Minerals Beneficiation - Neutral Molecules in Flotation Collection

Long-chained neutral molecules (decyl alcohol) increase the flotation of corundum with sodium dodecylsulfate and trimethyldodecylammonium chloride as collectors. This phenomenon is postulated to result from coadsorption of the neutral molecules with the collector ions. Flotation and streaming potential experiments have shown that sodium laurate is an effective collector for corundum at more dilute concentrations than sodium dodecylsulfate or sulfonate.1>2 It has been postulated that this phenomenon results from the adsorption of both laurate ions and lauric acid molecules, whereas sodium dodecylsulfate can be adsorbed only as dodecylsulfate ions, since this collector does not hydrolyze under flotation conditions. Similar effects have been observed in alkaline solutions with dodecylammonium chloride and trimethyldodecylammonium chloride as collectors.' If in- creased flotation occurs with the collectors which hydrolyze because of adsorption of the neutral molecules, purposeful addition of long-chained molecules should increase the flotation rate of minerals with such collectors as sodium dodecylsulfate or trimethyldodecylammonium chloride because these long-chained molecules should coadsorb with the collector ions. The effect of neutral molecules on flotation in these cases must depend on an adsorption mechanism which differs from that proposed by Cook for the adsorption of xanthic acid molecules by galena. For neutral molecules to function as collectors in the flotation of insoluble oxide minerals, adsorption of organic ions must first occur to provide a means of anchoring the fatty acid or amine molecules. Without adsorption of collector ions, flotation does not occur even in the presence of large quantities of neutral molecules, as is indicated by the cessation of flotation at low pH values with soaps as collectors or at high pH values with primary amine salts as collectors.' Neutral molecules, such as fatty acids, must be adsorbed through van der Waals attraction between the hydrocarbon chains of the adsorbed soap ions and the hydrocarbon chains of the fatty acid molecules. The mutual association of hydrocarbon chains results