CA2564338A1 - Method for recovering gold - Google Patents
Method for recovering gold Download PDFInfo
- Publication number
- CA2564338A1 CA2564338A1 CA 2564338 CA2564338A CA2564338A1 CA 2564338 A1 CA2564338 A1 CA 2564338A1 CA 2564338 CA2564338 CA 2564338 CA 2564338 A CA2564338 A CA 2564338A CA 2564338 A1 CA2564338 A1 CA 2564338A1
- Authority
- CA
- Canada
- Prior art keywords
- gold
- copper
- chloride
- leaching
- solution
- Prior art date
- Legal status (The legal status 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 status listed.)
- Abandoned
Links
- 239000010931 gold Substances 0.000 title claims abstract description 43
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 229910052737 gold Inorganic materials 0.000 title claims abstract description 42
- 238000000034 method Methods 0.000 title claims abstract description 42
- 238000002386 leaching Methods 0.000 claims abstract description 44
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 42
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052802 copper Inorganic materials 0.000 claims abstract description 24
- 239000010949 copper Substances 0.000 claims abstract description 24
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000005864 Sulphur Substances 0.000 claims abstract description 22
- 229910052742 iron Inorganic materials 0.000 claims abstract description 21
- 239000002253 acid Substances 0.000 claims abstract description 12
- 239000002994 raw material Substances 0.000 claims abstract description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 11
- 239000003513 alkali Substances 0.000 claims abstract description 9
- 239000013067 intermediate product Substances 0.000 claims abstract description 9
- 230000033116 oxidation-reduction process Effects 0.000 claims abstract description 9
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 8
- 239000000460 chlorine Substances 0.000 claims abstract description 8
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 claims description 28
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 16
- 229910021592 Copper(II) chloride Inorganic materials 0.000 claims description 13
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
- 238000004090 dissolution Methods 0.000 claims description 9
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 8
- 239000011780 sodium chloride Substances 0.000 claims description 8
- 239000000725 suspension Substances 0.000 claims description 7
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 6
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 4
- 235000010216 calcium carbonate Nutrition 0.000 claims description 4
- 238000005868 electrolysis reaction Methods 0.000 claims description 4
- 238000009835 boiling Methods 0.000 claims description 3
- 239000000292 calcium oxide Substances 0.000 claims description 3
- QYFMQRSFRCFZNM-UHFFFAOYSA-K copper;sodium;trichloride Chemical compound [Na+].[Cl-].[Cl-].[Cl-].[Cu+2] QYFMQRSFRCFZNM-UHFFFAOYSA-K 0.000 claims description 3
- 239000000395 magnesium oxide Substances 0.000 claims description 3
- 238000009388 chemical precipitation Methods 0.000 claims description 2
- 238000011084 recovery Methods 0.000 abstract description 12
- 229910052751 metal Inorganic materials 0.000 abstract description 5
- 239000002184 metal Substances 0.000 abstract description 5
- 150000002739 metals Chemical class 0.000 abstract description 5
- 238000006386 neutralization reaction Methods 0.000 abstract description 4
- SRWFBFUYENBCGF-UHFFFAOYSA-M sodium;chloride;hydrochloride Chemical compound [Na+].Cl.[Cl-] SRWFBFUYENBCGF-UHFFFAOYSA-M 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 22
- 239000012141 concentrate Substances 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 3
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 3
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 3
- 229910052794 bromium Inorganic materials 0.000 description 3
- 235000011149 sulphuric acid Nutrition 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 2
- BWFPGXWASODCHM-UHFFFAOYSA-N copper monosulfide Chemical compound [Cu]=S BWFPGXWASODCHM-UHFFFAOYSA-N 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 description 2
- 230000008719 thickening Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- 241001354491 Lasthenia californica Species 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- GJCXHYNLSNVSQZ-UHFFFAOYSA-L [Cu](Cl)Cl.Cl Chemical compound [Cu](Cl)Cl.Cl GJCXHYNLSNVSQZ-UHFFFAOYSA-L 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 125000001309 chloro group Chemical group Cl* 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- JJLJMEJHUUYSSY-UHFFFAOYSA-L copper(II) hydroxide Inorganic materials [OH-].[OH-].[Cu+2] JJLJMEJHUUYSSY-UHFFFAOYSA-L 0.000 description 1
- AEJIMXVJZFYIHN-UHFFFAOYSA-N copper;dihydrate Chemical compound O.O.[Cu] AEJIMXVJZFYIHN-UHFFFAOYSA-N 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- RCJVRSBWZCNNQT-UHFFFAOYSA-N dichloridooxygen Chemical compound ClOCl RCJVRSBWZCNNQT-UHFFFAOYSA-N 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 1
- 238000009854 hydrometallurgy Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 150000002506 iron compounds Chemical class 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 238000005406 washing 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
- C22B11/042—Recovery of noble metals from waste materials
- C22B11/044—Recovery of noble metals from waste materials from pyrometallurgical residues, e.g. from ashes, dross, flue dust, mud, skim, slag, sludge
-
- 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
- C22B11/06—Chloridising
-
- 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
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention relates to a method for recovering gold from an intermediate product or residue containing sulphur and iron generated in the leaching of a sulphidic raw material. The recovery of gold and the other valuable metals in the raw material takes place in a chloride environment. The gold contained in the intermediate product or residue is leached with divalent copper and chlorine in a copper (11) chloride - sodium chloride solution in conditions where the oxidation-reduction potential is in the range of 650-750 mV and the pH between 1 and 1.6. The acid generated during the feed of chlorine is neutralized with a suitable alkali. Neutralization avoids the costs of dissolving the iron.
Description
METHOD FOR RECOVERING GOLD
FIELD OF THE INVENTION
The invention relates to a method for recovering gold from an intermediate product or residue containing sulphur and iron generated in the leaching of a sulphidic raw material. The recovery of gold and the other valuable metals in the raw material takes place in a chloride environment. The gold contained in the intermediate product or residue is leached with divalent copper and chlorine in a copper (II) chloride - sodium chloride solution in conditions io where the oxidation-reduction potential is in the range of 650-750 mV and the pH between 1 and 1.6. The acid generated during the feed of chlorine is neutralized with a suitable alkali. Neutralization avoids the costs of dissolving the iron.
BACKGROUND OF THE INVENTION
Several methods are known in the prior art, which are used to leach gold from material containing sulphur and iron in connection with a chloride-based copper recovery process.
US patent 4,551,213 describes a method in which gold can be leached from sulphur-containing material, in particular the residue from hydrometallurgical processes. The preferred starting material for the method is the residue from the CLEAR process. The CLEAR process is a hydrometallurgical copper recovery process, which occurs in a chloride environment and at elevated pressure. The gold-containing residue is elutriated into water and the chloride concentration of the resulting suspension is adjusted so that it is - 38 weight percent. The oxidation-reduction potential is adjusted to the range of 650 - 750 mV and the pH to below 0. Copper (II) chloride or iron (III) chloride are added to the suspension to oxidize the gold contained in the 3o raw material, so that it dissolves.
EP patent 646185 relates to the recovery of copper from sulphidic concentrates with chloride leaching in atmospheric conditions. The gold from the leach residue is dissolved into electrolyte, which includes two or more halides, such as sodium chloride and sodium bromide. The purpose is to store oxidising energy in the bromine complex on the copper electrolysis anode, and thereby leach the gold from the residue.
There are certain drawbacks to the above-mentioned methods. In the method of US patent 4,551,213 the leaching conditions are very severe. The lo patent mentions that sulphur is not dissolved in the patent conditions, but the mention is not universally applicable, since the dissolving tendencies of elemental sulphur and the iron compounds mentioned in the patent depend on the manner in which the sulphur and the compounds in question are generated. In the tests we carried out it was found that when leaching residues formed in atmospheric conditions are treated in conditions in accordance with the said patent, the dissolution of sulphur and iron is considerable. Since, according to the publication, the sulphur and iron do not dissolve, there is no mention either of how to recover them from the solution.
The gold leaching method used in EP patent 646185 using a bromine complex is not advantageous from an environmental point of view because harmful bromine emissions may be generated in the concentrate leaching stage.
WO patent application 03/091463 describes a method for leaching gold from leaching residue or intermediate product containing iron and sulphur, generated in the atmospheric chloride leaching of copper sulphide concentrate. The publication states that gold may be leached from an iron-and sulphur-containing material into an aqueous solution of copper (II) chloride and sodium chloride with copper and oxygen in conditions where the oxidation-reduction potential is below 650 mV and the pH value of the solution in the range 1 - 3. In these conditions iron does not dissolve and the sulphur remains undissolved to a large extent. Thus the costs that arise when iron and sulphur are removed from the solution are avoided. The recovery of gold from the solution is made by one of the methods of the prior art such as electrolysis or active carbon. The method in question is in itself quite good, but in practice however it is somewhat slow.
PURPOSE OF THE INVENTION
Now a method has been developed for the recovery of gold from an intermediate product or residue that contains sulphur and iron, generated in the leaching of a sulphidic raw material. Raw material leaching is carried out io using a concentrated aqueous solution of alkali chloride and copper (II) chloride in atmospheric conditions. When oxygen or oxygen-containing gas is fed into the sulphidic concentrate leaching stages, iron is oxidised and precipitated as oxide or hydroxide and the valuable metals, with the exception of gold, dissolve. The leaching of gold from the remaining residue is carried out with an alkali chloride - copper (II) chloride aqueous solution and chlorine in atmospheric conditions. The oxidation-reduction potential of the leaching stage is raised to the range of 650-750 mV by means of chlorine. A high oxidation-reduction potential enables the elemental sulphur in the residue to dissolve and as a consequence, acid is formed in the stage, which is neutralised by some suitable alkali. The simultaneous neutralisation of the acid keeps the pH at a value of 1.0 - 1.6, whereby the dissolution of iron is prevented. The dissolved gold is recovered by some method known as such in the prior art.
The essential features of the invention will be made apparent in the attached claims.
SUMMARY OF THE INVENTION
A gold-bearing intermediate product or residue is leached into sodium chloride solution containing copper(II) chloride forming a suspension and the oxidation-reduction potential required for gold leaching is obtained particularly by means of divalent copper and chlorine gas. If the feed to gold leaching still contains undissolved copper- or other sulphide, oxygen-containing gas can be fed to the start of the leaching stage in order to dissolve it. The oxidation-reduction potential is measured with Pt- and Ag/AgCl electrodes and the potential is kept at a value of 650-750 mV. The amount of divalent copper, Cu2+, in the solution is preferably 20 - 80 g/I and the amount of sodium chloride in the region of 200 - 330 g/l. Gold dissolves as a chloro complex in accordance with the following reaction:
Au + 3 Cu2+ + 6 CI" 4 AuC14 + 3 Cu+ + 2 CI" (1) lo Leaching occurs in atmospheric conditions at a temperature, which is between room temperature and the boiling point of the suspension, preferably, however, between 80 C and the boiling point of the suspension.
Thus, tests have now revealed that raising the redox potential of the reacting slurry with chlorine gas accelerates the dissolution of gold. There is however a drawback to this acceleration. Raising the redox potential increases the dissolution of the elemental sulphur (S ) in the material to be leached, which probably occurs in accordance with the following reaction (2):
S + 3 C12 + 4 H20 4 H2SO4 + 6 HCI (2) Reaction (2) shows that a lot of acid is generated (8 mol H+/ mol S ). The acid generated in the solution must however be neutralised, since at pH
values under 1 the iron in the solids begins to dissolve. The dissolution of iron causes process costs, as dissolved iron is circulated and consumes reagents. The preferred pH region to keep iron in the residue is between 1.0 and 1.6.
Some suitable alkali from the group NaOH, KOH, CaO, CaCO3 or MgO is used to neutralise the acid. If the process is combined with a chloride-based hydrometallurgical method of producing copper, in which basic copper (II) chloride is generated in the precipitation of divalent copper from leaching, the use of the copper (II) chloride is the best option. When basic copper (II) chloride dissolves, the copper (II) chloride generated can be used for raw material leaching. The neutralization of hydrochloric acid and copper (II) 5 oxychloride leaching occur according to the following reaction:
3 Cu(OH)2.CuC12 + 6 HCI 4 4 CuC12 + 6 H20 (3) The sulphuric acid generated can be neutralised for example with lime:
H2SO4 + CaCO3 4 CaSO4 2H2O + CO2 (4) The recovery of gold from the solution takes place by some method known as such in the prior art, for instance active carbon, electrolysis or chemical precipitation.
LIST OF DRAWINGS
The method of the invention is further described in the flow chart of Fig 1, where the recovery of gold is combined with the hydrometallurgical recovery of copper.
DETAILED DESCRIPTION OF THE DRAWINGS
According to Fig. 1, a sulphidic raw material such as copper sulphide concentrate 2 is fed to the first leaching stage 1, and solution 3 from a later process stage, which is an aqueous solution of copper (II) chloride and sodium chloride, is also circulated to this stage. The thicker arrows denote solids and the thinner arrows the flow of solution. The stage always includes one or more reactors and thickening. The copper and other valuable metals of the concentrate mainly dissolve into the process solution and the resulting solution 4 includes copper chloride, in which about 70 g/I of copper is mainly monovalent. The further treatment of the copper chloride solution is not presented in more detail here.
FIELD OF THE INVENTION
The invention relates to a method for recovering gold from an intermediate product or residue containing sulphur and iron generated in the leaching of a sulphidic raw material. The recovery of gold and the other valuable metals in the raw material takes place in a chloride environment. The gold contained in the intermediate product or residue is leached with divalent copper and chlorine in a copper (II) chloride - sodium chloride solution in conditions io where the oxidation-reduction potential is in the range of 650-750 mV and the pH between 1 and 1.6. The acid generated during the feed of chlorine is neutralized with a suitable alkali. Neutralization avoids the costs of dissolving the iron.
BACKGROUND OF THE INVENTION
Several methods are known in the prior art, which are used to leach gold from material containing sulphur and iron in connection with a chloride-based copper recovery process.
US patent 4,551,213 describes a method in which gold can be leached from sulphur-containing material, in particular the residue from hydrometallurgical processes. The preferred starting material for the method is the residue from the CLEAR process. The CLEAR process is a hydrometallurgical copper recovery process, which occurs in a chloride environment and at elevated pressure. The gold-containing residue is elutriated into water and the chloride concentration of the resulting suspension is adjusted so that it is - 38 weight percent. The oxidation-reduction potential is adjusted to the range of 650 - 750 mV and the pH to below 0. Copper (II) chloride or iron (III) chloride are added to the suspension to oxidize the gold contained in the 3o raw material, so that it dissolves.
EP patent 646185 relates to the recovery of copper from sulphidic concentrates with chloride leaching in atmospheric conditions. The gold from the leach residue is dissolved into electrolyte, which includes two or more halides, such as sodium chloride and sodium bromide. The purpose is to store oxidising energy in the bromine complex on the copper electrolysis anode, and thereby leach the gold from the residue.
There are certain drawbacks to the above-mentioned methods. In the method of US patent 4,551,213 the leaching conditions are very severe. The lo patent mentions that sulphur is not dissolved in the patent conditions, but the mention is not universally applicable, since the dissolving tendencies of elemental sulphur and the iron compounds mentioned in the patent depend on the manner in which the sulphur and the compounds in question are generated. In the tests we carried out it was found that when leaching residues formed in atmospheric conditions are treated in conditions in accordance with the said patent, the dissolution of sulphur and iron is considerable. Since, according to the publication, the sulphur and iron do not dissolve, there is no mention either of how to recover them from the solution.
The gold leaching method used in EP patent 646185 using a bromine complex is not advantageous from an environmental point of view because harmful bromine emissions may be generated in the concentrate leaching stage.
WO patent application 03/091463 describes a method for leaching gold from leaching residue or intermediate product containing iron and sulphur, generated in the atmospheric chloride leaching of copper sulphide concentrate. The publication states that gold may be leached from an iron-and sulphur-containing material into an aqueous solution of copper (II) chloride and sodium chloride with copper and oxygen in conditions where the oxidation-reduction potential is below 650 mV and the pH value of the solution in the range 1 - 3. In these conditions iron does not dissolve and the sulphur remains undissolved to a large extent. Thus the costs that arise when iron and sulphur are removed from the solution are avoided. The recovery of gold from the solution is made by one of the methods of the prior art such as electrolysis or active carbon. The method in question is in itself quite good, but in practice however it is somewhat slow.
PURPOSE OF THE INVENTION
Now a method has been developed for the recovery of gold from an intermediate product or residue that contains sulphur and iron, generated in the leaching of a sulphidic raw material. Raw material leaching is carried out io using a concentrated aqueous solution of alkali chloride and copper (II) chloride in atmospheric conditions. When oxygen or oxygen-containing gas is fed into the sulphidic concentrate leaching stages, iron is oxidised and precipitated as oxide or hydroxide and the valuable metals, with the exception of gold, dissolve. The leaching of gold from the remaining residue is carried out with an alkali chloride - copper (II) chloride aqueous solution and chlorine in atmospheric conditions. The oxidation-reduction potential of the leaching stage is raised to the range of 650-750 mV by means of chlorine. A high oxidation-reduction potential enables the elemental sulphur in the residue to dissolve and as a consequence, acid is formed in the stage, which is neutralised by some suitable alkali. The simultaneous neutralisation of the acid keeps the pH at a value of 1.0 - 1.6, whereby the dissolution of iron is prevented. The dissolved gold is recovered by some method known as such in the prior art.
The essential features of the invention will be made apparent in the attached claims.
SUMMARY OF THE INVENTION
A gold-bearing intermediate product or residue is leached into sodium chloride solution containing copper(II) chloride forming a suspension and the oxidation-reduction potential required for gold leaching is obtained particularly by means of divalent copper and chlorine gas. If the feed to gold leaching still contains undissolved copper- or other sulphide, oxygen-containing gas can be fed to the start of the leaching stage in order to dissolve it. The oxidation-reduction potential is measured with Pt- and Ag/AgCl electrodes and the potential is kept at a value of 650-750 mV. The amount of divalent copper, Cu2+, in the solution is preferably 20 - 80 g/I and the amount of sodium chloride in the region of 200 - 330 g/l. Gold dissolves as a chloro complex in accordance with the following reaction:
Au + 3 Cu2+ + 6 CI" 4 AuC14 + 3 Cu+ + 2 CI" (1) lo Leaching occurs in atmospheric conditions at a temperature, which is between room temperature and the boiling point of the suspension, preferably, however, between 80 C and the boiling point of the suspension.
Thus, tests have now revealed that raising the redox potential of the reacting slurry with chlorine gas accelerates the dissolution of gold. There is however a drawback to this acceleration. Raising the redox potential increases the dissolution of the elemental sulphur (S ) in the material to be leached, which probably occurs in accordance with the following reaction (2):
S + 3 C12 + 4 H20 4 H2SO4 + 6 HCI (2) Reaction (2) shows that a lot of acid is generated (8 mol H+/ mol S ). The acid generated in the solution must however be neutralised, since at pH
values under 1 the iron in the solids begins to dissolve. The dissolution of iron causes process costs, as dissolved iron is circulated and consumes reagents. The preferred pH region to keep iron in the residue is between 1.0 and 1.6.
Some suitable alkali from the group NaOH, KOH, CaO, CaCO3 or MgO is used to neutralise the acid. If the process is combined with a chloride-based hydrometallurgical method of producing copper, in which basic copper (II) chloride is generated in the precipitation of divalent copper from leaching, the use of the copper (II) chloride is the best option. When basic copper (II) chloride dissolves, the copper (II) chloride generated can be used for raw material leaching. The neutralization of hydrochloric acid and copper (II) 5 oxychloride leaching occur according to the following reaction:
3 Cu(OH)2.CuC12 + 6 HCI 4 4 CuC12 + 6 H20 (3) The sulphuric acid generated can be neutralised for example with lime:
H2SO4 + CaCO3 4 CaSO4 2H2O + CO2 (4) The recovery of gold from the solution takes place by some method known as such in the prior art, for instance active carbon, electrolysis or chemical precipitation.
LIST OF DRAWINGS
The method of the invention is further described in the flow chart of Fig 1, where the recovery of gold is combined with the hydrometallurgical recovery of copper.
DETAILED DESCRIPTION OF THE DRAWINGS
According to Fig. 1, a sulphidic raw material such as copper sulphide concentrate 2 is fed to the first leaching stage 1, and solution 3 from a later process stage, which is an aqueous solution of copper (II) chloride and sodium chloride, is also circulated to this stage. The thicker arrows denote solids and the thinner arrows the flow of solution. The stage always includes one or more reactors and thickening. The copper and other valuable metals of the concentrate mainly dissolve into the process solution and the resulting solution 4 includes copper chloride, in which about 70 g/I of copper is mainly monovalent. The further treatment of the copper chloride solution is not presented in more detail here.
The leaching of the solids 5 from the first leaching stage is continued in the second leaching stage 6 with solution 7, which is taken from a later process stage. Air is fed into the reactors at this stage in order to enhance leaching of the valuable metals and to precipitate the iron. Thickening is done at the end of this stage.
The solution 3 from the second stage is routed to the first leaching stage 1 to leach the concentrate. The leaching of the solids 8 from the second leaching io stage is continued in the third stage 9 in order to leach the rest of the copper and the gold. In the third leaching stage i.e. the gold leaching stage, the residue is leached with copper (II) chloride - sodium chloride solution 10, in which the Cu2+-content is 20 - 80 g/I and the sodium chloride content 200 -330 g/l. If the residue entering this leaching stage still contains undissolved sulphide, oxygen, preferably in the form of air, can also be routed to the first reactor at the beginning of the stage. Copper and other sulphides should be leached out of the residue before the gold dissolves. In order to raise the redox potential to the range of 650-750 mV, chlorine gas 11 is also fed into the reactor. Because of the high potential, sulphur starts to dissolve and as a 2o result acid is formed in the stage. So that the pH of the stage does not fall below 1.0, some alkali 12 is fed into it such as NaOH, KOH, CaO, CaCO3 or MgO. If the process is combined with a chloride-based hydrometallurgical method to produce copper, in which basic copper (II) chloride is generated in the precipitation of divalent copper from leaching, the basic copper (II) chloride is used.
The gold-chloro complex solution 13 obtained from the leaching stage is routed either as it is or filtered to gold recovery, which in this case occurs in a carbon column 14 by means of active carbon. The gold product 15 is obtained from the column. The solution exiting column 14 is a gold-free solution 16, which is circulated to the second stage of leaching 6 and sodium chloride solution is routed there as required to achieve a suitable copper (II) chloride content for leaching. The residue of the gold recovery stage, after normal after-treatment such as filtration and washing (not shown in detail in the diagram), becomes the final leach residue 17, which contains nearly all the sulphur and iron of the concentrate. The residue filtrate and rinse water are returned for example to the concentrate leaching process.
The flow chart in Fig. 1 presents a gold leaching method in connection with copper-bearing raw material leaching, but the method of the invention is not limited to the copper-bearing raw material leaching process shown in the lo chart. The crux of our method is that the leaching of gold-bearing material is performed with divalent copper and chlorine in conditions where the redox potential of the solution is raised to a value of 650-750 mV, and the acid formed during the dissolution of sulphur is neutralized so that the pH is minimum 1, preferably at least 1.0 - 1.6.
The solution 3 from the second stage is routed to the first leaching stage 1 to leach the concentrate. The leaching of the solids 8 from the second leaching io stage is continued in the third stage 9 in order to leach the rest of the copper and the gold. In the third leaching stage i.e. the gold leaching stage, the residue is leached with copper (II) chloride - sodium chloride solution 10, in which the Cu2+-content is 20 - 80 g/I and the sodium chloride content 200 -330 g/l. If the residue entering this leaching stage still contains undissolved sulphide, oxygen, preferably in the form of air, can also be routed to the first reactor at the beginning of the stage. Copper and other sulphides should be leached out of the residue before the gold dissolves. In order to raise the redox potential to the range of 650-750 mV, chlorine gas 11 is also fed into the reactor. Because of the high potential, sulphur starts to dissolve and as a 2o result acid is formed in the stage. So that the pH of the stage does not fall below 1.0, some alkali 12 is fed into it such as NaOH, KOH, CaO, CaCO3 or MgO. If the process is combined with a chloride-based hydrometallurgical method to produce copper, in which basic copper (II) chloride is generated in the precipitation of divalent copper from leaching, the basic copper (II) chloride is used.
The gold-chloro complex solution 13 obtained from the leaching stage is routed either as it is or filtered to gold recovery, which in this case occurs in a carbon column 14 by means of active carbon. The gold product 15 is obtained from the column. The solution exiting column 14 is a gold-free solution 16, which is circulated to the second stage of leaching 6 and sodium chloride solution is routed there as required to achieve a suitable copper (II) chloride content for leaching. The residue of the gold recovery stage, after normal after-treatment such as filtration and washing (not shown in detail in the diagram), becomes the final leach residue 17, which contains nearly all the sulphur and iron of the concentrate. The residue filtrate and rinse water are returned for example to the concentrate leaching process.
The flow chart in Fig. 1 presents a gold leaching method in connection with copper-bearing raw material leaching, but the method of the invention is not limited to the copper-bearing raw material leaching process shown in the lo chart. The crux of our method is that the leaching of gold-bearing material is performed with divalent copper and chlorine in conditions where the redox potential of the solution is raised to a value of 650-750 mV, and the acid formed during the dissolution of sulphur is neutralized so that the pH is minimum 1, preferably at least 1.0 - 1.6.
Claims (9)
1. A method for recovering gold from an intermediate product or leach residue containing sulphur and iron generated in the leaching of a sulphidic raw material in atmospheric chloride leaching, characterised in that the gold is leached from the intermediate product or residue in an aqueous copper (II) chloride - sodium chloride solution in atmospheric conditions with chlorine and the divalent copper contained in the solution, where the oxidation-reduction potential of the suspension that is formed is kept in the range of 650-750 mV; the acid generated during the dissolution of sulphur is neutralized with alkali and thus the pH is kept at a value between 1 - 1.6, so that the iron remains mainly undissolved; the dissolved gold is recovered by some method known as such.
2. A method according to claim 1, characterised in that the amount of divalent copper in solution is 20 - 80 g/l.
3. A method according to claim 1 or 2, characterised in that the amount of sodium chloride in solution is 200 - 330 g/l.
4. A method according to any of preceding claims 1-3, characterised in that the temperature is maintained in the range between 80 °C and the boiling point of the suspension.
5. A method according to any of preceding claims 1-4, characterised in that the acid generated during the dissolution of sulphur is neutralized with basic copper (II) chloride.
6. A method according to any of preceding claims 1-4, characterised in that the acid generated during the dissolution of sulphur is neutralized with an alkali, which is one of the group NaOH, KOH, CaO, CaCO3 or MgO.
7. A method according to any of preceding claims 1-6, characterised in that the dissolved gold is recovered using active carbon.
8. A method according to any of preceding claims 1-6, characterised in that the dissolved gold is recovered by electrolysis.
9. A method according to any of preceding claims 1-6, characterised in that the dissolved gold is recovered by chemical precipitation.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20040621A FI117709B (en) | 2004-04-30 | 2004-04-30 | Procedure for the extraction of gold |
| FI20040621 | 2004-04-30 | ||
| PCT/FI2005/000194 WO2005106052A1 (en) | 2004-04-30 | 2005-04-25 | Method for recovering gold |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2564338A1 true CA2564338A1 (en) | 2005-11-10 |
Family
ID=35185129
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2564338 Abandoned CA2564338A1 (en) | 2004-04-30 | 2005-04-25 | Method for recovering gold |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US20070245856A1 (en) |
| EP (1) | EP1740730A1 (en) |
| CN (1) | CN1950524A (en) |
| AP (1) | AP2006003793A0 (en) |
| AR (1) | AR049633A1 (en) |
| AU (1) | AU2005238241A1 (en) |
| BR (1) | BRPI0510505A (en) |
| CA (1) | CA2564338A1 (en) |
| EA (1) | EA009726B1 (en) |
| FI (1) | FI117709B (en) |
| PE (1) | PE20060226A1 (en) |
| WO (1) | WO2005106052A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI118302B (en) * | 2006-02-17 | 2007-09-28 | Outotec Oyj | Procedure for the extraction of gold |
| KR100787205B1 (en) | 2007-06-11 | 2007-12-21 | 광해방지사업단 | Method for recovering precious metal using seawater from mining waste |
| CN100582261C (en) * | 2008-04-08 | 2010-01-20 | 昆明贵研药业有限公司 | Method and device for reclaiming platinum-silver-iodine form platinum-containing silver iodide slag |
| FI124954B (en) * | 2013-04-30 | 2015-04-15 | Outotec Oyj | A process for preparing a solution containing gold and a process arrangement for recovering gold and silver |
| MX2018005014A (en) | 2015-10-29 | 2018-08-01 | Outotec Finland Oy | Method for recovering gold. |
| CN105969990A (en) * | 2016-06-20 | 2016-09-28 | 昆山鸿福泰环保科技有限公司 | Method for adsorbing and recovering gold in activated carbon method |
| EP3822374B1 (en) * | 2019-11-18 | 2023-10-04 | Heraeus Deutschland GmbH & Co. KG | Method for recovering pure metal |
| AU2021329906A1 (en) * | 2020-08-18 | 2023-04-27 | Enviro Metals, LLC | Metal refinement |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4551213A (en) * | 1984-05-07 | 1985-11-05 | Duval Corporation | Recovery of gold |
| AP538A (en) * | 1992-06-26 | 1996-09-18 | Intec Pty Ltd | Production of metal from minerals |
| US5542957A (en) * | 1995-01-27 | 1996-08-06 | South Dakota School Of Mines And Technology | Recovery of platinum group metals and rhenium from materials using halogen reagents |
| FI113667B (en) * | 2002-04-23 | 2004-05-31 | Outokumpu Oy | Method for recovering gold |
-
2004
- 2004-04-30 FI FI20040621A patent/FI117709B/en active IP Right Grant
-
2005
- 2005-04-21 PE PE2005000442A patent/PE20060226A1/en not_active Application Discontinuation
- 2005-04-25 BR BRPI0510505-6A patent/BRPI0510505A/en not_active IP Right Cessation
- 2005-04-25 AP AP2006003793A patent/AP2006003793A0/en unknown
- 2005-04-25 CN CNA2005800138063A patent/CN1950524A/en active Pending
- 2005-04-25 US US11/579,092 patent/US20070245856A1/en not_active Abandoned
- 2005-04-25 AU AU2005238241A patent/AU2005238241A1/en not_active Abandoned
- 2005-04-25 WO PCT/FI2005/000194 patent/WO2005106052A1/en active Application Filing
- 2005-04-25 EA EA200601774A patent/EA009726B1/en not_active IP Right Cessation
- 2005-04-25 EP EP20050735875 patent/EP1740730A1/en not_active Withdrawn
- 2005-04-25 CA CA 2564338 patent/CA2564338A1/en not_active Abandoned
- 2005-04-29 AR ARP050101714 patent/AR049633A1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| AP2006003793A0 (en) | 2006-10-31 |
| EA009726B1 (en) | 2008-02-28 |
| AR049633A1 (en) | 2006-08-23 |
| FI117709B (en) | 2007-01-31 |
| CN1950524A (en) | 2007-04-18 |
| FI20040621A (en) | 2005-10-31 |
| EA200601774A1 (en) | 2007-04-27 |
| WO2005106052A1 (en) | 2005-11-10 |
| PE20060226A1 (en) | 2006-04-25 |
| US20070245856A1 (en) | 2007-10-25 |
| AU2005238241A1 (en) | 2005-11-10 |
| BRPI0510505A (en) | 2007-10-30 |
| EP1740730A1 (en) | 2007-01-10 |
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| FZDE | Discontinued |