TW202314047A - Process for electrolytic production of metal powder - Google Patents

Abstract

The present invention relates to a process for production of a powder of metal in an electrolytic cell comprising an anode made of the metal, a cathode and an electrolyte solution, which comprises (a) anodic dissolution to form ions of the metal in the electrolyte solution and cathodic deposition of metal particles from the electrolyte solution, (b) removal of the metal particles from the cathode into the electrolyte solution, and (c) isolation of the metal particles from the electrolyte solution, wherein the metal is copper or silver, and wherein the electrolyte solution comprises (i) an alkane sulfonic acid or alkanol sulfonic acid and (ii) a soluble metal salt of an alkane sulfonic acid or alkanol sulfonic acid. The present invention also relates to the copper or silver powder obtained or obtainable by the process and use an alkane sulfonic acid or alkanol sulfonic acid in an electrolyte solution for production of a silver or copper powder by electrolytic deposition.

Description

Method for producing metal powder by electrolysis

The invention relates to a method for the electrolytic production of metal powders and the metal powders obtained by the method.

Fine metal powders such as copper and silver powders are widely used in various applications such as electronic pastes, lubricants, catalysts, pharmaceuticals and biofilters. Electrowinning of metal powders has been an important industrial method because it can provide high-quality metal powders under mild conditions with low requirements on starting materials.

In a conventional method of producing copper powder by electrodeposition, an aqueous solution of copper sulfate containing sulfuric acid is generally used. This method requires certain measures to prevent the release of corrosive sulfuric acid from the electrolyte solution into the environment, especially at elevated process temperatures. In a conventional method of producing silver powder by electrodeposition, an aqueous silver nitrate electrolyte solution containing nitric acid is generally used. This method also suffers from the release of nitric acid from the electrolyte solution into the environment at elevated programmed temperatures.

Furthermore, the inventors of the present invention found that, in the conventional method using a silver nitrate electrolyte solution, the deposition of silver particles on the cathode is accompanied by the rapid growth of dendritic aggregates, especially at the corners of the cathode. Dendritic aggregates may extend to the anode, increasing the risk of short circuits.

There remains a need for alternative methods of making copper and silver powders by electrowinning. Desirably, these methods may provide metal powders of comparable or even improved quality to metal powders obtained by conventional methods.

It is an object of the present invention to provide a method of manufacturing copper and/or silver powders which does not use electrolyte solutions containing any corrosive acids which may be released into the environment at elevated electrolysis temperatures. Another object of the present invention is to provide a method of producing copper or silver powder with a desired particle size or even smaller particle size.

It has been found that the objects of the invention can be achieved by using an electrolyte solution comprising metal sulphonates and sulphonic acids.

Accordingly, in one aspect, the present invention provides a method of producing metal powder in an electrolytic cell comprising an anode made of metal, a cathode and an electrolyte solution, the method comprising a) anodic dissolution to form metal ions in the electrolyte solution and cathodic deposition of metal particles from the electrolyte solution, b) removing the metal particles from the cathode into the electrolyte solution, and c) separating the metal particles from the electrolyte solution, in the metal is copper or silver, and The electrolyte solution contains (i) alkanesulfonic acid or alkanolsulfonic acid and (ii) a soluble metal salt of alkanesulfonic acid or alkanolsulfonic acid.

In another aspect, the invention provides copper or silver powder obtained or obtainable by a method described herein.

In another aspect, the present invention provides the use of alkanesulfonic acid or alkanolsulfonic acid in an electrolyte solution for the manufacture of silver or copper powder by electrowinning.

The present invention will be described in detail below. It should be understood that the invention may be embodied in many different ways and should not be construed as limited to the specific examples set forth herein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

As used herein, the singular forms "a", "an", "an" and "the" also include plural referents unless the context clearly dictates otherwise.

As used herein, the terms "comprise", "comprising", etc. are used interchangeably with "contain", "containing", etc., and are to be read in a non-limiting, open-ended manner. That is, for example, additional components or elements may be present. The terms "consisting of" or "consisting essentially of" or cognates may be encompassed within "comprising" or cognates.

As used herein, the term "aqueous" means that the electrolyte solution comprises a solvent containing at least 50% water. Preferably at least 75%, more preferably 90% of the solvent is water. It is conceivable that the solvent of the electrolyte solution consists essentially of water without any intentionally added organic solvent. Any type of water can be used, preferably distilled or deionized water.

In a first aspect, the present invention provides a method of producing metal powder in an electrolytic cell comprising an anode made of metal, a cathode and an electrolyte solution, the method comprising a) anodic dissolution to form metal ions in the electrolyte solution and cathodic deposition of metal particles from the electrolyte solution, b) removing the metal particles from the cathode into the electrolyte solution, and c) separating the metal particles from the electrolyte solution, in The metal is copper or silver, and the electrolyte solution contains (i) alkanesulfonic acid or alkanolsulfonic acid and (ii) a soluble metal salt of alkanesulfonic acid or alkanolsulfonic acid.

As is well known, the anode is made of a metal to be deposited on the cathode, thus continuously supplying metal ions into the electrolyte solution during operation of the electrolytic cell. Typically, the anode may be made of a metal having a purity of at least 95%, such as at least 98% or at least 99%. In the method according to the invention, the anode is made of copper or silver with a purity within the above-mentioned range.

The material of the cathode is not particularly limited. Cathodes that can be used in the method according to the invention can be made of, for example, stainless steel or titanium.

The anode and cathode can be arranged at a distance of 1 cm to 10 cm, preferably 3 cm to 6 cm, such as 3 cm to 5.5 cm.

The inventors of the present invention have found that at elevated electrolysis temperatures, electrolyte solutions comprising (i) alkanesulfonic acids or alkanolsulfonic acids and (ii) soluble metal salts of alkanesulfonic acids or alkanolsulfonic acids are useful for the production of silver powder and copper powder. The powder is effective and there are no problems with release of acid into the environment.

Useful alkanesulfonic acids as component (i) may be C ₁ -C ₁₂ -alkanesulfonic acids, preferably C ₁ -C ₆ -alkanesulfonic acids. Alkanesulfonic acids can be monosulfonic and disulfonic acids. Examples of alkane monosulfonic acids include, but are not limited to, methanesulfonic acid, 1-ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, 1-pentanesulfonic acid, 1-hexanesulfonic acid, 1-decanesulfonic acid and 1-dodecanesulfonic acid. Examples of alkanedisulfonic acids include, but are not limited to, methanedisulfonic acid, 1,1-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,1-propanedisulfonic acid, 1,3-propanedisulfonic acid , 1,1-butanedisulfonic acid and 1,4-butanedisulfonic acid. One alkanesulfonic acid or any mixture of two or more alkanesulfonic acids can be used in the electrolyte solution in the process according to the invention.

Useful alkanolsulfonic acids as component (i) may be C ₂ -C ₁₂ -alkanolsulfonic acids, preferably C ₂ -C ₆ -alkanolsulfonic acids, ie hydroxy-substituted C ₂ -C ₁₂ -Alkanesulfonic acids, preferably hydroxy-substituted C ₂ -C ₆ -alkanesulfonic acids. The hydroxyl group can be on the terminal or internal carbon of the alkyl chain of the alkanesulfonic acid. Examples of useful alkanolsulfonic acids include, but are not limited to, 2-hydroxy-1-ethanesulfonic acid, 1-hydroxy-2-propanesulfonic acid, 2-hydroxy-1-propanesulfonic acid, 3-hydroxy-1-propanesulfonic acid acid, 2-hydroxy-1-butanesulfonic acid, 4-hydroxy-1-butanesulfonic acid, 4-hydroxy-2-butanesulfonic acid, 2-hydroxy-1-pentanesulfonic acid, 4-hydroxy-1-pentanesulfonic acid acid, 2-hydroxy-1-hexanesulfonic acid, 2-hydroxy-1-decanesulfonic acid and 2-hydroxy-1-dodecanesulfonic acid. One alkanolsulfonic acid or any mixture of two or more alkanolsulfonic acids can be used in the electrolyte solution according to the method of the invention.

The alkanesulfonic acid and alkanolsulfonic acid may be prepared by any method known in the art or commercially available without particular limitation.

Alkanesulfonic acid or alkanolsulfonic acid as component (i) may be contained in the electrolytic solution at a rate of 1 to 200 grams (g/L), especially 5 to 180 g/L, preferably Concentration range from 10 to 150 g/L.

Herein, the soluble metal salt of alkanesulfonic acid or alkanolsulfonic acid as component (ii) refers to the soluble silver or copper salt of alkanesulfonic acid or alkanolsulfonic acid. Soluble silver or copper salts of alkanesulfonic acids or alkanolsulfonic acids are also referred to below as soluble metal sulfonates.

The alkanesulfonic acid or alkanolsulfonic acid from which the soluble metal sulfonate is derived may be the same as or different from the alkanesulfonic acid or alkanolsulfonic acid as component (i), and may be selected from the above-mentioned component (i).

Preferably, the soluble metal sulfonate is a soluble silver or copper salt of an alkanesulfonic acid or alkanolsulfonic acid as component (i).

For example, the electrolytic solution may contain methanesulfonic acid as component (i) and copper or silver methanesulfonate as component (ii).

The soluble metal sulfonate as component (ii) may be contained in the electrolyte solution at a concentration of 1 to 200 g/L electrolyte solution, especially 5 to 150 g/L, preferably 5 to 120 g/L range (calculated as metal ions).

The electrolyte solution can be prepared by any known method, for example by dissolving a metal (i.e. copper or silver), a metal oxide, a metal hydroxide or a metal carbonate in the above-mentioned alkanesulfonic acid or alkanesulfonic acid acid solution to provide a solution with the desired concentration of metal ions and sulfonic acid.

The electrolyte solution may optionally contain one or more additives known in the art to be useful, eg gelatin derived from collagen (eg animal glue), glucose, urea. Some inorganic additives can also be mentioned, such as copper chloride, to improve the conductivity of the electrolyte solution in copper powder production or to adjust the pH value of the electrolyte solution in copper powder production. Additives, if present, may be included in the electrolyte solution at a concentration of up to 20 g/L, more preferably up to 10 g/L.

In some embodiments, the present invention provides a method of producing silver powder in an electrolytic cell comprising an anode made of silver, a cathode and an electrolyte solution, wherein the electrolyte solution comprises (i) an alkanesulfonic acid or an alkanesulfonic acid acid and (ii) soluble silver alkane sulfonate or alkanol sulfonate.

In a specific example of the method for producing silver powder, alkanesulfonic acid or alkanesulfonic acid as component (i) is preferably contained in the electrolytic solution at an amount of 1 to 50 grams (g/L) per liter of electrolytic solution, especially It is the concentration range of 5 to 30 g/L, preferably 10 to 20 g/L. Additionally or alternatively, as component (ii) soluble silver alkane sulfonate or alkanol sulfonate is preferably contained in the electrolyte solution at 50 to 200 g/L electrolyte solution, especially 60 to 150 g /L, preferably a concentration range of 80 to 120 g/L (calculated as silver ions).

In some other embodiments, the present invention provides a method of producing copper powder in an electrolytic cell comprising an anode made of copper, a cathode and an electrolyte solution, wherein the electrolyte solution comprises (i) an alkane sulfonic acid or an alkane Alcohol sulfonic acids and (ii) soluble copper alkane sulfonates or copper alkanol sulfonates.

In a specific example of the method for producing copper powder, alkanesulfonic acid or alkanesulfonic acid as component (i) is preferably contained in the electrolytic solution at a rate of 50 to 200 grams (g/L) per liter of electrolytic solution, In particular a concentration range of 80 to 200 g/L, preferably 100 to 160 g/L. Additionally or alternatively, soluble copper alkane sulfonate or alkane sulfonate copper salt as component (ii) is preferably contained in the electrolyte solution at 1 to 50 g/L electrolyte solution, especially 5 to 30 g /L, preferably a concentration range of 5 to 15 g/L (calculated as copper ions).

In step a), anodic dissolution and cathodic deposition can be carried out at ambient temperature or at elevated temperature, depending on the temperature of the electrolyte solution. For example, the method may be carried out at a temperature ranging from 20°C to 70°C, preferably from 30°C to 60°C, more preferably from 40°C to 50°C.

During step a), the electrolyte solution may be pumped, at a flow rate of about 5 to 20 liters per minute (L/min). The electrolyte solution can be pumped from a storage tank, pumped into the electrolytic cell from the top and discharged from the bottom of the electrolytic cell, or can be pumped into the electrolytic cell from the bottom and discharged from the top of the electrolytic cell.

Step a) may be carried out at a current density in the range of 2 to 20 A/dm ² (ASD), in particular 3 to 15 A/dm ² , for example 3 to 10 A/dm ² for the production of silver powder, and 8 to 15 A/dm ² for the manufacture of copper powder.

The anodic dissolution and cathodic deposition in step a) are typically carried out for a period of 10 to 60 minutes, eg 10 to 30 minutes, before metal particles deposited on the cathode are removed in step b).

In step b), metal particles can be removed from the cathode into the electrolyte solution by any mechanical means known in the art without any limitation.

In step c), the metal particle-containing electrolyte solution obtained from step b) is separated to provide metal powder. Optionally, the separated metal powder can be further post-treated, including washing, drying and/or anti-oxidation treatment. Post-processing can be performed by any conventional method. For example, the isolated metal powder can be washed with deionized water, dried under vacuum and reduced under a hydrogen atmosphere.

Therefore, the method according to the present invention may further comprise the following steps: d) washing the separated metal particles from step c), preferably with deionized water, e) vacuum dried, and f) Anti-oxidation of metal particles, preferably reduction under hydrogen atmosphere.

In some exemplary embodiments, the present invention provides a method of making silver powder in an electrolytic cell comprising an anode made of silver, a cathode and an electrolyte solution, the method comprising a) anodic dissolution to forming silver ions in the electrolyte solution, and cathodic deposition of silver particles from the electrolyte solution, b) removing the silver particles from the cathode into the electrolyte solution, and c) removing the silver particles from the electrolyte solution wherein the electrolyte solution comprises (i) C ₁ -C ₆ -alkanesulfonic acid or C ₁ -C ₆ -alkanolsulfonic acid and (ii) soluble C ₁ -C ₆ -alkanesulfonic acid Silver salts or silver salts of C ₁ -C ₆ -alkanolsulfonates.

Preferably, in an exemplary embodiment of the method for producing silver powder, the electrolyte solution comprises (i) C ₁ -C ₆ -alkane sulfonic acid or C ₁ -C ₆ -alkanol sulfonic acid at 1 to 50 g/ L electrolyte solution concentration range, and (ii) soluble silver C ₁ -C ₆ -alkane sulfonate or C ₁ -C ₆ -alkanol sulfonate silver salt, in a concentration range of 50 to 200 g/L electrolyte solution .

More preferably, in an exemplary embodiment of the method of manufacturing silver powder, the electrolyte solution comprises (i) C ₁ -C ₆ -alkane sulfonic acid or C ₁ -C ₆ -alkanol sulfonic acid at 5 to 30 g/ L electrolyte solution, preferably in a concentration range of 10 to 20 g/L, and (ii) soluble silver salts of C ₁ -C ₆ -alkane sulfonates or C ₁ -C ₆ -alkane sulfonate silver salts, with 60 to 150 g/L electrolyte solution concentration (calculated as silver ions).

Most preferably, in an exemplary embodiment of the method of making silver powder, the electrolyte solution comprises (i) C ₁ -C ₆ -alkane sulfonic acid or C ₁ -C ₆ -alkanol sulfonic acid at 5 to 30 g/ L electrolyte solution, preferably in a concentration range of 10 to 20 g/L, and (ii) soluble silver salts of C ₁ -C ₆ -alkane sulfonates or C ₁ -C ₆ -alkane sulfonate silver salts, with 80 to 120 g/L electrolyte solution concentration (calculated as silver ions).

In any exemplary embodiment of the method of making silver powder, step a) is carried out at a temperature in the range of 40 to 50°C, preferably 45 to 50°C.

In some other embodiments, the present invention provides a method of making copper powder in an electrolytic cell comprising an anode made of copper, a cathode and an electrolyte solution, the method comprising a) anodic dissolution to forming copper ions in the electrolyte solution, and cathodic deposition of copper particles from the electrolyte solution, b) removing the copper particles from the cathode into the electrolyte solution, and c) removing the copper particles from the electrolyte solution wherein the electrolyte solution comprises (i) C ₁ -C ₆ -alkanesulfonic acid or C ₁ -C ₆ -alkanolsulfonic acid and (ii) soluble C ₁ -C ₆ -alkanesulfonic acid Copper salts or copper salts of C ₁ -C ₆ -alkanolsulfonates.

Preferably, in an exemplary embodiment of the method for producing copper powder, the electrolytic solution comprises (i) C ₁ -C ₆ -alkane sulfonic acid or C ₁ -C ₆ -alkanol sulfonic acid in 50 to 200 g Concentration range of /L electrolyte solution, and (ii) soluble C ₁ -C ₆ -alkane sulfonate copper salt or C ₁ -C ₆ -alkanol sulfonate copper salt, at a concentration of 1 to 50 g/L electrolyte solution scope.

More preferably, in an exemplary embodiment of the method of manufacturing copper powder, the electrolyte solution comprises (i) C ₁ -C ₆ -alkane sulfonic acid or C ₁ -C ₆ -alkanol sulfonic acid, in 80 to 200 g /L electrolyte solution, preferably in a concentration range of 100 to 160 g/L, and (ii) soluble copper salts of C ₁ -C ₆ -alkane sulfonates or copper salts of C ₁ -C ₆ -alkanol sulfonates, With a concentration of 5 to 30 g/L electrolyte solution (calculated as copper ions).

Optimally, in an exemplary embodiment of the method of manufacturing copper powder, the electrolyte solution comprises (i) C ₁ -C ₆ -alkane sulfonic acid or C ₁ -C ₆ -alkanol sulfonic acid, in the form of 80 to 200 g /L, preferably a concentration range of 100 to 160 g/L electrolyte solution, and (ii) soluble C ₁ -C ₆ -alkane sulfonate copper salt or C ₁ -C ₆ -alkanol sulfonate copper salt, With a concentration of 5 to 15 g/L electrolyte solution (calculated as copper ions).

In any exemplary embodiment of the method of making copper powder, step a) is performed at a temperature in the range of 40 to 50°C.

In a second aspect, the present invention provides a copper or silver powder obtainable or obtainable by a method according to the invention as described herein.

The particle size _D50 of the copper powder obtained or obtainable by the method according to the present invention is 20 to 120 micrometers (μm), preferably 30 μm to 100 μm, more preferably 40 μm to 90 μm, The optimum range is from 40 μm to 80 μm.

The particle size _D50 of the silver powder obtained or obtainable by the method according to the invention is in the range of 100 to 600 micrometers (μm), preferably 150 μm to 500 μm, more preferably 200 μm to 400 μm Inside. Additionally or alternatively, the particle size D ₉₀ of the silver powder obtained or obtainable by the method according to the invention is in the range of 200 to 1,000 micrometers (μm), preferably 400 to 800 μm.

The _D50 is the diameter value as measured by a particle size laser analyzer, where 50% of the total number of characterized particles consists of particles having a diameter smaller than the _D50 diameter value.

The D ₉₀ is characterized by 90% of the total number of particles being composed of particles with a diameter smaller than the D ₉₀ diameter value, as measured by a particle size laser analyzer.

In a third aspect, the present invention provides the use of alkanesulfonic acid or alkanolsulfonic acid in an electrolyte solution for the manufacture of silver or copper powder by electrowinning. EXAMPLES Description of measurements in the examples:

Scanning Electron Microscope (SEM): Zeiss Supra® 55 from Carl Zeiss AG.

Particle size measurement: Malvern Mastersizer 2000G.

In each example, the current efficiency (η) was calculated according to the following equation: n = m × 100% q × I × t Wherein η represents the current efficiency, expressed in %; m represents the mass of metal powder deposited by each cell in the t time period, expressed in g; I represents the current intensity, expressed in A; t represents the electroplating time period, expressed in hours; and q represents the electrochemical equivalent of the metal, copper is 1.186 g/(A h), and silver is 4.025 g/(A h).

Calculate the power consumption (W) according to the following equation: W = U × 1000 × 100% η×q where W represents energy consumption, expressed in kW·h/t; η represents current efficiency, expressed in %; and U represents average cell voltage, expressed in V. The manufacture embodiment 1.1 of embodiment 1 copper powder

Black CuO was dissolved in a dilute aqueous solution of methanesulfonic acid (MSA) to obtain a solution containing 12 g/L copper ions and 140 g/L free methanesulfonic acid as the electrolyte solution. This solution was poured into the electrolytic cell and kept at a temperature of 40 °C. The anode of the phosphor bronze plate and the cathode of the titanium plate are arranged in the electrolytic cell with a distance of 5 cm. Electrowinning was performed by applying a direct current with a current density of 13 A/dm ² for 15 minutes. The obtained copper particles are then removed from the cathode and separated from the electrolyte solution. The collected copper particles were filtered by vacuum filtration and washed with DI water, dried in a vacuum oven at a temperature of 60°C, and then subjected to reduction treatment by heating to 500°C in a reducing atmosphere of hydrogen.

The cell voltage is 2.3V (as determined by Kocour power supply), the current efficiency (η) is 89.32%, and the power consumption (W) is 2171 kW·h/t. The copper powder observed by SEM is sparse and thin dendritic crystals, as shown in Figure 1. The particle size D ₅₀ of the copper powder was 79.5 μm. Example 1.2

The method was carried out in the same manner as described in Example 1.1, except that the electrolyte solution was kept at a temperature of 25°C.

The cell voltage is 2.8 V, the current efficiency (η) is 82.7%, and the power consumption (W) is 2854 kW·h/t.

The particle size D ₅₀ of the copper powder is 81.6 μm. Example 1.3

The method was carried out in the same manner as described in Example 1.1, except that the electrolyte solution was kept at a temperature of 30°C.

The cell voltage is 2.5 V, the current efficiency (η) is 85.1%, and the power consumption (W) is 2476 kW·h/t.

The particle size _D50 of the copper powder is 89.2 μm. Example 1.4

The method was carried out in the same manner as described in Example 1.1, except that the electrolyte solution was kept at a temperature of 35°C.

The cell voltage is 2.6 V, the current efficiency (η) is 87.8%, and the power consumption (W) is 2496 kW·h/t.

The particle size D ₅₀ of the copper powder is 100.9 μm. Example 1.5

The method was carried out in the same manner as described in Example 1.1, except that the electrolyte solution was kept at a temperature of 45°C.

The cell voltage is 2.35 V, the current efficiency (η) is 89.16%, and the power consumption (W) is 2222 kW·h/t.

The particle size D ₅₀ of the copper powder is 78.4 μm. Example 1.6

The method was carried out in the same manner as described in Example 1.1, except that the electrolyte solution was kept at a temperature of 50°C.

The cell voltage is 2.2 V, the current efficiency (η) is 91.53%, and the power consumption (W) is 2026 kW·h/t.

The particle size D ₅₀ of the copper powder was 46.3 μm. Comparative Example 1.1

Copper sulfate pentahydrate was dissolved in sulfuric acid aqueous solution to obtain a solution containing 12 g/L copper ions and 142 g/L free sulfuric acid as an electrolyte solution. This solution was poured into the electrolytic cell and maintained at a temperature of 25 °C. The anode of the phosphor bronze plate and the cathode of the titanium plate are arranged in the electrolytic cell with a distance of 5 cm. Electrowinning was performed by applying a direct current with a current density of 13 A/dm ² for 15 minutes. The obtained copper particles are then removed from the cathode and separated from the electrolyte solution. The collected copper particles were filtered by vacuum filtration and washed with DI water, dried in a vacuum oven at a temperature of 60°C, and then subjected to reduction treatment by heating to 500°C in a reducing atmosphere of hydrogen.

The cell voltage is 2.3V (as determined by Kocour power supply), the current efficiency (η) is 79.86%, and the power consumption (W) is 2428 kW·h/t. The copper powder observed by SEM is a thick dendritic crystal, as shown in Figure 2.

The particle size _D50 of the copper powder is 99.3 μm. Embodiment 2 The manufacture embodiment 2.1 of silver powder

Black Ag ₂ O was dissolved in a dilute aqueous solution of methanesulfonic acid (MSA) to provide a solution containing 108 g/L silver ions and 15.25 g/L free methanesulfonic acid as the electrolyte solution. This solution was poured into the electrolytic cell and maintained at a temperature of 50 °C. The anode of the pure silver plate and the cathode of the stainless steel plate are arranged in the electrolytic cell with a distance of 3.5 cm. Electrowinning was performed by applying a direct current with a current density of 5 A/dm ² for 15 minutes. The silver particles obtained are then removed from the cathode and separated from the electrolyte solution. The collected silver particles were filtered by vacuum filtration and washed with DI water, dried in a vacuum oven at a temperature of 60°C.

The cell voltage is 1.23V (as determined by Kocour power supply), the current efficiency (η) is 98%, and the power consumption (W) is 312 kW·h/t. The silver powder observed by SEM is a granular crystal, as shown in FIG. 3 .

The particle size D ₅₀ of the silver powder was 328.8 μm, and the D ₉₀ was 525.4 μm.

Silver particles were observed to deposit on the cathode with slow and slight dendritic growth, as shown in Figure 4. Example 2.2

The method was carried out in the same manner as described in Example 2.1, except that the electrolyte solution was kept at a temperature of 25°C.

The cell voltage is 1.5 V, the current efficiency (η) is 95%, and the power consumption (W) is 392 kW·h/t.

The particle size D ₅₀ of the silver powder is 545.1 μm, and the D ₉₀ is 966.9 μm. Example 2.3

The method was carried out in the same manner as described in Example 2.1, except that the electrolyte solution was kept at a temperature of 40°C.

The cell voltage is 1.26 V, the current efficiency (η) is 96%, and the power consumption (W) is 326 kW·h/t.

The particle size D ₅₀ of the silver powder is 571.5 μm, while the D ₉₀ is 920.1 μm. Comparative Example 2.1

Black Ag ₂ O was dissolved in a dilute aqueous solution of nitric acid (HNO 3 ) to provide a solution containing 108 g/L silver ions and 10 g/L free nitric acid as electrolyte solution. This solution was poured into the electrolytic cell and maintained at a temperature of 25 °C. The anode of the pure silver plate and the cathode of the stainless steel plate are arranged in the electrolytic cell with a distance of 3.5 cm. Electrowinning was performed by applying a direct current with a current density of 5 A/dm ² for 15 minutes. The silver particles obtained are then removed from the cathode and separated from the electrolyte solution. The collected silver particles were filtered by vacuum filtration and washed with DI water, dried in a vacuum oven at a temperature of 60°C.

The cell voltage is 1.4V, the current efficiency (η) is 95.04%, and the power consumption (W) is 366 kW·h/t. The silver powder observed by SEM is a granular crystal, as shown in FIG. 5 . The particle size D ₅₀ of the silver powder was 78.7 μm and the D ₉₀ was 758.6 μm.

It was observed that silver particles were deposited on the cathode with rapid and severe dendritic growth, especially at the corners of the cathode, as shown in Fig. 6. Comparative Example 2.2

The method was carried out in the same manner as described in Comparative Example 2.1, except that the electrolyte solution was kept at a temperature of 40°C.

The cell voltage is 1.11V, the current efficiency (η) is 96%, and the power consumption (W) is 287 kW·h/t.

The particle size D ₅₀ of the silver powder is 395.2 μm, and the D ₉₀ is 648.1 μm. Comparative Example 2.3

The method was carried out in the same manner as described in Comparative Example 2.1, except that the electrolyte solution was kept at a temperature of 50°C.

The cell voltage is 1.04V, the current efficiency (η) is 98%, and the power consumption (W) is 264 kW·h/t.

The particle size D ₅₀ of the silver powder is 340.3 μm, and the D ₉₀ is 1167.3 μm.

As shown in Figures 7 and 8, silver powders produced according to the present invention at temperatures above 40°C have particle sizes at least comparable to silver powders conventionally produced with nitric acid electrolyte systems.

none

[ FIG. 1 ] shows a SEM image of copper powder produced by the method according to the present invention as described in Example 1.1.

[ FIG. 2 ] shows a SEM image of copper powder produced by a method not according to the present invention as described in Comparative Example 1.1.

[ FIG. 3 ] shows a SEM image of silver powder produced by the method according to the present invention as described in Example 2.1.

[ FIG. 4 ] Diagram showing the morphology of silver deposits on cathodes produced by the method according to the invention as described in Example 2.1.

[ FIG. 5 ] shows a SEM image of silver powder produced by a method not according to the present invention as described in Comparative Example 2.1.

[ FIG. 6 ] Diagram showing the morphology of silver deposits on cathodes produced by a method not according to the invention as described in Comparative Example 2.1.

[ FIG. 7 ] shows the particle size _D50 of the silver powder produced by the method according to the invention as described in Examples 2.1 to 2.3 and produced by the method not according to the invention as described in Comparative Examples 2.1 to 2.3 The particle size of the silver powder is D ₅₀ .

[ FIG. 8 ] shows the particle size _D90 of the silver powder produced by the method according to the invention as described in Examples 2.1 to 2.3 and produced by the method not according to the invention as described in Comparative Examples 2.1 to 2.3 The particle size of the silver powder is D ₉₀ .

Claims (11)

A method of producing metal powder in an electrolytic cell comprising an anode made of metal, a cathode and an electrolyte solution, the method comprising a) anodic dissolution to form metal ions in the electrolyte solution and cathodic deposition of metal particles from the electrolyte solution, b) removing the metal particles from the cathode into the electrolyte solution, and c) separating the metal particles from the electrolyte solution, in the metal is copper or silver, and The electrolyte solution contains (i) alkanesulfonic acid or alkanolsulfonic acid and (ii) a soluble metal salt of alkanesulfonic acid or alkanolsulfonic acid. The method according to claim 1, wherein the alkanesulfonic acid is selected from C ₁ -C ₁₂ -alkanesulfonic acids, preferably C ₁ -C ₆ -alkanesulfonic acids. The method of claim 1, wherein the alkanolsulfonic acid is selected from C ₂ -C ₁₂ -alkanolsulfonic acids, preferably C ₂ -C ₆ -alkanolsulfonic acids. The method of claim item 2, wherein the alkanesulfonic acid is selected from methanesulfonic acid, 1-ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, 1 -pentanesulfonic acid, 1-hexanesulfonic acid, 1-decanesulfonic acid, 1-dodecanesulfonic acid, methanedisulfonic acid, 1,1-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1 , 1-propanedisulfonic acid, 1,3-propanedisulfonic acid, 1,1-butanedisulfonic acid, 1,4-butanedisulfonic acid and any combination thereof. The method as any one of claims 1 to 4, wherein step a) is at 20°C to 70°C, preferably 30°C to 60°C, more preferably 40°C to 50°C within the temperature range. The method of claim 5, wherein what is produced is silver powder, and step a) is carried out at a temperature ranging from 40°C to 50°C, preferably from 45°C to 50°C. The method as in claim 5, wherein what is produced is copper powder, and step a) is carried out at a temperature ranging from 40°C to 50°C. The method according to any one of claims 1 to 7, further comprising an anti-oxidation step of the metal particles, preferably a reduction step under a hydrogen atmosphere. A copper powder or silver powder obtained or obtainable by the method according to any one of claims 1 to 8. A use of alkane sulfonic acid or alkanol sulfonic acid in electrolyte solution for producing silver powder or copper powder by electrolytic deposition. The use according to claim 10, wherein the alkanesulfonic acid or alkanolsulfonic acid is as defined in any one of claims 2-4.

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