JPH11267648A - Electrochemical water treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical water treatment device capable of effectively sterilizing microorganisms existing in water and stably performing sterilization treatment of water over a long period. SOLUTION: This device is provided with an electrolytic cell 4 loaded with a porous carbon body which is formed by binding carbonaceous particles 14 and insulating particles 15 together, in the space between two terminal electrodes 5 and 6 (i.e., the anode and the cathode) of the cell 4. As the insulating particles 15, particles of a thermoplastic resin, thermosetting resin or ceramic material are used. Preferably, the particle size of each of the carbonaceous particles 14 and insulating particles 15 in 0.3 to 5 mm and the blending radio of (carbonaceous particles 14)/(insulating particles 15) is 10/90 to 50/50. Also preferably, each of the carbonaceous particles 14 has such crystal properties that the average lattice spacing (d002 ) is <=0.35 nm and the constituent crystallite size (Lc (002)) is >=2 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment apparatus for electrochemically disinfecting microorganisms existing in water, such as various kinds of treated water in the field of drinking water and food, bath water, domestic water or industrial water.

[0002]

2. Description of the Related Art Microorganisms such as fungi, protozoa, algae, and bacteria are present in various waters including drinking water such as tap water and well water. As a method for disinfecting these microorganisms, a method of adding a drug such as chlorine or hydrogen peroxide is widely used, and in addition, a disinfection method such as ultraviolet irradiation, heating and boiling is adopted. Although the method of adding a drug is simple, for example, the method of adding chlorine may require the treatment of residual chlorine, and the method of adding hydrogen peroxide or ozone, in which the residue does not matter, increases the cost. Therefore, it is not suitable for treating a large amount of water. Similarly, a sterilization method using ultraviolet irradiation or heating and boiling treatment is also unfavorable as a means for efficiently sterilizing a large amount of water because of high cost.

[0003] In recent years, a method for sterilizing microorganisms by electrochemical oxidation has been developed as a means for sterilizing large amounts of water efficiently and at low cost. In this method, porous carbon electrodes sandwiched between mesh-shaped metal electrodes via an insulating material are stacked in multiple stages, and a DC voltage is applied to the upper and lower mesh-shaped metal electrodes to polarize the porous carbon electrodes, thereby removing microorganisms. The water to be treated contains an electrochemical reaction at the anode portion polarized in the process of flowing through the fine pores of the porous carbon electrode, that is, the transfer of electrons between the microorganism and the electrode to kill the microorganism.

In this method of electrochemically sterilizing microorganisms in water, for example, as shown in FIG. 2, water 2 to be treated in a water storage tank 1 is continuously supplied to a lower part of an electrolytic cell 4 by a pump 3. The to-be-processed water 2 which has been electrochemically sterilized in the electrolytic cell 4 is discharged from the upper part and circulated to the water storage tank 1 for sterilization. For example, a voltage is applied to the electrolytic cell 4 by a DC power supply 7 using the lower electrode 5 as a cathode and the upper electrode 6 as an anode.

FIG. 3 is a schematic vertical sectional view illustrating the configuration of the electrolytic cell 4. In FIG. 3, a cylindrical case 8 is made of an electrically insulating material such as a synthetic resin, and a lower electrode 5 serving as a positive / negative terminal electrode is provided on both upper and lower ends inside the case 8.
(Cathode) and an upper electrode 6 (anode).
A plurality of porous carbon electrodes 9 are laminated between the upper and lower electrodes via a ring-shaped spacer 10 for maintaining electrical insulation. Titanium, platinum are provided on the upper and lower surfaces of the porous carbon electrode 9. A metal mesh electrode 11 such as that described above is applied. When a DC voltage is applied between the lower electrode 5 and the upper electrode 6, the porous carbon electrode 9 is polarized, and the water to be treated 2 containing the microorganisms supplied from the lower inlet 12 of the water treatment device 4 is supplied to the inside of the porous carbon electrode 9. Electrons are transferred between the microorganism and the electrode by an electrochemical reaction at the polarized anode in the process of flowing through the many fine pores, and the microorganism is killed by the redox reaction. The water 2 to be sterilized is discharged from the upper outlet 13 of the electrolytic cell 4.

As the porous carbon electrode for water treatment, for example, Japanese Patent Application Laid-Open No. 8-126888 includes a porous carbon electrode plate obtained by heat-treating and carbonizing a plurality of plant fiber sheets laminated using an organic binder. Is disclosed. This is intended to enhance the bactericidal efficiency (electrolytic efficiency) of microorganisms living in the water to be treated and to improve the anodic oxidation collapse characteristics and blocking resistance of the porous carbon electrode plate.

Japanese Patent Application Laid-Open No. 8-173972 discloses a porous carbon electrode having a small corrosion current in electrochemical water treatment, a large bactericidal action, and a high bending strength. An organic polymer substance is impregnated into a sheet of an electrochemical water treatment porous carbon electrode integrally bonded with a carbide, and a carbon fiber or a sheet of an organic polymer fiber that becomes a carbon fiber by carbonization, and the sheet is laminated. ,
A production method of heating and carbonizing is disclosed.

[0008] These porous carbon electrodes have a structure in which pores are complicated because they have a texture structure in which carbides of fibers are entangled, and water to be treated flowing in the pores flows while sufficiently contacting the pore surface, that is, the electrode surface. Therefore, there is an advantage that high sterilization efficiency can be obtained. On the other hand, when the pressure loss increases and there are many suspended matters, calcium, magnesium, etc. in the water to be treated, there is a problem that scales are generated by these suspended matters, calcium, magnesium, etc., and pores are blocked.

As a porous carbon electrode for water treatment, a graphite carbon electrode has been used. Graphitic carbon electrodes are made of particle-bonded porous texture produced by adding coal-based or petroleum-based pitch as a binder to aggregates such as coke powder, kneading, molding, and firing graphite. It is. This graphite porous carbon electrode has high strength and can control the porosity by adjusting the particle size of the aggregate particles.However, in order to increase the flow rate of the water to be treated and increase the treatment efficiency, the pore diameter and porosity are increased. If it is large, the sterilization efficiency decreases because the flow path of the water to be treated is linear and short,
The strength is also low. Therefore, the graphite particles are apt to fall off due to the water flow pressure during the water treatment, and the corrosion of the graphite due to anodic oxidation hardly progresses evenly. .

[0010]

As described above, if the pore diameter and the porosity of the porous carbon electrode are increased in order to increase the treatment efficiency of the electrochemical water treatment apparatus, the sterilization efficiency is reduced and the strength is also reduced. Become. On the other hand, in order to increase the sterilization efficiency, the water to be treated flowing in the pores needs to flow while being in sufficient contact with the pore surface, that is, the electrode surface, and the pore form is complicated and the pore diameter and porosity are small. It is desired. However, with such a porous property, the pressure loss during the flow of the water to be treated increases, and the pores are easily blocked, resulting in a reduction in the processing efficiency.

The present invention solves these problems and aims to efficiently sterilize microorganisms and to electrochemically remove microorganisms existing in water at a high treatment efficiency with less stomata clogging. An object of the present invention is to provide a water treatment apparatus capable of performing a sterilization process.

[0012]

In order to achieve the above object, an electrochemical water treatment apparatus according to the present invention is a porous water treatment apparatus in which carbonaceous particles and insulating particles are bound between positive and negative terminal electrodes. It is characterized by having an electrolytic cell equipped with a porous carbon body.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A water treatment apparatus for electrochemically disinfecting microorganisms has a low resistance to flow of the water to be treated passing through the pores of the porous carbon body, and the water to be treated and the porous carbon body Characteristics such as a large contact area with the metal, high corrosion resistance and high strength, and low resistance to electrolytic corrosion (anodic oxidation).

Among these properties, the flow resistance of the water to be treated and the contact area with the porous carbon body are largely affected by the pore properties of the porous carbon body. In the present invention, the porosity is controlled by the voids formed by binding the carbonaceous particles and the insulating particles to reduce the water flow resistance and increase the contact area. The carbonaceous particles and the insulating particles may have various shapes such as a sphere, an ellipse, and a column. However, in order to control the shape of the voids, a sphere having a uniform particle diameter is preferable.

As carbonaceous particles, coke particles are carbonized,
Graphitized granules can be used, but for example, those obtained by calcining and graphitizing resin spheres obtained by spheroidizing easily carbonizable resin such as phenol resin or furan resin in a non-oxidizing atmosphere are preferably used. . Further, it is preferable to use spherical particles of a thermoplastic resin such as polyvinyl chloride or polyethylene, a thermosetting resin such as a phenol resin or an epoxy resin, or ceramics such as silica or alumina as the insulating particles.

According to the present invention, a porous carbon body formed by binding these carbonaceous particles and insulating particles is mounted in an electrolytic cell in which water to be treated flows and a microorganism is sterilized by an electrochemical reaction. It is characterized by the following points. Since the flow resistance and sterilization efficiency of the water to be treated are greatly affected by the pore properties of the porous carbon body, in the present invention, in order to control the void properties formed by the carbonaceous particles and the insulating particles. ,
As the carbonaceous particles and the insulating particles, spherical particles having a uniform particle diameter are preferably used, and spherical particles having a particle diameter of 0.3 to 5 mm are preferably used.

The mixing ratio between the carbonaceous particles and the insulating particles is preferably set to a weight ratio of 10/90 to 50/50. Since the individual carbonaceous particles are polarized by the applied voltage and sterilize microorganisms on the polarized anode surface, if the mixing ratio of the carbonaceous particles is less than 10%, the number of polarized surfaces on which an electrochemical reaction occurs decreases. This is because sterilization effects such as sterilization efficiency and sterilization efficiency are reduced. However, if the mixing ratio of the carbonaceous particles exceeds 50%, a short circuit is likely to occur between the carbonaceous particles, making it difficult to polarize.

Further, in order to enhance the bactericidal effect and to impart high corrosion resistance, it is necessary that the surface activity of the carbonaceous particles is high, that is, the degree of graphitization is high and the crystallization of graphite is advanced. . When the surface activity is low, the germicidal effect is reduced because the current flowing with respect to the applied voltage is extremely small, and when the applied voltage is increased to enhance the germicidal effect, electrolytic corrosion due to anodic oxidation increases and carbonaceous material is increased. This is because the particles may collapse.

Therefore, it is preferable that the carbonaceous particles have a specific crystal structure in which the crystallization of graphite is advanced. Specifically, the value of the average lattice spacing d ₀₀₂ is 0.35 nm or less, and the size of the crystallite is Those having a crystal property with a value of Lc (002) of 2 nm or more are preferred. Average lattice spacing d _{002 of the} hexagonal graphite layer
Is greater than 0.35 nm and the crystallite size Lc (002) is less than 2 nm, the graphitization becomes insufficient and the activity of the surface becomes small, and the bactericidal effect and This is because the corrosion resistance is reduced. The crystal properties of such carbonaceous particles can be controlled, for example, by adjusting the firing carbonization temperature of the resin spheres when preparing the carbonaceous particles. The value of the average lattice spacing d ₀₀₂ and the crystallite size Lc
As the value of (002), a value measured by powder X-ray diffraction is used.

By bonding these carbonaceous particles and insulating particles, a porous carbon body is formed. The method of binding both particles is to cover the surface of the insulating particles with a solution of a resin such as phenolic resin or epoxy resin dissolved in an organic solvent,
After drying, it can be bound in a block shape and heat-treated. When the insulating particles are made of a thermoplastic resin or silica, they can be bound by heating to a temperature near the glass transition point of the insulating particles. In this way, the particle size and the mixing ratio of the carbonaceous particles and the insulating particles, the crystal properties of the carbonaceous particles, and the like can be adjusted to control the void properties by binding the two particles, and the electrolytic cell Thus, a porous carbon body to be attached to the device is obtained.

FIG. 1 is a schematic longitudinal sectional view illustrating the configuration of an electrolytic cell 4 of an electrochemical water treatment apparatus according to the present invention. In FIG. 1, a lower electrode 5 (cathode) and an upper electrode 6 serving as positive and negative terminal electrodes provided at both upper and lower ends of a cylindrical case 8.
The electrolytic cell 4 is formed by mounting a porous carbon body in which the carbonaceous particles 14 and the insulating particles 15 are bound between (anode). Reference numeral 16 denotes a void formed by the carbonaceous particles and the insulating particles. The porous carbon body is mounted between the positive and negative terminal electrodes 5 and 6. In addition to the porous carbon body provided in one stage as illustrated in FIG. 1, the porous carbon body may be provided in a multi-layered manner in the case 8.

[0022]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Examples 1-5 A spherical phenol resin having an average particle diameter of 1 mm was calcined and carbonized in an argon gas atmosphere at a temperature of 2500 ° C. to produce carbonaceous particles having an average particle diameter of 0.8 mm. The average lattice spacing d ₀₀₂ of the carbonaceous particles was 0.345 nm, and the crystallite size Lc (002) was 3 nm. Polyamide particles having an average particle diameter of 0.8 mm were used as insulating particles, and the surface of the polyamide particles was thinly coated with a phenol resin solution dissolved in ethanol and dried. After dispersing and mixing the carbonaceous particles and the insulating particles in water while changing the mixing ratio, put in a cylindrical case, filter and dry, and then apply a pressing force of 0.1 kg / cm ² to 150 ° C. Heated to a temperature of 70 to bind the carbonaceous particles and the insulating particles to a diameter of 76 mm and a height of 70 mm
Was prepared.

Example 6 A porous carbon body was produced under the same conditions as in Example 2 except that carbonaceous particles having an average particle diameter of 0.2 mm and insulating particles were used.

Example 7 The average lattice spacing d of the hexagonal mesh layer of graphite as carbonaceous particles
₀₀₂ is 0.337 nm, crystallite size Lc (002) is 35 nm
A porous carbon body was produced under the same conditions as in Example 2 except that cylindrical artificial graphite particles having a diameter of 3 mm and a height of 3 mm having the graphite crystalline properties described above were used.

Example 8 The average lattice spacing d of a hexagonal reticular layer of graphite as carbonaceous particles
₀₀₂ is 0.337 nm, crystallite size Lc (002) is 35 nm
A porous carbon body was produced under the same conditions as in Example 2 except that cylindrical artificial graphite particles having a diameter of 6 mm and a height of 6 mm having the graphite crystalline properties described above were used.

Example 9 A phenol resin ball was placed in an argon gas atmosphere for 15 hours.
Average particle size 0.8 produced by firing and carbonizing at a temperature of 00 ° C
A porous carbon body was produced under the same conditions as in Example 2 except that carbonaceous particles of mm were used.

Table 1 shows a comparison of the conditions for producing the porous carbon body thus produced.

[0029]

[Table 1]

These porous carbon bodies were mounted between positive and negative terminal electrodes to assemble the electrolytic cell shown in FIG. After sufficiently sealing the electrolytic cell so as not to leak water, a constant voltage of 35 V is applied from a DC power supply, and the water to be treated (well water) having a water temperature of 20 ° C. in the water storage tank is applied at a water pressure of 1.0 kg / cm ^2. A sterilization test was performed by circulating water. In this way, when the water treatment test was performed for two months, the change in the water flow rate, the state of the porous carbon body, and the 1-pass sterilization rate [｛1- (the number of viable bacteria on the exit side /
The number of living bacteria on the inlet side)｝ × 100 (%)] and the sterilization rate of water in the water storage tank after 24 hours were measured. Table 2 shows the obtained results.

Comparative Example 1 Coke particles were kneaded with a pitch binder, molded and calcined to produce a disk-shaped particle-bonded porous carbon body having a diameter of 76 mm and a thickness of 9 mm. A mesh-shaped wire net was attached to the upper and lower surfaces of the porous carbon body, and was stacked in eight stages between positive and negative terminal electrodes via a ring-shaped spacer to assemble the electrolytic cell shown in FIG. A sterilization test was performed using this electrolytic cell under the same conditions as in the examples, and the results are shown in Table 2.

[0032]

[Table 2]

From the results shown in Tables 1 and 2, it can be seen from the results that the electrochemical water of the embodiment was prepared by using an electrolytic cell having a porous carbon body formed by binding carbonaceous particles and insulating particles between positive and negative terminal electrodes. It is recognized that the treatment apparatus has little clogging generated in the voids, has a small decrease in the amount of flowing water even after the water-passing test for two months, and has little damage such as falling off of particles. In addition, the one-pass sterilization rate is high, and it can be seen that the water in the water storage tank is also sterilized at a high rate. On the other hand, the electrochemical water treatment apparatus of Comparative Example 1 used an electrolytic cell equipped with a particle-bonded porous carbon body, and thus had high strength and no abnormality even after a two-month water flow test. However, it is recognized that the decrease in water flow rate due to clogging of pores is somewhat large. Accordingly, the sterilization rate is low.

In the examples, when the particle size of the carbonaceous particles and the insulating particles constituting the porous carbon body is smaller than 0.3 mm, the pore size formed is also small, so that the water flow rate tends to decrease. On the other hand, in the case of a large particle diameter exceeding 5 mm, the pores formed are large, so that the water to be treated easily passes therethrough, and the electrochemical reaction on the polarized anode surface decreases, and the sterilization efficiency tends to decrease. Similarly, when the mixing ratio of the carbonaceous particles is less than 10%, the number of polarization interfaces decreases, and the sterilization efficiency decreases. Further, the degree of graphitization of the crystalline state of the carbonaceous particles progresses, and the value of the average lattice spacing d ₀₀₂ becomes 0.35 nm.
Hereinafter, it will be understood that when the crystallite size Lc (002) has a crystalline property of 2 nm or more, the sterilization efficiency is high and the corrosion resistance is improved, so that clogging is hardly caused and the decrease in water flow is small.

[0035]

As described above, according to the electrochemical water treatment apparatus of the present invention, an electrolytic cell in which a porous carbon body in which carbonaceous particles and insulating particles are bonded is mounted between positive and negative terminal electrodes. Therefore, the electrochemical reaction proceeds smoothly in the voids formed in the porous carbon body, so that the microorganisms in the water to be treated can be efficiently killed. Furthermore, by setting the particle size of the carbonaceous particles and the insulating particles, the mixing ratio, and the crystallinity indicating the degree of graphitization of the carbonaceous particles to a specific range, the corrosion resistance is excellent, the clogging hardly occurs, and the long term. Water treatment with high sterilization efficiency. Therefore, it is extremely useful as a water treatment apparatus for electrochemically sterilizing microorganisms existing in water such as drinking water, various kinds of treated water in the food field, and industrial water.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view illustrating the configuration of an electrolytic cell of an electrochemical water treatment apparatus according to the present invention.

FIG. 2 is a process chart showing an example of an electrochemical water treatment.

FIG. 3 is a schematic longitudinal sectional view illustrating the configuration of a conventional electrolytic cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water storage tank 2 Treated water 3 Pump 4 Electrolyzer 5 Lower electrode 6 Upper electrode 7 DC power supply 8 Electrolyzer case 9 Porous carbon electrode 10 Ring spacer 11 Mesh electrode 12 Treated water inlet 13 Treated water outlet 14 Carbon Particles 15 insulating particles 16 voids

Claims (5)

[Claims] 1. An electrochemical water treatment apparatus comprising: an electrolytic cell having a porous carbon body formed by binding carbonaceous particles and insulating particles between positive and negative terminal electrodes. 2. The electrochemical water treatment apparatus according to claim 1, wherein the insulating particles are particles of a thermoplastic resin, a thermosetting resin, or ceramics. 3. The carbonaceous particles and the insulating particles having a particle size of 0.
2. The electrochemical water treatment device according to claim 1, wherein the size is 3 to 5 mm. 4. The mixing ratio of carbonaceous particles and insulating particles constituting the porous carbon body is from 10/90 to 50/50.
The electrochemical water treatment device according to claim 1. 5. The carbonaceous particle has an average lattice spacing d ₀₀₂ of 0.35 nm or less and a crystallite size Lc (002) of 2 nm.
2. The electrochemical water treatment apparatus according to claim 1, wherein the apparatus has the above crystal properties.