CA1094819A - Hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites - Google Patents
Hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferritesInfo
- Publication number
- CA1094819A CA1094819A CA272,620A CA272620A CA1094819A CA 1094819 A CA1094819 A CA 1094819A CA 272620 A CA272620 A CA 272620A CA 1094819 A CA1094819 A CA 1094819A
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- Prior art keywords
- stage
- jarosite
- solution
- ferrite
- ferrites
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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
- C22B17/00—Obtaining cadmium
- C22B17/04—Obtaining cadmium by wet processes
-
- 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
- C22B15/00—Obtaining copper
- C22B15/0063—Hydrometallurgy
- C22B15/0065—Leaching or slurrying
- C22B15/0067—Leaching or slurrying with acids or salts thereof
- C22B15/0071—Leaching or slurrying with acids or salts thereof containing sulfur
-
- 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
- C22B15/00—Obtaining copper
- C22B15/0063—Hydrometallurgy
- C22B15/0084—Treating solutions
- C22B15/0089—Treating solutions by chemical methods
-
- 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
- C22B19/00—Obtaining zinc or zinc oxide
- C22B19/20—Obtaining zinc otherwise than by distilling
- C22B19/22—Obtaining zinc otherwise than by distilling with leaching with acids
-
- 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
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
- C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Compounds Of Iron (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites by treating the ferrites under atmospheric conditions in a sulfuric acid-bearing solution in the presence of potassium, sodium, or ammonium ions at 80-105°C in order to precipitate, as jaro-site, the iron present in the ferrites, separating a jaro-site-bearing solid from the solution, feeding the solution to a neutral leach stage, to which acid and calcine are also fed and from which a solution containing zinc, copper, and cadmium is recovered and feeding the ferrite-bearing solid to the ferrite treatment stage, and recycling a portion of the jarosite-bearing solid obtained from the ferrite treatment stage to the process.
A hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites by treating the ferrites under atmospheric conditions in a sulfuric acid-bearing solution in the presence of potassium, sodium, or ammonium ions at 80-105°C in order to precipitate, as jaro-site, the iron present in the ferrites, separating a jaro-site-bearing solid from the solution, feeding the solution to a neutral leach stage, to which acid and calcine are also fed and from which a solution containing zinc, copper, and cadmium is recovered and feeding the ferrite-bearing solid to the ferrite treatment stage, and recycling a portion of the jarosite-bearing solid obtained from the ferrite treatment stage to the process.
Description
OUTOKUMPU OY, Outokumpu Hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites ' .
The present invention relates to a process for -the recovery of zinc, copper, and cadmium from their ferrites by precipitating, as jarosize, the iron present in the ferrites and by returninq the solution to the neutral leach stage in which calcine is leached, the products thereby bein~ a solution which contains zinc, copper and cadmium, and a ferrite-b~aring solid.
:, :
United States Patent 3,959,437 discloses a leach process.for zinc calcine, which is divided into a neutral leach and a stage for treating ferritic solids.
. .
An optimally performed neutral leach produces a raw solution and a ferritic leach residue which is nearly devoid of zinc oxide, its main component being zinc ferrite tZnFe204). The purpose of the neutral leach is to dissolve the main component of the calcine, zinc oxide (ZnO), as completely as possible. Zinc sulfate, which is always present in the calcine in a concentration of a few percent, is also dissolved during this stage, while the zinc .
, 0~-~8~
ferrite and the uncalcined zinc sulfide remain undissolved The raw solution from the neutral leach stage, with a pH of 4-5, is an iron-free zinc sulfate solution which still contains, in the form of sulfates, other metals having been present in the calcine (Cu, Cd, Co, Ni, ...) and from which the metals nobler than zinc must be removed before the electrolysis stage.
The ferritic leach residue is fed to its treatment stage, to which electrolysis return acid, sulfuric acid, and an ammonium, sodium or potassium compound, for example, a sulfate, are fed in amounts suitable with regard to the ferrite. At this stage the nonferrous metals ~Zn, Cu, Cd) present in the ferrites pass into the solution as sulfates, and the iron passes throu~h the solution into the jarosite which is produced durinq the same stage. The treatment period and the reaction conditions are selected so ~hat at the end of the stage the solid is practically devoid of ferrites and the iron content of the solution so low that it can be returned directly to the neutral leach.
During the ferrite treatment stage there occurs the following total reaction 3 ZnO Fe203(s) + 6 H2SO4(aq) + A2 4( q 2A lFe3~so4)2(oH)6] (s) + 3 Zn~04 (aq) (1) (A = NH4, Na, K), which consists of partial reactions 3 ZnO Fe203(s) + 12 H2504(aq) - ~
3 ZnS04(aq) + 3 Fe2(SO4)3(aq) + 12 H20 (aq) (2) and
The present invention relates to a process for -the recovery of zinc, copper, and cadmium from their ferrites by precipitating, as jarosize, the iron present in the ferrites and by returninq the solution to the neutral leach stage in which calcine is leached, the products thereby bein~ a solution which contains zinc, copper and cadmium, and a ferrite-b~aring solid.
:, :
United States Patent 3,959,437 discloses a leach process.for zinc calcine, which is divided into a neutral leach and a stage for treating ferritic solids.
. .
An optimally performed neutral leach produces a raw solution and a ferritic leach residue which is nearly devoid of zinc oxide, its main component being zinc ferrite tZnFe204). The purpose of the neutral leach is to dissolve the main component of the calcine, zinc oxide (ZnO), as completely as possible. Zinc sulfate, which is always present in the calcine in a concentration of a few percent, is also dissolved during this stage, while the zinc .
, 0~-~8~
ferrite and the uncalcined zinc sulfide remain undissolved The raw solution from the neutral leach stage, with a pH of 4-5, is an iron-free zinc sulfate solution which still contains, in the form of sulfates, other metals having been present in the calcine (Cu, Cd, Co, Ni, ...) and from which the metals nobler than zinc must be removed before the electrolysis stage.
The ferritic leach residue is fed to its treatment stage, to which electrolysis return acid, sulfuric acid, and an ammonium, sodium or potassium compound, for example, a sulfate, are fed in amounts suitable with regard to the ferrite. At this stage the nonferrous metals ~Zn, Cu, Cd) present in the ferrites pass into the solution as sulfates, and the iron passes throu~h the solution into the jarosite which is produced durinq the same stage. The treatment period and the reaction conditions are selected so ~hat at the end of the stage the solid is practically devoid of ferrites and the iron content of the solution so low that it can be returned directly to the neutral leach.
During the ferrite treatment stage there occurs the following total reaction 3 ZnO Fe203(s) + 6 H2SO4(aq) + A2 4( q 2A lFe3~so4)2(oH)6] (s) + 3 Zn~04 (aq) (1) (A = NH4, Na, K), which consists of partial reactions 3 ZnO Fe203(s) + 12 H2504(aq) - ~
3 ZnS04(aq) + 3 Fe2(SO4)3(aq) + 12 H20 (aq) (2) and
2( 4)3 (aq) + A2SO4(aq) + 12 H20(aq) ~--~
2 AlFe3(so4)2(oH)6~(s) + 6 H2S4( q 8~
The objective in the selection of the reaction conditions has been that Reactions ~2) and (3) proceed to a maximum degree during the same stage, i.e., that the ferrites dissolve in prac~ice completely and the iron which thus passes into the solution is precipitated almost completely as jarosite, whereby the sulfuric acid produced in the iron precipitation is immediately consumed in the leaching o-f the ferrites. In this case, Reactions (2) and
2 AlFe3(so4)2(oH)6~(s) + 6 H2S4( q 8~
The objective in the selection of the reaction conditions has been that Reactions ~2) and (3) proceed to a maximum degree during the same stage, i.e., that the ferrites dissolve in prac~ice completely and the iron which thus passes into the solution is precipitated almost completely as jarosite, whereby the sulfuric acid produced in the iron precipitation is immediately consumed in the leaching o-f the ferrites. In this case, Reactions (2) and
(3) can be combined into Reaction (1), which illustrates the total procedure.
If it were now possible to increase -the velocity of Reaction (1), the delay required by the ferrite treatment stage would be shortened and the reactor volume required by the stage would be diminished. Reaction (3) is in a key position in this respect.
If this reaction can be accelerated, it produces suifuric acid at a faster rate, which again accelerates the dissolving of the ferrites. From this follows an elevation of the iron content in the solution, which again accelerates Reaction (3), etc.
:.~
In considering Reaction (3) and the factors which affect its velocity, it is obvious that the elevation of the ferric iron and A-ion contents in the solution accelerates the reaction, and the elevation of the sulfuric acid content decelerates it~ Since a solid phase, jarosite phase, is produced in the reaction, it is also evident that the start of the reaction is facilitated if the reaction milieu already contains at the beginning some amount of the phase in ~uestion in the form of inoculating crystals, as suggested in Spanish Patent 407 811. In practice the latter factor does not, however, constitute a problem because at the ferrite treatment stage there is always present such a number of jarosite crystals that Reaction (3) cannot be prevented in terms of reaction kinetics, owing to lack or shortage of crystal nuclei. In advance it cannot, however, be expected that the jarosite content in the reaction system would accelerate Reaction (3), i.e., it would push the reaction from the left to the right. On the other hand, it obviously should have an effect on the velocity of the reaction in the opposite direction, i.e., from the right to the left.
,, , ,: . , ~ '" ; ' '~ ' - ~
a~sl~ ~
Therefore it was surprising to observe during our experiments relating to the ferrite treatment stage that the jarosite content in the re-action system did influence, within a wide concentration range, the velocity of Reaction (3), specifically from the left to the right -and thereby also the velocity of total Reaction (l). Figure 3 de-picts the iron(III) concentration in the solution as a function of time in a reaction system in which Reaction (3) occurs at a tempera-ture of 95C and in which the sodium ion concentration in the solu-tion has been maintained at 8-9 g/l by means of Na2SO4 additions and the sulfuric acid concentration at approximately 30 g/l by means of ZnO additions, and the jarosite concentration in the system at : the initial moment of the reaction has varied between 50 g/l and 400 g/l. From this figure it can be seen that the elevation of the jarosite concentration from 50 g/l to 400 g/l accelerates Reaction (3) many times over.
In accordance with the present invention there is provided in a hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites comprising treating the ferrites under atmospheric conditions in a sulfuric acid-bearing solution in the 20 presence of potassium, sodium, or ammonium ions at 80-105C in order to precipitate, as jarosite, the iron present in the ferrites, separating a jarosite-bearing solid from the solution, feeding the solution to a neutral leach stage, to which acid and calcine are also fed and from which another solution containing zinc, copper, and cadmium is recovered, and feeding the ferrite-bearing solid to the ferrite treatment stage; the improvement of recycling to the process a portion of the jarosite-bearing solid obtained from the ferrite treatment stage.
If it were now possible to increase -the velocity of Reaction (1), the delay required by the ferrite treatment stage would be shortened and the reactor volume required by the stage would be diminished. Reaction (3) is in a key position in this respect.
If this reaction can be accelerated, it produces suifuric acid at a faster rate, which again accelerates the dissolving of the ferrites. From this follows an elevation of the iron content in the solution, which again accelerates Reaction (3), etc.
:.~
In considering Reaction (3) and the factors which affect its velocity, it is obvious that the elevation of the ferric iron and A-ion contents in the solution accelerates the reaction, and the elevation of the sulfuric acid content decelerates it~ Since a solid phase, jarosite phase, is produced in the reaction, it is also evident that the start of the reaction is facilitated if the reaction milieu already contains at the beginning some amount of the phase in ~uestion in the form of inoculating crystals, as suggested in Spanish Patent 407 811. In practice the latter factor does not, however, constitute a problem because at the ferrite treatment stage there is always present such a number of jarosite crystals that Reaction (3) cannot be prevented in terms of reaction kinetics, owing to lack or shortage of crystal nuclei. In advance it cannot, however, be expected that the jarosite content in the reaction system would accelerate Reaction (3), i.e., it would push the reaction from the left to the right. On the other hand, it obviously should have an effect on the velocity of the reaction in the opposite direction, i.e., from the right to the left.
,, , ,: . , ~ '" ; ' '~ ' - ~
a~sl~ ~
Therefore it was surprising to observe during our experiments relating to the ferrite treatment stage that the jarosite content in the re-action system did influence, within a wide concentration range, the velocity of Reaction (3), specifically from the left to the right -and thereby also the velocity of total Reaction (l). Figure 3 de-picts the iron(III) concentration in the solution as a function of time in a reaction system in which Reaction (3) occurs at a tempera-ture of 95C and in which the sodium ion concentration in the solu-tion has been maintained at 8-9 g/l by means of Na2SO4 additions and the sulfuric acid concentration at approximately 30 g/l by means of ZnO additions, and the jarosite concentration in the system at : the initial moment of the reaction has varied between 50 g/l and 400 g/l. From this figure it can be seen that the elevation of the jarosite concentration from 50 g/l to 400 g/l accelerates Reaction (3) many times over.
In accordance with the present invention there is provided in a hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites comprising treating the ferrites under atmospheric conditions in a sulfuric acid-bearing solution in the 20 presence of potassium, sodium, or ammonium ions at 80-105C in order to precipitate, as jarosite, the iron present in the ferrites, separating a jarosite-bearing solid from the solution, feeding the solution to a neutral leach stage, to which acid and calcine are also fed and from which another solution containing zinc, copper, and cadmium is recovered, and feeding the ferrite-bearing solid to the ferrite treatment stage; the improvement of recycling to the process a portion of the jarosite-bearing solid obtained from the ferrite treatment stage.
-4-- . , , L~L8~
This observation opens a possibility for utilizing the phenomenon in the leaching system for zinc concentrate. It is, however, advisable first to make some observations on the role of the neutral leach in the leaching process.
In the leaching of zinc calcine the role of the neutral leach is to dissolve the zinc oxide (and zinc sulfate) present in the calcine and to produce a neutral solution with a pH of 4-5, raw solution for the zinc electrolysisO The optimal performance of the neutral leach involves that the pH of the raw solution is 4-5, the solution is :, devoid of iron and solids, the ferritic solid left as a leach residue is nearly devoid of zinc oxide, the reactor volume required by the leach stage is small, and the control of the stage is simple and reliable in operation.
Figure 1 depicts a lea~h system according to United States Patent : 3,959,437.
As can be seen from Figure 1, the solution PL separated after the ~: ferrite treatment stage 2 returns to the neutral leach 1. It is disclosed in Finnish Patent Application 410/73 that the sulfuric acid concentratlon in the solution PL is 15-80 g/l, most commonly 30-40 g/l, and its iron concentration most commonly 5-10 , .
~ -4a-. ,, ,: , : :
:; :
g/l. When such a solution PL is fed to the neutral leach 1, its sulfuric acid is neutralized by the zinc oxide of the calcine P and the iron is precipitated completely - obviously a large part of it as a hydroxide. After the neutral leach 1 the solid F is separated E from the raw solution RL, usually by settling. This requires that the settling properties of the solid F are good.
Special care must be taken that the solid content in the overflow of the settler E is small and that it does not contain a notable quantity of ferrihydroxide flocs; the iron present in the latter is-reduced during the solution purification stage from the ferric form to the ferrous form and passes along with the solution to the electrolysis stage, where it may cause disturbances in the electrolysis.
It is also advantageous for the leach procedure lf ~he solid content in the underflow of the settler E of the neutral leach 1 is as high as possible. The amount of inert (in terms of the operation of the stage) raw solution carried along to the treatment stage by the ferritic solid is thereby - in this manner of separation - minimized, as are the secondary flow passing through the treatment stage 2 and the reactor volume required by this stage. However, in certain cases it proves to be even more appropriate to separate from the underflow of the settler E the solid material F from the raw solution ~L by, for example, filtration or centrifugation. This does involve an additional procedure, but at the same time it provides a considerable advantage for the operation of the ferrite treatment stage 2 because now the passage of an unnecessary circulating load (raw solution) through this stage has been practically eliminated and at the same time the concentrations of the reaction components are maxirnal, which accelerates total Reaction (1).
It has been shown above that ~or the operation of the leach process it is important that the iron amount returning from the ferrite treatment stage 2 does not cause disturbances in the process.
This disturbance would manifest itself during the neutral stage 1 as a worsening of the settling properties of the solid material, i.e., ferrihydroxide flocs would pass along with the overflow of the settler, thereby causing processing problems, and in ~9~
pa~ticular, the underflow of the settler would be diluted, which would lead to an unnecessarily large liquid circulation through the ferrite treatment stage with all the resulting disadvantages. It is true that the iron tolerance of the stage can be affected considerably by the manner of operating the neutral leach 1, but it is advisable particularly to emphasize in this connection that all the steps which improve the settlin~ and separation properties of the solid F of the neutral leach stage 1 and all the steps which diminish the circulation of the raw electrolyte through the ferrite treatment stage 2 also strongly promote the total leach process.
It has been shown that, for example, in the leach process illustrated in Fig. 1 it is advantageous for the operation of the ferrite treatment stage 2 if the reactions of this stage occur at a high jarosite concentration, i.e., at a concentration considerably higher than that caused by the jarosite normally produced at this stage. This elevated jarosite concentration is obtained according to the present invention by returning a sufficient amount o the jarosite produced during the stage 2 to the beginning of the same stage. In addition it has been surprisingly observed that it is especially advantageous for the entire operation of, for example, the known leach process illustrated in Fig. 1 i~ the return of jarosite takes place through the neutral leach stage 1 because there it according to our experience surprisingly improves the settling and separation properties of the solid F of the neutral leach stage 1 and, in particular, elevates the solid content in the underflow of the neutral settler E, but it also diminishes the amount of iron hydroxide flocs in the overflow and thereby increases the iron tolerance of the stage 1. From the neutral stage 1 the jarosite is carried along with the ferrites F to the treatment stage 2, where it accelerates and promotes -the operation of this stage in the manner described above.
The invention is described below in more detail with the help of examples and with reference to enclosed Fig. 2, whicn depicts the process according to the invention, applied to the leach system according to Uni-~ed States Patent 3,959,437, illustrated in Fig. 1.
..
. . , . :
:
a~s~
:
":
The symbols used in Fig. 2 are the same as those in Fig. 1 and are:
1 neutral leach stage 2 ferrite treatment stage E separation of solid and solution P calcine H return acid RL raw solution F ferritic leach residue R sulfuric acid + ammonium, sodium or potassium sulfate J iron precipitate (jarosite precipitate) PL treatment stage return solution J' jarosite precipitate portion returned to the same stage, i.e., ferrite treatment stage J" jarosite precipitate portion to be fed to the neutral leach stage and returned through it to the ferrite treatment stage Of the examples below, Example 1 is a reference example of an experiment performed in accordance with Fig. 1 by the process shown in United States Patent 3,959,437. Examples 2-6 relate to an embodiment of the process according to the invention in which the return portion of the jarosite precipitate is fed back to the beginning of the ferrite treatment stage. Example 7 illustrates another embodiment of the process according to the invention, in which the return portion of the jarosite precipitate is fed together with the solution to the neutral leach stage. It is evident that the process according to the invention can also be performed in such a manner that part of the jarosite precipitate is returned both to the beginning of the ferrite treatment stage and to the neutral leach stage.
Example 1 (reference example) 360 g of ferritic leach residue F from the neutral leach stage 1 was fed to the treatment stage 2, to which 2 1 of electrolysis return acidH was fed simultaneously. The composition of the ferritic leach residue F was:
:::
:
-'.1^ 1~
~.~
" : ' : . ~. - , ... . .
. . . . .
8~9 ZnFe204 62 %
ZnO 11 %
ZnS 1 %
jarosite 4 %
others (SiO2, CaSO~, PbS04...)22 %
The sulfuric acid concentration H in the return acid was 132 g/l, zine coneentration 40 g/1, and sodium coneentration 8 g/l. The temperature at the treatmen~. stage 2 was 95C. The following table shows the iron, sulfurie aeid, and sodium eoneentrations in the solution phase and the zinc concentration in the solid phase as functions of the treatment period. The results illustrate the course of the proeess.
Time Solution Solid h Fe H2S04 Na Zn g/l g/l g/l %
1 15.3 47 8.0 2 18.9 37 20.7 32 19.0 30 7.6 15.9 18.6 29 16.8 33 12.8 15~2 3~ 7.3 12.7 34 11.4 34 6.6 8.2 6.6 35 5.5 100 5.3 33 3.8 120 4.7 32 508 2.8 Example 2 As in Example 1, but in this ease 100 g of Na jarosite J' (50 g/l) from the ferrite treatment stage 2 was also added to the beginning of the treatment stage 2. The course of the process ean be seen from the following table.
~'' .
.
Time Solution Solid h Fe H2S04 Na Zn g/l g/l g/l %
1 22.8 46 7.7 2 24.1 37 22.8 33 5.8 15.5 33 6.2 11.1 36 3.7 9.0 38 8.0 7.5 39 4.9 2.0 Example 3 As in Example 1, but in this case the Na jarosite return J' was `~ 400 g (200 g/l) Time Solution Solid h Fe H2S04 Na Zn~
g/l g/l g/l %
1 16.3 52 7.5 2 19.5 44 16.0 40 11.0 35 5.8 3.8 6.8 32
This observation opens a possibility for utilizing the phenomenon in the leaching system for zinc concentrate. It is, however, advisable first to make some observations on the role of the neutral leach in the leaching process.
In the leaching of zinc calcine the role of the neutral leach is to dissolve the zinc oxide (and zinc sulfate) present in the calcine and to produce a neutral solution with a pH of 4-5, raw solution for the zinc electrolysisO The optimal performance of the neutral leach involves that the pH of the raw solution is 4-5, the solution is :, devoid of iron and solids, the ferritic solid left as a leach residue is nearly devoid of zinc oxide, the reactor volume required by the leach stage is small, and the control of the stage is simple and reliable in operation.
Figure 1 depicts a lea~h system according to United States Patent : 3,959,437.
As can be seen from Figure 1, the solution PL separated after the ~: ferrite treatment stage 2 returns to the neutral leach 1. It is disclosed in Finnish Patent Application 410/73 that the sulfuric acid concentratlon in the solution PL is 15-80 g/l, most commonly 30-40 g/l, and its iron concentration most commonly 5-10 , .
~ -4a-. ,, ,: , : :
:; :
g/l. When such a solution PL is fed to the neutral leach 1, its sulfuric acid is neutralized by the zinc oxide of the calcine P and the iron is precipitated completely - obviously a large part of it as a hydroxide. After the neutral leach 1 the solid F is separated E from the raw solution RL, usually by settling. This requires that the settling properties of the solid F are good.
Special care must be taken that the solid content in the overflow of the settler E is small and that it does not contain a notable quantity of ferrihydroxide flocs; the iron present in the latter is-reduced during the solution purification stage from the ferric form to the ferrous form and passes along with the solution to the electrolysis stage, where it may cause disturbances in the electrolysis.
It is also advantageous for the leach procedure lf ~he solid content in the underflow of the settler E of the neutral leach 1 is as high as possible. The amount of inert (in terms of the operation of the stage) raw solution carried along to the treatment stage by the ferritic solid is thereby - in this manner of separation - minimized, as are the secondary flow passing through the treatment stage 2 and the reactor volume required by this stage. However, in certain cases it proves to be even more appropriate to separate from the underflow of the settler E the solid material F from the raw solution ~L by, for example, filtration or centrifugation. This does involve an additional procedure, but at the same time it provides a considerable advantage for the operation of the ferrite treatment stage 2 because now the passage of an unnecessary circulating load (raw solution) through this stage has been practically eliminated and at the same time the concentrations of the reaction components are maxirnal, which accelerates total Reaction (1).
It has been shown above that ~or the operation of the leach process it is important that the iron amount returning from the ferrite treatment stage 2 does not cause disturbances in the process.
This disturbance would manifest itself during the neutral stage 1 as a worsening of the settling properties of the solid material, i.e., ferrihydroxide flocs would pass along with the overflow of the settler, thereby causing processing problems, and in ~9~
pa~ticular, the underflow of the settler would be diluted, which would lead to an unnecessarily large liquid circulation through the ferrite treatment stage with all the resulting disadvantages. It is true that the iron tolerance of the stage can be affected considerably by the manner of operating the neutral leach 1, but it is advisable particularly to emphasize in this connection that all the steps which improve the settlin~ and separation properties of the solid F of the neutral leach stage 1 and all the steps which diminish the circulation of the raw electrolyte through the ferrite treatment stage 2 also strongly promote the total leach process.
It has been shown that, for example, in the leach process illustrated in Fig. 1 it is advantageous for the operation of the ferrite treatment stage 2 if the reactions of this stage occur at a high jarosite concentration, i.e., at a concentration considerably higher than that caused by the jarosite normally produced at this stage. This elevated jarosite concentration is obtained according to the present invention by returning a sufficient amount o the jarosite produced during the stage 2 to the beginning of the same stage. In addition it has been surprisingly observed that it is especially advantageous for the entire operation of, for example, the known leach process illustrated in Fig. 1 i~ the return of jarosite takes place through the neutral leach stage 1 because there it according to our experience surprisingly improves the settling and separation properties of the solid F of the neutral leach stage 1 and, in particular, elevates the solid content in the underflow of the neutral settler E, but it also diminishes the amount of iron hydroxide flocs in the overflow and thereby increases the iron tolerance of the stage 1. From the neutral stage 1 the jarosite is carried along with the ferrites F to the treatment stage 2, where it accelerates and promotes -the operation of this stage in the manner described above.
The invention is described below in more detail with the help of examples and with reference to enclosed Fig. 2, whicn depicts the process according to the invention, applied to the leach system according to Uni-~ed States Patent 3,959,437, illustrated in Fig. 1.
..
. . , . :
:
a~s~
:
":
The symbols used in Fig. 2 are the same as those in Fig. 1 and are:
1 neutral leach stage 2 ferrite treatment stage E separation of solid and solution P calcine H return acid RL raw solution F ferritic leach residue R sulfuric acid + ammonium, sodium or potassium sulfate J iron precipitate (jarosite precipitate) PL treatment stage return solution J' jarosite precipitate portion returned to the same stage, i.e., ferrite treatment stage J" jarosite precipitate portion to be fed to the neutral leach stage and returned through it to the ferrite treatment stage Of the examples below, Example 1 is a reference example of an experiment performed in accordance with Fig. 1 by the process shown in United States Patent 3,959,437. Examples 2-6 relate to an embodiment of the process according to the invention in which the return portion of the jarosite precipitate is fed back to the beginning of the ferrite treatment stage. Example 7 illustrates another embodiment of the process according to the invention, in which the return portion of the jarosite precipitate is fed together with the solution to the neutral leach stage. It is evident that the process according to the invention can also be performed in such a manner that part of the jarosite precipitate is returned both to the beginning of the ferrite treatment stage and to the neutral leach stage.
Example 1 (reference example) 360 g of ferritic leach residue F from the neutral leach stage 1 was fed to the treatment stage 2, to which 2 1 of electrolysis return acidH was fed simultaneously. The composition of the ferritic leach residue F was:
:::
:
-'.1^ 1~
~.~
" : ' : . ~. - , ... . .
. . . . .
8~9 ZnFe204 62 %
ZnO 11 %
ZnS 1 %
jarosite 4 %
others (SiO2, CaSO~, PbS04...)22 %
The sulfuric acid concentration H in the return acid was 132 g/l, zine coneentration 40 g/1, and sodium coneentration 8 g/l. The temperature at the treatmen~. stage 2 was 95C. The following table shows the iron, sulfurie aeid, and sodium eoneentrations in the solution phase and the zinc concentration in the solid phase as functions of the treatment period. The results illustrate the course of the proeess.
Time Solution Solid h Fe H2S04 Na Zn g/l g/l g/l %
1 15.3 47 8.0 2 18.9 37 20.7 32 19.0 30 7.6 15.9 18.6 29 16.8 33 12.8 15~2 3~ 7.3 12.7 34 11.4 34 6.6 8.2 6.6 35 5.5 100 5.3 33 3.8 120 4.7 32 508 2.8 Example 2 As in Example 1, but in this ease 100 g of Na jarosite J' (50 g/l) from the ferrite treatment stage 2 was also added to the beginning of the treatment stage 2. The course of the process ean be seen from the following table.
~'' .
.
Time Solution Solid h Fe H2S04 Na Zn g/l g/l g/l %
1 22.8 46 7.7 2 24.1 37 22.8 33 5.8 15.5 33 6.2 11.1 36 3.7 9.0 38 8.0 7.5 39 4.9 2.0 Example 3 As in Example 1, but in this case the Na jarosite return J' was `~ 400 g (200 g/l) Time Solution Solid h Fe H2S04 Na Zn~
g/l g/l g/l %
1 16.3 52 7.5 2 19.5 44 16.0 40 11.0 35 5.8 3.8 6.8 32
5.0 32 4.2 2.0 Example 4 As in Example 1, but in this case the amount of ferritic leach residue F was 490 g, the sulfuric acid concentration in the return acid H was 174 g/l and sodium concentration approx. 10 g/l, and thé Na jarosite return J' was 550 g (275 g/l).
Time Solution Solid h Fe H2S04 Na Zn . g/l g/l g/l %
1 28.5 56 10.7 2 26.8 ~3 22.6 39 8.5 14.9 35 6.1 8.3 33 1.9 7.6 34
Time Solution Solid h Fe H2S04 Na Zn . g/l g/l g/l %
1 28.5 56 10.7 2 26.8 ~3 22.6 39 8.5 14.9 35 6.1 8.3 33 1.9 7.6 34
6.6 35 4.3 1.4 - . : , . .. : -: ,. ,- -8~g Example 5 The experiment was performed as in Example 1 but in this case the amount of ferritic leach .residue F was 500 g and its compo-sition was:
ZnFe204 67 %
ZnO 4 %
ZnS 1 %
jarosite 1 %
others (SiO2, CaS04, PbS04... ) 22 %
The sulfuric acid concentration in the return acid H was 172 g/l, zinc concentration 40 g/l, and sodium concentration approx. 10 g/l.
The Na jarosite return J' was 100 g (50 g/l).
Results of the experiment: .
Time Solution Solid h Fe H2S04 Na Zn g/l g!l g/l %
1 48.2 26 2 48.1 26
ZnFe204 67 %
ZnO 4 %
ZnS 1 %
jarosite 1 %
others (SiO2, CaS04, PbS04... ) 22 %
The sulfuric acid concentration in the return acid H was 172 g/l, zinc concentration 40 g/l, and sodium concentration approx. 10 g/l.
The Na jarosite return J' was 100 g (50 g/l).
Results of the experiment: .
Time Solution Solid h Fe H2S04 Na Zn g/l g!l g/l %
1 48.2 26 2 48.1 26
7,5 28 6 30.9 30 7.9 21.6 33 16.7 35 10.0 40 4.3 1.7 Example 6 The experiment was performed according to Example 1, but in this case the amount of ferritic leach residue F was 430 g and its composition was:
ZnFe24 75 %
ZnO
ZnS - 1 %
jarosite 3 %
others 18 %
The sulfuric acid concentration in the return acid H was 160 g/l, zinc concentration 40 g/l, and NH4 concentration 12 g/l. The NH4 jarosite return J' was 200 g (100 g/l)O
, ~'.': ~: ,:
-Results of the experiment:
Time Solution Solid h Fe H2S04 NH4 Zn g/l g/l g/l 1 24.5 48 2 26.3 35 20.5 30 4-5 5.0 14.2 33 11.2 33 2.6 7.2 34 2.8 1.
Example 7 On an industrial scale the two-stage leach process for zinc calcine was operated according to the flow diagram ~ig. 2, in which case portion J" of the jarosite-bearing precipitate separated after the ferrite treatment stage 2 was returned to the neutral leach stage 1. The results shown in the following table show the effect of the return on the iron tolerance of the neutral stage 1 and on the solid content in the underflow of the settler E. In the table, Fe (g/l) stands for the content produced in -the subsequent stage by the iron amount returning from the treatment stage 2 to the neutral leach stage 1 and precipitating there: :
:: :
Jarosite Fe Solid content return g/l in underflow g/l no 3.7 250 yes 4 7 400 no 5.2 190 yes 6.0 410 no 1-1.5 -350-450 The jarosite return to the neutral leach stage 1 and its further passage to the ferrite treatment stage 2 raised the jarosite concentration at the latter stage by 50-100 g/1.
- ~ - .: . ~ . -,:
, ~, - - . ~ , .
,
ZnFe24 75 %
ZnO
ZnS - 1 %
jarosite 3 %
others 18 %
The sulfuric acid concentration in the return acid H was 160 g/l, zinc concentration 40 g/l, and NH4 concentration 12 g/l. The NH4 jarosite return J' was 200 g (100 g/l)O
, ~'.': ~: ,:
-Results of the experiment:
Time Solution Solid h Fe H2S04 NH4 Zn g/l g/l g/l 1 24.5 48 2 26.3 35 20.5 30 4-5 5.0 14.2 33 11.2 33 2.6 7.2 34 2.8 1.
Example 7 On an industrial scale the two-stage leach process for zinc calcine was operated according to the flow diagram ~ig. 2, in which case portion J" of the jarosite-bearing precipitate separated after the ferrite treatment stage 2 was returned to the neutral leach stage 1. The results shown in the following table show the effect of the return on the iron tolerance of the neutral stage 1 and on the solid content in the underflow of the settler E. In the table, Fe (g/l) stands for the content produced in -the subsequent stage by the iron amount returning from the treatment stage 2 to the neutral leach stage 1 and precipitating there: :
:: :
Jarosite Fe Solid content return g/l in underflow g/l no 3.7 250 yes 4 7 400 no 5.2 190 yes 6.0 410 no 1-1.5 -350-450 The jarosite return to the neutral leach stage 1 and its further passage to the ferrite treatment stage 2 raised the jarosite concentration at the latter stage by 50-100 g/1.
- ~ - .: . ~ . -,:
, ~, - - . ~ , .
,
Claims (6)
1. In a hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites comprising treating the ferrites under atmospheric conditions in a sulfuric acid-bearing solution in the presence of potassium, sodium, or ammonium ions at 80-105°C in order to precipitate, as jarosite, the iron present in the ferrites, separating a jarosite-bearing solid from the solution, feeding the solution to a neutral leach stage, to which acid and calcine are also fed and from which another solution containing zinc, copper, and cadmium is recovered, and feeding the ferrite-bearing solid to the ferrite treatment stage; the improvement of recycling to the process a portion of the jarosite-bearing solid obtained from the ferrite treatment stage.
2. The process of Claim 1, in which the jarosite concen-tration at the beginning of the ferrite treatment stage is adjusted to 50-400 g/l.
3. The process of Claim 1, in which the jarosite concen-tration of the beginning of the ferrite treatment stage is controlled to 200-300 g/l.
4. The process of Claim 1, in which a portion of the jaro-site-bearing solid separated from the solution is recycled to the beginning of the ferrite treatment stage.
5. The process of Claim 1, in which a portion of the jarosite-bearing solid obtained from the ferrite treatment is fed to the neutral leach stage together with the solution.
6. The process of claims 1 or 5 in which from 14% to 67% by weight of the total jarosite precipitated is re-cycled.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI760486A FI58793B (en) | 1976-02-25 | 1976-02-25 | HYDROMETALLURGICAL ROD FOER FOER AOTERVINNING AV ZINK KOPPAR OCH CADMIUM UR DERAS FERRITER |
| FI760486 | 1976-02-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094819A true CA1094819A (en) | 1981-02-03 |
Family
ID=8509784
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA272,620A Expired CA1094819A (en) | 1976-02-25 | 1977-02-24 | Hydrometallurgical process for the recovery of zinc, copper, and cadmium from their ferrites |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1094819A (en) |
| DE (1) | DE2708059B2 (en) |
| FI (1) | FI58793B (en) |
| IN (1) | IN145617B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998006879A1 (en) * | 1996-08-12 | 1998-02-19 | Outokumpu Base Metals Oy | Method for leaching zinc concentrate in atmospheric conditions |
| WO2014013092A1 (en) | 2012-07-16 | 2014-01-23 | Tam 5, S.L. | Hydrometallurgical method for recovering zinc in a sulphuric medium from zinc sulphide concentrates having a high iron content |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT366717B (en) * | 1980-02-06 | 1982-05-10 | Voest Alpine Ag | METHOD FOR HYDROMETALLURGIC WORKING UP OF RAW MATERIALS CONTAINING ZINC |
| FI65804C (en) * | 1980-09-30 | 1984-07-10 | Outokumpu Oy | HYDROMETALLURGICAL SYSTEM FOR FARING AOTERVINNING AV BLY SILVEROCH GULD SAMT ZINK UR ORENA JAROSITAOTERSTODEN FRAON EN E LETROLYTISK ZINKPROCESS |
| US4485073A (en) * | 1984-02-08 | 1984-11-27 | Kerr-Mcgee Chemical Corporation | Process of producing manganese sulfate solutions |
| US4489043A (en) * | 1984-02-08 | 1984-12-18 | Kerr-Mcgee Chemical Corporation | Manufacture of manganous sulfate solutions |
| FI83335C (en) * | 1988-03-31 | 1993-06-29 | Pekka Juhani Saikkonen | Process for the recovery of non-ferrous metals, especially nickel, cobalt, copper, zinc, manganese and magnesium by melting and melting film sulfation from raw materials containing these metals |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NO123248B (en) | 1969-10-02 | 1971-10-18 | Norske Zinkkompani As | |
| ES407811A2 (en) * | 1972-10-20 | 1976-02-01 | Asturiana De Zinc Sa | Process for recovering zinc from ferrites |
-
1976
- 1976-02-25 FI FI760486A patent/FI58793B/en not_active Application Discontinuation
-
1977
- 1977-02-24 DE DE2708059A patent/DE2708059B2/en not_active Withdrawn
- 1977-02-24 CA CA272,620A patent/CA1094819A/en not_active Expired
- 1977-08-22 IN IN1312/CAL/77A patent/IN145617B/en unknown
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998006879A1 (en) * | 1996-08-12 | 1998-02-19 | Outokumpu Base Metals Oy | Method for leaching zinc concentrate in atmospheric conditions |
| AU725971B2 (en) * | 1996-08-12 | 2000-10-26 | Outotec Oyj | Method for leaching zinc concentrate in atmospheric conditions |
| WO2014013092A1 (en) | 2012-07-16 | 2014-01-23 | Tam 5, S.L. | Hydrometallurgical method for recovering zinc in a sulphuric medium from zinc sulphide concentrates having a high iron content |
| US9463986B2 (en) | 2012-07-16 | 2016-10-11 | Tam 5, S.L. | Hydrometallurgical method for recovery of zinc in sulphuric medium starting from sulphidic zinc concentrates with high iron content |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2708059B2 (en) | 1981-04-02 |
| IN145617B (en) | 1978-11-18 |
| FI58793B (en) | 1980-12-31 |
| FI760486A (en) | 1977-08-26 |
| DE2708059A1 (en) | 1977-09-01 |
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