CA2070315A1 - Recovery of metal from an ore - Google Patents
Recovery of metal from an oreInfo
- Publication number
- CA2070315A1 CA2070315A1 CA 2070315 CA2070315A CA2070315A1 CA 2070315 A1 CA2070315 A1 CA 2070315A1 CA 2070315 CA2070315 CA 2070315 CA 2070315 A CA2070315 A CA 2070315A CA 2070315 A1 CA2070315 A1 CA 2070315A1
- Authority
- CA
- Canada
- Prior art keywords
- electrowinning
- solution
- leachate
- copper
- metals
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- 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
Abstract
ABSTRACT OF THE DISCLOSURE
The process is a hydrometallurgical process consisting of two parts: a leaching process conducted at temperatures in the range of 115 to 120 C and at slightly below one atmosphere in which a concentrate (or very rich ore) is subjected to a solution of 50% by volume sulfuric acid and 3 M ammonium nitrate for 10 to 20 minutes (in the batch operation). Most of the Fe present is deposited as an iron ammonium sulfate, the copper as cuprous ammonium sulfate, the arsenic as arsenious oxide, about 2/3 of the sulfur as flowers of sulfur, the silver as silver sulfate, the gold in the metallic state. The hot solution contains all of the Zn, about 1/2 of the Fe and a small amount of the copper as well as any Ni, Co, Mo etc. The solution is cooled in an open heat exchanger (the excess heat returned to the leach tank) some water is evaporated and the wash water from the tailings added before the Zn electrowinning stage. The electrowinning also reoxidizes the nitrogen oxides to nitrate ion and the barren solution is returned to the leach tanks. The remaining Fe, S, Cu, Ag, Au and As are selectively solubilized for separating. The uniqueness of the process is that the Zn electrowinning reoxidizes the nitrate and does not require elimination of nitrate, the copper is electrowon separately and up to 1/2 of the copper is produced as copper powder, the other 50%
is electrowon for a saving of about one half the power and any other metal, precious, or base can be separately treated, plus no polluting effluents are released.
The process is a hydrometallurgical process consisting of two parts: a leaching process conducted at temperatures in the range of 115 to 120 C and at slightly below one atmosphere in which a concentrate (or very rich ore) is subjected to a solution of 50% by volume sulfuric acid and 3 M ammonium nitrate for 10 to 20 minutes (in the batch operation). Most of the Fe present is deposited as an iron ammonium sulfate, the copper as cuprous ammonium sulfate, the arsenic as arsenious oxide, about 2/3 of the sulfur as flowers of sulfur, the silver as silver sulfate, the gold in the metallic state. The hot solution contains all of the Zn, about 1/2 of the Fe and a small amount of the copper as well as any Ni, Co, Mo etc. The solution is cooled in an open heat exchanger (the excess heat returned to the leach tank) some water is evaporated and the wash water from the tailings added before the Zn electrowinning stage. The electrowinning also reoxidizes the nitrogen oxides to nitrate ion and the barren solution is returned to the leach tanks. The remaining Fe, S, Cu, Ag, Au and As are selectively solubilized for separating. The uniqueness of the process is that the Zn electrowinning reoxidizes the nitrate and does not require elimination of nitrate, the copper is electrowon separately and up to 1/2 of the copper is produced as copper powder, the other 50%
is electrowon for a saving of about one half the power and any other metal, precious, or base can be separately treated, plus no polluting effluents are released.
Description
RECOVERY OF ~qETAL FROM AN ORE
This invention relates to the recovery of metals from an ore. Specifically it is concerned with a hydrometallurgical process for separating and recovering the various metallic and non-metallic constituents of a complex ore, usually after concentration.
It has previously been proposed to use acidic and oxidizing solutions to leach compounds of metal combined with sulfur. The use of such media to leach arsenical concentrates is also known but it would seem that most of the media currently known consists of sulfuric and nitric acid with some men~ion of nitrate salts.
In United States Patent No. 3,888,748 (issued June 10, 1975 - Brennecke) a metal recovery process is described. Copper may be recovered from sulfide ore concentrates containing minerals such as chalcopyrite (CuFeS2), for example, by contacting thle ore concentrate with a dilute a~ueous solution of nitric and sulfuric acids to give a leachate and a residue. The leachate is subjected to further processing in which copper is recovered and iron is precipitated as ~arosite. The latter apparently has no value and it would appear that the leachate must have the nitrate ion and its derivates substantially removed before electrowinning and this is a disadvantage.
In United States patent No. 3,910,636 (issued 1976 - Hard) a process is disclosed for in-situ mining and holes are drilled into an ore body and the holes are filled with an acid leaching solution containing nitrate ions at a pH range of 0.2 to about 2Ø However, the solution is diluted, the process relatively slow and cannot normally be used in limestone formations.
This invention relates to the recovery of metals from an ore. Specifically it is concerned with a hydrometallurgical process for separating and recovering the various metallic and non-metallic constituents of a complex ore, usually after concentration.
It has previously been proposed to use acidic and oxidizing solutions to leach compounds of metal combined with sulfur. The use of such media to leach arsenical concentrates is also known but it would seem that most of the media currently known consists of sulfuric and nitric acid with some men~ion of nitrate salts.
In United States Patent No. 3,888,748 (issued June 10, 1975 - Brennecke) a metal recovery process is described. Copper may be recovered from sulfide ore concentrates containing minerals such as chalcopyrite (CuFeS2), for example, by contacting thle ore concentrate with a dilute a~ueous solution of nitric and sulfuric acids to give a leachate and a residue. The leachate is subjected to further processing in which copper is recovered and iron is precipitated as ~arosite. The latter apparently has no value and it would appear that the leachate must have the nitrate ion and its derivates substantially removed before electrowinning and this is a disadvantage.
In United States patent No. 3,910,636 (issued 1976 - Hard) a process is disclosed for in-situ mining and holes are drilled into an ore body and the holes are filled with an acid leaching solution containing nitrate ions at a pH range of 0.2 to about 2Ø However, the solution is diluted, the process relatively slow and cannot normally be used in limestone formations.
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Another in-situ chemical mining process is disclosed in United States patent No. 3,912,33Q
(issued 1976 - Carnahan et al) which is specifically directed at dealing witb copper porphry ores. This patent specifically discloses the use of catalytic amounts of nitrate ion added to an oxygenated sulphuric acid leach medium which is stated to improve the rate of copper extraction from copper sulfide ores. The nitrate concentrations cited are from 0.05 to 0.50% and it is disclosed that the acid media is oxygenated at oxygen pressures from 25 psi to 200 psi. Jarosite is said to be precipated and is acknowledged to be unsuitable for surface heap leaching.
United States patent Mo. 4,647,307 (issued 1987 - Beatty et al) teaches that complex copper ores can be treated with oxidizing acid media. The patent is directed mainly to arsenical ores and does not use elevated temperatures.
Public knowledge from published literature in the field includes a Ph.D. dissertation (G. Van Weert, 1989) which contains an appendix giving a summary of treatments for complex ores and concentrates containing chalcopyrite. Avramides et al (Hydrometallurgy, 5, 325-36 (1980)) describe a process in which the chalcopyrite leaching process consists of leaching with acetonitrile solutions of cupric and cuprous ions, not treating the leach residue. Kiknadze et al (Izv. Akad. ~auk Gruz. SSR, Ser. Xhim., 6 363-6 (1980)) describe a ferric ion leach of chalcopyrite where the ferric ion is regenerated with chlorine. Another ferric ion leach is described by Tkacova and Balaz (Hydrometallurgy, 21 103-12 (1988)) purports to increase the surface area of chalcopyrite but mentions also that the sulfur on the surface retards the dissolution of the chalcopyrite. Pomanianowski's group ~. . . .
Another in-situ chemical mining process is disclosed in United States patent No. 3,912,33Q
(issued 1976 - Carnahan et al) which is specifically directed at dealing witb copper porphry ores. This patent specifically discloses the use of catalytic amounts of nitrate ion added to an oxygenated sulphuric acid leach medium which is stated to improve the rate of copper extraction from copper sulfide ores. The nitrate concentrations cited are from 0.05 to 0.50% and it is disclosed that the acid media is oxygenated at oxygen pressures from 25 psi to 200 psi. Jarosite is said to be precipated and is acknowledged to be unsuitable for surface heap leaching.
United States patent Mo. 4,647,307 (issued 1987 - Beatty et al) teaches that complex copper ores can be treated with oxidizing acid media. The patent is directed mainly to arsenical ores and does not use elevated temperatures.
Public knowledge from published literature in the field includes a Ph.D. dissertation (G. Van Weert, 1989) which contains an appendix giving a summary of treatments for complex ores and concentrates containing chalcopyrite. Avramides et al (Hydrometallurgy, 5, 325-36 (1980)) describe a process in which the chalcopyrite leaching process consists of leaching with acetonitrile solutions of cupric and cuprous ions, not treating the leach residue. Kiknadze et al (Izv. Akad. ~auk Gruz. SSR, Ser. Xhim., 6 363-6 (1980)) describe a ferric ion leach of chalcopyrite where the ferric ion is regenerated with chlorine. Another ferric ion leach is described by Tkacova and Balaz (Hydrometallurgy, 21 103-12 (1988)) purports to increase the surface area of chalcopyrite but mentions also that the sulfur on the surface retards the dissolution of the chalcopyrite. Pomanianowski's group ~. . . .
(Electrocatal., Mater. Symp. Electrochem. Sect. Pol. Chem.
Soc., 9th meeting date 1987, 241-7, Edited by Pawel Nowak, Pol. Chem. Soc.: Warsaw Pol.) found that deposition of minor amounts of silver on the surface of chalcopyrite catalysed the rate of dissolution by electrochemical means. Obviously use of high temperatures and acetonitrile and nitrate oxidizing acid media are known, but, as will be shown, a unique combination and e~tension of all of these factors results in a new and eminently useful process.
It would be desirable to have an economical process for removing metal from complicated ores and concentrates that did not require smelting or produce polluting effluents by other means. In cases where the feedstock consisted primarily of zinc, copper and iron ~but might also include Co, Ni, Pb and precious metals) it would be desirable to separate all three, Zn largely in the leachate, Cu in the residue with most of the iron which could be removed from the residue with hot water.
It is an object of the present invention to provide a process in which at least the above-identified disadvantage is obviated or substantially reduced.
According to the present invention there is provided a process for the recovery o metal from a feedstock including at least two metals comprising the steps of contacting said feedstock with an aqueous mixture leachate comprising ammonium nitrate of a concentration greater than 3.S M and sulfuric acid having a concentration of more than 65~ by weight to produce a residue comprising cuprous salt, an iron salt and sulfur;
separating residue from said leachate; cementing the cupric ion in the leachate with zinc powder; separating the cemented copper powder from leachate of one of said at least two metals; passing said leachate through a heat ., ,~ ", . . . !
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exchanger to reduce the amount o~ soluble iron salt and bring the leachate to a temperature of 60 to 80C for electrowinning; electrowinning said one of said at least two metals; dissolving the cuprous salt in a suitable solvent; disproportionating the cuprous solution;
separating the copper powder from the cupric solution;
electrowinning the cupric ion solution; and treating appropriately the remaining solids.
BRIEF DESCRIPTION OF THE DRAWINGS
The single figure of the accompanying drawing shows a process according to one embodiment of the invention.
DETAILED DESCRIPTION OE THE PREFERRED EMBODIMENT
Referring to the figure, the feedstock, preferably a concentrate containing Zn and Cu in their sulfide minerals, is fed to a primary leaching tank 2 where the zinc (Zn) is dissolved. Iron (Fe) is also dissolved as well as any other base metal which is present excep,t lead (Pb) which will be only partially dissolved with the white residue containing some iron, cuprous salt, milk of sulfur and precious metals.
The pregnant solution is passed through a heat exchanger 4 where its temperature is reduced from about 120C to about 60C. Excess iron salts will be precipitated and removed and then distributed between the anode and cathode compartments (6,8) of a subsequent electrowinning cell 10. The two compartments are separated by a cation exchange membrane 12, such as NAFION*. Zinc is removed at the cathode as a product and the barren solution is returned through the heat exchanger 4 to the leaching tank 2. Any gaseous nitrogen oxides are sparged into the anode chamber 6 for reoxidation to nitrate ion or the 2 produced in the electrowinning (both Cu and Zn) and returned with the barren solution to the leaching tank 2. Sul~uric acid and ammonium nitrate are * Trade Mark .:
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added as reactants to the leaching tank 2 to start the process step. When the process is operating sufficient some sulfur will be oxidized to sulfuric acid to supply the process. The nitrate ion (or its active products) will be regenerated but some ammonia will need to be added. - -The residue is preferably blown down periodically to a wash tank 14 where hot water will dissolve the ferrous ammonium sulfate as iron (Fe) product for use as `
fertilizer. The water will be evaporated and the vapour condensed in the multiple heat exchanger (4, 16) to produce the hot water for the wash stage 14. The residue is then dried (the water being again condensed to provide some of the hot water wash) and the residue leached in vessel 16 for cuprous salts with acetonitrile. The copper acetonitrile leach solution is pumped to a disproportionation chamber 18 where the cupric solution is removed and the copper powder washed and stored as a product.
The cupric solution is evaporated, the acetonitrile vapour being condensed in the copper leach vessel 16 and the cupric salt made up with water from the wash water circuit 20 for electrowinning in cell 22. From the cathode of the electrowinning cell 22 the copper is stored ~
as product and the barren solution added to the barren ;
solution from the zinc electrowinning circuit incorporating cell 10. Some oxygen will be produced at the anode of the copper electrowinning cell 22 unless some of the nitrogen oxides are introduced into the anode compartment for reoxidizing to the nitrate ion for return to the primary leach tank 2.
The residue from the cuprous acetonile leach is heated to 150 to 200C in unit 24 to vaporize the sulfur which is condensed on a cold surface 2~ as flowers of sulfur and stored as product. Alternatively, the sulfur can be removed by dissolving it in toluene and evaporating the toluene.
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The remaining residue is further treated for precious metals of palladium (Pd) or silver (Ag). If silver is present, the residue is leached in chamber 28 with strong ammonium hydroxide and the solution is electrowon in cell 30. This gives silver to be stored as product and the ammonium hydroxide barren solution is reused as leach in chamber 23.
If gold (Au) is present, it can be removed or recovered in any of the usual ways such as gravity separation if present in large particles, cyanidation and electrowinning if not. The residue could also be treated with aqua regia in tank 32 and electrowon from that solution. In the electrowinning cell 34 there would, in the first case, be some oxygen produced which could be used (and is necessary in the cyanidation process. The other oxygen produced in other electrowinning tanks could also contribute to the rate of cyanidat.ion in a pachuca tank (not shown) or for oxidation of N0x (x being an appropriate number). A wash tank 36 is shown in the figure.
As will be appreciated, oxygen can be sold or used to burn sulfur to make sulfuric acid for sale, or to give more efficient thermal return ~rom burning fuels for the heat needed for sulfur vaporization.
In the described embodiment above it will be understood the ore of copper, zinc etc. is treated without having to include a 10tation step for separating the metals. The zinc goes into solution. Half the usual energy for an electrowinning step is saved and the described process is always above the melting point of sulphur. No trouble was experienced with iron.
As will be seen above the process includes the following steps:
(a) contacting the feedstock with an aqueous solution comprised of sulfuric acid with a concentration greater than lO M, preferably 65% by weight or more, or about equal parts by volume or water and sulfuric acid, - ~ , - ` ~ - ~ .
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ammonium nitrate of concentration greater than 3 M which produces a residue comprising a cuprous salt, a ferrous salt, arsenius oxide if arsenic is present, silver sulfate if silver is present, metallic gold if gold is present, milk of sulfur and gangue;
(b? separating the residue from the leachate;
(c) electrowinning zinc from the leachate;
(d) taking up the cuprous salt in acetonitrile;
(e) causing the acetonitrile solution to disproportionate into copper powder and cupric ion; and (f) electrowinning the copper from the solution, or evaporating the solution and making an acidic aqueous solution for electrowinning the copper.
It iS believed that there are no particular restrictions on the feedstock, but prefera~ly the feedstock is a concentrate, a rich ore or a combination Of the two. Suitable but non-limiting examples of feedstocks include chalcopyrite, chalcocite, bornite, tetrahedrite, sphalerite, galena, molybdite, pyrite and arsenopyrite.
Typically, the ~eedstock is preferably in particulate form, ground so that 75% passes 275 mesh before contacting with the aqueous solution.
In certain cases the feedstock may comprise a variety of metals including the three mentioned, copper, zinc an iron. Examples are mixtures of chalcopyrite and sphalerite, and bornite and sphalerite as well as some arsenical minerals. A preferred aspect is to recover as useful products Zn, Cu and Fe and any precious metals or other base metals present.
In the initial step of contacting the feedstock with the leach solution, the leach solution should consist of more than 50% by volume sulfuric acid and water or about 10 M or more, but preferably about 10 M. The ammonium nitrate should be 2 to 4 M by preference 3 M.
The reaction should be conducted slightly above the melting point of sulfur (112 - 119) at about 120 to 130 C
and just below the boiling point of the solution, 140 C.
In step (b) of the process the leachate is separated from the residue, the leachate containing mainly zinc and iron, and the residue containing cuprous salts, sulfur and ferrous salts. There are no particular restrictions on how the residue is separated from the leachate. The leachate can be tapped off continuously above the expected level of the residue, the residue can be "blown down" at intervals if continuous operation is used, or the residue can be washed out of the leach tank.
By step (c) the leachate solution can be electrowon for zinc after cooling and separating from the ferrous compound expected to precipitate (because the temperature coefficient of ferrous salts is greater than that of Zn salts) during heat exchange cooling. Some water may be allowed to evaporate during the heat exchange.
The residue from step (b) in a preferred aspect will be further treated to recover copper. This preferred treatment consists of several steps:
(i) treating the residue with hot water to remove the ferrous compound;
(ii) dissolving the cuprous salt in a suitable nitrogen-containing solvent, preferably ,acetonitrile;
(iii) heating the remaining residue to 150 to 200C
to vaporize the sulfur which is condensed on a cool surface as flowers of sulfur;
(iv) disproportionating the cuprous salt producing cupric ion in solution and a precipate of metallic copper powder;
(v) separating the solution from the copper powder;
(vi~ recovering the cupric ion from solution by vapour distillation to recover the cupric ion as a cupric salt;
(vii) recovering the solvent by condensing the solvent vapour;
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(viii) preparing a suitable electrowinning solution from the cupric salt; and (ix) electrowinning the copper.
It will be seen that the process is a hydrometallurgical process consisting of two parts:
a leaching process conducted at temperatures in the range of 120 to 130C and at slightly below one atmosphere in which a concentrate (or very rich ore) is subjected to a solution of 50% by volume sulfuric acid and 3 M ammonium nitrate for 10 to 20 minutes (in the batch operation).
Most of the Fe present is deposited as an iron ammonium sulfate, the copper as cuprous ammonium sulfate, the ~-arsenic as arsenious oxide, about 2/3 of the sulfur as flowers of sulfur, the silver as silver sulfate, the gold in the metallic state. The hot solution contains all of the Zn, about 1/2 of the Fe and a small amount of the copper as well as any Ni, Co, Mo etc. The solution is cooled in an open heat exchanger (the excess heat returned to the leach tank) some water is evaporated and the wash water from the tailings added before the Zn electrowinning stage. The electrowinning also reoxidizes the nitrogen ox;des to nitrate ion and the barren so:lution is returned to the leach tanks. The remaining Fe, S, Cu, Ag, Au and As are selectively solubilized for separating. The ;`
uniqueness of the process is that the Zn electrowinning or anode oxygen reoxidizes the nitrate and does not reguire elimination of nitrate, the copper is electrowon separately and up to 1/2 of the copper is produced as copper powder, the other 50% is electrowon for a saving of about one half the power and any other metal, precious, or base can be separately treated, plus no polluting effluents are released.
As mentioned above, oxygen is shown as a product from the Cu electrowinning. It is possible that all of the oxygen generated (including the alternative of generating oxygen at the Zn refining anodes) will be - ., - ~ :
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needed to regenerate the oxidizing solution for the leach tank, and perhaps some air will be needed as well. The oxidized gases will be absorbed in the barren solutions coming back into the concentrate leach tank. There will be come nitrous oxide and nitrogen as tail gases to be vented, and if there is some air needed even more nitrogen for venting.
It will thus be readily apparent -to a person skilled in the art that a number of variations and modifications can be made without departing from the true spirit of the invention which will now be pointed out in the appended claims.
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Soc., 9th meeting date 1987, 241-7, Edited by Pawel Nowak, Pol. Chem. Soc.: Warsaw Pol.) found that deposition of minor amounts of silver on the surface of chalcopyrite catalysed the rate of dissolution by electrochemical means. Obviously use of high temperatures and acetonitrile and nitrate oxidizing acid media are known, but, as will be shown, a unique combination and e~tension of all of these factors results in a new and eminently useful process.
It would be desirable to have an economical process for removing metal from complicated ores and concentrates that did not require smelting or produce polluting effluents by other means. In cases where the feedstock consisted primarily of zinc, copper and iron ~but might also include Co, Ni, Pb and precious metals) it would be desirable to separate all three, Zn largely in the leachate, Cu in the residue with most of the iron which could be removed from the residue with hot water.
It is an object of the present invention to provide a process in which at least the above-identified disadvantage is obviated or substantially reduced.
According to the present invention there is provided a process for the recovery o metal from a feedstock including at least two metals comprising the steps of contacting said feedstock with an aqueous mixture leachate comprising ammonium nitrate of a concentration greater than 3.S M and sulfuric acid having a concentration of more than 65~ by weight to produce a residue comprising cuprous salt, an iron salt and sulfur;
separating residue from said leachate; cementing the cupric ion in the leachate with zinc powder; separating the cemented copper powder from leachate of one of said at least two metals; passing said leachate through a heat ., ,~ ", . . . !
' ' ' ~ . ' ' _ 4 _ ~ ~ r~
exchanger to reduce the amount o~ soluble iron salt and bring the leachate to a temperature of 60 to 80C for electrowinning; electrowinning said one of said at least two metals; dissolving the cuprous salt in a suitable solvent; disproportionating the cuprous solution;
separating the copper powder from the cupric solution;
electrowinning the cupric ion solution; and treating appropriately the remaining solids.
BRIEF DESCRIPTION OF THE DRAWINGS
The single figure of the accompanying drawing shows a process according to one embodiment of the invention.
DETAILED DESCRIPTION OE THE PREFERRED EMBODIMENT
Referring to the figure, the feedstock, preferably a concentrate containing Zn and Cu in their sulfide minerals, is fed to a primary leaching tank 2 where the zinc (Zn) is dissolved. Iron (Fe) is also dissolved as well as any other base metal which is present excep,t lead (Pb) which will be only partially dissolved with the white residue containing some iron, cuprous salt, milk of sulfur and precious metals.
The pregnant solution is passed through a heat exchanger 4 where its temperature is reduced from about 120C to about 60C. Excess iron salts will be precipitated and removed and then distributed between the anode and cathode compartments (6,8) of a subsequent electrowinning cell 10. The two compartments are separated by a cation exchange membrane 12, such as NAFION*. Zinc is removed at the cathode as a product and the barren solution is returned through the heat exchanger 4 to the leaching tank 2. Any gaseous nitrogen oxides are sparged into the anode chamber 6 for reoxidation to nitrate ion or the 2 produced in the electrowinning (both Cu and Zn) and returned with the barren solution to the leaching tank 2. Sul~uric acid and ammonium nitrate are * Trade Mark .:
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added as reactants to the leaching tank 2 to start the process step. When the process is operating sufficient some sulfur will be oxidized to sulfuric acid to supply the process. The nitrate ion (or its active products) will be regenerated but some ammonia will need to be added. - -The residue is preferably blown down periodically to a wash tank 14 where hot water will dissolve the ferrous ammonium sulfate as iron (Fe) product for use as `
fertilizer. The water will be evaporated and the vapour condensed in the multiple heat exchanger (4, 16) to produce the hot water for the wash stage 14. The residue is then dried (the water being again condensed to provide some of the hot water wash) and the residue leached in vessel 16 for cuprous salts with acetonitrile. The copper acetonitrile leach solution is pumped to a disproportionation chamber 18 where the cupric solution is removed and the copper powder washed and stored as a product.
The cupric solution is evaporated, the acetonitrile vapour being condensed in the copper leach vessel 16 and the cupric salt made up with water from the wash water circuit 20 for electrowinning in cell 22. From the cathode of the electrowinning cell 22 the copper is stored ~
as product and the barren solution added to the barren ;
solution from the zinc electrowinning circuit incorporating cell 10. Some oxygen will be produced at the anode of the copper electrowinning cell 22 unless some of the nitrogen oxides are introduced into the anode compartment for reoxidizing to the nitrate ion for return to the primary leach tank 2.
The residue from the cuprous acetonile leach is heated to 150 to 200C in unit 24 to vaporize the sulfur which is condensed on a cold surface 2~ as flowers of sulfur and stored as product. Alternatively, the sulfur can be removed by dissolving it in toluene and evaporating the toluene.
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The remaining residue is further treated for precious metals of palladium (Pd) or silver (Ag). If silver is present, the residue is leached in chamber 28 with strong ammonium hydroxide and the solution is electrowon in cell 30. This gives silver to be stored as product and the ammonium hydroxide barren solution is reused as leach in chamber 23.
If gold (Au) is present, it can be removed or recovered in any of the usual ways such as gravity separation if present in large particles, cyanidation and electrowinning if not. The residue could also be treated with aqua regia in tank 32 and electrowon from that solution. In the electrowinning cell 34 there would, in the first case, be some oxygen produced which could be used (and is necessary in the cyanidation process. The other oxygen produced in other electrowinning tanks could also contribute to the rate of cyanidat.ion in a pachuca tank (not shown) or for oxidation of N0x (x being an appropriate number). A wash tank 36 is shown in the figure.
As will be appreciated, oxygen can be sold or used to burn sulfur to make sulfuric acid for sale, or to give more efficient thermal return ~rom burning fuels for the heat needed for sulfur vaporization.
In the described embodiment above it will be understood the ore of copper, zinc etc. is treated without having to include a 10tation step for separating the metals. The zinc goes into solution. Half the usual energy for an electrowinning step is saved and the described process is always above the melting point of sulphur. No trouble was experienced with iron.
As will be seen above the process includes the following steps:
(a) contacting the feedstock with an aqueous solution comprised of sulfuric acid with a concentration greater than lO M, preferably 65% by weight or more, or about equal parts by volume or water and sulfuric acid, - ~ , - ` ~ - ~ .
.; , . .
~, . , :
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ammonium nitrate of concentration greater than 3 M which produces a residue comprising a cuprous salt, a ferrous salt, arsenius oxide if arsenic is present, silver sulfate if silver is present, metallic gold if gold is present, milk of sulfur and gangue;
(b? separating the residue from the leachate;
(c) electrowinning zinc from the leachate;
(d) taking up the cuprous salt in acetonitrile;
(e) causing the acetonitrile solution to disproportionate into copper powder and cupric ion; and (f) electrowinning the copper from the solution, or evaporating the solution and making an acidic aqueous solution for electrowinning the copper.
It iS believed that there are no particular restrictions on the feedstock, but prefera~ly the feedstock is a concentrate, a rich ore or a combination Of the two. Suitable but non-limiting examples of feedstocks include chalcopyrite, chalcocite, bornite, tetrahedrite, sphalerite, galena, molybdite, pyrite and arsenopyrite.
Typically, the ~eedstock is preferably in particulate form, ground so that 75% passes 275 mesh before contacting with the aqueous solution.
In certain cases the feedstock may comprise a variety of metals including the three mentioned, copper, zinc an iron. Examples are mixtures of chalcopyrite and sphalerite, and bornite and sphalerite as well as some arsenical minerals. A preferred aspect is to recover as useful products Zn, Cu and Fe and any precious metals or other base metals present.
In the initial step of contacting the feedstock with the leach solution, the leach solution should consist of more than 50% by volume sulfuric acid and water or about 10 M or more, but preferably about 10 M. The ammonium nitrate should be 2 to 4 M by preference 3 M.
The reaction should be conducted slightly above the melting point of sulfur (112 - 119) at about 120 to 130 C
and just below the boiling point of the solution, 140 C.
In step (b) of the process the leachate is separated from the residue, the leachate containing mainly zinc and iron, and the residue containing cuprous salts, sulfur and ferrous salts. There are no particular restrictions on how the residue is separated from the leachate. The leachate can be tapped off continuously above the expected level of the residue, the residue can be "blown down" at intervals if continuous operation is used, or the residue can be washed out of the leach tank.
By step (c) the leachate solution can be electrowon for zinc after cooling and separating from the ferrous compound expected to precipitate (because the temperature coefficient of ferrous salts is greater than that of Zn salts) during heat exchange cooling. Some water may be allowed to evaporate during the heat exchange.
The residue from step (b) in a preferred aspect will be further treated to recover copper. This preferred treatment consists of several steps:
(i) treating the residue with hot water to remove the ferrous compound;
(ii) dissolving the cuprous salt in a suitable nitrogen-containing solvent, preferably ,acetonitrile;
(iii) heating the remaining residue to 150 to 200C
to vaporize the sulfur which is condensed on a cool surface as flowers of sulfur;
(iv) disproportionating the cuprous salt producing cupric ion in solution and a precipate of metallic copper powder;
(v) separating the solution from the copper powder;
(vi~ recovering the cupric ion from solution by vapour distillation to recover the cupric ion as a cupric salt;
(vii) recovering the solvent by condensing the solvent vapour;
., ~ . , .. :, . .
9 ~'7~3~ ~
(viii) preparing a suitable electrowinning solution from the cupric salt; and (ix) electrowinning the copper.
It will be seen that the process is a hydrometallurgical process consisting of two parts:
a leaching process conducted at temperatures in the range of 120 to 130C and at slightly below one atmosphere in which a concentrate (or very rich ore) is subjected to a solution of 50% by volume sulfuric acid and 3 M ammonium nitrate for 10 to 20 minutes (in the batch operation).
Most of the Fe present is deposited as an iron ammonium sulfate, the copper as cuprous ammonium sulfate, the ~-arsenic as arsenious oxide, about 2/3 of the sulfur as flowers of sulfur, the silver as silver sulfate, the gold in the metallic state. The hot solution contains all of the Zn, about 1/2 of the Fe and a small amount of the copper as well as any Ni, Co, Mo etc. The solution is cooled in an open heat exchanger (the excess heat returned to the leach tank) some water is evaporated and the wash water from the tailings added before the Zn electrowinning stage. The electrowinning also reoxidizes the nitrogen ox;des to nitrate ion and the barren so:lution is returned to the leach tanks. The remaining Fe, S, Cu, Ag, Au and As are selectively solubilized for separating. The ;`
uniqueness of the process is that the Zn electrowinning or anode oxygen reoxidizes the nitrate and does not reguire elimination of nitrate, the copper is electrowon separately and up to 1/2 of the copper is produced as copper powder, the other 50% is electrowon for a saving of about one half the power and any other metal, precious, or base can be separately treated, plus no polluting effluents are released.
As mentioned above, oxygen is shown as a product from the Cu electrowinning. It is possible that all of the oxygen generated (including the alternative of generating oxygen at the Zn refining anodes) will be - ., - ~ :
:~ ~ : , ., : ..
. . ' ~, , .:
:
~ ~ '7 ~
needed to regenerate the oxidizing solution for the leach tank, and perhaps some air will be needed as well. The oxidized gases will be absorbed in the barren solutions coming back into the concentrate leach tank. There will be come nitrous oxide and nitrogen as tail gases to be vented, and if there is some air needed even more nitrogen for venting.
It will thus be readily apparent -to a person skilled in the art that a number of variations and modifications can be made without departing from the true spirit of the invention which will now be pointed out in the appended claims.
-:
-, : , -, ,:: ~ ;
Claims (29)
1. A process for the recovery of metal from a feedstock including at least two metals comprising the steps of:
(a) contacting said feedstock with an aqueous mixture leachate comprising ammonium nitrate of a concentration greater than 3.5 M and sulfuric acid having a concentration of more than 65% to produce a residue comprising cuprous salt, an iron salt and sulfur;
(b) separating residue from said leachate;
(c) cementing the cupric ion in the leachate with zinc powder;
(d) separating the cemented copper powder from leachate of one of said at least two metals;
(e) passing said leachate through a heat exchanger to reduce the amount of soluble iron salt and bring the leachate to a temperature of 60 to 80°C for electrowinning;
(f) electrowinning said one of said at least two metals;
(g) dissolving the cuprous salt: in a suitable solvent;
(h) disproportionating the cuprous solution;
(i) separating the copper powder from the cupric solution;
(j) electrowinning the cupric ion solution; and (k) treating appropriately the remaining solids.
(a) contacting said feedstock with an aqueous mixture leachate comprising ammonium nitrate of a concentration greater than 3.5 M and sulfuric acid having a concentration of more than 65% to produce a residue comprising cuprous salt, an iron salt and sulfur;
(b) separating residue from said leachate;
(c) cementing the cupric ion in the leachate with zinc powder;
(d) separating the cemented copper powder from leachate of one of said at least two metals;
(e) passing said leachate through a heat exchanger to reduce the amount of soluble iron salt and bring the leachate to a temperature of 60 to 80°C for electrowinning;
(f) electrowinning said one of said at least two metals;
(g) dissolving the cuprous salt: in a suitable solvent;
(h) disproportionating the cuprous solution;
(i) separating the copper powder from the cupric solution;
(j) electrowinning the cupric ion solution; and (k) treating appropriately the remaining solids.
2. A process for the recovery of metal from a feedstock including at least two metals comprising the steps of:
(a) contacting said feedstock with an aqueous mixture leachate comprising ammonium nitrate of a concentration greater than 3.5 M and sulfuric acid having a concentration of more than 65% to produce a residue comprising cuprous salt, an iron salt and sulfur;
(b) separating residue from said leachate;
(c) cementing the cupric ion in the leachate with zinc powder;
(d) separating the cemented copper powder from leachate of one of said at least two metals;
(e) passing said leachate through a heat exchanger to reduce the amount of soluble iron salt and bring the leachate to a temperature of 60 to 80°C for electrowinning;
(f) electrowinning said one of said at least two metals;
(g) dissolving the cuprous salt in a suitable solvent;
(h) disproportionating the cuprous solution;
(i) separating the copper powder from the cupric solution;
(j) electrowinning the cupric ion solution;
(k) treating appropriately the remaining solids;
(l) treating any gaseous nitrogen oxides at the anode in step (f) or separately with O2 generated at the anode or air as required; and (m) reabsorbing the oxidized nitrogen oxides in the barren solution from step (f) for return to the leach cycle.
(a) contacting said feedstock with an aqueous mixture leachate comprising ammonium nitrate of a concentration greater than 3.5 M and sulfuric acid having a concentration of more than 65% to produce a residue comprising cuprous salt, an iron salt and sulfur;
(b) separating residue from said leachate;
(c) cementing the cupric ion in the leachate with zinc powder;
(d) separating the cemented copper powder from leachate of one of said at least two metals;
(e) passing said leachate through a heat exchanger to reduce the amount of soluble iron salt and bring the leachate to a temperature of 60 to 80°C for electrowinning;
(f) electrowinning said one of said at least two metals;
(g) dissolving the cuprous salt in a suitable solvent;
(h) disproportionating the cuprous solution;
(i) separating the copper powder from the cupric solution;
(j) electrowinning the cupric ion solution;
(k) treating appropriately the remaining solids;
(l) treating any gaseous nitrogen oxides at the anode in step (f) or separately with O2 generated at the anode or air as required; and (m) reabsorbing the oxidized nitrogen oxides in the barren solution from step (f) for return to the leach cycle.
3. A process as defined in claim 1 or 2 wherein said two metals are copper and zinc.
4. The process as defined in claim 1 or 2, wherein said feedstock is selected from at least one of an ore, a concentrate or a combination thereof.
5. The process as defined in claim 1, wherein said ore or concentrate is selected from the group consisting essentially of sulfide ore and arsenide ore.
6. The process as defined in claim 5, wherein said arsenide ore comprises at least one member of the group consisting essentially of iron diarsenide and other base and noble metals.
7. The process as defined in claim 6, wherein said sulfide ore comprises at least one member selected from the group consisting of chalcopyrite, chalcocite, covelite, bornite, molydate, pyrite, arsenopyrite, sphalerite and tetrahedrite.
8. The process as defined in claim 1 or 2, wherein step (a) is conducted at a temperature above 120 degrees Celcius and below the boiling point of the solution (about 140 C).
9. The process as defined in claim 1 or 2, wherein the ore concentrate is ground to a size where 75%
passes 275 mesh screen prior to contact with the aqueous mixture.
passes 275 mesh screen prior to contact with the aqueous mixture.
10. The process as defined in claim 4, wherein the ore concentrate is ground to a size such that 75% will pass a 275 mesh sieve prior to contact with the aqueous mixture.
11. The process as defined in claim 1 wherein step (g) includes further treatment.
12. The process as defined in claim 1 wherein the cuprous salt is leached with a suitable solvent, disproportionated, the metallic copper removed and the remaining cupric ion solution evaporated and the solvent condensed for further leaching.
13. The process as defined in claim 12 wherein said suitable solvent is acetonitrile.
14. The process as defined in claim 1 wherein said sulfur is vapour distilled by heating said residue to approximately 200 degrees Celcius and impinging said vapour on a cold plate to collect the sulfur.
15. The process as defined in claim 1 wherein said iron salt is partially soluble and is dissolved in hot water, the solution cooled and separated from the iron salt and reserved for further iron salt leaches.
16. The process as defined in claim 1 wherein any remaining residue is treated for precious and other base metals.
17. The process as defined in claim 12 wherein the cupric salt is now taken up in water and the copper is electrowon.
18. The process as defined in claim 3 wherein barren solutions from the electrowinning steps for both Zn and Cu are passed through the heat exchanger and then added to the original leachate with a new charge of ore.
19. The process as defined in claim 18 wherein said barren electrowinning solutions are mixed with an incoming charge consisting of ammonium nitrate, ammonia gas and the ore/concentrate.
20. The process as defined in claim 19 wherein the leaching operation is operated at just below the ambient pressure and any nitrogen oxide gasses are passed into the Zn electrowinning cells in an anode compartment.
21. The process as defined in claim 20 wherein the Zn electrowinning anode compartment is isolated from the cathode compartment by a cation exchange membrane to prevent nitrogen oxide gasses diffusing to a respective cathode compartment.
22. The process as defined in claim 16 including the additional steps of (a) determining if any precious metals are present;
(b) if precious metals are present, leaching any residue with strong ammonium hydroxide to solubilize any silver;
(c) electrowinning said silver; and (d) retaining the resultant barren solution for further leaches.
(b) if precious metals are present, leaching any residue with strong ammonium hydroxide to solubilize any silver;
(c) electrowinning said silver; and (d) retaining the resultant barren solution for further leaches.
23. The process as defined in claim 22 wherein any surplus is added as appropriate to the original leach solution.
24. The process as defined in claim 22 including the step of removing any gold by gravity separation.
25. The process as defined in claim 24 wherein said gravity separation is in a jig.
26. The process as defined in claim 24 including the steps of (a) boiling in aqua regia; and (b) electrowinning.
27. The process as defined in claim 24 including the steps of (a) treating with potassium cyanide in basic solution; and (b) electrowinning.
28. The process as defined in claim 24 including the steps of (a) amalgamating with mercury; and (b) distilling off the mercury.
29. The process as defined in claim 24 wherein any final residue is washed and discarded and the wash water is reserved as make-up water for other processes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2070315 CA2070315A1 (en) | 1992-06-03 | 1992-06-03 | Recovery of metal from an ore |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2070315 CA2070315A1 (en) | 1992-06-03 | 1992-06-03 | Recovery of metal from an ore |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2070315A1 true CA2070315A1 (en) | 1993-12-04 |
Family
ID=4149958
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2070315 Abandoned CA2070315A1 (en) | 1992-06-03 | 1992-06-03 | Recovery of metal from an ore |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2070315A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1994017216A1 (en) * | 1993-01-27 | 1994-08-04 | R & O Mining Processing Ltd. | Hydrometallurgical recovery of metals from complex ores |
| US5711922A (en) * | 1994-08-15 | 1998-01-27 | R & O Mining Processing Ltd | Preferential hydrometallurgical conversion of zinc sulfide to sulfate from zinc sulfide containing ores and concentrates |
| CN113426818A (en) * | 2021-07-02 | 2021-09-24 | 昆明理工大学 | Method for fixing heavy metal by adding lime powder after pyrolysis of tailings |
-
1992
- 1992-06-03 CA CA 2070315 patent/CA2070315A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1994017216A1 (en) * | 1993-01-27 | 1994-08-04 | R & O Mining Processing Ltd. | Hydrometallurgical recovery of metals from complex ores |
| EP0677118A1 (en) * | 1993-01-27 | 1995-10-18 | R & O Mining Processing Ltd | Hydrometallurgical recovery of metals from complex ores. |
| US5484579A (en) * | 1993-01-27 | 1996-01-16 | R & O Mining Processing Ltd. | Hydrometallurical recovery of copper and zinc from complex sulfide ores |
| AU670670B2 (en) * | 1993-01-27 | 1996-07-25 | R & O Mining Processing Ltd. | Hydrometallurgical recovery of metals from complex ores |
| US5711922A (en) * | 1994-08-15 | 1998-01-27 | R & O Mining Processing Ltd | Preferential hydrometallurgical conversion of zinc sulfide to sulfate from zinc sulfide containing ores and concentrates |
| CN113426818A (en) * | 2021-07-02 | 2021-09-24 | 昆明理工大学 | Method for fixing heavy metal by adding lime powder after pyrolysis of tailings |
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