JP3180313B2 - Anion contaminant removal equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to CrO ₄ ^2- , Cr
^{_{2 O 7 2-, AsO 4 3-}} , AsO 3 3-, SeO 4 2-, SeO 3 2-, CN -, PbO 2 2-
The present invention relates to a device for removing anionic contaminants such as contaminated soil.

[0002]

2. Description of the Related Art Soil contaminated by factory wastewater, factory waste, mine wastewater, and the like may contain contaminants such as cadmium, lead, copper, zinc, arsenic, selenium, nickel, and chromium. However, if such soil is left as it is, there is a risk that such substances will diffuse into the environment via groundwater and biological cycles.

For this reason, the contaminated soil is excavated and removed and subjected to a predetermined treatment. Thereafter, the contaminated soil is disposed of in a management type or cut-off type disposal site. It is common to return to the original state on the land.

[0004] However, such a method has a problem that contaminated soil is disturbed during excavation, which may cause secondary pollution. In addition, a large amount of contaminated soil must be carried out and transported. The problem that excavation removal itself becomes difficult directly underneath occurs. Therefore, recently, in-situ purification technology has begun to be studied, and as one of the methods, a method of recovering contaminants by energization has been disclosed in Japanese Patent Laid-Open No. 5-59716.
No. 6,086,045.

[0005] In the method, first, a water blocking wall is constructed in a ground area to be treated, and then an anode and a cathode each formed of a hollow tube having a large number of water passage holes are inserted into the ground area, A DC voltage is applied between the electrodes after water is appropriately sprayed on the ground area, and then water collected on the cathode side by an electroosmosis phenomenon is drained and collected through a hollow tube.

According to such a method, the predetermined contaminants are:
The contaminants can be removed by collecting the waste water by flowing into the cathode side by riding on the flow of water caused by the electroosmosis phenomenon.

[0007]

On the other hand, chromium, arsenic,
Selenium, cyanide, copper, etc. are CrO ₄ ^2- , Cr
^{_{2 O 7 2-, AsO 4 3-}} , AsO 3 3-, SeO 4 2-, SeO 3 2-, CN -, PbO 2 2-
(Under alkalinity) in the form of anions. The experiment conducted by the applicant that these anion contaminants could be hardly recovered on the cathode side because, when energized, they were subjected to a force in the anode direction by electrophoresis while opposing the flow of water moving to the cathode. It turned out.
Therefore, the only way to collect anion contaminants is to remove those collected near the anode together with the soil. However, a series of operations such as excavation, transportation, and soil of the soil are required, and the removal efficiency is extremely poor.

The present invention has been made in view of the above circumstances, and has as its object to provide an anion contaminant removal apparatus capable of efficiently collecting anion contaminants from contaminated soil.

[0009]

To achieve the above object, an apparatus for removing anionic contaminants according to the present invention is defined in claim 1.
As described in the above, a permeable layer communicating with the drain port is provided near the bottom of the treatment tank, an anode is provided above the permeable layer, and the cathode is separated through the accommodation space of the contaminated soil containing anionic contaminants. A water supply means for supplying water to the storage space is provided, and the cathode and the anode are arranged such that the cathode is above and the anode is below, and the cathode side is undrained. is there. Further, the anion contaminant removal apparatus according to the present invention monitors the water level in the treatment tank so that the water level is maintained near the ground surface or slightly higher than the ground surface. Further, the anion contaminant removal apparatus according to the present invention includes an anode and a cathode in the treatment tank such that the cathode is on the upper stage and contains anion contaminants therebetween, as described in claim 3. It is installed substantially parallel so that a storage space for storing the contaminated soil is formed, and near the bottom of the treatment tank, when the contaminated soil is stored in the storage space, the weight of the contaminated soil is supported and the water in the contaminated soil is supported. Attached to the permeable support plate is a water permeable support plate, and the anode is installed on the permeable support plate, while a water sprayer is installed above the treatment tank to supply water to the contaminated soil in the storage space. In the lower part of the treatment tank, a drain port communicating with a permeable layer formed below the permeable support plate is provided,
The cathode side is not drained.

In the apparatus for removing anionic contaminants according to the present invention, the cathode is disposed at least one of the upper side and the side, and the cathode is not drained, so that water flows from the cathode toward the anode by gravity. It is devised to move, preventing the movement of water to the cathode by electroosmosis, and in such a state, water in the contaminated soil is drained from the anode side.

[0011] Then, the anionic contaminants naturally collect on the anode by electrophoresis and are collected together with the water without opposing the movement of water to the cathode by electroosmosis.
In addition, the closer to the anode, the higher the acidity and the higher the solubility of the anion contaminants, so that they can be more efficiently collected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the anion contaminant removal apparatus according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an apparatus for removing anionic contaminants according to this embodiment. In the removing apparatus 1 of the present embodiment, an anode 3 and a cathode 4 are installed in a processing tank 2 formed in a box shape of concrete or the like so as to be substantially parallel so that the cathode 4 is located at an upper stage. Between 4, Cr
^{_{O 4 2-, Cr 2 O 7}} 2-, AsO 4 3-, AsO 3 3-, SeO 4 2-, SeO 3 2-, C
An accommodation space 5 for accommodating contaminated soil containing anionic contaminants such as N ⁻ and PbO ₂ ²⁻ is formed.

Here, the anode 3 is preferably constituted by arranging a predetermined number of carbon rods, for example, and the cathode 4 is preferably constituted by assembling reinforcing bars in a lattice shape, for example. The interval between the anode 3 and the cathode 4 is preferably, for example, about 1.5 to 2 m.

In the vicinity of the bottom of the treatment tank 2, a water permeable support plate 6 for supporting the weight of the contaminated soil when it is stored in the storage space 5 and permeating the water in the contaminated soil downward is attached. The anode 3 is preferably set on the permeable support plate 6.

On the other hand, a sprinkler 7 connected to a water supply pump (not shown) is provided above the treatment tank 2 so that contaminated soil in the storage space 5 can be supplied with water.

A drain 8 communicating with a permeable layer 9 formed below the permeable support plate 6 is provided below the treatment tank 2, and the treatment tank 2 is provided with a drain port 8 at the side of the treatment tank 2. A water level gauge 10 communicating with the inside of the tank 2 is installed. In addition, the drain port 8 is
It is configured to be openable and closable by a valve (not shown).

In the apparatus for removing anionic contaminants according to the present embodiment, first, the cathode 4 is detached from the processing tank 2 and Cr is removed.
^{_{O 4 2-, Cr 2 O 7}} 2-, AsO 4 3-, AsO 3 3-, SeO 4 2-, SeO 3 2-, C
After charging the contaminated soil containing anionic contaminants such as N ^- and PbO ₂ ^2- into the storage space 5, the cathode 4 is attached again (FIG. 2,
Step 101).

Next, as shown in FIG. 3, the sprinkler 7 is operated to supply water to the contaminated soil 11 so that the water level in the treatment tank 2 is maintained near the ground surface or slightly higher. While monitoring with the total 10, a direct current voltage is applied between the anode 3 and the cathode 4 to energize, and the supplied water is drained through the permeable layer 9 and the drain port 8 to collect the anionic contaminants (Step 102). .

Here, regarding the method of water supply / drainage and energization, there is a method of repeating the procedure of supplying water, energizing for a predetermined number of days, then draining and collecting anionic contaminants, and simultaneously performing water supply / drainage and energization. However, there is a method of continuously exchanging a certain amount of water, and which method to use may be appropriately selected depending on the amount and properties of the contaminated soil, the type of anion contaminants, and the like.

It is to be noted that the cathode 4 side is not drained from the start to the end of the current flow, and the movement of water to the cathode 4 due to electroosmosis is prevented. That is, the water in the soil tends to move to the cathode 4 by electroosmosis, but if the water is not drained on the cathode side, the force for moving to the cathode 4 and the pressure or its own weight due to the rise in the water level near the cathode are reduced. Equilibrium and water stops moving. Alternatively, when performing continuous processing, water moves downward.

When electricity is supplied in such a state, the anionic contaminants naturally collect on the anode 3 by electrophoresis and downward water flow without opposing the movement of water to the cathode 4 by electroosmosis as in the prior art. . In addition, the closer to the anode 3, the higher the acidity and the higher the solubility of anionic contaminants, so that more efficient recovery is possible.

Next, the water recovered from the anode is subjected to a water treatment using an ion exchange resin or the like in an acidic environment to separate and remove anionic contaminants in the water (step 103). Next, the treated water from which the anionic contaminants have been removed is recycled for water supply (step 104), and finally, the treated soil is taken out of the treatment layer 2 and returned to the original ground to restore (step 105). .

The water recovered on the anode side has a high acidity. Therefore, rather than making this an alkali and performing general water treatment, if the anionic environment is used as it is to separate and treat the anion contaminants, and the treated water after treatment is recycled for water supply, Water that easily dissolves anionic contaminants can be supplied to the soil.

The wastewater from which the anion contaminants have been separated and removed is subjected to a pH treatment after the completion of the construction and discharged to sewage.

As described above, according to the apparatus for removing anionic contaminants according to the present embodiment, the cathode side is not drained and only the anode side is drained, so that CrO ₄ ²⁻ and Cr ₂ O ² are removed.
^{_{7 2-, AsO 4 3-, AsO}} 3 3-, SeO 4 2-, SeO 3 2-, CN -, PbO 2 2- anion contaminants, such as, being obstructed by the flow of water by electroosmosis Instead, the anode smoothly reaches the anode by the electrophoresis and the downward water flow, and thus, it becomes possible to efficiently collect and collect the anion contaminants at the anode.

Further, the solubility of the anionic contaminants increases as the distance from the anode increases, so that the vicinity of the anode can be efficiently decontaminated.

In addition, the non-drainage of the cathode eliminates the movement of water due to electroosmosis, and accordingly the flow of water in the soil can be controlled by the amount and position of water supply and drainage.

Further, the separation and removal of the anion contaminants in the wastewater is performed in an acidic state, and the treated water is recycled for water supply, so that the anion contaminants in the soil are easily dissolved. This makes it possible to more efficiently collect and remove anionic contaminants in the soil than to return to alkali once and separate and remove it, and then recycle it for water supply.

In this embodiment, a method using an ion-exchange resin is employed as a method for performing water treatment in an acidic environment. Instead of such a method, for example, arsenic or selenium is adsorbed on an iron compound to remove it. You may employ the method of aiming.

In the present embodiment, the drained water is treated in an acidic environment. However, it is not always necessary to treat the discharged water in an acidic environment. Water treatment may be performed, and in such a case, the treated water need not be recycled for water supply.

Further, in the present embodiment, the cathode is disposed so as to be opposed to the anode in parallel. However, the present invention is not limited to such a positional relationship. May be formed. For example, the cathode position may be set laterally instead of or in addition to the above-mentioned position. FIG. 4 shows an example in which a cathode 12 formed of a metal plate is attached to the inside of the processing tank 2 in addition to the cathode 4 described in FIG. With this configuration, the decontamination effect is further improved. Furthermore, the processing tank 2 may be made of an iron plate, and the entire processing tank 2 may be used as a cathode.

[0033]

As described above, according to the apparatus for removing anionic contaminants according to the present invention, anionic contaminants can be efficiently recovered from the contaminated soil.

[0034]

[Brief description of the drawings]

FIG. 1 is a schematic view showing a device for removing anionic contaminants according to an embodiment.

FIG. 2 is a flowchart illustrating a method of using the anion contaminant removal apparatus according to the embodiment.

FIG. 3 is an explanatory diagram showing a state during energization in the removal apparatus of the embodiment.

FIG. 4 is a schematic view showing a modification of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Removal apparatus 2 Processing tank 3 Anode 4, 12 Cathode 5 Contaminated soil accommodation space 7 Sprinkler (water supply means) 8 Drainage port 9 Permeable layer 11 Contaminated soil

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-48827 (JP, A) JP-A-5-336842 (JP, A) JP-A-7-236879 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B09C 1/00-1/10 A62D 3/00 E02D 3/11 E21B 43/00

Claims (3)

(57) [Claims] 1. A water-permeable layer communicating with a drain port is provided near the bottom of a treatment tank, an anode is provided above the water-permeable layer, and a cathode is provided across a space for containing contaminated soil containing anionic contaminants. A water supply means for supplying water to the accommodation space is provided, and the cathode and the anode are arranged such that the cathode is located above and the anode is located below, and the cathode side is not drained. Anion contaminant removal equipment. 2. The anion contaminant removal apparatus according to claim 1, wherein the water level in the treatment tank is monitored by a water level meter so as to be maintained near or slightly higher than the ground surface. 3. An anode and a cathode are installed in a treatment tank substantially parallel to each other so that the cathode is on the upper stage and a storage space for storing contaminated soil containing anion contaminants is formed therebetween. In the vicinity of the bottom of the treatment tank, a water permeable support plate for supporting the weight of the contaminated soil when the contaminated soil is stored in the storage space and permeating the water in the contaminated soil downward is attached. While the anode is installed on the upper side, a sprinkler is installed above the processing tank so that water can be supplied to the contaminated soil in the storage space, and the water permeable support plate is provided at the lower part of the processing tank. A drain port communicating with a water-permeable layer formed underneath, and the cathode side is not drained.