CA2098638C - Method for preventing the formation of jarosite and ammonium and alkali based double salts in solvent extraction circuits connected to acidic leaching processes - Google Patents
Method for preventing the formation of jarosite and ammonium and alkali based double salts in solvent extraction circuits connected to acidic leaching processesInfo
- Publication number
- CA2098638C CA2098638C CA002098638A CA2098638A CA2098638C CA 2098638 C CA2098638 C CA 2098638C CA 002098638 A CA002098638 A CA 002098638A CA 2098638 A CA2098638 A CA 2098638A CA 2098638 C CA2098638 C CA 2098638C
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- Prior art keywords
- extraction
- ammonium
- solution
- alkali
- nickel
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0453—Treatment or purification of solutions, e.g. obtained by leaching
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0476—Separation of nickel from cobalt
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/38—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds containing phosphorus
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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
The present invention relates to a method for preventing the formation of jarosite and ammonium- and alkali-based double salts in the solvent extraction of acidic extraction processes. The organic extraction solution is neutralized by ammonium or alkali salts prior to the separation of valuable metals in order to improve the extraction recovery. In a pre-extraction step after the neutralization, the extraction agent is contacted with an aqueous solution containing a metal which replaces the ammonium or alkali ions contained in the extraction solution.
Thus the ammonium or alkali ions are removed from the extraction circuit prior to separation of the valuable metals by extraction.
Thus the ammonium or alkali ions are removed from the extraction circuit prior to separation of the valuable metals by extraction.
Description
2~3~'8 The present invention relates to a method for preventing the formation of jarosite and ammonium- and alkali-based double salts in the solvent extraction of acidic leaching processes, whereby valuable metals are separated.
The organic leaching solution is neutralized by ammonium or alkali salts prior to the separation of valuable metals in order to improve the extraction recovery. In a pre-extraction step after neutralization, the extractant is contacted with an aqueous solution containing a metal which replaces the ammonium or alkali ions contained in the extraction solution.
Thus the ions are removed from the solvent used for extraction prior to the separation of valuable metals in the main solvent extraction stages.
The treatment of iron is an important factor when processing metallurgical concentrates and ores. In particular, the behaviour of iron is an extremely important consideration in leaching processes and cases where the treatment is based on the combination of leaching and smelting. One of the characteristics of iron is that, in its trivalent state, iron forms alkali double salts with a composition D[Fe3(SO4)2(OH)6]. In these so-called jarosite compounds, D represents an alkali metal such as sodium, potassium or ammonium.
Jarosite compounds are formed from acidic solutions cont~;n;ng trivalent iron and ammonium, sodium or potassium.
In particular, jarosite is formed within the pH range of from 0.5 to 5Ø An increase in temperature supports this formation. Jarosite is readily formed at a temperature in the range of from 60 to 220~C. The higher the temperature, the lower the pH at which jarosite is formed.
In leaching-based zinc processes iron is typically removed from zinc-bearing solutions by formation of jarosite compounds. The present invention in turn relates to processes where the formation of jarosite and other ammonium- and alkali-based double salts should be avoided. Such processes include nickel, cobalt and copper production processes. The raw material can be an ore, a concentrate or an intermediate 20~6~8 product obtained from the smelting of a concentrate or other similar metal-bearing material.
The process in question includes processing steps conducted at temperatures greater than ambient temperature.
These steps are atmospheric or pressurized leaching steps conducted at temperatures greater than 60~C and containing from 0.5 to 85% iron. The removal of iron from process solutions obtained from these leaching steps is also within the scope of the processing steps, when the applied method is a normal hydrolysis conducted at a temperature in the range of from 60 to 220~C.
In the above-mentioned cases, the formation of jarosite cannot be avoided if the process requires an addition of ammonium- or alkali-bearing materials. Such materials are, for example, ammonium or sodium used to adjust the pH value and to intensify solution cleaning which occurs at a higher pH value than leaching and iron removal. For example, in a nickel process, zinc, copper and cobalt are generally removed from the raw material. However, ammonium double salts, such as ammonium nickel sulfate, can be formed in the process causing problems in crystallization.
Earlier, the creation of jarosite and double salts during processing was not as problematic as it is today.
However, there is now an increased demand for environmental protection which restricts these processes. When ammonia is used for neutralization, the creation of ammonium jarosite causes nitrogen emissions, in the form of NOX. Under these process conditions used, the formation of jarosite cannot be prevented in the leaching and iron removal steps. The inevitable result is that the leach residue contains jarosite in these cases.
The jarosite is decomposed in a subsequent processing step, such as smelting, thereby consuming energy and reducing the cost efficiency. Similarly, an iron precipitate consumes energy in the smelting treatment.
However, the iron is bound to the inert slag of the smelting treatment to an e~cellent degree, thereby eliminating the 209~638 problems connected to the storage of finely divided iron precipitates. Alkali metals in turn are traditionally non-desirable materials in smelting.
According to the present invention, there is provided a method for preventing the formation of jarosite and ammonium- and alkali-based double salts in a solvent extraction process of an acidic leaching process, comprising the steps of neutralizing an organic extraction solution with an ammonium or alkali salt prior to separating a valuable metal by solvent extraction, conducting the extractant solution to pre-extraction, contacting an extractant with an aqueous solution containing a metal as an exchange ion, whereby the exchange ion replaces the ammonium or alkali ions contained in the extraction solution, so that formation of - i and alkali-based double salts in the leach process solution is prevented, and the extraction solution can be conducted to the main extraction contact with the aqueous solution containing valuable metals.
The present invention relates to a method for avoiding the formation of jarosite or ammonium- and alkali-based double salts in solvent extraction by preventing the access of ammonium, sodium or potassium to solution circulation, even in cases where ammonium or sodium is used to boost the solution cleaning. The extraction solution obtained from the circulation of the extraction process is neutralized by an ammonium or alkali salt, but the access of these ions into the main extraction circuit, where the valuable metals are separated, is prevented by using a pre-extraction step, wherein the ammonium or alkali ions are transferred into an aqueous solution, and are replaced in the extraction solution by a so-called exchange ion. Preferably, of the valuable metals to be separated in the solvent extraction step, at least one is extracted more intensively than the exchange ion. when the ammonium and alkali ions are removed from the solution, a higher temperature can be used for intensifying the leaching, and smelting can be applied as a natural further processing step for recovering one of the metals to be separated and for improving environmental protection.
A preferred aspect of the invention provides a method for preventing the formation of jarosite, or ammonium or alkali metal double salts during leaching and solvent extraction of nickel and cobalt, comprising:
1) neutralizing an organic extraction solution of a di-(2,4,4,trimethylpentyl)-phosphinic acid with an ammonium, sodium or a potassium base;
2) conducting the neutralized organic extraction solution to a pre-extraction step, where the organic extraction solution is contacted with an aqueous solution containing magnesium exchange ions, wherein the magnesium exchange ions replace the ammonium or alkali ions in the organic extraction solution;
The organic leaching solution is neutralized by ammonium or alkali salts prior to the separation of valuable metals in order to improve the extraction recovery. In a pre-extraction step after neutralization, the extractant is contacted with an aqueous solution containing a metal which replaces the ammonium or alkali ions contained in the extraction solution.
Thus the ions are removed from the solvent used for extraction prior to the separation of valuable metals in the main solvent extraction stages.
The treatment of iron is an important factor when processing metallurgical concentrates and ores. In particular, the behaviour of iron is an extremely important consideration in leaching processes and cases where the treatment is based on the combination of leaching and smelting. One of the characteristics of iron is that, in its trivalent state, iron forms alkali double salts with a composition D[Fe3(SO4)2(OH)6]. In these so-called jarosite compounds, D represents an alkali metal such as sodium, potassium or ammonium.
Jarosite compounds are formed from acidic solutions cont~;n;ng trivalent iron and ammonium, sodium or potassium.
In particular, jarosite is formed within the pH range of from 0.5 to 5Ø An increase in temperature supports this formation. Jarosite is readily formed at a temperature in the range of from 60 to 220~C. The higher the temperature, the lower the pH at which jarosite is formed.
In leaching-based zinc processes iron is typically removed from zinc-bearing solutions by formation of jarosite compounds. The present invention in turn relates to processes where the formation of jarosite and other ammonium- and alkali-based double salts should be avoided. Such processes include nickel, cobalt and copper production processes. The raw material can be an ore, a concentrate or an intermediate 20~6~8 product obtained from the smelting of a concentrate or other similar metal-bearing material.
The process in question includes processing steps conducted at temperatures greater than ambient temperature.
These steps are atmospheric or pressurized leaching steps conducted at temperatures greater than 60~C and containing from 0.5 to 85% iron. The removal of iron from process solutions obtained from these leaching steps is also within the scope of the processing steps, when the applied method is a normal hydrolysis conducted at a temperature in the range of from 60 to 220~C.
In the above-mentioned cases, the formation of jarosite cannot be avoided if the process requires an addition of ammonium- or alkali-bearing materials. Such materials are, for example, ammonium or sodium used to adjust the pH value and to intensify solution cleaning which occurs at a higher pH value than leaching and iron removal. For example, in a nickel process, zinc, copper and cobalt are generally removed from the raw material. However, ammonium double salts, such as ammonium nickel sulfate, can be formed in the process causing problems in crystallization.
Earlier, the creation of jarosite and double salts during processing was not as problematic as it is today.
However, there is now an increased demand for environmental protection which restricts these processes. When ammonia is used for neutralization, the creation of ammonium jarosite causes nitrogen emissions, in the form of NOX. Under these process conditions used, the formation of jarosite cannot be prevented in the leaching and iron removal steps. The inevitable result is that the leach residue contains jarosite in these cases.
The jarosite is decomposed in a subsequent processing step, such as smelting, thereby consuming energy and reducing the cost efficiency. Similarly, an iron precipitate consumes energy in the smelting treatment.
However, the iron is bound to the inert slag of the smelting treatment to an e~cellent degree, thereby eliminating the 209~638 problems connected to the storage of finely divided iron precipitates. Alkali metals in turn are traditionally non-desirable materials in smelting.
According to the present invention, there is provided a method for preventing the formation of jarosite and ammonium- and alkali-based double salts in a solvent extraction process of an acidic leaching process, comprising the steps of neutralizing an organic extraction solution with an ammonium or alkali salt prior to separating a valuable metal by solvent extraction, conducting the extractant solution to pre-extraction, contacting an extractant with an aqueous solution containing a metal as an exchange ion, whereby the exchange ion replaces the ammonium or alkali ions contained in the extraction solution, so that formation of - i and alkali-based double salts in the leach process solution is prevented, and the extraction solution can be conducted to the main extraction contact with the aqueous solution containing valuable metals.
The present invention relates to a method for avoiding the formation of jarosite or ammonium- and alkali-based double salts in solvent extraction by preventing the access of ammonium, sodium or potassium to solution circulation, even in cases where ammonium or sodium is used to boost the solution cleaning. The extraction solution obtained from the circulation of the extraction process is neutralized by an ammonium or alkali salt, but the access of these ions into the main extraction circuit, where the valuable metals are separated, is prevented by using a pre-extraction step, wherein the ammonium or alkali ions are transferred into an aqueous solution, and are replaced in the extraction solution by a so-called exchange ion. Preferably, of the valuable metals to be separated in the solvent extraction step, at least one is extracted more intensively than the exchange ion. when the ammonium and alkali ions are removed from the solution, a higher temperature can be used for intensifying the leaching, and smelting can be applied as a natural further processing step for recovering one of the metals to be separated and for improving environmental protection.
A preferred aspect of the invention provides a method for preventing the formation of jarosite, or ammonium or alkali metal double salts during leaching and solvent extraction of nickel and cobalt, comprising:
1) neutralizing an organic extraction solution of a di-(2,4,4,trimethylpentyl)-phosphinic acid with an ammonium, sodium or a potassium base;
2) conducting the neutralized organic extraction solution to a pre-extraction step, where the organic extraction solution is contacted with an aqueous solution containing magnesium exchange ions, wherein the magnesium exchange ions replace the ammonium or alkali ions in the organic extraction solution;
3) crystallizing the aqueous solution containing the ammonium or alkali ions to recover ammonium or alkali salt;
4) contacting the organic extraction solution with an aqueous solution containing nickel and cobalt to selectively extract cobalt into the organic extraction solution, leaving nickel in the aqueous solution;
5) recovering cobalt from the organic extraction solution; and 6) recovering nickel from the aqueous solution.
In drawings which illustrate an embodiment of the present invention, Figure 1 is a flowchart of a preferred embodiment of the invention; and Figure 2 illustrates the extraction of some metals as a function of the pH value with a fixed extractant.
Certain process technical advantages are also achieved in accordance with the method of the present invention. When a neutral salt, such as ammonium, sodium or potassium sulfate, is not accumulated in the solution circulation, the solubility of nickel sulfate, for example, is increased. This can be utilized to raise the capacity of the reduction and electrolysis steps included in the process.
Furthermore, thickening, filtering and electrolysis become easier. A high metal content also improves the quality of the metal produced. Another specific advantage is that it is not necessary to introduce a separate removal of neutral salt from the main process solutions by crystallization, for example.
Referring now to Figure 1, according to the present invention, a process including smelting steps, leaching and recoveries of two valuable metals, A and B, by means of reduction and/or electrolysis is further complemented by extraction process steps complemented with crystallization.
Another metal C is also utilized in the process. Metal C does not necessarily have to be a valuable metal. A C-bearing solution is conducted from a recovery step of the valuable metal B, for example from the reduction step, to a pre-extraction step. The amount of metal C in the solution is continuously increased to a degree that compensates the losses. Substance D, for example, ammonium, sodium or potassium salt, is used as a neutralizing agent. In the pre-extraction step, the extraction solution is neutralized by mixing with the neutralizing agent D. Generally the extraction solution is kerosene-based and contains an extractant which, according to its extraction equilibriums, has a preference to extracting metal A in the subsequent extraction separation step, whereto a solution containing A, B and C is conducted from the iron removal step. The aqueous solution is advantageously a sulfate solution.
In the pre-extraction step, the extraction solution containing substance D contacts a C- and D-bearing solution from the reduction step. An ion exchange reaction takes place and C is extracted into the extraction solution. At the same time, substantially all of D is exchanged out of the extraction solution to an aqueous phase which is conducted to the separation of D-salt, such as a crystallization step. The extraction solution containing metal C is conducted to the main extraction separation together with an aqueous solution containing the valuable metals A and B, so that an ion exchange takes place between C and A. C is transferred back to the aqueous phase and returns, via the recovery of B, to pre-extraction for a new cycle of solvent extraction. Thus C serves as a type of exchange ion. First, C displaces D from the extraction solution in the pre-extraction step, and then returns to the aqueous solution in the extraction separation itself. Thus C is not consumed in the process, apart from small quantities along with D and A. This consumption of C
can be replenished with an addition of a small amount of C
prior to the pre-extraction step. Metal A is recovered from the extraction solution by extraction with acid, and subjected to further processing steps.
The method of the present invention does not require the use of any special metals or extraction solutions. In accordance with the present invention, the extraction equilibrium favours the extraction of metal A over metals B
and C. It is advantageous but not necessary that C is extracted more intensively than B, thereby enabling the selective extraction of A relative to B. The metals are mainly extracted by cation exchange with extractants requiring neutralizer addition in order to boost the extraction reaction. Such extractants are di-(alkyl)-phosphoric acids, monoalkyl esters of alkyl phosphonic acid and di-(alkyl)-phosphinic acids and organic carboxylic acids, for example C-10 acids, as well as a large number of other acidic organic extractant compounds.
The following Example illustrates the invention for the production of pure nickel and the recovery of cobalt.
Example In this example, metal A is cobalt and metal B is nickel. Metal C is advantageously magnesium, and D ammonia.
The nickel separation process is advantageously arranged in connection with nickel and copper smelting processes, wherein the leaching object may be a sulfidic nickel concentrate and/or matte produced in a smelting process. The copper sulfide-bearing material formed as leaching residue is advantageously further processed in copper smelting for recovering copper and possible precious metals.
According to the method of the invention, the magnesium-bearing solution, separated in hydrogen reduction, is conducted to the pre-extraction step to which is also supplied an extraction solution preneutralized with ammonia.
This is advantageously composed of di-(alkyl)-phosphinic acid dissolved in kerosene. It is also advantageous that the phosphinic acid is a di-(2,4,4-trimethyl-pentyl)-phosphinic acid, which according to its extraction properties is capable of separating cobalt and nickel.
In the pre-extraction step, nearly all magnesium is transferred to the extraction solution, which returns an equivalent quantity of ammonium to the aqueous solution. Next the aqueous solution is conducted to the ammonia/sulfate crystallization step. This procedure ensures that ammonium, which is beneficial to the extraction, is not emitted to the nickel solution circulation. Also the crystallization of the so-called neutral salt is avoided in the main process flow.
Next the extraction solution, in magnesium form, is conducted to the extraction separation, where it is contacted with an aqueous solution of cobalt-bearing nickel. As is seen from the extraction curves of Figure 2, cobalt is extracted more intensively than magnesium with Cyanex 2720. The extraction solution is a technical di-(2,4,4-trimethyl-pentyl)-phosphinic acid product. Thus cobalt displaces magnesium from the extraction solution. As a result, a nickel solution free of cobalt and a cobalt-concentrated extraction solution are produced. To recover cobalt, the next step is the treatment of the extraction solution with acid and further treatment of the re-extraction solution.
In accordance with the present invention, the magnesium does not adversely affect the nickel recovery in the successive electrolysis and/or reduction steps, but remains in the solution and can again be extracted therefrom in the pre-extraction during the next process cycle. Magnesium is used as an exchange ion for cobalt extraction thereby preventing the access of magnesium to the process circulation.
However, the use of an exchange ion such as magnesium is necessary, because the cobalt extraction would be seriously incomplete without the use of ammonia to boost the extraction step.
In the above-described example, metal A can also be some other metal than cobalt. A general requirement is that A is extracted more intensively than magnesium. In the method of the invention, it is thus possible also to remove such metals as zinc, manganese, cadmium, copper, iron, vanadium, molybdenum and uranium. Furthermore it is possible to simultaneously remove several of these metals.
In all of the above-described cases, the valuable metal B could be cobalt instead of nickel, or B could be a solution mixture of nickel and cobalt. Then the amount of ammonia used and, therefore, the amount of the extraction solution in magnesium form are reduced, so that the pH value of the extraction separation is adjusted substantially with the quantity of the extraction solution in magnesium form.
Then the extraction separation succeeds with a pH where the metal or metals to be extracted are capable of taking the ion exchange places of the extraction solution, whereas cobalt is not. As with nickel, cobalt can be electrolyzed or reduced from magnesium-bearing solutions.
The method of the present invention can be applied in a corresponding fashion for cleaning a number of solutions containing metals B and C. This is technically efficient and economical in cases where B and C represent metals which can be separated with known methods. Metal A, to be removed in extraction separation, must be extracted more intensively, i.e. at a lower pH, than the metals B and C. B can also be extracted more intensively than C. In order to achieve the desired extraction separation, the extent of the extraction solution from which C is extracted, is adjusted, so that the pH of the extraction separation is suitable for the metal separation.
When treating zinc-, copper- and cobalt-bearing raw materials, it is also difficult to combine acidic leaching and the use of ammonia as the neutralizing agent, owing to the limited solubility of double salts containing ammonia and cobalt. For example, metal A is zinc, metal B is copper, and metal C is also copper. The decisive factors are the relative proportions of the metals and other further processing steps.
As above, metal A can also represent other metals that are extracted more intensively than metals B and C, such as iron and indium.
Other metal groups, such as zinc, manganese and copper, can be separated in a corresponding fashion. In this case metal A is zinc and/or iron. Manganese is either B or C, and C can also be copper.
While extractants of the di-(alkyl)-phosphine type are advantageous when separating cobalt from nickel because of their separation sharpness, the method of the present invention is not restricted to these extractants. For example, monoalkyl esters of alkyl phosphonic acid and di-(alkyl)-phosphoric acids can be used to extract metals in the following order: UO22 > Fe3 > zn2 > Mn2 > Cu2 > Cd2 >
Co2 > Mg2 > Ni2. Calcium does not show consistent behaviour, as it is dependent on the type of extractant used. This must be taken into account when grouping metals into the categories A, B and C according to their extraction behaviour in order to apply the method of the invention.
Carboxylic acids, generally C-10 acids, form a group of extractants that is used in extraction. When arranging metals into groups according to the invention, the following extraction order must be taken into account: Fe3 > UO22 >
> Hg > Cu > zn2 > pb2~ > Cd2' > N2+ > C 2~ 2- z Ca > Mg .
Other extractants behaving on the ion exchange basis can also be used in the metal separation based on the method of the invention. The most important of these are kelatine-formers such as oximes, as far as they need neutralization.
Usually neutralization is applied when the metal to be extracted has a high content in the leach solution.
In drawings which illustrate an embodiment of the present invention, Figure 1 is a flowchart of a preferred embodiment of the invention; and Figure 2 illustrates the extraction of some metals as a function of the pH value with a fixed extractant.
Certain process technical advantages are also achieved in accordance with the method of the present invention. When a neutral salt, such as ammonium, sodium or potassium sulfate, is not accumulated in the solution circulation, the solubility of nickel sulfate, for example, is increased. This can be utilized to raise the capacity of the reduction and electrolysis steps included in the process.
Furthermore, thickening, filtering and electrolysis become easier. A high metal content also improves the quality of the metal produced. Another specific advantage is that it is not necessary to introduce a separate removal of neutral salt from the main process solutions by crystallization, for example.
Referring now to Figure 1, according to the present invention, a process including smelting steps, leaching and recoveries of two valuable metals, A and B, by means of reduction and/or electrolysis is further complemented by extraction process steps complemented with crystallization.
Another metal C is also utilized in the process. Metal C does not necessarily have to be a valuable metal. A C-bearing solution is conducted from a recovery step of the valuable metal B, for example from the reduction step, to a pre-extraction step. The amount of metal C in the solution is continuously increased to a degree that compensates the losses. Substance D, for example, ammonium, sodium or potassium salt, is used as a neutralizing agent. In the pre-extraction step, the extraction solution is neutralized by mixing with the neutralizing agent D. Generally the extraction solution is kerosene-based and contains an extractant which, according to its extraction equilibriums, has a preference to extracting metal A in the subsequent extraction separation step, whereto a solution containing A, B and C is conducted from the iron removal step. The aqueous solution is advantageously a sulfate solution.
In the pre-extraction step, the extraction solution containing substance D contacts a C- and D-bearing solution from the reduction step. An ion exchange reaction takes place and C is extracted into the extraction solution. At the same time, substantially all of D is exchanged out of the extraction solution to an aqueous phase which is conducted to the separation of D-salt, such as a crystallization step. The extraction solution containing metal C is conducted to the main extraction separation together with an aqueous solution containing the valuable metals A and B, so that an ion exchange takes place between C and A. C is transferred back to the aqueous phase and returns, via the recovery of B, to pre-extraction for a new cycle of solvent extraction. Thus C serves as a type of exchange ion. First, C displaces D from the extraction solution in the pre-extraction step, and then returns to the aqueous solution in the extraction separation itself. Thus C is not consumed in the process, apart from small quantities along with D and A. This consumption of C
can be replenished with an addition of a small amount of C
prior to the pre-extraction step. Metal A is recovered from the extraction solution by extraction with acid, and subjected to further processing steps.
The method of the present invention does not require the use of any special metals or extraction solutions. In accordance with the present invention, the extraction equilibrium favours the extraction of metal A over metals B
and C. It is advantageous but not necessary that C is extracted more intensively than B, thereby enabling the selective extraction of A relative to B. The metals are mainly extracted by cation exchange with extractants requiring neutralizer addition in order to boost the extraction reaction. Such extractants are di-(alkyl)-phosphoric acids, monoalkyl esters of alkyl phosphonic acid and di-(alkyl)-phosphinic acids and organic carboxylic acids, for example C-10 acids, as well as a large number of other acidic organic extractant compounds.
The following Example illustrates the invention for the production of pure nickel and the recovery of cobalt.
Example In this example, metal A is cobalt and metal B is nickel. Metal C is advantageously magnesium, and D ammonia.
The nickel separation process is advantageously arranged in connection with nickel and copper smelting processes, wherein the leaching object may be a sulfidic nickel concentrate and/or matte produced in a smelting process. The copper sulfide-bearing material formed as leaching residue is advantageously further processed in copper smelting for recovering copper and possible precious metals.
According to the method of the invention, the magnesium-bearing solution, separated in hydrogen reduction, is conducted to the pre-extraction step to which is also supplied an extraction solution preneutralized with ammonia.
This is advantageously composed of di-(alkyl)-phosphinic acid dissolved in kerosene. It is also advantageous that the phosphinic acid is a di-(2,4,4-trimethyl-pentyl)-phosphinic acid, which according to its extraction properties is capable of separating cobalt and nickel.
In the pre-extraction step, nearly all magnesium is transferred to the extraction solution, which returns an equivalent quantity of ammonium to the aqueous solution. Next the aqueous solution is conducted to the ammonia/sulfate crystallization step. This procedure ensures that ammonium, which is beneficial to the extraction, is not emitted to the nickel solution circulation. Also the crystallization of the so-called neutral salt is avoided in the main process flow.
Next the extraction solution, in magnesium form, is conducted to the extraction separation, where it is contacted with an aqueous solution of cobalt-bearing nickel. As is seen from the extraction curves of Figure 2, cobalt is extracted more intensively than magnesium with Cyanex 2720. The extraction solution is a technical di-(2,4,4-trimethyl-pentyl)-phosphinic acid product. Thus cobalt displaces magnesium from the extraction solution. As a result, a nickel solution free of cobalt and a cobalt-concentrated extraction solution are produced. To recover cobalt, the next step is the treatment of the extraction solution with acid and further treatment of the re-extraction solution.
In accordance with the present invention, the magnesium does not adversely affect the nickel recovery in the successive electrolysis and/or reduction steps, but remains in the solution and can again be extracted therefrom in the pre-extraction during the next process cycle. Magnesium is used as an exchange ion for cobalt extraction thereby preventing the access of magnesium to the process circulation.
However, the use of an exchange ion such as magnesium is necessary, because the cobalt extraction would be seriously incomplete without the use of ammonia to boost the extraction step.
In the above-described example, metal A can also be some other metal than cobalt. A general requirement is that A is extracted more intensively than magnesium. In the method of the invention, it is thus possible also to remove such metals as zinc, manganese, cadmium, copper, iron, vanadium, molybdenum and uranium. Furthermore it is possible to simultaneously remove several of these metals.
In all of the above-described cases, the valuable metal B could be cobalt instead of nickel, or B could be a solution mixture of nickel and cobalt. Then the amount of ammonia used and, therefore, the amount of the extraction solution in magnesium form are reduced, so that the pH value of the extraction separation is adjusted substantially with the quantity of the extraction solution in magnesium form.
Then the extraction separation succeeds with a pH where the metal or metals to be extracted are capable of taking the ion exchange places of the extraction solution, whereas cobalt is not. As with nickel, cobalt can be electrolyzed or reduced from magnesium-bearing solutions.
The method of the present invention can be applied in a corresponding fashion for cleaning a number of solutions containing metals B and C. This is technically efficient and economical in cases where B and C represent metals which can be separated with known methods. Metal A, to be removed in extraction separation, must be extracted more intensively, i.e. at a lower pH, than the metals B and C. B can also be extracted more intensively than C. In order to achieve the desired extraction separation, the extent of the extraction solution from which C is extracted, is adjusted, so that the pH of the extraction separation is suitable for the metal separation.
When treating zinc-, copper- and cobalt-bearing raw materials, it is also difficult to combine acidic leaching and the use of ammonia as the neutralizing agent, owing to the limited solubility of double salts containing ammonia and cobalt. For example, metal A is zinc, metal B is copper, and metal C is also copper. The decisive factors are the relative proportions of the metals and other further processing steps.
As above, metal A can also represent other metals that are extracted more intensively than metals B and C, such as iron and indium.
Other metal groups, such as zinc, manganese and copper, can be separated in a corresponding fashion. In this case metal A is zinc and/or iron. Manganese is either B or C, and C can also be copper.
While extractants of the di-(alkyl)-phosphine type are advantageous when separating cobalt from nickel because of their separation sharpness, the method of the present invention is not restricted to these extractants. For example, monoalkyl esters of alkyl phosphonic acid and di-(alkyl)-phosphoric acids can be used to extract metals in the following order: UO22 > Fe3 > zn2 > Mn2 > Cu2 > Cd2 >
Co2 > Mg2 > Ni2. Calcium does not show consistent behaviour, as it is dependent on the type of extractant used. This must be taken into account when grouping metals into the categories A, B and C according to their extraction behaviour in order to apply the method of the invention.
Carboxylic acids, generally C-10 acids, form a group of extractants that is used in extraction. When arranging metals into groups according to the invention, the following extraction order must be taken into account: Fe3 > UO22 >
> Hg > Cu > zn2 > pb2~ > Cd2' > N2+ > C 2~ 2- z Ca > Mg .
Other extractants behaving on the ion exchange basis can also be used in the metal separation based on the method of the invention. The most important of these are kelatine-formers such as oximes, as far as they need neutralization.
Usually neutralization is applied when the metal to be extracted has a high content in the leach solution.
Claims (19)
1. A method for preventing the formation of jarosite and ammonium- and alkali-based double salts in a solvent extraction process of an acidic leaching process, comprising the steps of neutralizing an organic extraction solution with an ammonium or alkali salt prior to separating a valuable metal by solvent extraction, conducting the extractant solution to pre-extraction, contacting an extractant with an aqueous solution containing a metal as an exchange ion, whereby the exchange ion replaces the ammonium or alkali ions contained in the extraction solution, so that formation of ammonium- and alkali-based double salts in the leach process solution is prevented, and the extraction solution can be conducted to the main extraction contact with the aqueous solution containing valuable metals.
2. A method according to claim 1, wherein the ammonium or alkali ions are removed from the aqueous solution after the pre-extraction step.
3. A method according to claim 1, wherein at least one of the valuable metals to be separated by solvent extraction is extracted more intensively than the exchange ion.
4. A method according to claims 1 or 3, wherein the more intensively extracted valuable metal replaces the exchange ion in the extraction solution, so that the exchange ion is transferred back to the aqueous solution.
5. A method according to claim 1, wherein at least one valuable metal and the exchange ion are both extracted more intensively than other valuable metals.
6. A method according to claim 1, wherein the extraction or the leaching treatment is conducted at a temperature in the range of from 60° to 220°C.
7. A method according to claim 1, wherein the exchange ion is magnesium.
8. A method according to claim 1, wherein the valuable metals to be separated are cobalt and nickel.
9. A method according to claim 1 or 3, wherein the most intensively extracted metal is cobalt.
10. A method according to claim 1, wherein the extractant is di-(alkyl)-phosphinic acid.
11. A method according to claim 1, wherein the extractant is di-(2,4,4-trimethyl-pentyl)-phosphinic acid.
12. A method according to claim 1, wherein the extractant is a mono-alkyl ester of alkylphosphonic acid.
13. A method according to claim 1, wherein the extractant is di-(alkyl)-phosphoric acid.
14. A method according to claim 1, wherein the most intensively extracted metal is one of zinc, manganese, cadmium, copper, iron, vanadium, molybdenum and uranium.
15. A method according to claim 1 or 14, wherein the least intensively extracted metal is copper or manganese.
16. A method for preventing the formation of jarosite, or ammonium or alkali metal double salts during leaching and solvent extraction of nickel and cobalt, comprising:
1) neutralizing an organic extraction solution of a di-(2,4,4,trimethylpentyl)-phosphinic acid with an ammonium, sodium or a potassium base;
2) conducting the neutralized organic extraction solution to a pre-extraction step, where the organic extraction solution is contacted with an aqueous solution containing magnesium exchange ions, wherein said magnesium exchange ions replace the ammonium or alkali ions in the organic extraction solution;
3) crystallizing the aqueous solution containing the ammonium or alkali ions to recover ammonium or alkali salt;
4) contacting the organic extraction solution with an aqueous solution containing nickel and cobalt to selectively extract cobalt into the organic extraction solution, leaving nickel in the aqueous solution;
5) recovering cobalt from the organic extraction solution; and 6) recovering nickel from the aqueous solution.
1) neutralizing an organic extraction solution of a di-(2,4,4,trimethylpentyl)-phosphinic acid with an ammonium, sodium or a potassium base;
2) conducting the neutralized organic extraction solution to a pre-extraction step, where the organic extraction solution is contacted with an aqueous solution containing magnesium exchange ions, wherein said magnesium exchange ions replace the ammonium or alkali ions in the organic extraction solution;
3) crystallizing the aqueous solution containing the ammonium or alkali ions to recover ammonium or alkali salt;
4) contacting the organic extraction solution with an aqueous solution containing nickel and cobalt to selectively extract cobalt into the organic extraction solution, leaving nickel in the aqueous solution;
5) recovering cobalt from the organic extraction solution; and 6) recovering nickel from the aqueous solution.
17. A method according to claim 16, wherein the nickel is recovered by hydrogen reduction or electrolysis.
18. A method according to claim 16, wherein the nickel and the exchange ion are recovered by hydrogen reduction.
19. A method according to claim 16, wherein the nickel is recovered by hydrogen reduction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI922842 | 1992-06-18 | ||
| FI922842A FI93973C (en) | 1992-06-18 | 1992-06-18 | Method for preventing the formation of jarosite and ammonium- and alkali-based double salts in liquid-liquid extraction of acidic leaching processes |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2098638A1 CA2098638A1 (en) | 1993-12-19 |
| CA2098638C true CA2098638C (en) | 1998-04-21 |
Family
ID=8535496
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002098638A Expired - Lifetime CA2098638C (en) | 1992-06-18 | 1993-06-17 | Method for preventing the formation of jarosite and ammonium and alkali based double salts in solvent extraction circuits connected to acidic leaching processes |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JP3386516B2 (en) |
| AU (1) | AU667539B2 (en) |
| CA (1) | CA2098638C (en) |
| DE (1) | DE4320314C2 (en) |
| FI (1) | FI93973C (en) |
| NO (1) | NO300429B1 (en) |
| ZA (1) | ZA934326B (en) |
| ZW (1) | ZW7693A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5650057A (en) * | 1993-07-29 | 1997-07-22 | Cominco Engineering Services Ltd. | Chloride assisted hydrometallurgical extraction of metal |
| US5378262A (en) * | 1994-03-22 | 1995-01-03 | Inco Limited | Process for the extraction and separation of nickel and/or cobalt |
| AU739497B2 (en) * | 1997-06-12 | 2001-10-11 | Wmc Resources Limited | Pre-equilibration of a cationic extractant |
| AUPO732797A0 (en) * | 1997-06-12 | 1997-07-03 | Wmc Resources Limited | Pre-equilibration of a cationic extractant |
| AUPQ489399A0 (en) | 1999-12-24 | 2000-02-03 | Wmc Resources Limited | Solvent extraction of impurity metals from a valuable metal sulphate solution |
| US6231823B1 (en) | 2000-03-27 | 2001-05-15 | Dynatec Corporation | Solvent extraction process for the separation of cobalt from nickel in aqueous sulphate-containing solutions |
| GT200600062A (en) * | 2005-02-14 | 2006-09-07 | PROCESS FOR THE IMPROVEMENT OF IMPROVED ACID OF LATERITA MINERALS | |
| FI120943B (en) | 2008-02-19 | 2010-05-14 | Norilsk Nickel Finland Oy | Method for the separation of zinc, iron, calcium, copper and manganese from aqueous cobalt and / or nickel solutions |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS556460A (en) * | 1978-06-29 | 1980-01-17 | Nippon Mining Co Ltd | Extracting and separating method of nickel and cobalt |
| JPS605650B2 (en) * | 1978-07-18 | 1985-02-13 | 日本鉱業株式会社 | Method for cleaning organic solvents used in solvent extraction methods |
| JPS6053730B2 (en) * | 1981-06-26 | 1985-11-27 | 康勝 玉井 | Nickel refining method |
| JPH0776394B2 (en) * | 1989-06-06 | 1995-08-16 | 工業技術院長 | Extraction and separation of cobalt from cobalt and nickel oxide |
| US5176802A (en) * | 1991-07-19 | 1993-01-05 | Willem P. C. Duyvesteyn | Treatment of copper sulfide concentrates |
-
1992
- 1992-06-18 FI FI922842A patent/FI93973C/en not_active IP Right Cessation
-
1993
- 1993-06-14 ZW ZW7693A patent/ZW7693A1/en unknown
- 1993-06-16 NO NO932223A patent/NO300429B1/en not_active IP Right Cessation
- 1993-06-16 AU AU41267/93A patent/AU667539B2/en not_active Expired
- 1993-06-17 ZA ZA934326A patent/ZA934326B/en unknown
- 1993-06-17 CA CA002098638A patent/CA2098638C/en not_active Expired - Lifetime
- 1993-06-18 DE DE4320314A patent/DE4320314C2/en not_active Expired - Fee Related
- 1993-06-18 JP JP17088893A patent/JP3386516B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE4320314A1 (en) | 1993-12-23 |
| JP3386516B2 (en) | 2003-03-17 |
| NO932223L (en) | 1993-12-20 |
| JPH0770656A (en) | 1995-03-14 |
| NO300429B1 (en) | 1997-05-26 |
| AU4126793A (en) | 1993-12-23 |
| AU667539B2 (en) | 1996-03-28 |
| ZA934326B (en) | 1994-01-13 |
| NO932223D0 (en) | 1993-06-16 |
| FI922842A (en) | 1993-12-19 |
| FI93973C (en) | 1995-06-26 |
| CA2098638A1 (en) | 1993-12-19 |
| FI93973B (en) | 1995-03-15 |
| DE4320314C2 (en) | 2001-11-08 |
| ZW7693A1 (en) | 1994-02-02 |
| FI922842A0 (en) | 1992-06-18 |
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