Multiple batch recovery of acid dissolved molybdenum
AssigneeWestinghouse Electric Corp.
InventorHerman R. Heytmeijer
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Abstract
Rapid recovery of molybdenum from an acid solution containing dissolved molybdenum is accomplished by using a multiple batch method. A first batch of ammonium molybdate precipitate is formed by diluting a first portion of acid with 1.5 times that volume of water, adding anhydrous ammonia, and seeding with ammonium molybdate particles while maintaining a temperature between 90.degree. C. and boiling. Subsequent batches of precipitate are formed by dissolving the previous precipitate in additional acid, similarly diluting as above, and adding anhydrous ammonia while maintaining temperature as above. All precipitates are coarse and fast settling.
Claims5
A multiple batching method for rapidly and efficiently recovering molybdenum from a mixed sulfuric acid-nitric acid aqueous solution having substantial quantities of molybdenum dissolved therein, said mixed acid solution having been used to dissolve molybdenum mandrels from coiled tungsten filaments, which method comprises:
- a. diluting a first portion of said mixed acid solution with water to a first predetermined acid-water volume ratio,
- b. adding anhydrous ammonia to said diluted first portion of said solution at a predetermined rate sufficient to cause the solution temperature to rise to at least about 90.degree. C., maintaining the solution temperature at less than its boiling temperature, and continuing the controlled anhydrous ammonia addition to said solution while maintaining the solution temperature of at least about 90.degree. C. but less than the solution boiling temperature until the solution pH is from about 1.5 to about 3.5,
- c. seeding the partially neutralized solution with a small predetermined amount of ammonium molybdate solid particles,
- d. maintaining the seeded solution at a temperature of at least about 90.degree. C. but less than the solution boiling temperature until substantially all molybdenum is precipitated therefrom as ammonium molybdate, and separating the resulting precipitated ammonium molybdate from residual solution,
- e. adding an additional portion of said mixed acid solution to said separated ammonium molybdate, diluting said added additional portion of said mixed acid solution with water to a second predetermined acid-water volume ratio, redissolving the precipitated ammonium molybdate while adding anhydrous ammonia to said solution at a predetermined rate sufficient to cause the solution temperature to rise to at least about 90.degree. C. but less than its boiling temperature, and continuing the controlled anhydrous ammonia addition to said solution while maintaining the solution temperature of at least about 90.degree. C. but less than the solution boiling temperature until the solution pH is from about 1.5 to about 3.5, maintaining the solution at a temperature of at least about 90.degree. C. but less than the solution boiling temperature until substantially all molybdenum is precipitated therefrom as ammonium molybdate, separating the resulting precipitated ammonium molybdate from residual solution, and repeating the foregoing steps utilizing additional batch amounts of spent acid solution to accumulate additional batch amounts of precipitated ammonium molybdate,
- f. washing the precipitate by adding water to the precipitated ammonium molybdate, agitating the slurry, allowing substantially all the precipitate to settle, removing the wash water from the settled precipitate, and repeating the foregoing washing as required to remove substantially all soluble impurities from said precipitate.
Dependencies are inferred from the claim text.