Patent EA-000432-B1 (EA)
Title: Method of purifying gold
Inventor: HANNA MOURAD MICHAEL
IPC: C22B3/06
Filed: 1996-07-19
Abstract: 1. A method of increasing the gold content of a metallic gold composition comprising the steps of (i) subjecting the metallic gold composition to at least one of roasting and gas atomization, and (ii) treating the metallic gold composition obtained from step (i) with a strongly acidic oxidizing leach liquor, the leach liquor being selected to dissolve the impurities from the metallic gold composition, the leach liquor further being selected such that gold has a low solubility in the leach liquor. 2. The method of increasing the gold content of a metallic gold composition of Claim 1 in which the leach liquor comprises a solution of a strong acid and an oxidizing agent. 3. The method of increasing the gold content of a metallic gold composition of any one of Claims 1-2 further comprising the step of plastically deforming the metallic gold composition prior to exposure to the leaching solution. 4. The method of increasing the gold content of a metallic gold composition of Claim 3 further comprising the step of roasting the metallic gold composition in an oxidizing atmosphere, in step (i), after plastic deformation. 5. The method of increasing the gold content of a metallic gold composition of Claim 3 in which the metallic gold composition is plastically deformed by rolling. 6. The method of increasing the gold content of a metallic gold composition of any one of Claims 1-5 further comprising the step of roasting the metallic gold ' composition in an oxidative atmosphere after the metallic gold composition is exposed to the leaching liquor and then exposing the roasted metallic gold composition to the leaching liquor to remove the further impurities. 7. The method of increasing gold content of any one of Claims 1-6 in which at least one roasting is carried out in a reducing atmosphere. 8. The method of increasing the gold content of a metallic gold composition of any one of Claims 1-7 in which the metallic gold composition is roasted in an oxidizing atmosphere before exposure to the leaching solution. 9. The method of increasing the gold content of a metallic gold composition of any one of Claims 1-8 in which the roasting step is carried out at a temperature of at least 500 degree C in an oxygen atmosphere. 10. The method of increasing gold content of Claim 10 in which the temperature is at least 800 degree C. 11. The method of increasing, the gold content of a metallic gold composition of any one of Claims 1-10 in which the metallic gold composition is spray atomized before treating with the leaching liquor. 12. The method of increasing the gold content of a metallic gold composition of Claim 11 in which the metallic gold composition is spray atomized in an oxygen atmosphere and then quenched before treating with the leaching liquor. 13. The method of increasing gold content of any one of Claims 1-12 in which the metallic gold composition is treated to increase the ratio of surface area to volume. 14. The method of increasing gold content of any one of Claims 1-13 in which the leach liquor is Caro's acid. 15. The method of increasing gold content of any one of Claims 1-13 in which the leach liquor is nitric acid. 16. The method of increasing gold content of any one of Claims 1-13 in which the leach liquor is nitric acid in the presence of gaseous oxygen. 17. The method of increasing the gold content of a metallic gold composition of any one of Claims 1-16 in which the leach liquor further comprises a wetting agent.