Claims
- 1. A process for refining impure silver bullion containing metals from the group consisting of Pb, Se, Cu, Au and platinum group metals as impurities, comprising:leaching the silver bullion with HNO3 at a temperature above 50° C., followed by filtration, thereby separating a Au bearing residue from an Ag rich liquor; heating the Ag rich liquor, thereby evaporating H2O and forming an AgNO3 bearing melt; maintaining the AgNO3 bearing melt at a temperature of 300-350° C. for at least 15 minutes, thereby forming a mixture of a purified AgNO3 and a denitration residue containing essentially all the Cu and platinum group metals as oxides; and separating the purified AgNO3 from the denitration residue.
- 2. The process according to claim 1, wherein said leaching the silver bullion takes place in an O2 enriched atmosphere.
- 3. The process according to claim 1, wherein said separating the purified AgNO3 from the denitration residue involves filtrating the mixture at a temperature above 220° C., thereby obtaining purified molten AgNO3.
- 4. The process according to claim 1, wherein said separating the purified AgNO3 from the denitration residue involves reacting the mixture with water, followed by filtration, thereby obtaining a purified AgNO3 solution.
- 5. The process according to claim 1, wherein the leaching is preceded by:heating the silver bullion, thereby forming a molten metallic phase; and granulating the molten metallic phase in water, thereby forming Ag righ granules; and wherein the leaching is performed on the Ag righ granules.
- 6. The process according to claim 5, including removing Se as gaseous SeO2 from the molten metallic phase by injecting air into the metallic phase at a temperature of 1000-1250° C.
- 7. The process according to claim 6, wherein the air injected is O2 enriched.
- 8. The process according to claim 6, wherein the metallic phase is at a temperature of 1000-1100° C.
- 9. The process according to claim 5, including contacting the molten metallic phase with an acidic flux at a temperature of 1000-1300° C., and slagging off Pb from the molten metallic phase.
- 10. The process according to claim 9, wherein the molten metallic phase is at a temperature of 1000-1150° C.
- 11. The process according to claim 1, wherein the purified molten AgNO3 is further processed to elemental Ag by:decomposing the purified molten AgNO3 at a temperature above 400° C. into purified Ag and NOx; and scrubbing the NOx with H2O in an exiting atmosphere, thereby forming HNO3.
- 12. The process according to claim 11, including recycling the HNO3 for use in said leaching.
- 13. The process according to claim 1, wherein a purified AgNO3 solution is obtained from said separations, and wherein said purified AgNO3 solution is further processed to elemental Ag by hydrolyzing the purified AgNO3 solution with NaOH or KOH, thereby forming a Ag2O precipitate, which is separated by filtration, and decomposing the Ag2O at a temperature above 300° C. into elemental Ag and O2.
- 14. The process according to claim 1, wherein a purified AgNO3 solution is obtained from said separating, and wherein said purified AgNO3 solution is further processed to elemental Ag by:reacting the purified AgNO3 solution with HCl, thereby forming AgCl and HNO3, which are separated by filtration, and transforming the AgCl to elemental Ag and NaCl by one of reacting the AgCl with an NaOH solution in presence of a reducing agent, and heating the AgCl with a soda flux above 1000° C.
- 15. The process according to claim 14, further comprising recycling the HNO3 formed by said reacting and separation by filtration, to said leaching.
Priority Claims (1)
Number |
Date |
Country |
Kind |
00200294 |
Jan 2000 |
EP |
|
RELATED APPLICATIONS
This application is a U.S. national stage filing of International Application No. PCT/EP01/00613, filed Jan. 17, 2001, which, in turn, claims priority of European Application No. 00200294.7, filed Jan. 28, 2000.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/EP01/00613 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO01/55462 |
8/2/2001 |
WO |
A |
US Referenced Citations (3)
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GB |
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JP |
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RU |
Non-Patent Literature Citations (1)
Entry |
Copy of International Search Report from related PCT/EP01/00613 mailed Jun. 13, 2001, 3 pages. |