CA2386614C - The elution of gold from anion exchange resins - Google Patents
The elution of gold from anion exchange resins Download PDFInfo
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- CA2386614C CA2386614C CA2386614A CA2386614A CA2386614C CA 2386614 C CA2386614 C CA 2386614C CA 2386614 A CA2386614 A CA 2386614A CA 2386614 A CA2386614 A CA 2386614A CA 2386614 C CA2386614 C CA 2386614C
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- Prior art keywords
- gold
- resin
- thiosulphate
- copper
- nitrate
- Prior art date
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- 239000010931 gold Substances 0.000 title claims abstract description 88
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 title claims abstract description 87
- 229910052737 gold Inorganic materials 0.000 title claims abstract description 87
- 239000003957 anion exchange resin Substances 0.000 title claims abstract description 13
- 238000010828 elution Methods 0.000 title claims description 38
- 239000011347 resin Substances 0.000 claims abstract description 73
- 229920005989 resin Polymers 0.000 claims abstract description 73
- 238000000034 method Methods 0.000 claims abstract description 57
- DHCDFWKWKRSZHF-UHFFFAOYSA-L thiosulfate(2-) Chemical compound [O-]S([S-])(=O)=O DHCDFWKWKRSZHF-UHFFFAOYSA-L 0.000 claims abstract description 45
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 claims abstract description 26
- 238000011068 loading method Methods 0.000 claims abstract description 22
- 238000011084 recovery Methods 0.000 claims abstract description 17
- 150000002823 nitrates Chemical class 0.000 claims abstract description 12
- 239000010949 copper Substances 0.000 claims description 34
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 32
- 229910052802 copper Inorganic materials 0.000 claims description 31
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 20
- 229910002651 NO3 Inorganic materials 0.000 claims description 14
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 12
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 claims description 10
- 229910021529 ammonia Inorganic materials 0.000 claims description 9
- 238000002386 leaching Methods 0.000 claims description 9
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical group N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims description 8
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims description 8
- 235000011130 ammonium sulphate Nutrition 0.000 claims description 8
- 239000001166 ammonium sulphate Substances 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 4
- CIBSCSHCRMBLHW-UHFFFAOYSA-L copper(1+);dioxido-oxo-sulfanylidene-$l^{6}-sulfane Chemical compound [Cu+].[Cu+].[O-]S([O-])(=O)=S CIBSCSHCRMBLHW-UHFFFAOYSA-L 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- 229910021653 sulphate ion Inorganic materials 0.000 claims description 4
- 238000005363 electrowinning Methods 0.000 claims description 2
- 238000004064 recycling Methods 0.000 claims description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 11
- 229910052709 silver Inorganic materials 0.000 description 11
- 239000004332 silver Substances 0.000 description 11
- -1 nitrate ions Chemical class 0.000 description 5
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 4
- XYXNTHIYBIDHGM-UHFFFAOYSA-N ammonium thiosulfate Chemical compound [NH4+].[NH4+].[O-]S([O-])(=O)=S XYXNTHIYBIDHGM-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 239000010970 precious metal Substances 0.000 description 3
- 241000693467 Macroporus Species 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- SOIFLUNRINLCBN-UHFFFAOYSA-N ammonium thiocyanate Chemical compound [NH4+].[S-]C#N SOIFLUNRINLCBN-UHFFFAOYSA-N 0.000 description 2
- 238000003556 assay Methods 0.000 description 2
- ADPOBOOHCUVXGO-UHFFFAOYSA-H dioxido-oxo-sulfanylidene-$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 2
- 238000002474 experimental method Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- ZNNZYHKDIALBAK-UHFFFAOYSA-M potassium thiocyanate Chemical compound [K+].[S-]C#N ZNNZYHKDIALBAK-UHFFFAOYSA-M 0.000 description 2
- 229940116357 potassium thiocyanate Drugs 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- KRURGYOKPVLRHQ-UHFFFAOYSA-L trithionate(2-) Chemical compound [O-]S(=O)(=O)SS([O-])(=O)=O KRURGYOKPVLRHQ-UHFFFAOYSA-L 0.000 description 2
- VMQMZMRVKUZKQL-UHFFFAOYSA-N Cu+ Chemical compound [Cu+] VMQMZMRVKUZKQL-UHFFFAOYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 241000409201 Luina Species 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000010349 cathodic reaction Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 1
- ANVWDQSUFNXVLB-UHFFFAOYSA-L copper;dioxido-oxo-sulfanylidene-$l^{6}-sulfane Chemical compound [Cu+2].[O-]S([O-])(=O)=S ANVWDQSUFNXVLB-UHFFFAOYSA-L 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 230000003278 mimic effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J41/00—Anion exchange; Use of material as anion exchangers; Treatment of material for improving the anion exchange properties
- B01J41/04—Processes using organic exchangers
-
- 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
- C22B3/20—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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
A process for the recovery of gold from anion exchange resins, the method comprising eluting with a nitrate salt to displace gold from the resin. The gold has been loaded on to the resin from a thiosulphate leach solution or pulp. The nitrate salt is preferably provided in the form of ammonium nitrate. Also provided is a process for the recovery of gold from thiosulphate leach solution or pulp, the method comprising the method steps of loading gold from a thiosulphate leach solution on to an anion exchange resin, eluting with a nitrate salt to displace gold from the resin, and recovering thiosulphate from the leach solution using a resin.
Description
TITLE
"THE ELUTION OF GOLD FROM ANION EXCHANGE RESINS"
FIELD OF THE INVENTION
This invention relates to an improved process for the elution of gold from anion exchange resins.
More particularly, the improved process of the present invention may be used in the recovery of gold from thiosulphate leach pulps and solutions.
BACKGROUND ART
Precious metals, including gold, have traditionally been leached from ore using cyanide-containing solutions. The precious metal is then recovered from that solution or pulp. Importantly however, several factors have made cyanide unsuitable for precious metal recovery. The most important of these are the increasing environmental concerns with the use of cyanide and the increasing proportion of so-called refractory gold ores which do not respond favourably to cyanidation. For these reasons, alternative lixiviants such as thiosulphate have been proposed.
The conventional method for the recovery of gold from cyanide leach pulps is based on the use of activated carbon granules. However, activated carbon does not adsorb gold from thiosulphate solutions or pulps. For this reason, ion exchange resins have been suggested as alternatives to activate carbon. If looking to recover gold from a thiosulphate leach pulp using an anion exchange resin where that leach pulp also contains copper which is used as a catalyst in the leaching process, a number of particular problems arise. For example, known procedures for the elution of gold thiosulphate from resins involve the use of g/L ammonium thiosulphate or 200 g/L potassium thiocyanate. Copper has been shown to be selectively eluted using initially 200 g/L ammonium thiosulphate solution followed by elution of the gold using 200 g/L potassium thiocyanate.
CA 02386614 2002-04-05 Received 27 July 2001
"THE ELUTION OF GOLD FROM ANION EXCHANGE RESINS"
FIELD OF THE INVENTION
This invention relates to an improved process for the elution of gold from anion exchange resins.
More particularly, the improved process of the present invention may be used in the recovery of gold from thiosulphate leach pulps and solutions.
BACKGROUND ART
Precious metals, including gold, have traditionally been leached from ore using cyanide-containing solutions. The precious metal is then recovered from that solution or pulp. Importantly however, several factors have made cyanide unsuitable for precious metal recovery. The most important of these are the increasing environmental concerns with the use of cyanide and the increasing proportion of so-called refractory gold ores which do not respond favourably to cyanidation. For these reasons, alternative lixiviants such as thiosulphate have been proposed.
The conventional method for the recovery of gold from cyanide leach pulps is based on the use of activated carbon granules. However, activated carbon does not adsorb gold from thiosulphate solutions or pulps. For this reason, ion exchange resins have been suggested as alternatives to activate carbon. If looking to recover gold from a thiosulphate leach pulp using an anion exchange resin where that leach pulp also contains copper which is used as a catalyst in the leaching process, a number of particular problems arise. For example, known procedures for the elution of gold thiosulphate from resins involve the use of g/L ammonium thiosulphate or 200 g/L potassium thiocyanate. Copper has been shown to be selectively eluted using initially 200 g/L ammonium thiosulphate solution followed by elution of the gold using 200 g/L potassium thiocyanate.
CA 02386614 2002-04-05 Received 27 July 2001
-2-These eluants are relatively costly. Eluant concentrations at this level are relatively high and may prove uneconomical in a commercial plant setting.
A major problem with thiosulphate leaching is the high concentrations of thiosulphate needed and the high rate of lixiviant losses during a leach. The thiosulphate can be lost from solution through oxidation to tetrathionate, complexation with other noble metal ions or solution losses to the tails, which adds to the cost of the process.
The improved process for the recovery of gold from anion exchange resins of the present invention has as one object thereof to overcome the above-mentioned problems of the prior art.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention 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
In accordance with the present invention there is provided a process for the recovery of gold from thiosulphate leach solution or pulp, the method comprising the method steps of:
a) Loading gold from a thiosulphate leach solution on to an anion exchange resin;
b) Eluting with a nitrate salt to displace gold from the resin; and AMlEEoED SHEET
rP+E~u ~
A major problem with thiosulphate leaching is the high concentrations of thiosulphate needed and the high rate of lixiviant losses during a leach. The thiosulphate can be lost from solution through oxidation to tetrathionate, complexation with other noble metal ions or solution losses to the tails, which adds to the cost of the process.
The improved process for the recovery of gold from anion exchange resins of the present invention has as one object thereof to overcome the above-mentioned problems of the prior art.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention 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
In accordance with the present invention there is provided a process for the recovery of gold from thiosulphate leach solution or pulp, the method comprising the method steps of:
a) Loading gold from a thiosulphate leach solution on to an anion exchange resin;
b) Eluting with a nitrate salt to displace gold from the resin; and AMlEEoED SHEET
rP+E~u ~
-3-c) Recovering gold from the eluate.
Preferably, the nitrate salt is provided in the form of ammonium nitrate. The ammonium nitrate is further preferably provided at a concentration of less than or about 2M (160 g/L).
The gold may be recovered in step c) by way of electrowinning or precipitation, or any other similar process.
The process of the present invention may comprise the additional method step of recovering thiosulphate from the leach solution by absorbing same onto a resin and subsequently eluting it therefrom.
Preferably, the process further comprises the method step of recycling the recovered thiosulphate to a leaching process from which the thiosulphate leach solution was obtained. The elution of thiosulphate from the resin may be performed with either a nitrate or sulphate solution.
Where the method of the present invention is conducted in the presence of copper, before eluting with a nitrate salt the method comprises the additional step of exposing the resin to excess oxygenated ammonia which displaces the copper, loaded on the resin as copper (I) thiosulphate, as copper (li) ammine.
According to an aspect of the present invention, there is provided a process for the recovery of gold from thiosulphate leach solution or pulp, the method comprising the method steps of:
a) loading gold from a thiosulphate leach solution on to an anion exchange resin;
b) eluting with a nitrate salt to displace gold from the resin to yield an eluate; and -3a-c) recovering gold from the eluate.
Preferably, a buffer is provided to maintain pH at about 9.2. The buffer may preferably be ammonium sulphate.
BRIEF DESCRIPTION OF THE DRAWINGS
The improved process of the present invention will now be described, by way of example only, with reference to one embodiment thereof and the accompanying drawings, in which:
Figure 1 is a graphical representation of the elution of gold from a commercial strong base anionic exchange resin by ammonium nitrate, ammonium thiocyanate and ammonium thiosulphate;
Received 27 July 2001
Preferably, the nitrate salt is provided in the form of ammonium nitrate. The ammonium nitrate is further preferably provided at a concentration of less than or about 2M (160 g/L).
The gold may be recovered in step c) by way of electrowinning or precipitation, or any other similar process.
The process of the present invention may comprise the additional method step of recovering thiosulphate from the leach solution by absorbing same onto a resin and subsequently eluting it therefrom.
Preferably, the process further comprises the method step of recycling the recovered thiosulphate to a leaching process from which the thiosulphate leach solution was obtained. The elution of thiosulphate from the resin may be performed with either a nitrate or sulphate solution.
Where the method of the present invention is conducted in the presence of copper, before eluting with a nitrate salt the method comprises the additional step of exposing the resin to excess oxygenated ammonia which displaces the copper, loaded on the resin as copper (I) thiosulphate, as copper (li) ammine.
According to an aspect of the present invention, there is provided a process for the recovery of gold from thiosulphate leach solution or pulp, the method comprising the method steps of:
a) loading gold from a thiosulphate leach solution on to an anion exchange resin;
b) eluting with a nitrate salt to displace gold from the resin to yield an eluate; and -3a-c) recovering gold from the eluate.
Preferably, a buffer is provided to maintain pH at about 9.2. The buffer may preferably be ammonium sulphate.
BRIEF DESCRIPTION OF THE DRAWINGS
The improved process of the present invention will now be described, by way of example only, with reference to one embodiment thereof and the accompanying drawings, in which:
Figure 1 is a graphical representation of the elution of gold from a commercial strong base anionic exchange resin by ammonium nitrate, ammonium thiocyanate and ammonium thiosulphate;
Received 27 July 2001
-4-Figure 2 is a graphical representation of the elution of gold from the same resin by two concentrations of ammonium nitrate in accordance with the present invention;
Figure 3 is a graphical representation of gold elution from the same resin by different nitrate salts in accordance with the present invention;
Figure 4 is a graphical representation of the total recovery and separation of copper, then gold, for a commercial gel type resin (A) and a commercial macroporous resin (B);
Figure 5 is a graphical representation of the elution of thiosulphate from resin by either a nitrate or sulphate solution in accordance with a further embodiment of the present invention;
Figure 6 is a graphical representation of the equilibrium loading of gold onto the resins (A) and (B) in the presence of varying ammonium nitrate concentrations;
Figure 7 is a graphical representation of consecutive equilibrium loadings onto resin with a simulated leach solution containing gold, silver and copper;
Figure 8 is a graphical representation of the rate at which gold is eluted from resins (A) and (B); and Figure 9 is a graphical representation of the elution of copper and gold from a loaded resin from a small scale resin-in-pulp operation by ammonium sulphate and ammonium nitrate solutions respectively.
BEST MODE(S) FOR CARRYING OUT THE INVENTION
The improved process for the recovery of gold from anion exchange resins of the present invention will now be described with reference to a preferred embodiment.
However, it is to be appreciated that the following description of a preferred form of the invention is not to limit the above generality of the invention.
AMS, D:';-, St'iE=-T
IP-~, A F 1
Figure 3 is a graphical representation of gold elution from the same resin by different nitrate salts in accordance with the present invention;
Figure 4 is a graphical representation of the total recovery and separation of copper, then gold, for a commercial gel type resin (A) and a commercial macroporous resin (B);
Figure 5 is a graphical representation of the elution of thiosulphate from resin by either a nitrate or sulphate solution in accordance with a further embodiment of the present invention;
Figure 6 is a graphical representation of the equilibrium loading of gold onto the resins (A) and (B) in the presence of varying ammonium nitrate concentrations;
Figure 7 is a graphical representation of consecutive equilibrium loadings onto resin with a simulated leach solution containing gold, silver and copper;
Figure 8 is a graphical representation of the rate at which gold is eluted from resins (A) and (B); and Figure 9 is a graphical representation of the elution of copper and gold from a loaded resin from a small scale resin-in-pulp operation by ammonium sulphate and ammonium nitrate solutions respectively.
BEST MODE(S) FOR CARRYING OUT THE INVENTION
The improved process for the recovery of gold from anion exchange resins of the present invention will now be described with reference to a preferred embodiment.
However, it is to be appreciated that the following description of a preferred form of the invention is not to limit the above generality of the invention.
AMS, D:';-, St'iE=-T
IP-~, A F 1
-5-The strong base anion exchange resins used in the embodiment include a gel type resin (A), being Vitrokele 911, and a macroporous resin (B), being Amberjet 4200. The resins used were of a particular size fraction, being 0.85<x<0.6 mm in diameter. The inventors have found that gold loading rates onto each of these resins is similar and followed a simple first-order rate equation for absorption to equilibrium. The kinetics of loading of gold onto these resins is largely unaffected by the presence of thiosulphate.
After trials of methods of the prior art and several other known eluants, nitrate salts have been found to be the preferred eluant for gold. A concentration of 2M (160 g/L) ammonium nitrate was determined to be the most efficient at eluting the gold. Figure 1 shows results for tests of the gold elution characteristics of ammonium nitrate, ammonium thiocyanate and ammonium thiosulphate. A result of 99% recovery of gold was achieved. 1 M(80 g/L) ammonium nitrate was also found to account for 99% of the gold. However, the elution curve was broad compared to that of the 2M ammonium nitrate.
Figure 2 shows the results for the elution of gold from the gel resin (A) by the two concentrations of ammonium nitrate.
After trials of methods of the prior art and several other known eluants, nitrate salts have been found to be the preferred eluant for gold. A concentration of 2M (160 g/L) ammonium nitrate was determined to be the most efficient at eluting the gold. Figure 1 shows results for tests of the gold elution characteristics of ammonium nitrate, ammonium thiocyanate and ammonium thiosulphate. A result of 99% recovery of gold was achieved. 1 M(80 g/L) ammonium nitrate was also found to account for 99% of the gold. However, the elution curve was broad compared to that of the 2M ammonium nitrate.
Figure 2 shows the results for the elution of gold from the gel resin (A) by the two concentrations of ammonium nitrate.
6 PCT/AUOO/01203 To confirm that the active species is the nitrate ion, a number of nitrate solutions of the same concentration, but from different salts were used, as shown in Figure 3. It is apparent that it is the nitrate ions in solution which are eluting the gold from the resin and the cations of the salt play no part in the elution process.
The presence of copper in the system was determined to be problematic as copper simultaneously loads onto the resin and does not selectively elute off the resin. For example, it was found that treatment with a lower concentration of ammonium nitrate (0.1 M) did not elute any of the copper or gold off the resin.
Further, treatment with 0.5M ammonium nitrate eluted 70% of the copper and 15% of the gold. Whilst this demonstrates some selectivity, gold was lost in the initial strip (with 0.5M ammonium nitrate) and there was carry over of copper into the final strip for the gold using the 2M ammonium nitrate. The inventors have consequently observed that the copper thiosulphate complex behaves on the resin in a similar manner to the gold thiosulphate complex.
A clue to the solution for the above problem may be found in the chemistry of the leaching of gold with thiosulphate in the presence of copper and ammonia. It is to be noted that the exact mechanism of this process is presently uncertain.
However, it is known that there is a cyclic system that reverts from copper (II) to copper (I) and which promotes the dissolution of gold.
The copper (II) ammine drives the cathodic reaction for the dissolution of gold. As such, it should be desirable to have as high a concentration of copper (II) ammine present within a leach solution. However, a high copper (II) ammine concentration would result in increased degradation of thiosulphate.
The most likely cycle of copper during the dissolution of gold in a thiosulphate leach solution is copper (II) ammine to copper (I) thiosulphate. Copper (II) ammine is the more stable complex in aerated solutions. As such, the copper (I) thiosulphate that loads onto the resin should be displaced off the resin by converting back to the copper (II) ammine complex with the addition of excess oxygenated ammonia solution. Figure 4 shows the separation of copper and gold for both resins under this process.
The presence of copper in the system was determined to be problematic as copper simultaneously loads onto the resin and does not selectively elute off the resin. For example, it was found that treatment with a lower concentration of ammonium nitrate (0.1 M) did not elute any of the copper or gold off the resin.
Further, treatment with 0.5M ammonium nitrate eluted 70% of the copper and 15% of the gold. Whilst this demonstrates some selectivity, gold was lost in the initial strip (with 0.5M ammonium nitrate) and there was carry over of copper into the final strip for the gold using the 2M ammonium nitrate. The inventors have consequently observed that the copper thiosulphate complex behaves on the resin in a similar manner to the gold thiosulphate complex.
A clue to the solution for the above problem may be found in the chemistry of the leaching of gold with thiosulphate in the presence of copper and ammonia. It is to be noted that the exact mechanism of this process is presently uncertain.
However, it is known that there is a cyclic system that reverts from copper (II) to copper (I) and which promotes the dissolution of gold.
The copper (II) ammine drives the cathodic reaction for the dissolution of gold. As such, it should be desirable to have as high a concentration of copper (II) ammine present within a leach solution. However, a high copper (II) ammine concentration would result in increased degradation of thiosulphate.
The most likely cycle of copper during the dissolution of gold in a thiosulphate leach solution is copper (II) ammine to copper (I) thiosulphate. Copper (II) ammine is the more stable complex in aerated solutions. As such, the copper (I) thiosulphate that loads onto the resin should be displaced off the resin by converting back to the copper (II) ammine complex with the addition of excess oxygenated ammonia solution. Figure 4 shows the separation of copper and gold for both resins under this process.
-7-A buffer of ammonium sulphate is desirable when ammonia is added to the system so as to maintain the desired pH at 9.2.
Accordingly, once gold and copper have loaded onto the resin, the process of the present invention is able to selectively elute these species by initially displacing the copper as the copper (II) ammine with ammonia, then finally eluting with ammonium nitrate for the displacement of the gold.
A means to minimise the loss of thiosulphate during thiosulphate leaching may be to recover as much of the thiosulphate from the leach solution before it leaves to the tail, and then to recycle it back into the leaching process. Resin could be used to absorb the anionic species (which would include all the poly-thionate compounds) from leach solutions.
The elution of thiosulphate from the resin could be performed with either a nitrate or sulphate solution, see Figure 5. Since the eluted thiosulphate would be reused in the leaching process, ammonium sulphate would be the prefered eluant since nitrate ions may prevent gold loading onto resin. Another good reason for using ammonium sulphate is that it would not elute any gold so any absorbed anions other than gold would be eluted prior to using nitrate solution for gold.
To obtain a thermodynamic understanding of the elution process, equilibrium loadings of gold in the presence of ammonium nitrate were performed on the two resins (A) and (B). Both resins gave similar gold loadings for a particular ammonium nitrate concentration and the data in Figure 6 contains the results from both resins. The results show that nitrate ions are very good at preventing the gold from loading onto the resin. The results also show that as the ammonium nitrate concentration decreases the gold loading increases greatly, indicating that nitrate ions absorbed to the resin after elution could have minimal effect on the gold loading onto the resin if reintroduced to the absorption process.
Therefore there is no need for regeneration of the resin from the nitrate form.
Accordingly, once gold and copper have loaded onto the resin, the process of the present invention is able to selectively elute these species by initially displacing the copper as the copper (II) ammine with ammonia, then finally eluting with ammonium nitrate for the displacement of the gold.
A means to minimise the loss of thiosulphate during thiosulphate leaching may be to recover as much of the thiosulphate from the leach solution before it leaves to the tail, and then to recycle it back into the leaching process. Resin could be used to absorb the anionic species (which would include all the poly-thionate compounds) from leach solutions.
The elution of thiosulphate from the resin could be performed with either a nitrate or sulphate solution, see Figure 5. Since the eluted thiosulphate would be reused in the leaching process, ammonium sulphate would be the prefered eluant since nitrate ions may prevent gold loading onto resin. Another good reason for using ammonium sulphate is that it would not elute any gold so any absorbed anions other than gold would be eluted prior to using nitrate solution for gold.
To obtain a thermodynamic understanding of the elution process, equilibrium loadings of gold in the presence of ammonium nitrate were performed on the two resins (A) and (B). Both resins gave similar gold loadings for a particular ammonium nitrate concentration and the data in Figure 6 contains the results from both resins. The results show that nitrate ions are very good at preventing the gold from loading onto the resin. The results also show that as the ammonium nitrate concentration decreases the gold loading increases greatly, indicating that nitrate ions absorbed to the resin after elution could have minimal effect on the gold loading onto the resin if reintroduced to the absorption process.
Therefore there is no need for regeneration of the resin from the nitrate form.
-8-To examine the effect of consecutive loading/elution cycles on equilibrium loadings a simulated leach solution was prepared consisting of 0.01 M
trithionate, 0.05 M thiosulphate, 0.2 M ammonia at pH 9.5. Trithionate was added to the solution to mimic a real pulp solution. To this solution 10 ppm Cu, 10 ppm Ag or ppm Au was added to investigate the effect of copper and silver on the loading of gold. Although it is known that gold, silver and copper will load onto the resin it was considered desirable to investigate the capacity of the resin after many cycles in order to assess how practical a resin-in-pulp (RIP) process would be for the recovery of gold from thiosulphate leach solutions.
In the elution cycle the resin was initially eluted with 0.5 M ammonia buffered with 1 M ammonium sulphate, then further eluted with 2 M ammonium nitrate. The ammonia solution was buffered to prevent any precipitation of metal complexes onto the resin during elution and to recover the loaded thiosulphate. The copper that was loaded as the copper(l) thiosulphate [Cu(S203)z]3" was eluted by converting it to the copper(II) tetrammine [Cu(NH3) 4]2+ with the addition of excess oxygenated ammonia solution. The gold was then eluted with a nitrate solution.
The resin was then dried and the loading and elution cycles repeated.
Evaluation of the elution data is presented in Table 1. Although the conditions were not optimised for the silver and gold elution, the low overall recovery for silver and gold would suggest some precipitation of these metal ions onto the resin surface over time. It can also be noted that there will be some carry over of gold and silver back to the leaching circuit in the ammonia eluate.
Table 1. Averaged metal recovery over eight cycles.
Metal ion Ammonia elution Nitrate elution Overall recovery Copper 98 8 110 Gold 2 91 93 Silver 12 65 77
trithionate, 0.05 M thiosulphate, 0.2 M ammonia at pH 9.5. Trithionate was added to the solution to mimic a real pulp solution. To this solution 10 ppm Cu, 10 ppm Ag or ppm Au was added to investigate the effect of copper and silver on the loading of gold. Although it is known that gold, silver and copper will load onto the resin it was considered desirable to investigate the capacity of the resin after many cycles in order to assess how practical a resin-in-pulp (RIP) process would be for the recovery of gold from thiosulphate leach solutions.
In the elution cycle the resin was initially eluted with 0.5 M ammonia buffered with 1 M ammonium sulphate, then further eluted with 2 M ammonium nitrate. The ammonia solution was buffered to prevent any precipitation of metal complexes onto the resin during elution and to recover the loaded thiosulphate. The copper that was loaded as the copper(l) thiosulphate [Cu(S203)z]3" was eluted by converting it to the copper(II) tetrammine [Cu(NH3) 4]2+ with the addition of excess oxygenated ammonia solution. The gold was then eluted with a nitrate solution.
The resin was then dried and the loading and elution cycles repeated.
Evaluation of the elution data is presented in Table 1. Although the conditions were not optimised for the silver and gold elution, the low overall recovery for silver and gold would suggest some precipitation of these metal ions onto the resin surface over time. It can also be noted that there will be some carry over of gold and silver back to the leaching circuit in the ammonia eluate.
Table 1. Averaged metal recovery over eight cycles.
Metal ion Ammonia elution Nitrate elution Overall recovery Copper 98 8 110 Gold 2 91 93 Silver 12 65 77
-9-The equilibrium loadings from eight cycles showed very little difference in the equilibrium loading for any metal ion, see Figure 7. Although there was no effect of elution on the equilibrium loading, the resin darkened when cycled. At the conclusion of these experiments, some of the resin was washed in nitrate solution and some in thiosulphate solution (2M), both were then fire assayed to determine what was precipitating onto the resin, see Table 2. The fire assay results showed there was about 7000 ppm silver and about 3000 ppm gold. There was very little copper precipitated on the resin. The thiosulphate removed 99 % of the silver, % of the copper and 30 % of the gold. Therefore, it is apparent that the resin may be successfully cleaned with thiosulphate when needed.
Table 2. Fire Assay of resin for gold, silver or copper.
Experiment Metal ion Concentration Concentration Average (ppm) (ppm) Concentration Nitrate Copper 111 111 111 Elution Gold 2760 2980 2870 Silver 6640 6710 6675 Thiosulphate Copper 38 38 38 Elution Gold 1790 1820 1805 Silver 38 50 44 To improve the understanding of the rate at which the gold is eluted from the resin, a loaded resin was added to a solution of ammonium nitrate and samples taken over time. Both resins, the macroporus resin (A) and the gel resin (B) gave similar elution profiles. There was an initial fast elution of the gold from the resin followed by a slower elution, see Figure 8. This slower elution is expected as the nitrate solution now needs to diffuse into the pores of the resin before releasing the gold into solution. The rate of elution was very fast for 1.0 and 2.0 M
ammonium nitrate with both solutions reaching the expected equilibrium loading calculated from the thermodynamic study. The macroporus resin (B) eluted faster since having greater rate of prenetration of the eluant into the pores of the resin.
Table 2. Fire Assay of resin for gold, silver or copper.
Experiment Metal ion Concentration Concentration Average (ppm) (ppm) Concentration Nitrate Copper 111 111 111 Elution Gold 2760 2980 2870 Silver 6640 6710 6675 Thiosulphate Copper 38 38 38 Elution Gold 1790 1820 1805 Silver 38 50 44 To improve the understanding of the rate at which the gold is eluted from the resin, a loaded resin was added to a solution of ammonium nitrate and samples taken over time. Both resins, the macroporus resin (A) and the gel resin (B) gave similar elution profiles. There was an initial fast elution of the gold from the resin followed by a slower elution, see Figure 8. This slower elution is expected as the nitrate solution now needs to diffuse into the pores of the resin before releasing the gold into solution. The rate of elution was very fast for 1.0 and 2.0 M
ammonium nitrate with both solutions reaching the expected equilibrium loading calculated from the thermodynamic study. The macroporus resin (B) eluted faster since having greater rate of prenetration of the eluant into the pores of the resin.
-10-A fixed-bed elution of some of the resin from the counter-current adsorption run showed that there is fast and effective elution of copper and gold when using the elution cycle of 1 M ammonium sulphate and 2 M ammonium nitrate solutions respectively, see Figure 9. The volume of solution required by either eluant was low with only 5 bed volumes necessary to elute 95 % copper and 98 % gold from the resin.
It is envisaged that the process of the present invention may be used to ultimately provide a cost effective and viable process for the recovery of gold from thiosulphate leach pulp.
Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.
It is envisaged that the process of the present invention may be used to ultimately provide a cost effective and viable process for the recovery of gold from thiosulphate leach pulp.
Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.
Claims (10)
1. A process for the recovery of gold from thiosulphate leach solution or pulp, the method comprising the method steps of:
a) loading gold from a thiosulphate leach solution on to an anion exchange resin;
b) eluting with a nitrate salt to displace gold from the resin to yield an eluate; and c) recove(ng gold from the eluate.
a) loading gold from a thiosulphate leach solution on to an anion exchange resin;
b) eluting with a nitrate salt to displace gold from the resin to yield an eluate; and c) recove(ng gold from the eluate.
2. A process according to claim 1, wherein the nitrate salt is provided in the form of ammonium nitrate.
3. A process according to claim 2, wherein the ammonium nitrate is provided at a concentration of less than or about 2M (160 g/L).
4. A process according to any one of claims 1 to 3, wherein gold is recovered in step c) by way of electrowinning or precipitation.
5. A process according to any one of claims 1 to 4, further comprising the additional process step of recovering thiosulphate from the leach solution by absorbing same onto a resin and subsequently eluting it therefrom.
6. A process according to claim 5, wherein the process further comprises the process step of recycling the recovered thiosulphate to a leaching process from which the thiosulphate leach solution was obtained.
7. A process according to claim 5 or 6, wherein the elution of thiosulphate from the resin is performed with either a nitrate or sulphate solution.
8. A process according to any one of claims 1 to 7, where the process is conducted in the presence of copper, wherein before eluting with the nitrate salt the method comprises the additional step of exposing the resin to excess oxygenated ammonia which displaces the copper, loaded on the resin as copper (I) thiosulphate, as copper (II) ammine.
9. A process according to claim 8, wherein a buffer is provided to maintain pH at about 9.2.
10. A process according to claim 9 wherein the buffer is ammonium sulphate.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPQ3157A AUPQ315799A0 (en) | 1999-09-29 | 1999-09-29 | Improved process for the elution of gold from anion exchange resins |
| AUPQ3157 | 1999-09-29 | ||
| PCT/AU2000/001203 WO2001023626A1 (en) | 1999-09-29 | 2000-09-29 | The elution of gold from anion exchange resins |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2386614A1 CA2386614A1 (en) | 2001-04-05 |
| CA2386614C true CA2386614C (en) | 2010-03-23 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2386614A Expired - Fee Related CA2386614C (en) | 1999-09-29 | 2000-09-29 | The elution of gold from anion exchange resins |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AUPQ315799A0 (en) |
| CA (1) | CA2386614C (en) |
| WO (1) | WO2001023626A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2604287C1 (en) * | 2015-08-17 | 2016-12-10 | Лидия Алексеевна Воропанова | Method for selective extraction of gold and silver ions from hydrochloric acid solutions with tributyl phosphate |
Families Citing this family (8)
| 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 |
| ES2927467T3 (en) | 2010-12-07 | 2022-11-07 | Barrick Gold Corp | Cocurrent and countercurrent resin leaching in gold leaching processes |
| 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 |
| RU2652337C1 (en) * | 2017-07-18 | 2018-04-25 | Общество с ограниченной ответственностью "Сольвекс" | Method of extracting of gold from water-salt solutions |
| PE20211512A1 (en) | 2019-01-21 | 2021-08-11 | Barrick Gold Corp | METHOD FOR CARBON-CATALYZED THOSULFATE LEACHING OF MATERIALS CONTAINING GOLD |
| US20200377970A1 (en) | 2019-06-03 | 2020-12-03 | Barrick Gold Corporation | Method for recovering precious metals from thiosulfate leach solutions |
| CN114481229B (en) * | 2022-01-28 | 2023-07-25 | 江苏电科环保有限公司 | Precious metal recovery method for precious metal refining wastewater |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB901572A (en) * | 1959-10-12 | 1962-07-18 | Permutit Co Ltd | Improvements in or relating to ion-exchange processes |
| 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 |
| CA2256764A1 (en) * | 1996-06-26 | 1997-12-31 | Henkel Corporation | Process for the recovery of precious metal values from aqueous ammoniacal thiosulfate leach solutions |
-
1999
- 1999-09-29 AU AUPQ3157A patent/AUPQ315799A0/en not_active Abandoned
-
2000
- 2000-09-29 CA CA2386614A patent/CA2386614C/en not_active Expired - Fee Related
- 2000-09-29 WO PCT/AU2000/001203 patent/WO2001023626A1/en active IP Right Grant
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2604287C1 (en) * | 2015-08-17 | 2016-12-10 | Лидия Алексеевна Воропанова | Method for selective extraction of gold and silver ions from hydrochloric acid solutions with tributyl phosphate |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2001023626A1 (en) | 2001-04-05 |
| AUPQ315799A0 (en) | 1999-10-21 |
| CA2386614A1 (en) | 2001-04-05 |
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