KR20010105915A - Process for the decontamination of soil containing toxic organic materials and heavy metal - Google Patents

Abstract

A television with multiple display windows (72) and placement dependent cursor (74) and function control is configured to receive and simultaneously display video and graphics input from multiple devices, including but not limited to personal computers (14), video cassette recorders (17), settop boxes (11), video cameras (18) and video disk players (21), as well as display video input signals from cable, antenna and satellite sources. The size of each display window is adjustable to encompass a predetermined amount of the diplay screen of the television (10). Multiple input windows driven by multiple devices can be viewed simultaneously. One or more cursor control and input devices (16) are used to control the operation of the television and of the devices driving the display windows. The cursor control and input devices control the position of the cursor on the television screen. When the cursor is positioned within one of the input display windows, the cursor control and input devices are used to control the operation of the device driving that input window, through signals sent from the television to the appropriate device. Preferably, the devices are coupled to the television through an IEEE 1394 serial bus network.

Description

Process for the decontamination of soil containing toxic organic materials and heavy metal}

The present invention relates to a method for purifying soil contaminated with heavy metals and harmful organic substances, and more particularly, to easily form complexes with heavy metals and increase the activity of microorganisms present in contaminated soil to induce biodegradation of harmful organic substances. The present invention relates to a method for purifying soil contaminated with heavy metals and harmful organic substances by using the composition for the eluent.

In general, soils contain some heavy metals, either naturally occurring or through artificial routes. Many heavy metals, including lead, copper, cadmium, zinc, and mercury, are essential for a variety of organisms, such as plants that receive a lot of nutrients from the soil when they are maintained in the soil, while excessively high It can have very harmful effects on humans through direct and indirect routes. As industrialization progresses rapidly, various harmful substances are dumped and spilled, which seriously pollutes soil and groundwater. In particular, in industrial areas, urban waste treatment areas, and abandoned mines and coal mines, the concentration of heavy metals in the soil is reported to be several hundred times higher than that of natural soils in the general area. Soil pollution caused by high industrialization is far exceeding the natural purification capacity of the soil and is a major hazard to mankind. Therefore, the problem of purifying the contaminated soil by removing heavy metals contained in the soil is appropriate for the ecosystem. It is recognized as a problem of human survival beyond coordination.

In addition, recently, the use of harmful organic substances to the human body and the environment, including oil, has been increased, and due to frequent spills, harmful organic substances are leaked into the surrounding soil from underground storage tanks and connecting pipes to pollute the soil. Soil contamination by these harmful organic substances is not contaminated with any one component but is contaminated with various mixtures, which makes it difficult to purify the soil.

Heavy metals spilled due to accident or unauthorized dumping react with the soil through various paths, and the reaction rate varies depending on the amount and nature of organic matter, clay component and hydroxide in the soil. Conventionally, various studies have been made to remove heavy metals present in the soil, and among them, ion exchange resins or electrolysis have been the mainstream.

However, the above methods have useful aspects for the treatment and recovery of heavy metals with high purity, but the disadvantages are that they are not as efficient as general soil purification methods, in which the purity of heavy metals is slightly reduced and other pollutants other than heavy metals are contained. I have it. Moreover, there is a problem in that the economic feasibility of investing in the facilities is not secured in the purification of heavy metal contaminated soils over a vast area.

Therefore, the technical problem to be achieved by the present invention is to provide a new purification method that can simultaneously purify heavy metals and harmful organic substances in contaminated soil.

1 schematically shows a soil purification method according to the present invention.

<Brief description of symbols for the main parts of the drawings>

11 ..... underground injection 12 ..... spraying

13 ..... Contaminated soil 14 ..... Groundwater

15 ..... Groundwater Recovery Well 16 ..... Heavy Metal Recovery Equipment

The present invention to achieve the above technical problem,

(a) digging soil contaminated with heavy metals and harmful organics and installing a groundwater recovery well;

(b) injecting into said contaminated soil at least one low molecular weight organic acid selected from the group consisting of citric acid, acetic acid and oxalic acid and hydrogen peroxide into said contaminated soil to form a complex with a heavy metal electrode; At the same time the oxygen in the hydrogen peroxide is used for the respiration of microorganisms in the soil to promote decomposition of harmful organics; And

(c) recovering the groundwater containing the heavy metal complex compound through the groundwater recovery well and separating the heavy metal, thereby providing a method for the purification of soil contaminated with heavy metals and harmful organic substances.

In the purification method according to the invention, the pH of the composition is preferably 5 to 7.

In the purification method according to the present invention, the concentration of the low molecular organic acid of the composition is preferably 10 to 100mM.

In the purification method according to the invention, the concentration of hydrogen peroxide of the composition is preferably 10 to 1,000ppm.

In the purification method according to the invention, the step of injecting the composition into the contaminated soil can be made by underground injection or spraying.

In general, soils contaminated with heavy metals can be cleaned by applying soil washing techniques using low molecular weight organic acids. However, when the low molecular weight organic acid used as the eluent binds to the heavy metal, the harmful organic material may act as an interfering material, and thus the heavy metal cannot be removed smoothly. In addition, when it is desired to remove harmful organic substances to which heavy metals are added using biological treatment technology, it is difficult to efficiently treat them due to toxic effects by heavy metals. Therefore, the present inventors have conducted many studies and experiments on the method of simultaneously treating heavy metals and harmful organic substances from soils containing heavy metals and harmful organic substances, and have excellent properties of desorbing heavy metals in the soil. The present invention has been completed by devising a method of simultaneously removing heavy metals and harmful organic substances from contaminated soil using a composition that can also serve as an oxygen medium to microorganisms present in the soil for biodegradation.

As used herein, the term "eluent" refers to a kind of medium having excellent solubility in an extract, and refers to a material commonly used in so-called chemical treatment methods in the field of environmental engineering. The extracted object is generally separated into the liquid phase with the eluent and then recycled through a recovery process.

Hereinafter, the present invention will be described in detail with reference to FIG. 1, which schematically illustrates a method for purifying contaminated soil according to the present invention.

First, a composition comprising a low molecular weight organic acid and hydrogen peroxide selected from the group consisting of citric acid, acetic acid and oxalic acid is prepared, and the composition is injected into soil contaminated with heavy metals and harmful organic substances.

The method of injecting the composition for the eluent into the soil can be divided into underground injection formula (11) and spraying formula (12) as shown in FIG. Underground injection method is to excavate the soil contaminated with heavy metals and harmful organic materials to a certain depth and embed the pipe to inject the composition for the eluent, and then put the composition directly into the soil through the pipe. It refers to the spreading of the composition for the eluent on the contaminated soil using a device capable of. Underground and spreading methods can be selected appropriately depending on the nature of the contaminated area. In other words, for soils with large porosity, the spraying method is appropriate, and in other cases, it is appropriate to select the ground injection formula.

In the case of soils with high porosity, it is easy to penetrate the soil even if spraying the composition for eluent on the soil, but in the case of soil with low porosity, it is not easy to penetrate the soil. It is to choose the injection method.

Low molecular organic acids such as citric acid, acetic acid or oxalic acid contained in the eluent composition form complexes with heavy metals present in the soil. That is, the heavy metal existing in the ionic state of the soil is removed from the soil by forming a complex compound by reacting with the low molecular organic acid ions. Generally, the higher the concentration of the low molecular organic acid in the composition to be added, the higher the removal efficiency of the heavy metal, but preferably a concentration in the range of 10 to 100mM. Because, when the concentration of the low molecular weight organic acid is less than 10mM heavy metal removal efficiency can not be maintained at the desired level, on the other hand, if it exceeds 100mM can be excessively expensive and at the same time harmful to the natural environment.

In addition, hydrogen peroxide included in the composition for the eluent acts as an oxygen source to the degradable microorganisms of harmful organic substances present in the soil. That is, by supplying oxygen to the microorganisms present in the soil to increase the activity of the microorganisms to biologically decompose and remove harmful organic substances. Microorganisms present in soil contaminated with heavy metals and harmful organic substances exist due to the toxic effects of heavy metals, and microorganisms are present in extremely low levels, which makes it difficult to decompose high concentrations of harmful organic substances. If you put the activity of the microorganism increases. In general, the higher the concentration of hydrogen peroxide in the composition to be added, the more effective it is to increase the activity of the microorganism, but preferably a concentration in the range of 10 to 1,000 ppm. Because, if the concentration of hydrogen peroxide is less than 10ppm can not increase the activity of the microorganism to the desired level, on the other hand, if it exceeds 1,000ppm it is uneconomical because of excessive drug costs.

In addition, the pH range of the composition to be added is preferably adjusted to 5 to 7, since the complex compound formation reaction between the low molecular organic acid and heavy metal ions occurs most actively when the pH is in the above range. In general, heavy metal ions present in the soil are known to dissociate from low molecular organic acids or have a greater reaction activity with the low molecular organic acid ions than hydrogen ions present in the soil. In other words, since the stability constant of the heavy metal-low molecular weight organic acid ion, which is a measure of complex compound formation between the low molecular weight organic acid and heavy gold, is larger than the reaction constant value of the low molecular weight organic acid-hydrogen ion, the amount of hydrogen ion and heavy metal ion In similar cases, complex-forming reactions can occur actively.

Therefore, when the pH of the composition is too low, that is, when the hydrogen ion concentration is high, the complex-forming reaction between the low molecular organic acid ion and the heavy metal ion is disturbed. Therefore, it is preferable that the pH range of the composition is 5-7. In the above pH range, since the concentrations of heavy metal ions and hydrogen ions are generally similar, the complex compound formation reaction between heavy metals and low molecular weight organic acid ions takes place first.

When the composition for the eluent according to the present invention is injected into the soil contaminated with heavy metals and harmful organic substances as described above, hydrogen peroxide is decomposed into water and oxygen, oxygen is used for the respiration of microorganisms, and water is combined with the groundwater flowing in the contaminated soil. Or low molecular weight organic acids form complexes with heavy metals and flow into the groundwater in the soil.

Next, as shown in FIG. 1, the groundwater recovery well 15 is installed in the groundwater 14, and the groundwater containing the complex compound is used as a heavy metal by using an apparatus (not shown) capable of raising groundwater such as a motor pump. To the recovery device (16). In the heavy metal recovery apparatus, the complex compound is decomposed into heavy metal and low molecular organic acid, and the low molecular organic acid is reused in the purification method and the heavy metal is recovered. The heavy metal recovery apparatus may be used in the present invention without particular limitation as long as it is widely known to be used for the purpose in the art.

Hereinafter, a method for purifying contaminated soil according to the present invention will be described in detail through Examples and Comparative Examples.

<Example 1>

Contaminated lead concentration was 500ppm, and microorganisms (POB-PC) were added to artificial soils to which 20 g of diesel oil was added to prepare soil for test.

The eluent composition containing 10 mM of citric acid and 50 ppm of hydrogen peroxide was adjusted to pH 6 and then injected into the artificial soil.

In order to evaluate the effect of the cleaning composition according to the present invention on the decomposition efficiency of harmful organic substances by microorganisms, the concentration of total petroleum hydrocarbon (TPH) in the test soil was measured two weeks after the injection. The results are shown in Table 1.

4 weeks after the injection, the concentration of total petroleum hydrocarbons present in the test soil was measured, and the results are shown in Table 2.

<Examples 2 to 6>

Except for changing the type of microorganism and the concentration of lead as shown in Table 1 and Table 2, the concentration of total petroleum hydrocarbon after 2 weeks and 4 weeks after the injection was measured in the same manner as in Example 1 Table 1 and Table 2 are shown.

Comparative Example 1

A test soil was prepared in the same manner as in Example 1, except that no microorganisms were added for use as a control sample, and the test petroleum hydrocarbons after 2 weeks and 4 weeks of neglect without any treatment on the test soil were prepared. The concentration was measured and the results are shown in Table 1 and Table 2, respectively.

Comparative Example 2-3

Except for changing the type of microorganism and the composition of the composition as shown in Table 1, the concentration of the total petroleum hydrocarbon two weeks after the injection in the same manner as in Example 1 was measured and the results are shown in Table 1, respectively.

Type of microorganism Lead ion concentration (ppm) Citric Acid Concentration (mM) Hydrogen peroxide concentration (ppm) PH of the composition TPH concentration (mg / kg) Example 1 POB-PC 500 10 50 6 5486 Example 2 POB-PC 100 10 50 6 4552 Example 3 POB-PC 10 10 50 6 4781 Example 4 A 500 10 50 6 6683 Example 5 A 100 10 50 6 8127 Example 6 A 10 10 50 6 7433 Comparative Example 1 None 500 None None 6 12411 Comparative Example 2 POB-PC 500 10 None 6 10505 Comparative Example 3 A 500 10 None 6 11230

Type of microorganism Lead ion concentration (ppm) Citric Acid Concentration (mM) Hydrogen peroxide concentration (ppm) PH of the composition TPH concentration (mg / kg) Example 1 POB-PC 500 10 50 6 2046 Example 2 POB-PC 100 10 50 6 2151 Example 3 POB-PC 10 10 50 6 2966 Example 4 A 500 10 50 6 3168 Example 5 A 100 10 50 6 3724 Example 6 A 10 10 50 6 3562 Comparative Example 1 None 500 None None 6 8650

In Table 1, it was shown that the diesel oil decomposition efficiency of microorganisms according to the concentration of lead in the same microorganism and the same washing composition did not show a big difference, but in the case of microbial POB-PC, TPH of Comparative Example 1 was used as a control standard. The concentration showed about 60 decomposition efficiency, and the microbial A showed a decomposition efficiency of about 40, indicating that the diesel oil decomposition efficiency was considerably higher than Comparative Examples 2 and 3 using only citric acid as the cleaning composition.

Also in Table 2, the microbial diesel oil decomposition efficiency did not show a significant difference according to the lead concentration change, and the microbial POB-PC showed about 80 decomposition efficiency for the TPH concentration of Comparative Example 1 used as a control standard. , In the case of microorganism A showed a decomposition efficiency of about 70.

As described above, the contaminated soil purification method according to the present invention has the advantage of simultaneously purifying soil contaminated with various types of heavy metals and harmful organic substances in one treatment process.

Although the present invention has been described with reference to the embodiments, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent implementations are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (5)

(a) digging soil contaminated with heavy metals and harmful organics and installing a groundwater recovery well; (b) injecting into said contaminated soil at least one low molecular weight organic acid selected from the group consisting of citric acid, acetic acid and oxalic acid and hydrogen peroxide into said contaminated soil to form a complex with a heavy metal electrode; At the same time the oxygen in the hydrogen peroxide is used for the respiration of microorganisms in the soil to promote decomposition of harmful organics; And and (c) recovering the groundwater containing the heavy metal complex compound through the groundwater recovery well to separate the heavy metals. The method of claim 1, wherein the pH of the composition is 5 to 7 characterized in that the soil contaminated with heavy metals and harmful organic substances. The method of claim 1, wherein the concentration of the low molecular weight organic acid in the composition is 10 to 100mM. The method of claim 1, wherein the concentration of hydrogen peroxide in the composition is 10 to 1,000 ppm. The method of claim 1, wherein the step of injecting the composition into the contaminated soil is performed by underground injection or spraying.