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Precious metal recovery using thiocyanate lixiviant

A technology of thiocyanate and precious metals, applied in the field of mineral treatment to recover precious metals, can solve the problems of unrealistic use of thiourea, lack of research to a great extent, and difficult adsorption

Active Publication Date: 2008-10-08
NEWMONT USA LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] A problem with cyanide leaching of residual solids after oxidative pretreatment is that the residual solids are often strongly acidic, whereas cyanide leaching must generally be performed at alkaline pH
However, the use of thiourea is usually not practical due to its high susceptibility to oxidative degradation resulting in high consumption of thiourea
Greater success has been achieved using thiosulfate leach solutions, however, it is worth noting that thiosulfate leaching operations must often be performed at alkaline pH, leading in many cases to the same conditions as previously noted for cyanide leaching same technical issue
Moreover, gold removal from metal-rich thiosulfate leachate is more difficult than removal of gold from metal-rich cyanide leachate because gold-thiosulfate complexes are not easily adsorbed on activated carbon. Granular
Other leachates have also been suggested as alternatives to cyanide, but have not been studied to a great extent and their practical implementation is uncertain

Method used

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  • Precious metal recovery using thiocyanate lixiviant
  • Precious metal recovery using thiocyanate lixiviant
  • Precious metal recovery using thiocyanate lixiviant

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0130] Example 1 - Column leaching of a moderately refractory ore

[0131] Trials were conducted on moderately refractory sulphide ore from the Lone Tree mine in Nevada, USA. XRD / XRF semi-quantitative analysis shows that the ore is composed of about 86% quartz, 6% kaolin, 3% pyrite, 2% alunite, 1% gypsum, 1% jarosite and 1% composed of barite. Representative analytical information for this ore sample is shown in Table 3. The ore does not exhibit a pre-recovery trend.

[0132] Table 3 Analysis of representative ore samples

[0133] Au

g / t (1)

S-Total (2)

weight%

S-sulfide (3)

weight%

Fe

weight%

As

ppm

2.26

1.643

0.951

1.551

655.9

[0134] (1) g / t

[0135] (2) Total content of sulfur

[0136] (3) Content of sulfide type sulfur

[0137] Two sets of experiments were conducted, one using cyanide leachate and the other using thiocyanate leachate. All tests were performed o...

Embodiment 2

[0153] Example 2 - Biological oxidation pretreatment of refractory sulfide ores followed by bottle roll leaching

[0154] Trials were conducted on refractory sulphide gold ore from the Lone Tree mine. A 65.8 gram sample crushed to allow 100% passage through 2 inches (50.8 mm) was biooxidatively pretreated in a column with an internal diameter of 11 inches (279.4 mm), simulating biooxidation in a heap. 1920 mL of a mixed culture medium of acidophilic bacteria capable of oxidizing iron (containing Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans) was mixed with the ore before it was placed in the column. During biooxidation, containing 0.4g / L (NH 4 ) 2 SO 4 , 0.4g / L MgSO 4 ·7H 2 O and 0.04g / L K 2 HPO 4 The nutrient solution was continuously recirculated through the column at a flow rate of approximately 6.5 mL / min. The column was filled with air continuously from the bottom at an air flow rate of 28.3 L / h. The biooxidative pretreatment was carried out cont...

Embodiment 3

[0166] Example 3 - Spinner leaching after biooxidative pretreatment of refractory sulfide ores

[0167] Using the biooxidized ore of Example 2, spinner bottle leaching tests were performed as described in Example 2. Tests were performed using freshly prepared thiocyanate leachates containing dissolved thiocyanate and iron ions as shown in Table 9. In each test, leaching lasted a total of 24 hours. For each test, leachate samples were obtained and analyzed at 2 hours, 4 hours, 6 hours, 12 hours and 24 hours. For comparison, the ore was determined to have a cyanide leachable gold of 69%. "Cyanide-leachable gold" means gold extracted from mineral material (such as ore or concentrate) by the following standardized test procedure: A 5 g sample of mineral material comminuted to a minimum size of 200 mesh is mixed with ionized water containing 0.3 A solution of wt% sodium cyanide and 0.3 wt% sodium hydroxide was placed in the test tube. The test tubes were rotated for 1 hour at r...

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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.

Description

technical field [0001] The invention described herein relates to a method for mineral processing to recover precious metals, and more particularly to the use of thiocyanate leachate for recovery of gold. Background technique [0002] A common technique for recovering gold from gold-bearing ores is to leach the gold into an aqueous cyanide leachate, where the gold dissolves in the form of the gold-cyanide complex. In some cases, gold is leached directly from the ore or from concentrates made from the mineral. This is true of many oxide ores. In other cases, the ore or ore concentrate is pretreated prior to cyanide leaching to undergo chemical changes that enhance cyanide leaching performance. For example, gold-bearing sulfide ores are often refractory to direct cyanide leaching. Therefore, prior to cyanide leaching, such refractory sulfide ores, or sulfide concentrates made from such refractory sulfide ores, are often subjected to an oxidative pretreatment to decompose the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22B11/08
Inventor 万荣玉K·马克·莱维尔
Owner NEWMONT USA LTD