JPS5922607A - Electrodialysis device - Google Patents

Abstract

PURPOSE:To perform electrodialysis without requiring any external power source by providing two kinds of porous material layers having different oxidation-reduction potentials near both surfaces of films. CONSTITUTION:Sodium chloride solns. are introduced through an inlet 5 for concd. liquid, an inlet 4 for dilute liquid and an inlet 4a for capturing liquid into respective concentrating chambers C and dilution chambers D. The porous copper layers 1a and porous nickel layers 1b adhered tightly to ion exchange membranes A, K in this state are impregnated respectively in electrolytes, thus exhibiting respectively different potentials. Potential differences are then generated between said potentials. About 340mV potential difference is generated in, for example, a 0.1N sodium chloride soln. Electric current flows through a short circuiting part 3 in accordance with the potential difference thereof, but nickel ions elute continuously as anode eluting ions from the layers 1b to the chambers D; therefore, the potential difference between both layers are not annihilated. Thus, both layers maintain the polarization state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrodialysis device. More specifically, the present invention relates to an electrodialysis device that has an energy-saving configuration that does not require an external power supply and is useful for seawater desalination, food desalination processing, and the like.

Conventionally, electrodialysis devices that combine an ion-permeable membrane and an electrolytic cell have been used to concentrate and/or dilute an electrolyte solution (parent electrolyte).
It is used for various purposes. Among these, the schematic diagram of the multiple ion-permeable membrane electrodialysis device is shown in the first section.
As shown in the figure. Figure 1 shows an example of a sodium chloride solution as an electrolyte solution, and the sodium chloride solution is applied from the concentrate inlet (5) to the anion-permeable membrane (A) and the cation-permeable membrane (phantom) to the treatment tank (2° ) is introduced into the concentration chamber (2), which is partitioned by extending alternately between the diluent (2).Meanwhile, the diluent (II) chloride solution is also introduced into the dilution chamber (2) from the diluent inlet (4). In this state, when a DC voltage is applied to electrodes 03 and 04) in the processing tank, sodium ions (Na") are drawn toward the cathode e, and chlorine ions (C1-) are drawn toward the anode Na+ and O/- in Φ pass through the cation-permeable membrane (K) and anion-permeable membrane (A>, respectively) to the adjacent fC concentration chamber. On the other hand, Na+ and at- in the concentration chamber ■ (Due to the action of phantom and (A), it cannot pass through and does not move to dilution chamber ■ (see arrow in the figure). In other words, the sodium chloride concentration in dilution chamber 0 decreases [-1 The sodium chloride concentration in concentration chamber ■ Rise.

Therefore, the electrolyte solution will be concentrated and/or diluted.

However, in the conventional apparatus as described above, it is necessary to continuously supply DC voltage from the outside to the electrodes (lj and 04) in the processing tank, which is disadvantageous in that it requires high power and increases operating costs.

The present invention has been made to eliminate these drawbacks, and provides an energy-saving electrodialysis device that does not require an external power supply.

Thus, according to the present invention, anion-permeable membranes and cation-permeable membranes are alternately stretched and partitioned in a treatment tank, and two types of porous membranes having different redox potentials are formed near both sides of each membrane. By providing regular material layers and alternately setting concentration chambers and dilution chambers, and by short-circuiting each of the two porous material layers outside the processing solution, concentrated and diluted electrolyte-containing solutions can be prepared. The ion-permeable membrane is configured to generate ions in the concentration chamber and dilution chamber, respectively, and the ion-permeable membrane, which is opposite to the ions eluted from the porous material layer, is generated in the corresponding porous material in the dilution chamber and/or concentration chamber. There is provided an electrodialysis apparatus which does not require an external power source and is structured so as to prevent the above-mentioned ions from being mixed into the diluted solution and/or concentrated solution by providing a section in the vicinity of the layer.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a configuration explanatory diagram showing a specific example of the electrodialysis apparatus of the present invention. In the figure, first a copper porous layer (la) and a nickel porous layer (l) with different redox potentials are shown.
An anion permeable film (A) in which a copper porous layer (la) and a nickel porous layer (1b) are formed in close contact with each other on both sides by vapor deposition, and a cation permeable film (K) in which a copper porous layer (la) and a nickel porous layer (1b) are similarly formed in close contact with each other. ) are installed alternately at predetermined intervals in a rectangular parallelepiped processing tank (2), and these membranes and processing tanks are constructed to form a large number of concentration chambers (■) and dilution chambers (■) alternately. has been done. The copper porous layer (1a) and the nickel porous layer (11) regularly adhered to both sides of the ion-permeable membrane (Shu, (6)) are connected to the outside of the processing tank by short-circuit parts (31) consisting of copper connections, respectively. electrically connected.

Further, an anion-permeable membrane (la) is stretched in the vicinity of the nickel porous layer (11) in each dilution chamber Φ, and a nickel ion trapping section (■) is formed in this. There is. In addition, the concentration chamber (■) and the dilution chamber (■) have a concentrated liquid inlet (5) and an outlet (5) and a diluted liquid inlet (4) and an outlet (4) similar to those shown in Fig. 1, which are connected through a liquid feed pipe. In addition, the nickel ion collecting section ■ of the dilution chamber Φ is also provided with a collecting liquid inlet (4a) and an outlet (4a).
') is connected through the liquid feed pipe.

In the above configuration, the function when a sodium chloride solution is used as the electrolyte will be explained. First, as before, the concentrate inlet (5), the diluted liquid inlet (4), and the collection liquid inlet (
Through 4a) a sodium chloride solution is introduced into each concentration chamber ⑦ and dilution chamber Φ.

In this state, the ion exchange membrane (A), the copper porous layer (1a) and the nickel porous layer (1b), which are in close contact with each other, are each immersed in the electrolyte and each has a different potential. For example, in a 0.IN sodium chloride solution, a potential difference of about 840 m
A potential difference of 'V occurs. Based on this potential difference, a current flows through the short circuit part (3), but the potential difference between the two layers disappears because nickel ions are continuously eluted from the nickel porous layer (1b) to the dilution tank 2 as anode eluted ions. Therefore, both layers maintain the polarization state (e) shown in FIG.

Therefore, Na in the dilution chamber except for the collection section (2) passes through the copper porous layer (1a) and the cation-permeable membrane (the negatively polarized nickel porous layer (1a) in the adjacent concentration chamber (2) as shown by the arrows). Move to the vicinity of layer (11)). Similarly, C1- in the dilution chamber Φ passes through the nickel porous layer (lb) and the anion-permeable membrane (A) and enters the vicinity of the positively polarized copper porous layer (Xa) in the adjacent concentration chamber ■. Moving.

On the other hand, Na+ and aZ- in the concentration chamber (2) do not move into the adjacent dilution chamber (x) due to the polarization of the porous layer and the ion-permeable membrane (A) as shown by the arrow, but remain as they are due to the phantom action. stay.

Therefore, Na+ and O/- are concentrated in the concentration chamber ■, and Na+ and O/- are concentrated in the dilution chamber ■, except for the nickel ion collection section ■
+ and C1- are diluted, and the electrolyte is concentrated and/or diluted in the conventional manner.

Furthermore, an anion permeable membrane (Ao) is
nickel porous layer (lb
The nickel ions eluted from ) are retained and retained in the collection section (1), and do not mix into the diluted solution containing Na+ and at- in the dilution chamber [F].

Therefore, a diluted solution with a diluted concentration of Na+ and O/- can be obtained without contamination with new ions from the porous layer.

The two porous material layers having different redox potentials in this invention are not limited to those made of metals as mentioned above, but are at least a combination of materials that produce a sufficient potential difference when immersed in an electrolyte solution. Various metals, conductive substances, etc. can be used. Further, the porosity is sufficient as long as it allows the target ions to pass through, and may be in the form of a network.

As the TFC, anion-permeable membrane, and cation-permeable membrane, various types known in the art can be used, such as various anion-exchange membranes and cation-exchange membranes having ion selectivity.

On the other hand, the two porous material layers may be located on both sides of the ion-permeable membrane or in the vicinity thereof, but they are usually formed in close contact with both sides by a method such as electroless plating, vapor deposition, or sputtering. This is preferable in terms of increased efficiency, ease of handling, etc.

Further, in the present invention, the short-circuit portion may be made of a material with relatively low electrical resistance and has no power supply element, and may be, for example, a short-circuit portion that penetrates the end of the membrane and is fixed with a bolt and nut. It is also possible to insert an ammeter or the like into this short circuit to manage the operating status, but as long as the impedance of these is small, the desired electrodialysis phenomenon will occur, so it is assumed that there is a short circuit. It will be done.

In the above specific example, if it is desired to generate a concentrated liquid that does not contain nickel ions, an anion-permeable membrane is further installed near the nickel porous layer (lb) in the concentration chamber O to collect the nickel ions. This can be done by providing a section (3), but in some cases, one section may do just this. Furthermore, in addition to the ions eluted from the anode, various anions that can be eluted from the cathode (for example, TTF-TOI as a porous material layer)
To prevent contamination of diluted and/or concentrated liquids (there is a risk that anions may be eluted from the cathode when organic polymer materials such as JQ, polyacetylene, and fluorinated graphite are used as cathodes) A section may be provided with a cation permeable membrane-A4. That is, at least an ion-permeable membrane having a polarity opposite to the ions that can be eluted from the porous material layer serving as the anode and cathode is placed near the corresponding porous material layer (which elutes ions) in the dilution chamber and/or the concentration chamber. It is sufficient if it is divided into sections. This can prevent contaminant ions from entering the diluted solution and/or concentrated solution.

The electrodialysis device of the present invention can be applied not only to seawater desalination but also to desalination of foods such as milk and soy sauce, water electrolysis, alkaline electrolysis, salt production, etc., and in all cases, external power is not required. It is useful in that it does not. Moreover, it is suitable for electrodialysis in places where it is difficult to obtain electric power, such as ships and remote islands.

Hereinafter, the present invention will be explained in more detail by showing examples.

EXAMPLE An electrodialyzer was prepared as shown in FIG. 8, the groove bottom of which is shown. In the figure, (61, (7), and (81) are the diluted solution, concentrated solution, and nickel ion collection solution, respectively, with a flow rate of 5 layers V min.
This is a flow path that circulates at 0-.
01]) is attached. Anion permeable membrane (A)
(As for A, the membrane surface area is about 28i, the thickness is about 0.11~
A 0.15U anion exchange membrane (Celemion A8V, Asahi Glass Co., Ltd. or trade name) was used. On the other hand, the cation-permeable membrane (K) had a membrane surface area of about 28d1 and a thickness of about 0.15U.
16-0.17ff cation exchange membrane (Neosebuta 0
L-25T (trade name of Tokuyama Soda Co., Ltd.) was used. And an anion permeable membrane (A) and a cation permeable membrane ((
A copper porous layer (la) is placed on each layer (la) in the arrangement shown in the figure.
And a nickel porous layer (lb) is closely formed by electroless plating (thickness: about 0.5 μm). The other configurations are the same as those shown in FIG. 2 above. Note that the volume of each compartment is approximately 5.6 g. Depending on the case, the collection section (2) may also have a volume comparable to that of the concentration section (O).

In such a configuration, Nap/solution (
2oooppm) was introduced and circulated.

Then, in the detection part α2 equipped with a sodium ion-selective glass electrode, a chloride ion electrode, and a reference electrode, the diluted solution is
When the il concentration was measured, it was found that the N in the diluted solution decreased after about 50 minutes.
It was confirmed that the apl concentration had decreased to about 200 ppm. Further, when this diluted solution was sampled and subjected to an atomic absorption spectrometer, no nickel ions were detected (the detection limit for nickel ions by an atomic absorption spectrometer was dO,02/j).

FIG. 4 shows the changes over time in the concentration of Na+ and CI- in the diluted solution in the above example.

On the other hand, when the NaCl solution was electrodialyzed in the same manner as in the above example except that the anion-permeable membrane (A and the collection liquid channel (7) were removed), the changes over time of Na+ and at- were similar. However, it was found that nickel ions of o, axq/1 were mixed in the diluted solution.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an example of a conventional electrodialysis device, FIG. 2 is a configuration explanatory diagram showing a specific example of the electrodialysis device of the present invention, and FIG. 8 is a configuration explanatory diagram showing an example of the electrodialysis device of the present invention. FIG. 4 is a graph showing an example of the dialysis effect of the electrodialysis apparatus of the present invention. (1a)...Copper porous layer, (ib)...Nickel porous layer, (2), (2°)...Processing tank, (3)...
Short circuit part, (4)... Diluent inlet, (45... Diluent outlet, (4a)... Collection liquid inlet, (4a9... Collection liquid outlet, (5)...・Concentrate inlet, (5°)...
Concentrate outlet, (6), (7), (81-... flow path, t9
1, (ld, flll...liquid pump, 02...
Detection part, 03... cathode, α leak... anode, C9...
Cathode chamber, C61... Anode chamber, C71... Cathode chamber liquid,
[1B+...Anode chamber liquid, (A)...Anion permeable membrane, (K)...Cation permeable membrane, ■...Concentration chamber,
■...Dilution chamber, ■...Nickel ion collection section. 18- Figure 1 Figure 3-33- Figure 4 Time (minutes) →

Claims (1)

[Scope of Claims] 1. Anion-permeable membranes and cation-permeable membranes are alternately stretched and partitioned in the treatment tank, and two types of porous membranes having different redox potentials are formed near both sides of each membrane. Concentration chambers and dilution chambers are set up alternately by providing the material layers regularly, and the two types of porous material layers are short-circuited outside the processing solution to separate the concentrated and diluted electrolyte-containing solutions, respectively. an ion-permeable membrane having a polarity opposite to that of ions that can be eluted from the porous material layer in the vicinity of the corresponding porous material layer in the dilution chamber and/or the concentration chamber; An electrodialysis apparatus that does not require an external power source, and is configured to prevent the above-mentioned ions from being mixed into the diluted solution and/or concentrated solution. 2.7 The device according to claim 1, wherein the ion-permeable membrane and the cation-permeable membrane are an anion-exchange membrane and a cation-exchange membrane having ion selectivity.