Claims
- 1. A process for recovering cyanide from feed material containing cyanide and copper comprising the steps of:
(a) contacting said feed material with a strong base anion exchange resin whereby copper and cyanide from said feed material are adsorbed onto said resin; (b) contacting the resulting resin with an eluant solution containing free cyanide ion to elute copper and cyanide from said resin, the amount of copper removed being approximately equivalent to the amount of copper adsorbed onto said resin in step (a); (c) separating the eluted resin from the eluting solution or eluate from step (b); (d) acidifying the eluate from step (b) to precipitate copper; (e) separating the acidified solution from the precipitate in step (d) and alkalizing directly or after concentration the separated solution containing HCN; (f) contacting the eluted resin from step (b) with an acid to condition the resin and remove additional cyanide while leaving most of the copper in the resin phase; (g) converting the HCN solution formed in step (f) to cyanide ion, directly or after concentration of the HCN solution, by the addition of alkali; and (h) returning the conditioned resin from step (f) to step (a) above.
- 2. A process as set forth in claim 1 wherein the copper precipitated in step (d) is optionally discarded before or after cyanide treatment or recovery from the precipitates.
- 3. A process as set forth in claim 1 wherein the precipitate from step (d) is smelted for recovery of copper.
- 4. A process as set forth in claim 1 wherein the copper in step (d) is precipitated as copper cyanide, copper thiocyanate or copper sulfide.
- 5. A process as set forth in claims 3 and 4 wherein said copper cyanide or copper thiocyanate is converted to copper sulfide prior to smelting.
- 6. A process as set forth in claim 5 wherein cyanide is recovered from copper cyanide as the result of its conversion to copper sulfide.
- 7. A process as set forth in claim 1 wherein the copper in step (d) is precipitated as copper cyanide or copper thiocyanate which is then used as the feed to a copper electrowinning or electroplating process with optional recovery of cyanide.
- 8. A process as set forth in claim 1 wherein a portion of the copper precipitated in step (d) is recycled to said feed material in order to reduce the CN:Cu molar ratio in said feed material or on said resin thereby aiding in the loading of free CN− on the resin.
- 9. A process as set forth in claim 1 wherein the copper precipitated in step (d) is diluted with gypsum and subjected to selective precipitation in which part of the gypsum is precipitated with little or no copper product present.
- 10. A process as set forth in claim 1 wherein the copper precipitate from step (d) is diluted with gypsum and the gypsum/copper precipitate subjected to flotation to separate the copper compound from the gypsum.
- 11. A process as set forth in claim 1 wherein said resin from step (a) is treated with a solution of ferric sulfate, ferric chloride or ferric nitrate for the removal of excess thiocyanate.
- 12. A process as set forth in claim 1 wherein the loading of said resin in step (a) is carried out so that the resin exchange sites are substantially loaded with metal cyanide complexes or thiocyanate ion thereby increasing the loading of cyanide and copper on said resin.
- 13. A process as set forth in claims 1 and 2 wherein said resin is substantially completely loaded with metal cyanide complexes so that most of the thiocyanate ion in said feed material is transported through step (a) of claim 1 and remains in the treated feed material.
- 14. A process as set forth in claim 1 wherein the copper concentration on said resin is intentionally increased by allowing copper in the resin phase leaving the second elution step (f) to increase above approximately 1.0 moles of copper per liter of said resin.
- 15. A process as set forth in claim 1 wherein calcium is excluded from said eluant in step (b) and said eluant contains sodium based compounds thereby preventing the formation of calcium sulfate (gypsum) when sulfuric acid is present in said elution steps (b) and (f).
- 16. A process as set forth in claim 1 wherein hydrochloric acid resulting from the reaction of calcium chloride with sulfuric acid is used in precipitation step (d).
- 17. A process as set forth in claim 1 wherein the HCN removal from said acidified solution in step (e) is incomplete and the residual HCN is alkalized for use in elution step (b).
- 18. A process as set forth in claim 1 wherein the conditioned resin from step (f) is first washed to recover residual HCN prior to being returned to step (a) for loading.
- 19. In a process for recovering cyanide and optionally copper utilizing a strong base anion exchange resin wherein cyanide soluble copper compounds are contained in the resin phase which is to be loaded with cyanide and copper, the improvement which comprises making the copper content of said resin phase greater than about 0.7 moles of Cu per mole of active anion exchange resin sites.
- 20. In a process for recovering cyanide and optionally copper utilizing a strong base anion exchange resin wherein cyanide soluble copper compounds are contained in the resin phase which is to be loaded with cyanide and copper, the improvement which comprises limiting the flow of loaded resin to a subsequent elution step so that the loaded resin has a CN:Cu ratio of 2:1 or less and the eluates therefrom approach a CN:Cu ratio of approximately 2-3.
- 21. A process as set forth in claim 1 wherein compounds of zinc or copper which complex with cyanide are added to said feed material to reduce the free cyanide concentration or CN:CU ratio to facilitate loading of cyanide on said strong base anion exchange resin.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of U.S. Ser. No. 09/651,553 filed Aug. 30, 2000 which claims the benefit of U.S. Provisional Application No. 60/157,307 filed Oct. 1, 1999.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60157307 |
Oct 1999 |
US |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09651553 |
Aug 2000 |
US |
Child |
10373006 |
Feb 2003 |
US |