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Schematic diagram depicting variations in configurations of PEI polymer molecules with respect to pH (Zhu et al., 2007) PEI molecules primarily adsorb onto negative faces of kaolin particles via unlike charge attractions. At low PEI dosages, only a fraction of kaolin surfaces will be covered by PEI molecules. Regardless of PEI Mw, with 0.4dwb%, 0.04dwb% and 0.004dwb% PEI added, the surface coverage of kaolin particles were calculated to be ~35.6, ~355.7 and ~3557.2 Ǻ 2 /repeating unit respectively. Surface coverage of kaolin particles was calculated based on its total BET surface area. A value of ~35.6 Ǻ 2 /repeating unit represents near saturation 5
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The need to improve water recovery and reduce impoundment areas of mineral waste tailings containing clay particles is urgent. In this paper, effects of dosages and molecular weights (Mw) of branched polyethylenimine (PEI) flocculants and shear on the sedimentation of kaolin slurries at pH ~8 are investigated by calculating solids content (wt%) and...
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... they transform from extended (or near flat) to coiled (or umbrella-like) configurations due to reducing intra- repulsive forces between interacting PEI particles on each polymer molecule ( Meszaros et al., 2004, Zhu et al., 2007. At pH ~8, they continue to carry positive charges and exist as slightly coiled structures as shown in Figure 4. Charges and configurations of PEI molecules identified correspond to present slurry conditions studied at low ionic strengths or conductivities of 0.3-1.7µS/cm at 22ºC. ...
Citations
... Wet methods consist of both physical and chemical processes. Major wet physical processes constitute sedimentation [6] and electromagnetic separation [7,8]. Important wet chemical processes Figure 1 demonstrates the location of Nagar Parker on a map of Pakistan. ...
Clay minerals are one of the most utilized minerals among non-metals. These are hydrous aluminum silicates with a layer (sheet-like) structure. Kaolin is a hydrous aluminosilicate mineral with a thin platelet structure. Kaolin is extensively used in paper, paint, and many other industries. Wet processing of kaolin will not be sustainable over the long term because global freshwater resources are becoming scarce. Hence, a process is necessary that does not consume water during the beneficiation of kaolin. This study developed a dry beneficiation process for low-grade kaolin of 59.6%, with 12% quartz and about 6% titaniferous impurities from Nagar Parkar, Sindh province, Pakistan. To develop a size difference between kaolinite and impurities, steel balls clad with rubber were used as the grinding media in a selective grinding unit. Screens of 60 and 400 mesh were employed to classify the feed of air classifier. Oversize +60 mesh was reground, 400 to 60 mesh fractions were sent to an air classifier, and −400 mesh was considered to be a product with the grade and recovery of 90.6% and 20.5%, respectively. Air classifier experiments were designed using central composite design. An experiment using a fan speed of 1200 rpm and a shutter opening of 4.0 showed optimum results, with maximum kaolinite grade and recovery of 91.5% and 35.9%, respectively. The statistical models developed for grade and recovery predicted the optimum results at a fan speed of 1251 rpm and shutter opening of 3.3 with the maximum kaolinite grade recovery of 91.1% and 24.7%, respectively. The differences between experimental and predicted grade and recovery were 0.1% and 2.4%, respectively. The characterization results showed the total upgrade of kaolin from 59.6% to 91.2%, with 27.1% recovery. The designed methodology has the potential to improve the yield of the product by focusing on its recovery. Furthermore, the designed process can be improved by using different sized balls in the selective grinding unit. This beneficiation process can utilize more than one air classifier in series to achieve the targeted results.
... The reason may stem from the repulsion force between the particles and the reversal in the suspension's zeta potential (Fig. 4), which hinders the sedimentation of the aluminum oxide particles (Fig. 8). In one study, the polyethyleneimine flocculant dosage upsurging from 0.004 to 0.4 g in the kaolin suspension led to suspension of particles due to the elevated repulsion force, achieving a sediment with lower compactness [55]. ...
In this work, oxidized and sulfomethylated lignin was used as a flocculant for aluminum oxide suspension. The oxidized sulfomethylated lignin (OSML) samples had a similar charge density (− 3.5 μeq/g) but varied molecular weights (between 26 and 46 kg/mol). The performance of the produced flocculants was evaluated in altering the relative turbidity and zeta potential of the aluminum oxide suspension. The chord length of particles was increased the most in the suspension by adsorbing OSML with the highest molecular weight. The flocs strength analysis revealed that the flocculation process was reversible. Flocculation analysis depicted that the molecular weight of OSML could influence the turbidity of the suspension dramatically. The settling velocity of the flocs was increased, and the sediment compactness was reduced as the flocs enlarged. The charge neutralization and patching mechanisms were estimated to be dominant for coagulating the particles.
