Recovery of Cr2 O3 from a chromium bearing solution

Claim 1

A method for recovering high purity Cr 2 O 3 from chromium ore which comprises: (i) roasting in a gaseous oxidizing environment a mixture of chromium ore with Na 2 CO 3 and CaO at a temperature in the range of about 600° C. to 1100° C. for from about 0.5 to 6 hours, the amount of Na 2 CO 3 being that which provides from about 1.4 to 4.2 pounds of Na 2 CO 3 per pound of Cr 2 O 3 in the ore and the amount of CaO being that which provides from about 0.6 to 1 pound of CaO per pound of Cr 2 O 3 in the ore; (ii) water leaching roasted material obtained in step (i) at a temperature of from about 5° C. to the boiling point of water for from about 5 minutes to 5 hours; (iii) adding acid to the leach liquor obtained in step (ii) to provide a pH of from about 3 to 9.5 to cause precipitation of aluminum impurities and separating said impurities from the leach liquor; (iv) adding acid to the leach liquor to provide a pH of about 1 to 2; (v) contacting the acidified leach liquor obtained in step (iv) with a tertiary amine dissolved in an organic solvent essentially free of isodecanol to inhibit the formation of emulsion, to recover chromium values from the acidified leach liquor in a chromium containing organic liquid phase; (vi) treating the chromium containing organic phase with a water solution of NH 4 OH to obtain a solution of (NH 4 ) 2 CrO 4 ; (vii) subjecting the solution of (NH 4 ) 2 CrO 4 to evaporation to provide a solid chromium-bearing material; and (viii) igniting the solid chromium-bearing material to obtain Cr 2 O 3 .

Claim 2

A method for recovering high purity Cr 2 O 3 from chromium ore which comprises: (i) roasting in a gaseous oxidizing environment a mixture of chromium ore with Na 2 CO 3 and CaO at a temperature in the range of about 600° C. to 1100° C. for from about 0.5 to 6 hours, the amount of Na 2 CO 3 being that which provides from about 1.4 to 4.2 pounds of Na 2 CO 3 per pound of Cr 2 O 3 in the ore and the amount of CaO being that which provides from about 0.6 to 1 pound of CaO per pound of Cr 2 O 3 in the ore; (ii) water leaching roasted material obtained in step (i) at a temperature of from about 5° C. to the boiling point of water for from about 5 minutes to 5 hours; (iii) adding acid to the leach liquor obtained in step (ii) to provide a pH of from about 3 to 9.5 to cause precipitation of aluminum impurities and separating said impurities from the leach liquor; (iv) adding acid to the leach liquor to provide a pH of about 1 to 2; (v) contacting the acidified leach liquor obtained in step (iv) with a tertiary amine dissolved in an organic solvent essentially free of isodecanol to inhibit the formation of emulsion, to recover chromium values from the acidified leach liquor in a chromium containing organic liquid phase; (vi) treating the chromium containing organic phase with a water solution of NH 4 OH to obtain a solution of (NH 4 ) 2 CrO 4 ; (vii) subjecting the solution of (NH 4 ) 2 CrO 4 to evaporation to provide a solid chromium-bearing material; and (viii) igniting the solid chromium-bearing material to obtain Cr 2 O 3 .