JPH06325983A - Flat liquid-passing-type electric double-layer capacitor and liquid processing method - Google Patents

Abstract

PURPOSE:To provide a flat liquid-passing-type electric double-layer capacitor with a high and stable elimination ratio of ionic material and a liquid processing method using the double-layered capacitor used on a manufacturing scale. CONSTITUTION:A flat liquid-passing-type electric double-layer capacitor has active carbon layers 2 mainly made of active carbon with a high specific surface area thereof with a separator 1 made of electrically insulating porous liquid- passing sheet in between, current collecting electrodes 3 provided outside the active carbon layers 2, and holding plates 4 provided outside the collecting electrode 3. While a solution including an ionic material is passed through the electric double-layer capacitor, the treatment is carried out by repeating alternately a step, in which a DC stabilized voltage is applied to the collecting electrodes 3 and a step, in which short-circuit or reverse connection is carried out between the collecting electrodes 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat plate liquid-permeable electric double layer capacitor using an activated carbon layer. The present invention also relates to a method of treating a liquid containing an ionic substance by using the flat plate-type liquid-passing electric double layer capacitor.

[0002]

2. Description of the Related Art There is known a method of removing an ionic substance from water containing the ionic substance by using electrostatic force by using an electric double layer capacitor.

For example, US Pat. No. 5,192,432 discloses a through-type capacitor used in a column for constant-charge chromatography for the purpose of purifying a liquid, which comprises a first conductive support layer, a first conductive support layer, and A plurality of layers including a surface area conductive layer, a first non-conductive porous spacer layer, a second conductive support layer, a second high surface area conductive layer, a second non-conductive porous spacer layer, etc. A through-type capacitor in which adjacent layers are spirally wound is shown. It is also shown therein that the condenser can be used for the purification of water containing ionic substances such as sodium chloride.

[0004]

Problems to be Solved by the Invention US Pat. No. 5,192,924
The through-flow type capacitor disclosed in the specification No. 32 is of interest, and the present applicant is currently conducting research from each position in cooperation with the right holder of this US patent.

However, since this liquid-flowing type capacitor has a structure in which adjacent layer groups are spirally wound, uneven flow is apt to occur during liquid-flowing, and this liquid-flowing type capacitor is applied to the purification of a liquid containing an ionic substance. In this case, it was found that the removal rate of the ionic substance fluctuates during the purification operation and is not stable, and the removal rate is considerably low on average. For this reason, it has been difficult to use this liquid-conducting capacitor for refining liquid on an industrial scale.

Under the circumstances described above, the present invention provides a through-flow type electric double layer capacitor which has a high ionic substance removal rate and is stable, and which can be carried out on an industrial scale. It is an object of the present invention to provide a liquid treatment method using the liquid-passing type electric double layer capacitor.

[0007]

Means for Solving the Problems The flat plate-type liquid permeable type electric double layer capacitor of the present invention comprises a high specific surface area activated carbon as a main material with a separator (1) made of an electrically insulating porous liquid permeable sheet sandwiched therebetween. The activated carbon layers (2), (2) are arranged, the collecting electrodes (3), (3) are arranged outside the activated carbon layers (2), (2), and the collecting electrodes (3), ( The pressing plate (4), (4) is arranged outside of (3).

Further, the liquid treating method of the present invention is characterized in that a direct current to the collecting electrodes (3) and (3) is applied while the liquid containing an ionic substance is passed through the flat plate type liquid-passing electric double layer capacitor. It is characterized in that a constant voltage is applied and a short circuit or a reverse connection between both collector electrodes (3) and (3) is alternately repeated.

The present invention will be described in detail below.

As the separator (1), a filter paper, a porous polymer film, a woven fabric, a non-woven fabric, or the like, which is made of an organic or inorganic sheet which allows liquid to easily pass therethrough and which has electric insulation, is used. The thickness of the separator (1) is 0.01 to 0.
About 5 mm, especially about 0.02 to 0.3 mm is suitable.

As the activated carbon layers (2) and (2), layers having high specific surface area activated carbon as a main material are used. High specific surface area activated carbon means BET specific surface area of 1000 m ² / g or more, preferably 15
00m ² / g or more, more preferably 2000-2500m ²
Says / g of activated carbon. When the BET specific surface area is too small, the removal rate of the ionic substance when passing through the liquid containing the ionic substance decreases. If the BET specific surface area becomes too large, the removal rate of the ionic substance tends to decrease, so that it is not necessary to increase the BET specific surface area more than necessary.

The shape of the activated carbon to be used is arbitrary such as powdery or fibrous. In the case of powdery particles, it is used after being formed into a flat plate or sheet, and in the case of fibrous materials, it is processed into a cloth and used. Forming the powdery granular activated carbon into a flat plate shape or a sheet shape and using it is significantly advantageous in terms of cost, as compared with the case where the fibrous activated carbon is processed into a cloth shape and used.

Molding into a flat plate or a sheet is carried out, for example, by mixing powdered granular activated carbon with a binder component (polytetrafluoroethylene, phenol resin, carbon black, etc.) and / or a dispersion medium (solvent, etc.) into a plate. It is obtained by appropriately heat-treating after molding. Activated carbon layer
When a flat plate or sheet is used as (2) and (2), it may be perforated if necessary. Regarding the technique of using flat plate-shaped or sheet-shaped activated carbon, JP-A-63-107011, JP-A-3-122008, and JP-A-3-228814.
No. 63-110622, 63-226.
No. 019, Japanese Patent Laid-Open No. 64-1219, etc. are also disclosed, and those disclosed in those publications can be referred to.

The thickness of the activated carbon layers (2), (2) is often about 0.1 to 3 mm, especially about 0.5 to 2 mm, but is not limited to this range.

The collector electrodes (3), (3) are electrically good conductors such as copper plate, aluminum plate, carbon plate, foil graphite, etc., and can make close contact with the activated carbon layers (2), (2). What is used. The thickness of the collecting electrodes (3), (3) is not limited, but those having a thickness of about 0.1 to 0.5 mm are often used. In order to facilitate the application, terminals (leads) (3a) are usually provided on the collecting electrodes (3), (3).

As the pressing plates (4), (4), flat plates made of an electrically insulating material such as a plastics plate and hard to deform are used. A liquid inlet, a liquid outlet, a fixing bolt hole, and the like can be appropriately provided in the holding plates (4) and (4).

Frame-like gaskets (5) and (5) are preferably interposed between the collector electrodes (3) and (3) and the holding plates (4) and (4). Instead of providing such gaskets (5), (5) independently, a member having a sealing function may be provided on the holding plates (4), (4) side.

Using the above members, a holding plate (4) / (gasket (5) /) collector electrode (3) / activated carbon layer (2) / separator
(1) / activated carbon layer (2) / collector electrode (3) / (gasket (5)
/) A flat plate liquid-permeable electric double layer capacitor having the structure of the holding plate (4) is assembled.

A liquid containing an ionic substance is treated using the flat plate type liquid-conducting electric double layer capacitor having the above structure. Liquid treatment means not only purification of water, desalination of seawater, denitrification of waste liquid, but also recovery of precious metals,
It also includes processing for capturing and recovering ionic substances such as purification of inorganic salts and quantification of dissolved ionic substances. Examples of the liquid include water and other inorganic solvents, organic solvents, or mixed solvents thereof, which may be blood or the like. Examples of the ionic substance include an electrolyte and a chargeable substance such as a metal salt, an amine salt, an ammonium salt, an inorganic acid and an organic acid which can be dissociated in a liquid.

In carrying out the treatment of a liquid containing an ionic substance according to the present invention, the following procedure is adopted.・ Assemble a flat-plate liquid-flow type electric double-layer capacitor, and use a liquid feed pump, etc., to flow liquid containing ionic substances from the liquid inlet.・ Apply 0.5 to 5 V from the DC constant voltage source (in the case of an aqueous solution, keep it to about 2 V so that water will not be electrolyzed) or a voltage around it from the terminals of the collector electrodes (3), (3). To do. In the case of an aqueous solution: ・ Monitor the liquid at the liquid outlet using a conductivity meter, etc., and short-circuit (or reverse-connect) at appropriate timing and repeat application. Time control by a timer is also possible. When shorted (or reverse connection), activated carbon layer (2),
Ionic substances that were electrically adsorbed in (2) are desorbed,
It becomes a concentrated liquid and is discharged from the liquid outlet.

[0021]

The principle of processing a liquid containing an ionic substance by using the flat-plate through-flow type electric double layer capacitor of the present invention is illustrated by taking the case where the liquid containing an ionic substance is saline as an example. 6 shows.

As shown in FIG. 6 (a), when voltage is applied, the sodium ions in the water that has passed through the water flow into the anode side collecting electrode.
The activated carbon layer (2) in contact with (3) is electrically adsorbed, and the chlorine ions are electrically adsorbed in the activated carbon layer (2) in contact with the collector electrode (3) on the cathode side. Decrease significantly. Adsorption of both ions to the activated carbon layers (2) and (2) reaches saturation when water flow is continued, so the salt concentration at the outlet becomes close to that of the stock solution. If the cathode side and the anode side are short-circuited or reversely connected while seeing appropriate timing,
As shown in Fig. 6 (b), sodium and chlorine ions adsorbed on the activated carbon layers (2) and (2) are desorbed, and saline solution having a much higher concentration than the salt concentration in the stock solution is discharged from the outlet. It At this time, the concentration of salt in the outlet water is further increased by devising measures such as reducing the flow velocity during passage.

In the present invention, since the flat activated carbon layers (2) and (2) are used and each member is arranged and pressed to have a flat plate-shaped structure, the activated carbon layers (2) and (2) are Can be uniformly compressed, and uneven flow of the liquid at the time of liquid passage can be effectively prevented. Therefore, the removal rate of ionic substances can be stabilized, and the removal rate can be increased to the maximum.

[0024]

EXAMPLES The present invention will be further described with reference to examples.

<Production of Liquid-Passing Electric Double Layer Capacitor> Device Example FIG. 1 is an exploded view of a liquid-feeding electric double layer capacitor of the present invention,
FIG. 2 is an assembly diagram thereof. In FIG. 2, the collector electrodes (3) and (3) are shown in cross section.

The following members were prepared and the liquid-passing type electric double layer capacitor shown in FIG. 2 was produced.

(1) is a flat plate-shaped separator having a thickness of about
0.2 mm filter paper is used.

(2) and (2) are an activated carbon layer having a specific gravity of 0.4 and a size of 120 mm × 120 mm, and the BET specific surface area 2 produced by activating petroleum coke with potassium hydroxide.
It consists of 200 m ² / g powdery granular high specific surface area activated carbon mixed with polytetrafluoroethylene, carbon black and a suitable dispersion medium and compression molded into a 1.0 mm thick plate. The compounding ratio of activated carbon at the time of molding is 80% by weight.
The total amount of activated carbon contained in one activated carbon layer (2), (2) is 10
It is g.

(3) and (3) are collector electrodes having a thickness of 125 μm.
Made of foil-like graphite. One collector electrode
(3) The lower half has a through hole (3b) with a diameter of about 1 mm, and the upper half of the other collector electrode (3) has a similar through hole (3b). is there. A terminal (3a) is attached to each of these collector electrodes (3), (3).

(4) and (4) are holding plates, which are made of a polymethylmethacrylate plate having a thickness of 10 mm. Bolt holes (8) are provided on the periphery of the holding plates (4), (4). A liquid inlet (6) is provided at the lower corner of one holding plate (4), and a liquid outlet (7) is provided at the diagonally upper corner of the other holding plate (4). .

(5) and (5) are both frame-shaped gaskets having a thickness of 1 mm, which are obtained by punching a silicone rubber sheet into a frame shape.

The above-mentioned members were arranged in the arrangement shown in FIG. 1, and the liquid-flow electric double layer capacitor shown in FIG. 2 was assembled by pressing the bolts and nuts (9).

<Treatment of Liquid Containing Ionic Substance> Treatment Example 1 Using the through-flow type electric double layer capacitor obtained above, as shown in FIG. 2, the terminals (3a) of the collecting electrodes (3), (3), Connect (3a) to a 1 volt DC power supply, and press the 0.01% solution from the liquid inlet (6) of the holding plate (4).
A mol / liter saline solution was passed, and it was allowed to flow out from the liquid outlet (7) while being allowed to flow.

The flow rate at the time of passing saline solution is 0.9 ml / mi, respectively.
FIG. 3 shows the relationship between the cumulative liquid flow rate and the outlet solution salt concentration when n and 9.1 ml / min.

From FIG. 3, when the constant voltage of 1 volt is applied, the salt concentration at the outlet drops sharply, and at the flow rate of 0.9 ml / min, 93% of the maximum salt is removed. At the flow rate of 9.1 ml / min. It can be seen that up to 70% of the salt is removed.

Treatment Example 2 FIG. 4 shows the cumulative amount of liquid passing and the salt concentration of the outlet liquid when saline is passed through the liquid electric double layer capacitor of FIG. 2 and constant voltage application and short circuit are alternately repeated. It is a graph showing the relationship of.

Using the liquid-passing type electric double layer capacitor obtained above, as shown in FIG. 2, the terminals (3a) and (3a) of the collecting electrodes (3) and (3) were connected to a DC power source of 1 volt and held. Plate (4) Liquid Inlet (6)
A saline solution having a concentration of 0.01 mol / liter was passed through at a flow rate of 0.9 ml / min, and was allowed to flow out from the liquid outlet (7) while being allowed to flow.

Application of a constant voltage of 1 volt and short-circuiting were repeated at the timings shown in FIG. 4 to measure the salt concentration in the liquid flowing out from the liquid outlet (7). The results are shown in Fig. 4.

From FIG. 4, when the constant voltage of 1 volt was applied, the salt concentration at the outlet dropped sharply to remove 93% of the salt at the maximum, and when it was short-circuited, the salt concentration increased to about 4 times at maximum. When the application is started again when the salt concentration at the outlet is close to that of the stock solution, the salt concentration at the outlet drops sharply and salt is removed up to 93% in the same manner. A solution with a salt concentration that is doubled is derived.
It can be seen that similar results are obtained even when repeated more than once, and therefore the stability of the deionization rate is excellent.

Treatment Example 3 As the activated carbon layers (2) and (2), a felt-like cloth made of fibrous activated carbon having a BET specific surface area of 1450 m ² / g was used.
A through-flow type electric double layer capacitor was assembled in the same manner as in the above device example.

Using the liquid-passing type electric double layer capacitor obtained above, as shown in FIG. 2, the terminals (3a) and (3a) of the collecting electrodes (3) and (3) were connected to a DC power source of 1 volt and held. Plate (4) Liquid Inlet (6)
Saline solution having a concentration of 0.01 mol / liter was passed from the above, and it was made to flow out from the liquid outlet (7) in a state where it was allowed to flow.

The flow rate when passing saline solution is 1.0 ml / mi
FIG. 5 shows the relationship between the cumulative liquid flow rate and the outlet solution salt concentration when n is 10 ml / min. The flow rate is 2 activated carbon beds.
(2) The flow rate per 10 g of the total amount of fibrous activated carbon constituting (2).

From FIG. 5, it is found that the concentration of salt at the outlet drops sharply when a constant voltage of 1 volt is applied, and the flow rate is 1.0 ml / min.
It is understood that not only is the salt removal rate excellent in the case of 1, but the salt removal rate is large even when the flow rate is 10 ml / min.

[0044]

As described in the section of the operation, in the liquid-flow type electric double layer capacitor of the present invention, the flat activated carbon layers (2) and (2) are used and each member is arranged and compressed. Because of the flat plate-shaped structure, the activated carbon layers (2) and (2) can be uniformly compressed, and uneven flow of the liquid at the time of liquid passage can be effectively prevented. Therefore, the removal rate of ionic substances can be stabilized, and the removal rate can be increased to the maximum. In addition, even if the size is increased, the total thickness is thin, so that it is easy to arrange them in parallel in multiple stages to increase the capacity. Thus, the present invention enables the treatment of liquids on an industrial scale.

[Brief description of drawings]

FIG. 1 is an exploded view of a liquid-flow type electric double layer capacitor of the present invention.

FIG. 2 is an assembly diagram of the liquid through type electric double layer capacitor of FIG.

FIG. 3 is a graph showing the relationship between the cumulative liquid flow rate and the salt concentration of the outlet liquid when the flow rates during saline flow were 0.9 ml / min and 9.1 ml / min, respectively, in Treatment Example 1.

FIG. 4 is a graph showing the accumulated liquid passing amount and the outlet liquid salt concentration when salt water is passed through the liquid flow type electric double layer capacitor of FIG. 2 and a constant voltage application and a short circuit are alternately repeated in Treatment Example 2. It is a graph showing the relationship of.

FIG. 5 is a graph showing the relationship between the cumulative liquid flow rate and the outlet liquid salt concentration when the flow rate during saline solution flow was set to 1.0 ml / min and 10 ml / min in Treatment Example 3.

FIG. 6 is a principle diagram when a liquid containing an ionic substance is processed by using the flat plate liquid-permeable electric double layer capacitor of the present invention.

[Explanation of symbols]

(1) ... separator, (2) ... activated carbon layer, (3) ... collector electrode, (3
a) ... terminal, (3b) ... liquid passage hole, (4) ... holding plate, (5) ... gasket, (6) ... liquid inlet, (7) ... liquid outlet, (8) ... bolt hole,
(9)… Bolts and nuts

Claims (3)

[Claims] 1. An activated carbon layer (2), (2) having a high specific surface area activated carbon as a main material is disposed with a separator (1) made of an electrically insulating porous liquid-permeable sheet sandwiched therebetween, and the activated carbon layer ( 2), collecting electrodes (3), (3) are placed outside (2), and further collecting electrodes (3), (3)
A plate-shaped liquid-flow type electric double layer capacitor having a structure in which holding plates (4) and (4) are arranged outside (3). 2. The gasket according to claim 1, wherein frame-shaped gaskets (5), (5) are interposed between the collector electrodes (3), (3) and the holding plates (4), (4). Liquid type electric double layer capacitor. 3. A constant DC voltage is applied to the collecting electrodes (3), (3) while passing a liquid containing an ionic substance through the flat liquid-flowing type electric double layer capacitor of claim 1. Both collector electrodes (3),
(3) A method for treating a liquid, characterized by alternately repeating short-circuiting or reverse connection.