An active reaction medium, a permeable reaction wall and a method for its preparation, use and a method for early warning or online monitoring of pollutants

Abstract

The application provides an active reaction medium, a permeable reaction wall and a preparation method, a use method and a method for early warning or online monitoring of pollutants, and belongs to the field of groundwater pollutant degradation.The application provides an active reaction medium, which comprises porous biochar composed of carbon particles; and the surface of the carbon particles outside the porous biochar is coated with a transition metal element layer.The carbon particles of the outer layer of the porous biochar in the application have an outer metal-inner carbon structure, forming a primary cell; on the basis of retaining the high pollutant adsorption capacity of the porous biochar, the primary cell is used to drive electroactive microorganisms to efficiently degrade pollutants, so that the removal efficiency of the pollutants is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of groundwater pollutant degradation, and in particular to an active reaction medium, a permeable reaction wall and a preparation method and use method thereof, and a method for early warning or online monitoring of pollutants. BACKGROUND

[0002] Groundwater resources are an important part of water resources in China and are widely used for agricultural irrigation.

[0003] At present, there are three types of main groundwater pollutants, namely heavy metals, organic matter (pesticides) and inorganic ions (nitrate, ammonia nitrogen, total phosphorus, etc.). For single pollutants, soil and groundwater remediation technology is relatively mature. For example, residual pesticides are generally treated by ex-situ remediation technology, which can reduce the pollution area and the degree of pollution by pumping out the contaminated groundwater, and can achieve cleaning by transferring the pollutants in the aquifer through the water body. However, the ex-situ remediation technology has obvious shortcomings, such as high cost and unsuitability for long-term use. For heavy metal pollutants, physical, chemical and biological methods are mainly used to remove them. Among them, precipitation, ion exchange, adsorption and membrane separation are common methods for treating heavy metal wastewater. For inorganic ion pollutants (nitrate), the main methods include physical and chemical methods, chemical methods and biological methods. Physical and chemical methods mainly include electrodialysis, reverse osmosis, ion exchange method, etc. Ex-situ biological denitrification technology is based on the traditional nitrification-denitrification principle, which uses external carbon source as denitrification substrate to achieve groundwater denitrification.

[0004] However, multiple pollutants exist in the same environmental unit at the same time, or react with other pollutants during migration and transformation, resulting in environmental pollution phenomena that stress organisms, which is called complex pollution. Different pollutants complex, chelate, precipitate, oxidize and reduce, etc. to change their respective biological absorption, migration and transformation and produce complex biological effects. For example, mercury, tin and other heavy metals can react with organic pollutants to generate more toxic heavy metal organic compounds (methyl mercury, trimethyl tin, etc.).

[0005] Permeable reactive barrier (PRB) is a new method for in-situ removal of groundwater complex pollution in recent years. The PRB device is filled with active reaction medium. When the pollutants reach the corresponding area and contact the reaction medium, a series of physical, chemical or biological reactions will occur, and the pollutants will be degraded, adsorbed and finally removed. PRB has certain effect on various pollutants.

[0006] The PRB technology is closely related to the treatment principle of the pollutants in the groundwater and the filled reaction medium. When the reaction medium is zero-valent iron, the reduction of the valence of the heavy metals or the degradation of the organic matters are mainly utilized to reduce the migration or toxicity of the pollutants. When the reaction medium is apatite, zeolite, slag (volcanic rock slag) or mineral matter such as organic matter clay, the adsorption and precipitation are mainly utilized. When the reaction medium is carbon source, nutrient substance or microbial carrier, the microbial reaction activity is mainly utilized to degrade the organic pollutants. However, the existing reaction wall medium still has a low removal efficiency for various pollutants (organic matters, heavy metals, inorganic ions and various pollutants). SUMMARY

[0007] The present application aims to provide an active reaction medium, a permeable reaction wall, a preparation method, a use method and a method for early warning or online monitoring of pollutants, and the active reaction medium has a high removal efficiency for pollutants.

[0008] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions.

[0009] The present application provides an active reaction medium, which comprises porous biochar composed of carbon particles.

[0010] The surface of the carbon particles outside the porous biochar is coated with a transition metal element layer.

[0011] Preferably, the transition metal element comprises iron.

[0012] The present application further provides a preparation method of the active reaction medium.

[0013] The solution containing the transition metal salt is sprayed on the porous biochar, and then drying and calcination are sequentially performed to obtain the active reaction medium.

[0014] The volume ratio of the solution containing the transition metal salt to the porous biochar is 0.1-0.5:1, and the concentration of the transition metal salt in the solution is 0.1-1.0 mol / L.

[0015] The calcination temperature is 300-600 DEG C, and the time is 10-60 min.

[0016] Preferably, the solution of the transition metal salt further comprises one or more of ethylene glycol, polyhydroxy compound, polyvinylpyrrolidone and ammonia water.

[0017] The present application further provides a permeable reaction wall, which comprises a power supply, a wall body with a cavity, an active reaction medium, a conductive biofilm, degradation bacteria adsorbed on the conductive biofilm, an anode and a cathode.

[0018] The conductive biofilm covers the surface of the transition metal element layer of the outer carbon particles of the porous biochar and the surface of the internal carbon particles of the porous biochar of the active reaction medium.

[0019] The active reaction medium is filled in the cavity of the wall body.

[0020] The anode is located at the outer side of the wall body, and the cathode is inserted in the active reaction medium.

[0021] The positive pole and the negative pole of the power supply are connected with the anode and the cathode respectively.

[0022] The active reaction medium is the active reaction medium in the above technical solution or the active reaction medium prepared by the preparation method in the above technical solution.

[0023] Preferably, the degradation bacteria include oxidizing bacteria and / or reducing bacteria; the degradation bacteria adsorbed on the surface of the transition metal element layer in the active reaction medium are oxidizing bacteria, and the degradation bacteria adsorbed on the surface of the internal carbon particles of the porous biochar are reducing bacteria.

[0024] The application further provides a preparation method of the permeable reaction wall in the above technical solution, comprising the following steps:

[0025] (1) pouring concrete in the groundwater to be treated to obtain a wall body;

[0026] (2) placing the cathode and the anode in the corresponding positions, then adding the active reaction medium and the electrochemical conductive bacteria into the cavity of the wall body in sequence, and then applying an electric potential to form a conductive biofilm;

[0027] (3) adding the degradation bacteria into the cavity of the wall body, and then standing to make the degradation bacteria adsorbed on the conductive biofilm;

[0028] (4) connecting the positive pole and the negative pole of the power supply with the anode and the cathode respectively.

[0029] The step (4) has no sequence with the steps (1)-(3).

[0030] The application further provides a use method of the permeable reaction wall in the above technical solution or the permeable reaction wall prepared by the preparation method in the above technical solution, comprising the following steps:

[0031] (1) starting the treatment of the groundwater to be treated after the permeable reaction wall is prepared, and the transition metal layer in the active reaction medium generates a hydroxide precipitate through oxidation reaction;

[0032] (2) after the transition metal layer is partially or completely consumed, electrolyzing the permeable reaction wall to reduce the transition metal ions in the hydroxide precipitate into transition metal elements.

[0033] Steps (1)-(2) are repeated.

[0034] The application also provides a method for early warning or online monitoring of pollutants by the permeable reaction wall or the permeable reaction wall prepared by the preparation method.

[0035] The cathode is used as a working electrode to perform cyclic voltammetry curve scanning at intervals to obtain a cyclic voltammetry characteristic curve;

[0036] The consumption and degradation of pollutants are identified by the height change of the characteristic peak of the pollutants on the cyclic voltammetry characteristic curve before and after the scanning;

[0037] If the redox peak of the transition metal element is lower than the initial value, the permeable reaction wall is invalid.

[0038] Preferably, the interval is 1-5 days; the window range of the cyclic voltammetry characteristic curve scanning is-1.0-1.0 V, and the speed is 1-50 mV / s.

[0039] The application provides an active reaction medium, which comprises porous biochar composed of carbon particles; and a transition metal element layer is coated on the surface of the carbon particles outside the porous biochar. The carbon particles outside the porous biochar in the application have an outer metal-inner carbon structure, forming a primary battery, which can drive electroactive microorganisms to efficiently degrade pollutants on the basis of retaining the high pollutant adsorption capacity of the porous biochar, and improve the removal efficiency of pollutants.

[0040] The transition metal particles in the active reaction medium are consumed when treating groundwater, and intermittent electrolysis can supply electrons to the transition metal at intervals, so that the consumed transition metal elements are restored to the reduced state, thereby restoring the activity, which greatly improves the service life of the primary battery and achieves the ability of continuously degrading composite pollutants in groundwater. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is a structural schematic diagram of the permeable reaction wall of the embodiment;

[0042] Figure 2 It is a removal result diagram of the permeable reaction wall of the application example 1 on organic matters in groundwater;

[0043] Figure 3 It is a removal result diagram of the permeable reaction wall of the application example 1 on nitrate and sulfate;

[0044] Figure 4 It is a result diagram of the influence of the permeable reaction wall of the application example 1 on the conventional water quality of groundwater;

[0045] Figure 5 Figure for biological toxicity result of permeable reaction wall of application example 1 for treating groundwater. DETAILED DESCRIPTION

[0046] The application provides an active reaction medium, which comprises porous biochar composed of carbon particles; and a transition metal element layer is coated on the surface of the carbon particles outside the porous biochar.

[0047] The carbon particles inside the porous biochar are used for adsorbing reducing bacteria and also adsorbing pollutants as cathodes.

[0048] In the application, the transition metal element preferably comprises iron.

[0049] The application further provides a preparation method of the active reaction medium.

[0050] The solution containing the transition metal salt is sprayed on the porous biochar, and then drying and calcination are sequentially performed to obtain the active reaction medium.

[0051] The volume ratio of the solution containing the transition metal salt to the porous biochar is 0.1-0.5:1; and the concentration of the transition metal salt in the solution containing the transition metal salt is 0.1-1.0 mol / L.

[0052] The calcination temperature is 300-600 DEG C, and the time is 10-60 min.

[0053] In the application, the volume ratio of the solution containing the transition metal salt to the porous biochar is 0.1-0.5:1, and preferably 0.2-0.4:1. The solution cannot be sprayed too much, otherwise the entire porous biochar will be soaked in the solution, so that the internal carbon particles cannot be separated from the outer carbon particles; and the solution cannot be sprayed too little, otherwise the amount of active metal will be too small, and the catalytic effect will be poor.

[0054] In the application, the preparation raw material of the porous biochar preferably comprises one or more of residual sludge, waste tires, straws, excrement and kitchen waste.

[0055] In the application, the transition metal salt preferably comprises a chloride salt of a transition metal.

[0056] In the present application, the solution of the transition metal salt preferably further comprises one or more of ethylene glycol, a polyhydroxy compound, polyvinylpyrrolidone and ammonia water, and the total concentration of the one or more of ethylene glycol, a polyhydroxy compound, polyvinylpyrrolidone and ammonia water in the solution is preferably 50-200 g / L, more preferably 100-180 g / L, and further preferably 120-160 g / L. Ethylene glycol, a polyhydroxy compound, polyvinylpyrrolidone and ammonia water are used as reducing agents and surfactants: as reducing agents to help reduce the transition metal salt to transition metal elements, while the size and morphology of the nanoparticles can also be controlled by adjusting the reaction conditions; as surfactants, to help stabilize the dispersion state of the iron nanoparticles, prevent their agglomeration and precipitation, and maintain the dispersibility and stability of the material.

[0057] In the present application, the calcination is preferably carried out under anaerobic conditions; the temperature of the calcination is 300-600℃, preferably 350-500℃, and further preferably 400-450℃; and the time is 10-60 min, preferably 20-50 min, and further preferably 30-40 min. The calcination temperature cannot be too low, as too low a temperature will result in the transition metal salt being unable to be reduced to the elemental state by the porous biochar, and too high a temperature will result in wasted energy; the calcination time also cannot be too short, as too short a time will result in the iron catalytic material not being fully formed, and too long a time will result in wasted energy.

[0058] In the present application, after the calcination, the obtained product is preferably further cooled to obtain the active reaction medium. In the present application, the cooling is preferably carried out under anaerobic conditions.

[0059] The present application provides a permeable reaction wall, comprising a power supply, a wall body having a cavity, an active reaction medium, a conductive biofilm, degrading bacteria adsorbed on the conductive biofilm, an anode and a cathode.

[0060] The conductive biofilm covers the surface of the carbon particles inside the porous biochar of the active reaction medium and the surface of the transition metal element layer of the carbon particles outside the porous biochar;

[0061] The active reaction medium is filled in the cavity of the wall body;

[0062] The anode is located on the outside of the wall body, and the cathode is inserted into the active reaction medium;

[0063] The positive and negative poles of the power supply are connected to the anode and the cathode, respectively;

[0064] The active reaction medium is the active reaction medium described in the above technical solution or prepared by the preparation method described in the above technical solution.

[0065] The permeable reaction wall comprises a power supply, wherein the positive pole and the negative pole of the power supply are connected with the anode and the cathode respectively, and the power supply is preferably a stabilized direct current power supply.

[0066] The permeable reaction wall preferably further comprises a central control platform, wherein the central control platform is used for controlling the power supply.

[0067] The permeable reaction wall comprises a wall body, wherein the wall thickness of the wall body is preferably 60-100 cm.

[0068] The permeable reaction wall comprises an active reaction medium, wherein the active reaction medium is filled in the cavity of the wall body.

[0069] The permeable reaction wall comprises a conductive biofilm covering the surface of the active reaction medium, wherein the conductive biofilm is used for connecting the oxidizing microorganism with the transition metal element layer and the reducing microorganism with the carbon particles inside the porous biochar.

[0070] The permeable reaction wall comprises degrading bacteria adsorbed on the conductive biofilm, wherein the degrading bacteria preferably comprise oxidizing bacteria and / or reducing bacteria, the degrading bacteria adsorbed on the surface of the conductive biofilm covering the surface of the transition metal element layer are preferably oxidizing bacteria, and the degrading bacteria adsorbed on the surface of the conductive biofilm covering the surface of the carbon particles inside the porous biochar are preferably reducing bacteria.

[0071] The permeable reaction wall comprises an anode, wherein the anode is located on the outer side of the wall body, and the area of the anode is preferably 50-100% of the area of the cathode.

[0072] The permeable reaction wall comprises a cathode, wherein the cathode is inserted into the active reaction medium, and the material of the cathode preferably comprises one or more of carbon-based materials, metal materials and conductive polymers, and is further preferably a metal material, and the metal material preferably comprises stainless steel and / or titanium.

[0073] In the permeable reaction wall, the area ratio of the cathode to the single wall surface is preferably 0.1-0.5:1, and more preferably 0.2-0.4:1.

[0074] The application further provides a preparation method of the permeable reaction wall.

[0075] (1) pouring concrete in the groundwater to be treated to obtain a wall body;

[0076] (2) placing a cathode and an anode in corresponding positions, then adding an active reaction medium and electrochemical conductive bacteria into a cavity of the wall body in sequence, and then applying an electric potential to form a conductive biofilm;

[0077] (3) adding degrading bacteria into the cavity of the wall body and then standing to make the degrading bacteria adsorbed on the conductive biofilm;

[0078] (4) connecting a positive pole and a negative pole of a power supply to the anode and the cathode respectively;

[0079] The step (4) and the steps (1)-(3) have no sequence.

[0080] (1) pouring concrete in the groundwater to be treated to obtain a wall body.

[0081] The application places a cathode and an anode in corresponding positions, then adds an active reaction medium and electrochemical conductive bacteria into a cavity of the wall body in sequence, and then applies an electric potential to form a conductive biofilm.

[0082] In the application, the electrochemical conductive bacteria preferably include Geobacter and / or Shewanella; and the open circuit potential of the electrochemical conductive bacteria is preferably-0.4 V. In the application, the thickness of the conductive biofilm is preferably 1-20 μm.

[0083] When the open circuit potential of the electrochemical conductive bacteria is-0.4 V, the electric potential applied is preferably-0.3-0.2 V vs Ag / AgCl, the time is preferably 6-48 h, more preferably 12-36 h, and further preferably 18-24 h. The electric potential applied is preferably applied at the cathode; the open circuit potential of-0.4 V and the slightly positive electric potential applied are beneficial to the rapid formation of the electrochemical conductive bacteria. A conductive biofilm is formed on the surface of the transition metal element layer and the surface of the carbon particles inside the porous biochar.

[0084] After the conductive biofilm is formed, the application adds degrading bacteria into the cavity of the wall body and then stands to make the degrading bacteria adsorbed on the conductive biofilm.

[0085] In the present application, the degrading bacteria preferably include oxidizing bacteria and / or reducing bacteria; the surface-adsorbed degrading bacteria of the conductive biofilm covering the surface of the transition metal element layer are oxidizing bacteria, and the surface-adsorbed degrading bacteria of the conductive biofilm covering the surface of the carbon particles inside the porous biochar are reducing bacteria. In the present application, the degrading bacteria are preferably obtained by domestication and screening from the activated sludge in a local sewage plant. The method for domestication in the present application is not particularly limited, and the degrading bacteria in the sludge can be sufficiently propagated.

[0086] In the present application, the standing time is preferably 6-48 h, more preferably 12-36 h, and further preferably 18-24 h. During the standing process, the degrading bacteria complete adsorption and accumulation on the surface layer of the conductive biofilm. Since the primary cell base is porous biochar, it has extremely high adsorption capacity and can quickly adsorb these degrading bacteria to the surface. Then, the degrading bacteria are adhered by extracellular polymers on the surface of the conductive biofilm and can quickly form a biofilm. The potentials of the external and internal carbon particles are different, and different degrading bacteria will spontaneously select different potentials for adsorption.

[0087] In the present application, step (3) preferably further comprises: applying a potential to make the metal layer that has been consumed restore to a reduced state again.

[0088] In the present application, the potential applied in the step is preferably -1.0 to -0.5 V vs Ag / AgCl, and the time is preferably 1-2 h. The step of applying a potential is to make the metal layer that has been consumed restore to a reduced state again. Too long time of the step will result in waste of energy consumption and affect the activity of oxidizing microorganisms, and too short time of the step will result in insufficient metal reduction effect.

[0089] The present application also provides a use method of the permeable reaction wall prepared by the preparation method of the above technical solution, comprising the following steps:

[0090] (1) The permeable reaction wall starts to treat the groundwater to be treated after being prepared, and the transition metal layer undergoes an oxidation reaction to generate a hydroxide precipitate;

[0091] (2) After the transition metal layer is partially or completely consumed, the permeable reaction wall is electrolyzed to reduce the transition metal ions in the hydroxide precipitate to transition metal elements;

[0092] Steps (1)-(2) are repeated.

[0093] In the application, the interval time of the electrolysis is preferably 6-48h, more preferably 12-36h, and further preferably 18-24h; the potential during the electrolysis is preferably -1.0--0.5V vs Ag / AgCl, and the time is preferably 1-2h. Traditional bioelectrochemistry is to form a biological membrane on the electrode surface to react, but the reaction only occurs on the electrode surface, so the reaction efficiency is low, and the reaction medium is deactivated and is disposable. The Fe-C ball can greatly increase the reaction area, and can be recovered by electrochemistry, thereby improving the efficiency and being reusable.

[0094] The application can permeate the reaction wall, and the principle of degrading pollutants is as follows:

[0095] The Fe-C primary battery generates a micro-electrolysis process, the outer layer iron loses electrons and transfers to the inner carbon particles: after the outer layer iron loses electrons, the electrons are obtained from the loaded microorganisms, and then the microorganisms obtain electrons from the external pollutants, thereby promoting the oxidation reaction (such as converting organic matter into carbon dioxide) of the outer layer; the inner carbon particles obtain electrons, and then transfer the electrons to the loaded microorganisms, and then the microorganisms use the electrons for the reduction reaction (such as denitrification and denitrification) of the pollutants; in addition, some organic pollutants need to be oxidized and reduced cooperatively, such as nitrobenzene, which needs to be reduced and denitrified, and then oxidized and mineralized. After the outer layer iron loses electrons, ferrous and ferric iron are gradually generated to form iron hydroxide precipitate, but most of the iron hydroxide precipitate is adsorbed by the inner carbon particles (a small amount of iron hydroxide precipitate is lost), and after the outer layer iron is completely consumed, the electron transfer does not occur, at this time, electrolysis is performed to reduce the ferrous and ferric iron to the elemental iron.

[0096] The application also provides a method for early warning or online monitoring of pollutants by the permeable reaction wall or the permeable reaction wall prepared by the preparation method.

[0097] The cathode is used as a working electrode to perform cyclic voltammetry curve scanning at intervals, and a cyclic voltammetry characteristic curve is obtained;

[0098] The change in the height of the pollutant characteristic peak on the cyclic voltammetry characteristic curve before and after the cyclic voltammetry characteristic curve is used to identify whether the pollutant is consumed and degraded;

[0099] If the redox peak of the transition metal element is lower than the initial redox peak, the permeable reaction wall is invalid.

[0100] In the application, the interval time is preferably 1-5 days; the window range of the cyclic voltammetry characteristic curve scanning is preferably -1.0-1.0V, and the speed is preferably 1-50mV / s.

[0101] The structure of the permeable reaction wall of the embodiment of the present application is shown in the figure as follows: 1-permeable reaction wall outer wall, 2-anode electrode, 3-active reaction medium, 4-cathode, 5-control system, 301-reducing microorganism, 302-carbon particle, 303-metal layer modified carbon particle, 304-oxidizing microorganism. Figure 1

[0102] The active reaction medium, the permeable reaction wall, the preparation method, the use method and the method for early warning or online monitoring of pollutants provided by the present application will be described in detail below in combination with the embodiments, but they cannot be understood as limiting the protection scope of the present application.

[0103] Embodiment 1

[0104] The preparation method of the active reaction medium is as follows:

[0105] The solution containing 100 g / L ethylene glycol and 0.2 mol / L ferric chloride is sprayed on the porous biochar, and then drying, calcination and cooling are sequentially performed to obtain the active reaction medium;

[0106] The volume ratio of the solution containing the transition metal salt to the porous biochar is 0.3:1;

[0107] The calcination is performed under anaerobic condition, the temperature of the calcination is 500 DEG C, and the time is 20 min; the cooling is performed under anaerobic condition.

[0108] Application Example 1

[0109] The present application provides a permeable reaction wall, which is composed of a central control platform, a stable voltage direct current power supply, a wall body, an active reaction medium, a conductive biofilm covering the surface of the active reaction medium, degrading bacteria adsorbed on the conductive biofilm, an anode and a cathode.

[0110] The concrete is poured in the groundwater (the main pollutants are organic matters such as p-chloronitrobenzene and naphthalene, and inorganic ions such as nitrate, and the groundwater flow rate is about 2 m / day) of an industrial plot to obtain a wall body with a depth of 4 meters and a length of 10 meters (the wall thickness of the wall body is 20 cm respectively; the wall surface spacing of the wall body is 40 cm);

[0111] After the cathode and the anode are placed in the corresponding positions, 16 m 3 The active reaction medium of the pile volume embodiment 1 and the Geobacter bacteria are added into the cavity of the wall body (the Geobacter is added in the form of bacterial liquid, and the total amount of solid microorganism is 10 kg), and then the electric potential (the electric potential is 0 V vs Ag / AgCl, and the time is 40 h) is applied to form a conductive biofilm with a thickness of 1-20 μm;

[0112] ​The anode is located on the outside of the wall, and the cathode is inserted into the active reaction medium; the anode is located on the outside of the wall; the area of ​​the anode is 50% of the area of ​​the cathode, and the anode is made of titanium. The cathode is also made of titanium; the area of ​​the cathode is 0.2:1 compared to the area of ​​a single wall surface, with a total area of ​​8m². 2 It consists of 8 electrodes, each 4 meters deep and 0.25 meters wide.

[0113] Effective degradation bacteria were domesticated and screened from activated sludge from a local wastewater treatment plant. After the degradation bacteria were added to the cavity of the wall, they were allowed to stand to allow them to fully adsorb onto the conductive biofilm. Then, an electric potential was applied. The standing time was 10 hours. The applied electric potential was -0.8V vsAg / AgCl for 2 hours.

[0114] Connect the positive and negative terminals of the power supply to the anode and cathode, respectively;

[0115] During the treatment process, the permeable reactive wall is subjected to intermittent electrolysis; the interval between intermittent electrolysis is 24 hours; the electrolysis potential is -1V vsAg / AgCl, and the time is 2 hours.

[0116] The residence time of polluted groundwater in the permeable reactive barrier of this invention is approximately 19.2 days, and its removal results of organic matter in the groundwater are as follows: Figure 2 As shown, the removal results of nitrates and sulfates are as follows: Figure 3 As shown; the results of the impact on conventional groundwater quality are as follows. Figure 4 As shown; biotoxicity results are as follows Figure 5 As shown.

[0117] Depend on Figure 2 It can be seen that the permeable reactive wall of the present invention has a removal rate of more than 80% for a variety of organic pollutants;

[0118] Depend on Figure 3 It is known that the permeable reactive wall of the present invention has a 100% nitrate removal rate and can also remove some sulfate pollutants;

[0119] Depend on Figure 4 It can be seen that the permeable reactive wall of the present invention has no significant impact on the conventional water quality (conductivity, pH, etc.) of groundwater;

[0120] Depend on Figure 5 It can be seen that after treatment with the permeable reactive wall of the present invention, the biotoxicity of groundwater is reduced from 66% to 41%.

[0121] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A permeable reactive barrier, characterized in that, The wall body comprises a power supply, a wall body with a cavity, an active reaction medium, a conductive biofilm, degrading bacteria adsorbed on the conductive biofilm, an anode and a cathode. The active reaction medium comprises porous biochar composed of carbon particles; the surface of the carbon particles outside the porous biochar is coated with a transition metal element layer. The conductive biofilm covers the surface of the carbon particles inside the porous biochar and the surface of the transition metal element layer of the carbon particles outside the porous biochar. The active reaction medium is filled in the cavity of the wall body. The anode is located on the outer side of the wall body, and the cathode is inserted into the active reaction medium. The positive and negative poles of the power supply are connected with the anode and the cathode respectively.

2. The permeable reactive wall of claim 1, wherein, The transition metal element comprises iron.

3. The permeable reactive wall of claim 1, wherein, The preparation method of the active reaction medium comprises the following steps: a solution containing a transition metal salt is sprayed on the porous biochar, followed by drying and calcination to obtain the active reaction medium; the volume ratio of the solution containing the transition metal salt to the porous biochar is 0.1-0.5:1; the concentration of the transition metal salt in the solution is 0.1-1.0 mol / L; the calcination temperature is 300-600 ℃, and the time is 10-60 min.

4. The permeable reactive wall of claim 3, wherein, The solution of the transition metal salt further comprises one or more of ethylene glycol, a polyhydroxy compound, polyvinylpyrrolidone and ammonia.

5. The permeable reactive wall of claim 1, wherein, The degrading bacteria comprise oxidizing bacteria and reducing bacteria; the degrading bacteria adsorbed on the surface of the conductive biofilm covering the surface of the transition metal element layer are oxidizing bacteria, and the degrading bacteria adsorbed on the surface of the conductive biofilm covering the surface of the carbon particles inside the porous biochar are reducing bacteria.

6. The method of making a permeable reactive barrier according to any one of claims 1 to 5, wherein, The method comprises the following steps: (1) pouring concrete in the groundwater to be treated to obtain a wall body; (2) placing the cathode and the anode in the corresponding positions, then adding the active reaction medium and the electrochemical conductive bacteria into the cavity of the wall body in sequence, and then applying an electric potential to form a conductive biofilm; (3) adding degrading bacteria into the cavity of the wall body and standing to allow the degrading bacteria to be adsorbed on the conductive biofilm; (4) connecting the positive and negative poles of the power supply with the anode and the cathode respectively; The step (4) has no sequence with steps (1)-(3).

7. Use of a permeable reactive barrier according to any one of claims 1 to 5 or a permeable reactive barrier produced according to the method of claim 6, characterized in that, The method comprises the following steps: (1) the permeable reaction wall starts to treat the groundwater to be treated after being prepared, and the transition metal element layer in the active reaction medium generates a hydroxide precipitate through oxidation reaction; (2) after the transition metal element layer is partially or completely consumed, electrolysis is performed on the permeable reaction wall to reduce the transition metal ions in the hydroxide precipitate to transition metal elements; steps (1)-(2) are repeated.

8. A method for early warning or on-line monitoring of pollutants by the permeable reactive barrier according to any one of claims 1 to 5 or produced by the method according to claim 6, characterized in that, The method comprises the following steps: at intervals, the cathode is used as a working electrode to perform cyclic voltammetry curve scanning to obtain a cyclic voltammetry characteristic curve; whether the pollutants are consumed and degraded is identified by the height change of the characteristic peaks of the pollutants on the front and back cyclic voltammetry characteristic curves; if the redox peaks of the transition metal elements become lower than the initial redox peaks, the permeable reaction wall is invalid.

9. The method of claim 8, wherein, The interval is 1-5 days; the window range of the cyclic voltammetry characteristic curve scanning is -1.0-1.0 V, and the speed is 1-50 mV / s. The interval is 1-5 days; the window range of the cyclic voltammetry characteristic curve scanning is -1.0-1.0 V, and the speed is 1-50 mV / s.

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