Leaching of chromium, nickel, cobalt and manganese from ores

Claim 1

A PROCESS FOR THE RECOVERY OF CHROMIUM AND AT LEAST ONE OF NICKEL AND COBALT AND AS WELL ANY OTHER VALUABLE NON-FERROUS METAL PRESENT IN THE LATERIITIC, LIMONITE ORE TO BE TREATED, WHICH COMPRISES MIXING THE LIMONITE ORE HAVING A CONTENT OF SAID METALS TO BECOVERED WITH A TETRAVALENT MANGANIC OXIDE MINERAL IN A QUANTITY AT LEAST EQUIVALENT TO THE QUANTITY STOICHIOMETRICALLY CALCULATED TO OXIDIZE THE CHROMIUM TO A FORM SOLUBLE IN SULFURIC ACID, AND WITH SULFURIC ACID AND WATER TO FORM A SLURRY, THE QUANTITY OF SULPHURIC ACID EQUALLING AT LEAST 40% OF THE DRY WEIGHT OF SAID ORE AND BEING PRESENT IN THE SLURRY IN A QUANTITY REQUIRED IN THE PROCESS TO SOLUBILIZE ONLY THE NON-FERROUS METALS TO BE RECOVERED, HEATING THE RESULTING MIXTURE TO A TEMPERATURE OF AT LEAST ABOUT 450* F. UNTIL THE CHROMIUM AN OTHER DESIRED NONFERROUS METALS HAVE DISSOLVED, SEPARATING THE RESULTING PRODUCT LIQUID CONTAINING THE SAID SOLUBILIZED METALS FROM THE ORE TAILINGS CONTAINING THE IRON, SUBJECTING THE PRODUCT LIQUOR TO THE ACTION OF A REDUCING AGENT WHICH REDUCES THE DICHROMATE IONS, CONVERTING THE CONTENTS OF NICKEL AND COBALT IN SAID ALTERED SOLUTION TO THE SULFIDE PRECIPITATE FORM AND SEPARATING THE PRECIPITATE FROM THE SOLUTION STILL CONTAINING THE CHROMIUM THEREIN.