Flotation after a Direct Contact of Flotation Reagents with Carbonate Particles – Part 2: Phosphate Ore

Beneficiation of a deslimed, +0.038/−0.25 mm in size, phosphate ore containing carbonate fluorapatite (francolite), calcite, dolomite, and quartz by froth flotation is accomplished by a special approach based on conditioning the ore with a micro-emulsion consisting of 20 wt.- % Custafloat AR27 (collector, blend of fatty acid soaps and sulfates), 55 wt.- % No. 5 fuel oil and 25 wt.- % water at 70 wt.- % solid content and subsequent flotation after pulp dilution with water to 25 wt.- % solids. A good selectivity of separation was achieved at pH 8.5 and after 1.5 min conditioning time with micro-emulsion and flotation of the diluted pulp in the next 2 min. The maximum curvature of the upgrading Halbich grade-recovery curve indicated that the most efficient separation for the deslimed phosphate ore having 16.86 wt.- % P in the feed occurred at 0.6 kg/Mg providing concentrates containing 33 wt.- % P with P recovery equal to 70 wt.- %. The same flotation reagents used in a traditional way provided much worse concentrates containing 27 wt.- % P with recovery of 60 wt.- % at 0.9 kg/Mg of reagents.