KR20120017867A - Electrode for electrokinetic soil remediation and soil remediation system using the same - Google Patents

Abstract

PURPOSE: An electro-dynamically soil pollution restoring electrode and a soil pollution restoring system using the same are provided to increase current density in soil while an electro-dynamical process and to eliminate pollutants by connecting the soil and the electrode without an intermediate medium. CONSTITUTION: An electro-dynamically soil pollution restoring electrode includes a hollow cylindrical body(20) and a filling material(62). The hollow cylindrical body includes a wire connecting part in connection with a voltage supplying unit(101), an electrolyte inlet, and an electrolyte outlet. A plurality of pores is formed on a surface between the upper side and the lower side of the body. The filling material is filled inside of the body. The filling material is selected from a material adsorbing or precipitating pollutants, a material containing electrolyte, and the mixture of the same.

Description

Electrodynamic Soil Remediation Electrode and Soil Remediation System Using Them {ELECTRODE FOR ELECTROKINETIC SOIL REMEDIATION AND SOIL REMEDIATION SYSTEM USING THE SAME}

The present invention can remove the pollutants while increasing the current density in the soil compared to the existing electromechanical soil pollution restoration process, and electrodynamic soil pollution restoration, which can reduce the cost required for wastewater treatment such as electrolyte or effluent generated. It relates to an electrode and a soil pollution recovery system using the same.

Due to the development of industrial activities, soils and sediments are contaminated with various harmful substances. In particular, pollution of soil and sediment by heavy metals, oils, organic pollutants, etc. has a harmful effect on the human body as well as the surrounding environment.

As a method for solving such soil and sediment contamination problems, there are various methods such as soil washing, soil vapor extraction, solidification / stabilization, thermal desorption / pyrolysis, and bio restoration. However, the soil and sediment is present in a large amount of organic matter that can adsorb contaminants, due to the inhomogeneity of the soil has a disadvantage of low removal efficiency or high treatment costs. In particular, in the case of clay and silty soil, the surface area is high, so that it can adsorb a large amount of contaminants, and since the permeability is poor, air is difficult to pass through water, and thus there is a limit in effectively removing contaminants by the conventional methods as described above.

In order to solve this problem, electrokinetic recovery techniques are used. Electrokinetic recovery is a method of removing contaminants by applying direct current or direct current to electrodes in low permeable soils, especially clay and silty soils.

Mechanisms for removing contaminants using electrokinetic recovery techniques are generally known to be electroosmosis, electromigration and electrophoresis. Electroosmotic is a potential difference is formed by applying a DC voltage or current to the soil, the phenomenon refers to the phenomenon that the pore water in the soil by this potential difference. Electroosmotic is electrostatic phenomena due to the charge of soil particles, the soil particles are negatively charged, the pore water moves from the anode to the cathode, and the soil particles are positively charged and move in the opposite direction. Electrophoresis refers to the movement of metals or ions in the pore water of the soil to the electrodes of opposite charge by electrical attraction, and electrophoresis refers to the movement of colloidal particles charged with charge to the electrodes of opposite charge. The main mechanism for removing contaminants is different depending on the contaminants in the electrodynamic restoration process. When the pollutants are ions or metals, the main mechanisms for removing the pollutants are electrophoresis and electroosmosis, whereas when the pollutants are organic pollutants that are not primarily charged, electrochemical osmosis is the main mechanism.

Factors affecting the removal efficiency of the contaminants in the electrokinetic restoration process include soil characteristics, pollutant concentration of the pollutants and adsorption and desorption characteristics and solubility characteristics of the soil, the characteristics of the pore fluid, the voltage gradient. In particular, when DC voltage or DC current is applied to the electrode, electrolysis occurs around the electrode, which affects the effect of removing the contaminants. Specifically, water is decomposed at the anode to generate hydrogen ions (H ⁺ ) and oxygen, and at the cathode, hydroxide ions (OH ⁻ ) and hydrogen are generated. The produced hydrogen ions and hydroxide ions change the pH of the positive electrode and the negative electrode to acidic or basic, respectively. Since the electrophoretic rate of hydrogen ions in solution is faster than that of hydroxide ions, the soil is generally acidified as the hydrogen ions progress from the anode to the cathode. That is, the pH of the soil is lowered around the anode and the pH of the soil is increased around the cathode, thereby forming a pH gradient of the soil. Due to this pH gradient, the rate of electroosmotic affecting the removal of contaminants is reduced, or contaminants such as heavy metals meet with hydroxide ions around the cathode to form a precipitate. As a method for solving this problem, a method of maintaining a constant pH of the solution by circulating a catholyte or anolyte with a control solution or a method of reducing the pH change of the soil by installing an ion exchange membrane around the electrode is used. (See Korean Patent No. 10-0954274 and US Patent No. 5,190,628).

The electrokinetic soil restoration process places electrodes in the soil at regular intervals and applies a DC current of 0.1 to 10 mA / cm ² or a DC voltage of 0.1 to 10 V / cm to the electrodes. The removal efficiency of contaminants in electrodynamic processes is related to the efficiency of power use and current flow in the soil. For example, a small amount of ions in the soil results in a lower current density, which increases the recovery period for removing contaminants below a certain concentration. In order to solve this problem, a method of replacing the electrolyte to enrich soil ions, or using an electrodynamic restoration technique using a pulse process to increase the efficiency of electric power use (Korea Patent No. 10-0578020 and 10-0735037), a stepwise application method using a voltage step by step in the soil (Korean Patent No. 10-0912817) and the like.

In addition, the electrokinetic restoration process removes a lot of contaminants by electroosmosis, so the more soil remains wet or saturated with water, the higher the removal efficiency of the contaminants, and the higher the amount of charged clay or silt, The increased movement of contaminants due to electroosmotic enables efficient removal of contaminants.

Since contaminants are present in electrolytes or effluents generated in such electrodynamic processes, wastewater treatment processes are generally required for electrodynamic soil contamination recovery systems. The effluent from the electrode system is drawn to the ground, and the contaminants are removed by wastewater treatment and then reused as electrolyte or discharged to the surrounding water system.

Electrodes used in electrodynamic processes are carbon, stainless steel, iron, precious metal coating materials and the like. In order to remove contaminants around the electrode, it is known to charge activated carbon, adsorbents, etc. so that the movement of contaminants is carried out using an electrodynamic process and the removal of contaminants is known using the adsorbents (US Pat. No. 6,221,237). And Korean Patent No. 10-0519909). However, such an electrode system has a disadvantage in that the current density in the soil is lowered because there is a filler such as an adsorbent, an electrode solution, and the like between the electrode and the soil.

As described above, various electrokinetic soil contamination restoration processes have been developed, but still require an electrode and a system having various functions in the field.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode capable of removing contaminants while increasing current density in soil in an electrodynamic process in a method of restoring soil contaminated with organic and inorganic substances, and a soil contamination restoration system using the same.

In order to achieve the above object, in the present invention

i) the wire connecting portion 31 which is connected to the voltage supply device 101 is provided at the top, and the electrode liquid inlet 41 and the electrode liquid outlet 42 are formed, and the lower part 22 is conical or b. A hollow cylindrical body 20 having a sand shape and having a plurality of holes 51 formed on a surface between the upper part and the lower part; And

ii) a filler 62 selected from the group consisting of a substance capable of adsorbing or sedimenting contaminants in the cylindrical body 21, a substance containing an electrode water, and a mixture thereof;

It provides a, electrodynamic soil contamination restoration electrode.

The present invention also provides a soil contamination recovery system using the electrode.

According to the electromechanical soil restoration electrode and system of the present invention, the current density is improved because there is no interference material between the electrode and the soil compared to the conventional electrodynamic soil restoration process, and the contaminants present in the electrode solution are removed in the electrode. It is possible to do this, and there is no need to separately perform the electrode solution treatment process. In addition, it is possible to prevent the loss of the electrode liquid to the soil by filling a material that may contain water in the electrode.

1 is a schematic diagram of a contaminated soil purification system using the electrode of the present invention.
2 is a schematic diagram of the electrode for electrodynamic soil restoration of the present invention.
3 is a schematic diagram of a packing capable of sedimenting and adsorbing contaminants in an electrode and a container capable of holding it.

The electrode for restoring the electrokinetic soil contamination of the present invention is hollow in the form of a hollow body, and has a cylindrical shape, and the bottom of the electrode has a conical shape so that the electrode can be directly installed in the soil. It is provided with a wire connection part to connect the supply device, an electrode liquid inlet and an outlet for replenishing and discharging the electrode liquid, and for the movement between the pore water in the soil and the electrode liquid inside the electrode on the surface between the upper and lower parts of the electrode. A plurality of holes are formed, and the inside of the electrode includes a filler selected from a substance capable of adsorbing or sedimenting contaminants, a substance containing an electrode water, or a mixture thereof, in addition to rainfall and foreign matter. Lids to prevent entry, and for replacement while retaining the fillers And it may further comprise a network in the form of a container for the reaction of the filler and the electrode solution.

In addition, in the present invention, in order to prevent the soil from entering the hole formed in the electrode surface or to prevent the generation of the pH gradient between the electrode and the soil, porous membrane made of cellulose, cloth, glass fiber, plastic or paper material Alternatively, an ion exchange membrane may be provided around the electrode.

With reference to the accompanying drawings will be described in detail the electrokinetic soil contamination recovery electrode and the system using the same. In the following description of the preferred embodiments of the present invention by way of example, the scope of the present invention is not limited to the specific embodiments as described above, the patent of the present invention by those skilled in the art to which the present invention belongs Changes may be made as appropriate within the scope of the claims and are provided to explain the invention in more detail.

1 is a view showing an example of an electrodynamic soil purification system using the electrode of the present invention, Figure 2 is a view showing an example of the electrode structure for electrodynamic soil purification of the present invention. As shown in FIG. 2, the electrode of the present invention is configured to include a hollow cylindrical body 20 having an empty interior 21. In order to install the existing electrodes in the soil, drill holes (coring) into the soil using drilling equipment, install the electrodes inside the soil, and use the plastic or clay material to prevent the soil from flowing through the holes. Although the electrode is provided in the form of filling, in the present invention, in order to directly install the electrode itself in the soil, the electrode bottom 22 is configured in a conical shape. In order to reduce the damage of the electrode when injecting it directly into the soil, the electrode bottom 22 is deformable conical or threaded. Existing electrode system has a disadvantage in that the current density decreases because the filling material such as electrode liquid, bentonite, plastic pipe, etc. is present between the electrode and the soil, but the electrode of the present invention is in direct contact with the soil and the electrode without such an intermediate medium Therefore, when the same voltage is applied, the resistance between the electrodes decreases, thereby increasing the current density.

In the present invention, the material of the electrode body 20 is a material having a strength that can penetrate the electrode directly into the soil while the current can pass, iron, stainless steel, iron or stainless steel coated with a precious metal, carbon material Coated iron or stainless steel and the like are preferred, but are not limited thereto.

The upper portion of the electrode body 20 is provided with a wire connection portion 31 to which the wire 102 connecting the electrode and the voltage supply device 101 can be coupled. As a method of coupling the electric wire to the connection portion 31, as shown in FIG. 2, a hole 31 is formed in the electrode body 20 to connect the electric wire, and a bolt and a nut in the hole 31 are connected. Using a method of connecting the wire and the electrode, or a method of directly soldering the wire to the wire connecting portion 31 provided in the electrode body (20).

In addition, an electrode solution inlet 41 and an electrode solution outlet 42 for replenishing and discharging the electrode solution in the electrode are formed on the electrode body 20. The replenishment liquid inlet 41 and the electrode liquid outlet 42 in the electrode body 20 may be located at the same position as, for example, the cross section 40, but the replenishment liquid inlet 41 is positioned higher than the electrode liquid outlet 42. It is desirable to. In order to adjust the level of the electrode liquid in the electrode, it is possible to install the water level measuring sensor 71, which is connected to the level control device 92 to automatically adjust the operation of the pump (81, 82) for controlling the injection liquid and the effluent liquid It is also possible. These pumps are connected to the anolyte reservoir and the catholyte reservoir to replenish the insufficient electrode solution and to extract the electrode solution generated by the electroosmotic phenomenon. If necessary, the anolyte and catholyte reservoirs can be used as a single reservoir. Since the contaminants present in the catholyte and the anolyte are removed by the filler 62 in the electrode according to the present invention, the outflowing electrode solution contains little or no contaminants and can be reused.

Also, on the surface 50 between the upper and lower portions of the electrode body 20, there are a plurality of holes 51 so that the pore water of the electrode liquid and the soil inside the electrode can be exchanged directly. The size of the hole 51 for the flow between the electrode solution and the soil pore water is preferably 0.1 to 20 mm in diameter. In this regard, in order to prevent clogging of these holes 51 by the soil or to prevent pH gradient of the soil, a porous material of cellulose, cloth, glass fiber, plastic or paper material around the electrode with a material which can wrap the electrode. A membrane or an ion exchange membrane can be provided.

In addition, since the electrode of the present invention is directly infiltrated into the soil and there is a wire connected to the electrical supply device at the top, the electrode operation when the hollow upper part of the electrode is exposed to the soil surface and rain water or foreign matter enters the inside of the electrode 21 Since adversely affects, as a means for solving this may further include a lid (10). The material of the electrode lid 10 may be, for example, plastic, iron, stainless steel, etc. as the material capable of achieving the above object, but is not limited thereto. In addition, the lid 10 can be connected by forming a screw thread on the upper portion of the electrode body 20 and the lower portion of the lid 10 so as not to be blown by wind, etc., and a connection ring is installed on the electrode body 20 and the lid 10. It is also possible.

In addition, the electrode of the present invention includes a filler 62 selected from a substance capable of adsorbing or sedimenting contaminants or a substance containing electrode water or a mixture thereof, as shown in FIG. The filler 62 may be inserted into the electrode body 20 in a container 60 having a handle 61 and provided in a mesh form capable of holding the filler 62 for convenience of replacement. If necessary, it is also possible to put the filling directly inside the electrode body 20 without the vessel 60.

Materials that can precipitate and adsorb contaminants in the electrode include lime, concrete, ash, dolomite, zeolite, silica, diatomaceous earth, activated carbon, iron oxide, aluminum oxide, manganese oxide, ductile iron, carbon nanotubes, apatite, and biosorbents. , Ion exchange resins, mixtures of these materials or processed materials. In addition, the water-retaining material that can contain the number of electrodes in the electrode is composed of a super absorbent material (SAM) and an absorbent gel material (AGM) that absorb water from tens to hundreds of times its own weight. Superabsorbent resins (e.g. starch (potato starch) or graft copolymers of cellulose and acrylonitrile, block copolymers of acrylic acid and vinyl alcohol, sodium polyacrylates, polyacrylamide hydrogels), Soil improvers, soil moisturizers, etc., mainly composed of absorbent resins, are included. By filling a material that can contain such an electrode water, it is possible to obtain an effect of preventing the electrode current from flowing out to the outside of the electrode so that soil current does not flow.

Hereinafter, in order to grasp the applicability of the electrodynamic electrode and the system of the present invention described above, an experimental example for checking the change of the current, the change of the electroosmotic amount and the heavy metal removal rate according to the configuration of the electrode was presented.

Experimental Example

The electromechanical treatment system applied to the experiment was manufactured using a plastic reactor having a width of 15 cm, a length of 15 cm, and a height of 15 cm for the convenience of experiment. After filling the reactor with a height of 10 cm, the electrode of the present invention was directly introduced into the soil, and the lower part of the electrode was installed to reach the bottom of the soil reactor. The soil used was tailings around the mine in Docheon-ri, Jucheon-myeon, Yeongwol-gun, Gangwon-do, which was contaminated with arsenic, lead, and copper. The electrode body 20 is a cylindrical stainless steel (SUS) material having a diameter of 2.5 cm, a height of 18 cm, and a thickness of 0.1 cm, and the inside of the electrode is hollow, and a 0.2 cm circular hole is drilled at 2.5 cm intervals on the body surface, and the bottom of the body is Has a conical shape. 0.1 M NaOH was used as the electrode solution, and interlocking pumps were used for the injection and discharge of the electrode solution. For the comparative experiment, under the same conditions as this experiment, install a PVC pipe with a diameter of 3 cm and a thickness of 0.2 cm to surround the electrode and make a PVC pipe hole at the same position as the hole formed in the electrode body to introduce the electrode liquid into the soil. By mounting as much as possible, the electrodes in conventional conventional electrodynamic processes are simulated. In the installation of the comparison electrode, a PVC pipe was installed by drilling holes in the soil, and the electrode was inserted into the PVC pipe. That is, in the existing electromechanical process, a hole for inserting the electrode through the coring is made, and a PVC pipe is inserted therein so that the soil does not block the hole and provides a space for the electrode and the electrode solution. In the electrode system of the PVC pipe and the electrode is integrated by inserting the electrode itself into the soil, replacing the process of coring, PVC pipe installation, electrode installation with a single process of injecting the electrode according to the present invention into the soil. The voltage gradient was applied at 5 V / cm, and the electroosmotic flow rate was calculated using a value measured using a measuring cylinder for the volume difference of the electrode solution.

Initial soil contamination and removal of pollutants after 48 hours of operation Example As Cu Ni Pb Zn Initial Pollution Degree (mg / kg) 136 278 12 517 246 When using the electrode of the present invention
Contaminant Removal (mg) 21.4 24.5 1.4 1.8 1.6 With conventional electrode systems
Contaminant Removal (mg) 2.1 2.2 0.1 0.1 0.1

As shown in Table 1, when the soil contaminated with arsenic, copper, nickel, lead, zinc, etc. using the electrode of the present invention in which the electrode and the soil directly contact, the contaminants are removed, PVC pipe between the electrode and the soil Compared to the conventional electrode system, the removal of most contaminants is more than 10 times.

In addition, in the case of a general electrode system having a cylindrical pipe installed outside the electrode, an electric osmotic flow rate of 0.44 L was generated as a result of operation for 2 days, while using the electrode of the present invention, a much higher value of 3.36 L was generated. The current was also measured to be 2-10 mA in a typical electrode system but 173-337 mA in an electrode system of the present invention. The increase in the electroosmotic flow rate and the current results in an increase in the removal rate because of the increase in contaminants.

Cylindrical electrode according to the present invention 10 g of DOWEX 1X4 (Dow Chemical Co.), an arsenic removal adsorbent capable of adsorbing contaminants in the electrode in the electrode system including the electrode according to the present invention in order to determine the efficacy of the internal filling of the electrode It was injected inside of. The voltage gradient was applied at 5 V / cm, and the effluent generated in the electrodynamic process was installed to move through the peristaltic pump with the electrode solution (1 L) of the electrode solution storage tank (2 L). That is, the electrode solution was moved to the electrode solution storage tank through the peristaltic pump and the electrode solution in the electrode solution storage tank was again injected into the electrode through the peristaltic pump. When the heavy metal treated in the electrodynamic process was transferred to the electrode solution, it was adsorbed by the adsorbent packed inside the electrode, and when 1 L of the electrode solution leaked, 91% of the arsenic leaked was removed. These results show that the adsorbent or precipitant can be loaded inside the electrode to treat contaminants contained in the effluent from the electrodynamic process, and the treated effluent can be reused as an electrolyte. That is, when the soil is treated using the electrode system of the present invention having a filler inside the electrode that can adsorb the contaminants, the processing time of the contaminants is shortened and the electrodynamic treatment system is shortened compared to the existing process in which the adsorbing of the contaminants is impossible due to the absence of the fillers. It is suggested that miniaturization or removal of the wastewater treatment plant for treating the wastewater can be achieved.

The preferred embodiments of the present invention have been described above, and the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention.

10: lid
20: electrode body 21: inside the electrode 22: the lower part of the electrode
30: cutting edge of the wire connection 31: wire connection
40: cutting surface of electrode liquid exchange part 41: electrode liquid inlet 42: electrode liquid outlet
50: cutting surface of the electrode body 51: hole of the electrode
60: filler holding container 61: filler holding container handle
62: Fill
71: level sensor
81: outflow pump 82: infusion pump
82: outflow hose 84: injection hose
92: level controller 94: connecting line between the level sensor and the regulator
101: voltage supply 102: electric wire

Claims (8)

i) the wire connecting portion 31 which is connected to the voltage supply device 101 is provided at the top, and the electrode liquid inlet 41 and the electrode liquid outlet 42 are formed, and the lower part 22 is conical or b. A hollow cylindrical body 20 having a sand shape and having a plurality of holes 51 formed on a surface between the upper part and the lower part; And
ii) a filler 62 selected from the group consisting of a substance capable of adsorbing or sedimenting contaminants in the cylindrical body 21, a substance containing an electrode water, and a mixture thereof;
Including, electrodynamic soil contamination restoration electrode. The electrode according to claim 1, wherein the electrode body (20) is made of iron, stainless steel, iron or stainless steel coated with a noble metal, or iron or stainless steel coated with a carbon material. 2. An electrode according to claim 1, further comprising a net-shaped container (60) capable of retaining a fill (62) inside the electrode body (20). The method of claim 1, wherein the material capable of adsorbing or depositing contaminants is lime, concrete, ash, dolomite, zeolite, silica, diatomaceous earth, activated carbon, iron oxide, aluminum oxide, manganese oxide, ferrous iron, carbon nanotubes, apatite , An electrode selected from the group consisting of biosorbents, ion exchange resins, mixtures of these materials and workpieces. The electrode according to claim 1, wherein the material which can contain the number of electrodes comprises at least one member selected from the group consisting of a super absorbent polymer, an improved soil agent, and a soil repair agent. 6. The superabsorbent polymer, the improved soil agent and the soil repair agent according to claim 5 are starch, graft interpolymers of cellulose and acrylonitrile, block interpolymers of acrylic acid and vinyl alcohol, sodium polyacrylates and polyacrylamide hydrogels. An electrode comprising one selected from the group consisting of. Electrodynamic soil recovery system using the electrode of claim 1. 8. The electrokinetic soil recovery system of claim 7, wherein a porous membrane or ion exchange membrane of cellulose, cloth, fiberglass, plastic or paper is provided between the electrode and the soil.

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