Papers by Keyword: Kaolinite

Abstract: The mineral mullite has many outstanding refractory properties. The content of aluminum oxide in the raw material is the basic factor influencing the content of mullite in the final product. Depending on Al₂O₃ content, silica-alumina materials can be divided into fireclay and high-alumina with the Al₂O₃ content of 45 % and more. The study describes the influence of raw material, the influence of homogenization of raw material and influence of firing temperature on the mullite formation in fireclay refractory material. Three kinds of refractory clay with different chemical composition were used as raw material for fireclay grog production. Three kinds of homogenization and three different temperatures were studied as factors influencing mullite formation. Powder X-ray diffraction was used to determine mullite content in material. Quantitative phase analysis was conducted by the Rietveld method. Mullite crystals morphology was observed by scanning electron microscopy.

Abstract: The research aimed to investigate the effect of calcium hydroxide content on pozzolanic reaction of calcined clays. Pozzolanic reaction of calcined clay was determined in terms of its mechanical properties, phase development and microstructures. Three clay minerals (two kaolinitic clays and kaolinite-montmorillonite clay) were chosen to produce pozzolanic materials via calcination at temperature of 700 °C to allow dehydroxylation of clay minerals. Ratios of calcium hydroxide to calcined clays were varied from 0.1 to 0.5. Mixing water contents or liquid to solid ratios (0.62, 0.75 and 0.80) and curing times (7 and 28 days) were also studied. It was found that calcium aluminosilicate hydrate (stratlingite) could be formed after pozzolanic reactions of all clay minerals. The development of stratlingite agreed with the strength development showing the highest compressive strength at 26 MPa (28 days) when kaolinite-montmorillonite clay was used as pozzolanic material and the ratio of calcium hydroxide to calcined clay was 0.5.

Abstract: Cracking, shrinkage, and curling of soils, in general, take place due to drying. These deformations lead to many problems include the development of main paths for water flow and pollutant transport, reduction of soil strength (and impact on other mechanical properties of soils), erosion in slopes, landslides, increase infiltration capacity of the soil and the differential settlement problems. Few studies have investigated the effect of wetting-drying (W-D) cycles on desiccation cracks of soils. The effect of multiple wetting-drying cycles in the cracking behavior was investigated in this research by performing several wetting-drying (W-D) cycles on the initially saturated samples (of pure kaolinite and a mixture of kaolinite with bentonite) under the lab atmosphere (24 ± 1 °C, and 52 ± 2% of RH). The weight of each sample was monitored using a computerized scale (with an accuracy of 0.01 g) connected to the computer. During the test, the water evaporation path with the development of surface cracks and volume shrinkage was monitored by means of digital images. It was observed that the crack patterns changed during the initial cycles, but there was an equilibrium state in the third and fourth W-D cycles. Additionally, it was observed that the main cracks formed in the first dry path were virtually closed after 10 minutes of the second wetting path; in the meantime, small cracks (fissures) were initiated after this wetting process. It was, also, detected that soils with high plasticity required more W-D cycles to reach the equilibrium condition than soils with low plasticity. The results of these experiments are useful for understanding the effect of different seasons on soil behavior.

Abstract: Alum is a useful product in both leather tanning and water treatment purposes where it serves as a coagulant and disinfectant. High quality alum has recently been produced from some Nigerian kaolinite (Bauchi and Kankara) via the energy-saving process. This process utilizes the heat generated when sulfuric acid is mixed with water to dealuminate the metakaolin, instead of the usual application of external heat source. This study focuses on testing their effectiveness in actual water treatment process in comparison with a commercial alum. Several parameters of the raw water and 50 to 300 ppm of alum-raw water solution were measured to determine the effects of the alum addition. The influence of both alums was found to be strikingly similar. While the total dissolved solids (TDS) and conductivity increased with alum concentration, the biological oxygen demand (BOD), chemical oxygen demand (COD), and alkalinity of the water showed reduction. The coagulating effectiveness of both alums was demonstrated by over 95% reduction in the turbidity of the raw water sample. The results also revealed that the alum from Nigerian kaolinites showed remarkable and desirable water treatment qualities and compares well with the commercial alum for all the tested parameters. The development of alum production plant using Nigerian kaolinite is therefore recommended as it can serve as alternative to the present commercial alum that is majorly imported.

Abstract: Mixing of nano-sized powders with soils (macro-sized powders) is a noteworthy issue for geotechnical projects. Thus, this study examined the horizontal ball mill mixing of nano-copper oxide with kaolinite. Ball milling parameters (rotation speed, weight ratio of balls to powder and milling time) of the planetary ball milling were optimized for proper mixing of nano-copper oxide and kaolinite powder. Results showed that increase in mixing time decreased the agglomeration of nano-copper powders and kaolinite and increased the homogeneity of nano-copper powder with kaolinite particles. The quality of mixing was assessed through intensity and scale of segregation using concentration data obtained through energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses. It was observed through these two tests that, increase in ball milling time after 6 hours resulted in grain size reduction. Field emission scanning electron microscopy analysis showed that nano-coppers were regularly found on the surface of kaolinite particles after 6 hrs. of horizontal milling at 4:1 ratio of balls to powder mixture. Furthermore, 24 hrs. mixing resulted in grinding of kaolinite particles and hence their size was reduced. Particle size analysis confirmed these results, as the highest size span value of 3.417 was observed after 6 hrs. milling with speed of 200 rpm.

Abstract: Mesoporous boehmite (γ-AlOOH) was synthesized from naturally occurring coal-bearing kaolinite (CBK) by direct sulfuric acid leaching and hydrothermal method to explore a new possible route to the synthesis of product with high value added using the CBK. The Brunauner-Emmett-Teller (BET) surface area and the average crystallite size of the γ-AlOOH powder could be controlled in the range from 6.3 to 192.5 m² g^-1 and from 5.5 to 14.4 nm, respectively, by varying the reaction temperature and reaction time. Owing to its porous structure and high surface area, the synthesized mesoporous γ-AlOOH powder exhibited better adsorption abilities for CR and fluoride in contrast to commercial boehmite, and it only took 20 min to reach removal efficiency of 99.6% for CR and 90.5% for fluoride, when the initial concentration of CR and fluoride was 100 and 10 mg L^-1, respectively.

Abstract: In this article the results of research to develop energy - and resource-saving technologies of production on local raw material base of the Ural Federal district of the white portland cement with high performance are represented. An x-ray phase analysis of the obtained building material is performed. The possibility of obtaining white portland cement-based pyrophillite mining waste,the composition of the raw mix for high-temperature synthesis of clinker white portland cement at low temperatures was studied. This reduces the costs for grinding of the mixture, and firing the clinker. The result of this work was the experimental batch of cement and studied all of its construction and technical characteristics.

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: Polymer nanocomposites using natural clays such as nanofiller have mechanical properties, flame-retardant, the gas barrier improvement compared to polymers without nanoclay. The aim of this work is intercalated molecules between the clay layers and characterize it with a view to its use in polymer nanocomposites. The kaolinite neat and modified used was characterized by fourier transform spectroscopy (FTIR), X-ray diffraction (XDR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetry (TGA). The results showed that kaolinite can be used as a nanofiller in polymer nanocomposites.

Abstract: The effect of milling on structure of kaolinite-urea intercalates were studied. Untreated and treated kaolinite samples were examined by Field scanning electron microscopy (FESEM), X-ray powder diffraction (XRPD) and Fourier transform infrared (FT-IR) spectroscopy. The basal spacing of kaolinite measured by X-ray powder diffraction (XRPD) increased from 1.02 to 3.62 nm after intercalation by urea. Significantly, nature of intercalation was reached through formation of hydrogen bonds between urea and both Si-O and AlOH groups of the interlayer surface of kaolinite.