. At optimal conditions (1.0 mol/L C 2 H 2 O 4 , 75°C), 92.0% of the initial 10 g/L ore was reacted within 120 min. The dissolution curves from the shrinking core model were analyzed and found to conform to the assumption of surface diffusion reaction, and the calculated activation energy of 33.2 kJ/mol supported the proposed model. The unreacted product (~8.0%) analyzed by XRD was found to contain siliceous impurities and could serve as a valuable by-product for certain industries.
Clays and Clay Minerals, 2022
Kaolin waste dumps contain a huge volume of material that cannot be commercialized due to the presence of variable amounts of iron minerals, which impart a yellowish color to the kaolin. Elimination of iron from kaolin using either a chemical or a biological method was the aim of this study. The chemical leaching of iron from kaolin was carried out using response surface methodology to optimize the reaction conditions. Time was found to be the most influential variable, although oxalic acid must be present to leach 32% of the iron. Biological leaching was also assayed for 14 days using a Bacillus strain. The results of bacterial leaching of iron from kaolin showed <1% iron elimination. Keywords Bacillus. Iron leaching. Kaolin waste. Oxalic acid. Response surface methodology structural formula: Al 2 (Si 2 O 5)(OH) 4 , and its centesimal composition includes 46.54% SiO 2 ; 39.50% Al 2 O 3 , and 13.96% H 2 O (Mathur, 2002; Prasad et al., 1991). Kaolin can be extracted from two types of deposits: primary and secondary. Primary deposits are formed by residual weathering or hydrothermal alteration of crystalline rock (granite) and, as is the case with the kaolin used in this study (mine Caobar SA, Poveda de la Sierra, Guadalajara, Spain), are located in the place where they were formed. Secondary deposits are sedimentary in nature and are formed by erosion of primary deposits. Primary clays are generally thick and contain much less iron oxide than secondary ones (Prasad et al., 1991). The main applications of kaolin are: (1). The paper industry, as kaolin provides good opacity, white color, high brightness, and good print quality in paper. (2). The ceramics industry, as the products require kaolin to produce a white color for the pieces after Clays Clay Miner.
Thermodynamic analysis of stability in iron removal from kaolin by using oxalic acid
Cerâmica, 2013
The graphical representation of global stability for a system, or Pourbaix diagram, was constructed to perform a thermodynamic study of iron removal from kaolin using oxalic acid as an oxidant. To do this the free energies of formation of the oxalate complex of the system were calculated, and it was found that the more stable specie is Fe(C2O4)3-3, with a calculated free energy of formation of -3753.88 kcal/mol. Thermodynamic stability functions were estimated for the system as a function of pH and Eh known as potential of oxide reduction. It was built a global stability diagram for the removal system; it showed that the specie trioxalate Fe(C2O4)3-3 is the only oxalate in equilibrium with other compounds associated with the removal of iron in kaolin.
Removal of Iron Oxides in Meetiyagoda Kaolin by Chemical Leaching to Improve Whiteness
Industrial grade Kaolin deposits in Sri Lanka are located in Boralesgamuwa and Meetiyagoda. Two distinct grades of Kaolin are produced at Meetiyagoda refinery, based on the whiteness index (WI). The presence of iron oxides significantly affects the WI of the Kaolin. Upgrading of the whiteness will result in a huge increase in the product prices as high as 35%. However, no effective methods are currently in place for the whiteness improvement at Meetiyagoda Kaolin refinery. Hence, this study was carried out to assess the whiteness enhancement capability of Meetiyagoda Kaolin by chemical leaching process using oxalic and citric acids. The treatment time (0–120 min) in steps and concentration of acids (0.01, 0.1, 0.2, 0.3, 0.4 and 0.5 M) were considered as the main variables of this study. Leachate and treated samples were analysed by using spectrophotometric and XRF methods respectively. The results depict that the oxalic acid is more effective in leaching iron oxides from Kaolin compared to citric acid for the Kaolin at Meetiyagoda. It was observed that 25% and 14% of Fe in Kaolin filter cakes can be removed by 0.4 M oxalic and 0.5 M citric acid respectively, within a treatment time of 120 mins at the room temperature.
Iron removal from a kaolinitic clay by leaching to obtain high whiteness index
IOP Conference Series: Materials Science and Engineering, 2013
Beige kaolin clays were crushed and sieved. The mineral was characterized by X-ray diffraction and chemically analyzed by atomic absorption spectrophotometry. The material below 37 microns was leached with oxalic acid. A study of main variables of the leaching process in different ranges was realized: time (0 to 120 min), temperature (25 to 100 °C) and acid concentration (0.01 to 0.5 M). Crystallographic analysis of the initial sample indicates the presence of kaolinite, iron oxides in the form of magnetite and iron-titanium oxides. By this method it was possible to obtain iron extraction percentages over 80% and whiteness index above to 90%.