US20120247971A1 - Metal electrowinning anode and electrowinning method - Google Patents

Metal electrowinning anode and electrowinning method Download PDF

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US20120247971A1
US20120247971A1 US13/514,858 US201013514858A US2012247971A1 US 20120247971 A1 US20120247971 A1 US 20120247971A1 US 201013514858 A US201013514858 A US 201013514858A US 2012247971 A1 US2012247971 A1 US 2012247971A1
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electrowinning
anode
catalytic layer
oxide
electrolyte
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Masatsugu Morimitsu
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Doshisha Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/16—Electrolytic production, recovery or refining of metals by electrolysis of solutions of zinc, cadmium or mercury
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/06—Electrolytic production, recovery or refining of metals by electrolysis of solutions or iron group metals, refractory metals or manganese
    • C25C1/08—Electrolytic production, recovery or refining of metals by electrolysis of solutions or iron group metals, refractory metals or manganese of nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02—Electrodes; Connections thereof

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  • the present invention relates to an electrowinning anode for electroextracting a desired metal from an electrolyte and an electrowinning method for electroextracting a desired metal from an electrolyte.
  • an anode and a cathode are dipped into a solution (hereinafter, an electrolyte) containing ions of a metal to be recovered and are brought into conduction, thereby depositing the metal on the cathode.
  • an electrolyte often used is made of lead or a lead alloy.
  • the electrolyte used include various electrolytes, such as sulfuric acid-based and chloride-based electrolytes.
  • a sulfuric acid-based electrolyte that contains zinc ions extracted from a zinc ore is used in zinc electrowinning.
  • zinc is deposited on the cathode, and the main reaction on the anode is oxygen evolution.
  • oxygen evolution occurs on the anode, and manganese compounds, such as manganese oxyhydroxide (MnOOH) and manganese dioxide (MnO 2 ), are deposited on the anode.
  • manganese compounds such as manganese oxyhydroxide (MnOOH) and manganese dioxide (MnO 2 ), are deposited on the anode.
  • MnOOH manganese oxyhydroxide
  • MnO 2 manganese dioxide
  • Such manganese compounds have extremely low catalytic properties with respect to oxygen evolution and also have low conductivity, and therefore they increase the oxygen evolution potential, resulting in an increase in electrolysis voltage.
  • divalent cobalt cations might be added to the electrolyte for the purpose of enhancing the durability of the electrode.
  • a side reaction occurs on the anode where divalent cobalt cations are oxidized, generating trivalent cobalt cations, which react with the electrode to generate a compound.
  • electrolysis lasts for a long period of time, such a compound precipitates in the electrolyte as sludge. Thereafter, the precipitate is partially dissolved into the electrolyte, so that lead and cobalt ions elute and are mingled into zinc generated on the cathode, resulting in reduced purity of the zinc metal.
  • a sulfuric acid-based electrolyte is also used in cobalt and nickel electrowinning.
  • cobalt or nickel is deposited on the cathode, and oxygen evolution occurs on the anode as a main reaction, so that divalent manganese cations, which are present in the electrolyte as impurities, cause a side reaction as mentioned above, resulting in an increased electrolysis voltage.
  • CoOOH cobalt oxyhydroxide
  • cobalt electrowinning uses a hydrochloric acid electrolyte which contains divalent cobalt cations extracted from a cobalt-containing ore.
  • hydrochloric acid electrolyte which contains divalent cobalt cations extracted from a cobalt-containing ore.
  • cobalt is deposited on the cathode, and chlorine evolution occurs on the anode as a main reaction.
  • oxidation of divalent cobalt cations contained in the electrolyte occurs on the anode as a side reaction, so that cobalt oxyhydroxide is deposited on the anode, causing a raised electrolysis voltage as in the case mentioned above.
  • the main reaction on the anode is oxygen evolution or chlorine evolution
  • an anode made of lead or a lead alloy is often used.
  • Lead or lead alloy electrodes are advantageous in that they are low-cost, but they have a high overvoltage for oxygen evolution, hence a high electrolysis voltage, and have an issue in that lead ions elute into the electrolyte, as described above, so that the purity of a metal deposited on the cathode is reduced.
  • they have low catalytic properties with respect to chlorine evolution, and are not preferable in that overvoltage is higher than in the case of oxide evolution.
  • Patent Document 1 discloses a conventional copper electrowinning method which uses an insoluble electrode covered with an active coating containing iridium oxide.
  • Patent Document 1 Japanese Laid-Open Patent Publication No. 2007-162050
  • Electrowinning using the anode described in Patent Document 1 does not have an issue due to the aforementioned elution of lead ions.
  • the issue with a high electrolysis voltage can be solved to a certain degree.
  • even the use of such an anode cannot solve various issues caused by an insulating side reaction product being deposited on the anode due to a side reaction.
  • the electrolysis voltage can be reduced at the early stage of electrolysis, but the electrolysis voltage rises as manganese compounds are accumulated, resulting in a large amount of power being consumed at the time of electrolysis.
  • the catalytic layer is damaged when removing the manganese compounds, reducing the durability of the insoluble electrode.
  • divalent cobalt cations which are expected to be reduced on the cathode, are consumed around the anode to generate cobalt oxyhydroxide;
  • cobalt oxyhydroxide grows to the outside of an anode bag provided around the anode, so that chlorine evolution occurs outside the anode bag, releasing chlorine, which is harmful to the human body, in the environment where electrowinning is performed.
  • the present invention has been made under the above circumstances, and a problem thereof is to provide an electrowinning anode and an electrowinning method capable of decreasing an electrolysis voltage compared to conventional lead or lead alloy electrodes and insoluble electrodes which act as anodes and suppressing deposition and accumulation of a side reaction product on the anode and a rise of the electrolysis voltage caused thereby.
  • the present inventor carried out various studies to solve the above problem, and arrived at the present invention based on findings that an electrode having a catalytic layer, containing amorphous iridium oxide, formed on a conductive substrate is used as an anode for electrowinning using a sulfuric acid-based electrolyte, and an electrode having a catalytic layer, containing amorphous iridium oxide or amorphous ruthenium oxide, formed on a conductive substrate is used as an anode for electrowinning using a chloride-based electrolyte.
  • a first electrowinning anode according to the present invention to solve the problem is for use in electrowinning of any one of nickel, zinc or cobalt, and includes a conductive substrate and a catalytic layer formed on the conductive substrate, in which the catalytic layer contains amorphous iridium oxide, so that a side reaction on the anode is suppressible.
  • valve metals such as titanium, tantalum, zirconium and niobium
  • valve metal-based alloys such as titanium-tantalum, titanium-niobium, titanium-palladium and titanium-tantalum-niobium
  • conductive diamonds e.g., boron-doped diamonds
  • they can take various shapes, including plate-like, meshed, rod-like, sheet-like, tubular, linear, porous plate-like shapes, and shapes of three-dimensional porous materials composed of bonded spherical metal particles.
  • conductive substrates to be used may be metals other than valve metals, such as iron and nickel, or conductive ceramics, having surfaces coated with the aforementioned valve metals, alloys, or conductive diamonds.
  • a substantial reactive surface area (effective surface area) of the amorphous iridium oxide in the catalytic layer is larger than that of crystalline iridium oxide. Accordingly, by incorporating amorphous iridium oxide in the catalytic layer, it is rendered possible to achieve an anode having high catalytic activity for oxygen evolution, i.e., the anode has a low oxygen evolution potential and is capable of promoting oxygen evolution. Moreover, oxygen evolution accompanies proton (H + ) generation and, therefore, as oxygen evolution is promoted, the electrolyte on the anode surface has a higher proton concentration.
  • the main reaction on the anode is oxygen evolution.
  • This oxygen evolution is promoted by a catalytic layer containing amorphous iridium oxide, so that the proton concentration on the anode surface naturally increases.
  • the main reaction on the anode is normally chlorine evolution, which does not accompany proton generation, but amorphous iridium oxide has extremely high catalytic activity for oxygen evolution and, therefore, oxygen evolution occurs simultaneously with chlorine evolution, which is the main reaction. Accordingly, either in the case where a chloride-based electrolyte is used or in the case where a sulfuric acid-based electrolyte is used, the proton concentration on the anode surface is high.
  • both generation of manganese oxyhydroxide and generation of manganese dioxide accompany proton generation, and particularly the reaction where manganese oxyhydroxide and protons are generated from trivalent manganese cations is promoted when the pH of the electrolyte in which the reaction occurs is high (the proton concentration is low) and is suppressed when the pH is low (the proton concentration is high).
  • the electrolysis current is consumed by oxygen evolution and manganese compound generation (side reaction), which simultaneously progress on the anode.
  • oxygen evolution is promoted by using an anode with a catalytic layer, containing amorphous iridium oxide, formed thereon, therefore, in the first electrowinning anode according to the present invention, the proportion of electrolysis current to be consumed by oxygen evolution is high, and the proton concentration on the anode surface is high as well. Consequently, manganese compound generation, which is a side reaction, is suppressed, so that deposition/accumulation of a manganese compound (side reaction product) on the anode is suppressed.
  • a catalytic layer which contains amorphous iridium oxide having high catalytic activity for oxygen evolution, is formed so that the oxygen evolution potential is reduced, making it possible to decrease the electrolysis voltage.
  • the catalytic layer of the first electrowinning anode preferably further contains amorphous tantalum oxide.
  • a second electrowinning anode according to the present invention to solve the problem is for use in electrowinning of any one of nickel, zinc or cobalt, and includes a conductive substrate and a catalytic layer formed on the conductive substrate, in which the catalytic layer contains amorphous ruthenium oxide, so that a side reaction on the anode is suppressible.
  • the conductive substrate of the first electrowinning anode can be used.
  • the amorphous ruthenium oxide in the catalytic layer has higher catalytic activity for chlorine evolution than crystalline ruthenium oxide. Accordingly, by incorporating amorphous ruthenium oxide in the catalytic layer, it is rendered possible to achieve an anode having a low chlorine evolution potential and capable of promoting chlorine evolution.
  • cobalt electrowinning cobalt oxyhydroxide, which is a side reaction product, is kept from being generated and accumulated on the anode, and in nickel electrowinning, manganese oxyhydroxide and manganese dioxide, which are side reaction products, are kept from being generated and accumulated on the anode.
  • electrowinning can be carried out in a sulfuric acid-based electrolyte using an anode with a catalytic layer, containing amorphous ruthenium oxide, formed, but for a sulfuric acid-based electrolyte, it is preferable, from the viewpoint of durability, to use an anode with a catalytic layer, containing amorphous iridium oxide, formed.
  • the amorphous ruthenium oxide in the catalytic layer of the second electrowinning anode is preferably a composite oxide of amorphous ruthenium oxide and titanium oxide.
  • metallic elements in the catalytic layer are preferably 10 to 90 at. %, particularly preferably 25 to 35 at. %, of ruthenium oxide in terms of metal and preferably 90 to 10 at. %, particularly preferably 75 to 65 at. %, of titanium oxide in terms of metal.
  • an intermediate layer made of tantalum or a tantalum alloy can be formed between the conductive substrate and the catalytic layer.
  • Forming the intermediate layer makes it possible to prevent the conductive substrate from being oxidized and corroded by an acidic electrolyte penetrating through the catalytic layer, resulting in improved durability of the anode.
  • the intermediate layer is beneficial particularly in the case where electrowinning is carried out over a long period of time using electrolysis current with its density raised to about 0.1 A/cm 2 . Note that sputtering, ion plating, CVD, electroplating, etc., can be used as methods for forming the intermediate layer.
  • the first and second electrowinning systems have been described for zinc, nickel, or cobalt electrowinning, but in the case where deposition/accumulation of a side reaction product as mentioned above causes an issue, they can be expected to exert action/achieve effect on reduction of the electrolysis voltage and suppression of side reaction product generation/accumulation for electrowinning of metals other than zinc, nickel, and cobalt as well.
  • any one of nickel, zinc or cobalt is recovered using any of the aforementioned electrowinning anodes.
  • the present invention can provide an electrowinning anode capable of suppressing accumulation of a side reaction product on an anode and a rise of an electrolysis voltage caused thereby, and the invention can also provide an electrowinning method using the electrowinning anode.
  • the electrowinning anode and the electrowinning method according to the present invention can suppress accumulation of a side reaction product on an anode, not only the aforementioned issue (1) but also the aforementioned issues (2) to (8) can be solved as well.
  • FIG. 1 is a graph for electrolysis voltage where zinc electrowinning is carried out using electrowinning systems according to Example 1, Comparative Example 1, and Comparative Example 2.
  • Example 1 zinc electrowinning was carried out using an electrowinning system which included a sulfuric acid-based electrolyte containing zinc ions, an electrowinning anode (hereinafter, simply referred to as an “anode”) having a catalytic layer, containing amorphous iridium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • an electrowinning anode hereinafter, simply referred to as an “anode” having a catalytic layer, containing amorphous iridium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • a commercially available titanium plate (5 cm long, 1 cm wide, 1 mm thick) was dipped and etched in a 10% oxalic acid solution at 90° C. for 60 minutes, and then washed with water and dried.
  • a coating solution was prepared by adding iridium chloride acid hexahydrate (H 2 IrCl 6 .6H 2 O) and tantalum chloride (TaCl 5 ) to a butanol (n-C 4 H 9 OH) solution containing 6 vol. % concentrated hydrochloric acid, such that the molar ratio of iridium to tantalum was 80:20 and a total amount of iridium and tantalum was 70 mg/mL in terms of metal.
  • the coating solution was applied to the dried titanium plate and then dried at 120° C. for 10 minutes before thermal decomposition for 20 minutes in an electric furnace maintained at 360° C.
  • the coating, drying and thermal decomposition was repeated five times in total, thereby producing an anode having a catalytic layer formed on the titanium plate, which acted as a conductive substrate.
  • the anode was structurally analyzed by X-ray diffraction, resulting in an X-ray diffraction pattern with no diffraction peak profile corresponding to either IrO 2 or Ta 2 O 5 . That is, the catalytic layer of the anode was formed of amorphous iridium oxide and amorphous tantalum oxide.
  • a zinc plate (2cm ⁇ 2cm) was used as the cathode, and the electrolyte used was a sulfuric acid-based electrolyte obtained by dissolving 0.8 mol/L ZnSO 4 in distilled water and adjusting the pH to ⁇ 1.1 with sulfuric acid. Moreover, the anode was embedded in a polytetrafluoroethylene holder, so that the electrode area to be contacted with the electrolyte was regulated to 1 cm 2 .
  • the anode and the cathode were placed in the electrolyte so as to oppose each other at a predetermined inter-electrode distance. Then, an inter-terminal voltage (electrolysis voltage) between the anode and the cathode was measured while carrying out zinc electrowinning in which electrolysis current with current densities of 10 mA/cm 2 , 50 mA/cm 2 , and 100 mA/cm 2 based on the electrode area of the anode was applied between the anode and the cathode.
  • electrolysis current with current densities of 10 mA/cm 2 , 50 mA/cm 2 , and 100 mA/cm 2 based on the electrode area of the anode was applied between the anode and the cathode.
  • Example 1 zinc electrowinning was carried out using the same electrowinning system as in Example 1 under the same conditions as in Example 1 except that the thermal decomposition temperature at which to form the catalytic layer was changed from 360° C. to 470° C.
  • the anode according to Comparative Example 1 was structurally analyzed by X-ray diffraction, the result being that a sharp diffraction peak profile corresponding to IrO 2 was recognized but any diffraction peak profile corresponding to Ta 2 O 5 was not recognized. That is, the catalytic layer of the anode was made of crystalline iridium oxide and amorphous tantalum oxide.
  • Example 2 zinc electrowinning was carried out using the same electrowinning system as in Example 1 under the same conditions as in Example 1 except that a commercially available Pb—Sb (5% Sb) alloy electrode was used as the anode.
  • a commercially available Pb—Sb (5% Sb) alloy electrode was used as the anode.
  • the electrolysis voltage was 0.12V to 0.20V lower in Example 1, where the catalytic layer containing amorphous iridium oxide was used, than in Comparative Example 1, where the catalytic layer containing crystalline iridium oxide was used. Moreover, the electrolysis voltage was even 0.54V to 0.58V lower in Example 1 than in Comparative Example 2, where the commercially available Pb—Sb alloy electrode was used as the anode. That is, the electrowinning system according to Example 1 of the present invention succeeded in significantly reducing power consumption for electrolysis.
  • the electrolysis voltage was 0.11 V to 0.19V lower in Example 1, where the catalytic layer containing amorphous iridium oxide was used, than in Comparative Example 1, where the catalytic layer, containing crystalline iridium oxide, was used. Moreover, the electrolysis voltage was even 0.48V to 0.55V lower in Example 1 than in Comparative Example 2, where the commercially available Pb—Sb alloy electrode was used as the anode. That is, the electrowinning system according to Example 1 of the present invention succeeded in significantly reducing power consumption for electrolysis as well for the case where the electrolyte temperature was in the range from 40° C. to 60° C.
  • Example 2 cobalt electrowinning was carried out using an electrowinning system according to the present invention, which included a sulfuric acid-based electrolyte containing cobalt ions, an anode having a catalytic layer, containing amorphous iridium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • an electrowinning system which included a sulfuric acid-based electrolyte containing cobalt ions, an anode having a catalytic layer, containing amorphous iridium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • the present example used the same anode as in Example 1, i.e., an anode which had a catalytic layer, containing amorphous iridium oxide, formed on a titanium plate and whose electrode area for acting on electrolysis was regulated to 1 cm 2 . Moreover, a cobalt plate (2cm ⁇ 2cm) was used as the cathode, and the electrolyte used was a sulfuric acid-based electrolyte obtained by dissolving 0.3 mol/L CoSO 4 in distilled water and adjusting the pH to 2.9 with sulfuric acid.
  • Comparative Example 3 used the same anode as in Comparative Example 1, i.e., an anode which had a catalytic layer, containing crystalline iridium oxide, formed on a titanium plate and whose electrode area for acting on electrolysis was regulated to 1 cm 2 .
  • the same electrowinning system as in Example 2 was used for cobalt electrowinning.
  • Comparative Example 4 the same electrowinning system as in Example 2 was used for cobalt electrowinning, except that a commercially available Pb—Sb alloy electrode (5% Sb) was used as the anode.
  • the electrolysis voltage was 0.10V lower in Example 2, where the catalytic layer containing amorphous iridium oxide was used, than in Comparative Example 3, where the catalytic layer containing crystalline iridium oxide was used, and also 0.17V lower in Example 2 than in Comparative Example 4, where the commercially available Pb—Sb alloy electrode was used as the anode. That is, also in cobalt electrowinning using a sulfuric acid-based electrolyte, the electrowinning system according to Example 2 of the present invention succeeded in significantly reducing power consumption for electrolysis.
  • Example 3 nickel electrowinning was carried out using an electrowinning system, which included a chloride-based electrolyte containing nickel ions, an anode having a catalytic layer, containing amorphous iridium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • an electrowinning system which included a chloride-based electrolyte containing nickel ions, an anode having a catalytic layer, containing amorphous iridium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • the present example used the same anode as in Example 1, i.e., an anode which had a catalytic layer, containing amorphous iridium oxide, formed on a titanium plate and whose electrode area for acting on electrolysis was regulated to 1 cm 2 .
  • a nickel plate (2 cm ⁇ 2cm) was used as the cathode, and the electrolyte used was a chloride-based electrolyte obtained by dissolving 0.08 mol/L NiCl 2 in a 0.5 mol/L HCl aqueous solution.
  • Comparative Example 5 used the same anode as in Comparative Example 1, i.e., an anode which had a catalytic layer, containing crystalline iridium oxide, formed on a titanium plate and whose electrode area for acting on electrolysis was regulated to 1 cm 2 .
  • the same electrowinning system as in Example 3 was used for nickel electrowinning.
  • Comparative Example 6 the same electrowinning system as in Example 3 was used for nickel electrowinning, except that a commercially available Pb—Sb alloy electrode (5% Sb) was used as the anode.
  • the electrolysis voltage was 0.06V lower in Example 3, where the catalytic layer containing amorphous iridium oxide was used, than in Comparative Example 5, where the catalytic layer containing crystalline iridium oxide was used, and also even 0.99V lower in Example 3 than in Comparative Example 6, where the commercially available Pb—Sb alloy electrode was used as the anode. That is, also in nickel electrowinning using a chloride-based electrolyte, the electrowinning system according to Example 3 of the present invention succeeded in significantly reducing power consumption for electrolysis.
  • Example 4 cobalt electrowinning was carried out using an electrowinning system, which included a chloride-based electrolyte containing cobalt ions, an anode having a catalytic layer, containing amorphous ruthenium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • an electrowinning system which included a chloride-based electrolyte containing cobalt ions, an anode having a catalytic layer, containing amorphous ruthenium oxide, formed on a conductive substrate, and a cathode placed in the electrolyte along with the anode.
  • the anode was structurally analyzed by X-ray diffraction, resulting in an X-ray diffraction pattern with no diffraction peak profile corresponding to RuO 2 , but a weak diffraction line in a broadened pattern corresponding to a RuO 2 —TiO 2 solid solution was recognized. That is, the catalytic layer of the anode was made of a composite oxide of amorphous ruthenium oxide and titanium oxide.
  • a platinum plate (2 cm ⁇ 2cm) was used as the cathode, and the electrolyte used was a chloride-based electrolyte obtained by dissolving 0.9 mol/L CoCl 2 in distilled water and adjusting the pH to 1.6 with hydrochloric acid. Moreover, the anode was embedded in a polytetrafluoroethylene holder, so that the electrode area for acting on electrolysis was regulated to 1 cm 2 .
  • the anode and the cathode were placed in the electrolyte so as to oppose each other at a predetermined inter-electrode distance. Then, cobalt electrowinning was carried out for 40 minutes with electrolysis current having a current density of 10 mA/cm 2 based on the electrode area of the anode and the electrolyte temperature at 60° C.
  • the anode according to Comparative Example 7 was structurally analyzed by X-ray diffraction, resulting in an X-ray diffraction pattern in which a sharp diffraction peak profile corresponding to a solid solution (composite oxide) of crystalline RuO 2 and TiO 2 was recognized. That is, the catalytic layer of the anode contained crystalline ruthenium oxide but did not contain amorphous ruthenium oxide.
  • Example 4 As shown in Table 7, in Example 4, where the catalytic layer containing amorphous ruthenium oxide was used, the current efficiency was about 1 ⁇ 3 of that in Comparative Example 7, where the catalytic layer containing crystalline ruthenium oxide was used. Specifically, in Example 4, most of the electrolysis current (90% or more) was consumed for chlorine evolution, the main reaction, resulting in a considerable reduction of power required for electrowinning of the same amount of cobalt. Moreover, in Example 4, cobalt oxyhydroxide was kept from being accumulated on the anode, thereby suppressing a rise of the electrolysis voltage while electrowinning was continued for a long period of time.
  • amorphous tantalum oxide can be omitted from the catalytic layers of the electrowinning anodes according to Examples 1 to 3, so long as amorphous iridium oxide is at least included.
  • the catalytic layers preferably include both amorphous iridium oxide and amorphous tantalum oxide.
  • titanium oxide can be omitted from the catalytic layer of the electrowinning anode according to Example 4, so long as amorphous ruthenium oxide is at least included.
  • the catalytic layers of the electrowinning anodes according to Examples 1 to 3 may be formed on protective layers, containing crystalline iridium oxide, formed on the conductive substrates.
  • the protective layers containing crystalline iridium oxide adhere well to the conductive substrates, and also to the catalytic layers, so that the catalytic layers can be more stably formed on the conductive substrates, resulting in enhanced durability.
  • Particularly suitable for such a protective layer is a mixed oxide layer made of crystalline iridium oxide and amorphous tantalum oxide.
  • an intermediate layer made of tantalum or a tantalum alloy is preferably formed between the conductive substrate and the catalytic layer. Forming the intermediate layer makes it possible to prevent the conductive substrate from being oxidized and corroded by an acidic electrolyte penetrating through the catalytic layer, resulting in improved durability of the anode.
  • the intermediate layer can be formed by methods such as sputtering, ion plating, CVD, electroplating, etc.
  • electrowinning anode and the electrowinning method according to the present invention can electrowin noble metals, rare metals, and other metals.

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JP7341395B2 (ja) * 2019-10-30 2023-09-11 住友金属鉱山株式会社 廃リチウムイオン電池からの銅、ニッケル、コバルトの回収方法
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