Adsorption Mechanism of Sodium Oleate on Scheelite

Abstract

The adsorption mechanism of oleate ion on scheelite surface has been investigated from the measurement of adsorption amount, of zeta potential, and infrared spectrum analysis of a species formed on the surface, in connection with flotation tests.In alkaline solution, oleate ion is adsorbed on scheelite surface to the bimolecular layer, where further adsorption is restrained. The monomolecular adsorption is induced by the exchange of oleate ion with tungustate ion on scheelite surface and calcium oleate is formed, rendering the surface hydrophobic. The bimolecular adsorption in which oleate ion is oriented in such a manner that the carboxyl group faces toward the solution and the alkyl group faces toward the scheelite surface, begins to occur partially before the completion of the monomolecular layer and results in decreasing the hydrophobicity.In acidic solution, undissociated oleic acid is adsorbed on scheelite surface. However, the adsorption does not render the surface hydrophobic.