RU2553319C1 - Method of metal powder manufacturing by electrolysis - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes simultaneous use of soluble and insoluble anodes. Water solution of electrolyte contains salt of the appropriate metal and buffer additions. The soluble and insoluble anodes are arranged in separate cells having common electrolyte recirculating circuit and independent cathodes. The soluble and insoluble anodes are connected to separate current sources to ensure permanent electrolysis conditions in the cell with soluble anodes due to deposition in the cell with insoluble anodes of the surplus metal ions on the cathode, and hydrogen ions separation on insoluble anode.

EFFECT: invention ensures electrolyte updating during electrolysis as per metal ions content and pH value, and reduces operation expenses.

6 dwg

Description

The invention relates to the field of powder metallurgy, in particular to methods for producing metal powders by electrolysis.

Obtaining electrolytic metal powders is based on the electrolysis of aqueous solutions containing the salts of the corresponding metals and buffer additives (Kudra O., Gitmen E., “Electrochemical production of metal powders”, Kiev, 1952) [1].

There are a number of methods for producing metal powder, which include dissolving cast anodes and isolating metal powder at the cathode described in the USSR inventor certificates for invention No. 1025757 “Method for producing magnetic powder” (CL IPC C25C 5/02, priority date 02/01/1982) [2 ], No. 1104193 “Method for producing highly dispersed magnetic powder” (class MPK S25C 5/02, priority date 04/08/1983) [3], No. 956627 “Method for producing highly dispersed magnetic powders” (class MPK C25C 5/02, priority date 02/20/1981) [4], No. 1183566 "Electrolyte for the production of metal powders" (class MP To C25C 5/02, priority date 06/13/1983) [5], No. 1199827 “Electrolyte for the production of nickel powder” (CL IPC C25C 5/02, priority date 01/10/1983) [6], No. 1257120 “Method for the production of nickel powder from sulfate-chloride electrolyte ”(CL IPC C25C 5/02, priority date 04/15/1985) [7].

There is a method of producing metal powder in the processing of metal-containing waste, described in the USSR author's certificate for invention No. 2319 "Method for the electrolytic processing of brass into powdered copper and zinc chloride" (class MPK C25C 5/00, priority date 04/15/1924) [8], consisting in the smelting of metal-containing waste to obtain cast anodes, and the subsequent operation of refining cast anodes to obtain a powdery material.

A number of methods for producing metal powder are known, which consist in preparing an electrolyte from salts and subsequent electrolysis of the resulting solution using insoluble anodes described in the USSR copyright certificates for invention No. 933811 “Method for the electrolytic production of nickel powder” (class IPC C25C 5/02, priority date 03/26/1980) [9], No. 189155 “Method for the electrolytic production of highly dispersed magnetic cobalt powder” (class MPK S25C 5/00, priority date 01/06/1965) [10], No. 990882 “Electrolyte for producing metal powder of alloy c NCA nickel "(Cl. IPC S25S 5/02, priority date 23.07.1980) [11].

There are a number of methods for producing metal powder in the processing of metal-containing materials and waste, which consists in dissolving them in various solvents and subsequent electrolysis of the resulting solution using insoluble anodes, described in RF patents for invention No. 2469111 "Method for producing copper powders from copper-containing ammonia waste" (cl IPC С22В 7/00, priority date 04/05/2011) [12], No. 2157417 "Method for the disposal of copper-containing waste" (cl. IPC С22В 7/00, priority date 06/18/1996) [13], No. 2126312 "Method for producing metal since casing, copper oxides and copper foil "(CL IPC B22F 9/23, priority date 03/17/1994) [14], No. 2134311" Method for producing metal powder, copper oxides and copper foil "(CL IPC C25C 1/12, priority date 06/17/1996) [15], application for Eurasian patent No. 200700275 “Method for the electrolytic production of copper powder in a flowing electrolytic cell” (class IPC C25C 5/02, priority date 15.07.2005) [16].

The disadvantages of these methods is:

- the presence of an additional operation of smelting and casting anodes;

- the lack of the possibility of complete dissolution of the cast anode;

- the inability to recycle all types of metal-containing waste due to the inefficiency and impossibility of the smelting process of some materials;

- lack of stationary electrolysis conditions;

- obtaining a powder with an uneven particle size;

- short-term use of the solution with the subsequent need for its adjustment in composition or complete replacement;

- high consumption of reagents for dissolving waste.

There are a number of methods for producing metal powder, consisting in the use of combined anodes: soluble and insoluble, described in the RF patent for invention No. 2022717 "Method for producing copper powder by electrolysis from sulfate solutions and a device for its implementation" (CL IPC B22F 9/16, date priority 03.07.1991) [17], USSR copyright certificates for invention No. 410127 “Method for the electrolytic production of cobalt-tungsten alloys” (class IPC C25C 1/24, priority date 02.28.1972) [18], No. 33680 “Method for electrolytic joint precipitation I have cadmium and iron in sponge form ”(CL IPC С25С 1/06, priority date 09/09/1931) [19].

The disadvantages of these methods is:

- the presence of an additional operation of smelting and casting anodes;

- the lack of the possibility of complete dissolution of the cast anode;

- the lack of regulation in the process of electrolysis of the dissolution of the soluble anode;

- the difficulty in choosing the ratio of the areas of soluble and insoluble anodes, since the ratio of the areas of the combined anodes changes during the electrolysis time.

A known method of improving methods for producing pure metallic cobalt powder (UK patent for invention No. 403.281 (class IPC C25C 5/02, priority date 04.29.1932) [20], according to which electrolytic cobalt powder can be obtained by electrolysis of an aqueous solution of cobalt salt (mainly cobalt sulfate) using an anode, mainly from platinum or pure cobalt, and also when combining two types of anodes, which form a special platinum section that does not form electrolytic th screen relative to cobalt placed in this place.

In this method, the simultaneous use of soluble and insoluble anodes reduces the intensity of dissolution of cobalt plates by reducing their working surface. Also, the use of a backfill type anode design in the form of a platinum section with cobalt material placed in it allows you to load other types of metal-containing material for processing without preliminary melting and casting anodes. At the same time, the specified method for producing cobalt powder still has difficulty in choosing the optimal ratio of the area of the soluble anode to the area of the insoluble anode, which allows you to maintain a constant concentration of cobalt ions during a long electrolysis process. In addition, over time, the cobalt plate dissolves in the platinum section, which leads to a change in the working surface of the soluble anode and, therefore, to a violation of the ratio of the areas of the anodes of the two types and a change in the composition of the electrolyte.

The closest in technical essence and therefore selected as a prototype is the method for producing electrolytic metal powders described in the patent of the Russian Federation for invention No. 2420613 "Method for producing electrolytic metal powders" (CL IPC C25C 5/02, priority date 04/13/2010) [21 ], according to which electrolytic metal powders can be obtained by electrolysis from an aqueous solution containing a salt of the corresponding metal and buffer additives. In this case, soluble and insoluble anodes are used, which are connected to separate current sources to control the dissolution of the soluble anode during the electrolysis process and the concentration of metal ions in the solution by adjusting the ratio of the anode current strengths of the soluble and insoluble anodes at a constant cathode current density.

In the prototype, a constant value of the cathodic current density (a prerequisite for obtaining a powder with specified characteristics) is achieved by the constancy of the cathode area and the sum of the currents on the soluble and insoluble anode. The application of the technical solution of the prototype is described by the example of processes for the production of nickel and cobalt powders, in which anode of the filling type is used, which allows the processing of metal-containing waste.

However, according to the prototype, with an increase in the number of cells, it will also be necessary to increase the number of current sources used. So, for example, according to the prototype, for a device consisting of two cells, 3 current sources are required, for three cells - four current sources, for four five and so on. This fact leads to clutter of the installation and an increase in operating costs.

The increase in the cells used can be caused by the need to increase the powder productivity of the installation and, therefore, for devices containing more than one cell, a different approach is required.

The objective of the proposed technical solution is to create a method for processing metal-containing waste into metal powder under constant conditions (electrolysis mode) of powder production for a long time with constant characteristics and with the possibility of adjusting the electrolyte composition in the electrolysis process according to the content of the metal ion and the pH value of the solution and lowering operating costs.

These tasks in the inventive method for producing metal powder by electrolysis are solved due to the fact that in the known method, including obtaining metal powders by electrolysis from an aqueous solution containing a salt of the corresponding metal and buffer additives, using soluble and insoluble anodes at the same time, it is proposed, according to the claimed technical solution , additionally arrange soluble and insoluble anodes in separate cells having a common electrolyte circulation circuit and independent cathodes, and connect it to their individual sources of constant current for electrolysis conditions in the cell with soluble anodes by precipitation in a cell with insoluble anodes excess of metal ions on the cathode and the evolution of hydrogen ions at the anode. In this case, the processing of metal waste (screenings of powders, scrap, scrap, etc.) is carried out by dissolving them at the anode of the filling type and depositing the metal on the cathode in the form of a powder.

The claimed technical solution is illustrated by drawings and diagrams presented in figures 1, 2 and 3.

Figure 1 presents examples of embodiments of the backfill anode. The filling anode consists of a fabric cover (not shown in Fig. 1), a basket (1) placed in it of insoluble and current-conducting material, such as titanium, and a soluble anode material filled into it (powder screenings, scrap, scrap, etc.). d.). The filling anodes are placed in a fabric cover in order to exclude the possibility of powder contamination with anode sludge.

Figure 2 schematically shows the installation used in the claimed method for producing metal powder by electrolysis and the scheme of its power supply, the installation consists, for example, of four cells, where 2 are working cells with soluble anodes, 3 is a regenerating cell with insoluble anodes, 4 and 5 - current sources, 6 - cathodes in cells with soluble anodes, 7 - cathodes in a cell with insoluble anodes, 8 - charge soluble anodes, 9 - insoluble anodes, 10 - electrolyzer body, 11 - bulkheads between cells that are impermeable to electrolyte.

Figure 3 shows a variant of the electrolyte circulation scheme, for example, four cells, where 12 are working cells with soluble anodes, 13 is a regenerating cell with insoluble anodes, 14 is a centrifugal circulation pump, 15 is an electrolyte circulation circuit.

According to the claimed technical solution, this method of producing powder by electrolysis allows us to ensure the constancy of the electrolyte composition in terms of pH and ion content of the deposited metal for a long time using processes that occur in a cell with insoluble anodes:

- deposition of excess metal ions on the cathode in a compact form;

- the release of hydrogen ions at the anode.

In the claimed technical solution, the cell with insoluble anodes is regenerative. The number of cathodes and anodes in the regenerating cell and the supplied current strength varies and depends on the nature of the metal ion and the magnitude of the increase in its concentration in the electrolyte. The regenerating cell performs the function of controlling the electrolysis process, since the current supplied to it is regulated, if necessary, during the entire electrolysis process.

The metal cathode sheet obtained in the regenerating cell can be used as a raw material for producing metal powder by loading it into the soluble anode basket of the charge cell of the working cell type. This opportunity makes the inventive method of producing a powder of metal waste-free production.

When applying the claimed technical solution, the used electrolysis unit may contain any number of cells, any suitable shape, combination and number of cathodes and anodes in them.

The powder that has grown on the cathodes can be cleaned periodically by a device for removing powder of any known design. The choice of design for powder removal devices depends on the shape of the anodes and cathodes used.

The claimed technical solution can be used to obtain any metal powder or alloy of metal powders that can be obtained by electrolysis of aqueous solutions.

Case Studies

An example of a specific application of the proposed method for producing metal powder by electrolysis can be a description of the technological process for producing nickel powder in an electrolyzer with a volume of 3 m ³ with a conical bottom, for example, with four cells, one of which is regenerative. The power supply circuit of the cells is shown in figure 2. Each working cell with a soluble anode (2) contains two cathodes (6) in the form of a titanium plate and three soluble bulk anodes (8). The bulk soluble anode (8) consists of a fabric cover (not shown in FIG. 2) made of polypropylene, a titanium basket (1), the construction of which is shown in FIG. 1, and nickel powder screenings placed therein. A regenerating cell with an insoluble anode (3) contains two ruthenium oxide insoluble anodes (9) and three cathodes (7) in the form of a nickel plate. The electrolysis was carried out in an electrolyte containing nickel sulfate in an amount of 10 g / l and a buffer additive, which was taken as ammonium sulfate in an amount of 60 g / l, with an electrolyte pH of 5.5 ± 0.5 and a temperature of 50 ± 5 ° С. The cathodic current density in the working cells with a soluble anode (2) is 20 A / dm ² . The cathodic current density in the regenerating cell with an insoluble anode (3) is 3.5 A / dm ² . When applying electric current to the electrodes of the working cells with a soluble anode (2), the following electrochemical reactions occur:

at the cathode (6):

Ni ²⁺ + 2e → Ni;

2H ⁺ 2e → H ₂ ,

on the backfill soluble anode (8):

Ni-2e → Ni ²⁺ ;

H ₂ O-2e → 2H ⁺ + 0.5O ₂ .

When applying electric current to the electrodes of the regenerating cell with an insoluble anode (3), the following electrochemical reactions proceed:

at the cathode (7):

Ni ²⁺ + 2e → Ni;

2H ⁺ + 2-> H ₂ ;

on an insoluble anode (9):

H ₂ O-2e → 2H ⁺ + 0.5O ₂ .

The nickel formed in the cell with soluble anodes on the cathode (6) in powder form is brushed off every 30 minutes using an automated guillotine-type powder removal device. A device that cleans the powder immediately on both sides of the electrode is set in motion after a certain time with the load on the electrodes turned off. Nickel powder accumulated over 24 hours at the bottom of the bath is filtered off from the electrolyte, washed with demineralized water, dried, heat treated in a hydrogen atmosphere and sieved. The average particle size of the obtained nickel powder is 28 μm. Figure 4 presents the particle size distribution (determined by sedimentation) of nickel powder obtained by the above-described inventive method, which confirms its uniformity when using the claimed technical solution.

A second example of the application of the claimed technical solution can be a description of the technological process for producing copper powder (Fig. 5) in an electrolyzer (16) with a volume of 10 liters, for example, with two cells, one of which is regenerative. The power supply circuit of the cells for producing copper powder is shown in Fig.5. The cells are separated by a septum impermeable to electrolyte (17). A working cell with a soluble anode (18) contains a cathode (19) in the form of a rod of titanium and two soluble bulk anodes (20). The bulk soluble anode (20) consists of a fabric cover (not shown in FIG. 5) made of polypropylene, a titanium basket (design is shown in FIG. 1) and BrKMts3-1 grade copper shavings placed in it. A regenerating cell with an insoluble anode (21) contains one insoluble lead anode (22) and two cathodes (23) in the form of a copper plate. The electrodes of the working cell with a soluble anode (18) are connected to a current source (24). The electrodes of the regenerating cell with an insoluble anode (21) are connected to a current source (25). The electrolysis was carried out in an electrolyte containing copper sulfate in an amount of 13.5 g / l and a buffer additive, which was taken as sulfuric acid in an amount of 170 g / l at an electrolyte temperature of 50 ± 5 ° C. The cathodic current density in the working cell with a soluble anode (18) is 31 A / dm ² . The cathodic current density in the regenerating cell with an insoluble anode (21) is 2.8 A / dm ² . When applying electric current to the electrodes of the working cell with a soluble anode (18), the following electrochemical reactions proceed:

at the cathode (19):

Cu ²⁺ + 2e → Cu;

2H ⁺ + 2e → H ₂ ;

on a soluble anode (20):

Cu-2e → Cu ²⁺ ;

H2O-2e → 2H ⁺ + 0.5O ₂ .

When an electric current is applied to the electrodes of a regenerating cell with an insoluble anode (21), the following electrochemical reactions proceed:

at the cathode (23):

Cu ²⁺ + 2e → Cu;

2H ⁺ + 2e → H ₂ ;

on an insoluble anode (22):

H2O-2e → 2H ⁺ + 0.5O ₂ .

The copper formed on the cathode (19) in powder form is cleaned every 90 minutes with the load on the electrodes turned off. Copper powder accumulated over the course of 24 hours at the bottom of the bath is filtered off from the electrolyte, washed with distilled water, dried, heat treated in a hydrogen atmosphere and sieved. The average particle size of the obtained copper powder is 26 μm. Figure 6 presents the particle size distribution (determined by sedimentation method) of copper powder obtained by the method described above, which confirms its uniformity when applying the claimed technical solution.

The claimed technical solution allows to ensure the constancy of the electrolysis conditions (the concentration of the deposited metal and the pH of the solution) for a long time and thereby reduce the time-consuming operation of adjusting the composition of the electrolyte, to ensure the possibility of processing metal waste from various industries to produce products in the form of a metal powder with constant characteristics, which leads in general to lower operating costs of the installation and the cost of the obtained metal powders.

The use of a metal cathode sheet obtained in a regenerating cell as a raw material for producing a metal powder by loading it into a soluble anode basket of a charge type of a working cell makes the inventive method for producing metal powder a non-waste production.

INFORMATION SOURCES

1. Kudra O., Gitman E., “Electrochemical production of metal powders”, Kiev, 1952

2. USSR author's certificate for the invention No. 1025757 "Method for producing magnetic powder."

3. USSR author's certificate for the invention No. 1104193 "Method for producing highly dispersed magnetic powder."

4. Copyright certificate of the USSR on the invention.

Resolution No. 956627 “Method for the production of highly dispersed magnetic powders” 5. USSR copyright certificate for the invention No. 1183566 “Electrolyte for the production of metal powders”.

6. USSR author's certificate for the invention No. 1199827 "Electrolyte for the production of nickel powder."

7. USSR author's certificate for the invention No. 1257120 “Method for producing nickel powder from sulfate-chloride electrolyte”.

8. USSR author's certificate for invention No. 2319 “Method for the electrolytic processing of brass into powdered copper and zinc chloride”.

9. USSR copyright certificate for the invention No. 933811 "Method for the electrolytic production of nickel powder".

10. USSR author's certificate for the invention No. 189155 “Method for the electrolytic production of highly dispersed magnetic cobalt powder”.

11. USSR author's certificate for the invention No. 990882 "Electrolyte for producing metal powder of zinc alloy with nickel."

12. RF patent for the invention No. 2469111 "Method for producing copper powders from copper-containing ammonia waste."

13. RF patent for the invention No. 2157417 "Method for the disposal of copper-containing waste."

14. RF patent for the invention No. 2126312 "Method for producing metal powder, copper oxides and copper foil."

15. RF patent for the invention No. 2134311 "Method for producing metal powder, copper oxides and copper foil."

16. Application for Eurasian patent No. 200700275 "Method for the electrolytic production of copper powder in a flowing electrolytic cell."

17. RF patent for the invention No. 2022717 "Method for producing copper powder by electrolysis from sulfate solutions and a device for its implementation."

18. USSR author's certificate for the invention No. 410127 "Method for the electrolytic production of cobalt-tungsten alloys"

19. USSR author's certificate for invention No. 33680 “Method for the electrolytic co-deposition of cadmium and iron in a sponge form”.

20. UK patent for the invention No. 403.281 "Method for improving methods for producing pure metallic cobalt powder."

21. RF patent for the invention No. 2420613 "Method for producing electrolytic metal powders."

Claims (1)

A method of producing metal powders by electrolysis from an aqueous solution containing a salt of the corresponding metal and buffer additives using soluble and insoluble anodes at the same time, characterized in that the soluble and insoluble anodes are located in separate cells having a common electrolyte circuit and independent cathodes, connected to separate current sources and ensure a constant electrolyte composition in terms of pH and ion content of the deposited metal in a cell with soluble anodes by precipitation the excess of metal ions at the cathode and the release of hydrogen ions at the insoluble anode in the cell with insoluble anodes.

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