Precious metal recovery using thiocyanate lixiviant
First Claim
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, and 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, after the recovering barren effluent of the thiocyanate leach solution comprises 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.
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Accused Products
Abstract
Precious metal-containing mineral material is subjected to an acidic thiocyanate leach to dissolve the precious metal as a precious metal-thiocyanate complex. A feed of the thiocyanate leach solution may include a large molar ratio of ferric iron to thiocyanate. Precious metal may be removed from pregnant thiocyanate leach solution, such as by transferring precious metal from precious metal-thiocyanate complex to precious metal-cyanide complex and then loading the precious metal-cyanide complex onto an adsorbent material. Remaining cyanide in the thiocyanate leach solution may be converted to thiocyanate for additional leaching of precious metal.
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Citations
40 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, and 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, after the recovering barren effluent of the thiocyanate leach solution comprises 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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Specification