CA2898986C - Method of pretreating gold ore - Google Patents
Method of pretreating gold ore Download PDFInfo
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- CA2898986C CA2898986C CA2898986A CA2898986A CA2898986C CA 2898986 C CA2898986 C CA 2898986C CA 2898986 A CA2898986 A CA 2898986A CA 2898986 A CA2898986 A CA 2898986A CA 2898986 C CA2898986 C CA 2898986C
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- CA
- Canada
- Prior art keywords
- gold
- ore
- leaching
- pyrite
- pretreatment
- Prior art date
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- 239000010931 gold Substances 0.000 title claims abstract description 160
- 229910052737 gold Inorganic materials 0.000 title claims abstract description 147
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 title claims abstract description 146
- 238000000034 method Methods 0.000 title claims abstract description 46
- 229910052683 pyrite Inorganic materials 0.000 claims abstract description 52
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 claims abstract description 52
- 239000011028 pyrite Substances 0.000 claims abstract description 52
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 44
- 150000002506 iron compounds Chemical class 0.000 claims abstract description 6
- NFMAZVUSKIJEIH-UHFFFAOYSA-N bis(sulfanylidene)iron Chemical compound S=[Fe]=S NFMAZVUSKIJEIH-UHFFFAOYSA-N 0.000 claims abstract description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 31
- 230000001590 oxidative effect Effects 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 18
- 239000012298 atmosphere Substances 0.000 claims description 9
- 230000002378 acidificating effect Effects 0.000 claims description 7
- 125000000101 thioether group Chemical group 0.000 claims description 2
- 238000002386 leaching Methods 0.000 abstract description 99
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 abstract description 11
- 239000000243 solution Substances 0.000 description 39
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 21
- 238000006243 chemical reaction Methods 0.000 description 19
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 16
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 15
- -1 iron ions Chemical class 0.000 description 15
- 239000012141 concentrate Substances 0.000 description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 12
- 238000000197 pyrolysis Methods 0.000 description 12
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 229910052742 iron Inorganic materials 0.000 description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- 238000009854 hydrometallurgy Methods 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 229910052717 sulfur Inorganic materials 0.000 description 10
- 239000011593 sulfur Substances 0.000 description 10
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 9
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 9
- 229910001431 copper ion Inorganic materials 0.000 description 9
- 230000014759 maintenance of location Effects 0.000 description 9
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 8
- 239000002245 particle Substances 0.000 description 8
- 239000007800 oxidant agent Substances 0.000 description 7
- 230000033116 oxidation-reduction process Effects 0.000 description 7
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 229960003280 cupric chloride Drugs 0.000 description 6
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 6
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical compound S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 238000011282 treatment Methods 0.000 description 6
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 5
- TXKMVPPZCYKFAC-UHFFFAOYSA-N disulfur monoxide Inorganic materials O=S=S TXKMVPPZCYKFAC-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- GYCHYNMREWYSKH-UHFFFAOYSA-L iron(ii) bromide Chemical compound [Fe+2].[Br-].[Br-] GYCHYNMREWYSKH-UHFFFAOYSA-L 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- OMZSGWSJDCOLKM-UHFFFAOYSA-N copper(II) sulfide Chemical compound [S-2].[Cu+2] OMZSGWSJDCOLKM-UHFFFAOYSA-N 0.000 description 4
- QTMDXZNDVAMKGV-UHFFFAOYSA-L copper(ii) bromide Chemical compound [Cu+2].[Br-].[Br-] QTMDXZNDVAMKGV-UHFFFAOYSA-L 0.000 description 4
- 230000002708 enhancing effect Effects 0.000 description 4
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 4
- 239000012299 nitrogen atmosphere Substances 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 description 4
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 229910021591 Copper(I) chloride Inorganic materials 0.000 description 3
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 238000013019 agitation Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- ODWXUNBKCRECNW-UHFFFAOYSA-M bromocopper(1+) Chemical compound Br[Cu+] ODWXUNBKCRECNW-UHFFFAOYSA-M 0.000 description 3
- OXBLHERUFWYNTN-UHFFFAOYSA-M copper(I) chloride Chemical compound [Cu]Cl OXBLHERUFWYNTN-UHFFFAOYSA-M 0.000 description 3
- 229940045803 cuprous chloride Drugs 0.000 description 3
- 229910001447 ferric ion Inorganic materials 0.000 description 3
- 229960002089 ferrous chloride Drugs 0.000 description 3
- FBAFATDZDUQKNH-UHFFFAOYSA-M iron chloride Chemical compound [Cl-].[Fe] FBAFATDZDUQKNH-UHFFFAOYSA-M 0.000 description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910001510 metal chloride Inorganic materials 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910052952 pyrrhotite Inorganic materials 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- BMYNFMYTOJXKLE-UHFFFAOYSA-N 3-azaniumyl-2-hydroxypropanoate Chemical compound NCC(O)C(O)=O BMYNFMYTOJXKLE-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910021590 Copper(II) bromide Inorganic materials 0.000 description 2
- CPELXLSAUQHCOX-UHFFFAOYSA-N Hydrogen bromide Chemical compound Br CPELXLSAUQHCOX-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 150000001342 alkaline earth metals Chemical class 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- 229910052790 beryllium Inorganic materials 0.000 description 2
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 2
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 2
- 229910052794 bromium Inorganic materials 0.000 description 2
- 229910052792 caesium Inorganic materials 0.000 description 2
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 150000003841 chloride salts Chemical class 0.000 description 2
- 230000001186 cumulative effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910052730 francium Inorganic materials 0.000 description 2
- KLMCZVJOEAUDNE-UHFFFAOYSA-N francium atom Chemical compound [Fr] KLMCZVJOEAUDNE-UHFFFAOYSA-N 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 150000002367 halogens Chemical class 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910001509 metal bromide Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 229910052705 radium Inorganic materials 0.000 description 2
- HCWPIIXVSYCSAN-UHFFFAOYSA-N radium atom Chemical compound [Ra] HCWPIIXVSYCSAN-UHFFFAOYSA-N 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 229910052701 rubidium Inorganic materials 0.000 description 2
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 238000000638 solvent extraction Methods 0.000 description 2
- 229910052712 strontium Inorganic materials 0.000 description 2
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 2
- DHCDFWKWKRSZHF-UHFFFAOYSA-N sulfurothioic S-acid Chemical compound OS(O)(=O)=S DHCDFWKWKRSZHF-UHFFFAOYSA-N 0.000 description 2
- 238000002076 thermal analysis method Methods 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- FEONEKOZSGPOFN-UHFFFAOYSA-K tribromoiron Chemical compound Br[Fe](Br)Br FEONEKOZSGPOFN-UHFFFAOYSA-K 0.000 description 2
- 238000013022 venting Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 229910021589 Copper(I) bromide Inorganic materials 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 229910021575 Iron(II) bromide Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052964 arsenopyrite Inorganic materials 0.000 description 1
- MJLGNAGLHAQFHV-UHFFFAOYSA-N arsenopyrite Chemical compound [S-2].[Fe+3].[As-] MJLGNAGLHAQFHV-UHFFFAOYSA-N 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 229910052951 chalcopyrite Inorganic materials 0.000 description 1
- DVRDHUBQLOKMHZ-UHFFFAOYSA-N chalcopyrite Chemical compound [S-2].[S-2].[Fe+2].[Cu+2] DVRDHUBQLOKMHZ-UHFFFAOYSA-N 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- NKNDPYCGAZPOFS-UHFFFAOYSA-M copper(i) bromide Chemical compound Br[Cu] NKNDPYCGAZPOFS-UHFFFAOYSA-M 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005363 electrowinning Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 229940046149 ferrous bromide Drugs 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 229910052949 galena Inorganic materials 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000011019 hematite Substances 0.000 description 1
- 229910052595 hematite Inorganic materials 0.000 description 1
- 229910000042 hydrogen bromide Inorganic materials 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 1
- RLJMLMKIBZAXJO-UHFFFAOYSA-N lead nitrate Chemical compound [O-][N+](=O)O[Pb]O[N+]([O-])=O RLJMLMKIBZAXJO-UHFFFAOYSA-N 0.000 description 1
- XCAUINMIESBTBL-UHFFFAOYSA-N lead(ii) sulfide Chemical compound [Pb]=S XCAUINMIESBTBL-UHFFFAOYSA-N 0.000 description 1
- 231100001231 less toxic Toxicity 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 1
- 230000001473 noxious effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000009853 pyrometallurgy Methods 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- PFUVRDFDKPNGAV-UHFFFAOYSA-N sodium peroxide Chemical compound [Na+].[Na+].[O-][O-] PFUVRDFDKPNGAV-UHFFFAOYSA-N 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910052950 sphalerite Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052815 sulfur oxide Inorganic materials 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 229910052726 zirconium Inorganic materials 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
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/02—Roasting 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
- C22B11/00—Obtaining noble metals
- C22B11/04—Obtaining noble metals by wet processes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The present invention provides a method of pretreating gold ore for leaching gold from gold ore containing pyrite that enables to enhance the gold-leaching speed while the generation of sulfur dioxide is suppressed. The method of pretreating gold ore for hydrometallurgically recovering gold from gold ore which contains pyrite (FeS2), the method comprising a step of converting pyrite contained in the gold ore to iron compound soluble to hydrochloric acid.
Description
= 1 SPECIFICATION
[Title of the invention]
Method of Pretreating Gold Ore (0001) [Technical field]
The present invention relates to a method of pretreating gold ore for hydrometallurgically recovering gold from gold ore which contains pyrite.
[Title of the invention]
Method of Pretreating Gold Ore (0001) [Technical field]
The present invention relates to a method of pretreating gold ore for hydrometallurgically recovering gold from gold ore which contains pyrite.
(0002) As a method for recovering gold from sulfide ore containing gold, a technique relying on the hydrometallurgical process is known. Traditionally, the leaching of gold from the sulfide ore into a solution has been conducted by using reagents such as cyanide, thiourea, thiosulfate, halogen gas or the like. Recently, a gold-leaching solution containing chloride ions, iron ions, copper ions and bromide ions is proposed as a less toxic leaching solution as described in (Patent document 1) and Japanese Patent Application Publication No. 2009-235525 (Patent document 2).
(0003) Further, as a pretreatment for facilitating the leaching of gold from sulfide ore, a method of subjecting sulfide ore to oxidizing roasting is known and, recently, a pretreatment method comprising the oxidizing roasting process combined with one or other processes has been proposed. For example, Japanese Patent Application Publication No. 2010-235999 (Patent Document 3) proposed a method of subjecting copper sulfide ore to leaching treatment at a temperature below the melting point of the sulfur, allowing the resulting fine sulfur particles and remaining non-leached sulfide particles to float up from the leached residue through utilization of the difference in their hydrophobicity from other iron oxide and gangue components, and separating iron oxide or gangue by precipitation or as ore tailings, whereby the gold contained in the residual solution is concentrated. Thereafter, the condensed components containing gold is subjected to sulfur removal and then to the oxidizing roasting so as to transform the iron component into iron oxide (hematite) which, in turn, is dissolved in sulfuric acid, whereby the residue containing the concentrated gold is recovered.
(0004) With respect to pyrite only, it has been known that pyrite decomposes into pyrrhotite, which is readily-soluble to acid, and sulfur. Japanese Patent Application Publication No. 2005-042155 (Patent document 4) suggests utilizing the reaction to remove pyrite from the residue obtained after leaching copper sulfide ore containing pyrite and to enrich the noble metal.
(0005) [Description of prior art]
Patent document 1: Japanese Patent Application Publication No. 2008-106347 Patent document 2:-Japanese Patent Application Publication No. 2009-235525 Patent document 3: Japanese Patent Application Publication No. 2010-235999 Patent document 4: Japanese Patent Application Publication No. 2005-042155 (0000 The method disclosed in Japanese Patent Application Publication No. 2009-(Patent document 2), which does not use highly toxic cyanide, thiourea, thiosulfate, =
halogen gas, or the like and facilitates leaching of the gold contained in copper sulfide ore, is highly practical for leaching the gold included in the copper sulfide ore.
However, when this method is applied to the pyrite ore, the gold-leaching speed is not sufficient.
(0007) As such, a pretreatment which uses the oxidizing roasting by supplying oxygen as disclosed in Japanese Patent Application Publication No. 2010-235999 (Patent document 3) is considered to remove sulfur in advance and to facilitate iron leaching.
(0008) However, if the method of the oxidizing roasting of sulfide ore, including the method disclosed in the Patent document 3, is adopted, the following chemical reactions, 2CuS+302---2Cu0+2S02, 4CuFeS2+1302-4Cu0+8S02+2Fe203 and 4FeS2+1102¨,2Fe203+8S02 will occur predominantly, and accordingly the problem of generation of sulfur dioxide (S02), which is known as environmental contaminant, cannot be avoided. In particular, as the content of pyrite in the gold ore is higher, the amount of generation of sulfur dioxide becomes larger. Accordingly there is a problem to be solved in terms of practical use.
(0009) As for pretreatment for enhancing the gold-leaching speed, it is desirable, from the aspects of the safety and the protection of the environment, to decrease the sulfur dioxide which is generated during a treatment method of ores for gold-leaching, thereby enhancing the safety and reducing the influence on the environment. It is assumed that a pretreatment applicable to gold ore containing a lot of pyrite, which has been considered difficult to put to practical use, would greatly contribute to the progress of gold mining development.
(0010) The Patent document 4 is related to a process predicated on recovering noble metal with pyrometallurgy in view of the problem residing in recovering noble metal with hydrometallurgy. As such, there is no supposition that noble metal should be leached with a hydrometallurgical process (see paragraphs 0007-0008, 0078 of the patent document 4). Further, it does not suggest the effect achieved by utilizing a hydrometallurgical process at all.
[Summary of the invention]
(0011) Therefore, the present invention has been invented under the above-mentioned situations, and has an object of providing a method for pretreating gold ore for hydrometallurgically recovering gold from gold ore containing pyrite, and has an object of enhancing the gold-recovering speed while the generation of sulfur dioxide is suppressed.
(0012) The present invention, in one aspect, provides a method of pretreating gold ore for hydrometallurgically recovering gold from gold ore which contains pyrite (FeS2), the method comprising a step of converting pyrite contained in the gold ore to iron compound soluble to hydrochloric acid.
(0013) In one embodiment of the method of pretreating gold ore according to the present invention, the method includes a step of converting the pyrite such that a ratio of a content of Fe soluble to hydrochloric acid (Fesoi) contained in the gold ore after pretreatment with respect to a content of total Fe (Feaii) contained in the gold ore after pretreatment becomes 0.6 or more.
(0014) In another embodiment of the method of pretreating gold ore according to the present invention, the iron compound soluble to hydrochloric acid contained in the gold ore after pretreatment is sulfide.
(0015) In a further embodiment of the method of pretreating gold ore according to the present invention, a content of the pyrite in the gold ore prior to pretreatment is 5 to 80 mass%.
(0016) In a further embodiment of the method of pretreating gold ore according to the present invention, S (mass %)/Au (mass ppm) in the gold ore prior to pretreatment is 1 to 20.
(0017) In a further embodiment of the method of pretreating gold ore according to the present invention, the pretreatment involves heat treatment.
(0018) In a further embodiment of the method of pretreating gold ore according to the present invention, the heat treatment comprises heating the gold ore to 450 C
or more under a non-oxidative atmosphere.
(0019) In a further embodiment of the method of pretreating gold ore according to the present invention, the heat treatment is carried out under the conditions of retaining the gold ore at 600-750 C for 5-60 minutes.
(0020) By conducting the pretreatment according to some embodiments of the present invention on the gold ore containing the pyrite ore and then conducting a hydrometallurgical process, improved gold-recovering speed may be attained, while the generation of noxious sulfur oxide may be suppressed. Especially, improvements in gold leaching speed may be seen when using a particular gold-leaching solution according to some embodiments of the present invention. In other words, some embodiments of the present invention may provide a practical gold-leaching method in the safety and preservation of the environment.
(0021) [Brief explanation of the drawings]
Fig. 1 is a graph showing the relation between the leaching time and the Au grade in the residues with respect to Example and Comparative Example.
Fig. 2 is a TG/DTA curve obtained during thermal analysis under a nitrogen atmosphere for ground pyrite concentrate used in Example 1.
(0022) [Mode of practicing the invention]
The present invention will be explained in details in the following.
(0023) 1. Pretreatment One embodiment of pretreatment of gold ore for hydrometallurgically recovering gold contained in the gold ore containing pyrite (FeS2) according to the present invention includes a step of converting pyrite contained in the gold ore to compound soluble to hydrochloric acid. In a preferred embodiment of pretreatment of gold ore according to the present invention includes a step of converting the pyrite such that a ratio of a content of Fe soluble to hydrochloric acid (Fest>) contained in the gold ore after pretreatment with respect to a content of total Fe (Fean) contained in the gold ore after pretreatment becomes 0.6 or more.
(0024) (1) Gold ore The object of the present invention is gold ore containing pyrite. This is because the present invention aims at the enhancement of the leaching ratio of gold in the pyrite, which is difficult to dissolve and has a low gold-leaching ratio. However, the other conditions, such as the concentration of gold in the ore, for example, are not questioned. The gold ore, which is the object of treatment, may be those having been subjected to conventional beneficiation such as floatation or gravity separation. It is also possible to grind the ore to smaller particle sizes so that the contact of gold-leaching solution with gold within the ore is facilitated. The gold concentration of the gold ore is typically in the order of 0.1-100 ppm by mass, and more typically in the order of 1-20 ppm by mass.
(0025) In addition to pyrite, the gold ore may contain chalcopyrite, galena, sphalerite, arsenopyrite, antimonite, and pyrrhotite. In a typical example of the present invention, gold ore containing at least 5 mass% of pyrite, more typically at least 10 mass %, and yet more typically at least 30 mass% of pyrite, is used. In this type of gold ore, as the ratio of sulfur content to gold content (S/Au) in the ore becomes higher, it is generally difficult to efficiently recover gold. Therefore, by using such gold ore having a high concentration of pyrite, the effect of the pretreatment of the present invention is remarkably achieved. Specifically, S (mass%)/Au (mass ppm) is 1 to 20, preferably 1.5 to 20, more preferably 1.5 to 10. There is no particular upper limit to the content of the pyrite in the gold ore and 100 mass% is allowable but typically the content is at most 80 mass%.
(0026) (2) Conversion step In the conventional technique, the ores were subjected to oxidizing roasting under the presence of the oxygen or air, and hence the sulfur contained in the sulfide ores was combined with the oxygen, resulting in generation of sulfur oxide. In the present invention, such oxidizing roasting is not carried out substantially. In the present invention, the pretreatment preferably converts pyrite to iron sulfide soluble to hydrochloric acid while still remaining iron sulfide in terms of suppression of sulfur oxide formation. If the iron in the ore exists as iron sulfide soluble to hydrochloric acid in a certain amount or more, a remarkably improved leaching speed of gold can be achieved in the subsequent leaching step.
(0027) While pyrite (FeS2) is insoluble to hydrochloric acid, the iron sulfide soluble to hydrochloric acid is expected to improve a recovering speed of gold when hydrometallurgically recovering gold. Especially, it was found that it showed remarkable effect for a particular leaching solution. The particular leaching solution will be explained later in "2. Hydrometallurgical step".
(0028) According to the research by the present inventors, supposed that a content of total Fe contained in the gold ore after pretreatment is represented by Feat' and a content of Fe soluble to hydrochloric acid is represented by Fes.' contained in the gold ore after pretreatment, the "certain amount or more" should mean that Fesoi/Fean is 0.6 or more, preferably 0.8 or more, more preferably 0.9 or more. When pyrite is completely converted, Fesoi/Fean reaches 1.0, which is the upper limit.
(0029) In the present invention, Fean is calculated according to the following procedure. 0.2g of gold ore after pretreatment, 4g of sodium peroxide, lg of sodium carbonate are charged in a crucible made of zirconium and heated with a gas burner for alkali fusion. After the crucible is cooled with water, 30mL of 35 mass% hydrochloric acid is charged for leaching of the melt. The post-leaching solution is subjected to determination by ICP-AES (in Example, Model:SPS4000 available from Hitachi High-Technologies Corporation (formerly SIT) was used.). Based on the determined Fe concentration, the amount of liquid and the amount of ore, Fean is calculated.
Specifically, it is represented as follows: Feau = determined Fe concentration (g/L) x liquid amount (30mL) sample amount (0.2g).
(0030) In the present invention, Fes.' is calculated according to the following procedure. 50g of the gold ore after pretreatment is subjected to leaching at 85 C for 180min with agitation in 1L of hydrochloric acid (1.0mo1/L) containing lmol/L of Fe3+, which is then filtered. The Fe concentration in the filtrate is determined by ICP-AES
(in Example, Model:SPS4000 available from Hitachi High-Technologies Corporation (formerly SID was used.) (Fe initially contained in the hydrochloric acid should be deducted.). Based on the determined Fe concentration, the amount of liquid and the amount of ore, Fesot is calculated. Specifically, it is represented as follows: Fes.' =
(determined Fe concentration ¨ initial Fe concentration) (g/L) x liquid amount (1L) ore amount (50g).
(0031) In the conversion step of pyrite, it is desirable that the pretreated pyrite remain sulfide. When pyrite is converted into oxide, the formation of sulfur oxide is unavoidable, the amount of which is so large that simple means for its removal such as a shower tower is not sufficient and a device enabling sufficient removal is necessary. Accordingly, heat treatment by which pyrite still remains sulfide after pretreatment is desirable.
(0032) The step of conversion can be carried out by heat treatment. From the standpoint of suppressing the generation of sulfur oxides, it is preferable to conduct the conversion step in a condition that oxygen feed is suppressed (in a non-oxidative atmosphere).
The condition of such suppressed oxygen feed means in the present invention that the molar ratio of oxygen/pyrite ore = 1/ 2 or less. Also, the non-oxidative atmosphere means that the molar ratio of oxygen /pyrite = 1/5 or less, preferably 1/10 or less.
(0033) If the mixing of oxygen is suppressed, the amount of sulfur oxide generation is low and accordingly there is no necessity of installing a separate sulfuric acid production facility. A shower tower will be enough to remove it. If the non-oxidative atmosphere is used, even the shower tower may be dispensed with.
(0034) The gold ore after the conversion step exhibits remarkably enhanced solubility into the gold leaching solution as will be explained hereafter and the leaching speed of gold may increase by approximately ten times more than the case without the conversion step. It was quite amazing that such remarkable result has been attained.
Patent document 1: Japanese Patent Application Publication No. 2008-106347 Patent document 2:-Japanese Patent Application Publication No. 2009-235525 Patent document 3: Japanese Patent Application Publication No. 2010-235999 Patent document 4: Japanese Patent Application Publication No. 2005-042155 (0000 The method disclosed in Japanese Patent Application Publication No. 2009-(Patent document 2), which does not use highly toxic cyanide, thiourea, thiosulfate, =
halogen gas, or the like and facilitates leaching of the gold contained in copper sulfide ore, is highly practical for leaching the gold included in the copper sulfide ore.
However, when this method is applied to the pyrite ore, the gold-leaching speed is not sufficient.
(0007) As such, a pretreatment which uses the oxidizing roasting by supplying oxygen as disclosed in Japanese Patent Application Publication No. 2010-235999 (Patent document 3) is considered to remove sulfur in advance and to facilitate iron leaching.
(0008) However, if the method of the oxidizing roasting of sulfide ore, including the method disclosed in the Patent document 3, is adopted, the following chemical reactions, 2CuS+302---2Cu0+2S02, 4CuFeS2+1302-4Cu0+8S02+2Fe203 and 4FeS2+1102¨,2Fe203+8S02 will occur predominantly, and accordingly the problem of generation of sulfur dioxide (S02), which is known as environmental contaminant, cannot be avoided. In particular, as the content of pyrite in the gold ore is higher, the amount of generation of sulfur dioxide becomes larger. Accordingly there is a problem to be solved in terms of practical use.
(0009) As for pretreatment for enhancing the gold-leaching speed, it is desirable, from the aspects of the safety and the protection of the environment, to decrease the sulfur dioxide which is generated during a treatment method of ores for gold-leaching, thereby enhancing the safety and reducing the influence on the environment. It is assumed that a pretreatment applicable to gold ore containing a lot of pyrite, which has been considered difficult to put to practical use, would greatly contribute to the progress of gold mining development.
(0010) The Patent document 4 is related to a process predicated on recovering noble metal with pyrometallurgy in view of the problem residing in recovering noble metal with hydrometallurgy. As such, there is no supposition that noble metal should be leached with a hydrometallurgical process (see paragraphs 0007-0008, 0078 of the patent document 4). Further, it does not suggest the effect achieved by utilizing a hydrometallurgical process at all.
[Summary of the invention]
(0011) Therefore, the present invention has been invented under the above-mentioned situations, and has an object of providing a method for pretreating gold ore for hydrometallurgically recovering gold from gold ore containing pyrite, and has an object of enhancing the gold-recovering speed while the generation of sulfur dioxide is suppressed.
(0012) The present invention, in one aspect, provides a method of pretreating gold ore for hydrometallurgically recovering gold from gold ore which contains pyrite (FeS2), the method comprising a step of converting pyrite contained in the gold ore to iron compound soluble to hydrochloric acid.
(0013) In one embodiment of the method of pretreating gold ore according to the present invention, the method includes a step of converting the pyrite such that a ratio of a content of Fe soluble to hydrochloric acid (Fesoi) contained in the gold ore after pretreatment with respect to a content of total Fe (Feaii) contained in the gold ore after pretreatment becomes 0.6 or more.
(0014) In another embodiment of the method of pretreating gold ore according to the present invention, the iron compound soluble to hydrochloric acid contained in the gold ore after pretreatment is sulfide.
(0015) In a further embodiment of the method of pretreating gold ore according to the present invention, a content of the pyrite in the gold ore prior to pretreatment is 5 to 80 mass%.
(0016) In a further embodiment of the method of pretreating gold ore according to the present invention, S (mass %)/Au (mass ppm) in the gold ore prior to pretreatment is 1 to 20.
(0017) In a further embodiment of the method of pretreating gold ore according to the present invention, the pretreatment involves heat treatment.
(0018) In a further embodiment of the method of pretreating gold ore according to the present invention, the heat treatment comprises heating the gold ore to 450 C
or more under a non-oxidative atmosphere.
(0019) In a further embodiment of the method of pretreating gold ore according to the present invention, the heat treatment is carried out under the conditions of retaining the gold ore at 600-750 C for 5-60 minutes.
(0020) By conducting the pretreatment according to some embodiments of the present invention on the gold ore containing the pyrite ore and then conducting a hydrometallurgical process, improved gold-recovering speed may be attained, while the generation of noxious sulfur oxide may be suppressed. Especially, improvements in gold leaching speed may be seen when using a particular gold-leaching solution according to some embodiments of the present invention. In other words, some embodiments of the present invention may provide a practical gold-leaching method in the safety and preservation of the environment.
(0021) [Brief explanation of the drawings]
Fig. 1 is a graph showing the relation between the leaching time and the Au grade in the residues with respect to Example and Comparative Example.
Fig. 2 is a TG/DTA curve obtained during thermal analysis under a nitrogen atmosphere for ground pyrite concentrate used in Example 1.
(0022) [Mode of practicing the invention]
The present invention will be explained in details in the following.
(0023) 1. Pretreatment One embodiment of pretreatment of gold ore for hydrometallurgically recovering gold contained in the gold ore containing pyrite (FeS2) according to the present invention includes a step of converting pyrite contained in the gold ore to compound soluble to hydrochloric acid. In a preferred embodiment of pretreatment of gold ore according to the present invention includes a step of converting the pyrite such that a ratio of a content of Fe soluble to hydrochloric acid (Fest>) contained in the gold ore after pretreatment with respect to a content of total Fe (Fean) contained in the gold ore after pretreatment becomes 0.6 or more.
(0024) (1) Gold ore The object of the present invention is gold ore containing pyrite. This is because the present invention aims at the enhancement of the leaching ratio of gold in the pyrite, which is difficult to dissolve and has a low gold-leaching ratio. However, the other conditions, such as the concentration of gold in the ore, for example, are not questioned. The gold ore, which is the object of treatment, may be those having been subjected to conventional beneficiation such as floatation or gravity separation. It is also possible to grind the ore to smaller particle sizes so that the contact of gold-leaching solution with gold within the ore is facilitated. The gold concentration of the gold ore is typically in the order of 0.1-100 ppm by mass, and more typically in the order of 1-20 ppm by mass.
(0025) In addition to pyrite, the gold ore may contain chalcopyrite, galena, sphalerite, arsenopyrite, antimonite, and pyrrhotite. In a typical example of the present invention, gold ore containing at least 5 mass% of pyrite, more typically at least 10 mass %, and yet more typically at least 30 mass% of pyrite, is used. In this type of gold ore, as the ratio of sulfur content to gold content (S/Au) in the ore becomes higher, it is generally difficult to efficiently recover gold. Therefore, by using such gold ore having a high concentration of pyrite, the effect of the pretreatment of the present invention is remarkably achieved. Specifically, S (mass%)/Au (mass ppm) is 1 to 20, preferably 1.5 to 20, more preferably 1.5 to 10. There is no particular upper limit to the content of the pyrite in the gold ore and 100 mass% is allowable but typically the content is at most 80 mass%.
(0026) (2) Conversion step In the conventional technique, the ores were subjected to oxidizing roasting under the presence of the oxygen or air, and hence the sulfur contained in the sulfide ores was combined with the oxygen, resulting in generation of sulfur oxide. In the present invention, such oxidizing roasting is not carried out substantially. In the present invention, the pretreatment preferably converts pyrite to iron sulfide soluble to hydrochloric acid while still remaining iron sulfide in terms of suppression of sulfur oxide formation. If the iron in the ore exists as iron sulfide soluble to hydrochloric acid in a certain amount or more, a remarkably improved leaching speed of gold can be achieved in the subsequent leaching step.
(0027) While pyrite (FeS2) is insoluble to hydrochloric acid, the iron sulfide soluble to hydrochloric acid is expected to improve a recovering speed of gold when hydrometallurgically recovering gold. Especially, it was found that it showed remarkable effect for a particular leaching solution. The particular leaching solution will be explained later in "2. Hydrometallurgical step".
(0028) According to the research by the present inventors, supposed that a content of total Fe contained in the gold ore after pretreatment is represented by Feat' and a content of Fe soluble to hydrochloric acid is represented by Fes.' contained in the gold ore after pretreatment, the "certain amount or more" should mean that Fesoi/Fean is 0.6 or more, preferably 0.8 or more, more preferably 0.9 or more. When pyrite is completely converted, Fesoi/Fean reaches 1.0, which is the upper limit.
(0029) In the present invention, Fean is calculated according to the following procedure. 0.2g of gold ore after pretreatment, 4g of sodium peroxide, lg of sodium carbonate are charged in a crucible made of zirconium and heated with a gas burner for alkali fusion. After the crucible is cooled with water, 30mL of 35 mass% hydrochloric acid is charged for leaching of the melt. The post-leaching solution is subjected to determination by ICP-AES (in Example, Model:SPS4000 available from Hitachi High-Technologies Corporation (formerly SIT) was used.). Based on the determined Fe concentration, the amount of liquid and the amount of ore, Fean is calculated.
Specifically, it is represented as follows: Feau = determined Fe concentration (g/L) x liquid amount (30mL) sample amount (0.2g).
(0030) In the present invention, Fes.' is calculated according to the following procedure. 50g of the gold ore after pretreatment is subjected to leaching at 85 C for 180min with agitation in 1L of hydrochloric acid (1.0mo1/L) containing lmol/L of Fe3+, which is then filtered. The Fe concentration in the filtrate is determined by ICP-AES
(in Example, Model:SPS4000 available from Hitachi High-Technologies Corporation (formerly SID was used.) (Fe initially contained in the hydrochloric acid should be deducted.). Based on the determined Fe concentration, the amount of liquid and the amount of ore, Fesot is calculated. Specifically, it is represented as follows: Fes.' =
(determined Fe concentration ¨ initial Fe concentration) (g/L) x liquid amount (1L) ore amount (50g).
(0031) In the conversion step of pyrite, it is desirable that the pretreated pyrite remain sulfide. When pyrite is converted into oxide, the formation of sulfur oxide is unavoidable, the amount of which is so large that simple means for its removal such as a shower tower is not sufficient and a device enabling sufficient removal is necessary. Accordingly, heat treatment by which pyrite still remains sulfide after pretreatment is desirable.
(0032) The step of conversion can be carried out by heat treatment. From the standpoint of suppressing the generation of sulfur oxides, it is preferable to conduct the conversion step in a condition that oxygen feed is suppressed (in a non-oxidative atmosphere).
The condition of such suppressed oxygen feed means in the present invention that the molar ratio of oxygen/pyrite ore = 1/ 2 or less. Also, the non-oxidative atmosphere means that the molar ratio of oxygen /pyrite = 1/5 or less, preferably 1/10 or less.
(0033) If the mixing of oxygen is suppressed, the amount of sulfur oxide generation is low and accordingly there is no necessity of installing a separate sulfuric acid production facility. A shower tower will be enough to remove it. If the non-oxidative atmosphere is used, even the shower tower may be dispensed with.
(0034) The gold ore after the conversion step exhibits remarkably enhanced solubility into the gold leaching solution as will be explained hereafter and the leaching speed of gold may increase by approximately ten times more than the case without the conversion step. It was quite amazing that such remarkable result has been attained.
6 (0035) As the non-oxidative atmosphere for conducting the conversion step, reductive atmosphere such as ammonia, carbon monoxide and hydrogen sulfide, and inert atmosphere such as rare gas (e.g. argon or helium), nitrogen and carbon dioxide may be cited. Among them, inert atmosphere is preferable in terms of preventing unexpected reaction to occur. Alternatively, the exhausted gas used in the pyrolysis may be reused by recycling.
(0036) During the conversion step, it is necessary to maintain the temperature of the gold ore at least 450 C, preferably at least 550 C and more preferably at least 650 C to enhance the pyrolysis of pyrite. Also, it is preferable to keep the retention temperature for at least 5 minutes, preferably for at least 15 minutes.
This is to sufficiently progress the pyrolysis reaction. However, if the temperature of the gold ore is excessively high, the energy for heating the ore and the processing time become too excessive, and accordingly the retention temperature is preferably 800 C or less, and more preferably 750 C or less.
Similarly, the time for maintaining the retention temperature is preferably minutes or less, more preferably 60 minutes or less.
(0037) Although there is no particular restriction to the type of the heating furnace for the conversion step, a tubular furnace or a rotary kiln, for example, may be used.
(0038) The elemental sulfur generated by pyrolysis of pyrite has been gasified in the high temperature furnace and accordingly the elemental sulfur can be subjected to solid/gas separation and then can be delivered together with the atmospheric gas to a venting system. However, if the elemental sulfur is sent to the venting system, the sulfur will deposit with the decreasing temperature and may cause trouble such as clogging of the gas flue. Therefore, it is desired to recover the sulfur with a wet scrubber. Alternatively, the gaseous elemental sulfur may be cooled together with the pyrrhotite generated in the conversion step. In this case, they are recovered as solids, which in turn are sent together to the gold-leaching step. The elemental sulfur is separated in the leaching step as leaching residue without interfering with the leaching of gold. In this case, this method is economical because the wet scrubber becomes unnecessary.
(0039) Depending on the operational limitation, there may be a case where pyrolyzed gold ore and unpyrolyzed gold ore are comingled and subjected to the iron-leaching step and subsequent steps. However, even in such case, the gold ore which has been subjected to the pyrolysis step is contained and accordingly such embodiment, too, belongs to the technical scope of the present invention.
(0040) 2. Hydrometallurgical process The effect of the present invention can be exerted by recovering gold from the pretreated gold ore through hydrometallurgical process. Hydrometallurgical process includes, but not limited to, gold leaching in a cyanide bath combined with autoclave treatment and gold leaching in an acidic bath.
, 6a (0041) Gold leaching using a cyanide bath generally includes reacting gold ore containing pyrite with water and oxygen in a pressure-resistant container at a high temperature under a high pressure (e.g. 200 C, 30atm) to convert iron sulfide into iron oxide, then ,
(0036) During the conversion step, it is necessary to maintain the temperature of the gold ore at least 450 C, preferably at least 550 C and more preferably at least 650 C to enhance the pyrolysis of pyrite. Also, it is preferable to keep the retention temperature for at least 5 minutes, preferably for at least 15 minutes.
This is to sufficiently progress the pyrolysis reaction. However, if the temperature of the gold ore is excessively high, the energy for heating the ore and the processing time become too excessive, and accordingly the retention temperature is preferably 800 C or less, and more preferably 750 C or less.
Similarly, the time for maintaining the retention temperature is preferably minutes or less, more preferably 60 minutes or less.
(0037) Although there is no particular restriction to the type of the heating furnace for the conversion step, a tubular furnace or a rotary kiln, for example, may be used.
(0038) The elemental sulfur generated by pyrolysis of pyrite has been gasified in the high temperature furnace and accordingly the elemental sulfur can be subjected to solid/gas separation and then can be delivered together with the atmospheric gas to a venting system. However, if the elemental sulfur is sent to the venting system, the sulfur will deposit with the decreasing temperature and may cause trouble such as clogging of the gas flue. Therefore, it is desired to recover the sulfur with a wet scrubber. Alternatively, the gaseous elemental sulfur may be cooled together with the pyrrhotite generated in the conversion step. In this case, they are recovered as solids, which in turn are sent together to the gold-leaching step. The elemental sulfur is separated in the leaching step as leaching residue without interfering with the leaching of gold. In this case, this method is economical because the wet scrubber becomes unnecessary.
(0039) Depending on the operational limitation, there may be a case where pyrolyzed gold ore and unpyrolyzed gold ore are comingled and subjected to the iron-leaching step and subsequent steps. However, even in such case, the gold ore which has been subjected to the pyrolysis step is contained and accordingly such embodiment, too, belongs to the technical scope of the present invention.
(0040) 2. Hydrometallurgical process The effect of the present invention can be exerted by recovering gold from the pretreated gold ore through hydrometallurgical process. Hydrometallurgical process includes, but not limited to, gold leaching in a cyanide bath combined with autoclave treatment and gold leaching in an acidic bath.
, 6a (0041) Gold leaching using a cyanide bath generally includes reacting gold ore containing pyrite with water and oxygen in a pressure-resistant container at a high temperature under a high pressure (e.g. 200 C, 30atm) to convert iron sulfide into iron oxide, then ,
7 leaching gold. The process is called "autoclave treatment" as an autoclave is used as the pressure-resistant container.
In case where the pretreatment is not conducted, the oxidation reaction of iron sulfide is represented by the following formula.
4FeS2 +1502 +8H2 0 2Fe2 03 +8E12 SO4 ¨ (1) On the contrary, in case where the pretreatment is conducted, oxidation of sulfide generates sulfuric acid, which can leach iron compound soluble to acid, enabling reduction of reaction time.
(0042) Also, in the gold leaching using an acidic bath, it is generally important to bring gold locked in the iron sulfide ore into contact with a leaching solution. The pretreatment according to the present invention can bring gold in the iron sulfide ore into contact with the leaching solution in a shorter period since it can convert pyrite in the gold ore to iron sulfide soluble to acid.
(0043) Though the time required for the hydrometallurgical process following the pretreatment can be reduced in either hydrometallurgical process, the gold leaching using an acidic leaching solution is advantageous since it can be conducted under a mild operational condition (under atmospheric pressure, less than 100 C) and without toxic cyanide. The gold leaching using an acidic bath will be hereafter explained in detail.
(0044) Types and steps for performing gold leaching using an acidic bath for the pretreated gold ore are not restrictive but the following gold leaching step, which includes contacting with a gold-leaching solution containing halide ions, copper ions and iron ions while supplying an oxidant, thereby to leach gold component in the gold ore, can be mentioned as a gold leaching step exhibiting a great effect.
(0045) The leaching of gold proceeds as follows. The dissolved gold reacts with halide ions, particularly chloride ions or bromide ions, to form a gold halide complex, particularly chloride complex or bromide complex of gold. Though chloride ions may be singly used as the halide ions in the gold-leaching solution, the combined use of chloride and bromide ions allows formation of a complex at a lower oxidation-reduction potential, thereby enhancing the leaching efficiency of gold. Further, iron ions in the form of ferric ions formed under supply of oxidant, or ferric ions from the beginning, function to oxidize the gold. The gold-leaching solution preferably contains copper ions.
Although the copper ions do not directly participate in the reaction, the oxidation of the iron ions is accelerated in the presence of the copper ions.
(0046) As the source of chloride ions, though there is no particular restriction, hydrogen chloride, hydrochloric acid, metal chloride and chorine gas, etc. may be cited for instance. From the aspects of economy and safety, it is preferable to feed the ions as metal chloride salt. Cited as metal chloride salts are copper chloride (cuprous chloride, cupric chloride), iron chloride (ferrous chloride, ferric chloride), chloride of alkaline metal (lithium, sodium, potassium, rubidium, cesium, francium), alkaline earth metal (beryllium, magnesium, calcium, strontium, barium, radium) can be cited. Sodium chloride is preferred from the standpoints of cost and easy availability.
It is also preferable to use copper chloride and iron chloride because they are utilized also as sources of copper ions and iron ions.
In case where the pretreatment is not conducted, the oxidation reaction of iron sulfide is represented by the following formula.
4FeS2 +1502 +8H2 0 2Fe2 03 +8E12 SO4 ¨ (1) On the contrary, in case where the pretreatment is conducted, oxidation of sulfide generates sulfuric acid, which can leach iron compound soluble to acid, enabling reduction of reaction time.
(0042) Also, in the gold leaching using an acidic bath, it is generally important to bring gold locked in the iron sulfide ore into contact with a leaching solution. The pretreatment according to the present invention can bring gold in the iron sulfide ore into contact with the leaching solution in a shorter period since it can convert pyrite in the gold ore to iron sulfide soluble to acid.
(0043) Though the time required for the hydrometallurgical process following the pretreatment can be reduced in either hydrometallurgical process, the gold leaching using an acidic leaching solution is advantageous since it can be conducted under a mild operational condition (under atmospheric pressure, less than 100 C) and without toxic cyanide. The gold leaching using an acidic bath will be hereafter explained in detail.
(0044) Types and steps for performing gold leaching using an acidic bath for the pretreated gold ore are not restrictive but the following gold leaching step, which includes contacting with a gold-leaching solution containing halide ions, copper ions and iron ions while supplying an oxidant, thereby to leach gold component in the gold ore, can be mentioned as a gold leaching step exhibiting a great effect.
(0045) The leaching of gold proceeds as follows. The dissolved gold reacts with halide ions, particularly chloride ions or bromide ions, to form a gold halide complex, particularly chloride complex or bromide complex of gold. Though chloride ions may be singly used as the halide ions in the gold-leaching solution, the combined use of chloride and bromide ions allows formation of a complex at a lower oxidation-reduction potential, thereby enhancing the leaching efficiency of gold. Further, iron ions in the form of ferric ions formed under supply of oxidant, or ferric ions from the beginning, function to oxidize the gold. The gold-leaching solution preferably contains copper ions.
Although the copper ions do not directly participate in the reaction, the oxidation of the iron ions is accelerated in the presence of the copper ions.
(0046) As the source of chloride ions, though there is no particular restriction, hydrogen chloride, hydrochloric acid, metal chloride and chorine gas, etc. may be cited for instance. From the aspects of economy and safety, it is preferable to feed the ions as metal chloride salt. Cited as metal chloride salts are copper chloride (cuprous chloride, cupric chloride), iron chloride (ferrous chloride, ferric chloride), chloride of alkaline metal (lithium, sodium, potassium, rubidium, cesium, francium), alkaline earth metal (beryllium, magnesium, calcium, strontium, barium, radium) can be cited. Sodium chloride is preferred from the standpoints of cost and easy availability.
It is also preferable to use copper chloride and iron chloride because they are utilized also as sources of copper ions and iron ions.
8 (0047) As the source of the bromide ions, although there is no particular restriction, hydrogen bromide, hydrobromic acid, metal bromide and bromine gas can be cited. As metal bromide, copper bromide (cuprous bromide and cupric bromide), iron bromide (ferrous bromide, ferric bromide), bromide of alkaline metal (lithium, sodium.
potassium, rubidium, cesium and francium), bromide of alkaline earth metal (beryllium, magnesium, calcium, strontium, barium, radium), and from the economical standpoint and easy availability, sodium bromide is preferred.
Also, copper bromide and iron bromide are preferred because they can be also used as sources of copper ions and iron ions.
(0048) Copper ions and iron ions are usually supplied in the form of their salts, for example, halide salts. The copper ions are preferably supplied in the form of copper chloride and/or copper bromide, and the iron ions are preferably supplied in the form of iron chloride and/or iron bromide, from the standpoint that they can be also used as sources of chloride ions and/or bromide ions. As the copper chloride and iron bromide, it is preferable to use cupric chloride (CuC12) and ferric chloride (FeCl3), respectively, but cuprous chloride (CuC1) and ferrous chloride (FeC12) may also be used because they are respectively oxidized into cupric chloride (CuC12 ) and ferric chloride (FeCl3) by supplying oxidant to the leaching solution.
(0049) The concentration of the chloride ions in the gold-leaching solution used in the gold leaching step is preferably 30g/L-180g/L. The concentration of the bromide ions in the gold- leaching solution is preferably 1g/L-100g/L from the standpoints of the reaction rate and the solubility, and more preferably 10g/L-40g/L from the economical standpoint. And, the total concentration of the chloride ions and bromide ions is preferably 120g/L-200g/L. Also, the weight ratio of bromide ions to chloride ions in the gold- leaching solution is preferably at least 1.
(0050) The oxidation-reduction potential (reference electrode is Ag/AgC1 electrode) of the leaching solution at the beginning of the gold leaching step (right before contacting of the ores with leaching-solution) is preferably at least 550mV, more preferably at least 600mV, from the standpoint of acceleration of the gold-leaching. Also, during gold-leaching process, it is preferred to maintain the potential at 550mV or more and more preferably at least 600 mV. Also, to promote the gold-leaching, the pH of the leaching solution is preferably maintained at 2.0 or less and preferably 1.8 or less.
The temperature of the gold-leaching solution is preferably at least 45 C, and more preferably at least 60 C from the standpoint of acceleration of the gold-leaching.
However, excessively high temperature will cause evaporation of the leaching solution or increase the costs for heating, and accordingly 95 C or less is preferable and 85 C or less is more preferable.
(0051) Accordingly, in a preferred embodiment of the present invention, a mixed solution containing at least one of hydrochloric acid and hydrobromic acid, at least one of the cupric chloride and cupric bromide, and at least one of ferric chloride and ferric bromide may be used as the gold-leaching solution in the gold leaching step on the condition that both of chloride ions and bromide ions are contained in the leaching solution.
(0052)
potassium, rubidium, cesium and francium), bromide of alkaline earth metal (beryllium, magnesium, calcium, strontium, barium, radium), and from the economical standpoint and easy availability, sodium bromide is preferred.
Also, copper bromide and iron bromide are preferred because they can be also used as sources of copper ions and iron ions.
(0048) Copper ions and iron ions are usually supplied in the form of their salts, for example, halide salts. The copper ions are preferably supplied in the form of copper chloride and/or copper bromide, and the iron ions are preferably supplied in the form of iron chloride and/or iron bromide, from the standpoint that they can be also used as sources of chloride ions and/or bromide ions. As the copper chloride and iron bromide, it is preferable to use cupric chloride (CuC12) and ferric chloride (FeCl3), respectively, but cuprous chloride (CuC1) and ferrous chloride (FeC12) may also be used because they are respectively oxidized into cupric chloride (CuC12 ) and ferric chloride (FeCl3) by supplying oxidant to the leaching solution.
(0049) The concentration of the chloride ions in the gold-leaching solution used in the gold leaching step is preferably 30g/L-180g/L. The concentration of the bromide ions in the gold- leaching solution is preferably 1g/L-100g/L from the standpoints of the reaction rate and the solubility, and more preferably 10g/L-40g/L from the economical standpoint. And, the total concentration of the chloride ions and bromide ions is preferably 120g/L-200g/L. Also, the weight ratio of bromide ions to chloride ions in the gold- leaching solution is preferably at least 1.
(0050) The oxidation-reduction potential (reference electrode is Ag/AgC1 electrode) of the leaching solution at the beginning of the gold leaching step (right before contacting of the ores with leaching-solution) is preferably at least 550mV, more preferably at least 600mV, from the standpoint of acceleration of the gold-leaching. Also, during gold-leaching process, it is preferred to maintain the potential at 550mV or more and more preferably at least 600 mV. Also, to promote the gold-leaching, the pH of the leaching solution is preferably maintained at 2.0 or less and preferably 1.8 or less.
The temperature of the gold-leaching solution is preferably at least 45 C, and more preferably at least 60 C from the standpoint of acceleration of the gold-leaching.
However, excessively high temperature will cause evaporation of the leaching solution or increase the costs for heating, and accordingly 95 C or less is preferable and 85 C or less is more preferable.
(0051) Accordingly, in a preferred embodiment of the present invention, a mixed solution containing at least one of hydrochloric acid and hydrobromic acid, at least one of the cupric chloride and cupric bromide, and at least one of ferric chloride and ferric bromide may be used as the gold-leaching solution in the gold leaching step on the condition that both of chloride ions and bromide ions are contained in the leaching solution.
(0052)
9 The oxidation-reduction potential is controlled by supplying the oxidant while conducting the gold-leaching step. If the oxidant is not supplied, the oxidation-reduction potential will be decreased and thus the leaching reaction will not proceed.
Though there is no particular restriction to the oxidant, oxygen, air, chlorine, bromine and hydrogen peroxide or the like may be cited. An oxidant having excessively high oxidation-reduction potential is not necessary and the air is sufficient. The air is preferred from the standpoint of the cost and safety.
(0053) After pretreatment but before the gold-leaching step, various treatments for removing impurities in the gold ore may be performed. For example, elemental sulfur can be removed by heating the pretreated gold ore to a temperature at which the elemental sulfur is molten and then separating the elemental sulfur and gold by filtration.
(0054) After the leaching of gold and the subsequent solid/liquid separation, gold can be recovered from the resulting gold solution. Although there is no particular restriction to the method for recovering the gold, adsorption on activated carbon, electrowinning, solvent extraction, reduction, cementation and ion exchange or the like may be utilized. Sulfur component may remain as sulfate, sulfide and elemental sulfur in the post gold-leaching solution but the gold leached in the solution can be separated from them by solvent-extraction.
(0055) Further, it is also effective to recover gold during the leaching reaction, whereby the concentration of gold in the leaching solution is lowered, and as a result the leaching ratio of gold is increased. This can be performed, for example, by introducing activated carbon with or without lead nitrate into the gold-leaching solution during the leaching reaction.
(0056) [Examples]
In the following, the present invention will further be specifically explained by way of working examples. It should be noted that the present invention is not restricted to the examples. The analysis of the metals used in the working examples was performed according to ICP-AES. However, the analysis of the gold used in the examples was conducted according to ICP-AES for quantitative analysis after causing deposition of gold in the specimens by cupellation process (JIS M8111).
(0057) [Comparative Example 1]
Pyrite ore concentrate (produced in Papua New Guinea) was prepared as gold ore.
The content of pyrite in this pyrite ore concentrate was determined by XRD and chemical analysis, and 17 mass% of pyrite was confirmed. In addition, the ratio of S
(mass%)/Au(mass ppm) in the concentrate was 1.4. Fesoi/Feati was determined to be 0 by the method explained earlier.
(0058) The pyrite ore concentrate was milled and ground in a ball mill to adjust the particle size to 50p.m at the particle size d80, namely, the particle size at which the cumulative weight becomes 80% in the distribution curve of cumulative weight particle sizes. The d80 was the average of three measurements which were conducted using the laser diffraction particle size distribution analyzer (Shimadzu Corporation Model No. SALD2100). Subsequently, leaching operation was conducted on the ground pyrite ore concentrate (200g), using a hydrochloric acidic gold leaching solution having the composition as listed in Table 1, with pulp concentration of 100 g/L at a temperature of 85 C for 90 hrs. Air was blown in (0.1 L/min per 1L of the concentrate) during the leaching operation with continuous agitation and the oxidation-reduction potential (ORP: vs. Ag/AgC1) was maintained at 530mV or higher.
Also, during the leaching, the pH of the gold leaching solution was maintained at 1.0-1.1 by appropriately adding hydrochloric acid.
(0059) Gold leaching solution FeCl3-6H20(g/L) 10 CuC12-2H20(g/L) 48 NaCl(g/L) 25 NaBr(g/L) 103 All chloride ions(g/L) 40 All bromide ions(g/D 80 ORP(mV) 717 (vs.Ag/AgC1) pH 1.52 (0060) During the leaching test, samples of the leaching residue were periodically taken and the Au grade was determined. Fig. 1 shows the relation between the leaching time versus Au grade in the residue obtained from the test. Refer to the plotting of FeS2 (refer to the plot of "without FeS2 pyrolysis" in Fig. 1). From this result, it is ascertained that it took 90 hours for the Au grade in the residue, which was approximately 6g/t at the start, to decrease to 0.9g/t.
(0061) <Example 1>
The ground pyrite ore concentrate (1.5kg) which was identical with that of Comparative Example 1 was charged in a tubular furnace and one hour was spent to raise the temperature to 700 C (the rate of temperature increase=10 C /min) under the nitrogen atmosphere. It was thereafter heated for one hour. After allowing it to cool to a room temperature, it was confirmed that the peak of FeS2 contained in the original ore had disappeared and a peak of FeS had been found by the XRD
analysis before and after the heat treatment, the elemental sulfur resulting from the heat treatment was naturally removed from pyrite ore by solid-gas separation.
(0062) For the pyrite concentrate after the heat treatment, Fesot/Feall was determined to be 0.98 by the method explained earlier.
(0063) Subsequently, using a hydrochloric acidic solution of the gold-leaching solution having the same composition as in Comparative Example 1, leaching was conducted on the heat-treated pyrite ore concentrate with pulp concentration of 100g/L
at the solution temperature of 85 C for 18 hours. Air was blown during the leaching (at the rate of 0.1L/min per 1L of the concentrate) while agitation was kept and the oxidation-reduction potential (ORP:vs Ag/AgCD was maintained at least 400mV.
During the leaching, hydrochloric acid was appropriately added to keep the pH
of the gold-leaching solution at 1.0-1.1.
(0064) During leaching test, samples of the leaching residue were periodically taken and the Au grade was determined. Fig. 1 shows the relation between the leaching time versus Au grade in the residue obtained from the test (refer to the plot of "with FeS2 pyrolysis" in Fig. 1). From this result, it is ascertained that it took only 12 hours for the Au grade in the residue, which was approximately 6g/t at the start, to decrease to 0.6g/t. Incidentally, when using a gold leaching solution with no bromide ions, roughly similar results were obtained though the Au leaching speed was lower than the case with bromide ions.
(0065) <The change in Fesoi/Feall caused by pyrolysis condition>
Using 1.5 kg of the ground pyrite ore concentrate used in Example 1, the change of Fesot/Fean was investigated when the retention temperature and the retention time was changed as shown in Table 2. The value of Fesoi/Feau was determined in the same procedure as in Example 1. The test was conducted using a tubular furnace under the nitrogen atmosphere. The elemental sulfur generated by pyrolysis was evaporated and purged by a nitrogen stream. The temperature was increased at a rate of C/min for all tests. Cooling was conducted by allowing it cool to a room temperature. The results are shown in Table2.
(0066) Table 2 Heating Condition Feso/Fean Retention Retention temp.( C) time(min) Before heat treatment 0 550 60 0.48 550 120 0.54 600 5 0.49 600 30 0.61 600 60 0.76 650 60 0.95 700 60 0.98 (0067) From the result shown in Table 2, it is understood that the retention temperature of 650 C or more and the retention time of 60 minutes or more is most preferable as Fesol/Fean reaches close to 1.
(0068) <Example 2: The temperature at which pyrolysis occurs.>
On the ground pyrite ore concentrate used in Example 1, the weight change and the endothermic/exothermic heat at respective temperatures were monitored, using the thermal analysis device (Model TG/DTA6300 manufactured by Seiko). The results are shown in Fig. 2. From the fact that the mass decrease begins at 450 C and simultaneously the change of calorific value is observed. It is confirmed that the pyrolysis of the pyrite begins. Under the nitrogen atmosphere, pyrolysis does not occur until the temperature reaches 450 C. It should be noted that, from the results of the XRD analysis, a long period of time is necessary for pyrolisys and accordingly heat treatment at 600 C or higher is desirable.
Though there is no particular restriction to the oxidant, oxygen, air, chlorine, bromine and hydrogen peroxide or the like may be cited. An oxidant having excessively high oxidation-reduction potential is not necessary and the air is sufficient. The air is preferred from the standpoint of the cost and safety.
(0053) After pretreatment but before the gold-leaching step, various treatments for removing impurities in the gold ore may be performed. For example, elemental sulfur can be removed by heating the pretreated gold ore to a temperature at which the elemental sulfur is molten and then separating the elemental sulfur and gold by filtration.
(0054) After the leaching of gold and the subsequent solid/liquid separation, gold can be recovered from the resulting gold solution. Although there is no particular restriction to the method for recovering the gold, adsorption on activated carbon, electrowinning, solvent extraction, reduction, cementation and ion exchange or the like may be utilized. Sulfur component may remain as sulfate, sulfide and elemental sulfur in the post gold-leaching solution but the gold leached in the solution can be separated from them by solvent-extraction.
(0055) Further, it is also effective to recover gold during the leaching reaction, whereby the concentration of gold in the leaching solution is lowered, and as a result the leaching ratio of gold is increased. This can be performed, for example, by introducing activated carbon with or without lead nitrate into the gold-leaching solution during the leaching reaction.
(0056) [Examples]
In the following, the present invention will further be specifically explained by way of working examples. It should be noted that the present invention is not restricted to the examples. The analysis of the metals used in the working examples was performed according to ICP-AES. However, the analysis of the gold used in the examples was conducted according to ICP-AES for quantitative analysis after causing deposition of gold in the specimens by cupellation process (JIS M8111).
(0057) [Comparative Example 1]
Pyrite ore concentrate (produced in Papua New Guinea) was prepared as gold ore.
The content of pyrite in this pyrite ore concentrate was determined by XRD and chemical analysis, and 17 mass% of pyrite was confirmed. In addition, the ratio of S
(mass%)/Au(mass ppm) in the concentrate was 1.4. Fesoi/Feati was determined to be 0 by the method explained earlier.
(0058) The pyrite ore concentrate was milled and ground in a ball mill to adjust the particle size to 50p.m at the particle size d80, namely, the particle size at which the cumulative weight becomes 80% in the distribution curve of cumulative weight particle sizes. The d80 was the average of three measurements which were conducted using the laser diffraction particle size distribution analyzer (Shimadzu Corporation Model No. SALD2100). Subsequently, leaching operation was conducted on the ground pyrite ore concentrate (200g), using a hydrochloric acidic gold leaching solution having the composition as listed in Table 1, with pulp concentration of 100 g/L at a temperature of 85 C for 90 hrs. Air was blown in (0.1 L/min per 1L of the concentrate) during the leaching operation with continuous agitation and the oxidation-reduction potential (ORP: vs. Ag/AgC1) was maintained at 530mV or higher.
Also, during the leaching, the pH of the gold leaching solution was maintained at 1.0-1.1 by appropriately adding hydrochloric acid.
(0059) Gold leaching solution FeCl3-6H20(g/L) 10 CuC12-2H20(g/L) 48 NaCl(g/L) 25 NaBr(g/L) 103 All chloride ions(g/L) 40 All bromide ions(g/D 80 ORP(mV) 717 (vs.Ag/AgC1) pH 1.52 (0060) During the leaching test, samples of the leaching residue were periodically taken and the Au grade was determined. Fig. 1 shows the relation between the leaching time versus Au grade in the residue obtained from the test. Refer to the plotting of FeS2 (refer to the plot of "without FeS2 pyrolysis" in Fig. 1). From this result, it is ascertained that it took 90 hours for the Au grade in the residue, which was approximately 6g/t at the start, to decrease to 0.9g/t.
(0061) <Example 1>
The ground pyrite ore concentrate (1.5kg) which was identical with that of Comparative Example 1 was charged in a tubular furnace and one hour was spent to raise the temperature to 700 C (the rate of temperature increase=10 C /min) under the nitrogen atmosphere. It was thereafter heated for one hour. After allowing it to cool to a room temperature, it was confirmed that the peak of FeS2 contained in the original ore had disappeared and a peak of FeS had been found by the XRD
analysis before and after the heat treatment, the elemental sulfur resulting from the heat treatment was naturally removed from pyrite ore by solid-gas separation.
(0062) For the pyrite concentrate after the heat treatment, Fesot/Feall was determined to be 0.98 by the method explained earlier.
(0063) Subsequently, using a hydrochloric acidic solution of the gold-leaching solution having the same composition as in Comparative Example 1, leaching was conducted on the heat-treated pyrite ore concentrate with pulp concentration of 100g/L
at the solution temperature of 85 C for 18 hours. Air was blown during the leaching (at the rate of 0.1L/min per 1L of the concentrate) while agitation was kept and the oxidation-reduction potential (ORP:vs Ag/AgCD was maintained at least 400mV.
During the leaching, hydrochloric acid was appropriately added to keep the pH
of the gold-leaching solution at 1.0-1.1.
(0064) During leaching test, samples of the leaching residue were periodically taken and the Au grade was determined. Fig. 1 shows the relation between the leaching time versus Au grade in the residue obtained from the test (refer to the plot of "with FeS2 pyrolysis" in Fig. 1). From this result, it is ascertained that it took only 12 hours for the Au grade in the residue, which was approximately 6g/t at the start, to decrease to 0.6g/t. Incidentally, when using a gold leaching solution with no bromide ions, roughly similar results were obtained though the Au leaching speed was lower than the case with bromide ions.
(0065) <The change in Fesoi/Feall caused by pyrolysis condition>
Using 1.5 kg of the ground pyrite ore concentrate used in Example 1, the change of Fesot/Fean was investigated when the retention temperature and the retention time was changed as shown in Table 2. The value of Fesoi/Feau was determined in the same procedure as in Example 1. The test was conducted using a tubular furnace under the nitrogen atmosphere. The elemental sulfur generated by pyrolysis was evaporated and purged by a nitrogen stream. The temperature was increased at a rate of C/min for all tests. Cooling was conducted by allowing it cool to a room temperature. The results are shown in Table2.
(0066) Table 2 Heating Condition Feso/Fean Retention Retention temp.( C) time(min) Before heat treatment 0 550 60 0.48 550 120 0.54 600 5 0.49 600 30 0.61 600 60 0.76 650 60 0.95 700 60 0.98 (0067) From the result shown in Table 2, it is understood that the retention temperature of 650 C or more and the retention time of 60 minutes or more is most preferable as Fesol/Fean reaches close to 1.
(0068) <Example 2: The temperature at which pyrolysis occurs.>
On the ground pyrite ore concentrate used in Example 1, the weight change and the endothermic/exothermic heat at respective temperatures were monitored, using the thermal analysis device (Model TG/DTA6300 manufactured by Seiko). The results are shown in Fig. 2. From the fact that the mass decrease begins at 450 C and simultaneously the change of calorific value is observed. It is confirmed that the pyrolysis of the pyrite begins. Under the nitrogen atmosphere, pyrolysis does not occur until the temperature reaches 450 C. It should be noted that, from the results of the XRD analysis, a long period of time is necessary for pyrolisys and accordingly heat treatment at 600 C or higher is desirable.
Claims (6)
1. A method of hydrometallurgically recovering gold from gold ore which contains pyrite (FeS2), comprising a pretreatment of converting the pyrite contained in the gold ore to iron compound soluble to hydrochloric acid, and a step of hydrometallurgically recovering gold using an acidic bath from the gold ore after the pretreatment, wherein the pretreatment involves heating the gold ore to 450°C or more under a non-oxidative atmosphere.
2. The method of hydrometallurgically recovering gold according to claim 1, wherein a ratio of a content of Fe soluble to hydrochloric acid (Fe sol) contained in the gold ore after pretreatment with respect to a content of total Fe (Fe all) contained in the gold ore after pretreatment becomes 0.6 or more.
3. The method of hydrometallurgically recovering gold according to claim 1 or 2, wherein the iron compound soluble to hydrochloric acid contained in the gold ore after pretreatment is sulfide.
4. The method of hydrometallurgically recovering gold according to any one of claims 1 to 3, wherein a content of the pyrite in the gold ore prior to pretreatment is 5 to 80 mass%.
5. The method of hydrometallurgically recovering gold according to any one of claims 1 to 4, wherein S (mass%)/Au (mass ppm) in the gold ore prior to pretreatment is 1 to 20.
6. The method of hydrometallurgically recovering gold according to any one of claims 1 to 5, wherein the heat treatment is carried out under the conditions of retaining the gold ore at 600-750°C for 5-60 minutes.
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