JP3474349B2 - Decomposition method of halogen-containing organic compounds - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for decomposing a halogen-containing organic compound into a harmless substance, and more particularly to a method for decomposing a halogen-containing organic compound in a liquid phase by irradiation with ultraviolet rays.

[0002]

2. Description of the Related Art Trichlorene, polychlorobiphenyl (P
The halogen-containing organic compounds such as CB) and chlorofluorocarbon are widely used in various fields such as the electronic component industry and the chemical industry. However, toxicity of chlorine compounds such as trichlene and PCB has been revealed to the human body, and problems of fluorine compounds such as CFCs have been clarified in recent years in terms of global environmental destruction as seen in ozone layer destruction. Under such circumstances, a method for decomposing the halogen-containing organic compound to render it harmless is required, and various methods have been studied. Method 1
Finally, there is an ultraviolet decomposition method, which is being developed as a method for decomposing a minute amount of halogen-containing organic compounds such as trichlene dissolved in water such as factory wastewater.

Since the concentration of the halogen-containing organic compound decomposed in the above method is below the ppm level and the solubility of the halogen-containing organic compound in water is very low, a large amount of the halogen-containing organic compound is decomposed by this method. It was considered difficult to do.

Therefore, as an improved method, a method has been proposed in which alcohol is used as a solvent in order to dissolve the halogen-containing organic compound, and ultraviolet irradiation is carried out (JP-A-6-
63177 publication). In this method, an alkali is added in order to salt out and remove hydrogen halide and the like generated by ultraviolet irradiation.

[0005]

However, when the alcohol solvent as described above is used, the alcohol causes a side reaction due to ultraviolet rays, so that the solution is colored and a polymer-like precipitate is produced as a by-product. . Therefore, the ultraviolet transmittance is reduced, and the post-treatment for discarding or reusing the reaction solution is complicated due to the mixing of the produced salt and the precipitate,
There is also the problem of increased costs.

[0006]

The present invention provides a method for decomposing a halogen-containing organic compound, which can efficiently decompose and detoxify a halogen-containing organic compound without causing the above-mentioned problems and facilitate post-treatment. The purpose is to

The method for decomposing a halogen-containing organic compound according to the present invention is a method of stirring a liquid containing a halogen-containing organic compound and water or a liquid containing a halogen-containing organic compound, water and an alkaline substance while dispersing them in an emulsion state. It is characterized by irradiation with ultraviolet rays.

[0008]

According to the above method, water is used in a volume ratio of 5 times or more with respect to the halogen-containing organic compound.

The contact area of the halogen-containing organic compound and water increases by stirring or by forming a dispersion. By irradiating with ultraviolet rays in this state, the decomposition reaction that occurs through the interface is promoted, so that the decomposition rate of the halogen-containing organic compound is improved. As a result, it becomes possible to decompose the halogen-containing organic compound having a saturated amount or more in water by ultraviolet light.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

Since the saturated dissolution amount of the halogen-containing organic compound in water is as low as about 4000 ppm or less, even if both are combined, they are separated with almost no dissolution. Even when UV rays are irradiated in the separated state, the decomposition rate of halogen-containing organic compounds is very slow,
Irradiation with gentle stirring improves the decomposition rate slightly, but not sufficiently. However, when the halogen-containing organic compound is dispersed in water with vigorous stirring and irradiated with ultraviolet rays in an emulsion state, the concentration of halogen ions in water considerably increases. That is, the decomposition rate is improved. From this, it is understood that the process of the decomposition reaction proceeds through the contact interface between the aqueous phase and the halogen-containing organic compound phase, and the reaction step through the contact interface is rate-determining. That is, the decomposition rate depends on the contact area between the aqueous phase and the organic phase. Therefore,
It is important to increase the contact area between the two phases as much as possible in order to promote the ultraviolet decomposition reaction of the halogen-containing organic compound in water.

One method for achieving this is the mechanical method such as stirring and shaking described above, and the dispersion efficiency such as the stirring (or shaking) speed, the shape of the stirring blade or stirrer, and the shape of the container is controlled. The factors that influence control the factors that affect the improvement of reaction efficiency. Further, the mixing ratio of the halogen-containing organic compound and water is also an important factor for efficiently increasing the contact area. Increasing the amount of water increases the stability of the dispersion formed by stirring, and also increases the standing time required for the dispersion to separate from the emulsion state into two phases again. In order to effectively disperse the halogen-containing organic compound in water,
A volume ratio of water to the halogen-containing organic compound is about 5 times or more, preferably about 10 times or more, and particularly when the amount of water is 25 times or more, the progress of the decomposition reaction becomes remarkable.
However, in order to optimize the treatment efficiency per volume of the decomposition apparatus, it is desirable to set the amount of water used to an amount that can saturate the halogen-containing organic compound or less, preferably about 50 times or less.

Another method is to prepare an emulsion using a surfactant or the like as an emulsifier and irradiate it with ultraviolet rays. However, it is desirable to keep the amount of the surfactant used as small as possible. The reason for this is to prevent a large amount of the surfactant from being concentrated at the interface and substantially preventing the flow inside and outside the emulsion. Therefore, it is desirable that the amount of the surfactant be equal to or less than the amount of the halogen-containing organic compound in a volume ratio.

According to the above, the halogen-containing organic compound is dispersed in water and irradiated with ultraviolet rays. The decomposition reaction by irradiation with ultraviolet rays proceeds almost completely by ultraviolet rays of relatively high energy. Irradiation in the far-ultraviolet region, that is, a wavelength of about 300 nm or less is preferable. The decomposition rate becomes slower as the irradiation wavelength becomes longer, but when a sensitizer is used, it is also possible to use lower energy ultraviolet light in the near ultraviolet region (400 to 300 nm). As the sensitizer, acetone, ethyl methyl ketone,
Those having a ketone structure such as acetaldehyde or an aldehyde structure are used. The addition amount of the photosensitizer is preferably appropriately changed depending on the decomposition conditions, but in general,
Sufficient efficacy is obtained with an equimolar amount or less with respect to the halogen-containing organic compound that decomposes.

Further, use of an alkaline substance can accelerate the progress of the decomposition reaction. The alkaline substance has a function of desorbing from the halogen-containing organic compound and capturing and neutralizing the halogen existing as an ion in water. Further, halogen-containing organic compounds such as Freon HCFC-21, HCFC-22, and CFC-12 are easily decomposed in the presence of alkali. Similarly, the presence of the alkaline substance facilitates the reaction of the second and subsequent halogen elimination steps in the ultraviolet decomposition of CFC-11. Therefore, it is desirable to add an alkaline substance in order to accelerate the complete decomposition of the halogen-containing organic compound into carbon dioxide. As the alkaline substance, it is preferable to use a water-soluble alkaline substance in order to capture halogen in the aqueous phase, and examples thereof include metal hydroxides such as sodium hydroxide, potassium hydroxide and calcium hydroxide, ammonia and soap. Examples thereof include saponified products of organic compounds with alkali metals. Since soap is also a surfactant, it is effective in stabilizing the dispersion.

The above-mentioned alkaline substance may be added to water in advance, or may be added to water during the irradiation of ultraviolet rays.

The decomposition reaction can also be promoted by adding one having a function of removing halogen ions out of the reaction system. For example, when an anion exchange resin is added, the halogen ions existing in water after being desorbed are adsorbed by the anion exchange resin, so that the halogen ions are removed from the reaction system. As a result, it is possible to suppress the recombination of the decomposition intermediate substance and the eliminated halogen due to the reverse reaction. Alternatively, the halogen can be precipitated and removed from the decomposition reaction system by introducing into the reaction system a compound that forms a sparingly soluble compound with a halogen ion such as calcium.

The above-described disassembling method can be carried out by the disassembling apparatus 1 as shown in FIG. 1, for example. Disassembly device 1
Is composed of a decomposition tank 3, a magnetic stirrer 5, a stirrer 7 and an ultraviolet lamp 9, and the stirrer 7 is rotated by the magnetic stirrer 5 in the water and the halogen-containing organic compound charged into the decomposition tank 3. Water and the halogen-containing organic compound are stirred to disperse the halogen-containing organic compound in water. The halogen-containing organic compound is decomposed by irradiating the water W, in which the halogen-containing organic compound is dispersed, with ultraviolet rays from the ultraviolet lamp 9. When the alkaline substance is added in parallel with the ultraviolet irradiation, an alkali adding device is attached to the decomposition tank 3.

As described above, the decomposition method according to the present invention is
It decomposes by irradiating a halogen-containing organic compound with water together with ultraviolet light. Methyl chloride, methylene chloride, chloroform, carbon tetrachloride, trichlene, PCB,
It can be applied to the decomposition of freon, dichloroethene, etc. The reaction liquid after decomposition can be safely discarded by neutralizing halogen ions with alkali. At this time, since the undecomposed halogen-containing organic compound is separated from water, it is easy to remove it from water and perform the decomposition reaction treatment again. When a trace amount of undecomposed halogen-containing organic compound is dissolved in water, the ultraviolet decomposition treatment may be performed again. Therefore, the treatment after the decomposition reaction is extremely easy and the economical burden is small.

[0021]

The present invention will be further described below with reference to examples.

(Embodiment 1) Decomposition tank 3 of the decomposition apparatus shown in FIG.
In addition, 50 ml of Freon (CFC-113) in 500 ml of pure water
Was added and the mixture was vigorously stirred for 5 minutes with a magnetic stirrer. While stirring,
Freon was dispersed in water and became an emulsion. Further, while continuing stirring, this dispersion was irradiated with ultraviolet rays (254 nm, 32 W) by an ultraviolet lamp 9 for 1 hour, and the chlorine ion concentration and the fluorine ion concentration in water after the irradiation were measured. The measurement results are shown in Table 1.

Example 2 As in Example 1, pure water and chlorofluorocarbon were vigorously stirred by the magnetic stirrer 5 for 5 minutes. After that, ultraviolet rays were irradiated in the same manner as in Example 1 while lowering the stirring speed and performing gentle stirring. During the irradiation, the stirring liquid was separated into a water phase and a freon phase. Table 1 shows the results of measuring the chlorine ion concentration and the fluorine ion concentration in the water after the irradiation.

(Example 3) As in Example 1, pure water and chlorofluorocarbon were vigorously stirred for 5 minutes with a magnetic stirrer. After this,
The stirring was stopped, and the liquid separated into water and chlorofluorocarbon was irradiated with the same ultraviolet rays as in Example 1. Table 1 shows the results of measuring the chlorine ion concentration and the fluorine ion concentration in the water after the irradiation.

(Comparative Example) The same amounts of pure water and Freon as in Example 1 were vigorously stirred for 5 minutes as in Example 1, and the chlorine ion concentration and the fluorine ion concentration in the water after the stirring were measured. It shows in Table 1.

[0026]

[Table 1] --------------------------------------- Chloride ion concentration (ppm) Fluoride ion concentration (ppm) ----- ----------------------- Example 1 115 48 Example 2 86 36 Example 3 67 25 Control Example 0.03 0.28 --- From the above, it is clear that if the stirring during UV irradiation is intense, the number of halogen ions in the water after irradiation increases. From this, it is understood that the decomposition reaction of freon is promoted. Further, when the same ultraviolet ray irradiation is performed on water and freon without any stirring, the concentration of chlorine ions and fluorine ions after the irradiation becomes smaller than the values in Example 3. From this, it is understood that in Example 3, some of the particles dispersed by vigorous stirring before irradiation remained until irradiation.

(Example 4) The same operation as in Example 1 was carried out except that the amount of freon was changed to 10 ml, and the chlorine ion concentration and the fluorine ion concentration in the water after ultraviolet irradiation were measured. Shown in.

(Example 5) The same operation as in Example 1 was carried out except that the amount of freon was changed to 20 ml, and the chlorine ion concentration and the fluorine ion concentration in the water after ultraviolet irradiation were measured. Shown in.

(Example 6) The same operation as in Example 1 was carried out except that the amount of Freon was changed to 30 ml, and the chlorine ion concentration and the fluorine ion concentration in the water after ultraviolet irradiation were measured. Shown in.

(Example 7) The same operation as in Example 1 was carried out except that the amount of Freon was changed to 100 ml, and the chlorine ion concentration and the fluorine ion concentration in the water after ultraviolet irradiation were measured. Shown in.

[0031]

[Table 2] ------------------------------------------ Chloride ion concentration (ppm) Fluoride ion concentration (ppm) ----- Example 4 195 104 Example 5 250 150 Example 6 134 58 Example 1 115 48 Example 7 112 46 − −−−−−−−−−−−−−−−−−−−−−−−−− In Table 2, there is a big difference in the halogen ion concentration after the reaction between Example 1 and Example 7. Although not seen, when these results are considered with reference to a unit volume of CFC, the reaction rate of Example 1 is about twice as high as that of Example 7. or,
As shown in Examples 4 and 5, the concentration of halogen ions rapidly increases as the amount of CFC added to water decreases. Therefore, the results of Examples 1 and 7 are not suppressed by the reaction due to concentration equilibrium. I can say no. Furthermore, it is considered that the area of the contact interface in the dispersion and the stability of the dispersed particles are remarkably increased by the decrease in the amount of freon, and thereby the decomposition reaction rate is improved. From the results in Table 2, 500 ml of water
It is suggested that the area of the contact interface and the stability of the dispersed particles are remarkably increased when the amount of CFCs to C.sub.2 is about 20 ml or less (water volume to CFCs = about 25 times).

[0032]

As described above, according to the present invention,
UV decomposition of halogen-containing organic compounds in water is promoted, which makes it easy to treat unnecessary halogen-containing organic compounds, and is also excellent in that it is easy to treat after the reaction.
Its value in industry and environmental protection is great.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a decomposition apparatus for carrying out a decomposition method of a halogen-containing organic compound according to the present invention.

[Explanation of symbols]

3 decomposition tank 5 magnetic stirrer 7 Stirrer 9 UV lamp

Continuation of the front page (56) Reference JP-A-7-128318 (JP, A) JP-A-6-7474 (JP, A) JP-A-4-293517 (JP, A) JP-A-8-206250 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B01J 19/12 A62D 3/00 C07B 35/06

Claims (2)

(57) [Claims] Consisting 1. A halogen-containing organic compound and water
Liquid or halogen-containing organic compound, water and alkaline substance
A method for decomposing a halogen-containing organic compound, which comprises irradiating ultraviolet rays while agitating a liquid containing the above and dispersing it in an emulsion state . 2. The method for decomposing a halogen-containing organic compound according to claim 1, wherein the water is used 5 times or more in volume ratio with respect to the halogen-containing organic compound.