CA2506780A1 - Recovery of cadmium from zinc-containing acid soluble ore using precipitation method - Google Patents
Recovery of cadmium from zinc-containing acid soluble ore using precipitation method Download PDFInfo
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- CA2506780A1 CA2506780A1 CA002506780A CA2506780A CA2506780A1 CA 2506780 A1 CA2506780 A1 CA 2506780A1 CA 002506780 A CA002506780 A CA 002506780A CA 2506780 A CA2506780 A CA 2506780A CA 2506780 A1 CA2506780 A1 CA 2506780A1
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- Prior art keywords
- zinc
- cadmium
- leach solution
- leaching
- copper
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- 239000011701 zinc Substances 0.000 title claims abstract description 100
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 title claims abstract description 99
- 229910052725 zinc Inorganic materials 0.000 title claims abstract description 92
- 238000000034 method Methods 0.000 title claims abstract description 70
- 239000002253 acid Substances 0.000 title claims abstract description 32
- 229910052793 cadmium Inorganic materials 0.000 title claims abstract description 20
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 238000001556 precipitation Methods 0.000 title description 19
- 238000011084 recovery Methods 0.000 title description 10
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims abstract description 108
- 239000011787 zinc oxide Substances 0.000 claims abstract description 46
- 239000000463 material Substances 0.000 claims abstract description 39
- 238000002386 leaching Methods 0.000 claims abstract description 32
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000001117 sulphuric acid Substances 0.000 claims abstract description 20
- 235000011149 sulphuric acid Nutrition 0.000 claims abstract description 20
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052802 copper Inorganic materials 0.000 claims abstract description 19
- 239000010949 copper Substances 0.000 claims abstract description 19
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 16
- 230000001376 precipitating effect Effects 0.000 claims abstract description 15
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000000292 calcium oxide Substances 0.000 claims abstract description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 30
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 24
- 229910052751 metal Inorganic materials 0.000 claims description 15
- 239000002184 metal Substances 0.000 claims description 15
- 239000000377 silicon dioxide Substances 0.000 claims description 15
- 238000000926 separation method Methods 0.000 claims description 14
- 239000007787 solid Substances 0.000 claims description 14
- 229910052742 iron Inorganic materials 0.000 claims description 12
- 150000002739 metals Chemical class 0.000 claims description 10
- 238000006386 neutralization reaction Methods 0.000 claims description 10
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 9
- 239000000920 calcium hydroxide Substances 0.000 claims description 9
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 9
- 235000011116 calcium hydroxide Nutrition 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 8
- 239000000395 magnesium oxide Substances 0.000 claims description 8
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 7
- -1 copper and cadmium Chemical class 0.000 claims description 3
- 150000007514 bases Chemical class 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 48
- 238000005188 flotation Methods 0.000 description 24
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 18
- 238000004513 sizing Methods 0.000 description 15
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 10
- 229910052602 gypsum Inorganic materials 0.000 description 10
- 239000010440 gypsum Substances 0.000 description 10
- 239000001175 calcium sulphate Substances 0.000 description 9
- 235000011132 calcium sulphate Nutrition 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 9
- 239000011686 zinc sulphate Substances 0.000 description 9
- 235000009529 zinc sulphate Nutrition 0.000 description 9
- 239000011575 calcium Substances 0.000 description 8
- 239000002244 precipitate Substances 0.000 description 8
- 229910052787 antimony Inorganic materials 0.000 description 7
- 238000005363 electrowinning Methods 0.000 description 7
- 239000000706 filtrate Substances 0.000 description 7
- 239000002002 slurry Substances 0.000 description 7
- 229910052785 arsenic Inorganic materials 0.000 description 6
- 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
- IZBZQUREHISXFJ-UHFFFAOYSA-N 2-[4-chloro-5-methyl-3-(trifluoromethyl)pyrazol-1-yl]acetic acid Chemical compound CC1=C(Cl)C(C(F)(F)F)=NN1CC(O)=O IZBZQUREHISXFJ-UHFFFAOYSA-N 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- 229910000368 zinc sulfate Inorganic materials 0.000 description 5
- FMRLDPWIRHBCCC-UHFFFAOYSA-L Zinc carbonate Chemical compound [Zn+2].[O-]C([O-])=O FMRLDPWIRHBCCC-UHFFFAOYSA-L 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 125000002091 cationic group Chemical group 0.000 description 4
- GTGUCSIFKYFMNY-UHFFFAOYSA-N dodecylazanium;hydrogen sulfate Chemical compound OS(O)(=O)=O.CCCCCCCCCCCCN GTGUCSIFKYFMNY-UHFFFAOYSA-N 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 238000000605 extraction Methods 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 230000003472 neutralizing effect Effects 0.000 description 4
- YIBBMDDEXKBIAM-UHFFFAOYSA-M potassium;pentoxymethanedithioate Chemical compound [K+].CCCCCOC([S-])=S YIBBMDDEXKBIAM-UHFFFAOYSA-M 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000011667 zinc carbonate Substances 0.000 description 4
- 229910000010 zinc carbonate Inorganic materials 0.000 description 4
- 235000004416 zinc carbonate Nutrition 0.000 description 4
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 235000011941 Tilia x europaea Nutrition 0.000 description 3
- 239000004110 Zinc silicate Substances 0.000 description 3
- 238000013019 agitation Methods 0.000 description 3
- 238000013459 approach Methods 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 239000012141 concentrate Substances 0.000 description 3
- ZOIVSVWBENBHNT-UHFFFAOYSA-N dizinc;silicate Chemical compound [Zn+2].[Zn+2].[O-][Si]([O-])([O-])[O-] ZOIVSVWBENBHNT-UHFFFAOYSA-N 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 3
- 235000019352 zinc silicate Nutrition 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000005083 Zinc sulfide Substances 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 150000004760 silicates Chemical class 0.000 description 2
- UGZADUVQMDAIAO-UHFFFAOYSA-L zinc hydroxide Chemical compound [OH-].[OH-].[Zn+2] UGZADUVQMDAIAO-UHFFFAOYSA-L 0.000 description 2
- 229910021511 zinc hydroxide Inorganic materials 0.000 description 2
- 229940007718 zinc hydroxide Drugs 0.000 description 2
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 2
- HJTAZXHBEBIQQX-UHFFFAOYSA-N 1,5-bis(chloromethyl)naphthalene Chemical compound C1=CC=C2C(CCl)=CC=CC2=C1CCl HJTAZXHBEBIQQX-UHFFFAOYSA-N 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical group [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- GOLCXWYRSKYTSP-UHFFFAOYSA-N arsenic trioxide Inorganic materials O1[As]2O[As]1O2 GOLCXWYRSKYTSP-UHFFFAOYSA-N 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000008396 flotation agent Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 239000011133 lead Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000001226 reprecipitation Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910021653 sulphate ion Inorganic materials 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
- 150000003751 zinc Chemical class 0.000 description 1
- 150000003752 zinc compounds Chemical class 0.000 description 1
- 235000014692 zinc oxide Nutrition 0.000 description 1
Classifications
-
- 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
- Manufacture And Refinement Of Metals (AREA)
Abstract
The present invention relates to an apparatus and a process for producing zinc oxide from an acid soluble zinc-bearing material. The process according to the present invention comprises the steps of leaching the zinc oxide material with sulphuric acid;
precipitating copper and cadmium from the leach solution using a base such as calcium oxide; removing copper, cadmium from the leach solution by cementation with zinc dust.
precipitating copper and cadmium from the leach solution using a base such as calcium oxide; removing copper, cadmium from the leach solution by cementation with zinc dust.
Description
WO 02/065.11 PCT/CA01/0087.1 PRODUCTION OF ZINC OXIDE FROM ACID SOLUBLE ORE USING
PRECIPITATION METHOD
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to method and apparatus for the extraction and recovery of zinc from zino-bearing materials (solutions or solids) through a process carried out in a sulphuric acid media by leaching the zinc followed by precipitation of zinc as oxide and upgrading zinc content in precipitates by flotation or granulometric sizing.
Description of the Related Art Acid soluble zinc ores (zinc oxide, zinc carbonate, zinc silicate, etc.) have been used in the production of zinc metal since the very beginnings of the industry. The leaching of theses ores and purification of impurities associated with these ores are well established. Wood, in a paper published in the Journal of Metals, Vol. 29, page 7, incorporated herein by reference, describes a process for the hydrometallurgical treatment of zinc silicate. U.S. Patent No. 3,954,937, incorporated herein by reference, provide a process which utilizes a series of leaching tanks in which the acidity is progressively increased over a period of at least three hours, in such a quantity that the final acidity of the solution will be 1.5 to 1 S gn, while carefully maintaining the temperature at 70° to 90°C, thereby inducing the lixiviation of the material and simultaneously the reprecipitation of silica in a crystalline form which can be eliminated by filtration. U.S.
Patent No.
3,656,941, incorporated herein by reference, describes a process for the recovery of metal values from a siliceous zinc ore whereby the ore is treated with sulphuric acid in a WO 02/065.11 PCT/CA0110087~
PRECIPITATION METHOD
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to method and apparatus for the extraction and recovery of zinc from zino-bearing materials (solutions or solids) through a process carried out in a sulphuric acid media by leaching the zinc followed by precipitation of zinc as oxide and upgrading zinc content in precipitates by flotation or granulometric sizing.
Description of the Related Art Acid soluble zinc ores (zinc oxide, zinc carbonate, zinc silicate, etc.) have been used in the production of zinc metal since the very beginnings of the industry. The leaching of theses ores and purification of impurities associated with these ores are well established. Wood, in a paper published in the Journal of Metals, Vol. 29, page 7, incorporated herein by reference, describes a process for the hydrometallurgical treatment of zinc silicate. U.S. Patent No. 3,954,937, incorporated herein by reference, provide a process which utilizes a series of leaching tanks in which the acidity is progressively increased over a period of at least three hours, in such a quantity that the final acidity of the solution will be 1.5 to 1 S gn, while carefully maintaining the temperature at 70° to 90°C, thereby inducing the lixiviation of the material and simultaneously the reprecipitation of silica in a crystalline form which can be eliminated by filtration. U.S.
Patent No.
3,656,941, incorporated herein by reference, describes a process for the recovery of metal values from a siliceous zinc ore whereby the ore is treated with sulphuric acid in a WO 02/065.11 PCT/CA0110087~
continuous manner in stirred tanks. U.S. Patent No. 5,585,079, incorporated herein by reference, describes a method for recovering zinc from a zinc oxide bearing material containing silicates. According to this method, the leaching of zinc compounds is carried out in circumstances where the silicates remain undissolved and consequently do not cause filtering problems. The silicate bearing residue is treated in a Waelz process.
Although, there are many processes that can provide a method to dissolve zinc from .
the acid soluble zinc ore and precipitate impurities such as iron and silica to make filtrate filterable, none of the above-mentioned techniques addresses a process to recover zinc from zinc bearing solutions. Most of the above-mentioned processes use conventional electrowinning process to recover zinc from zinc sulphate solutions.
Electrowinning is well known technology, however, it requires high capital cost. Therefore, it is only suitable technology if the metal value is significant enough to build an electrowinning plant or, otherwise, a recovery process has to be located at and integrated with present zinc refineries.
Another problem with the conventional electrowinning process is that the zinc concentration level must be higher than a certain level to operate. Therefore, if the zinc concentration in the final filtrate of the leaching operation is not high enough, the zinc concentration in the ~Itrate of leached acid soluble zinc materials has to be upgraded.
Zinc in the solution can be conc~trated by several known methods, such as solvent extraction or ion exchange. However, those processes have several drawbacks, such as limitation of extraction capacity, organic substance contamination and high capital cost. In addition, these approaches still require a conventional electrowinning process to recover , zinc from zinc bearing solution.
Another approach to recover zinc from the zinc bearing solution is to precipitate WO 02/065x1 PCT/CAOI/0087.~
zinc from the solution itself. The precipitated zinc now can be easily sent to the zinc refineryor other facilities which requires such materials. Zinc can be precipitated from zinc sulphate solution as zinc oxide, zinc hydroxide, or basic zinc sulphate by adding alkaline. Also, zinc can be precipitated as zinc sulphide by adding sulphide or as zinc carbonate by adding carbon dioxide. However, the operation of the process for producing zinc sulphide or zinc carbonate is expensive. Also, producing zinc hydroxide causes severe filtering problems and producing basic zinc sulphate results in high transportation cost since the grade of zinc in basic zinc sulphate is very low. Producing zinc oxide is the most suitable approach, but unless you are using sodium hydroxide, which is very expensive reagent, the zinc oxide will be contaminated with a large amount of gypsum that is co-precipitated during zinc oxide precipitation.
Therefore, it is desirable to develop a process for producing zinc oxide from zinc sulphate solution that is originated from acid soluble zinc materials.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an apparatus for producing zinc oxide firom an acid soluble zino-containing material. The apparatus comprises a leaching unit for leaching the acid soluble zinc-containing material with sulphuric acid, a first precipitating unit for precipitating iron, silica and other metals (Al, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH~, MgO, Zn0), and removing, copper, cadmium, nickel and cobalt from the leach solution by cementation with zinc dust. A second precipitating unit is used to precipitate zinc oxide from the leach solution using calcium oxide (or Ca(OH)Z). Then the precipitated zinc oxide is separated from calcium sulphate by flotation with cationic collectors such as dodecylamine hydrochloride, and dodecylamine sulphate, WO 02/06~.t1 PCT/CA01/0087.1 andlor potassium amyl xanthate as a collector. This separation of zinc oxide from calciut»
sulphate also can be achieved by granulometric sizing. In addition, a combination of the two techniques (sizing and flotation) can be used for separating of zinc oxide from calcium sulphate, In addition, the tailing of these steps can be recycled to the leaching step to recover zinc value.
A further object of the present invention is to provide a process for producing zinc oxide from an acid soluble zinc-containing material. The process comprises the steps of leaching the acid soluble zinc material with sulphuric acid, precipitating iron, silica and other metals (Al, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH)2, MgO, Zn0), cementing copper, cadmium, nickel and cobalt in the Ieach solution with zinc dust, and precipitating zinc oxide from the leach solution using calcium oxide (or Ca(OH)2). Then the precipitated zinc oxide is separated from calcium sulphate by flotation with cationic collectors such as dodecylamine hydrochloride, and dodecylamine sulphate, andlor potassium amyl xanthate. The separation of zinc oxide from calcium sulphate can also be achieved by granulometric sizing. In addition, a combination of the two techniques (granulometric sizing and flotation) can be used for separating zinc oxide from calcium sulphate. The tailing of these steps can also be recycled to the leaching step to recover zinc value.
Still another object of the present invention is to provide a zinc oxide precipitate thaf is substantially free of basic zinc sulphate by leaching an acid soluble zinc-containing material with sulphuric acid. Iron, silica and other metals {Al, As, Sb, etc.) are precipitated from the hch solution u~ing calcium oxide (or Ca(OH~, MgO, Zn0), and copper, , cadmium, nickel and cobalt are cemented from the leach solution using zinc dust. Zinc oxide is precipitated from the leach solution using calcium oxide.
WO 02/0651 PCT/CA01/0087.1 A further object of the present invention is to provide a process for recovering copper and cadmium from an acid soluble zino-containing material. The process comprises the steps of leaching the acid soluble zinc material with sulphuric acid, precipitating iron, silica and other metals (Al, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH)2, MgO, Zn0) and recovering copper and cadmium from the leach solution by cementing with zinc dust.
Still another object of the present invention is to provide a process for separating zinc oxide from gypsum, which precipitates during zinc oxide precipitation.
The process comprisesd the steps of leaching the acid soluble zinc-containing material with sulphuric acid, precipitating iron, silica and other metals (AL, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH~, MgO, Zn0), and cementing copper, cadmium, nickel and cobalt frorri the leach solution using zinc dust. The precipitated zinc oxide is separated from co-precipitated gypsum by flotation with cationic collectors such as dodecylamine hydrochloride, and dodecylamine sulphate, and/or potassium amyl xanthate as a collector.
The separation of zinc oxide from calcium sulphate can also be achieved by granulometric sizing. In addition, a combination of the two techniques (granulometric sizing and flotation) can be used for separating zinc oxide from calcium sulphate. The tailing of the flotation step can also be recycled to the leaching step to recover zinc value.
The invention is described in more detail below with reference to the accompanying figure.
BRIEF DESCRIPTION OF THE DRAWIrIGS
Figure 1 is a flowchart illustrating the preferred process for producing zinc oxide from an acid soluble zinc material using the invented process.
wo ozio6:;.n pcT~cAOnoog~.~
Figure 2 is a flowchart illustrating the preferred process for producing zinc oxide from an acid soluble zinc material using the invented process including the granulometric sizing stage.
Figure 3 is a schematic block diagram depicting the apparatus according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
1. Introduction The present invention relates to method and apparatus for the extraction and recovery of zinc from zino-bearing materials (solutions or solids) through a process carried out in a sulphuric acid media by leaching the zinc followed by precipitation of zinc as oxide and upgrading the zinc content in precipitates by flotation or granulometric sizing.
This upgrading of zinc also can be achieved by using a granulometric sizing technique.
This process also allows for the recovery of other metals, such as iron, copper, nickel, cobalt, lead, silver, cadmium, etc. The present invention further relates to a process for producing zinc oxide from an acid soluble zinc material, an apparatus for performing the process, and processes for recovering iron, copper, and cadmium from an acid soluble zinc material. More particularly, the invention relates to a pmcess of producing zinc oxide from such an acid soluble zinc material by, preferably, leaching the acid soluble zinc material with sulphuric acid, followed by precipitation of iron, silica and other metals (AI, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH)2, MgO, Zn0), and cementation of copper, cadmium and cobalt using zinc dust. Zinc oxide may then be precipitated from the leach solution using calcium oxide as a mixture of zinc oxide and calcium sulphate. The zinc grade in the mixture of zinc oxide and calcium sulphate may WO 02/065.11 PCT/CA01/0087.1 be improved by flotation andlor granulometric sizing techniques. The novelty of this invention is precipitating zinc oxide from zinc sulphate solution and upgrading zinc content by flotation and/or granulometric sizing techniques.
By the phrase "acid soluble zinc materials" as used in this specification is meant primarily a zinc silicate ore but it is also intended to include zinc oxide ore, zinc carbonate ore and a zinc materials containing substantial quantities of soluble zinc in sulphuric acid The presently preferred process of the present invention is comprised of a series of steps, as will be described in detail below.
2. Leaching and Neutralization According to a preferred embodiment of the present invention there is provided a process for the recovery of metal values from an acid soluble ore, where the process is conducted in a continuous concurrent manner. A process comprises a first stage, effected in one or more vessels, in which the said ore is leached with aqueous sulphuric acid to an end-point pH in the range 1.0 to 4.0, preferably in the range 1.5 to 2.5, to obtain a leach liquor or pulp containing dissolved zinc values and other impurities including silica and iron. A second stage, effected in one or more vessels, in which the pH of the liquor or pulp from the first stage is raised, for example by addition of neutralising agent, to a pH in the range 3 to 6, preferably in the range 3.5 to 4.5, such that substantially the whole or a major part of the silica. content of said leach liquor or pulp is converted into a form in which it is readily separated by conventional techniques.
Both process stages may be operated successfully at temperatures up to the boiling points of the solutions at atmospheric pressure, and operating temperatures between ambient temperature and about 95°C are therefore envisaged. The aqueous sulphuric acid WO 02/065.11 PCT/CA01/0087.!
s necessary for the treatment of the acid soluble ores. Spent electrolyte from a conventional process for the electrowinning of zinc, or such spent electrolyte fortified to compensate for acid losses, may conveniently be used as a leaching agent. Residence times of the liquor or pulp in each of the process stages may lie in the range 30 minutes to 10 hours, with a preferred residence time in the first stage of 1 - 4 hours, and a preferred residence time in the second stage of 1 to 6 hours.
The pulp leaving from the second stage contains suspended silica and iron hydroxide in particulate form, and will be subjected to solid liquid separation by using thickening process or conventional filtering technology. In some circumstance it may be desirable to re-circulate portions of pulp or thickened pulp from the second stage to first or second stages of the process.
The filtrate from this step is sent to cementation.
Although, there are many processes that can provide a method to dissolve zinc from .
the acid soluble zinc ore and precipitate impurities such as iron and silica to make filtrate filterable, none of the above-mentioned techniques addresses a process to recover zinc from zinc bearing solutions. Most of the above-mentioned processes use conventional electrowinning process to recover zinc from zinc sulphate solutions.
Electrowinning is well known technology, however, it requires high capital cost. Therefore, it is only suitable technology if the metal value is significant enough to build an electrowinning plant or, otherwise, a recovery process has to be located at and integrated with present zinc refineries.
Another problem with the conventional electrowinning process is that the zinc concentration level must be higher than a certain level to operate. Therefore, if the zinc concentration in the final filtrate of the leaching operation is not high enough, the zinc concentration in the ~Itrate of leached acid soluble zinc materials has to be upgraded.
Zinc in the solution can be conc~trated by several known methods, such as solvent extraction or ion exchange. However, those processes have several drawbacks, such as limitation of extraction capacity, organic substance contamination and high capital cost. In addition, these approaches still require a conventional electrowinning process to recover , zinc from zinc bearing solution.
Another approach to recover zinc from the zinc bearing solution is to precipitate WO 02/065x1 PCT/CAOI/0087.~
zinc from the solution itself. The precipitated zinc now can be easily sent to the zinc refineryor other facilities which requires such materials. Zinc can be precipitated from zinc sulphate solution as zinc oxide, zinc hydroxide, or basic zinc sulphate by adding alkaline. Also, zinc can be precipitated as zinc sulphide by adding sulphide or as zinc carbonate by adding carbon dioxide. However, the operation of the process for producing zinc sulphide or zinc carbonate is expensive. Also, producing zinc hydroxide causes severe filtering problems and producing basic zinc sulphate results in high transportation cost since the grade of zinc in basic zinc sulphate is very low. Producing zinc oxide is the most suitable approach, but unless you are using sodium hydroxide, which is very expensive reagent, the zinc oxide will be contaminated with a large amount of gypsum that is co-precipitated during zinc oxide precipitation.
Therefore, it is desirable to develop a process for producing zinc oxide from zinc sulphate solution that is originated from acid soluble zinc materials.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an apparatus for producing zinc oxide firom an acid soluble zino-containing material. The apparatus comprises a leaching unit for leaching the acid soluble zinc-containing material with sulphuric acid, a first precipitating unit for precipitating iron, silica and other metals (Al, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH~, MgO, Zn0), and removing, copper, cadmium, nickel and cobalt from the leach solution by cementation with zinc dust. A second precipitating unit is used to precipitate zinc oxide from the leach solution using calcium oxide (or Ca(OH)Z). Then the precipitated zinc oxide is separated from calcium sulphate by flotation with cationic collectors such as dodecylamine hydrochloride, and dodecylamine sulphate, WO 02/06~.t1 PCT/CA01/0087.1 andlor potassium amyl xanthate as a collector. This separation of zinc oxide from calciut»
sulphate also can be achieved by granulometric sizing. In addition, a combination of the two techniques (sizing and flotation) can be used for separating of zinc oxide from calcium sulphate, In addition, the tailing of these steps can be recycled to the leaching step to recover zinc value.
A further object of the present invention is to provide a process for producing zinc oxide from an acid soluble zinc-containing material. The process comprises the steps of leaching the acid soluble zinc material with sulphuric acid, precipitating iron, silica and other metals (Al, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH)2, MgO, Zn0), cementing copper, cadmium, nickel and cobalt in the Ieach solution with zinc dust, and precipitating zinc oxide from the leach solution using calcium oxide (or Ca(OH)2). Then the precipitated zinc oxide is separated from calcium sulphate by flotation with cationic collectors such as dodecylamine hydrochloride, and dodecylamine sulphate, andlor potassium amyl xanthate. The separation of zinc oxide from calcium sulphate can also be achieved by granulometric sizing. In addition, a combination of the two techniques (granulometric sizing and flotation) can be used for separating zinc oxide from calcium sulphate. The tailing of these steps can also be recycled to the leaching step to recover zinc value.
Still another object of the present invention is to provide a zinc oxide precipitate thaf is substantially free of basic zinc sulphate by leaching an acid soluble zinc-containing material with sulphuric acid. Iron, silica and other metals {Al, As, Sb, etc.) are precipitated from the hch solution u~ing calcium oxide (or Ca(OH~, MgO, Zn0), and copper, , cadmium, nickel and cobalt are cemented from the leach solution using zinc dust. Zinc oxide is precipitated from the leach solution using calcium oxide.
WO 02/0651 PCT/CA01/0087.1 A further object of the present invention is to provide a process for recovering copper and cadmium from an acid soluble zino-containing material. The process comprises the steps of leaching the acid soluble zinc material with sulphuric acid, precipitating iron, silica and other metals (Al, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH)2, MgO, Zn0) and recovering copper and cadmium from the leach solution by cementing with zinc dust.
Still another object of the present invention is to provide a process for separating zinc oxide from gypsum, which precipitates during zinc oxide precipitation.
The process comprisesd the steps of leaching the acid soluble zinc-containing material with sulphuric acid, precipitating iron, silica and other metals (AL, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH~, MgO, Zn0), and cementing copper, cadmium, nickel and cobalt frorri the leach solution using zinc dust. The precipitated zinc oxide is separated from co-precipitated gypsum by flotation with cationic collectors such as dodecylamine hydrochloride, and dodecylamine sulphate, and/or potassium amyl xanthate as a collector.
The separation of zinc oxide from calcium sulphate can also be achieved by granulometric sizing. In addition, a combination of the two techniques (granulometric sizing and flotation) can be used for separating zinc oxide from calcium sulphate. The tailing of the flotation step can also be recycled to the leaching step to recover zinc value.
The invention is described in more detail below with reference to the accompanying figure.
BRIEF DESCRIPTION OF THE DRAWIrIGS
Figure 1 is a flowchart illustrating the preferred process for producing zinc oxide from an acid soluble zinc material using the invented process.
wo ozio6:;.n pcT~cAOnoog~.~
Figure 2 is a flowchart illustrating the preferred process for producing zinc oxide from an acid soluble zinc material using the invented process including the granulometric sizing stage.
Figure 3 is a schematic block diagram depicting the apparatus according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
1. Introduction The present invention relates to method and apparatus for the extraction and recovery of zinc from zino-bearing materials (solutions or solids) through a process carried out in a sulphuric acid media by leaching the zinc followed by precipitation of zinc as oxide and upgrading the zinc content in precipitates by flotation or granulometric sizing.
This upgrading of zinc also can be achieved by using a granulometric sizing technique.
This process also allows for the recovery of other metals, such as iron, copper, nickel, cobalt, lead, silver, cadmium, etc. The present invention further relates to a process for producing zinc oxide from an acid soluble zinc material, an apparatus for performing the process, and processes for recovering iron, copper, and cadmium from an acid soluble zinc material. More particularly, the invention relates to a pmcess of producing zinc oxide from such an acid soluble zinc material by, preferably, leaching the acid soluble zinc material with sulphuric acid, followed by precipitation of iron, silica and other metals (AI, As, Sb, etc.) from the leach solution using calcium oxide (or Ca(OH)2, MgO, Zn0), and cementation of copper, cadmium and cobalt using zinc dust. Zinc oxide may then be precipitated from the leach solution using calcium oxide as a mixture of zinc oxide and calcium sulphate. The zinc grade in the mixture of zinc oxide and calcium sulphate may WO 02/065.11 PCT/CA01/0087.1 be improved by flotation andlor granulometric sizing techniques. The novelty of this invention is precipitating zinc oxide from zinc sulphate solution and upgrading zinc content by flotation and/or granulometric sizing techniques.
By the phrase "acid soluble zinc materials" as used in this specification is meant primarily a zinc silicate ore but it is also intended to include zinc oxide ore, zinc carbonate ore and a zinc materials containing substantial quantities of soluble zinc in sulphuric acid The presently preferred process of the present invention is comprised of a series of steps, as will be described in detail below.
2. Leaching and Neutralization According to a preferred embodiment of the present invention there is provided a process for the recovery of metal values from an acid soluble ore, where the process is conducted in a continuous concurrent manner. A process comprises a first stage, effected in one or more vessels, in which the said ore is leached with aqueous sulphuric acid to an end-point pH in the range 1.0 to 4.0, preferably in the range 1.5 to 2.5, to obtain a leach liquor or pulp containing dissolved zinc values and other impurities including silica and iron. A second stage, effected in one or more vessels, in which the pH of the liquor or pulp from the first stage is raised, for example by addition of neutralising agent, to a pH in the range 3 to 6, preferably in the range 3.5 to 4.5, such that substantially the whole or a major part of the silica. content of said leach liquor or pulp is converted into a form in which it is readily separated by conventional techniques.
Both process stages may be operated successfully at temperatures up to the boiling points of the solutions at atmospheric pressure, and operating temperatures between ambient temperature and about 95°C are therefore envisaged. The aqueous sulphuric acid WO 02/065.11 PCT/CA01/0087.!
s necessary for the treatment of the acid soluble ores. Spent electrolyte from a conventional process for the electrowinning of zinc, or such spent electrolyte fortified to compensate for acid losses, may conveniently be used as a leaching agent. Residence times of the liquor or pulp in each of the process stages may lie in the range 30 minutes to 10 hours, with a preferred residence time in the first stage of 1 - 4 hours, and a preferred residence time in the second stage of 1 to 6 hours.
The pulp leaving from the second stage contains suspended silica and iron hydroxide in particulate form, and will be subjected to solid liquid separation by using thickening process or conventional filtering technology. In some circumstance it may be desirable to re-circulate portions of pulp or thickened pulp from the second stage to first or second stages of the process.
The filtrate from this step is sent to cementation.
3. Zinc oxide precipitation At a third stage, the pH of the liquor from solid-liquid separation process right after second stage is raised, for example by the addition of neutralising agent such as lime, to a pH in the range of 5 to 14, preferably in the range of 8.5 to 9.5 such that substantially the whole of metal values including zinc is precipitated as oxide forms and the whole or a major part of lime is converted to gypsum. The third stage may be operated successfully at temperature up to boiling points of the solution at atrnospheric pressure, preferably in the range of 60 to 95°C. The pulp leaving the third stage is sent to the flotation stage with or without solid-liquid separation. In some circumstance, it may be desirable to re-circulate portions of pulp or thickened pulp from the third stage to very beginning or in the process of third stages of the process.
WO 02/0651 PCT/CA01/0087a In some circumstances, it may be desirable to purify the liquor before third stage.
1n this case, zinc dust may be added into the solution with or without other reagent such as copper sulphate, arsenic trioxide and/or antimony. The preferable condition will be pH in the range of 3 to 6, preferably in the range of 4.0 to 5.0, and temperature in the range of 60 to 95°C. The residence time of this process maybe in the range of 1 to 4 hours.
The use of Ca0 as the neutralizing reagent results, theoretically, in the following reactions:
ZnS04 + HZO ~ Zn0 + H2S04 (hydrolysis) (1) H2S04 + Ca0 -~ Ca S04 + H20 (neutralization) {2) ZnS04 + Ca0 ~ Zn0 + CaS04 (overall) (3) This series of reactions represents a conventional neutralization process with the objective of generating a Zn0 product of high purity.
4. Flotation The next stage is where the pulp from the third stage or the re-pulped cake from the solid-liquid separation is subjected to the flotation step. Flotation is a process for separating finely ground minerals from their associated gangue. This process is usually used to separate one solid from another by using the affinity of air bubbles to solids. In this stage, zinc oxide including metal oxides or hydroxides is recovered by flotation concentrate and gypsum is recovered as tailing. Cationic collectors, such as dodecylamine hydrochloride, are used as flotation agents. Potassium amyl xanthate or dodecylamine sulphate may be used for this purpose. Any frother could be used, but a Dowfroth 250 was found useful. The flotation procxss may be operated at ambient temperature and also successfully at temperature up to 90°C and the pulp from the third stage may be used WO 02/06i.t1 PCT/CA01/0087~
without any heating or cooling stages. The gypsum from the flotation step can be recycled to either of the leaching or neutralization steps.
The Zn0 product obtained according to the present invention could be introduced in an entirely independent circuit in a zinc refinery, or it could be introduced in an existing plant circuit for increasing plant capacity through full operation of a cellhouse. The Zn0 product can be dissolved very easily in spent electrolyte at room temperature and the dissolved zinc can be recovered by electrowinning method.
WO 02/0651 PCT/CA01/0087a In some circumstances, it may be desirable to purify the liquor before third stage.
1n this case, zinc dust may be added into the solution with or without other reagent such as copper sulphate, arsenic trioxide and/or antimony. The preferable condition will be pH in the range of 3 to 6, preferably in the range of 4.0 to 5.0, and temperature in the range of 60 to 95°C. The residence time of this process maybe in the range of 1 to 4 hours.
The use of Ca0 as the neutralizing reagent results, theoretically, in the following reactions:
ZnS04 + HZO ~ Zn0 + H2S04 (hydrolysis) (1) H2S04 + Ca0 -~ Ca S04 + H20 (neutralization) {2) ZnS04 + Ca0 ~ Zn0 + CaS04 (overall) (3) This series of reactions represents a conventional neutralization process with the objective of generating a Zn0 product of high purity.
4. Flotation The next stage is where the pulp from the third stage or the re-pulped cake from the solid-liquid separation is subjected to the flotation step. Flotation is a process for separating finely ground minerals from their associated gangue. This process is usually used to separate one solid from another by using the affinity of air bubbles to solids. In this stage, zinc oxide including metal oxides or hydroxides is recovered by flotation concentrate and gypsum is recovered as tailing. Cationic collectors, such as dodecylamine hydrochloride, are used as flotation agents. Potassium amyl xanthate or dodecylamine sulphate may be used for this purpose. Any frother could be used, but a Dowfroth 250 was found useful. The flotation procxss may be operated at ambient temperature and also successfully at temperature up to 90°C and the pulp from the third stage may be used WO 02/06i.t1 PCT/CA01/0087~
without any heating or cooling stages. The gypsum from the flotation step can be recycled to either of the leaching or neutralization steps.
The Zn0 product obtained according to the present invention could be introduced in an entirely independent circuit in a zinc refinery, or it could be introduced in an existing plant circuit for increasing plant capacity through full operation of a cellhouse. The Zn0 product can be dissolved very easily in spent electrolyte at room temperature and the dissolved zinc can be recovered by electrowinning method.
5. Granulometric Sizing This operation may be used in conjunction with, or as an alternative to, flotation.
The sizing may be performed by any method, either individually or in combination.. For example, sizing may be performed by using one or more of the following techniques:
classifier, elutriation, settling, screening, tables, and cyclones. A
classifier is a device for subjecting comminuted ore to the action of water either in such a way that a division of the ore particle is made into two or more products according to relative settling powers.
Cyclones are devices primarily used for separation of solids from fluids.
Cyclones oppose centrifugal forces collinear to fluid drag, substantially at right angles to a rapid carrying current. Since such separation depends on relative particle size and specific gravity, it can be used for separation of solids from each other.
From the zinc oxide precipitation step, the zinc oxide in the precipitated slurry can be separated from gypsum by a screening technology that uses appropriate sieves. In this stage, the precipitated slurry is wet-screened with a series of sieves and the undersized materials are collected for the final product. The oversized materials are collected and WO 02/065.11 PCT/CA01/0087.t recycled to the leaching or neutralization step. Also, the oversized materials can be leached with sulphuric acid to dissolve zinc. Then, the zinc bearing solution can be recycled to the leaching, neutralization or precipitation stage to recover zinc. The leached residue can be washed and recovered as pure gypsum. The undersized materials also can be treated further by flotation or granulometric operation, as described in the previous sections, to increase zinc grade.
Fig. 3 depicts an apparatus of the present invention. Leaching Tank 2 is used to leach an acid soluble zinc-containing material with sulphuric acid. After separation in the Solid-liquid Separation Tank 4, the leach solution is then sent to Precipitating Tank 6 where the precipitation is performed. After the precipitate solution is sent to Flotation Cell 8 to separate the precipitated zinc oxide from gypsum, which is co-precipitated during the precipitation process. It is, however, to be understood that the apparatus is not limited to the disclosed embodiment. Persons with skill in the art will know that many different apparatuses can be constructed with equivalent arrangements and still be within the spirit and scope of the appended claims. For example, the precipitation means can take place in one or more tanks (vessels). In addition, the means to convey the material from each of these tanks are numerous and well known in the art.
Ezamples The present invention will now be described with reference to the following examples. It should be noted that although a complete process described in here is applicable for any leaching solutions which bear zinc, the following examples will focus on the precipitation of zinc oxide from leaching solutions originated from the zinc oxide WO 02/065.11 PCT/CA01/0087a is ores.
Example 1 A zinc oxide ore containing 31.4% total zinc, 5.06% silica and 2.49 % iron was treated by two-stage continuous process in accordance with the invention using sulphuric acid solution. Leaching (first stage) and silica removal (second stage) tests were conducted in 4.0-L reactor equipped with baffle. The pH of the pulp was maintained by adding sulphuric acid at 2.0 and leaching temperature was controlled at SO°C
for 4 hours. The agitation speed was set at 750 rpm. The second stage was performed in the same reactor without previous solid-liquid separation using Ca(OH~ for neutralisation to pH
4.0 for 3 hours. The agitation speed was set at 900 rpm. After neutralisation, the slurry was filtered and the filtrate was saved for the precipitation test.
The zinc extraction was 90% and the acid consumption was 2.52 tlt of zinc extracted. The Ca(OH)2 consumption for neutralisation was 0.18 t/t of zinc extracted. The final filtrate contained 47.1 g/1 zinc, and 119 mg/1 silica.
Zinc precipitation (third stage) test was conducted in 2.0-L reactor equipped with baffle.
The pH was monitored and controlled at 9.5 with a pH meter. Precipitation temperature was controlled at 90 °C and the agitation speed at 750 rpm. The tests were conducted in a continuous mode for three retention times of 30 minutes, for total test duration of 90 minutes. The test consisted in neutralizing a ZnS04 solution from the second stage with Ca(OH)2. The zinc sulphate solution at 47.1 g/L of Zn was pumped continuously at 50.0 ml/min into a 2.0-L reactor. The zinc solution was neutralized to pH 9.5 with a calcium hydroxide slurry at 20%. During the test, 5000 ml of ZnS04 at 47.1 g/1 of Zn was neutralized with 1455 ml of lime slurry at 20% producing 923 g of precipitate.
Results WO 021065.11 PCT/CA01/0087.1 showed a complete removal of Zn (more than 99.9%) from the ZnS04 solution with a residual Zn concentration in the filtrate of 1.6 mg/L. The solids produced were approximately 25% Zn, this Zn content indicated production of good quality Zn0 and CaS04.2H20 since Zn content of pure mixture of Zn0 and CaS04.2H20 i~' 26%. In addition, analysis of the solids by X-Ray Diffraction confirmed the presence of hexagonal Zincite (Zn0) and monoclinic Gypsum (CaS04.2Hz0) as major phases.
Stoichiometric calculation based on equation (3) showed that only 4% excess of Ca(OH)z was used to precipitate Zn content of the total volume of ZnSOa solution treated. In addition, calculated mass of Zn0 + CaS04.2H20 produced according to equation (3) and based on the Zn treated would be 954 g or 103% of the mass of precipitate measured.
The solid from third stage {zinc precipitation) was mixed with filtrate of the precipitation test and mechanically stirred to obtain a slurry. The weight of the solid taken on dry basis was 166.0 g. The flotation test.was conducted in a 1 liter laboratory Denver flotation cell at 1204 rpm. The collector solution of the required, DDA
(dodecylamine hydrochloride, C,zH23NHz~HC1), was mixed with flotation pulp. The volume of collector added was 3 mg followed by adding 0.05 ml of frother, Dowfroth 250C. The concentrate was collected for 3 minutes and filter, dried and weighed. Result showed 77.5%
of zinc was recovered and the grade of concentrate was 41.2% zinc. The amount of zinc in the tailing was found to be 10.8%, however, this zinc can be recycled to the first stage for recovery.
Example 2 From the same solid of the third stage of Example 1, the slurry was screened with 400 mesh sieve. The undersized material is 48% Zn and the zinc recovery was 92%. The WO 02/0651 PCT/CA01/0087.1 oversized material is 22.7% Ca and 3.8% Zn. The same sample was screened with mesh sieve. The undersized material was 56.5% Zn and the zinc recovery was 87.4%.
While the present invention has been described for what are presently considered the preferred embodiments, the invention is not so limited. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions
The sizing may be performed by any method, either individually or in combination.. For example, sizing may be performed by using one or more of the following techniques:
classifier, elutriation, settling, screening, tables, and cyclones. A
classifier is a device for subjecting comminuted ore to the action of water either in such a way that a division of the ore particle is made into two or more products according to relative settling powers.
Cyclones are devices primarily used for separation of solids from fluids.
Cyclones oppose centrifugal forces collinear to fluid drag, substantially at right angles to a rapid carrying current. Since such separation depends on relative particle size and specific gravity, it can be used for separation of solids from each other.
From the zinc oxide precipitation step, the zinc oxide in the precipitated slurry can be separated from gypsum by a screening technology that uses appropriate sieves. In this stage, the precipitated slurry is wet-screened with a series of sieves and the undersized materials are collected for the final product. The oversized materials are collected and WO 02/065.11 PCT/CA01/0087.t recycled to the leaching or neutralization step. Also, the oversized materials can be leached with sulphuric acid to dissolve zinc. Then, the zinc bearing solution can be recycled to the leaching, neutralization or precipitation stage to recover zinc. The leached residue can be washed and recovered as pure gypsum. The undersized materials also can be treated further by flotation or granulometric operation, as described in the previous sections, to increase zinc grade.
Fig. 3 depicts an apparatus of the present invention. Leaching Tank 2 is used to leach an acid soluble zinc-containing material with sulphuric acid. After separation in the Solid-liquid Separation Tank 4, the leach solution is then sent to Precipitating Tank 6 where the precipitation is performed. After the precipitate solution is sent to Flotation Cell 8 to separate the precipitated zinc oxide from gypsum, which is co-precipitated during the precipitation process. It is, however, to be understood that the apparatus is not limited to the disclosed embodiment. Persons with skill in the art will know that many different apparatuses can be constructed with equivalent arrangements and still be within the spirit and scope of the appended claims. For example, the precipitation means can take place in one or more tanks (vessels). In addition, the means to convey the material from each of these tanks are numerous and well known in the art.
Ezamples The present invention will now be described with reference to the following examples. It should be noted that although a complete process described in here is applicable for any leaching solutions which bear zinc, the following examples will focus on the precipitation of zinc oxide from leaching solutions originated from the zinc oxide WO 02/065.11 PCT/CA01/0087a is ores.
Example 1 A zinc oxide ore containing 31.4% total zinc, 5.06% silica and 2.49 % iron was treated by two-stage continuous process in accordance with the invention using sulphuric acid solution. Leaching (first stage) and silica removal (second stage) tests were conducted in 4.0-L reactor equipped with baffle. The pH of the pulp was maintained by adding sulphuric acid at 2.0 and leaching temperature was controlled at SO°C
for 4 hours. The agitation speed was set at 750 rpm. The second stage was performed in the same reactor without previous solid-liquid separation using Ca(OH~ for neutralisation to pH
4.0 for 3 hours. The agitation speed was set at 900 rpm. After neutralisation, the slurry was filtered and the filtrate was saved for the precipitation test.
The zinc extraction was 90% and the acid consumption was 2.52 tlt of zinc extracted. The Ca(OH)2 consumption for neutralisation was 0.18 t/t of zinc extracted. The final filtrate contained 47.1 g/1 zinc, and 119 mg/1 silica.
Zinc precipitation (third stage) test was conducted in 2.0-L reactor equipped with baffle.
The pH was monitored and controlled at 9.5 with a pH meter. Precipitation temperature was controlled at 90 °C and the agitation speed at 750 rpm. The tests were conducted in a continuous mode for three retention times of 30 minutes, for total test duration of 90 minutes. The test consisted in neutralizing a ZnS04 solution from the second stage with Ca(OH)2. The zinc sulphate solution at 47.1 g/L of Zn was pumped continuously at 50.0 ml/min into a 2.0-L reactor. The zinc solution was neutralized to pH 9.5 with a calcium hydroxide slurry at 20%. During the test, 5000 ml of ZnS04 at 47.1 g/1 of Zn was neutralized with 1455 ml of lime slurry at 20% producing 923 g of precipitate.
Results WO 021065.11 PCT/CA01/0087.1 showed a complete removal of Zn (more than 99.9%) from the ZnS04 solution with a residual Zn concentration in the filtrate of 1.6 mg/L. The solids produced were approximately 25% Zn, this Zn content indicated production of good quality Zn0 and CaS04.2H20 since Zn content of pure mixture of Zn0 and CaS04.2H20 i~' 26%. In addition, analysis of the solids by X-Ray Diffraction confirmed the presence of hexagonal Zincite (Zn0) and monoclinic Gypsum (CaS04.2Hz0) as major phases.
Stoichiometric calculation based on equation (3) showed that only 4% excess of Ca(OH)z was used to precipitate Zn content of the total volume of ZnSOa solution treated. In addition, calculated mass of Zn0 + CaS04.2H20 produced according to equation (3) and based on the Zn treated would be 954 g or 103% of the mass of precipitate measured.
The solid from third stage {zinc precipitation) was mixed with filtrate of the precipitation test and mechanically stirred to obtain a slurry. The weight of the solid taken on dry basis was 166.0 g. The flotation test.was conducted in a 1 liter laboratory Denver flotation cell at 1204 rpm. The collector solution of the required, DDA
(dodecylamine hydrochloride, C,zH23NHz~HC1), was mixed with flotation pulp. The volume of collector added was 3 mg followed by adding 0.05 ml of frother, Dowfroth 250C. The concentrate was collected for 3 minutes and filter, dried and weighed. Result showed 77.5%
of zinc was recovered and the grade of concentrate was 41.2% zinc. The amount of zinc in the tailing was found to be 10.8%, however, this zinc can be recycled to the first stage for recovery.
Example 2 From the same solid of the third stage of Example 1, the slurry was screened with 400 mesh sieve. The undersized material is 48% Zn and the zinc recovery was 92%. The WO 02/0651 PCT/CA01/0087.1 oversized material is 22.7% Ca and 3.8% Zn. The same sample was screened with mesh sieve. The undersized material was 56.5% Zn and the zinc recovery was 87.4%.
While the present invention has been described for what are presently considered the preferred embodiments, the invention is not so limited. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions
Claims (8)
1. A method for recovering any of copper and cadmium from an acid soluble zinc-containing material, comprising the steps of leaching the acid soluble zinc-containing material with sulphuric acid thereby producing a leach solution; and precipitating metals, including copper and cadmium, from the leach solution by neutralization of said leach solution with a basic compound selected from the group consisting of calcium oxide, Ca(OH)2, MgO, and ZnO; and recovering any of copper and cadmium from said leach solution by cementing with zinc dust.
2. A method according to Claim 1, wherein said acid soluble zinc-containing material is leached with sulphuric acid to an end-point pH that is between substantially pH 1.5 and substantially pH 2.5.
3. A method according to any one of Claims 1 to 2, wherein the step of precipitating iron and silica raises the end-point pH of the leach solution to between substantially pH 3.5 and pH 4.5.
4. A method according to any one of Claims 1 to 3, wherein the copper and cadmium cemented with zinc dust is subjected to a solid liquid separation process from the leach solution.
5. An apparatus for recovering any of copper and cadmium from an acid soluble zinc-containing material, comprising:
leaching means for leaching the acid soluble zinc-containing material with sulphuric acid and providing a leaching solution;
precipitating means for precipitating metals, including copper and cadmium, from the leach solution by using any of calcium oxide, Ca(OH)2, MgO, and ZnO;
and recovering means for recovering any of copper and cadmium from said leach solution by cementing with zinc dust.
leaching means for leaching the acid soluble zinc-containing material with sulphuric acid and providing a leaching solution;
precipitating means for precipitating metals, including copper and cadmium, from the leach solution by using any of calcium oxide, Ca(OH)2, MgO, and ZnO;
and recovering means for recovering any of copper and cadmium from said leach solution by cementing with zinc dust.
6. An apparatus according to Claim 5, wherein said leaching means reaches an end-point pH of the acid-soluble zinc-containing solution that is between substantially pH 1.5 and substantially pH 2.5.
7. An apparatus according to any one of Claims 5 to 6, wherein said precipitating means raises the end-point pH of the leach solution to between substantially pH 3.5 and pH 4.5.
8. An apparatus according to any one of Claims S to 7, further comprising solid liquid separating means to separate the copper and cadmium cemented with zinc dust from the leach solution.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US61753400A | 2000-07-14 | 2000-07-14 | |
| US09/617,534 | 2000-07-14 | ||
| CA002415732A CA2415732C (en) | 2000-07-14 | 2001-06-19 | Production of zinc oxide from acid soluble ore using precipitation method |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002415732A Division CA2415732C (en) | 2000-07-14 | 2001-06-19 | Production of zinc oxide from acid soluble ore using precipitation method |
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| CA2506780A1 true CA2506780A1 (en) | 2002-01-24 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002506780A Abandoned CA2506780A1 (en) | 2000-07-14 | 2001-06-19 | Recovery of cadmium from zinc-containing acid soluble ore using precipitation method |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2506780A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3763681A1 (en) * | 2019-07-11 | 2021-01-13 | China Enfi Engineering Corporation | System and method for treating zinc-containing waste liquid |
| CN112501433A (en) * | 2020-11-16 | 2021-03-16 | 上海大学 | Method for purifying zinc sulfate electrolyte |
-
2001
- 2001-06-19 CA CA002506780A patent/CA2506780A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3763681A1 (en) * | 2019-07-11 | 2021-01-13 | China Enfi Engineering Corporation | System and method for treating zinc-containing waste liquid |
| CN112501433A (en) * | 2020-11-16 | 2021-03-16 | 上海大学 | Method for purifying zinc sulfate electrolyte |
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