CA1074530A - Methods of separating and recovering copper from materials containing copper - Google Patents
Methods of separating and recovering copper from materials containing copperInfo
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- CA1074530A CA1074530A CA257,138A CA257138A CA1074530A CA 1074530 A CA1074530 A CA 1074530A CA 257138 A CA257138 A CA 257138A CA 1074530 A CA1074530 A CA 1074530A
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- copper
- sulphate
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- solution
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Abstract
ABSTRACT OF THE DISCLOSURE
Cuprous sulphate solutions, suitable for thermal or electochemical disproportionation to yield copper, are obtained by dissolving copper sulphites, such as Chevreul's salt or cuprous ammonium sulphite, in acetonitrile-water or 2 hydroxycyanoethane-water mixtures, preferably in the presence of cupric sulphate. This discovery is capable of a number of applications, one of which is the recovery of copper from chalcopyrite by the following five steps.
An oxidising roast of chalcopyrite such as to produce either cupric sulphate and/or copper oxide, leaching of cupric sulphate from the calcine, precipitation of Chevreul's salt and/or other copper sulphites with a soluble salt of sulphurous acid, including bisulphites, dissolution of the copper sulphite as cuprous sulphate, using cupric sulphate in an acetonitrile-water solution as oxidant; precipitation of pure copper by thermal disproportionation of the cuprous sulphate solution. Acetonitrile and acidic cupric sulphate solution may be recycled. Advantages over conventional processes, much as roast, leach-electrowin, or smelt, convert, electrorefine, include lower cost, lower energy comsumption, sulplur removal as ammonium sulphate or gypsum, rather than as sulphur dioxide, and rapid throughput. The nett reaction is:
2CuFeS2 + 4H20 + 2 02 + 8NH3 + 2Cu + 4(NH4)2SO4 + Fe203,
Cuprous sulphate solutions, suitable for thermal or electochemical disproportionation to yield copper, are obtained by dissolving copper sulphites, such as Chevreul's salt or cuprous ammonium sulphite, in acetonitrile-water or 2 hydroxycyanoethane-water mixtures, preferably in the presence of cupric sulphate. This discovery is capable of a number of applications, one of which is the recovery of copper from chalcopyrite by the following five steps.
An oxidising roast of chalcopyrite such as to produce either cupric sulphate and/or copper oxide, leaching of cupric sulphate from the calcine, precipitation of Chevreul's salt and/or other copper sulphites with a soluble salt of sulphurous acid, including bisulphites, dissolution of the copper sulphite as cuprous sulphate, using cupric sulphate in an acetonitrile-water solution as oxidant; precipitation of pure copper by thermal disproportionation of the cuprous sulphate solution. Acetonitrile and acidic cupric sulphate solution may be recycled. Advantages over conventional processes, much as roast, leach-electrowin, or smelt, convert, electrorefine, include lower cost, lower energy comsumption, sulplur removal as ammonium sulphate or gypsum, rather than as sulphur dioxide, and rapid throughput. The nett reaction is:
2CuFeS2 + 4H20 + 2 02 + 8NH3 + 2Cu + 4(NH4)2SO4 + Fe203,
Description
BACKGROUND OF INVENTION
It has long been known (see Habashi F. and Du~dale R., Metall, 28, 129 (1974) - Reference 1) that a variety of copper sulphites, including cupric-cuprous sulphite (Chevreul's salt), can be precipitated from solutions of cupric sulphate, using sulphur dioxide sulphurous acid or soluble salts of sulphurous acid as the source of sul-phite ion. Copper sulphites have a variety of stoichio-metries and some contain both copper (II) and copper (I), so it is difficult to define them other than as those salts which are precipitated from copper salt solutions in water by addition of soluble salts of sulphurous acid, which contains sulphite ions. But all are potentially useful intermediates in copper processing. This observation has proved difficult to utilize in the extractive metallurgy of copper, because effective reduction of copper sulphites to metal has required elevated pressures and temperatures well above 100C (see reference 1 above and Arbiter ~., Milligan D., and Mc Clincy, R., I, Chem E. Symposium .
- :. ' :
~ . : . :.. ::: -'' ' ~ -' .~ :
Series No. 42, 1.1 (1975) - Reference 2~. Reduction is often incomplete. Recent work has shown that cuprous ammonium sulphites can be precipitated from copper ammine salt solutions obtained by the oxidative ammonia leaching of chalcopyrite (see Reference 2 above). These were converted to copper metal by heating in an autoclave at 150C and 150 psig. It has also been shown that solutions of cuprous sulphate in water containing per mole of cuprous ion at least 3 moles of certain organic nitriles, notably acetonitrile and 2-hydroxycyanoethane, can be disproportion-ated either thermally (if acetonitrile or other volatile nitriles) to give particul~e copper and cupric sulphate solutions or electrochemically (if acetonitrile or 2-hydroxycyanoethane) to give copper cathodes and cupric sulphate solutions, i.e. Cu2S04 ~ CuS04 + Cu. Solutions of cuprous sulphate in water containing organic nitriles have considerable value as a source of copper (see Parker A.J., Search, 4, 426 (1973) - Reference 3). Thus a method of converting cupric sulphate and slightly soluble copper sulphites to solutions of cuprous sulphate in water con-taining organic nitriles, has useful applications.
SUMMARY OF INVENTION
-In one form the invention resides in a method of pre-paring cuprous sulphate solutions suitable for thermal or electrochemical disproportionation which comprises 11~7~53Q
dissolving copper sul.phites such as Chevreul's salt or copper ammonium sulphites in acetonitrile-water or 2-hydroxycyanoethane-water mixtures, the amount of acet-onitrile or 2-hydroxycyanoethane being at least sufficient to stabilize the resulting cuprous sulphate solution.
Preferably the amount of organic nitrile is greater than 3 moles per mole of Cu+.
In another form, the invention resides in a method of preparing cuprous sulphate solutions suitable for thermal.
or electrochemical disproportionation which comprises dissolving copper sulphites such as Chevreul's salt in acetonitrile-water or 2-hydroxycyanoethane-water mixtures in the presence of cupric sulphate, the amount of acet-onitrile or 2-hydroxycyanoethane being at least sufficient to stabilize the resulting cuprous sulphate solution.
In another form the invention resides in a method of preparing cuprous sulphate solutions suitable for thermal or electrochemical disproportionation which comprises treating a copper sulphate solution with soluble salts of sulphurous acid or with sulphurous acid to precipitate copper sulphites such as Chevreul's salt or cuprous amm-onium sulphite by known processes, separating the salt from the supernatant liquors and dissolving it in an acetonitrile-water or 2-hydroxycyanoethane-water mixture containing cupric sulphate, the amount of acetonitrile or 1~7453~ I
It has long been known (see Habashi F. and Du~dale R., Metall, 28, 129 (1974) - Reference 1) that a variety of copper sulphites, including cupric-cuprous sulphite (Chevreul's salt), can be precipitated from solutions of cupric sulphate, using sulphur dioxide sulphurous acid or soluble salts of sulphurous acid as the source of sul-phite ion. Copper sulphites have a variety of stoichio-metries and some contain both copper (II) and copper (I), so it is difficult to define them other than as those salts which are precipitated from copper salt solutions in water by addition of soluble salts of sulphurous acid, which contains sulphite ions. But all are potentially useful intermediates in copper processing. This observation has proved difficult to utilize in the extractive metallurgy of copper, because effective reduction of copper sulphites to metal has required elevated pressures and temperatures well above 100C (see reference 1 above and Arbiter ~., Milligan D., and Mc Clincy, R., I, Chem E. Symposium .
- :. ' :
~ . : . :.. ::: -'' ' ~ -' .~ :
Series No. 42, 1.1 (1975) - Reference 2~. Reduction is often incomplete. Recent work has shown that cuprous ammonium sulphites can be precipitated from copper ammine salt solutions obtained by the oxidative ammonia leaching of chalcopyrite (see Reference 2 above). These were converted to copper metal by heating in an autoclave at 150C and 150 psig. It has also been shown that solutions of cuprous sulphate in water containing per mole of cuprous ion at least 3 moles of certain organic nitriles, notably acetonitrile and 2-hydroxycyanoethane, can be disproportion-ated either thermally (if acetonitrile or other volatile nitriles) to give particul~e copper and cupric sulphate solutions or electrochemically (if acetonitrile or 2-hydroxycyanoethane) to give copper cathodes and cupric sulphate solutions, i.e. Cu2S04 ~ CuS04 + Cu. Solutions of cuprous sulphate in water containing organic nitriles have considerable value as a source of copper (see Parker A.J., Search, 4, 426 (1973) - Reference 3). Thus a method of converting cupric sulphate and slightly soluble copper sulphites to solutions of cuprous sulphate in water con-taining organic nitriles, has useful applications.
SUMMARY OF INVENTION
-In one form the invention resides in a method of pre-paring cuprous sulphate solutions suitable for thermal or electrochemical disproportionation which comprises 11~7~53Q
dissolving copper sul.phites such as Chevreul's salt or copper ammonium sulphites in acetonitrile-water or 2-hydroxycyanoethane-water mixtures, the amount of acet-onitrile or 2-hydroxycyanoethane being at least sufficient to stabilize the resulting cuprous sulphate solution.
Preferably the amount of organic nitrile is greater than 3 moles per mole of Cu+.
In another form, the invention resides in a method of preparing cuprous sulphate solutions suitable for thermal.
or electrochemical disproportionation which comprises dissolving copper sulphites such as Chevreul's salt in acetonitrile-water or 2-hydroxycyanoethane-water mixtures in the presence of cupric sulphate, the amount of acet-onitrile or 2-hydroxycyanoethane being at least sufficient to stabilize the resulting cuprous sulphate solution.
In another form the invention resides in a method of preparing cuprous sulphate solutions suitable for thermal or electrochemical disproportionation which comprises treating a copper sulphate solution with soluble salts of sulphurous acid or with sulphurous acid to precipitate copper sulphites such as Chevreul's salt or cuprous amm-onium sulphite by known processes, separating the salt from the supernatant liquors and dissolving it in an acetonitrile-water or 2-hydroxycyanoethane-water mixture containing cupric sulphate, the amount of acetonitrile or 1~7453~ I
2-hydroxycyanoethane being sufficient to stabilize the cuprous ion with respect to its disproportionation. It should be noted that 2-hydroxycyanoethane is suitable only in the case where the solution is electrochemically disproportionated, because it is a high boiling nitrile and cannot be distilled from aqueous solution.
In yet another form the invention resides in a method of recovering copper from copper sulphides including chal-copyrite, which comprises roasting the copper sulphide to produce a calcine containing acid soluble copper salts, such as CuS04 and CuO, leaching the calcine by known methods to produce a solution of cupric sulphate, treating the cupric sulphate solution with a soluble salt of sul-phurous acid or with sulphurous acid by known methods to produce copper sulphites such as Chevreul's salt or cuprous ammonium sulphite, separating the copper sulphite from the supernatant liquor and dissolving it in an acetronitrile-water or 2-hydroxycyanoethane-water mixture containing cupric sulphate to produce a cuprous sulphate solution and disproportionating the cuprous sulphate solution to produce copper.
The sulphur dioxide produced during the oxidative roasting of copper sulphides may be absorbed in a solution of a water solubls base such as acqueous ammonia, sodium hydroxide, or sodium carbonate to produce a water soluble salt of sulphurous acid which may be used in the production lV'~'4~3C~
of the copper sulphites such as Chevreul's salt or cuprous ammonium sulphite, whilst the cupric sulphate and acetonitrile or 2-hydroxycyanoethane from the disproportiion-ation of the cuprous sulphate may be recycled.
DESCRIPTION
.
It has been found that the presence of acetonitrile or 2-hydroxycyanoethane strongly enhances the solubility of Chevreul's salt and other cuprous salts, including CuNH4S03 in water. The reaction is less useful but still possible in the presence of ammonium ions (CuNH4S03) than with Chevreul's salt because ammonium sulphate which is a product of the dissolution decreases the solubility of acetonitrile in water and sometimes two layers of solvent form. It has been found that (equationl~ Chevreul's salt under ambient conditions dissolves readily in water con-taining at least 3 moles of acetonitrile per mole of copper produced, to give a solution of cuprous sulphate and cuprous sulphite. Naturally the rate and extent of dissolution increases at higher temperatures.
2CU2So3.CUS03.2H20 ~ Cu2S04 + 2CuHS03 + Cu2S03 + 3H20) ..... (1) Cuprous ammonium sulphite gives a solution of cuprous sulphate, cuprous sulphite and ammonium sulphite in water containing acetonitrile or 2-hydroxycyanoethane.
107~S3(J
An excess of Chevreul's salt gave a solution containing 20 g/litre cuprous ion at 25C and 35 g/litre Cu+ at 50C
when treated with water containing 5.8 M acetonitrile. On distillation of this solution, some S02 was evolved and the acidity increased to 0.04 molar H . Under otherwise identical conditions, but in the absence of acetonitrile less than 2 g/litre of copper could be dissolved from Chevreul's salt.
Distillation of the acetonitrile from one litre of the above acetonitrile-containing solution from reaction (1) at 50C
with the addition of sulphuric acid such as to maintain a pH of 2 or less gave 17 g of particulate copper and blue cupric sulphate solution. Some sulphur dioxide was evolved.
Another useful method of preparing a cuprous sulphate solution is to react a copper sulphite such as Chevreul's salt with various proportions of cupric sulphate in water containing acetonitrile. The sulphite ion reduced cupric sulphate in the presence of acetonitrile provided that the pH is above 1. The proportion of acetonitrile should be at-least 3 moles per mole of Cu+ produced and preferably greater. The reaction proceeds at 25C but faster reactions and higher concentrations of cuprous ion (up to 160 g/litre) can be obtained if reaction is at 50-70C. The resulting cuprous sulphate solution is acidic. Distillation of acetonitrile gives copper if the pH is maintained in the 1074S3(~
vicinity of and preferably below 2 during distillation, the cupric sulphate and acetonitrile are recycled if necessary. The reaction is thought to be as follows:
3CuS04 + Cu2S03.CuS03.2H20 ~ 3Cu2S04 2 4 -(2) The final acidity of the solution depends on the pro-portion of Chevreul's salt to cupric sulphate, the pH
being lower the greater the proportion of cupric sulphate according to equation 2. A desirable ratio is 3 moles of CuS04 per mole of Chevreul's salt. The pH preferably should not go below 1 during reaction, otherwise reaction 2 is incomplete, probably because of acid decomposition of Chevreul's salt to give sulphurous acid. Reactions 1 and 2 produce various amounts of cuprous sulphate, according not only to the proportions of cupric sulphate and Chevreul's salt, but also to the concentration of acetonitrile, the temperature, and the pH of the solution. Some relevant data are in Table I.
Table I: Formation of cuprous sulphate from excess Chevreul's salt and cupric sulphate at 25C in-acetonitrile-water.
(CH3CN) moles litre 1 o 1.95 3.90 5-85 8.ooC
(CuS04) moles litre~1 0.63 0.63 o.63 0.63 excessa (Cu+~a g litre~1 0 33 55 77 l40C
Copper g 0 16 22.5 38.5 70 1~74S30 a) As sulphate b) Copper produced by thermal disproportionation of one litre of solution.
c3 At 65C after 3 hours, total copper (Cu+ + Cu2+) is 158 g/l.
Table II shows the effect of varying the ratio of cupric sulphate to Chevreul's salt in a solution containing 3.90M
acetonitrile and .05 M sulphur dioxide at 25C. The greater the proportion of cupric sulphate to Chevreul's salt, the greater the acidity of the solutions from reaction (2). This variation of the proportion of CuS04 provides a means of controlling the acidity and this is important because in a continuous process the acid gen-erated can be recycled to leach any basic calcine. The reaction has a half life of about 10 minutes and is usually complete after one hour at 25C with stirring. However, the final proportions of Cu+ and Cu2+ are dependent on the temperature. More cuprous sulphate is produced as the temperature is raised above 25 (Table I).
Table II: Effect of proportion of CuS04 to Chevreul~s salt on reaction (2) at 25C.
(CH3CN) = 3.9 M: (S02) = 0.5 M: Reaction time 1 hour.
~074S3~
(Clls04) ChevraeUl's (Cu +Cu ) (cu+) (H2S04) Ma Ma g/litreb g/litreb Mb o.oo 0.31 49 46 o-ol 0.16 0.26 58 51 0.02 0.32 0.21 58 51 o.o6 o.50 0.15 59 5 0.14 o .64 o . lo 38 23 0.13 o .80 o . oS 38 23 0.18 l.oO - 34 16 0.28 a) Initial concentrations b) Concentrations after 1 hour of reaction.
We believe that the optimum conditions for producing copper from Chevreul's salt via reaction ( 2) is to mix cuso4 and Chevreul~s salt in the molar proportion of 2: 1-
In yet another form the invention resides in a method of recovering copper from copper sulphides including chal-copyrite, which comprises roasting the copper sulphide to produce a calcine containing acid soluble copper salts, such as CuS04 and CuO, leaching the calcine by known methods to produce a solution of cupric sulphate, treating the cupric sulphate solution with a soluble salt of sul-phurous acid or with sulphurous acid by known methods to produce copper sulphites such as Chevreul's salt or cuprous ammonium sulphite, separating the copper sulphite from the supernatant liquor and dissolving it in an acetronitrile-water or 2-hydroxycyanoethane-water mixture containing cupric sulphate to produce a cuprous sulphate solution and disproportionating the cuprous sulphate solution to produce copper.
The sulphur dioxide produced during the oxidative roasting of copper sulphides may be absorbed in a solution of a water solubls base such as acqueous ammonia, sodium hydroxide, or sodium carbonate to produce a water soluble salt of sulphurous acid which may be used in the production lV'~'4~3C~
of the copper sulphites such as Chevreul's salt or cuprous ammonium sulphite, whilst the cupric sulphate and acetonitrile or 2-hydroxycyanoethane from the disproportiion-ation of the cuprous sulphate may be recycled.
DESCRIPTION
.
It has been found that the presence of acetonitrile or 2-hydroxycyanoethane strongly enhances the solubility of Chevreul's salt and other cuprous salts, including CuNH4S03 in water. The reaction is less useful but still possible in the presence of ammonium ions (CuNH4S03) than with Chevreul's salt because ammonium sulphate which is a product of the dissolution decreases the solubility of acetonitrile in water and sometimes two layers of solvent form. It has been found that (equationl~ Chevreul's salt under ambient conditions dissolves readily in water con-taining at least 3 moles of acetonitrile per mole of copper produced, to give a solution of cuprous sulphate and cuprous sulphite. Naturally the rate and extent of dissolution increases at higher temperatures.
2CU2So3.CUS03.2H20 ~ Cu2S04 + 2CuHS03 + Cu2S03 + 3H20) ..... (1) Cuprous ammonium sulphite gives a solution of cuprous sulphate, cuprous sulphite and ammonium sulphite in water containing acetonitrile or 2-hydroxycyanoethane.
107~S3(J
An excess of Chevreul's salt gave a solution containing 20 g/litre cuprous ion at 25C and 35 g/litre Cu+ at 50C
when treated with water containing 5.8 M acetonitrile. On distillation of this solution, some S02 was evolved and the acidity increased to 0.04 molar H . Under otherwise identical conditions, but in the absence of acetonitrile less than 2 g/litre of copper could be dissolved from Chevreul's salt.
Distillation of the acetonitrile from one litre of the above acetonitrile-containing solution from reaction (1) at 50C
with the addition of sulphuric acid such as to maintain a pH of 2 or less gave 17 g of particulate copper and blue cupric sulphate solution. Some sulphur dioxide was evolved.
Another useful method of preparing a cuprous sulphate solution is to react a copper sulphite such as Chevreul's salt with various proportions of cupric sulphate in water containing acetonitrile. The sulphite ion reduced cupric sulphate in the presence of acetonitrile provided that the pH is above 1. The proportion of acetonitrile should be at-least 3 moles per mole of Cu+ produced and preferably greater. The reaction proceeds at 25C but faster reactions and higher concentrations of cuprous ion (up to 160 g/litre) can be obtained if reaction is at 50-70C. The resulting cuprous sulphate solution is acidic. Distillation of acetonitrile gives copper if the pH is maintained in the 1074S3(~
vicinity of and preferably below 2 during distillation, the cupric sulphate and acetonitrile are recycled if necessary. The reaction is thought to be as follows:
3CuS04 + Cu2S03.CuS03.2H20 ~ 3Cu2S04 2 4 -(2) The final acidity of the solution depends on the pro-portion of Chevreul's salt to cupric sulphate, the pH
being lower the greater the proportion of cupric sulphate according to equation 2. A desirable ratio is 3 moles of CuS04 per mole of Chevreul's salt. The pH preferably should not go below 1 during reaction, otherwise reaction 2 is incomplete, probably because of acid decomposition of Chevreul's salt to give sulphurous acid. Reactions 1 and 2 produce various amounts of cuprous sulphate, according not only to the proportions of cupric sulphate and Chevreul's salt, but also to the concentration of acetonitrile, the temperature, and the pH of the solution. Some relevant data are in Table I.
Table I: Formation of cuprous sulphate from excess Chevreul's salt and cupric sulphate at 25C in-acetonitrile-water.
(CH3CN) moles litre 1 o 1.95 3.90 5-85 8.ooC
(CuS04) moles litre~1 0.63 0.63 o.63 0.63 excessa (Cu+~a g litre~1 0 33 55 77 l40C
Copper g 0 16 22.5 38.5 70 1~74S30 a) As sulphate b) Copper produced by thermal disproportionation of one litre of solution.
c3 At 65C after 3 hours, total copper (Cu+ + Cu2+) is 158 g/l.
Table II shows the effect of varying the ratio of cupric sulphate to Chevreul's salt in a solution containing 3.90M
acetonitrile and .05 M sulphur dioxide at 25C. The greater the proportion of cupric sulphate to Chevreul's salt, the greater the acidity of the solutions from reaction (2). This variation of the proportion of CuS04 provides a means of controlling the acidity and this is important because in a continuous process the acid gen-erated can be recycled to leach any basic calcine. The reaction has a half life of about 10 minutes and is usually complete after one hour at 25C with stirring. However, the final proportions of Cu+ and Cu2+ are dependent on the temperature. More cuprous sulphate is produced as the temperature is raised above 25 (Table I).
Table II: Effect of proportion of CuS04 to Chevreul~s salt on reaction (2) at 25C.
(CH3CN) = 3.9 M: (S02) = 0.5 M: Reaction time 1 hour.
~074S3~
(Clls04) ChevraeUl's (Cu +Cu ) (cu+) (H2S04) Ma Ma g/litreb g/litreb Mb o.oo 0.31 49 46 o-ol 0.16 0.26 58 51 0.02 0.32 0.21 58 51 o.o6 o.50 0.15 59 5 0.14 o .64 o . lo 38 23 0.13 o .80 o . oS 38 23 0.18 l.oO - 34 16 0.28 a) Initial concentrations b) Concentrations after 1 hour of reaction.
We believe that the optimum conditions for producing copper from Chevreul's salt via reaction ( 2) is to mix cuso4 and Chevreul~s salt in the molar proportion of 2: 1-
3:1 at 50-65C in water containing 30-40% v/v acetonitrile to give a solution containing 100-120 g/l Cu+ as Cu2S04, 15-30 g/l Cu as CUS04, 0.2 - 0.3 M H2S04 and about 0.05 M S02. Thermal disproportionation, gives approximately 50-60 g of pure copper powder per litre of solution if the pH is below 2. Disproportionation at higher pH gives some copper oxides and copper sulphites together with the copper.
One method of producing copper sulphites is indicated below.
Ammonium sulphite solution in water was prepared by bubbling 1~74~30 S2 into 7 M ammonia to give a colourless~ odourless solution of pH 6. This was mixed with various proportions of 0.5 M cupric sulphate solutions in water at 60C to precipitate dark red crystalline Chevreul's salt or brick red (NH4)2S03Cu2S03.2H20)~depending on the molar ratio of cupric ion to ammonium sulphate. The final pH
was 3.5 and some S02 was evolved.
With 1.5 moles (NH4)2S03 to one mole of cupric ion 96%
of the copper was precipitated mainly as Chevreul's sal~;
with 2 ~oles of (NH4)2S03 to one mole of Cu2+, 98% of the copper was precipitated mainly as (NH4)2S03Cu2S03.2H20.
The reactions described above, when coupled with existing technology, provide two promising and rapid methods for -converting copper sulphides to pure copper.
(a) The concentrate is roasted by known methods (cf.
USBM Report of Investigation 7996 - Reference 4) at a temperature of the order 500-800C preferably in a fluid bed roaster and preferably with oxygen enriched air, containing S02 and S03. The reaction is strongly exother-mic, i.e. ~H973K is about 1400 kJ mole 1 of CuFeS2 (10).
The products are often CuO and some copper ferrite as well as the CuS04 shown in equation (5) S + 15 2 ~ 2CuSo4 + 2so2 2 3 according to the roasting conditions, but the ferrites can be kept very low and more than 95% of acid-soluble copper 1(~7~30 can be produced in such a roast. The effluent gas normally contains 5-12% S02, with some S03. The heat produced by the roast may be used for the thermal disproportionation step (Vide infra~.
(b) The calcine is leached of its copper by known methods to give a solution of cupric sulphate.
(c) The S02 produced from the roast is converted to sodium or ammonium sulphite solution by scrubbing the exhaust gases from the roaster with solution of the appropriate base (Na2C03, NaOH, NH3)-(d) The solutions (b) and (c) are mixed so as to precipitate copper sulphites, including CuNH4S03, by known methods.
The copper sulphite is separated from supernatant liquor.
(e) The copper sulphites are dissolved in a solution of cupric sulphate containing water and approximately 40%
v/v acetonitrile so as to give a solution of cuprous sulphate. This is filtered from any residual solids.
(f) The cuprous sulphate solution is thermally dispropor-tionated to give copper powder. Cupric sulphate and the acetonitrile-water distillate are recycled, with provision for a bleed circuit as necessary, to purify the recycling liquors.
~1~'74530 COPPER PURITY
Thermal disproportionation of cuprous sulphate solutions has given coarse copper powder of 99.9% purity. Some relevant data is set out in Table III. They indicate that a relatively coarse, high purity copper powder, suitable for briquetting, should be a possible product of thermal disproportionation. A considerable amount of control over the type of powder produced by thermal disproportionation is possible.
Table III: Purity (ppm) of copper powder produced from cupric sulphate solutions via precipitation of Chevreul's salt, dissolution as cuprous sulphate and thermal dispro-portionation of the resulting cuprous sulphate solution.
.
Impurity Ni Fe Mg Zn Solutiona 9000 9000 24000C 9000 Powder ~5 ~ 5 ~ 7 4 a) These elements were added as their sulphate to a cupric sulphate solution (40 g/litre Cu2+) which was converted to Chevreul's salt, then as described herein dissolved in acetonitrile/water/CuS04 andthermally disproportionated to give copper powder of the purity shown below. b) by atomic absorption. c) This proportion of magnesium as sulphate was in the cuprous sulphate solution, prior to disproportionation.
It should be noted that the Parker method (Reference 3) of refining particulate copper via solutions of cuprous sulphate and disproportionation is applicable to particulate copper from S02 reduction of copper ammine solutions via thermal decomposition of copper sulphites (Reference 2).
~he following specific examples will serve to further describe the invention.
Example I
500 g of chalcopyrite concentrate supplied by Mt. Isa Mines Pty. Ltd. (25% Cu, 28% Fe, 32% S) was roasted wit;h air to 690C in a rotating kiln. When leached with dilute H2S04 at constant pH 2 for one hour, 95% of the copper and 2% of the iron was extracted to give a solution containing 41 g/litre cupric ion. A 0.7 M magnesium bisulphite solution was prepared by bubbling S02 from a cylinder through magnesium carbonate. This was mixed at 70C with an equal volume (500 ml) of the 0.7 M cupric sulphate solution leached from the calcine to precipitate 36 g of Chevreul's salt. A further 4 g of Chevreul's salt was obtained by adding a further 250 ml of 0.7 M Mg (HS03)2.
The 40 g of Chevreul's salt was dissolved in 500 ml of o.63 M cupric sulphate solution at 50C containing 80 g acetonitrile. The solution contained 24 g/litre Mg as MgS04. After 10 minutes a clear lime green solution was 1074S3~3 produced. Steam distillation precipitated 14 g of cry-stalline copper powder containing 10 ppm Mg, and less than 5 ppm Fe, Ni or Zn. The experiment was repeated using copper sulphate containing 9 g/litre Fe, Zn and Ni as sulphates and 24 g/l Mg as sulphate. The copper powder produced, contained 7 ppm Mg, 4 ppm Zn and <5 ppm Fe and Ni by atomic absorption.
Example II
The above experiment was repeated to the stage of diss-olution of the Chevreul's salt, prior to steam distillation at 1/10 the quantities indicated, using twice the con-centration of 2-hydroxycyanoethane (MW = 70) in place of acetonitrile (MW = 41). A solution of 65 gl lCu+ as cuprous sulphate was obtained. 56 g of cuprous ammonium sulphite was dissolved in 500 ml of a solution containing 160 g acetonitrile water and 140 g of CuS04.5H20 at 65C. A
clear solution containing about 100 gl 1 cuprous sulphate was obtained and distillation of the acidified solution gave particulate copper.
The various aspects of the invention are illustrated in the self explanatory flow diagrams shown in the accompanying drawings wherein:
Fig. 1 is a flow diagram showing the production of copper from Chevreul's salt;
Fig. 2 is a flow diagram showing the production of copper from copper ammonium sulphate; and 1~74S30 Fig. 3 is a flow diagram showing the production of copper from copper ore via the Chevreul's salt procedure.
One method of producing copper sulphites is indicated below.
Ammonium sulphite solution in water was prepared by bubbling 1~74~30 S2 into 7 M ammonia to give a colourless~ odourless solution of pH 6. This was mixed with various proportions of 0.5 M cupric sulphate solutions in water at 60C to precipitate dark red crystalline Chevreul's salt or brick red (NH4)2S03Cu2S03.2H20)~depending on the molar ratio of cupric ion to ammonium sulphate. The final pH
was 3.5 and some S02 was evolved.
With 1.5 moles (NH4)2S03 to one mole of cupric ion 96%
of the copper was precipitated mainly as Chevreul's sal~;
with 2 ~oles of (NH4)2S03 to one mole of Cu2+, 98% of the copper was precipitated mainly as (NH4)2S03Cu2S03.2H20.
The reactions described above, when coupled with existing technology, provide two promising and rapid methods for -converting copper sulphides to pure copper.
(a) The concentrate is roasted by known methods (cf.
USBM Report of Investigation 7996 - Reference 4) at a temperature of the order 500-800C preferably in a fluid bed roaster and preferably with oxygen enriched air, containing S02 and S03. The reaction is strongly exother-mic, i.e. ~H973K is about 1400 kJ mole 1 of CuFeS2 (10).
The products are often CuO and some copper ferrite as well as the CuS04 shown in equation (5) S + 15 2 ~ 2CuSo4 + 2so2 2 3 according to the roasting conditions, but the ferrites can be kept very low and more than 95% of acid-soluble copper 1(~7~30 can be produced in such a roast. The effluent gas normally contains 5-12% S02, with some S03. The heat produced by the roast may be used for the thermal disproportionation step (Vide infra~.
(b) The calcine is leached of its copper by known methods to give a solution of cupric sulphate.
(c) The S02 produced from the roast is converted to sodium or ammonium sulphite solution by scrubbing the exhaust gases from the roaster with solution of the appropriate base (Na2C03, NaOH, NH3)-(d) The solutions (b) and (c) are mixed so as to precipitate copper sulphites, including CuNH4S03, by known methods.
The copper sulphite is separated from supernatant liquor.
(e) The copper sulphites are dissolved in a solution of cupric sulphate containing water and approximately 40%
v/v acetonitrile so as to give a solution of cuprous sulphate. This is filtered from any residual solids.
(f) The cuprous sulphate solution is thermally dispropor-tionated to give copper powder. Cupric sulphate and the acetonitrile-water distillate are recycled, with provision for a bleed circuit as necessary, to purify the recycling liquors.
~1~'74530 COPPER PURITY
Thermal disproportionation of cuprous sulphate solutions has given coarse copper powder of 99.9% purity. Some relevant data is set out in Table III. They indicate that a relatively coarse, high purity copper powder, suitable for briquetting, should be a possible product of thermal disproportionation. A considerable amount of control over the type of powder produced by thermal disproportionation is possible.
Table III: Purity (ppm) of copper powder produced from cupric sulphate solutions via precipitation of Chevreul's salt, dissolution as cuprous sulphate and thermal dispro-portionation of the resulting cuprous sulphate solution.
.
Impurity Ni Fe Mg Zn Solutiona 9000 9000 24000C 9000 Powder ~5 ~ 5 ~ 7 4 a) These elements were added as their sulphate to a cupric sulphate solution (40 g/litre Cu2+) which was converted to Chevreul's salt, then as described herein dissolved in acetonitrile/water/CuS04 andthermally disproportionated to give copper powder of the purity shown below. b) by atomic absorption. c) This proportion of magnesium as sulphate was in the cuprous sulphate solution, prior to disproportionation.
It should be noted that the Parker method (Reference 3) of refining particulate copper via solutions of cuprous sulphate and disproportionation is applicable to particulate copper from S02 reduction of copper ammine solutions via thermal decomposition of copper sulphites (Reference 2).
~he following specific examples will serve to further describe the invention.
Example I
500 g of chalcopyrite concentrate supplied by Mt. Isa Mines Pty. Ltd. (25% Cu, 28% Fe, 32% S) was roasted wit;h air to 690C in a rotating kiln. When leached with dilute H2S04 at constant pH 2 for one hour, 95% of the copper and 2% of the iron was extracted to give a solution containing 41 g/litre cupric ion. A 0.7 M magnesium bisulphite solution was prepared by bubbling S02 from a cylinder through magnesium carbonate. This was mixed at 70C with an equal volume (500 ml) of the 0.7 M cupric sulphate solution leached from the calcine to precipitate 36 g of Chevreul's salt. A further 4 g of Chevreul's salt was obtained by adding a further 250 ml of 0.7 M Mg (HS03)2.
The 40 g of Chevreul's salt was dissolved in 500 ml of o.63 M cupric sulphate solution at 50C containing 80 g acetonitrile. The solution contained 24 g/litre Mg as MgS04. After 10 minutes a clear lime green solution was 1074S3~3 produced. Steam distillation precipitated 14 g of cry-stalline copper powder containing 10 ppm Mg, and less than 5 ppm Fe, Ni or Zn. The experiment was repeated using copper sulphate containing 9 g/litre Fe, Zn and Ni as sulphates and 24 g/l Mg as sulphate. The copper powder produced, contained 7 ppm Mg, 4 ppm Zn and <5 ppm Fe and Ni by atomic absorption.
Example II
The above experiment was repeated to the stage of diss-olution of the Chevreul's salt, prior to steam distillation at 1/10 the quantities indicated, using twice the con-centration of 2-hydroxycyanoethane (MW = 70) in place of acetonitrile (MW = 41). A solution of 65 gl lCu+ as cuprous sulphate was obtained. 56 g of cuprous ammonium sulphite was dissolved in 500 ml of a solution containing 160 g acetonitrile water and 140 g of CuS04.5H20 at 65C. A
clear solution containing about 100 gl 1 cuprous sulphate was obtained and distillation of the acidified solution gave particulate copper.
The various aspects of the invention are illustrated in the self explanatory flow diagrams shown in the accompanying drawings wherein:
Fig. 1 is a flow diagram showing the production of copper from Chevreul's salt;
Fig. 2 is a flow diagram showing the production of copper from copper ammonium sulphate; and 1~74S30 Fig. 3 is a flow diagram showing the production of copper from copper ore via the Chevreul's salt procedure.
Claims (8)
1. A method of preparing cuprous sulphate solutions which comprises dissolving copper sulphites, selected from Chevreul's salt and cuprous ammonium sulphite, in a solvent selected from acetonitrile-water, and 2-hydroxy-cyanoethane-water mixtures containing cupric sulphate, the amount of acetonitrile and 2-hydroxycyanoethane being sufficient to stabilize the resulting cuprous sulphate solution.
2. A method of preparing cuprous sulphate solutions as claimed in claim 1 wherein the molar ratio of CuS04 to copper sulphite is 1 to 3.
3. A method of preparing cuprous sulphate solutions which comprises dissolving copper sulphites, selected from Chevreul's salt and coprous ammonium sulphite in a solvent selected from acetonitrile-water and 2-hydroxycyanoethane--water mixtures at temperatures below 95°C, the amount of acetonitrile or 2-hydroxycyanoethane being sufficient to stabilize the resulting cuprous sulphite solution.
4. A method as claimed in claims 1, 2 or 3 wherein the amount of acetonitrile or 2-hydroxycyanoethane is greater than 3 moles per mole of cuprous copper ions (Cu+).
5. A method of preparing cuprous sulphate solutions from cupric sulphate solutions which comprises treating a cupric sulphate solution with a reagent selected from soluble salts of sulphurous acid and sulphurous acid to precipitate slightly water soluble copper sulphites, separating the copper sulphites from the supernatant liquors and dissolving them in a solvent selected from acetonitrile--water and 2-hydroxy-cyanoethane-water mixture containing cupric sulphate to give cuprous sulphate solutions, the amount of acetoni-trile or 2-hydroxycyanoethane being sufficient to stabilize the cuprous ion with respect to its disproportionation.
6. A method of recovering copper from copper sulphides which comprises roasting the copper sulphides under oxi-dising conditions to produce a calcine containing copper salts, leaching the calcine to produce a solution of cupric sulphate, treating the cupric sulphate solution with a reagent selected from a soluble salt of sulphurous acid and with sulphurous acid to precipitate a copper sulphite, sep-arating the copper sulphite from the supernatant liquor and dissolving it in an acetonitrile-water mixture containing cupric sulphate to produce a coprous sulphate solution, then thermally disproportionating the cuprous sulphate solution to produce copper.
7. A method of recovering copper from a member selected from chalcopyrite, other copper ores and concentrates com-prising roasting the ore or other copper containing material to produce a calcine containing copper salts, leaching the calcine with water and dilute acid to produce a solution of cupric sulphate, treating the cupric sulphate solution with a reagent selected from a soluble sulphite salt and with sulphurous acid to produce Chevreal's salt, separating the Chevreul's salt from the supernatant liquor and dissolving it in a solvent selected from acetonitrile-water and 2-hydroxycyanoethane-water mixture containing cupric sulphate to produce a cuprous sulphate solution at a pH of less than 4 and thermally or electrochemically disproportioning the cu-prous sulphate solution to produce copper.
8. A method of recovering copper from a member selected from chalcopyrite, other copper ores and concentrates com-prising roasting the ore or other copper containing material to produce a calcine containing copper salts, leaching the calcine with water and dilute acid to produce a solution of cupric sulphate, heating the cupric sulphate solution with a reagent selected from ammonium, other soluble sulphite and sulphurous acid to a temperature in excess of 100°C to produce particulate copper, separating the particulate copper from the supernatant liquor and dissolving it in a solution of copper sulphate at a pH of less than 4.0 in a solvent selected from water containing sufficient acetoni-trile and 2-hydroxycyanoethane to stabilize the resulting cuprous sulphate solution and thermally or electrochemically disproportionating the cuprous sulphate to produce copper.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA257,138A CA1074530A (en) | 1976-07-16 | 1976-07-16 | Methods of separating and recovering copper from materials containing copper |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA257,138A CA1074530A (en) | 1976-07-16 | 1976-07-16 | Methods of separating and recovering copper from materials containing copper |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1074530A true CA1074530A (en) | 1980-04-01 |
Family
ID=4106443
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA257,138A Expired CA1074530A (en) | 1976-07-16 | 1976-07-16 | Methods of separating and recovering copper from materials containing copper |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1074530A (en) |
-
1976
- 1976-07-16 CA CA257,138A patent/CA1074530A/en not_active Expired
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