WO2011154607A1 - Method of gold leaching - Google Patents

Method of gold leaching Download PDF

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Publication number
WO2011154607A1
WO2011154607A1 PCT/FI2011/050537 FI2011050537W WO2011154607A1 WO 2011154607 A1 WO2011154607 A1 WO 2011154607A1 FI 2011050537 W FI2011050537 W FI 2011050537W WO 2011154607 A1 WO2011154607 A1 WO 2011154607A1
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WO
WIPO (PCT)
Prior art keywords
thallium
gold
leaching
liquor
acid
Prior art date
Application number
PCT/FI2011/050537
Other languages
French (fr)
Inventor
Gabor Csicsovszki
Justin Salminen
Original Assignee
Outotec Oyj
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Outotec Oyj filed Critical Outotec Oyj
Publication of WO2011154607A1 publication Critical patent/WO2011154607A1/en

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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

Definitions

  • the invention is related to a process for recovering precious metals from ore.
  • the invention in more particularly relates to a method of extracting gold from gold-bearing ore.
  • a leaching liquor dissolves gold from an ore into a stable solution phase containing gold ligand (i.e., lixiviants).
  • gold ligand i.e., lixiviants
  • the dissolved gold is collected by a recovery process, to produce solid gold metal.
  • gold lixiviant is cyanide salts. Cyanidation, however, has a number of problems. For example, cyanide is an extremely toxic chemical which, if released into the environment, may cause serious environmental damage.
  • Thiosulfate has been proposed as the most promising alternative for leaching of gold from ores. Thus, it is not surprising that numerous thiosulfate leaching studies have been published in the last decades.
  • Patent publication WO 2007/098603 discloses that the addition of EDA/cupric to the thiosulfate system can reduce the consumption of thiosulfate. The same effect can be achieved by using ferric-EDTA with thiourea in the thiosulphate system. Moreover, applying of nickel with ammonia can reduce the thiosulfate consumption also. However, there are still some crucial technical challenges to overcome, such as high concentration of toxic EDA, ammonia or thiourea in solution.
  • the object of the present invention is to overcome disadvantages of the prior art processes and to provide a new and advantageous hydrometallurgical method for recovering gold.
  • the method of the invention is based on a thiosulfate leaching media.
  • the invention provides a method where the advantages of a less toxic thiosufate method is utilised with combination of lowered thiosulfate consumption.
  • the overall reagent consumption is lower compared to prior art methods and there is no need for high concentrations of toxic ammonia, EDA, thiourea and heavy metals.
  • a special advantage of the present invention is that it provides a process where gold is easy to recover from the leach solution by ion exchange.
  • the chemistry of the process is very simple as only oxygen and/or other oxidants are used for oxidation. In addition no toxic substances report to tailings pond.
  • the invention provides a process for extracting gold from a gold-bearing raw material, such as gold-bearing ore.
  • the process includes, first, grinding the gold bearing raw material, second, providing a leach liquor comprising thiosulfate anions and trace amounts of thallium ions.
  • the leaching liquor is brought into contact with the gold-bearing ore in the presence of oxidant such as dispersed oxygen to form a pregnant leach solution including gold dissolved from the gold-bearing ore.
  • oxidant such as dispersed oxygen
  • a method of removing thallium containing reagent from the leaching liquor and recycling thallium back to the leaching step is provided.
  • a thallium precursor dissolving in an aqueous media is used.
  • organic thallium salts or thallium salts of mineral acids are used the form Tl ions or Tl complexes in the leach liquor.
  • the thallium salt can be selected from a group of thallium salt of sulphuric acid, hydrochloride acid, nitric acid and ethylenediaminetetraacetic acid.
  • the thallium precursor added to the leaching step of the process may be formed of a mixture of two or more salts of thallium.
  • Dissolved thallium may be recovered from the leaching liquor and at least partly recycled and in a controlled amount back to the leaching step. Excess of the thallium ions and compounds may be removed from the process.
  • Figure 1 represents a flow diagram of the preferred embodiment of the present invention.
  • ground gold bearing raw material is added to a leaching liquor comprising thallium ions and thiosulphate salt to perform leaching in a leaching step 10.
  • the equipment of the leaching step 10 is designed to provide the leaching liquor with an appropriate amount of oxidant.
  • the oxidant may be dispersed air, oxygen enriched air or oxygen.
  • the appropriate amount of the oxidant ensures proper reaction rate of the second half reaction (2).
  • gold is dissolved in the lixiviant.
  • the reactor in the leaching step 10 may operate in atmospheric pressure or in an elevated pressure meaning that an autoclave reactor may be applied.
  • the amount of the thallium compound in the leaching liquor is controlled and adjusted so as to form a desired thallium ion concentration.
  • the dissolved Tl -ion concentration in the leaching liquor is preferably between 1 and 50 mg/l.
  • ion exchange resin is added to the leaching step 10 to form a loaded resin which contains gold from the leach liquor.
  • the ion exchange resin is selected from commercially available resins capable of removing gold.
  • suitable resins are strong base anion exchangers.
  • Gold bearing resin is conducted to process step 14 to elute gold from the resin to form gold containing liquid.
  • the dissolved liquid from the gold bearing eluant may subjected to a gold electrowinning process 13 to recover metallic gold from the liquid.
  • the regenerated gold resin is fed back from the gold elution step 14 to the leaching stage 10.
  • Dissolved thallium ions are recovered from the leaching pulp with another ion exchange resin in a resin-in-pulp step 1 1 after the leaching step 10. As the thallium is removed from the liquor with aid of the thallium resin, the lodaded thallium resin is separated with screening from the tailings and barren solution.
  • the separated thallium loaded resin is fed to thallium elution step 12 for eluting thallium from the resin and to recycle recovered thallium containing solution back to the thiosulphate leaching step 10.
  • the regenerated thallium free resin is recycled back to the resin-in-pulp step 1 1 for reuse.
  • the concentration of thallium ions in the leaching step 10 is controlled.
  • a 24-hour batch leaching test was carried out in a 3 liter agitated reactor using 0.1 mol/l Na 2 S 2 0 3 solution with 10 mg/l ⁇ (as sulfate) and only atmospheric oxygen as the oxidant.
  • the slurry density of the pulp was set to 33% in the beginning of the test. Slurry temperature was not controlled during the experiment and remained at ambient temperature.
  • the ore sample contained 77% Si0 2 , 16.8% Al 2 0 3 , 2.1 % K 2 0, 1 .1 % FeO, and 5.9 ppm Au, determined by fire assay. Gold occured mainly as fine-grained native grains containing an average of 5% Ag.
  • Gold was present also in tellurides mainly as calaverite AuTe 2 , sylvanite AuAgTe 4 and kostovite CuAuTe 4 .
  • the ore was mildly refractory because of the Au-tellurides.
  • the ore sample was ground to 75% -80 ⁇ .
  • Gold was determined in the leach residue by graphite furnace atomic absorption spectrometry (GFAAS). Thiosulfate was analyzed by high performance liquid chromatography (HPLC).
  • the said lixiviant extracted 70% of the gold after 24 hours of leaching.
  • the degradation rate of thiosulfate was very low, not detectable by HPLC.
  • the typical recovery of gold using standard cyanide leaching for the same ore was slightly higher, 80%.
  • the respective Cu 2 7EDA/thiosulphate experiment gave 60 % gold extraction, lower than with the method presented in this work.

Abstract

A process for recovering gold from gold-bearing raw material is provided. The method comprises a step of leaching the raw material in leach solution comprising thiosulphate anions and trace amount of thallium ions.

Description

METHOD OF GOLD LEACHING
FIELD OF THE INVENTION
The invention is related to a process for recovering precious metals from ore. The invention in more particularly relates to a method of extracting gold from gold-bearing ore.
BACKGROUND OF THE INVENTION
Various leaching processes are known for extracting precious metals (e.g., gold, platinum, silver) from minerals. In known processes, a leaching liquor dissolves gold from an ore into a stable solution phase containing gold ligand (i.e., lixiviants). The dissolved gold is collected by a recovery process, to produce solid gold metal. The most commonly used gold lixiviant is cyanide salts. Cyanidation, however, has a number of problems. For example, cyanide is an extremely toxic chemical which, if released into the environment, may cause serious environmental damage. Thiosulfate has been proposed as the most promising alternative for leaching of gold from ores. Thus, it is not surprising that numerous thiosulfate leaching studies have been published in the last decades.
It is well known that atmospheric oxygen as oxidising agent alone is not efficient enough to leach gold in the thiosulphate system because of the slow kinetics of both the gold oxidation half reaction (reaction 1 ) and the oxygen reduction on the surface of gold (reaction 2).
Au + 2S2O3 2"— [Au(S2O3)2]3" + e- E0 = 0.150 V (1 ) O2 + 2H2O + 4e-— 4OH" E0 = 0.401 V (2)
Therefore, certain additives have been proposed to accelerate the overall dissolution rate of gold in thiosulfate solution. Such proposed additives are ammonia (NH3) combined with cupric ions (Cu2+), NH3 combined with nickel salts, oxidised with 02 giving nickelous oxide (Ni304) , ferric sulfate + Na- EDTA (sodium salt of ethylenediaminetetraacetic acid) combined with thiourea, and EDA/cupric - ethylenediamine combined with cupric ions.
One of the major drawbacks of the thiosulphate leaching is the high consumption of the thiosulphate reagent. Patent publication WO 2007/098603 discloses that the addition of EDA/cupric to the thiosulfate system can reduce the consumption of thiosulfate. The same effect can be achieved by using ferric-EDTA with thiourea in the thiosulphate system. Moreover, applying of nickel with ammonia can reduce the thiosulfate consumption also. However, there are still some crucial technical challenges to overcome, such as high concentration of toxic EDA, ammonia or thiourea in solution.
OBJECT OF THE INVENTION
The object of the present invention is to overcome disadvantages of the prior art processes and to provide a new and advantageous hydrometallurgical method for recovering gold. The method of the invention is based on a thiosulfate leaching media.
The invention provides a method where the advantages of a less toxic thiosufate method is utilised with combination of lowered thiosulfate consumption. In this invention the overall reagent consumption is lower compared to prior art methods and there is no need for high concentrations of toxic ammonia, EDA, thiourea and heavy metals.
A special advantage of the present invention is that it provides a process where gold is easy to recover from the leach solution by ion exchange. The chemistry of the process is very simple as only oxygen and/or other oxidants are used for oxidation. In addition no toxic substances report to tailings pond. SUMMARY OF THE INVENTION
The invention provides a process for extracting gold from a gold-bearing raw material, such as gold-bearing ore. The process includes, first, grinding the gold bearing raw material, second, providing a leach liquor comprising thiosulfate anions and trace amounts of thallium ions. Next, the leaching liquor is brought into contact with the gold-bearing ore in the presence of oxidant such as dispersed oxygen to form a pregnant leach solution including gold dissolved from the gold-bearing ore. Finally, at least part of the gold is recovered from the pregnant leach solution.
In another aspect of the present invention, a method of removing thallium containing reagent from the leaching liquor and recycling thallium back to the leaching step is provided. In accordance with the present invention, a thallium precursor dissolving in an aqueous media is used. Preferably organic thallium salts or thallium salts of mineral acids are used the form Tl ions or Tl complexes in the leach liquor. The thallium salt can be selected from a group of thallium salt of sulphuric acid, hydrochloride acid, nitric acid and ethylenediaminetetraacetic acid. Further, the thallium precursor added to the leaching step of the process may be formed of a mixture of two or more salts of thallium.
In the method of this invention it is essential to control and adjust the concentration of dissolved thallium ions in the leaching liquor, thus a method of recovering and recycling thallium in the leaching process is provided. Dissolved thallium may be recovered from the leaching liquor and at least partly recycled and in a controlled amount back to the leaching step. Excess of the thallium ions and compounds may be removed from the process.
LIST OF DRAWINGS
Figure 1 represents a flow diagram of the preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Next the invention is described in more detail with reference to the accompanied drawing.
In the beginning of the process of the present invention, ground gold bearing raw material is added to a leaching liquor comprising thallium ions and thiosulphate salt to perform leaching in a leaching step 10. The equipment of the leaching step 10 is designed to provide the leaching liquor with an appropriate amount of oxidant. The oxidant may be dispersed air, oxygen enriched air or oxygen. The appropriate amount of the oxidant ensures proper reaction rate of the second half reaction (2). As a result of the thallium catalyzed reactions (1 ,2) gold is dissolved in the lixiviant.
The reactor in the leaching step 10 may operate in atmospheric pressure or in an elevated pressure meaning that an autoclave reactor may be applied.
The amount of the thallium compound in the leaching liquor is controlled and adjusted so as to form a desired thallium ion concentration. The dissolved Tl -ion concentration in the leaching liquor is preferably between 1 and 50 mg/l.
According to the first preferred embodiment of the invention as shown in Fig. 1 , ion exchange resin is added to the leaching step 10 to form a loaded resin which contains gold from the leach liquor. The ion exchange resin is selected from commercially available resins capable of removing gold. For example, suitable resins are strong base anion exchangers. After leaching, the leaching pulp is subjected to screening so as to separate loaded resin from the non-dissolved solids and the leach liquor.
Gold bearing resin is conducted to process step 14 to elute gold from the resin to form gold containing liquid. The dissolved liquid from the gold bearing eluant may subjected to a gold electrowinning process 13 to recover metallic gold from the liquid. The regenerated gold resin is fed back from the gold elution step 14 to the leaching stage 10. Dissolved thallium ions are recovered from the leaching pulp with another ion exchange resin in a resin-in-pulp step 1 1 after the leaching step 10. As the thallium is removed from the liquor with aid of the thallium resin, the lodaded thallium resin is separated with screening from the tailings and barren solution. The separated thallium loaded resin is fed to thallium elution step 12 for eluting thallium from the resin and to recycle recovered thallium containing solution back to the thiosulphate leaching step 10. The regenerated thallium free resin is recycled back to the resin-in-pulp step 1 1 for reuse. The concentration of thallium ions in the leaching step 10 is controlled.
The thiosulphate containing barren solution (reclaimed solution) is separated (step 15) from the tailings and recycled back to the thiosulphate leaching step 10. EXAMPLE 1
A 24-hour batch leaching test was carried out in a 3 liter agitated reactor using 0.1 mol/l Na2S203 solution with 10 mg/l Τ (as sulfate) and only atmospheric oxygen as the oxidant. The slurry density of the pulp was set to 33% in the beginning of the test. Slurry temperature was not controlled during the experiment and remained at ambient temperature. The ore sample contained 77% Si02, 16.8% Al203, 2.1 % K20, 1 .1 % FeO, and 5.9 ppm Au, determined by fire assay. Gold occured mainly as fine-grained native grains containing an average of 5% Ag. Gold was present also in tellurides mainly as calaverite AuTe2, sylvanite AuAgTe4 and kostovite CuAuTe4. The ore was mildly refractory because of the Au-tellurides. The ore sample was ground to 75% -80 μΐη. Gold was determined in the leach residue by graphite furnace atomic absorption spectrometry (GFAAS). Thiosulfate was analyzed by high performance liquid chromatography (HPLC).
The said lixiviant extracted 70% of the gold after 24 hours of leaching. The degradation rate of thiosulfate was very low, not detectable by HPLC. The typical recovery of gold using standard cyanide leaching for the same ore was slightly higher, 80%. The respective Cu27EDA/thiosulphate experiment gave 60 % gold extraction, lower than with the method presented in this work.

Claims

1 . A method of extracting gold from gold-bearing raw material, such as ore, comprising steps of
grinding the gold-bearing raw material;
providing a leaching liquor comprising thiosulphate anions and trace amount of thallium ions;
contacting said leaching liquor and ground raw material in the presence of oxidant to form a pregnant leach solution comprising dissolved gold from the raw material;
recovering at least part of the dissolved gold from the pregnant leach solution.
The method according to claim 1 , characterized in that the thallium ions are provided in the leach liquor as a thallium salt of mineral acid or any organic salt of thallium.
The method according to claim 1 or 2, characterized in that the thallium ions are provided in the leach liquor as thallium salt selected from a group of thallium salt of sulphuric acid, hydrochloric acid, nitric acid and ethylenediaminetetraacetic acid.
The method according to claim 1 or 2, characterized in that the thallium ions are provided in the leach liquor as salt of sulphuric acid, nitric acid, hydrochloric acid or ethylenediaminetetraacetic acid.
The method according to claim 1 , characterized in that the oxidant in the leaching liquor is dispersed oxygen.
6. The method according to claim 1 to 3, characterized in that the
dissolved Tl -ion concentration in the leach liquor is between 1 and 50 mg/l. The method according to any of the preceding claim, characterized in that thallium concentration in the leaching step 10 is controlled and adjusted to desired concentration.
The method according to any of the preceding claim, characterized in that thallium is recovered from the leaching liquor and at least partly recycled back to the leaching step 10.
The method according to any of the preceding claim, characterized in that dissolved gold is recovered in an electrowining process.
10. The method according to any of the preceding claim, characterized in that the leaching reactor in the thiosulphate leaching step is an autoclave reactor.
1 1 . The method according to any of the preceding claim, characterized in that the leaching reactor in the thiosulphate leaching step operates in atmospheric pressure.
PCT/FI2011/050537 2010-06-10 2011-06-08 Method of gold leaching WO2011154607A1 (en)

Applications Claiming Priority (2)

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FI20100245A FI20100245A (en) 2010-06-10 2010-06-10 Method for dissolving gold
FI20100245 2010-06-10

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107400778A (en) * 2017-08-08 2017-11-28 中南大学 A kind of method that golden thiosulfate anion complex ion is desorbed from strong-base anion-exchange resin
CN107488789A (en) * 2017-08-11 2017-12-19 中南大学 A kind of method of the co-desorption gold thiosulfate anion complex ion from strong-base anion-exchange resin
US10362720B2 (en) 2014-08-06 2019-07-23 Greene Lyon Group, Inc. Rotational removal of electronic chips and other components from printed wire boards using liquid heat media
US11136681B2 (en) 2015-06-24 2021-10-05 Greene Lyon Group, Inc. Selective removal of noble metals using acidic fluids, including fluids containing nitrate ions
US11193214B2 (en) 2013-12-20 2021-12-07 Greene Lyon Group, Inc. Method and apparatus for recovery of noble metals, including recovery of noble metals from plated and/or filled scrap
US11408053B2 (en) 2015-04-21 2022-08-09 Excir Works Corp. Methods for selective leaching and extraction of precious metals in organic solvents
CN115572833A (en) * 2022-11-07 2023-01-06 昆明理工大学 Method capable of effectively leaching gold in printed circuit board

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US4552589A (en) * 1984-01-27 1985-11-12 Getty Oil Company Process for the recovery of gold from refractory ores by pressure oxidation
US5484470A (en) * 1994-07-28 1996-01-16 E. I. Du Pont De Nemours And Company Enhancement of gold lixiviation using nitrogen and sulfur heterocyclic aromatic compounds
WO2005017215A1 (en) * 2003-08-18 2005-02-24 Murdoch University Improved thiosulphate leach process
WO2007098603A1 (en) 2006-03-03 2007-09-07 Metal Asia International Ltd. Process for extracting gold from gold-bearing ore
WO2009067039A1 (en) * 2007-11-23 2009-05-28 Shapovalov Viatcheslav Dmitrie Method for extracting precious metals from refractory ores and concentrates

Patent Citations (5)

* Cited by examiner, † Cited by third party
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US4552589A (en) * 1984-01-27 1985-11-12 Getty Oil Company Process for the recovery of gold from refractory ores by pressure oxidation
US5484470A (en) * 1994-07-28 1996-01-16 E. I. Du Pont De Nemours And Company Enhancement of gold lixiviation using nitrogen and sulfur heterocyclic aromatic compounds
WO2005017215A1 (en) * 2003-08-18 2005-02-24 Murdoch University Improved thiosulphate leach process
WO2007098603A1 (en) 2006-03-03 2007-09-07 Metal Asia International Ltd. Process for extracting gold from gold-bearing ore
WO2009067039A1 (en) * 2007-11-23 2009-05-28 Shapovalov Viatcheslav Dmitrie Method for extracting precious metals from refractory ores and concentrates

Non-Patent Citations (1)

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Title
KOZIN L F ET AL: "Extraction of Gold from ores and concentrates by leaching with the use of cyanides and alternative reagents", RUSSIAN JOURNAL OF APPLIED CHEMISTRY, NAUKA/INTERPERIODICA, MO, vol. 77, no. 10, 1 October 2004 (2004-10-01), pages 1573 - 1592, XP019299209, ISSN: 1608-3296 *

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11193214B2 (en) 2013-12-20 2021-12-07 Greene Lyon Group, Inc. Method and apparatus for recovery of noble metals, including recovery of noble metals from plated and/or filled scrap
US10362720B2 (en) 2014-08-06 2019-07-23 Greene Lyon Group, Inc. Rotational removal of electronic chips and other components from printed wire boards using liquid heat media
US11343950B2 (en) 2014-08-06 2022-05-24 Greene Lyon Group, Inc. Rotational removal of electronic chips and other components from printed wire boards using liquid heat media
US11427886B2 (en) 2015-04-21 2022-08-30 Excir Works Corp. Methods for simultaneous leaching and extraction of precious metals
US11408053B2 (en) 2015-04-21 2022-08-09 Excir Works Corp. Methods for selective leaching and extraction of precious metals in organic solvents
US11814698B2 (en) 2015-04-21 2023-11-14 Excir Works Corp. Methods for simultaneous leaching and extraction of precious metals
US11136681B2 (en) 2015-06-24 2021-10-05 Greene Lyon Group, Inc. Selective removal of noble metals using acidic fluids, including fluids containing nitrate ions
US11566334B2 (en) 2015-06-24 2023-01-31 Greene Lyon Group, Inc. Selective removal of noble metals using acidic fluids, including fluids containing nitrate ions
CN107400778B (en) * 2017-08-08 2019-01-18 中南大学 A method of desorbing golden thiosulfate anion complex ion from strong-base anion-exchange resin
CN107400778A (en) * 2017-08-08 2017-11-28 中南大学 A kind of method that golden thiosulfate anion complex ion is desorbed from strong-base anion-exchange resin
CN107488789B (en) * 2017-08-11 2019-01-18 中南大学 A method of the co-desorption gold thiosulfate anion complex ion from strong-base anion-exchange resin
CN107488789A (en) * 2017-08-11 2017-12-19 中南大学 A kind of method of the co-desorption gold thiosulfate anion complex ion from strong-base anion-exchange resin
CN115572833A (en) * 2022-11-07 2023-01-06 昆明理工大学 Method capable of effectively leaching gold in printed circuit board

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