Effect of Hydrophobicity on Talc Grinding in Attritor Mill

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 mu m 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 mu m changes the talc structure drastically in both grinding modes.