JPH03284272A - Decomposing treatment method of halogenated organic compound - Google Patents

Abstract

PURPOSE:To quickly and continuously decompose and treat a halogenated organic compound at a high efficiency without producing hazardous decomposed byproducts by a method wherein specified ultraviolet rays are radiated to the halogenated organic compound in the presence of alkaline solution. CONSTITUTION:Ultraviolet rays having a wave length of 100-400nm are radiated to a halogenated organic compound with presence of an alkaline solution. That is, when the halogenated organic compound is decomposed with use of a decomposing equipment, a sample gas such as fluorocarbon gas is introduced into a decomposing vessel 1 through a fluorocarbon gas inlet pipe 2, an alkaline solution 7 is sprayed to the sample gas through spray pipes, and simultaneously the sample gas is irradiated with the ultraviolet rays by an ultraviolet fluorescent light 5.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to the use of fluorocarbons, chlorocarbons,
This invention relates to a method for decomposing halogenated organic compounds such as chlorofluorocarbons and trichloroethylene.

(Prior art) CFCs (common name for fluorocarbons, chlorofluorocarbons), which have been widely used in refrigerants, blowing agents, cleaning agents, aerosols, etc., and chlorocarbons, which are used in cleaning and degreasing, destroy the stratospheric ozone layer and pose a threat to human health.・There are concerns about its negative impact on the environment, and efforts are being made to reduce its usage and legal regulations.

On the other hand, halogenated organic compounds such as fluorocarbons and chlorocarbons are chemically very stable, and their decomposition treatment has been difficult. Recently, as methods for decomposing halogenated organic compounds, (1) combustion method, (2) high-frequency plasma method,
(3) supercritical aqueous and (4) microbial decomposition methods are beginning to be considered. However, methods that utilize high temperatures, such as (1) the combustion method and (2) the high-frequency plasma method, have the disadvantage that extremely harmful free chlorine and fluorine are generated as decomposition by-products. In addition, (3) supercritical water-based requires an ultra-high pressure container;
The decomposition efficiency was rather low, and (4) the microbial decomposition method had the disadvantage of requiring a long time for decomposition.

(Problems to be Solved by the Invention) As described above, conventional methods for decomposing halogenated organic compounds have problems such as generating harmful decomposition by-products and requiring a long time. The present invention was made to solve the problems of the conventional technology, and its purpose is to rapidly and continuously decompose halogenated organic compounds without producing harmful decomposition by-products. The object of the present invention is to provide a highly efficient decomposition method.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to achieve the above object, the method for decomposing a halogenated organic compound of the present invention provides a method for decomposing a halogenated organic compound in the presence of an aqueous alkali solution. It is characterized by irradiating ultraviolet light with a wavelength of 100 to 400 nm.

To explain the method of the present invention in detail, a halogenated organic compound attached to a liquid, gas, or solid has a wavelength of 100 to 40%.
Irradiation with 0 nm ultraviolet rays causes a dissociative decomposition reaction, and the hydrogen halides such as hydrogen fluoride and hydrogen chloride generated in the process or as a result are neutralized and absorbed into an alkaline aqueous solution to make them harmless, and this product is This method accelerates the decomposition reaction by removing it from the decomposition system. That is,
In halogenated organic compounds, the binding energies of c-cl and cF are 78.5 and 105.4 K ca, respectively.
ll/mol, and the photon energy of ultraviolet light with a wavelength of 400nI11 is 3,1einstein
This corresponds to a dissociation energy of 72 K caIL/mol, so a wavelength of 400 nm is applied to a halogenated organic compound.
If ultraviolet rays of less than m are irradiated, there is a possibility that the above-mentioned bonds will be cleaved.

However, when a molecule absorbs light with an energy higher than the bond dissociation energy, not only bond dissociation occurs, but also recombination, so simply irradiating with ultraviolet light has low decomposition efficiency. Therefore, in the present invention, in addition to irradiating ultraviolet rays, hydrogen halides such as hydrogen fluoride and hydrogen chloride, which are intermediate products and decomposition products generated after the dissociation and decomposition of halogenated organic compounds, are neutralized using an alkaline aqueous solution. By converting it into harmless salts such as sodium fluoride and sodium chloride and removing them from the decomposition system, chemical equilibrium is promoted and decomposition efficiency is improved.

By the way, if the wavelength of the ultraviolet rays to be irradiated is longer than 400 nm, sufficient energy cannot be given to the halogenated organic compound to cause the above-mentioned bond dissociation, so the wavelength needs to be 400 nm or less. On the other hand, if the wavelength is less than 1100 nm, there is a high possibility that harmful fluorine gas and the like will be produced as intermediate products or decomposition products in addition to harmless salts, which is not preferable. Therefore, it is preferable that the wavelength of the ultraviolet rays to be irradiated is 100 to 400 nm.

In addition, the halogenated organic compounds to be covered by the present invention include at least one halogen atom such as fluorine atom, chlorine atom, bromine atom, etc., especially saturated, unsaturated or aromatic compounds substituted with fluorine atom or chlorine atom. There are no limitations as long as it is an organic compound, but preferred examples include fluorocarbon, chlorocarbon, chlorofluorocarbon, trichloroethylene, and carbon tetrachloride.

The alkaline aqueous solution used in the present invention is not particularly limited as long as it can neutralize and absorb hydrogen halides, and examples include alkali metal hydroxides such as sodium hydroxide and hydrium hydroxide, calcium hydroxide, etc. Examples include aqueous solutions of alkaline earth metal hydroxides, ammonia, etc.
The concentration thereof is preferably pH 8-12. For example, when using an aqueous sodium hydroxide solution, the concentration is preferably 0.1 to 1.0 N (4 to 40 g/hour).

The treatment temperature is preferably 0 to 100°C, more preferably 30 to 80°C. The processing time varies depending on the type of halogenated organic compound, the wavelength of ultraviolet rays, etc., but it is usually 3.
The duration is 0 minutes to 2 hours.

Next, to explain the effect of the present invention, in the method of the present invention, the decomposition reaction is not carried out at high temperatures as in conventional combustion methods, so harmful decomposition by-products such as free chlorine and fluorine are not generated. , less corrosion and damage to the decomposition equipment.

In addition, hydrogen halides such as hydrogen fluoride and hydrogen chloride, which are decomposition products, are easily absorbed into alkaline aqueous solutions and rendered harmless as salts such as sodium fluoride and sodium chloride. . Furthermore, by irradiating ultraviolet light in the presence of an alkaline aqueous solution, hydrogen halides such as hydrogen fluoride and hydrogen chloride generated as intermediate products and decomposition products are removed as neutralizing salts, so the decomposition reaction is prevented. It is possible to carry out the decomposition efficiently and continuously.

(Examples) The present invention will be described in further detail with reference to Examples below, but these Examples do not limit the scope of the present invention in any way.

In the following examples, experiments were conducted using a decomposition treatment apparatus as shown in FIG. This equipment continuously decomposes halogenated organic compounds that can be gasified, such as chlorine gas, trichlorethylene, and carbon tetrachloride.

As shown in the figure, this decomposition treatment equipment consists of a quartz decomposition vessel 1
A fluorocarbon inlet pipe 2 for introducing sample gas such as fluorocarbon into the
, a fluorocarbon mountain back 3 for discharging the sample gas, and a drain pipe 4 for discharging waste liquid are provided, and the upper part of the decomposition vessel 1 is for spraying an alkaline aqueous solution such as a sodium hydroxide solution into the decomposition vessel 1. A spray pipe 6 with a nozzle is attached. An ultraviolet fluorescent lamp 5 is installed inside the decomposition vessel 1-.

When decomposing a halogenated organic compound using this decomposition device, first introduce a sample gas such as chlorofluorocarbon gas into the decomposition vessel 1 from the fluorocarbon inlet pipe 2, and then spray the aqueous alkali solution 7 onto the sample gas from the spray pipe. At the same time, an ultraviolet fluorescent lamp 5
The sample gas is irradiated with ultraviolet light. The sample gas becomes hydrogen halides such as hydrogen fluoride and hydrogen chloride due to the ultraviolet rays, and is absorbed by the alkaline aqueous solution 7 and converted into harmless salts such as sodium fluoride and sodium chloride.

The alkaline aqueous solution 7 that has absorbed the hydrogen halide can be continuously taken out of the system through the drain pipe 4, thereby removing the decomposition products of the sample gas from the decomposition vessel 1 and promoting chemical equilibrium. Decomposition reactions are promoted. In this way, the sample gas can be decomposed continuously.

Example 1 Using the above decomposition treatment apparatus, fluorocarbons (CHC12; fluorocarbons 22) were continuously decomposed.

A 0.5N-NaOH solution was used as the alkaline aqueous solution, and ultraviolet rays with a wavelength of 254 nm were irradiated at 60°C. As a result, after 2 hours, Freon was converted to sodium fluoride with a recovery rate of 88%.

[Effects of the Invention] As explained above, according to the method of the present invention, halogenated organic compounds harmful to the environment can be continuously and efficiently decomposed into harmless salts without producing harmful decomposition by-products. becomes possible. Therefore, the industrial value is extremely large.
Furthermore, it is possible to improve environmental safety.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view schematically showing the configuration of a decomposition treatment apparatus used in an embodiment of the present invention. 1... Decomposition container 2... Freon inlet pipe 3... Freon mountain back 4... Drain pipe 5... Ultraviolet fluorescent lamp 6... Spray tube 7... Alkaline aqueous solution

Claims (1)

[Claims] A halogenated organic compound is mixed with an alkaline aqueous solution,
A method for decomposing a halogenated organic compound, the method comprising irradiating ultraviolet light with a wavelength of 100 to 400 nm.