Method and technique employing a novel extractant to enhance recovery of gold and palladium from hydrochloric acid media
An extraction component enabling the concurrent recovery of gold and/or palladium selectively from a hydrochloric acid media containing the base metals and other contaminants. The disclosed extractant disclosed eliminates the conventional multi-step process for such extraction by providing for an extraction method which uses a single solvent extraction reagent. Further enhancing the conventional multi step process, the conventional scrubbing stage is eliminated by a single stripping stage. The resulting solutions can be obtained from leaching many types of material such as copper anode slimes, the treatment of scrap such as electronic circuit boards and plating effluents, PGM, or refractory gold ores.
1. A method of separating at least one of gold and palladium from an acid solution containing chloride complexes of at least one of these metals, said method comprising the steps of:
employing an extractant selected from dithiobiuret derivative compounds represented by the following structure formula:
wherein R is cyclohexyl or isopropyl and Z represents a group selected from the group consisting of: —CH 2 —, —CH 2 —CH 2 —, CH 2 —CH 2 —CH 2 , CH 2 —CH(CH 3 )—CH 2 , CH 2 (CH 2 ) 2 CH 2 , CH 2 —NH—CH 2 , CH 2 —CHOH—CH 2 —, CHOH—CH 2 —CH 2 —, and —CH 2 —O—CH 2 —; and
contacting said acid solution with a quantity of said extractant, for a sufficient length of time to form a loaded organic consisting of either or both of gold and palladium to allow for a single step extraction of substantially all the gold and palladium present.
2. The method of claim 1 additionally comprising: employing a hydrochloric acid solution as said acid solution.
3. The method of claim 2 , additionally comprising:
employing the extractant for extraction of at least one of gold and palladium from said hydrochloric acid solution containing Pt, Ba, Al, Cu, Fe, Ni, Zn, Co, and mixtures thereof.
4. The method of claim 3 , additionally comprising:
employing said hydrochloric acid solution at a concentration of substantially 1 M HCl.
5. The method of claim 2 with the additional step of:
employing an acidified thiourea solution in a stripping stage to yield a substantially yellow precipitate containing palladium concurrently with a strip solution containing gold which is free of base metals, to concurrently selectively separate said palladium from said gold.
6. The method of claim 5 comprising the additional step of:
employing a treatment of said strip solution to produce gold precipitate, said treatment including one or a combination of electrolysis and reducing said strip solution with hydrogen or sodium borohydride.
7. The method of claim 5 with the additional step of:
separating said extractant to yield recovered extractant from said strip solution for reuse.
8. The method of claim 7 including the additional step of:
employing said recovered extractant with a subsequent new feed solution, said recovered extractant reusable at least 15 times.
9. The method of claim 5 , additionally comprising:
employing said acidified thiourea solution containing from substantially 0.5-3 M H2SO4.
10. The method of claim 5 , additionally comprising:
employing said acidified thiourea solution containing from substantially 0.5-1 M thiourea.
11. The method of claim 10 , additionally comprising:
employing an extraction rate of palladium in acidic aqueous solution of 0.5 M HCl in contact with organic phase of 2.2 mol of said extractant for 1 mol of palladium for 90 seconds.
12. The method of claim 10 , additionally comprising:
employing an extraction rate of palladium in acidic aqueous solution of 0.5 M HCl in contact with organic phase of 2.2 mol of said extractant for 1 mol of gold for 90 seconds.
13. The method of claim 1 , additionally comprising:
employing said extractant to extract gold and Palladium concurrently and selectively from a copper anode slime in 1M HCL or less.