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Talc, as an industrial mineral, is usually used at fine and ultrafine sizes in different applications. However, reaching the ultrafine sizes depends simultaneously on grinding conditions and the characteristics of the mineral to be ground. In this paper, the effect of talc hydrophobicity and grinding conditions in terms of grinding balls size, mill filling, grinding time, stirrer speed, and solids% on producing –45 microns in an attritor mill were studied. The change in talc particle size in dry and wet grinding modes was recorded along with monitoring the structural change by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the d50 of the ground product reaches 10 µm or less at 10 mm media size, 60 min grinding time, 385 rpm stirring speed, 40% solids, and 25% mill filling. Nevertheless, under the same conditions, dry grinding not only gives a smaller product but also has higher structural changes than wet grinding. The talc hydrophobicity leads to talc particles agglomeration in aqueous media and consequently, a part of grinding energy is consumed in agglomerates breakdown resulting in delaying not only the reach to the same size as in the dry grinding but also the crystal lattice destruction. Inevitably, the intensive grinding to ≤ –5 µm changes the talc structure drastically in both grinding modes. [ABSTRACT FROM AUTHOR]

Oil shale impurities prevent its direct usage as a source of energy. Removing or reducing of these impurities before retorting can reduce the cost of oil shale processing. In that regard, pretreatment of oil shale by flotation represents one of the favorable solutions. Therefore, in this work, (a) microscopic examinations were carried out to study the mineralogical characteristics of oil shale sample and (b) flotation of oil shale was used to separate organic matter (kerogen) from associating gangue by adjusting the flotation pH, stirring speed and pulp density without adding a collector. The results of oil shale characterization showed that kerogen content in the studied sample was 10%, while the results of flotation experiments proved the possibility of oil shale upgrading to about 20% kerogen with recovery reaching to more than 70%. [ABSTRACT FROM AUTHOR]

The commonly utilized flotation scheme in phosphate industry is reverse flotation using fatty acids in acidic media adjusted by H2SO4. The acidity of the flotation pulp results in presence of different ionic species that play a crucial role in modifying the minerals’ surfaces. Therefore, the flotation of pure phosphate was investigated in presence of H2SO4 for pH adjustment and potassium oleate, potassium dihydrogen phosphate, potassium oxalate, calcium nitrate and potassium sulfate. The reason behind using these chemical reagents is to study the effect of different ionic species on the phosphate flotation. Flotation results as well as thermodynamic analysis indicated that the formation of aqueous calcium/phosphate complexes (i.e., CaHPO4(aq)) on hydroxyapatite surface is the most significant species in depressing phosphates. The Ca++ concentration, particularly in acidic pH, showed a great effect on the formation of aqueous CaHPO4. The aqueous CaHPO4 concentration sharply decreased by increasing Ca++ concentration where the depression becomes more challenging. Therefore, the main purpose of adding depressants is to reduce Ca++ ions by forming Ca-depressant complexes. [ABSTRACT FROM AUTHOR]