JPS62258741A - Treatment of ion in solution by conductive organic polymer electrode - Google Patents

Abstract

PURPOSE:To perform the deionization of water electrochemically, by a method wherein the anion in a solution is caught and oxidized by a first electrode comprising a P-type conductive org. polymer and the cation in the solution is caught and reduced by a second electrode comprising a P-type conductive org. polymer. CONSTITUTION:A P-type conductive org. polymer having anion catching capacity is electrochemically oxidized in an ion-containing solution and a P-type conductive org. polymer having cation exchange capacity is electrochemically reduced in said solution. By this method, the anion in the solution is caught by a first electrode and the cation in the solution is caught by a second electrode. Further, by electrochemically reducing the first electrode and electrochemically oxidizing the second electrode, the anion is released from the first electrode and the cation is released from the second electrode and, at the same time, the first and second electrodes are regenerated electrochemically.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating ions in a solution using a conductive organic polymer electrode. The present invention relates to a method of electrochemically treating ions in a solution by applying a voltage between a pair of electrodes made of a combination, causing these electrodes to reversibly capture or release ions in the solution.

BACKGROUND OF THE INVENTION Ion treatment methods are well known in which various ions present in a solution are captured and removed by ion exchange resins having positive or negative dissociative groups capable of ion exchange. However, in this method, a large amount of acid or alkali, or a large amount of salt is required to regenerate the ion exchange resin, so the regeneration process is cumbersome, and the above-mentioned 1iiiI group of the ion exchange resin is removed from the solution. If ions are strongly adsorbed, regeneration is difficult.

Therefore, it has already been proposed to electrochemically remove ions from solutions and regenerate ion exchange resins using polymers with redox functions, so-called redox polymers (A, Factor et al.).

J, E1ectrochen+1cal Soc,,
127.1313 (1980)).

According to this method, the first
The cross-linked polymesityl viologen on the second electrode is oxidized to trap anions on this electrode, and the composite polymer consisting of polyxylyl viologen and polystyrene sulfonic acid on the second electrode is reduced to form a solution. cations can be trapped on this electrode and in this way the solution can be deionized.

However, according to this method, since the polymer used is electrically insulating in nature, its thickness on the electrode is limited in order to effectively deionize, and therefore the amount of ion exchange is naturally limited. Ru. Furthermore, since the polymer is electrically insulating, it is necessary to manufacture the polymer in advance and then form a film on the electrode, which requires time and cost to manufacture the electrode.

On the other hand, various conductive organic polymers have been known. Most of these are p-type semiconductors, and are themselves cationic polymers doped with low molecular weight anions such as perchlorate ions, chloride ions, and boron tetrafluoride ions. The coalescence of the electrically conductive mine is also electrochemically reversibly oxidized. In other words, it has a redox function and functions as a redox polymer. More specifically, when such a conductive organic polymer is reduced in a solution, it releases anions and becomes neutral.
By reoxidation, the anion is again captured as a dopant. That is, the p-type conductive organic polymer doped with low molecular weight anions has an anion-trapping ability.

However, the present inventors have already developed a p-type conductive organic polymer doped with a high molecular weight polymer having a large number of anionic groups in the molecule (hereinafter referred to as polyanion) in place of the low molecular weight anion. In contrast to the low molecular weight anion-doped p-type conductive organic polymer,
Since the polyanion has a high molecular weight in the conductive organic polymer, it is difficult to diffuse. Therefore, by reducing the conductive organic polymer in a solution, the cation in the solution is incorporated into the molecule, and then, It has been discovered that the captured cations can be released by reoxidizing the conductive organic polymer (Otani et al., Proceedings of the 34th Society of Polymer Science, p. 2829 (1985)). That is, the p-type conductive organic polymer doped with a polyanion has the cation exchange ability originally possessed by the polyanion due to its reduction.

Problems to be Solved by the Invention Therefore, the present inventors conducted extensive research to solve the above-mentioned problems in ion treatment in a solution and in manufacturing electrodes used for this ion treatment, and as a result, the first and second problems were solved. The electrodes are made by doping conductive organic polymers with low-molecular weight and high-molecular weight dopants, respectively, as p-type semiconductors, and by applying a voltage between the electrodes, ions in the solution are transferred to the electrodes. The present invention was achieved by discovering that it is possible to capture and release reversibly and to regenerate the electrode electrochemically.

Therefore, the present invention treats ions in a solution by applying a voltage between a pair of electrodes made of a conductive organic polymer to reversibly capture or release ions in the solution, Another aspect of the present invention is to provide a method for electrochemically regenerating the electrode.

Hirato To solve the problem, the first method of treating ions in a solution using a conductive organic polymer electrode according to the present invention is to treat ions in a solution containing ions.
A p-type thick conductive organic polymer with anion-trapping ability is electrochemically oxidized as the first electrode, and a p-type conductive organic polymer with cation exchange ability is electrochemically oxidized as the second electrode. The method is characterized in that anions in the solution are captured by the first electrode and cations are captured by the second electrode.

The second method for treating ions in a solution using a conductive organic polymer electrode according to the present invention is to
A p-type conductive organic polymer with anion-trapping ability is electrochemically oxidized as the first electrode, and a p-type conductive organic polymer with cation exchange ability is electrochemically oxidized as the second electrode. By reducing, anions in the solution are captured by the first electrode, cations are captured by the second electrode, and then the first electrode is electrochemically reduced, and the second electrode The anions are released from the first electrode, the cations are released from the second electrode, and at the same time, the first and second electrodes are electrochemically regenerated. It is characterized by

The method of the present invention will be explained in detail below.

The conductive organic polymer used in the present invention is doped with an anion during its preparation and is itself a p-type semiconductor having cationic properties. Specific examples of such conductive organic polymers include pyrrole, derivatives having substituents at the nitrogen, 3rd and/or 4th positions, thiophene, derivatives having substituents at the 3rd and/or 4th positions, furan, Electrolytic oxidative polymerization or chemical oxidation of heterocyclic compound monomers such as derivatives having a substituent at the 3- and/or 4-position, and aromatic compound monomers such as aniline, phenol, thiophenol, and their derivatives. Examples include polymers obtained by polymerization.

The p-aligned conductive organic polymer having anion-trapping ability used in the present invention means a conductive organic polymer doped with a low molecular weight anion that can easily diffuse through the conductive organic polymer. Specific examples of low molecular weight anions include inorganic and organic anions such as the aforementioned chlorine ion, boron tetrafluoride ion, and ethyl sulfate ion.

On the other hand, a p-aligned conductive organic polymer having cation exchange ability means a conductive organic polymer doped with the polyanion that cannot easily diffuse into the conductive organic polymer. A specific example of such a polyanion is “
A fluoropolymer commercially available as "Nafion" (manufactured by DuPont, USA) can be mentioned. This polymer has a large number of sulfonic acid groups in the side chains of the molecule. but,
In the present invention, the polyanion is not limited to these, and for example, polyvinyl sulfuric acid, polystyrene sulfonic acid, etc. are also preferably used.

In this way, conductive organic polymers consisting of a composite of a p-aligned conductive organic polymer and an anion as a dopant are known (e.g., J. Chem. S.
oc, Chew, Commun, + 1979.
635, JP-A No. 59-98615), the above-mentioned low molecular weight anion or polyanion is dissolved in a solution of the monomer capable of forming the above-mentioned conductive organic polymer, and the above-mentioned monomer is dissolved in this solution. It can be obtained by subjecting the body to oxidative polymerization. The above oxidative polymerization method is not particularly limited, but since the polymerization can be easily controlled,
Electrolytic oxidative polymerization is preferred.

In the present invention, the p-balanced conductive organic polymer having anion-capturing ability is partially reduced in advance so as to be able to trap a large amount of anions in the solution. It is preferable that the electrically bonded low molecular weight anions are partially dedoped. In general, conductive organic polymers change from conductive to insulating through dedoping. It is selected appropriately according to
Generally, it is preferable that the conductive organic polymer has a conductivity of 10-'S/cm or more. The method of reducing the tetraelectric organic polymer for this dedoping is not limited in any way and may be either electrolytic reduction or chemical reduction, but electrolytic reduction can easily control the amount of dedoping. Preferably.

In the method of the present invention, the first electrode is a p-aligned conductive organic polymer having an anion-trapping ability as described above, preferably a p-aligned conductive organic polymer partially dedoped as described above. A p-aligned conductive organic polymer with cation exchange ability is used as the second electrode, these electrodes are electrically connected in a solution containing ions through a potential loading device, and a voltage is applied between these electrodes. the ions in the solution are reversibly captured and released by the electrode, thus
It processes ions and electrochemically regenerates electrodes.

To explain in more detail, according to the method of the present invention, in a solution containing ions, p
An electrode made of a conductive organic polymer (hereinafter referred to as an anion-trapping electrode) is used as an anode, and a p
A voltage is applied using an electrode having a conductive organic polymer (hereinafter referred to as a cation exchange electrode) as a cathode to oxidize the p conductive organic polymer having an anion trapping ability, and at the same time improve the cation exchange ability. By reducing the p-aligned conductive organic polymer with 11n, anions in the solution are captured by the anion-trapping electrode, while cations in the solution are captured by the cation-exchanging electrode.

The load voltage applied between the electrodes is appropriately selected depending on the redox potential of each p-aligned conductive organic polymer on the electrodes, but is usually several square meters.

Then, in accordance with the method of the present invention, the polarity of the applied voltage is reversed, the anion-trapping electrode is used as the cathode, and the cation-exchangeable electrode is used as the anode, thereby producing a p-aligned conductive organic polymer having anion-trapping ability. By reducing and oxidizing the p-type charged organic polymer with cation exchange ability, the anions and cations captured by each electrode are released into the solution, and in this way, each electrodes are electrochemically regenerated. In addition, when releasing anions and cations from each electrode or regenerating the electrode, the electrode may be immersed in a solution containing a different electrolyte as necessary or according to the purpose.

The medium of the solution containing ions used in the present invention may be water, an organic compound, or a mixture thereof, and the medium is not limited in any way.

According to the method of the present invention, as described above, the first electrode and the second electrode are not simultaneously immersed in a solution containing ions, but the first electrode is immersed together with a conventional electrode made of platinum, for example. immersed in a solution containing ions and applying a voltage between these electrodes to oxidize the first electrode to trap the desired anions in the first electrode; By replacing the electrode with the second electrode and reducing the second electrode, cations in the solution can be captured by the second electrode. Of course, this order can also be reversed. Furthermore, as described above, after this, the polarity of the voltage applied to the first and second electrodes is reversed to release anions and cations from each electrode simultaneously or individually, thereby regenerating the electrodes. can do.

Matasato □□□As mentioned above, in the method of the present invention, each electrode is formed to have anion trapping ability and cation exchange ability, so that these ions can be removed in a solution containing ions. Only if it can be electrochemically captured at the electrode to effect electrolytic deionization of water, for example, and can be reversibly released from the electrode to electrochemically regenerate the electrode. In particular, since each electrode is formed from a doped p-type buried organic polymer, it is possible to increase the thickness of the conductive organic polymer layer on the electrode to increase the amount of ion exchange. (can do)

Further, the electrode used in the method of the present invention can be easily manufactured, for example, by electrochemically forming a film of a conductive organic polymer on the electrode, and therefore, the electrode can be easily manufactured. During the manufacturing process, the thickness of the conductive organic polymer can also be arbitrarily controlled.

Although the method of the present invention is not limited in any way to its specific application, for example, in addition to the production of deionized water described above, the method of the present invention can be used to soften water or to improve the ionicity of agitation in an organic solution. , can be suitably used for recovery and separation of valuable metal ions, etc.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 A platinum plate (5 cal) was used as a working electrode, a platinum wire was used as a counter electrode,
Using a saturated calomel electrode (S CE) as a reference electrode, virol (0.1 mol/l) and potassium chloride (0.01
Polypyrrole doped with chlorine ions was prepared on the electrode by electrolyzing at a constant current of 7.5 mA for 2 hours on an aqueous solution containing potassium chloride (0.1 mol/I). Constant N flow reduction (SCE) in an aqueous solution until the current reaches 4 coulombs.
-1, OV), and polypyrrole was partially dedoped to form an anion-trapping electrode.

Separately, a platinum plate (5-) was used as a working electrode, a platinum wire was used as a counter electrode, and SCE was used as a reference electrode.
I) and polyvinyl potassium sulfate (0°01 mol/
An aqueous solution containing 1) was subjected to constant current electrolysis at 7.5 mA for 2 hours to prepare polypyrrole with polyvinyl sulfate doped on the electrode. This was used as a cation exchange electrode.

Regarding the electrode obtained as described above, the anion-trapping electrode was used as an anode and the cation-exchanging electrode was used as a cathode.
0.5 mA in various electrolyte solutions shown in the table
After performing constant current electrolysis for 1 hour to remove ions, the concentration of each ion in the electrolyte solution was measured. The results are shown in Table 1.

Next, the voltage applied to the electrodes was reversed, and the anion-trapping electrode was used as the cathode and the cation-exchanging electrode was used as the anode.
After performing constant current electrolysis at mA for 1 hour and regenerating the electrode to release ions from the electrode, the concentration of each ion in the electrolyte solution was measured.

The results are shown in Table 1.

It will be appreciated that the first operation effectively removes the ions in the solution and the subsequent operation regenerates the electrode.

Example 2 Using a platinum plate (5 cffl) as a working electrode, a platinum wire as a counter electrode, and an SCE as a reference electrode, an aqueous solution containing aniline hydrochloride (10% by weight) was subjected to constant current electrolysis at 10 mA for 2 seconds.
Polyaniline doped with chloride ions on the electrode was prepared over a period of time.

Next, the polyaniline was subjected to potentiostatic reduction (S) in hydrochloric acid (0.1 mol/I) until the amount of current reached 5 coulombs.
-0.8 V vs. CE) to form an anion-trapping electrode.

Separately, the acid form of Nafion (5% by weight) in water-lower alcohol mixed solution) (10% by weight in water) and aniline (0.02% by weight)
A platinum plate (
5 col) was used as a working electrode, a platinum wire was used as a counter electrode, and SCE was used as a reference electrode, constant current electrolysis at 2 mA was performed for 10 hours to prepare polyaniline doped with Nafion on the electrode, and this was used as a cation exchange electrode. And so.

Using these electrodes, an aqueous potassium chloride solution was desalted in the same manner as in Example 1. The results are shown in Table 2.

Example 3 Thiophene (0.1 mol/I) and tetra-n-butylammonium boron tetrafluoride (0.01 mol/I)
Platinum plate (5 cal) in an acetonitrile solution containing
is used as a working electrode, a platinum wire is used as a counter electrode, and IO is connected between these electrodes.
A voltage of V was applied and a current of 60 coulombs was passed to form a film of polythiophene doped with boron tetrafluoride ions on the electrode. Next, this polythiophene was mixed with tetra-n-butylammonium boron tetrafluoride (0.1 m
In an acetonitrile solution containing ol/I), a constant current of 5 yuan (-0.5 V versus SCE) was applied until the current amount reached 5 coulombs to obtain an anion-trapping electrode.

Separately, a water-lower alcohol mixed solution (water 10% by weight) of the acid form of Nafion (5% by weight) and thiophene (0.05% by weight) were prepared.
A water-lower alcohol solution (10% by weight) of thiophene (0.05 mol/l) and the acid form of Nafion (5% by weight) was mixed in a solution obtained by mixing thiophene (0.05 mol/l) and the acid form of Nafion (10% by weight), and this was mixed with a platinum plate. (5 cal) was used as a working electrode, a platinum wire was used as a counter electrode, and SCE was used as a reference electrode. Constant current electrolysis at 10 mA was performed for 1.5 hours to prepare a polythiophene doped with Nafion on the electrode, which was then cationized. It was used as an exchangeable electrode.

Using these electrodes, an aqueous potassium chloride solution was desalted in the same manner as in Example 1. The results are shown in Table 2.

Example 4 Polythiophene having an electrode doped with boron tetrafluoride ions was prepared in the same manner as in Example 3, and then constant current electrolysis was performed in the same manner as in Example 3 to obtain an anion-trapping electrode.

On the other hand, polypyrrole doped with polystyrene sulfonic acid on the electrode was obtained in the same manner as in Example 1 except that sodium polystyrene sulfonate was used in place of potassium polyvinyl sulfate, and this was It was used as an electrode.

Using these electrodes, an aqueous potassium chloride solution was desalted in the same manner as in Example 1. The results are shown in Table 2.

Example 5 A film of polyaniline doped with chlorine ions was formed on an electrode in the same manner as in Example 2, and then constant current electrolysis was performed in the same manner as in Example 2 to obtain an anion-trapping electrode.

In addition, an aqueous solution of aniline (0.02 mol/l) and acid form of polystyrene sulfonic acid (0.02 mol/l) was mixed, a platinum plate (5 col) was used as a working electrode, a platinum wire was used as a counter electrode, and SCE Using this as a reference electrode, constant current electrolysis at 2 mA was performed for 10 hours to form a film of polyaniline doped with polystyrene sulfonic acid on the electrode, which was used as a cation exchange electrode.

The anion-trapping electrode is set at +1°5■ with respect to SCE,
When constant potential electrolysis was performed for 60 minutes in a potassium chloride aqueous solution (1 mmole/I) using the above cation exchange electrode as the counter electrode, the concentration of potassium ions was 0.81 m
mole/l, and the concentration of chloride ions is 0.77
mmole/I, respectively.

The anion-trapping electrode is then applied to the SCE-i,
As a result of constant potential electrolysis for 60 minutes, the concentration of potassium ions was 0.95 mmole/1, and the concentration of chlorine ions was 0.93 ++a+ole/1.
each increased.

Claims (10)

[Claims] (1) In a solution containing ions, electrochemically oxidize a p-type conductive organic polymer with anion-trapping ability as the first electrode, and a p-type conductive polymer with cation-exchange ability as the second electrode. A conductive organic polymer electrode characterized in that anions in a solution are captured by a first electrode and cations are captured by a second electrode by electrochemically reducing the conductive organic polymer. method of processing ions in solution. (2) A p-type conductive organic polymer with anion-trapping ability is
A method for treating ions in a solution using a conductive organic polymer electrode according to claim 1, wherein the conductive organic polymer electrode is partially dedoped in advance. (3) The conductive organic polymer electrode according to claim 1 or 2, characterized in that the conductive organic polymer is an oxidized polymer of a heterocyclic compound monomer, is used in a solution. How to process ions. (4) Ions in a solution produced by the conductive organic polymer electrode according to claim 1 or 2, wherein the conductive organic polymer is an oxidized polymer of an aromatic compound monomer. processing method. (5) A p-type conductive organic polymer with anion-trapping ability is
The conductive organic polymer has a low molecular weight anion as a dopant to the extent that this conductive organic polymer has anion-trapping ability, and the conductive organic polymer has cation exchange ability to the extent that this conductive organic polymer has cation exchange ability. The conductive organic polymer according to any one of claims 1 to 4, characterized in that the conductive organic polymer has a polymer having a large number of anionic groups in the molecule as a dopant. A method for processing ions in solution using a coalescing electrode. (6) In a solution containing ions, electrochemically oxidize a p-type conductive organic polymer with anion-trapping ability as the first electrode, and a p-type conductive polymer with cation-exchange ability as the second electrode. By electrochemically reducing the conductive organic polymer, anions in the solution are captured at the first electrode, cations are captured at the second electrode, and then,
By electrochemically reducing the first electrode and electrochemically oxidizing the second electrode, the anion is released from the first electrode and the cation is released from the second electrode. A method for treating ions in a solution using a conductive organic polymer electrode, characterized in that the first and second electrodes are electrochemically regenerated at the same time. (7) A p-type conductive organic polymer with anion-trapping ability is
7. A method for treating ions in a solution using a conductive organic polymer electrode according to claim 6, wherein the conductive organic polymer electrode is partially undoped in advance. (8) In a solution using the conductive organic polymer electrode according to claim 6 or 7, the conductive organic polymer is an oxidized polymer of a heterocyclic compound monomer. How to process ions. (9) Ions in a solution produced by the conductive organic polymer electrode according to claim 6 or 7, wherein the conductive organic polymer is an oxidized polymer of an aromatic compound monomer. processing method. (10) A p-type conductive organic polymer having an anion-trapping ability has a low molecular weight anion as a dopant that gives the conductive organic polymer an anion-trapping ability, and a conductive organic polymer having a cation-exchanging ability A patent claim characterized in that the conductive organic polymer has a polymer having a high molecular weight to the extent that it has a cation exchange ability and has a large number of anionic groups in the molecule as a dopant. A method for treating ions in a solution using the conductive organic polymer electrode according to any one of items 6 to 9.