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The flotation characteristics of artificial goethite were investigated with sodium dodecyl benzen sulfonate (S. D. B. S.) or sodium oleate and then the flotation test has been made on a mixture of artificial goethite and kaolinite.
In the flotation of artificial goethite using S. D. B. S., a high floatability is gained in the acidic or neutral region, but this anionic collector is not effective in the alkaline region. Since the isoelectric point of artificial goethite is approximately at pH 6.4, the surface of the mineral is positively charged at pH values lower than 6.4 and negatively charged at higher pH values. Therefore, it may be considered that artificial goethite is floated with the aerophilic film formed by the electrostatic adsorption of dodecyl benzen sulfonate ion on the surface of the mineral.
On the other hand, in the flotation using sodium oleate, despite of anionic collector, artificial goethite shows a, high floatability in the alkaline region where the surface of. the mineral is negatively charged. Its floatability, however, is diminished in the acidic region, where the concentration of oleate ion is decreased by hydrolysis of sodium oleate.
A high selectivity can not be attained using S. D. B. S. in the flotation of goethite from a mixture of artificial goethite and kaolinite. It may be mainly ascribed to the so-called slime coating.
Optimum flotation of goethite from the mixture above remarked using sodium oleate occurs in the weak alkaline, region where the slime coating is almost inhibited.
Furthermore, according to the infra-red spectroscopic observation or the settling test in the organic solvent, oleate ion may be adsorbed chemically on the surface of artificial goethite.