The flotation of fine pyrite using colloidal gas aphrons

Fine mineral flotation is known to be problematic, however there is evidence that flotation performance is improved by the use of fine bubbles. In this work, a comparison is made between the flotation performance of two flotation systems; a conventional batch flotation cell and flotation using a spinning disc impeller as is used to generate very small bubble suspensions called colloidal gas aphrons (CGA's). The comparison of the CGA and the standard impeller was made using an artificial ore consisting of gravity concentrated pyrite from Durban Roodepoort Deep (South Africa) and quartz from Delmas (South Africa) finer than 38 microns. The collector was sodium n-propyl xanthate, the frother Dow 400. The comparison of the flotation performance was made at the following conditions; pH 4 and 8 and copper sulphate addition nil and 50 g/ton. The froths found in the two systems had significantly different structures. The CGA impeller yielded a froths surface with considerably larger bubbles and a wider distribution of bubble sizes than the conventional batch cell. The CGA float yielded higher grades (50% sulphur) than the conventional float (35%), although the flotation rate was somewhat lower. The results obtained indicate that this flotation system may have application for the selective recovery of finely ground minerals.