CA1094973A - Removal of cobalt from zinc electrolyte using zinc dust and copper arsenate - Google Patents
Removal of cobalt from zinc electrolyte using zinc dust and copper arsenateInfo
- Publication number
- CA1094973A CA1094973A CA328,544A CA328544A CA1094973A CA 1094973 A CA1094973 A CA 1094973A CA 328544 A CA328544 A CA 328544A CA 1094973 A CA1094973 A CA 1094973A
- Authority
- CA
- Canada
- Prior art keywords
- zinc
- copper
- electrolyte
- cobalt
- residue
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- 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
Landscapes
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT
Hydrometallurgical process for the recovery of copper arsenate from zinc plant cement copper cake residues and the use thereof in the purification of zinc electrolyte, with the attendant upgrading of the copper value in the treated cement copper residues. The cake residues are first subjected to an acid leach followed by an alkali addition to adjust the pH of the slurry to about 3.5 to 4.0 and to extract zinc, cadmium and cobalt in solution and provide a copper-enriched residue. Cobalt is then precipitated and separated from the extraction solution. The copper-enriched residue is subjected to caustic leach to extract arsenic in solution therefrom and provide a copper-enriched cement copper cake product. The arsenic containing extraction solution is then reacted with a copper salt to form copper arsenate residue and leave purified zinc electrolyte. This divisional case deals with the process of purifying zinc electrolyte contain-ing cobalt contaminant prior to electrolysis thereof in the electrowinning of metallic zinc comprising maintaining said electrolyte at a temperature of about 80 to 90°C, adding zinc dust and copper arsenate then raising the temperature to and maintaining it in the range of about 90 to 95°C until the cobalt level of said electrolyte is less than 0.1 ppm, and adjusting the pH to about 4.0 and then removing the solids from said electrolyte.
Hydrometallurgical process for the recovery of copper arsenate from zinc plant cement copper cake residues and the use thereof in the purification of zinc electrolyte, with the attendant upgrading of the copper value in the treated cement copper residues. The cake residues are first subjected to an acid leach followed by an alkali addition to adjust the pH of the slurry to about 3.5 to 4.0 and to extract zinc, cadmium and cobalt in solution and provide a copper-enriched residue. Cobalt is then precipitated and separated from the extraction solution. The copper-enriched residue is subjected to caustic leach to extract arsenic in solution therefrom and provide a copper-enriched cement copper cake product. The arsenic containing extraction solution is then reacted with a copper salt to form copper arsenate residue and leave purified zinc electrolyte. This divisional case deals with the process of purifying zinc electrolyte contain-ing cobalt contaminant prior to electrolysis thereof in the electrowinning of metallic zinc comprising maintaining said electrolyte at a temperature of about 80 to 90°C, adding zinc dust and copper arsenate then raising the temperature to and maintaining it in the range of about 90 to 95°C until the cobalt level of said electrolyte is less than 0.1 ppm, and adjusting the pH to about 4.0 and then removing the solids from said electrolyte.
Description
1.0~ 1 ~73 Zinc i5 the twenty-fourth most abundant element in the earth's crust and finds many industrial applications, the most important being the oxidation-resistant treatment of iron surfaces, and others being in variGus fields, including topical medicines, chemical reagents, etc.
Zinc is not found in the metallic state in nature.
Its chief ore is zine blend or sphalerite tZnS) which is the source of ninety percent of the zinc produced today. The zinc production methods employed today have heavy treatment costs and consequently zinc metal producers demand high-grade con~
centrates.
There are two main methods of zinc recovery from its ores, i.e., thermal reduction and electrolytic deposition, the latter requiring the availability of relatively inexpensive electrical power in view of the fact that the production of one ton of zinc requires approximately 4500 kilowatt-hours.
The purest zinc (99.99%) is achieved by the electrolytic methods.
The current world production of zinc is about 3,800,000 metric tons per year, 47~ by electrolytic methods and the balance by thermal methods.
The thermal methods involve the following general reactions:
heat ZnS ~ ZnO
heat
Zinc is not found in the metallic state in nature.
Its chief ore is zine blend or sphalerite tZnS) which is the source of ninety percent of the zinc produced today. The zinc production methods employed today have heavy treatment costs and consequently zinc metal producers demand high-grade con~
centrates.
There are two main methods of zinc recovery from its ores, i.e., thermal reduction and electrolytic deposition, the latter requiring the availability of relatively inexpensive electrical power in view of the fact that the production of one ton of zinc requires approximately 4500 kilowatt-hours.
The purest zinc (99.99%) is achieved by the electrolytic methods.
The current world production of zinc is about 3,800,000 metric tons per year, 47~ by electrolytic methods and the balance by thermal methods.
The thermal methods involve the following general reactions:
heat ZnS ~ ZnO
heat
2 ZnO + C ~ 2 Zn + CO2 The electrolytic methods generally involve the following reactions:
g~-10~1973 heat ZnS ~ > ZnO
2nO + H2SO4 3 Zn SO4 + H2O
Zn SO4 ~ Zn + H2SO4 Electrolytic zinc plants utilize four operations:
(1) roasting of zinc sul~ide concentrate; (2) leaching of the roasted concentrate or calcine to extract the soluble zinc;
g~-10~1973 heat ZnS ~ > ZnO
2nO + H2SO4 3 Zn SO4 + H2O
Zn SO4 ~ Zn + H2SO4 Electrolytic zinc plants utilize four operations:
(1) roasting of zinc sul~ide concentrate; (2) leaching of the roasted concentrate or calcine to extract the soluble zinc;
(3) purification of the resulting solution; and (4) electrolysis of the solution to obtain metallic zinc.
Zinc electrolyte typically contains impurities of copper, cobalt, nickel and cadmium that are detrimental to the plating of 7inc and must be removed prior to electrolysis.
These elements are removed by a hot copper sulfate/arsenic trioxidefzinc dust purification procedure.
The precise mechanism of the hot copper sulfate/arsenic trioxide/zinc dust purification technique is not thoroughly understood. ~owever, a plausible explanation is as follows:
Zinc dust displaces copper and arsenic from solutions which are thought to precipitate as a metallic couple. Zinc dust ordinarily does not displace cobalt and nickel from solution, but in the presence of the copper/arsenic couple such metals are quantitati~ely precipitated. The abo~e copper sulfate addition may not be necessary if sufficient copper is already present in the impure zinc electrolyte.
The byproduct of the purification procedure is a cement copper cake residue containing, in addition to copper, varying amounts of zinc, cadmium, cobalt, nickel and arsenic.
The market value of such cake is primarily dependent on the percentage of copper contained therein.
10~1973 There are several disadvantages to the above described purification procedure.
~1) The process requires the addition of arsenic trioxide and possibly copper sulfate, which affects the economics of the overall process.
(2) The cement copper cake residue, because of its arsenic content, has a greatly reduced market value.
(3) The zinc, cadmium and cobalt values in the cement copper cake are not reflected in the marketable value of the latter and consequently reflect losses in the overall process economics.
The present invention relates to the electrolytic production of zinc metal and involves the treatment of residue from such production processes to provide copper arsenate to be recycled for use in the preliminary purification of the zinc electrolyte, and simultaneously to upgrade the copper and reduce the arsenic content in the treated residue to increase the market value thereof and thereby process economics.
Thus, the present invention provides , in a process for electrowinning zinc metal wherein copper, cadmium and cobalt contaminants are removed from impure electrolyte prior to electrolysis, includlng the formation of a cement copper cake residue fraction contalning zinc, cadmium, cobalt and arsenic, the improvement comprising:
(a) subjecting said cement copper cake to an acid leach to form a slurry, followed by an alkali addition to adjust the pH of the slurry to about 3.5 to 4.0 and to extract zinc, cadmium and cobalt in-solution and provide a copper-enriched residue;
(b) precipitating cobalt from the extraction solution of step (a);
10~ ~973 (c) separating the precipitated cobalt from the solution in step (b);
(d) subjecting said copper-enriched residue of step (a) to a caustic leach to extract arsenic in solution therefrom and provide a copper-enriched cement copper cake product;
(e) reacting the arsenic-containing solution from step (d) with a copper salt to form copper arsenate residue and leave a zinc-containing solution;
(f) treating said impure electrolyte with said copper arsenate residue to remove said contaminants and to prepare purified zinc electrolyte.
In the aspect which forms the principal subject of this divisional specification, the present invention provides a process of purifying zinc electrolyte containing cobalt contaminant prior to electrolysis thereof in the electrowinning of metallic zinc, comprising adding to said electrolyte zinc dust in an amount of about 1.5 to 2.5 grams per liter and copper arsenate in an amount of about 0.25 grams per liter, maintaining the temperature of the electrolyte at about 90 to 95C until the cobalt level of said electrolyte is less than 0.1 ppm, adjusting the pH to about 4, and then removing the solids from said electrolyte.
In a preferred embodiment the invention provides such a process of purifying zinc electrolyte containing cobalt contaminant up to 330 ppm prior to electrolysis thereof in the electrowinning of metallic zinc comprising adding to said electrolyte, at a temperature of about 80 to 90C, zinc dust in an amount of about 1.5 to 2.5 grams/liter and copper arsenate in an amount of about 0.25 grams/liter, then raising the temperature to and maintaining it in the range or about 90 to 95C until the cobalt level of said electrolyte is less than .~.................................................................. .
" ~0~73 0.1 ppm, and adjusting the pH to about 4 and then removing the solids from said electrolyte.
Upgrading of cement copper cake and recovery of arsenic is accomplished in four basic operations: (1) Acid leaching; (2) cobalt removal; (3) caustic leach; and (4) arsenic removal. The acid leach is conducted under optimum conditions for the dissolution of zinc, cadmium and cobalt while at the same time suppressing copper extraction.
Zinc electrolyte typically contains impurities of copper, cobalt, nickel and cadmium that are detrimental to the plating of 7inc and must be removed prior to electrolysis.
These elements are removed by a hot copper sulfate/arsenic trioxidefzinc dust purification procedure.
The precise mechanism of the hot copper sulfate/arsenic trioxide/zinc dust purification technique is not thoroughly understood. ~owever, a plausible explanation is as follows:
Zinc dust displaces copper and arsenic from solutions which are thought to precipitate as a metallic couple. Zinc dust ordinarily does not displace cobalt and nickel from solution, but in the presence of the copper/arsenic couple such metals are quantitati~ely precipitated. The abo~e copper sulfate addition may not be necessary if sufficient copper is already present in the impure zinc electrolyte.
The byproduct of the purification procedure is a cement copper cake residue containing, in addition to copper, varying amounts of zinc, cadmium, cobalt, nickel and arsenic.
The market value of such cake is primarily dependent on the percentage of copper contained therein.
10~1973 There are several disadvantages to the above described purification procedure.
~1) The process requires the addition of arsenic trioxide and possibly copper sulfate, which affects the economics of the overall process.
(2) The cement copper cake residue, because of its arsenic content, has a greatly reduced market value.
(3) The zinc, cadmium and cobalt values in the cement copper cake are not reflected in the marketable value of the latter and consequently reflect losses in the overall process economics.
The present invention relates to the electrolytic production of zinc metal and involves the treatment of residue from such production processes to provide copper arsenate to be recycled for use in the preliminary purification of the zinc electrolyte, and simultaneously to upgrade the copper and reduce the arsenic content in the treated residue to increase the market value thereof and thereby process economics.
Thus, the present invention provides , in a process for electrowinning zinc metal wherein copper, cadmium and cobalt contaminants are removed from impure electrolyte prior to electrolysis, includlng the formation of a cement copper cake residue fraction contalning zinc, cadmium, cobalt and arsenic, the improvement comprising:
(a) subjecting said cement copper cake to an acid leach to form a slurry, followed by an alkali addition to adjust the pH of the slurry to about 3.5 to 4.0 and to extract zinc, cadmium and cobalt in-solution and provide a copper-enriched residue;
(b) precipitating cobalt from the extraction solution of step (a);
10~ ~973 (c) separating the precipitated cobalt from the solution in step (b);
(d) subjecting said copper-enriched residue of step (a) to a caustic leach to extract arsenic in solution therefrom and provide a copper-enriched cement copper cake product;
(e) reacting the arsenic-containing solution from step (d) with a copper salt to form copper arsenate residue and leave a zinc-containing solution;
(f) treating said impure electrolyte with said copper arsenate residue to remove said contaminants and to prepare purified zinc electrolyte.
In the aspect which forms the principal subject of this divisional specification, the present invention provides a process of purifying zinc electrolyte containing cobalt contaminant prior to electrolysis thereof in the electrowinning of metallic zinc, comprising adding to said electrolyte zinc dust in an amount of about 1.5 to 2.5 grams per liter and copper arsenate in an amount of about 0.25 grams per liter, maintaining the temperature of the electrolyte at about 90 to 95C until the cobalt level of said electrolyte is less than 0.1 ppm, adjusting the pH to about 4, and then removing the solids from said electrolyte.
In a preferred embodiment the invention provides such a process of purifying zinc electrolyte containing cobalt contaminant up to 330 ppm prior to electrolysis thereof in the electrowinning of metallic zinc comprising adding to said electrolyte, at a temperature of about 80 to 90C, zinc dust in an amount of about 1.5 to 2.5 grams/liter and copper arsenate in an amount of about 0.25 grams/liter, then raising the temperature to and maintaining it in the range or about 90 to 95C until the cobalt level of said electrolyte is less than .~.................................................................. .
" ~0~73 0.1 ppm, and adjusting the pH to about 4 and then removing the solids from said electrolyte.
Upgrading of cement copper cake and recovery of arsenic is accomplished in four basic operations: (1) Acid leaching; (2) cobalt removal; (3) caustic leach; and (4) arsenic removal. The acid leach is conducted under optimum conditions for the dissolution of zinc, cadmium and cobalt while at the same time suppressing copper extraction.
- 4(a) -10~ 973 The solution and residue of the acid leach are separated by filtration for further processing. In order to make a zinc/cadmium solution suitable for recycle to the zinc plant, cobalt is removed from the acid leach solution.
The copper and arsenic containing residue from the acid leach is subjected to a caustic leach to dissolve the arsenic. The caustic leach slurry is then filtered. This leaves a residue containing 60 to 80 percent copper and less than 1 percent arsenic,providing an improved market-able product for its copper values.
Arsenic is removed from the caustic leachsolution by precipitation as copper arsenate which is used as a substitute for arsenic trioxide and copper sulfate in the first stage purification of zinc electrolyte.
The drawing is a schematic flow diagram of the overall process of the invention.
As can be seen in reference to the drawing, showing the process of the present invention in schematic form, the process involves the electrolytic refining of zinc in zinc plant 10. Not shown in the drawing is the preliminary processing of the zinc ore which is-conventional.
~0~3~11973 Zinc sulfide ore is ln accordance with known procedures roasted to form zinc oxide, then leached with sulfuric acid to form zinc sulfate. The zinc sulfate leach solution also includes impurities that must be removed prior to electrolysis in order to avoid contamination of the final zinc product.
The impure feed solution typically contains 0,5 - 1.0 grams per liter copper, 20-30 parts per million cobalt, 1-2 parts per million nickel and in addition may also contain cadmium.
The impure feed solution 11 is fed to the zinc electrolyte purification section 12 where it is treated in accordance with the present invention with zinc dust and copper arsenate as described in more detail below in order to precipitate the aforementioned contaminating impurities using the cobalt level in the solution as a control. The final cobalt level must be less than 0.1 parts per million in order to ensure sufficient purity of the electrolyte for the electrolysis step.
~ he residue from the purification step 12 is separated by any conventional means such as filtration at 13 and con-stitutes what is known as cement copper cake 14 which typically has the following composition:
43~4% copper 6.64~ zinc 1.89% cadmium 1.25% cobalt o.05% nickel 6.89~ arsenic ~1.0~973 The purified zinc electrolyte filtrate isdelivered through line 15 to the electrolytic zinc plant 10 for electrolysis. The cement copper cake 14 is treated in order to (a) upgrade the copper content and purity of the residue to increase the market value thereof and (b) to recover the arsenic content and convert the latter to copper arsenate and recycle the copper arsenate to the purification step 12 and use it in conjunction with zinc dust for the previously described precipitation step in place of the prior art copper sulfate/arsenic trioxide reagents.
The cement copper cake 14 is subjected to an acid leaching step 16 in order to recover zinc, cadmium and cobalt constituents therefrom as a filtrate and provide a residue separated by filters 17. The filtrate is delivered to the cobalt removal stage 18 to separate the cobalt therefrom so that the remaining zinc/cadmium solution can be delivered through line 19 to recycle line 20 through which it is delivered to the electrolytic zinc plant 10 for reuse. The residue from cobalt removal stage 18 has a high cobalt content which has market value.
The residue from filtration step 17 is subjected to a caustic leach 21 to dissolve the arsenic and leave a high copper residue which is separated in filtration step 22. The latter residue, designated as the treated cement copper cake, has an enhanced copper content which increases its market value. The filtrate from step 22 is treated with copper sulfate in arsenic removal stage 22 to provide copper arsenate which may be recycled through ~0~'1973 return line 24 to the electrolytic purification step previously described. The remaining zinc containing solution is delivered to recycle line 20 for delivery to the electrolytic zinc plant 10.
Acid Leaching Temperature of the acid leach slurry in step 16 is maintained at about 95C with 20 percent initial solids loading and 15 to 20 grams per liter initial sulfuric acid addition. After about two hours, the acid leach slurry is neutralized to pH 3.5 to 4.0 with sodium hydroxide to precipitate any leached copper. The quantity of sodium hydroxide used in this step varies with different copper cake samples, and so also does the final pH. However, control is easily maintained by observing the color of the leach solution. Copper precipitation is complete when the solution loses its blue color. Consumption of sodium hydroxide is generally 75 to 150 pounds per dry ton of copper cake. Fresh copper cake consumes more sodium hydroxide than stockpiled copper cake. It should be noted that some degree of attritioning to break up lumps is necessary either before or during the acid leaching of stockpiled copper cake. Attrition is not needed for fresh cake.
The acid leach slurry is filtered at 17 and the arsenic rich residue displacement washed. The residue is black and finely divided. It is amenable to ~iltration by filter press, and behaves similarly to regular copper cake.
10~ 973 Typical products of the acid leach, based on an average sample of copper cake assaying 6.24~ Zn, 1.89% Cd, 1.25% Co, 0.71~ Mn, 43.4% Cu, 6.89% As, O.lC% Na and 15.5%
SO~, have the following analysis.
TABLE I
Results of Acid Leach Extractions Stockleiled Cake Recovery (as %
Filtrate metal value 10comPonent (grams/liter)Residue % in feed) _ _ Zn 11.8 2.16 71.4 Cd 3.95 0.46 81.9 Co 2.77 0.22 87.0 Mn 1.71 0.05 94.3 Cu 0.22 57.8 0.20 As 1.99 8.14 11.4 Na 6.52 0.13 96.4 s SO4 42.2 6.81 76.4 Fresh Cake .
Recovery (as %
Filtrate metal value Component (~rams/liter)Residue % in feed*) Zn 13.6 1.21 85.5 Cd 3.27 0.84 67.9 Co 1.87 0.70 58.8 Mn 1.76 0.03 97.0 Cu 55 ppm 57.9 0.05 As 1.68 8.30 9.62 Na 11.5 0.32 94.5 * Copper cake plus added reagents.
_ g _ ~0~3973 Cobalt Removal Cobalt removal is carried out at 18 under the following conditions. Filtrate 23 from the acid leach process stage 16 is heated to about 95C and solid potassium permanganate is added until a slight excess of permanganate is noted, as seen by a deep purple color. Sodium hydroxide is then added in an amount sufficient to maintain pH of the resulting slurry at about 3.0 to 3.5 These conditions are maintained for about two hours. Total cobalt removal may be accomplished by using a longer reaction time but is not mandatory in this process. The slurry is filtered at 25 and the residue displacement washed.
Average reagent consumption per pound of cobalt rem~ved is 3~8 pounds of potassium permanganate and 2.0 pounds of sodium hydroxide. These figures constitute a considerable excess over the theoretical requirement.
The reason for this is that potassium permanganate is consumed in oxidizing manganese and arsenic in addition to cobalt in the acid leach solution.
Typical products of the cobalt removal stage obtained from as typical acid leach solution analyze as shown below in Tahle II. The filtrate is returnable to the zinc plant for recovery of zinc and cadmium. The amount of zinc and cadmium reporting to the cobalt rich residue is largely dependent on washing efficiency. This residue requires a thorough displacement wash to remove zinc and cadmium.
10~3'~973 TABLE II
Results_of Cobalt ~em~
Recovery (as %
Filtrate metal value s Component (grams~llter) Residue % in feed*) Zn 11.0 2.45 5 Cd 3.48 1.64 10 * Solution from acid leach stage plus added reagents.
Results of Cobalt Removal Recovery (as %
Filtrate metal value Component (grams/liter) Residue %in feed_*) Co less than S ppm 11.5 100 Mn less than 5 ppm 22.4 100 Cu 0.11 0.45 50 As 0.20 7.45 90 Na 9.11 2.03 5 * Solution from acid leach stage plus added reagents.
Caustic L~ach The residue of high arsenic content from the acid leach process stage 16 is leached with caustic at 21 to dissolve ~ -the arsenic. Temperature of the caustic leach slurry is maintained at a~out 95C with 10% initial loading of residue from the acid leach stage and addition of 5~ sodium hydroxide solution. Air is continuously added to the slurry at the rate of approximately 500 standard cuhic feet per minute per dry ton of acid leach residue. These reaction conditions are maintained for about six hours. The slurry is then filtered at 22 and the residue displacement washed. The residue from the filtration stage 22 is usually brown or green and is slower filtering than other residues in this process.
1~9~973 Typical products of the caustic leach stage obtained from the feed to this stage analyze as follows:
TABLE III
Results of Caustic Leach Recovery (as %
Filtrate metal value Component (grams/liter) Residue % in feed*) Zn 0.51 2.07 21.4 Cd less than 1 ppm 0.56 0 Co less than 1 ppm ~.26 0 Mn less than 1 ppm 0.07 0 Cu less than 60 ppm 70.4 less than 0.1 As 8.29 0.75 92.4 Na 28.0 0.32 99~0 SO4 7.16 0.42 95.0 * Residue from acid leach stage plus added reagents.
Many other caustic leaches using slightly different conditions also extract more than 90% of the arsenic.
Arsenic Removal Arsenic compounds are removed from the caustic leach solution as an insoluble solid at 23. The purified solution 26 is ret~rnable to the zinc plant. In the preferred embodiment, the following conditions are used. The filtrate 27 from the caustic leach stage is heated to 75-80C. Because formation of copper arsenate is not complete if copper sulfate is added directly to the solution, sufficient sulfuric acid is first added to bring the solution to about pH 8. Copper sulfate is then added; about 60 pounds of CuSO4-5H2O per water ton o.
solution is required. The 1091~973 amount of copper sulfate required may vary depending on the arsenic content of the solution. The resulting slurry is maintained for about two hours. A small amount of lime, usually about 3 pounds per water ton, is then added to ensure a final pH above 4. The slurry is then filtered.
Arsenic removal is usually greater than 95% by this method.
The filtrate is returnable to the zinc plant. The residue, a pale blue quick filtering solid, is returnable through line 24 for use as a substitute for arsenic trioxide and copper sulfate in first stage purification of zinc electrolyte. Typical products of the arsenic removal stage obtained from the feed to this stage analyze as follows:
TABLE IV
Results of Arsenic Removal Recovery (as %
Filtrate metal value Component (grams/liter)Resi ue ~ in feed*) Zn 0.12 1.30 75.0 Cd 1 ppm 10 ppm -Co 1 ppm 10 ppm - -~
Mn 1 ppm 10 ppm Cu 0.32 24.6 95.7 As 0.18 27.6 97.7 Na 25.9 4.33 4.54 Ca 0.5 2.33 56.0 * Solution from caustic leach stage plus added reagents.
Electrolyte Purification The copper arsenate product from the ~ 13 -~0~ 973 arsenic removal stage 23 is sued as a substitute for copper sulfate and arsenic trioxide in the removal of copper, cobalt and nickel from impure zinc electrolyte at stage 12. Impure zinc electrolyte solution typically contains 0.5-1.0 grams/liter copper, 20-30 parts per million cobalt, and 1-2 parts per million nickel. Electrolyte ¦ purification is performed as follows: 1.5 to 2.5 grams/liter of zinc dust and 0.25 grams (dry)/liter of copper arsenate product are added to impure zinc electrolyte solution at about 80 to 90C. The temperature is then maintained at about 90 to 95C until the cobalt level in the solution is less than 0.1 ppm. When this cobalt level is reached, the pH of the solution is adjusted to approximately pH 4 and the slurry is then filtered. Total reaction time is usually about two hours. The filtrate is fed to the zinc plant for electrolytic recovery of metallic zinc. The cement copper cake residue is treated according to the present invention to remove and recycle its arsenic con-tent, with attendant upgrading of the copper cake.
Example 1 Six plant runs were made using the electrolyte purification process of the present invention. Impure zinc electrolyte solution of pH about 4 and at about 80-90C was treated with 1.5 to 2.5 grams/liter of zinc dust and 0.25 grams (dry)/liter of copper arsenate product from the arsenic removal stage. The temperature was maintained at about 30 to 95C until the cobalt level in the solution was less than 0.1 ppm. The results are summarized below:
109~973 TABLE V
Results of Use of Copper Arsenate Product In Removal of Cobalt from Impure Zinc Electrolyte >
Amount Time Initial of Copper Taken Cobalt Amount Arsenate For Cobalt Level In of Zinc Product To Reach Impure Dust Added (55% Less Than Run No. Feed Added moisture) 0.1 ppm 1 16 ppm 550 pounds 160 pounds 85 minutes The laboratory procedure differs somewhat from the plant procedure. It was found that on a small (1 liter) ~ -scale the reagent requirements are greater and the purification is more difficult to control. The following example illustrates the laboratory procedure:
Example 2 Four 1 liter samples of impure zinc electrolyte containing 16 ppm Co were treated with copper arsenate and zinc dust in the following way. The samples were heated to 90C in beakers; 1 g dry powdered copper arsenate product was added to each beaker together with 2, 3, 4 and 5 g, respectively, of zinc dust. The beakers were stirred for 1 hour, and solution samples were removed from each at 10 minute inter~als. The solutions treated with 2 and 3 g of zinc dust did not achieve the required cobalt level of less than 0.1 Fpm. In those treated with 4 and 5 g of zinc ~0'~ 373 dust the co~alt level fell to less than 0.1 ppm after 20 minutes.
It is thought that performance on a plant scale is more effective than on a bench scale because the reducing conditions required for the purification are more easily maintained in a large tank than in a 1 liter beaker.
As can be seen from the above description, accord-ing to the present invention a copper arsenate product is made from cement copper cake residue and reused in purification of zinc electrolyte. Two superior features of this invention are:
1. Arsenic is recycled; therefore only a small makeup of supply of arsenic trioxide is required: and 2. The cement copper residue is considerably upgraded during treatment, the final residue containing more than 70~ copper and less than 1% arsenic.
The copper arsenate product is derived from zinc plant cement copper residue in a four stage process compris-ing:
1. An acid leach in which about 74% of the zinc, 82% of the cadmium and 87% of the cobalt are extracted.
2. A cobalt removal stage in which cobalt is precipitated from the acid leach filtrate leaving a zinc/cadmium solution suitable lOq~73 "
for recycle to the zinc plant.
3. A hot aerated caustic leach in which over 90% of the arsenic is extracted from the acid leach residue.
4. An arsenic removal stage in which arsenic is precipitated as copper arsenate for the caustic leach filtrate, again leaving a solution which is returnable to the zinc plant~
Expected benefits from the present invention include:
1. Reduced expenditure for arsenic trioxide as a purification reagent.
2. Reduced dependence on outside sources for supply of arsenic trioxide. -3. Increased value of upgraded copper 2~ residue.
While one embodiment of the present invention has been shown and described herein, it is to be understood that certain changes and/or additions may be made thereto by those skilled in the art without departing from the scope and spirit of the invention.
The copper and arsenic containing residue from the acid leach is subjected to a caustic leach to dissolve the arsenic. The caustic leach slurry is then filtered. This leaves a residue containing 60 to 80 percent copper and less than 1 percent arsenic,providing an improved market-able product for its copper values.
Arsenic is removed from the caustic leachsolution by precipitation as copper arsenate which is used as a substitute for arsenic trioxide and copper sulfate in the first stage purification of zinc electrolyte.
The drawing is a schematic flow diagram of the overall process of the invention.
As can be seen in reference to the drawing, showing the process of the present invention in schematic form, the process involves the electrolytic refining of zinc in zinc plant 10. Not shown in the drawing is the preliminary processing of the zinc ore which is-conventional.
~0~3~11973 Zinc sulfide ore is ln accordance with known procedures roasted to form zinc oxide, then leached with sulfuric acid to form zinc sulfate. The zinc sulfate leach solution also includes impurities that must be removed prior to electrolysis in order to avoid contamination of the final zinc product.
The impure feed solution typically contains 0,5 - 1.0 grams per liter copper, 20-30 parts per million cobalt, 1-2 parts per million nickel and in addition may also contain cadmium.
The impure feed solution 11 is fed to the zinc electrolyte purification section 12 where it is treated in accordance with the present invention with zinc dust and copper arsenate as described in more detail below in order to precipitate the aforementioned contaminating impurities using the cobalt level in the solution as a control. The final cobalt level must be less than 0.1 parts per million in order to ensure sufficient purity of the electrolyte for the electrolysis step.
~ he residue from the purification step 12 is separated by any conventional means such as filtration at 13 and con-stitutes what is known as cement copper cake 14 which typically has the following composition:
43~4% copper 6.64~ zinc 1.89% cadmium 1.25% cobalt o.05% nickel 6.89~ arsenic ~1.0~973 The purified zinc electrolyte filtrate isdelivered through line 15 to the electrolytic zinc plant 10 for electrolysis. The cement copper cake 14 is treated in order to (a) upgrade the copper content and purity of the residue to increase the market value thereof and (b) to recover the arsenic content and convert the latter to copper arsenate and recycle the copper arsenate to the purification step 12 and use it in conjunction with zinc dust for the previously described precipitation step in place of the prior art copper sulfate/arsenic trioxide reagents.
The cement copper cake 14 is subjected to an acid leaching step 16 in order to recover zinc, cadmium and cobalt constituents therefrom as a filtrate and provide a residue separated by filters 17. The filtrate is delivered to the cobalt removal stage 18 to separate the cobalt therefrom so that the remaining zinc/cadmium solution can be delivered through line 19 to recycle line 20 through which it is delivered to the electrolytic zinc plant 10 for reuse. The residue from cobalt removal stage 18 has a high cobalt content which has market value.
The residue from filtration step 17 is subjected to a caustic leach 21 to dissolve the arsenic and leave a high copper residue which is separated in filtration step 22. The latter residue, designated as the treated cement copper cake, has an enhanced copper content which increases its market value. The filtrate from step 22 is treated with copper sulfate in arsenic removal stage 22 to provide copper arsenate which may be recycled through ~0~'1973 return line 24 to the electrolytic purification step previously described. The remaining zinc containing solution is delivered to recycle line 20 for delivery to the electrolytic zinc plant 10.
Acid Leaching Temperature of the acid leach slurry in step 16 is maintained at about 95C with 20 percent initial solids loading and 15 to 20 grams per liter initial sulfuric acid addition. After about two hours, the acid leach slurry is neutralized to pH 3.5 to 4.0 with sodium hydroxide to precipitate any leached copper. The quantity of sodium hydroxide used in this step varies with different copper cake samples, and so also does the final pH. However, control is easily maintained by observing the color of the leach solution. Copper precipitation is complete when the solution loses its blue color. Consumption of sodium hydroxide is generally 75 to 150 pounds per dry ton of copper cake. Fresh copper cake consumes more sodium hydroxide than stockpiled copper cake. It should be noted that some degree of attritioning to break up lumps is necessary either before or during the acid leaching of stockpiled copper cake. Attrition is not needed for fresh cake.
The acid leach slurry is filtered at 17 and the arsenic rich residue displacement washed. The residue is black and finely divided. It is amenable to ~iltration by filter press, and behaves similarly to regular copper cake.
10~ 973 Typical products of the acid leach, based on an average sample of copper cake assaying 6.24~ Zn, 1.89% Cd, 1.25% Co, 0.71~ Mn, 43.4% Cu, 6.89% As, O.lC% Na and 15.5%
SO~, have the following analysis.
TABLE I
Results of Acid Leach Extractions Stockleiled Cake Recovery (as %
Filtrate metal value 10comPonent (grams/liter)Residue % in feed) _ _ Zn 11.8 2.16 71.4 Cd 3.95 0.46 81.9 Co 2.77 0.22 87.0 Mn 1.71 0.05 94.3 Cu 0.22 57.8 0.20 As 1.99 8.14 11.4 Na 6.52 0.13 96.4 s SO4 42.2 6.81 76.4 Fresh Cake .
Recovery (as %
Filtrate metal value Component (~rams/liter)Residue % in feed*) Zn 13.6 1.21 85.5 Cd 3.27 0.84 67.9 Co 1.87 0.70 58.8 Mn 1.76 0.03 97.0 Cu 55 ppm 57.9 0.05 As 1.68 8.30 9.62 Na 11.5 0.32 94.5 * Copper cake plus added reagents.
_ g _ ~0~3973 Cobalt Removal Cobalt removal is carried out at 18 under the following conditions. Filtrate 23 from the acid leach process stage 16 is heated to about 95C and solid potassium permanganate is added until a slight excess of permanganate is noted, as seen by a deep purple color. Sodium hydroxide is then added in an amount sufficient to maintain pH of the resulting slurry at about 3.0 to 3.5 These conditions are maintained for about two hours. Total cobalt removal may be accomplished by using a longer reaction time but is not mandatory in this process. The slurry is filtered at 25 and the residue displacement washed.
Average reagent consumption per pound of cobalt rem~ved is 3~8 pounds of potassium permanganate and 2.0 pounds of sodium hydroxide. These figures constitute a considerable excess over the theoretical requirement.
The reason for this is that potassium permanganate is consumed in oxidizing manganese and arsenic in addition to cobalt in the acid leach solution.
Typical products of the cobalt removal stage obtained from as typical acid leach solution analyze as shown below in Tahle II. The filtrate is returnable to the zinc plant for recovery of zinc and cadmium. The amount of zinc and cadmium reporting to the cobalt rich residue is largely dependent on washing efficiency. This residue requires a thorough displacement wash to remove zinc and cadmium.
10~3'~973 TABLE II
Results_of Cobalt ~em~
Recovery (as %
Filtrate metal value s Component (grams~llter) Residue % in feed*) Zn 11.0 2.45 5 Cd 3.48 1.64 10 * Solution from acid leach stage plus added reagents.
Results of Cobalt Removal Recovery (as %
Filtrate metal value Component (grams/liter) Residue %in feed_*) Co less than S ppm 11.5 100 Mn less than 5 ppm 22.4 100 Cu 0.11 0.45 50 As 0.20 7.45 90 Na 9.11 2.03 5 * Solution from acid leach stage plus added reagents.
Caustic L~ach The residue of high arsenic content from the acid leach process stage 16 is leached with caustic at 21 to dissolve ~ -the arsenic. Temperature of the caustic leach slurry is maintained at a~out 95C with 10% initial loading of residue from the acid leach stage and addition of 5~ sodium hydroxide solution. Air is continuously added to the slurry at the rate of approximately 500 standard cuhic feet per minute per dry ton of acid leach residue. These reaction conditions are maintained for about six hours. The slurry is then filtered at 22 and the residue displacement washed. The residue from the filtration stage 22 is usually brown or green and is slower filtering than other residues in this process.
1~9~973 Typical products of the caustic leach stage obtained from the feed to this stage analyze as follows:
TABLE III
Results of Caustic Leach Recovery (as %
Filtrate metal value Component (grams/liter) Residue % in feed*) Zn 0.51 2.07 21.4 Cd less than 1 ppm 0.56 0 Co less than 1 ppm ~.26 0 Mn less than 1 ppm 0.07 0 Cu less than 60 ppm 70.4 less than 0.1 As 8.29 0.75 92.4 Na 28.0 0.32 99~0 SO4 7.16 0.42 95.0 * Residue from acid leach stage plus added reagents.
Many other caustic leaches using slightly different conditions also extract more than 90% of the arsenic.
Arsenic Removal Arsenic compounds are removed from the caustic leach solution as an insoluble solid at 23. The purified solution 26 is ret~rnable to the zinc plant. In the preferred embodiment, the following conditions are used. The filtrate 27 from the caustic leach stage is heated to 75-80C. Because formation of copper arsenate is not complete if copper sulfate is added directly to the solution, sufficient sulfuric acid is first added to bring the solution to about pH 8. Copper sulfate is then added; about 60 pounds of CuSO4-5H2O per water ton o.
solution is required. The 1091~973 amount of copper sulfate required may vary depending on the arsenic content of the solution. The resulting slurry is maintained for about two hours. A small amount of lime, usually about 3 pounds per water ton, is then added to ensure a final pH above 4. The slurry is then filtered.
Arsenic removal is usually greater than 95% by this method.
The filtrate is returnable to the zinc plant. The residue, a pale blue quick filtering solid, is returnable through line 24 for use as a substitute for arsenic trioxide and copper sulfate in first stage purification of zinc electrolyte. Typical products of the arsenic removal stage obtained from the feed to this stage analyze as follows:
TABLE IV
Results of Arsenic Removal Recovery (as %
Filtrate metal value Component (grams/liter)Resi ue ~ in feed*) Zn 0.12 1.30 75.0 Cd 1 ppm 10 ppm -Co 1 ppm 10 ppm - -~
Mn 1 ppm 10 ppm Cu 0.32 24.6 95.7 As 0.18 27.6 97.7 Na 25.9 4.33 4.54 Ca 0.5 2.33 56.0 * Solution from caustic leach stage plus added reagents.
Electrolyte Purification The copper arsenate product from the ~ 13 -~0~ 973 arsenic removal stage 23 is sued as a substitute for copper sulfate and arsenic trioxide in the removal of copper, cobalt and nickel from impure zinc electrolyte at stage 12. Impure zinc electrolyte solution typically contains 0.5-1.0 grams/liter copper, 20-30 parts per million cobalt, and 1-2 parts per million nickel. Electrolyte ¦ purification is performed as follows: 1.5 to 2.5 grams/liter of zinc dust and 0.25 grams (dry)/liter of copper arsenate product are added to impure zinc electrolyte solution at about 80 to 90C. The temperature is then maintained at about 90 to 95C until the cobalt level in the solution is less than 0.1 ppm. When this cobalt level is reached, the pH of the solution is adjusted to approximately pH 4 and the slurry is then filtered. Total reaction time is usually about two hours. The filtrate is fed to the zinc plant for electrolytic recovery of metallic zinc. The cement copper cake residue is treated according to the present invention to remove and recycle its arsenic con-tent, with attendant upgrading of the copper cake.
Example 1 Six plant runs were made using the electrolyte purification process of the present invention. Impure zinc electrolyte solution of pH about 4 and at about 80-90C was treated with 1.5 to 2.5 grams/liter of zinc dust and 0.25 grams (dry)/liter of copper arsenate product from the arsenic removal stage. The temperature was maintained at about 30 to 95C until the cobalt level in the solution was less than 0.1 ppm. The results are summarized below:
109~973 TABLE V
Results of Use of Copper Arsenate Product In Removal of Cobalt from Impure Zinc Electrolyte >
Amount Time Initial of Copper Taken Cobalt Amount Arsenate For Cobalt Level In of Zinc Product To Reach Impure Dust Added (55% Less Than Run No. Feed Added moisture) 0.1 ppm 1 16 ppm 550 pounds 160 pounds 85 minutes The laboratory procedure differs somewhat from the plant procedure. It was found that on a small (1 liter) ~ -scale the reagent requirements are greater and the purification is more difficult to control. The following example illustrates the laboratory procedure:
Example 2 Four 1 liter samples of impure zinc electrolyte containing 16 ppm Co were treated with copper arsenate and zinc dust in the following way. The samples were heated to 90C in beakers; 1 g dry powdered copper arsenate product was added to each beaker together with 2, 3, 4 and 5 g, respectively, of zinc dust. The beakers were stirred for 1 hour, and solution samples were removed from each at 10 minute inter~als. The solutions treated with 2 and 3 g of zinc dust did not achieve the required cobalt level of less than 0.1 Fpm. In those treated with 4 and 5 g of zinc ~0'~ 373 dust the co~alt level fell to less than 0.1 ppm after 20 minutes.
It is thought that performance on a plant scale is more effective than on a bench scale because the reducing conditions required for the purification are more easily maintained in a large tank than in a 1 liter beaker.
As can be seen from the above description, accord-ing to the present invention a copper arsenate product is made from cement copper cake residue and reused in purification of zinc electrolyte. Two superior features of this invention are:
1. Arsenic is recycled; therefore only a small makeup of supply of arsenic trioxide is required: and 2. The cement copper residue is considerably upgraded during treatment, the final residue containing more than 70~ copper and less than 1% arsenic.
The copper arsenate product is derived from zinc plant cement copper residue in a four stage process compris-ing:
1. An acid leach in which about 74% of the zinc, 82% of the cadmium and 87% of the cobalt are extracted.
2. A cobalt removal stage in which cobalt is precipitated from the acid leach filtrate leaving a zinc/cadmium solution suitable lOq~73 "
for recycle to the zinc plant.
3. A hot aerated caustic leach in which over 90% of the arsenic is extracted from the acid leach residue.
4. An arsenic removal stage in which arsenic is precipitated as copper arsenate for the caustic leach filtrate, again leaving a solution which is returnable to the zinc plant~
Expected benefits from the present invention include:
1. Reduced expenditure for arsenic trioxide as a purification reagent.
2. Reduced dependence on outside sources for supply of arsenic trioxide. -3. Increased value of upgraded copper 2~ residue.
While one embodiment of the present invention has been shown and described herein, it is to be understood that certain changes and/or additions may be made thereto by those skilled in the art without departing from the scope and spirit of the invention.
Claims (2)
1. The process of purifying zinc electrolyte containing cobalt contaminant prior to electrolysis therein in the electrowinning of metallic zinc, comprising adding to said electrolyte zinc dust in an amount of about 1.5 to 2.5 grams per liter and copper arsenate in an amount of about 0.25 grams per liter, maintaining the temperature of the electrolyte at about 90 to 95°C until the cobalt level of said electrolyte is less than 0.1 ppm, adjusting the pH to about 4, and then removing the solids from said electrolyte.
2. The process as in Claim 1 of purifying zinc electrolyte containing cobalt contaminant up to 330 ppm prior to electrolysis thereof in the electrowinning of metallic zinc comprising adding to said electrolyte, at a temperature of about 80 to 90°C, zinc dust in an amount of about 1.5 to 2.5 grams/liter and copper arsenate in an amount of about 0.25 grams/liter, then raising the temperature to and maintaining it in the range of about 90 to 95°C until the cobalt level of siad electrolyte is less than 0.1 ppm, and adjusting the pH
to about 4 and then removing the solids from said electrolyte.
to about 4 and then removing the solids from said electrolyte.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA328,544A CA1094973A (en) | 1976-03-11 | 1979-05-29 | Removal of cobalt from zinc electrolyte using zinc dust and copper arsenate |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA247,665A CA1063967A (en) | 1976-03-11 | 1976-03-11 | Zinc hydrometallurgical process |
| CA328,544A CA1094973A (en) | 1976-03-11 | 1979-05-29 | Removal of cobalt from zinc electrolyte using zinc dust and copper arsenate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094973A true CA1094973A (en) | 1981-02-03 |
Family
ID=25668233
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA328,544A Expired CA1094973A (en) | 1976-03-11 | 1979-05-29 | Removal of cobalt from zinc electrolyte using zinc dust and copper arsenate |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1094973A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5002748A (en) * | 1988-09-02 | 1991-03-26 | Cominco Ltd. | Method for the preparation of copper arsenate |
| AP3297A (en) * | 2011-10-09 | 2015-05-31 | Mintek | Direct electrowinning of cobalt |
| CN109778229A (en) * | 2019-03-15 | 2019-05-21 | 瑞安市南方电解厂 | Using the production technology of waste copper slag remanufacture electrolytic zinc copper |
| CN113621993A (en) * | 2021-08-25 | 2021-11-09 | 湖南福尔程环保科技有限公司 | Purification method of zinc electrolyte |
| CN114774693A (en) * | 2022-05-06 | 2022-07-22 | 新疆紫金有色金属有限公司 | Comprehensive utilization method of zinc hydrometallurgy two-clean slag |
| CN114774692A (en) * | 2022-04-29 | 2022-07-22 | 新疆紫金有色金属有限公司 | Method for removing cadmium and cobalt from poor cadmium solution of zinc hydrometallurgy system |
-
1979
- 1979-05-29 CA CA328,544A patent/CA1094973A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5002748A (en) * | 1988-09-02 | 1991-03-26 | Cominco Ltd. | Method for the preparation of copper arsenate |
| AP3297A (en) * | 2011-10-09 | 2015-05-31 | Mintek | Direct electrowinning of cobalt |
| CN109778229A (en) * | 2019-03-15 | 2019-05-21 | 瑞安市南方电解厂 | Using the production technology of waste copper slag remanufacture electrolytic zinc copper |
| CN113621993A (en) * | 2021-08-25 | 2021-11-09 | 湖南福尔程环保科技有限公司 | Purification method of zinc electrolyte |
| CN114774692A (en) * | 2022-04-29 | 2022-07-22 | 新疆紫金有色金属有限公司 | Method for removing cadmium and cobalt from poor cadmium solution of zinc hydrometallurgy system |
| CN114774693A (en) * | 2022-05-06 | 2022-07-22 | 新疆紫金有色金属有限公司 | Comprehensive utilization method of zinc hydrometallurgy two-clean slag |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2154560C (en) | Hydrometallurgical recovery of metals from complex ores | |
| CA1155084A (en) | Process for the recovery of metal values from anode slimes | |
| US4440569A (en) | Recovery of zinc from zinc-containing sulphidic material | |
| RU2023728C1 (en) | Method of extracting zinc, copper, lead and silver from zinc-iron-containing sulfide stock | |
| NO142995B (en) | PROCEDURE FOR THE TREATMENT OF ZINC FACTORY RESIDUUM FOR THE EXCLUSION OF ZINCALCININATE WITH SULFUR ACID | |
| CA2202289C (en) | Recovery of zinc from sulphidic concentrates | |
| US4150976A (en) | Method for the recovery of metallic copper | |
| CN101994008B (en) | Zinc-cobalt separation process for producing nickel-cobalt slag by zinc smelting purification | |
| US5078786A (en) | Process for recovering metal values from jarosite solids | |
| CA2666229A1 (en) | Method for production of metallic cobalt from the nickel solvent extraction raffinate | |
| US3691038A (en) | Process for the recovery of zinc from zinc- and iron-containing materials | |
| CA1117897A (en) | Continuous process for the purification of zinc plant electrolyte | |
| CA1094973A (en) | Removal of cobalt from zinc electrolyte using zinc dust and copper arsenate | |
| US4789446A (en) | Method of processing residues from the hydrometallurgical production of zinc | |
| US3883345A (en) | Process for the recovery of antimony | |
| US4049514A (en) | Zinc hydrometallurgical process | |
| CN109913647B (en) | Wet processing method for recovering copper and zinc in bismuth middling | |
| EP0025466B1 (en) | A process for the recovery of arsenic as zinc arsenate from cement copper cake and a process for the purification of an impure zinc electrolyte using zinc arsenate so obtained | |
| CA2304064A1 (en) | Recovery of lead from flue dusts | |
| CA1156048A (en) | Process for the recovery of lead and silver from minerals and process residues | |
| AU2010217184A1 (en) | Zinc oxide purification | |
| GB2114966A (en) | Recovery of zinc from sulphidic material | |
| US2473962A (en) | Process for recovering cadmium | |
| CA1066658A (en) | Recovery of zinc | |
| RU2079561C1 (en) | Method of oxidized polymetallic materials processing |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |