AU2022325439A1

AU2022325439A1 - Process for electrolytic production of metal powder

Info

Publication number: AU2022325439A1
Application number: AU2022325439A
Authority: AU
Inventors: Jin Bo SONG; Jing Cheng XIA; Si Jun ZHU
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2021-08-13
Filing date: 2022-08-03
Publication date: 2024-02-22
Also published as: CN117813420A; TW202314047A; KR20240038984A; WO2023016896A1

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

PROCESS FOR ELECTROLYTIC PRODUCTION OF METAL POWDER

FIELD OF THE INVENTION

The present invention relates to a process for electrolytic production of metal powder and the metal powder obtained from the same.

BACKGROUND

Fine metal powders such as copper powder and silver powder are widely used in various applications, for example in electronic pastes, lubricants, catalysts, medicines and biofilters. Electrolytic deposition of metal powders has always been an important industrial process, as the process can provide metal powders with high quality under mild conditions and does not impose high requirements of starting materials.

In conventional processes of producing copper powder by electrolytic deposition, an aqueous copper sulfate solution comprising sulfuric acid was generally adopted. The process needs certain measures for protection against corrosive sulfuric acid release from the electrolyte solution into ambient, particularly under an elevated process temperature. In conventional processes of producing silver powder by electrolytic deposition, an aqueous silver nitrate electrolyte solution comprising nitric acid was generally adopted. The process also has the problem of nitric acid release from the electrolyte solution into ambient under elevated process temperature.

Additionally, it was found by the inventors of the present invention that the deposition of silver particles on the cathode is accompanied with quick growth of dendritic aggregates, especially at the corner of the cathode, in the conventional processes using a silver nitrate electrolyte solution. The dendritic aggregates may extend to anode and thus increase the risk of short circuit.

There is still a need of alternative processes for producing copper powder and silver powder by electrolytic deposition. It is desirable that the processes can provide the metal powders having comparable or even improved quality than those obtained from those conventional processes.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process for production of copper powder and/or silver powder without using an electrolyte solution comprising any corrosive acid which may release into ambient under an elevated electrolysis temperature. A further object of the present invention is to provide a process for production of copper powder or silver powder with desirable or even smaller particle size.

It has been found that the objects of the present invention can be achieved by using an electrolyte solution comprising a metal sulfonate and a sulfonic acid. Accordingly, in one aspect, the present invention provides 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

- 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.

In another aspect, the present invention provides the copper or silver powder obtained or obtainable by the process as described herein.

In a further aspect, the present invention provides use of an alkane sulfonic acid or alkanol sulfonic acid in an electrolyte solution for production of a silver or copper powder by electrolytic deposition.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an SEM image of the copper powder as produced by the process according to the present invention, as described in Example 1.1.

Fig. 2 shows an SEM image of the copper powder as produced by a process not according to the present invention, as described in Comparative Example 1.1.

Fig. 3 shows an SEM image of the silver powder as produced by the process according to the present invention, as described in Example 2.1.

Fig. 4 shows a morphology picture of the silver deposit on the cathode as produced by the process according to the present invention, as described in Example 2.1.

Fig. 5 shows an SEM image of the silver powder as produced by a process not according to the present invention, as described in Comparative Example 2.1.

Fig. 6 shows a morphology picture of the silver deposit on the cathode as produced by a process not according to the present invention, as described in Comparative Example 2.1.

Fig. 7 shows particle size D50 of the silver powder as produced by the process according to the present invention as described in Examples 2.1 to 2.3 and not according to the present invention as described in Comparative Examples 2.1 to 2.3.

Fig. 8 shows particle size Dgo of the silver powder as produced by the process according to the present invention as described in Examples 2.1 to 2.3 and not according to the present invention as described in Comparative Examples 2.1 to 2.3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described in detail hereinafter. It is to be understood that the present invention may be embodied in many different ways and shall not be construed as limited to the embodiments set forth herein. Unless mentioned 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 the present invention belongs.

As used herein, the singular forms “a”, “an” and “the” 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 interpreted in a non-limiting, open manner. That is, e.g., further components or elements may be present. The expressions “consists of” or “consists essentially of” or cognates may be embraced within “comprises” or cognates.

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

In the first aspect, the present invention provides 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

- 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. As well-known, the anode is made of the metal to be deposited on cathode and thus supplies metal ions into the electrolyte solution continuously during the operation of the electrolytic cell. Generally, the anode may be made of the metal having a purity of at least 95%, for example at least 98% or at least 99%. In the process according to the present invention, the anode is made of copper or silver having a purity within above ranges.

There is no particular restriction to the material of cathode. The cathode useful for the process according to the present invention may be made of, for example, stainless steel or titanium.

The anode and the cathode may be arranged at a distance of 1 cm to 10 cm, preferably 3 cm to 6 cm, for example 3 cm to 5.5 cm.

The inventors of the present invention found that the electrolyte solution comprising (i) an alkane sulfonic acid or alkanol sulfonic acid and (ii) a soluble metal salt of an alkane sulfonic acid or alkanol sulfonic acid is effective for producing silver and copper powders under an elevated electrolysis temperature, without the problem of acid release into ambient.

Useful alkane sulfonic acids as the component (i) may be Ci-Ci2-alkane sulfonic acids, preferably Ci-Ce-alkane sulfonic acids. The alkane sulfonic acids may be monosulfonic acids 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 alkane disulfonic 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 alkane sulfonic acid or any mixture of two or more alkane sulfonic acids may be used in the electrolyte solution in the process according to the invention.

Useful alkanol sulfonic acids as the component (i) may be C2-Ci2-alkanol sulfonic acids, preferably C2-Ce-alkanol sulfonic acids, i.e., hydroxy substituted C2-C12-, preferably C2-C6- alkane sulfonic acids. The hydroxy may be on a terminal or internal carbon of alkyl chain of the alkane sulfonic acids. Examples of useful alkanol sulfonic 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, 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, 2-hydroxy- 1 -hexanesulfonic acid, 2-hydroxy-1- decanesulfonic acid and 2-hydroxy-1-dodecanesulfonic acid. One alkanol sulfonic acid or any mixture of two or more alkanol sulfonic acids may be used in the electrolyte solution in the process according to the invention.

The alkane sulfonic acids and alkanol sulfonic acids may be those prepared by any methods known in the art or commercially available ones without particular restrictions. The alkane sulfonic acid or alkanol sulfonic acid as the component (i) may be comprised in the electrolyte solution at a concentration in a range of 1 to 200 grams per liter (g/L) of the electrolyte solution, particularly 5 to 180 g/L, preferably 10 to 150 g/L.

Herein, the soluble metal salt of an alkane sulfonic acid or alkanol sulfonic acid as the component (ii) refers to a soluble silver or copper salt of alkane sulfonic acid or alkanol sulfonic acid. The soluble silver or copper salt of alkane sulfonic acid or alkanol sulfonic acid will also be referred to as soluble metal sulfonate hereinbelow.

The alkane sulfonic acid or alkanol sulfonic acid from which the soluble metal sulfonate is derived may be same as or different from the alkane sulfonic acid or alkanol sulfonic acid as the component (i), and selected from those as described hereinabove for the component (i).

Preferably, the soluble metal sulfonate is a soluble silver or copper salt of the alkane sulfonic acid or alkanol sulfonic acid as the component (i).

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

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

The electrolyte solution may be prepared by any known processes, for example by dissolving the metal (i.e. , copper or silver), an oxide of the metal, a hydroxide of the metal, or a carbonate of the metal in a solution of the alkane sulfonic acid or alkanol sulfonic acid as described hereinabove, to provide a solution with desired concentrations of the metal ions and the sulfonic acid.

The electrolyte solution may optionally comprise one or more additives known useful in the art, for example, gelatins derived from collagen (e.g., animal glue), glucose, urea. Some inorganic additives may also be mentioned, for example cupric chloride to improve the electrical conductivity or adjust the pH of the electrolyte solution in the copper powder production. The additives, if present, may be comprised in the electrolyte solution at concentration of up to 20 g/L, more preferably up to 10 g/L.

In some embodiments, the present invention provides a process for production of 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 alkane sulfonic acid or alkanol sulfonic acid and (ii) a soluble silver alkane sulfonate or alkanol sulfonate.

In those embodiments of the process for production of silver powder, the alkane sulfonic acid or alkanol sulfonic acid as the component (i) is preferably comprised in the electrolyte solution at a concentration in a range of 1 to 50 grams per liter (g/L) of the electrolyte solution, particularly 5 to 30 g/L, preferably 10 to 20 g/L. Additionally or alternatively, the soluble silver alkane sulfonate or alkanol sulfonate as the component (ii) is preferably comprised in the electrolyte solution at a concentration in a range of 50 to 200 g/L of the electrolyte solution, particularly 60 to 150 g/L, preferably 80 to 120 g/L, calculated as silver ions.

In some other embodiments, the present invention provides a process for production of 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 alkanol sulfonic acid and (ii) a soluble copper alkane sulfonate or alkanol sulfonate.

In those embodiments of the process for production of copper powder, the alkane sulfonic acid or alkanol sulfonic acid as the component (i) is preferably comprised in the electrolyte solution at a concentration in a range of 50 to 200 grams per liter (g/L) of the electrolyte solution, particularly 80 to 200 g/L, preferably 100 to 160 g/L. Additionally or alternatively, the soluble copper alkane sulfonate or alkanol sulfonate as the component (ii) is preferably comprised in the electrolyte solution at a concentration in a range of 1 to 50 g/L of the electrolyte solution, particularly 5 to 30 g/L, preferably 5 to 15 g/L, calculated as copper ions.

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

The electrolyte solution may be pumped at a flow rate of about 5 to 20 liters per minute (L/min) during step a). The electrolyte solution may be pumped from a reservoir into the electrolytic cell from the top and exit from the bottom of the electrolytic cell, or may be pumped into the electrolytic cell from the bottom and exit 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/dm² (ASD), particularly 3 to 15 A/dm², for example 3 to 10 A/dm² for the production of silver powder, and 8 to 15 A/dm² for the production of copper powder.

The anodic dissolution and cathodic deposition in step a) are generally carried out for a period of 10 to 60 mins, for example 10 to 30 mins, before removing the metal particles deposited on the cathode in step b).

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

In step c), the electrolyte solution comprising the metal particles as obtained from step b) are subjected to an isolation to provide the metal powder. Optionally, the isolated meal powder may further be subjected to a post treatment including washing, drying and/or anti-oxidation treatment. The post treatment may be carried out with any conventional means. For example, the isolated meal powder may be washed with deionized water, dried under vacuum and reduced under an atmosphere of hydrogen.

Accordingly, the process according to the present invention may further comprises following steps: d) washing the metal particles isolated from step c), preferably with deionized water, e) vacuum drying, and f) anti-oxidation of the metal particles, preferably reduction under an atmosphere of hydrogen.

In some illustrative embodiments, the present invention provides a process for production of a silver powder in an electrolytic cell comprising an anode made of silver, a cathode and an electrolyte solution, which comprises a) anodic dissolution to form silver ions in the electrolyte solution and cathodic deposition of silver particles from the electrolyte solution, b) removal of the silver particles from the cathode into the electrolyte solution, and c) isolation of the silver particles from the electrolyte solution, wherein the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid and (ii) a soluble silver Ci-Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate.

Preferably, in the illustrative embodiments of the process for production of silver powder, the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid at a concentration in a range of 1 to 50 g/L of the electrolyte solution, and (ii) a soluble silver Ci- Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate at a concentration of 50 to 200 g/L of the electrolyte solution.

More preferably, in the illustrative embodiments of the process for production of silver powder, the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid at a concentration in a range of 5 to 30 g/L, preferably 10 to 20 g/L of the electrolyte solution, and (ii) a soluble silver Ci-Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate at a concentration of 60 to 150 g/L of the electrolyte solution, calculated as silver ions.

Most preferably, in the illustrative embodiments of the process for production of silver powder, the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid at a concentration in a range of 5 to 30 g/L, preferably 10 to 20 g/L of the electrolyte solution, and (ii) a soluble silver Ci-Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate at a concentration of 80 to 120 g/L of the electrolyte solution, calculated as silver ions.

In any of the illustrative embodiments of the process for production of 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 process for production of copper powder in an electrolytic cell comprising an anode made of copper, a cathode and an electrolyte solution, which comprises a) anodic dissolution to form copper ions the in the electrolyte solution and cathodic deposition of copper particles from the electrolyte solution, b) removal of the copper particles from the cathode into the electrolyte solution, and c) isolation of the copper particles from the electrolyte solution, wherein the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid and (ii) a soluble copper Ci-Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate.

Preferably, in the illustrative embodiments of the process for production of copper powder, the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid at a concentration in a range of 50 to 200 g/L of the electrolyte solution, and (ii) a soluble silver Ci- Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate at a concentration of 1 to 50 g/L of the electrolyte solution.

More preferably, in the illustrative embodiments of the process for production of copper powder, the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid at a concentration in a range of 80 to 200 g/L, preferably 100 to 160 g/L of the electrolyte solution, and (ii) a soluble silver Ci-Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate at a concentration of 5 to 30 g/L of the electrolyte solution, calculated as copper ions.

Most preferably, in the illustrative embodiments of the process for production of copper powder, the electrolyte solution comprises (i) a Ci-Ce-alkane sulfonic acid or alkanol sulfonic acid at a concentration in a range of 80 to 200 g/L, preferably 100 to 160 g/L of the electrolyte solution, and (ii) a soluble silver Ci-Ce-alkane sulfonate or Ci-Ce-alkanol sulfonate at a concentration of 5 to 15 g/L of the electrolyte solution, calculated as copper ions.

In any of the illustrative embodiments of the process for production of copper powder, step a) is carried out at a temperature in the range of 40 to 50 °C.

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

The copper powder obtained or obtainable by the process according to the present invention has a particle size D50 in the range of 20 to 120 microns (pm), preferably 30 to 100 pm, more preferably 40 to 90 pm, most preferably 40 to 80 pm. The silver powder obtained or obtainable by the process according to the present invention has a particle size D50 in the range of 100 to 600 microns (pm), preferably 150 to 500 pm, more preferably 200 to 400 pm. Alternatively or additionally, the silver powder obtained or obtainable by the process according to the present invention has a particle size D90 in the range of 200 to 1 ,000 microns (pm), preferably 400 to 800 pm.

D50 is the diameter value at which 50 % of the total number of particles as characterized consists of particles with a diameter less than the value, as measured by a particle size laser analyzer.

D90 is the diameter at which 90% of the total number of particles as characterized consists of particles with a diameter less than this value, as measured by a particle size laser analyzer.

In the third aspect, the present invention provides use of an alkane sulfonic acid or alkanol sulfonic acid in an electrolyte solution for production of a silver or copper powder by electrolytic deposition.

Examples

Description of Measurements in Examples:

Scanning electron microscopy (SEM): Zeiss Supra® 55 from Carl Zeiss AG.

Particle size measurement: Malvern Mastersizer 2000G.

In each example, the current efficiency (q) was calculated in accordance with the following equation: in which q represents current efficiency, expressed in %; m represents mass of the metal powder deposited per cell over a period of t, expressed in g;

I represents electric current intensity, expressed in A; t represents period of electroplating, expressed in hour; and q represents electrochemical equivalent of the metal, which is 1.186 g/(A h) for copper and 4.025 g/(A h) for silver.

Electrical energy consumption (W) was calculated in accordance with the following equation:

U x 1000 in which

W represents energy consumption, expressed in kW h/t; q represents current efficiency, expressed in %; and II represents average bath voltage, expressed in V.

Example 1 Production of Copper powder

Example 1.1

Black CuO was dissolved in an aqueous diluent solution of methanesulfonic acid (MSA) to provide a solution containing 12 g/L of copper ions and 140 g/L of free methanesulfonic acid as the electrolyte solution. The solution was poured into an electrolytic cell and kept at a temperature of 40 °C. An anode of phosphorus copper plate and a cathode of titanium plate were arranged in the electrolytic cell at a distance of 5 cm. The electrolytic deposition was conducted by applying a direct current with the current density of 13 A/dm² for 15mins. Then, the obtained copper particles were removed from the cathode and isolated from the electrolyte solution. The collected copper particles were filtered with vacuum filtration and washed by DI water, dried at a temperature of 60 °C in a vacuum drying oven, then subjected to reduction treatment by heating to 500 °C in a reducing atmosphere of hydrogen.

The bath voltage is 2.3V, as determined by Kocour power supply, the current efficiency (q) is 89.32% and the electrical energy consumption (W) is 2171 kW h/t. Sparse and thin dendritic crystals were observed via SEM for the copper powder, as shown in Figure 1. The copper powder has a particle size D50 of 79.5 pm.

Example 1.2

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

The bath voltage is 2.8 V, the current efficiency (q) is 82.7% and the electrical energy consumption (W) is 2854 kW h/t.

The particle size D50 of the copper powder is 81.6pm.

Example 1.3

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

The bath voltage is 2.5 V, the current efficiency (q) is 85.1% and the electrical energy consumption (W) is 2476 kW h/t.

The particle size D50 of the copper powder is 89.2 pm. Example 1.4

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

The bath voltage is 2.6 V, the current efficiency (q) is 87.8% and the electrical energy consumption (W) is 2496 kW h/t.

The particle size D50 of the copper powder is 100.9pm.

Example 1.5

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

The bath voltage is 2.35 V, the current efficiency (q) is 89.16% and the electrical energy consumption (W) is 2222 kW h/t.

The particle size D50 of the copper powder is 78.4pm.

Example 1.6

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

The bath voltage is 2.2 V, the current efficiency (q) is 91.53% and the electrical energy consumption (W) is 2026 kW h/t.

The particle size D50 of the copper powder is 46.3 pm.

Comparative Example 1.1

Copper sulfate pentahydrate was dissolved in an aqueous sulfuric acid solution to obtain a solution containing 12 g/L copper ions and 142 g/L free sulfuric acid as the electrolyte solution. The solution was poured into the electrolytic cell and kept at a temperature of 25 °C. An anode of phosphorus copper plate and a cathode of titanium plate were arranged in the electrolytic cell at a distance of 5 cm. The electrolytic deposition was conducted by applying a direct current with a current density of 13 A/dm² for 15 minutes. Then, the obtained copper particles were removed from the cathode and isolated from the electrolyte solution. The collected copper particles were filtered with vacuum filtration and washed by DI water, dried at a temperature of 60 °C in a vacuum drying oven, and then subjected to a reduction treatment by heating to 500 °C in a reducing atmosphere of hydrogen.

The bath voltage is 2.3V, as determined by Kocour power supply, the current efficiency (q) is 79.86% and the electrical energy consumption (W) is 2428 kW h/t. Thick dendritic crystals were observed via SEM for the copper powder, as shown in Figure 2.

The copper powder has a particle size D50 of 99.3 pm.

Example 2 Production of Silver powder

Example 2.1

Black Ag2<D was dissolved in an aqueous diluent solution of methanesulfonic acid (MSA) to provide a solution containing 108 g/L of silver ions and 15.25 g/L of free methanesulfonic acid as the electrolyte solution. The solution was poured into the electrolytic cell and kept at a temperature of 50 °C. An anode of pure silver plate and a cathode of stainless steel plate were arranged in the electrolytic cell at a distance of 3.5 cm. The electrolytic deposition was conducted by applying a direct current with the current density of 5 A/dm² for 15mins. Then, the obtained silver particles were removed from the cathode and isolated from the electrolyte solution. The collected silver particles were filtered with vacuum filtration and washed by DI water, dried at a temperature of 60 °C in a vacuum drying oven.

The bath voltage is 1.23V, as determined by Kocour power supply, the current efficiency (q) is 98% and the electrical energy consumption (W) is 312 kW h/t. Granular crystals were observed via SEM for the silver powder, as shown in Figure 3.

The particle size D50 of the silver powder is 328.8 pm and D90 is 525.4pm.

It was observed that the silver particles were deposited on the cathode with slow and slight dendritic growth, as shown in Figure 4.

Example 2.2

The process was carried out in the same manner as described in Example 2.1 expect the electrolyte solution was kept at a temperature of 25 °C.

The bath voltage is 1.5 V, the current efficiency (q) is 95% and the electrical energy consumption (W) is 392 kW h/t.

The particle size D50 of the silver powder is 545.1 pm and D90 is 966.9pm.

Example 2.3

The process was carried out in the same manner as described in Example 2.1 expect the electrolyte solution was kept at a temperature of 40 °C.

The bath voltage is 1.26 V, the current efficiency (q) is 96% and the electrical energy consumption (W) is 326 kW h/t. The particle size D₅o of the silver powder is 571.5 pm and Dgo is 920.1 pm.

Comparative Example 2.1

Black Ag2<D was dissolved in an aqueous diluent solution of nitric acid (HNO3) to provide a solution containing 108 g/L silver ions and 10 g/L free nitric acid as the electrolyte solution. The solution was poured into the electrolytic cell and kept at a temperature of 25 °C. An anode of pure silver plate and a cathode of stainless steel plate were arranged in the electrolytic cell at a distance of 3.5 cm. The electrolytic deposition was conducted by applying a direct current with a current density of 5 A/dm² for 15 minutes. Then, the obtained silver particles were removed from the cathode and isolated from the electrolyte solution. The collected silver particles were filtered with vacuum filtration and washed by DI water, dried at a temperature of 60 °C in a vacuum drying oven.

The bath voltage is 1.4V, the current efficiency (q) is 95.04% and the electrical energy consumption (W) is 366 kW h/t. Granular crystals were observed via SEM for the silver powder, as shown in Figure 5. The particle size D50 of the silver powder is 78.7 pm and Dgo is 758.6 pm.

It was observed that the silver particles were deposited on the cathode with quick and severe dendritic growth, especially at the corner of the cathode, as shown in Figure 6.

Comparative Example 2.2

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

The bath voltage is 1.11V, the current efficiency (q) is 96% and the electrical energy consumption (W) is 287 kW h/t.

The particle size D50 of the silver powder is 395.2 pm and Dgo is 648.1 pm.

Comparative Example 2.3

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

The bath voltage is 1.04V, the current efficiency (q) is 98% and the electrical energy consumption (W) is 264 kW h/t.

The particle size D50 of the silver powder is 340.3 pm and Dgo is 1167.3 pm.

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

Claims

1. 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

2. The process according to claim 1, wherein the alkane sulfonic acid is selected from Ci- Ci2-alkane sulfonic acids, preferably Ci-Ce-alkane sulfonic acids.

3. The process according to claim 1 , wherein the alkanol sulfonic acid is selected from C2- Ci2-alkanol sulfonic acids, preferably C2-Ce-alkanol sulfonic acids.

4. The process according to claim 2, wherein the alkane sulfonic 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-butenedisulfonic acid, and any combinations thereof.

5. The process according to any of claims 1 to 4, wherein step a) is carried out at a temperature in the range of 20 °C to 70 °C, preferably 30 °C to 60 °C, more preferably 40 to 50 °C.

6. The process according to claim 5, wherein silver powder is produced and step a) is carried out at a temperature in the range of 40 to 50 °C, preferably 45 to 50°C.

7. The process according to claim 5, wherein copper powder is produced and step a) is carried out at a temperature in the range of 40 to 50 °C.

8. The process according to any one of claims 1 to 7, which further comprises a step of antioxidation of the metal particles, preferably a step of reduction under an atmosphere of hydrogen.

9. Copper or silver powder obtained or obtainable by the process according to any of claims 1 to 8.

10. Use of an alkane sulfonic acid or alkanol sulfonic acid in an electrolyte solution for production of a silver or copper powder by electrolytic deposition.

11. Use according to claim 10, wherein the alkane sulfonic acid or alkanol sulfonic acid is as defined in any of claims 2 to 4.