Fine Kaolin Research Articles

Compositional Design of New Environmentally Friendly Geopolymer Mortar Based on Kaolin and Granite Residues.

The use of industrial residues in civil construction is an exciting alternative to mitigate environmental impacts and promote the circular economy. This work developed new compositions of geopolymer mortars activated by NaOH from fine kaolin residue (RCF), coarse kaolin residue (RCG) and granite (RG). All residues were benefited and characterized by chemical analysis (X-ray fluorescence), mineralogical phases (X-ray diffraction) and granulometry (laser granulometry). Additionally, the RCF was calcined at 650 °C for 2 h (RCFC) to produce metakaolin, which is the starting point for the geopolymer reaction. A mixture of experimental designs was accomplished to evaluate the water/binder factor (Wexp (%)) necessary for new geopolymer mortar compositions to reach the consistency index (260 mm, ASTM C1437-15) and the effect of different curing conditions on the simple compressive strength (SCS). The geopolymeric compositions with RCFCs, pre-cured at room temperature, exhibited the highest Wexp% values (>40%) and significant SCS, with curing conditions A and B reaching 6 MPa and 7 MPa, respectively. Such behavior can be explained by the fact that the pre-curing step at room temperature keeps the system humidity relatively high, favoring the dissolution of Si4+ and Al3+ ions and, therefore, increasing the Si/Al ratio, which positively influences the geopolymerization kinetics reaction.

Ceramic Fine Wares of Natakamani and the Problem of Identifying the “Imperial Style” in the Material Culture of Meroe (Sudan)

The article analyzes ceramic fine wares of the ancient Meroitic Kingdom, made of white kaolinite clays (“eggshell wares”). This pottery appeared not earlier than the 1st century B.C. and gained popularity in the 1st–2nd centuries A.D., during the reign of king Natakamani and his successors. The kaolinite clays required professionalism and specific skills from ancient potters, as well as the availability of improved pottery wheels and kilns. Clay deposits were located near Meroe Royal City and in several other regions. The vessels were decorated with stamped or painted decoration in Egyptian or Hellenistic style and were distributed from Sennar and Abu Geili in the south to Karanog and Shablul in the north, being a clear marker of the Meroitic civilization. These complex wares could not be produced locally and became a marketable commodity. The morphological assortment of Meroitic fine wares is quite modest, while standardization of the shape and volume is noticeable, which may indicate centralized control over pottery workshops. The stylistic uniformity of the vessels suggests the existence of a special “Imperial” style of pottery in the time of Natakamani and his successors. At the same period plans of settlements, the architecture of palaces and temples, cult objects also demonstrated uniformity, which could be associated with state control of administrative centers and craft workshops. The decline of royal power in the 3rd – mid-4th centuries A.D. was synchronous with the degradation of Meroitic fine kaolin ceramics and its gradual replacement with wadi clays of grayish-beige colour and simplified decoration.

Preparation of gamma alumina nanoparticles from kaolinitic sandstone and their application as a selective adsorbent for REEs from liquid waste

A process for synthesizing Gamma alumina from kaolinitic sandstone ore has been described in this paper. Fine kaolin was recovered from the sandstones after aggressive attrition scrubbing process followed by 2" and 1" hydro- cyclone classification. The produced −25 μm kaolin was transformed to active meta-kaolin via calcination at 750 °C for 5 h. Through metakaolin- H2SO4 interactions, and consequently precipitation in ethanol solution, aluminum sulfate was formed. After dryness and calcination at 900 °C for 2 h γ-alumina was prepared. The FT-IR, DLS, BET, XRD, SEM and EDX analyses confirmed the high purity of the nanosized γ-alumina product. In addition, the prepared γ-alumina was examined as the sorbent for rare earth species from waste materials. Adsorption and thermodynamic studies, in addition to the adsorption selectivity, desorption process, and reusability showed promising performance results. The maximum adsorption capacity of the prepared γ-alumina reached 142 mg/g.

Enhancing the floatability of smithsonite mixed with silicate minerals by using a novel dispersant of cetylpyridinium bromide

Silicate minerals often coexist in nonferrous metal ores. In the flotation process, the fine clay particles are easy to slime-coating on the target mineral surface and lead to the deterioration of the flotation efficiency. In this study, the flotation behaviors of single smithsonite and its mixture with fine kaolin or chlorite were studied using octadecvlamine acetate (OCTA) as the collector. It was found that the single mineral of smithsonite had a high flotation recovery, while the mixed minerals of smithsonite with kaolin or chlorite possessed a poor processability. To eliminate the adverse effect of kaolin and chlorite on the floatability of smithsonite, a cetylpyridinium bromide (CPB) was introduced in the flotation process as a novel dispersant. The micro-flotation results showed that the addition of CPB greatly improved the separation efficiency of smithsonite from the mixed ores. It was believed that the adsorption of CPB on the surface of kaolin and chlorite eliminated the hydrophobic attractive force between the smithsonite and clay particles and thus prevented the slime-coating of kaolin and chlorite on the smithsonite surface. As a result, the floatability of smithsonite mixed with kaolin or chlorite was greatly enhanced. This work deepens our understanding of the flotation process of nonferrous metal ores mixed with fine clay minerals, and provides a novel dispersant of CPB which is expected to be applied in the flotation separation of mixed ores.

Synthesis of Kaolin Geopolymer as Ceramic Reinforcement in Lead-Free Solder

This paper elucidates the fabrication of kaolin geopolymer as the ceramic material. The kaolin geopolymer ceramic (KGC) was used as a new potential reinforcement in the lead-free solder. The fabrication of KGC was started through combination of alkaline solution of NaOH and Na2SiO3 reaction with kaolin material. The mixture of kaolin geopolymer were prepared and the homogenised mixture were curing for 24 hours. The kaolin geopolymer is sintered at 1200°C and then crushed to produces a fine kaolin geopolymer. The KGC were then mixed with lead-free solder through powder metallurgy technique. The elemental distribution in the KGC was investigated by using Synchrotron Micro-XRF. Meanwhile, the phase analysis involved in KGC and composite solder with addition of KGC were investigated as well.

The use of refractory materials in the artistic painting of glass panels

Based on the analysis of the glass use evolution in architecture and construction, the need to improve or search for new types of glass as an element of the interior or exterior and ways to decorate them and the feasibility of using artistic painting was shown. The purpose of this work was its use in the manufacture of decorative elements for architectural and construction purposes with different surface textures and relief of polished float sheet glass while providing significant resource and energy savings with the use of refractory materials. The equipment and materials which were used included: Z. Bavelloni grinder; muffle furnace CGB-100.150.55-10- 380 for painting and annealing; sprayer type LVLP 1.3 mm INTERTOOL PT-0132 for spraying fine kaolin suspension; degreasing solution; panels from the polished float glass with the following chemical composition, wt. %: SiO2 — 73.0; Al2O3 — 1.0; Fe2O3 — 0.1; CaO — 8.6; MgO — 3.6; Na2O — 13.4; SO3 — 0.3 and 6 mm thick; refractory plates LYTX—264B and heat-resistant paper LYTX—236B from ceramic fibers. The coefficient of thermal linear expansion of glasses and refractories was determined using a quartz vertical dilatometer. As a result of the carried out researches the possibility of obtaining the set texture and three-dimensional relief of the surface of architectural and construction decorative products from polished float glass sheet by artistic painting with the use of refractory materials was shown. The factors that are decisive in the choice of such materials and their effectiveness were identified. Significant simplification and cheapening of the method of making decorative glass by artistic painting has been achieved due to the fact that to obtain each effect on the surface of the product it is enough to replace the refractory fragments of the composition and their arrangement instead of making new support plates. Further research of forming processes and phase generations in compositions based on applied and new refractory materials and their waste will contribute to a significant expansion of the range and areas of use the artistic and decorative glass products use.

Iron Bearing Minerals Flotation from Silica Sand Using Hydroxyl Surfactants

A technological clayey sandstone sample from Wadi Qena locality, Eastern Desert of Egypt, was directed to processing. Fine kaolin and clean silica sand were produced after intensive attrition scrubbing of the sample. To increase the quality of the produced silica, it was subjected to reverse anionic flotation to minimize its iron content. In this respect, conventional flotation tests using three anionic oxyhydryl surfactants namely: sodium dodecyl benzene sulphonate, sodium naphtha sulphonate, and sodium dodecyl sulphate, were tried. Results showed a privilege action for sodium dodecyl sulphate to remove most of the iron oxide content of the sample. A statistical Box-Behnken design was constructed to optimize the process efficiency. It was shown that from a flotation feed contained 360 ppm Fe2O3 and 1190 ppm Al2O3, sand concentrate contained 29 ppm Fe2O3 and 564 ppm Al2O3, was produced. The optimum flotation conditions were 3.86 kg/t sodium dodecyl sulphate dose, 3.22 flotation pulp pH, 1226 rpm impeller speed, and 22.24 L/min airflow rate. Variables interaction effects results showed that flotation separation efficiency was significantly influenced by air flow rate and cell impeller speed of the process.

Rare-metal granites as a potential source of critical metals: A geometallurgical case study

Because of their low grades in critical metals such as Light Rare Earth Elements (LREE) or Sn, rare-metal granites are not considered as economic for metal recovery but, when altered, they are often exploited for their industrial minerals. The St Austell rare-metal granite is well known for its world-class kaolin deposits which formed as a result of the extensive weathering and alteration of the underlying granite. The St Austell granite body is composed of several granite components, each having its own accessory minerals assemblage. As a result of the kaolinisation process, some metal-bearing accessory minerals of the granite, such as monazite (LREE) or cassiterite (Sn), are partially liberated from the gangue which allow their pre-concentration in the micaceous residue which is considered as a potential source for critical metals recovery. Similarities with other similar rare-metal granites suggest that topaz granite is the most prospective for disseminated magmatic Sn-Nb-Ta-REE mineralization. However, comparison of the potentiality of 3 granite types i.e., biotite, topaz and tourmaline granites suggest that biotite granites is actually the most prospective due to higher degree of kaolinisation of the biotite granite which favour pre-concentration of its accessory mineral in the micaceous residue. In order to develop a geometallurgical framework for extraction of kaolin and metals from the selected granite component, a field sampling campaign is performed. Core samples are processed in the laboratory using a characterisation program that mimics the full-scale kaolin refining route. Two main products are recovered through this program, viz. MR180 (−180 +53 µm) and P5 (−5 µm), which correspond to a fine micaceous residue and a fine kaolin product respectively. These products are both analysed routinely for major and minor trace elements by XRF and yields are recorded to indicate process performance. A selected number of MR180 samples are also being characterised in terms of particle size by laser light scattering, geochemistry by ICP-MS, and mineralogy by QEMSCAN®. Comparison of characterisation results of MR180 samples and corresponding industrial residue samples shows a good correlation, suggesting that sample analyses are representative for the in-situ deposit and the processing behaviour. Monazite is found to be either fully liberated or fully locked from one sample to the other. Next, pilot-scale gravity concentration tests are performed on micaceous residue samples. Characterisation of the processing products shows that monazite lost in the tailings is mostly locked within tourmaline or micas and is fine grained. Then, predictive regression models for spiral separation performance in terms of recovery, product grade and enrichment as a function of the feed grade are developed for MR180 LREE grade data. Finally, kaolin resources can be classified using quantitative indicators such as yield of the P5 product and the iron oxides content which provides insight into the kaolin quality in terms of whiteness. This geometallurgical classification can be used to delineate zones of interest within the deposit. Although kaolin quality and recovery primarily inform extraction planning, zones which are also of interest for metal recovery can be identified. The proposed model predicts whether the expected LREE grade and recovery satisfy the by-product requirements.

Scavenging of refractory elements (Ca, Mg, Fe) by kaolin during low rank coal combustion

In this paper, special attention is paid to the scavenging of refractory elements (Ca, Mg, Fe) by kaolin during combustion of a low rank coal. Combustion experiments were carried out on an electrically-heated drop tube furnace at 1300 °C. The raw coal and its blends with kaolin additive (1–10 wt% of coal mass) were respectively burned in simulated air atmosphere. Combustion-generated ashes were collected and analyzed by Computer-Controlled Scanning Electron Microscopy (CCSEM). The data were used to elucidate the scavenging of Na/Ca/Mg/Fe by kaolin and the transformation of inorganic species after kaolin addition. Quantitative X-ray diffraction (XRD) analysis and ash fusion tests were carried out to characterize the amount of amorphous species and the fusion temperatures of bulk ashes after kaolin addition, respectively. Backscattered electron images (BSE) were collected on the raw coal and coal/kaolin mixtures to demonstrate the role of the dispersion state of kaolin in metal scavenging. It is found that apart from Na, the added kaolin can also strongly scavenge the refractory elements (Ca and Mg, except Fe) during low rank coal combustion. The scavenging of Na/Ca/Mg by kaolin promotes the formation of amorphous and molten alumino-silicate particles. The high dispersion of fine kaolin particles in coal is a key factor affecting the scavenging process, which provides sufficient opportunities for the contact and reaction between Ca/Mg species and kaolin. Two possible routes are proposed for the scavenging of Ca/Mg by kaolin. One is that kaolin firstly reacts with sodium vapors, forming melting sodium alumino-silicates that favor the capture of Ca/Mg containing species. Another possible route is that, kaolin directly reacts with active CaO/MgO fumes produced from coal combustion, forming Ca/Mg containing alumino-silicates. Kaolin dosage has significant impacts on the ash fusion temperatures. Which firstly decreased with the increase of kaolin dosage, reaching to the lowest at 4 wt%. Then it sharply increased with the increase of kaolin dosage.

DMC-grafted cellulose as green-based flocculants for agglomerating fine kaolin particles

Novel cellulose based flocculants C-g-P (DMC) with various chain architectures are synthesized through a situ graft copolymerization. The cationic ammonium chloride group (DMC) is grafted onto cellulose by two separate inverse emulsion polymerization with γ-methacryloxypropyl trimethoxy silane (KH-570) and double bond addition reactions, which is a new and simple method to employ KH-570 as a bridge for the connection of cellulose matrix and DMC group. The effects of pH, flocculant dose, standing time on turbidity of kaolin suspensions and particle sizes have been studied systematically. In addition, the response surface methodology (RSM) study confirms that PAC and C-g-P (DMC) have synergy in turbidity removal with a higher removal efficiency of 98.32%. Moreover, C-g-P (DMC) 1 has higher removal efficiency with 96.5% at a low dosage of 0.6 mg L−1 and better floc properties than C-g-P (DMC) 2 and C-g-P (DMC) 3, suggesting that the length and quantity of cationic branch chains play a crucial role in Kaolin flocculation due to their dramatically enhanced bridging effects.

Adsorption characteristics of chitosan grafted copolymer on kaolin

Efficient destabilization of colloidal dispersions is the top challenge facing solid-liquid separation processes. In this study, an in-house synthesized environmentally friendly graft copolymer, chitosan-graft-polyacrylamide (chi-g-PAM), was investigated as a potential flocculant of fine kaolin dispersions. Chi-g-PAM was successfully prepared by combining the properties of synthetic monomer (acrylamide) and natural polymer (chitosan) using ceric ammonium nitrate as an initiator. The physical and chemical characteristics of the copolymer were analyzed using Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Zetasizer Nano ZS in order to identify the active adsorption sites in the polymer structure.The performance of chi-g-PAM as a flocculant was evaluated by treating 5wt% kaolin despersion (d50 and mean diameter of 6.63 and 9.24μm, respectively) with different dosages of the polymer and calculating the initial settling rates (ISR). The flocculation mechanism and the adsorption capacity were investigated using zeta potential and total organic carbon (TOC) measurements. Results showed that ISR increased with increasing chi-g-PAM dosages before reaching maximum values at corresponding optimal ones; then, the settling rate slightly decreased. Chi-g-PAM showed a better flocculation and settling behavior (ISR 24.84m/h) as compared to chitosan (ISR of 7.2m/h) at optimun dosages and performed similar to commercial PAM (ISR of 25.92m/h). Reliable correlation of zeta potential measurement and adsorption isotherms obtained from TOC mesaurements demonstrated that bridging and charge neutralization were the dominant adsorption mechanisms involved. The experimental adsorption data were analyzed using Langmuir and Freundlich models. The best fit was obtained using the Langmuir isotherm model with a correlation coefficient value of 0.991 as compared with 0.895 for the Freundlich model. The TOC method has proven to be suitable and feasible for explaining the adsorption mechanism and determination of the adsorbed amount of chi-g-PAM on kaolin.

Study of Alkali Emission and Control with Firing a High Alkali Coal

In this study, the sodium emission and control with firing a high-alkali coal was investigated in a high-temperature muffle furnace. Kaolin was chosen as an additive tested to clarify its sodium capture mechanism and assess its capture performance. The influence of some firing-related factors, such as kaolin dosage, temperature, and particle sizes, of both kaolin and coal on sodium release and sodium capture performance of kaolin was also studied. It was found that more sodium was released when the combustion temperature rose or fine fuel particles were combusted. Kaolin could efficiently capture sodium species to form high-melting sodium aluminosilicates, primarily nepheline or carnegieite. Increasing kaolin dosage led to the promoted sodium retention. However, the promotion was not that pronounced in high kaolin dosages. High temperature had a negative effect on sodium capture by kaolin, which could be ascribed to the increasing sodium emission with temperature. Fine kaolin particles exhibited a good sodium capture performance. Coal particle size had little impact on the interactions between kaolin and sodium species. More than 80% of the total sodium was retained in ash by kaolin when firing coal (30 μm) with 3 μm kaolin addition in the dosage of 6 wt% at 1100°C.

Electrocoagulation for the Treatment of Oil Sands Tailings Water

Title: Electrocoagulation for the treatment of oil sands tailings water The Canadian oil sands industry has been receiving widespread International criticism on environmental issues, among which is its use of water resources. A major process to recover the valuable bitumen (a heavy, viscous form of petroleum) from the oil sands resource is surface mining. A by-product of mining operations is large volumes of toxic tailings water which are stored in large dykes, the infamous ‘tailings ponds’, covering a total area greater than 175 sq. km. These have led to significant environmental damage because of land displacement, the contamination of natural waters, and impact on wildlife such as waterfowl that land into the water surface. Large volumes of fresh water are withdrawn to make up for the water being stored as tailings water. On average about 3 barrels of fresh water are withdrawn per barrel of bitumen produced, the main source of fresh water being the Athabasca River. The local communities and stakeholders have expressed concerns about fresh water withdrawal rates, potentially creating water shortage issues. The nature of contaminants in tailings wastewaters makes the treatment processes costly in order to minimize environmental impact, hence the operators are forced to store the water as ponds. Tailings water is a complex mixture of contaminants, very fine clay particles that take decades to settle, toxic organic compounds such as naphthenic acids and polycyclic aromatic hydrocarbons (PAH’s), silica, and heavy metals including nickel, vanadium, arsenic and mercury. Since the start of mining operations in 1967, the oil sands industry is yet to implement a method to treat tailings water, alleviate the use of tailings ponds, and significantly increase recycle rates. Electrocoagulation (EC) is one technology that could address these issues. Prior research on various other wastewaters has shown that EC can remove several contaminants including fine suspended solids, toxic organic matter, silica, and heavy metals [1] which are the common contaminants in oil sands tailings water. In its simplest form, EC uses an electrochemical cell to generate coagulating agents in the wastewater by electrochemical reactions, resulting in flocculation of contaminated particles which separate out by settling or flotation. Currently, coagulation and flocculation of most industrial wastewaters are performed by the use of chemicals like metal salts. However, EC has many advantages over the chemical method. The electric field used in EC enhances the flocculation process by setting the charged colloidal particles in motion resulting in the coagulation of even very fine suspended solids [2]. This will be advantageous when applied to tailings water because the most difficult to remove contaminant it contains are the very fine, slow settling clay particles. In addition, EC simultaneously removes heavy metals by precipitation as the pH increases during the process. Furthermore, hydrogen gas bubbles generated at the cathode by water reduction reaction will float the flocculated particles to the water surface, thus providing better separation of contaminants. Another major advantage is that no chemicals are required, minimizing secondary pollution. The high conductivity of tailings water is an advantage, as it will provide low electrolytic solution resistance, leading to low energy requirement. Increased contaminants removal rates, the avoidance of chemical addition, and lower energy consumption suggest that EC could reduce the environmental impact and cost of water treatment for treating tailings water. The main research objectives are to investigate the effectiveness of EC for the treatment of tailings water and by removing several contaminants simultaneously. The potential to eliminate tailings ponds by using EC have been explored. Experiments with EC have been conducted on real industrial samples of tailings water and on synthetic wastewater samples prepared in the lab. Contaminant removals have been assessed by measuring various water quality parameters such as turbidity, total suspended solids, “Chemical Oxygen Demand (COD)” and “Total Organic Carbon (TOC)” both of which quantifies the amount of oil present, and the concentrations of heavy metals. Moreover, special attention has been given to the removal of fine particles by the use of water contaminated with fine kaolin clay, the most burdensome of all the contaminants. Also, the effect of different electrochemical reactor designs have been explored. The results are very promising, several contaminants are being removed simultaneously, with removal rates as high as 90%. The results gathered demonstrate that some of the different types of reactor designs tested not just improve contaminant removal rates but also reduce energy consumption significantly.

Separation of fine particles at different frequencies and HRTs using acoustic standing waves

The objective of this study was to evaluate the separation of fine particles using several frequencies and hydraulic retention times (HRTs) in an acoustic standing wave reactor without any separate cooling devices. The acoustic standing wave reactor consisted of sufficient space (over 100 mm) between the transducer and reflector, resulting in a slight increase in temperature. However, the increase in temperature did not affect the formation of standing waves and particle aggregations in our experiments. The results indicated that the turbidity removal efficiencies of fine kaolin particles, when using frequencies of 580 kHz, 1, and 2 MHz, increased with longer standing wave operation time. Especially, the turbidity removal efficiencies for 1 and 2 MHz were higher than that for 580 kHz because the wavelength (λ) of the 580 kHz wave was longer than that of the 1 and 2 MHz waves. Furthermore, the turbidity removal efficiency of kaolin in a continuous reactor improved with increasing hydraulic retention times (HRTs), and the reactor was more effective with 1 and 2 MHz used in parallel instead of 1 and 2 MHz used individually under the same HRT conditions with the entrance length (EL) having no adverse effect.

Adsorption of organic–inorganic hybrid polymers on kaolin from aqueous solutions

Adsorption of two in-house synthesized organic-inorganic hybrid polymers, Al(OH)3-polyacrylamide (Al-PAM) and Fe(OH)3-polyacrylamide (Fe-PAM) on kaolin and corresponding flocculation of fluid fine kaolin suspensions were investigated. For comparison, a commercial anionic flocculant (partially hydrolyzed polyacrylamide or known as H-PAM) was also examined. The flocculation dynamics of fine kaolin suspensions were determined using an on-line focused beam reflectance measurement (FBRM) probe. As an example of applications, flocculation of a laboratory oil sands extraction tailings sample was studied. A quartz crystal microbalance with dissipation (QCM-D) was used to determine adsorption kinetics of the polymers on silica and alumina as representative of T- and O-basal planes of kaolin.Al-PAM, Fe-PAM and H-PAM were shown to be excellent flocculant of kaolin suspensions, with H-PAM being less effective and more sensitive to overdosing. The flocculation performance was greatly influenced by proper mixing. Strong flocculation of kaolin suspension by Al-PAM and Fe-PAM is attributed to their ability to adsorb on both basal planes of kaolin, in contrast to relatively weak flocculation of kaolin by H-PAM which adsorbs only on positively charged aluminum oxy-hydroxyl basal planes. The electrostatic attraction or repulsion is identified as a critical parameter in determining polymer adsorption and hence corresponding flocculation of kaolin suspensions.

Effect of Thai Kaolin on properties of agricultural ash blended geopolymers

Abstracts Geopolymer has been developed as an alternative material to Portland cement. It is based on the polymerization of alkali activators and oxides of silicon and aluminium from pozzolans. Pozzolans are materials mainly SiO2 and/or Al2O3 which reacts with NaOH and Na2SiO3 to generate a three dimentional aluminosilicate structure. The clean and fine kaolin from south of Thailand transforms into metakaolin at 550–600 °C, as determined by DTA. In this research, kaolin was heated at 600 °C, 700 °C and 800 °C for 2 and 6 h to optimize its transformation into metakaolin as pozzolans for geopolymers preparation. Additionally, the as-received kaolin was exploited also as a pozzolan for geopolymers in order to reduce heat energy consumption. However, it was found that kaolin alone did not display sufficient pozzolanic behavior to form geopolymer at 7 days of age unless specimens were slightly warm cured. Therefore, it was blended with more active pozzolans such as bagasse ash and rice husk ash. Finally, the results of compressive strength and microstructures were investigated and discussed.

Screening of Colloids by Semicontinuous Centrifugation

AbstractThis work contributes to the field of solid‐liquid separation in focusing on the screening of colloidal particles in a semicontinuous process. The aim of the study is to provide the basics for a continuous classification process in industry. After a short introduction to the field of particle screening, a review of the possibilities of classification in the gas or liquid phase is presented, including analytical methods, devices for the fractionation on the laboratory scale as well as apparatus for screening on the pilot and industrial scale. The results show the dispersion, stabilization and classification of fine kaolin and polystyrene particles. Kaolin was used to demonstrate the possibility of removing the fraction of fine particles, polystyrene particles were used to investigate the removal of the coarse fraction. The diameter of the particles used in this study ranges from 250 nm to 3 μm.

Suspended solid abatement in a conical fluidized bed flocculator

With the random movement of silica gel beads in a conical fluidized bed, micro-vortices resulting from the fluidization promoted the collision and aggregation of suspended fine kaolin powders. The abatement efficiencies of the suspended fine solids under several hydrodynamic conditions were studied, and a suitable control strategy for operating the conical fluidized bed flocculators was identified. The suspended solids abatement efficiency was found to increase with increasing Camp Number and flocculation time (T), but decreased with the increase of velocity gradient (G) within the range studied in this research (165.1–189.6 s−1). The abatement efficiencies were all more than 60% at the range of G = 165−180 s−1 and T = 15−33 s at an initial kaolin solid concentration of 150 mg·L−1, polymer aluminum chloride dosage of 60 mg·L−1 and sedimentation time of 20 min. However, the formation of flocs was influenced by the liquid backmixing. Excessive backmixing caused the breakup of flocs and resulted in difficulty for the fine powders to aggregate and sediment to the reactor bottom. The results of the calculated fractal dimension and measured free sedimentation velocity of flocs obtained at different runs showed similar flocs properties, and indicated an easy control strategy for sedimentation of the flocs.

Removal of lipophilic extractives from debarking wastewater by adsorption on kaolin or enhanced coagulation with chitosan and kaolin

Finnish kaolin samples of two different size fractions, fine (<0.063mm) and coarse (<2mm), were tested as adsorbents and coagulant aids for the removal of lipophilic extractives from debarking plant wastewater. In the adsorption tests (24h, 20g/L), commercial talc (Finntalc F15) removed slightly more extractives (46%) than the fine kaolin (42%), whereas the coarse kaolin removed only 28% of the extractives. In the coagulation–flocculation studies, the chitosan coagulant alone removed 85–89% of the lipophilic extractives, the optimum dosage being in the range of 30–85mg/L based on turbidity. 87–91% of the lipophilic extractives were removed in the presence of 2 or 5g/L kaolin. However, kaolin addition improved the removal of resin acids. The charge quantity of the wastewater correlated with the required dosage of chitosan at the two different sampling times. Both the fine and coarse kaolin fraction significantly increased the settling rate of the chitosan flocs.

The influence of fine kaolin and ground calcium carbonates on the efficiency and distribution of fluorescence whitening agents (FWA) in paper coating

Article The influence of fine kaolin and ground calcium carbonates on the efficiency and distribution of fluorescence whitening agents (FWA) in paper coating was published on August 1, 2008 in the journal Nordic Pulp & Paper Research Journal (volume 23, issue 3).