JP3933604B2 - Decomposition method of organic halogen compounds - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic halogen compound decomposition method for decomposing organic halogen compounds including harmful substances such as dioxins.
[0002]
[Prior art]
In recent years, interest in trace amounts of harmful substances in the environment has increased greatly. Analytical techniques and human impact assessment techniques are still under development for substances that are likely to affect living organisms, such as organic halogen compounds such as dioxins and environmental hormones (endocrine disrupting chemical substances). Countermeasures are required. For this purpose, not only the emission control technology but also the removal and detoxification technology of what has already been accumulated in the environment is considered indispensable.
[0003]
Among these, for dioxins, the standards for air, water quality and soil are set by the Special Measures Law for Dioxins (Ministry of the Environment, December 1999), so the demand for analysis and the treatment of pollutants is increasing. .
[0004]
However, a method for treating liquids containing organic halogen compounds such as dioxins has not been established, and in particular, liquids containing dioxins etc. must be stored without being treated, such as not being picked up by industrial waste disposal contractors. There is no situation.
[0005]
In order to solve this problem, the present inventors invented a composite photocatalyst. (See Patent Document 1) The organic halogen compound treatment method disclosed herein uses a composite photocatalyst in which a carbon material, a dehalogenation catalyst, and a photocatalyst that decomposes an organic compound by light irradiation are integrated, In the state in which the liquid to be treated and the composite photocatalyst are brought into contact with each other, the light irradiation is performed for the decomposition treatment. The composite photocatalyst can efficiently and continuously cause adsorption of an organic halogen compound in the liquid to be treated by the carbon material component, dehalogenation reaction by the dehalogenation catalyst component, and decomposition reaction by the photocatalyst component. The decomposition treatment of the compound can be decomposed by a simple treatment. However, the method disclosed here is a batch-type processing method in which processing is performed in a state where a liquid to be processed is stored in a tank. Especially when the main component of the liquid to be treated is a solvent with relatively low solubility of organic halogen compounds such as water, the concentration of the organic halogen compound in the liquid is very dilute. There was a problem that it had to be treated for a long time in the state of being stored in the tank. Furthermore, when the amount of liquid to be treated is large, there is a problem that the tank capacity must be increased.
[0006]
Further, a flow-type application is also conceivable as a method for treating a liquid to be treated using such a catalyst. (For example, refer to Patent Document 2) However, a light irradiation time for complete processing is required. Furthermore, in order to earn light irradiation time, it is necessary to lengthen the flow path, and there is a problem that the apparatus becomes large.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-269583
[Patent Document 2]
JP 2000-254667 A
[0008]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned problems, and is an organic halogen which makes a liquid to be treated harmless in a short time and further enables a large amount of liquid to be harmed with a compact apparatus. It aims at providing the decomposition | disassembly method of a compound.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is directed to bringing a liquid to be treated containing an organic halogen compound into contact with a composite photocatalyst comprising a carbon material, a dehalogenation catalyst, and a photocatalyst that decomposes an organic substance by light irradiation, to form the organic halogen compound Adsorbing to the composite photocatalyst,
A separation step of separating the liquid to be treated obtained in the adsorption step and the composite photocatalyst that has adsorbed the organic halogen compound;
A decomposition step of decomposing the organic halogen compound adsorbed by light irradiation on the composite photocatalyst obtained in the separation step;
Is a method for decomposing an organic halogen compound.
[0010]
The present invention also provides a liquid to be treated containing an organic halogen compound in contact with a composite photocatalyst comprising a carbon material, a dehalogenation catalyst, and a photocatalyst that decomposes an organic substance by light irradiation to convert the organic halogen compound into the composite photocatalyst. After repeating the adsorption separation step of performing the adsorption step to adsorb and the separation step of separating the liquid to be treated obtained in the adsorption step and the composite photocatalyst adsorbing the organic halogen compound a plurality of times,
An organic halogen compound decomposition method comprising performing a decomposition step of decomposing the organic halogen compound adsorbed by irradiating the composite photocatalyst obtained in the adsorption separation step with light.
[0011]
The present inventors, when treating an organic halogen compound in a liquid to be treated using a composite photocatalyst comprising a carbon material, a dehalogenation catalyst, and a photocatalyst that decomposes organic matter by light irradiation, adsorbing ability of the catalyst to the organic halogen compound The liquid to be treated was quickly detoxified by bringing the liquid to be treated into contact with the composite photocatalyst, adsorbing the organic halogen compound, and then separating the composite photocatalyst from the organic halogen compound. It becomes possible to discharge in the state.
[0012]
Furthermore, since this composite photocatalyst has high ability to adsorb organic halogen compounds as well as organic halogen compounds, the composite photocatalyst is once brought into contact with the liquid to be treated to adsorb the organic halogen compounds in the liquid to be treated. After removing the organic halogen compound from the treatment liquid, the liquid to be treated is separated, and contacted with a new liquid to be treated containing an organic halogen compound to repeatedly adsorb the organic halogen compound. By performing the method of decomposing the compound, the ability of the composite photocatalyst can be maximized, the liquid to be treated can be rendered harmless and the organic halogen compound can be decomposed with a short time of light irradiation. it can.
[0013]
In other words, the composite photocatalyst has a very high ability to adsorb organic halogen compounds, and therefore, by repeating the contact with the liquid to be processed and the separation of the liquid to be processed, it is possible to organically remove a large amount of liquid from the liquid to be processed without using a large tank. The liquid to be treated can be rendered harmless by adsorbing the halogen compound and discharged quickly. Furthermore, in this case, the organic halogen compound is concentrated on the composite photocatalyst to a higher concentration than in the conventional method. However, since the composite photocatalyst has a very high resolution of the organic halogen compound, the organic photocatalyst is organic on the composite photocatalyst. Since the halogen compounds are concentrated, many organic halogen compounds can be decomposed by light irradiation in a shorter time than the conventional method. Therefore, according to the present invention, it is possible to reduce the damage of a large amount of liquid to be processed in a short time with a compact apparatus.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The composite photocatalyst used in the present invention is a composite photocatalyst comprising a carbon material, a dehalogenation catalyst, and a photocatalyst that decomposes organic substances by light irradiation. As the composite photocatalyst, for example, those described in JP-A-2001-269583 are desirable because they have both excellent adsorption power and decomposition power of organic halogen compounds.
[0015]
The composite photocatalyst includes a carbon material, a dehalogenation catalyst supported on the carbon material, and a photocatalyst supported on the dehalogenation catalyst.
[0016]
The mechanism of decomposition of the organic halogen compound by the composite photocatalyst according to the present invention will be described below. FIG. 1 is a conceptual diagram schematically showing the mechanism of an organic halogen compound by a composite photocatalyst according to the present invention. A dehalogenation catalyst made of, for example, metal particles 2 is carried on the surface of the carrier made of carbon material 1, and photocatalyst particles 3 made of titanium dioxide or the like carried on the surface of metal particles 2 are present to form a composite photocatalyst. The composite photocatalyst is in an immersed state in which the organic halogen compound 4 as a decomposition target is dissolved or dispersed in water or the like.
[0017]
As shown in FIG. 1, when light is irradiated on the surface of the photocatalyst particle 3, electrons and holes are generated. Since the metal particles 2 such as Pd and Pt are in contact with the surface of the photocatalyst particle 3, electrons generated by light irradiation move to the metal and recombination with holes is difficult to occur, and the electrons and holes are separated. If electrons and holes are recombined, they do not participate in the reaction, but electrons move to the metal particles 2 and are separated without recombination and react with water to generate OH radicals from the holes. Hydrogen is generated from electrons. Hydrogen is mainly generated on the metal particles 2 in contact with the photocatalyst particles 3 and can move on the carbon material 1 by spillover. The generated hydrogen is used to perform a dehalogenation reaction. Thus, since hydrogen required for performing the dehalogenation reaction can be generated by the photocatalyst particles 3, it is possible to remove the halogen element from the organic halogen compound in water.
[0018]
Since the dehalogenation reaction occurs at a place where the metal particles 2 on the photocatalyst and the support made of the carbon material 1 are in contact with each other, the metal particles 2 are supported on the support made of the carbon material 1. It is important for promoting the halogenation reaction.
[0019]
Then, the organic compound obtained by subjecting the organic halogen compound to the dehalogenation reaction is quickly decomposed by the OH radical generated by irradiating the photocatalyst particles 2 with light, and finally, if the reaction is performed for a sufficient time, CO ₂ And H ₂ Detoxification by complete decomposition into O is also possible.
[0020]
The carbon material is used as a carrier for the dehalogenation catalyst, and the removal effect and the concentration effect due to adsorption are enhanced by using a material having a high adsorption power for the organic halogen compound. The removal efficiency is poor when an organic halogen compound such as dioxin is dispersed in the liquid to be treated. Here, the purpose of removing the organic chlorine compound from the original liquid to be treated is achieved by adsorbing the organic halogen compound with the carbon material. Furthermore, the efficiency of performing the decomposition is increased because the object is collected after being collected.
[0021]
The composite photocatalyst according to the present invention can be applied whether the liquid to be treated is a liquid containing water as a main component or a liquid containing an organic solvent as a main component.
[0022]
The treatment method of the present invention using the composite photocatalyst as described above will be described with reference to FIG. FIG. 2 is a schematic view showing one embodiment of a method for treating an organic halogen compound according to the present invention.
[0023]
As shown in FIG. 2, first, an adsorption step 21 is performed in which a liquid to be treated 20 containing an organic halogen compound is brought into contact with a composite photocatalyst to adsorb the organic halogen compound onto the composite photocatalyst. The contacting method may be a method of suspending or immersing the composite photocatalyst in the liquid to be treated, or a method of fixing the catalyst and circulating the liquid to be treated therefor, simultaneously with adsorption, the composite photocatalyst and the liquid to be treated. Is also performed at the same time. When the catalyst is suspended or immersed, stirring is preferably performed to improve contact efficiency.
[0024]
Next, instead of directly decomposing the liquid to be treated, a separation step 22 for separating the liquid to be treated 23 and the composite photocatalyst 24 adsorbing the organic halogen compound is performed. When contact is made by suspension or immersion during the adsorption step 21, the separation step 22 is performed after the adsorption treatment by contact. At this time, the separation includes a method of recovering the catalyst using a filter or the like, a method of sedimenting the catalyst and discharging the supernatant. Further, when the liquid to be treated is circulated through the immobilized catalyst in the adsorption step 21, the separation step 22 is also performed at the same time, and after the circulation, the composite photocatalyst 24 that adsorbs the liquid to be treated 23 and the organic halogen compound is adsorbed. And are separated. Since the organohalogen compound is removed by adsorption by the composite photocatalyst in the liquid to be treated 23 thus separated, the detoxification of the liquid to be treated is completed in a short time.
[0025]
Next, the organic halogen compound is rendered harmless by performing the decomposition step 25 of the organic halogen compound adsorbed on the separated composite photocatalyst 24. Decomposition is performed by irradiating the composite photocatalyst adsorbing the organic halogen compound with light irradiation.
[0026]
The composite photocatalyst after decomposing the adsorbed organohalogen compound can be discarded or reused as it is.
[0027]
When the main component of the liquid to be processed 20 containing an organic halogen compound is an organic solvent, the adsorption step 21 and the separation step 22 are performed by evaporating the solvent of the liquid to be processed while bringing the liquid to be processed into contact with the composite photocatalyst. A method in which a halogen compound is adsorbed and separated by a catalyst is preferable. The contact method may be a method of suspending or immersing the catalyst in the liquid to be treated. Further, the liquid to be treated may be evaporated in a container formed or coated with the composite photocatalyst. Evaporation can be performed by reducing the pressure or raising the temperature, and there is also a method of applying a gas such as air or a nitrogen stream. The evaporated solvent can be recovered and discarded or reused, or it can be collected by an activated carbon adsorption tower and discarded as it is.
[0028]
In order to process a larger amount of liquid to be processed in the method of the present invention, the following processing method described with reference to FIG. 3 can also be performed. FIG. 3 is a schematic view showing one embodiment of a method for treating an organic halogen compound.
[0029]
As shown in FIG. 3, a first adsorption step 31 in which a liquid to be treated 30 containing an organic halogen compound is brought into contact with a composite photocatalyst to adsorb the organic halogen compound to the composite photocatalyst, followed by the liquid to be treated and the organic halogen. The first separation step 32 for separating the composite photocatalyst adsorbing the compound is sequentially performed (the first separation step and the first separation step are collectively referred to as the first adsorption separation step), and the organic halogen compound is adsorbed. The composite photocatalyst 33 and the liquid to be treated 34 are obtained. The method of the first adsorption process may be the same as the adsorption process 21 shown in FIG. 2, and the method of the first separation process may be the same as the separation process 22 shown in FIG.
[0030]
Next, a new adsorption liquid 35 containing an organic halogen compound is brought into contact with the composite photocatalyst 33 obtained in the first separation step to perform a second adsorption step 36 for further adsorbing the organic halogen compound, and further, A second separation step 37 for separating the liquid to be treated obtained in the second adsorption step 36 and the composite photocatalyst adsorbing the organic halogen compound is sequentially performed. (The second adsorption step and the second separation step are collectively referred to as a second adsorption separation step), and the composite photocatalyst 38 having adsorbed the organic halogen compound and the liquid to be treated 39 rendered harmless are obtained. The second adsorption step 36 and the second separation step 37 may be the same method as the first separation step 31 and the second adsorption step 32. Thus, by repeating the operation of separating the liquid to be treated after adding a new liquid to be treated to the same composite photocatalyst, the liquid to be treated is rendered harmless and at the same time, the organic halogen compound is concentrated on the composite photocatalyst. It will be. Such repetition of the adsorption separation process is not limited to the two times shown in FIG. 3, but the third adsorption process, the third separation process, the fourth adsorption process, the fourth adsorption process, and the like as long as the adsorption limit of the composite photocatalyst is reached. Separation process. . . . . . . . . You may repeat 3 times or more like. As the number of times increases, the amount of liquid to be processed can be increased. However, it is not necessary to increase the capacity of the tank to be used, and processing can be performed with a compact apparatus.
[0031]
The organic halogen compound adsorption limit on the composite photocatalyst is preferably 10 pg or more and 1000 ng or less for 1 g of the composite photocatalyst. At this time, the ratio of the composite photocatalyst amount to the liquid to be treated is preferably 0.01 g or more and 5 g or less with respect to 1 L of the liquid to be treated.
[0032]
Finally, the organic halogen compound is rendered harmless by performing the decomposition step 40 of the organic halogen compound adsorbed on the composite photocatalyst 38 separated in the second separation step. The decomposition step 40 may be performed in the same manner as the decomposition step 25 shown in FIG. 2, and is performed by irradiating the composite photocatalyst 38 that has adsorbed the organic halogen compound with light.
[0033]
The composite photocatalyst according to the present invention will be specifically described below.
[0034]
Specifically, it is desirable to use activated carbon as the carbon material used in the composite photocatalyst.
[0035]
Examples of the dehalogenation catalyst supported on the activated carbon include predetermined metals. In this case, the metal is not particularly limited as long as it is a metal that exhibits a dehalogenation ability by being placed in contact with a carbon material, and at least selected from palladium, platinum, rhodium, ruthenium, iron, copper, silver, zinc, and the like. One type may be used. In particular, the use of palladium or platinum increases the dehalogenation ability.
[0036]
The photocatalyst according to the present invention is not particularly limited as long as it is excited by light irradiation and generates electrons and holes. For example, titanium dioxide, SrTiO ₃ Or CdS, SnO ₂ , ZnS, ZnO, WO ₃ , SiC, Fe ₂ O ₃ A semiconductor photocatalyst such as GaP or CdSe can be used. In particular, titanium dioxide is desirable because of its high efficiency. Moreover, electroconductive particle can also be separately supported on the photocatalyst surface. When the photocatalyst is in contact with only the predetermined metal, electrons generated by excitation move only to the predetermined metal, but by separately supporting conductive particles on the photocatalyst, the generated electrons increase in the place of movement, Recombination of electrons and holes is less likely to occur. As a result, OH radicals are more likely to be generated, and the decomposition of the organic compound can be promoted more rapidly.
[0037]
The carbon material, the dehalogenation catalyst, and the photocatalyst are arranged such that at least the carbon material and the dehalogenation catalyst are in contact with each other, and the dehalogenation catalyst and the photocatalyst are in contact with each other. If the carbon material is not in contact with the dehalogenation catalyst, it will not function as a catalyst. In addition, if the photocatalyst is not in contact with the dehalogenation catalyst, the electrons and holes generated by the photocatalyst may recombine as described above.
[0038]
The shapes of the carbon material, the dehalogenation catalyst, and the photocatalyst are not particularly limited. Particularly, when a metal is used as the dehalogenation catalyst, the photocatalyst and the dehalogenation catalyst are usually used in the form of particles.
[0039]
The photocatalyst is desirably made as small as possible in order to enhance the quantum size effect in the photocatalytic reaction. For example, the photocatalyst may be used as a particle having an average particle diameter of about 5 nm to 50 nm.
[0040]
In particular, when a metal is used as the dehalogenation catalyst, it is desirable that the dehalogenation catalyst has a small particle size in order to increase the contact area with carbon and further increase the contact area with the organic halogen compound. What is necessary is just to use it as a particle | grain with an average particle diameter of 5 nm-about 100 nm.
[0041]
The particle diameter of the carbon material is not particularly limited, but when it is used as a powder, a material of about 1 μm to 200 μm is usually used.
[0042]
Moreover, it is desirable that the average particle size of the predetermined metal particles is larger than the average particle size of the photocatalyst. That is, if the particle size of the predetermined metal particles is larger than the particle size of each of the carbon material and photocatalyst used as the carrier, the photocatalyst is directly supported on the carbon surface when the metal particles and the photocatalyst are supported on the carbon material surface. There is a risk that the carbon material is not supported via the metal.
[0043]
The weight ratio of the predetermined metal to the carbon material is desirably 0.1% to 20%, preferably 5% to 10%. If it is out of this range, the dehalogenation function cannot be fully exhibited.
[0044]
The ratio between the total amount of the carbon material and the dehalogenation catalyst and the photocatalyst is preferably within the range of the total of the carbon material and the dehalogenation catalyst: photocatalyst = 50: 50 to 5:95, and more preferably 30. : It is desirable to be in the range of 70 to 10:90. If the ratio of the photocatalyst is too low, the amount of hydrogen supplied to the dehalogenation reaction may not be sufficient, or the decomposition rate of the dehalogenated organic compound may decrease. This is because the contact area between the dehalogenation catalyst and the organic halogen compound is reduced and the decomposition rate may be reduced.
[0045]
Such a composite photocatalyst can be easily prepared by mechanically mixing particles having a predetermined metal supported on a carbon surface in advance with a photocatalyst in a mortar or the like.
[0046]
In addition, it can be obtained by adsorbing the photocatalyst precursor to particles with a predetermined metal supported on the carbon surface by an impregnation method or the like, followed by firing, or by applying the precursor by spraying instead of impregnation. And may be fired. Moreover, you may employ | adopt the method of fixing a photocatalyst to the predetermined | prescribed metal surface by performing heat processing as needed using a sol-gel method, CVD method, or a binder.
[0047]
This composite photocatalyst can be used in the form of a powder suspended in liquid, but considering the separation of the catalyst after the decomposition treatment, the composite photocatalyst is molded into a sphere or pellet of about several millimeters or a film It is also possible to use a plate or plate. Further, it is convenient to use the above-mentioned powdery composite photocatalyst as a catalyst unit fixed to another carrier such as a sponge structure or a honeycomb structure.
[0048]
As an energy source for irradiating the composite photocatalyst during the decomposition process and exciting the composite photocatalyst, for example, when using titanium dioxide as a photocatalyst, an ultraviolet light source usually using a high pressure mercury lamp, a low pressure mercury lamp, a sterilizing lamp, a black lamp, etc. Is used. In addition, it is possible to use sunlight instead of the ultraviolet lamp, and in this case, the energy cost can be reduced. In the decomposition process, when the composite photocatalyst is powder, it is more effective to add water or organic solvent, or both, and then irradiate with light suspended in the solvent, or add water vapor and irradiate with light. Good. Examples of the organic solvent include at least one organic solvent selected from toluene, n-hexane, 2-propanol, acetone, dichloromethane, methanol, and ethanol.
[0049]
In addition, the composite photocatalyst according to the present invention is used in the presence of water as a supply source of OH radicals and hydrogen as described above, but if necessary, by adding hydrogen peroxide water, The generation amount can be increased and the decomposition of the organic compound can be promoted.
[0050]
Thus, according to the method of the present invention, wastewater containing organic halogen compounds such as p-chlorophenol, dioxin, PCB (polychlorobiphenyl), DDT (dichlorodiphenyltrichloroethane), CNP (chloronitrophene), organic solvent, etc. It becomes possible to process the liquid to be processed.
[0051]
【Example】
Examples of the present invention are shown below.
[0052]
Example 1
A weight ratio of 2: 8 (Pd / C: TiO) on a Pd / C catalyst supporting 10 wt% of Pd with respect to activated carbon. ₂ The following treatment was performed using a composite photocatalyst carrying titanium dioxide at a ratio of
[0053]
The treatment liquid 14L (aqueous solution) containing 2,3,7,8-tetrachlorodibenzo-p-dioxin at a concentration of 100 pg / L was subjected to a decomposition treatment using the following treatment apparatus.
[0054]
FIG. 4 shows a schematic diagram of the processing apparatus. The liquid to be processed is injected into the reaction tank 41 from the liquid tank 44 to be processed. The reaction tank 41 is provided with a stirring device 43 so that the inside can be stirred. Two outlets are provided in the reaction tank 41, one is a catalyst-containing liquid outlet 45, and the other is a supernatant liquid outlet 46. A black light blue 42 is installed so that the liquid to be treated in the reaction tank 41 can be irradiated with ultraviolet rays.
[0055]
One-seventh of the liquid to be treated was placed in the reaction tank 41 of the reaction apparatus shown in FIG. 4, and 1 g of the composite photocatalyst (in powder form) was added and stirred for 30 minutes. (Adsorption process)
[0056]
Then, after allowing the catalyst to settle by standing, the supernatant water was discharged from the supernatant liquid outlet 46. (Separation process) When the concentration of dioxin contained in the discharged water was measured, no dioxin was detected.
[0057]
Thereafter, the liquid to be treated was further introduced into the reaction tank 41 one-seventh, followed by stirring, catalyst sedimentation, and discharge of the supernatant water five times. (Adsorption process and separation process) Dioxins were not detected in all discharged water.
[0058]
Thereafter, the remaining one-seventh liquid to be treated was introduced into the reaction tank 41 and stirred, and then the reaction tank 41 was irradiated with ultraviolet rays using the black light blue 42 (main wavelength 352 nm, 10 W, five) while stirring. Irradiated. (Disassembly process)
[0059]
After 2 hours of ultraviolet irradiation, the catalyst was allowed to settle and the supernatant water was discharged. Dioxin was not detected in the supernatant water. After the catalyst was discharged from the catalyst-containing liquid discharge port 45, it was originally discarded, but when the contained dioxin was measured, it was not detected.
[0060]
(Comparative Example 1)
Using the same composite photocatalyst and processing apparatus as in Example 1, a dioxin decomposition test was conducted. Dioxin is a solution (aqueous solution) 2L in which the concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin is 700 pg / L is placed in the reaction tank 41 of the apparatus shown in FIG. ) Was added. While the catalyst was suspended as it was, the reaction tank 41 was irradiated with ultraviolet rays using Black Light Blue 42 (main wavelength: 352 nm, 10 W, 5). After 2 hours of ultraviolet irradiation, the waste liquid containing the catalyst was discharged. When dioxins contained in the catalyst and the waste liquid were measured, dioxins of 20 pg / L or less were detected, and the irradiation time of ultraviolet rays was insufficient.
[0061]
(Example 2)
A dioxin decomposition test was carried out using the same composite photocatalyst as in Example 1. Dioxins are 2,3,7,8-tetrachlorodibenzo-p-dioxin, 1,2,3,7,8-pentachlorodibenzo-p-dioxin, 1,2,3,4,7,8-hexachlorodibenzo -P-dioxin, 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin, 1,2,3,7,8,9-hexachlorodibenzo-p-dioxin, 1,2,3,4 , 6,7,8-heptachlorodibenzo-p-dioxin was subjected to decomposition treatment using the following treatment apparatus for 1 L of the liquid to be treated (solvent was toluene) having a concentration of 40 ng / L.
[0062]
FIG. 5 shows a schematic diagram of the processing apparatus. The liquid to be processed is injected into the reaction tank 51 from the liquid tank 54 to be processed. In addition, a solvent is introduced from the solvent introduction tank 57 and a gas is introduced from the gas introduction port 60 into the reaction tank. The reaction tank 51 is provided with a stirring device 53 so that the inside can be stirred. Two outlets are provided in the reaction tank 51, one is a catalyst-containing liquid outlet 55, and the other is a supernatant liquid outlet 56. A black light blue 52 is installed so that the liquid to be treated in the reaction tank 51 can be irradiated with ultraviolet rays. A heater 58 for heating the reaction tank 51 is installed at the lower part of the reaction tank 51. An activated carbon adsorption tower 59 for adsorbing gas generated from the liquid to be treated is also installed.
[0063]
The liquid to be treated was placed in a reaction tank 51 of the reaction apparatus shown in FIG. 5, and 1 g of the catalyst (powder) was charged. Thereafter, the reaction vessel 1 was heated to 50 ° C., and a nitrogen stream was applied to the surface of the liquid to be treated from the gas inlet 60 to evaporate the solvent. (Adsorption process and separation process) The nitrogen stream containing the evaporated solvent was led to the activated carbon adsorption tower 59 to collect the solvent.
[0064]
After the solvent is completely evaporated, water is introduced into the reaction tank 51 from the solvent introduction tank 57 and stirred, and the catalyst adsorbed with dioxin is suspended in the black light blue 52 (main wavelength 352 nm, 10 W, 5 lines). Was used to irradiate the reaction tank 51 with ultraviolet rays. (Decomposition step) After 2 hours of ultraviolet irradiation, the catalyst was allowed to settle, and the supernatant water was discharged from the supernatant liquid discharge port 56. Dioxin was not detected in the supernatant water. After the catalyst was discharged from the catalyst-containing liquid discharge port 55, it was originally discarded, but when the contained dioxin was measured, it was not detected.
[0065]
(Comparative Example 2)
Using the same composite photocatalyst and processing apparatus as in Example 2, a dioxin decomposition test was conducted. As dioxin, 1 L of waste liquid (solvent is toluene) having a concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin of 40 ng / L is placed in the reaction tank 51 of the apparatus shown in FIG. ) Was added. While the catalyst was suspended as it was, the reaction vessel 51 was irradiated with ultraviolet rays using Black Light Blue 52 (main wavelength: 352 nm, 10 W, 5). After 12 hours of ultraviolet irradiation, the waste liquid containing the catalyst was discharged. When dioxins contained in the catalyst and the waste liquid were measured, 10 pg / L or less of dioxins was detected, and the irradiation time of ultraviolet rays was insufficient.
[0066]
【The invention's effect】
As described above, according to the present invention, according to the present invention, a large amount of waste liquid containing organic halogen compounds such as dioxins can be reduced in a short time using a composite photocatalyst. it can.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing the mechanism of an organic halogen compound by a composite photocatalyst according to the present invention.
FIG. 2 is a schematic view showing a method for treating an organic halogen compound according to the present invention.
FIG. 3 is a schematic diagram showing a method for treating an organohalogen compound according to the present invention.
FIG. 4 is a schematic view of an organic halogen compound decomposition apparatus according to an embodiment of the present invention.
FIG. 5 is a schematic view of an organic halogen compound decomposition apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1. Carbon material
2 ... Metal particles
3 ... Photocatalyst particles
4 ... Organic halogen compounds
20 ... Liquid to be treated
21 ... Adsorption process
22 ... Separation process
23 ... Liquid to be treated
24 ... Composite photocatalyst
30 ... Liquid to be treated
31 ... 1st adsorption process
32 ... 1st separation process
33 ... Composite photocatalyst
34 ... Liquid to be treated
35 ... New liquid to be treated
36 ... 2nd adsorption process
37 ... Second separation step
38 ... Composite photocatalyst
39: Liquid to be treated
40 ... Decomposition process
41 ... Reaction tank
42 ... Black light blue
43 ... Agitator
44 ... Liquid tank to be treated
45 ... Catalyst-containing liquid outlet
46 ... Supernatant liquid outlet
51 ... Reaction tank
52 ... Black light blue
53 ... Agitator
54 ... Liquid tank to be treated
55 ... Catalyst-containing liquid outlet
56 ... Supernatant liquid outlet
57 ... Solvent introduction tank
58 ... Heater
59 ... Activated carbon adsorption tower
60 ... Gas inlet

Claims (6)

An adsorption step in which a liquid to be treated containing an organic halogen compound is brought into contact with a composite photocatalyst comprising a carbon material, a dehalogenation catalyst, and a photocatalyst that decomposes an organic substance by light irradiation to adsorb the organic halogen compound to the composite photocatalyst;
A separation step of separating the liquid to be treated obtained in the adsorption step and the composite photocatalyst that has adsorbed the organic halogen compound;
A decomposition step of decomposing the organic halogen compound adsorbed by light irradiation on the composite photocatalyst obtained in the separation step;
And a method for decomposing an organic halogen compound. An adsorption step in which a liquid to be treated containing an organic halogen compound is brought into contact with a composite photocatalyst comprising a carbon material, a dehalogenation catalyst, and a photocatalyst that decomposes an organic substance by light irradiation to adsorb the organic halogen compound to the composite photocatalyst; A separation step of separating the liquid to be treated obtained in the adsorption step and the composite photocatalyst that has adsorbed the organic halogen compound is repeated a plurality of times,
A method for decomposing an organic halogen compound, comprising performing a decomposition step of decomposing the organic halogen compound adsorbed by irradiating the composite photocatalyst obtained in the adsorption separation step with light. 3. The method for decomposing an organic halogen compound according to claim 1, wherein the adsorption step and the separation step are simultaneously performed by evaporating the liquid while bringing the composite photocatalyst into contact with the liquid to be treated. The decomposition step comprises suspending the composite photocatalyst adsorbed with the organic halogen compound in water or at least one solvent selected from toluene, n-hexane, 2-propanol, acetone, dichloromethane, methanol, and ethanol. Irradiation is performed, The decomposition method of the organic halogen compound according to claim 1 or 2. In the composite photocatalyst, a dehalogenation catalyst which is at least one metal selected from the group consisting of palladium, platinum, rhodium, ruthenium, iron, copper, silver and zinc is supported on the carbon material, and the photocatalyst is supported on the metal surface. 3. The method for decomposing an organic halogen compound according to claim 1, wherein the organic halogen compound is supported on the organic halide. 3. The method for decomposing an organic halogen compound according to claim 1, wherein the photocatalyst is titanium dioxide.

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