Precious metal recovery using thiocyanate lixiviant
First Claim
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1. A method for processing precious metal-containing mineral material to recover precious metal from the mineral material using a circulating thiocyanate leach solution, the method comprising:
- thiocyanate leaching the mineral material with the thiocyanate leach solution, the thiocyanate leach solution comprising dissolved thiocyanate and dissolved ferric iron and during the thiocyanate leaching at least a portion of the precious metal from the mineral material is dissolved into the thiocyanate leach solution in the form of precious metal-thiocyanate complex;
supplying feed of the thiocyanate leach solution to the thiocyanate leaching, the feed of the thiocyanate leach solution comprising a pH in a range of from pH 1 to pH 3 and comprising a molar ratio of the dissolved ferric iron to the dissolved thiocyanate of at least 2, wherein the molar ratio of the dissolved ferric iron to the dissolved thiocyanate is determined by dividing molar concentration of the dissolved ferric iron by molar concentration of the dissolved thiocyanate, and wherein during the thiocyanate leaching at least a portion of the dissolved ferric iron in the feed of the thiocyanate leach solution is reduced to dissolved ferrous iron;
recovering at least a portion of the precious metal from the thiocyanate leach solution, to produce a barren effluent of the thiocyanate leach solution comprising concentration of the dissolved ferric iron that is smaller than a concentration of the dissolved ferric iron in the feed of the thiocyanate leach solution;
conditioning the thiocyanate leach solution to prepare the feed of the thiocyanate leach solution, at least a portion of the barren effluent of the thiocyanate leach solution being supplied to the conditioning for use to prepare the feed of the thiocyanate leach solution, and the conditioning comprising increasing a concentration of the dissolved ferric iron in the thiocyanate leach solution relative to the concentration of the dissolved ferric iron in the barren effluent of the thiocyanate leach solution supplied to the conditioning;
wherein the recovering comprises introducing dissolved cyanide into the thiocyanate leach solution and transferring at least a portion of the precious metal in the thiocyanate leach solution from the precious metal-thiocyanate complex to precious metal-cyanide complex.
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Abstract
For removal of precious metal from thiocyanate leach solution, precious metal is transferred from precious metal-thiocyanate complex to precious metal-cyanide complex. Preparation of thiocyanate leach solution includes dissolving cyanide in an aqueous liquid and converting the cyanide to dissolved thiocyanate.
26 Citations
21 Claims
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1. A method for processing precious metal-containing mineral material to recover precious metal from the mineral material using a circulating thiocyanate leach solution, the method comprising:
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thiocyanate leaching the mineral material with the thiocyanate leach solution, the thiocyanate leach solution comprising dissolved thiocyanate and dissolved ferric iron and during the thiocyanate leaching at least a portion of the precious metal from the mineral material is dissolved into the thiocyanate leach solution in the form of precious metal-thiocyanate complex; supplying feed of the thiocyanate leach solution to the thiocyanate leaching, the feed of the thiocyanate leach solution comprising a pH in a range of from pH 1 to pH 3 and comprising a molar ratio of the dissolved ferric iron to the dissolved thiocyanate of at least 2, wherein the molar ratio of the dissolved ferric iron to the dissolved thiocyanate is determined by dividing molar concentration of the dissolved ferric iron by molar concentration of the dissolved thiocyanate, and wherein during the thiocyanate leaching at least a portion of the dissolved ferric iron in the feed of the thiocyanate leach solution is reduced to dissolved ferrous iron; recovering at least a portion of the precious metal from the thiocyanate leach solution, to produce a barren effluent of the thiocyanate leach solution comprising concentration of the dissolved ferric iron that is smaller than a concentration of the dissolved ferric iron in the feed of the thiocyanate leach solution; conditioning the thiocyanate leach solution to prepare the feed of the thiocyanate leach solution, at least a portion of the barren effluent of the thiocyanate leach solution being supplied to the conditioning for use to prepare the feed of the thiocyanate leach solution, and the conditioning comprising increasing a concentration of the dissolved ferric iron in the thiocyanate leach solution relative to the concentration of the dissolved ferric iron in the barren effluent of the thiocyanate leach solution supplied to the conditioning; wherein the recovering comprises introducing dissolved cyanide into the thiocyanate leach solution and transferring at least a portion of the precious metal in the thiocyanate leach solution from the precious metal-thiocyanate complex to precious metal-cyanide complex. - View Dependent Claims (2, 3, 4)
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5. A method for processing precious metal-containing mineral material to recover precious metal from the mineral material using a circulating thiocyanate leach solution, the method comprising:
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thiocyanate leaching the mineral material with the thiocyanate leach solution, the thiocyanate leach solution comprising dissolved thiocyanate and dissolved ferric iron and during the thiocyanate leaching at least a portion of the precious metal from the mineral material is dissolved into the thiocyanate leach solution in the form of precious metal-thiocyanate complex; supplying feed of the thiocyanate leach solution to the thiocyanate leaching, the feed of the thiocyanate leach solution comprising a pH in a range of from pH 1 to pH 3 and comprising a molar ratio of the dissolved ferric iron to the dissolved thiocyanate of at least 2, wherein the molar ratio of the dissolved ferric iron to the dissolved thiocyanate is determined by dividing molar concentration of the dissolved ferric iron by molar concentration of the dissolved thiocyanate, and wherein during the thiocyanate leaching at least a portion of the dissolved ferric iron in the feed of the thiocyanate leach solution is reduced to dissolved ferrous iron; recovering at least a portion of the precious metal from the thiocyanate leach solution, to produce barren effluent of the thiocyanate leach solution comprising a concentration of the dissolved ferric iron that is smaller than a concentration of the dissolved ferric iron in the feed of the thiocyanate leach solution; conditioning the thiocyanate leach solution to prepare the feed of the thiocyanate leach solution, at least a portion of the barren effluent of the thiocyanate leach solution being supplied to the conditioning for use to prepare the feed of the thiocyanate leach solution, and the conditioning comprising increasing a concentration of the dissolved ferric iron in the thiocyanate leach solution relative to the concentration of the dissolved ferric iron in the barren effluent of the thiocyanate leach solution supplied to the conditioning; wherein the conditioning comprises introducing dissolved cyanide into the thiocyanate leach solution and converting at least a portion of the dissolved cyanide to thiocyanate prior to supplying the feed of the thiocyanate leach solution to the thiocyanate leaching. - View Dependent Claims (6)
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7. A method for recovering precious metal from mineral material containing the precious metal, the method comprising:
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thiocyanate leaching the mineral material with a thiocyanate leach solution to dissolve at least a portion of the precious metal from the mineral material into the leach solution in the form of precious metal-thiocyanate complex; introducing dissolved cyanide into the thiocyanate leach solution and transferring at least a portion of the precious metal from the precious metal-thiocyanate complex to precious metal-cyanide complex; removing from the thiocyanate leach solution at least a portion of the precious metal transferred to the precious metal-cyanide complex. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A method for recovering precious metal from a thiocyanate leach solution in which precious metal is dissolved in the form of precious metal-thiocyanate complex, the method comprising:
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introducing cyanide into the thiocyanate leach solution; transferring at least a portion of the precious metal from the precious metal-thiocyanate complex in the thiocyanate leach solution to precious metal-cyanide complex in the thiocyanate leach solution; and removing from the thiocyanate leach solution at least a portion of the precious metal transferred to the precious metal-cyanide complex. - View Dependent Claims (14, 15, 18, 19, 20, 21)
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- 16. The method of claim, wherein the transferring comprises adding the cyanide to the thiocyanate leach solution at a molar ratio of the cyanide to the gold in the thiocyanate leach solution that is no larger than 20:
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