Method for decomposing organic environmental pollutant

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for decomposing and treating organic environmental pollutants such as dioxins, PCBs, tetrachlorethylene, and other environmental hormones contained in water systems and soils.

【0002】

[Conventional technology]

In general, polychlorinated dibenzo-para-dioxin (PCDD), polychlorinated dibenzofuran (PCDF) and coplanar PCBs are collectively referred to as "dioxins", which are extremely toxic and are also exogenous endocrine disruptors. It is known.

【0003】

These dioxins are generated when the waste material of plastic containing chlorine atoms is burned, and have the property of being hard to dissolve in water and resistant to heat, and the property of being hard to be easily decomposed by microorganisms, so that they are incinerated, for example. It polluted the soil around the site and other areas around the human living environment, and the amount was gradually accumulated.

【0004】

In recent years, it has been necessary to quickly decompose and detoxify organic environmental pollutants such as dioxins, PCBs, tetrachlorethylene, and other environmental hormones that have accumulated in the environment. It became clear.

【0005】

By the way, according to Chapter 4, Section 6, "Current Status of Dioxin Decomposition by Ultraviolet Rays, Ozone, Microorganisms, etc.", "Prospects for Solving Dioxin Pollution Problems" published by the Industrial Technology Association, 2,3,7,8 -Studies have reported that 97% of dioxins were decomposed after 50 hours by suspending tetrachlorodibenzodioxin in water and carbon tetrachloride and injecting ozone.

【0006】

Ozone has the molecular formula O₃It is an allotrope of oxygen represented by, and is mixed in ordinary air at a dilute concentration, has a redox potential (under oxidation conditions) of 2.07 eV, and has a high standard free energy of generation, and all of them. It shows the physical properties of decomposing into oxygen at temperature.

【0007】

[Problems to be Solved by the Invention]

However, as described above, the conventional method for decomposing dioxin using ozone has a problem that it takes a long time of 50 hours.

【0008】

Further, in the above-mentioned conventional method, only a method for treating dioxins in an aqueous solution in which dioxins are relatively easily decomposed is disclosed, and dioxins mixed in particulate solids such as massive or granular soil are decomposed. In the case of processing, it is considered that the processing efficiency is further lowered.

【0009】

Therefore, the subject of the present invention is to solve the above-mentioned problems, improve the decomposition treatment efficiency of dioxins and other organic environmental pollutants, and efficiently decompose the organic environmental pollutants in a short time. That is.

【0010】

Another object of the present invention is that even when dioxins and other organic environmental pollutants mixed in particulate solids such as soil are decomposed, the decomposition treatment can be efficiently performed in a short time. It is a method.

【0011】

[Means for solving problems]

In order to solve the above problems, ozone gas is mixed with atomized hydrogen peroxide solution, and this gas-liquid mixing system is irradiated with ultraviolet rays, ultrasonic waves, or both in combination to oxidatively decompose hydroxyl radicals. This was a method for decomposing organic environmental pollutants, which consisted of preparing a sex gas and stirring and mixing the oxidatively degradable gas and organic environmental pollutants.

【0012】

When ultraviolet rays are applied to ozone that has been atomized and dissolved in fine-grained hydrogen peroxide solution, HO radicals (.OH) are generated by the following ozone oxidation reaction involving water.

【0013】

The following shows the reaction in which HO radicals are directly generated from ozone, and shows the reaction in which HO radicals are generated from ozone via the formation of hydrogen peroxide. O₃ O₂+ O (¹D) O (¹D) + H₂O 2 OH O₃+ H₂O O₂+ H₂O₂ H₂O₂ 2 OH [0014]

In addition, ozone oxidation in the presence of hydrogen peroxide causes a reaction to generate OH (hydroxy radical). If this reaction is divided into more stages, the first step requires dissociation of hydrogen peroxide as shown in Eq. (A), and then the HO produced by this reaction.₂^-Reacts with ozone as shown in (b), and OH is produced. O₃+ H₂O₂ OH + HO₂+ O₂ H₂O₂= HO₂^-+ H⁺ (a) O₃+ HO₂^- OH + O₂-+ O₂ (b) [0015]

Since the above manufacturing method is a gas-liquid mixing system in which ozone gas and atomized hydrogen peroxide solution are mixed, the contact area between the two substances is wide and the contact efficiency is high. Therefore, ozone that has absorbed ultraviolet rays, ultrasonic waves, or energy waves that are used in combination of both is decomposed, and the oxygen atoms generated at this time efficiently react with the hydrogen peroxide solution to generate a large amount of HO radicals.

【0016】

Further, in the above method, ultrasonic waves may be irradiated instead of or together with ultraviolet rays. When irradiating ultrasonic waves, cavitation may occur in the aqueous solution, or a mass of particulate medium containing water such as soil may be cracked or destroyed by ultrasonic vibration. Make it fine particles.

【0017】

When ultrasonic waves are irradiated in this way, when minute cavities (cavities) generated in water collapse, liquid molecules collide with each other at extremely large accelerations, and a state of ultra-high temperature and high pressure is locally generated shockingly. Therefore, the autolysis of ozone and the activity of free radicals in water increase, and HO radicals and hydrogen peroxide are easily generated.

【0018】

By integrating these methods, ozone gas is mixed with atomized hydrogen peroxide solution, and this gas-liquid mixing system is irradiated with ultraviolet rays and ultrasonic waves to generate a large amount of HO radicals. It is preferable to prepare (also referred to as active ozone).

【0019】

Then, in the present invention, the oxidatively decomposable gas (active ozone) obtained as described above and an organic environmental pollutant such as dioxins are stirred and mixed to cause a contact reaction for a required time to be organic. Decomposes system environmental pollutants in a short time.

【0020】

Since the oxidatively decomposable gas is a gas, organic environmental pollutants or particulate solid substances such as soil containing the oxidatively decomposable gas may be mixed and contact with each other even if they are solid, and HO radicals having a large oxidizing power are generated. Since it is contained in a large amount, it is considered that organic environmental pollutants such as dioxin are dechlorinated or decomposed until the basic molecular structure such as multiple bonds between carbons is broken.

【0021】

In addition, in a granular medium containing water such as soil, particles tend to adhere to each other to form a lump, but dioxins existing inside such a lump are less likely to come into contact with oxidatively decomposable gas. Therefore, oxidative decomposition is less likely to occur.

【0022】

Therefore, by adopting a means in which the stirring and mixing is performed while irradiating ultrasonic waves, a mass made of a particulate medium containing water such as soil is destroyed by ultrasonic vibration and becomes finer. The vibration of ultrasonic waves that become particles or are irradiated causes cracks in the mass, improving the contact efficiency between organic environmental pollutants and oxidatively decomposable gas.

【0023】

Further, in the method for decomposing organic environmental pollutants, sodium hydrogencarbonate is added and stirred when the oxidatively decomposable gas and the particulate solid containing the organic environmental pollutants are stirred and mixed in the container. By adopting the mixing means, the dechlorination reaction is promoted, and the decomposition efficiency of organic environmental pollutants is improved accordingly.

【0024】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an apparatus for producing an oxidatively decomposable gas of an organic substance used in the present invention will be described with reference to the accompanying drawings.

【0025】

The device shown in FIG. 1 is used as a method for producing an oxidatively decomposable organic substance that produces hydroxyl radicals in the gas by mixing atomized hydrogen peroxide solution with ozone gas and irradiating the gas-liquid mixing system with ultraviolet rays. This is the device to be used.

【0026】

That is, this device supplies oxygen as a raw material from the oxygen cylinder 1 to the ozonizer 3 via the pressure reducing valve 2, and the ozone gas generated by the ozonizer 3 is sent to the atomizer 5 via the pipe 4. A hydrogen peroxide solution 7 having a predetermined concentration is put into the container 6 of the atomizer 5, and this is sucked up by the pipe of the atomizer 5 and sprayed from the nozzle at the tip thereof to generate ozone gas (gas-liquid mixed gas) containing fine particles of the hydrogen peroxide solution. ) Is introduced into the reaction vessel 8 made of a glass tube. Then, an ultraviolet light bulb 9 is provided close to the reaction vessel 8 into which the gas-liquid mixing system gas has been introduced to irradiate the ultraviolet rays, and the gas-liquid mixing system gas after the ultraviolet irradiation is introduced into the decomposition treatment container 10 and the decomposition treatment container 10 In addition to joining the pipe 11 into which the substance to be treated is introduced via the check valve 12, an ozone decomposer 13 (filled with activated charcoal or a manganese-based catalyst) for removing ozone remaining after the treatment is installed in the container. It is a device for producing and processing organic oxidatively decomposable gas that releases the gas that has passed through to the atmosphere.

【0027】

The organic environmental pollutants to be treated in the present invention refer to all environmental pollutants that pollute water, air, or soil except inorganic substances, for example, dioxins contained in water systems and soil. It is an organic environmental pollutant such as PCBs, tetrachloroethylene, and other environmental hormones. Organic environmental pollutants often have chlorine in their molecular structure and contain multiple (double or triple) bonds of carbon.

【0028】

The hydrogen peroxide solution used in the present invention is not particularly limited in its concentration, but is preferably an aqueous solution having a predetermined concentration in view of the reaction pathway for producing HO radicals. High-concentration hydrogen peroxide solution may cause a reaction to eliminate HO radicals. In the embodiment, a preferable result is obtained by using a hydrogen peroxide aqueous solution having a concentration of 10% by weight, and the concentration range of the preferable hydrogen peroxide solution is, for example, 1 to 20% by weight, more preferably 1 to 10% by weight. %.

【0029】

To spray the hydrogen peroxide solution, use a well-known spraying device to suck up the hydrogen peroxide solution into an ozone-containing air stream and spray and disperse it as fine particles from a nozzle, or peroxidize using ultrasonic vibration. There is a method in which hydrogen peroxide water is made into fine particles and dispersed in an ozone-containing atmosphere, and any method can be adopted.

【0030】

The ultraviolet rays used in the present invention may be any light having a wavelength absorbed by ozone, which includes ultraviolet rays in a wavelength range of 220 to 300 nm, which is usually regarded as an ultraviolet region. Incidentally, the absorption peak is around 255 nm from the ultraviolet absorption spectrum of ozone. Further, ultraviolet rays having a wavelength of 200 nm or less, which are called vacuum ultraviolet rays, have a property of directly decomposing water molecules to generate HO radicals. Therefore, it is also preferable to adopt ultraviolet rays including such vacuum ultraviolet rays. The low-pressure mercury lamp (VUV lamp) has 185 nm (vacuum ultraviolet rays) and 254 nm (near ultraviolet rays) as main wavelengths, and ultraviolet rays suitable for the present invention can be obtained.

【0031】

In order to decompose organic environmental pollutants such as dioxins using the oxidatively decomposable gas thus obtained, they are placed in an appropriate container and stirred and mixed to cause a contact reaction to cause organic environmental pollutants. Is disassembled.

【0032】

When an organic environmental pollutant and an oxidatively decomposable gas are agitated and mixed while irradiating ultrasonic waves, as described above, in order to cause cavitation, crack a mass such as soil, or even break into particles. The frequency of the ultrasonic wave is preferably about 20 to 100 kHz, or more preferably 20 to 40 kHz.

【0033】

[Example]

[Example 1] An organic oxidatively decomposable gas was produced under the following conditions using the production apparatus shown in FIG.

【0034】

That is, the ozone concentration generated by Ozonizer (manufactured by Ozonia, Switzerland) 3 is 141 g / m.³The ozone gas of the above is supplied to the atomizer 5, 100 ml of hydrogen peroxide solution having a concentration of 10% by weight is stored in the container 6, and the glass tube (length 30 cm) is sprayed with the ozone gas of 15 liters / minute. ) From one end, and irradiate this gas-liquid mixing system with ultraviolet rays with an ultraviolet light bulb 9 (wavelength 254 nm, 15 watts, Toshiba black light) to generate HO radicals. Produced an oxidatively decomposable gas of organic matter.

【0035】

The decomposition performance of dioxin in the obtained oxidatively decomposable gas was confirmed by the following experiment.

【0036】

That is, 30 g of a dioxin-contaminated soil sample (dioxin concentration 97 pg-TeQ / g) is placed in a 5 liter polyethylene bag, and 3.5 liters of the oxidative decomposition gas obtained by the above method is placed in the bag at room temperature. The mixture was shaken and stirred for 1 hour, and the dioxin concentration was measured before and after the treatment. The results are shown in Table 1.

【0037】

[Comparative Example 1] In Example 1, a sample of the same contaminated soil was treated in exactly the same manner except that air containing 141 g of ozone (ozone gas) was used instead of the oxidatively decomposable gas. The dioxin concentration of the sample was measured before and after the treatment, and the results are also shown in Table 1.

【0038】

[Example 2, Comparative Example 2] In Example 1 or Comparative Example 1, the shaking stirring at the time of the experiment was performed with sodium hydrogen carbonate (LVDS).₃) Each sample of contaminated soil was treated in exactly the same way, except that 5 g was added. The dioxin concentration of the sample was measured before and after the treatment, and the results of Example 2 or Comparative Example 2 are also shown in Table 1.

【0039】

[table 1]

<img file="JP2003001237A_D0001.tif" />【0040】

As is clear from the results in Table 1, treatment of Example 1 using an oxidatively decomposable gas for dioxins, which are harmful pollutants of organic substances that cannot be sufficiently decomposed by ordinary ozone gas (Comparative Example 1). In, the decomposition rate was high by about 20% in a short time of 1 hour, and it was recognized that oxidative decomposition was performed efficiently.

【0041】

Further, by adding sodium hydrogen carbonate and shaking and stirring as in Example 2, the decomposition rate of dioxins was 14% higher than that in the treatment method of Example 1 in which this was not added, and the addition was added. Usefulness is recognized. Furthermore, when comparing Example 2 and Comparative Example 2, the decomposition rate of dioxins was 36% in the treatment of Example 2 using active ozone as compared with the treatment method of Comparative Example 2 in which normal ozone gas was added. It was high, and the usefulness of adding active ozone was also recognized.

【0042】

Next, an example of stirring and mixing while irradiating ultrasonic waves in the presence of a predetermined oxidatively decomposable gas and a comparative example of stirring and mixing under other conditions will be described.

【0043】

[Example 3] Using the oxidatively degradable gas used in Example 1, 30 g of a dioxin-contaminated soil sample (dioxin concentration 97 pg-TeQ / g) was placed in a 5 liter polyethylene bag and placed in the bag. 3.5 liters of the obtained oxidatively decomposable gas was added, and the mixture was shaken and stirred under ultrasonic irradiation at 28 KHz for 30 minutes at room temperature, and the dioxin concentration was examined before and after the treatment.

【0044】

[Example 4] In Example 3, each sample of contaminated soil was treated in exactly the same manner except that shaking and stirring were performed by adding 5 g of sodium hydrogen carbonate. The dioxin concentration of the sample was examined before and after the treatment.

【0045】

[Comparative Example 3] In Example 4, the ozone concentration was 141 g / m instead of the oxidatively decomposable gas.³Samples of contaminated soil were treated in exactly the same manner, except that the ozone gas was used. The dioxin concentration of the sample was examined before and after the treatment.

【0046】

[Comparative Example 4] In Example 3, the ozone concentration was 141 g / m instead of the oxidatively decomposable gas.³Samples of contaminated soil were treated in exactly the same manner, except that the ozone gas was used. The dioxin concentration of the sample was examined before and after the treatment.

【0047】

[Example 5] In Example 4, a sample of contaminated soil was treated in exactly the same manner except that 5 g of calcium oxide (CaO) was used instead of sodium hydrogen carbonate. The dioxin concentration of the sample was examined before and after the treatment.

【0048】

When the dioxin concentrations of Examples and Comparative Examples were compared as described above, Examples 3 and 4 in which the dioxin concentrations of Examples 3 and 4 were stirred and mixed while irradiating ultrasonic waves in the presence of a predetermined oxidative decomposition gas (active ozone) were found in Examples 3 and 4. The decomposition rate was higher than that of Example 1 in which decomposition treatment was performed without using ultrasonic waves.

【0049】

Further, in Example 4 in which sodium hydrogen carbonate was added during stirring and mixing, and in Example 5 in which calcium oxide was added instead of sodium hydrogen carbonate, the decomposition rate was further improved as compared with Example 3.

【0050】

[Example 6] Using the oxidatively degradable gas used in Example 1, 30 g of a soil sample contaminated with tetrachloroethylene was placed in a 5 liter polyethylene bag, and the obtained oxidatively decomposable gas 3.5 was placed in the bag. After adding liters, the mixture was shaken and stirred under ultrasonic irradiation at 28 KHz for 30 minutes at room temperature, and the tetrachloroethylene concentration before and after the treatment was examined.

【0051】

[Comparative Example 5] In Example 5, the ozone concentration was 141 g / m instead of the oxidatively decomposable gas.³Samples of soil contaminated with tetrachlorethylene were treated in exactly the same manner, except that the ozone gas was used. Before and after this treatment, the tetrachlorethylene concentration of the sample was examined.

【0052】

[Example 7] In Example 6, a sample of contaminated soil was treated in exactly the same manner except that 5 g of sodium hydrogen carbonate was used. The tetrachlorethylene concentration of the sample was examined before and after the treatment.

【0053】

[Example 8] In Example 7, a sample of contaminated soil was treated in exactly the same manner except that 5 g of calcium oxide (CaO) was used instead of sodium hydrogen carbonate. The tetrachlorethylene concentration of the sample was examined before and after the treatment.

【0054】

As a result, Example 6 in which stirring and mixing were performed while irradiating ultrasonic waves in the presence of a predetermined oxidatively decomposable gas had a higher decomposition rate than Comparative Example 5. Further, in Example 7 in which sodium hydrogen carbonate was added during stirring and mixing, and in Example 8 in which calcium oxide was added instead of sodium hydrogen carbonate, the decomposition rate was further improved as compared with Comparative Example 5.

【0055】

[Effect of the invention]

In the present invention, as described above, ozone gas is mixed with atomized hydrogen peroxide solution, and the gas-liquid mixing system is irradiated with ultraviolet rays to obtain an oxidatively decomposable organic gas, which is used as dioxins and the like. Since the method of decomposing organic environmental pollutants that is agitated and mixed with the organic environmental pollutants in the above is used, the decomposition treatment efficiency of organic environmental pollutants is improved, and the decomposition treatment of organic environmental pollutants can be performed efficiently in a short time. It has the advantage of being able to do it.

【0056】

Further, in the invention in which the stirring mixture is a method for decomposing organic environmental pollutants, which is a stirring mixture performed while irradiating ultrasonic waves, organic environmental pollution such as dioxins mixed in massive or granular soil. Even when a substance is decomposed, there is an advantage that the decomposition treatment can be performed efficiently in a short time.

[Simple explanation of drawings]

[Figure 1]

Explanatory drawing of the oxidative decomposition gas production apparatus used for the processing method of embodiment [Explanation of symbols]

1 Oxygen cylinder 2 Pressure reducing valve 3 Ozonizer 4, 11 tubes 5 nebulizer 6 container 7 Hydrogen peroxide solution 8 Reaction vessel 9 UV bulb 10 Disassembly processing container 12 Check valve 13 Ozonolyzer