Several soluble minerals are recovered by flotation in the potash industry. The leading example of the flotation of soluble salts is the separation of sylvite (KCI) from halite (NaCI). While the practice of flotation of these minerals is relatively well established, the mechanism of flotation is less clear. The purpose of this paper is to examine the mechanism of flotation of these minerals, and to propose a novel mechanism. It is argued that the collector is adsorbed onto the mineral surface by electrostatic forces. It is proposed that the charging of the surface charging is caused by the dissolution of ions from and deposition of ions onto the mineral surface. It is shown that this model displays the observed features of zeta potential measurements as a function of pH, that is, it is pseudo-Nernstian and asymmetrical in nature, is consistent with the thermodynamic model for reversible interfaces, and is consistent with the thermodynamics of the overall reaction and its solubility. Application of the proposed theory is discussed for the flotation of sylvite.
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