Particle Size Of Kaolin Research Articles

Effect of Calcination Processes on the Crystallite Size, Grain Size and Particle Size of Water-Washed Kaolin Particles

Sustainable kaolin particles can be used as supplementary cementitious materials in the construction industry, helping to achieve the goal of promoting sustainability. To achieve it, kaolin particles must be calcined in order to change into the most reactive form of metakaolin. However, calcination processes can influence the crystallite, grain, and particle size of kaolin, affecting its reactivity degree. In this study, water-washed kaolin particles were calcined by using a general purpose furnace at various calcination processes (temperatures = 600°C, 700°C and 800°C, duration = 3 h and 4 h, and heating rate = 10°C/min). The effects of calcination processes to the crystallite, grain, and particle size of kaolin particles were investigated. The crystallite size was computed by using the Scherrer equation, the grain size was measured by using ImageJ software, and the particle size was determined using the Zetasizer particle size analyzer. The size of the crystallite increased from 302.94 nm to 680.93 nm, while the temperature was elevated from 600°C to 800°C for 3 h to 4 h. Similarly, as calcination temperatures and duration increased, the average grain size increased from 580.15 nm to 843.19 nm. Meanwhile, as calcination temperatures and duration increased, the average particle size increased from 4168.88 nm to 4295.35 nm. It can be seen that the gap value showed only a very slightly increase with increasing calcination processes in the crystallite, grain, and particle size of kaolin particles. However, this increased sizing can reduce the degree of pozzolanic reactivity of the kaolin particles.

Research on the Tribological Properties of Layered Kaolin Lubricant Additives

Lubricant additives are the main means to improve the performance of lubricants. In this article, green and inexpensive layered kaolin were selected as lubricant additives, and the effects of the type of modifier, concentration, particle size of kaolin additives, and working temperatures on the tribological performance of lubricants were investigated. The results showed that the Span80 modifier can effectively improve the dispersibility and friction reduction effects of kaolin oil samples. Compared with kaolin oil samples without the modifier, the modified kaolin oil can reduce the friction coefficient by 40.9% and the wear spot diameter of the steel balls by 43.8%. The layered kaolin additive can significantly reduce the friction coefficient and wear of steel balls in lubrication, and the friction coefficient showed a trend of decreasing and then increasing with increasing kaolin additive concentration and particle size. The optimal added concentration and particle size of kaolin are 5 wt% and 2 μm, respectively, which can reduce the friction coefficient by 41.9% and 65.63% and the wear spot diameter by 12.31% and 50.72%, respectively, compared with the base oil. At five temperatures, compared with the base oil, the kaolin oil samples all showed better friction reduction and anti-wear properties. The micro and nano size of the kaolin additive, the layered structure, and the chemically reactive film generated on the surface are the main reasons for its good lubrication performance.

Straight synthesis of α and γ alumina from kaolin by HCl acid leaching

In this work the preparation of alumina from kaolinite by leaching with hydrochloric acid is studied. Crude kaolin was calcined at 850?C and then leached with 6 M hydrochloric acid at 90?C. Aluminum hydroxide was precipitated by adding 6 M HCl solution to the leaching water. Finally, the precipitated aluminum hydroxide was heated at 1100?C and converted to aluminum oxide. The materials were identified by XRF, XRD and SEM-EDX techniques. The percentage of alumina recovery was determined at different kaolin particle sizes (?200 to ?400 standard Tyler sieve), different times (1, 2, 3 and 4 h), different leaching temperatures (80, 90, 100 and 104?C) and different concentrations of hydrochloric acid (20, 25, 30 and 37%). The phase changes of alumina were also investigated at two calcination temperatures (1100 and 1200?C). The purity of aluminum oxide obtained by this method is about 97% and the percentage of recovery is about 98%. It was observed that the kaolin granulation with dimensions smaller than 75 ?m had no significant effect on the percentage of alumina recovery. It was also found that the percentage of alumina recovery increased with increasing leaching temperature.

Modeling Potassium Capture by Aluminosilicate, Part 1: Kaolin

Additives rich in Si and Al such as kaolin may be applied in PF biomass boilers to fix alkali metals in species that are more benign than the alkali salts released in biomass combustion. In this study, models for the reaction of gas-phase potassium salts with kaolin particles are developed for the conditions appearing in PF boilers such as short residence times, high temperatures, and small size of the additive particles. The reaction between gaseous potassium components and kaolin particles has been modeled with a shrinking core model (SCM) and a uniform conversion model (UCM). The SCM takes into account the effects of chemical kinetics, diffusion in a gas film surrounding the particle, diffusion in a product layer, and thermochemical equilibrium on the reaction progress. The UCM covers diffusion in a gas film surrounding the particles, chemical kinetics, and thermochemical equilibrium. Both models are able to accommodate the effects of change in temperature, particle size, reaction time, and potassium component concentration. Literature data from experiments in an entrained flow-reactor (EFR) at 800–900 °C were used to derive the chemical kinetic rate coefficients of the reaction between kaolin and KOH. The models were then evaluated against experimental data for alkali salts of KCl, KOH, K2CO3, and K2SO4 covering temperatures of 800–1450 °C, kaolin particle sizes of 4–14 μm, residence times of 0.8–1.9 s, and salt/additive molar ratios of 0.05–0.96. The evaluation indicated that both SCM and UCM were suitable for a wide range of conditions, but the UCM captured the effect of particle size better. The modeling outcomes suggested that if the reaction time was long enough, the thermochemical equilibrium would be the major limitation in capturing potassium by kaolin at high temperatures and high potassium concentrations. At lower temperatures, however, the conversion was mainly limited by chemical kinetics. The mass-transfer limitation was less critical under the investigated conditions. The developed models can account for the reaction of gas-phase potassium salts with kaolin at local conditions relevant to PF boilers using biomass.

Effect of Kaolin Particle Size Towards Preparation of Kaolin Ceramic Membrane

The purpose of this work is to study the effect of kaolin particle size for the preparation of low cost ceramic membrane suspension and ceramic membrane structure. Kaolin particle size is categorized into two categories; i) ≤ 1µm and ii) ≥ 1 µm. The suspension is prepared via stirring technique under 1000 rpm at 60°C. The particle size of kaolin is characterized using field emission scanning electron microscope (FESEM) and the prepared suspension is characterized in term of its viscosity. Results indicate that the particle size gave significant effect to the viscosity of ceramic membrane suspension. Preliminary data showed that kaolin with particle size ≤ 1µm resulted ceramic membrane with dense structure.

Numerical Analysis on Reduction of Ultrafine Particulate Matter by a Kaolin Additive during Pulverized Coal Combustion

Adding additives into the furnace is an effective way to reduce particulate matter (PM) formed during coal combustion. However, a numerical model that can predict the performance of additives on PM reduction is still lacking. In this work, a numerical framework, which contains the submodels for ash formation and ash–additive interactions, was developed to predict the ash particle size distribution with and without kaolin additives. The model fully considers the physical–chemical reaction process between the combustion gaseous products (alkali metal vapor) and the Si-/Al-based adsorbent particles. The simulation results are validated by experimental measurements of PM formed during the combustion of high-sodium Zhundong coal on a lab-scale furnace. Given the typical conditions of the lab-scale furnace, adding 3% (by weight) kaolin reduces the mass yield of PM0.3 by 33.35% but has no obvious influence on PM>1. On the basis of a time-scale analysis, we show that the chemical adsorption of the mineral precursors is the dominant mechanism for PM reduction. The influences of the kaolin particle size and dosage on PM reduction are evaluated. The PM reduction efficiency quickly increases and then enters into a plateau as the kaolin mass ratio increases. When a certain critical value is reached, a further increase of the addition ratio has a negligible effect on PM reduction. The critical kaolin mass ratio is 4.1% for 2.1 μm of kaolin and quadratically increases to 4.9% for 21.3 μm of kaolin. Increasing the kaolin size, in contrast, has a negative impact on PM reduction. On the basis of the simulation results, it can be concluded that there exists an optimal condition for PM1 reduction by kaolin addition. The numerical framework developed in the current work can help to quickly find the optimal addition strategy under different additive/coal properties, combustion temperatures, and atmospheres.

Interactions of PbCl2 capture and CdCl2 capture by kaolin in the high-temperature PbCl2-CdCl2-Kaolin reaction system

Using kaolin for capturing hazardous metals is an effective and promising technology. However, interactions of multiple-metals with kaolin are not been clearly understood. Interactions of PbCl2 capture and CdCl2 capture by kaolin in high-temperature PbCl2-CdCl2-Kaolin reaction system were investigated in a two-stage fixed bed at 800 °C. Capture efficiency considering kaolin dihydroxylation and Pb/Al or Cd/Al were used to evaluate capture performance of kaolin. The results showed that kaolin captured more PbCl2 or CdCl2 in the cases that kaolin captured PbCl2 and CdCl2 at the same time, kaolin captured CdCl2 after its first capture of PbCl2 and kaolin captured PbCl2 after its first capture of CdCl2 than in the case that kaolin only captured PbCl2 or kaolin only captured CdCl2. PbCl2 vapor promoted absorption of kaolin for CdCl2, and CdCl2 vapor also promoted adsorption of kaolin for PbCl2. Heavy metal capture effects were controlled by chemical kinetics due to small particle size of kaolin and short contract time between heavy metal chloride and kaolin. PbCl2 vapor or adsorption products on kaolin surface promoted capture effect of CdCl2 through inhibiting desorption rate of CdCl2. Adsorption products promoted eutectic melting of kaolin surface, and slightly melted kaolin surface exposed new layers with more active sites to continue reactions of kaolin with PbCl2 and CdCl2. Therefore, PbCl2 vapor in the gas flow promoted absorption of kaolin for CdCl2, and CdCl2 vapor also promoted adsorption of kaolin for PbCl2. The results can provide an important reference for Pb and Cd capture during MSW incineration.

The effect of different particle sizes and HCl-modified kaolin on catalytic pyrolysis characteristics of reworked polypropylene plastics

At present, the catalysts used to produce high value products by catalytic pyrolysis of high calorific value waste plastics are expensive. In this study, the catalytic pyrolysis characteristics of reworked polypropylene (PP) plastics were studied by using low-cost kaolin with different particle sizes and HCl-modified kaolin. The results show that the catalysts reduced the condensate oil yield and increased the gas yield. C6–C20 was the major components of condensate oil ranging from 90% to 97% in catalyst pyrolysis by significantly decreasing the heavy components (above C20). Kaolin has high cracking efficiency of heavy components into alkanes and alkenes (the range of diesel components). The stronger acid sites on the modified kaolin further promoted the secondary cracking of diesel components, resulting in a great increase in the C6–C11 content. Moreover, HCl-modified kaolin significantly increased the aromaticity of the condensate oil because of the aromatization and Diels-Alder reaction of alkanes and alkenes. Meanwhile, kaolin significantly increased the yield of H2, and the H2 yield was increased with the decrease of kaolin particle size. HCl-modified kaolin further promoted the yield and quality of gas. It is found that kaolin is a potential cheap and efficient pyrolysis catalyst.

Stability of kaolin particles subjected to elevated temperatures using various dispersing agents

The stability of kaolin particles is largely influenced by nature and the behaviour of dispersing agents introduced to the system. This study analysed the size of kaolin particles subjected to elevated temperatures by using various dispersing agents such as ultrapure water (UPW), acetone (Ace) and sodium hydroxide (NaOH). It was found that kaolin particles in UPW formed a stable dispersion compared to particles in Ace and NaOH without further aggregation. Interestingly, kaolin particles under UPW, Ace, and NaOH dispersants had a strong affinity for water and can be classified as possessing hydrophilic behaviour. The mean size of kaolin particles was reduced under UPW and Ace dispersion but increased under NaOH suspension. Under UPW dispersion, kaolin particles ranged from 141.8nm to 5560nm, creating a mid-range monodisperse size distribution (0.08 < PDI < 0.7) without any presence of agglomeration due to high potential energy barrier and electrostatic repulsion. Kaolin particles subjected to NaOH dispersant produced a narrow distribution of particle sizes ranging from 295.3nm to 1106nm but appeared to agglomerate because of Van der Waals interactions. In contrast, the Ace dispersant produced a very broad polydisperse particle size distribution (PDI > 0.7) of greater than 10μm in kaolin with a little aggregation but lacking consistency in terms of stability. However, all dispersants contributed to the kaolin particles dispersion but UPW shown more stability dispersion due to increase in number of hydroxyl groups in dispersant molecule. In conclusion, this simple and low cost methodology can be useful in characterising kaolin particle sizes with limited resources.

Effect of Kaolin particle size on the removal of Pb(II) from aqueous solutions by Kaolin-supported nanoscale zero-valent iron

The removal of Pb(II) from aqueous solutions was investigated using kaolin with two different particle sizes (2.3 and 45 μm) with and without nanoscale zero-valent iron (nZVI, at a Fe content close to 30%). The experimental results show that 2.3 μm kaolin loaded with nZVI (K-nZVI) had the best Pb(II) removal performance under various test conditions. After 24 h, it removed 99.5% of Pb(II) ions in the solution, followed by 45 μm K-nZVI, 2.3 μm kaolin, and 45 μm kaolin (89.01%, 68.8%, and 65.8%, respectively). The removal rates by all four kaolin samples increased with increasing pH in the range of 2–6, and with increasing temperature between 30 °C–60 °C. The results show that using finer carrier particles improves the performance of K-nZVI for removing Pb(II) in aqueous solutions.

Cationic kraft lignin-acrylamide copolymer as a flocculant for clay suspensions: (2) Charge density effect

Abstract Kraft lignin valorization is achievable via making it soluble in water for treating wastewater effluents. In this paper, acrylamide (AM), (2-methacryloyloxyethyl) trimethyl ammonium chloride (DMC) and kraft lignin (KL) were polymerized in an aqueous solution to produce a water-soluble lignin-based copolymer. Two cationic KAD polymers, with the same molecular weight, but different charge densities, were used as flocculants for simulated clay suspensions. The higher charge density copolymer (KAD1) had greater adsorption on kaolin (2.58 mg/g) and bentonite particles (1.83 mg/g) at 4 mg/g (based on clay) adsorption. Furthermore, KAD's higher charge density improved its performance in changing zeta potential and turbidity of the clay suspensions. At 4 mg/g copolymer dosage in clay suspensions, the particle size of kaolin was increased from 4.7 to 22.3 and 16.2 μm, and that of bentonite was increased from 6.1 to 31.9 and 19.8 μm for KAD1 and KAD2, respectively. In addition, the interfacial tension between water and kaolin and between water and bentonite dropped from 12.3 mN/m to 5.8 mN/m and from 9.5 mN/m to 5.2 mN/m when KAD1 was used, respectively. Moreover, KAD1 produced stronger flocs and showed high regrowth affinity at different shear rates.

Effect of kaolin on ash partitioning during combustion of a low-rank coal in O2/CO2 atmosphere

This paper aims to clarify the effect of kaolin on the ash partitioning during combustion of a low-rank coal in O2/CO2 atmosphere. The coal sample was mixed mechanically with 10% kaolin and then combusted in a lab-scale drop tube furnace at 1400 °C in oxy-fuel atmosphere (28% O2 balanced with CO2). The resulting ash was segregated as bottom ash, fine ash and ultrafine ash. The ash distribution as a function of the particle size of kaolin added was examined. The results indicated that the particle size range of kaolin with 106–150 µm was the optimal for shifting the fine/ultrafine ash to the bottom ash, in which the total amount of fine and ultrafine ash was decreased by 18.1% compared with that of the raw coal combustion. The ultrafine ash with particle size less than 0.5 µm generated from combustion of the coal mixed with kaolin (106–150 µm) was decreased remarkably since alkali and alkaline earth metals (AAEM) including Na, K, Ca and Mg were captured by kaolin at high temperature. The formation of liquid layer on the surface of kaolin and coalescence of AAEM-rich particles were the main reason for shifting the fine/ultrafine ash to the bottom ash.

Experiment study on the thermal properties of paraffin/kaolin thermal energy storage form-stable phase change materials

In this paper, different particle sizes of kaolin were employed to incorporate paraffin via vacuum impregnation method. The paraffin/kaolin composites were characterized by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeter (DSC) and Thermogravimetry (TG). The results showed that the paraffin/kaolin composite with the largest particle size of kaolin (K4) has the highest thermal conductivity (0.413W/(mK) at 20°C) among the diverse composites. The latent heat capacity of paraffin/K4 is 119.49J/g and the phase change temperature is 62.4°C. In addition, the thermal properties and thermal conductivities of paraffin/K4 with different mass fraction of K4 (0–60%) were investigated. The thermal conductivities of the composites were explained in microcosmic field. The phonon mean free path determines the thermal conductivity, and it can be significantly affected by temperature and the contact surface area. The leaks, thermal storage and release properties of pure paraffin and paraffin/kaolin composites were investigated and the composites presented good thermal stabilities.

Effect of kaolin particle size and loading on the characteristics of kaolin ceramic support prepared via phase inversion technique

In this study, low cost ceramic supports were prepared from kaolin via phase inversion technique with two kaolin particle sizes, which are 0.04–0.6 μm (denoted as type A) and 10–15 μm (denoted as type B), at different kaolin contents ranging from 14 to 39 wt.%, sintered at 1200 °C. The effect of kaolin particle sizes as well as kaolin contents on membrane structure, pore size distribution, porosity, mechanical strength, surface roughness and gas permeation of the support were investigated. The support was prepared using kaolin type A induced asymmetric structure by combining macroporous voids and sponge-like structure in the support with pore size of 0.38 μm and 1.05 μm, respectively, and exhibited ideal porosity (27.7%), great mechanical strength (98.9 MPa) and excellent gas permeation. Preliminary study shows that the kaolin ceramic support in this work is potential to gas separation application at lower cost.

Mid-Infrared Features of Kaolinite-Dickite

AbstractTransformation of kaolinite to dickite is a common diagenetic reaction. The present report is part of a wider study to investigate the pathways of this polytype change. Fourier-transform infrared spectroscopy (FTIR) was used to attempt quantification of the relative proportions of kaolinite and dickite, validated by X-ray diffraction (XRD) results, in order to link mineral and structural features during the mineralogical changes. A group of kaolinite and dickite samples was investigated: 13 samples from the Frøy and Rind oil fields (North Sea), three kaolinite specimens with different crystal order and particle size (KGa-2, kaolinite API 17, Keokuk kaolinite), and two dickite-rich samples (Natural History Museum collection). Six FTIR spectral features were analyzed: (1) intensity ratio of the minima at 3675 and 3635 cm−1; (2) position of the band at ~1115 cm−1; (3) difference between the frequency of the bands at ~1030 and ~1000 cm−1; (4) intensity ratio of the bands generating shoulders at ~922 and ~900 cm−1; (5) position of the band at ~370 cm−1; and (6) intensity of the band at ~268 cm−1. Correlation of the features above with polytype relative proportions derived from XRD showed non-linear behavior, with maximum curvature at the dickite end, which precludes kaolinite-dickite quantification. Increasing kaolin particle size is known to cause decreased intensity of the FTIR spectra. A model was developed to test whether this effect is consistent with the non-linear progression of the IR features. The relative intensity of kaolinite and dickite IR features were calculated in a series of kaolinite-to-dickite transformations, where the size of particles increases with dickite proportion, and where dickite-dominated particles reach a larger size than kaolinite-dominated particles. The results indicated that the differential particle size increase is possibly the cause of the lack of linearity between IR- and XRD-measured dickite proportions.

Principal component analysis to evaluate the spatial variation of major elements in kaolin deposit

This paper explores the variations in major elements concentrations in kaolins from four different deposits in Botswana. The data were obtained from four different kaolin deposits with an additional four-class label based on particle sizes of the rock – providing a natural comparative basis between detected structural features with those of the original data attributes. Using principal component analysis (PCA), the paper reduces the data dimensionality and establishes inherent distinctive attributes of major elements accounting for the highest variation in chemical compositions of the kaolins. The principal components extracted are validated using graphical data visualization tools applied on a 28x11- dimensional data matrix of the oxides of Na, Mg, Al, Si, P, K, Ti, Mn and Fe, and loss on ignition (LOI). The validated results show that structures based on three retained components exhibit clearly discernible variations within the samples. Discretisation of the particle sizes is highlighted as both a challenge and an opportunity and it is recommended that it be used as a tuning parameter in gauging kaolin variations across samples and in validating new predictive modeling applications. Successful applications will depend on how clay and data scientists keep track, synchronise and share information relating to potentially dynamic data such as the impact of discretisation of kaolin particle sizes. KEY WORDS: Graphical data visualization, Kaolin, Kaolinite, Particle size, X-Ray fluorescence spectrophotometry, Multi-collinearity Bull. Chem. Soc. Ethiop. 2015, 29(1), 41-51DOI: http://dx.doi.org/10.4314/bcse.v29i1.4

Coefficient of Thermal Diffusivity of Insulation Brick Developed from Sawdust and Clays

This paper presents an experimental result on the effect of particle size of a mixture of ball clay, kaolin, and sawdust on thermal diffusivity of ceramic bricks. A mixture of dry powders of ball clay, kaolin of the same particle size, and sawdust of different particle sizes was mixed in different proportions and then compacted to high pressures before being fired to 950°C. The thermal diffusivity was then determined by an indirect method involving measurement of thermal conductivity, density, and specific heat capacity. The study reveals that coefficient of thermal diffusivity increases with decrease in particle size of kaolin and ball clay but decreases with increase in particle size of sawdust.

Feasible Synthesis of TiO2 Deposited on Kaolin for Photocatalytic Applications

AbstractThe aim of the present study was to synthesize a photocatalyst on the basis of TiO2 with kaolin as the support material. Properties such as layered structure and a suitable particle size of kaolin could be beneficial in the production of a high-quality and relatively cheap photocatalyst on an industrial scale. Homogeneous hydrolysis with urea as a precipitation agent and kaolin as support material was used to obtain a kaolin surface covered with TiO2. Samples were characterized by means of X-ray powder diffraction, infrared and Raman spectroscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller surface area, and Barrett-Joyner-Halenda porosity determination. Photocatalytic activity was assessed by a Reactive Black 5 azo dye discoloration in a water suspension and by acetone decomposition on a thin layer of sample in a gas phase. The characterization confirmed that the well crystallized TiO2 was distributed effectively over the whole surface of a kaolin substrate, and photocatalytic tests revealed that the active surface layer of titania particles on kaolin performed well, suggesting that kaolin acts as a suitable support.

Barrier properties of latex/kaolin coatings

The inclusion of plate-like pigments such as kaolin to a styrene–butadiene dispersion is a well-known approach for enhancing barrier properties. Latex coatings containing kaolin with different treatments were evaluated. The in situ dispersion of kaolin in latex-bound coatings were characterised by Focused Ion Beam (FIB) imaging, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The effects of parameters such as the kaolin particle size distribution (PSD) and aspect ratio (AR), and the particle orientation distribution on the barrier properties of coatings were investigated. It is found that the barrier properties of the composites are independent of PSD and are mainly dominated by the AR distribution range and the degree of disorientation of the kaolin platelets (given a similar volume concentration of flakes). Large platelets with high AR contribute more to the improvement of barrier properties than do small platelets with low AR. Finally, the influence of platy pigments on the water vapor permeability was simulated using traditional models, which shows good agreement with the experimental data.

Effects of Kaolin particle size and annealing temperature on the Resistivity of Zinc- Kaolin Composite Resistors

The effects of kaolin particle sizes on the resistivity of zinc-kaolin composite resistors have been investigated. The composite resistors have been produced from kaolin particle sizes ranging from 0.063 mm to 0.5 mm. The resistors were produced in a mould to a dimension of 65 mm x 6.5 mm x 3.2 mm with dry zinc and kaolin powders to which a drop or two of sodium silicate have been added as a binder. The resistors were annealed at temperatures ranging from 300 oC to 1000 oC in steps of 100 oC for composites of 0%, 5%, 40% and 60%(vol.) zinccontent. Results showed that composite resistivity at all the zinc concentrations considered and at all annealing temperatures increased exponentially with increasing kaolin particle size. The effect of annealing showed that composite resistance is highest for composites annealed at 1000 oC and lowest for cermets annealed between 500 oCand 600 oC. Composite resistance increased with increasing kaolin particle size due to the large contact area presented by the insulating kaolin particles resulting in reduction of the number of zinc particle-particle contact. The results from this study will help in the development of conducting ceramics which could find use in chemical industries as electrodes in environments not conducive for metallic electrodes.