JP2001000964A - Removing method of organic solvent from aqueous phase by ultrasonic wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently treat a large quantity of a waste soln. low in concn. by irradiating an org. solvent present in an aq. phase in a dispersed or dissolved state with ultrasonic waves to separate the org. solvent from the aq. phase to a gaseous phase. SOLUTION: Trichloroethylene or tetrachloroethylene and benzene in an aq. phase are allowed to be present in a dissolved or dispersed state and these harmful chemical substances are irradiated with ultrasonic waves in this state. That is, tap water is put in the washing tub of a washing machine and an Erlenmeyer flask is placed and water, a small amt. of trichloroethylene or tetrachloroethylene and benzene are put in this flask to be irradiated with ultrasonic waves. By this method, about 99% of the org. solvents are separated from the aq. phase to a gaseous phase and, further, air stirring is performed at the same time to separate about 100% of the org. solvents. By this constitution, a large amt. of a waste soln. low in concn. can be efficiently treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic solvent dispersed and / or dissolved in an aqueous phase, such as trichloroethylene, tetrachloroethylene and / or benzene, which is irradiated with ultrasonic waves to separate them from the aqueous phase. How to

[0002]

2. Description of the Related Art Trichloroethylene and tetrachloroethylene are used as degreasing detergents for metal processing parts, raw materials for chemical products,
Used in solvents. Further, tetrachloroethylene is widely used in detergents for dry cleaning.
Benzene is used as a raw material and solvent for synthetic rubber, synthetic detergents and synthetic fibers, and as an extractant. Factories in these industries need to treat contaminated wastewater, which must be purified if it leaks during use and contaminates soil and groundwater.

In a chemical operation such as solvent extraction, a residual solvent in an aqueous phase is separated by back washing. If a separation method that does not rely on backwashing is developed, the amount of organic solvent used can be reduced.

[0004] Furthermore, methods for purifying contaminated soil include:
There are methods of separating by suction separation by a vacuum extraction well, volatilization by high-pressure air, and volatilization by reaction heat of quicklime and water, and adsorbing and recovering the activated carbon.

In the 1997 Air Pollution Control Act, the Environment Agency specified that trichloroethylene, tetrachloroethylene, benzene,
Dioxins have been designated as Cabinet Order as a designated substance that is particularly dangerous for health. Of these harmful chemicals, trichlorethylene and tetrachloroethylene flow into soil during use or wastewater treatment, polluting groundwater,
Causing social problems. For this reason, the Water Pollution Control Law, which aims to prevent pollution of public water bodies, etc., has established drainage standards. For the treatment and disposal of these harmful chemical substances, methods using supercritical water or metallic sodium have been developed and studied.

[0006]

The above-mentioned trichloroethylene, tetrachloroethylene and benzene are water-soluble in a small amount. In factories that use these harmful compounds, low-concentration polluted waste liquid such as exhaust gas cleaning water containing an organic solvent is generated. In addition, when it flows into the environment and contaminates groundwater and the like, it is necessary to purify the soil and treat and dispose of a large amount of low-concentration waste liquid. As a method for decomposing and disposing of this harmful organic chemical substance, there is a method using supercritical water, metallic sodium or the like. In order to efficiently dispose of large amounts of low-concentration waste liquid using these methods,
It is desirable to separate by pretreatment.

In the chemical separation by solvent extraction, the aqueous phase is backwashed with another organic solvent, and the residual solvent is separated and recovered.
If the aqueous phase is backwashed by another method, the amount of the organic solvent used can be reduced.

[0008]

Ultrasound has the function of destroying cells and tissues, extracting components, emulsifying and dispersing, and washing. Among these effects, the present invention is a method of dispersing and separating a harmful organic compound from a liquid phase to a gas phase by ultrasonic irradiation, focusing on the effect of dispersion.

In particular, the present invention relates to a method of irradiating an ultrasonic wave to an organic solvent dispersed and / or dissolved in an aqueous phase and separating the organic solvent from the aqueous phase into a gaseous phase. In this method, the organic solvent dispersed and / or dissolved therein is irradiated with ultrasonic waves and stirred with air to separate the organic solvent from an aqueous phase into a gas phase.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Trichlorethylene, tetrachloroethylene, benzene and the like in an aqueous phase exist in a dissolved or dispersed state. About 99% of the harmful chemicals in this state are in the gas phase from the water phase by irradiating ultrasonic waves.
If air stirring is performed simultaneously, about 100% can be separated in a short time. This method is considered to be effective for the use of harmful chemical substances in the first stage of the treatment and disposal method and for the purification of contaminated water and soil. The present invention relates to separation of an organic solvent in an aqueous phase into a gaseous phase, and can be used in other chemical fields such as solvent extraction.

For the ultrasonic irradiation, a transmission frequency of 26 kHz,
An ultrasonic cleaner UO300FB manufactured by Kokusai Electric L-Tech Co., Ltd. having an output of 300 W was used. Tap water was put into the washing tank of the washing machine, an Erlenmeyer flask was placed, and water, a small amount of trichloroethylene, tetrachloroethylene, and benzene were mixed into each container and irradiated. In each of the following examples, tap water was continuously flowed during irradiation, overflowed from the drain port, and the vessel was cooled to a water temperature of about 20 ° C. or less.

As the harmful organic compound in the aqueous solution separates into the gas phase, its concentration in the aqueous phase decreases. Therefore, the concentration in the aqueous phase was measured, and the removal rate was determined by comparing with the amount of the harmful organic compound used. This concentration measurement is performed by high performance liquid chromatography, and an analytical sample is collected from the aqueous phase over time with a volume of 1 ml, diluted twice with a solution of methyl alcohol 7: water 3 and then subjected to high performance liquid chromatography manufactured by Tosoh Corporation. Analyzed by LC-8020. The column used for this analysis was TSKgel ODS-80 at 40 ° C.
Ts, a solution of methyl alcohol 7: water 3 was used for elution, and the wavelength of the ultraviolet-visible detector was 254 nm.

[0013]

Example 1 (Example 1) Removal of trichlorethylene When trichlorethylene and water are mixed and irradiated with ultrasonic waves, the concentration of trichlorethylene in the aqueous phase may be close to the detection limit of the measurement conditions by high-performance liquid chromatography. is there. At this concentration, it is difficult to measure the decrease in concentration due to dispersion, so the amount of dissolution was increased by using dilutable ethyl alcohol in this combination, and ultrasonic irradiation was performed.

1 ml of trichloroethylene, 229 m of water
The relationship between the ultrasonic irradiation time and the concentration of trichlorethylene in the aqueous phase when 1 and 20 ml of ethyl alcohol are mixed is shown below.

Ultrasonic irradiation time Concentration of trichlorethylene in aqueous phase (min) (μ1 / ml) 60 0.272 120 0.135 180 0.059 240 0.071 300 0.230 360 0.092 420 0. 123 480 0.226 540 0.070 600 0.024 660 0.012 690 0.006 Removal rate (%) 99.8 In this example, trichloroethylene, which is insoluble in the aqueous phase, has a specific gravity higher than that of water. Due to its heavy weight, it is present in a granular form as an organic phase under the aqueous phase. In this two-phase state, the concentration in the aqueous phase changes and the state corresponds to the solubility thereafter, and the particles of the organic phase disappear and the concentration decreases. After about 700 minutes,
99.8% were removed.

Example 2 Removal of Tetrachloroethylene The relationship between the ultrasonic irradiation time and the change in concentration in the aqueous phase when 500 μl of tetrachloroethylene and 250 ml of water are used is shown below.

Ultrasonic irradiation time Concentration of tetrachlorethylene in aqueous phase (min) (μ1 / ml) 60 0.045 120 0.077 180 0.043 240 0.091 300 0.075 390 0.045 450 0.051 480 0.093 510 0.050 570 0.042 600 0.021 630 to 0.008 660 to 0.005 690 to 0.003 Removal Efficiency (%) 99.8 Also in this example, the amount insoluble in the aqueous phase Of tetrachloroethylene exists under the aqueous phase like trichloroethylene and disappears soon. After that, it becomes a state corresponding to solubility,
The concentration decreases. After about 700 minutes, 99.8% had been removed. Here, the concentration from 630 minutes to 690 minutes is a value close to the detection limit.

(Example 3) Removal of benzene The relationship between the ultrasonic irradiation time and the benzene concentration in the aqueous phase when 500 μl of benzene and 250 ml of water are used is shown below.

Ultrasonic irradiation time Concentration of benzene in aqueous phase (min) (μ1 / ml) 30 0.898 60 0.821 90 0.516 150 0.378 210 0.249 270 0.202 330 0.139 390 0.126 450 0.069 510 0.045 570 0.038 630 0.019 Removal efficiency (%) 99.0 In this example, the specific gravity of benzene is lighter than that of water. It exists as an organic phase on the water surface, but disappears 30 minutes after ultrasonic irradiation. On the other hand, the concentration of benzene dissolved in the aqueous phase gradually decreased to 630.
After one minute, 99.0% of the used amount was removed.

(Example 4) In the case of air stirring 500 μl of each of trichloroethylene, tetrachloroethylene and benzene and 250 ml of water were subjected to ultrasonic irradiation in a sealed state for 30 minutes, and a sample in which a part of each harmful chemical substance was dissolved was subsequently processed. The results obtained by flowing 1.1 l / min of air and stirring are shown. Elapsed time Concentration in aqueous phase (μl / ml) (min) Trichlorethylene tetrachloroethylene benzene 0 0.102 0.0350.555 30 Below detection limit ~ 0.004 0.015 60 Below detection limit ~ 0.003 0.007 90 Below detection limit Below detection limit ~ 0.001 120 Below detection limit Below detection limit ~ 0.001 Remaining (μl) 222 319 143 Removal rate (%) 55.6 36.2 71.4 Organic phase in this example Is present even when the concentration of each harmful chemical in the aqueous phase drops below the detection limit. The remaining amount in the table is
The organic phase is aspirated by a pipette, diluted with a solution of methyl alcohol 7: water 3 and quantified by high performance liquid chromatography.

Example 5 When Ultrasonic Irradiation and Air Stirring are Used Together 500 μl each of trichloroethylene, tetrachloroethylene, and benzene and 250 ml of water are ultrasonically irradiated in a sealed state for 30 minutes to dissolve a part of each harmful chemical substance. Subsequently, the sample was irradiated with ultrasonic waves, and at the same time, 1.1 l / min of air was flown and the result of stirring was shown. Elapsed time Concentration in aqueous phase (μl / ml) (min) Trichloroethylene tetrachloroethylene benzene 0 0.145 0.018 0.741 30 0.252 0.141 0.223 60 Below detection limit ~ 0.007-0. 004 90 Detection limit or less Detection limit or less Detection limit or less 120 Detection limit or less Detection limit or less Detection limit or less Remaining amount (μl) ~ 0.0 ~ 0.0 ~ 0.0 Removal rate (%) ~ 100 ~ 100 ~ 100 In the examples, the organic phase disappeared after 90 minutes. Each harmful chemical substance was below the detection limit, and the removal rate was about 100%.

[0022]

According to Examples 1 to 3, 99% of trichloroethylene and tetrachloroethylene dissolved in the aqueous phase and existing as the organic phase and benzene were separated into the gas phase by ultrasonic irradiation for about 700 minutes. From this, it was confirmed that the ultrasonic wave was effective in separating the organic phase in the aqueous phase and the dissolved organic phase into the gas phase. Next, in Example 4, each harmful chemical substance dissolved by air stirring was separated, but the organic phase was not separated. When the ultrasonic irradiation and the air stirring of Example 5 were used in combination, there was an effect on the organic phase and the dissolved organic phase in the aqueous phase, and after 90 minutes,
About 100% was separated. From the above results, it is clear that in the present invention, the organic phase in the aqueous phase, the trichlorethylene and the tetrachloroethylene and the benzene present in the dissolved state can be separated into the gas phase.

This effect is also considered to be effective for other organic chemical substances having the same physical properties as those used in the examples, and can be used in other fields.

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[Procedure amendment]

[Submission date] June 24, 1999 (1999.6.2
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

(Example 4) In the case of air stirring 500 μl of each of trichloroethylene, tetrachloroethylene and benzene and 250 ml of water were subjected to ultrasonic irradiation in a sealed state for 30 minutes, and a sample in which a part of each harmful chemical substance was dissolved was subsequently processed. The results obtained by flowing 1.1 l / min of air and stirring are shown. Elapsed time Concentration in aqueous phase (μl / ml) (min) Trichlorethylene tetrachloroethylene benzene 0 0.102 0.035 0.555 30 Below detection limit ~ 0.004 0.015 60 Below detection limit ~ 0.003 0. 007 90 Below detection limit Below detection limit ~ 0.001 120 Below detection limit Below detection limit ~ 0.001 Remaining (μl) 222 319 143 Removal rate (%) 55.6 36.2 71.4 Organic in this example The phases are present even when the concentration of each hazardous chemical in the aqueous phase drops below the detection limit. The remaining amount in the table is
The organic phase is aspirated by a pipette, diluted with a solution of methyl alcohol 7: water 3 and quantified by high performance liquid chromatography.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

Example 5 When Ultrasonic Irradiation and Air Stirring are Used Together 500 μl each of trichloroethylene, tetrachloroethylene, and benzene and 250 ml of water are ultrasonically irradiated in a sealed state for 30 minutes to dissolve a part of each harmful chemical substance. Subsequently, the sample was irradiated with ultrasonic waves, and at the same time, 1.1 l / min of air was flown and the result of stirring was shown. Elapsed time Concentration in aqueous phase (μl / ml) (min) Trichloroethylene tetrachloroethylene benzene 0 0.145 0.018 0.741 30 0.252 0.141 0.223 60 Below detection limit ~ 0.007 ~ 0. 004 90 Below detection limit Below detection limit Below detection limit 120 Below detection limit Below detection limit Below detection limit Remaining amount (μl) ~ 0.0 ~ 0.0 ~ 0.0 Removal rate (%) ~ 100 ~ 100 ~ 100 In the examples, the organic phase disappeared after 90 minutes. Each harmful chemical substance was below the detection limit, and the removal rate was about 100%.

Claims (2)

[Claims] 1. A method of irradiating an ultrasonic wave to an organic solvent dispersed and / or dissolved in an aqueous phase and separating the organic solvent from the aqueous phase into a gas phase. 2. A method of separating an organic solvent present in a water phase by dispersing and / or dissolving it into a gas phase from an aqueous phase by ultrasonic irradiation and stirring with air.