Method for removing heavy metals in fly ash

Abstract

The invention relates to the field of household garbage treatment, in particular to a method for removing heavy metal in fly ash. Comprising the following steps: preparing a reaction container and electrodes, uniformly mixing to-be-treated fly ash and water, adding an acid solution to obtain a weakly acidic fly ash suspension, starting a low-voltage power supply to apply a voltage of 1.2 V or below to a positive electrode and a negative electrode, turning off the power supply, taking out the treated fly ash, sending the treated fly ash for inspection, and performing landfill or resource utilization after the treated fly ash is detected to be qualified. Heavy metal ions in the fly ash can be rapidly removed, heavy metal in the fly ash is eliminated, the operation cost and the maintenance cost of electric power fly ash treatment equipment can be further reduced by combining the characteristics of low voltage and low energy consumption, and good economic feasibility is achieved.

Description

Technical Field

[0001] The present application relates to the field of domestic waste treatment, and particularly to a method for removing heavy metals from fly ash. Background Art

[0002] Fly ash is the capture product of the flue gas purification system of domestic waste incineration facilities and the bottom ash sedimented at the bottom of the flue and chimney. Fly ash is usually in the form of light gray or yellowish-brown powder, with uneven particle sizes, complex structures and variable properties, and mostly exists in the form of amorphous and polycrystalline aggregate structures. Fly ash often contains high concentrations of heavy metals such as mercury, lead, cadmium, copper, chromium and zinc. These heavy metals are toxic, non-degradable and easy to accumulate in the environment. Once discharged into the environment with fly ash, they will cause serious pollution to soil, water bodies and the atmosphere, and then endanger human health and the stability of the ecosystem through the transmission of the food chain.

[0003] At present, fly ash treatment technologies mainly include solidification / stabilization technology, leaching technology and electrokinetic treatment technology, etc. Solidification / stabilization technology is the most commonly used technical means. Although it can reduce the leaching toxicity of heavy metals to a certain extent, the heavy metals still remain in the fly ash and are not removed, and often gradually re-release after several years and enter the environment. At the same time, such technologies often require the use of a large amount of chemical agents, posing a risk of secondary pollution.

[0004] Leaching technology is one of the most commonly used resource utilization technologies. Leaching technology can significantly reduce the chloride salt and heavy metal concentrations in fly ash by adding acid, water, etc., but it is difficult to completely remove heavy metals, with a certain proportion of residues; at the same time, its treatment results are significantly affected by the differences in fly ash components. Moreover, due to the addition of a large amount of acid or water during the leaching process, the generated polluted wastewater has problems such as secondary pollution and too high secondary disposal costs.

[0005] Existing electrokinetic fly ash treatment technologies all drive the migration of fly ash particles and heavy metal ions through relatively high voltages, with extremely high energy consumption, but the treatment effect is not significant and the efficiency is low. There are currently no practical application cases.

[0006] Therefore, developing a new type of fly ash treatment technology with low cost, environmental friendliness, high efficiency and the ability to remove heavy metals has an important role in practical applications. Summary of the Invention

[0007] In order to solve the problems of low removal efficiency, secondary pollution and high cost in the treatment of fly ash heavy metals in the prior art, the present application provides a method for removing heavy metals from fly ash.

[0008] The method for removing heavy metals from fly ash provided by the present application adopts the following technical solution: A method for removing heavy metals from fly ash, comprising the following steps: S1. Prepare a reaction vessel and electrodes. The reaction vessel includes an anode tank, a treatment tank, and a cathode tank. The treatment tank is located between the anode tank and the cathode tank. There are microporous structure walls between the anode tank and the treatment tank, and between the cathode tank and the treatment tank. A positive electrode is provided in the anode tank, and a negative electrode is provided in the cathode tank. The positive electrode and the negative electrode are respectively connected to a low-voltage power supply. The preparation materials of the positive electrode and the negative electrode include conductive activated carbon, which consists of activated carbon, conductive carbon, a binder, and a conductive mesh. The mixture of conductive carbon and activated carbon is bonded to the conductive mesh through the binder to form a conductive activated carbon electrode; S2. Put the pre-prepared fly ash suspension into the treatment tank. The preparation process of the fly ash suspension is as follows: Mix the fly ash to be treated and water evenly, and obtain a weakly acidic fly ash suspension by adding acid solution; S3. Start the low-voltage power supply and apply a voltage of less than 1.2 V to the positive electrode and the negative electrode; S4. After treatment for a set time, turn off the power supply, take out the treated fly ash and send it for inspection, and carry out landfill or resource utilization after passing the inspection.

[0009] By adopting the above technical solution, after the fly ash is acid-adjusted, heavy metal ions are ionized. After the positive and negative electrodes are energized, a potential difference is generated, attracting heavy metal cations to move from the treatment tank to the cathode tank, thus realizing the treatment of heavy metals in the fly ash. Since the decomposition voltage of water is 1.23 V, the present application controls the low voltage, which will not cause water decomposition, directly realizes the migration of ionic impurities driven by a stable electric field, and combined with the above-mentioned special electrodes, realizes the efficient removal of heavy metals in the fly ash under low energy consumption conditions, thus effectively treating the fly ash to meet the environmental protection standards of domestic waste and greatly improving the resource utilization value.

[0010] As a further improvement of the above technical solution, in step S2, when preparing the fly ash suspension, dehydrate the obtained weakly acidic fly ash suspension, and mix the dehydrated fly ash with an appropriate amount of activation liquid to obtain a new fly ash suspension.

[0011] By adopting the above technical solution, the activation liquid can inhibit the pH value of the liquid in the reaction vessel, making the acidity and alkalinity not easily unbalanced. At the same time, the reaction of the whole treatment process is stable, which can promote the movement of heavy metal ions and reduce the consumption of electrode materials.

[0012] As a further improvement of the above technical solution, the voltage applied to the positive electrode and the negative electrode is lower than the decomposition voltage of the activation liquid.

[0013] By adopting the above technical solution, the applied voltage is lower than the decomposition voltage of the activation liquid, aiming to effectively control the occurrence of water decomposition.

[0014] As a further improvement of the above technical solution, the activation solution includes one or more mixed solutions of a sodium dihydrogen phosphate-disodium hydrogen phosphate system, a potassium dihydrogen phosphate-sodium hydroxide system, a citric acid-sodium citrate system, a disodium hydrogen phosphate-citric acid system, an acetic acid-sodium acetate system, a formic acid-sodium formate buffer solution, a sodium oxalate-oxalic acid buffer solution, and a sodium sulfite-sulfite buffer solution. The pH value of the sodium dihydrogen phosphate-disodium hydrogen phosphate system is 6.5-7.5, and the pH value of the acetic acid-sodium acetate system is 3.75-6.5.

[0015] By adopting the above technical solution, the ions ionized by the activation liquid are weakly alkaline or weakly acidic, which are easy to react with hydrogen ions or hydroxide ions, regulate the acid-base balance of the soil area near the electrode, and maintain a neutral environment. The activation liquid stabilizes the reaction of the entire treatment process, can promote the movement of heavy metal ions, and reduce the consumption of electrode materials.

[0016] As a further improvement of the above technical solution, the conductive mesh includes one of a flexible metal mesh, a flexible non-metal mesh, a rigid non-metal mesh and a rigid metal mesh.

[0017] By adopting the above technical solutions, metal conductive mesh can be used in low-chlorine (chlorine-free) environments, non-metallic conductive mesh can be used in high-chlorine environments, and can also be used in low-chlorine (chlorine-free) environments. Flexible mesh can adapt to different shapes (such as cylindrical, L-shaped), with more application scenarios. Flexible mesh has better space utilization, and can be folded to fit a larger area of ​​material in a limited space; rigid mesh is more convenient for recycling.

[0018] As a further improvement of the above technical solution, the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, perfluorosulfonic acid resin, polyvinylidene fluoride-hexafluoropropylene copolymer, isocyanate binder, epoxy resin binder and guar gum.

[0019] By adopting the above technical solution, the binder plays a role of bonding the components, combining the activated carbon and the conductive carbon black together, and firmly attaching them to the conductive net.

[0020] As a further improvement of the above technical solution, in S4, the fly ash suspension after removal and treatment is dehydrated and then sent for inspection.

[0021] By adopting the above technical scheme, the fly ash after acid leaching contains a large amount of heavy acid, metal elements and chloride ions. Dehydration is not only to remove pollutants, but also to reduce the corrosion of chloride ions to the electrode and extend the service life of the electrode.

[0022] As a further improvement of the above technical solution, the microporous structure wall includes permeable bricks, silica aerogel, soil or graphite felt.

[0023] By adopting the above technical solution, the structural wall of the above material can permeate water and metal ions, enabling the free transmission of ionic impurities, but playing a certain blocking role on non-ionic substances, that is, allowing electromigration and restricting diffusion and convection.

[0024] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application can quickly remove heavy metal ions in fly ash and truly eliminate the heavy metal problem of fly ash; through electrodes with special properties, efficient electrokinetic treatment can be achieved at low voltage, while effectively controlling the occurrence of water decomposition, directly realizing the migration of ionic impurities driven by a stable electric field, greatly reducing energy consumption, saving treatment costs, and improving energy utilization efficiency.

[0025] 2. During the electrokinetic treatment process, an activation liquid is added. The ion pairs in the activation liquid can react with the hydrogen ions and hydroxide ions generated near the two electrodes respectively to regulate the pH value in the reaction vessel, making the acidity and alkalinity not easily unbalanced. The activation liquid has a spontaneous dynamic regulation ability and is not affected by either acidification or alkalization, making the reaction process of the entire treatment process very stable, promoting the movement of heavy metal ions, and reducing the consumption of electrode materials. Description of the Drawings

[0026] Figure 1 is a flowchart of the method for removing heavy metals in fly ash of the present application.

[0027] Figure 2 is a schematic structural diagram of the reaction vessel and electrodes in the method for removing heavy metals in fly ash of the present application.

[0028] Description of the reference numerals: 1. Anode tank; 2. Treatment tank; 3. Cathode tank; 4. Microporous structural wall; 5. Anode electrode; 6. Cathode electrode. Detailed Embodiments

[0029] The following is a further detailed description of the present application in conjunction with the attached Figure 1-2 drawings.

[0030] The orientation words such as "upper", "lower", "left", "right", "front", and "rear" in the present application only represent the relative positions in the drawings, which are for the convenience of describing the present application and do not represent the absolute positions of the products, and should not be construed as a limitation to the present application.

[0031] The embodiments of the present application disclose a method for removing heavy metals in fly ash.

[0032] As Figure 1 and Figure 2 shown, for the method for removing heavy metals in fly ash of this embodiment, first, prepare a reaction vessel and electrodes: The reaction vessel includes an anode tank 1, a treatment tank 2, and a cathode tank 3. The treatment tank 2 is located between the anode tank 1 and the cathode tank 3. A microporous structure wall 4 is provided between the anode tank 1 and the treatment tank 2, and a microporous structure wall 4 is provided between the cathode tank 3 and the treatment tank 2. The microporous structure wall 4 has water-permeable micropores that can pass water molecules and solutes dissolved therein, but prevent the convection of the solutions on both sides of the structure wall.

[0033] The electrodes include a positive electrode 5 and a negative electrode 6. The positive electrode 5 is arranged in the anode tank 1, and the negative electrode 6 is arranged in the cathode tank 3. The positive electrode 5 and the negative electrode 6 are respectively connected to a low-voltage power supply (not shown in the figure). The preparation materials of the positive electrode 5 and the negative electrode 6 include conductive activated carbon. The conductive activated carbon includes activated carbon, conductive carbon, a binder, and a conductive mesh. The mixture of conductive carbon and activated carbon is bonded to the conductive mesh through the binder to form a conductive activated carbon electrode. The electrode is set as conductive activated carbon. On the one hand, it is convenient to accommodate heavy metal ions. On the other hand, it has a large specific surface area and a large capacity for storing heavy metal ions. This electrode has an extremely large specific surface area and conductivity, which can greatly increase the contact area between the electrode and the solution and provide favorable conditions for maintaining the current during the treatment process.

[0034] Secondly, after the reaction vessel and the electrodes are prepared, the pre-prepared fly ash suspension is put into the treatment tank 2. Among them, the preparation process of the fly ash suspension is as follows: The fly ash to be treated is mixed evenly with water, and a weakly acidic fly ash suspension is obtained by adding an acid solution. The acid solution can be a strong acid such as nitric acid, hydrochloric acid, or sulfuric acid. The purpose is to ionize the heavy metal elements in the fly ash.

[0035] Thirdly, next, the low-voltage power supply is started. Here, the low voltage is a voltage below 1.2V, that is, a voltage below 1.2V is applied to the positive electrode 5 and the negative electrode 6 (forming an ultra-low-voltage electric field). Since the decomposition voltage of water is 1.23V, the electrolysis of water is controlled at this time. After the positive electrode 5 and the negative electrode 6 are energized, a potential difference is generated. The heavy metal cations after the ionization of the heavy metal ions in the fly ash move from the treatment tank 2 of the fly ash through the microporous structure wall 4 into the cathode tank 3 and are adsorbed on the negative electrode 6, realizing the treatment of the heavy metals in the fly ash. Since the specific surface area of the conductive activated carbon is relatively large and there are holes in the structure for accommodating ions. After the heavy metal ions enter the conductive activated carbon, they stop moving and are accommodated in its holes. The workers replace the electrodes regularly.

[0036] Finally, after that, after treatment for a set time, the power supply is turned off, the treated fly ash is taken out and sent for inspection, and after the heavy metal ion content is qualified in the test, it is landfilled or used for resource utilization.

[0037] Since the fly ash suspension after acid adjustment of fly ash may contain chloride ions, and chloride ions will corrode the electrodes. In this embodiment, in order to improve the service life of the electrodes, make the reaction more stable and the cost lower, when preparing the above fly ash solution, the obtained weakly acidic fly ash suspension is dehydrated, and the dehydrated fly ash is mixed with an appropriate amount of activation liquid to obtain a new fly ash suspension. Because after acid adjustment, there are a large number of heavy metal ions and chloride ions in the acid solution. The heavy metal ions affect the treatment efficiency, and the chloride ions will corrode the metal electrodes. Dehydration is to remove pollutants on the one hand, protect various equipment, and at the same time reduce the corrosion of the electrodes by chloride ions and extend the service life of the electrodes. In order to avoid the electrolysis of water in the activation liquid, the voltage applied to the anode 5 and the cathode 6 is lower than the decomposition voltage of the activation liquid. In this embodiment, the preferred voltage is 0.8 - 1.2V.

[0038] In this embodiment, the core function of the activation liquid is stabilization, preventing phenomena such as overpotential at the microscopic level. The activation liquid is located on the outer peripheral side of the anode and cathode. After the electrodes are energized, the water molecules (the water in the activation liquid) in the reaction vessel may be electrolyzed (the theoretical electrochemical stability window of water is 1.23V. In reality, under the influence of the concentration polarization of the electrolyte, although the external circuit voltage is lower than 1.23V, but at the electrode interface, the voltage will be higher than the applied voltage, and may be higher than 1.23V, thus triggering the local electrolysis of water) into hydrogen ions and hydroxide ions. Under the influence of the electric field, the hydrogen ions will move towards the cathode 6, and the hydroxide ions will move towards the anode 5, resulting in a change in the acidity and alkalinity near the two electrodes. The ion pairs in the activation liquid can react with the hydrogen ions and hydroxide ions generated near the two electrodes respectively, regulate the pH value in the reaction vessel, and make the acidity and alkalinity not easily unbalanced. At the same time, the activation liquid plays a role in enriching the heavy metal ions around the cathode 6. The activation liquid has a spontaneous dynamic regulation ability and is not affected by either acidification or alkalization, making the reaction in the whole treatment process stable, promoting the movement of heavy metal ions, and reducing the consumption of the electrode material. It should be noted that due to concentration polarization, the interfacial voltage between the electrode and the electrolyte may be higher than 1.23V, resulting in the electrolysis of water. Therefore, an activation liquid needs to be added. Adding the activation liquid will increase the concentration of cations and anions, and can eliminate the influence brought by the electrolysis of water, that is, the cations and anions ionized by the activation liquid combine with the hydrogen ions and hydroxide ions electrolyzed by water to maintain the pH value near the anode and cathode unchanged, and prevent the formation of acid bands and alkali bands in the device. Generally speaking, in order to prevent the occurrence of water electrolysis and maintain the current intensity of the reaction, this embodiment takes two measures: "controlling the voltage below 1.2V" and "using the activation liquid to eliminate the negative impact brought by the electrolysis of water".

[0039] In this embodiment, the activation solution is a weakly acidic buffer solution. The activation solution includes one or more mixed solutions selected from the sodium dihydrogen phosphate-disodium hydrogen phosphate system, the potassium dihydrogen phosphate-sodium hydroxide system, the citric acid-sodium citrate system, the disodium hydrogen phosphate-citric acid system, the acetic acid-sodium acetate system, the formic acid-sodium formate buffer solution, the sodium oxalate-oxalic acid buffer solution, and the sodium sulfite-sulfurous acid buffer solution. The pH value of the sodium dihydrogen phosphate-disodium hydrogen phosphate system is 6.5 to 7.5, and the pH value of the acetic acid-sodium acetate system is 3.75 to 6.5.

[0040] In this embodiment, the conductive network includes one of a flexible metal mesh, a flexible non-metal mesh, a rigid non-metal mesh, and a rigid metal mesh. The metal conductive network is used in a low-chlorine (chlorine-free) environment, and the non-metal conductive network can be used in a high-chlorine environment and can also be used in a low-chlorine (chlorine-free) environment. The flexible mesh can adapt to different shapes (such as cylindrical, L-shaped), has more application scenarios, has a better space utilization rate, and can be folded to place a larger area of material in a limited space; the rigid mesh is more convenient for recycling. Since the mesh is a three-dimensional structure, it can carry more conductive materials.

[0041] In this embodiment, the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, perfluorosulfonic acid resin, polyvinylidene fluoride-hexafluoropropylene copolymer, isocyanate binders, epoxy resin binders, and guar gum. The binder plays a role in bonding the components, binding the activated carbon and the conductive carbon black together, and firmly adhering them to the conductive network.

[0042] In this embodiment, the microporous structure wall 4 includes one of permeable bricks, silica aerogel, soil, or graphite felt. Its function is to permeate water and metal ions, enabling the free transmission of ionic impurities, but acting as a certain barrier to non-ionic substances, that is, allowing electromigration and restricting diffusion and convection.

[0043] The principle of the method for removing heavy metals from fly ash in this embodiment is as follows: 1) After the fly ash to be treated is acidified, the heavy metal elements react with the acid, with some forming suspensions and some dissolving in water; 2) The part dissolved in water ionizes into charged ions or ion groups, and a part will be removed with water during dehydration, and the remaining part adheres to the fly ash after dehydration; 3) After adding the activation solution, no chemical reaction will occur. After applying a voltage to the electrodes in the reaction vessel, the heavy metal ions will detach from the fly ash and migrate to the positive and negative electrodes respectively according to their electricities, completing the treatment; This application effectively controls the occurrence of water decomposition by controlling the low voltage, directly realizes the migration of ionic impurities driven by a stable electric field, and achieves low energy consumption. In the prior art, the removal of ionic impurities is carried out by electrolyzing water to achieve the movement of acid bands and alkali bands. The electrolysis of water requires a large amount of energy, with huge energy consumption, and high voltage and high energy consumption are needed to meet the requirements.

[0044] The complete process of the method for removing heavy metals from fly ash in this embodiment is as follows: (1) Equipment structure and assembly Construct a fly ash treatment reaction vessel with a structure of "anode tank - microporous structure wall - treatment tank - microporous structure wall - cathode tank", install the prepared anode electrode 5 and cathode electrode 6 in the anode tank 1 and cathode tank 3 of the reaction vessel respectively, and connect equipment such as a low-voltage power supply.

[0045] 1. Preparation of fly ash suspension Mix the fly ash to be treated and water evenly, control the pH value to be stable between 5 and 6 through dilute acid, and perform dehydration. Mix the dehydrated fly ash with an appropriate amount of activation liquid to obtain a fly ash suspension.

[0046] (3) Fly ash feeding Put the obtained fly ash suspension into the treatment tank 2 of the reaction vessel.

[0047] (4) Electrodynamic treatment Turn on the low-voltage power supply, apply a voltage of 0.8 - 1.2V, after 1 - 72h of treatment, turn off the power supply, take out the treated fly ash and dehydrate it, send it for inspection, and carry out landfill or resource utilization after passing the inspection.

[0048] The above fly ash test results are as follows: (a) The test result of Pb is shown in Table 1-1 Table 1-1 Note: Tested according to the standard of HJ766-2015; The admission value of Pb for domestic waste landfill is 0.25mg / L.

[0049] (b) The test results of other metals are shown in Table 1-2 Table 1-2 Sample number Initial Cr leaching value Treatment duration Cr leaching value after treatment 1 1.18 mg / L 2h 0.03 mg / L 2 1.19 mg / L 5h 0.03 mg / L 3 1.03 mg / L 12h 0.02 mg / L Sample number Initial Zn leaching value Treatment duration Zn leaching value after treatment 1 1.59 mg / L 2 0.06 mg / L 2 1.17 mg / L 5 0.02 mg / L 3 1.59 mg / L 12 0.01 mg / L Sample number Initial Ni leaching value Treatment duration Ni leaching value after treatment 1 3.38 72 2.28 Note: Tested according to the standard of HJ766-2015; The admission value of Cr for domestic waste landfill is 4.5mg / L; Zn is 100mg / L; Ni is 0.5mg / L.

[0050] The above are all preferred embodiments of this application. The protection scope of this application is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A method for removing heavy metals from fly ash, characterized in that: The following steps are involved: S1. Prepare a reaction container and electrodes. The reaction container comprises an anode tank (1), a treatment tank (2) and a cathode tank (3). The treatment tank (2) is located between the anode tank (1) and the cathode tank (3). A microporous structure wall (4) is provided between the anode tank (1) and the treatment tank (2). A microporous structure wall (4) is provided between the cathode tank (3) and the treatment tank (2). An anode electrode (5) is provided in the anode tank (1). A cathode electrode (6) is provided in the cathode tank (3). The anode electrode (5) and the cathode electrode (6) are respectively connected to a low-voltage power supply. The preparation materials of the anode electrode (5) and the cathode electrode (6) comprise conductive activated carbon. The conductive activated carbon comprises activated carbon, conductive carbon, a binder and a conductive mesh. A mixture of the conductive carbon and the activated carbon is bonded to the conductive mesh by the binder to form a conductive activated carbon electrode. S2, putting the pre-prepared fly ash suspension into the treatment tank (2), wherein the preparation process of the fly ash suspension is: uniformly mixing the fly ash to be treated and water, and adding acid solution to obtain a weakly acidic fly ash suspension; S3, starting the low voltage power supply, and applying a voltage of less than 1.2 V to the anode electrode (5) and the cathode electrode (6); S4. After the set treatment time, turn off the power, take out the treated fly ash and send it for inspection. After passing the inspection, landfill or resource utilization will be carried out.

2. The method for removing heavy metals from fly ash according to claim 1, characterized in that: In the above-mentioned S2, when preparing the fly ash suspension, the obtained weakly acidic fly ash suspension is dehydrated, and the dehydrated fly ash is mixed with a proper amount of activation liquid to obtain the latest fly ash suspension.

3. The method for removing heavy metals from fly ash according to claim 2, characterized in that: The voltage applied to the anode (5) and the cathode (6) is lower than the decomposition voltage of the activation solution.

4. The method for removing heavy metals from fly ash according to claim 2, characterized in that: The activation solution comprises one or more mixed solutions of a sodium dihydrogen phosphate-disodium hydrogen phosphate system, a potassium dihydrogen phosphate-sodium hydroxide system, a citric acid-sodium citrate system, a disodium hydrogen phosphate-citric acid system, an acetic acid-sodium acetate system, a formic acid-sodium formate buffer solution, a sodium oxalate-oxalic acid buffer solution, and a sodium sulfite-sulfite buffer solution. The pH value of the sodium dihydrogen phosphate-disodium hydrogen phosphate system is 6.5-7.5, and the pH value of the acetic acid-sodium acetate system is 3.75-6.

5.

5. The method for removing heavy metals from fly ash according to any one of claims 1 to 4, characterized in that: The conductive mesh includes one of a flexible metal mesh, a flexible non-metal mesh, a rigid non-metal mesh and a rigid metal mesh.

6. The method for removing heavy metals from fly ash according to any one of claims 1 to 4, characterized in that: The binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, perfluorosulfonic acid resin, polyvinylidene fluoride-hexafluoropropylene copolymer, isocyanate binder, epoxy resin binder and guar gum.

7. The method for removing heavy metals from fly ash according to any one of claims 1 to 4, characterized in that: In S4, the fly ash after removal and treatment is dehydrated and then sent for inspection.

8. The method for removing heavy metals from fly ash according to any one of claims 1 to 4, characterized in that: The microporous structure wall (4) comprises permeable bricks, silica aerogel, soil or graphite felt.

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