KR100406766B1 - Method for decontamination of soil using electrokinetic - Google Patents

Abstract

The present invention relates to a soil purifying method using a coin machine, and more particularly, by injecting a cleaning agent into a soil contaminated with heavy metals and a precious metal tailings, and controlling the pH of the soil smoothly and by using a galvanic technology. In addition, the present invention relates to a soil purifying method using an electrokinetic device which can purify the soil by efficiently removing heavy metals from the soil and recovering the precious metals from the precious metal tailings in the same principle.

Description

Soil Purification Method using Electrokinetic Device {METHOD FOR DECONTAMINATION OF SOIL USING ELECTROKINETIC}

The present invention relates to a soil purifying method using a galvanic, more specifically injecting a cleaning agent in the soil contaminated with heavy metals, while adjusting the pH in the soil and heavy metals in the soil by the electrical reaction caused during galvanic technology The present invention relates to a soil purifying method using electrokinetic devices, which enables the efficient removal and recovery of heavy metals and precious metals in the soil by concentrating them in specific regions.

Soil pollution is a phenomenon in which pollutants that penetrate underground contaminate the lipids, and everything that exists in the lipids such as groundwater or underground air is targeted. With the development of industrial society in the 20th century, environmental pollution of water quality, air, soil and ocean has become a serious problem due to the mass generation of organic waste through the process of mass production and mass consumption.

In particular, water pollution and air pollution have attracted much attention from scientists and the national level due to the high rate of damage transmitted to mankind. On the other hand, soil pollution has been relatively less concerned than other environmental pollution problems since it has not been an environmental problem that is encountered directly or visually. In addition, soil pollution is often delayed due to the fact that the survey is difficult in terms of survey cost and institutional compared with the air or water environment. As a result, in most cases, the costs and periods of purification are high. Therefore, as the industrial society is further developed, soil pollution has become serious as a large amount of various industrial wastes and heavy metals including oil are generated.

Among the methods to clean up the heavy metal-contaminated soil on site, the shielding treatment, steam extraction, and soil washing techniques are mentioned. Shielding techniques include blockers, liners, cover, planters, etc., which are applied according to the soil pollution level. These are techniques applicable to most contaminated soils, but they are not fundamental solutions because their main purpose is to prevent the spread of contaminants rather than to clean up contaminated soils. In addition, the steam extraction is a method of removing the organic pollutants by vaporizing the organic contaminants by lowering the pressure in the soil is effective in the removal of highly volatile organic pollutants, but has a disadvantage in that a lot of power and equipment costs. In addition, the soil washing technique can purify the soil with high efficiency in a relatively short time if the appropriate cleaning agent is selected through a basic research according to the type of contaminants to be removed, but the soil is always the limiting factor in soil washing. For compact soils of small particle size and small porosity, the cleaning agent flow may not be smooth due to pressure / vacuum. In order to remove contaminants while smoothly injecting / recovering these soils, the energy cost to generate high pressure / vacuum increases, while channeling phenomena in which the flow of the detergent spreads / moves into uneven gaps in the soil. As a result, cleaning agents and contaminants may be moved to non-contaminated areas, thereby reducing treatment efficiency and increasing the consumption of cleaning agents used and the risk of secondary contamination.

The present invention has been made in order to solve the above problems, the object of the present invention is to inject a cleaning agent into soil contaminated with heavy metals (copper, zinc, etc.), so that the pH of the soil is smoothly made and galvanic By using the, to provide a soil purification method using a coin machine that can efficiently remove contaminants.

Another object of the present invention is to remove heavy metals from heavy metal contaminated soil, economically remove heavy metals directly from the contaminated site without the complex steps such as excavation, transport, treatment of soil contaminated areas, and recovers To provide a soil purification method used.

Still another object of the present invention is to recover the precious metals remaining in the precious metal mines and the tailings tailed after development, which have lost economic feasibility on the same principle as above. To provide a purification method.

1 is a schematic diagram of a soil purification apparatus for implementing a soil purification method using a voltaic device according to the present invention

Figure 2 is a graph showing the measurement of the concentration of the desorbed heavy metals according to the detergent injection concentration according to the first embodiment of the present invention

Figure 3 is a graph showing the measurement of the concentration of heavy metal desorbed in accordance with the PH change in accordance with a second embodiment of the present invention

Figure 4 is a graph showing the measurement of the concentration of the desorbed heavy metals according to the concentration change of the cleaning agent according to a third embodiment of the present invention

5 is a graph of the pH measurement in the final soil according to the first experimental example of the present invention

In order to achieve the above object, the present invention provides a method for purifying soil contaminated with heavy metals, the method comprising: providing an anode chamber and a cathode chamber each having an anode and a cathode interposed therebetween; Filling an electrolyte into the anode chamber and the cathode chamber; Injecting detergent into the contaminated soil; Installing a Marriott bottle on one side of the anode chamber so that a hydraulic gradient in the soil does not occur, maintaining a constant water level, and replenishing the anode with the buffer solution lost by electroosmotic; Exchanging an electrolyte solution to prevent acidification of the anode; And conducting power to the anode chamber and the cathode chamber.

In this case, it is preferable to use one of the detergents selected from Ethylene-Diaminetetraacetic Acid (EDTA), cyanide (CN), and an organic acid to increase the solubility of heavy metals.

And, in the step of exchanging the electrolyte solution to the positive electrode it is preferable to replace every 24 hours.

In particular, the present invention is to inject a cleaning agent into the soil while controlling the pH of the soil by neutralizing the hydrogen ions generated at the positive electrode and the hydroxyl group generated at the negative electrode by the electrical reaction by circulating the electrolyte to the buffer solution in the electrokinetic soil purification process It is about.

Electrodynamic purification is an on-site soil purification technology that removes contaminants by placing electrodes in contaminated soil and applying a low DC current. Electric power phenomenon can be classified into three categories. Electroosmisis, the movement of metals or ions in the direction of the opposite electrode, electromigration, the phenomenon of colloid or charged particles moving in the direction of the opposite electrode due to the potential difference. It is called electrophoresis. The electroosmotic refers to a phenomenon in which a liquid in the medium moves in a specific direction when an electric field is present in a porous medium such as soil. The reason for the electroosmosis is that most soil particles come in contact with water and have a weak negative charge. Therefore, a liquid with a high positive charge density collects in the spaces between the particles. Because it occurs. In order to generate the electroosmotic in the soil, the anode and the cathode are installed around the polluted area, and the electrodes are supplied to supply the current to the polluted area.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. This embodiment is not intended to limit the scope of the invention, but is presented by way of example only.

1 is a schematic view of a soil purification apparatus for implementing a soil purifying method using the electrokinetic device according to the present invention, the rectangular tube without a lid made of acrylic plate 15 cm long, 8 cm high, 8 cm wide, and both ends of the barrel The anode chamber 10 and the cathode chamber 20 were installed by making a space formed by the porous membrane 30 such as polypropylene, filter paper, glass paper, or glass wool to allow the electrode to enter and to fill the electrolyte solution. . In each of the anode chamber 10 and the cathode chamber 20, one graphite plate electrode having a size of 5 cm by 5 cm is provided to form the anode 40 and the cathode 45, and a power source capable of generating a constant current to these electrodes ( power supply; The acrylic plate cylinder is filled with contaminated soil, and the anode chamber 10 made of a porous membrane 30 having no reactivity prevents the anode 40 made of a flat electrode plate from contacting with surrounding soil particles. Provide a space for (buffer). The soil was artificially contaminated with copper (Cu) and zinc (Zn) at 1000 ppm and 500 ppm, respectively. The contaminated soil was uniformly filled with a compaction device using distilled water or detergent solution, and after filling the soil, the distilled water or detergent solution was filled in each electrode chamber, and a Marriott Bottle was connected to the anode and left for 24 hours. . The purpose of the Marriott bottle is to replenish the anode with the buffer solution lost by electroosmosis while maintaining a constant water level without generating a hydraulic gradient in the soil.

As can be seen from the above-mentioned soil purification apparatus, the soil purification method using the electrokinetic device according to the present invention is a method of purifying contaminated soil by injecting a cleaning agent, and provides an anode chamber and a cathode chamber with the soil contaminated therebetween. The cleaning agent is injected into the contaminated soil, the electrolyte is charged and exchanged in the anode chamber and the cathode chamber, and power is supplied to the anode chamber and the cathode chamber. In this case, a phosphate solution or an ammonium solution may be used as the electrolyte in the anode chamber, a mixed solution thereof may be used, or an alkaline solution such as NaOH or NH ₄ OH may be filled. In addition, the cathode chamber may be filled with an acid solution such as H ₂ SO ₄ , HNO ₃ , CH ₃ COOH, Citiric acid, and H ₂ PO ₄ . In addition, the washing agent injected into the soil is preferably used to increase the solubility of heavy metals (EDTA; Ethylene-Diaminetetraacetic acid), cyan (CN), organic acid and the like.

As described above, it is the main contents of the present invention to inject a cleaning agent into the soil contaminated with heavy metals and to concentrate the heavy metals in the soil in a specific region. The invention will be described in detail.

<First Embodiment>

FIG. 2 is a graph showing the concentration of desorbed heavy metals according to the detergent injection concentration according to the first embodiment of the present invention. It has been observed that, at 0.05M or more was removed almost 100%. Detergents have groups in the molecular structure that can form complexes with heavy metals, and the complexes form, which increases the solubility of heavy metals. The corresponding constants, ie log K _MY values, of the cleaning agents for copper (Cu) and zinc (Zn) used in this experiment are 18.8 and 16.5, respectively.

Second Embodiment

3 is a graph showing the concentration of the desorbed heavy metals according to the change in PH according to the second embodiment of the present invention, when the pH is less than 3, it can be seen that the overall desorption more than 80%. This suggests that when the pH of the soil drops below 3 as the hydrogen ions formed at the anode flow into the soil when the electrokinetic technology is applied, the heavy metals adsorbed on the soil are easily eluted and moved to the electromigration.

Third Embodiment

Figure 4 is a graph showing the desorption of heavy metals (Cu) and zinc (Zn) while changing the pH of the 0.05M detergent solution according to a third embodiment of the present invention, the detergent is simply represented by H ₄ Y , Where Y is a cleaning agent. The pKa values of H ₃ Y ⁻ , H ₂ Y ²⁻ , HY ^{3 −} and Y ^{4 −} were 2, 2.26, 6.16, and 10.26, respectively, and H ₄ Y below PH 2 and H ₃ below PH 2-3. Y ⁻ , H ₂ Y ^{2- at} PH 3-6, HY ^{3- at} PH 6-10, Y ⁻⁴ at pH 10 and above. As shown in FIG. 4, it was observed that heavy metals had a low desorption rate below pH 3, and white precipitates were formed when the pH of the detergent solution was below 2.7, which is H ₄ Y, H ₃ Y ^{− of the} detergent. The form means that the complex formation is weak. Therefore, the desorption in Figure 4 is not all the effect of the cleaning agent, as shown in Figure 3 rather than the effect of heavy metal was eluted from the soil.

<Experimental Example 1>

Figure 5 is a graph measuring the pH in the soil after the experiment by electrokinetic technology, the soil near the anode by the H ⁺ and OH ^- formed by the electrode reaction when applying the electrokinetic acid, the soil near the cathode proceeds alkalizing do. The EK-2 experiment (96 hours) also measured pH 2 as a whole, with a cathode chamber of 12 and a pH of 6 at 1.5 cm in front of the cathode chamber. This is due to the fact that H ⁺ ions are faster than OH ⁻ ions and acidification proceeds as time progresses. The pH of EK-3 was less than pH 3 from the positive electrode to 7.5cm, and the pH was measured from 11 to 10.5cm to the negative electrode. In the case of EK-4, 5, 6, 0.2N NaOH was changed in units of 24 hours to prevent acidification of the positive electrode.

<Experimental Example 2>

The heavy metal removal rate after completion of the heavy metal removal experiment performed in six conditions is shown in [Table 1], and the residual heavy metal concentration in the soil and the heavy metal concentration of each electrode chamber were measured and shown in [Table 2].

[Table 1] Heavy metal removal rate

division Initial Copper Concentration Copper concentration removed % Removal Initial zinc concentration Removed zinc concentration % Removal EK-1 1000 mg 388 mg 38 500 mg 283 mg 56 EK-2 1000 mg 93 mg 9 500 mg 19 mg 3 EK-3 985 mg 15 mg One 525 mg 21 mg 4 EK-4 1180 mg 101 mg 9 533 mg 34 mg 6 EK-5 1224 mg 661 mg 54 554 mg 386 mg 69 EK-6 1136 mg 805 mg 70 542 mg 411 mg 75

The EK-1 experiment was a control experiment, in which only the electrokinetic technique was applied without injecting the detergent, and EK-2 and 3 were the heavy metal removal experiment using the detergent without adjusting the pH of the positive electrode. On the other hand, EK-4, 5, 6 by replacing the 0.2N NaOH solution in the unit of 24 hours to prevent the lowering of the pH of the positive electrode. After 36 hours in the EK-1 experiment, 38% and 56% of copper (Cu) and zinc (Zn) were removed into the cathode chamber, respectively. After the EK-1 experiment, most of the soil was acidified to PH 2, so that the heavy metal of the anode was eluted into the solution phase and moved to the cathode, so that the amount of heavy metal at the anode decreased, while the amount of heavy metal at the soil near the cathode was increased.

[Table 2] Residual Heavy Metals in Soil (Unit: mg)

division Anode chamber 0-3 cm 3-6 cm 6-9 cm 9-12 cm 12-15 cm Cathode chamber Cu Zn Cu Zn Cu Zn Cu Zn Cu Zn Cu Zn Cu Zn EK-1 47 47 70 20 65 50 82 20 225 32 513 161 341 263 EK-2 35 11 18 4.3 26 7 16 4.6 115 22 832 456 58 8 EK-3 28 18 85 28 154 83 281 117 408 184 66 14 17 2 EK-4 83 28 305 178 226 139 216 110 116 54 80 52 18 5 EK-5 652 378 346 91 106 42 192 16 86 34 22 2 8 4

In the EK-2 experiment, 9% copper (Cu) and 3% zinc (Zn) were removed. In the EK-3 experiment, the removal efficiency was lower than that of the control experiment, EK-1, which was 1% copper and 4% zinc. In the soil distribution of heavy metals, heavy metals were concentrated at one point. Heavy metal to form a cleaning solution and the complexes are in the detergent complex case when complex are here noticeable negative ions doedaga moves to the positive electrode by the electrophoresis, the PH by the H ⁺ ions formed from the anode by the electrode reaction drops to 3 or less, an electric field is present The cations, which are heavy metal ions, were dissociated and then moved back to the cathode by electrophoresis, and the OH ^- ions formed from the cathode were introduced into the soil and concentrated.

In the EK-4 experiment, the removal rate of copper (Cu) and zinc (Zn) was 9% and 6%, and in the EK-6 experiment which increased the experimental period up to 9 days, copper (Cu) and zinc (Zn) were 70%, respectively. And 75% were removed.

In addition, 54% of copper (Cu) and 69% of zinc (Zn) were removed from the contaminated soil in the EK-5 experiment. On the other hand, although the removal rate of heavy metals in the EK-4 experiment is low, as shown in Table 1, it was found that the distribution of heavy metals moved to the positive electrode much as in the previous experiment. As the soil forms high pH as a whole, heavy metals are poorly desorbed from the soil, and the desorbed metals are only formed with detergents and complexes, and are moved to the anode by electrophoresis.

In addition, the present invention is limited to heavy metals (copper, zinc, etc.), but the present invention is not limited thereto, and it is possible to recover precious metals economically and efficiently by concentrating precious metals in specific regions by applying to precious metals and the like.

The present invention is not limited to the above-described embodiment, and it will be apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Therefore, as described above, the present invention injects a detergent into the electrokinetic purification technology to remove heavy metals from the soil, and concentrates and recovers the heavy metals in a specific area according to the pH of the detergent and the detergent injection. There is an advantage that can remove the heavy metal spread on.

In addition, by applying the soil purifying method using the electrokinetic device according to the present invention, there is an advantage that the precious metal can be recovered from the precious metal waste mine and its pit soil.

Claims (3)

A soil purification method for purifying soil contaminated with heavy metals, the method comprising: providing an anode chamber and a cathode chamber each having an anode and a cathode interposed therebetween; Filling an electrolyte into the anode chamber and the cathode chamber; Injecting detergent into the contaminated soil; Installing a Marriott bottle on one side of the anode chamber so that a hydraulic gradient in the soil does not occur, maintaining a constant water level, and replenishing the anode with the buffer solution lost by electroosmotic; Exchanging an electrolyte solution to prevent acidification of the anode; And Soil purifying method using the electrokinetic device comprising the step of connecting the power supply to the anode chamber and the cathode chamber. The method of claim 1, The cleaning agent is a soil purification method using an electrokinetic device, characterized in that any one selected from EDTA, cyan, organic acids to increase the solubility of heavy metals and precious metals. The method of claim 1, Soil purification method using an electrokinetic device, characterized in that for every 24 hours in the step of exchanging the electrolyte solution to the positive electrode.