Claims
- 1-59. (Canceled)
- 60. A process for recovering a precious metal from a precious metal-containing material, comprising:
(a) contacting the precious metal-containing material with a lixiviant to solubilize the precious metal and form a pregnant leach solution containing the solubilized precious metal; and (b) thereafter electrowinning the precious metal in the presence of sulfite.
- 61. The process of claim 60, wherein the lixiviant includes thiosulfate and further comprising before step (b):
(c) contacting the pregnant leach solution with an extraction agent at a temperature of less than about 70° C. to collect the precious metal and convert polythionates in the pregnant thiosulfate leach solution into thiosulfate; and (d) thereafter removing the precious metal from the extraction agent.
- 62. The process of claim 61, wherein the contacting step (a) includes:
(i) contacting the precious metal-containing material with a first lixiviant at a first pressure to solubilize a first portion of the precious metal in the precious metal-containing material; and (ii) contacting the precious metal-contacting material with a second lixiviant at a second pressure greater than the first pressure to solubilize a second portion of the precious metal in the precious metal-containing material.
- 63. The process of claim 62, wherein the first and second lixiviants each include thiosulfate.
- 64. The process of claim 60, wherein in the contacting step (a) the thiosulfate lixiviant has a temperature of from about 40 to about 80° C., the molecular oxygen partial pressure is superatmospheric, and the lixiviant includes at least about 0.005M thiosulfate and less than 0.05M of ammonia.
- 65. The process of claim 60, wherein in the contacting step (a) the thiosulfate lixiviant contains less than 20 ppm of added copper.
- 66. A precious metal recovered by the process of claim 60.
- 67. A process for recovering a precious metal from a precious metal-containing material, comprising:
(a) contacting the precious metal-containing material with a thiosulfate leach solution to solubilize the precious metal and form a pregnant thiosulfate leach solution containing solubilized precious metal; (b) maintaining a dissolved molecular oxygen content in at least one of the thiosulfate leach solution and the pregnant thiosulfate leach solution at or below about 1 ppm to inhibit the formation of trithionate and tetrathionate; and (c) recovering the solubilized precious metal from the pregnant thiosulfate leach solution.
- 68. The process of claim 67, wherein, in the maintaining step (b), the at least one of the thiosulfate leach solution and the pregnant thiosulfate leach solution is maintained in an atmosphere that is at least substantially free of molecular oxygen, the atmosphere is inert and includes at least about 85 vol. % molecular nitrogen.
- 69. The process of claim 67, wherein the contacting step (a) occurs in a reactor and the pregnant leach solution is maintained in a molecular oxygen depleted atmosphere after removal from the reactor.
- 70. The process of claim 67, wherein in the maintaining step (b) a gas containing no more than about 5 vol. % oxidants is sparged through the pregnant thiosulfate leach solution.
- 71. The process of claim 67, wherein in the contacting step (a) the thiosulfate lixiviant contains less than 20 ppm of copper ion and less than 0.05M of ammonia.
- 72. A precious metal recovered by the process of claim 67.
- 73-96. (Canceled)
- 97. A process for recovering a precious metal from a precious metal-containing material, comprising:
(a) contacting the precious metal-containing material with a thiosulfate lixiviant to solubilize the precious metal and form a pregnant thiosulfate leach solution containing the solubilized precious metal; (b) electrowinning, in the presence of sulfite, the solubilized precious metal from the pregnant thiosulfate leach solution and/or a solution derived therefrom to form recovered gold and a barren leach solution.
- 98. The process of claim 97, wherein the contacting step comprises the substeps:
(i) forming the precious metal-containing material into a heap; (ii) applying the thiosulfate lixiviant to the heap; and (iii) aerating the heap with a molecular oxygen-containing gas during the applying step.
- 99. The process of claim 98, wherein the thiosulfate lixiviant comprises less than 0.05M ammonia.
- 100. The process of claim 99, wherein the thiosulfate lixiviant comprises less than 20 ppm copper ion.
- 101. The process of claim 98, wherein the thiosulfate lixiviant comprises dissolved molecular oxygen.
- 102. The process of claim 98, wherein the thiosulfate lixiviant, during the applying step, comprises no more than about 0.02 M sulfite.
- 103. The process of claim 98, wherein a pH of the thiosulfate during the applying step is less than pH 9.
- 104. The process of claim 97, further comprising before step (b):
(c) contacting the pregnant leach solution with an extraction agent at a temperature of less than about 70° C. to collect at least most of the precious metal in the pregnant thiosulfate leach solution and convert at least most of the polythionates in the pregnant thiosulfate leach solution into thiosulfate; and (d) eluting the precious metal from the extraction agent to form a pregnant solution comprising at least most of the precious metal collected on the extraction agent, wherein the pregnant solution is subjected to the electrowinning step (b).
- 105. The process of claim 97, wherein the thiosulfate lixiviant comprises from about 0.005 to about 2 M thiosulfate and from about 0.0005 to about 0.025 M polythionates.
- 106. The process of claim 97, wherein the pregnant thiosulfate leach solution comprises polythionates and further comprising after step (a) and before step (b):
(c) contacting the pregnant thiosulfate leach solution with a polythionate reductant to convert at least most of the polythionate to thiosulfate.
- 107. The process of claim 106, wherein the contacting step (c) is conducted under conditions to at least substantially inhibit precipitation of the dissolved precious metal in the pregnant leach solution.
- 108. The process of claim 107, wherein the reductant comprises at least one of a bisulfide, a polysulfide other than a bisulfide, and a sulfide other than a bisulfide and a polysulfide, and wherein the pH of the pregnant thiosulfate leach solution during the contacting step (c) ranges from about pH 5.5 to about pH 10.5.
- 109. The process of claim 107, wherein the reductant comprises sulfite, wherein the pH of the pregnant thiosulfate leach solution during the contacting step (c) ranges from about pH 5.5 to about pH 10.5, and wherein the temperature of the pregnant thiosulfate leach solution during the contacting step (c) is less than 60° C.
- 110. The process of claim 97, wherein the pregnant thiosulfate leach solution comprises polythionates and further comprising after step (a) and before step (b):
(c) maintaining the pregnant thiosulfate leach solution at a temperature in the range of from about 60 to about 150° C. in the substantial absence or complete absence of molecular oxygen to convert at least most of the polythionate to thiosulfate.
- 111. The process of claim 108, wherein, during contacting step (c), at least some of the dissolved precious metal is precipitated and further comprising:
(d) contacting the pregnant thiosulfate leach solution with an oxidant to resolubilize at least most of the precipitated precious metal while inhibiting conversion of thiosulfate to polythionates.
- 112. The process of claim 106, wherein, during at least one of steps (b) and (c) the pregnant leach solution is maintained in an inert atmosphere and/or is sparged with an inert gas.
- 113. The process of claim 97, further comprising after step (b):
contacting the barren leach solution with a reductant to convert at least most of any polythionates in the barren leach solution into thiosulfate.
- 114. The process of claim 97, wherein the pregnant leach solution during step (b) comprises at least about 0.01M sulfite.
- 115. A precious metal recovered by the process of claim 114.
- 116. The process of claim 67, wherein the recovering step (c) comprises the substep:
electrowinning, in the presence of sulfite, the solubilized precious metal from the pregnant thiosulfate leach solution and/or a solution derived therefrom to form recovered gold and a barren leach solution.
- 117. The process of claim 67, wherein the pregnant thiosulfate leach solution comprises polythionates and further comprising after step (a) and before step (b):
(d) contacting the pregnant thiosulfate leach solution with a polythionate reductant to convert at least most of the polythionate to thiosulfate.
- 118. The process of claim 117, wherein the contacting step (d) is conducted under conditions to at least substantially inhibit precipitation of the dissolved precious metal in the pregnant leach solution.
- 119. The process of claim 118, wherein the reductant comprises at least one of a bisulfide, a polysulfide other than a bisulfide, and a sulfide other than a bisulfide and a polysulfide, and wherein the pH of the pregnant thiosulfate leach solution during the contacting step (d) ranges from about pH 5.5 to about pH 10.5.
- 120. The process of claim 118, wherein the reductant comprises sulfite, wherein the pH of the pregnant thiosulfate leach solution during the contacting step (c) ranges from about pH 5.5 to about pH 10.5, and wherein the temperature of the pregnant thiosulfate leach solution during the contacting step (d) is less than 60° C.
- 121. The process of claim 67, wherein the pregnant thiosulfate leach solution comprises polythionates and further comprising after step (a) and before step (b):
(c) maintaining the pregnant thiosulfate leach solution at a temperature in the range of from about 60 to about 150° C. in the substantial absence or complete absence of molecular oxygen to convert at least most of the polythionate to thiosulfate.
- 122. The process of claim 118, wherein, during contacting step (d), at least some of the dissolved precious metal is precipitated and further comprising:
(e) contacting the pregnant thiosulfate leach solution with an oxidant to resolubilize at least most of the precipitated precious metal while inhibiting conversion of thiosulfate to polythionates.
- 123. The process of claim 67, further comprising after step (c):
(d) contacting the barren leach solution with a reductant to convert at least most of any polythionates in the barren leach solution into thiosulfate.
- 124. The process of claim 116, wherein the pregnant leach solution during step (c) comprises at least about 0.01M sulfite.
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from U.S. Provisional Application Serial No. 60/205,472, filed May 19, 2000, which is incorporated herein by this reference.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60205472 |
May 2000 |
US |
Divisions (2)
|
Number |
Date |
Country |
Parent |
10446548 |
May 2003 |
US |
Child |
10836480 |
Apr 2004 |
US |
Parent |
09852699 |
May 2001 |
US |
Child |
10446548 |
May 2003 |
US |