JPH02305986A - Plural-electrode electrolytic cell - Google Patents

Abstract

PURPOSE:To increase the surface of an electrode contributing to electrolysis and to make electrolysis efficient by arranging plural electrode structures each contg. a fibrous carbon cathode and an anode connected to the cathode so that both anodes are opposed to each other through an insulating part. CONSTITUTION:The electrode structure 6 in which a plate-shaped anode 4 consisting of Ti, etc., coated with lead dioxide, a noble metal oxide, and a plate-shaped cathode 5 of fibrous carbon are joined is laminated through a meshy insulator 7 except both left and right ends in a box-type electrolytic cell main body 1. Only the anode 4 is arranged on the left end in the main body 1, and a current is supplied to the anode and led to the outside of the cell from the cathode 5 at the right end through the structure 6. When a dil. metal soln. is supplied to the main body 1 from a liq. supply port 2, oxygen is generated on the anode 4 by the electrolysis of water in the soln., hydrogen is generated on the cathode 5, and the metal is deposited. In this case, since the surface area of the cathode is large and the metal is deposited on almost the entire surface, the current efficiency is increased, and the metal is continuously deposited for a long time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is applicable to waste liquid treatment, metal recovery, impurity decomposition or removal,
This invention relates to a bipolar electrolytic cell that can be used for various electrolytic reactions such as salt electrolysis, water electrolysis, and organic electrolysis.

(Prior art and its problems) Conventionally, conventional electrolytic reactions such as generation of caustic soda by salt electrolysis and generation of oxygen and hydrogen by water electrolysis, treatment of plating waste liquid and recovery of precious metals etc. from the waste liquid have been used. Electrolysis is widely used in For example, when waste liquid treatment is performed by a method other than electrolysis, the waste liquid generally contains waste organic matter that is highly viscous and difficult to handle, making it difficult to perform normal treatment operations and often resulting in the waste organic matter being unable to be decomposed and being disposed of as is. ing. However, when treating the waste liquid using electrolysis, the waste liquid is not introduced into the electrolytic tank (
The decomposition of the organic matter occurs on the electrode surface by just using the electrode, and it can be decomposed into harmless gas, water, and the like.

Organic electrolysis, which is used to generate organic reactions and convert organic compounds into other compounds, almost completely suppresses the side reactions that occur almost inevitably in organic reactions, and produces the desired compounds in high yields. and selectivity. Furthermore, the target substance can be similarly obtained in high yield in the aforementioned salt electrolysis and water electrolysis.

As described above, electrolytic reactions have many advantages compared to general organic and inorganic reactions, and are therefore widely used industrially. Various techniques have been proposed.

For example, there is a method of using a porous electrode as an electrode, and it is known that this method increases the surface area of the electrode and contacts the electrolytic solution over a wide area, thereby increasing the rate of electrolytic reaction. However, when electrolysis is carried out using, for example, a porous carbon plate as an electrode, the electrode reaction actually occurs only on the flat surface facing the counter electrode, and the area contributing to electrolysis does not increase.

Furthermore, in order to perform purification by removing impurity metals from a metal solution containing a small amount of impurity metals, conventionally, a reagent is added to precipitate and remove the impurity metals. As the cost of reagents used for purification has become expensive, a more efficient and economical purification method is required, and electrolysis technology has been proposed as a method to meet this demand, and as mentioned above, there is also a need to reduce electricity costs in electrolysis. There is.

(Objective of the Invention) An object of the present invention is to provide a bipolar electrolytic cell that can efficiently cause an electrolytic reaction by using an electrode with an increased surface area of the electrode surface that contributes to the electrolytic reaction. .

(Means for Solving the Problems) The present invention first provides a plurality of electrode structures each including a fibrous carbon cathode and an anode connected to the cathode, with the positive and negative electrodes facing each other through an insulating part. A bipolar electrolytic cell is characterized in that the electrolytic cell of the first invention is arranged in a horizontal direction, and the electrode structure is arranged in a gap perpendicular to the direction of movement of the electrolytic solution. It is a bipolar electrolytic cell characterized in that the electrolytic solution is forced to pass through the electrode structure to perform electrolysis; The present invention is a bipolar electrolytic cell formed by stacking unit electrolytic cells, characterized in that a fibrous carbon connected to a current collector serves as a cathode.

The present invention will be explained in detail below.

The bipolar electrolytic cell according to the present invention can be used for waste liquid treatment, metal recovery,
It can be used for various electrolytic reactions such as removing impurities in solutions, decomposing cyanide, etc., salt electrolysis, water electrolysis, and organic electrolysis.

The present invention uses a fibrous carbon cathode as the cathode. The fibrous carbon cathode may be used as it is or may be formed into a plate shape using pitch or resin, but the fibers must ultimately remain as a cathode material. As mentioned above, when electrolysis is carried out using a normal porous material such as a porous carbon plate as an electrode, even though the electrode itself has a high surface area, the only part that effectively functions as an electrode is the one facing the counter electrode. does not lead to an increase in the electrolytic area.

On the other hand, in the electrolytic cell according to the present invention using a fibrous carbon cathode, although the reason is not clear, almost the entire surface of each fiber of the fibrous carbon cathode undergoes an electrode reaction, resulting in an increase in the effective electrode area. becomes enormous. This effect is due to the fact that the length of the fibrous carbon is long enough so that there is no potential gradient within the cathode and the potential is the same in every part of the cathode, so electrolytic reactions occur in any part of the cathode and almost the entire surface of the cathode acts as an electrode. It can be assumed that this is because it functions.

Therefore, the cathode current density becomes extremely small, thereby dramatically improving current efficiency. For example, when precious metals in waste liquid are recovered by electrolytically depositing them on electrodes, the concentration of the precious metals is about 10 to 1000 mg/It, and this is IB/It.
j! If a conventional plate-shaped carbon electrode is used in the following cases, the current efficiency is about 1 to 10%, whereas in the bipolar electrolytic cell using the fibrous carbon cathode according to the present invention, the current efficiency is about 1 to 10%.
It increases to about 0 to 30%.

The fibrous carbon used in the present invention may be commercially available, and may be molded into a plate shape, felt shape, or the like, or a cotton-like carbon material may be used as is.

Since the fibrous carbon itself does not have an electrolysis voltage reduction function, in order to reduce power consumption by reducing the voltage, it is necessary to support a noble metal catalyst such as palladium, ruthenium, or platinum on the fibrous carbon. There is. This makes it possible to reduce the electrolytic voltage and promote the electrolytic reaction, as well as to extend the life of the fibrous carbon cathode.

The anode used in the electrolytic cell according to the present invention is not particularly limited, and a noble metal oxide electrode, a lead dioxide electrode, a carbon electrode, etc. may be selected depending on the application, and the anode may be joined to the cathode or integrally formed. By using only fibrous carbon as an electrode, it can be decentralized by applying electricity to function as both negative and negative poles.In the present invention, this latter aspect is also said to have the negative and negative poles electrically connected.

The fibrous carbon cathodes are connected in a bipolar type to constitute a bipolar electrode cell, but the connection structure is not particularly limited. For example, in electrolysis for waste liquid treatment, metal recovery, or removal of impurity metals in solutions, there is no need to divide the anode and cathode chambers, so the partition wall becomes a lower tooth, ensuring the prevention of short circuits between the opposing electrodes where electrolysis occurs. The structure in which this can be carried out is +().In addition, if oxygen is generated as an anode reaction in a structure in which the bipolar chambers are not partitioned, in order to prevent the oxidation of the fibrous carbon by this oxygen, the fibrous carbon cathode is It is desirable to have an auxiliary material such as lead dioxide, iridium oxide, or platinum oxide in close contact with the cathode, and if the anode reaction is to generate chlorine, it is possible to use the fibrous carbon cathode alone. In this type of bipolar electrolytic cell, not only a vertical structure in which the electrodes are arranged vertically, but also a horizontal structure in which the electrodes are arranged in the horizontal direction are possible. The latter horizontal structure is particularly advantageous when electrolysis is performed by positioning the electrodes without gaps in the entire direction perpendicular to the direction in which the electrolytic solution travels in the electrolytic cell and forcing the electrolytic solution to pass through the electrodes.

Furthermore, in electrolytic reactions such as salt electrolysis, it is necessary to separate the anode and cathode products by partitioning the anode chamber and the cathode chamber. To this end, it is preferable to partition the bipolar chambers by a diaphragm which is an ion exchange membrane in salt electrolysis and the like, and by a diaphragm which does not have an ion exchange function such as a clay plate in water electrolysis, etc., as usual.

In this type of electrolytic cell, the presence of the diaphragm prevents the gas generated at the anode from coming into contact with the cathode, so there is no need to use the auxiliary material. Furthermore, in this diaphragm type electrolytic cell, it is possible to fill the entire cathode chamber with the fibrous carbon cathode,
As a result, the cathode comes into contact with the diaphragm to enable so-called zero-gap type electrolysis, which can contribute to reducing the electrolysis voltage and further increase the electrolysis area.

Next, preferred embodiments of the bipolar electrolytic cell according to the present invention will be illustrated based on the accompanying drawings, but the present invention is not limited to these electrolytic cells.

FIG. 1 is a longitudinal sectional view showing an embodiment of a bipolar electrolytic cell according to the present invention, and shows an electrolytic cell that is effective for use in waste liquid treatment, metal recovery, etc.

1 is a box-shaped electrolytic cell main body having a liquid supply port 2 and a waste liquid port 3 on the left and right sides, and inside the electrolytic cell main body l, a plate-shaped anode 4 made of lead dioxide or noble metal oxide-coated titanium, etc., and the aforementioned fibers are placed inside the electrolytic cell main body l. An electrode structure 6, which is joined to a cathode 5 made of carbon shaped like a plate, is laminated with mesh-like insulators 7 interposed therebetween except at both left and right ends. Said main body! Only the anode 4 is disposed at the left end of the chamber, and a current is supplied to the anode 4 and led out of the tank from the cathode 5 at the right end through the plurality of electrode structures 6.

When, for example, a diluted metal solution is supplied to the electrolytic cell body 1 from the liquid supply port 2, oxygen is generated on the anode 4 due to the electrolysis of water in the solution, while on the cathode, hydrogen is generated due to water electrolysis and hydrogen is generated on the cathode. Precipitation of metallic palladium occurs by reduction of the metal, for example palladium ions.

In this case, since the surface area of the cathode 1 is large and metal deposition occurs over almost the entire surface, current efficiency increases and metal deposition can be continued for a long time.

FIG. 2 is a longitudinal sectional view showing a second embodiment of the bipolar electrolytic cell according to the present invention, in which an electrolytic cell for salt electrolysis, water electrolysis, organic electrolysis, etc. is divided into an anode chamber and a cathode chamber. Can be used for electrolysis.

1) is a unit electrolytic chamber whose interior is divided into an anode chamber 13 and a cathode chamber 14 by a diaphragm 12 such as an ion exchange membrane, and the unit electrolytic chambers 1) are stacked in the left-right direction to form an electrolytic cell main body 15. ing. An anode 16 made of lead dioxide or titanium coated with a noble metal is disposed in the anode chamber 13, and a cathode 17 made of fibrous carbon formed into a plate shape is disposed in the cathode chamber 14 via a current collector 18. An anode chamber manifold 20 is connected to the bottom surface of each anode chamber 13 via a conduit 19 for supplying and discharging an electrolyte, and an anode chamber manifold 20 is connected to the top surface of each cathode chamber 14 via a conduit 21 for supplying and discharging an electrolyte. A cathode chamber manifold 22 is connected.

A concentrated saline solution is passed through the anode chamber manifold 20 into the electrolytic cell body 15, and the cathode chamber manifold 2
When diluted caustic soda aqueous solution is supplied through 2, chlorine gas is generated in the anode chamber 13 by oxidation of chlorine ions in the salt, and hydrogen is generated in the cathode chamber 14 by electrolysis of water, and the gas is transferred from the anode chamber 13 to the cathode chamber 14 through the diaphragm 12. Sodium ions that have penetrated combine with hydroxide ions to generate caustic soda.

In this case as well, the cathode surface area is large and electrolysis occurs over almost the entire surface, so that the current efficiency increases.

FIG. 3 is a longitudinal cross-sectional view showing a modification of the electrolytic cell shown in FIG. 1, which can be used as an electrolytic cell of a type that promotes electrolysis by forcing an electrolytic solution to pass through the electrode structure.

31 is a liquid supply port 32 in the center of the bottom surface, and an outlet 33 in the upper right side surface.
It is a box-shaped electrolytic cell main body having a gas outlet 34 in the center of the top surface, and inside the electrolytic cell main body 31, except for the upper and lower ends,
An electrode structure 37 in which a plate-shaped anode 35 made of lead dioxide or titanium coated with a noble metal oxide, etc. and a cathode 36 made of fibrous carbon formed into a plate shape are laminated with a mesh-shaped insulator 38 in between, and the electrode The periphery of the structure 37 is connected to the electrolytic cell body 31.
It adheres tightly to the inner wall of the Only the anode 35 is disposed at the upper end of the main body 31, and a current is supplied to the anode 35 and led out of the tank from the cathode 36 at the lower end through the plurality of electrode structures 37. When an aqueous zinc solution containing, for example, copper and cadmium as impurities is added to the electrolytic cell main body 31 from the liquid supply port 32, when the solution is forced to pass through the cathode 36, the ionization tendency in the solution is reduced. Low amounts of copper and cadmium are almost selectively deposited on the cathode 36, so that a solution containing only zinc can be obtained at the outlet 33. In this case as well, since the cathode surface area is large and almost the entire surface can be effectively used for metal deposition, the current efficiency is increased and metal deposition can be continued for a long time. Since the electrolyte is located perpendicular to the direction, the electrolyte always reaches each cathode 36.
The precipitation efficiency can be improved by contacting with (Example) Next, an example of an electrolytic reaction using the bipolar electrolytic cell of the present invention will be described, but the present invention is not limited to this example.

An electrolytic cell similar to the bipolar electrolytic cell shown in FIG. 1 was used to collect palladium metal in solution.

The electrolytic cell body is a cylinder made of vinyl chloride with a diameter (inner diameter) of 5 cm and a thickness of 1Ocs+, and the electrode structure is made of fibrous carbon with a diameter of 5 cm and a thickness of 5 mm (Nippon Carbon Co., Ltd.) without installing the anode and cathode separately. The electrode structure was laminated using an insulator made of a polyvinyl chloride mesh using "Carboron-P Felt" (Bulk Specific Gravity: about 0.1 g/cIiI), manufactured by Co., Ltd.

A sample solution was prepared by dissolving 2.0 g of palladium chloride in 5.0β diluted hydrochloric acid, and the sample solution was supplied from the liquid supply port of the electrolytic cell, electrolysis was performed under the conditions of room temperature, 3 A, and 12 V, and then the sample solution was dissolved from the waste liquid port. The sample solution taken out was again circulated through the liquid supply port, and electricity was continued for 30 minutes.

After the electricity was stopped, the palladium concentration in the electrolyte was measured and found to be less than 1cmg1), and the current efficiency was approximately 20%.
Met. When the fibrous carbon electrode was observed through a magnifying glass, it was found that almost the entire surface of the electrode functioning as a cathode was coated with a substance having metallic luster.

The sample solution was electrolyzed under the same conditions as in Example 1, except that a porous plate carbon electrode (manufactured by Toyo Carbon Co., Ltd.) was used as the cathode, and after the current supply was stopped, the palladium concentration in the electrolyte was When measured, it was 180 mg7N, and the current efficiency was 5%. Further, when the plate-shaped cathode was observed using a looper, only the surface functioning as a cathode was coated with a substance having metallic luster.

Large stop plate 1 Caustic soda was produced by electrolysis of a saline solution using a bipolar electrolytic cell shown in FIG.

A 250 g/# concentrated saline solution was used as the anolyte, and a 140 g/1 diluted caustic soda aqueous solution was used as the catholyte. As an anode, 5cn+X 5cmX 1.5
A dimensionally stable anode of 1.0 mm is used, and a fibrous carbon cathode with the same shape and carrying metal palladium ("Carboron-P Felt" manufactured by Nippon Carbon Co., Ltd.) is used as the cathode, and both electrodes are made of Nafion (registered trademark). It was housed in an anode chamber and a cathode chamber divided by 710, and a carbon plate was used as a cathode current collector. While supplying the anolyte and catholyte from both manifolds, electrolysis was carried out under the conditions of 50° C., 5A, and 13.6V, and the anolyte and catholyte taken out from the manifold were circulated again and the current was continued for 2.25 hours.

After the current supply was stopped, the caustic soda concentration in the catholyte was measured and found to be 205 r/l, and the current efficiency was 97%.

(Effects of the Invention) The present invention is a base electrode type electrolytic cell that uses carbon maintained in a fibrous form after molding as a cathode.

Unlike porous electrodes such as conventional carbon electrodes in which only the part facing the counter electrode exhibits electrode action, the fibrous carbon cathode has a sufficiently long length of fibrous carbon and there is no potential gradient within the cathode. Since the potential is the same in all parts of the cathode, it is assumed that electrolytic reactions occur in any part of the cathode, and almost the entire surface of the cathode functions as an electrode, making the electrolytic conditions more favorable, including reducing the current density. be able to.

The structure of the bipolar electrolytic cell of the present invention that uses a fibrous carbon cathode having such characteristics can be roughly divided into a type in which the anode chamber and cathode chamber are not separated and a type in which the bipolar chamber is separated by a diaphragm. Furthermore, the electrodes can be divided into types in which the electrodes are positioned perpendicularly to the direction of movement of the electrolytic solution with no gaps, and types in which the electrodes may be positioned with gaps.

In any type of electrolytic cell, the fibrous carbon cathode dramatically increases the effective electrolytic area of the cathode, making it possible to increase current efficiency. Further, by supporting a noble metal catalyst on the cathode, it is possible to reduce the electrolysis voltage, and it is possible to realize a reduction in power consumption in terms of both current efficiency and electrolysis voltage. □Although any of the above-mentioned types of bipolar electrolytic cells have the above-mentioned advantages, in non-diaphragm type electrolytic cells, the anolyte and catholyte are mixed, and the substances oxidized at the anode are reduced again at the cathode, resulting in the On the other hand, the structure of the electrolytic cell is simple, and in particular, substances that have been oxidized or reduced by the electrolytic reaction are precipitated on the electrodes. It is advantageous to use it in reactions in which impurity metals are decomposed and cannot be restored by electrolysis, such as removal of impurity metals by electrodeposition, waste liquid treatment, or cyanide decomposition.

Furthermore, in the non-diaphragm type electrolytic cell, if at least the cathode is disposed vertically with no gap to the direction of movement of the electrolytic solution and the electrolytic solution is forced to pass through the electrode structure to perform electrolysis, the electrolysis can be carried out. ) The night can reliably contact the cathode and promote the predetermined electrolytic reaction.

On the other hand, diaphragm-type electrolytic cells that use a diaphragm to divide into an anode chamber and a cathode chamber have a slightly more complicated structure because they use a diaphragm. can be used.

When the diaphragm-type electrolytic cell adopts a structure in which the entire cathode chamber is filled with the fibrous carbon cathode, the cathode can be disposed vertically to the direction of movement of the electrolyte without gaps in the non-diaphragm-type electrolytic cell. Not only does the same effect, that is, the effect of promoting a predetermined electrolytic reaction by ensuring that the electrolyte comes into contact with the cathode, but also zero-gap type electrolysis in which the cathode and the diaphragm come into contact becomes possible, and even more Power can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of a bipolar electrolytic cell according to the present invention, FIG. 2 is a vertical cross-sectional view showing the second embodiment, and FIG. It is a longitudinal cross-sectional view showing an example.

Claims (4)

[Claims] (1) A bipolar electrolytic cell characterized in that a plurality of electrode structures each including a fibrous carbon cathode and an anode connected to the cathode are arranged such that the positive and negative electrodes face each other with an insulating part interposed therebetween. . (2) A plurality of horizontal electrode structures each including a fibrous carbon cathode and an anode connected to the cathode are arranged so that the positive and negative electrodes face each other with an insulating part interposed therebetween, and the electrode structures are 1. A bipolar electrolytic cell, characterized in that the electrolytic solution is disposed vertically with no gaps in the direction of movement of the electrolytic solution, and the electrolytic solution is forced to pass through the electrode structure to perform electrolysis. (3) A bipolar electrolytic cell formed by stacking unit electrolytic cells divided into an anode chamber and a cathode chamber via a diaphragm, characterized in that a fibrous carbon connected to a current collector serves as a cathode. Bipolar electrolytic cell. (4) Claim (3) in which the entire cathode chamber is filled with fibrous carbon.
The bipolar electrolytic cell described in .