JP2000355785A - Electrochemical cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a decomposition rate by making the distance between an anode and a cathode constant with a relatively simple structure. SOLUTION: The electrochemical cell has a perforated partition wall 16 of a blind cylindrical form which partitions a liquid vessel 11 in such a manner that an cathode chamber 19 in which an anolyte 17 is stored is formed on the inner side and a cathode chamber 20 in which a catholyte 18 is stored is formed on the outer side, respectively, the cylindrical anode 12 which is disposed within the cathode chamber and allows the flow of the anolyte, the cylindrical cathode 13 which is disposed in the cathode chamber so as to enclose the anode via the partition wall, and a circulating means 21 which circulates the anolyte solusion as to pass the anode. The cell is provided with a supply section 22 for supplying the material to be treated. The circulating means 21 has an electric motor 21a, a revolving shaft 21b which is disposed in a perpendicular direction at the center of the partition wall 16, has the bottom end arriving at the bottom of the partition wall 16 and is connected at its top end to a motor shaft of the electric motor 21a, and rotary vanes 21c which are fixed to the revolving shaft 21b and circulating the anolyte 17 and the material to be treated so as to be passed through the anode 12 and to be returned into the anode 12 by centrifugal force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical cell for subjecting a substance to be treated to oxidative decomposition by an electrochemical method.

[0002]

2. Description of the Related Art As a method for oxidatively decomposing a solvent by an electrochemical method, a potential difference is given to an aqueous electrolyte containing nitric acid as a main component and a silver ion as a redox species which functions as a strong oxidizing species by electrolytic oxidation. There is known a method in which a monovalent Ag ion is changed to a divalent Ag ion, and a solvent is mixed with the electrolytic solution (Japanese Patent Laid-Open No. 1-3068).
9). In this method, the solvent is decomposed by the divalent Ag ions, and the divalent Ag ions contribute to the decomposition to convert the monovalent Ag ions into monovalent Ag ions.
The monovalent Ag ions are converted into divalent Ag ions again due to the potential difference applied to the aqueous electrolyte, are regenerated, and contribute to decomposition again. When the solvent is decomposed by this method, in order to increase the decomposition rate, it is required that the divalent Ag ions generated by the potential difference by flowing the electrolytic solution and the solvent be immediately consumed by the decomposition treatment.

[0003] As an electrochemical cell for this purpose, a cell having means for circulating an organic solvent and an electrolyte has been proposed (Japanese Patent Application Laid-Open No. 4-504303). The circulating means in this electrochemical cell is a vertical pipe provided with a rotating body having a plurality of holes formed therein and a plurality of wings provided in a substantially central portion of a tank for storing an organic solvent and an electrolytic solution. It is inserted in. The plurality of blades are configured to rotate together with the rotating body to push out the organic solvent and the electrolyte that have entered the inside of the draft tube from the surrounding holes downward. On the other hand, in the above-mentioned electrochemical cell, electrodes composed of a plurality of spheres are arranged in layers at the lower part of the tank, and the organic solvent and the electrolyte discharged from the lower opening of the draft tube to the lower part of the tank by the rotation of the wings are Is configured to pass between a plurality of spheres, which are electrodes, from above to below. In this electrochemical cell, when passing between a plurality of spheres, monovalent Ag ions are changed into divalent Ag ions, and the divalent Ag ions passing through the layered electrode are immediately subjected to a decomposition treatment of an organic solvent. Can be contributed to.

[0004]

However, in the above-mentioned electrochemical cell, since a plurality of spherical electrodes are disposed in a layered manner at the bottom of the tank, there is a problem that the structure becomes relatively complicated. In the above-described electrochemical cell, the cathode is provided on the side of the tank, and the anode is provided in a layer at the bottom of the tank. For this reason, the distance between each part of the anode and the cathode differs, and the current density on the electrode surface becomes non-uniform. In general, a significant increase in current density at the anode is caused by the reaction of the redox species with the oxidized species by electro-oxidation (in the case of silver ions;
In addition to Ag ⁺ → Ag ²⁺ + e ⁻ ), a water decomposition reaction is caused as a side reaction to lower the efficiency of electrolytic generation of oxidized species. For this reason, the unevenness of the current density causes the amount of current to increase locally, which leads to a decrease in the efficiency of electrolytic generation of oxidizing species in the local area. Therefore, in the above-mentioned electrochemical cell in which the distance between the electrodes is non-uniform, even if a relatively large current is passed in order to increase the decomposition rate of the solvent, the amount of current locally increases and the electrolytic oxidation of oxidized species occurs locally. There is a disadvantage that the decomposition rate does not increase as expected because the production efficiency is reduced. An object of the present invention is to make the distance between the anode and the cathode uniform with a relatively simple structure to make the current density uniform, and to increase the decomposition rate by flowing a relatively large current without lowering the efficiency of electrolytic generation of oxidizing species. It is to provide an electrochemical cell which can be used.

[0005]

The invention according to claim 1 is
As shown in FIG. 1, an anode chamber 19 in which an anolyte 17 is stored.
And a bottomed porous cylindrical partition 16 which partitions the liquid tank 11 so as to form a catholyte chamber 20 in which a catholyte 18 is stored, respectively.
, A cylindrical cathode 13 provided in the cathode chamber 20 so as to surround the anode 12 via a partition 16, and an anode provided in the anode 12 and inside the anode 12. A circulating means 21 for circulating the liquid 17 so as to pass through the anode 12 and return to the inside of the anode 12.

In the invention according to the first aspect, since the cathode 13 is provided so as to surround the anode 12, the distance between each part of the anode 12 and the cathode 13 becomes substantially equal, and
The current density when a potential difference is applied between the cathode 2 and the cathode 13 is made substantially uniform. For this reason, as compared with the conventional electrochemical cell in which the current density becomes non-uniform, even if the electrode area is the same, it is possible to flow a larger current without lowering the efficiency of electrolytic generation of oxidizing species. The circulation means 21 is provided with the anolyte 17.
Is circulated through the anode 12 so that the ions changed at the anode 12 immediately degrade the substance to be treated contained in the anolyte 17 after passing through the anode 12. For this reason, a relatively large current can be passed without lowering the efficiency of electrolytic generation of oxidizing species, and the decomposition rate can be increased as compared with the conventional case. The catholyte 18 is exemplified by an oxo acid such as sulfuric acid (H ₂ SO ₄ ) or nitric acid (HNO ₃ ), and the anolyte 17 is a redox species which functions as a strong oxidizing species by electrolytic oxidation, for example, a monovalent silver ion And oxo acids containing divalent cobalt ions or trivalent cerium ions. These are changed to divalent silver ions, trivalent cobalt ions or tetravalent cerium ions due to the potential difference between the anode 12 and the cathode 13.

The invention according to a second aspect is the electrochemical cell according to the first aspect, wherein a supply part 22 for supplying a substance to be treated into the partition 16 is provided above the liquid tank 11.
Since the anolyte 17 is constantly circulated by the circulating means 21, in the invention according to the second aspect, the material to be treated is supplied from the supply section 22 so that the anolyte 1
It is decomposed by circulating together with 2 and can perform both so-called batch processing and continuous processing. The substances to be treated include those generated in the field of nuclear power and those in the general industrial field. In the field of nuclear power, dodecane, TBP (tributyl phosphate), decalin, C generated as waste containing radioactive materials
MPO (carbamoylmethylphosphine oxide), toluene,
Kerosene, pump oil, or scintillator cocktail can be mentioned, and the organic solvent contained in the scintillator cocktail includes xylene, decalin, Shersol A, terphenyl, triethylbenzene, and phenylcyclohexane. Examples in the general industrial field include cycloalkanes such as cyclohexane, ethers such as methyl ether, benzenes such as ethylbenzene, and higher alcohols excluding polyhydric alcohols.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the circulating means 21 is arranged vertically between the electric motor 21a provided above the liquid tank 11 and the center of the partition wall 16. A rotating shaft 21b having a lower end reaching the bottom of the partition 16 and an upper end connected to the motor shaft of the electric motor 21a;
A rotating blade 21c fixed to the rotating shaft 21b and circulating the anolyte 17 inside the anode 12 and the substance supplied from the supply unit 22 through the anode 12 by centrifugal force and returning to the inside of the anode 12; It is a chemical cell. The circulating means 21 including the electric motor 21a, the rotating shaft 21b, and the rotating blades 21c is different from the circulating means in the related art including a draft tube provided with a rotating body having a plurality of holes formed therein and a plurality of blades provided therein. In the invention according to claim 3, the structure can be simplified as compared with the electrochemical cell in the related art.

The invention according to claim 4 is the invention according to claims 1 to 3
In the invention according to any one of the above, the anolyte 17 contains oxo acid and a redox species that functions as a strong oxidizing species by electrolytic oxidation, the catholyte 18 contains oxo acid, and the substance to be treated is an organic solvent. An electrochemical cell configured to cause a redox species to function as an oxidizing species by applying a potential difference between the anode 12 and the cathode 13 to oxidatively decompose an organic solvent. The “organic solvent” according to the fourth aspect includes, in addition to the organic solvent alone, a solvent in which an oxidizable substance is dissolved. The oxidizable substances to be dissolved include nuclear fuel substances such as uranium dioxide and plutonium dioxide, and metals, metal oxides, or solid organic substances mixed in the operation process of a factory. Solid organic substances include filter paper, Kimwipes, Kim towels, and the like. Biological samples such as mice, activated carbon and the like are included.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. As shown in FIGS. 1 and 2,
The electrochemical cell 10 of the present invention is provided with an anode 12 and a cathode 13 in a liquid tank 11 which is a cylindrical bottomed container, and the liquid tank 11 is closed at its upper part by a lid plate 14. The cover plate 14 has a first gas hole 14a for dispersing CO ₂ generated from an anolyte 17 described later to the outside, and a catholyte 18 described later.
A second gas hole 14b is formed to allow NOx generated from the gas to communicate with the NOx processing system. A cylindrical porous wall 16 having a bottom is provided on the cover plate 14 so as to partition the liquid tank 11 substantially concentrically with the liquid tank 11. An anode chamber 19 for storing an anolyte 17 is formed inside the porous partition 16, and a cathode chamber 20 for storing a catholyte 18 outside the porous partition 16.
Is formed. As the porous partition wall 16, porous alumina, Vycor glass, fluorine resin film (trade name: n
afion) and the like.

The anolyte 17 is mainly composed of an oxo acid such as sulfuric acid (H ₂ SO ₄ ) or nitric acid (HNO ₃ ), and electrolytically oxidizes monovalent silver ions, divalent cobalt ions or trivalent cerium ions. And a catholyte 18 comprising only oxo acid. The anolyte 17 in this embodiment contains nitric acid and monovalent Ag ions, and the catholyte 18 contains nitric acid and does not contain Ag ions. Anode 12
The cathode 13 is made of platinum, and the anode 12 is formed in a cylindrical shape so that the anolyte 17 can flow therethrough. This anode 12
Is provided concentrically with the partition 16 in the anode chamber 19. The cathode 13 is formed in a cylindrical shape capable of surrounding the anode 12, and the cathode 13 is placed in a cathode chamber 20 through a partition 16.
. The anode 12 and the cathode 13
The electrochemical cell 10 is configured to allow the redox species contained in the anolyte 17 to function as an oxidizing species by providing a potential difference between the redox species and the oxidizing species. The cathode 12b may be stainless steel or another steel material as long as it can withstand oxoacid.

Inside the anode 12, a circulating means 21 for circulating the anolyte 17 inside the anode 12 so as to pass through the anode 12 and return to the inside of the anode 12 again is provided. The circulating means 21 in this embodiment includes an electric motor 21 a provided above the liquid tank 11, a vertically provided center at the center of the partition 16, a lower end reaching the bottom of the partition 16, and an upper end serving as a rotating shaft of the electric motor 21 a. It has a rotating shaft 21b connected thereto and a rotating wing 21c fixed to a lower portion of the rotating shaft 21b.
The rotating blade 21c is fixed to a rotating shaft 21b corresponding to the center and lower part of the anode chamber 19, and is not provided on the rotating shaft 21b corresponding to the upper part of the anode chamber 19. On the other hand, a supply unit 22 for supplying the substance to be treated into the partition 16 is provided on the lid plate 14 above the liquid tank 11, and when the electric motor 21a is driven, the rotary blade 21c rotates together with the rotary shaft 21b, and the rotary blade 21c Is configured to circulate the anolyte 17 inside the anode 12 and the substance to be processed supplied from the supply unit 22 so as to pass through the anode 12 by centrifugal force and return to the inside of the anode 12.

An oxidative decomposition method in the case where an object to be treated is an organic solvent using the thus constructed electrochemical cell will be described. First, when oxidative decomposition of the organic solvent, the partition 1
An anolyte 17 containing nitric acid and monovalent Ag ions is stored in an anode chamber 19 partitioned by 6, and a catholyte 18 containing nitric acid and containing no Ag ions is stored in a cathode chamber 20. afterwards,
A potential difference is applied between the anode 12 and the cathode 13 to form an anolyte 17
To convert monovalent Ag ions contained in the electrolytic solution into divalent Ag ions. Thereafter, the electric motor 21a of the circulating means 21 is driven to rotate the rotary blade 21c together with the rotary shaft 21b, and the organic solvent as the substance to be treated is injected into the anolyte 17 from the supply unit.

As the rotor 21c rotates, the anolyte 17 inside the anode 12 corresponding to the central part and lower part of the anode chamber 19 and the organic solvent supplied from the supply part 22 are indicated by arrows in FIG. 1 by centrifugal force. The anode 12 is passed from inside to outside. The anolyte solution 17 and the organic solvent that have passed through the anode 12 reach the partition 16, and then rise to rise in the anode chamber 1.
9 returns to the center from the upper part and circulates so as to descend again.
Divalent A changed when passing through anode 12 due to potential difference
The g ion oxidizes and decomposes the organic solvent by mixing with the organic solvent circulating with the anolyte 17. An organic solvent is additionally supplied from the supply unit 22 according to the amount of the oxidative decomposition. As an example of the decomposition reaction when the organic solvent is benzene, the decomposition is performed as shown by the following reaction formula (1).
The CO ₂ generated during this decomposition is discharged from the first gas hole 14a toward an exhaust gas system (not shown).

[0015] _{C 6 H 6 + 42H 2 O} + 30Ag 2+ → 6CO 2 ↑ + 30H 3 0 + + 30Ag + ... (1) In the embodiment described above, corresponding rotor blades 21c in the central portion and the lower portion of the anode chamber 19 The anolyte and the like are fixed to the rotating shaft 21b, and the wings 21c are rotated to move the anolyte and the like outward from the central portion and the lower portion of the anode chamber 19, rise along the partition wall 16, return to the center from the upper portion of the anode chamber 19, and descend again. However, the rotating blades 21c are fixed to the rotating shaft 21b corresponding to the central portion and the upper portion of the anode chamber 19, and the rotating blades 21c are fixed.
c to rotate the anolyte and the like outward from the central part and the upper part of the anode chamber 19, and move down along the partition 16 to form the anode chamber 1.
It may be circulated so that it returns to the center from the lower part of 9 and goes up and down again.

[0016]

As described above, according to the present invention, a cylindrical bottomed porous partition partitioning a liquid tank so that an anode chamber is formed inside and a cathode chamber is formed outside, respectively, is provided in the anode chamber. And a cylindrical anode through which the anolyte can flow, and a cylindrical cathode provided so as to surround the anode through a partition in the cathode chamber, so that the distance between each part of the anode and the cathode is reduced. The current density can be made substantially equal, the current density on the electrode surface can be made uniform, and a relatively large current can flow without lowering the efficiency of electrolytic generation of oxidizing species. In addition, since the circulation means for circulating the anolyte by passing through the anode is provided, the ions changed at the anode can immediately contribute to the decomposition of the substance to be treated contained in the anolyte immediately after passing through the anode, and the decomposition rate can be increased. Can be faster than before.
In addition, if a supply unit for supplying the substance to be treated into the partition is provided, both the so-called batch processing and the continuous processing of the substance to be treated can be performed, and the structure is simpler than the electrochemical cell in the related art. Can be

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of an electrochemical cell of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Liquid tank 12 Anode 13 Cathode 16 Porous partition wall 17 Anolyte 18 Catholyte 19 Anode chamber 20 Cathode chamber 21 Circulation means 21a Electric motor 21b Rotary shaft 21c Rotor blade 22 Supply part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K021 AB25 BA04 BA06 BA17 BC03 CA10 DB01 DB05 DB40 DC11 DC15

Claims (4)

[Claims] A liquid tank (11) so that an anode chamber (19) storing an anolyte (17) is formed inside and a cathode chamber (20) storing a catholyte (18) is formed outside. A cylindrical porous partition (16) having a bottom that partitions the anode chamber (19), a cylindrical anode (12) provided in the anode chamber (19), and through which the anolyte (17) can flow, and the cathode chamber (20) The anode (12) through the partition (16) in
A cylindrical cathode (13) provided so as to surround the anolyte (1) provided inside the anode (12) and provided inside the anode (12).
A circulating means (21) for circulating 7) back through the anode (12) and back into the anode (12). 2. The electrochemical cell according to claim 1, further comprising a supply section (22) for supplying the substance to be treated into the partition (16) above the liquid tank (11). 3. A circulating means (21) comprising: an electric motor (21a) provided above the liquid tank (11); and a circulating means (21) provided vertically in the center of the partition (16) and a lower end of the partition (16). A rotating shaft (21b) reaching the bottom and having an upper end connected to the motor shaft of the electric motor (21a)
And the anolyte fixed to the rotating shaft (21b) and inside the anode (12).
(17) and a rotating blade (21c) for circulating the substance to be processed supplied from the supply unit (22) through the anode (12) by centrifugal force and returning to the inside of the anode (12). Item 3. The electrochemical cell according to Item 1 or 2. 4. An anolyte (17) comprising oxo acid and a redox species which functions as a strong oxidizing species by electrolytic oxidation,
The catholyte (18) contains oxo acid, the substance to be treated is an organic solvent, and the redox species functions as an oxidizing species by giving a potential difference between the anode (12) and the cathode (13). 4. The electrochemical cell according to claim 1, wherein the electrochemical cell is configured to oxidatively decompose an organic solvent.