Separation of trace molybdenum from tungstate solutions
AssigneeAmax Inc.
InventorsDale K. Huggins, Paul B. Queneau, Robert C. Ziegler, Leo W. Beckstead, Robert F. Hogsett
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Abstract
Dissolved molybdenum is removed from sodium tungstate solutions by adding sulfuric acid to lower the pH value of the solution to between about 8 and about 5, adding to the sodium tungstate solution a water-soluble sulfide in an amount of at least 0.5 gram per liter (gpl) in excess of that required to precipitate as sulfides molybdenum and certain other metals, then lowering the pH value of the sodium tungstate solution to between about 4.0 and about 1.5 as rapidly as possible with sulfuric acid in such a way as to precipitate molybdenum trisulfide while minimizing co-precipitation of tungsten.
Claims27
A process for separating dissolved molybdenum values from a sodium tungstate solution having pH value above about 8 which comprises adjusting the pH value of the sodium tungstate solution with sulfuric acid to a pH value between about 8 and about 5, adding at least one water-soluble sulfide to the neutralized solution to provide and maintain a sulfide ion concentration of at least about 0.5 gram per liter in excess of that required to form sulfides of molybdenum and other metal impurities, and acidifying the sulfidized sodium tungstate solution through the pH range between about 5 and about 4.5 in less than about 8 minutes to a final pH value between about 4 and about 1.5 to precipitate molybdenum trisulfide and to provide a product solution containing less than about 3 ppm molybdenum.
A process for separating dissolved molybdenum values from a sodium tungstate solution having a pH value above about 8 which comprises:
- adjusting the pH value of the sodium tungstate solution with sulfuric acid to a pH value between about 8 and about 5, adding at least one water soluble sulfide to the pH adjusted solution to provide and maintain a sulfide ion concentration of at least about 0.5 gram per liter in excess of that required to form sulfides of molybdenum and other impurities, establishing a heel solution having a pH value between about 4 and about 1.5, and feeding sulfuric acid and the sulfidized sodium tungstate solution to the heel solution at a rate to maintain the pH value of the heel solution between about 4 and about 1.5 and to precipitate molybdenum trisulfide.
A process for separating dissolved molybdenum values from a sodium tungstate solution having a pH value between about 8 and about 5 which comprises adding at least one water-soluble sulfide to the sodium tungstate solution to provide and maintain a sulfide ion concentration of at least about 0.5 gram per liter in excess of that required to form sulfides of molybdenum and other metal impurities, and acidifying the sulfidized sodium tungstate solution through the pH range between about 5 and about 4.5 in less than about 8 minutes to a final pH value between about 4 and about 1.5 to precipitate molybdenum trisulfide and to provide a product solution containing less than about 3 ppm molybdenum.
A process for separating dissolved molybdenum values from a sodium tungstate solution having a pH value between about 8 and about 5 which comprises adding at least one water-soluble sulfide to the sodium tungstate solution to provide and maintain a sulfide ion concentration of at least about 0.5 gram per liter in excess of that required to form sulfides of molybdenum and other impurities, establishing a heel solution having a pH value between about 4 and about 1.5, and feeding sulfuric acid and the sulfidized sodium tungstate solution to the heel solution at a rate to maintain the pH value of the heel solution between about 4 and about 1.5 and to precipitate molybdenum trisulfide.
Dependencies are inferred from the claim text.