ZA200601504B - Improved thiosulphate leach process - Google Patents
Improved thiosulphate leach process Download PDFInfo
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- ZA200601504B ZA200601504B ZA200601504A ZA200601504A ZA200601504B ZA 200601504 B ZA200601504 B ZA 200601504B ZA 200601504 A ZA200601504 A ZA 200601504A ZA 200601504 A ZA200601504 A ZA 200601504A ZA 200601504 B ZA200601504 B ZA 200601504B
- Authority
- ZA
- South Africa
- Prior art keywords
- process according
- thiosulphate
- gold
- leach
- thiourea
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims description 54
- DHCDFWKWKRSZHF-UHFFFAOYSA-L thiosulfate(2-) Chemical compound [O-]S([S-])(=O)=O DHCDFWKWKRSZHF-UHFFFAOYSA-L 0.000 title claims description 39
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical group [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 52
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims description 52
- 239000010931 gold Substances 0.000 claims description 48
- 229910052737 gold Inorganic materials 0.000 claims description 48
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 26
- 239000007800 oxidant agent Substances 0.000 claims description 23
- 230000001590 oxidative effect Effects 0.000 claims description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 21
- 239000003153 chemical reaction reagent Substances 0.000 claims description 15
- 238000011084 recovery Methods 0.000 claims description 13
- 229910052742 iron Inorganic materials 0.000 claims description 10
- 239000002184 metal Substances 0.000 claims description 9
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 6
- 150000003839 salts Chemical class 0.000 claims description 6
- GJLUFTKZCBBYMV-UHFFFAOYSA-N carbamimidoylsulfanyl carbamimidothioate Chemical compound NC(=N)SSC(N)=N GJLUFTKZCBBYMV-UHFFFAOYSA-N 0.000 claims description 5
- 150000002894 organic compounds Chemical class 0.000 claims description 4
- BRWIZMBXBAOCCF-UHFFFAOYSA-N hydrazinecarbothioamide Chemical compound NNC(N)=S BRWIZMBXBAOCCF-UHFFFAOYSA-N 0.000 claims description 3
- 238000005342 ion exchange Methods 0.000 claims description 3
- 159000000014 iron salts Chemical class 0.000 claims description 2
- 238000002386 leaching Methods 0.000 description 34
- 239000000243 solution Substances 0.000 description 18
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 6
- 239000010949 copper Substances 0.000 description 6
- 239000002002 slurry Substances 0.000 description 6
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 6
- 235000019345 sodium thiosulphate Nutrition 0.000 description 6
- 239000004133 Sodium thiosulphate Substances 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- BDHRLLGRXHZAQG-UHFFFAOYSA-L copper azane dioxido-oxo-sulfanylidene-lambda6-sulfane Chemical compound N.[Cu+2].[O-]S([O-])(=O)=S BDHRLLGRXHZAQG-UHFFFAOYSA-L 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 2
- 238000005273 aeration Methods 0.000 description 2
- 229910001431 copper ion Inorganic materials 0.000 description 2
- 238000009837 dry grinding Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
- 238000007885 magnetic separation Methods 0.000 description 2
- JVXHQHGWBAHSSF-UHFFFAOYSA-L 2-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]acetate;hydron;iron(2+) Chemical compound [H+].[H+].[Fe+2].[O-]C(=O)CN(CC([O-])=O)CCN(CC([O-])=O)CC([O-])=O JVXHQHGWBAHSSF-UHFFFAOYSA-L 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 241000272165 Charadriidae Species 0.000 description 1
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 1
- 241000416536 Euproctis pseudoconspersa Species 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- XYXNTHIYBIDHGM-UHFFFAOYSA-N ammonium thiosulfate Chemical compound [NH4+].[NH4+].[O-]S([O-])(=O)=S XYXNTHIYBIDHGM-UHFFFAOYSA-N 0.000 description 1
- 239000007853 buffer solution Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- ADPOBOOHCUVXGO-UHFFFAOYSA-H dioxido-oxo-sulfanylidene-$l^{6}-sulfane;gold(3+) Chemical compound [Au+3].[Au+3].[O-]S([O-])(=O)=S.[O-]S([O-])(=O)=S.[O-]S([O-])(=O)=S ADPOBOOHCUVXGO-UHFFFAOYSA-H 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- NPEWZDADCAZMNF-UHFFFAOYSA-N gold iron Chemical compound [Fe].[Au] NPEWZDADCAZMNF-UHFFFAOYSA-N 0.000 description 1
- 231100000086 high toxicity Toxicity 0.000 description 1
- 125000000717 hydrazino group Chemical group [H]N([*])N([H])[H] 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910021653 sulphate ion Inorganic materials 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 238000001238 wet grinding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B11/00—Obtaining noble metals
- C22B11/04—Obtaining noble metals by wet processes
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
- C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/42—Treatment or purification of solutions, e.g. obtained by leaching by ion-exchange extraction
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Description
“Improved Thiosulphate Leach Process” EE oo
The present invention relates to an improved thiosulphate leach process. More "particularly, the thiosulphate leach process of the present invention is intended for use in the extraction of gold from ores or Other gold-bearing materials using : thiosulphate as a lixiviant in the absence of amemonia/ammonium and copper ions.
Background Art : : “The process of alkaline cyanidation for the extraction of gold from its ores has been practised for over a century and remaims the predominant method world © 10 wide in gold production. Despite its proven re cords, there have been increasing concems in the community over the high toxicity of cyanide, which poses serious health and environmental risks. In fact, somes countries have now banned the construction of new cyanidation plants. Unde-r these circumstances, alternative non-toxic fixiviants for the extraction of gold hawe been investigated, including the use of a thiosulphate lixiviant. : ‘Ina thiosulphate solution containing an oxidart such as dissolved oxygen, gold may be dissolved as the gold-thiosulphate cosmpiex according to the following reaction. : 4AU + 8,037 + Oj + 2H,0 — 4ALI(S203),” + 40H" ’ . ’ i
Although the reaction is favoured thermodynaamically, the rate at which gold dissolves is very slow uniess a catalyst and a re=dox mediator are present. This is thought to be the result of: (i) Oxygen is not am effective oxidant because of its slow reduction on the gold surface. (ii) The dissoelution of gold is hindered because : of the passivation of the gold surface in the thios ulphate solution.
In order to obtain a reasonably fast leaching ra-te; it is generally understood that ammonia and copper ions are required in the thijosulphate solution under alkaline oo WO 2005/017215 PCT/AU2004/001104 : a. - conditions (e.g. pH > 9). Ammonia, uswially added as the ammonium thiosulphate salt, helps stabilise the copper as the copper(ll) tetrammine complex which serves as an effective oxidant. The copper(ll) tetrammine is regenerated by oxidation of the copper(l) complex by dissolved oxwgen. In addition, it has been shown that both ammonia and copper may have catalytic effect on the anodic half reaction of gold oxidation. This process is described in, for example, US Patent 4269622 (Kerley, Jr.), US Patent 4369061 (Kerley Jr.) and US Patent 4654078 (Perez et al.). :
There are several substantial drawbacks associated with the ammonia- copper- thiosulphate leaching process. Firstly, copper is known to catalyse the oxidation of thiosulphate. This not only results in very high reagent consumption, but also generates significant amounts of polythionates which may be detrimental to the down-stream gold recovery process. Secondly, the process is not robust, with the leaching conditions having to be controlled very carefully and often ore- specifically. Thirdly, concerns have beeen raised over the widespread use of ammonia in fairly large concentrations, which may be.a potential hazard fo the environment. For these reasons; no commercial applications of the ammonia- copper-thiosulphate process have yet be2en implemented.
The present invention has as one object thereof to overcome substantially the above problems associated with the perior art, or to at least provide a useful altemative thereto.
The preceding discussion of the background art is intended to facilitate an understanding of the present inyention only. It should be appreciated that the , discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.
Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.
Disclosure of the Invention - Co
In accordance with the present invention there is provided an improved thiosulphate leach process, the process characterised by the method steps «of submitting a gold-bearing material to a leach in a thiosulphate solution, where in thiourea or a reagent chemically related thereto, and at least one oxidant, are present in the thiosulphate leach solution, and subsequently recovering gold frorm the resulting pregnant leach solution. oo
Preferably, thiourea is provided irm a concentration of about 0.01 mole/L.. : Preferably, the oxidant present is a complex of ethylenediamenetetraacetates (EDTA) with a multivalent metal. The multivalent metal may be iron and the complex FeEDTA. .
Stilt preferably, thiosulphate is addled in the form of a soluble salt. in one form of the present invention the soluble salt is the sodium or ammonium salt off thiosulphate. - .
In one form of the present invention thiosulphate is provided in a concentration of” : about 0.1to 0.3 moles. : -
The preferred oxidant FeEDTA m ay be prepared prior to addition to the leach solution or it may be prepared by a dding suitable amounts of iron saits and EDTA directly to the leach solution.
Preferably, the concentration of FeEDTA il the leach solution is about 0.002 mole/L.
The pH of the leach is preferably masintained between about 6 to 7.
The reagent chemically related to thiourea may preferably include one or more thio-substituted organic compoundss, including but not limited to formamidine disulphide and thiosemicarbazide.
oo UE } : “In accordance with the present invention there is further provided an improved thiosulphate leach process for the recovery of gold from ores and other gold- bearing materials, characterised in that the leach solution comprises thiosulphate, _ thiourea or a reagent chemically related thereto, and an oxidant that does not oxidise thiosulphate, the process producing a pregnant leach solution from which gold may be recovered. .
Preferably, the oxidant present is a complex of ethylenediamenetetraacetate (EDTA) with a multivalent metal. The multivalent metal may be iron and the - complex FeEDTA. - 40 The FeEDTA may be provided ata concentration of about 0.002 mole/L. :
Still preferably, the thiosulphate is provided at a concentration of 0.1 to 0.3 mole/L. Further, thiourea is preferably provided ata concentration of 0.01 mole/l.
In one form of the present inve=ntion gold is recovered from the pregnant leach solution by way of either cementation or ion exchange.
The pH of the leach is preferably maintained between about 6 to 7.
The reagent chemically related to thiourea may preferably include one or more . thio-substituted organic compo unds, including but not limited to formamidine disulphide and thiosemicarbazide. oo
Best Mode(s) for Carrying Out the Invention . : +
In one embodiment of the procezss of the present invention, that process involves the leaching of gold using a solution containing thiosulphate, thiourea and an effective oxidant. The oxidant iss provided in the form of an EDTA complex with a multivalent metal, for example iron, which provides the complex FeEDTA.
Thiosulphate can be added as the sodium salt or any other soluble salt of thiosulphate. The preferred coracentration of thiosulphate is 0.1 — 0.3 mole/L, but lower or higher concentrations ir the range of 0,02 to 1 mole/L may also be used.
- WoNsImIs © PCT/AU2004/001104
The role of thiourea is to ) catalyse -the. half reaction of gold oxidation. The preferred concentration of thiourea is 0.01 mole/L though higher or lower concentrations are also applicable, in t he range of 0.002 to 0.1 mole/L.
The inventor has determined that reag ents chemically related to thiourea have the same impact on the process of the present invention as does thiourea. These chemically related reagents are unclerstood to include other thio-substituted organic compounds, including buE not limited to formamidine disulfide (NH2(NH)CSSC(NH)NH2) and thiosemuicarbazide (SC(NH2)NHNH2).
An oxidant is essential for the leachi ng of gold and one of the least expensive oxidants is dissolved oxygen. Howewer, oxygen alone is not sufficient to extract gold effectively in’ such a system. A practical thiosulphate leaching system requires an oxidant that: 1. Has a reduction potential in excess of about 0.2V; 2. Does not oxidise thiosulphate 3 : g 16 3. Can be preferably rapidly re-osxidised by oxygen; and : 4. Is not too expensive.
The applicant has determined that Fe=EDTA is such an oxidant. The oxidant can be prepared prior to leaching by mixirag a ferric sait, such as ferric nitrate or ferric sulphate, in a solution with EDTA. Alternatively, it can be prepared using a ferrous salt in the ‘presence of dissolv-ed oxygen using the same procedure. The ferrous EDTA complex formed is thwen oxidised to FeEDTA by the dissolved oxygen. It is also possible to prepare the FeEDTA by adding suitable amounts of iron salts and EDTA directly to the leaching slurry where the complex is formed in- situ. The concentration of the FeEDT.A may be as low as about 0.001 mole/L, but is preferably about 0.002 mole/L, to muinimise the cost. It is envisaged that higher concentrations, up to about 0.01 mole/L, may result in better kinetics and gold recoveries.
Ideally, the leach is carried out in neutral pH and at ambient temperature . (understood to mean between about 20-30°C) and over a period of up to 48 to 72 hours. The leach may be comducted at elevated temperatures, although gold recovery may be inversely affected by the increase in temperature. Temperatures of up to about 50°C are envisaged for ores, whilst higher temperatures may be : employed with concentrates.
The process described is simple and provides leaching kinetics comparable to known cyanidation processes. Another important advantage is that the FEEDTA oxidant oxidises only gold ard not thiosulphate. As a result, the reagent consumption is low in contrast to the relatively heavy loss of thiosulphate associated with the prior art ammonia-copper-thiosulphate leaching process.
After leaching, the gold in the pregnant solution can be recovered using those techniques proposed for the ammonia-copper-thiosulphate process, such as . cementation or ion exchange. -
The improved thiosulphate lea ch process of the present invention will now be described with reference to several non-limiting examples: .
EXAMPLE 1 : .
Gold powder prepared by redduction precipitation from a AuCly solution was leached using an oxygenated sodium thiosulphate solution (0.1 mole/L) containing thiourea (0.01 M) at pH 6 and ambient temperature. The leach was run for 96 hours in a stirred reactor with 19.4 ppm gold dissolved (69.3% recovery). For comparison, only 3.6 ppm gold was dissolved (18.4% recovery) under the same conditions but in the absence of thiourea. This example indicates that the addition of thiourea catalyses the oxidati on of gold and that oxygen alone is understood to be insufficient for satisfactory leaching kinetics for practicable gold plant operation (typically 24 to 48 hours maximum leach times) and gold adequate recovery.
' EXAMPLE 2 oo .
An ore sample (Ore 1) obtained from 2 cyclone overflow was used for the leaching tests using the improved process of the present invention, at a grind size of 75% passing 75 pm. This ore contai ns about 2 g/t gold in average. The leaching conditions are outlined below:
Sodium thiosulphate concentration: 0. 3mole/lL . Thiourea concentration: ~*~ 0.01 moKe/L initially and extra 0.01 mole/lL was oo added after 8 hours FeEDTA concentration: 0.4003 mole/L initially and extra 0.002 oo m ole/L was added after 8 hours -Sturry pulp density: CL AD% wt) . pH range: 6.5-8 ) : Temperature: Awmnbient
Leaching time: 24 hours
The gold recovery was 88-90%.
EXAMPLE 3
An ore sample (Ore 1) collected from cyclone underflow, was ground and screened and the portion with particle size=s of —150 pm was used for the leaching , tests. The average grade of gold is abaut 17.4 g/t. The leaching conditions were:
Sodium thiosulphate concentration: 0 .3 mole/L
Thiourea concentration: - 0.01 mole/L initially and extra 0.01 raole/L was added after 8 hours
FoEDTA concentration: 0.003 mole/L initially and extra 0.002 meole/L. was added after 8 hours
Slurry pulp density: . 40% (wt.)
=u 8. "pH range: 65 8 oo . Temperature: Ambient
Leaching time: 24 hourss ‘Gold recoveries of 92.5-97.5% were achieved using the above specified leaching -5 conditions. . EXAMPLE 4 : © An ore sample (Ore 2) was obtained containing 2.5 git gold, sized as 100% passing 150 um. The thiosulphate leaching tests were performed under the following conditions: -10 Sodium thiosulphate concentration: 0.3 mole/L :
Thiourea concentration: 0.01 moele/L :
FeEDTA concentration: 0.003 muole/L
Slurry pulp density: 40% (wi. pH range: 65-85 © 15 Temperature: ambient
Leaching time: : 24 hours :
The recovered values of gold after leaching umder such conditions are typically 89.6-98%. ' .
Examples 1 to 4 described the technical details of the improved thiosulfate leaching process and provide details for thes leaching of pure gold powder (Example 1) and ore (Examples 2 to. 4), with &he ore samples prepared by dry grinding. Further tests were carried out using another ore which was prepared using both dry and wet grinding methods. The leaching of dry ground (ring milled)
-9- a samples yielded similar results to those obtained from the Ores of Examples 2 to 4, with gold recoveries of around 90% achieved. : EXAMPLE 5 : :
An ore saample containing 2.5-5 git gold was crushed and then ground in a ring millto a P 10 Of -150 ym. The leaching was conducted in rol ing bottles or in stirred tank reactors under the conditions summarised below:
Sodium thiosulfate concentration: 0.3 mole/L : * Thio-urea concentration: 0.01 mole/L. ' FeE DTA concentration: | 0.003 mole/L.
Pulp density: 40% (wt) + pH range: 6.5-85 :
Temperature: ambient (20-25°C)
Leaching time: 24 hours "Gold recoveries obtained under the above conditions were Typically 83-91%. - 45 The wet ground (rod milled) samples may be contaminated with metallic iron. If this happens, direct leaching of the ore after grinding rnay not be successful because the metallic iron consumes the FeEDTA oxidant. However, this problem can be solved by pre-aeration of the slurry for a few hours 10 oxidise the metallic iron, or bey magnetic separation to remove the metallic iro n. ‘After the removal of the metallic iron gold leaching can be proceeded umder similar conditions described in the previous examples.
The Exarmnples 1 to 5 were conducted without particular ceontrol of pH. The initial pH was about 6.5 which increased gradually to above 8 upon contact with the ores. Howvever, it has now been found that the reduction of the FeEDTA oxidant becomess less effective at pH values above about 7. This can result in significant
. decreases in gold leaching rate and, consequently, gold recovery. A solution to this problem is to carry out the leaching with the pH controlled below about 7, as oo demonstrate=d by the following Example. oo
EXAMPLE 6 oo
An ore sample containing 2.5-5 g/t gold, was crushed and then grosund in a rod mill at 50% solids to-99.6% -150 ym. The ore was contaminated by" metallic iron during the grinding. The metallic iron was then removed either by magnetic separation or by pre-aeration of the slurry for 24 hours before the reagents were added. The= leaching was conducted in stirred tank reactors and the pH of the slurry was controlled between 6 and 7 throughout the leach. This was done either by addition of dilute sulphuric acid during the leaching, or by using a buffer solution cortaining 0.25 mole/L. KHPO4 and a suitable concentratio n of NaOH to adjust the pH to 6-7. Other leaching conditions are specified below: "sodium thiosulfate concentration: 0.3 mole/L
Thiouwea concentration: 0.01 mole/L "
FeED TA concentration: 0.003 mole/L
Pulp density: 40% (wt.) oo
Tempeerature: a ambient (23-28°C)
Leaching time: 24 hours
Under the above specified conditions, the gold recovered was typically 87-92%.
Modificatio ns and variations such as would be apparent to a skilled addressee are considered to fall within the scope of the present invention.
Claims (24)
1. An improved thiosulphate leach process, the process characterisedk by the : method steps of submitting a gold-bearing material. to a leach in a thiosulpheate solution, wherein thiourea or a reagent chemically related thereto, and at least one oxidant, are present in the thiosulphate leach solution, and subsequently recovering gold from the resulting pregna nt leach solution.
"2. A process according to claim 1, wherein thiourea is provided in a concentration of about 0.01 mole/L. -
3. A process according to claim 1 or 2, wherein the oxidant present is a complex of ethylenediamenetetraacetate (EDTA) with a multivalent metal.
4. A process according to claim 3, wherein the muitivalent metal is irora and the complex FeEDTA. _
5. A process according to any one of the proceeding claims, wherein thiosulphhate is added in the form of a soluble salt.
6. A process according to claim 5, wherein the soluble salt is the soditam salt of thiosulp hate.
7. A process according to any one of the preceding claims, wherein thiosulp hate is provided in a concentration of about 0.1 to 0.3 mole/L_. ,
8. A process according to any one of claims 4 to 8, wherein the oxidant FeEDTA is prepared prior to addition to the leach solution.
9. A process according to any one of claims 4 to 8, wherein the oxidant FeEDTA is prepared by adding suitable amounts of iron salts and EDTA directly to the leach solution.
: 10. A process according to any one of” claims 4 to 9, wherein the concentration of FeEDTA in the leach solution is at>out 0.002 mole/L. :
11. A process according to any one of the preceding claims, wherein the pH of . the leach is preferably maintained between about 6 to 7.
12. A process according to any one off the preceding claims, wherein the reagent chemically related to thiourea is a thio-substituted organic compound. .
13. A process according to claim 12, wherein the reagent chemically related to thiourea Is one of formamidine dis ulphide or thiosemicarbazide.
14. An improved thiosulphate leach process for the recovery of gold from ores and other gold-bearing materials, characterised in that the leach solution comprises thiosulphate, thiourea or a reagent chemically related thereto, and an oxidant that does not oxidise thiosulphate, the process producing a pregnant leach solution from whicth gold may be recovered.
15. A process according to ciaim 14, wvherein the oxidant present is a complex of ethylenediamenetetraacetate (EDTA) with a multivalent metal.
16. A process according to claim 15, wherein the multivalent metal is iron and the complex FeEDTA. | :
17. A process according to any one ef claims 14 to 16, wherein the FEEDTA is provided at a concentration of about 0.002 mole/L.
1 . . +
18. A process according to any one of claims 14 to 17, wherein the thiosulphate is provided at a concentration of bretween about 0.1 to 0.3 mole/L. :
19. A process according to any one of claims 14 to 17, wherein thiourea is provided at a concentration of about 0.01 mole/L.
20. A process according to any one of claims 14 to 18, wherein gold is recovered : from the pregnant leach solution by way Of either cementation or ion exchange.
21. A process according to any one of claims 14 to 19, wherein the pH of the 8 leach is preferably maintained between about & to 7.
22. A process according to any one claims 12 to 21, wherein the reagent chemically related to thiourea is a thio-substitufted organic compound.
23. A process according to claim 22, wherein the reagent chemically related to thiourea is one of formamidine disulphide or th iosemicarbazide: 1 0
24. An improved thiosulphate leach process substantially as hereinbefore described with reference to Examples 2 to 6.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2003904385A AU2003904385A0 (en) | 2003-08-18 | 2003-08-18 | Improved Thiosulphate Leach Process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| ZA200601504B true ZA200601504B (en) | 2007-04-25 |
Family
ID=32476656
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| ZA200601504A ZA200601504B (en) | 2003-08-18 | 2006-02-21 | Improved thiosulphate leach process |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US20070266827A1 (en) |
| AU (1) | AU2003904385A0 (en) |
| CA (1) | CA2536138A1 (en) |
| WO (1) | WO2005017215A1 (en) |
| ZA (1) | ZA200601504B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6660059B2 (en) | 2000-05-19 | 2003-12-09 | Placer Dome Technical Services Limited | Method for thiosulfate leaching of precious metal-containing materials |
| US7722840B2 (en) | 2002-11-15 | 2010-05-25 | Placer Dome Technical Services Limited | Method for thiosulfate leaching of precious metal-containing materials |
| WO2007098603A1 (en) * | 2006-03-03 | 2007-09-07 | Metal Asia International Ltd. | Process for extracting gold from gold-bearing ore |
| US7972413B2 (en) | 2006-04-07 | 2011-07-05 | Metal Asia International Ltd. | Precious metal recovery from solution |
| EP2226401A4 (en) * | 2007-11-23 | 2011-01-26 | Viatcheslav Dmitrievich Shapovalov | Method for extracting precious metals from refractory ores and concentrates |
| MX2008003602A (en) * | 2008-03-14 | 2009-02-25 | Univ Autonoma Metropolitana | Process for the lixiviation and recovery of silver and gold with copper ammonia thiosulfate solutions. |
| FI20100245A (en) * | 2010-06-10 | 2011-12-11 | Outotec Oyj | Method for dissolving gold |
| BR112013014005B1 (en) | 2010-12-07 | 2020-01-28 | Barrick Gold Corp | gold and / or silver leaching method |
| AR086933A1 (en) | 2011-06-15 | 2014-01-29 | Barrick Gold Corp | METHOD FOR RECOVERING PRECIOUS METALS AND COPPER OF LIXIVIATE SOLUTIONS |
| US10161016B2 (en) | 2013-05-29 | 2018-12-25 | Barrick Gold Corporation | Method for pre-treatment of gold-bearing oxide ores |
| CN103276206B (en) * | 2013-06-09 | 2014-07-02 | 中南大学 | Method for leaching gold in alkaline thiourea system efficiently and stably |
| CN107287437B (en) * | 2016-10-24 | 2019-03-05 | 中南大学 | A kind of leaching gold method reducing thiosulfate dosage |
| CN107893160B (en) * | 2017-12-19 | 2019-04-12 | 东北大学 | Thiosulfate and the technique for mentioning gold from difficult-treating gold mine is prepared in situ |
| PE20211512A1 (en) | 2019-01-21 | 2021-08-11 | Barrick Gold Corp | METHOD FOR CARBON-CATALYZED THOSULFATE LEACHING OF MATERIALS CONTAINING GOLD |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4369061A (en) * | 1979-12-28 | 1983-01-18 | Kerley Jr Bernard J | Recovery of precious metals from difficult ores |
| US4269622A (en) * | 1979-12-28 | 1981-05-26 | Kerley Jr Bernard J | Recovery of precious metals from difficult ores |
| US4654078A (en) * | 1985-07-12 | 1987-03-31 | Perez Ariel E | Method for recovery of precious metals from difficult ores with copper-ammonium thiosulfate |
| NZ237011A (en) * | 1990-02-23 | 1992-06-25 | Cra Services | Extraction and recovery of gold by treatment with an acidic lixiviant solution |
| US5785736A (en) * | 1995-02-10 | 1998-07-28 | Barrick Gold Corporation | Gold recovery from refractory carbonaceous ores by pressure oxidation, thiosulfate leaching and resin-in-pulp adsorption |
| US6344068B1 (en) * | 2000-04-04 | 2002-02-05 | Barrick Gold Corporation | Process for recovering gold from thiosulfate leach solutions and slurries with ion exchange resin |
| US6602319B1 (en) * | 2002-04-01 | 2003-08-05 | Council Of Scientific And Industrial Research | Process for the recovery of gold and silver from used refractory bricks |
-
2003
- 2003-08-18 AU AU2003904385A patent/AU2003904385A0/en not_active Abandoned
-
2004
- 2004-08-18 CA CA002536138A patent/CA2536138A1/en not_active Abandoned
- 2004-08-18 WO PCT/AU2004/001104 patent/WO2005017215A1/en active Application Filing
- 2004-08-18 US US10/568,804 patent/US20070266827A1/en not_active Abandoned
-
2006
- 2006-02-21 ZA ZA200601504A patent/ZA200601504B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| AU2003904385A0 (en) | 2003-08-28 |
| WO2005017215A1 (en) | 2005-02-24 |
| US20070266827A1 (en) | 2007-11-22 |
| CA2536138A1 (en) | 2005-02-24 |
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