Concentration of phosphate minerals

Claim 1

A PROCESS FOR CONCENTRATING PHOSPHATE MINERALS FROM THEIR ORES WHICH COMPRISES THE FOLLOWING OPERATIONS: (I) SUBJECTING SUITABLY SIZED PHOSPHATE ORE TO FROTH FLOATATION TREATMENT, IN AN AQUEOUS PULP, WITH NEGATIVE-ION REAGENTS, THEREBY PRODUCING ROUGHER CONCENTRATE MATERIAL (FROTHPRODUCT) AND SILICIOUS WASTE MATERIAL (TAILING); (2) SUBJECTING THE ROUGHER CONCENTRATE FROM PART OF THE SAID ORE TO RETARDED FROTH FLOTATION TREATMENT IN AN AQUEOUS PULP AND REMOVING, AS PART OF THE FINAL PRODUCT, A CONCENTRATE FROTH-PRODUCT HAVING A LOW INSOLUBLE CONTENT AND A PHOSPHATE-RICH MIDDLING RESIDUE; (3) SUBJECTING THE ROUGHER CONCENTRATE FROM THE REMAINING PART OF SAID ORE, IN AN AQUEOUS PULP, TO TREATMENT WITH A MINERAL ACID FOLLOWED BY RINSING WITH WATER, THUS REMOVING FROM SAID ROUGHER CONCENTRATE SUBSTANTIALLY ALL OF THE ADHERING NEGATIVE-ION REAGENTS: (4) SUBJECTING SAID ACID-TREATED AND RINSED ROUGHER CONCENTRATE, IN AN AQUEOUS PULP, TO FROTHFLOTATION TREATMENT WITH POSITIVE-ION REAGENTS, THEREBY PRODUCING A FROTH-PRODUCT COMPOSED MOSTLY OF SILICIOUS GANGUE WHICH IS DISCARDED, AND A RESIDUE WHICH IS A HIGH GRADE PHOSPHATE CONCENTRATE WHICH CAN BE COMBINED WITH THE HIGH GRADE PHOSPHATE CONCENTRATE FROM THE PREVIOUSLY MENTIONED (2) RETARDED FLOATS: (5) COMBINING AT LEAST A SUBSTANIAL PORTION OF THE PHOSPHATE-RICH MIDDLING RESIDUE FROM THE RETARDED FLOTATION OPERATION (2)-DIRECTLY WITH THAT PART OF THE ORE FROM WHICH IS SUBSEQUENTLY PRODUCED THE ROUGHER CONCENTRATE FOR THE PREVIOUSLY MENTIONED (4) POSITIVE-ION FLOTATION TREATMENT.