CN112845559A - System and method for deep layering treatment of heavy metal contaminated soil - Google Patents
System and method for deep layering treatment of heavy metal contaminated soil Download PDFInfo
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- CN112845559A CN112845559A CN202110010505.6A CN202110010505A CN112845559A CN 112845559 A CN112845559 A CN 112845559A CN 202110010505 A CN202110010505 A CN 202110010505A CN 112845559 A CN112845559 A CN 112845559A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/02—Extraction using liquids, e.g. washing, leaching, flotation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
- B09C1/085—Reclamation of contaminated soil chemically electrochemically, e.g. by electrokinetics
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
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Abstract
The invention discloses a system and a method for deeply and hierarchically treating heavy metal contaminated soil. The electrode group comprises at least one group of electrode devices, each electrode device comprises an anode and a cathode, and a power supply connected with the anode and the cathode. The anode comprises an anode insulating section and an anode electrode section, and the cathode comprises a cathode insulating section and a cathode electrode section. When the cathode is in a hollow tubular structure, the cathode is used as a liquid collecting pipe; when the cathode adopts a solid structure, the liquid collecting pipe is arranged between the cathode and the adsorption ring. The heavy metal contaminated soil field is divided into a leaching treatment area and an electric treatment area in a deep layering mode, so that the anode insulation section and the cathode insulation section are located in the depth range of the leaching treatment area, and the anode electrode section and the cathode electrode section are located in the depth range of the electric treatment area. The invention can effectively improve the heavy metal removal efficiency, and has the advantages of low power consumption, low treatment cost, capability of treating soil with larger depth and the like.
Description
Technical Field
The invention relates to a system and a method for deep layering treatment of heavy metal contaminated soil, and belongs to the technical field of environmental protection.
Background
With the rapid development of economy, the problem of soil environmental pollution is increasingly highlighted. The heavy metal pollution of the soil refers to the phenomenon that the content of heavy metal in the soil is obviously higher than the natural background value due to excessive deposition of metal elements with the density of more than 5.0 in the soil due to the activity of human beings, and the phenomena of ecological damage and environmental quality deterioration are caused. The first general survey of soil in China shows that about 30% of industrial wasteland and industrial park have excessive heavy metals such as lead, arsenic, cadmium, chromium, mercury, zinc, copper and the like in the surveyed soil point positions. Unlike organic pollutants, most heavy metals are not affected by microbial and chemical degradation and can accumulate in soil for long periods of time. Heavy metals in soil can also enter the food chain through media such as water and plants, thus threatening human health.
At present, the remediation technology aiming at the heavy metal pollution of soil mainly comprises the following steps: phytoremediation, in-situ chemical leaching, ex-situ chemical leaching, soil property improvement, solidification remediation technology, physical separation remediation technology, vitrification remediation, thermodynamics remediation, thermal desorption remediation, electric remediation, soil replacement remediation and the like. The electric remediation technology as a novel and green soil remediation technology shows high efficiency in soil heavy metal remediation. Electrokinetic remediation techniques can be used to remediate low permeability soils that are otherwise difficult to treat with traditional soil remediation techniques.
The electric restoration technology is that an electric field is applied to the polluted soil, so that the pollutants are directionally migrated through electromigration and electrodialysis under the action of the electric field, are enriched to the vicinity of an electrode and are subjected to concentrated treatment, and therefore pollution reduction or cleaning of a polluted soil sample is achieved. Electromigration refers to the movement of ions in solution along electric field lines toward an opposite electrode under the action of an applied electric field, e.g., metal cations migrate toward the cathode. Electrodialysis is the phenomenon in which pore fluid moves towards an electrode relative to a stationary soil body under the action of an electric field. Electroosmotic flow carries heavy metals dissolved and suspended in the soil solution to the cathode.
Under the action of the electric field, the soil solution is subjected to electrolytic reaction at the electrode. OH generated by cathode and anode respectively-And H+Resulting in an increase in cathode pH and a decrease in anode pH. During electrokinetic treatment, heavy metals accumulate and eventually precipitate at the cathode, clogging the soil pores and hindering the remediation process from proceeding. For soils with high acid buffering capacity, the anode pH will not decrease in a short time if only H produced by the anode electrode is used+To promote heavy goldDissolution and desorption of the metal, the repair process will progress very slowly. In the electric restoration process, when the voltage gradient is kept constant, the larger the depth of the electrode entering the soil is, the higher the loop current is, along with the increase of the treatment depth. The over-high current can generate joule heat to heat the soil and the electrolyte, and the energy consumption in the restoration process is increased. Therefore, the development of the high-efficiency, simple and convenient electric remediation method capable of treating the heavy metal contaminated soil with large depth has important practical significance.
Disclosure of Invention
The invention aims to provide a system and a method for deeply processing heavy metal contaminated soil in a layered mode.
The invention is realized by the following technical scheme:
an electrode device can be used for a repairing electric field of heavy metal contaminated soil, and comprises a power supply, an anode and a cathode which are respectively connected with the power supply, wherein the anode comprises an anode insulating section and an anode electrode section, a conductive material is embedded in the anode insulating section, and the anode insulating section can be connected with the power supply and the anode electrode section to form a conductive path; the cathode comprises a cathode insulating section and a cathode electrode section, wherein a conductive material is embedded in the cathode insulating section, and the cathode insulating section can be communicated with the power supply and the cathode electrode section to form a conductive path.
A system for deep layered treatment of heavy metal contaminated soil comprises an electrode device, an additive spraying and collecting system and an adsorbent ring; the electrode device comprises at least one anode and at least one cathode, and a power supply connected with the anode and the cathode; the anode comprises an anode insulation section and an anode electrode section, wherein a conductive material is embedded in the anode insulation section and can be connected with the power supply and the anode electrode section to form a conductive path; the cathode comprises a cathode insulating section and a cathode electrode section, wherein a conductive material is embedded in the cathode insulating section and can be communicated with the power supply and the cathode electrode section to form a conductive path; the additive spraying and collecting system comprises an additive storage tank, a spraying device, a liquid collecting pump, a liquid collecting tank and a liquid collecting pipe, wherein the additive storage tank is connected with the spraying device; the adsorbent ring is arranged outside the cathode electrode section in a surrounding mode, and an adsorbent filling area is formed between the adsorbent ring and the wall surface of the cathode electrode section and used for filling the adsorbent.
The cathode is of a hollow tubular structure, the wall surface of the cathode electrode section is provided with a plurality of through holes, and the hollow tubular cathode is used as a liquid collecting tube; or the cathode adopts a solid structure, and the liquid collecting pipe is arranged between the cathode and the adsorption ring.
An adsorbent filling area is formed between the adsorbent ring and the liquid collecting pipe and used for filling the adsorbent, and an inlet of the liquid collecting pump is communicated with the lower part of the liquid collecting pipe.
In the above technical solution, the adsorbent ring and the cathode electrode section have the same height.
A method for deeply and hierarchically treating heavy metal contaminated soil comprises the following steps:
dividing the heavy metal contaminated soil field into a leaching treatment area and an electric treatment area in a deep layering manner according to the heavy metal content of the heavy metal contaminated soil field and the required restoration depth;
electrode devices with corresponding depths are arranged according to the depths of the leaching treatment area and the electric treatment area, so that the lengths of the anode electrode section and the cathode electrode section are equal to the depth of the electric treatment area, and the lengths of the anode insulation section and the cathode insulation section are more than or equal to the depth of the leaching treatment area;
respectively fixing a proper amount of anodes and proper amount of cathodes on the heavy metal contaminated soil field, and enabling the anode insulation sections and the cathode insulation sections to be located within the depth range of the leaching treatment area, and enabling the anode electrode sections and the cathode electrode sections to be located within the depth range of the electric treatment area; enabling an adsorbent to surround the liquid collecting pipe, and enabling the periphery of the cathode electrode section to surround to form an adsorbent filling area, wherein the adsorbent filling area is internally provided with an adsorbent; the anode and the cathode are correspondingly connected with a power supply;
arranging the spraying device on the surface of the leaching area, and enabling the surface of the leaching area to be positioned in the spraying range of the spraying device; uniformly spraying the additive solution in the additive storage tank on a heavy metal contaminated soil field through a spraying device, wherein the additive solution migrates in the heavy metal contaminated soil field to form a leaching treatment area, and heavy metal compounds in the soil are dissolved and/or desorbed into the additive solution to form a leaching solution containing heavy metals; under the action of gravity, the leacheate carries heavy metals to migrate to the deep part of the soil;
when the leaching solution containing the heavy metals enters the soil and reaches the electric treatment area, the power supply is connected, and an electric field is formed between the anode and the cathode, so that the heavy metals in the leaching solution form directional movement towards the cathode under the action of the electric field;
when the leacheate passes through the adsorbent filling area, heavy metals in the leacheate are adsorbed by the adsorbent, and residual liquid enters the liquid collecting pipe to be collected and is sucked and discharged through the liquid collecting pump and is collected into the liquid collecting tank as recovery liquid.
In the technical scheme, the strength of the electric field of the electric treatment area is 0.5-3.0V/cm.
In the above technical scheme, the adsorbent comprises any one or more of activated carbon, biomass semi-coke, zeolite and a porous material made of fly ash.
In the above technical scheme, the additive solution comprises any one or a mixture of more of citric acid, oxalic acid, malic acid, tartaric acid, acetic acid and ethylenediamine tetraacetic acid.
One embodiment in the above technical solution is to collect the adsorbent having adsorbed the heavy metal from the soil and then perform centralized treatment.
In another embodiment of the above technical solution, a heavy metal curing agent and/or a stabilizer is injected into the adsorbent, the heavy metal is fixed in the adsorbent material, and the adsorbent with the fixed heavy metal is retained in the deep soil layer.
The invention has the following advantages and beneficial effects: firstly, the heavy metal contaminated soil is treated by deep layering, so that the problem of overlarge current caused by overlarge depth of the electrode inserted into the soil can be avoided, the soil is prevented from heating, and the electric energy loss is reduced; on the other hand, heavy metals can be enriched in the electric treatment area through leaching, so that the electric repair efficiency is improved; a small amount of additive can improve the solubility of heavy metal pollutants in the soil solution in a short time, increase the activity and mobility of the heavy metal and further improve the electric remediation efficiency; arranging an adsorbent layer in the cathode region, and controlling the pH change of soil near the cathode region while adsorbing heavy metals so as to reduce the generation of metal precipitates; moreover, as the porosity of the adsorbent is larger, the problem of pore blockage cannot be caused by a small amount of metal precipitation, and the repair process is ensured; and fourthly, the heavy metal curing agent and/or the stabilizer is injected into the adsorbent to fix the heavy metal in the adsorbent material, and the adsorbent is reserved in the deep layer of the soil, so that the treatment burden of the subsequent heavy metal-containing adsorbent is reduced.
Compared with the existing electric restoration method, the method has the advantages of low power consumption, high heavy metal removal efficiency and simple and convenient treatment of the heavy metal-containing adsorbent, and can be used for treating and restoring the heavy metal contaminated soil with larger depth.
Drawings
FIG. 1 is a schematic diagram of a system for deep layering treatment of heavy metal contaminated soil according to one embodiment of the invention.
In the figure: 1-a power supply; 2-liquid collection tank; 3-liquid collecting pump; 4-a cathode insulation section; 5-a spraying device; 6-anode insulation section; 7-a liquid adding pump; 8-additive storage tank; 9-an adsorbent ring; 10-an anode electrode segment; 11-a cathode electrode segment; 12-a leaching treatment area; 13-electrokinetic treatment zone.
Detailed Description
The following describes the embodiments and operation of the present invention with reference to the accompanying drawings.
The terms of orientation such as up, down, left, right, front, and rear in the present specification are established based on the positional relationship shown in the drawings. The corresponding positional relationship may also vary depending on the drawings, and therefore, should not be construed as limiting the scope of protection.
Existing electrokinetic remediation methods treat soils of different contamination depths by changing the electrode insertion depth. However, as the treatment depth increases, the greater the depth of insertion of the electrode into the soil, the higher the loop current. The over-high current can generate joule heat to heat the soil and the electrolyte, and the electric energy loss in the repair process is increased. Research shows that when the distance between the anode and the cathode is 80cm and the voltage is 40.5V, the loop current increases from 2cm to 50cm along with the insertion depth of the electrode, the loop current increases to 3.273A, and when the loop current continues to increase to 80cm, the loop current continues to increase to 3.715A. In the process, not only the loop current is increased along with the increase of the insertion depth of the electrode, but also the heating of the activated carbon is serious along with the increase of the insertion depth of the electrode, and the recovered liquid in the cathode well is boiled.
As shown in figure 1, the system for deeply and hierarchically treating the heavy metal contaminated soil comprises an electrode device, an additive spraying and collecting system and an adsorbent ring 9. The electrode arrangement comprises at least one anode and at least one cathode, and a power supply 1 connecting the anode and the cathode. Preferably, the electrode assembly includes a cathode and a plurality of anodes. As another preferred scheme, the electrode device includes a plurality of cathodes and a plurality of anodes, wherein the cathodes and the anodes may correspond to each other, or one cathode corresponds to more than two anodes.
The anode comprises an anode insulating section 6 and an anode electrode section 10, wherein a conductive material is embedded in the anode insulating section, and the anode insulating section can be connected with the power supply 1 and the anode electrode section 10 to form a conductive path. The anode can be in a solid structure or a hollow structure.
The cathode comprises a cathode insulating section 4 and a cathode electrode section 11, wherein a conductive material is embedded in the cathode insulating section, and the cathode insulating section can be communicated with the power supply 1 and the cathode electrode section 11 to form a conductive path.
The additive spraying and collecting system comprises an additive storage tank 8, a spraying device 5, a liquid collecting pump 3, a liquid collecting tank 2 and a liquid collecting pipe, wherein the additive storage tank 8 is connected with the spraying device 5.
In one embodiment, the cathode is a hollow tubular structure, the wall surface of the cathode electrode section is provided with a plurality of through holes, and the hollow tubular cathode is used as a liquid collecting pipe at the same time.
In another embodiment, the cathode is of a solid structure, and the liquid collecting pipe is arranged between the cathode and the adsorption ring. And the liquid inlet of the liquid collecting pipe is positioned at the inner side of the adsorbent ring and is close to the lower surface of the adsorbent ring.
The adsorbent ring 9 is as high as the cathode electrode section 11, is arranged around the liquid collecting pipe and forms an adsorbent filling area with the wall surface of the liquid collecting pipe for filling the adsorbent. The inlet of the liquid collecting pump 3 is arranged at the lower part of the liquid collecting pipe.
And selecting a to-be-repaired heavy metal contaminated soil field, and determining the heavy metal enrichment degree according to the characteristics of the heavy metal contaminated soil field and the required repair depth, so that the heavy metal contaminated soil field is divided into a leaching treatment area and an electric treatment area in a deep layering manner. The heavy metal enrichment degree n is the ratio of the concentration of a certain element or compound in the soil deep layer region to the original concentration of the substance in the soil after the soil heavy metal is leached and enriched, the heavy metal in the soil shallow layer region migrates and is enriched to the soil deep layer region. Under the condition that heavy metals in original soil are approximately uniformly distributed, the heavy metal enrichment degree n is the ratio of the required restoration depth to the thickness of the electric treatment area. When the content of heavy metal in the field is too low, the efficiency of directly using the electric restoration technology is low, so that the heavy metal in the soil shallow region needs to be enriched in the electric treatment region through leaching, and the electric restoration efficiency is improved. For the heavy metal contaminated soil field to be repaired with too low heavy metal content, the electric repair efficiency needs to be ensured by determining higher heavy metal enrichment degree. For the heavy metal contaminated soil field to be repaired with high heavy metal content, the heavy metal enrichment degree needs to be determined according to the required repair depth. When the required restoration depth is large, the direct use of the electric restoration technology can cause the depth of the electrode conductive section inserted into the soil to be too large, thereby causing the current to be too large and causing the problem of electric energy loss. For a field needing to be repaired with a large depth, a high heavy metal enrichment degree needs to be determined to ensure a small thickness of an electric treatment area and a short electrode conducting section is used, so that electric energy loss is reduced and electric repair efficiency is improved.
Generally, when the required restoration depth is less than 1m, the heavy metal enrichment degree n is 2; when the required restoration depth is 1-5 m and the heavy metal content of the site is less than the first-class construction land soil pollution risk screening value (GB36600-2018), the heavy metal enrichment degree n is 10; when the required restoration depth is 1-5 m and the heavy metal content of the site is greater than the first-class construction land soil pollution risk screening value (GB36600-2018), the heavy metal enrichment degree n is 5; and when the required restoration depth is more than 5m, the heavy metal enrichment degree n is a value obtained by integrating the required restoration depth.
And determining the depth ranges of the leaching treatment area and the electric treatment area according to the heavy metal enrichment degree n. Dividing the heavy metal contaminated soil field into n layers according to the heavy metal enrichment degree n, wherein the first n-1 layer close to the surface layer of the soil is a leaching treatment area, and the nth layer is an electric treatment area.
And arranging electrode devices with corresponding depths according to the depths of the leaching treatment area and the electric treatment area, so that the lengths of the anode electrode section and the cathode electrode section are equal to the depth of the electric treatment area, and the lengths of the anode insulating section and the cathode insulating section are more than or equal to the depth of the leaching treatment area.
And respectively fixing a proper amount of anodes and cathodes in a heavy metal polluted soil field, and enabling the anode insulation sections and the cathode insulation sections to be positioned in the depth range of the leaching treatment area, and enabling the anode electrode sections and the cathode electrode sections to be positioned in the depth range of the electric treatment area. And the boundary between the anode insulating section and the anode electrode section or the boundary between the cathode insulating section and the cathode electrode section is usually positioned at the boundary between the leaching treatment area and the electric treatment area.
When the cathode is in a hollow tubular structure, the hollow tubular cathode is used as a liquid collecting tube, so that the periphery of the cathode electrode section surrounds to form an adsorbent filling area. When the cathode is of a solid structure, a liquid collecting pipe is arranged outside the cathode, an adsorbent filling area is formed around the outside of the liquid collecting pipe, and the height of the adsorbent filling area is equal to that of the cathode electrode section.
The adsorbent filling area is internally provided with an adsorbent. The adsorbent comprises any one or more of activated carbon, biomass semi-coke, zeolite and a porous material made of fly ash. When the adsorbent adsorbing heavy metals is treated in a remote place, the adsorbent can be prefabricated into a tubular structure comprising the adsorbent or a net structure is arranged outside the adsorbent particles to wrap the granular adsorbent. The pre-fabricated adsorbent tube or adsorbent pack is then filled in the adsorbent filling zone.
The number of the electrodes is usually set according to the area of a repair field and the electric field intensity, and each group of the anodes and the cathodes are correspondingly connected with a power supply and are in parallel connection with each other. The number of electrodes directly affects the effective utilization rate of the electric field: the area of an ineffective electric field is large due to the fact that the number of the electrodes is too small and the arrangement of the electrodes is sparse, the effective utilization rate of the electric field is low, and the electric restoration efficiency is low; the electrode cost is increased due to the excessive number of the electrode groups and the dense arrangement of the electrodes, and the electric energy loss is caused due to joule heat generated by soil due to excessive current. In one embodiment, a two-dimensional arrangement electric field with a cathode as a central electrode and an anode arranged at the periphery is selected. The distance between the cathode and the anode is 0.5-2m, and the electric field intensity is 0.5-3.0V/cm. In this case, a higher electric field strength should be selected when a smaller cathode-anode spacing is selected. Conversely, a larger cathode-anode spacing should be selected with a lower electric field strength.
And arranging the spraying devices on the surface of the leaching area, and enabling the surface of the leaching area to be positioned in the spraying range of the spraying devices 5. The additive solution in the additive storage tank 8 is uniformly sprayed on the heavy metal contaminated soil field through the spraying device 5, and the main components of the additive solution comprise any one or a mixture of citric acid, oxalic acid, malic acid, tartaric acid, acetic acid and ethylenediamine tetraacetic acid. The additive solution migrates in the heavy metal contaminated soil field to form a leaching treatment zone 12. On one hand, the heavy metal compounds in the soil are dissolved and/or desorbed into the additive solution through the dissolution effect and on the other hand, carboxyl and hydroxyl form soluble complexes with the heavy metals, so that the leacheate containing the heavy metals is formed. The additive can promote the dissolution and desorption of heavy metals, thereby improving the removal rate of the heavy metals in the soil. Under the action of gravity, the leacheate carries heavy metals to migrate to the deep part of the soil.
When the leacheate containing the heavy metals enters the soil and reaches the electric treatment area 13 deeply, the power supply is connected, an electric field is formed between the anode and the cathode, and the heavy metals in the leacheate move towards the cathode in a directional mode under the action of the electric field. Heavy metals exist in the leacheate in the modes of heavy metal cations or additive complexing heavy metal cations and the like, so that the heavy metals in the leacheate can form directional movement towards the cathode 11 under the action of the repairing electric field. In the electric repairing process, the electric field intensity is 0.5-3.0V/cm. The electric field intensity is lower than 0.5V/cm, the electromigration and electrodialysis flow rate are reduced, so that the heavy metal migration rate is reduced, and the heavy metal removal effect is further influenced; higher current is generated when the voltage is higher than 3.0V/cm, so that more heat is generated to heat soil, the electromigration and electroosmosis processes are influenced, and unnecessary electric energy loss is caused.
When the leaching solution containing heavy metals passes through the adsorbent filling area, a large amount of OH generated by cathode hydrolysis is arranged near the cathode electrode section 11 under the action of an electric field-Heavy metal ion and OH-The insoluble precipitate is adsorbed by the adsorbent, and the residue is collected in the collecting pipe and sucked and discharged by the liquid collecting pump 3, and collected as a recovered liquid in the collecting tank 2.
Collecting the adsorbent adsorbing the heavy metal and then carrying out centralized treatment, or injecting a heavy metal curing agent and/or a stabilizing agent into the adsorbent to fix the heavy metal in the adsorbent material, wherein the adsorbent is reserved in the deep layer of the soil.
Example one
Kaolin is selected as experimental soil, and lead nitrate (Pb (NO) is used3)2) And (4) mixing the experimental soil with the solution to prepare the artificial contaminated lead soil. The artificially contaminated soil is aged and air-dried for 2 weeks, and then collected for later use. After the soil sample is digested by mixed acid, the content of lead in the artificially contaminated soil is measured by ICP-MS, and is 47.4 mg/kg. The volume of the experimental device is 2m multiplied by 0.9m, and the volume weight of the experimental device is 0.8g/cm32880kg of heavy metal contaminated soil. And determining the heavy metal enrichment degree to be 2 according to the required restoration depth (0.9m) and the heavy metal content (47.4mg/kg) of the soil. According to the numerical value of the heavy metal enrichment degree, the soil is divided into 2 layers (the depth of each layer is 45cm) for treatment, 1 layer close to the surface layer of the soil is a leaching treatment area, and the 2 nd layer is an electric treatment area.
The cathode is set as a central electrode, 4 anodes are arranged in a two-dimensional arrangement electric field around the cathode at equal intervals, the interval between the cathode and the anode is 60cm, and the voltage is 120V. The anode is of a columnar structure, the cathode is of a hollow tubular structure, a plurality of through holes are formed in the wall surface of the cathode section, and the hollow tubular cathode is used as a liquid collecting pipe at the same time. The lengths of the anode insulating section and the cathode insulating section are 60cm, and the lengths of the anode conducting section and the cathode conducting section are 45 cm. Coconut shell activated carbon with the particle size of 2mm is arranged around the cathode conductive section to serve as an adsorbent. The inner diameter of the activated carbon adsorbent ring is 10cm, the outer diameter is 20cm, and the height is 45 cm. A spraying device is arranged in the middle of the cathode and the anode, the leacheate is 0.1mol/L citric acid solution, and the dosage of the leacheate is 1150L.
After 240h of repair treatment, the lead removal rate of the leaching treatment area is 73.6%, the lead removal rate near the anode of the electric treatment area reaches 92.0%, the content of the soil Pb in contact with the anode conductive segment is 0, the soil Pb removal rate in the range of radius 25cm with the anode conductive segment as the center exceeds 75%, and the lead removal rate near the cathode is 46.2%. With the increase of the electrokinetic remediation time, the low Pb content region near the anode gradually expands, and Pb in the soil gradually enriches to the adsorbent layer near the cathode. And after the repairing is finished, taking out the adsorbent and carrying out centralized treatment on the adsorbent.
The above description is only an example of the present invention, and is not intended to limit the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. An electrode device can be used for a repairing electric field of heavy metal contaminated soil, and is characterized by comprising a power supply, an anode and a cathode which are respectively connected with the power supply (1), wherein the anode comprises an anode insulating section (6) and an anode electrode section (10), a conductive material is embedded in the anode insulating section, and the power supply (1) and the anode electrode section (10) can be connected to form a conductive path; the cathode comprises a cathode insulation section (4) and a cathode electrode section (11), wherein a conductive material is buried in the cathode insulation section, and the cathode insulation section can be communicated with the power supply (1) and the cathode electrode section (11) to form a conductive path.
2. The system for treating heavy metal contaminated soil in a deep layering manner is characterized by comprising an electrode device, an additive spraying and collecting system and an adsorbent ring (9);
the electrode arrangement comprises at least one anode and at least one cathode, and a power supply (1) connecting the anode and the cathode; the anode comprises an anode insulation section (6) and an anode electrode section (10), wherein a conductive material is buried in the anode insulation section, and the anode insulation section can be connected with the power supply (1) and the anode electrode section (10) to form a conductive path; the cathode comprises a cathode insulation section (4) and a cathode electrode section (11), wherein a conductive material is buried in the cathode insulation section and can be communicated with the power supply (1) and the cathode electrode section (11) to form a conductive path;
the additive spraying and collecting system comprises an additive storage tank (8), a spraying device (5), a liquid collecting pump (3), a liquid collecting tank (2) and a liquid collecting pipe, wherein the additive storage tank (8) is connected with the spraying device (5); the adsorbent ring (9) is arranged around the cathode section (11);
the cathode is of a hollow tubular structure, the wall surface of the cathode electrode section is provided with a plurality of through holes, and the hollow tubular cathode is used as a liquid collecting tube; or the cathode adopts a solid structure, and the liquid collecting pipe is arranged between the cathode and the adsorption ring (9);
an adsorbent filling area is formed between the adsorbent ring (9) and the liquid collecting pipe and used for filling adsorbent, and an inlet of the liquid collecting pump (3) is communicated with the lower part of the liquid collecting pipe.
3. The system for deep stratified treatment of heavy metal contaminated soil according to claim 2, wherein the adsorbent ring (9) is flush with the cathode electrode segments (11).
4. A method for deep layering treatment of heavy metal contaminated soil, which uses the system for deep layering treatment of heavy metal contaminated soil according to any one of claims 2 to 3, wherein the method comprises:
dividing the heavy metal contaminated soil field into a leaching treatment area and an electric treatment area in a deep layering manner according to the heavy metal content of the heavy metal contaminated soil field and the required restoration depth;
electrode devices with corresponding depths are arranged according to the depths of the leaching treatment area and the electric treatment area, so that the lengths of the anode electrode section and the cathode electrode section are equal to the depth of the electric treatment area, and the lengths of the anode insulation section and the cathode insulation section are more than or equal to the depth of the leaching treatment area;
respectively fixing a proper amount of anodes and proper amount of cathodes on the heavy metal contaminated soil field, and enabling the anode insulation sections and the cathode insulation sections to be located within the depth range of the leaching treatment area, and enabling the anode electrode sections and the cathode electrode sections to be located within the depth range of the electric treatment area; an adsorbent ring (9) is arranged around the liquid collecting pipe, so that an adsorbent filling area is formed around the cathode electrode section, and an adsorbent is arranged in the adsorbent filling area; connecting the anode and the cathode with a power supply correspondingly;
arranging the spraying devices on the surface of the leaching area, and enabling the surface of the leaching area to be positioned in the spraying range of the spraying devices (5); the additive solution in the additive storage tank (8) is uniformly sprayed on the heavy metal contaminated soil field through the spraying device (5), the additive solution migrates in the heavy metal contaminated soil field to form a leaching treatment area, and heavy metal compounds in the soil are dissolved and/or desorbed into the additive solution to form leaching solution containing heavy metals; under the action of gravity, the leacheate carries heavy metals to migrate to the deep part of the soil;
when the leaching solution containing the heavy metals enters the soil and reaches the electric treatment area, the power supply is connected, and an electric field is formed between the anode and the cathode, so that the heavy metals in the leaching solution form directional movement towards the cathode under the action of the electric field;
when the leacheate passes through the adsorbent filling area, heavy metals in the leacheate are adsorbed by the adsorbent, and residual liquid enters the liquid collecting pipe to be collected and is sucked and discharged through the liquid collecting pump (3) and is collected into the liquid collecting tank (2) as recovery liquid.
5. The method for deep layering treatment of heavy metal contaminated soil according to claim 4, wherein the electric field intensity of the electrokinetic treatment area is 0.5-3.0V/cm.
6. The method for deeply and hierarchically treating heavy metal contaminated soil according to claim 4, wherein the adsorbent comprises any one or more of activated carbon, biomass semi-coke, zeolite and a porous material made of fly ash.
7. The method for deep layering of heavy metal contaminated soil according to claim 4, wherein the additive solution comprises any one or more of citric acid, oxalic acid, malic acid, tartaric acid, acetic acid, ethylenediaminetetraacetic acid.
8. The method for deep layering treatment of heavy metal contaminated soil according to claim 4, wherein the adsorbent with heavy metals adsorbed in the adsorbent filling area is collected from the soil and then subjected to centralized treatment.
9. The method for deep layering treatment of heavy metal contaminated soil according to claim 4, wherein a heavy metal curing agent and/or a stabilizing agent is injected into the adsorbent filling area to fix the heavy metal in the adsorbent material, and the adsorbent with the fixed heavy metal is retained in the deep soil layer.
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