US3766026A - Electrolytic process for the recovery of nickel, cobalt and iron from their sulfides - Google Patents
Electrolytic process for the recovery of nickel, cobalt and iron from their sulfides Download PDFInfo
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- US3766026A US3766026A US00251940A US3766026DA US3766026A US 3766026 A US3766026 A US 3766026A US 00251940 A US00251940 A US 00251940A US 3766026D A US3766026D A US 3766026DA US 3766026 A US3766026 A US 3766026A
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- 238000000034 method Methods 0.000 title claims abstract description 65
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims description 67
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims description 52
- 229910052759 nickel Inorganic materials 0.000 title claims description 31
- 229910052742 iron Inorganic materials 0.000 title claims description 24
- 239000010941 cobalt Substances 0.000 title claims description 20
- 229910017052 cobalt Inorganic materials 0.000 title claims description 20
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims description 20
- 238000011084 recovery Methods 0.000 title abstract description 16
- 150000003568 thioethers Chemical class 0.000 title 1
- 229910052751 metal Inorganic materials 0.000 claims abstract description 52
- 239000002184 metal Substances 0.000 claims abstract description 52
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 45
- 239000003792 electrolyte Substances 0.000 claims abstract description 45
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims abstract description 23
- 150000002739 metals Chemical class 0.000 claims abstract description 18
- 229910001617 alkaline earth metal chloride Inorganic materials 0.000 claims abstract description 13
- 229910001514 alkali metal chloride Inorganic materials 0.000 claims abstract description 10
- 239000002245 particle Substances 0.000 claims abstract description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 3
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical group [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 34
- 235000002639 sodium chloride Nutrition 0.000 claims description 21
- 239000011780 sodium chloride Substances 0.000 claims description 17
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical class [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 8
- 150000004763 sulfides Chemical class 0.000 claims description 8
- 235000011148 calcium chloride Nutrition 0.000 claims description 5
- 235000011147 magnesium chloride Nutrition 0.000 claims description 5
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical class [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 3
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical group [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 3
- 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 claims description 3
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical group [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 3
- 239000011575 calcium Substances 0.000 claims description 3
- 229910052791 calcium Inorganic materials 0.000 claims description 3
- 239000001110 calcium chloride Substances 0.000 claims description 3
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 3
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 3
- 239000011591 potassium Substances 0.000 claims description 3
- 229910052700 potassium Inorganic materials 0.000 claims description 3
- 235000011164 potassium chloride Nutrition 0.000 claims description 3
- 239000011734 sodium Substances 0.000 claims description 3
- 229910052708 sodium Inorganic materials 0.000 claims description 3
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical class [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 claims description 2
- 238000004070 electrodeposition Methods 0.000 claims description 2
- 239000012141 concentrate Substances 0.000 abstract description 11
- 229910021645 metal ion Inorganic materials 0.000 abstract description 6
- 230000002378 acidificating effect Effects 0.000 abstract description 4
- 230000000737 periodic effect Effects 0.000 abstract description 4
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 238000004090 dissolution Methods 0.000 abstract description 3
- 239000011593 sulfur Substances 0.000 description 27
- 229910052717 sulfur Inorganic materials 0.000 description 27
- 238000006243 chemical reaction Methods 0.000 description 10
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 7
- 239000010949 copper Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- WWNBZGLDODTKEM-UHFFFAOYSA-N sulfanylidenenickel Chemical compound [Ni]=S WWNBZGLDODTKEM-UHFFFAOYSA-N 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 229910052976 metal sulfide Inorganic materials 0.000 description 5
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 238000005868 electrolysis reaction Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- 238000003915 air pollution Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000009853 pyrometallurgy Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- XIUMQSREFXCDGE-UHFFFAOYSA-L S(=O)(=O)([O-])O.[Na+].[Cl-].[Na+] Chemical compound S(=O)(=O)([O-])O.[Na+].[Cl-].[Na+] XIUMQSREFXCDGE-UHFFFAOYSA-L 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- INPLXZPZQSLHBR-UHFFFAOYSA-N cobalt(2+);sulfide Chemical compound [S-2].[Co+2] INPLXZPZQSLHBR-UHFFFAOYSA-N 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- GRWZHXKQBITJKP-UHFFFAOYSA-L dithionite(2-) Chemical compound [O-]S(=O)S([O-])=O GRWZHXKQBITJKP-UHFFFAOYSA-L 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000010310 metallurgical process Methods 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000135 prohibitive effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910052569 sulfide mineral Inorganic materials 0.000 description 1
- FZUJWWOKDIGOKH-UHFFFAOYSA-N sulfuric acid hydrochloride Chemical compound Cl.OS(O)(=O)=O FZUJWWOKDIGOKH-UHFFFAOYSA-N 0.000 description 1
- DHCDFWKWKRSZHF-UHFFFAOYSA-N sulfurothioic S-acid Chemical compound OS(O)(=O)=S DHCDFWKWKRSZHF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
- C25C1/06—Electrolytic production, recovery or refining of metals by electrolysis of solutions or iron group metals, refractory metals or manganese
Definitions
- ABSTRACT A pollution-free process for the electrolytic dissolution of sulfide concentrates of the metals of Group VIII of the Periodic Table in aqueous acidic media with the formation of metal ions and elemental sulfur followed by recovery of the metal ion from solution in the electrolyte media, the process characterized by certain critical process conditions, these being the use of:
- an alkali metal and/or alkaline earth metal chloride electrolyte being above about 0.5N to saturation in chloride ion
- US. Pat. No. 2,839,461 describes an electrolytic process for the recovery of nickel from nickel sulfide utilizing an acid sulfate-chloride electrolyte and which is dependent upon the anode current being passed through a nickel matte anode.
- the process has the disadvantage of requiring concentrates suitable for the production of the required anode matte and is subject to the substantial expense of anode preparation and removal from the cells with subsequent treatment.
- the process herein disclosed has the advantage over prior pyrometallurgical process of converting the sulfide sulfur to elemental sulfur rather than sulfur dioxide with its attendant air pollution and the advantage over the process disclosed in US. Pat. No. 2,839,461 of being adaptable to low grade and complex concentrates, and not requiring the production of a matte anode in the case of nickel and cobalt.
- metal sulfide as contained herein is inclusive of the complex as well as the simple sulfide minerals which contain economically recoverable amounts of the specified metals.
- the invention is a pollution-free process for recovery of metals of Group VIII of the Periodic Table from their sulfide and mixed sulfide ores in which the sulfide is electrochemically dissociated in an acid aqueous media into elemental sulfur and metal ions which are then recovered from solution in the electrolyte media by conventional techniques.
- the electrolysis process is characterized by certain critical process conditions which render it economically feasible, these being the use of:
- the process parameters which have been found to control the current requirement for the process are electrolyte composition, feed particle size, operating acidity, operating temperature, and anode current density. As the examples which follow show, these factors are mutually interacting and dependent as respects their effect on current requirements.
- the electrolytic media for the process must be acidic as an alkaline electrolyte has proven unsatisfactory. Elemental sulfur is not stable in an alkaline environment because oxidation of the sulfur proceeds rapidly in this media through thiosulfate, hydrosulfite, sulfite to sulfate. The presence of sulfate ions is undesirable because at high sulfate concentrations oxygen is rapidly evolved at the anode resulting in a decrease in current efficiency.
- the preferred electrolyte media is an aqueous acidic solution of alkali metal chloride or alkaline earth metal chloride or mixtures thereof.
- the chlorides of sodium, potassium, barium and calcium or mixtures thereof, have been found suitable. Concentrations from 0.5N to saturation may be used. Voltage across the cell is lower at higher salt concentrations so that these are preferred except where low grade feeds are used and where salt losses would therefore become significant.
- the particle size of the feed material is critical as it directly effects the conversion to elemental sulfur.
- the sulfur produced is extremely fine.
- the anode current attacks the metal sulfide preferentially to sulfur provided the sulfide has sufficient activity near the anode.
- the activity of the sulfide is a function of its concentration and its exposed surface area. Therefore the presence of a high concentration of fine sulfide near the anode prevents the continuing oxidation of sulfur and results in higher efficiency and consequently lower current consumption.
- An average grain size range for the feed sulfide smaller than about 60 mesh US. Standard is the operable range.
- An acidity for the electrolyte media up to about 3.9 is critical. Current efficiency is reduced at a pH above 3.9.
- the preferred acidity is about pH 0.5.
- the reaction temperature of the electrolyte is critical and high process efficiency is not obtained at low temperature. At temperature below about 50 C, the reaction for the conversion of sulfide to sulfate rather than to sulfur is increasingly favored. A temperature range of about 50 to 105 C is the operable range. A temperature of about C is most preferred.
- Anode current density is also critical as used with the other critical parameters with a preferred range being between 12 amperes/ft and 240 amperes/ft with the minimum being about 12 amperes/ft? While high efficiency may be maintained at relatively high current densities when ample fresh feed is present, it is necessary to decrease current density as the concentration of sulfur becomes high in proportion to that of the mineral being attacked.
- the metal dissolved in the electrolyte can be finally recovered by conventional methods such as, electrolysis, precipitation, cementation, etc. Under certain conditions the metal can be plated out on the cathode during the dissociation process and recovered in this manner.
- Elemental sulfur is readily recovered from the electrolyte media by the process disclosed in co-pending patent application Ser. No. 233,352 filed in the US Patent Office on Mar. 9, 1972, William G. Kazel, entitled Sulfur Recovery Process.
- the feed concentrate for all of the examples was 60 mesh US. Standard. Current density is given in amperes per square foot. Current requirement is expressed in amperes per pound of metal or combined metal recovered.
- Examples 1-4 400 grams of a nickel sulfide concentrate assaying 8.3 percent nickel, 5.2 percent copper, 37.8 percent iron were slurried in 2 liters of electrolyte and subjected to 60 ampere hours of current.
- EXAMPLE 1 The following tests were performed to determine the approximate lower limit of the operable temperature range for recovering nickel and iron from nickel sulfide using a sodium chloride electrolyte and other parameters of the process.
- EXAMPLE 2 The following tests were selected to show the effect of pH on the recovery of nickel and iron from nickel sulfide by the process.
- EXAMPLE 5 The following test was selected to show the operativeness of the process for the recovery of cobalt, nickel and iron from their sulfides. 400 grams of nickel sulfide concentrate assaying 8.3 percent nickel, 5.2 percent copper, 37.8 percent iron and 0.337 percent cobalt were slurried in two liters of electrolyte and subjected to 90 ampere hours of current.
- the process is effective for the recovery of cobalt as well as iron and nickel from their sulfides with good conversion of sulfur and satisfactory current requirements.
- the power requirements set forth in the examples are well within commercial feasibility ranges for large scale production of nickel, iron and cobalt from their sulfide and mixed sulfide ores.
- the cost of the recovery of the metals and sulfur from the electrolyte after electrolysis by conventional techniques is comparatively small.
- the high percentage recovery of sulfur from the sulfides as elemental sulfur substantially reduces or eliminates the pollution problems associated with prior art processes. Accordingly, the invention provides a process for the recovery of nickel and cobalt from their sulfide and mixed sulfide ores which has the advantages of being commercially feasible and pollution free.
- a process for the recovery of metals selected from the group consisting of iron, nickel and cobalt from their sulfides and mixed sulfides, and mixtures thereof, by electrolytic dissolution with the formation of elemental sulfur which process comprises:
- an electrolyte in an electrolytic cell including at least an anode and a cathode, the electrolyte comprising an acidic aqueous solution of at least one chloride salt selected from the group consisting of alkali metal chlorides and alkaline earth metal chlorides, the solution having a concentration from about 0.5N to saturation;
- alkali metal chlorides are sodium and potassium chlorides and the alkaline earth metal chlorides are calcium and magnesium chlorides.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
A pollution-free process for the electrolytic dissolution of sulfide concentrates of the metals of Group VIII of the Periodic Table in aqueous acidic media with the formation of metal ions and elemental sulfur followed by recovery of the metal ion from solution in the electrolyte media, the process characterized by certain critical process conditions, these being the use of: 1. AN ALKALI METAL AND/OR ALKALINE EARTH METAL CHLORIDE ELECTROLYTE BEING ABOVE ABOUT 0.5N to saturation in chloride ion, 2. A SULFIDE FEED OF AVERAGE PARTICLE SIZE SMALLER THAN 60 MESH U.S. Standard, 3. A PH range of about 0.01 - 3.9, 4. AN ELECTROLYTE TEMPERATURE OF ABOUT 50*C - 105* C, and 5. AN ANODE CURRENT DENSITY ABOVE ABOUT 12 AMPERES/FT2.
Description
nited States Patent [1 1 Kruesi [75] Inventor: Paul R. Kruesi, Golden, C010.
[73] Assignee: Cyprus Metallurgical Processes Corporation, Los Angeles, Calif.
[22] Filed: May 10, 1972 [21] Appl. No.: 251,940
[52] U.S. Cl. 204/113, 204/128 [51] Int. Cl...... C22d l/14, C22d 1/24, COlb 17/06 [58] Field of Search 204/113, 128
[56] References Cited UNITED STATES PATENTS 967,996 8/1910 Summers 204/130 840,511 l/l907 Packard 204/130 3,673,061 6/1972 Kruesi 204/105 R 3,464,904 9/1969 Brace 204/105 R FOREIGN PATENTS 0R APPLICATIONS 556,169 4/1958 Canada 204/128 Oct. 16, 1973 Primary Examiner-John H. Mack Assistant Examiner-R. L. Andrews Attorney-Sheridan, Ross & Fields [5 7] ABSTRACT A pollution-free process for the electrolytic dissolution of sulfide concentrates of the metals of Group VIII of the Periodic Table in aqueous acidic media with the formation of metal ions and elemental sulfur followed by recovery of the metal ion from solution in the electrolyte media, the process characterized by certain critical process conditions, these being the use of:
1. an alkali metal and/or alkaline earth metal chloride electrolyte being above about 0.5N to saturation in chloride ion,
2. a sulfide feed of average particle size smaller than 60 mesh U.S. Standard,
3. a pH range of about 0.01 3.9,
4. an electrolyte temperature of about 50C 105 C, and
5. an anode current density above about 12 amperes/ft 15 Claims, No Drawings ELECTROLYTIC PROCESS FOR THE RECOVERY OF NICKEL, COBALT AND IRON FROM THEIR SULFIDES BACKGROUND OF THE INVENTION Metals of Group VIII of the Periodic Table have been conventionally recovered from their sulfide concentrates by pyrometallurgical smelting techniques. This has required a high degree of concentration for economic processing particularly for nickel and cobalt and thus low grade concentrates or complex concentrates which were not amenable to physical separation are often considered valueless or of low value.
The pyrometallurgical processes in which sulfur contained in the ores is oxidized to sulfur dioxide of which a substantial proportion is released to the atmosphere with consequent damage to the environment are a cause of substantial concern. An electrolytic process requiring only economic quantities of power, in which substantially all of the sulfur in the above metal sulfides is converted to elemental sulfur is an answer to this air pollution problem.
US. Pat. No. 2,839,461 describes an electrolytic process for the recovery of nickel from nickel sulfide utilizing an acid sulfate-chloride electrolyte and which is dependent upon the anode current being passed through a nickel matte anode. The process has the disadvantage of requiring concentrates suitable for the production of the required anode matte and is subject to the substantial expense of anode preparation and removal from the cells with subsequent treatment.
The process herein disclosed has the advantage over prior pyrometallurgical process of converting the sulfide sulfur to elemental sulfur rather than sulfur dioxide with its attendant air pollution and the advantage over the process disclosed in US. Pat. No. 2,839,461 of being adaptable to low grade and complex concentrates, and not requiring the production of a matte anode in the case of nickel and cobalt.
STATEMENT OF THE INVENTION The term metal sulfide as contained herein is inclusive of the complex as well as the simple sulfide minerals which contain economically recoverable amounts of the specified metals.
The invention is a pollution-free process for recovery of metals of Group VIII of the Periodic Table from their sulfide and mixed sulfide ores in which the sulfide is electrochemically dissociated in an acid aqueous media into elemental sulfur and metal ions which are then recovered from solution in the electrolyte media by conventional techniques. The electrolysis process is characterized by certain critical process conditions which render it economically feasible, these being the use of:
1. an alkali or alkaline earth metal chloride electrolyte,
2. a sulfide feed particle size smaller than about 60 mesh U.S. Standard,
3. a pH range below about 3.9,
4. an electrolyte temperature range of about 50 105 C, and
5. an anode current density above about 12 ampereslft DETAILED DESCRIPTION OF THE INVENTION The economic feasibility of the process is dependent upon the current required to produce a given quantity of metal. It is expressed herein in terms of the ampere hours of current required to release a pound of metal. Because nickel ores frequently contain substantial quantities of iron and copper which may be coproducts, the efficiency here is expressed as the ampere hours necessary to release one pound of the combined metal.
The process parameters which have been found to control the current requirement for the process are electrolyte composition, feed particle size, operating acidity, operating temperature, and anode current density. As the examples which follow show, these factors are mutually interacting and dependent as respects their effect on current requirements.
The electrolytic media for the process must be acidic as an alkaline electrolyte has proven unsatisfactory. Elemental sulfur is not stable in an alkaline environment because oxidation of the sulfur proceeds rapidly in this media through thiosulfate, hydrosulfite, sulfite to sulfate. The presence of sulfate ions is undesirable because at high sulfate concentrations oxygen is rapidly evolved at the anode resulting in a decrease in current efficiency.
The preferred electrolyte media is an aqueous acidic solution of alkali metal chloride or alkaline earth metal chloride or mixtures thereof. The chlorides of sodium, potassium, barium and calcium or mixtures thereof, have been found suitable. Concentrations from 0.5N to saturation may be used. Voltage across the cell is lower at higher salt concentrations so that these are preferred except where low grade feeds are used and where salt losses would therefore become significant.
It is highly important that a high percentage of the sulfur in the metal sulfide be recovered as elemental sulfur both from the standpoint of pollution control and from the electrical efficiency of the process. Each mole of sulfur which is oxidized from elemental sulfur to sulfate rather than being converted to elemental sulfur requires six Faradays which is equivalent to 2,275 ampere hours per pound of sulfur. This renders oxidation of the sulfur to sulfate prohibitive for an economically acceptable process.
The particle size of the feed material is critical as it directly effects the conversion to elemental sulfur. The sulfur produced is extremely fine. The anode current attacks the metal sulfide preferentially to sulfur provided the sulfide has sufficient activity near the anode. The activity of the sulfide is a function of its concentration and its exposed surface area. Therefore the presence of a high concentration of fine sulfide near the anode prevents the continuing oxidation of sulfur and results in higher efficiency and consequently lower current consumption. An average grain size range for the feed sulfide smaller than about 60 mesh US. Standard is the operable range.
An acidity for the electrolyte media up to about 3.9 is critical. Current efficiency is reduced at a pH above 3.9. The preferred acidity is about pH 0.5.
The reaction temperature of the electrolyte is critical and high process efficiency is not obtained at low temperature. At temperature below about 50 C, the reaction for the conversion of sulfide to sulfate rather than to sulfur is increasingly favored. A temperature range of about 50 to 105 C is the operable range. A temperature of about C is most preferred.
Anode current density is also critical as used with the other critical parameters with a preferred range being between 12 amperes/ft and 240 amperes/ft with the minimum being about 12 amperes/ft? While high efficiency may be maintained at relatively high current densities when ample fresh feed is present, it is necessary to decrease current density as the concentration of sulfur becomes high in proportion to that of the mineral being attacked.
The metal dissolved in the electrolyte can be finally recovered by conventional methods such as, electrolysis, precipitation, cementation, etc. Under certain conditions the metal can be plated out on the cathode during the dissociation process and recovered in this manner.
Elemental sulfur is readily recovered from the electrolyte media by the process disclosed in co-pending patent application Ser. No. 233,352 filed in the US Patent Office on Mar. 9, 1972, William G. Kazel, entitled Sulfur Recovery Process.
The following examples are illustrative of the invention but not limiting thereof.
The examples were performed in apparatus well known in the art consisting of an anode section provided with means for agitation, a suitable anode, a cloth diaphragm and a suitable cathode in a cathode section. Conventional non-diaphragm cells may be used.
The feed concentrate for all of the examples was 60 mesh US. Standard. Current density is given in amperes per square foot. Current requirement is expressed in amperes per pound of metal or combined metal recovered.
1n Examples 1-4, 400 grams of a nickel sulfide concentrate assaying 8.3 percent nickel, 5.2 percent copper, 37.8 percent iron were slurried in 2 liters of electrolyte and subjected to 60 ampere hours of current.
EXAMPLE 1 The following tests were performed to determine the approximate lower limit of the operable temperature range for recovering nickel and iron from nickel sulfide using a sodium chloride electrolyte and other parameters of the process.
TEST NO. 1 2 3 4N 4N 4N Electrolyte NaCl NaCl NaCl Temperature 80C' 50C 30C pH 0.5 0.5 0.5 Anode Current Density (Amps/ft) 120 120 120 Metal and Sulfur Recovered (gm.)
Fe 69.5 27.7- 21.0 Ni 6.5 3.1 2.8 Cu 6.4 1.3 3.3 S 42.2 1 1.4 7.8 Amp. Hrs./lb. Combined Metals 330.5 848.5 1005.2 Recovered The tests show that reduction of the operating temperature below about 50 C results in excessive current requirements and drastic reduction in the conversion of sulfide sulfur to elemental sulfur.
EXAMPLE 2 The following tests were selected to show the effect of pH on the recovery of nickel and iron from nickel sulfide by the process.
TEST NO. 1 2 3 4 5 Electrolyte NaCl NaCl NaCl NaCl NuCl Temperature C 80C 80C 80C 80C pH 0.01(5%HC|) 0.5 1.5 2.0 4.0 Anode Current Density Amps/ft 120 120 120 120 Metal and Sulfur Recovered (gm) Fe 71.8 69.5 51.3 37.8 9.8 Ni 5.6 6.5 3.2 1.2 0.6 Cu 3.5 6.4 5.6 1.1 0.5 S 52.8 42.2 36.3 28.6 22.2 Amp. Hrs/1b. Combined Metals 336.9 330.5 453.1 679.2 2499.3 Recovered The increase in current requirement and decrease in conversion of sulfide sulfur to elemental sulfur above pH 1.5 as acidity decreases indicates the preferred pH. Above pH 3.9, the upper limit of pH range, 2,499.3 amperes/lb. of metal recovered were required and sulfur conversion was reduced to 22.2 grams.
EXAMPLE 3 The following tests were made to explore the preferred current density range for the process.
TEST NO. 1 2 3 4 4N 4N 4N 4N Electrolyte NaCl NaCl NaCl NaCl Temperature 80C 80C 80C 80C p 0.5 0.5 0.5 0.5 Anode Current Density(Amps/ft 480 240 120 60 Metal and Sulfur Recovered (gm.)
Fe 38.8 36.2 69.5 66.1 Ni 4.0 4.4 6.5 5.0 Cu 5.2 6.3 6.4 3.7 S 24.2 27.0 42.2 39.0 Amp. Hrs/lb. Combined Metals Recovered 567.5 580.7 330.5 364.1
The results indicate that current densities at or below about 120 amps/ft are preferable to those above this figure. The lower limit of the economically feasible current density range is about 12 amps/ft? EXAMPLE 4 The tests below were performed to explore the effectiveness of other electrolytes than NaCl and to determine the effect of the presence of sulfate ion in the electrolyte on the operativeness of the process for recovering nickel and iron from nickel sulfide concentrate.
The tests show that potassium chloride as well as the alkaline earth metal chlorides, calcium chloride and magnesium chloride, are effective electrolytes for the process. In Test No. 5 the sodium sulfate-sodium chloride electrolyte of U.S. Pat. No. 2,839,461 is shown to be less effective than the other electrolytes as indicated by the decrease in sulfur conversion.
EXAMPLE 5 The following test was selected to show the operativeness of the process for the recovery of cobalt, nickel and iron from their sulfides. 400 grams of nickel sulfide concentrate assaying 8.3 percent nickel, 5.2 percent copper, 37.8 percent iron and 0.337 percent cobalt were slurried in two liters of electrolyte and subjected to 90 ampere hours of current.
Electrolyte 4N NaCl Temperature 80C p 0.5 Anode Current Density(Amps/ft) 60 Metal and Sulfur of Feed Metal Recovered (gms.) Recovered Fe 88.7 61.8 Ni 16.6 54.1 Cu 9.35 49.1 Co 0.63 51.7 S 58.4 Amp.Hrs./lb.
Combined Metals Recovered 354.6
As the results indicate, the process is effective for the recovery of cobalt as well as iron and nickel from their sulfides with good conversion of sulfur and satisfactory current requirements.
EXAMPLE 6 Electrolyte 4N NaCl Temperature 80C p 0.01 5% HCl) Anode Current Density (Amps/ft) l20 Metal and Sulfur Recovered (gms) Co 0.5 Ni 0.2
S 19.9 Amps. HrsJlb. Combined Metals Recovered 472.2
The high conversion of sulfur and the relatively low current requirements with satisfactory recovery of cobalt show that the process can be used economically for the recovery of cobalt from low grade complex cobalt sulfide ores.
The power requirements set forth in the examples are well within commercial feasibility ranges for large scale production of nickel, iron and cobalt from their sulfide and mixed sulfide ores. The cost of the recovery of the metals and sulfur from the electrolyte after electrolysis by conventional techniques is comparatively small. The high percentage recovery of sulfur from the sulfides as elemental sulfur substantially reduces or eliminates the pollution problems associated with prior art processes. Accordingly, the invention provides a process for the recovery of nickel and cobalt from their sulfide and mixed sulfide ores which has the advantages of being commercially feasible and pollution free.
I claim:
1. A process for the recovery of metals selected from the group consisting of iron, nickel and cobalt from their sulfides and mixed sulfides, and mixtures thereof, by electrolytic dissolution with the formation of elemental sulfur, which process comprises:
a. providing an electrolyte in an electrolytic cell including at least an anode and a cathode, the electrolyte comprising an acidic aqueous solution of at least one chloride salt selected from the group consisting of alkali metal chlorides and alkaline earth metal chlorides, the solution having a concentration from about 0.5N to saturation;
b. mixing with the electrolyte a solid feed sulfide of the metal having an average particle size smaller than about 60 mesh U.S. Standard;
c. maintaining the temperature of the electrolyte media at about 50 to C, and the pH of the electrolyte media below about 3.9 while introducing electric current into the electrolytic cell to provide an anode current density above about 12 amperes per square foot to dissociate the metal sulfide into metal ions and elemental sulfur; and
d. recovering the metal from the electrolyte.
2. The process of claim l in which cobalt and nickel are recovered from the sulfides in the presence of iron sulfides.
3. The process of claim 1 including the final step of recovering the metal from solution in the electrolyte by electrode-position on the cathode.
4..The process of claim it including the step of recovering elemental sulfur from the electrolyte.
5. The process of claim 1 in which the metal recovered is nickel.
6. The process of claim 1 in which the metal recovered is cobalt.
7. The process of claim 1 in which the metal recovered is iron.
8. The process of claim l in which the alkali metal chlorides are sodium and potassium chlorides and the alkaline earth metal chlorides are calcium and magnesium chlorides.
9. The process of claim 8 in which the electrolyte is sodium chloride and the metal'recovered is a metal selected from the group consisting of iron, nickel and cobalt.
10. The process of claim 9 in which the metal recovered is nickel.
11. The process of claim 9 in which the metal recovered is cobalt.
12. The process of claim 9 in which the metal recovered is iron.
13. The process-of claim 8 in which the alkali metal chloride is potassium and the metals recovered are nickel and iron.
14. The process of claim 8 in which the alkaline earth metal chloride is calcium chloride and the metals recovered are nickel and iron.
15. The process of claim 8 in which the alkaline earth metal chloride is magnesium chloride and the metals recovered are nickel and iron.
Claims (19)
1. AND ALKALI METAL AND/OR ALKALINE EARTH METAL CHLORIDE ELECTROLYTE BEING ABOVE ABOUT 0.5N TO SATURATION IN CHLORIDE ION,
2. A SULFIDE FEED OF AVERAGE PARTICLE SIZE SMALLER THAN 60 MESH U.S. STANDARD,
2. The process of claim 1 in which cobalt and nickel are recovered from the sulfides in the presence of iron sulfides.
3. The process of claim 1 including the final step of recovering the metal from solution in the electrolyte by electrode-position on the cathode.
3. A PH RANGE OF ABOUT 0.01-3.9,
4. AND ELECTROLYTE TEMPERATURE OF ABOUT 50*C-105*C, AND
4. The process of claim 1 including the step of recovering elemental sulfur from the electrolyte.
5. The process of claim 1 in which the metal recovered is nickel.
5. AN ANODE CURRENT DENSITY ABOVE ABOUT 12 AMPERES-FT2.
6. The process of claim 1 in which the metal recovered is cobalt.
7. The process of claim 1 in which the metal recovered is iron.
8. The process of claim 1 in which the alkali metal chlorides are sodium and potassium chlorides and the alkaline earth metal chlorides are calcium and magnesium chlorides.
9. The process of claim 8 in which the electrolyte is sodium chloride and the metal recovered is a metal selected from the group consisting of iron, nickel and cobalt.
10. The process of claim 9 in which the metal recovered is nickel.
11. The process of claim 9 in which the metal recovered is cobalt.
12. The process of claim 9 in which the metal recovered is iron.
13. The process of claim 8 in which the alkali metal chloride is potassium and the metals recovered are nickel and iron.
14. The process of claim 8 in which the alkaline earth metal chloride is calcium chloride and the metals recovered are nickel and iron.
15. The process of claim 8 in which the alkaline earth metal chloride is magnesium chloride and the metals recovered are nickel and iron.
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US25194072A | 1972-05-10 | 1972-05-10 |
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US00251940A Expired - Lifetime US3766026A (en) | 1972-05-10 | 1972-05-10 | Electrolytic process for the recovery of nickel, cobalt and iron from their sulfides |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4060464A (en) * | 1974-06-26 | 1977-11-29 | Boliden Aktiebolag | Method for extracting and recovering iron and nickel in metallic form |
US20050266165A1 (en) * | 2004-05-27 | 2005-12-01 | Enthone Inc. | Method for metallizing plastic surfaces |
US11753732B2 (en) | 2021-03-24 | 2023-09-12 | Electrasteel, Inc. | Ore dissolution and iron conversion system |
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US840511A (en) * | 1906-01-11 | 1907-01-08 | Robert L Packard | Extracting metals from sulfid ores. |
US967996A (en) * | 1909-04-08 | 1910-08-23 | Leland L Summers | Method of extracting or eliminating sulfur, phosphorus, and other impurities from coal, ore, &c. |
CA556169A (en) * | 1958-04-22 | H. Dolloff Norman | Polarization prevention in electrolysis of sulfide ores | |
US3464904A (en) * | 1964-12-21 | 1969-09-02 | Banner Mining Co | Method for treating metallic sulfide compounds |
US3673061A (en) * | 1971-02-08 | 1972-06-27 | Cyprus Metallurg Process | Process for the recovery of metals from sulfide ores through electrolytic dissociation of the sulfides |
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Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA556169A (en) * | 1958-04-22 | H. Dolloff Norman | Polarization prevention in electrolysis of sulfide ores | |
US840511A (en) * | 1906-01-11 | 1907-01-08 | Robert L Packard | Extracting metals from sulfid ores. |
US967996A (en) * | 1909-04-08 | 1910-08-23 | Leland L Summers | Method of extracting or eliminating sulfur, phosphorus, and other impurities from coal, ore, &c. |
US3464904A (en) * | 1964-12-21 | 1969-09-02 | Banner Mining Co | Method for treating metallic sulfide compounds |
US3673061A (en) * | 1971-02-08 | 1972-06-27 | Cyprus Metallurg Process | Process for the recovery of metals from sulfide ores through electrolytic dissociation of the sulfides |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4060464A (en) * | 1974-06-26 | 1977-11-29 | Boliden Aktiebolag | Method for extracting and recovering iron and nickel in metallic form |
US20050266165A1 (en) * | 2004-05-27 | 2005-12-01 | Enthone Inc. | Method for metallizing plastic surfaces |
US11753732B2 (en) | 2021-03-24 | 2023-09-12 | Electrasteel, Inc. | Ore dissolution and iron conversion system |
US11767604B2 (en) | 2021-03-24 | 2023-09-26 | Electrasteel, Inc. | 2-step iron conversion system |
US12054837B2 (en) | 2021-03-24 | 2024-08-06 | Electrasteel, Inc. | Ore dissolution and iron conversion system |
US12065749B2 (en) | 2021-03-24 | 2024-08-20 | Electrasteel, Inc. | 2-step iron conversion system |
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