EK-PRB device for repairing heavy metal contaminated soil

Abstract

The EK-PRB device for repairing the heavy metal contaminated soil comprises an osmotic reaction rod, the osmotic reaction rod is composed of N sections of hollow rods, an inverted-cone-shaped bottom cover and a blocking block, internal threads are arranged at the upper end of the Mth hollow rod, and external threads matched with the internal threads at the upper end of the Mth hollow rod are arranged at the lower end of the (M-1) th section; limiting devices are arranged on the upper end side surface of the first hollow rod and the lower end side surface of the Nth hollow rod; the inverted-cone-shaped bottom cover is connected with the external thread at the lower end of the Nth hollow rod through the internal thread arranged at the upper end of the inverted-cone-shaped bottom cover; and the blocking block can move in the hollow rod. The EK-PRB device disclosed by the utility model is simple in process, low in cost and capable of efficiently repairing heavy metal contaminated soil.

Description

Technical Field

[0001] This utility model relates to the field of ecological environment governance technology, specifically to an EK-PRB device for remediating heavy metal contaminated soil. Background Technology

[0002] Heavy metals can transfer to coastal soils in various forms through water bodies. Excessive heavy metal levels in soil can alter its physicochemical properties, reduce crop yields, and enter the human body through the food chain, posing serious health risks. Cadmium, a typical heavy metal pollutant, forms cadmium-sulfuron-protein after entering the human body, reaching the whole body via the bloodstream and accumulating in organs such as the liver and kidneys, affecting organ function. Chronic cadmium poisoning can also cause osteoporosis and bone atrophy; the well-known Itai-itai disease is caused by excessive cadmium levels in the human body. Therefore, effectively remediating heavy metal-contaminated soil is currently one of the main research directions in the environmental field.

[0003] Currently, the main technologies for remediating heavy metal contaminated soil include topsoil replacement, soil leaching, electrokinetic remediation, and bioremediation. Topsoil replacement (e.g., CN118140639A) has very limited application scenarios; for large-scale contaminated soil remediation, it suffers from excessively high costs in terms of manpower and resources. Soil leaching (e.g., CN118222291A) is currently the mainstream soil remediation technology. Although it can completely remove heavy metals from the soil, nutrients may also bind with the leaching agent, leading to nutrient loss and decreased fertility. Furthermore, the leaching solution requires further treatment to prevent secondary pollution. Electrokinetic remediation (e.g., CN118268363A) can effectively remediate soil without adding chemical reagents; however, this technology is not suitable for soils with high permeability and poor conductivity. Additionally, metals may deposit near the electrode area, causing localized increases in heavy metal levels in the soil, and prolonged application of high voltage can corrode the electrodes, resulting in secondary pollution. Bioremediation (such as CN118218390A) is a relatively new remediation method with advantages of low cost and environmental friendliness. However, it suffers from problems such as poor genetic stability of microorganisms, susceptibility to mutation, and the inability to completely remove pollutants. Therefore, developing a soil remediation method with good removal efficiency, low energy consumption, and no secondary pollution is urgently needed.

[0004] PRB (Permeable Reactive Barrier) technology, an in-situ remediation technique, emerged in the United States in the 1980s. It is typically installed in underground aquifers, perpendicular to the direction of groundwater flow. When contaminants flow along the permeable reactive barrier, they react with the filling material within the barrier. PRB technology primarily utilizes the precipitation, adsorption, oxidation-reduction, and biodegradation reactions that occur when contaminants pass through the reactive material to remove them. It is frequently used in groundwater remediation projects.

[0005] Electrokinetic-permeable reactive barrier (EK-PRB, e.g., CN114951258A) is a technology combining electrokinetic remediation and permeable reactive barriers. EK technology moves heavy metals towards the electrode, but before reaching the electrode, they pass through the PRB wall, where they react with the filling material within the PRB wall, removing the heavy metals through adsorption or precipitation. Currently, this combined EK-PRB treatment technology shows good removal efficiency for heavy metal contaminated soil, but certain problems exist. The development of high-performance PRB materials and the need for a large amount of filling material in the PRB wall both increase costs.

[0006] Patent CN 101880087 A discloses a PRB annular columnar structure. This patent improves the traditional permeable reactive wall into a permeable reactive rod, and uses curtain grouting technology to fix the deactivated packing column (permeable reactive rod). This method does not meet the requirements of green economy and will cause serious local soil pollution in the long run. Therefore, it is of great significance to develop an EK-PRB device that is reusable, low-cost, and can efficiently remediate soil. Utility Model Content

[0007] The purpose of this invention is to provide an EK-PRB device that has a detachable permeation reaction rod, is low in cost, and can efficiently remediate heavy metal contaminated soil.

[0008] An EK-PRB device for remediating heavy metal contaminated soil includes an infiltration reaction rod comprising N hollow rod sections, an inverted conical bottom cover, and a plug. The upper end of the Mth hollow rod has an internal thread, and the lower end of the (M-1)th hollow rod section has an external thread matching the internal thread at the upper end of the Mth hollow rod. Limiting devices are provided on the upper side of the 1st hollow rod and the lower side of the Nth hollow rod. The inverted conical bottom cover is connected to the external thread at the lower end of the Nth hollow rod via its upper internal thread. The plug is movable within the hollow rod.

[0009] Where N and M are both integers not less than 2, and M≤N.

[0010] This invention features a detachable permeation reaction rod. After opening the inverted conical bottom cover, the deactivated PRB material is pushed out of the hollow rod using a plug, and then new PRB material is filled into the hollow rod. Finally, the inverted conical bottom cover is tightened, enabling the permeation reaction rod structure to be used multiple times.

[0011] Optionally, the number of osmotic reaction rods is 4-8, arranged in two rows with a spacing of 5-7cm.

[0012] Optionally, the surface of the hollow rod is provided with a plurality of circular micropores, the diameter of which is 5 to 10 mm.

[0013] The EK-PRB device used in this invention has a rod-shaped structure with multiple circular holes of 5-10 mm in diameter on the hollow rod. Compared to traditional PRB walls, this rod-shaped structure increases the contact area between the PRB material and the soil, and allows for multiple reactions with heavy metals during migration, thus improving the removal efficiency. Since the volume of the permeation reaction rod is much smaller than that of the permeation reaction wall, the amount of packing material in the permeation reaction rod is correspondingly reduced, significantly lowering the process cost.

[0014] Optionally, the limiting device includes a screw.

[0015] Optionally, the voltage gradient of the DC power supply is 1–2 V cm. -1 .

[0016] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0017] 1. This utility model provides an EK-PRB device with a detachable permeation reaction rod, which is low in cost and can efficiently remediate heavy metal contaminated soil. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an osmotic reaction rod.

[0019] Figure 2 This is a schematic diagram of a hollow rod.

[0020] Figure 3 This is a schematic diagram of the EK-PRB rod and EK-PRB wall assembly.

[0021] Figure 4 This is a graph showing the heavy metal removal efficiency of EK-PRB walls and EK-PRB rods.

[0022] Figure 5 This is a diagram showing the current changes in the EK-PRB wall and the EK-PRB rod.

[0023] Figure 6 This is a diagram showing the pH changes in the electrode chambers of the EK-PRB wall and the EK-PRB rod.

[0024] In the diagram, there is a hollow rod 1, an inverted conical bottom cover 2, a plug 3, a hollow rod internal thread 1-1, a hollow rod external thread 1-2, a bolt hole 3-1, and a limit screw 3-2. Detailed Implementation

[0025] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. Unless otherwise specified, the relevant percentages refer to mass percentages.

[0026] Example 1

[0027] An EK-PRB device for remediating heavy metal contaminated soil includes a permeation reaction rod, which consists of a hollow rod 1, an inverted conical bottom cover 2, and a plug 3. The upper end of the second hollow rod 1 is provided with an internal thread 1-1, and the lower end of the first hollow rod 1 is provided with an external thread 1-2 that matches the internal thread at the upper end of the second hollow rod 1. Limiting screws 3-2 are provided on the upper side of the first hollow rod 1 and the lower side of the second hollow rod 1. The inverted conical bottom cover 2 is connected to the external thread at the lower end of the second hollow rod 1 through the internal thread at its upper end. The plug 3 is located inside the hollow rod 1 and has bolt holes 3-1.

[0028] When filling the hollow rod 1 with PRB material, first open the inverted conical bottom cover 2, move the plug 3 to the top of the hollow rod, and add 0.5-1g of PRB material into the hollow rod 1 through the bottom opening. Then close the inverted conical bottom cover 2 to obtain the permeation reaction rod. When the PRB material is saturated, remove the permeation reaction rod from the soil, open the inverted conical bottom cover 2, move the plug 3 to the bottom of the hollow rod 1, and remove the PRB material from the hollow rod 1 through the bottom opening. Repeating the above process allows for the recycling of the permeation reaction rod.

[0029] In this embodiment, the electrodes are titanium meshes, the spacing between the electrodes is 25–35 cm, and the facing area of ​​the electrodes is 80–120 cm². 2 The voltage gradient of the DC power supply is 1–2 V cm. -1 .

[0030] In this embodiment, the volume of the soil chamber is 2000–4000 cm³. 3 The volume of the anode and cathode chambers is 500–1000 cm³. 3 .

[0031] In this embodiment, the hollow rod 1 has a height of 5-10cm and a diameter of 3-5cm, and the surface of the hollow rod 1 has multiple round holes of 5-10mm.

[0032] In this embodiment, the heavy metal contaminated soil is cadmium (Cd) contaminated soil, wherein the concentration of Cd is ≤5 mg / kg; the electrolyte solution is a 0.2-0.3 mol / L citric acid solution.

[0033] In this embodiment, a 350-mesh filter cloth is placed between the cathode / anode chamber and the soil chamber to prevent soil particles from entering the electrode chamber. Then, 1-1.5 kg of soil that has passed through a 20-mesh sieve is added to the soil chamber and compacted. A permeation reaction rod is inserted into the soil chamber every 5-7 cm, arranged in two rows for a total of six rods. Then, 1.5-3 L of the optimal concentration of soil extraction reagent is added to the cathode / anode chamber and allowed to stand for 24 hours to allow the optimal concentration of soil extraction reagent to fully penetrate the soil. The electrodes are fixed to the cathode / anode chamber using shark clips, and an ammeter is connected to a DC power supply using wires, applying a 1-2 V cm⁻¹ voltage. -1 After applying a constant voltage, the remediation of Cd-contaminated soil began, with electrolyte replenished periodically to the initial level during the remediation process. The reaction time was 100–140 hours.

[0034] Figure 4 As shown, when using EK-PRB rods to treat heavy metal contaminated soil, the removal rate of Cd is 82.9%, while when using EK-PRB walls to treat heavy metal contaminated soil, the removal rate of Cd is only 31.6%. The EK-PRB rod of this invention has great advantages for the remediation of heavy metal contaminated soil. Figure 5 As shown, the current of the EK-PRB rod is always higher than that of the EK-PRB wall, which makes the migration rate of metal ions in the EK-PRB rod system faster, allowing more metal ions to contact and react with the EK-PRB rod, ultimately resulting in a higher removal rate. Figure 6 As shown, the pH of the EK-PRB rod is lower than that of the EK-PRB wall, regardless of whether it is the catholy or anolyte. Under acidic conditions, heavy metals in the soil are more easily precipitated by the electrolyte and then adsorbed and removed by the PRB material. This also indicates that the EK-PRB rod has a higher removal rate of heavy metals in the soil than the EK-PRB wall.

[0035] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention by those skilled in the art in various equivalent forms fall within the scope defined by the appended claims.

Claims

1. An EK-PRB device for remediating heavy metal contaminated soil, comprising an infiltration reaction rod, characterized in that, The permeation reaction rod consists of a hollow rod (1), an inverted conical bottom cover (2), and a plug (3). There are N hollow rods (1). The upper end of the Mth hollow rod (1) is provided with an internal thread (1-1), and the lower end of the (M-1)th hollow rod (1) is provided with an external thread (1-2) that matches the internal thread at the upper end of the Mth hollow rod (1). Limiting devices (3-2) are provided on the upper side of the 1st hollow rod (1) and the lower side of the Nth hollow rod (1). The inverted conical bottom cover (2) is connected to the external thread (1-2) at the lower end of the Nth hollow rod (1) through its upper internal thread. The plug (3) can move inside the hollow rod. Wherein, N and M are both integers not less than 2, and M≤N.

2. The EK-PRB device for remediating heavy metal contaminated soil according to claim 1, characterized in that, The number of permeation reaction rods is 4-8, arranged in two rows with a spacing of 5-7cm.

3. The EK-PRB device for remediating heavy metal contaminated soil according to claim 1, characterized in that, The hollow rod (1) has a plurality of circular holes on its surface, the diameter of which is 5 to 10 mm.

4. The EK-PRB device for remediating heavy metal contaminated soil according to claim 1, characterized in that, The limiting device (3-2) includes screws.

5. The EK-PRB device for remediating heavy metal contaminated soil according to claim 1, characterized in that, Bolt holes (3-1) are provided on the upper surface of the block (3).

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