Method for continuous degradation of pollutants in water bodies by metal composite electrocatalytic membranes

Abstract

The application discloses a method for continuously degrading pollutants in water bodies by a metal composite electrocatalytic membrane, wherein FeOCl / MWCNTs-COOH / PTFE electrochemical membranes are used as cathode membranes, Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membranes are used as anode membranes, and an external power supply is connected; the cathode membranes and the anode membranes divide the reactor into three reaction chambers; the water body to be treated flows from the end where the cathode membranes are located to the end where the anode membranes are located in the reactor in one direction; the power supply is turned on; persulfate is added into the reactor; and under the action of an external electric field, the persulfate is activated to generate free radicals so as to degrade the pollutants in the water body. The method is convenient, simple and easy to implement, does not need special equipment, instruments and chemical reagents, does not contain any noble metal, is low in cost, and is high in stability of the prepared electrode membrane, and is easy to popularize and apply.

Description

Technical Field

[0001] This application relates to the field of pollutant degradation technology, specifically to the preparation of a metal composite electrocatalytic membrane and its application in the continuous degradation of pollutants in water. Background Technology

[0002] Pollutant and wastewater treatment have always been important issues in the field of environmental protection. With population growth and industrial development, large amounts of organic and inorganic pollutants are discharged into water bodies, posing a serious threat to the environment and human health. Traditional pollutant treatment methods, such as chemical precipitation, biological treatment, and adsorption, can remove pollutants to a certain extent, but they suffer from low treatment efficiency, complex operation, and high energy consumption. To overcome the limitations of traditional treatment methods, researchers have begun to explore new, highly efficient pollutant treatment technologies. In this regard, the emergence of polytetrafluoroethylene (PTFE) conductive membranes has attracted widespread attention. During the preparation of conductive membranes, by adding conductive fillers or performing specific treatments on PTFE filter membranes, they can be made conductive, thereby forming metal-doped PTFE electrochemical membranes.

[0003] Electrocatalytic membrane technology effectively and efficiently treats organic wastewater through a combination of adsorption, filtration, and electrochemical degradation. On one hand, the integration of electrochemistry can mitigate membrane fouling by degrading organic molecules in situ, thus maintaining optimal membrane permeability. On the other hand, compared to traditional bipolar systems, the flowing solution increases convective mass transfer from molecules to active sites, which is beneficial to electrochemical reaction kinetics. Related literature reports an electrocatalytic membrane reactor for treating industrial wastewater, which uses a tubular carbon membrane as a self-cleaning conductive membrane and exhibits excellent performance in treating oily water.

[0004] In recent years, various pollutants in daily life have posed a significant threat to the health and safety of humans and even animals and plants. These include antibiotic pollutants (tetracycline, sulfamethoxazole) and organic pollutants (bisphenol A). Currently, the main methods reported in the literature for removing these pollutants include adsorption, photocatalytic oxidation, membrane separation, and Fenton oxidation. Among these, membrane technology has advantages such as simple operation, stable water quality, and small footprint, but it is prone to membrane fouling. Electrochemical technology has attracted widespread attention due to its high efficiency and modular configuration, and can remove various pollutants such as pharmaceuticals and personal care products, endocrine-disrupting compounds, disinfection byproducts, dyes, and phenolic compounds. Conductive membrane technology integrates membrane filtration and electrochemical reaction, enabling simultaneous pollutant retention and electrochemical degradation. Summary of the Invention

[0005] This application provides a method for continuous degradation of pollutants using a metal composite electrocatalytic membrane. The method is convenient, simple, and easy to implement, requiring no special equipment or chemical reagents. It does not contain any precious metals, is low in cost, and produces a highly stable electrode membrane, making it easy to promote and apply.

[0006] A method for continuously degrading pollutants in water using a metal composite electrocatalytic membrane includes:

[0007] In the reactor, FeOCl / MWCNTs-COOH / PTFE electrochemical membrane serves as the cathode membrane, while Bi-SnO2 / MWCNTs-COOH / PTFE and FeOCl / MWCNTs-COOH / PTFE metal oxide electrochemical membranes can serve as the anode membrane and be connected to an external power source. The selected metal oxides may include metal materials such as Fe, Bi, and Sn. The cathode and anode membranes divide the reactor into three reaction chambers. The water to be treated flows unidirectionally from the cathode membrane end to the anode membrane end in the reactor. When the power source is turned on, persulfate is added to the water. Under the action of the applied electric field, the persulfate is activated to generate free radicals, thereby degrading pollutants in the water.

[0008] The preparation of the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane includes:

[0009] Carboxylated multi-walled carbon nanotubes were dispersed in an aqueous solution of N,N-dimethylformamide to obtain a mixed reaction solution. The mixed reaction solution was filtered using a pretreated finished PTFE membrane as a filtration membrane. The precipitate after filtration adhered to the pretreated finished PTFE membrane and was dried to obtain the MWCNTs-COOH / PTFE membrane.

[0010] The prepared MWCNTs-COOH / PTFE membrane was immersed in ferric chloride ethanol solution and then dried to obtain the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane.

[0011] The preparation of the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane includes:

[0012] Bismuth nitrate and stannous chloride dihydrate were dissolved in a mixed solution of hydrochloric acid and deionized water to obtain an adsorption electrolyte. The MWCNTs-COOH / PTFE membrane was placed in the adsorption electrolyte as a cathode and a titanium plate as an anode, and an external power supply was connected to carry out an electro-adsorption reaction.

[0013] After the electroadsorption reaction is completed, the MWCNTs-COOH / PTFE membrane after electroadsorption treatment is subjected to water bath heating treatment and then dried to obtain the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane.

[0014] The substrate membrane used in this application is a PTFE ultrafiltration membrane, which has high mechanical strength, good antifouling performance, and its small pore size can effectively block large molecular pollutants. The carboxylated multi-walled carbon nanotube material loaded on this membrane has more chemical reaction sites and good compatibility.

[0015] The advantages of using different metal doping in the cathode and anode films of this application are:

[0016] Anode film: To increase the oxygen evolution potential (OEP) and improve the efficiency of organic degradation, tin dioxide (SnO2) is an n-type semiconductor with an OEP as high as 1.7V (vs Ag / AgCl), while the OEP of carbon nanotubes is only about 1.0V (vs Ag / AgCl). Therefore, SnO2 nanoparticles can serve as an excellent coating material for carbon nanotube modification, and metal-doped SnO2 can achieve higher conductivity and electrocatalytic activity.

[0017] If FeOCl / MWCNTs-COOH / PTFE electrochemical membrane is used as the anode membrane, the combination of FeOCl and carbon nanotube materials has excellent electrochemical performance and more electrochemical active sites.

[0018] Cathode membranes not only have a retention function, but also rely on metal ions to electroactivate persulfate under the action of electric field to form an electro-Fenton system, thereby generating hydroxyl radicals and sulfate radicals to degrade pollutants.

[0019] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0020] In the preparation of the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane:

[0021] Optionally, the pretreatment process includes: immersing the finished PTFE membrane in distilled water for 2-4 hours; and then drying it for later use.

[0022] This pretreatment process can improve the membrane permeability, allowing more carboxylated carbon nanotubes to penetrate into the membrane during subsequent ultrafiltration, thereby increasing the adhesion strength between the carboxylated carbon nanotubes and the membrane, making them less prone to detachment during subsequent applications; it can also remove impurities from the membrane.

[0023] The filtration process is considered complete when the entire mixed reaction solution is filtered onto the PTFE membrane. The filtration process itself is a conventional filtration operation.

[0024] Optionally, the concentration of carboxylated multi-walled carbon nanotubes in the mixed reaction solution is 0.2–0.3 g / L, and the concentration of the N,N-dimethylformamide aqueous solution is 0.1–0.5 mol / L.

[0025] Furthermore, the concentration of carboxylated multi-walled carbon nanotubes in the mixed reaction solution is 0.25 g / L.

[0026] Specifically, 25 mg of carboxylated multi-walled carbon nanotubes can be dispersed in 100 mL of an aqueous solution of 0.1-0.5 mol / L N,N-dimethylformamide. Optionally, the dispersion process can be carried out under ultrasonic conditions for 30 min.

[0027] After ultrasonic treatment of the above-mentioned carboxylated multi-walled carbon nanotubes and DMF mixed solution, the mixed solution is filtered onto a pretreated PTFE ultrafiltration membrane and then dried in a vacuum drying oven to obtain the MWCNTs-COOH / PTFE conductive membrane.

[0028] Optionally, the drying conditions after filtration are: drying at 50-70℃ for about 1 hour.

[0029] Optionally, the concentration of ferric chloride in the ferric chloride ethanol solution is 1–1.5 mol / L; the soaking time in the ferric chloride ethanol solution is 0.5–1.5 h; and the drying temperature after soaking is 220–250 °C.

[0030] Furthermore, the concentration of ferric chloride in the ferric chloride ethanol solution is 1.2 mol / L; the soaking time in the ferric chloride ethanol solution is 1 h; and the ethanol is anhydrous ethanol.

[0031] Optionally, the drying time after soaking is 1 hour.

[0032] In the preparation of the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane:

[0033] The doped metal anode film is prepared by electro-adsorption coupled water bath heating method on the basis of the above MWCNTs-COOH / PTFE substrate film to increase its oxygen evolution potential.

[0034] The preparation process of the MWCNTs-COOH / PTFE membrane is the same as that of the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane.

[0035] Optionally, in the adsorbed electrolyte, the molar ratio of bismuth nitrate to stannous chloride dihydrate is 0.05:1; the molar concentration of bismuth nitrate is 0.003 to 0.004 mol / L, preferably 0.004 mol / L.

[0036] Optionally, the hydrochloric acid concentration is 37%, and the volume ratio of hydrochloric acid to deionized water is 1:1.

[0037] Optionally, in the electroadsorption reaction, the distance between the MWCNTs-COOH / PTFE membrane and the titanium plate is 1 to 3 cm; the applied voltage is 1 to 2 V; and the electroadsorption reaction time is 0.5 to 1.5 h.

[0038] Optionally, the water bath heating treatment conditions are: 80-100℃ water bath for 0.5-1.5 hours.

[0039] Furthermore, the conditions for water bath heating treatment are: 90℃ water bath for 1 hour.

[0040] Optionally, the drying conditions after the water bath are: drying at 90℃ for 1 hour.

[0041] Optionally, the contaminant is sulfamethoxazole, tetracycline, or bisphenol A; the concentration of the contaminant is 5–15 mg / L.

[0042] Furthermore, the concentration of the pollutant is 10 mg / L.

[0043] Optionally, the persulfate is potassium persulfate or ammonium persulfate.

[0044] Furthermore, the concentration of the persulfate is 1 mM to 3 mM.

[0045] Optionally, during the degradation of pollutants in water under the action of an external electric field: the distance between the cathode membrane and the anode membrane is 2-3 cm; the applied voltage is 2-4 V.

[0046] Furthermore, the distance between the cathode film and the anode film is 2 cm.

[0047] Optionally, the water to be treated flows into the cathode membrane from one end and flows out from the anode membrane from the other end during the treatment process, forming a unidirectional continuous pollutant degradation reaction system; the hydraulic residence time of the water to be treated in the reactor is 42 min to 12 min; the flow rate is 1 mL / min to 3 mL / min, which is adjusted by a peristaltic pump.

[0048] Optionally, the concentration of persulfate in the water to be treated is 1 mM to 3 mM. Sodium persulfate can be used as the persulfate.

[0049] This invention provides an application of a bimetallic composite electrocatalytic membrane as the anode and cathode in a unidirectional flow system for degrading pollutants.

[0050] Compared with the prior art, this application has at least one of the following advantages:

[0051] (1) Carboxylated multi-walled carbon nanotubes with good optical and electrical properties and PTFE ultrafiltration membrane are used to form a conductive membrane to degrade pollutants;

[0052] (2) This application is simple and easy to implement, and the raw materials do not contain any precious metals. The elements are abundant in nature, which is conducive to its promotion and application.

[0053] (3) After the two metal films are combined, the metal particles on the anode surface are doped with carbon nanotubes, which can increase the oxygen evolution potential and thus improve the organic degradation efficiency. In addition to the electrochemical effect, it also has a certain effect of retaining pollutants. At the same time, the cathode will also retain pollutants, and the iron ions on its surface will activate persulfate under the action of electric field force, thereby generating hydroxyl radicals and sulfate radicals to degrade pollutants. Attached Figure Description

[0054] Figure 1 This is an image of the MWCNTs-COOH / PTFE membrane.

[0055] Figure 2 This is an image showing the appearance of two electrochemical membranes.

[0056] Figure 3 This is a schematic diagram of the reaction system.

[0057] Figure 4 The figure shows the results of sulfamethoxazole degradation using a doped metal composite film.

[0058] Figure 5 The image shows the results of tetracycline degradation using a doped metal composite film.

[0059] Figure 6 The image shows the results of bisphenol A degradation using a doped metal composite film. Detailed Implementation

[0060] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0062] Example 1

[0063] Preparation of MWCNTs-COOH / PTFE doped metal cathode film:

[0064] (1) The commercial PTFE membrane purchased from the market was pretreated by soaking it in distilled water for 3 hours, and then the soaked membrane was placed in an oven to dry.

[0065] (2) Weigh 25 mg of commercial carboxylated multi-walled carbon nanotubes and dissolve them in 100 mL of 0.1 mol / L DMF surfactant (DMF aqueous solution), and sonicate for 30 min;

[0066] (3) Vacuum filter the prepared mixed solution onto the pre-treated PTFE ultrafiltration membrane, then place it in a vacuum drying oven and dry it at 50°C for 1 hour before use. This membrane is designated as MWCNTs—COOH / PTFE membrane. Figure 1 As shown.

[0067] (4) First, weigh 9.72g of ferric chloride hexahydrate into 30mL of anhydrous ethanol solution to form ferric chloride ethanol solution;

[0068] (5) Immerse the prepared MWCNTs—COOH / PTFE membrane in ferric chloride ethanol solution for 1 hour;

[0069] (6) Finally, the soaked membrane is transferred to an oven and dried at 220℃ for 1 hour. It is then stored in deionized water for use, yielding a FeOCl / MWCNTs-COOH / PTFE electrochemical membrane. Figure 2 The membrane on the right side of the middle section is shown.

[0070] Example 2: Preparation of MWCNTs-COOH / PTFE doped metal anode film:

[0071] (1) First, weigh 0.214 g of bismuth nitrate and 2 g of stannous chloride dihydrate, and control their molar ratio to be 0.05:1;

[0072] (2) Next, add the weighed medicine to 50 mL of 37% hydrochloric acid and 50 mL of deionized water solution as an electroadsorption electrolyte.

[0073] (3) The MWCNTs-COOH / PTFE membrane (cathode) prepared in step (3) of Example 1 was placed together with a titanium plate (anode) in an electrolyte solution, with a 2 cm gap between the anode and cathode. A DC power supply control system was used to provide a 2V voltage for 1 hour, followed by a 1 hour water bath at 90°C, and finally drying at 90°C for 1 hour to obtain a Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane, as shown below. Figure 2 The membrane is shown on the left side of the middle section.

[0074] The preparation process of the other control electrode films in Example 3 is as follows:

[0075] MWCNTs / PTFE electrochemical membrane: The preparation process is the same as steps (1) to (3) in Example 1, except that non-carboxylated carbon nanotubes are used in step (2).

[0076] SnO2 / MWCNTs-COOH / PTFE electrochemical membrane: Compared with the preparation of MWCNTs-COOH / PTFE doped metal anode membrane, bismuth nitrate is not added, and other processes are the same.

[0077] Bi-SnO2 / FeOCl / MWCNTs-COOH / PTFE electrochemical membrane: The preparation process is the same as in Example 3, except that the cathode membrane in step (3) is the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane prepared in Example 1.

[0078] Example 4

[0079] This application utilizes the electrochemical degradation of bisphenol A in a mud-water mixture:

[0080] The electrochemical degradation process takes place on the constructed reaction platform, with an external electric field as the power source. The reaction process is as follows: Figure 3 As shown, 50g of kaolin was weighed and placed in the reaction vessel for the degradation reaction. The FeOCl / MWCNTs-COOH / PTFE electrochemical membrane prepared in Example 1 was used as the cathode membrane; the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane was used as the anode membrane and connected to an external power source. The distance between the cathode and anode was 2-3cm (preferably 2cm). The cathode and anode membranes were connected to the negative and positive terminals of the power source, respectively. Both the cathode and anode membranes were vertically inserted and placed parallel to each other in the reaction vessel. The reactor was divided into three independent reaction chambers by the cathode membrane and the anode membrane. The inlet of the reaction vessel was located at the top of the end where the cathode membrane was located (the first reaction chamber). The outlet is located at the bottom of the anode membrane (third reaction chamber). The inlet is connected to the inlet water storage container via a peristaltic pump, and the outlet is connected to the storage water container. 250 mL of a 0.1 mol / L Na2SO4 solution and 10 mg / L bisphenol A pollutant are pumped into the reactor via the peristaltic pump. The reacted solution is returned to the storage beaker, forming a unidirectional flow degradation, that is, the water to be treated flows unidirectionally from the inlet to the outlet in the reaction vessel. In this application example, the hydraulic residence time of the water to be treated in the reactor is controlled to be 12–42 min; the flow rate is 1–3 mL / min; and sampling is performed in the storage container at 0.5 h intervals.

[0081] The mud-water sample obtained from the intermediate reaction chamber was extracted three times with 2 mL, 1 mL, and 1 mL of methanol, respectively. Each extraction was performed by shaking in a constant temperature shaker at 160 rpm for 1 hour. After extraction, the methanol from the three extractions was combined and centrifuged at 6500 rpm. The centrifuged methanol was then transferred to a distillation flask for concentration, reducing the volume to approximately 1 mL. The concentrated sample, along with samples from the anode and cathode reservoirs, was analyzed using a Tianmei liquid chromatograph equipped with a Diamonsil C18 analytical column to determine the concentration of bisphenol A.

[0082] The result after batch processing 5 times is as follows Figure 6 As shown, the ability of the cathode and anode membranes to degrade bisphenol A after being reused 5 times did not change significantly, indicating that the electrode membranes prepared in this application have good stability.

[0083] Example 5

[0084] This application utilizes the electrochemical degradation of sulfamethoxazole in a mud-water mixture:

[0085] The experimental procedure was the same as in Example 4, except that 10 mg / L of sulfamethoxazole was added to the water to be treated.

[0086] The methods for determining the concentrations of sulfamethoxazole and tetracycline are the same as those for bisphenol A, both using a Tianmei liquid chromatograph equipped with a Diamonsil C18 analytical column.

[0087] Comparative Example 1

[0088] Compared with Example 5, the cathode membrane and other reaction conditions remained unchanged, but the anode membrane was replaced with SnO2 / MWCNTs-COOH / PTFE electrochemical membrane, FeOCl / MWCNTs-COOH / PTFE electrochemical membrane, and Bi-SnO2 / FeOCl / MWCNTs-COOH / PTFE electrochemical membrane, respectively, as a comparison.

[0089] Comparative Example 2

[0090] The difference from Example 5 is that no external voltage is applied.

[0091] The test results are as follows Figure 4 As shown, from Figure 4As can be seen, sulfamethoxazole hardly degrades when no external voltage is applied. When the anode membrane is replaced with SnO2 / MWCNTs-COOH / PTFE, FeOCl / MWCNTs-COOH / PTFE, and Bi-SnO2 / FeOCl / MWCNTs-COOH / PTFE, the degradation effect is not as good as that of the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane, and the degradation effect is significantly reduced. When the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane is used as the anode membrane, the degradation rate can reach 95% in only about 20 minutes.

[0092] The vertical axis in the figure represents the ratio C / C0 of the concentration of the sample taken at a certain moment during the reaction process to the initial sample concentration.

[0093] Example 6

[0094] This application utilizes the electrochemical degradation of tetracycline in a mud-water mixture:

[0095] The experimental procedure was the same as in Example 4, except that 10 mg / L of tetracycline was added to the water to be treated.

[0096] Comparative Example 3

[0097] Compared with Example 6, the cathode membrane and other reaction conditions remained unchanged, but the anode membrane was replaced with MWCNTs / PTFE, MWCNTs-COOH / PTFE, FeOCl / MWCNTs-COOH / PTFE and Bi-SnO2 / FeOCl / MWCNTs-COOH / PTFE respectively as a comparison.

[0098] Comparative Example 4

[0099] The difference from Example 6 is that no external voltage is applied.

[0100] The test results are as follows Figure 5 As shown, from Figure 5 As can be seen, sulfamethoxazole hardly degrades when no external voltage is applied. When the anode membrane is replaced with MWCNTs / PTFE, MWCNTs-COOH / PTFE, FeOCl / MWCNTs-COOH / PTFE and Bi-SnO2 / FeOCl / MWCNTs-COOH / PTFE, the degradation effect decreases significantly.

[0101] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for continuous degradation of pollutants in water using a metal composite electrocatalytic membrane, characterized in that, include: In the reactor, the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane serves as the cathode membrane, and the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane serves as the anode membrane, both connected to an external power source. The cathode and anode membranes divide the reactor into three reaction chambers. The water to be treated flows unidirectionally from the cathode membrane end to the anode membrane end within the reactor. When the power source is turned on, persulfate is added. Under the action of the applied electric field, the persulfate is electroactivated to generate free radicals that degrade pollutants in the water. The pollutant is tetracycline, and the concentration of the pollutant is 5~15 mg / L; The preparation of the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane includes: Carboxylated multi-walled carbon nanotubes were dispersed in an aqueous solution of N,N-dimethylformamide to obtain a mixed reaction solution, wherein the concentration of carboxylated multi-walled carbon nanotubes in the mixed reaction solution was 0.2~0.3 g / L; the mixed reaction solution was filtered using a pretreated finished PTFE membrane as a filtration membrane, and the precipitate after filtration adhered to the pretreated finished PTFE membrane. After drying, a MWCNTs-COOH / PTFE membrane was obtained. The prepared MWCNTs-COOH / PTFE membrane was immersed in ferric chloride ethanol solution and then dried to obtain the FeOCl / MWCNTs-COOH / PTFE electrochemical membrane. The preparation of the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane includes: Bismuth nitrate and stannous chloride dihydrate were dissolved in a mixed solution of hydrochloric acid and deionized water to obtain an adsorption electrolyte. The molar ratio of bismuth nitrate to stannous chloride dihydrate was 0.05:

1. The molar concentration of bismuth nitrate was 0.003~0.005 mol / L. The MWCNTs-COOH / PTFE membrane was used as the cathode, and a titanium plate was used as the anode. The membrane was placed in the adsorption electrolyte and connected to an external power source to carry out an electroadsorption reaction. After the electroadsorption reaction is completed, the MWCNTs-COOH / PTFE membrane treated with electroadsorption is subjected to a water bath at 80~100℃ for 0.5~1.5h, and then dried to obtain the Bi-SnO2 / MWCNTs-COOH / PTFE electrochemical membrane.

2. The method according to claim 1, characterized in that, The concentration of the N,N dimethylformamide aqueous solution is 0.1-0.5 mol / L.

3. The method according to claim 1, characterized in that, The pretreatment process includes: immersing the finished PTFE membrane in distilled water for 2-4 hours; and then drying it for later use.

4. The method according to claim 1, characterized in that, The concentration of ferric chloride in the ferric chloride ethanol solution is 1~1.5 mol / L; the soaking time in the ferric chloride ethanol solution is 0.5~1.5 h; and the drying temperature after soaking is 220~250℃.

5. The method according to claim 1, characterized in that, In the electroadsorption reaction, the distance between the MWCNTs-COOH / PTFE membrane and the titanium plate is 1~3 cm; the applied voltage is 1~2V; and the electroadsorption reaction time is 0.5~1.5 h.

6. The method according to claim 1, characterized in that, During the degradation of pollutants in water under the action of an external electric field: the distance between the cathode membrane and the anode membrane is 2~3cm; the applied voltage is 2~4V.

7. The method according to claim 1, characterized in that, The hydraulic retention time of the water to be treated in the reactor is 42 min to 12 min; the flow rate is 1 mL / min to 3 mL / min; and the concentration of persulfate in the water to be treated is 1 mM to 3 mM.

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