Evaluation of flotation strategies for sedimentary phosphates with siliceous and carbonates gangues

Different flotation strategies to separate both calcite and silica from a sedimentary phosphate ore are studied in this paper. The results show that a single stage for flotation of phosphate or calcite is not enough to obtain high grade concentrates. Among three different processes for carbonate flotation, the results reveal better selectivity when phosphoric acid is used as depressant for phosphate. A circuit consists of a flotation stage for carbonate and another for either phosphate or silica presents the best strategy for upgrading such ore. Separation of calcite in the first stage seems to be essential where the selectivity margin tends to operate in favor of carbonate rather than phosphate mineral. Concentrates with P2O5 above 30% are obtained while using such flotation strategy from a feed ground to −0.15 mm.