Adsorption of dodecylammonium ion on quartz in relation to its flotation

Abstract

The flotation of −10μm diameter quartz particles using dodecylammonium acetate (DAA) as a collector was carried out at pH 5 and pH 9.8 by varying DAA concentration. The adsorption density of DAA and the zeta potential of quartz were also measured in order to analyze the flotation results. At pH 5, complete flotation of quartz was achieved at a DAA adsorption density of only about 1% surface monolayer coverage, while at pH 9.8 the complete flotation of quartz required the adsorption density of DAA to be more than equivalent monolayer adsorption. The isoelectric point of quartz in the presence of DAA at pH 5 was best described by adopting Δp K (=p K −−p K +) = 6, where K − and K + are the dissociation constants of anionic and cationic sites on quartz surfaces, respectively. Analysis of the results of zeta potential measurements at pH 9.8 on the basis of the site dissociation model suggests that the adsorbed species on quartz surfaces are dominated by undissociated free amine molecules at this pH. The mechanism of the free amine adsorption on fine quartz in alkaline media is discussed.