RU2763699C1 - Electrolyzer for the extraction of metal from solution - Google Patents

Abstract

FIELD: electroplating.

SUBSTANCE: invention relates to an electrolytic cell for extracting metal from solution and can be used in electroplating devices for electrochemical production. The electrolyzer contains a housing, a means for injecting a solution with a metal to be extracted and alternately located anodes and cathodes, the cathode being made of the extracted metal, the anode made of a different electrically conductive material, and the cathode surface area is 1.5-2.5 times greater than the anode surface area.

EFFECT: reduced risk of dendrite formation on electrolytic cell cathodes for metal extraction from solution with concomitant increase in its productivity.

4 cl, 5 dwg

Description

The invention relates to electroplating devices for electrochemical industries and can be applied in the metallurgical industry.

Known cell for extracting metal from a solution containing a housing with inlet and outlet openings for the solution, alternately located inside the housing anodes and cathodes, and arc walls separating the anodes and cathodes, while the surface area of the anodes is equal to the surface area of the cathodes [US4863580A publication date: 05.09 .1989, IPC: C02F 1/461; C22B 3/02; C25C 7/00].

The disadvantage of the known technical solution is the increased turbulence of the electrolyte flow due to the presence of arc partitions separating the electrodes, as a result of which uneven layers of the extracted metal will form on the cathodes, reducing the performance of the cell. In this case, it becomes necessary to increase the voltage on the electrodes to maintain the efficiency of the electrolysis process, which will lead to contamination of the cathodes with sludge from the solution as a result of the formation of dendrites.

Known cell for extracting metal from a solution containing a housing with inlet and outlet holes for the solution and alternately located inside the housing anodes of lead and cathodes of copper, while the surface area of the anodes is equal to the surface area of the cathodes [CN202148353U, publication date: 22.02.2012, IPC : C25C 1/10, C25C7/00].

As a prototype, an electrolytic cell was selected for extracting metal from a solution, containing a housing that contains cells with n number of cathodes and (n + 1) anodes arranged vertically and in parallel, while the cathodes are made of copper, and the anodes of lead, metal deposition occurs when supply of electric current to the electrodes, the maximum value of which is about one third of the limiting cathode current, while the surface area of the cathodes is equal to or less than the surface area of the anodes [EP3420123A1, publication date: 01/02/2019, IPC: C25C 1/12, C25C 7/00 , C25D 17/02].

The advantage of the prototype over the well-known technical solution is higher reliability due to the improved design of the location of the electrodes, which does not require the installation of additional partitions.

A common disadvantage of the prototype and known technical solutions is the increased risk of dendrites formation on the cathode surface, since the total area of the cathodes is equal to or exceeds the area of the anodes, while the formed dendrites will capture a solution containing impurities from the tank, resulting in contamination of the cathodes with the anode material and a decrease in the performance of the cell .

The technical problem to be solved by the invention is to improve the performance of the cell for extracting the metal from the solution.

The technical result, to which the invention is directed, is to reduce the risk of dendrites formation on the cathodes of the electrolyzer for extracting metal from solution with a concomitant increase in its productivity.

The essence of the invention is as follows.

An electrolyzer for extracting metal from a solution, containing a housing equipped with a means for introducing a solution with a recoverable metal and alternately located anodes and cathodes, the cathode being made of the recoverable metal, while the anode is made of another electrically conductive material. Unlike the prototype, the surface area of the cathodes exceeds the surface area of the anodes by 1.5-2.5 times.

The body can be represented by a tank in the form of a rectangular parallelepiped, cylinder or cone made of an acid-resistant polymer material, such as polypropylene, polyethylene, polyvinyl chloride, or any material with an acid-resistant coating. The means for supplying the electrolyte with the metal to be recovered can be represented by a hole in the housing, and/or a pipe and a pump connected to it and resistant to aggressive media.

Anodes and cathodes under the influence of electric current provide the transportation of electrons to extract the metal from the solution (electrolyte). They may be in the form of grids, plates or cylinders. In this case, the anodes and cathodes can be fixed on guides fixed in the housing. Anodes or cathodes fixed on one guide can be represented as a row containing two, three or more electrodes of the same name.

Cathodes ensure the extraction of metal by reducing it from solution to a metallic state. The cathodes are made of a metal extracted from solution, such as copper, tellurium, silver, nickel, cadmium, or another metal.

Anodes provide oxidation of the metal by releasing electrons. The anodes are made of a different electrically conductive material, by which is meant a material different from the material from which the cathodes are made. Such material may be lead, tin, graphite or other material.

The surface area of the cathodes exceeds the surface area of the anodes by 1.5-2.5 times. With such a ratio of areas, the anodes, due to the smaller area, limit the electric current, limiting the area of contact with the electrolyte, which makes it possible to provide a more uniform formation of a metal coating on the cathodes, reducing the risk of dendrites and increasing the productivity of the cell.

If the surface area of the cathodes exceeds the surface area of the anodes by less than 1.5 times, then a decrease in the growth rate of the metal coating and the formation of dendrites on the cathodes may occur. In this case, an increase in the current strength at such a ratio of areas leads to a proportional increase in the speed of the dendrites and the deposition of the anode material on the cathode.

If the surface area of the cathodes exceeds the surface area of the anodes by more than 2.5, the possibility of the formation of dendrites on the cathode is excluded, however, the rate of growth of the metal coating on it at a constant current strength decreases, as a result of which the performance of the cell deteriorates. In the most preferred embodiment, which provides an optimal balance between the absence of dendritic formation and the productivity of the cell, the surface area of the cathodes exceeds the surface area of the anodes by 2 times.

The anodes and cathodes are arranged alternately, which ensures a uniform change in the concentration of ions in the solution, reducing the risk of possible destruction of the electrodes due to overvoltages and increasing the performance of the cell. The alternating arrangement of anodes and cathodes means their opposite placement in the housing along the direction of the solution flow.

Anodes and cathodes can be presented in the form of rows of two, three or more electrodes of the same name, which ensures a more uniform distribution of ions of the extracted metal in the solution at the interface between the electrolyte and the surface of the cathodes, reducing the risk of dendrites formation due to the appearance of areas with a low content of the extracted metal along with with an increase in the performance of the electrolyzer.

The anodes and cathodes can be staggered relative to each other, which also reduces the risk of dendrite formation and increases the performance of the cell. With this design, the anodes and cathodes form two, three or more rows, which can be arranged vertically and in parallel. At the same time, the option is not ruled out when one, two or more similar electrodes can be located in each row, and opposite electrodes are located diagonally in different vertical rows.

The invention can be made from known materials using known means, which indicates that the invention meets the criterion of patentability "industrial applicability".

The invention has a set of essential features previously unknown from the prior art, characterized in that the surface area of the cathodes exceeds the surface area of the anodes by 1.5-2.5 times, as a result of which anodes with a smaller surface area will limit the electric current, limiting the area of contact with the electrolyte, which makes it possible to provide a more uniform formation of a metal coating on the cathodes, reducing the risk of dendritic formation and cathode contamination by the anode material with a simultaneous increase in the growth rate of the metal coating on the cathode.

This ensures the achievement of the technical result, which consists in reducing the risk of formation of dendrites on the cathodes of the electrolyzer for extracting metal from the solution with a concomitant increase in its productivity, thereby improving its performance.

The invention has essential features previously unknown from the prior art, which indicates that the invention complies with the criterion of patentability "novelty".

The prior art known cell, in which the surface area of the cathodes is equal to the surface area of the anodes. Also known from the prior art is an electrolytic cell in which the surface area of the cathodes is equal to the surface area of the anodes.

However, an electrolytic cell with a surface area of cathodes exceeding the surface area of anodes by 1.5-2.5 times is unknown. Also, the effect of this feature on the effect of reducing the risk of dendrite formation on the cathodes of the cell with a concomitant increase in its productivity, which is achieved by reducing the surface area of the anodes and limiting the effect of electric current on the cathodes, is not known. In view of this, the invention meets the criterion of patentability "inventive step".

The invention is illustrated by the following figures and tables.

Fig. 1 - Hardware scheme of the electrolytic cell for extracting metal from solution.

Fig. 2 - Schematic layout of the electrodes in a checkerboard pattern, top view.

Fig. 3 - Table with performance indicators of the cell with copper cathodes and lead anodes.

Fig. 4 - Table with performance indicators of the cell with nickel cathodes and graphite anodes.

Fig. 5 - Table with performance indicators of the cell with cadmium cathodes and zinc anodes.

In order to illustrate the possibility of implementation and a better understanding of the essence of the invention, embodiments of its implementation are presented below, which can be modified or supplemented in any way, while the present invention is by no means limited to the presented options.

An electrolytic cell for extracting metal from a solution contains a housing 1, a means of introducing an electrolyte in the form of a solution of copper sulfate, consisting of a pipe 2 connected to a pump 5, copper cathodes 3 and lead anodes 4 connected to a power source (not shown in the drawings) and arranged in turn .

The invention works as follows.

With the help of pump 5, electrolyte in the form of a solution of copper sulphate is fed into pipe 2, from which it enters the electrolyzer with electrodes in the form of cathodes 3 and anodes 4, while cathodes 3 are used with different total surface area relative to the total surface area of anodes 4.

Electric current, density - 84 A/m², is supplied to the electrodes by means of a DC power supply (not shown in the drawings) connected to them. On the anodes 4, the chemical reaction Pb²⁺ + 2OHˉ → Pb(OH)₂, where Pb(OH)₂↓ can be considered as a weak acid or a weak base H₂PbO₂ ↔2H⁺ + РbО₂ ²ˉ , after which lead oxide precipitates on the anodes 4 in the form of a dense precipitate PbO₂ ²ˉ - 2еˉ → РbО₂↓, which reduces the risk of cathode 3 contamination with lead.

The released electrons arrive at cathodes 3, which transfer them to copper ions, which are restored on the surface of cathodes 3 in the form of copper Сu ²⁺ + 2е ^ˉ → Сu ⁰ . Anodes 4, due to their smaller area, limit the electric current, limiting the area of contact with the electrolyte, which makes it possible to provide a more uniform formation of a copper coating on cathodes 3, reducing the risk of dendrites and increasing the performance of the cell.

At the same time, the design of the cell, in which cathodes 3 and anodes 4 are alternately arranged in a checkerboard pattern, provides an additional effect, which consists in reducing the risk of dendrites formation and increasing the productivity of the cell due to a more uniform distribution of copper ions in the solution at the electrolyte interface and the surface of cathodes 3.

Thus, separate areas with a low copper content will not appear on the cathodes 3, due to which the contact area with the electrolyte is reduced, which will require the supply of higher currents.

To confirm the above information, a 14-day experiment is carried out, during which the formation of dendrites on cathodes 3 is visually recorded, and the mass of the extracted metal is recorded by weighing all cathodes 3 after the completion of the experiment.

The invention is illustrated by the following experimental data.

Example 1

The electrolyte was presented in the form of a solution of copper sulfate, and the cell contained copper cathodes 3 and lead anodes 4, while the area S _{1 of the} surface of the cathodes 3 was equal to the area S _{2 of the} surface of the anodes 4. The growth rate of the copper coating on the cathodes 3 was 3.8 kg / 24 hours, however, already a day later, the formation of dendrites on cathodes 3, constituting 0.7 wt % of the copper coating, was recorded, after which the experiment was stopped.

Example 2

According to example 1, while the surface area of the cathodes 3 exceeded the surface area of the anodes 4 (S ₁ /S ₂ ) 1.5 times. The formation of dendrites was not recorded, while the growth rate of the copper coating on the cathodes 3 was 5.2 kg/day. For 14 days, a copper coating with a total mass of 72.8 kg was formed on cathodes 3.

Example 3

According to example 1, while S ₁ /S ₂ = 2, the growth rate of the copper coating on the cathodes 3 was 9.0 kg/day. For 14 days, a copper coating weighing 126.0 kg was formed on cathodes 3.

Example 4

According to example 1, while S ₁ /S ₂ = 2.5. The growth rate of the copper coating on the cathodes 3 was 8.9 kg/day. For 14 days, a copper coating weighing 124.6 kg was formed on cathodes 3.

Example 5

According to example 1, while S ₁ /S ₂ = 3. The growth rate of the copper coating on the cathodes 3 was - 8.7 kg/day. For 14 days, a copper coating weighing 121.8 kg was formed on cathodes 3.

Example 6

The electrolyte was presented in the form of a nickel sulfate solution, and the cell contained nickel cathodes 3 and graphite anodes 4, while the area S _{1 of the} surface of the cathodes 3 was equal to the area S _{2 of the} surface of the anodes 4. The growth rate of the copper coating on the cathodes 3 was 2.9 kg / day, however, already a day later, the formation of dendrites on the cathodes 3, constituting 0.63 wt.% of the nickel coating, was recorded, after which the experiment was stopped.

Example 7

According to example 6, while S ₁ /S ₂ = 1.5. Dendritic formation was not observed. The growth rate of the nickel coating on the cathodes 3 was 4.2 kg/day. For 14 days, a nickel coating weighing 58.8 kg was formed on cathodes 3.

Example 8

According to example 6, while S ₁ /S ₂ = 2.0. Dendritic formation was not observed. The growth rate of the nickel coating on the cathodes 3 was 7.7 kg/day. For 14 days, a nickel coating weighing 107.8 kg was formed on cathodes 3.

Example 9

According to example 6, while S ₁ /S ₂ = 2.5. The formation of dendrites was not recorded. The growth rate of the nickel coating on the cathodes 3 was 7.6 kg/day. For 14 days, a nickel coating weighing 106.4 kg was formed on cathodes 3.

Example 10

According to example 6, while S ₁ /S ₂ = 3.0. The formation of dendrites was not recorded. The growth rate of the nickel coating on the cathodes 3 was 7.4 kg/day. For 14 days, a nickel coating weighing 103.6 kg was formed on cathodes 3.

Example 11.

The electrolyte was presented in the form of a solution of cadmium sulfate, and the cell contained cathodes 3 from cadmium and anodes 4 from zinc, while the area S _{1 of the} surface of the cathodes 3 was equal to the area S _{2 of the} surface of the anodes 4. The growth rate of the copper coating on the cathodes 3 was 4.7 kg/day, however, already a day later, the formation of dendrites on cathodes 3, constituting 0.88 mass% of the cadmium coating, was recorded, after which the experiment was stopped.

Example 12.

According to example 11, while S ₁ /S ₂ = 1.5. Dendritic formation was not observed. The growth rate of the cadmium coating on cathodes 3 was 6.9 kg/day. For 14 days, a cadmium coating weighing 96.6 kg was formed on cathodes 3

Example 13

According to example 11, while S ₁ /S ₂ = 2.0. Dendritic formation was not observed. The growth rate of the cadmium coating on the cathodes 3 was 12.8 kg/day. For 14 days, a cadmium coating weighing 179.2 kg was formed on cathodes 3.

Example 14

According to example 11, while S ₁ /S ₂ = 2.5. Dendritic formation was not observed. The growth rate of the cadmium coating on the cathodes 3 was 12.7 kg/day. For 14 days, a cadmium coating weighing 177.8 kg was formed on cathodes 3.

Example 15

According to example 11, while S ₁ /S ₂ = 3.0. Dendritic formation was not observed. The growth rate of the cadmium coating on the cathodes 3 was 12.4 kg/day. For 14 days, a cadmium coating weighing 173.6 kg was formed on cathodes 3.

Thus, in examples 1, 6 and 11, where S ₁ /S ₂ was equal to 1, the experiment was stopped due to the formation of dendrites. During the experiment, all variants of the cell, in which the ratio of the surface area of the cathodes 3 to the surface area of the anodes 4 ranged from 1.5-2.5, demonstrated the absence of the formation of dendrites on the surface of the cathodes 3, while the best results were shown in examples 3, 8 and 13 with the value of the ratio of the area of the cathodes 4 to the area of the anodes 3, equal to 2.0. In the variants of this electrolyzer, not only dendrites were not formed, but the performance of the electrolyzer was maximum. In examples 5, 10 and 15, the coating buildup rate began to decrease due to the high difference (3 times) in the ratio of the surface area of the cathodes 4 to the surface area of the anodes 3.

Thus, a technical result is achieved, which consists in reducing the risk of dendritic formation on the cathodes of the electrolytic cell for extracting metal from solution with a concomitant increase in its productivity, thereby improving its performance.

Claims (4)

1. An electrolytic cell for extracting metal from a solution, containing a housing equipped with a means for introducing a solution with a recoverable metal, and alternately located anodes and cathodes, the cathode being made of a recoverable metal, and the anode being made of another electrically conductive material, characterized in that the surface area of the cathodes exceeds the surface area of the anodes by 1.5-2.5 times. 2. The cell according to claim 1, characterized in that the surface area of the cathodes exceeds the surface area of the anodes by 2 times. 3. The cell according to claim 1, characterized in that the anodes and cathodes are presented in the form of rows of two, three or more electrodes of the same name. 4. The cell according to claim 1, characterized in that the anodes and cathodes are located relative to each other in a checkerboard pattern.

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