Iron removal from a kaolinitic clay by leaching to obtain high whiteness index (original) (raw)
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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.
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.
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
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...
Kinetics of Iron Leaching from Kaolinitic Clay, Using Phosphoric Acid
Minerals, 2016
Kaolin is important because it has many applications in the paper, paint-coating, functional filler, extender and pigment industries. This material needs to be bleached by iron leaching to be useful for these applications because this element can be the principal cause of its undesirable coloration. In this work, the kinetics of leaching of iron contained in kaolin clays from the community of Agua Blanca Iturbide, Hidalgo, Mexico, was studied. The leaching experiments were carried out using phosphoric acid as the reagent of leaching for the iron dissolution process. Temperature, acid concentration, and particle size were investigated to determine the most important kinetics parameters during iron leaching. It was determined that the rate of iron dissolution increases with increasing of phosphoric acid concentration, the temperature, and decreased particle size of clay. Data obtained showed that iron dissolution from kaolin clay is due to the diffusion of iron through the product layer. The results revealed that the activation energy of the process was 10.18 kJ¨mol´1.
Characterization, beneficiation and utilization of a kaolinite clay from Assam, India
Applied Clay Science, 2003
Kaolin available in Deopani, Assam of northeastern region of India was characterized by FTIR, XRD, DTA and by wet chemical analysis methods. The major impurities in the clay are quartz and siderite. Wet sieving of the clay by À 53-Am sieve removes almost all the quartz and a major amount of Fe bearing impurities. The iron content of the clay may be reduced further by treating with wet high intensity magnetic separator (WHIMS) or leaching with organic acids. The effectiveness of various leachants follows the order: Oxalic>Oxalic + EDTA>Malonic>Citric acid. Almost all the nonstructural iron may be removed at room temperature by using 0.4 M oxalic acid solution. The leached clay may find use as a ceramic raw material and filler material for paper and other materials. D
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.
Removal of iron and titanium contaminants from Jordanian Kaolins by using chemical leaching
Journal of Taibah University for Science, 2018
The present study deals with chemical leaching tests conducted on Batn El-Ghoul kaolin clay deposit, south Jordan. Mineral identification and characterization studies were conducted using X-ray diffraction. The chemical analyses were performed by X-ray fluorescence. The chemical leaching study with sodium dithionite (Na 2 S 2 O 4) as leachant was accomplished with the fraction below 44 μm, after classification by screening. The main objective of this study was to evaluate the conditions of chemical leaching for removal of the colouring materials and to improve the brightness. The leaching tests improved the brightness from 56% to 86%. The corresponding iron-oxide removal was in the order of 94%. Removal of 94% iron gives a product containing 0.48% Fe 2 O 3 , which is fit for industrial applications such as fine ceramics and as a filler materials in paper, plastic and rubber industries.
Effect of Organic Acids on Iron Dissolution From Kaolinitic Clay
The aim of the paper is to study the dissolution capacity of iron from an iron-stained kaolinitic clay, using two organic acids (oxalic and citric acids) at two different concentration (0.1M and 0.01M, respectively) and at room temperature, to improve kaolin's whiteness. The influence of pH on dissolution is also studied. The results show that, for both acids, the diluted solutions (0.01M) solubilize more iron from the mineral structure, comparable with the concentrated (0.1M) solutions of acids. Among these two acids, the oxalic acid is capable of dissolving large amounts of iron from kaolin and is suitable to use it on a large scale of applications. The effect of these two acids on iron dissolution was investigated at pH between 2 and 5 and the experiments show that the maximum dissolution corresponds to the pH between 2.0 and 3.0 and decrease after pH = 3.
Statistical Treatment of Bleaching Kaolin by Iron Removal
Journal of the Mexican Chemical Society
In the present study, oxalic acid was used as a leaching reagent to remove iron from a kaolin mineral. Statistical analysis was conducted to determine the most influential factors in the dissolution of iron from the kaolin mineral. Our goal was ferric iron solubilization and its reduction to ferrous iron to improve the iron removal in the acid medium. Leaching experiments were conducted at atmospheric pressure. A two-level factorial design of the type 2<sup>4</sup> was utilized. The dependent variable was the percentage of dissolved iron, and the dependent variables in this study were acid concentration (0.35 and 0.50 M), temperature (75 °C and 100 °C), leaching time (2 and 4 h), and pH (1.5 and 2.5). An analysis of variance revealed that the effects of the factors temperature (b), pH (d), and the combined effects of temperature and time (bc) resulted in the maximum dissolution of iron of 88% at 100 °C, giving a kaolin mineral with a whiteness index 93.50%.