KR20110092171A - Simultaneous removal method of petroleum hydrocarbons and heavy metals from contaminated soil - Google Patents

Abstract

PURPOSE: A method for simultaneously eliminating petroleum and heavy metal from polluted soil is provided to prevent the generation of secondary pollution such as water pollution and air pollution. CONSTITUTION: A chelating agent is added soil polluted with heavy metal and petroleum in order to obtain a mixture. The mixture is introduced into a reactor(5) and is left at temperature between 40 and 50 degrees Celsius. Carbon dioxide in a supercritical state is supplied to the reactor. The pressure of the reactor is maintained between 12 and 16MPa. Ultrasonic wave is supplied to the reactor to extract pollutants in a static extracting process. Carbon dioxide is discharged to extract pollutants in a dynamic extracting process. The static extracting process and the dynamic extracting process are successively repeated. The carbon dioxide is eliminated from the mixture.

Description

Simultaneous removal method of petroleum hydrocarbons and heavy metals from contaminated soil}

The present invention relates to a method of simultaneously removing petroleum and heavy metals of contaminated soil in one process, and more particularly, from supercontaminated carbon dioxide, chelating agents that are well soluble in carbon dioxide, and ultrasonic contaminated soil. The present invention relates to a method of simultaneously removing petroleum and heavy metals having different properties.

Due to rapid industrialization and urbanization both at home and abroad, acute and chronic damages to humans and ecosystems due to soil pollution are increasing, and such soil pollution is spreading globally.

Soil pollution is characterized by the accumulation of pollutants remaining over a long period of time even if the pollutant is removed compared to other environmental pollutions such as water quality and air pollution, the potential, long-term, and staggered potential of pollution damage, and the identification of soil pollutant behavior and pollutant behavior. While difficult and time consuming and costly to treat contaminated soil, the treatment effect is invisible.

Major sources of soil pollution include petroleum, heavy metals, pesticides and fertilizers.In particular, the leakage of petroleum and heavy metals generated at gas stations, industrial facilities, oil storage facilities, abandoned mines, and military bases is a serious cause of soil and groundwater contamination. It acts as a source of pollution.

Soils contaminated by petroleum and heavy metals become more contaminated by water and continue to accumulate and accumulate in the soil. Soil pollution is further aggravated. .

Conventionally, in order to recover soil contaminated with petroleum such as gasoline, kerosene, diesel, heavy oil, etc., physicochemicals such as incineration, heat sorption, soil washing, soil vapor extraction, etc. Treatment techniques and biological treatment techniques such as bioopile and biodegradation have been applied, and soil washing, incineration and plant purification (to restore soils contaminated with heavy metals such as lead, cadmium, copper and zinc) have been applied. Treatment techniques such as phytoremediation, electrokinetic remediation, and solidification / stabilization have been applied.

In fact, contaminated soil is often mixed with petroleum and heavy metals, and the contaminated soil restoration technology that can simultaneously remove petroleum (non-polar) and heavy metal (polar) of different properties is very important due to soil washing, incineration, solidification / stabilization, etc. It is limited.

The soil washing method is a method using a large amount of surfactants, etc., and causes secondary pollution such as water pollution, along with the degeneration and cost increase of the soil by the surfactant, etc., incineration method is a method of incineration of contaminated soil. As a result, it causes secondary pollution such as air pollution along with soil denaturation and cost increase due to heating, and solidification / stabilization mixes solidifying agents / stabilizers such as cement with contaminated soil to physically isolate pollutants and chemically As a stabilization method, a large site for landfill is needed and there is a problem of generating long-term secondary soil pollution.

The problem to be solved by the present invention is to provide a method for removing petroleum and heavy metals from contaminated soil at the same time without causing secondary pollution such as water quality and air pollution in purifying the contaminated soil and At the same time, it provides a method of improving the removal rate of contaminants by applying ultrasonic waves.

In order to solve the above problems, the present invention comprises the steps of preparing a mixture by adding a chelating agent to soil contaminated with heavy metals and petroleum; Placing the mixture in a reactor and maintaining at 40 to 50 ° C; Supplying carbon dioxide in a supercritical state to the reactor, maintaining a pressure of 12 to 16 MPa, and then supplying ultrasonic waves to extract contaminants; A dynamic extraction step of extracting contaminants by discharging the same amount of carbon dioxide and the injected carbon dioxide while injecting supercritical carbon dioxide while the ultrasonic wave is supplied to the mixture of the static extraction step; Repeating the static extraction step and the dynamic extraction step once more sequentially; And removing carbon dioxide from the mixture, thereby providing a method for simultaneously removing petroleum and heavy metals of the contaminated soil.

At this time, the static extraction step is carried out for 7 to 11 minutes, the dynamic extraction step is preferably carried out for 5 to 9 minutes at a flow rate of 3 ~ 5mL / min.

In addition, the mixture is preferably prepared by adding 10 to 20 parts by weight of a chelating agent to 100 parts by weight of soil.

In addition, the chelating agent is preferably prepared by mixing 40 to 60 parts by weight of di- (2-ethylhexyl) phosphoric acid to 100 parts by weight of bis- (2,4,4-trimethylpentyl) phosphinic acid.

According to the present invention, nonpolar petroleum and polar heavy metal are simultaneously removed from the contaminated soil, and secondary pollution such as water quality and air pollution is hardly generated during the purification process.

In addition, the removal rate of contaminants is improved by applying ultrasonic waves during the purification process.

1 is a schematic configuration diagram of a device combining supercritical fluid extraction and ultrasonic waves according to an embodiment of the present invention.

The present invention removes nonpolar petroleum from the contaminated soil using carbon dioxide in a supercritical state, removes polar heavy metals from the contaminated soil using a chelating agent that is well dissolved in the carbon dioxide, and applies ultrasonic waves during the process. By improving the removal rate of contaminants, the process is implemented simultaneously in one process.

First, the soil contaminated with heavy metals and petroleum is prepared, and then a chelating agent is added thereto to prepare a mixture.

The chelating agent is a complex ion formed by coordinating one ligand with a metal ion at two or more sites, and is used to remove the heavy metal by binding to a heavy metal of contaminated soil.

The chelating agent used in the present invention can be used as long as it is well soluble in supercritical carbon dioxide, for example, bis- (2,4,4-trimethylpentyl) phosphinic acid (bis- (2,4,4-trimethylpentyl) phosphinic acid) or di- (2-ethylhexyl) phosphoric acid (DEHPA) is preferred, and 100 parts by weight of bis- (2,4,4-trimethylpentyl) phosphinic acid More preferably, 40 to 60 parts by weight of (2-ethylhexyl) phosphoric acid is mixed.

The amount of the chelating agent added in the mixture depends on the degree of soil contamination, and it is most preferable to add 10-20 parts by weight of the chelating agent to 100 parts by weight of the soil.

The mixture of soil and chelating agent is placed in a reactor and the reactor temperature is maintained at 40-50 ° C.

The temperature of the reactor is a temperature for maintaining the carbon dioxide is supercritical state, if less than 40 ℃ carbon dioxide may liquefy in the reactor beyond the critical point (31.1 ℃, 7.38 MPa), if it exceeds 50 ℃ This is undesirable because unnecessary energy is wasted.

Next, a liquid carbon dioxide is prepared and then introduced into the reactor, and the carbon dioxide introduced in the reactor maintained at 40 to 50 ° C. is maintained at 12 to 16 MPa by using a high pressure pump. Is maintained.

If the internal pressure of the reactor is less than 12 MPa, there is a fear that the dissolving power of carbon dioxide in the reactor is weakened, if it exceeds 16 MPa it is not preferable because the design pressure of the high pressure pump and the reactor must be increased.

A condenser may be installed on the inlet side of the high pressure pump to prevent the carbon dioxide introduced into the reactor from vaporizing, and a heating device may be installed on the inlet side of the reactor in order to prevent the temperature in the reactor from being lowered by the input carbon dioxide. .

Next, ultrasonic waves are supplied into the reactor by using an ultrasonic generator.

Ultrasound refers to sound waves in the higher frequency range than humans can hear and has been used in various fields such as washing, extraction, processing, non-destructive testing, and medical diagnosis.

The ultrasonic wave supplied to the reactor causes stirring and vibration effects of the contaminants to improve the removal rate of the contaminants and shorten the removal time.

The petroleum contained in the soil in the reactor is dissolved in supercritical carbon dioxide under the ultrasonically supplied environment, but the heavy metals contained in the soil are not easily dissolved in the supercritical carbon dioxide and coexist with chelating agents that are well soluble in carbon dioxide. Then dissolved in supercritical carbon dioxide.

As described above, a static extraction process of extracting petroleum and heavy metals from soil using carbon dioxide and chelating agent in a supercritical state is performed for 7-11 minutes.

As described above, the supercritical fluid extraction method using carbon dioxide in a supercritical state is an extraction method using supercritical fluids such as water, acetone, ethanol, methanol, and carbon dioxide having a temperature and pressure condition above a critical point. It has been applied to the extraction process of food industry, pharmaceutical industry, fine chemical industry, chemical reaction process, nanoparticle manufacturing process such as extracting essential oil and extracting caffeine from coffee beans.

Next, a dynamic extraction process of discharging the same amount of carbon dioxide and the injected carbon dioxide while injecting carbon dioxide in a supercritical state into the reactor in which the static extraction process is performed is performed for 5 to 9 minutes at a flow rate of 3 to 5 mL / min. By doing so, petroleum and heavy metals contaminated with soil continue to dissolve in carbon dioxide and, together with carbon dioxide, are removed from the contaminated soil.

In order to further remove petroleum and heavy metals, it is preferable to perform the static extraction process and the dynamic extraction process once more.

That is, the carbon dioxide in a supercritical state is put into the reactor that has undergone the dynamic extraction process, and the static extraction process is performed for 7 to 11 minutes, and then the carbon dioxide and the same amount of carbon dioxide injected while the supercritical carbon dioxide is injected into the reactor. A more purified soil can be obtained by performing a dynamic extraction process for 5 to 9 minutes at a flow rate of 3 to 5 mL / min.

In the static and dynamic extraction process, the ultrasonic wave may be continuously or intermittently provided, for example, by repeatedly operating the ultrasonic generator for 2-4 seconds and stopping for 4-6 seconds to reduce the ultrasonic generation cost. It is okay.

When the dynamic extraction process is completed, the removal of petroleum and heavy metals from the contaminated soil is completed by stopping the carbon dioxide injection into the reactor and discharging all the carbon dioxide from the reactor.

It is also possible to heat the carbon dioxide in which the petroleum and the heavy metal are dissolved to vaporize, separate and reuse the carbon dioxide from the petroleum and the heavy metal.

As described above, petroleum and heavy metals having different properties may be simultaneously removed from contaminated soil using carbon dioxide, chelating agent, and ultrasonic waves in a supercritical state, and the removal rate is improved and secondary pollution is hardly generated during the removal process.

Hereinafter, the present invention will be described in more detail based on the following examples, comparative examples and test examples.

It is to be understood, however, that the invention is not to be construed as limited to the embodiments set forth herein, but is capable of modifications and equivalents within the spirit and scope of the invention. Will be apparent to those skilled in the art to which the present invention pertains.

Example 1 Simultaneous removal of petroleum and heavy metals by supercritical fluid extraction and ultrasonic waves (50 ° C, 16 MPa)

In FIG. 1, a schematic configuration of an apparatus combining supercritical fluid extraction and ultrasonic waves for simultaneous removal of petroleum and heavy metals from contaminated soil according to an embodiment of the present invention is indicated by reference numeral 100.

The apparatus is composed of a supercritical fluid extraction portion and an ultrasonic portion, the supercritical fluid extraction portion is a liquid carbon dioxide storage device (1), condenser (2), syringe pump (syringe pump: 3), heating coil (4), high pressure It consists of a reactor (5), a temperature controller (6), a heating coil (7) and a separation tank (8), and the ultrasonic portion is composed of an ultrasonic generator (9) and an ultrasonic controller (10).

The high pressure reactor (Uto Engineering Co., Ltd., Korea: 5) is attached to the pressure gauge (P) and the thermometer (T) to indicate the pressure and temperature inside the high pressure reactor (5).

First, an appropriate amount of heavy metals and petroleum is added to the soil composed of 83.7% by weight of sand and 16.3% by weight of silt, and total petroleum hydrocarbons (TPH), cadmium (Cd), and lead (Pb) are the main pollutants. , Copper (Cu) and zinc (Zn) concentrations are measured and shown in Table 1 below.

A soil sample was prepared by passing the contaminated soil through a sieve having a body size of 2 mm.

Next, the autoclave 5 was maintained at 50 ° C. and di- (2-ethylhexyl) phosphate (DEHPA) 0.5 was added to 1.0 g of 85% bis- (2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272). 1.5 g of the mixed chelating agent and 10 g of the prepared soil sample were mixed well, and then, this was introduced into the high pressure reactor (5).

The pressure in the high pressure reactor (5) is controlled using liquid carbon dioxide, which is discharged from the liquid carbon dioxide storage device (1) and cooled by the refrigerant (ALPUS, SK Chemicals, Korea) of the condenser (2) Pressurized by the syringe pump (3) and heated by the heating coil (4) and then introduced into the high pressure reactor (5) is maintained in the supercritical state in the high pressure reactor.

The syringe pump (260D, manufactured by ISCO Inc., USA: 3) is a pump for injecting a chemical liquid at a constant injection speed using a syringe, and in the present invention, pressurized liquid carbon dioxide to meter in a high pressure reactor (5). To be used.

Maintaining the pressure of the high-pressure reactor (5) by the syringe pump (3) to 16MPa to block the carbon dioxide introduced, the ultrasonic generator (VCX 750, Sonics & Materials Co., Ltd.) installed on the high-pressure reactor (5) , US: 9) (frequency: 20 kHz) and the ultrasonic controller (VCX 750, manufactured by Sonics & Materials, USA: 10) to repeat the operation for 3 seconds and 5 seconds for the ultrasonic wave to repeat the high pressure reactor. (5) was intermittently supplied.

As described above, the petroleum and heavy metals contained in the contaminated soil were subjected to static extraction for 10 minutes to be dissolved in carbon dioxide in a supercritical state while ultrasonics were supplied.

After the static extraction, the carbon dioxide from the liquid carbon dioxide storage device 1 is injected into the high pressure reactor 5 at a flow rate of 5 mL / minute, and the dynamic to discharge carbon dioxide from the high pressure reactor 5 at a flow rate of 5 mL / minute. Extraction was performed for 8 minutes.

When the dynamic extraction was completed, the dynamic extraction was performed once more after the static extraction, and then the injection of liquid carbon dioxide was stopped and all the carbon dioxide of the high pressure reactor 5 was discharged over 2 minutes.

Carbon dioxide containing petroleum and heavy metal discharged from the high-pressure reactor (5) is heated to 70 ℃ by a heating coil (7) is introduced into the separation tank (8), the carbon dioxide in the separation tank (8) is vaporized Direction and contaminants were recovered downward.

Example 2 Simultaneous Removal of Petroleum and Heavy Metals by Supercritical Fluid Extraction and Ultrasonics (40 ° C, 16 MPa)

Except for maintaining the temperature of the high-pressure reactor (5) in Example 1 in the same manner as in Example 1 to remove the petroleum and heavy metals in the contaminated soil.

Example 3 Simultaneous Removal of Petroleum and Heavy Metals by Supercritical Fluid Extraction and Ultrasonics (50 ° C, 12 MPa)

Except that the pressure of the high-pressure reactor (5) was maintained at 12 MPa in Example 1, petroleum and heavy metals were removed from the contaminated soil in the same manner as in Example 1.

Example 4 Simultaneous Removal of Petroleum and Heavy Metals by Supercritical Fluid Extraction and Ultrasonic (40 ℃, 12MPa)

Petroleum and heavy metals were removed from the contaminated soil in the same manner as in Example 1 except that the temperature of the high pressure reactor 5 was maintained at 40 ° C. and the pressure was 12 MPa in Example 1.

Comparative Example 1 Simultaneous removal of petroleum and heavy metals by supercritical fluid extraction (50 ° C, 16 MPa)

Except that the ultrasonic wave was not supplied in Example 1, petroleum and heavy metals were removed from the contaminated soil in the same manner as in Example 1.

Comparative Example 2 Simultaneous Removal of Petroleum and Heavy Metals by Supercritical Fluid Extraction (40 ℃, 16MPa)

Except that the ultrasonic wave was not supplied in Example 2, petroleum and heavy metals were removed from the contaminated soil in the same manner as in Example 2.

Comparative Example 3 Simultaneous Removal of Petroleum and Heavy Metals by Supercritical Fluid Extraction (50 ℃, 12MPa)

Except that the ultrasonic wave was not supplied in Example 3, petroleum and heavy metals were removed from the contaminated soil in the same manner as in Example 3.

Comparative Example 4 Simultaneous Removal of Petroleum and Heavy Metals by Supercritical Fluid Extraction (40 ℃, 12MPa)

Except that the ultrasonic wave was not supplied in Example 4, petroleum and heavy metals were removed from the contaminated soil in the same manner as in Example 4.

Test Example Determination of Petroleum and Heavy Metals in Soil

Petroleum and heavy metal content of the soil contaminated with the petroleum and heavy metals and the soil from which the contaminants of Examples and Comparative Examples were removed are shown in Table 1 below.

The petroleum was analyzed using gas chromatography (GC-FID: 6890 N, manufactured by Agilent Technologies, USA) based on the Soil Pollution Process Test Criteria (2008-115). Heavy metals were tested by the US Environmental Protection Agency. According to the method (US EPA Method 3051B) was analyzed using an inductively coupled plasma luminescence analyzer (ICP-AES: Vista-pro, Varian Inc., USA).

Measurement result of petroleum and heavy metal content Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Petroleum
(TPH) Before treatment
(Mg / kg) 12145.7 After treatment
(Mg / kg) 578.2 640.8 803.6 1100.3 714.1 918.4 1336.3 1910.0 Removal rate
(%) 95.2 94.7 93.4 90.9 94.1 92.4 89.0 84.3 cadmium
(CD) Before treatment
(Mg / kg) 52.6 After treatment
(Mg / kg) 11.8 16.8 18.0 20.2 17.8 20.7 20.8 22.3 Removal rate
(%) 77.6 68.1 65.7 61.7 66.2 60.7 60.4 57.5 lead
(Pb) Before treatment
(Mg / kg) 250.4 After treatment
(Mg / kg) 56.5 78.9 87.3 95.3 82.7 94.8 95.8 105.2 Removal rate
(%) 77.4 68.5 65.1 62.0 67.0 62.1 61.7 58.0 Copper
(Cu) Before treatment
(Mg / kg) 293.2 After treatment
(Mg / kg) 64.6 88.1 95.3 103.9 93.2 111.0 107.0 117.5 Removal rate
(%) 78.0 70.0 67.5 64.6 68.2 62.2 63.5 59.9 zinc
(Z) Before treatment
(Mg / kg) 1657.1 After treatment
(Mg / kg) 391.4 481.2 501.3 511.3 419.4 485.2 539.1 542.3 Removal rate
(%) 76.4 71.0 69.8 69.1 74.7 70.7 67.5 67.3

As can be seen from the results of Table 1, the embodiment of the simultaneous removal of petroleum and heavy metals in parallel with the supercritical fluid extraction method and the ultrasonic wave from the contaminated soil, the simultaneous removal of contaminants by only the supercritical fluid extraction method without supplying ultrasonic waves Compared to the example, the removal rate of pollutants is very high.

In particular, in the case of heavy metals it can be seen that the ultrasonication is supplied to promote the chelation reaction to significantly increase the removal rate.

As described above, according to the removal method of the present invention, non-polar petroleum and polar heavy metal are simultaneously removed from the contaminated soil, and the removal rate of the pollutant can be improved by supplying ultrasonic waves during the purification process.

100: combined supercritical fluid extraction and ultrasonic, 1: storage device, 2: condenser, 3: syringe pump, 4: heating coil, 5: high pressure reactor, 6: temperature controller, 7: heating coil, 8: separation Joe, 9: Ultrasonic generator, 10: Ultrasonic controller, P: Pressure gauge, T: Thermometer

Claims (5)

Preparing a mixture by adding a chelating agent to soil contaminated with heavy metals and petroleum;
Placing the mixture in a reactor and maintaining at 40 to 50 ° C;
Supplying carbon dioxide in a supercritical state to the reactor, maintaining a pressure of 12 to 16 MPa, and then supplying ultrasonic waves to extract contaminants;
A dynamic extraction step of extracting contaminants by discharging the same amount of carbon dioxide and the injected carbon dioxide while injecting supercritical carbon dioxide while ultrasonic waves are supplied to the mixture of the static extraction step;
Repeating the static extraction step and the dynamic extraction step once more sequentially; And
Removing carbon dioxide from the mixture; simultaneously removing petroleum and heavy metals of the contaminated soil. The method of claim 1,
The static extraction step is carried out for 7 to 11 minutes, the dynamic extraction step is carried out for 5 to 9 minutes at a flow rate of 3 ~ 5mL / min, the method of removing petroleum and heavy metals of contaminated soil at the same time . The method of claim 1,
The mixture is prepared by adding 10 to 20 parts by weight of a chelating agent to 100 parts by weight of the soil, the method of removing petroleum and heavy metals of the contaminated soil at the same time. The method of claim 1,
The chelating agent is prepared by mixing 40 to 60 parts by weight of di- (2-ethylhexyl) phosphate to 100 parts by weight of bis- (2,4,4-trimethylpentyl) phosphinic acid, petroleum of contaminated soil And simultaneously removing heavy metals. The method of claim 1,
Ultrasonic waves applied to the reactor is provided intermittently, the method of removing petroleum and heavy metals in the contaminated soil at the same time.

Images