A reducing agent and repair method for hexavalent chromium-contaminated groundwater

Abstract

The present invention discloses a reducing agent and a repair and treatment method for hexavalent chromium-contaminated groundwater, and relates to the technical field of contaminated groundwater repair. The reducing agent includes a solid zero-valent iron material and acidic biological fermentation organic waste, the particle size of the solid zero-valent iron material is 1-100 μm, and the acidic biological fermentation organic waste is the acidic solid residue after the organic biological material is fermented by microorganisms. The repair and treatment method includes: forming a permeable reaction wall with a wall, a permeable separation layer, a biomass anti-sedimentation layer and an adsorption reduction layer; wherein the adsorption reduction layer is located in the biomass anti-sedimentation layer, and the adsorption reduction layer contains a reducing agent, and the hexavalent chromium-contaminated groundwater is passed through the permeable reaction wall, so that the hexavalent chromium in the groundwater can be reduced to low-toxic trivalent chromium. The present application improves the reduction efficiency and durability of micron-level zero-valent iron in repairing hexavalent chromium-contaminated groundwater, and can also utilize waste, save resources, and be more environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of contaminated groundwater remediation, and in particular to a reducing agent and a remediation method for hexavalent chromium-contaminated groundwater. Background Art

[0002] Groundwater pollution can cause serious harm to soil and human health. Currently, chromium contamination of groundwater is a widespread groundwater pollution problem in my country and many parts of the world. Chromium pollution mainly refers to the pollution of groundwater by hexavalent chromium. Hexavalent chromium is highly soluble and easy to migrate. Hexavalent chromium is a strong carcinogenic and mutagenic factor. It is easily absorbed by the human body, can affect the oxidation and reduction of cells, can combine with nucleic acids, and has irritating, carcinogenic, and mutagenic effects on the respiratory and digestive tracts. Internationally, hexavalent chromium is listed as one of the eight chemical substances that are most harmful to the human body. It is a recognized carcinogen and poses great harm to the environment.

[0003] In the related art, iron is used to reduce highly toxic hexavalent iron to repair chromium-contaminated groundwater. CN115055679A discloses a zero-valent iron reducing agent and its preparation method and application, and proposes that the reduction efficiency of existing nano zero-valent iron reducing agents is low and the recycling and reuse of the reducing agents is difficult to achieve mainly due to the following reasons: Fe 0 Inert iron oxide film (such as FeO x and FeOOH) hinder the reaction and inhibit activity; (2) the large block structure makes it difficult to utilize Fe in the bulk phase, resulting in a reduced Fe utilization rate; (3) the dissolution and loss of Fe species cause waste of Fe resources and secondary pollution. It was found that the use of vapor deposition-pyrolysis technology to activate the source reducing agent (zero-valent iron) can produce zero-valent iron nanoparticles with a carbon-doped nitrogen (CN) coating layer, namely zero-valent iron reducing agent. The zero-valent iron reducing agent has excellent reduction efficiency and stability, and its high stability enables the recovery, regeneration and reuse of the reducing agent. CN103949469A discloses a method for remediating hexavalent chromium-contaminated groundwater using stable zero-valent iron nanoparticles. The iron-based nanoparticles in this technology have the characteristics of strong mobility in soil and groundwater, large specific surface area, and high reaction rate. They can achieve faster, more efficient, and more direct reduction, precipitation, adsorption, or fixation of Cr(VI) from groundwater in contaminated sites. Water-soluble polysaccharide (CMC) is used as a stabilizer and dispersant to prepare the iron-based nanoparticles. The iron-based particles have the characteristics of higher dispersibility and longer-term reaction activity.

[0004] As can be seen from the aforementioned technologies, zero-valent iron (ZVI) is a widely recognized method for reducing hexavalent chromium. However, its efficiency is significantly improved only when the ZVI particles reach the nanoscale. Micron-scale ZVI is less efficient and requires additional methods. Furthermore, preparing ZVI nanoparticles with excellent reduction efficiency and stability requires complex processes and consumes significant resources.

[0005] Therefore, the inventors proposed to develop a new technology for repairing chromium-contaminated groundwater using micron-scale zero-valent iron, which not only has excellent reduction efficiency and durability, but also can save resources to improve the defects of the method of repairing chromium-contaminated groundwater using nano-scale zero-valent iron. Summary of the Invention

[0006] In order to improve the reduction efficiency and durability of micron-scale zero-valent iron in repairing hexavalent chromium-contaminated groundwater, the present application provides a reducing agent and a repair and treatment method for hexavalent chromium-contaminated groundwater.

[0007] In the first aspect, the present application provides a reducing agent for hexavalent chromium-contaminated groundwater, which adopts the following technical solution:

[0008] A reducing agent for hexavalent chromium-contaminated groundwater comprises a solid zero-valent iron material and acidic biological fermentation organic waste, wherein the particle size of the solid zero-valent iron material is 1-100 μm, and the acidic biological fermentation organic waste is the acidic solid residue after the organic biological material is fermented by microorganisms.

[0009] Organic biomaterials, including rice, wheat, sorghum, soybeans, fruits, and sugar beets, are the raw materials for fermentation processes. After microbial fermentation, these materials leave behind some solid residues, which are typically discarded or used as feed and fertilizer. The inventors have discovered that the solid residues of fermented organic biomaterials are mostly acidic and often contain active microorganisms such as Bacillus sp., Escherichia sp., Deinococcus sp., Micromonospora sp., Methylobacterium sp., Massilia sp., Acidobacterium sp., Comamonas sp., Bradyrhizobium sp., and Arthrobacter sp. When zero-valent iron is mixed with acidic bio-fermentation organic waste, it generates divalent iron under acidic and reducing conditions. Divalent iron is highly efficient at reducing hexavalent chromium, so acidic bio-fermentation organic waste can improve the efficiency of zero-valent iron in remediating hexavalent chromium-contaminated groundwater. Furthermore, the dissolution of iron in acidic bio-fermentation organic waste is a slow process. Compared to nanoscale zero-valent iron materials, micron-scale solid zero-valent iron materials with a particle size of 1-100μm have a longer dissolution process. Therefore, micron-scale solid zero-valent iron materials also have a long-lasting reducing effect in acidic bio-fermentation organic waste. Compared to other fillers such as activated carbon, micron-scale solid zero-valent iron materials have a longer service life.

[0010] Therefore, the synergy between micron-sized solid zero-valent iron materials with a particle size of 1-100 μm and acidic biological fermentation organic waste can simultaneously improve the reduction efficiency and durability of micron-sized zero-valent iron in repairing hexavalent chromium-contaminated groundwater. Moreover, it can also utilize waste, save resources, and be more environmentally friendly.

[0011] In a specific embodiment, the acidic biological fermentation organic waste is at least one of vinegar dregs, wine dregs, biogas residues, soy sauce dregs, furfural residues, xylose residues, acid enzyme residues, fermented starch residues, fermented tofu residues, fermented apple residues, fermented pear residues, fermented beet residues, fermented bagasse, chlortetracycline residues, oxytetracycline residues, penicillin residues or erythromycin residues.

[0012] The inventors studied the solid waste residues produced after fermentation by various microorganisms and found that the fermentation products after the above fermentations are all acidic. Moreover, after being compounded with micron-sized solid zero-valent iron materials, they can effectively reduce hexavalent chromium in chromium-contaminated groundwater and have excellent durability.

[0013] In a specific embodiment, the pH of the acidic biological fermentation organic waste is 5.8-6.8.

[0014] Adjusting the pH of the acidic biological fermentation organic waste within the above range allows zero-valent iron to generate divalent iron more efficiently, thereby further improving the reduction efficiency of the reducing agent of the present application for hexavalent chromium.

[0015] In a specific embodiment, the weight ratio of the solid zero-valent iron material to the acidic biological fermentation organic waste is (0.5-1.5):1.

[0016] The ratio of solid zero-valent iron material and acidic bio-fermentation organic waste has an important influence on the durability of the reducing agent of the present application. The inventors studied the ratio of solid zero-valent iron material and acidic bio-fermentation organic waste and unexpectedly found that adjusting the weight ratio of solid zero-valent iron material and acidic bio-fermentation organic waste to the range of (0.5-1.5): 1 not only makes the reducing agent of the present application maintain excellent durability, but also, when the reducing agent is used as a filler, it is not easy to collapse or lose, and it also has excellent permeability, making the reducing agent of the present application more suitable for groundwater in-situ remediation technology. Therefore, when treating hexavalent chromium-contaminated groundwater, it is only necessary to pass the hexavalent chromium-contaminated groundwater through the reducing agent of the present application to reduce the hexavalent chromium in the groundwater, which can reduce the cost of repair and treatment, shorten the treatment cycle, and reduce secondary pollution.

[0017] In a second aspect, the present application provides a permeable reaction wall using the above-mentioned reducing agent for hexavalent chromium-contaminated groundwater, which adopts the following technical solution:

[0018] A permeable reaction wall using the above-mentioned reducing agent for hexavalent chromium-contaminated groundwater comprises a wall body, a permeable separation layer, a biomass anti-sedimentation layer and an adsorption-reduction layer, wherein a plurality of the walls surround the periphery of the permeable separation layer, the permeable separation layer comprises a plurality of layers, the biomass anti-sedimentation layer is arranged between two relative permeable separation layers, the adsorption-reduction layer is arranged within the biomass anti-sedimentation layer, and the adsorption-reduction layer comprises a porous adsorption material and the above-mentioned reducing agent in a weight ratio of 1:(0.5-3).

[0019] When hexavalent chromium-contaminated groundwater passes through the permeable reaction wall, the biomass anti-sedimentation layer and the permeable separation layer work together to reduce the loss of porous adsorbent material and reducing agent with the water flow. Furthermore, the biomass anti-sedimentation layer prevents the solid zero-valent iron material in the reducing agent from settling under gravity, ensuring that the solid zero-valent iron material remains in contact with the acidic bio-fermentation organic waste, thereby helping the reducing agent of the present application maintain a high reduction efficiency. Furthermore, the permeable separation layer and the biomass anti-sedimentation layer can pre-filter impurities and pollutants in the hexavalent chromium-contaminated groundwater, reducing damage to the adsorption-reduction layer caused by these impurities and pollutants.

[0020] In a specific embodiment, the biomass anti-settling layer is a layer formed by a biomass anti-settling material. Based on the total weight of the biomass anti-settling material, the biomass anti-settling material includes 10-15 parts by weight of yellow mud, 1-3 parts by weight of natural mineral powder and 10-15 parts by weight of biomass debris. The biomass debris is at least one of sawdust, rice husks, bran and humic acid.

[0021] When exposed to water, the yellow mud, natural mineral powder, and water form a slurry with an adhesive effect that fills the gaps in the biomass debris. This not only binds the biomass debris together but also prevents solid zero-valent iron from passing through the gaps in the biomass anti-sedimentation layer. Furthermore, the biomass debris not only contains the biomass necessary for microbial growth, but also has minimal temperature fluctuations, providing an environment conducive to microbial growth within the biomass anti-sedimentation layer. The microorganisms themselves can reduce highly toxic hexavalent chromium to less toxic trivalent chromium. Furthermore, microbial fermentation of the biomass debris promotes the conversion of zero-valent iron to divalent iron, thereby increasing the efficiency of hexavalent chromium reduction.

[0022] In a specific embodiment, the porous adsorption material is at least one of activated carbon, bamboo charcoal, peat, and diatomaceous earth.

[0023] The above-mentioned porous adsorption materials can all adsorb pollutants in groundwater, so that the present application can not only remove hexavalent chromium in groundwater, but also remove other pollutants and deodorize groundwater.

[0024] In a specific embodiment, the permeable separation layer is a woven fabric woven from straw or rice straw.

[0025] Straw or rice straw are both by-products of agricultural production. Straw or rice straw woven fabrics have excellent permeability. Therefore, this application uses straw or rice straw woven fabrics as permeable separation layers, which not only allows groundwater to penetrate quickly, but also can recycle waste and save resources.

[0026] In a third aspect, the present application provides a method for remediating groundwater contaminated by hexavalent chromium, which adopts the following technical solution:

[0027] A method for repairing and treating hexavalent chromium-contaminated groundwater comprises the following steps:

[0028] A permeable separation layer is placed between several walls, a biomass anti-settling material is laid on the permeable separation layer, a porous adsorption material and the reducing agent are evenly mixed and laid on the biomass anti-settling material to form an adsorption-reduction layer, and then the biomass anti-settling material is laid on the adsorption-reduction layer. The biomass anti-settling materials on both sides of the adsorption-reduction layer constitute a biomass anti-settling layer, and a permeable separation layer is laid on the biomass anti-settling layer;

[0029] Repeat the above operation and obtain a permeable reaction wall after compaction;

[0030] Pass hexavalent chromium-contaminated groundwater through a permeable reactive wall.

[0031] By adopting the above method, the number of permeable separation layers, biomass anti-sedimentation layers and adsorption reduction layers to be laid can be freely selected according to the degree of groundwater pollution, thereby repairing and treating hexavalent chromium-contaminated groundwater with different degrees of pollution.

[0032] In summary, this application includes at least one of the following beneficial technical effects:

[0033] 1. This application utilizes micron-sized solid zero-valent iron materials with a particle size of 1-100 μm in conjunction with acidic biofermentation organic waste to simultaneously improve the reduction efficiency and durability of the micron-sized zero-valent iron in remediating hexavalent chromium-contaminated groundwater. Furthermore, it utilizes waste, conserves resources, and is more environmentally friendly.

[0034] 2. This application uses a reducing agent for hexavalent chromium-contaminated groundwater to form a permeable reaction wall, which can prevent the solid zero-valent iron material in the reducing agent from settling under the action of gravity, helping the reducing agent to maintain a high reduction efficiency.

[0035] 3. The remediation and treatment method of the present application can remediate and treat hexavalent chromium-contaminated groundwater of different pollution levels. DETAILED DESCRIPTION

[0036] In order to improve the reduction efficiency and durability of micron-level zero-valent iron in remediating hexavalent chromium-contaminated groundwater, the inventors used acidic fermented organic waste and micron-level zero-valent iron to prepare a reducing agent, and studied a variety of fermented organic wastes. It was found that organic wastes such as vinegar dregs, wine dregs, sludge, soy sauce dregs, furfural residue, xylose residue, acid enzyme residue, fermented starch residue, fermented tofu residue, fermented apple residue, fermented pear residue, fermented beet residue, fermented bagasse, chloramphenicol residue, oxytetracycline residue, penicillin residue or erythromycin residue not only have an acidic pH, but also usually contain microorganisms inside. After being combined with micron-level zero-valent iron, they can effectively reduce hexavalent chromium and have strong durability.

[0037] The inventors further explored methods for remediating hexavalent chromium-contaminated groundwater using the aforementioned reducing agent and discovered that as groundwater flows and gravity pulls in, the zero-valent iron material settles, causing it to lose contact with fermented organic waste and reduce reduction efficiency. Therefore, the inventors used a woven fabric made of straw or rice straw as a permeable separator, mixed biomass debris such as sawdust, rice husks, bran, and humic acid with yellow mud and natural mineral powder to create a biomass anti-sedimentation layer, and then mixed porous adsorption materials such as activated carbon, bamboo charcoal, peat, and diatomaceous earth with the reducing agent to create an adsorption-reduction layer, thereby forming an adsorbable reaction wall that prevents zero-valent iron from settling and improves the durability of the reducing agent. The inventors also explored natural mineral powders and discovered that natural montmorillonite powder, natural vermiculite powder, or zeolite powder all have permeability and excellent mechanical strength, which not only facilitates groundwater infiltration but also reduces the collapse of the biomass anti-sedimentation layer.

[0038] The present application is further described in detail below with reference to the embodiments.

[0039] The raw materials used in this embodiment were all purchased from commercial sources.

[0040] Example

[0041] Example 1

[0042] This embodiment provides a reducing agent for treating hexavalent chromium-contaminated groundwater. The reducing agent comprises the following raw materials: 10 kg of solid zero-valent iron material and 10 kg of acidic bio-fermentation organic waste. The solid zero-valent iron material is iron powder with a particle size of 30-80 μm, and the acidic bio-fermentation organic waste is vinegar grains with a pH of 6.2.

[0043] After the solid zero-valent iron material and the acidic biological fermentation organic waste are evenly mixed, a reducing agent for hexavalent chromium-contaminated groundwater is obtained.

[0044] This embodiment also provides a method for repairing and treating hexavalent chromium-contaminated groundwater, comprising the following steps:

[0045] First, weave rice straw into a rectangular fabric to create a permeable separator. Then, mix activated carbon and the aforementioned reducing agent in a 1:1 weight ratio to create an adsorption-reduction material. Then, mix 13 kg of yellow mud, 2 kg of zeolite powder, and 13 kg of sawdust to create a biomass anti-settling material.

[0046] Next, four walls are constructed end-to-end using concrete, forming a rectangular tube. All four walls are arranged vertically. A permeable separation layer is placed between the four walls. A biomass anti-settling material is then laid on the permeable separation layer and smoothed. The adsorption-reduction material is then laid on the biomass anti-settling material. After smoothing, the adsorption-reduction material forms an adsorption-reduction layer. A further layer of biomass anti-settling material is then laid on the adsorption-reduction layer. After smoothing, the biomass anti-settling material on both sides of the adsorption-reduction layer together form a biomass anti-settling layer. A further permeable separation layer is then laid on the biomass anti-settling layer, resulting in a set of adsorbable reaction units.

[0047] According to the above operation, three groups of adsorbable reaction units are laid in sequence from bottom to top in the four walls. After the three groups of adsorbable reaction units are compacted from top to bottom, the three groups of adsorbable reaction units and the walls together form an adsorbable reaction wall.

[0048] Then the hexavalent chromium-contaminated groundwater is allowed to penetrate through the four walls from top to bottom. The adsorbable reaction wall can filter the pollutants in the hexavalent chromium-contaminated groundwater and reduce the hexavalent chromium. The hexavalent chromium content in the effluent from the bottom of the adsorbable reaction wall is tested. When the hexavalent chromium content does not meet the standard, the effluent is circulated through the permeable reaction wall. When the hexavalent chromium content meets the standard, the remediation of the hexavalent chromium-contaminated groundwater is completed.

[0049] Example 2

[0050] The difference between this embodiment and embodiment 1 is that the solid zero-valent iron material is iron powder with a particle size of 1-30 μm.

[0051] Example 3

[0052] The difference between this embodiment and embodiment 1 is that the solid zero-valent iron material is iron powder with a particle size of 80-100 μm.

[0053] Example 4

[0054] The difference between this embodiment and embodiment 1 is that the acidic biological fermentation organic waste is vinegar grains with a pH of 5.8.

[0055] Example 5

[0056] The difference between this embodiment and embodiment 1 is that the acidic biological fermentation organic waste is vinegar grains with a pH of 6.8.

[0057] Example 6

[0058] The difference between this embodiment and embodiment 1 is that the acidic biological fermentation organic waste is vinasse with a pH of 6.2.

[0059] Example 7

[0060] The difference between this embodiment and embodiment 1 is that the acidic biological fermentation organic waste is biogas residue with a pH of 6.2.

[0061] Example 8

[0062] The difference between this embodiment and embodiment 1 is that the reducing agent includes the following raw materials by weight: 5 kg of solid zero-valent iron material and 10 kg of acidic biological fermentation organic waste.

[0063] Example 9

[0064] The difference between this embodiment and embodiment 1 is that the reducing agent includes the following raw materials by weight: 15 kg of solid zero-valent iron material and 10 kg of acidic biological fermentation organic waste.

[0065] Example 10

[0066] This embodiment differs from Example 1 in that, in the remediation method for hexavalent chromium-contaminated groundwater of this embodiment, activated carbon and the aforementioned reducing agent are uniformly mixed at a weight ratio of 1:0.5 to obtain an adsorption-reduction material. Furthermore, 15 kg of yellow mud, 3 kg of zeolite powder, and 10 kg of sawdust are uniformly mixed to obtain a biomass anti-sedimentation material.

[0067] Example 11

[0068] This embodiment differs from Example 1 in that, in the remediation method for hexavalent chromium-contaminated groundwater of this embodiment, activated carbon and the aforementioned reducing agent are uniformly mixed in a weight ratio of 1:3 to obtain an adsorption-reduction material. Furthermore, 10 kg of yellow mud, 1 kg of zeolite powder, and 15 kg of sawdust are uniformly mixed to obtain a biomass anti-sedimentation material.

[0069] Example 12

[0070] The difference between this embodiment and embodiment 1 is that an equal amount of diatomaceous earth is used to replace the activated carbon.

[0071] Example 13

[0072] The difference between this embodiment and embodiment 1 is that the sawdust is replaced by a mixture of equal amounts of sawdust, rice husks, bran and humic acid in a weight ratio of 1:1:1:1.

[0073] Comparative Example

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the solid zero-valent iron material with a particle size of 30-80 μm is replaced by an equal amount of quartz sand with a particle size of 30-80 μm.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 1 is that the vinegar grains with a pH of 6.2 are replaced by an equal amount of unfermented sorghum residue with a pH of 6.2.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 1 is that the vinegar grains with a pH of 6.2 are replaced by an equal amount of vinegar grains with a pH of 7.2.

[0080] Performance testing

[0081] For the permeable reaction walls provided in Examples 1-13 and Comparative Examples 1-3, a hexavalent chromium solution containing 50 mg / L was circulated through the permeable reaction wall at a flow rate of 0.5-0.7 m / d. The hexavalent chromium content of the water outlet from the bottom of the permeable reaction wall was detected after 1 day, 2 days, and 5 days, respectively. The test results are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] Combining Example 1 and Comparative Examples 1-3 with Table 1, it can be seen that compared with Example 1, the hexavalent chromium content in the effluent of the permeable reaction wall of Comparative Examples 1-3 after 1 day, 2 days, and 5 days is higher than the hexavalent chromium content in the effluent of Example 1. This shows that the use of the reducing agent and repair reduction method in Example 1 helps to improve the reduction efficiency and durability of zero-valent iron.

[0086] Combining Examples 1-3 with Table 1, it can be seen that the hexavalent chromium content in the effluent of the permeable reaction walls of Examples 1-3 was low after 1, 2, and 5 days. However, the hexavalent chromium content in the effluent of Example 2 after 5 days was higher than that of Examples 1 and 3. This indicates that maintaining the zero-valent iron particle size within a larger range helps to prolong the durability of the reducing agent.

[0087] Combining Example 1, Examples 4-7, and Table 1, it can be seen that compared with Example 1, the permeable reaction wall of Example 4-7 has a smaller change in the hexavalent chromium content in the effluent after 1 day, 2 days, and 5 days. This indicates that within the type and pH range of the acidic biological fermentation organic waste of Examples 4-7, it is helpful to improve the reduction efficiency and durability of zero-valent iron.

[0088] Combining Example 1, Examples 8-13, and Table 1, it can be seen that compared with Example 1, the permeable reaction wall of Examples 8-13 has a smaller change in the hexavalent chromium content in the effluent after 1 day, 2 days, and 5 days. This shows that under the raw material ratios of Examples 8-13, the reduction efficiency and durability of zero-valent iron are all improved.

[0089] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A reducing agent for hexavalent chromium contaminated groundwater, characterized in that: It includes solid zero-valent iron material and acidic biological fermentation organic waste, wherein the particle size of the solid zero-valent iron material is 1-100 μm, and the acidic biological fermentation organic waste is the acidic solid residue after the organic biological material is fermented by microorganisms; The acidic biological fermentation organic waste is at least one of vinegar lees, wine lees, biogas residue, soy sauce lees, xylose residue, acid enzyme residue, fermented starch residue, fermented bean curd residue, fermented apple residue, fermented pear residue, fermented beet residue, fermented bagasse, lincomycin residue, oxytetracycline residue, penicillin residue or erythromycin residue; The pH of the acidic biological fermentation organic waste is 5.8-6.8; The weight ratio of the solid zero-valent iron material to the acidic biological fermentation organic waste is (0.5-1.5):

1.

2. A permeable reaction wall using the reducing agent for hexavalent chromium-contaminated groundwater according to claim 1, characterized in that: It includes a wall, a permeable separation layer, a biomass anti-sedimentation layer and an adsorption reduction layer. Several walls surround the periphery of the permeable separation layer. The permeable separation layer has several layers. The biomass anti-sedimentation layer is arranged between two relative permeable separation layers. The adsorption reduction layer is arranged in the biomass anti-sedimentation layer. The adsorption reduction layer includes a porous adsorption material and a reducing agent in a weight ratio of 1:(0.5-3).

3. The permeable reactive wall according to claim 2, characterized in that: The biomass anti-settling layer is a layer formed by biomass anti-settling material. Based on the total weight of the biomass anti-settling material, the biomass anti-settling material includes 10-15 parts by weight of yellow mud, 1-3 parts by weight of natural mineral powder and 10-15 parts by weight of biomass debris. The biomass debris is at least one of sawdust, rice husks, bran and humic acid.

4. The permeable reactive wall according to claim 2, characterized in that: The porous adsorption material is at least one of activated carbon, bamboo charcoal, peat and diatomaceous earth.

5. The permeable reactive wall according to claim 2, characterized in that: The permeable separation layer is a woven fabric woven from straw or rice straw.

6. A method for repairing and treating a permeable reactive wall according to claim 2, characterized in that: The steps include: A permeable separation layer is placed between several walls, a biomass anti-settling material is laid on the permeable separation layer, a porous adsorption material and the reducing agent are evenly mixed and laid on the biomass anti-settling material to form an adsorption-reduction layer, and then the biomass anti-settling material is laid on the adsorption-reduction layer. The biomass anti-settling materials on both sides of the adsorption-reduction layer constitute a biomass anti-settling layer, and a permeable separation layer is laid on the biomass anti-settling layer; Repeat the above operation and obtain a permeable reaction wall after compaction; Pass hexavalent chromium-contaminated groundwater through a permeable reactive wall.

Images