An investigation of the recovery of cryolite from alumina-electrolyte froth by flotation

In the industrial production of aluminium by the electrolysis of alumina, electrolyte froth, which is a mixture of carbon and cryolite is obtained at a rate of 50 kg of froth per ton of aluminium produced. Cryolite can be recovered from this mixture by flotation. In this study, the effects of the following parameters on flotation were experimentally investigated: particle size, type, combination, dosage and ratio of reagents, and conditioning time. It is found that it is possible to decrease the carbon content of cryolite below 1% by suitably choosing the operating parameters. Electrolyte froth must be ground to —100 mesh size for the liberation of carbon particles captured in the cryolite matrix. Any combination of two of the reagents, kerosene, fuel oil, creosote and terebenthene yield good results if used together with pine oil. Pine oil is found to be a more effective frother compared to Pril, a commercial detergent. Satisfactory separations are obtained when a kerosene-fuel oil mixture (50:50, v/v) is used as the collector with a dosage of 3.7 kg per ton of feed together with pine oil, the frother, with a dosage of 0.095 kg per ton of feed.