In-situ permeable reactive wall device for remediation of heavy metal contaminated groundwater and remediation method

Abstract

This invention discloses an in-situ permeable reactive barrier remediation device and method for heavy metal-contaminated groundwater. The device comprises a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is equipped with permeation packing material, and the buffer zone is equipped with buffer packing material. The reaction zone is equipped with reaction packing material, which includes at least zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances. The surface of the attapulgite is coated with a gelatin layer. The particle size of the buffer packing material is smaller than that of the reaction packing material, and the particle size of the reaction packing material is smaller than that of the permeation packing material. This invention, by loading acidic substances into attapulgite and using it in combination with zeolite loaded with nano-zero valent iron, creates an acidic or weakly acidic environment for the zeolite loaded with nano-zero valent iron, effectively enhancing the removal of antimony from groundwater by the zeolite loaded with nano-zero valent iron, achieving excellent in-situ groundwater remediation results.

Description

Technical Field

[0001] This invention belongs to the field of groundwater pollution remediation technology, specifically relating to an in-situ permeable reactive wall remediation device and method for heavy metal-contaminated groundwater. Background Technology

[0002] With economic development, the discharge of domestic sewage, industrial wastewater, and leachate from solid waste have led to a significant increase in harmful substances in groundwater, such as heavy metals, inorganic salts, and organic matter. Soil and groundwater pollution is becoming increasingly serious, threatening human health and ecological security, and hindering sustainable economic development. Therefore, the remediation of polluted soil and groundwater is urgently needed.

[0003] Permeable reactive barrier (PRB) technology is widely regarded as a sustainable in-situ remediation method for contaminated groundwater. The remediation principle of PRB technology is as follows: a permeable reactive barrier is set up downstream of the contaminated site, perpendicular to the direction of groundwater flow. Groundwater containing contaminants flows through the reaction zone inside the barrier and undergoes a physicochemical reaction with the contaminants through the filler material inside the barrier, so that the contaminants reach the remediation concentration target.

[0004] my country is the country with the richest antimony resources. However, the processes of mining, beneficiation, and smelting antimony ore can accelerate the release and migration of antimony and other elements into the aquatic environment, significantly increasing the content of heavy metals in the water bodies of mining areas and surrounding areas, causing antimony pollution problems. Although permeable reactive barriers can achieve a certain degree of antimony removal, with the increasing environmental awareness and higher requirements for groundwater pollution remediation, existing permeable reactive barriers cannot meet people's needs and require further improvement. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ permeable reactive barrier remediation device and method for heavy metal contaminated groundwater, which effectively removes antimony from groundwater and achieves in-situ remediation of groundwater.

[0006] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution: A device for in-situ permeable reactive wall remediation of groundwater contaminated with heavy metals includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is provided with permeable filler, and the buffer zone is provided with buffer filler. The reaction zone is provided with reaction packing material, which includes at least zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances; wherein the surface of the attapulgite is coated with a gelatin layer. The particle size of the buffer packing is smaller than that of the reaction packing, and the particle size of the reaction packing is smaller than that of the permeation packing.

[0007] In one or more embodiments of the present invention, the acidic substance is at least one of acetic acid, lactic acid, citric acid, and tartaric acid.

[0008] In one or more embodiments of the present invention, the attapulgite loaded with acidic substances is prepared as follows: Dissolve acidic substances in water to prepare acidic solutions; The attapulgite was mixed with an acid solution, soaked, and filtered to obtain the attapulgite to be coated. The attapulgite to be coated is mixed with a gelatin solution, and glutaraldehyde is added to carry out the reaction. After the reaction is completed, the mixture is crushed to obtain attapulgite loaded with acidic substances.

[0009] In one or more embodiments of the present invention, the concentration of the acid solution is 45wt%-60wt%, and the mass ratio of the attapulgite to the acid solution is 1:(20-30); and / or, The concentration of the gelatin solution is 3 g / L-6 g / L, and the mass ratio of the attapulgite to be coated to the gelatin solution is 1:(50-70); and / or, The attapulgite has a particle size of 2mm-8mm.

[0010] In one or more embodiments of the present invention, an acidic substance is added to the gelatin solution, and the amount of the acidic substance added is 0.5%-1% of the volume of the gelatin solution.

[0011] In one or more embodiments of the present invention, the mass ratio of the zeolite loaded with nano-zero valent iron to the attapulgite loaded with acidic substances is 1:(3-5).

[0012] In one or more embodiments of the present invention, the permeation zone is provided with permeation packing material, the particle size of the permeation packing material is 1cm-2cm, and the permeation packing material is at least one selected from sand, gravel, ceramsite, and zeolite; and / or, The buffer zone is provided with buffer filler, the particle size of which is 0.5mm-1mm, and the buffer filler is at least one of sand, gravel, and zeolite.

[0013] In one or more embodiments of the present invention, a processing zone is further provided on one side of the buffer zone, the processing zone being provided with processing filler, the processing filler including at least iron hydroxyl oxide, activated carbon and attapulgite.

[0014] In one or more embodiments of the present invention, the particle size of the ferric hydroxide is 0.3 mm-0.5 mm, the particle size of the activated carbon is 2 mm-5 mm, and the particle size of the attapulgite is 2 mm-5 mm. The mass ratio of the hydroxyl iron oxide, activated carbon and attapulgite is 1:(2-3):(2-3).

[0015] Another specific embodiment of the present invention provides the following technical solution: A method for in-situ remediation of heavy metal contaminated groundwater using a permeable reactive barrier, comprising the aforementioned in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater, as detailed below: A seepage zone, a reaction zone, and a buffer zone are sequentially set along the direction of groundwater seepage, so that groundwater flows through the seepage zone, the reaction zone, and the buffer zone in sequence; By using zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances in the reaction zone to treat groundwater, in-situ remediation of groundwater contaminated with heavy metals can be achieved.

[0016] Compared with existing technologies, this invention loads acidic substances into attapulgite and uses it in combination with zeolite loaded with nano-zero ferric iron, so that the environment in which the zeolite loaded with nano-zero ferric iron is located is acidic or weakly acidic, thereby effectively enhancing the removal of antimony from groundwater by the zeolite loaded with nano-zero ferric iron, and achieving excellent in-situ groundwater remediation effect. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of an in-situ permeable reactive wall remediation device for heavy metal contaminated groundwater in one embodiment of the present invention; Figure 2 This is a schematic diagram of the treatment zone in an in-situ permeable reactive wall remediation device for heavy metal contaminated groundwater according to an embodiment of the present invention.

[0019] Explanation of key figure labels: 1. Infiltration zone; 2. Reaction zone; 3. Buffer zone; 4. Treatment zone. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0021] One specific embodiment of the present invention provides an in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater, such as... Figure 1 As shown, it includes a permeation zone 1, a reaction zone 2, and a buffer zone 3 arranged sequentially. The permeation zone 1 is provided with permeation packing material, the buffer zone 3 is provided with buffer packing material, and the reaction zone 2 is provided with packing material. The packing material includes at least zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances. The surface of the attapulgite is coated with a gelatin layer. The particle size of the buffer packing material is smaller than that of the reaction packing material, and the particle size of the reaction packing material is smaller than that of the permeation packing material.

[0022] Specifically, nano-zero-valent iron, as an effective remediation material for heavy metals, can be used to remove antimony pollution. By loading nano-zero-valent iron onto zeolite, the adsorption effect of nano-zero-valent iron on antimony can be effectively improved. Antimony mainly exists in three redox states: +3, -3, and +5. By setting attapulgite loaded with acidic substances, when the gelatin layer on the surface of attapulgite swells upon contact with water and releases acidic substances, the zeolite loaded with nano-zero-valent iron can be placed in an acidic or weakly acidic environment. In this environment, the removal rate of Sb(V) is higher than that in neutral or alkaline environments, while Sb(III) has a high removal rate over a wide pH range.

[0023] The particle size settings of the packing material in the infiltration zone, reaction zone, and buffer zone result in different groundwater flow velocities. Consequently, when groundwater flows through the reaction zone and buffer zone, the groundwater stays in the reaction zone for a longer time, allowing the zeolite loaded with nano-zero valent iron to fully adsorb antimony in the water, thereby effectively improving the removal efficiency of antimony.

[0024] Furthermore, the permeation zone is equipped with permeation packing material, which is at least one of sand, gravel, ceramsite, and zeolite, and the particle size of the permeation packing material is 1cm-2cm.

[0025] Furthermore, attapulgite loaded with acidic substances is prepared by the following method: the acidic substances are dissolved in water to prepare an acid solution; the attapulgite and the acid solution are mixed, soaked, and filtered to obtain the attapulgite to be coated; the attapulgite to be coated is mixed with a gelatin solution, glutaraldehyde is added to react, and after the reaction is completed, it is crushed to obtain the attapulgite loaded with acidic substances.

[0026] Specifically, the acidic substance is at least one of acetic acid, lactic acid, citric acid, and tartaric acid, with an acid solution concentration of 45wt%-60wt% and a mass ratio of attapulgite to acid solution of 1:(20-30). Suitable concentration and mass ratio ensure sufficient loading of the acidic substance into the attapulgite. Additionally, the attapulgite particle size is 2mm-8mm.

[0027] Gelatin is dissolved in water to prepare a gelatin solution with a concentration of 3g / L-6g / L. The attapulgite to be coated is mixed with the gelatin solution at a mass ratio of 1:(50-70). The gelatin is cross-linked with glutaraldehyde to form a gelatin layer on the surface of the attapulgite, thus achieving the coating of the attapulgite. Then, the gelatin layer swells when it comes into contact with water, which gradually releases acidic substances and makes the environment of the reaction zone acidic or weakly acidic.

[0028] Furthermore, during the preparation of attapulgite loaded with acidic substances, acidic substances are added to the gelatin solution at a concentration of 0.5%-1% of the gelatin solution volume. By loading acidic substances into the gelatin layer, the overall loading of acidic substances is increased, thereby achieving an acidic or weakly acidic environment in the reaction zone and prolonging the adsorption effect of zeolite loaded with nano-zero valent iron on antimony.

[0029] Furthermore, the mass ratio of zeolite loaded with nano-zero ferric iron to attapulgite loaded with acidic substances is 1:(3-5). If the amount of attapulgite loaded with acidic substances is too low, it will not be able to place the zeolite loaded with nano-zero ferric iron in an acidic or weakly acidic environment, thus affecting its adsorption of antimony. If the amount is too high, the zeolite loaded with nano-zero ferric iron will not be able to adsorb antimony in the water in a timely and effective manner.

[0030] Furthermore, the buffer zone is equipped with buffer filler, which is at least one of sand and gravel or zeolite, with a particle size of 0.5mm-1mm. The particle size of the buffer filler is smaller than that of attapulgite, which is smaller than that of the permeable filler. This slows down the flow rate of groundwater after it flows through the permeable zone. Combined with the obstruction of the buffer zone, the groundwater flows slowly through the reaction zone, thereby enabling the zeolite loaded with nano-zero valent iron to fully contact and adsorb antimony.

[0031] Furthermore, a treatment zone is set up on one side of the buffer zone, which is equipped with treatment packing material composed of ferric hydroxide, activated carbon, and attapulgite in a mass ratio of 1:(2-3):(2-3). When groundwater flows through the reaction zone, antimony is adsorbed and removed by zeolite loaded with nano-zero valent iron. To further improve the removal effect of antimony, ferric hydroxide can further remove antimony when groundwater flows through the treatment zone. At the same time, activated carbon and attapulgite can also adsorb other heavy metal elements, effectively improving the in-situ remediation effect of groundwater.

[0032] The particle size of ferric hydroxide is 0.3mm-0.5mm, the particle size of activated carbon is 2mm-5mm, and the particle size of attapulgite is 2mm-5mm. These particle sizes allow groundwater to flow quickly through the treatment area after passing through the buffer zone, thus ensuring the groundwater remediation effect while also ensuring the normal flow of groundwater.

[0033] Another specific embodiment of the present invention provides a method for in-situ remediation of heavy metal contaminated groundwater using a permeable reactive barrier, which utilizes the aforementioned in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater, as detailed below: A seepage zone, a reaction zone, and a buffer zone are sequentially set along the direction of groundwater seepage, so that groundwater flows through the seepage zone, the reaction zone, and the buffer zone in sequence; By using zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances in the reaction zone to treat groundwater, in-situ remediation of groundwater contaminated with heavy metals can be achieved.

[0034] Specifically, in in-situ remediation of heavy metal-contaminated groundwater, the infiltration zone, reaction zone, and buffer zone are set perpendicular to the groundwater flow direction, allowing groundwater to flow through them sequentially. The depth of the infiltration zone, reaction zone, and buffer zone can be set according to actual needs. Taking a top-down arrangement of the infiltration zone, reaction zone, and buffer zone as an example, the infiltration zone can be located 3m-5m below the surface, and the thicknesses of the infiltration zone, reaction zone, and buffer zone can be set at 1m-2m, 1m-2m, and 1m-2m, respectively, such as 1m, 1m, 1m; 1m, 2m, 1m; 1m, 1.5m, 2m; or 2m, 2m, 2m. Additionally, the treatment zone can also be set at a thickness of 1m-2m, such as 1m, 2m.

[0035] The present invention will be further described in detail below with reference to specific embodiments.

[0036] Preparation Example 1 Zeolites loaded with nano-zero valent iron were prepared using the following method: Take zeolite with an average particle size of 5 mm, soak it in a 1 mol / L nitric acid aqueous solution for 8 hours, then wash it three times with deionized water, and dry it at 80℃ for later use.

[0037] The dried zeolite and 0.2 mol / L FeCl3 aqueous solution were mixed at a solid-liquid ratio of 15 g: 100 ml and stirred continuously for 2 h. Then, under a nitrogen atmosphere, 100 ml of 0.2 mol / L potassium borohydride solution was added dropwise to the zeolite and FeCl3 aqueous solution at a rate of 2 ml / min, and the reaction was allowed to proceed for 1 h after the addition was completed. The reaction product was filtered and collected, washed three times with water and anhydrous ethanol, and then freeze-dried under vacuum (10 Pa, -45 °C, drying for 12 h) to obtain zeolite loaded with nano-zero valent iron.

[0038] Preparation Example 2 Acetic acid and water were mixed to prepare a 45 wt% acid solution. Attapulgite with an average particle size of 5 mm was mixed with the acid solution at a mass ratio of 1:25 and soaked for 5 hours. After filtration, the solution was vacuum dried at 30°C for 20 minutes to obtain the attapulgite to be coated.

[0039] Gelatin was dissolved in water at 40°C to prepare a 3 g / L gelatin solution. The attapulgite to be coated was mixed with the gelatin solution at a mass ratio of 1:50, and then glutaraldehyde was added. The mass ratio of gelatin to glutaraldehyde was 100:2. The mixture was reacted at 40°C for 1 hour and then dried at 30°C for 5 hours. After drying, the mixture was crushed by ball milling with a 15 mm agate ball at a ball-to-material ratio of 2:1 and a speed of 150 r / min for 5 minutes to obtain attapulgite loaded with acidic substances.

[0040] Preparation Example 3 Acetic acid and water were mixed to prepare a 50 wt% acid solution. Attapulgite with an average particle size of 5 mm was mixed with the acid solution at a mass ratio of 1:20 and soaked for 5 hours. After filtration, the solution was vacuum dried at 30°C for 20 minutes to obtain the attapulgite to be coated.

[0041] Gelatin was dissolved in water at 40°C to prepare a 6 g / L gelatin solution. The attapulgite to be coated was mixed with the gelatin solution at a mass ratio of 1:60, and then glutaraldehyde was added. The mass ratio of gelatin to glutaraldehyde was 100:2. The mixture was reacted at 40°C for 1 hour and then dried at 30°C for 5 hours. After drying, the mixture was crushed by ball milling with agate balls of 15 mm diameter at a ball-to-material ratio of 2:1 and a speed of 150 r / min for 5 minutes to obtain attapulgite loaded with acidic substances.

[0042] Preparation Example 4 Acetic acid and water were mixed to prepare a 60wt% acid solution. Attapulgite with an average particle size of 5mm was mixed with the acid solution at a mass ratio of 1:30 and soaked for 5 hours. After filtration, the solution was vacuum dried at 30℃ for 20 minutes to obtain the attapulgite to be coated.

[0043] Gelatin was dissolved in water at 40°C to prepare a 5 g / L gelatin solution. The attapulgite to be coated was mixed with the gelatin solution at a mass ratio of 1:70, and then glutaraldehyde was added. The mass ratio of gelatin to glutaraldehyde was 100:2. The mixture was reacted at 40°C for 1 hour and then dried at 30°C for 5 hours. After drying, the mixture was crushed by ball milling with a 15 mm agate ball at a ball-to-material ratio of 2:1 and a speed of 150 r / min for 5 minutes to obtain attapulgite loaded with acidic substances.

[0044] Preparation Example 5 Acetic acid and water were mixed to prepare a 45 wt% acid solution. Attapulgite with an average particle size of 5 mm was mixed with the acid solution at a mass ratio of 1:25 and soaked for 5 hours. After filtration, the solution was vacuum dried at 30°C for 20 minutes to obtain the attapulgite to be coated.

[0045] Gelatin was dissolved in water at 40°C to prepare a 3 g / L gelatin solution. Acetic acid was added to the gelatin solution at a volume of 0.5%. The attapulgite to be coated and the gelatin solution were mixed at a mass ratio of 1:50, and glutaraldehyde was added at a mass ratio of 100:2. The mixture was reacted at 40°C for 1 hour, and then dried at 30°C for 5 hours. After drying, the mixture was crushed by ball milling with agate balls of 15 mm diameter at a ball-to-material ratio of 2:1 and a speed of 150 r / min for 5 minutes to obtain attapulgite loaded with acidic substances.

[0046] Preparation Example 6 Acetic acid and water were mixed to prepare a 45 wt% acid solution. Attapulgite with an average particle size of 5 mm was mixed with the acid solution at a mass ratio of 1:25 and soaked for 5 hours. After filtration, the solution was vacuum dried at 30°C for 20 minutes to obtain the attapulgite to be coated.

[0047] Gelatin was dissolved in water at 40°C to prepare a 3 g / L gelatin solution. Acetic acid was added to the gelatin solution at a volume of 1%. The attapulgite to be coated and the gelatin solution were mixed at a mass ratio of 1:50, and glutaraldehyde was added at a mass ratio of 100:2. The mixture was reacted at 40°C for 1 hour, and then dried at 30°C for 5 hours. After drying, the mixture was crushed by ball milling with agate balls of 15 mm diameter at a ball-to-material ratio of 2:1 and a speed of 150 r / min for 5 minutes to obtain attapulgite loaded with acidic substances.

[0048] Example 1

[0049] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 2 at a mass ratio of 1:3. The buffer zone is composed of sand and gravel with an average particle size of 0.5 mm.

[0050] Example 2

[0051] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 2 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 2 at a mass ratio of 1:4. The buffer zone is composed of sand and gravel with an average particle size of 0.7 mm.

[0052] Example 3

[0053] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 2 at a mass ratio of 1:5. The buffer zone is composed of sand and gravel with an average particle size of 1 mm.

[0054] Example 4

[0055] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 3 at a mass ratio of 1:3. The buffer zone is composed of sand and gravel with an average particle size of 0.5 mm.

[0056] Example 5

[0057] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 4 at a mass ratio of 1:3. The buffer zone is composed of sand and gravel with an average particle size of 0.5 mm.

[0058] Example 6

[0059] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 5 at a mass ratio of 1:3. The buffer zone is composed of sand and gravel with an average particle size of 0.5 mm.

[0060] Example 7

[0061] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 6 at a mass ratio of 1:3. The buffer zone is composed of sand and gravel with an average particle size of 0.5 mm.

[0062] Example 8

[0063] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, a buffer zone, and a treatment zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 2 at a mass ratio of 1:3. The buffer zone is composed of sand and gravel with an average particle size of 0.5 mm. The treatment zone is composed of ferric hydroxide with an average particle size of 0.5 mm, activated carbon with an average particle size of 2 mm, and attapulgite with an average particle size of 2 mm at a mass ratio of 1:2:2.

[0064] Example 9

[0065] In this embodiment, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, a buffer zone, and a treatment zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm. The reaction zone is composed of zeolite loaded with nano-zero valent iron in Preparation Example 1 and attapulgite loaded with acidic substances in Preparation Example 2 at a mass ratio of 1:3. The buffer zone is composed of sand and gravel with an average particle size of 0.5 mm. The treatment zone is composed of ferric hydroxide with an average particle size of 0.3 mm, activated carbon with an average particle size of 5 mm, and attapulgite with an average particle size of 5 mm at a mass ratio of 1:3:3.

[0066] Comparative Example 1 In this comparative example, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is composed of sand and gravel with an average particle size of 1 cm, the reaction zone is composed of zeolite loaded with nano-zero valent iron as in Preparation Example 1, and the buffer zone is composed of sand and gravel with an average particle size of 0.5 mm.

[0067] Comparative Example 2 In this comparative example, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone consists of sand and gravel with an average particle size of 1 cm. The reaction zone consists of zeolite loaded with nano-zero valent iron and attapulgite with an average particle size of 5 mm in a mass ratio of 1:3, as described in Preparation Example 1. The buffer zone consists of sand and gravel with an average particle size of 0.5 mm.

[0068] Comparative Example 3 Acetic acid and water were mixed to prepare a 45 wt% acid solution. Attapulgite with an average particle size of 5 mm was mixed with the acid solution at a mass ratio of 1:25 and soaked for 5 hours. After filtration, the solution was vacuum dried at 30°C for 20 minutes to obtain uncoated attapulgite.

[0069] In this comparative example, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone consists of sand and gravel with an average particle size of 1 cm. The reaction zone consists of zeolite loaded with nano-zero valent iron and uncoated attapulgite in a mass ratio of 1:3, as described in Preparation Example 1. The buffer zone consists of sand and gravel with an average particle size of 0.5 mm.

[0070] Comparative Example 4 In this comparative example, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone consists of sand and gravel with an average particle size of 1 cm. The reaction zone consists of zeolite loaded with nano-zero valent iron from Preparation Example 1 and attapulgite loaded with acidic substances from Preparation Example 2, in a mass ratio of 1:1. The buffer zone consists of sand and gravel with an average particle size of 0.5 mm.

[0071] Comparative Example 5 In this comparative example, the in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone consists of sand and gravel with an average particle size of 1 cm. The reaction zone consists of zeolite loaded with nano-zero valent iron from Preparation Example 1 and attapulgite loaded with acidic substances from Preparation Example 2, in a mass ratio of 1:2. The buffer zone consists of sand and gravel with an average particle size of 0.5 mm.

[0072] Performance testing Combination Figure 1 and Figure 2 Examples 1-7 and Comparative Examples 1-5 use the following... Figure 1 The experimental column shown (including the permeation zone, reaction zone, and buffer zone from top to bottom) was used in Examples 8-9 as follows. Figure 2 The experimental column shown (including the permeation zone, reaction zone, buffer zone, and treatment zone from top to bottom) has a diameter of 10 cm. The permeation zone, reaction zone, buffer zone, and treatment zone in the experimental column are filled with corresponding fillers. The filling height of each zone is 10 cm. The fillers used in each zone are as described in the various embodiments and comparative examples.

[0073] The groundwater in antimony mining areas contains various ions. A simulated antimony-containing groundwater was prepared using potassium pyroantimonate, potassium antimony tartrate, sodium bicarbonate, calcium chloride, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, ammonium chloride, sodium nitrate, potassium phosphate trihydrate, sodium carbonate, sodium silicate nonahydrate, ferrous sulfate heptahydrate, sodium molybdate dihydrate, and zinc sulfate heptahydrate. The concentrations of each substance were: 22 mg / L potassium pyroantimonate, 22 mg / L potassium antimony tartrate, 9 mg / L NaHCO3, 6 mg / L CaCl2, 6 mg / L MgCl2·6H2O, 2 mg / L MgSO4·7H2O, 1 mg / L NH4Cl, 1 mg / L NaNO3, 0.5 mg / L K3PO4·3H2O, 0.1 mg / L Na2CO3, 0.1 mg / L Na2SiO3·9H2O, 0.05 mg / L FeSO4·7H2O, and 5 μg / L. Na2MoO4·2H2O, 5μg / L ZnSO4·7H2O.

[0074] Simulated antimony-containing groundwater was continuously introduced into the experimental column from the top at a rate of 1 mL / min. The initial time was taken as the moment when water began to emerge. Samples were then taken from the effluent at 30 min, 1 h, and 3 h to determine the concentrations of Sb(V) and Sb(III). The removal rates of Sb(V) and Sb(III) were calculated as follows: Removal rate = (Initial concentration - Measured concentration) / Initial concentration * 100%. The test was repeated three times, and the average value of the removal rate results was taken. The details are shown in Table 1.

[0075] Table 1. Removal rates of Sb(V) and Sb(III) from simulated antimony-containing groundwater at different time points using experimental columns. As can be seen from Table 1, compared with Comparative Example 1 and Comparative Example 2, the present invention uses zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances in combination, which can achieve better in-situ remediation effect on groundwater.

[0076] As can be seen from Comparative Example 3, without the use of gelatin to coat the attapulgite, the acidic substances loaded in the attapulgite were released in large quantities in a short period of time in the early stage of the test, resulting in excellent removal effect of antimony. However, as time went on, the removal effect decreased significantly. This indicates that coating the attapulgite with gelatin can prolong the removal of antimony in the reaction zone and improve the in-situ remediation effect of groundwater.

[0077] As can be seen from Comparative Examples 4 and 5, the mass ratio between zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances affects the removal effect of antimony in the reaction zone. Within the mass ratio range disclosed in this invention, a better antimony removal effect can be obtained by combining zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances.

[0078] As can be seen from Examples 6 and 7, adding an appropriate amount of acidic substance to the gelatin layer on the surface of attapulgite can further improve the removal effect of antimony in the reaction zone.

[0079] As can be seen from Examples 8 and 9, by further setting up treatment zones, the in-situ remediation effect of groundwater can be further improved.

[0080] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0081] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device for in-situ remediation of heavy metal contaminated groundwater using a permeable reactive barrier, characterized in that, It includes a permeation zone, a reaction zone, and a buffer zone arranged sequentially. The permeation zone is provided with permeation packing material, and the buffer zone is provided with buffer packing material. The reaction zone is provided with reaction packing material, which includes at least zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances; wherein the surface of the attapulgite is coated with a gelatin layer. The particle size of the buffer packing is smaller than that of the reaction packing, and the particle size of the reaction packing is smaller than that of the permeation packing.

2. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 1, characterized in that, The acidic substance is at least one of acetic acid, lactic acid, citric acid, and tartaric acid.

3. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 1, characterized in that, The attapulgite loaded with acidic substances is prepared as follows: Dissolve acidic substances in water to prepare acidic solutions; The attapulgite was mixed with an acid solution, soaked, and filtered to obtain the attapulgite to be coated. The attapulgite to be coated is mixed with a gelatin solution, and glutaraldehyde is added to carry out the reaction. After the reaction is completed, the mixture is crushed to obtain attapulgite loaded with acidic substances.

4. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 3, characterized in that, The concentration of the acid solution is 45wt%-60wt%, and the mass ratio of the attapulgite to the acid solution is 1:(20-30); and / or, The concentration of the gelatin solution is 3 g / L-6 g / L, and the mass ratio of the attapulgite to be coated to the gelatin solution is 1:(50-70); and / or, The attapulgite has a particle size of 2mm-8mm.

5. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 3, characterized in that, An acidic substance is added to the gelatin solution, and the amount of the acidic substance added is 0.5%-1% of the volume of the gelatin solution.

6. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 1, characterized in that, The mass ratio of the zeolite loaded with nano-zero valent iron to the attapulgite loaded with acidic substances is 1:(3-5).

7. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 1, characterized in that, The permeation zone is provided with permeation packing material, the particle size of which is 1cm-2cm, and the permeation packing material is at least one of sand, gravel, ceramsite, and zeolite; and / or, The buffer zone is provided with buffer filler, the particle size of which is 0.5mm-1mm, and the buffer filler is at least one of sand, gravel, and zeolite.

8. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 1, characterized in that, It also includes a processing zone located on one side of the buffer zone, the processing zone being provided with processing filler, the processing filler including at least iron hydroxyl oxide, activated carbon and attapulgite.

9. The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater according to claim 8, characterized in that, The ferric hydroxide has a particle size of 0.3 mm to 0.5 mm, the activated carbon has a particle size of 2 mm to 5 mm, and the attapulgite has a particle size of 2 mm to 5 mm. The mass ratio of the hydroxyl iron oxide, activated carbon and attapulgite is 1:(2-3):(2-3).

10. A method for in-situ remediation of heavy metal contaminated groundwater using a permeable reactive barrier, characterized in that, The in-situ permeable reactive barrier remediation device for heavy metal contaminated groundwater as described in claim 1 is used as follows: A seepage zone, a reaction zone, and a buffer zone are sequentially set along the direction of groundwater seepage, so that groundwater flows through the seepage zone, the reaction zone, and the buffer zone in sequence; By using zeolite loaded with nano-zero valent iron and attapulgite loaded with acidic substances in the reaction zone to treat groundwater, in-situ remediation of groundwater contaminated with heavy metals can be achieved.

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