Rhenium recovery
There is provided a hydrometallurgical process of recovering rhenium values from mixtures thereof with other metal values in which the rhenium values constitute a minority amount, for example super-alloys, which comprises subjecting the mixture to strongly oxidizing acid conditions, preferably an aqueous mixture of hydrochloric acid and nitric acid, so as to form perrhenate species of at least the major proportion of the rhenium values in the mixture, dissolving the perrhenate species and other soluble metal species in aqueous solution, removing insoluble metal species from the aqueous solution, and isolating the rhenium species from the solution.
1. A hydrometallurgical process of recovering rhenium values from a rhenium-containing super-alloy in the form of pieces having a volume of from about 20 cm 3 to about 100 cm 3 , in which the rhenium values constitute a minority amount, the process comprising the steps of:
a) subjecting the super-alloy to strongly oxidizing acid leaching conditions by contacting the super-alloy with a leaching composition comprising nitric acid and hydrochloric acid so as to form dissolved perrhenate species in an aqueous solution;
b) removing insoluble metal species from the aqueous solution; and
c) separating rhenium species from the aqueous solution.
2. The process as defined in claim 1 , wherein the ratio of hydrochloric acid to nitric acid (v/v) in step a) is from about 1:3 to about 10:1, on a concentrated acid basis.
3. The process as defined in claim 1 , wherein the hydrochloric acid constitutes a major portion of the leaching composition.
4. The process as defined in claim 1 , wherein step (a) is conducted at temperatures of from about 40° C. to about 80° C.
5. The process as defined in claim 1 , wherein step (a) is conducted over a period of time of from about 2 days to about 10 days.
6. The process as defined in claim 1 , wherein the weight proportion of rhenium values and other metals in step (a) is from about 5% to about 20% (W/W).
7. The process as defined in claim 1 , wherein at least step (a) is conducted at atmospheric pressure.
8. The process as defined in claim 1 , wherein the rhenium species is separated from the aqueous solution by sulfide precipitation of Re 2 S 7 , by absorption on activated carbon, by absorption on absorbent resin, or by solvent extraction.
9. The process as defined in claim 1 , wherein the rhenium species is separated from the aqueous solution as solid ammonium perrhenate NH 4 ReO 4 .