US4778519A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Recovery of precious metals from a thiourea leach
Assignee: Individual
•
Filing: 1987-04-07
•
Granted: 1988-10-18
•
Expires: 2007-04-07
Abstract
Abstract A method is provided for recovering gold and silver from precious metal bearing materials including ores, leaching residues, flue dust, electronic scrap, jewelry scrap, etc. In the method, the gold and silver are extracted from the precious metal bearing materials with a thiourea solution to form a thiourea leach, and the thiourea leach is contacted with carbon to adsorb the gold and silver and provide loaded carbon. The method is characterized by the step of contacting an alkaline solution of thiousulfate ion with the loaded carbon thereby desorbing the precious metals form the carbon. In one modification of the method, an additional step includes adding a salt to the aqueous thiousulfate solution. When needed, the method includes the step of protecting the thiousulfate ion from oxidizing agents. This is done by adding a reducing agent such as sodium sulfite to the thiousulfate solution. When copper is present, the method includes the addtional step of removing copper from the carbon prior to exposing the carbon to the thiourea solution containing the precious metals.
Inventors
- 👤 Batric Pesic
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 21:44
CPC Classifications
C; C01; C01G; C01G7/00; C01G7/003; C01G5/00; C01G5/003; C22; C22B; C22B11/00; C22B11/04; C22B11/042; C22B11/044; C22B11/046; C22B3/00; C22B3/20; C22B3/22; C22B3/24; C22B7/00; C22B7/02; Y; Y02; Y02P; Y02P10/00; Y02P10/20
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
75 words
A method for recovering precious metals from precious metal bearing materials, said method comprising the steps of: extracting the precious metal bearing materials with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the precious metals; contacting thiosulfate ion with the loaded carbon, the thiosulfate ion separating the precious metals from the carbon, the precious metals selected from the group consisting of silver and gold.
Claim 2
Independent Claim
75 words
A method for recovering precious metals from precious metal bearing materials, said method comprising the steps of: extracting the precious metal bearing materials with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the precious metals; contacting thiosulfate ion with the loaded carbon, the thiosulfate ion separating the precious metals from the carbon, the precious metals selected from the group consisting of silver and gold.
Claim 3
Dependent Claim
22 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the thiourea is in aqueous solution.
Claim 4
Dependent Claim
28 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the thiosulfate ion is contacted with the loaded carbon under alkaline conditions.
Claim 5
Dependent Claim
27 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the thiosulfate ion is obtained from a water soluble thiosulfate compound.
Claim 6
Dependent Claim
38 words
A method for recovering precious metals from precious metal bearing materials described in claim 4 wherein the thiosulfate ion is in the form of an aqueous solution and forms a thiosulfate leach solution upon contacting the loaded carbon.
Claim 7
Dependent Claim
28 words
A method for recovering precious metals from precious metal bearing materials described in claim 5, further including the step of adding a salt to the aqueous thiosulfate solution.
Claim 8
Dependent Claim
33 words
A method for recovering precious metals from precious metal bearing materials described in claim 6 wherein the added salt is selected from the group consisting of alkali-metal and alkaline-earth-metal chlorides, nitrates, and sulfates.
Claim 9
Dependent Claim
33 words
A method for recovering precious metals from precious metal bearing materials described in claim 5 wherein the thiosulfate concentration is in the range of from 0.1 gram per liter to a saturated solution.
Claim 10
Dependent Claim
89 words
A method for recovering precious metals from precious metal bearing materials described in claim 5 wherein the pH of the aqueous thiosulfate solution is in a range having a lower end and an upper end, the lower end of the range of pH of the solution being sufficiently high to maintain the stability of the thiosulfate ion in the aqueous solution, the upper end of the range of pH of the solution being sufficiently low to maintain the stability of the carbon in the presence of the aqueous solution.
Claim 11
Dependent Claim
29 words
A method for recovering precious metals from precious metal bearing materials described in claim 5 wherein the pH of the aqueous thiosulfate solution is in the range of pH=8-10.5.
Claim 12
Dependent Claim
35 words
A method for recovering precious metals from precious metal bearing materials described in claim 5 wherein the thiosulfate is contacted with the carbon at a temperature equal to the boiling point of the thiosulfate solution.
Claim 13
Dependent Claim
33 words
A method for recovering precious metals from precious metal bearing materials described in claim 5 wherein the thiosulfate is contacted with the carbon at a temperature in the range from 1-100 degrees centrigade.
Claim 14
Dependent Claim
39 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the thiosulfate is contacted with the carbon at a pressure in the range of normal atmospheric pressure to 100 pounds per square inch.
Claim 15
Dependent Claim
40 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the thiosulfate ion is obtained from a compound selected from the group consisting of alkali metal thiosulfates, alkaline earth metal thiosulfates, and ammonium thiosulfate.
Claim 16
Dependent Claim
39 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the thiosulfate ion is obtained from a compound selected from the group consisting of sodium thiosulfate, ammonium thiosulfate, potassium thiosulfate, and calcium thiosulfate.
Claim 17
Dependent Claim
21 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the carbon is activated carbon.
Claim 18
Dependent Claim
30 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the precious metals loaded on the carbon are in the form of thiourea complexes.
Claim 19
Dependent Claim
34 words
A method for recovering precious metals from precious metal bearing materials described in claim 1, further including the step of protecting the thiosulfate from oxidizing agents by adding a reducing agent to the thiosulfate.
Claim 20
Dependent Claim
27 words
A method for recovering precious metals from precious metal bearing materials described in claim 18 wherein the reducing agents are selected from the group consisting of sulfites.
Claim 21
Dependent Claim
22 words
A method for recovering precious metals from precious metal bearing materials described in claim 19 wherein the reducing agent is sodium sulfite.
Claim 22
Dependent Claim
51 words
A method for recovering precious metals from precious metal bearing materials described in claim 1, further including the initial step of preventing cooper from being adsorbed onto the carbon by removing copper from the thiourea leach solution prior to exposing the carbon to the thiourea leach solution containing the precious metal.
Claim 23
Dependent Claim
39 words
A method for recovering precious metals from precious metal bearing materials described in claim 1, further including the initial step of pretreating the carbon loaded with the precious metals with an oxidizer prior to contacting the metals with thiosulfate.
Claim 24
Dependent Claim
37 words
A method for recovering precious metals from precious metal bearing materials described in claim 1 wherein the carbon loaded with the precious metals is treated initially with a material selected from the group consisting of hydrogen peroxide.
Claim 25
Independent Claim
58 words
A method for recovering silver from silver bearing materials, said method comprising the steps of: extracting the silver bearing materials with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the silver; contacting thiosulfate ion with the loaded carbon, the thiosulfate ion separating the silver from the carbon.
Claim 26
Independent Claim
58 words
A method for recovering silver from silver bearing materials, said method comprising the steps of: extracting the silver bearing materials with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the silver; contacting thiosulfate ion with the loaded carbon, the thiosulfate ion separating the silver from the carbon.
Claim 27
Independent Claim
58 words
A method for recovering gold from gold bearing materials, said method comprising the steps of: extracting the gold bearing materials with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the gold; contacting thiosulfate ion with the loaded carbon, the thiosulfate ion separating the gold from the carbon.
Claim 28
Independent Claim
58 words
A method for recovering gold from gold bearing materials, said method comprising the steps of: extracting the gold bearing materials with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the gold; contacting thiosulfate ion with the loaded carbon, the thiosulfate ion separating the gold from the carbon.
Claim 29
Independent Claim
86 words
A method for recovering silver and gold from gold and silver bearing materials, said method comprising the steps of: extracting the gold and silver bearing material with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the gold and silver; contacting thiosulfate ion with the loaded carbon under a set of contacting conditions including temperature, concentration of thiosulfate ion, and duration of contact to form a thiosulfate leach solution containing both the gold and the silver.
Claim 30
Independent Claim
86 words
A method for recovering silver and gold from gold and silver bearing materials, said method comprising the steps of: extracting the gold and silver bearing material with thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the gold and silver; contacting thiosulfate ion with the loaded carbon under a set of contacting conditions including temperature, concentration of thiosulfate ion, and duration of contact to form a thiosulfate leach solution containing both the gold and the silver.
Claim 31
Independent Claim
55 words
A method for separating precious metals loaded on carbon from a thiourea solution, said method comprising the step of contacting thiosulfate ion with the carbon loaded with precious metals from the thiourea solution, the thiosulfate ion separating the precious metals from the carbon, the precious metals selected from the group consisting of gold and silver.
Claim 32
Independent Claim
55 words
A method for separating precious metals loaded on carbon from a thiourea solution, said method comprising the step of contacting thiosulfate ion with the carbon loaded with precious metals from the thiourea solution, the thiosulfate ion separating the precious metals from the carbon, the precious metals selected from the group consisting of gold and silver.
Claim 33
Independent Claim
111 words
A method for recovering precious metals from a material, said method comprising the steps of: extracting the material with acidified thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the precious metals; contacting thiosulfate ion under alkaline conditions with the loaded carbon, thereby desorbing the precious metals from the carbon and deactivating the carbon, the precious metals selected from the group consisting of silver and gold; recycling the carbon by contacting the deactivated carbon with another quantity of acidified thiourea leach solution, the acidified thiourea solution reactivating the carbon and permitting further adsorption of thiourea complexes of gold and silver thereon.
Claim 34
Independent Claim
111 words
A method for recovering precious metals from a material, said method comprising the steps of: extracting the material with acidified thiourea to form a thiourea leach solution; contacting the thiourea leach solution with carbon to load the carbon with the precious metals; contacting thiosulfate ion under alkaline conditions with the loaded carbon, thereby desorbing the precious metals from the carbon and deactivating the carbon, the precious metals selected from the group consisting of silver and gold; recycling the carbon by contacting the deactivated carbon with another quantity of acidified thiourea leach solution, the acidified thiourea solution reactivating the carbon and permitting further adsorption of thiourea complexes of gold and silver thereon.
References Cited (Backward Citations)
US3970737A
Cited
US3920403A
Cited
US3935006A
Cited
US4208378A
Cited
US4145212A
Cited
US4267069A
Cited
US4342591A
Cited
US4561947A
Cited
US4595572A
Cited
US4606766A
Cited
US4645535A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-10-18 | 1992-04-18 | 1992-10-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-18 | 1996-04-18 | 1996-10-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-18 | 2000-04-18 | 2000-10-18 | $7700.00 | Window Closed / Lapsed |