Crude Kaolin Research Articles

DETERMINATION OF OPTIMAL CONDITIONS FOR EXTRACTION OF ALUMINUM OXIDE FROM KAOLIN CLAY OF CHOVDARDAGH DEPOSIT

The increasing demand for aluminum around the world is increasing interest in developing alternative technologies for the production of alumina from non-bauxite sources, especially from clay. In this work, the extraction of aluminum from kaolin in the process of leaching using an aqueous solution of hydrochloric acid as a leaching agent is investigated. For this study, samples of burnt kaolin clay from the Chovdardagh deposit were used. Before leaching, crude kaolin was calcined; calcination achieves dehydroxylation of kaolinite, which is the main mineralogical phase of kaolin, and its transformation into metakaolin, an amorphous phase of Al-Si, from which aluminum is easily leached. The calcination of the raw kaolin used in this work was carried out at 7500C for 2 h, taking into account that these conditions were recognized as optimal in the corresponding experimental studies to achieve the maximum yield of alumina in solution. It was revealed that the leaching of kaolin clay in order to extract aluminum oxide is achieved using samples of kaolin clay calcined under the above conditions, with 20% hydrochloric acid for 2 hours at a leaching temperature of 950C. The degree of extraction of aluminum and iron oxide under these conditions is 96.7 and 94.1%, respectively

Properties of hydric and biodegradability of cassava starch-based bioplastics reinforced with thermally modified kaolin

In this study, hydric and biodegradability properties of cassava starch-based bioplastics reinforced with crude kaolin or treated kaolinitic clay at 700 °C called metakaolin were investigated using water adsorption and microbiological tests. Non-reinforced bioplastics (BP) and those containing 5 wt.% crude kaolin (BPKB) or metakaolin (BPMKB) were manufactured using the casting/evaporation method. Results obtained showed a decrease in the solubility and in the water diffusion and permeability of clay-reinforced bioplastics with respect to the ones without reinforcement. This improvement of the hydric properties has been attributed to the reduction in the free volumes existing between the starch macromolecules due to their interactions with clay platelets. These interactions might favor a more homogeneous and compact microstructure. The biodegradability of the clay reinforced bioplastics was significantly improved due to the bacterial proliferation. The thermal treatment of kaolinitic clay further improved the hydric and biodegradability properties of starch-based bioplastics.

Fabrication of kaolin hollow fibre membranes for bacteria removal

This study examines the influence of the particle size, extrusion rate and sintering temperature on the characteristics of kaolin hollow fibre membranes. In addition, the produced membranes were applied for bacteria removal from an aqueous suspension. The milling process reduced the size of kaolin particles from 8.7 to 5.1 ?m and greatly enhanced the morphology and mechanical resistance of the produced membranes. The increase in the sintering temperature up to 1250?C caused crystallographic phase modifications in the crude kaolin, which were mainly assigned to transformations of quartz and kaolinite to mullite and cristobalite phases. The fibres sintered at 1250?C have bending strength of 145MPa, but this relatively high sintering temperature caused a substantial particle densification and drastic decrease of the membrane water permeability. The kaolin hollow fibre membranes enabled almost total removal of the Enterobacter bacteria from an aqueous suspension.

Preliminary studies on hydrothermal synthesis of zeolite from Malaysian kaolinite clays

The use of kaolin as a source of silica and alumina for synthesis of zeolite has been widely reported with various compositions and processing routes. However, since kaolin is highly influenced by geological origin and geographical formation, coupled with the processing method, two different crude kaolin were obtained at various locations in Peninsular Malaysia to serve as precursor for synthesis of zeolite. Hydrothermal treatments were made at reasonable low temperature of 90°C in an oven. The synthesized product was then analyzed using X-ray diffraction and scanning electron microscopy, to evaluate the potentials of the process and the product. The outcome of the analysis suggested that the breaking down of the clay structure and the armophization process can improve raw material reactivity. However, the crystallinity and composition of the crude kaolin together with appropriate incubation time can greatly influence the synthesis process and the product.

Development of kaolin production, reserves and processing in the Czech Republic in 1999–2015

Abstract This paper aims to characterize and interpret the trends in reserves, resources, and in the mine production of crude kaolin and output of beneficiated kaolin between 1999 and 2015 in the Czech Republic. With nearly 1.2 billion tonnes of total resources, kaolin belongs to the key industrial minerals of the Czech Republic. With an annual output of about 3 to 4 million tonnes of crude kaolin and of around 0.6 million tonnes of beneficiated kaolin, the Czech Republic ranks among the top European and world kaolin producers. Mine production of crude kaolin has been relatively stable since 1997, while the output of beneficiated kaolin has been increasing gradually during the same period. The increased production and yield of beneficiated kaolin resulted from the use of progressive methods in kaolin processing, primarily high-intensity electromagnetic separation. The positive growth trend was not a reflection of the stability of the extractive sector and domestic industry, but it was the result of a pro-export orientation. The amount and share of exports are continuously increasing and constitute 80% of the entire kaolin production sector at the present time. The only exception occurred in 2005-2008, when exports declined by one-half as a result of the government´s export restrictions. The results of analyses were not optimistic for the Czech economy and indicated a sharp downturn in the domestic mining industry. Moreover, a similar situation exists in the case of other essential industrial minerals such as feldspar, clays, and silica sand.

Crude Kaolin Dissolution in the Absence and Presence of Sodium Poly(Acrylic Acid), Sodium Hexametaphosphate, and Sodium Silicate under Different Experimental Conditions

AbstractThe influence of anionic dispersing agents, such as sodium poly(acrylic acid), sodium hexametaphosphate, and sodium silicate on the dissolution of crude kaolin was examined by measuring the dissolved metals produced in the absence and presence of dispersing agents. For this purpose, the rheological and structural changes caused by the dissolution of kaolin metal constituents were studied in batch mode using several parameters, namely, solids (wt.%), pH, contact time (aging), and dispersing agent dose. A noteworthy increase in kaolin dissolution was caused by the presence of dispersing agents, particularly poly(acrylic acid) and sodium hexametaphosphate. These agents produced conspicuously large amounts of dissolved Al in comparison to the other experimental treatments. Little dissolved Si was measured under similar conditions in distilled water, but the amount of Si released using dispersing agents was nearly double that observed in distilled water only. Excess dispersing agents interacted with kaolin and dissolved accessory elements in the kaolin (i.e. Fe, Ca, Mg) and thus released enough Fe to form a stable Fe—dispersant complex. The present study showed that this phenomenon also contributed to a significant increase in the release of dissolved Al and Si through complexation.

Using Kaolin in Reduction of Arsenic in Rice Grains: Effect of Different Types of Kaolin, pH and Arsenic Complex.

Kaolin was used as a soil amendment to study the effect of different types of kaolin, pH and arsenic complex on arsenic accumulation in rice grains from arsenic (As) contaminated soil. It was found that kaolin released soluble aluminium (Al) and silicon at a pH value of 3. As adsorption by crude kaolin was higher than by washed kaolin and treated kaolin due to the higher Al content found in crude kaolin. Furthermore, the addition of 5 % (w/w) crude kaolin in the solution of As-contaminated soil was able to reduce water-soluble As in the solution. In mesocosm experiments, As accumulation in rice grain was not found under the addition of kaolin conditions. Scanning electron microscopy with energy dispersive X-ray spectroscopy study found the crystallinity of Al-As complex in plant roots. This implies that while kaolin adsorbs As from As-contaminated soil, rice plants also simultaneously take up As and Al into their cells. This caused the decrease in As accumulation in rice grain.

Experimental studies on the desorption of adsorbed sodium poly(acrylic acid) from crude kaolin particles

BackgroundThe controlled stability and fluidity of highly concentrated kaolin dispersion is a crucial problem when kaolin is used in industry due to the charge heterogeneity of its surface. To solve the common industrial problems of dispersions prepared at high solid loadings in terms of their rheological behavior, some organic and inorganic dispersing agents have to be added into the system to modify the particle surfaces. ObjectiveAdsorption and desorption behaviors of sodium poly(acrylic acid) (NaPAA) on the surface of kaolin particles were investigated to elucidate the adsorption mechanism of the PAA–kaolin dispersion system within the scope of the rheology and the colloidal stability. We also investigated the structural changes in the kaolin particles due to the extraction of Si4+ and Al3+ ions when a dispersing agent was used. MethodKaolin dispersions were prepared using NaPAA, and investigated in terms of the adsorption and desorption behaviors, the rheological and the electrokinetic properties and the extracted Al3+ and Si4+ ions from the particles. ResultsAs expected, PAA was strongly adsorbed on the positively charged alumina sites of the particles. According to the results obtained in the experiments of adsorption density, viscosity, ζ-potential and the dissolution of metal ion measurements for the adsorption/desorption, a strong and irreversible adsorption was observed between PAA and the surface of the kaolin surface, indicating the existence of unbreakable chemical bonds. This is due to the adsorption of negatively charged carboxylic acid groups (–COO−) from the PAA onto the positive alumina sites on the edges of the kaolin surface by electrostatic attraction. Due to the negative charge, no adsorption was observed on the silica surface of the particles within the working pH range of 5.3 to 8.4. ConclusionThe adsorption mechanism of PAA–kaolin interaction is attributed to chemical adsorption with the formation of chemical bonds between the charged carboxylic acid groups (–COO−) of the polymer and the alumina sites on the edges of the kaolin.

Beneficiation of Low Grade Kaolin by High Shear Agitation with Dispersant (HSD) Pre-Treatment for High Yield and Improved Fired Colour

Crude kaolin contains various amounts of discolouring elements such as anatase (TiO2), mica and iron oxide (Fe2O3), which give low brightness and are detrimental in use. In addition, the anatase (titaniferrous) and mica can also contain iron contaminants. Beneficiation of two crude low grade china clays, marked as KY and SR, was attempted through imitating existing industrial practice of levigation and hydrocyclone classification, and through an innovative technique of high shear agitation with dispersant (HSD) pre-treatment. HSD treated clays were subjected to impurity removal by sieving, demagnetizing and coarse/heavy impurity removal by sedimentation under gravity techniques. The results in terms of yield of clay (% on feed basis), grade of clay (kaolinite%) and effect of purified clays on the whiteness of porcelain were compared. It was found that by use of HSD pre-treatment, SR dump clay could be purified to contain 90.7% kaolinite and 0.75% free silica with a striking yield of 62.32% as compared to 88.90% kaolinite, 3.34% free silica and 30.2% only as yield by levigation and hydrocyclone. The KY dump clay was purified to contain 85.51% kaolinite and only 5.57% free silica with 44.3% yield by HSD pre-treatment as compared to 72.29% kaolinite, 16.29% free silica and 30.4% only as the yield by levigation and hydrocyclone classification. The kaolinite enrichment and removal of free silica to a major extent and chromophore impurities (although to a minor extent) in these dump clays after beneficiation rendered them suitable for polished vitrified porcelain tiles application as far as the development of white fired colour in the tiles body is concerned.

Polymer Partitioning Approach for Petroleum Hydrocarbon Reduction in a Clay Soil

Soil contamination by crude oil is a major environmental and health hazard. Extraction of the total petroleum hydrocarbons (TPH) sorbed to the clay soil (kaolin) was carried out using synthetic sorbent (Desmopan®) and 2-propanol as a mobilizing agent. The crude oil-loaded polymer beads were bioregenerated in a solid–liquid two-phase partitioning bioreactor (TPPB). A central composite design under response surface methodology was employed for the experimental design and analysis of the results. The independent variables were extraction phase to soil ratio, mobilizing agent to soil ratio, and initial concentration of crude oil in polluted soil. The influences of three independent variables on the TPH reduction efficiency were determined using a statistically significant quadratic model (R 2 = 0.9673). Remediation was more efficient when the mobilizing agent to the soil ratio was equal to 3.00 ml g−1, compared to the higher (4.00 ml g−1) and lower (2.00 ml g−1) levels. The results exhibited that the interaction between the extraction phase ratio and the initial concentration of crude oil in kaolin had significantly influenced the TPH removal. The bioregeneration studies showed a significant reduction (72.07 ± 0.63 %) of low-molecular-weight (two- to three-ring) polycyclic aromatic hydrocarbons and n-alkanes (97.75 ± 0.26 %) present in the crude oil-loaded solid polymers within a 10-day experiment. These findings show that solid polymer extraction followed by bioregeneration of sorbents in a TPPB is applicable to treat crude oil-contaminated kaolin.

Clinker brick based on crude kaolin and sludges from alkali etching

It is shown that sludges due to alkali etching and used as a grog additive in ceramic mixes based on crude kaolin clay make it possible to obtain clinker articles of high quality.

Elaboration and characterization of a refractory based on Algerian kaolin

A refractory material was elaborated from kaolin extracted from the region of Djebel Debbagh (Algeria). Kaolin grog was obtained by calcination at a temperature of 1350 °C during 1 h. It was used as aggregates with granulometric distribution composed of fine fraction (mean grain size: 100–250 μm) and coarse fraction (mean grain size: 1000–2500 μm). Crude kaolin (size < 75 μm) was also used as a binder with an amount representing 15% of the dry material. After a 9.28% moistening and a rotting of 1 day, cylindrical samples were shaped by uniaxial pressure at 80 MPa. The samples were submitted to a natural drying during 24 h, a stoving at 100 °C and a calcination at 600 °C during 1 h. They were fired at high temperatures between 1250 and 1450 °C. An X-ray diffraction (XRD) analysis showed that the refractory samples are composed of mullite and silica. Silica is a mixture of a vitreous phase and cristobalite at 1300, 1350 and 1400 °C and becomes completely amorphous when the samples are fired at higher temperature (1450 °C). The sample porosity is about 30%. The mechanical tests carried out as a function of temperature revealed different behaviours of the material. From the ambient up to 600 °C, the refractory behaviour is pseudo-plastic caused by micro-cracking. Between 700 and 900 °C, the samples become more rigid. At 1000 °C, the material exhibits a visco-plastic behaviour. The amorphous phase governs the sample properties variation with temperature increasing. Its content varies between 28% and 34% according to the firing temperature. Thermal shock tests realized in water showed that the refractory samples present good thermal shock resistance.

Influence of dispersing agents and solution conditions on the solubility of crude kaolin

Experiments measuring the solubility of kaolin particles in terms of the concentration of aluminum and silicon ions in supernatant were carried out as a function of the pH of the slurry over a wide range of dosages of different dispersing agents varying from 0.5 to 12 mg/(g solids). The concentrations of the metal ions in supernatant were found to be strongly affected by the type and the dosage of the dispersants and pH of the solution. In this study, the mechanism of the reaction between the dispersing agents and kaolin particles was studied and the dissolution capacities of metal ions (aluminum and silicon) were identified from kaolin particles in the absence and presence of dispersing agents. The three anionic dispersing agents used were sodium polyacrylate (Na-PAA), sodium hexametaphosphate (Na-HMP), and sodium silicate (Na-silicate), based on the industrial application of these agents and their ability to produce a stable dispersion for this purpose.

Effects of process variables and their interactions on solubility of metal ions from crude kaolin particles: results of a statistical design of experiments

Solubility of metal ions from kaolin particles was investigated in the presence of three different anionic dispersing agents [sodium salt of polyacrylic acid (NaPAA), sodium hexametaphosphate (NaHMP), and sodium silicate (Na-silicate)] by conducting statistically designed experiments based on Box Behnken method. Quadratic response model was used to: (1) study the relationship between the concentration of metal ions as the measured response to the input variables, which consist of wt.% solids, pH, time (aging), and dispersant dosage; and (2) find predictive models for the concentration of metal ions as a function of the above-mentioned input variables. Results indicate that both pH of the slurry and the dosage of the dispersing agent used to prepare the suspension significantly affect the concentration of metal ions in supernatant. When dispersing agents were added to the system, there was a significant increase in the concentration of metal ions in supernatant particularly in the presence of NaPAA and NaHMP. Results are presented and discussed.

THE USE OF KAOLIN TO REMOVE DIPHTHERIA BACILLI FROM THE NOSE AND THROAT

In a preliminary note, 1 the use of kaolin to remove bacteria from the nose and throat was suggested on the basis that kaolin by means of its adsorptive property would carry with it bacteria with which it came in contact. Since this report, a study has been made of this method in 100 unselected cases, ninety-six being diphtheria patients and four diphtheria carriers. By pure diphtheria carriers is meant a person with diphtheria bacilli in the nose or throat, who yields no history of sore throat or other symptom of diphtheria, and who gives a negative Schick test. The method of the application of kaolin is as follows: As crude kaolin, which is moist and lumpy, has not the adsorptive power of the thoroughly dried and finely powdered product, the crude material is first thoroughly dried for several days in a bacteriologic incubator. The lumps are then broken