From amine molecules adsorption to amine precipitate transport by bubbles: A potash ore flotation mechanism

Recent investigations summarized in this review have been conveniently grouped into (i) those dealing with the mechanism of action of the reagents applied in the flotation of potash ores, and (ii) those focused on the flotation properties of salt-type minerals and explanation of the remarkable selectivity between floatable sylvite, and non-floatable halite. This paper is confined to the first group. It is argued that in discussing the mode of action of long-chain primary amines in the flotation of potash ores account must be taken of the way in which these amines are applied by industry. Because they are water insoluble they are melted by heating up to 70-90 °C and then they are dispersed in acidified aqueous solution. Once added to the flotation pulp, the hot amine dispersion rapidly cools down to a temperature far below the Krafft point. The rapid conversion from a hot emulsion to a cold precipitate is a very severe transformation. Since nothing is known about the kinetics of these changes and phase instability only the lab tests in which the adopted reagent preparation procedures closely follow the industrial practice have been considered in this review.