On the adsorption of surfactants on non-sulphide minerals

Abstract

This work is concerned with basic studies on the flotative separation of three minerals: apatite, hornblende, and magnetite. Two anionic surfactants that differed in the solubility of their calcium salts were chosen as collectors (oleate and alkylsulphosuccinate). The flotation behavior of the minerals was characterized by determing adsorption isotherms and zeta-potentials, and by carrying out microflotation tests. It was shown that both collectors are adsorbed on all mineral surfaces, but at different equilibrium concentrations. As the concentration range of the onset of adsorption on apatite is lower than that on hornblende and magnetite, apatite can be separated from a mineral mixture or a respective ore. Calcium ions are often present in the flotation pulp and influence the adsorption behavior of the collectors. Due to the slight solubility of the calcium-containing minerals, apatite and hornblende, precipitation of calcium oelate occurs, as well as adsorption of oleate when a certain concentration is reached. Higher calcium ion concentrations induce more precipitation and make oleate less effective as a collector. Because of the higher solubility of the calcium alkylsulphosuccinate, precipitation does not occur in the considered concentration range. In contrast to oleate, the adsorption of alkylsulphsuccinate is shifted to lower equilibrium concentrations by calcium ions adsorbed on the mineral surface. This makes alkylsulphosuccinate a more effective collector in water with high calcium ion concentrations. The sequence of adsorption and hence, of flotation is not influenced by calcium ions, i.e., apatite, but not hornblende, can be separated from magnetitde.