JP5836203B2 - Treatment method of soil contaminated water with photocatalytic material - Google Patents

Description

  The present invention relates to a method for treating soil contaminated water with a photocatalytic material. Specifically, the present invention relates to a treatment method for detoxifying soil contaminated water due to harmful volatile organic compounds and heavy metals contained in soil and groundwater using a photocatalytic material.

  In recent years, volatile organic compounds used for industrial cleaning and toxic metals in industrial wastewater have infiltrated the soil, causing serious soil contamination.

  Various methods are used to treat volatile organic compounds such as dichloromethane, carbon tetrachloride, dichloroethane, dichloroethylene, trichloroethane, trichloroethylene, tetrachloroethylene, dichloropropane, benzene, chloroform, toluene, and xylene that have entered the soil. Yes. For example, a method is known in which contaminated groundwater pumped up from contaminated soil is pumped and aerated, and gas-liquid separated exhaust gas (gas phase) is treated by an adsorption process using activated carbon, a thermal decomposition process, or the like. However, the adsorption treatment with activated carbon has a problem in that the adsorption capacity reaches saturation immediately, so that the adsorption effect has only a short time. Further, the thermal decomposition treatment has a problem that a lot of energy is required.

  In the technology disclosed in Patent Document 1, a volatile organic compound is decomposed by pumping up contaminated groundwater to obtain a gaseous volatile organic compound, and using a photocatalytic material and irradiating with ultraviolet rays. The processing method is adopted. In Patent Document 1, in order to increase the reaction area of the photocatalytic material, a photocatalytic material in which a honeycomb-like material is coated with titanium oxide is used. However, in Patent Document 1, since a fine titanium oxide powder is used as a photocatalyst material in a binder, most of the titanium oxide particles are buried inside the binder. In addition, the technique disclosed in Patent Document 1 has a problem that the adhesion between the photocatalytic material and the substrate is weak.

  In addition, as a method for treating harmful heavy metals such as lead, cadmium, hexavalent chromium, arsenic, mercury, and copper that have entered the soil from factory wastewater, the heavy metals are fixed by chemical chelation and ion exchange. A technique, a technique of separating heavy metals by high-temperature treatment in an incinerator, and the like are employed. However, the processing method has a problem that not only the processing cost becomes high, but also it is difficult to recover a low concentration heavy metal.

  In the technique disclosed in Patent Document 2, a photocatalyst fine particle in which iron oxyhydroxide particles are dispersedly supported on a titanium oxide photocatalyst, and a photocatalyst material obtained by coating the photocatalyst fine particle on a plate-like body, porous material, or fibrous material A technique for removing lead, which is a heavy metal, is used. However, if the photocatalyst fine particles are treated as they are, there is a problem that it takes time and effort to separate the photocatalyst fine particles from the solution. Further, the method of coating the photocatalyst fine particles has a drawback that most of the titanium oxide particles are buried inside the binder because a fine particle titanium oxide powder is included in the binder. In addition, the technique disclosed in Patent Document 2 has a problem that adhesion between the photocatalytic material and the substrate is weak.

JP 2004-105817 A JP 2010-69449 A

  Therefore, the present invention aims to provide a new method for treating soil-contaminated water using a photocatalytic material that can efficiently remove volatile organic compounds and heavy metals causing soil contamination only by light irradiation. It is.

  As a result of intensive studies to solve the above problems, the present inventors have found that contaminated groundwater pumped (pumped) from the contaminated soil, an aqueous solution in which water is injected into the soil and volatile organic compounds are taken into the water. (Or mixed solution) (soil-contaminated water) is gas-liquid separated (preferably pumped explosion), and the resulting volatile organic compound contained in the gas phase is irradiated with light using a photocatalytic material (preferably It has been found that the volatile organic compound is decomposed and rendered harmless by performing ultraviolet irradiation. The reaction that decomposes the volatile organic compound with the photocatalyst material is a reaction in which the volatile organic compound touches the surface of the photocatalyst material. Therefore, when the decomposition proceeds and the concentration of the volatile organic compound decreases, the volatile organic compound of the photocatalyst material Decomposition efficiency is reduced. Therefore, when a volatile organic compound remains in the gas phase, in order to completely remove the volatile organic compound, a secondary treatment such as adsorption removal by activated carbon or removal by thermal oxidation may be used. I also found out.

  In addition, contaminated groundwater pumped from the contaminated soil (pumped water), an aqueous solution (or mixed solution) in which heavy metals are dissolved by injecting water into the soil (soil contaminated water), and gas-liquid separation (preferably It is found that heavy metals are removed and detoxified by carrying out light irradiation (preferably ultraviolet irradiation) to the heavy metals contained in the liquid phase obtained by carrying out light irradiation (preferably ultraviolet irradiation). It was. Similarly to the decomposition of the volatile organic compound by the photocatalyst material, when heavy metal remains in the liquid phase, the heavy metal is further removed by electrolytic treatment in order to completely remove the heavy metal. It has also been found that secondary treatments such as a removal method, a method of insolubilizing heavy metals by chemical chelation, and a method of separating heavy metals by carrying out a hydroxide treatment may be used.

  The photocatalyst material used in the present invention comprises a large amount of crystalline titanium oxide on the surface of metal titanium or titanium alloy, in particular anatase having high photocatalytic activity, by forming titanium nitride on the surface of metal titanium or titanium alloy and then anodizing it. It has been found that it is preferable to use a photocatalytic material having a large amount of type titanium oxide.

  The present invention has been completed based on such findings.

  That is, the present invention is a technique for efficiently removing harmful substances such as volatile organic compounds and heavy metals contained in the soil contaminated water and detoxifying the soil contaminated water.

Item 1. A method for treating soil contaminated water that detoxifies volatile organic compounds contained in soil contaminated water,
(1) Gas-liquid separation of soil contaminated water to obtain a gas phase, and (2) a step of decomposing a volatile organic compound contained in the gas phase obtained in Step 1 with a photocatalytic material. And a method for treating soil contaminated water with a photocatalytic material.

Item 2. A method for treating soil contaminated water that removes heavy metals contained in soil contaminated water,
(1) gas-liquid separation of soil contaminated water to obtain a liquid phase, and (2) a step of removing heavy metals contained in the liquid phase obtained in step 1 with a photocatalytic material, Treatment method of soil contaminated water with photocatalytic material.

  Item 3. Item 1 is characterized in that the photocatalyst material is a photocatalyst material having a crystalline titanium oxide film obtained by forming a titanium nitride on the surface of titanium metal or a titanium alloy and then anodizing it. Or the processing method of the soil contaminated water by the photocatalyst material of 2.

  Item 4. Item 4. The method for treating soil contaminated water with the photocatalytic material according to Item 3, wherein the crystalline titanium oxide is anatase-type titanium oxide.

Item 5. When the undecomposed volatile organic compound remains in the gas phase after the step 2,
(3) The above-mentioned item comprising a secondary treatment step by at least one method selected from the group consisting of adsorption removal by activated carbon and removal by thermal oxidation of volatile organic compounds in the gas phase. A method for treating soil-contaminated water using the photocatalytic material according to 1, 3 or 4.

Item 6. When unremoved heavy metal remains in the liquid phase after the step 2,
(3) The heavy metal in the liquid phase is selected from the group consisting of a method of removing heavy metal by electrolytic treatment, a method of insolubilizing heavy metal by chemical chelation, and a method of separating heavy metal by hydroxide treatment. Item 5. The method for treating soil contaminated water with the photocatalytic material according to Item 2, 3 or 4, further comprising a step of performing a secondary treatment by at least one method.

  Item 7. Using a photocatalytic material, characterized by comprising a gas phase preparation chamber for obtaining a gas phase by gas-liquid separation of soil contaminated water and a photocatalytic device for decomposing volatile organic compounds contained in the gas phase with a photocatalytic material A soil contaminated water treatment device that detoxifies volatile organic compounds contained in soil contaminated water.

  Item 8. Item 8. The soil-contaminated water according to Item 7, comprising a secondary treatment chamber for treating a volatile organic compound in the gas phase by at least one method selected from the group consisting of adsorption removal by activated carbon and thermal oxidation. Processing equipment.

  Item 9. Soil contamination using photocatalyst material, characterized by comprising a liquid phase preparation chamber that obtains a liquid phase by gas-liquid separation of soil contaminated water and a photocatalytic device that removes heavy metals contained in the liquid phase with a photocatalytic material Soil contaminated water treatment equipment that removes heavy metals contained in water.

  Item 10. At least one selected from the group consisting of a method of removing heavy metals in the liquid phase by electrolytic treatment, a method of insolubilizing heavy metals by chemical chelation, and a method of separating heavy metals by hydroxide treatment Item 10. The soil contaminated water treatment apparatus according to Item 9, further comprising a secondary treatment chamber for treatment by two methods.

  The present invention is described in detail below.

(1) Soil contaminated water Volatile organic compounds and heavy metals (or heavy metal ions) present in soil (or groundwater) enter the soil as volatile organic compounds and heavy metals (or heavy metal ions) from or near the ground surface. And penetrates underground. As a result, soil and groundwater are contaminated. In addition, volatile organic compounds and heavy metals (or heavy metal ions) that have flowed out from the pollution source penetrate into the ground in a liquid form, and part of them stay in the soil gap. In addition, the source solution of the pollution source reaching the aquifer descends in the aquifer when the gap between the formations is large and reaches an impermeable layer such as a clay layer, and stays near the groundwater surface when the gap is small.

  In the method and apparatus for treating soil contaminated water of the present invention, the soil contaminated water to be treated is an aqueous solution (or mixed solution) containing volatile organic compounds and heavy metals (or heavy metal ions) contaminating the soil and groundwater. ). Specifically, contaminated groundwater pumped (pumped) from contaminated soil containing volatile organic compounds and heavy metals (or heavy metal ions), water was injected into the soil, and volatile organic compounds were taken into the water. An aqueous solution (or mixed solution), an aqueous solution (or mixed solution) in which water is poured into soil and heavy metals (or heavy metal ions) are dissolved in water, or the like.

  If groundwater does not exist in the ground of the soil, water is poured into the soil and the water is pumped (pumped) from the soil so that volatile organic compounds and heavy metals (or heavy metal ions) are taken into or dissolved in the water. Volatile organic compounds and heavy metals (or heavy metal ions) can be recovered from the soil.

(2) Photocatalytic material As the photocatalytic material used in the present invention, titanium oxide having high activity and stability is preferable. Titanium oxide is a photocatalyst that undergoes a redox reaction by generating holes in the valence band and electrons in the conduction band when irradiated with ultraviolet light of 400 nm or less. By this oxidation-reduction reaction, active oxygen species such as OH radicals are generated, and this active oxygen oxidizes and decomposes organic substances in the gas phase and liquid phase and reduces metal ions and the like.

  As the photocatalyst material, a photocatalyst material having a crystalline titanium oxide film obtained by forming titanium nitride on the surface of titanium metal or a titanium alloy and then anodizing it is preferable.

  The crystalline titanium oxide is preferably anatase type titanium oxide. Anatase-type titanium oxide has a higher energy level in the conduction band than the rutile type, so electrons excited in the conduction band contribute to the reaction efficiently, so the photocatalytic activity of anatase-type titanium oxide is Higher than rutile type.

The anatase-type titanium oxide film has the following steps:
(i) forming titanium nitride on the surface of titanium or titanium alloy; and
(ii) Titanium obtained in the above step (i) in an electrolytic solution containing at least one acid selected from the group consisting of an inorganic acid having an etching action on titanium and an organic acid having the action Or it can prepare with the manufacturing method including the process of anodizing by immersing a titanium alloy and controlling the electric current which can apply the voltage more than a spark discharge generation voltage.

  In the present specification, titanium and a titanium alloy may be simply referred to as a titanium material.

  In the method for producing the anatase-type titanium oxide film, the formation of titanium nitride in the step (i) is performed by PVD, CVD, thermal spraying, heating in a nitrogen gas atmosphere, or nitrogen gas in combination with an oxygen trap agent. It is preferably performed by at least one treatment selected from the group consisting of heat treatment under an atmosphere.

  In the method for producing the anatase-type titanium oxide film, the heat treatment in a nitrogen gas atmosphere is preferably performed by heating titanium or a titanium alloy in a nitrogen gas atmosphere.

  In step (i), titanium nitride is formed on the surface of titanium or a titanium alloy.

  When a titanium alloy is used in the present invention, the type is not particularly limited. Examples of the titanium alloy include Ti-6Al-4V and Ti-0.5Pd.

  In step (i), a titanium nitride layer is usually formed on the surface of the titanium material in the range of 0.1 to 100 μm, preferably 0.5 to 50 μm, more preferably about 1 to 30 μm.

  The means for forming titanium nitride on the surface of the titanium material is not particularly limited. For example, a method of physically or chemically attaching titanium nitride to the surface of the titanium material, or titanium on the surface of the titanium material. There is a method of forming titanium nitride by reacting with nitrogen.

  As such methods, specifically, PVD (physical vapor deposition) treatment, CVD (chemical vapor deposition) treatment, thermal spray treatment (film formation by spraying), and heat treatment of titanium material under nitrogen gas atmosphere, Etc. can be illustrated. Examples of the PVD process include ion plating and sputtering. Examples of the CVD process include thermal CVD, plasma CVD, and laser CVD. Examples of the thermal spraying process include thermal spraying processes such as flame spraying, arc spraying, plasma spraying, and laser spraying.

  Specific examples of the heat treatment of the titanium material in a nitrogen gas atmosphere include a method of heating the titanium material to 500 ° C. or higher (preferably 750 ° C. or higher) in a nitrogen gas atmosphere. The nitrogen gas atmosphere during the heat treatment is not particularly limited, but the pressure of the nitrogen gas is usually 0.01 to 100 MPa, preferably 0.1 to 10 MPa, more preferably 0.1 to 1 MPa. As long as it is about.

  The heating time of the titanium material in the heat treatment can be generally set to 1 to 12 hours, preferably 2 to 8 hours, and more preferably 3 to 6 hours.

In the method of step (i), the type of titanium nitride formed on the surface of the titanium material is not particularly limited. Examples of the titanium nitride include TiN, Ti ₂ N, α-TiN _0.3 , η-Ti ₃ N _2-X , and ζ-Ti ₄ N _3-X (where x is a numerical value of 0 or more and less than 3) ), A mixture of these, and amorphous titanium nitride. Preferably Among these, TiN, _Ti 2 N, and mixture thereof, more preferably TiN, and inclusions of TiN and Ti ₂ N, particularly preferably exemplified is TiN.

  In the present invention, as a means for forming the titanium nitride, one of the above methods may be performed alone, or two or more methods may be arbitrarily combined. Among the methods for forming titanium nitride, from the viewpoints of simplicity, mass productivity, production cost, etc., heat treatment of the titanium material in a nitrogen gas atmosphere is preferable.

  In the method for producing the anatase-type titanium oxide film, it is preferable that in the anodic oxidation in the step (ii), the electrolytic solution contains sulfuric acid and phosphoric acid. In the method for producing the anatase-type titanium oxide film, it is preferable that the electrolytic solution further contains hydrogen peroxide in the anodic oxidation in the first step (ii).

  In the method for producing an anatase-type titanium oxide film, it is preferable that anodizing treatment is performed so as to control a current that can generate a spark discharge voltage in the anodic oxidation in the step (ii). In the step (ii), an electrolyte containing at least one acid selected from the group consisting of an inorganic acid having an etching action on titanium and an organic acid having the action is obtained in the step (i). Anodization is performed by immersing the obtained titanium or titanium alloy and applying a voltage higher than the spark discharge generation voltage.

  In the anodic oxidation in the step (ii), an aqueous solution containing an inorganic acid having an etching action on titanium and / or an organic acid having the action is used as an electrolytic solution. Examples of inorganic acids having an etching action on titanium include sulfuric acid, phosphoric acid, hydrofluoric acid, hydrochloric acid, nitric acid, aqua regia and the like.

  Moreover, as an organic acid which has an etching effect | action with respect to titanium, an oxalic acid, a formic acid, a citric acid, a trichloroacetic acid etc. are mentioned, for example. These acids may be used alone or in combination of two or more of these acids regardless of whether they are organic acids or inorganic acids. As an example of the preferable aspect of the electrolyte solution containing 2 or more types of acids, the aqueous solution containing a sulfuric acid and phosphoric acid is mentioned. The mixing ratio of the acid in the electrolytic solution varies depending on the type of acid used, anodizing conditions, and the like, but is usually 0.01 to 10 M, preferably 0.1 to 10 M, more preferably the total amount of the acid. The ratio which becomes 1-10M can be mentioned. For example, in the case of an electrolytic solution containing sulfuric acid and phosphoric acid, an electrolytic solution containing sulfuric acid 1 to 8M and phosphoric acid 0.1 to 2M can be exemplified.

  The electrolyte solution preferably contains hydrogen peroxide in addition to the organic acid and / or inorganic acid. By containing hydrogen peroxide in the electrolytic solution, an anatase-type titanium oxide film can be prepared more efficiently. When hydrogen peroxide is blended in the electrolytic solution, the blending ratio is not particularly limited. For example, the ratio is 0.01 to 5M, preferably 0.01 to 1M, and more preferably 0.1 to 1M. Is done.

  As an example of the preferable aspect of the electrolyte solution used by the anodic oxidation of process (ii), the aqueous solution contained in the ratio of 1-8M sulfuric acid, 0.1-2M phosphoric acid, and 0.1-1M hydrogen peroxide is mentioned. .

  By immersing the titanium or titanium alloy obtained in the step (i) in the electrolyte and applying a constant current so that a voltage equal to or higher than the spark discharge generation voltage can be applied, anatase-type titanium oxide A film is obtained.

In the anodic oxidation, the current density may be 0.1 A / dm ² or more, but 1 A / dm ² to 10 A / dm ² is preferable from the viewpoint of economy, simplicity, and performance.

  According to the said manufacturing method, the membrane | film | coat with many amounts of the anatase type titanium oxide with high photocatalytic activity can be formed.

  By adopting the above production method, it is possible to prepare a photocatalytic material in which a large amount of highly active anatase-type titanium oxide is formed on the surface of titanium metal or titanium alloy, so that the titanium oxide fine particles are coated on the substrate. Compared to conventional photocatalyst materials, it is possible to exhibit extremely high performance photocatalytic functions. By using the photocatalytic material obtained by the production method, it is possible to efficiently decompose volatile organic compounds and remove heavy metals.

(3) Method for Decomposing Volatile Organic Compound The method for treating soil contaminated water with the photocatalytic material of the present invention detoxifies volatile organic compounds contained in soil contaminated water,
(1) Gas-liquid separation of soil contaminated water to obtain a gas phase, and (2) a step of decomposing a volatile organic compound contained in the gas phase obtained in Step 1 with a photocatalytic material. And

When the undecomposed volatile organic compound remains in the gas phase after the step 2,
(3) It is preferable to include a step of secondary treatment by at least one method selected from the group consisting of adsorption removal by activated carbon and removal by thermal oxidation of volatile organic compounds in the gas phase.

  In step 1, the contaminated water (soil contaminated water) pumped from the contaminated soil is gas-liquid separated to obtain a gas phase. As a gas-liquid separation method, gaseous volatile organic compounds (gases) from polluted water (soil contaminated water) by explosive treatment, such as supplying pressurized air that is ejected from a nozzle in the explosive tower. Phase) and soil contaminated water (liquid phase). Since the volatile organic compound in the gas phase contains moisture, it is preferable to further reduce the moisture in the gas using a mist separator.

  Next, the volatile organic compound contained in the gas phase obtained in step 1 is decomposed with a photocatalytic material. The gaseous volatile organic compound from which moisture has been removed is sent to a photocatalyst device composed of a photocatalyst material and an ultraviolet lamp by a blower, and the volatile organic compound is decomposed and removed based on an oxidation reaction using the photocatalyst material to make it harmless. Plan. As the photocatalyst material, the above-described photocatalyst material is preferably used.

  As a method for decomposing and removing volatile organic compounds in the gas phase, a volatile organic compound gas flow system was constructed, and titanium nitride was formed on the titanium metal surface, and then anodized. A photocatalytic material having high activity is put in and decomposed by irradiating light (ultraviolet lamp) of 400 nm or less.

  Since the photocatalytic reaction is a surface reaction, the greater the chance of contact between the photocatalytic material and the volatile organic compound, the better the decomposition effect, so that the photocatalytic material can be arranged in a bellows shape or photocatalytic metal titanium or titanium alloy It is preferable to use a porous material itself and perform nitriding treatment or anodizing treatment.

  Examples of volatile organic compounds (VOC) to be decomposed include dichloromethane, carbon tetrachloride, dichloroethane, dichloroethylene, trichloroethane, trichloroethylene, tetrachloroethylene, dichloropropane, benzene, chloroform, toluene, xylene, and the like. The soil-contaminated water contains about 0.1 to 1000 ppmV of volatile organic compound, although it varies depending on the degree of soil contamination and the type of volatile organic compound. The gas phase obtained by gas-liquid separation of soil contaminated water contains about 0.1 to 1000 ppmV of volatile organic compounds.

  If an undecomposed volatile organic compound remains in the gas phase after the reaction in Step 2, further treatment with secondary treatment such as adsorption removal by activated carbon and thermal oxidation is performed to completely remove the volatile organic compound. Is preferably removed.

  Specifically, the volatile organic compound gas remaining in the decomposition treatment of the photocatalyst material is completely removed from the volatile organic compound remaining by performing adsorption removal or thermal decomposition treatment by passing through an activated carbon packed column. It is possible to remove it. In the secondary processing, each processing can be performed independently, and each processing can be performed in combination.

  An apparatus for treating soil contaminated water that detoxifies volatile organic compounds contained in soil contaminated water using the photocatalytic material of the present invention is a gas phase preparation chamber that obtains a gas phase by gas-liquid separation of soil contaminated water, It comprises a photocatalytic device that decomposes a volatile organic compound contained in the phase with a photocatalytic material.

  The apparatus for treating soil-contaminated water of the present invention is a secondary treatment in which a volatile organic compound in the gas phase is further treated by at least one method selected from the group consisting of adsorption removal by activated carbon and thermal oxidation. It is preferable to provide a chamber.

  The gas phase preparation chamber has an explosion tower for forming a jet for stirring and mixing the soil contaminated water and air, a nozzle for ejecting the soil contaminated water into the explosion tower, and pressurization An air supply pipe for supplying the air, and the explosion tower is configured to discharge the air containing the volatile organic compound separated from the soil contaminated water and the contaminated water that has been stirred and mixed. It is preferable to have a discharge port. The gas phase preparation chamber preferably has a mist separator for further reducing moisture.

  The gas phase preparation chamber preferably has a blower for supplying pressurized air to the air supply pipe.

  The gas phase preparation chamber preferably has a pump for pressurizing and ejecting soil contaminated water.

  In the explosion tower, soil contaminated water ejected from a nozzle and pressurized air are supplied from an air supply pipe. In the explosion tower, volatile organic compounds contained in soil contaminated water move to the gas phase. Therefore, the volatile organic compound contained in the soil contaminated water is removed from the contaminated water together with the air in the explosion tower, and is changed to one having less volatile organic compounds.

  The photocatalytic device preferably has a photocatalytic material and an ultraviolet lamp. The photocatalytic device preferably has a duct structure.

  The soil contaminated water treatment apparatus of the present invention preferably has a conduit for discharging a gas phase portion of the decontaminated soil contaminated water discharged from the photocatalyst device to the outside. Moreover, it is preferable to have a conduit for guiding the gas phase part of the decontaminated soil contaminated water (detoxified gas after the photocatalytic reaction) to the aeration tower. The gas phase part from the decontaminated soil contaminated water can be effectively used without being released to the outside.

(4) Method for removing heavy metal The method for treating soil contaminated water with the photocatalytic material of the present invention is to remove heavy metals contained in soil contaminated water,
(1) A step of gas-liquid separation of soil contaminated water to obtain a liquid phase, and (2) a step of removing heavy metals contained in the liquid phase obtained in step 1 with a photocatalytic material.

When unremoved heavy metal remains in the liquid phase after the step 2,
(3) The heavy metal in the liquid phase is selected from the group consisting of a method of removing heavy metal by electrolytic treatment, a method of insolubilizing heavy metal by chemical chelation, and a method of separating heavy metal by hydroxide treatment. It is preferable to include a secondary treatment step by at least one method.

  According to the photocatalyst material of the present invention, heavy metal ions such as mercury, lead, cadmium, arsenic, copper, hexavalent chromium and the like present in soil contaminated water are oxidized or reduced by light irradiation and precipitated as metal or oxide. Can be efficiently removed from soil contaminated water.

  In step 1, the contaminated water (soil contaminated water) pumped from the contaminated soil is gas-liquid separated to obtain a liquid phase. As a gas-liquid separation method, a solution (liquid phase) containing heavy metal ions is separated from contaminated water (soil-contaminated water) by explosive treatment in which a pressurized air is supplied from the nozzle in the explosion tower. Let

  Next, the heavy metal contained in the liquid phase obtained in step 1 is removed with a photocatalytic material. A solution (liquid phase) containing heavy metal ions is sent to a photocatalyst device composed of a photocatalyst material and an ultraviolet lamp by a liquid feed pump, and the heavy metal is removed based on the reduction reaction or oxidation reaction of the photocatalyst to make it harmless.

  As a specific removal method, removal treatment is performed by irradiating light (ultraviolet lamp) of 400 nm or less using a photocatalytic material. As the photocatalyst material, the above-described photocatalyst material is preferably used.

  Since the photocatalytic reaction is a surface reaction, the greater the chance of contact between the photocatalytic material and the heavy metal, the better the decomposition effect. Therefore, the photocatalytic material is arranged in a bellows shape, and the photocatalytic metal titanium or titanium alloy itself is porous. It is preferable to perform nitriding treatment or anodizing treatment using a high quality material.

Heavy metals to be removed are harmful heavy metals such as lead, cadmium, hexavalent chromium, arsenic, mercury, and copper. The soil-contaminated water contains about 0.01 to 1000 ppm of heavy metal, although it varies depending on the degree of soil contamination and the type of heavy metal.

  If unremoved heavy metal remains in the liquid phase after the reaction in step 2, a method of removing heavy metal by electrolytic treatment, a method of insolubilization by chemically chelating heavy metal, a hydroxide treatment It is preferable to carry out a secondary treatment such as a method for separating heavy metals in order to completely remove heavy metals.

  Specifically, as a method of removing heavy metals in the electrolytic treatment, a method of removing heavy metal ions from the liquid by electrolytic reduction of the liquid containing heavy metal ions remaining in the decomposition treatment of the photocatalytic material in an electrolytic cell There is. The chelating and insolubilizing method is a method of removing heavy metal ions by adding citric acid and EDTA (ethylenediaminetetraacetic acid), which are agents for chelating heavy metal ions, to a solution containing heavy metal ions. As a method for separating heavy metals in the hydroxide treatment, adding an alkaline substance such as sodium hydroxide or potassium hydroxide to the liquid containing heavy metal ions to make the heavy metals insoluble by making them into hydroxides. It is a technique to remove. In the secondary processing, each processing can be performed independently, and each processing can be performed in combination.

  An apparatus for treating soil contaminated water that removes heavy metals contained in soil contaminated water using the photocatalytic material of the present invention includes a liquid phase preparation chamber that obtains a liquid phase by gas-liquid separation of the soil contaminated water, and a liquid phase preparation chamber. And a photocatalyst device for removing heavy metal to be removed by a photocatalyst material.

  The apparatus for treating soil contaminated water according to the present invention includes a method for removing heavy metals in a liquid phase by electrolytic treatment, a method for insolubilizing heavy metals by chemical chelation, and a hydroxide treatment. It is preferable to provide a secondary processing chamber for processing by at least one method selected from the group consisting of methods for separating heavy metals.

  The liquid phase preparation chamber has an explosion tower for forming a jet for stirring and mixing soil contaminated water and air, and a nozzle for ejecting the soil contaminated water into the explosion tower, and pressurization A discharge port for discharging the agitated / mixed soil contaminated water and a liquid containing heavy metal separated from the contaminated water; It is preferable to have.

  The liquid phase preparation chamber preferably has a blower that supplies pressurized air to the air supply pipe.

  It is preferable that the liquid phase preparation chamber has a pump for causing the soil contaminated water to be jetted out under pressure.

  In the explosion tower, soil contaminated water ejected from a nozzle and pressurized air are supplied from an air supply pipe. In the explosion tower, the volatile organic compound contained in the soil contaminated water moves to the gas phase, so that the liquid containing heavy metal remains in the liquid phase.

  The photocatalytic device preferably has a photocatalytic material and an ultraviolet lamp. The photocatalytic device preferably has a duct structure.

  The soil contaminated water treatment apparatus of the present invention preferably has a conduit for discharging the liquid phase portion of the decontaminated soil contaminated water discharged from the photocatalyst device to the outside.

  In adopting the method according to the present invention, a photocatalytic material having high activity (for example, a photocatalytic material obtained by forming a titanium nitride on a metal titanium surface and then performing anodization) is used. In addition, harmful volatile organic compounds and heavy metals in the gas phase and liquid phase can be decomposed and removed quickly and extremely efficiently.

2 is a graph showing decomposition of trichlorethylene gas in Example 1.

Example 1
After holding at 950 ° C. for 3 hours under nitrogen gas flow to form titanium nitride on the metal titanium surface, current density using 1.5M sulfuric acid, 0.1M phosphoric acid, 0.3M hydrogen peroxide as the electrolyte A photocatalytic material was obtained by anodizing at 4 A / dm ² and electrolysis time of 30 minutes.

Using the photocatalyst material of 50 mm square, 100 ml of 100 ppmV trichlorethylene gas was collected in a glass container, and light irradiation was performed with a fluorescent lamp (black light, manufactured by Toshiba Lighting & Technology) that emits near-ultraviolet rays of 400 nm or less from the top. The light intensity at this time was adjusted to 1.1 mW / cm ² .

  The results of measuring the trichlorethylene concentration over time are shown in FIG.

  It is found that trichlorethylene gas is decomposed with high efficiency by using a photocatalytic material in which a large amount of anatase-type titanium oxide is formed on the surface of titanium metal by performing anodic oxidation after gas nitriding of titanium metal. It was.

Example 2
After holding at 950 ° C. for 1 hour under nitrogen gas flow to form titanium nitride on the titanium metal surface, current density using 1.5M sulfuric acid, 0.1M phosphoric acid, 0.3M hydrogen peroxide as the electrolyte Anodization was performed at 4 A / dm ² and an electrolysis time of 30 minutes to obtain a photocatalytic material (total surface area 52 m ² ).

  In addition, the contaminated groundwater (soil contaminated water) was pumped up (gas-liquid separation) to obtain a gas phase containing trichlorethylene.

A photocatalyst device composed of the photocatalyst material and 32 UV lamps with an output of 40 W is passed through trichloroethylene gas obtained from the soil-contaminated water and irradiated with a fluorescent lamp that emits ultraviolet light (254 nm). The concentration of each trichlorethylene at the inlet and outlet of the photocatalyst device was measured with a gas chromatograph. The flow rate of the gas containing trichlorethylene obtained by pumping up groundwater was set to about 5 to 9 m ³ / min.

  The results are shown in Table 1.

  From this result, groundwater contaminated with high efficiency can be obtained by using a photocatalytic material in which a large amount of anatase-type titanium oxide is formed on the surface of titanium metal by performing anodic oxidation after gas nitriding of titanium metal. It was found that the trichlorethylene gas in the gas obtained by pumping explosion was decomposed.

  Since undecomposed trichlorethylene remained in the gas phase after the reaction of the decomposition treatment using the photocatalyst material, the trichlorethylene can be completely removed by further performing a secondary treatment of adsorption removal with activated carbon.

Claims (8)

A method for treating soil contaminated water that detoxifies volatile organic compounds contained in soil contaminated water,
(1) A step of obtaining gas phase by gas-liquid separation of soil contaminated water,
(2) Crystalline titanium oxide obtained by anodizing the volatile organic compound contained in the gas phase obtained in step 1 after forming titanium nitride on the surface of titanium metal or titanium alloy A step of decomposing by a photocatalytic material having a film ; and (3) a secondary treatment by a method of removing undecomposed volatile organic compounds remaining in the gas phase by adsorption and thermal oxidation with activated carbon after the step 2 A method for treating soil contaminated water with a photocatalytic material, comprising the step of: A method for treating soil contaminated water that removes heavy metals contained in soil contaminated water,
(1) A step of obtaining a liquid phase by gas-liquid separation of soil contaminated water,
(2) A crystalline titanium oxide film obtained by anodizing the heavy metal contained in the liquid phase obtained in step 1 after forming titanium nitride on the surface of titanium metal or titanium alloy. (3) After the step 2, the unremoved heavy metal remaining in the liquid phase is insolubilized by a method of removing the heavy metal by electrolytic treatment, or chelating the heavy metal. A method for treating soil-contaminated water with a photocatalytic material, comprising a step of performing a secondary treatment by at least one method selected from the group consisting of a method and a method for separating heavy metals by hydroxide treatment. A method for treating soil contaminated water with a photocatalytic material ,
(A)
(1) A step of obtaining gas phase by gas-liquid separation of soil contaminated water,
(2) Crystalline titanium oxide obtained by anodizing the volatile organic compound contained in the gas phase obtained in step 1 after forming titanium nitride on the surface of titanium metal or titanium alloy A step of decomposing by a photocatalytic material having a film ; and (3) a secondary treatment by a method of removing undecomposed volatile organic compounds remaining in the gas phase by adsorption and thermal oxidation with activated carbon after the step 2 A treatment method for detoxifying volatile organic compounds contained in soil contaminated water including the step of :
(B)
(1) A step of obtaining a liquid phase by gas-liquid separation of soil contaminated water,
(2) A crystalline titanium oxide film obtained by anodizing the heavy metal contained in the liquid phase obtained in step 1 after forming titanium nitride on the surface of titanium metal or titanium alloy. (3) After the step 2, the unremoved heavy metal remaining in the liquid phase is insolubilized by a method of removing the heavy metal by electrolytic treatment, or chelating the heavy metal. A method for removing heavy metals contained in soil-contaminated water, including a step of performing a secondary treatment by at least one method selected from the group consisting of a method and a method for separating heavy metals by hydroxide treatment ,
Soil contaminated water treatment method. The method for treating soil contaminated water with a photocatalytic material according to any one of claims 1 to 3, wherein the crystalline titanium oxide is anatase type titanium oxide. A gas phase preparation chamber for gas-liquid separation of soil contaminated water and obtaining a gas phase;
A photocatalyst decomposed by a photocatalytic material having a crystalline titanium oxide film obtained by anodizing a volatile organic compound contained in the gas phase after forming titanium nitride on the surface of titanium metal or titanium alloy Equipment,
The volatile organic compounds in the gas phase, characterized in that it comprises a secondary process chamber for processing by a method of removing by adsorption removal and thermal oxidation with activated carbon, volatile contained in soil contaminated water using a photocatalyst material Soil contaminated water treatment equipment that detoxifies organic compounds. A liquid phase preparation chamber for obtaining a liquid phase by gas-liquid separation of soil contaminated water;
A photocatalytic device for removing heavy metal contained in the liquid phase by a photocatalytic material having a crystalline titanium oxide film obtained by anodizing after titanium nitride is formed on the surface of titanium metal or a titanium alloy ;
At least one selected from the group consisting of a method of removing heavy metals in the liquid phase by electrolytic treatment, a method of insolubilizing heavy metals by chemical chelation, and a method of separating heavy metals by hydroxide treatment And a secondary treatment chamber for treating the soil contaminated water using a photocatalyst material to remove heavy metals contained in the soil contaminated water. An apparatus for treating soil contaminated water using a photocatalytic material,
(A)
A gas phase preparation chamber for gas-liquid separation of soil contaminated water and obtaining a gas phase;
A photocatalyst decomposed by a photocatalytic material having a crystalline titanium oxide film obtained by anodizing a volatile organic compound contained in the gas phase after forming titanium nitride on the surface of titanium metal or titanium alloy Equipment,
The volatile organic compounds in the gas phase, a processor for harmless volatile organic compounds contained in soil contaminated water and a secondary process chamber for processing by a method of removing by adsorption removal and thermal oxidation with activated carbon,
(B)
A liquid phase preparation chamber for obtaining a liquid phase by gas-liquid separation of soil contaminated water;
A photocatalytic device for removing heavy metal contained in the liquid phase by a photocatalytic material having a crystalline titanium oxide film obtained by anodizing after titanium nitride is formed on the surface of titanium metal or a titanium alloy ;
At least one selected from the group consisting of a method of removing heavy metals in the liquid phase by electrolytic treatment, a method of insolubilizing heavy metals by chemical chelation, and a method of separating heavy metals by hydroxide treatment A treatment device for removing heavy metals contained in soil contaminated water, including a secondary treatment chamber treated by one method ,
Soil contaminated water treatment equipment . The apparatus for treating soil contaminated water according to any one of claims 5 to 7, wherein the crystalline titanium oxide is anatase type titanium oxide.

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