Method and device for treating soil heavy metal pollutants by electroosmosis technology

Abstract

The invention discloses a method and a device for treating soil heavy metal pollutants by an electroosmosis technology, and relates to the technical field of soil pollution treatment and remediation, and the method comprises the following steps: constructing an electroosmosis system, a liquid injection system and a pumping drainage system; liquid injection and pumping drainage are conducted, electroosmosis enhancer liquid medicine is injected into the soil, and meanwhile the liquid is pumped drainage till the concentration of the electroosmosis enhancer in the pumped drainage liquid reaches the preset requirement; soaking and electroosmosis are carried out; sampling detection is conducted, and liquid pumping sampling is conducted on the soil in the to-be-treated area till the pollutant residual concentration meets the preset requirement; water injection and pumping drainage are conducted, clear water is injected into the soil, meanwhile, liquid is pumped drainage, and soil treatment is finished until the concentration of the electroosmosis enhancer in the pumped drainage liquid is smaller than or equal to the preset concentration limit value. According to the method, a proper amount of electroosmosis enhancer liquid medicine is injected, heavy metal pollutants are dissociated through the electroosmosis effect and pumped and discharged to the hazardous waste pool, and heavy metal in soil is efficiently and reliably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of soil pollution control and remediation, and specifically to a method and device for treating heavy metal pollutants in soil using electroosmosis technology. Background Art

[0002] Early electroosmosis applications used expensive metal electrodes, which were also prone to corrosion and could not meet the electroosmosis duration requirements of engineering applications. Consequently, this early electroosmosis technology struggled to gain widespread adoption.

[0003] To address the issue of electrode corrosion, some researchers have developed electro-osmotic drainage consolidation methods using EKG (electric geosynthetics) materials into "electric plastic drainage boards" and "electro-osmotic electrode tubes." The EKG electrode tube core features axially grooved outer walls, drainage holes drilled into the tube walls, and copper wire embedded axially within the tube walls. The EKG electro-osmotic drainage board is threaded with copper wire, and the core is wrapped with a conductive geotextile filter membrane. This electro-osmotic technology using EKG materials has been widely used in treating industrial sludge, riverbed sediment, blown-fill mud, and mine tailings.

[0004] Engineering practice has shown that while the aforementioned electroosmosis technology can achieve drainage and consolidation, it is less effective in removing heavy metals, particularly when the soil contains high levels of heavy metals. This method struggles to meet regulatory requirements. These difficulties stem from the fact that some heavy metals in the soil are adsorbed on the surface of soil particles, where their strong adsorption forces prevent electroosmosis from dislodging them. Consequently, electroosmosis alone cannot effectively remove heavy metal contaminants from the soil to regulatory levels.

[0005] Therefore, it is necessary to develop a new electroosmosis technology method and device that is easy to construct, simple to operate, and combines electrode plates (electroosmosis drainage plates) and electrode tubes to quickly and effectively remove pollutants (such as heavy metal cations or anion groups containing heavy metals) in the soil. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the above-mentioned background technology and provide a new electroosmosis technology method and device that is easy to construct, simple to operate, combines electrode plates and electrode tubes, and can quickly and effectively remove heavy metal pollutants in the soil.

[0007] The technical solution of the present invention is: a method for treating heavy metal pollutants in soil using electroosmosis technology, comprising the following steps: Construct electroosmosis system, injection system and pumping system; Performing liquid injection and drainage, specifically including: injecting an electroosmosis enhancer solution into the soil of the to-be-treated area through the liquid injection system, and simultaneously draining the liquid from the soil through the drainage system; when the injection volume of the electroosmosis enhancer solution approaches a preset volume, detecting the electroosmosis enhancer concentration in the drained liquid and determining whether it meets the preset requirements; if so, proceeding to the next step of soaking and electroosmosis; if not, continuing the liquid injection and drainage until the preset requirements are met; The soaking and electroosmosis are carried out, specifically comprising: soaking the soil in the electroosmosis enhancer solution, and after the soaking is completed, turning on the power supply to energize the electroosmosis system to perform the electroosmosis treatment; Sampling and testing, specifically including: extracting liquid samples from the soil in the treatment area, testing the residual concentration of pollutants and determining whether it meets the preset requirements. If so, proceed to the next step of water injection and drainage; if not, repeat the previous step of immersion and electroosmosis until the residual concentration of pollutants meets the preset requirements; Carry out water injection and drainage, specifically including: injecting clean water into the soil in the area to be treated through the liquid injection system, and at the same time draining the liquid through the drainage system until the concentration of the electroosmosis enhancer in the drained liquid is ≤ the preset concentration limit, and the soil treatment is completed.

[0008] A preferred method for treating heavy metal pollutants in soil using electroosmosis technology, wherein the electroosmosis system includes multiple rows of electrode plates and multiple rows of electrode tubes inserted into the soil layer of the area to be treated and arranged alternately at intervals, as well as a power supply device dedicated to electroosmosis, wherein the electrode plates and electrode tubes are electrically connected to the two poles of the power supply device dedicated to electroosmosis.

[0009] A further method of using electroosmosis technology to treat heavy metal pollutants in soil is that when the soil pollutants are heavy metal cations, the electrode plates and electrode tubes are electrically connected to the negative and positive poles of the electroosmosis-specific power supply equipment respectively; when the soil pollutants are heavy metal anion groups, the electrode plates and electrode tubes are electrically connected to the positive and negative poles of the electroosmosis-specific power supply equipment respectively.

[0010] A preferred method for treating heavy metal pollutants in soil using electroosmosis technology, wherein the injection system includes an electroosmosis enhancement liquid pool and an injection pump arranged on the outside side of the area to be treated, and a liquid infusion pipeline whose inlet is connected to the electroosmosis enhancement liquid pool, and the liquid infusion pipeline is connected to the top of the electrode tube on the surface of the area to be treated for injecting liquid into the soil layer.

[0011] A further method for treating heavy metal pollutants in soil using electroosmosis technology is provided, wherein the drainage system includes a hazardous waste liquid pool and a drainage pump arranged on the other side of the area to be treated outside the area to be treated, and a drainage pipe whose outlet is connected to the hazardous waste liquid pool. The drainage pipe is connected to the top of the electrode plate on the surface of the area to be treated, and the surface of the area to be treated is sequentially laid with a woven geotextile and a sealing membrane.

[0012] A further method of treating heavy metal pollutants in soil using electroosmosis technology is described. In the injection and drainage steps, an electroosmosis enhancer solution with an original concentration of C0 is injected into the soil of the treated area through the injection system, and at the same time, the liquid in the soil is drained through the drainage system. The preset requirement is that the electroosmosis enhancer concentration C1 in the drained liquid is ≥60% C0.

[0013] A further method of treating heavy metal pollutants in soil using electroosmosis technology is to detect the concentration of the electroosmosis enhancer in the liquid to be pumped out when the injection volume of the electroosmosis enhancer solution approaches a preset volume V0 during the injection and drainage steps. V0 is 1.2 to 1.5 times the total volume of the soil pores to be repaired in the treatment area.

[0014] A preferred method for treating heavy metal pollutants in soil using electroosmosis technology, wherein in the soaking and electroosmosis steps, the potential difference between the positive and negative electrodes of the electroosmosis treatment is 20~60V, the first soaking time is the preset time T0, T0 is 7~10 days, and the first electroosmosis time is the preset time T1, T1 is 3~5 days.

[0015] When repeated soaking and electroosmosis are required in the sampling and testing steps, the subsequent soaking time is T0 / 3~T0, and the subsequent electroosmosis time is T1 / 3~T1.

[0016] In a further method for treating heavy metal pollutants in soil using electroosmosis technology, in the water injection and drainage steps, the preset concentration limit is 5%C0~10%C0.

[0017] The present invention also provides a device for use in any of the above methods for treating heavy metal contaminants in soil using electroosmosis technology, comprising: An electroosmosis system, comprising electrode plates and electrode tubes inserted into the soil layer of the area to be treated, and a dedicated power supply for electroosmosis, wherein the electrode plates and electrode tubes are arranged in rows with intervals, and the rows of electrode plates and electrode tubes are arranged alternately with intervals, and the electrode plates and electrode tubes are electrically connected to the two poles of the dedicated power supply for electroosmosis; An injection system comprising an electroosmosis enhancement liquid pool and an injection pump disposed outside the area to be treated, and a liquid delivery pipeline having an inlet connected to the electroosmosis enhancement liquid pool, the liquid delivery pipeline being connected to the top of the electrode tube at the surface of the area to be treated for injecting liquid into the soil layer; The pumping and drainage system includes a hazardous waste liquid pool and a pumping and drainage pump arranged on the other side of the area to be treated, and a drainage pipe whose outlet is connected to the hazardous waste liquid pool. The drainage pipe is connected to the top of the electrode plate on the surface of the area to be treated. The surface of the area to be treated is laid with woven geotextile and sealing membrane in sequence above the infusion pipe and the drainage pipe.

[0018] A preferred method for treating heavy metal contaminants in soil using electroosmosis technology uses a device in which a plurality of electrode plates are arranged in a row at a spacing d in the longitudinal direction of the area to be treated, a plurality of electrode tubes are arranged in a row at a spacing d in the longitudinal direction of the area to be treated, and the width of each electrode plate is arranged in the longitudinal direction of the area to be treated; Multiple rows of electrode plates and multiple rows of electrode tubes are arranged alternately at intervals d transversely along the area to be processed, and the electrode plates and electrode tubes corresponding to adjacent rows are aligned or staggered transversely.

[0019] A water outlet is provided on the electrode tube, and the electrode tube is wrapped with a first filter cloth. A foot cover with an open upper end is provided at the bottom, and the foot cover wraps the lower end of the filter cloth. The upper end of each electrode tube is connected to a first vertical pipe through a clamp, and a three-way joint is provided at the upper end of the first vertical pipe to communicate with the infusion pipeline.

[0020] A more preferred device for treating heavy metal pollutants in soil using electroosmosis technology is that the three-way connector is a T-shaped structure, the lower port is connected to the first vertical pipe, and the two upper ports are connected and arranged on the liquid infusion pipeline.

[0021] The preferred method for treating heavy metal pollutants in soil using electroosmosis technology uses a device, wherein the infusion pipeline includes a front-pump infusion pipe connected to the inlet of the injection pump, and a post-pump infusion pipe connected to the outlet of the injection pump, and the post-pump infusion pipe is connected to the top of the electrode tube on the surface of the area to be treated.

[0022] The preferred device used in the method of treating heavy metal pollutants in soil using electroosmosis technology is that the drainage pipe includes a front-pump drainage pipe connected to the inlet of the pump and a rear-pump drainage pipe connected to the outlet of the pump, and the top of the electrode plate is wrapped and tied to the front-pump drainage pipe on the surface of the area to be treated.

[0023] The preferred device used in the method for treating heavy metal pollutants in soil using electroosmosis technology is that the infusion pipeline is a water-impermeable PVC steel wire hose, and the drainage pipeline is a water-permeable PVC steel wire hose with a second filter cloth wrapped on its surface.

[0024] The preferred device used in the method for treating heavy metal pollutants in soil using electroosmosis technology is provided with a film outlet on the sealing membrane, and the liquid delivery pipeline and the drainage pipeline are sealed and pass through the sealing membrane via the film outlet.

[0025] The preferred device used in the method for treating heavy metal pollutants in soil using electroosmosis technology is that a film pressing trench is opened around the area to be treated, and soil is filled and compacted in the film pressing trench around the sealing membrane.

[0026] The beneficial effects of the present invention are: (1) The treatment method of the present invention can quickly and effectively remove pollutants in the soil, such as heavy metal cations (such as Cd 2+ , Pb 2+、Zn 2+ 、Cu 2+ 、Ni 2+ etc.), and heavy metal anion groups (such as heavy metal anion chromate CrO4 2- ), achieving soil purification in a relatively short period of time. Depending on the contaminants in the soil, an electroosmotic enhancer is selected that can efficiently separate and remove them. The method of the present invention can treat contaminated soil layers of varying thicknesses, effectively reaching depths of 30m or even greater.

[0027] (2) In the treatment method of the present invention, a hollow electrode tube is placed in the soil during the construction of the injection system. The electroosmosis enhancer solution is injected into the deep soil through the electrode tube. The electroosmosis enhancer solution interacts with the heavy metal pollutants, reducing their adsorption force on soil particles. The heavy metal ions are liberated through the electric field formed by the electrode tube and the electrode plate, and condensed around the electrode plate. The hazardous waste liquid containing pollutants is discharged to an external hazardous waste pool through a pump. This method of injecting appropriate electroosmosis enhancer solution, liberating pollutants through electroosmosis, and pumping them to the hazardous waste pool reliably and efficiently removes heavy metal pollutants from the soil.

[0028] (3) The soaking and electroosmosis steps of the treatment method of the present invention adopt the process of letting the enhancer solution soak in the soil, which can fully react the pollutants with the electroosmosis enhancer without requiring a large amount of enhancer solution, thus significantly reducing the removal cost. Select the appropriate electroosmosis enhancer according to the pollutants in the soil: if the pollutants are mainly Pb 2+ 、Cu 2+ , and the soil is acidic, sodium hydroxide or sodium carbonate can be selected as the electroosmotic enhancer; if the pollutant is mainly Cd 2+ , Pb 2+ 、Zn 2+ If the soil is alkaline, hydrochloric acid or nitric acid can be used as an electroosmotic enhancer; if the main pollutant is Cd 2+ 、Ni 2+ For heavy metals such as iodine, sodium chloride or ammonium chloride can be selected as electroosmotic enhancing agents.

[0029] (4) The water injection and drainage steps of the treatment method of the present invention inject clean water to displace and drain the heavy metal-containing enhancer solution (hazardous waste liquid). Therefore, the enhancer solution originally injected into the soil is also removed, thereby achieving a very ideal soil purification effect.

[0030] (5) In the treatment method of the present invention, since the electroosmotic enhancer solution is eventually replaced and discharged by clean water, there is no need to worry about the enhancer solution remaining in the soil causing soil acidification, excessive soil salt content, and groundwater pollution caused by difficult degradation. The choice of the type of agent is increased. For example, for Cd in the soil 2+ , Pb2+ 、Zn 2+ For heavy metals such as chlorinated metals, inorganic acids with extremely low cost and good desorption effect can be selected as electroosmosis enhancement agents for treatment. There is no need to worry about its impact on soil acidification. While achieving good heavy metal removal effect, it also greatly reduces the project cost.

[0031] (6) In the device of the present invention, the alternating arrangement of each row of electrode plates and each row of electrode tubes in the electroosmosis system can make the positive and negative electrodes correspond to each other, maintain the electric field effect, and gather the pollutant ions near the electrode plates; the electrode plates and electrode tubes in adjacent rows are arranged in a horizontally aligned or staggered arrangement. When the arrangement is staggered, the electrode tubes are more efficient in injecting liquid into the soil layer because the adjacent electrode plates have less obstruction to the injection of liquid into the electrode tubes.

[0032] (7) The electrode tube of the electroosmosis system of the present invention is a hollow tube made of EKG material with water outlet holes on all sides and wrapped with filter cloth on the outside. The length of the electrode tube is determined according to the thickness of the soil layer to be treated and can be up to 30m or longer, making it applicable to areas to be treated at various depths. A first vertical pipe (PVC pipe) is provided at the upper end of the electrode tube to quickly connect it to the infusion pipeline.

[0033] (8) The electroosmotic enhancement liquid pool of the injection system of the present invention can be excavated on site as needed and sealed with a polyethylene film to facilitate storage and use of sufficient electroosmotic enhancement liquid. The injection pump can be a reciprocating pump to provide sufficient injection pressure, and the infusion tube can be a PVC steel wire hose, which has high strength and is easy to adapt to ground subsidence.

[0034] (9) In the drainage system of the present invention, a woven geotextile and a sealing membrane are provided above the ground surface. The purpose of providing the woven geotextile is to protect the sealing membrane from being punctured by debris such as plate heads and wire heads. The sealing membrane is used to cover the entire treatment area and is pressed into the film pressing groove around the area to ensure that the vacuum pressure under the membrane meets the requirements during the drainage process.

[0035] The present invention can quickly and effectively remove heavy metal pollutants in the soil through the cooperation of the liquid injection system, the electroosmosis system and the pumping system, thereby achieving soil purification in a relatively short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Flow chart of the method of the present invention Figure 2 This is the overall schematic diagram of the device for this application (vertical) Figure 3 This is a schematic diagram of the liquid flow direction when the device of this application is working Figure 4 Electrode tube structure diagram Figure 5 Schematic diagram of the electrode plate and electrode tube plane layout (aligned layout) Figure 6 Schematic diagram of the planar layout of electrode plates and electrode tubes (staggered arrangement) Among them: 1-area to be treated; 2-electrode plate 3-electrode tube (31-water outlet 32-first filter cloth 33-foot cover) 4-hazardous waste liquid pool 5-liquid injection pump 6-infusion pipe before pump 7-infusion pipe after pump 8-film pressing groove 9-drainage pipe before pump 10-drainage pipe after pump 11-woven geotextile 12-sealing membrane 13-first wire 14-second wire 15-pumping pump 16-special power supply equipment for electroosmosis 17-electroosmosis enhanced liquid pool 18-clamp 19-first vertical pipe 20-tee joint. DETAILED DESCRIPTION

[0037] The following will be clearly and completely described with reference to the embodiments of the present invention and the technical effects produced, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without paying creative work all fall within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased commercially.

[0038] The following specific examples further illustrate the present invention in detail.

[0039] like Figure 2-6 As shown, the present invention provides an apparatus for treating heavy metal contaminants in soil using electroosmosis technology, comprising an electroosmosis system, an injection system, and a drainage system. The interaction of these systems allows for rapid and effective removal of heavy metal contaminants from contaminated soil, achieving soil purification in a relatively short period of time.

[0040] The electroosmosis system includes electrode plates 2 and electrode tubes 3 inserted into the soil layer of the area to be treated 1. Multiple electrode plates 2 and multiple electrode tubes 3 are arranged in rows at intervals, and multiple rows of electrode plates 2 and multiple rows of electrode tubes 3 are arranged alternately at intervals. The electroosmosis system also includes a power supply device 16 dedicated to electroosmosis. All electrode plates 2 are electrically connected to one of the positive and negative poles of the power supply device 16 dedicated to electroosmosis via a first wire 13, and all electrode tubes 3 are electrically connected to the other of the positive and negative poles of the power supply device 16 dedicated to electroosmosis via a second wire 14. The connection between the electrode plates 2 and the electrode tubes 3 and the positive and negative poles is determined by the substance to be removed: if heavy metal ions (such as Cd) are to be removed, 2+ , Pb 2+ 、Zn 2+ 、Cu 2+ 、Ni 2+When the electrode tube 3 is connected to the positive electrode of the electroosmosis power supply device 16, the electrode plate 2 is connected to the negative electrode of the electroosmosis power supply device 16; to remove heavy metal anion groups (such as heavy metal anion chromate CrO4 2- ), the electrode tube 3 is connected to the negative pole of the electroosmosis power supply device 16, and the electrode plate 2 is connected to the positive pole of the electroosmosis power supply device 16. The voltage range of the electroosmosis power supply device 16 is 20V~60V.

[0041] In a preferred example, one of the horizontal directions of the area to be treated is the longitudinal direction, and the other horizontal direction perpendicular to the longitudinal direction is the transverse direction. The specific arrangement of the electrode tube 3 and the electrode plate 2 is as follows: multiple electrode plates 2 are arranged in rows along the longitudinal direction of the area to be treated at a spacing d, and multiple electrode tubes 3 are arranged in rows along the longitudinal direction of the area to be treated at a spacing d. The width of all electrode plates 2 is arranged along the longitudinal direction of the area to be treated. At this time, the length direction of each electrode plate 2 is vertical, the thickness direction is transverse to the area to be treated, and the width direction is longitudinal to the area to be treated.

[0042] In a preferred embodiment, multiple rows of electrode plates 2 and multiple rows of electrode tubes 3 are arranged alternately at a spacing d across the horizontal direction of the treatment area. Adjacent rows of electrode plates 2 and electrode tubes 3 are arranged transversely aligned or staggered, and the spacing d ranges from 0.8 to 1.5 m. In a preferred embodiment, the number of electrode plates 2 and electrode tubes 3 in each row is the same, the number of rows of electrode plates 2 is the same as the number of rows of electrode tubes 3, and all rows of electrode plates 2 and electrode tubes 3 are arranged transversely aligned.

[0043] In a preferred embodiment, the area to be processed is square, with the width direction as the longitudinal direction, such as Figure 5-6 Middle and lower direction; take the length direction as horizontal direction, such as Figure 5-6 The six electrode plates 2 are arranged in a row at a spacing d in the longitudinal direction, and the six electrode tubes 3 are arranged in a row at a spacing d in the longitudinal direction. The three rows of electrode plates 2 and the three rows of electrode tubes 3 are arranged alternately at a spacing d in the transverse direction. The electrode plates 2 and electrode tubes 3 corresponding to adjacent rows can be arranged in a transversely aligned manner, such as Figure 5 As shown; the electrode plates 2 and electrode tubes 3 corresponding to adjacent rows can also be arranged in a transverse staggered manner, such as Figure 6 As shown, the staggered spacing is d / 2, that is, the longitudinal spacing between the electrode plates 2 and the electrode tubes 3 corresponding to adjacent rows is d / 2. At this time, there is no electrode plate 2 blocking the lateral sides of each electrode tube 3. Therefore, when the arrangement is staggered, the adjacent electrode plates 2 have less obstruction to the injection of the electrode tubes 3, and the electrode tubes are more efficient in injecting liquid into the soil layer.

[0044] The electrode tubes 3 are provided with water outlets 31. A first filter cloth 32 surrounds the electrode tubes 3, and a foot cover 33 with an open top is placed at the bottom, enclosing the lower end of the first filter cloth 32. The top end of each electrode tube 3 is connected to a first riser pipe 19 via a clamp 18. A tee connector 20 is provided at the top end of the first riser pipe 19, connecting it to the infusion pipeline. The tee connector 20 is a T-shaped structure, with its lower end connected to the first riser pipe 19 and its upper ends connected to the infusion pipeline. The electrode tubes 3 are hollow tubes made of EKG material. The water outlets 31 are spaced circumferentially along the length of the tube. In a preferred embodiment, the electrode tubes 3 generally have an outer diameter of 30 mm and are provided with grooves along the length of the tube. The grooves are spaced circumferentially, with the water outlets 31 located within the grooves. The length of the electrode tubes 3 is determined by the thickness of the soil layer to be treated. The first riser pipe 19 is preferably a DN40 PVC pipe with an outer diameter of 40 mm.

[0045] The injection system includes an electroosmosis enhancement liquid pool 17 and an injection pump 5 arranged on the side outside the area to be treated 1, as well as a liquid infusion pipeline whose inlet is connected to the electroosmosis enhancement liquid pool 17. The electroosmosis enhancement liquid pool 17 is excavated on site as needed and sealed with a polyethylene film. The liquid infusion pipeline is connected to the top of the electrode tube 3 on the surface of the area to be treated 1 for injecting liquid into the soil layer. In a preferred embodiment, the injection pump 5 can be a reciprocating pump with a rated pressure of 2.0~3.0Mpa. The liquid infusion pipeline includes a pump front liquid infusion pipe 6 connected to the inlet of the injection pump 5 and a pump rear liquid infusion pipe 7 connected to the outlet of the injection pump 5. The pump rear liquid infusion pipe 7 is connected to the top of the electrode tube 3 on the surface of the area to be treated 1 through a three-way connector 20 and a first vertical pipe 19. The pump rear liquid infusion pipe 7 is a water-tight PVC steel wire hose, preferably a DN25 PVC steel wire hose with an outer diameter of 25mm.

[0046] The pumping and drainage system includes a hazardous waste liquid pool 4 and a pumping and drainage pump 15, which are arranged on the other side of the area to be treated 1, and a drainage pipe whose outlet is connected to the hazardous waste liquid pool 4. The hazardous waste liquid pool 4 is excavated on site as needed and sealed with a polyethylene film. The drainage pipe is connected to the top of the electrode plate 2 on the surface of the area to be treated 1. A woven geotextile 11 and a sealing film 12 are laid upward in sequence above the infusion pipe and the drainage pipe on the surface of the area to be treated 1. In a preferred embodiment, the pumping and drainage pump 15 is preferably a water-gas separation pump, and the number of pumping and drainage pumps can be set according to its own power and the area of ​​the area to be treated. The drainage pipe includes a front-pump drainage pipe 9 connected to the inlet of the pumping and drainage pump 15 and a rear-pump drainage pipe 10 connected to the outlet of the pumping and drainage pump 15. The top of the electrode plate 2 is wrapped and tied to the front-pump drainage pipe 9 on the surface of the area to be treated 1. The front-pump drainage pipe 9 is a water-permeable PVC steel wire hose and the surface is wrapped with a second filter cloth.

[0047] The sealing membrane 12 is equipped with an outlet (not shown). The post-pump infusion line 7 and the pre-pump drainage line 9 are both sealed through the membrane outlet and pass through the sealing membrane 12. A membrane compression groove 8 is defined around the treatment area 1. The membrane 12 is filled with compacted soil to ensure that the required vacuum pressure is maintained under the membrane during the extraction process. For heavy metal removal only, the sub-membrane vacuum pressure ranges from 20 to 50 kPa. For simultaneous removal of heavy metals and improvement of soil mechanical properties, the sub-membrane vacuum pressure ranges from 60 to 80 kPa. The sealing membrane 12 can be made of polyethylene film with a thickness of 0.12 to 0.16 mm.

[0048] In a preferred embodiment, in order to prevent the liquid from spreading, the area to be treated 1 and the surrounding area can be separated by an isolation wall or isolation steel sheet piles.

[0049] Example 2 like Figure 1 As shown, the method of treating heavy metal pollutants in soil using electroosmosis technology of the present invention is carried out in the following steps. Before on-site construction, the preparatory work is completed first: ① According to the specific situation of heavy metals in the soil, select appropriate electroosmosis enhancer. For heavy metals in the soil, mainly Cd 2+ 、Ni 2+ etc., ammonium chloride can be selected as the electroosmotic enhancing agent; ② Determine the original concentration C0 of the electroosmotic enhancer solution and the intended immersion time T0 through batch testing; ③ Calculate the total amount of electroosmosis enhancer solution V0 required. V0 is 1.2-1.5 times the total pore volume of the soil to be repaired in the treatment area 1.

[0050] S1. Construct the electroosmosis system, injection system and pumping system according to the device structure of Example 1. 1) Construction of electrode plate 2: According to the plane layout required by the design (multiple rows of electrode plates 2 and multiple rows of electrode tubes 3 are arranged alternately), the electrode plate 2 is installed using a plate inserter, and the depth of the electrode plate 2 buried in the soil is 8~12m.

[0051] 2) Installing the Electrode Tube 3: Following the design layout (alternating rows of electrode plates 2 and electrode tubes 3), use a tube insertion machine to insert the electrode tube 3 to the same depth as the lower end of the electrode plates 2. Before insertion, the electrode tube 3 is wrapped with the first filter cloth 32, fitted with foot covers 33 at the bottom, and connected to the upper first riser 19. The wires are then extended. After the electrode tube 3 is inserted, the wires are brought to the surface, and the opening is then backfilled with soil to ensure that the electrode tube 3 is not loose.

[0052] 3) Excavate an electroosmosis enhanced liquid pool 17 on one side outside the area to be treated 1 and install a liquid injection pump 5; excavate a hazardous waste liquid pool 4 on the other side outside the area to be treated 1 and install a drainage pump 15; and install a dedicated electroosmosis power supply device 16 outside the area to be treated 1.

[0053] 4) Connection of the injection system: A post-pump infusion tube 7 is laid on the ground of the area to be treated 1, one end of which is connected to the electrode tube 3, and the other end is connected to the outlet of the injection pump 5 through the sealing membrane 12 through the membrane outlet. The inlet of the injection pump 5 is connected to the outlet of the front-pump infusion tube 6, and the inlet of the front infusion tube 6 is connected to the electroosmosis enhancement liquid pool 17.

[0054] 5) Electroosmosis System Connections: A first wire 13 connects all electrode plates 2, and a second wire 14 connects all electrode tubes 3. Both first and second wires 13, 14 are led out of the field through the bottom of the film-forming trench 8 and connected to a dedicated electroosmosis power supply 16. The first wire 13 connects to the negative electrode, and the second wire 14 connects to the positive electrode.

[0055] 6) Connection of the Pumping and Drainage System: Lay the pre-pump drainage pipe 9 on the ground in the treatment area 1. Connect the top of the electrode plate 2 to the pre-pump drainage pipe 9 using a winding method. The pre-pump drainage pipe 9 passes through the membrane outlet and through the sealing membrane 12 to the inlet of the pumping and drainage pump 15. The outlet of the pumping and drainage pump 15 is connected to the inlet of the post-pump drainage pipe 10. The outlet of the post-pump drainage pipe 10 is connected to the hazardous waste liquid tank 4.

[0056] 7) Laying the sealing membrane 12: A membrane pressing trench 8 has been dug around the area to be treated 1. A layer of woven geotextile 11 is laid on the ground first, and then the sealing membrane 12 is laid. The edge of the sealing membrane 12 is stepped into the membrane pressing trench 8 and backfilled and compacted.

[0057] S2, perform injection and drainage Start the injection pump 5 and inject the electroosmosis enhancer solution (ammonium chloride solution) with the original concentration C0 (C0=0.1~0.3mol / L) into the soil of the to-be-treated area 1 through the electrode tube 3 at an injection pressure of 20~50kPa. Simultaneously, start the drainage pump 15 to drain the original pore fluid in the soil at a sub-membrane vacuum pressure of 20~50kPa. When the amount of the injected enhancer solution is close to the preset total amount V0, check the electroosmosis enhancer concentration C1 in the drained fluid. When the electroosmosis enhancer concentration meets the preset requirement C1≥60%·C0, stop the injection pump 5 and the drainage pump 15. When C1<60%·C0, continue the injection and drainage until the preset requirement is met.

[0058] S3. Soaking and electroosmosis When the pump is stopped, the soil is left to soak in the electroosmosis enhancer solution. The initial soaking time is the preset time T0 (T0=7~10 days). After the soaking is completed, the electroosmosis special power supply device 16 is turned on, and the electrode plate 2 and the electrode tube 3 are energized for electroosmosis treatment. The potential difference is 20~60V. The initial power-on time is the preset time T1 (T1=3~5 days), and the power is turned off to stop the electroosmosis.

[0059] S4. Take samples for testing Start the drainage pump 15 to extract liquid samples from the soil in the treatment area, detect the residual concentration of pollutants in the drainage liquid and determine whether it meets the preset requirements (the preset requirements can refer to relevant industry regulations or be set according to needs, such as Cd 2+ ≤1.5mg / kg), if yes, proceed to the next step; if not, repeat the previous step of soaking and electroosmosis, continue soaking time T0 / 3 and electroosmosis time T1, until the residual concentration of pollutants meets the preset requirements.

[0060] S5. Water injection and drainage The injection pump 5 is started to inject clean water into the soil in the treatment area (injection pressure 20~50kPa), and the drainage pump 15 is started at the same time (drainage vacuum pressure 20~50kPa). The electroosmosis enhancer concentration of the drainage liquid is detected until the electroosmosis enhancer concentration is ≤ the preset concentration limit. The preset concentration limit ranges from 5%·C0 to 10%·C0, and is 5%·C0 in this embodiment. That is, when the electroosmosis enhancer concentration of the drainage liquid is ≤5%·C0, the water injection and drainage are stopped, and the soil treatment is completed.

Claims

1. A method for treating heavy metal pollutants in soil using electroosmosis technology, characterized in that: The following steps are involved: Construct electroosmosis system, injection system and pumping system; Performing liquid injection and drainage, specifically including: injecting an electroosmosis enhancer solution into the soil of the to-be-treated area through the liquid injection system, and simultaneously draining the liquid from the soil through the drainage system; when the injection volume of the electroosmosis enhancer solution approaches a preset volume, detecting the electroosmosis enhancer concentration in the drained liquid and determining whether it meets the preset requirements; if so, proceeding to the next step of soaking and electroosmosis; if not, continuing the liquid injection and drainage until the preset requirements are met; The soaking and electroosmosis are carried out, specifically comprising: soaking the soil in the electroosmosis enhancer solution, and after the soaking is completed, turning on the power supply to energize the electroosmosis system to perform the electroosmosis treatment; Sampling and testing, specifically including: extracting liquid samples from the soil in the treatment area, testing the residual concentration of pollutants and determining whether it meets the preset requirements. If so, proceed to the next step of water injection and drainage; if not, repeat the previous step of immersion and electroosmosis until the residual concentration of pollutants meets the preset requirements; Carry out water injection and drainage, specifically including: injecting clean water into the soil in the area to be treated through the liquid injection system, and at the same time draining the liquid through the drainage system until the concentration of the electroosmosis enhancer in the drained liquid is ≤ the preset concentration limit, and the soil treatment is completed.

2. The method for treating heavy metal contaminants in soil using electroosmosis technology according to claim 1, wherein: The electroosmosis system comprises multiple rows of electrode plates (2) and multiple rows of electrode tubes (3) inserted into the soil layer of the area to be treated (1) and arranged alternately, and a power supply device (16) dedicated to electroosmosis. The electrode plates (2) and the electrode tubes (3) are electrically connected to the two poles of the power supply device (16) dedicated to electroosmosis.

3. The method for treating heavy metal contaminants in soil using electroosmosis technology according to claim 2, characterized in that: The injection system comprises an electroosmosis enhancement liquid pool (17) and an injection pump (5) arranged on an off-site side of the area to be treated (1), and a liquid delivery pipeline whose inlet is connected to the electroosmosis enhancement liquid pool (17); the liquid delivery pipeline is connected to the top of the electrode tube (3) on the surface of the area to be treated (1) for injecting liquid into the soil layer.

4. The method for treating heavy metal contaminants in soil using electroosmosis technology according to claim 3, characterized in that: The pumping and drainage system comprises a hazardous waste liquid pool (4) and a pumping and drainage pump (15) arranged on the other side of the area to be treated (1) outside the site, and a drainage pipe whose outlet is connected to the hazardous waste liquid pool (4). The drainage pipe is connected to the top of the electrode plate (2) on the surface of the area to be treated (1). The surface of the area to be treated (1) is sequentially paved with a woven geotextile (11) and a sealing membrane (12).

5. The method for treating heavy metal contaminants in soil using electroosmosis technology according to claim 1, wherein: In the injection and drainage steps, an electroosmosis enhancer solution with an original concentration of C0 is injected into the soil of the treated area through the injection system, and the liquid in the soil is simultaneously drained through the drainage system. The preset requirement is that the electroosmosis enhancer concentration C1 in the drained liquid is ≥60% C0.

6. The method for treating heavy metal contaminants in soil using electroosmosis technology according to claim 1, wherein: In the soaking and electroosmosis steps, the potential difference between the positive and negative electrodes of the electroosmosis treatment is 20-60V, the first soaking time is the preset time T0, T0 is 7-10 days, and the first electroosmosis time is the preset time T1, T1 is 3-5 days.

7. The method for treating heavy metal contaminants in soil using electroosmosis technology according to claim 6, characterized in that: When repeated soaking and electroosmosis are required in the sampling and testing steps, the subsequent soaking time is T0 / 3~T0, and the electroosmosis time is T1 / 3~T1.

8. The method for treating heavy metal contaminants in soil using electroosmosis technology according to claim 5, characterized in that: In the water injection and pumping steps, the preset concentration limit is 5%C0~10%C0.

9. A device for treating heavy metal contaminants in soil using electroosmosis technology as claimed in any one of claims 1 to 8, characterized in that: include: An electroosmosis system, comprising an electrode plate (2) and an electrode tube (3) inserted into a soil layer of a to-be-treated area (1), and a dedicated electroosmosis power supply device (16), wherein a plurality of electrode plates (2) and a plurality of electrode tubes (3) are arranged in rows at intervals, and the plurality of rows of electrode plates (2) and the plurality of rows of electrode tubes (3) are arranged alternately at intervals, and the electrode plates (2) and the electrode tubes (3) are electrically connected to two poles of the dedicated electroosmosis power supply device (16); A liquid injection system, the liquid injection system comprising an electroosmosis enhancement liquid pool (17) and a liquid injection pump (5) arranged on an off-site side of the area to be treated (1), and a liquid delivery pipeline whose inlet is connected to the electroosmosis enhancement liquid pool (17), the liquid delivery pipeline being connected to the top of the electrode tube (3) on the surface of the area to be treated (1) for injecting liquid into the soil layer; A pumping and drainage system, comprising a hazardous waste liquid pool (4) and a pumping and drainage pump (15) arranged on the other side of the area to be treated (1), and a drainage pipe whose outlet is connected to the hazardous waste liquid pool (4), wherein the drainage pipe is connected to the top of the electrode plate (2) on the surface of the area to be treated (1), and a woven geotextile (11) and a sealing membrane (12) are laid upwardly in sequence above the liquid delivery pipe and the drainage pipe on the surface of the area to be treated (1).

10. The device used in the method for treating heavy metal pollutants in soil using electroosmosis technology according to claim 9, characterized in that: A plurality of electrode plates (2) are arranged in rows along the longitudinal direction of the area to be treated at a spacing d, and a plurality of electrode tubes (3) are arranged in rows along the longitudinal direction of the area to be treated at a spacing d, and the width of each electrode plate (2) is arranged along the longitudinal direction of the area to be treated; The multiple rows of electrode plates (2) and the multiple rows of electrode tubes (3) are arranged alternately at intervals d transversely along the area to be treated, and the electrode plates (2) and electrode tubes (3) corresponding to adjacent rows are arranged transversely aligned or staggered.

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