NEW REAGENT SYSTEMS FOR THE FLOTATION OF KAOLINITE

The selective flotation of kaolinite for the separation from feldspar is difficult because the two minerals have very similar surface properties and the flotation feed contains a high proportion of extremely fine particles (< 5-mu-m); nevertheless, this process is of great practical importance. The alkyl amines usually used as collectors in kaolinite flotation processes only give satisfactory results in strongly acidic pulps. Reagent systems based on cationic surfactants were developed to enable kaolinite to be separated from feldspar by flotation in weakly acidic to neutral pulps. Special importance is attached to the addition of suitable multivalent cations in this context. Furthermore, in the presence of these multivalent cations flotation can be carried out with suitable anionic surfactants that previously could not be used because of their low effectiveness. With the help of basic studies of the charge on the minerals and the adsorption of the surfactants and the multivalent cations on the mineral surfaces, a good understanding of the action mechanism of the developed reagents was obtained. During flotation with cationic surfactants the recovery of feldspar is reduced, and the selectivity of the flotation is thus improved, as a result of aluminium ions being competitively adsorbed rather than collector ions. By contrast, in the case of flotation with anionic surfactants the activation of the kaolinite surface by the multivalent cations is the crucial precondition for selective flotation. The effectiveness of the new reagent systems was demonstrated in laboratory scale flotation tests on natural kaolinite ores.