WO2022219247A1 - A hydrometallurgical method for recovering metals from sulfide minerals and a use of sulfide mineral as iron reductant - Google Patents
A hydrometallurgical method for recovering metals from sulfide minerals and a use of sulfide mineral as iron reductant Download PDFInfo
- Publication number
- WO2022219247A1 WO2022219247A1 PCT/FI2022/050250 FI2022050250W WO2022219247A1 WO 2022219247 A1 WO2022219247 A1 WO 2022219247A1 FI 2022050250 W FI2022050250 W FI 2022050250W WO 2022219247 A1 WO2022219247 A1 WO 2022219247A1
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- WO
- WIPO (PCT)
- Prior art keywords
- pls
- sulfide
- feed material
- leaching
- iron
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 100
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 82
- 239000002184 metal Substances 0.000 title claims abstract description 82
- 150000002739 metals Chemical class 0.000 title claims abstract description 63
- 229910052569 sulfide mineral Inorganic materials 0.000 title claims abstract description 49
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title abstract description 75
- 229910052742 iron Inorganic materials 0.000 title abstract description 38
- 239000003638 chemical reducing agent Substances 0.000 title description 6
- 239000000463 material Substances 0.000 claims abstract description 64
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 claims abstract description 41
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims abstract description 34
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000009854 hydrometallurgy Methods 0.000 claims abstract description 17
- 239000002699 waste material Substances 0.000 claims abstract description 13
- 230000001590 oxidative effect Effects 0.000 claims abstract description 9
- 238000002386 leaching Methods 0.000 claims description 56
- 239000000243 solution Substances 0.000 claims description 27
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 24
- 239000000126 substance Substances 0.000 claims description 22
- 229910021645 metal ion Inorganic materials 0.000 claims description 13
- 239000000725 suspension Substances 0.000 claims description 13
- 229910052759 nickel Inorganic materials 0.000 claims description 12
- 239000002253 acid Substances 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 11
- 238000001914 filtration Methods 0.000 claims description 11
- 229910052725 zinc Inorganic materials 0.000 claims description 8
- 229910052802 copper Inorganic materials 0.000 claims description 7
- 239000011790 ferrous sulphate Substances 0.000 claims description 7
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 7
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 7
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 229910052952 pyrrhotite Inorganic materials 0.000 claims description 6
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 claims description 5
- 238000005342 ion exchange Methods 0.000 claims description 5
- 244000005700 microbiome Species 0.000 claims description 5
- 238000000638 solvent extraction Methods 0.000 claims description 5
- 238000009388 chemical precipitation Methods 0.000 claims description 4
- 229910052951 chalcopyrite Inorganic materials 0.000 claims description 3
- DVRDHUBQLOKMHZ-UHFFFAOYSA-N chalcopyrite Chemical compound [S-2].[S-2].[Fe+2].[Cu+2] DVRDHUBQLOKMHZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000002425 crystallisation Methods 0.000 claims description 3
- 230000008025 crystallization Effects 0.000 claims description 3
- 239000007800 oxidant agent Substances 0.000 claims description 3
- 229910052683 pyrite Inorganic materials 0.000 claims description 3
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 claims description 3
- 239000011028 pyrite Substances 0.000 claims description 3
- UIFOTCALDQIDTI-UHFFFAOYSA-N arsanylidynenickel Chemical compound [As]#[Ni] UIFOTCALDQIDTI-UHFFFAOYSA-N 0.000 claims description 2
- 229910052948 bornite Inorganic materials 0.000 claims description 2
- 229910052947 chalcocite Inorganic materials 0.000 claims description 2
- 229910052963 cobaltite Inorganic materials 0.000 claims description 2
- 229910052955 covellite Inorganic materials 0.000 claims description 2
- 229910052965 gersdorffite Inorganic materials 0.000 claims description 2
- 229910052953 millerite Inorganic materials 0.000 claims description 2
- YGHCWPXPAHSSNA-UHFFFAOYSA-N nickel subsulfide Chemical compound [Ni].[Ni]=S.[Ni]=S YGHCWPXPAHSSNA-UHFFFAOYSA-N 0.000 claims description 2
- 229910052954 pentlandite Inorganic materials 0.000 claims description 2
- 229910052950 sphalerite Inorganic materials 0.000 claims description 2
- WWNBZGLDODTKEM-UHFFFAOYSA-N sulfanylidenenickel Chemical compound [Ni]=S WWNBZGLDODTKEM-UHFFFAOYSA-N 0.000 claims description 2
- 238000011084 recovery Methods 0.000 abstract description 24
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 20
- 229910052500 inorganic mineral Inorganic materials 0.000 description 11
- 239000011707 mineral Substances 0.000 description 11
- 235000010755 mineral Nutrition 0.000 description 11
- 238000006722 reduction reaction Methods 0.000 description 10
- 238000004090 dissolution Methods 0.000 description 8
- 229910001447 ferric ion Inorganic materials 0.000 description 8
- 239000011701 zinc Substances 0.000 description 8
- 229910017052 cobalt Inorganic materials 0.000 description 6
- 239000010941 cobalt Substances 0.000 description 6
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 6
- 239000010949 copper Substances 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 6
- -1 (FexNiy)å9S8 Chemical compound 0.000 description 5
- 230000003247 decreasing effect Effects 0.000 description 5
- 239000003456 ion exchange resin Substances 0.000 description 5
- 229920003303 ion-exchange polymer Polymers 0.000 description 5
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000005188 flotation Methods 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 150000004763 sulfides Chemical class 0.000 description 4
- 241000894006 Bacteria Species 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 239000012141 concentrate Substances 0.000 description 3
- 239000003085 diluting agent Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000009291 froth flotation Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910052976 metal sulfide Inorganic materials 0.000 description 3
- 239000011325 microbead Substances 0.000 description 3
- 238000005065 mining Methods 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- DHCDFWKWKRSZHF-UHFFFAOYSA-L thiosulfate(2-) Chemical compound [O-]S([S-])(=O)=O DHCDFWKWKRSZHF-UHFFFAOYSA-L 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 229910001448 ferrous ion Inorganic materials 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 150000002736 metal compounds Chemical class 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 241000605222 Acidithiobacillus ferrooxidans Species 0.000 description 1
- 241000605272 Acidithiobacillus thiooxidans Species 0.000 description 1
- 241000589921 Leptospirillum ferrooxidans Species 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 239000013522 chelant Substances 0.000 description 1
- INPLXZPZQSLHBR-UHFFFAOYSA-N cobalt(2+);sulfide Chemical compound [S-2].[Co+2] INPLXZPZQSLHBR-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- BWFPGXWASODCHM-UHFFFAOYSA-N copper monosulfide Chemical class [Cu]=S BWFPGXWASODCHM-UHFFFAOYSA-N 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910052598 goethite Inorganic materials 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 1
- NBZBKCUXIYYUSX-UHFFFAOYSA-N iminodiacetic acid Chemical compound OC(=O)CNCC(O)=O NBZBKCUXIYYUSX-UHFFFAOYSA-N 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- 238000007885 magnetic separation Methods 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000003134 recirculating effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 150000004764 thiosulfuric acid derivatives Chemical class 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/18—Extraction of metal compounds from ores or concentrates by wet processes with the aid of microorganisms or enzymes, e.g. bacteria or algae
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
-
- 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
- C22B15/00—Obtaining copper
- C22B15/0063—Hydrometallurgy
- C22B15/0065—Leaching or slurrying
- C22B15/0067—Leaching or slurrying with acids or salts thereof
- C22B15/0071—Leaching or slurrying with acids or salts thereof containing sulfur
-
- 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
- C22B19/00—Obtaining zinc or zinc oxide
-
- 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
- C22B19/00—Obtaining zinc or zinc oxide
- C22B19/20—Obtaining zinc otherwise than by distilling
- C22B19/22—Obtaining zinc otherwise than by distilling with leaching with acids
-
- 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
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0407—Leaching processes
- C22B23/0415—Leaching processes with acids or salt solutions except ammonium salts solutions
- C22B23/043—Sulfurated acids or salts thereof
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
- C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
-
- 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
Definitions
- the present invention relates to hydrometallurgical methods for recovering metals from sulfide minerals.
- the present invention also relates to a use of a sulfide mineral as an iron reductant in hydrometallurgical methods.
- Sulfide ores are often complex in structure, and may contain various valuable metals, such as copper, zinc, nickel, and cobalt, with a large fraction of iron that is currently considered as waste.
- the major conventional technology for recovering sulfide ores is froth flotation followed by treating the obtained metal concentrates in smelters.
- the main drawback in froth flotation is the requirement of the relatively high grade and simple ores. If the ores are complex or mineral liberation requires too fine milling, flotation is ineffective and plenty of valuables end to the tailings.
- the use of smelters for producing metals from concentrates may be environmentally problematic due to emissions, moreover, these plants require massive amounts of feed material and are not flexible.
- hydrometallurgical treatment is more flexible than froth flotation, but requires high acid input and possibly strong and expensive oxidation system.
- a hydrometallurgical process consists of three main steps: leaching, solution concentration and purification, and metal or metal compound recovery.
- the leaching step b) utilizes leaching chemicals that may work by altering the redox state of the ore, or by altering the pH.
- bioleaching e.g. BIOX ® type of process
- This process utilizes certain microorganisms, such as bacteria, that can produce the leaching chemicals (e.g., sulfuric acid and oxidant) from the sulfide mineral input itself, when supplemented with nutrients and air.
- leaching chemicals e.g., sulfuric acid and oxidant
- chemical costs can be greatly decreased.
- the drawback is a slower processing capacity compared to conventional chemical leaching.
- the system is somewhat sensitive to changes in operative parameters.
- FeS pyrrhotite
- PLS pregnant leach solution
- An object of the present invention is to eliminate the drawbacks present in the prior art.
- An object of the present invention is to provide a method for metal recovery from sulfide ores with an enhanced valuable metal efficiency and economic feasibility.
- a further object of the present invention is to provide a method for metal recovery from sulfide ores with a reduced consumption of process chemicals.
- a yet further object of the present invention is to provide a method for recovering valuable metals, as well as iron from sulfide ores with a decreased waste production and a decreased need of external acid.
- a method for recovering metals from a sulfide-containing feed material comprises the steps of a) mixing the feed material with an aqueous solution, forming a working suspension comprising sulfide minerals, the sulfide minerals originating from the feed material, b) dissolving valuable metals from the feed material in the working suspension by a leaching process with leaching chemicals, forming a pregnant leach solution (PLS) comprising ferric iron and valuable metal ions, c) circulating the PLS or at least part of the PLS back to step a), wherein the PLS constitutes the aqueous solution in step a), d) reducing the ferric iron contained in the PLS by the sulfide minerals originating from the feed material, forming a reduced PLS comprising ferrous iron and valuable metal ions, and e) optionally recovering the valuable metal ions from the reduced PLS, thus forming a ferrous sulfate solution.
- PLS pregnant leach solution
- the present invention provides a use of a pregnant leach solution in a hydrometallurgical process for oxidizing and/or dissolving sulfide minerals contained in a feed material.
- the pregnant leach solution is derived from leaching of sulfide minerals.
- the present invention further provides a use of sulfide minerals or a sulfide- containing waste material in a hydrometallurgical process for reducing ferric iron contained in a pregnant leach solution produced in the hydrometallurgical process.
- the pregnant leach solution is produced in leaching of sulfide minerals in said hydrometallurgical process.
- the ferric iron produced in a leaching process may be reduced to ferrous iron using the sulfides originating from the feed material by recirculating the leachate solution (pregnant leachate solution PLS) back to step a) and mixing the PLS with the sulfide minerals originating from the feed material.
- PLS leachate solution
- only a feed material containing sulfide minerals is needed in reducing the ferric iron to ferrous iron by utilizing recycling and double leaching.
- ferric iron oxidizes the feed material and reduces at the same time to ferrous iron leading thus to an efficient recovery of the valuable metals.
- the need of external acid may be reduced, or completely eliminated.
- the chemicals needed for reducing ferric iron into ferrous iron originate directly from the process itself.
- dissolution of sulfide minerals, such as pyrrhotite consumes large amounts of acid. This acid consumption can be completely avoided or partly reduced by using the method according to the present invention.
- the ferric iron contained in the PLS can oxidize and/or dissolve the sulfide minerals contained in the feed material.
- the process is compatible with the concept of circular economy.
- iron may be reduced into ferrous iron, whereby the iron recovery may take place after recovering the valuable metals.
- the iron recovery may take place after recovering the valuable metals.
- ferrous iron may also be recovered from the ore as a by-product and not as a waste material, increasing the economic feasibility of the method.
- a further advantage of the present invention is a reduced total process time.
- Figure 1 presents a simplified process chart for a metal recovery method according to the present invention
- Figure 2 presents a simplified process chart for a metal recovery method according to an embodiment of the present invention, comprising iron recovery and filtration steps.
- a method for recovering metals from a sulfide- containing feed material is provided.
- feed material is processed in an aqueous solution with leaching chemicals in a leaching process, whereby the metal ions of the feed material dissolve.
- FIG. 1 provides a simplified process scheme for the present invention.
- feed material is directed to a mixing step a).
- a working suspension produced in the mixing step a) is directed to a leaching step b), wherein the sulfide minerals contained in the feed material are dissolved, producing a pregnant leach solution (PLS).
- PLS pregnant leach solution
- the PLS or at least part of the PLS is circulated back to step a), now also termed a reduction step d), wherein sulfide minerals originating from the feed material reduce ferric iron contained in the PLS, with a simultaneous partial oxidation and/or dissolution of the feed material.
- the reduced PLS or at least part of the reduced PLS is then directed back to the leaching step b) for a next round of leaching.
- the reduced PLS or at least part of the reduced PLS may be directed to the valuable metal recovery process e).
- a use of a pregnant leach solution in a hydrometallurgical process for oxidizing and/or dissolving sulfide minerals contained in a feed material is provided.
- the pregnant leach solution is derived from leaching of sulfide minerals.
- a use of sulfide minerals or a sulfide- containing waste material in a hydrometallurgical process for reducing ferric iron contained in a pregnant leach solution produced in the hydrometallurgical process.
- the pregnant leach solution is produced in leaching of sulfide minerals in said hydrometallurgical process.
- the feed material originates from a sulfide mineral.
- Sulfide minerals are a class of minerals containing a sulfide (S 2 ) or persulfide (S2 2 ) as the main anion.
- the feed material originates solely from sulfide mineral(s).
- the sulfide mineral may comprise iron sulfide minerals comprising nickel, cobalt, zinc, copper, manganese, or any combination thereof.
- Usable minerals may be selected, for example, from pyrite, pyrrhotite, troilite, pentlandite, talnakhite, millerite, heazlewoodite, nickeline, maucherite, gersdorffite, mackinawite, linnaeite, polydymite, cobaltite, sphalerite, chalcopyrite, chalcocite, covellite, bornite, cubanite, or any combination thereof.
- Iron sulfide minerals also comprise a small fractions of other metals.
- the valuable metals may be selected from a group comprising Cu, Zn, Ni, and Co. In an embodiment, the valuable metals are selected from Cu, Zn, Ni, and Co.
- the feed material originates from a waste material, such as tailings or gangue.
- a waste material such as tailings or gangue.
- old nickel flotation tailings containing nickel, cobalt, zinc and/or copper sulfides and possibly pyrite and/or pyrrhotite may be used as a feed material for the present invention.
- Certain low-grade ore bodies may even be considered as a waste material in the mining industry. These low-grade ore bodies are not mined or are separated from the high grade ore as a gangue.
- the feed material originates from low-grade ore bodies or gangue.
- the method of the present invention is suitable for recovering valuable metals in an economically feasible way from waste materials and from ores that have previously been considered as inextractible.
- the feed material is directed into a reactor and mixed with an aqueous solution.
- the feed material may be pre-treated prior to directing into the reactor. Pre-treatment of the feed material may comprise e.g. grinding, crushing, sieving, magnetic separation, flotation, density separation, screening, or any combination thereof.
- a working suspension is formed upon mixing the feed material with the aqueous solution.
- the working suspension comprises sulfide minerals originating from the feed material.
- the method according to an embodiment of the present invention comprises a step wherein the valuable metals are dissolved from the feed material in a leaching process by bringing the working suspension comprising the feed material into contact with leaching chemicals.
- the leaching step b) may be carried out using methods and leaching chemicals known in the art.
- the leaching chemicals comprise acid, preferably sulfuric acid, and oxidant.
- the leaching chemicals dissolve the mineral in the aqueous solution.
- a pregnant leach solution (PLS) forms.
- the PLS comprises the metal ions originally contained in the feed material.
- the leaching process of sulfide minerals is a series of chemical redox reactions.
- the leaching process typically comprises the steps of i) spontaneous oxidation of sulfides in the ore to thiosulfate, sulfate or elemental sulfur by a ferric ion, ii) oxidation of ferrous ion into ferric ion, iii) oxidation of thiosulfate and possibly elemental sulfur from step i) to sulfate.
- the ferric iron produced in step ii) is used in step i) to oxidize the sulfide.
- Large amounts of ferric iron are present in the PLS due to the intermediate reaction (step ii)).
- iron is present in its ferrous form. In some minerals, such as goethite, however, iron may exist in its ferric form.
- the leaching process may be a bioleaching process, wherein the leaching chemicals are produced by microorganisms, such as bacteria.
- the microorganisms catalyse the dissolution reaction by oxidizing ferrous iron into ferric ion and thiosulfate into sulfate using oxygen.
- microorganisms There are numerous suitable microorganisms known in the art. A skilled person is able to select the best one for the process in question depending on the conditions of the process, for example.
- bacteria such as Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans , Leptospirillum ferrooxidans, or any combination thereof, may be used in the bioleaching process.
- the PLS comprises the metal ions originating from the feed material, alongside with sulfate anions.
- the PLS is circulated from the leaching step b) back to step a) of the process, i.e. back to the step where the feed material is mixed with an aqueous solution.
- the PLS constitutes the aqueous solution in step a). This circulation enables to reduce the ferric iron contained in the PLS by directly utilizing the feed material itself.
- the PLS is mixed with the feed material in step a), forming a working suspension comprising both sulfides originating from the feed material and ferric iron dissolved in the leaching step.
- the ferric iron contained in the PLS is reduced by the metal sulfides originating from the feed material, yielding ferrous iron, elemental sulfur, thiosulfates and sulfates.
- step d) may be termed a reduction step or a pre-leaching step.
- the ferric iron contained in the PLS oxidizes sulfide ions originating from the feed material, the sulfide ions being simultaneously leached from the feed material into the working suspension. Reduction of the ferric iron may be depicted with the reaction:
- Ferrous sulfide FeS in the reaction comprises the sulfide minerals originating from the feed material.
- Using the feed material directly as an iron reductant has the advantage of reducing or completely eliminating the need of external acid.
- large amounts of acid are required to dissolve sulfide minerals in the leaching step. This acid consumption may be remarkably reduced or completely avoided by using the leached ferric iron to oxidize and/or dissolve the sulfide minerals contained in the feed material.
- the ferric iron ions Fe 3+ originate from the leached feed material and are carried to the reduction step along with the circulated PLS. As a result of the reduction reaction, iron is in its ferrous form Fe 2+ .
- An advantage of the present invention is that the iron contained in the PLS after the reduction step is in ferrous form, enabling valuable metals recovery before iron removal.
- the ferric iron concentration in the PLS is at most 1 g/L. In one embodiment, the ferric iron concentration in the PLS is ⁇ 1 g/L. In one embodiment, the ferric iron concentration in the PLS is in the range of 0.1 g/L - 1 g/L.
- the ferric iron concentration in the PLS is 0.2 g/L, 0.3 g/L, 0.4 g/L, 0.5 g/L, 0.6 g/L, 0.7 g/L, 0.8 g/L or 0.9 g/L.
- Circulation of the PLS back to step a) of the process serves two purposes: i) the ferric iron contained in the PLS reduces to ferrous iron, therefore removing the need for a separate iron removal step and enabling valuable metals recovery prior to iron removal, and ii) the ferric iron contained in the PLS serves as a pre-leaching chemical for the sulfide minerals contained in the feed material, thus reducing or eliminating the need for external acids as a leaching chemical. Thus, there is no need for the removal of ferric iron before the recovery of the valuable metals.
- a reduced PLS is formed in the reduction step d).
- the reduced PLS comprises the ferrous ions obtained in the reduction step, as well as the valuable metals dissolved in the leaching step.
- the reduced PLS also comprises non-leached feed material.
- the reduced PLS or at least part of the reduced PLS is directed back to the leaching step b) for the next round of leaching.
- the valuable metals may be recovered from the PLS in step e) of the method, as also depicted in Figure 1 .
- the valuable metals may be recovered as metal sulfides, metal sulfates, or metal hydroxides.
- the present invention is suitable for producing metal sulfides, common metal compounds in metal recovery industry.
- the valuable metals may also be recovered as sulfates.
- An advantage of recovering the valuable metals as sulfates is that the sulfates may be directly suitable for the production of rechargeable batteries.
- the method according to the present invention is also suitable for producing metal hydroxides, especially in small plants.
- recovering the valuable metal ions may be carried out by ion-exchange, solvent extraction or chemical precipitation methods, or any combination thereof.
- recovering the valuable metals may be carried out by ion- exchange methods.
- Ion-exchange involves the use of ion-exchange resins.
- Ion-exchange resins are insoluble matrices typically in the form of small microbeads, with a radius of 0.1-0.8 mm.
- the microbeads are typically fabricated from an organic polymer substrate.
- the microbeads are typically porous, providing a large surface area.
- Ion-exchange resins function by binding or trapping ions from e.g. a solution, accompanied by releasing other ions into the solution.
- the valuable metals are recovered by using chelating ion- exchange resins.
- Chelating ion-exchange resins may comprise reactive functional groups covalently attached to a polymer backbone.
- the reactive functional groups such as iminodiacetate or b/s-picolylamine, chelate to the valuable metal ions to trap them.
- recovering the valuable metals may be carried out using solvent extraction methods.
- a diluent preferably an organic solvent, such as oil
- the metal will be extracted from the PLS to the diluent phase, resulting in a diluent phase bearing the metal, and a raffinate containing the remains of the PLS.
- recovering the valuable metals may be carried out using chemical precipitation methods.
- the valuable metals are precipitated out of the PLS into a solid form as an insoluble compound suitable for further purification.
- the valuable metals may be precipitated as sulfides, sulfates or hydroxides.
- the method further comprises a step of removing or recovering ferrous iron from the tailings.
- Figure 2 presents a simplified process scheme for such a method.
- Ferrous iron may be removed from the tailings as ferrous sulfate using crystallization.
- the invention provides a method for acquiring ferrous sulfate as a profitable byproduct alongside with the valuable metals, whereas in a conventional process iron will be lost to iron- gypsum-precipitate that is considered as waste.
- the method for recovering metals from sulfide-containing feed material may further comprise steps and processes needed for an optimal metal recovery. These steps, such as filtration and washing steps, may be carried out using conventional process equipment and process chemicals known to a person skilled in the art. These further steps may be incorporated or carried out in any appropriate phase of the processing cycle.
- the method may further comprise a filtration step or several filtration steps.
- the filtration step or filtration steps may be carried out for example after step a), after step b), and/or after step d).
- Embodiments of the present invention comprising filtration steps are depicted in Figure 2.
- a filtration step may optionally be performed after steps a) and/or d), i.e., after mixing the feed material with the aqueous solution and/or after reducing the ferric iron contained in the PLS.
- Liquid portion of the working suspension is directed to the valuable metals recovery step e), and solid portion of the working suspension is directed to the leaching step b) for a next round of leaching.
- Another filtration step may optionally be performed after the leaching step b).
- Liquid portion of the PLS is circulated (step c)) back to step a) and/or d) of the process for reduction. Solid leach residue is discarded and/or directed to a tailings pond.
- the method according to the present invention may also be used in a ferrous iron production process.
- iron is considered the valuable metal.
- concentration of metals such as copper, zinc, nickel, and cobalt is likely low in the feed material, such that these metals may be considered as impurities. These impurities need to be removed from the working suspension.
- the impurity removal is enhanced with the help of the iron reduction process.
- the metals considered as impurities may be removed from the process prior to iron removal, rendering the iron recovery process more efficient and yielding a more pure iron product. Iron may be recovered from the process as ferrous sulfate by crystallization.
- the ferric ion concentration of pregnant leach solutions may be greatly reduced.
- the ferric ion concentration in a PLS has been reduced from 30 g/L to 1 g/L.
- 100 mL of the PLS was mixed in a vessel at 60 °C with 38 g of fresh feed material, containing 230 g/kg of pyrrhotite. During agitation, concentration of Fe 3+ decreased to 0.9 g/L.
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Abstract
The present invention relates to hydrometallurgical methods for recovering metals from sulfide minerals. The present invention also relates to a use of a pregnant leach solution in a hydrometallurgical process for oxidizing and/or dissolving sulfide minerals contained in a feed material. The present invention further relates to a use of a sulfide-containing waste material in a hydrometallurgical process for reducing ferric iron contained in a pregnant leach solution produced in the hydrometallurgical process. The present invention enables valuable metals recovery prior to iron removal.
Description
A HYDROMETALLURGICAL METHOD FOR RECOVERING METALS FROM SULFIDE MINERALS AND A USE OF SULFIDE MINERAL AS IRON REDUCTANT
FIELD OF THE INVENTION
The present invention relates to hydrometallurgical methods for recovering metals from sulfide minerals. The present invention also relates to a use of a sulfide mineral as an iron reductant in hydrometallurgical methods.
BACKGROUND OF THE INVENTION
The ever-increasing need of batteries for consumer electronics and e.g. electric vehicles increases the need for valuable metals recovered from the Earth’s crust through mining. Metals such as nickel and cobalt are essential for several battery chemistries.
With the increasing demand for raw materials for batteries, mining industry will have to look for alternatives for high grade and good quality ores. Recovering valuable metals from low grade, polymetallic and refractory ores increases the energy, chemicals, and water consumption of the process. Sulfide ores are often complex in structure, and may contain various valuable metals, such as copper, zinc, nickel, and cobalt, with a large fraction of iron that is currently considered as waste.
The major conventional technology for recovering sulfide ores is froth flotation followed by treating the obtained metal concentrates in smelters. The main drawback in froth flotation is the requirement of the relatively high grade and simple ores. If the ores are complex or mineral liberation requires too fine milling, flotation is ineffective and plenty of valuables end to the tailings. The use of smelters for producing metals from concentrates may be environmentally problematic due to emissions, moreover, these plants require massive amounts of feed material and are not flexible.
Another conventional technology is hydrometallurgical treatment. Hydrometallurgical treatment is more flexible than froth flotation, but requires high acid input and possibly strong and expensive oxidation system. Typically, a hydrometallurgical process consists of three main steps: leaching, solution concentration and purification, and metal or metal compound recovery. The
leaching step b) utilizes leaching chemicals that may work by altering the redox state of the ore, or by altering the pH.
One hydrometallurgical option is bioleaching (e.g. BIOX® type of process). This process utilizes certain microorganisms, such as bacteria, that can produce the leaching chemicals (e.g., sulfuric acid and oxidant) from the sulfide mineral input itself, when supplemented with nutrients and air. Thus, chemical costs can be greatly decreased. However, the drawback is a slower processing capacity compared to conventional chemical leaching. Moreover, the system is somewhat sensitive to changes in operative parameters.
One of the main problems in hydrometallurgical processes is high iron dissolution. Selective leaching of valuable metals without major iron dissolution is challenging. Sometimes valuable metals exist in the same mineral as iron (e.g. (FexNiy)å9S8, CuFeS2, (Zn,Fe)S) and thus destruction of iron containing mineral is required for liberation of the valuable metal. Oxidative leaching of sulfide ores is one of the major process options. In this case, the sulfide minerals in the ore will dissolve in the order of nobility. High oxidation power is often required for dissolution of nickel and cobalt sulfide minerals. Less noble minerals like pyrrhotite (FeS) will dissolve before the dissolution of these more noble minerals take place. Especially when low grade ores are dissolved, the iron concentration in pregnant leach solution (PLS) may be very high compared to concentration of valuable metals.
Hydrometallurgical processes require rather complex down-stream processing to produce metal products. In majority of these, ferric iron present in the PLS is a major problem and needs to be removed by chemical precipitation before recovery of valuable metals can take place. A fraction of the valuable metals co-precipitate with the ferric iron. The co-precipitated valuable metals are lost in the process, with no possibility to recover in a profitable manner. The amount of co-precipitating Cu, Zn, Ni, and Co depends on iron concentration and precipitation conditions and it is typically approx. 10 wt-% of the total amount of these valuable metals in the ore, but in some cases it can be significantly higher. The co-precipitation undoubtedly decreases the efficiency of the metal recovering process.
Thus, improved processes for metal recovery from sulfide ores are needed.
BRIEF DESCRIPTION OF THE INVENTION
An object of the present invention is to eliminate the drawbacks present in the prior art.
An object of the present invention is to provide a method for metal recovery from sulfide ores with an enhanced valuable metal efficiency and economic feasibility.
A further object of the present invention is to provide a method for metal recovery from sulfide ores with a reduced consumption of process chemicals.
A yet further object of the present invention is to provide a method for recovering valuable metals, as well as iron from sulfide ores with a decreased waste production and a decreased need of external acid.
These objects are attained with the invention having the characteristics presented below in the independent claims. Some preferable embodiments are disclosed in the dependent claims.
The features recited in the dependent claims and the embodiments in the description are mutually freely combinable unless otherwise explicitly stated.
The exemplary embodiments presented in this text and their advantages relate by applicable parts to all aspects of the invention, both the method and the use aspects, even though this is not always explicitly mentioned.
A method for recovering metals from a sulfide-containing feed material according to the present invention comprises the steps of a) mixing the feed material with an aqueous solution, forming a working suspension comprising sulfide minerals, the sulfide minerals originating from the feed material, b) dissolving valuable metals from the feed material in the working suspension by a leaching process with leaching chemicals, forming a pregnant leach solution (PLS) comprising ferric iron and valuable metal ions, c) circulating the PLS or at least part of the PLS back to step a), wherein the PLS constitutes the aqueous solution in step a),
d) reducing the ferric iron contained in the PLS by the sulfide minerals originating from the feed material, forming a reduced PLS comprising ferrous iron and valuable metal ions, and e) optionally recovering the valuable metal ions from the reduced PLS, thus forming a ferrous sulfate solution.
The present invention provides a use of a pregnant leach solution in a hydrometallurgical process for oxidizing and/or dissolving sulfide minerals contained in a feed material. In one embodiment, the pregnant leach solution is derived from leaching of sulfide minerals.
The present invention further provides a use of sulfide minerals or a sulfide- containing waste material in a hydrometallurgical process for reducing ferric iron contained in a pregnant leach solution produced in the hydrometallurgical process. In one embodiment, the pregnant leach solution is produced in leaching of sulfide minerals in said hydrometallurgical process.
The inventors have surprisingly found that the ferric iron produced in a leaching process may be reduced to ferrous iron using the sulfides originating from the feed material by recirculating the leachate solution (pregnant leachate solution PLS) back to step a) and mixing the PLS with the sulfide minerals originating from the feed material. In an embodiment, only a feed material containing sulfide minerals is needed in reducing the ferric iron to ferrous iron by utilizing recycling and double leaching. In the method of the present invention, ferric iron oxidizes the feed material and reduces at the same time to ferrous iron leading thus to an efficient recovery of the valuable metals.
It is an advantage of the present invention that the valuable metals can be recovered before iron removal. Valency of iron has a significant effect on valuable metals recovery. Selective recovery of valuable metals is possible using either sulfide precipitation, solvent extraction or ion-exchange technologies if the iron is in its ferrous form instead of ferric form.
It is an advantage of the present invention that the need of external acid may be reduced, or completely eliminated. Using the method according to the present invention, the chemicals needed for reducing ferric iron into ferrous iron originate directly from the process itself. In conventional
hydrometallurgical treatment, dissolution of sulfide minerals, such as pyrrhotite, consumes large amounts of acid. This acid consumption can be completely avoided or partly reduced by using the method according to the present invention. The ferric iron contained in the PLS can oxidize and/or dissolve the sulfide minerals contained in the feed material. Thus, the process is compatible with the concept of circular economy.
It is an advantage of the present invention that iron may be reduced into ferrous iron, whereby the iron recovery may take place after recovering the valuable metals. When recovering iron as ferrous iron after the valuable metals recovery, loss of the valuable metals induced by co-precipitation is eliminated.
It is a further advantage of the present invention that the ferrous iron may also be recovered from the ore as a by-product and not as a waste material, increasing the economic feasibility of the method. A further advantage of the present invention is a reduced total process time.
It is an advantage of the present invention that valuable metals may be recovered from sulfide ores that are poor in valuable minerals. Using the method according to the present invention, the recovery of valuable metals may be economically feasible from even these ores with low target metal content. A further advantage of the present invention is that it may utilize sulfide minerals previously considered as waste, making the invention compatible with the concept of circular economy.
It is also an advantage of the present invention that valuable metals may be recovered from fine sulfide minerals containing feed materials, such as flotation concentrates, for example. Using the method according to the present invention, the recovery of valuable metals may be economically feasible from even such fine feed materials.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 presents a simplified process chart for a metal recovery method according to the present invention,
Figure 2 presents a simplified process chart for a metal recovery method according to an embodiment of the present invention, comprising iron recovery and filtration steps.
DETAILED DESCRIPTION OF THE INVENTION
In a first aspect of the invention, a method for recovering metals from a sulfide- containing feed material is provided. In the method, feed material is processed in an aqueous solution with leaching chemicals in a leaching process, whereby the metal ions of the feed material dissolve.
Figure 1 provides a simplified process scheme for the present invention. In the process, feed material is directed to a mixing step a). Thereafter, a working suspension produced in the mixing step a) is directed to a leaching step b), wherein the sulfide minerals contained in the feed material are dissolved, producing a pregnant leach solution (PLS). After the leaching step, the PLS or at least part of the PLS is circulated back to step a), now also termed a reduction step d), wherein sulfide minerals originating from the feed material reduce ferric iron contained in the PLS, with a simultaneous partial oxidation and/or dissolution of the feed material. The reduced PLS or at least part of the reduced PLS is then directed back to the leaching step b) for a next round of leaching. The reduced PLS or at least part of the reduced PLS may be directed to the valuable metal recovery process e).
In a second aspect of the present invention, a use of a pregnant leach solution in a hydrometallurgical process for oxidizing and/or dissolving sulfide minerals contained in a feed material is provided. In one embodiment, the pregnant leach solution is derived from leaching of sulfide minerals.
In a third aspect of the present invention, a use of sulfide minerals or a sulfide- containing waste material in a hydrometallurgical process for reducing ferric iron contained in a pregnant leach solution produced in the hydrometallurgical process. In one embodiment, the pregnant leach solution is produced in leaching of sulfide minerals in said hydrometallurgical process.
According to an embodiment of the present invention, the feed material originates from a sulfide mineral. Sulfide minerals are a class of minerals containing a sulfide (S2 ) or persulfide (S22 ) as the main anion. In one embodiment, the feed material originates solely from sulfide mineral(s).
In an embodiment of the present invention, the sulfide mineral may comprise iron sulfide minerals comprising nickel, cobalt, zinc, copper, manganese, or
any combination thereof. Usable minerals may be selected, for example, from pyrite, pyrrhotite, troilite, pentlandite, talnakhite, millerite, heazlewoodite, nickeline, maucherite, gersdorffite, mackinawite, linnaeite, polydymite, cobaltite, sphalerite, chalcopyrite, chalcocite, covellite, bornite, cubanite, or any combination thereof. Iron sulfide minerals also comprise a small fractions of other metals. These fractions of other metals may be considered as valuable metals due to their commercial value. In an embodiment, the valuable metals may be selected from a group comprising Cu, Zn, Ni, and Co. In an embodiment, the valuable metals are selected from Cu, Zn, Ni, and Co.
In an embodiment, the feed material originates from a waste material, such as tailings or gangue. For example, old nickel flotation tailings containing nickel, cobalt, zinc and/or copper sulfides and possibly pyrite and/or pyrrhotite may be used as a feed material for the present invention. Certain low-grade ore bodies may even be considered as a waste material in the mining industry. These low-grade ore bodies are not mined or are separated from the high grade ore as a gangue. In an embodiment, the feed material originates from low-grade ore bodies or gangue. The method of the present invention is suitable for recovering valuable metals in an economically feasible way from waste materials and from ores that have previously been considered as inextractible.
In an embodiment of the present invention, the feed material is directed into a reactor and mixed with an aqueous solution. In an embodiment, the feed material may be pre-treated prior to directing into the reactor. Pre-treatment of the feed material may comprise e.g. grinding, crushing, sieving, magnetic separation, flotation, density separation, screening, or any combination thereof.
In an embodiment of the present invention, a working suspension is formed upon mixing the feed material with the aqueous solution. In an embodiment, the working suspension comprises sulfide minerals originating from the feed material.
The method according to an embodiment of the present invention comprises a step wherein the valuable metals are dissolved from the feed material in a leaching process by bringing the working suspension comprising the feed
material into contact with leaching chemicals. The leaching step b) may be carried out using methods and leaching chemicals known in the art. In an embodiment, the leaching chemicals comprise acid, preferably sulfuric acid, and oxidant. In the leaching process, the leaching chemicals dissolve the mineral in the aqueous solution. As a result, a pregnant leach solution (PLS) forms. The PLS comprises the metal ions originally contained in the feed material.
The leaching process of sulfide minerals is a series of chemical redox reactions. The leaching process typically comprises the steps of i) spontaneous oxidation of sulfides in the ore to thiosulfate, sulfate or elemental sulfur by a ferric ion, ii) oxidation of ferrous ion into ferric ion, iii) oxidation of thiosulfate and possibly elemental sulfur from step i) to sulfate.
The ferric iron produced in step ii) is used in step i) to oxidize the sulfide. Large amounts of ferric iron are present in the PLS due to the intermediate reaction (step ii)). In most minerals, iron is present in its ferrous form. In some minerals, such as goethite, however, iron may exist in its ferric form.
In an embodiment of the present invention, the leaching process may be a bioleaching process, wherein the leaching chemicals are produced by microorganisms, such as bacteria. The microorganisms catalyse the dissolution reaction by oxidizing ferrous iron into ferric ion and thiosulfate into sulfate using oxygen. There are numerous suitable microorganisms known in the art. A skilled person is able to select the best one for the process in question depending on the conditions of the process, for example. In an embodiment, bacteria such as Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans , Leptospirillum ferrooxidans, or any combination thereof, may be used in the bioleaching process.
Along with the dissolution of iron in the leaching process, the valuable metals are dissolved in a similar manner. Thus, the PLS comprises the metal ions originating from the feed material, alongside with sulfate anions.
In an embodiment of the present invention, the PLS is circulated from the leaching step b) back to step a) of the process, i.e. back to the step where the feed material is mixed with an aqueous solution. According to the present invention, the PLS constitutes the aqueous solution in step a). This circulation enables to reduce the ferric iron contained in the PLS by directly utilizing the feed material itself.
In an embodiment of the present invention, the PLS is mixed with the feed material in step a), forming a working suspension comprising both sulfides originating from the feed material and ferric iron dissolved in the leaching step. The ferric iron contained in the PLS is reduced by the metal sulfides originating from the feed material, yielding ferrous iron, elemental sulfur, thiosulfates and sulfates. By utilizing the feed material as a source of iron reductant, the need of external chemical reductants may be decreased or even completely eliminated.
In an embodiment, step d) may be termed a reduction step or a pre-leaching step. The ferric iron contained in the PLS oxidizes sulfide ions originating from the feed material, the sulfide ions being simultaneously leached from the feed material into the working suspension. Reduction of the ferric iron may be depicted with the reaction:
Ferrous sulfide FeS in the reaction comprises the sulfide minerals originating from the feed material. Using the feed material directly as an iron reductant has the advantage of reducing or completely eliminating the need of external acid. In conventional hydrometallurgical methods, large amounts of acid are required to dissolve sulfide minerals in the leaching step. This acid consumption may be remarkably reduced or completely avoided by using the leached ferric iron to oxidize and/or dissolve the sulfide minerals contained in the feed material.
The ferric iron ions Fe3+ originate from the leached feed material and are carried to the reduction step along with the circulated PLS. As a result of the reduction reaction, iron is in its ferrous form Fe2+. An advantage of the present invention is that the iron contained in the PLS after the reduction step is in
ferrous form, enabling valuable metals recovery before iron removal. In one embodiment, the ferric iron concentration in the PLS is at most 1 g/L. In one embodiment, the ferric iron concentration in the PLS is < 1 g/L. In one embodiment, the ferric iron concentration in the PLS is in the range of 0.1 g/L - 1 g/L. In one embodiment, the ferric iron concentration in the PLS is 0.2 g/L, 0.3 g/L, 0.4 g/L, 0.5 g/L, 0.6 g/L, 0.7 g/L, 0.8 g/L or 0.9 g/L.
Circulation of the PLS back to step a) of the process serves two purposes: i) the ferric iron contained in the PLS reduces to ferrous iron, therefore removing the need for a separate iron removal step and enabling valuable metals recovery prior to iron removal, and ii) the ferric iron contained in the PLS serves as a pre-leaching chemical for the sulfide minerals contained in the feed material, thus reducing or eliminating the need for external acids as a leaching chemical. Thus, there is no need for the removal of ferric iron before the recovery of the valuable metals.
In an embodiment of the present invention, a reduced PLS is formed in the reduction step d). In other words, after the reduction step, the reduced PLS comprises the ferrous ions obtained in the reduction step, as well as the valuable metals dissolved in the leaching step. In addition, the reduced PLS also comprises non-leached feed material. The reduced PLS or at least part of the reduced PLS is directed back to the leaching step b) for the next round of leaching. In one embodiment, there is no need for milling/grinding or floatation between the leaching processes in the method of the present invention. In one embodiment, there is no need for feeding additional oxygen between the leaching processes in the method of the present invention
The valuable metals may be recovered from the PLS in step e) of the method, as also depicted in Figure 1 .
In an embodiment of the present invention, the valuable metals may be recovered as metal sulfides, metal sulfates, or metal hydroxides. The present invention is suitable for producing metal sulfides, common metal compounds in metal recovery industry. The valuable metals may also be recovered as sulfates. An advantage of recovering the valuable metals as sulfates is that the sulfates may be directly suitable for the production of rechargeable batteries.
The method according to the present invention is also suitable for producing metal hydroxides, especially in small plants.
According to an embodiment of the present invention, recovering the valuable metal ions may be carried out by ion-exchange, solvent extraction or chemical precipitation methods, or any combination thereof.
In an embodiment, recovering the valuable metals may be carried out by ion- exchange methods. Ion-exchange involves the use of ion-exchange resins. Ion-exchange resins are insoluble matrices typically in the form of small microbeads, with a radius of 0.1-0.8 mm. The microbeads are typically fabricated from an organic polymer substrate. The microbeads are typically porous, providing a large surface area. Ion-exchange resins function by binding or trapping ions from e.g. a solution, accompanied by releasing other ions into the solution.
In an embodiment, the valuable metals are recovered by using chelating ion- exchange resins. Chelating ion-exchange resins may comprise reactive functional groups covalently attached to a polymer backbone. The reactive functional groups, such as iminodiacetate or b/s-picolylamine, chelate to the valuable metal ions to trap them.
In an embodiment, recovering the valuable metals may be carried out using solvent extraction methods. In solvent extraction, a diluent, preferably an organic solvent, such as oil, is mixed with the PLS to form and emulsion and allowed to separate. The metal will be extracted from the PLS to the diluent phase, resulting in a diluent phase bearing the metal, and a raffinate containing the remains of the PLS.
In an embodiment, recovering the valuable metals may be carried out using chemical precipitation methods. The valuable metals are precipitated out of the PLS into a solid form as an insoluble compound suitable for further purification. In an embodiment, the valuable metals may be precipitated as sulfides, sulfates or hydroxides.
In an embodiment of the present invention, the method further comprises a step of removing or recovering ferrous iron from the tailings. Figure 2 presents
a simplified process scheme for such a method. Ferrous iron may be removed from the tailings as ferrous sulfate using crystallization. The invention provides a method for acquiring ferrous sulfate as a profitable byproduct alongside with the valuable metals, whereas in a conventional process iron will be lost to iron- gypsum-precipitate that is considered as waste.
In addition to the embodiments described herein, the method for recovering metals from sulfide-containing feed material may further comprise steps and processes needed for an optimal metal recovery. These steps, such as filtration and washing steps, may be carried out using conventional process equipment and process chemicals known to a person skilled in the art. These further steps may be incorporated or carried out in any appropriate phase of the processing cycle.
In an embodiment, the method may further comprise a filtration step or several filtration steps. The filtration step or filtration steps may be carried out for example after step a), after step b), and/or after step d).
Embodiments of the present invention comprising filtration steps are depicted in Figure 2. A filtration step may optionally be performed after steps a) and/or d), i.e., after mixing the feed material with the aqueous solution and/or after reducing the ferric iron contained in the PLS. Liquid portion of the working suspension is directed to the valuable metals recovery step e), and solid portion of the working suspension is directed to the leaching step b) for a next round of leaching. Another filtration step may optionally be performed after the leaching step b). Liquid portion of the PLS is circulated (step c)) back to step a) and/or d) of the process for reduction. Solid leach residue is discarded and/or directed to a tailings pond.
The method according to the present invention may also be used in a ferrous iron production process. In this embodiment, iron is considered the valuable metal. The concentration of metals such as copper, zinc, nickel, and cobalt is likely low in the feed material, such that these metals may be considered as impurities. These impurities need to be removed from the working suspension. With the presented method, the impurity removal is enhanced with the help of the iron reduction process. The metals considered as impurities may be removed from the process prior to iron removal, rendering the iron recovery
process more efficient and yielding a more pure iron product. Iron may be recovered from the process as ferrous sulfate by crystallization.
EXAMPLE By using the method according to the present invention, the ferric ion concentration of pregnant leach solutions may be greatly reduced. In laboratory experiments, the ferric ion concentration in a PLS has been reduced from 30 g/L to 1 g/L. In the experiment, a pregnant leach solution containing cobalt (Co) in a concentration of 690 mg/L, nickel (Ni) in a concentration of 290 mg/L, and iron as ferric iron (Fe3+) in a concentration of 35 g/L. 100 mL of the PLS was mixed in a vessel at 60 °C with 38 g of fresh feed material, containing 230 g/kg of pyrrhotite. During agitation, concentration of Fe3+ decreased to 0.9 g/L.
Claims
1. A hydrometallurgical method for recovering metals from a sulfide-containing feed material, the method comprising the steps of a) mixing the feed material with an aqueous solution, forming a working suspension comprising sulfide minerals, the sulfide minerals originating from the feed material, b) dissolving valuable metals from the feed material in the working suspension by a leaching process with leaching chemicals, forming a pregnant leach solution (PLS) comprising ferric iron and valuable metal ions, c) circulating the PLS or at least part of the PLS back to step a), wherein the PLS constitutes the aqueous solution in step a), d) reducing the ferric iron contained in the PLS by the sulfide minerals originating from the feed material, forming a reduced PLS comprising ferrous iron and valuable metal ions, and e) optionally recovering the valuable metal ions from the reduced PLS, thus forming a ferrous sulfate solution.
2. The method according to claim 1, wherein the feed material comprises sulfide minerals or a sulfide-containing waste material.
3. The method according to claim 1 or 2, wherein the feed material comprises pyrite, pyrrhotite, troilite, pentlandite, talnakhite, millerite, heazlewoodite, nickeline, maucherite, gersdorffite, mackinawite, linnaeite, polydymite, cobaltite, sphalerite, chalcopyrite, chalcocite, covellite, bornite, cubanite, or any combination thereof.
4. The method according to any of the preceding claims, wherein the valuable metals are selected from a group comprising Cu, Zn, Ni, and Co.
5. The method according to any of the preceding claims, wherein the leaching chemicals comprise acid, preferably sulfuric acid, and oxidant.
6. The method according to any of the preceding claims, wherein the leaching process is a bioleaching process, wherein the leaching chemicals are produced by microorganisms.
7. The method according to any of the preceding claims, wherein recovering the valuable metal ions is carried out by ion-exchange, solvent extraction or chemical precipitation methods.
8. The method according to any of the preceding claims, wherein the reduced PLS or at least part of the reduced PLS is directed back to the leaching step b) for the next round of leaching.
9. The method according to any of the preceding claims, wherein the method further comprises the step of recovering the valuable metal ions from the reduced PLS, thus forming a ferrous sulfate solution.
10. The method according to any of the preceding claims, wherein the method further comprises a filtration step or several filtration steps after step a), after step b), and/or after step d).
11 . The method according to any of the preceding claims, wherein the method further comprises a step of removing or recovering ferrous iron from the ferrous sulfate solution obtained in step d).
12. The method according to claim 11 , wherein recovering the ferrous iron is carried out by crystallization.
13. Use of a pregnant leach solution in a hydrometallurgical process for oxidizing and/or dissolving sulfide minerals contained in a feed material, wherein the pregnant leach solution is derived from leaching of sulfide minerals.
14. Use of sulfide minerals or a sulfide-containing waste material in a hydrometallurgical process for reducing ferric iron contained in a pregnant leach solution produced in the leaching of sulfide-containing feed material in the hydrometallurgical process.
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2021
- 2021-04-16 FI FI20215447A patent/FI130407B/en active
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US4359376A (en) * | 1980-01-23 | 1982-11-16 | Envirotech Corporation | Recovering copper from a copper-bearing source |
US20060002834A1 (en) * | 2004-07-01 | 2006-01-05 | Brierley James A | Processing of acid-consuming mineral materials involving treatment with acidic biooxidation effluent |
AU2008200206B2 (en) * | 2007-01-19 | 2012-09-06 | Ausenco Services Pty Ltd | Integrated hydrometallurgical and pyrometallurgical processing of base-metal sulphides |
WO2014169325A1 (en) * | 2013-04-15 | 2014-10-23 | Bhp Billiton Olympic Dam Corporation Pty Ltd | Method for processing ore |
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