KR890001132B1 - Electrode with lead base and method of making same - Google Patents

Abstract

Anode comprises a lead alloy base with catalytically activated titanium particles uniformly distributed and partly embedded at the surface of the base. The particles comprise a mirror amt. of ruthenium in oxide form, so that oxygen is anodically evolved at a reduced potential, at which the base remains electrochemically inactive and thus serves as a stable inert conductive support for the particles. The anode is partic. used for electrowinning metals such as In, Cu and Co, and can be operated at a considerably reduced potential. Conventional lead alloy anodes are easily converted. Ruthenium catalyst is economically used, in small amts. opt. admixed with less expensive stable material.

Description

Oxygen generating anode and its manufacturing method

The present invention relates to an electrode for generating oxygen in an acid electrolyte, as is used to electrolyze a metal from an dimensionally stable electrode, in particular an acid electrolyte.

Lead or lead alloy anodes have been used extensively in methods for electrowinning metals from sulphate solutions. However, they are limited because of the high oxygen and voltage and the loss of cathode material contaminating the electrolyte as well as the metal product obtained at the cathode.

Anodes made of lead-silver alloys reduce oxygen overvoltage and enhance current efficiency, but are generally subject to such limitations.

It has been proposed to use dimensionally stable titanium anodes with platinum metal oxide coatings to generate oxygen at the anodes, which are generally surface stabilized rather quickly and oxidize the titanium base.

It has also been proposed to provide a titanium base with a protective underlayer coating containing a platinum group metal under the outer coating, but such coatings generally use expensive precious metals and are therefore uneconomical for sufficient protection of the titanium base.

Electrolytes for metal electrolysis are generally operated at low current densities and have a large anode surface area for uniform electrical deposition on the cathode. Therefore, the cost of using titanium bases is relatively important and should be taken into account.

Dimensionally stable anodes with mixed oxide coatings containing platinum group metals and valve metals are described in US Pat. No. 36,324,98.

Embodiments of this patent describe a process for producing fine Ti-Pd mixed oxide powders used to make soft titanium rods by rolling or hammering. However, the amount of precious metal mixed in the mixed oxide powder and used in the electrode in the above method can be suppressed in various industrial fields. As such, when the electrode surface is essentially covered with the mixed oxide powder, especially when the electrode is operated at a relatively low current density, such as when used for metal electrowinning, the price of the precious metals used in the mixed oxide form is expensive and cannot be used.

It is an object of the present invention to provide an improved anode for generating oxygen in acid electrolytic nuclei.

It is another object of the present invention to improve the electrochemical reaction for oxygen generation of anodes in acid electrolytic nuclei to enable the use of conventional lead or lead alloy anodes by essentially avoiding the loss of anode material while the base of lead or lead alloys To the anode.

Another object of the present invention is to provide a simple method for enhancing the action of such an electrode.

These objects are essentially achieved by the present invention as described in the claims.

In accordance with the present invention, the electrochemical action of the anode comprises titanium particles which are catalytically activated by the ruthenium in oxide form and partially embedded in the surface of the anode base of lead or lead alloy, which are electrically connected and firmly fixed to the base. Promoted by providing to the anode. Therefore, the remaining non-filled portion of the catalyst particles may protrude from the surface of the anode base so that a surface larger than the lower layer surface of the anode base of lead or lead alloy may exist for oxygen generation.

Since the partially buried catalyst particles are well arranged according to the invention, the particles essentially cover the entire surface of the lead or lead alloy base and provide a maximum area for oxygen evolution, thereby more particularly anode density. To provide an essentially uniform dispersion of

The use of ruthenium for catalytically active titanium particles in accordance with the present invention is particularly advantageous because ruthenium can provide an excellent electrical catalyst for generating oxygen at a relatively low value compared to other metals of the platinum group. to be.

The catalyst particles used according to the invention are advantageously composed of titanium sponges and have a size of 150-1250 microns (preferably about 300-1000 microns).

The amount of catalyst particles used according to the invention per unit area of the cathode base should generally be suitable to essentially cover the anode base. It has been found that a relatively large amount of particles corresponding to more than 400 g / m 2 is required to produce an electrode with satisfactory action. An amount of as much as 1000 g / m 2 or more has been found to be advantageous as well.

The catalyst particles advantageously contain a minimum amount of ruthenium corresponding to at most 6% by weight of titanium in the particles uniformly dispersed on a very wide surface.

The use of a large amount of catalyst particles as noted above (eg 500-1000 g / m 2) can be expensive. After all, it is especially important to reduce the loss of ruthenium during the anode operation as much as possible.

Experiments have shown that activating titanium particles with manganese as well as ruthenium as an oxide form can increase the stability of the catalyst compared to ruthenium dioxide alone or other combinations.

The enhanced electrocatalytic action of Ru-Mn oxide-based stability under oxygen-generating conditions in the acid medium is a particularly advantageous feature of the catalytically activated titanium particles used in the lead delivery body according to the present invention.

It was found that the formation of titanium oxide by pyrolysis on the activated particles further enhances the stability of the particles. It was found that ruthenium can be used more effectively when the larger activated particles are first pressed into the lead anode base and then the smaller particles can be pressed to have a greater amount of ruthenium than larger particles. This two-step compaction process has been found to enhance contact with lead bases as well as long term stability of catalytically activated particles.

It has been found that further pressing to take advantage of inert particles of valve metal or valve metal oxide, especially zirconium dioxide, can further increase the stability of the activated particles. This is particularly important for the process of electrolytic retake of metal from an electrolyte solution containing Mn ²⁺ ions, when the conductivity of the poor MnO ₂ can inhibit the action of the anode.

The following examples illustrate different forms for practicing the present invention.

Example 1

The active solution was prepared by dissolving 0.57 g of RuCl ₃ and 1.33 g of Mn (NO ₃ ) ₂ in 4 ml of 1-butyl alcohol. This solution was diluted 6 fold with 4 ml of 1-butyl alcohol.

3.25 g of Ti sponge (particles of 630 microns or more) were greased off with trichloroethylene, dried and then impregnated with the active solution. After impregnation, the titanium sponge was dried at 100 ° C. for about 1 hour. Heat treatment was performed at 200 ° C. for 10 minutes and finally at 400 ° C. for about 10 minutes under an external air stream. This activation process was carried out five times. The Ru and Mn amounts thus obtained amounted to 28.4 mg Ru / g Ti and 36.0 mg Mn / g Ti.

The same active solution was also used for 4.9 g Ti sponge (particle size 315-630 microns). The number of impregnations as well as the drying and heating temperatures were the same as those used for the larger particles. However, the heat treatment period at 400 ° C. was 12 minutes. In this case, Ru and Mn contents amounted to 27 mg Ru and 34 mg Mn per gram of Ti sponge, respectively.

Activated titanium sponge particles were pressed into a lead sheet coupon. Larger particles (greater than 630 microns) were first compressed to a pressure of 290 kg / cm 2 and contained 322, 11.5 and 9.1 g / cm 2 Ti, Mn and Ru, respectively, per unit area of lead sheet. The smaller activated titanium particles (315-630 microns) are then compressed at a pressure of 360 kg / cm 2 to have Ti, Mn, Ru of 400, 13.7 and 10.8 g / m 2, respectively.

Thus, an electrode sample (L 62) having a lead base uniformly coated with titanium sponge particles activated with Ru-Mn oxide in an amount equivalent to 722 g / m 2 Ti sponge, 19.9 g / m 2 Ru and 25.2 g / m 2 Mn ) Was obtained.

This electrode sample was tested as an oxygen generating anode in H ₂ SO ₄ (150 g pl). At a current density of 500 A / m 2, the electrode potential (oxygen monopolar cell potential) reached 1.59 V after 68 days of anode operation, 1.59 V after 194 days, and 1.75 V after 210 days.

For comparison, another positive electrode sample (L 61) obtained by directly attaching smaller particles of activated Ti sponge to lead and having higher amounts of Ru and Mn corresponding to 27.9 and 35.4 g / m 2, respectively, was subjected to the same conditions. It had a positive potential of 1.62 V after 69 days of operation under 1.63 V when the operation was stopped after 194 days.

Another anode sample (L 76) was prepared as L 62, but larger particles were activated four times instead of five times. The overall Ru and Mn contents in this case amounted to 22.1 and 28.0 g / m 2, respectively. The anode was tested under the same conditions and showed a potential of 1.5V VS.NHE after 22 days of operation and 1.8V after 140 days.

Example 2

A positive electrode sample (L 64) having Ru and Mn contents of 23.1 and 29.3 g / m 2, respectively, was prepared as L 62 of Example 1. This anode was tested in a Zn electrowinning solution containing Mn ²⁺ as the main impurity.

The potentials reached 1.68 V and 1.73 V after 60 hours and 120 hours of operation as the oxygen generating anode in the solution. The current density was 400 A / m 2. Mn-oxide was not deposited during this period.

For comparison, a lead sample consisting of activated large particles (greater than 630 microns) or smaller particles (315-630 microns) and having Ru and Mn of 19-20 and 24-25 g / m 2, respectively, is approximately 60 hours after operation. A higher anode potential of 1.72-1.75 V VS.NHE was shown. In both cases a bipolar thick precipitate of Mn oxide was observed.

Example 3

Ti sponges (315-630 microns) were activated as in Example 1. It was pressed to lead at a pressure of 270 Kg / cm 2 to contain Ti, Mn and Ru of 427,15.1 and 11.9 g / m 2, respectively. Finally, ZrO ₂ particles (150-500 microns) were pressed onto the top of the Ti sponge at a pressure of about 410 kg / cm ₂ to contain 248 g / m 2 of ZrO ₂ .

The electrode sample L 82 thus obtained was tested as an oxygen generating anode at H ₂ SO ₄ (150 g pl.). At a current density of 500 A / m 2, the electrode potential reached 1.50 V VS.NHE after 150 hours of anode operation. This reached 1.59V after 293 days, and it worked until then. This translates into a voltage reduction of 410mV compared to untreated pure lead.

Example 4

Ti sponge (315-630) was first activated with Ru and Mn containing solutions as in Example 1. The activation method was the same as in Example 1. After activation, topcoating was performed by impregnation with a Ti-butoxide-containing solution obtained by dissolving 1.78 g of Ti-butoxide in 3.75 ml of 1-butyl alcohol and 0.25 ml of HCl.

The impregnated sponge was dried at 100 ° C. for about 1 hour. The heat treatment was carried out at 250 ° C. for 12 minutes and finally at 400 ° C. for about 12 minutes under an external air flow.

As a result, the activated titanium particles were pressed onto lead at a pressure of about 250 kg / cm 2. In this way, the electrode sample L 84 is Ru coated on top of Ti-oxide in an amount corresponding to 13,3g Ru / m 2, 16.9g Mn / m 2, 5,8g Ti / m 2 and 515g Ti sponge / m 2. It was made to have a lead base uniformly coated by -Mn oxide-activated titanium sponge particles.

This electrode sample was tested as an oxygen generating anode in H ₂ SO ₄ (150 gpl). At a current density of 500 A / m 2, the potential reached 1.49 V VS.NHE after 130 hours of anode operation. This is equivalent to 510 mV savings compared to untreated lead. The anode potential reached 1.64V after 128 days, equivalent to a 360mV saving over untreated lead.

Example 5

Ti sponge (315-630 microns) was first activated with a Ru containing solution obtained by dissolving 134 g of RuCl ₃ H ₂ O per 1 liter of butyl alcohol. Ti sponge was impregnated with Ru-containing solution, then heated at 120 ° C. for 20 minutes to evaporate the solvent, followed by heat treatment at 250 ° C. for 15 minutes and finally further heat treatment at 450 ° C. for 15 minutes. This impregnation, drying and heating steps were repeated four times. The ruthenium content in the titanium sponge thus obtained amounted to 30 mg per gram of Ti sponge.

After this activation step, TiO ₂ was top coated on the activated particles by impregnating 1.8 g of titanium butoxide with a solution obtained by mixing with 3.75 ml of butyl alcohol. Drying and heating were carried out in the same manner as in the Ru containing active solution. These steps were repeated twice to reach titanium (as TiO ₂ ) content of 5 mg per gram of Ti sponge.

Activated titanium particles were pressed onto the blade sheet coupon at a pressure of 250 kg / cm 2, and the particle content was 500 g / m 2 corresponding to 2.5 g / m 2 and Ru 15 g / m 2 used for particles uniformly dispersed on the lead surface.

This electrode sample was tested as an oxygen generating anode in H ₂ SO ₄ (150 gpl). At a current density of 500 A / m 2, the electrode potential reached 1.66 V VS.NHE after 2000 hours of anode operation.

Example 6

TiO ₂ rutile (rutile) particles having a particle size of 315-630 microns are 0.54 g of RuCl ₃ . Activated by impregnation with solution consisting of H ₂ O, 1.8 g butyl titanate, 0.25 ml HCl and 3.75 ml butyl alcohol.

After impregnation, the particles are dried in air at 100 ° C. and then heated at 440 ° C. for 10 minutes under air flow. Repeat this process four times. The resulting particles are activated with RuO ₂ -TiO ₂ .

The particles are pressed into a lead sheet coupon at a pressure of 250 kg / cm 2. The particle content amounted to 400 g / m 2, corresponding to Ru and Ti (used as RuO ₂ -TiO ₂ ) of 15 and 16 g / m 2, respectively.

The lead electrode thus activated was tested as a positive electrode in an aqueous solution containing 150 gpl of H ₂ SO ₄ at room temperature. The anode current density used was 500 A / m 2. The oxygen monopolar cell potential was 1.75 V VS.NHE after 300 hours of operation. After 1000 hours, the anode potential was the same as that of untreated pure lead.

Example 7

The active solution was prepared as in Example 1, but instead of diluted six-fold (Example 1), three-fold n-butyl alcohol was diluted.

4.11 g Ti sponge (400-630 microns) was impregnated with the active solution. After each impregnation the titanium sponge was dried at 100 ° C. for about 1 hour. After heat treatment at 250 ° C. for about 10 minutes, it was finally heat treated at 400 ° C. for about 10 minutes under an external air flow. This activation process was carried out three times. The Ru and Mn contents thus amounted to 36.2 mg Ru / g Ti and 45.8 mg / Mn / g Ti. For Ti sponges having a particle size of 630 microns or more, the activation process as in Example 1 was used for large particles (630 microns or more) in this case. However, activation was performed only four times. In this way, the Ru and Mn contents reached 23.5 mg Ru / g Ti and 29.9 mg Mn / g Ti.

Activated titanium sponge particles were compacted and then partially embedded in the surface of the lead sheet coupon. The larger particles (greater than 630 microns) were first pressed at a pressure of 240 kg / cm 2 to obtain 350, 10.5 and 8.3 g / m 2 of Ti, Mn and Ru content per unit area of lead sheet, respectively. Thus, an electrode sample having a lead base uniformly coated with titanium sponge particles activated with Ru—Mn oxide in an amount corresponding to 760 g / m 2 Ti sponge, 23.2 g / m 2 Ru and 29.3 g / m 2 Mn (L 95) was obtained. This electrode sample was tested as an oxygen generating anode in H ₂ SO ₄ (150 gpl). At a current density of 500 A / m 2, the electrode potential reached 1.65 V VS.NHE after 287 days of anode operation.

For comparison purposes, another positive electrode sample (L93) obtained by pressing small particles of activated Ti sponge directly at lead at 280 kg / cm 2 and having Ru and Mn contents of 15.4 and 19.5 g / m 2, respectively, under the same conditions Experiment. After 289 days the electrode potential was 1.78 V VS.NHE.

Another anode sample (L 92) was prepared as L95, but small particles (400-630 microns) were activated as in Example 1 (L 62). In this case, the total Ti, Mn and Ru contents amounted to 726, 22.5 and 17.7 g / m 2, respectively. Large and small particles were pressed at pressures of 290 kg / cm 2 and 410 kg / cm 2, respectively. The anode was tested under the same conditions and showed a potential of 1.78 V VS.NHE after 289 days of operation.

Example 8

The active solution was prepared as in Example 7, and 4.22 g of large particles (more than 630 microns) were activated twice under the specific conditions of Example 7 so that the Ru and Mn contents were 21.5 mg Ru / g Ti and 27.4 mg Mn, respectively. / g Ti.

Another active solution was used for Ti sponges with small particles (400-630 microns). This active solution is the same as in Example 7, except that the 1-butyl alcohol is diluted twice. It was activated twice according to Example 7. Ru and Mn contents per Tig reached 25.9 and 32.9 mg, respectively.

The anode sample (L 120) first squeezed the large particles at a pressure of 210 kg / cm 2 so that the Ti, Mn and Ru contents were 360, 9.8 and 7.7 g / m 2, respectively. Small activated titanium particles (400-630 microns) were pressed at a pressure of 320 kg / cm 2 to bring the Ti, Mn and Ru contents to 420, 13.9 and 10.9 g / m 2, respectively. In this way, the total Ti, Mn and Ru contents amounted to 780, 23.7 and 18.6 g / m 2, respectively. The electrode sample was tested as an oxygenated anode in H ₂ SO ₄ (150 gpl). At a current density of 500 A / m 2, the electrode potential reached 1.58 V VS.NHE after 218 days of anode operation.

Example 9

Ti sponge (400-630 microns) was oxidized as follows before being activated with Ru-Mn oxide.

4.74 g of titanium sponge was first activated with the active solution of Example 1. The Ti sponge was dried at 100 ° C. and then heat treated at 400 ° C. for 13 minutes under an external air stream. Ru and Mn contents were 5.2 and 6.6 mg / g Ti sponge, respectively. The sponges were then heat treated at 480 ° C. for 45 hours under external air flow to convert each oxide.

3.5 g of the oxidized Ti sponge thus obtained was activated in the same manner as in Example 1 except for the intermediate heat treatment at 250 ° C. instead of 200 ° C. after each activation. The Mn and Ru contents per g of sponge amounted to 32.8 and 25.8 mg, respectively. The peroxidized and activated Ti sponge was compressed in two stages at 230 kg / cm ₂ and 290 kg / cm 2, respectively, resulting in Mn and Ru contents of 21.1 and 16.6 g / m 2, respectively. The content of oxidized Ti sponge amounted to 643 g / m 2. The total Mn and Ru contents reached 25.3 and 19.9 g / m 2, respectively, considering the Mn and Ru contents in the Ti oxide before the final activation.

The electrode was tested at a current density of 500 A / m ₂ and 150 gpl of H ₂ SO ₄ , and after 275 days of operation, the potential of the electrode reached 1.65 V VS.NHE.

Example 10

Two active solutions were prepared with a higher Mn / Ru ratio than in Example 1. Solution A: 0.537 g RuCl ₃ aq, 2.0819 g Mn (NO ₃ ) ₂ .aq and 3.75 ml n-butyl alcohol solution B: 0.5 37 g RuCl ₃ .aq, 4,6844 g Mn (NO ₃ ) ₂ .aq and 3.75 ml of n-butyl alcohol. Both solutions A and B were diluted three-fold with n-butyl alcohol before use. Solution A had a MnO ₂ / RuO ₂ molar ratio of 4 and Solution B had 9.

4.27 g Ti sponge (315-630 microns) was impregnated with diluted active solution A. After each impregnation, the titanium sponge was dried at 100 ° C. for 1 hour. After heat treatment at 250 ° C. for 14 minutes, it was finally heat treated at 400 ° C. for about 14 minutes under an external air stream. This activation process was performed three times. The Ru and Mn contents thus obtained amounted to 29.3 mg Ru / g Ti and 63.8 mg Mn / g Ti.

4.16 g Ti sponge (particle size 315-630 microns) was impregnated with diluted active solution B. Activated in the same manner as the active solution A. In this way, the Ru and Mn contents reached 19.9 mg Ru / g Ti and 97.4 mg Mn / g Ti.

Activated Ti sponge particles were pressed into a lead sheet coupon. As in Example 8, the activated large particles (more than 630 microns) were first compressed at 230 kg / cm 2 to have Ti, Mn and Ru contents per unit area of the lead sheet of 449, 12.0 and 9.4 g / m 2, respectively. Ti particles (315-630 microns) activated with dilute solution A were pressed at 350 kg / cm 2 to obtain Ti, Mn and Ru contents of 399, 25.5 and 11.7 g / m 2, respectively.

In this way, an electrode sample (L 164) having a lead-acid body uniformly coated by sponge particles activated with Ru-Mn oxide in an amount corresponding to 848 g / m 2 Ti sponge, 20.8 g / m 2 Ru and 37.5 g / m 2 Mn )

This electrode sample was tested as an oxygen generating anode at 150 gpl of H ₂ SO ₄ . At a current density of 500 A / m 2, the potential reached 1.50 V VS.NHE after 36 days of anode operation.

For comparison purposes, another particle having Ti, Ru and Mn contents of 531,15.6 and 34.0 g / m 2, respectively, by direct compression of small particles of Ti sponges activated with solution A diluted at a pressure of 320 kg / cm 2 to lead A positive sample (L 161) was prepared.

This electrode L 161 was tested under the same conditions and showed a potential of 1.60 V VS.NH E after 70 days of operation.

In another experiment, activated 630 micron or larger Ti sponge particles, as in Example 8, were compressed at 230 kg / cm 2 to have Ti, Mn and Ru contents per unit area of lead-sheets of 428,11.5 and 9.0 g / m 2, respectively. . Small titanium sponge particles (315-630 microns) activated with active solution B were pressed at 350 kg / cm 2 to obtain Ti, Mn and Ru contents of 493,48.0 and 9.8 g / m 2, respectively. Thus, an electrode sample (L 163) having a lead base uniformly coated with sponge particles activated with Ru-Mn oxide in an amount corresponding to 921 g / m 2 Ti, 59.5 g / m 2 Mn and 18.8 g / m 2 Ru Was prepared.

This electrode was tested as an oxygen generating electrode at a current density of 550 A / m ₂ and 150 gpl of H ₂ SO ₄ . After 33 days of operation, the potential reached 1.57 V VS.NHE.

Example 11

To compare with L 163 in Example 10, the Ti, Ru and Mn contents were 652, 13.0 by pressing small particles (315-630 microns) of Ti sponge activated with diluted solution B directly into lead at 290 kg / cm 2, respectively. And another positive electrode sample (L 162) of 63.6 g / m 2.

The electrode was tested at a current density of 500 A / m ₂ and 150 gpl of H ₂ SO ₄ and showed a potential of 1.74 V VS.NHE after 18 days (430 hours) of operation under these conditions.

Example 12

The active solution was prepared by dissolving 0.54 g of RuCl ₃ aq (38% Ru) and 0.12 g of Pd cl ₂ in 15 ml of butyl alcohol. The solution was stirred until all salts dissolved and then 1.84 g of butyl titanate was added.

3.5 g of a titanium sponge having a particle size of 315-630 microns was impregnated with the activated solution, dried at 140 ° C. for 20 minutes, then heated at 250 ° C. for 15 minutes, and finally heated at 450 ° C. for 15 minutes. It was. All these heating steps were carried out in air. After cooling, the impregnation, drying and heating steps were repeated six times. The Ru and Pd contents in the particles thus obtained reached 300 mg Ru / g Ti and 11 mg Pd / g Ti. Activated titanium sponge particles were pressed into a lead sheet coupon under a pressure of 250 kg / cm 2 to obtain the following contents, respectively.

500 g / m 2 Ti sponge, 15 g / m 2 Ru, 5.5 g / m 2 pd.

This electrode sample was tested as an oxygen generating anode at H ₂ SO ₄ (150 gpl) and a current density of 500 A / m 2. The electrode potential (oxygen monopolar cell potential) reached 1.78VVS.NHE after 208 days of anode operation.

Example 13

7 g of titanium sponge (315-630 microns) was impregnated with 1.4 ml of a solution of 7 mg of Ir in 1 ml of isopropyl alcohol in the form of IrCl ₃ aq. After impregnation, the titanium sponge was dried at 140 ° C. for 15 minutes, then heated at 250 ° C. for 10 minutes and then again at 450 ° C. for 10 minutes, all of these steps being carried out in air.

Activated titanium sponge particles were pressed into a lead sheet coupon under a pressure of 250 kg / cm 2. The amount of particles was chosen to yield 700 g / m 2 and 1 g / m 2 of titanium and iridium, respectively.

The second active solution was used for the electrode sample in the following manner. The solution was prepared by dissolving 5.0 g of Mn (NO ₃ ) ₂ 4H ₂ O and 0.32 g of CO (NO ₃ ) ₂ 6H ₂ O in 0.5 ml of ethanol. This solution was used on the electrode surface and then dried at 140 ° C. for 15 minutes and then heated in 250 ° C. air for 10 minutes. After cooling, the painting, drying and heating steps were repeated five times, resulting in MnO ₂ and cobalt oxide contents of 240 g / m 2 and 12 g / m 2 (calculated as Co ₃ O ₄ ), respectively.

This electrode sample was tested as an oxygen generating anode in H ₂ SO ₄ (150 gpl). At a current density of 500 A / m 2, the electrode potential (oxygen monopolar cell potential) reached 1.78 V (VS. NHE) after 7 months of anode operation.

Example 14

The electrode sample was used in Example 13 except for using RuCl ₃ aq (14 mg / ml of Ru) instead of IrCl ₃ aq and repeating the impregnation step twice to obtain ruthenium 4 g / m 2 for the titanium sponge 700 g / m 2. It was prepared as follows.

When tested under the same conditions as in Example 13, the oxygen monopolar cell potential reached 1.80 V (VS.NHE) after 6.5 months of operation.

Example 15

The active solution was prepared by dissolving 0.44 g of RuCl ₃ aq (38 wt.% Ru) and 0.090 g of SnCl ₂ H ₂ O + 0.52 g of Mn (NO ₃ ) ₂ 4H ₂ O in 4 ml of butyl alcohol.

2.5 g of titanium sponge (315-630 microns) was impregnated with the active solution according to the following method: 0.77 ml of the solution was uniformly used in the titanium sponge, dried at 140 ° C. for 15 minutes, and then at 250 ° C. for 10 minutes. Heated for minutes and again heated at 420 ° C. for 10 minutes, these relationships being carried out in air. After cooling, the titanium sponge was activated twice with 0.5 ml of active solution, respectively, and then the dried and activated titanium particles were Ti 700g / m 2, Ru 20g / m 2, Sn 5.8g / m 2 and Mn 13.7g / The surface of the lead-calcium alloy (0.06% Ca) coupon was pressed at a pressure of 250 kg / cm 2 to obtain m 2.

This electrode sample was tested as an oxygen generating anode at a current density of 500 A / m ₂ of H ₂ SO ₄ (150 gpl). Electrode potential reached 1.67 V VS.NHE after 7 months of operation.

As shown in the above examples, the anode according to the present invention can be produced by a simple method and used to generate for a long time at a potential much lower than the anode potential corresponding to the generation of oxygen in lead or lead alloy under the same operating conditions. have.

As shown in the above examples, when the anode sample was tested according to the present invention, no lead was lost from the base body, whereas when the lead or lead alloy sample was tested under the same conditions, a significant amount of lead was lost to the electrolytic nuclei.

It is found that the use of heat and pressure simultaneously when partially filling valve metal particles in lead or lead alloy on the surface of the anode base can be easily fixed while preventing the particles from being completely embedded and / or flattened on the base. Paid.

Further improvements in the above examples can also be obtained by determining the best conditions for optimum, stable electrochemical operation at the most economical value of the precious metal at the anode according to the invention.

The catalyst particles can be used and fixed to the lead or lead alloy base of the positive electrode by other means such as compression rollers as well as the pressing means as in the above embodiments, and thus are suitable for achieving the fundamental advantages of the present invention.

It has been found that the heating (250 ° C.) catalyst in the compression step can facilitate the partial embedding of lead or lead alloy surfaces.

The present invention provides several advantages: (a) The anode according to the invention operates at a much lower potential than conventional anodes of lead or lead alloys currently used in industrial electrolysers for electrowinning metals from acid solutions. Can be. Therefore, the energy cost and electrolyzer voltage for electrolyzing the metal can be reduced.

(b) Because of the generation of oxygen at reduced potentials where lead or lead alloys in the anode base do not corrode and in the catalyst particles, deposition of cathodes by the material from the anode and contamination of the electrolyte can be avoided.

(c) The dendrite at the cathode, which can short circuit the anode and the circuit and burn the hole to the anode because oxygen is generated at reduced potentials where the exposed lead or part of the lead body does not corrode and because the catalyst particles produce oxygen. Despite the formation of tissues, the action of the anode according to the invention is not significantly reduced.

(d) Conventional lead or lead alloy anodes can be readily converted to the improved anode according to the present invention, thus making it possible to retrofit industrial electrolysers for electrowinning metals in a particularly simple and inexpensive way.

(e) The reduced electrolytic cell voltage obtained at the anode according to the invention can be easily monitored to quickly detect any rise that may occur at the anode potential. Therefore, the catalyst particles in the lead or lead alloy base can be easily reacted or replaced whenever necessary.

(f) Ruthenium can be used as a catalyst in a very economical way by mixing titanium sponge particles, which have been used in large quantities in the anode base of lead or lead alloys, and ruthenium in extremely rapid amounts. The value of ruthenium can shine by enhancing the action of the anode.

(g) As such, ruthenium can be used in very limited amounts and mixed with less expensive stabilizers.

(h) In the copper electrowinning plant installed as an anode according to the present invention, the short circuit was reduced. This is a result of the improved cathode current efficiency, since it already saves energy with a reduced electrolytic cell voltage due to the operation of the anode according to the invention at a reduced oxygen monopolar cell potential.

Industrial use

The anode according to the present invention is used instead of the lead of lead or lead alloy recently used in order to improve the purity of the metal produced in the cathode and to reduce the energy cost required for industrial electrowinning of metals such as zinc, copper, cobalt and nickel. Can be used advantageously.

These anodes can be useful for many processes that require the generation of oxygen at reduced voltages.

Claims (21)

In an anode composed of a lead base of lead or lead alloy and for generating oxygen in an acid electrolyte, (a) the base so that catalytically activated titanium particles are electrically connected to and firmly fixed to the base. (B) the underlying lead or lead alloy remains electrochemically inert, essentially acting as a stable and inert current conducting support for catalytically activated particles and reduced An anode for generating oxygen, wherein the catalytically activated titanium particles contain a small amount of ruthenium in oxide form so as to generate oxygen at the anode at a potential. The anode according to claim 1, wherein the particles consist of titanium sponge. The anode according to claim 1 or 2, wherein the particles further contain manganese in oxide form. 4. The anode according to claim 3, wherein titanium sponge particles of different sizes and catalytically activated are arranged in the base body. 5. The positive electrode of claim 4, wherein among the particles of different sizes, the smaller particles comprise a greater amount of ruthenium than the larger particles. The anode of claim 1, wherein the activated titanium particles further comprise titanium in oxide form. The positive electrode of claim 1, wherein the activated particles comprise titanium in an amount corresponding to at least 400 g per m 2 of the positive electrode base body. The anode of claim 1, further comprising particles of valve metal and valve metal oxide (preferably Z _r O ₂ ) in addition to the activated particles. (a) The titanium sponge particles containing a small amount of ruthenium and manganese in oxide form obtained by pyrolyzing ruthenium and manganese compounds used for catalytically activated titanium sponge particles are uniformly formed on the surface of the anode base of lead or lead alloy; And (b) partially embedding the catalytically activated particles in the lead or lead alloy of the positive electrode body. 10. The method of claim 9, wherein the activated large particles are first pressed onto the surface of the positive electrode body and then the activated small particles are pressed onto the surface of the positive electrode body. The method of claim 10, wherein the small particles are provided with a greater amount of ruthenium than the large particles. 12. The method of claim 10 or 11, wherein the size of the large particles is at least 600 microns and the size of the small particles is 300-600 microns. 10. The method of claim 9, wherein the activated particles contain titanium in an amount corresponding to at least 400 g per m 2 of the positive electrode base surface. 10. The method of claim 9, wherein titanium oxide is further formed in the particles by forming pyrolysis of the titanium compound used in the catalytically activated particles after the formation of ruthenium and manganese in oxide form. 10. The method of claim 9, wherein particles of the valve metal and / or valve metal oxide are further pressed onto the anode base after partially embedding the activated particles. The method of claim 15, wherein the particles of zirconium dioxide are pressed and likewise fixed to the anode base after the catalytically activated titanium particles are partially embedded. In an electrode comprising a catalyst for conducting an electrochemical reaction and a base of lead or lead alloy, a stable inert current conductivity for the catalyst particles by being kept electrochemically inert of the lead or lead alloy in the lower layer of the base Catalyst particles composed of inert and refractory oxides activated by a catalyst for the desired reaction are partially supported on the surface of the base, such that electrochemical reactions can be preferably carried out on the catalyst particles at a potential that essentially acts as a support. An electrode characterized in that it is buried or uniformly distributed to be firmly fixed and electrically connected to the base body. 18. The electrode of claim 17, wherein the inert and refractory oxide particles are activated by a catalyst containing a noble metal. 19. The electrode according to claim 17 or 18, wherein the refractory oxide is titanium oxide in rutile form. A method of using the electrode of claim 17 as an anode for generating oxygen in an acid electrolyte. 3. The anode according to claim 2, wherein titanium sponge particles of different sizes and catalytically activated are arranged in the base body.