Raw Kaolin Research Articles

Properties of hybrid cementitious composite with metakaolin, nanosilica and epoxy

The compressive strength and durability potentials of hybrid cementitious composites (HCC) that contain metakaolin (MK), produced in the laboratory using raw kaolin, nanosilica and epoxy resin was the main focus of this research study. The HCC specimens contain 10% metakaolin (MK), 1% colloidal nanosilica (CNS) and 1% epoxy resins and the specimens were examined for early ages of 7, 28, and 90days of exposure in both water and seawater. The durability properties investigated in this research study comprise of water absorption, intrinsic air permeability, chloride penetration and porosity. All tests were conducted to assess the influence of MK, CNS and epoxy on the compressive strength and the durability properties of the HCC specimens. The result showed that HCC specimens with 10% MK, 1% CNS was durable relative to all the properties. Nevertheless, the addition of both natural fibers (coconut and oil palm fruit bunch fibers) and synthetic fiber (bar chip fiber) has a slight negative impact on the durability properties of HCC specimens. Conclusively, the results showed that the menace of water, liquid and gas transportation by water absorption, capillary suction, porosity, chloride penetration, and intrinsic air permeability of HCC were lesser than that of control specimen.

Preparation of mullite whiskers from kaolin via the addition of tribasic calcium phosphate

AbstractMullite whiskers are potential candidates for improving the mechanical and thermal properties of ceramic, glass, and composite material. In this work, well‐developed whisker‐shaped mullite has been produced by adding tribasic calcium phosphate (Ca3(PO4)2) into kaolin before calcining in air. In the raw kaolin, rod‐like mullite crystal of ~0.5‐1.0 μm length and ~0.05‐0.2 μm diameter formed at 1350°C, and mullite whiskers were not be observed; however, by doping 6 wt% Ca3(PO4)2 into kaolin, mullite whiskers of ~5.5 μm length and ~0.05‐0.10 μm diameter grew at 1250°C. The formation of high aspect ratio of mullite whiskers can probably be explained by the synergistic effect of P2O5 and CaO, resulting in the formation of liquid phase with a relatively higher content of Si and a lower viscosity at low temperature of 1250°C, which facilitates the growth of mullite displaying acicular morphology. The results are of interest in producing high aspect ratio of mullite whiskers from kaolin at reduced calcination temperatures.

Synthesis of zeolite A using raw kaolin from Ethiopia and its application in removal of Cr(III) from tannery wastewater

AbstractBACKGROUNDThe commercial production of zeolite A mainly involves costly synthetic chemicals. However, cheaper raw materials such as clay minerals, coal ashes, natural zeolites, solid wastes and industrial sludge have been tested. Based on this, the objective of the present study is synthesis of zeolite A from two sources of raw kaolins (Ansho and Bombowha) from Ethiopia and evaluation of its application in tannery wastewater treatment.RESULTSThe synthesis result indicated high crystallinity (>90%) of zeolite A using Ansho kaolin. Lower grade Bombowha kaolin yielded zeolite A with crystallinity of 80%. In the tannery wastewater treatment study, a real sample having chromium concentration of 2036 mg L−1 was treated, obtaining 99.8% removal and about 200 mg g−1 adsorption capacity of Cr(III) using 100 g L−1 and 5 g L−1 adsorbent dose, respectively. This indicated that the synthesized zeolite A has great potential for Cr(III) removal from tannery wastewater.CONCLUSIONIn this study, zeolite A has been synthesized from two sources of kaolin from Ethiopia and has been evaluated in tannery wastewater treatment. The synthesis result indicated the formation of crystals of zeolite A with optimum crystallinity of 91% and the material exhibited chromium removal efficiency of 99.8%. © 2017 Society of Chemical Industry

Use of Brazilian Kaolin as a Potential Low-cost Adsorbent for the Removal of Malachite Green from Colored Effluents

This study investigated the potential of Brazilian kaolin as a low-cost adsorbent for the removal of Malachite Green (MG) from colored effluents. The morphology, chemical structure and surface properties of the adsorbent were investigated by characterization techniques such as X-ray diffraction, N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray fluorescence spectrometry, scanning electron microscopy, thermogravimetric analysis and particle size distribution. A possible technological application of raw kaolin is the MG removal from aqueous media, which was investigated using batch adsorption experiments. The adsorption kinetics was studied using the pseudo-first order, pseudo-second order and Elovich models. The adsorption isotherms were studied using the Langmuir, Freundlich and Sips models. The Elovich model was the more adequate to represent the adsorption kinetic, while the equilibrium was well represented by the Langmuir model. The maximum adsorption capacity, at pH of 6.3 and temperature of 25oC, was 128 mg g-1, and this satisfactory result may be associated with some adsorbent properties. Therefore, the results revealed that raw kaolin can be utilized as a promising low-cost adsorbent to remove MG from colored effluents.

Removal of organic carbon in coal-series kaolin using gravity separation

ABSTRACTCoal-series kaolin, a precious associated nonmetal mineral in coal mines, shows high industrial value. However, it usually contains organic carbon and a small amount of impurities including iron and titanium elements, which seriously decrease the whiteness of final kaolin products. In this investigation, gravity separation method was adopted to remove organic carbon from coal-series kaolin (decarbonized kaolin) based on the differences in density. It was found that compared with the raw kaolin, the loss on ignition (LOI) of decarbonized kaolin was decreased by 44.22%, and the contents of Fe2O3 and TiO2 were also decreased by 48.57% and 59.57%, respectively. The decarbonized kaolin was of high purity, and the whiteness of the decarbonized kaolin was much higher than that of the raw kaolin. The organic carbon separated from the coal-series kaolin can also be used in various ways depending on its coal rank and quality, which avoids the waste of coal resources. The coal-series kaolin can obtain a better use after removing the organic carbon using the gravity separation.

Iron removal from kaolin using thiourea dioxide: Effect of ball grinding and mechanism analysis

This study reports a series of experiments conducted to evaluate the suitability of thiourea dioxide (TD) under ball grinding, in leaching out iron-bearing impurities from two raw kaolin samples. The bleaching mechanism of kaolin was investigated. The results show that the combined application of ball grinding (at 400rpm) and AlCl3 (0.5wt%) could give the highest bleaching efficiency, wherein the Fe2O3 content decreased from 1.34% to 0.76% for Beihai kaolin, and 2.05% to 1.42% for Xingzi kaolin, corresponding to an increase of 4.98 and 12.12 percentage points, respectively. The values are acceptable in the ceramics industry. Through ball milling, the intrinsic stratiform structure of the kaolinite was gradually destroyed, the resultant particles became finer, and specific surface area was increased. The Al3+ ions added could fill the vacancy of Fe3+ on the kaolinite lattice, promoting the leaching out of Fe3+. The results obtained from X-ray energy-dispersive spectroscopy and X-ray fluorescence spectroscopy conform well to the theoretical analysis.

Refinement of industrial kaolin by removal of iron-bearing impurities using thiourea dioxide under mechanical activation

This study reports a series of experiments conducted to evaluate the suitability of thiourea dioxide (TD) under mechanical activation, in bleaching iron-bearing impurities from raw kaolin. The optimum conditions for the maximum whiteness of 76.32% were determined as follows: rotation speed of ball mill, 400rpm; activation time, 1.5h; TD dosage, 0.8% of kaolin mass; solid-to-liquid ratio, 1:2; pH, 8.0; room temperature. The effect of grinding causes the partial surface amorphization of kaolin particles and a decrease in the dehydroxylation temperature. The assistance of grinding leads to a higher iron removal when compared with the conventional bleaching method using sodium hydrosulfite.

RADIOLOGICAL IMPACTS ASSESSMENT FOR WORKERS IN CERAMIC INDUSTRY IN SERBIA.

Studies have been carried out to determine the natural radioactivity in some materials used in ceramic industry (zircon, zirkosil, Zircobit MO/S, zircon silicate, zirklonil frit, hematite, bentonite, wollastonite, raw kaolin, kaolinized granite, sileks ball, feldspar, pigment, white base serigraphic, engobe) and their associated radiation hazard. The external hazard index, Hex, values, radium equivalent activity, Raeq, total absorbed dose rates, D and annual effective dose, De were derived for all measured materials and compared with the recommended values to assess the external radiation hazards to workers who worked in ceramic industries in Serbia.

Optimization of modification condition of nano-kaoline as an adsorbent for textile dye removal

In this study, adsorption capacity of textile red dye on alkylated kaolin was investigated through batch mode. Accordingly, raw kaolin was alkylated via NaOH treatment. The work was carried out in two steps. At first step, the effect of various alkylation conditions of kaolin on its dye adsorption performance was studied using the model equation designed by 2-level factorial design. Three factors were changed in two level including NaOH solution temperature (45–75°C), mixing time (3–24 h), and NaOH solution concentration (0.1–2 M). The resultant model showed 91% of the variability in data used to fit dye adsorption capacity values. However, the analysis of variance revealed that the fitted model is high significant. Based on the predicting model, the optimal alkylation conditions with desirability factor of 0.911 were obtained at temperature of 75°C, NaOH concentration of 0.1 M and after 24 h mixing. At step two, chemical content, bonds and functional groups of the treated kaolin, which was prepared based on the optimum condition and compared with the raw kaolin via X-ray fluorescence (XRF) analysis and Fourier transform infrared analysis (FTIR). The results show slight reduction in SiO2 content. Finally, the adsorption capacity of dye on both treated and raw kaolin was investigated.

Viscosity of kaolin slurries: Effects of dispersant and urea-intercalation

Good fluidity (low viscosity) of highly concentrated kaolin is highly needed in paper-coating industry. We put forward an effective route to improve the viscosity concentration of Beihai kaolin slurries. The effects of various factors such as solid content, pH, dispersant content, and urea-intercalation on the viscosity of kaolin slurries were investigated. The results revealed that the viscosity of kaolin slurries significantly decreased with decreasing solid content or with increasing pH and dispersant content. It was worth noting that urea-intercalation was proven to be an efficient method for promoting the dispersion of highly concentrated kaolin as compared with adding dispersant. The intercalation ratio of urea-intercalated kaolin was increased from 17.36% with 2% of urea addition to 81.30% with 6% of urea addition. Meanwhile, the viscosity concentration of raw kaolin slurry was improved from 65.0% to 70.13% after the intercalation of urea with 6% addition, which was attributed to finer particle size, increased pH value and more negative charges of urea-intercalated kaolin. Therefore, the route is effective to improve the dispersion of highly concentrated kaolin for paper-coating.

Improvement adsorption capacity of methylene blue onto modified Tamazert kaolin

In this study, three adsorbents were prepared with the raw kaolin issued from the Tamazert region in Algeria (Tamazert kaolin (KT)), for the removal of basic dye methylene blue (MB) from aqueous solutions. The first absorbent, KT-1, was obtained by thermal treatment; the second, KT-2, was obtained by thermal followed by acid treatment; and the third, KT-3, was obtained by thermal followed by acid and alkaline treatments. These adsorbents were characterized by powder X ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area, and scanning electron microscopy. Adsorption equilibrium isotherms of MB were correlated with common isotherm equations such as Langmuir and Freundlich models. The modified kaolins (KT-1, KT-2, and KT-3) showed different capacities of the equilibrium adsorption in comparison with raw kaolin (KT). The maximal adsorption capacity (111 mg g−1) was observed with modified kaolin (KT-3). The effect of operating parameters such as the initial dye concentr...

Improved sodium adsorption by modified kaolinite at high temperature using intercalation-exfoliation method

Kaolin is one of the most widely used additives to alleviate fouling and slagging problems, which often occurred on the boilers burning coal with high sodium content. In order to improve the adsorption capacity in this condition, the intercalation-exfoliation method in material field was applied to modify kaolin. Six representative intercalation agents were selected to prepare samples, including hydrazine, urea, potassium acetate, formamide, methylformamide and dimethyl sulfoxide. Experimental results showed that both of pore volume and pore diameter were expanded through modification, which is beneficial to adsorption in physical aspect. On the other hand, the reduction of mass loss rate (from 10.6% to 6.8%), i.e. the loss of hydroxyl groups during modification process was verified, which contributed to sodium-capturing through providing more available adsorption sites. There was little difference between raw kaolin and modified kaolin with regard to XRD patterns, suggesting that the main crystal structure of kaolin remained after modification. Sodium reacted with modified kaolinite to form nepheline during adsorption process, realizing its chemical fixation. It is concluded that intercalation-exfoliation method is capable of improving the sodium-capturing capacity of kaolin at high temperature. Kaolin intercalated with potassium acetate has the most significant sodium-capturing capacity, which increased from 77mg/g to 100mg/g, with the adsorption efficiency reaching 100%.

The effect of citric acid on the kaolin activation and mullite formation

The mullite phase in porcelain is important to the porcelain strength; however, its formation from clay minerals usually requires high temperature. Here we found that the activation of kaolin by citric acid would lower the formation temperature of mullite phase to 935.1°C, which is 67.5°C lower than that for the raw kaolin. Needle-like mullite crystal, a desired crystal shape in kaolin, could be observed in activated kaolin at 1050°C. The reduction of mullite formation temperature is due mainly to the surface change in kaolin. Upon citric acid activation, the pseudohexagonal platelets of kaolinite crystal are disintegrated to non-uniform flakes, and the specific surface area increases from 8.18m2/g to 31.21m2/g, both leading to improved activity of kaolin and increased sintering driving force. The results are of interest in producing high-strength porcelain at reduced sintering temperatures and consequent energy saving for sintering process.

Immobilization of Candida antarctica lipase B on kaolin and its application in synthesis of lipophilic antioxidants

Lipase B from Candida antarctica was immobilized by adsorption onto laboratory prepared metakaolin. This support has great potential for enzyme immobilization since it has good mechanical characteristics and thermal stability and it is easily obtained from naturally abundant raw kaolin, as presented in this paper. Immobilization process was studied as a function of pH, ionic strength and protein concentration in terms of immobilization and activity yield. It was shown that immobilization occurred via the Langmuir model, and that electrostatic forces were major, but not exclusive contributor for the binding process. The optimum conditions were achieved in 10mM acetic buffer pH5. Biocatalyst obtained under optimum conditions was further successfully used in the synthesis of lipophilic antioxidants, where conversion yields as high as 100% were achieved.

Kinetic studies of the dehydroxylation and crystallization of raw kaolinite and fluorides-modified kaolinite

The effect of some fluoro compounds on the dehydroxylation and crystallization of kaolinite was investigated using thermal analysis. Samples were prepared starting from the raw kaolin (K-0) by adding 1 mass% fluorine, introduced as LiF (K-Li), NaF (K-Na) and CaF2 (K-Ca), respectively. The results show that the peak temperatures of the dehydroxylation process are less influenced by the fluorides presence, whilst the peak temperatures of the crystallization process decrease in the presence of fluorides, which confirm the mineralizer effect of fluorides on the crystallization process. The activation energies of the dehydroxylation and crystallization processes were calculated using the isoconversional methods described by Kissinger–Akahira–Sunose and Vyazovkin. For the dehydroxylation process, the values of the activation energy calculated as a function of the conversion extent are not significantly influenced by the fluorides presence. For the crystallization process, all the samples with fluorides show values of the activation energy higher than those of the sample without fluorides on the entire range of the conversion extent.

Beneficiation of Kaolins by Hydrocycloning

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.

Conventional versus alkali fusion synthesis of zeolite A from low grade kaolin

Synthesis of zeolite A using low grade Bombowha kaolin from Ethiopia has been carried out by two methods: the conventional hydrothermal synthesis and alkali fusion followed by hydrothermal treatment. In the synthesis process, the metakaolinization was achieved by calcination of the kaolin at 600°C for 3h for the conventional method and for the alkali fusion method, the activation of the raw kaolin was done by alkali fusion for only 1h. Zeolite A was the main product obtained using 3M NaOH concentration, 100°C reaction temperature and 3h crystallization time in both methods. The molar gel composition for the best synthesis conditions for both methods was Na2O: Al2O3: 2SiO2: 37H2O. The main advantage of the alkali fusion method is that it allows using a low grade virgin kaolin without purification, whereas the conventional method only yields good quality zeolite A when the raw kaolin is purified. The starting raw kaolin, metakaolin and synthetic products were characterized by X-ray diffraction (XRD), ICP-OES elemental analyses, Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and Cation Exchange Capacity (CEC). Cubic crystals with rounded edges of zeolite A having crystallinity of about 85% and Cation Exchange Capacity of 300mg CaCO3/g of anhydrous zeolite was achieved by the alkali fusion method of synthesis using raw, virgin Bombowha kaolin.

Mussel inspired preparation of amine-functionalized Kaolin for effective removal of heavy metal ions

Adsorption has been well regarded as a promising and efficient method for the removal of low concentration heavy metal ions in aqueous solutions. And kaolin has been considered as a kind of low cost and environment-friendly adsorbent for its abundant in nature. But the low adsorption capacity to heavy metal ions and severe aggregation in solution restrains its application. In this work, an environment-friendly adsorbent (denoted as Kaolin-PDA-PEI) was prepared based on mussel inspired chemistry and Michael addition reaction between high reaction activity of polydopamine (PDA) and polyethyleneimine (PEI), which was possesses a number of amine groups. The amine groups have displayed strong adsorption affinity towards copper ions. The successful modification of Kaolin by PDA and PEI was confirmed by a series of analyses, such as Fourier transform infrared spectroscopy, transmission electron microscopy, thermal gravimetry analysis and X-ray photoelectron spectroscopy. The effects of various parameters such as contact time, pH, initial concentrations of copper ions and temperature on copper ion adsorption by Kaolin-PDA-PEI were investigated. Kaolin-PDA-PEI shows higher adsorption capacity as compared with the raw Kaolin. The kinetic adsorption data were analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion model. The Langmuir isotherm and Freundlich isotherm equilibrium model were applied to adsorption isotherm data to find the better fit isotherm. The results showed that adsorption process was well fitted by Langmuir isotherm model. The values of thermodynamics constants such as entropy change (ΔS0), enthalpy change (ΔH0) and Gibbs free energy (ΔG0) were also calculated. The results indicated that the adsorption process of Kaolin-PDA-PEI were endothermic and spontaneous.

Enhanced removal capability of kaolin toward methylene blue by mussel-inspired functionalization

Adsorption is an effective and commonly adopted method for removal of organic pollutants from environment. In this work, we described the synthesis and the adsorption behavior of poly(sodium p-styrenesulfonate hydrate) (PSPSH)-modified kaolin, which was obtained by combination of mussel-inspired chemistry and Michael addition reaction. The amino-terminated PSPSH was synthesized by free radical polymerization using cysteamine hydrochloride as the chain transfer agent and sodium p-styrenesulfonate hydrate as the monomer. Raw kaolin and PSPSH-modified kaolin were characterized using several techniques including transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and X-ray photoelectron spectroscopy in detail. The adsorption of methylene blue onto modified kaolin from aqueous solution was investigated, in which the effects of contact time, temperature, solution pH, and initial methylene blue concentration were studied. The experiment data were analyzed using two common adsorption models: Langmuir and Freundlich isotherm models. The kinetic adsorption data were analyzed using pseudo-first-order, pseudo-second-order, and intraparticle diffusion model. The values of thermodynamics constants such as entropy change (ΔS 0), enthalpy change (ΔH 0) and Gibbs free energy (ΔG 0) were also determined. The modified kaolin showed favorable dispersibility and convenient separation, high efficiency, and good regeneration capability in the removal of methylene blue from solution.

Synthesis of Zeolite Na-A from Local Kaolin for Bioethanol Purification

Background/Objectives: Malaysia has abundant resources of kaolin. Currently, the kaolin industries are not able to attract large companies to mining due to lower price. An alternative method to increase the price of the local kaolin is by converting it to the zeolite. The zeolite of the type Na-A can be used to dehydrate ethanol water mixture during production of bioethanol. In this study,mesoporous silica Na-A zeolite was synthesized from local clay which obtained from Perak. Methods/Statistical Analysis: The raw kaolin was pretreatedby using sodium metaphosphate to remove impurities and activated at 800oC for 5 hours. By using the hydrothermal method, zeolite Na-A was synthesized by using NaOH as the activator. The mesoporous materials obtained were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analysis. Findings: The prepared materials showed a superior ability to adsorb water (H2O) from azeotrope water-ethanol mixture. From the water adsorption test, the average H2O adsorption capacity was 70mg H2O/g adsorbent. This value was almost twice the adsorption capacity of commercial zeolite 3A. Zeolite Na-A was the main product with quartz presences as minor impurities which was confirmed by XRD, FTIR and SEM analysis. Applications/Improvements: The local kaolin can be used to synthesize the zeolite Na-A by using a hydrothermal reaction method. This new application may increase the value of local kaolin.