JP2001129553A - Electrode coating type electrolyzing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode coating type electrolyzing system solving such a problem that secondary environmental pollution is generated and much money is required in maintenance taking out adsorbed matter in a conventional method for performing flocculation and sedimentation utilizing a flocculant or performing adsorption and separation using an ion exchange membrane or activated carbon in order to remove colloid or the like in an aqueous solution or to lower BOD or SS of waste water and providing a treatment method not generating secondary environmental pollution and low in cost. SOLUTION: (1) An electrode wherein a carbon rod is coated with porous conductive activated carbon is produced to be used in electrolysis and (2) the pH of a treated liquid is lowered and (3) colloid particles are gathered and sedimented by electrolysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial application fields] The present invention relates to treatment of wastewater such as domestic wastewater, industrial wastewater, and agricultural wastewater, and production treatment of industrial water.

[0002]

2. Description of the Related Art In the treatment of wastewater, a biochemical treatment method such as an activated sludge method is performed. After aeration treatment, dirt is extracted as floating sludge and settled sludge, and the BOD and SS of the treatment liquid are set to a certain standard value. The water is released into rivers, lakes and marshes, and public water bodies in the sea.

However, pollutants in treated water discharged below a certain reference value may re-elute and contaminate river water or cause red tide, etc., in the process of flowing through rivers and the like. Concentration by the food chain can cause harmful substances to accumulate biologically and biochemically in water systems, and there is a social demand that this standard must be stricter in terms of environmental protection and health protection.

Under these circumstances, in wastewater treatment, a method of chemically oxidizing and decomposing with chlorine, ozone, a strong acid, or the like, or a flocculant is used as a method of removing harmful substances that cannot be removed by biochemical treatment. Accordingly, physicochemical methods such as a method of insolubilizing and coagulating and separating, and a method of adsorbing using activated carbon or the like have been adopted.

[0005] However, the oxidative decomposition treatment is generally slow in reaction, and requires addition of another catalyst or heating.
In addition, toxic products may be generated in the process, and if the precipitated inorganic substance is treated as return sludge in the method of coagulation and separation, it may become a hindrance factor in biochemical treatment. Each of them had problems, such as difficult maintenance such as removal.

[0006] In view of the above, the inventors of the present application have proposed a Jinkasa method for maximizing the amount of oxygen supplied during aeration in biochemical treatment of wastewater treatment (Japanese Patent Application No. 10-30307).
Or a method using a differential pressure to generate fine bubbles (Japanese Patent Application No.
45227), and further propose a processing method (Japanese Patent Application No. 11-120313) corresponding to the production change of the utilization microorganisms such as “induction phase”, “log phase”, “stationary phase”, and “decrease phase”.
About aqua water (BOD ≒)
300ppm, SS ≒ 360ppm)
We have proposed an innovative method for treating microorganisms in wastewater and sewage, which can self-digest settled sludge.

In addition to such a biochemical treatment, a reverse electrolysis method (Japanese Patent Application No. 11-45228) for removing K, Ca, etc., which are contained in a treatment solution at a high concentration and have a high ionization tendency, as an electrochemical treatment method. ), And developed ecosystem-friendly treatment methods.

[0008] In these circumstances, the remaining problem is the removal of colloid particles from the treated water. The colloidal particles are approximately ^10-5 cm to ^10-7 c in diameter.
m, mainly divided into inorganic substances (gold, silver, platinum, carbon, sulfur, AgCl, As ₂ S ₃ ,
BaSO ₄ , Fe (OH) ₃ , Al (OH) ₃ , etc.)
And "hydrocolloids" mainly composed of organic compounds (soap, starch, agar, protein, etc.).

Since these are suspended in an aqueous solution, they cannot be separated as floating sludge or settled sludge, and it has been difficult to reduce BOD and SS in the case of wastewater. Also, when considered as industrial water, it was a major obstacle in removing impurities.

"Hydrocolloid" and "hydrocolloid"
Can be aggregated and precipitated by adding a small amount or a large amount of an electrolyte flocculant, separated into cations and anions, and removed using an ion-exchange membrane. However, problems still remain in terms of the properties, the cost of the coagulant itself and the maintenance cost.

[0011]

SUMMARY OF THE INVENTION In the treatment of waste water and the removal of impurities in industrial water, the removal of colloidal particles, which has been a problem, is not a conventional treatment method using a flocculant or the like. To remove the precipitate by a simple method.

[0012]

[Technology to solve the problem] A carbon rod is used as an electrode, covered with porous and conductive activated carbon to make both electrodes,
It was found that when the aqueous solution was electrolyzed, the pH changed from the upper surface of the aqueous solution to lower with time.

When the pH of the aqueous solution changes, ions that have an electrically double layer and are repelled by the same polarity charge are neutralized on the colloid surface constituting the “hydrophobic colloid”, and the intermolecular It was also found that the colloids aggregated and settled when force was applied.

Further, "hydrocolloid" tends to change from an anion to a cation when it becomes acidic from alkaline due to a change in pH. In the process of the change, the charge became zero, and it was found that the intermolecular force worked and the colloids aggregated and settled.

Therefore, the above-mentioned problem is solved by a method of changing the pH by electrolyzing an aqueous solution using the above-mentioned carbon electrode-coated electrode to precipitate and separate (remove) colloid.

[0016]

Hereinafter, specific examples of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of an electrode-coated electrolysis apparatus according to the present invention. (2) and (4) are electrodes obtained by coating carbon rods (6) and (8) with conductive activated carbon.
(2) is a positive electrode, and (4) is a negative electrode. (10) is a power source, (12) is an electrolytic cell, (14) is a bottom slope of the electrolytic cell with a slant, (16) is an aqueous solution, (18), (2)
0) is a drain port.

FIG. 2 is an enlarged sectional view of the electrodes (2) and (4) shown in FIG. This electrode has an elongated conical shape (φ1
Thick cylindrical shape (φ100) surrounding the carbon rod (6) of 0)
Of the activated carbon (2) and a carbon powder (22) having a size of several μm to increase the contact density between the carbon rod (6) and the activated carbon (2). In this way, we consider a structure that prevents carbon rods from gradually deforming during the electrolysis process while using carbon rods that are cheaper than electrodes using platinum, etc. Was.

When making this, conductive activated carbon (2)
In the center of the column, there is formed a cylindrical hole substantially larger than the diameter of the carbon rod (6). In this hole carbon powder (22)
Is filled, and a carbon rod (6) having a sharpened tip is protruded into it.

In one embodiment, as the aqueous solution (16) of the electrolytic cell (12) shown in FIG. 1, treated water (BOD and SS are both 5,000 to 14) after biochemical treatment of wastewater.
000 ppm, pH 8-10), and power supply (1
0), the DC voltage (20 to 22 V) and the DC current (1
A) was applied and the treated water was electrolyzed.

The pH of the treated water, in which the colloid particles float, gradually begins to decrease from the upper surface in contact with the air.
As the particle size changes, the colloid particles aggregate and precipitate. When electrolysis was continued for 24 hours, the aqueous solution (16)
The pH of the upper surface of the water was about 1.5 to 2.0, and the
The treated water from 8) also had a pH of about 2.

[0021] The sediment accumulates along the bottom slope (14), which is removed from the drain (20). The pH of the precipitate at this time is about 10 to 12. And B of processing solution
OD and SS were 20 to 30 ppm.

The colloidal particles in the waste water are composed of “hydrophobic colloid” mainly composed of inorganic substances such as carbon and sulfur, starch,
Both components of "hydrocolloid" mainly composed of organic matter such as protein are included. BOD and SS are 20-30pp
The decrease to m means that both colloids were able to collectively precipitate by electrolysis according to the method of the present invention.

From this example, the mechanism by which the colloid particles aggregate and precipitate can be considered as follows. This treatment solution contains sodium (Na ⁺ ) ions and chlorine (C
l ^-) to include a relatively high concentration of ions, consider a reaction with NaCl.

By the electrolysis, water (H ₂ O) is converted into hydrogen ions and hydroxyl (OH ⁻ ) ions. The hydrogen ions are attracted to the cathode, and electrons are supplied to generate hydrogen gas. Also, sodium chloride (NaCl)
⁺ ) Ions and chlorine (Cl ⁻ ) ions, and the chlorine ions are attracted to the anode to supply electrons and generate chlorine gas.

However, since both the anode and the cathode are covered with porous activated carbon, generation of hydrogen gas at the cathode and generation of chlorine gas at the anode can be suppressed. When actually measured, it was 1/10 or less of the normal generation amount. In addition, the temperature of the aqueous solution is 5 under the condition of the electrolysis and 5 under the normal electrode.
Although the temperature rises to 0 to 60 ° C., in this embodiment, it is 30 to 40 ° C.
The temperature rose to only ° C, confirming such a reaction.

As a result, it is considered that the concentration of hydrogen ions in the aqueous solution increased, and a change to decrease the pH occurred in the aqueous solution.

Among the colloids, the “hydrophobic colloid” floats without sedimentation because the same kind of charge is repelled on the surface and an electrically double layer is formed, but hydrogen ions and hydroxyl ions increase. As a result, it is considered that the charge was neutralized, the repulsion was lost, and the particles were settled and settled.

"Hydrocolloids" become cations or anions by changing the pH. For example, in the case of an amino acid, it acts as an anion when the solution is alkaline and as a cation when it is acidic. In the case of this treated water, the pH was originally 8 to 10 alkaline,
Is changed from an anion to a cation in the process of becoming acidic. At this time, since the ionic value passes through zero, the repulsive force due to the electric charge disappears at that time, and it is considered that the attractive force of the molecule of Van der Waals acts to collectively settle.

[0029]

As described above, in the present application, the carbon rod is used as the core of the electrode,
By electrolyzing this with an unconventional method of coating with conductive activated carbon, the pH can be temporarily lowered and changed from the upper surface of the aqueous solution, and if this change in pH is used, colloid particles are collected and precipitated, BO such as wastewater treatment liquid
D and SS could be greatly reduced. In this method, the power consumption used for the electrolysis can be extremely suppressed by the action of the coated porous activated carbon, and the precipitated colloid particles can be easily taken out from the lower drain port. In addition, this electrolyzer is composed of a carbon rod as a core and is designed to have good durability.The coating material is also activated carbon, and it is made of a low-cost material. It is easier to use industrially than it is.

If the treated wastewater is only discharged to a river or the like, BOD and SS of 20 to 30 ppm can be said to be sufficient, but if this electrolysis method is carried out for a little more time,
BOD and SS can be reduced to zero or unmeasurable region. Since the treated water at that time has no decay factor, the treated water is highly treated and has no impurities even if left for a long time (sealed).

The use of this method can be applied to the production of industrial water in which removal of impurities is required with high precision. The embodiment described in the above description is merely an example, and the present invention is not limited to this embodiment.

[Brief description of the drawings]

FIG. 1 is a view showing an electrolysis apparatus using an electrode coating type electrolysis system according to the present invention.

FIG. 2 is a drawing showing the structure of the electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D061 DA01 DA08 DB16 DC06 EA07 EB16 EB29 EB35 EB37 EB39 GA22 GC18 4K021 AA01 AB25 BA02 BB02 DA10 DA13 DC15

Claims (3)

[Claims] 1. An electrode-coated electrolysis system in which a carbon rod is used as an electrode and the carbon rod is coated with a porous conductive material such as activated carbon. 2. The method according to claim 1, further comprising the step of:
An electrode-coated electrolysis system, wherein an electrode characterized by changing the pH from the upper surface of an electrolytic solution is coated with a porous conductive material such as activated carbon. 3. The method according to claim 1, wherein the condition in which the colloid in the aqueous solution floats is removed by an electrochemical change due to the pH change.
A system for removing impurities from an aqueous solution, comprising using an electrode-coated electrolysis system as set forth in claim 2, wherein the system is subjected to collective sedimentation.