The recovery of sericite in flotation concentrates

Abstract

Sericite is a fine grained muscovite mica, which is widely distributed in nature. It commonly occurs in many base metal ores, where it can become a major diluent in the concentrates produced from these ores, as well as in igneous rocks. It can be strongly recovered in flotation froths under circumstances where it is both wanted and unwanted. Muscovite, which does not have any inherent natural flotability, responds readily to cationic flotation collectors to yield concentrates of high grade and recovery from granitic or pegmatite deposits, and the technology for this separation is well established. Sericite, on the other hand, often reports strongly to concentrates from base metal ores in which it occurs. Under these circumstances, the rejection of the sericite from the froth product is generally difficult, but nevertheless important, in order to minimise contamination of the base metal concentrate. This contamination can cause problems in subsequent smelting and/or leaching. Because in these flotation schemes no recognisable collector for sericite is present, it has been asserted that this mineral has a degree of natural flotability. However, there is little hard evidence to support this view. The reagents commonly used to depress sericite include polysaccharides, silicates and fluorosilicates. If these reagents are used on the basis that the sericite is truly floating, they will not be very helpful if, in fact, the recovery mechanism is different. Thus, the ultimate technique used to reject sericite from the froth of base metal concentrates will be different, depending on the mechanism by which the sericite reports to the concentrate, that is, whether by true flotation or entrainment. There is, however, no general agreement on the prevailing mechanism. Methods for the effective flotation of muscovite/sericite, as well as treatment schemes for the rejection of sericite from base metal concentrates, are briefly discussed, together with the proposed mechanisms by which sericite reports to the froth product.