Sequential Separation of Carbonate and Siliceous Gangue Minerals During Phosphate Ore Processing

Abstract

A unique fatty acid flotation process is described for sequential separation of carbonate and siliceous gangue minerals from low grade phosphate ores. The process involves a first stage of selective carbonate/phosphate separation followed by phosphate/silica separation during the second stage. In the first stage, a carbonate rich froth is removed without specific depression of the phosphate minerals and without conditioning of the pulp with the fatty acid collector prior to flotation. In the second stage, the same collector was selectively used to produce a market grade phosphate concentrate in the froth, in the presence or absence of a silica depressant. Selectivity was achieved using commercial grade fatty acid collectors, frothers and pH modifiers. The factors affecting carbonate/phosphate and phosphate/silica separation are discussed. Tests on a high-MgO siliceous phosphate matrix from south Florida, yielded phosphate concentrates analyzing 31% P₂O₅, 0.7% MgO and 4% acid insoluble matter with a P₂O₅ recovery of 80%.