JPH0338297A - Method for treating water contaminated by trichloroethylene and tetrachloroethylene - Google Patents

Abstract

PURPOSE:To decompose trichloroethylene or tetrachloroethylene contained in water to low molecular compounds so as not to remain in the environment by injecting a specified amount of ozone into water containing trichloroethylene, etc. CONSTITUTION:A gas dispersion pipe 4 equipped with fine glass filters is fitted to the tip of an ozone injection pipe 1 connected to an ozone generator 3, and this ozone injection pipe 4 is inserted into a treatment tank 2. 0.01 to 1.2mol ozone is injected for 1mol trichloroethylene or tetrachloroethylene contained in water. It is possible to decompose trichloroethylene or tetrachloroethylene in a very short time by the injected ozone and to prevent them from remaining in the environment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to trichlorethylene- and tetrachlorethylene-contaminated water, such as trichlorethylene- and tetrachlorethylene-contaminated wastewater and drinking water, which are used as cleaning agents in the cleaning industry and electronic device parts manufacturing industry. Regarding the processing method.

[Prior Art] In recent years, it has become a problem that if trichlorethylene or tetrachlorethylene is mixed with wastewater, it may enter the human body for a long period of time and harm health.

Conventionally, the following methods have been proposed as methods for removing trichlorethylene and tetrachlorethylene from the contaminated water.

■Method of adsorption and removal using substances such as activated carbon and cyclodextrin.

■Separation method using pressurized reverse osmosis using cellulose acetate membrane.

■A method of aerating contaminated water and expelling it from the water [Problem to be solved by the invention] However, all of the above methods only physically separate trichlorethylene and tetrachlorethylene from water; Tetrachlorethylene may volatilize into the atmosphere or remain as waste in the environment, potentially causing secondary pollution.1 The present invention was made in consideration of the above circumstances, and An object of the present invention is to provide a method for treating trichlorethylene and tetrachlorethylene-contaminated water by decomposing tetrachlorethylene into low molecules so that they do not remain in the environment.

[Means for Solving the Problems] In order to achieve the above object, the first claim of the present invention provides a method for feeding 0.01 mol to 1.2 mol of ozone per 1 mol of trichlorethylene or tetrachlorethylene contained in water. The second claim is characterized in that 0.01 mol to 1.2 mol of ozone is sent through a fine filter per 1 mol of trichlorethylene or tetrachlorethylene contained in water.

As the fine filter, a glass filter with a pore diameter of about 0.2 mm is suitable.

If the amount of ozone is less than 0.01 mole per mole of trichlorethylene or tetrachlorotidine, it is not practical, and if it exceeds 1 or 2 moles, the amount of decomposition will not increase.

[Operation] When ozone generated by discharge comes into contact with contaminated water, trichlorethylene and tetrachlorethylene in the contaminated water are decomposed by direct oxidation by ozone and by radicals generated by ozone reacting with water.

In addition, by using a fine filter, the contact area between ozone and contaminated water increases, improving decomposition efficiency.

[Example] Fig. 1 shows an example of a processing apparatus for implementing the present invention, in which an aeration pipe 4 equipped with a fine glass filter is installed at the tip of an ozone injection pipe 1 connected to an ozone generator 3. is attached, and this aeration pipe 4 is inserted into the treated water tank 2. 5, 6, and 7 are traps each containing hexane, and 8 is a degassing pipe, which are connected to an adsorption device (not shown).

Distilled water was added to cleaning factory waste liquid to prepare an approximately 0.1% tetrachlorethylene solution, which was used as a sample.

This sample solution IJ2 was put into the treated water tank 2, and the ozone 10.2
Air containing 0.60 ppm is supplied from diffuser pipe 4 at 2.54 per minute.
When the removal rate of tetrachlorethylene was investigated at room temperature (approximately 20°C), the results shown in Figure 2 were obtained. Note that the removed tetrachlorethylene is collected in hexane in traps 5 to 7.

In Figure 2, the amount of ozone injected is expressed in logarithms, but it was found that, regardless of the ozone concentration, if more than about 2 μmol of ozone was injected, more than 80% of tetrachlorethylene was removed.

However, if only air containing no ozone is blown at 2.5 floods per minute for 10 minutes, it will volatilize due to the aeration effect, so in order to determine the amount of decomposition due to ozone, it is necessary to correct the amount of volatilization due to aeration.

FIG. 3 shows the amount of tetrachlorethylene decomposed by correcting the removal rate when only air is blown from the removal rate of tetrachlorethylene using ozone and air.

Regardless of the ozone concentration, approximately 250 μmol of tetrachlorethylene can be decomposed and processed within 10 minutes when the ozone is blown in from approximately 2 μmol to approximately 25 μmol, and when the amount of ozone is 25 μmol or more, the amount of tetrachlorethylene decomposed increases slightly. Although not shown in the figure, this slight increase trend indicates that the molar ratio of ozone to the decomposed amount of tetrachlorethylene is 1.
Therefore, in terms of equivalent ratio, it can be said that 1 mole of tetrachlorethylene can be decomposed and treated with 0.01 to 1.2 moles of ozone.

The fact that more than 10 times as much tetrachlorethylene as the amount of ozone disappears from the system suggests that the decomposed compounds further chemically react with tetrachlorethylene. Moreover, as the amount of injection increases, tetrachlorethylene is volatilized from the wastewater due to the aeration effect, and the amount of tetrachlorethylene in the system decreases. Therefore, the contact with ozone becomes relatively small, and it is estimated that the amount of decomposition increases slightly when the amount of ozone is in the range of 1 to 1.2 moles of O per 1 mole of tetrachlorethylene.

Almost the same results were obtained for trichlorethylene, indicating that tetrachlorethylene and trichlorethylene contained in water decompose and decompose in a very short time due to a chemical reaction with ozone.
It turns out that it can be handled.

[Effects of the Invention] As described above, according to the present invention, trichlorethylene and tetrachlorethylene can be decomposed in a very short time by the blown ozone, and it is possible to prevent them from remaining in the environment. Furthermore, if ozone is blown through a fine filter, the decomposition efficiency of trichlorethylene and tetrachlorethylene will be improved due to the synergistic effect of the ozone decomposition ability and the action of fine ozone bubbles caused by aeration.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram showing an example of an apparatus for implementing the present invention, Figure 2 is a diagram showing the removal rate of tetrachlorethylene by ozone blowing, and Figure 3 is a diagram showing the amount of tetrachlorethylene decomposed by ozone. be. 2... Treated water tank, 3... Ozone generator, 4...
Air diffuser (with fine filter).

Claims (2)

[Claims] (1) A method for treating water contaminated with trichlorethylene and tetrachlorethylene, which comprises feeding 0.01 to 1.2 moles of ozone per 1 mole of trichlorethylene or tetrachlorethylene contained in water. (2) A method for treating trichlorethylene- and tetrachlorethylene-contaminated water, which comprises sending 0.01 to 1.2 moles of ozone per mole of trichlorethylene or tetrachlorethylene contained in water through a fine filter.