A cathode composite membrane, a preparation method and application thereof

Abstract

The application provides a cathode composite membrane and a preparation method and application thereof, and relates to the technical field of water treatment.The application provides a cathode composite membrane, which comprises a base film and acidized carbon nanotubes loaded on the surface of the base film; the surface of the acidized carbon nanotubes is loaded with triclinic FeVO4 and Pd 0 . The application selects CNTs as a cathode catalyst carrier, and simultaneously adds FeVO4 and Pd 0 catalysts, applies the composite membrane to a continuous flow system, significantly enhances the transmission of target pollutants to active sites on the surface of an electrode, improves the removal rate of CPs, and overcomes the problems of limited mass transfer and difficult recovery of catalysts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a cathode composite membrane and a preparation method and application thereof. BACKGROUND

[0002] Chlorophenols (CPs) are a kind of environmental endocrine disruptors, which exist in water bodies as fungicides, insecticides, herbicides, and intermediates in the production of dyes and pharmaceuticals. Although CPs only exist in trace amounts in water bodies, with concentration distribution in μg / L or even ng / L, CPs can accumulate in the body through bioaccumulation after entering the human body, and then affect the human adrenaline level, leading to human metabolic disorders and harming the health of the body. Therefore, the removal of CPs has very important practical significance.

[0003] Advanced oxidation technology (AOPs) is a new water treatment technology in recent years, which mainly produces strong oxidizing free radicals through catalytic oxidation of electricity, light, ultrasound, etc., and then attacks organic pollutants, and converts the refractory organic pollutants into CO2, H2O and other low-toxicity small molecular substances. AOPs has strong oxidation ability and fast reaction rate, and is often used to remove CPs. Traditional homogeneous Fenton belongs to one of AOPs, which has the advantages of simple operation and low requirement for external equipment, but it cannot work in neutral or alkaline water environment, and a certain amount of iron sludge will be produced, which limits the wide use of homogeneous Fenton. In view of this, the traditional homogeneous electric Fenton technology uses the advantages brought by the combination of electro-catalysis and Fenton reaction to alleviate the generation of iron sludge, but the problem of narrow pH application range still exists. In order to solve the above problem of narrow pH range, heterogeneous electric Fenton has been widely used in water treatment technology in recent years. Heterogeneous electric Fenton technology is to replace Fe2+ in homogeneous electric Fenton with heterogeneous Fenton catalysts mainly composed of iron oxides, which can not only alleviate the generation of iron sludge, but also expand the pH range, and has become a hot spot in the field of sewage treatment. 2+ Because this technology can not only alleviate the generation of iron sludge, but also expand the pH range, it has become a hot spot in the field of sewage treatment.

[0004] Heterogeneous electro-Fenton catalysts are usually Fe3O4, Fe2O3, FeS2 and the like, and such catalysts usually work by single Fe cation, while FeVO4 as a bidirectional catalyst, both Fe cation and vanadate anion have catalytic activity, and has higher catalytic activity than other traditional catalysts. Since FeVO4 is a loose, water-soluble powder, it needs to be loaded on a carrier for use. The cathode carrier has metal electrodes such as Ti and Pt, however, such electrodes have strong conductivity, but low H2O2 production performance, and have not attracted widespread attention; CNTs can improve the generation rate of H2O2 due to high catalytic activity, high conductivity and high specific surface area, and can be used as an excellent carrier for catalysts. In addition, further loading of noble metals on the cathode can effectively promote the generation of active hydrogen, so that the composite material exhibits excellent dehalogenation effect in the process of treating halogen-containing pollutants. However, the traditional cathode composite film is usually prepared by loading the catalyst on a plate electrode, and in the batch operation mode, there is usually a hydraulic diffusion layer with a thickness of about 100 μm on the surface of the electrode, which causes diffusion limitation in the mass transfer process. SUMMARY

[0005] The purpose of the present application is to provide a cathode composite film and a preparation method and application thereof, which relates to the technical field of water treatment. The cathode composite film provided by the present application is applied to a continuous flow system, which significantly enhances the transfer of target pollutants to active sites on the surface of the electrode, and improves the removal rate of CPs. The cathode composite film prepared by the present application simplifies the preparation method, has low preparation cost, and overcomes the problems of mass transfer limitation and catalyst recovery difficulty.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a cathode composite film, comprising a base film and acidified carbon nanotubes loaded on the surface of the base film; the surface of the acidified carbon nanotubes is loaded with triclinic FeVO4 and Pd 0 .

[0008] Preferably, based on the total mass of the acidified carbon nanotubes, triclinic FeVO4 and Pd 0 , the mass content of the acidified carbon nanotubes is 20-30%, the mass content of the triclinic FeVO4 is 20-35%, and the mass content of the Pd 0 is 30-50%.

[0009] The present application provides a preparation method of the cathode composite film according to the above technical solutions, comprising the following steps:

[0010] Mixing an iron source, a vanadate source and water to perform a hydrothermal reaction to obtain a FeVO4 precursor;

[0011] The FeVO4 precursor is calcined to obtain triclinic FeVO4;

[0012] The palladium source, the reducing agent and water are mixed to perform a reduction reaction to obtain Pd 0 ;

[0013] The carbon nanotubes are placed in an acidic solution to perform acidification to obtain acidified carbon nanotubes;

[0014] The acidified carbon nanotubes, triclinic FeVO4, Pd 0 and a solvent are mixed to obtain a mixed dispersion liquid;

[0015] The mixed dispersion liquid is suction filtered onto a substrate film to obtain the cathode composite film.

[0016] Preferably, the temperature of the hydrothermal reaction is 170-190 DEG C; the time of the hydrothermal reaction is 2-4h.

[0017] Preferably, the temperature of the calcination is 300-600 DEG C; the time of the calcination is 1-3h.

[0018] Preferably, the mass ratio of the acidified carbon nanotubes, triclinic FeVO4 and Pd 0 is 1:1-2:1-3.

[0019] Preferably, the substrate film comprises a polytetrafluoroethylene film or a polyvinylidene fluoride film.

[0020] The application provides application of the cathode composite film in the above technical solution or the cathode composite film prepared by the preparation method in the above technical solution in removal of organic pollutants in wastewater in a continuous flow system.

[0021] Preferably, the application comprises: taking the cathode composite film as a cathode, taking a platinum mesh as an anode, taking Ag / AgCl as a reference electrode, and making wastewater containing organic pollutants pass through the continuous flow system to filter and degrade the organic pollutants in the wastewater.

[0022] Preferably, the wastewater containing organic pollutants further comprises an electrolyte.

[0023] The application provides a cathode composite film, which comprises a substrate film and acidified carbon nanotubes loaded on the surface of the substrate film; the surface of the acidified carbon nanotubes is loaded with triclinic FeVO4 and Pd 0 . The application selects CNTs as a cathode catalyst carrier, simultaneously adds FeVO4 and Pd 0 catalysts, and applies the composite film to a continuous flow system, thereby significantly enhancing the transmission of target pollutants to active sites on the surface of the electrode, improving the removal rate of CPs, and overcoming the problems of limited mass transfer and difficult recovery of catalysts.

[0024] The application also provides a preparation method of the cathode composite film. 0 The CNTs / FeVO4 / Pd 0 cathode composite film is prepared by dissolving the CNTs, the triclinic FeVO4 and the Pd 0 in a solvent, uniformly dispersing, and then filtering onto a base film. 0 The application has the advantages of simple preparation method, low preparation cost and good conductivity, and can realize efficient removal of organic pollutants under the synergistic effect of an applied electric field and continuous flow enhanced mass transfer.

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] (1) The cathode composite film provided by the application has simple preparation raw materials, short cycle, mild conditions, and low raw material and preparation cost;

[0027] (2) The triclinic FeVO4 and the Pd 0 catalyst are mixed with the acidified CNTs, filtered onto the PTFE film, and compared with the granular catalyst, which increases the active sites of the reaction and solves the problem of difficult recovery of the granular catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The SEM image of the CNTs / FeVO4 / Pd 0 cathode composite film in Example 1 is shown in FIG. 1.

[0029] Figure 2 The EDS spectrum of the CNTs / FeVO4 / Pd 0 cathode composite film in Example 1 is shown in FIG. 2.

[0030] Figure 3 The SEM image of the CNTs cathode film in Comparative Example 1 is shown in FIG. 3.

[0031] Figure 4 The SEM image of the CNTs / FeVO4 cathode film in Comparative Example 2 is shown in FIG. 4.

[0032] Figure 5 The XRD image of the CNTs / FeVO4 / Pd 0 cathode composite film and the CNTs, the FeVO4 and the Pd 0 in Example 1 is shown in FIG. 5.

[0033] Figure 6 The structural schematic diagram of the continuous flow system reactor is shown in FIG. 6. Figure 6 In the figure, 1 is an electrochemical workstation, 2 is a reactor water inlet, 3 is an anode, 4 is a cathode, 5 is a reference electrode, 6 is a reactor water outlet, 7 is an air pump, 8 is a gas flow meter, 9 is a peristaltic pump, and 10 is a water collecting tank.

[0034] Figure 7 The degradation effect of different cathode materials on CA in water is shown in Example 1.

[0035] Figure 8 The graph shows the degradation effect of different catalyst loadings on CA in water in Example 2.

[0036] Figure 9 The graph shows the degradation effect of CA in water under different pH conditions in Example 3. Detailed Implementation

[0037] This invention provides a cathode composite film, comprising a substrate film and acidified carbon nanotubes (CNTs) loaded on the surface of the substrate film; the surface of the acidified carbon nanotubes is loaded with triclinic FeVO4 and Pd. 0 .

[0038] In this invention, the acidified carbon nanotubes, triclinic FeVO4, and Pd are used. 0 Based on a total mass of 100%, the preferred mass content of the acidified carbon nanotubes is 20-30%, the preferred mass content of the triclinic FeVO4 is 20-35%, and the preferred mass content of the Pd is... 0 The mass content is preferably 30-50%. In a specific embodiment of the present invention, the CNTs are preferably multi-walled CNTs; the diameter of the acidified carbon nanotubes is preferably 10-20 nm. In the present invention, the triclinic FeVO4 is nano-triclinic, with a length preferably 2-4 μm and a width preferably 50-200 nm. In the present invention, the Pd 0 The preferred particle size is 1–50 nm.

[0039] In this invention, the base membrane preferably comprises a polytetrafluoroethylene (PTFE) membrane or a polyvinylidene fluoride (PVDF) membrane. In this invention, the pore size of the base membrane is preferably 3–5 μm; the diameter of the base membrane is preferably 50 mm.

[0040] This invention provides a method for preparing the cathode composite film described in the above technical solution, comprising the following steps:

[0041] Iron source, vanadate source and water are mixed and subjected to hydrothermal reaction to obtain FeVO4 precursor;

[0042] The FeVO4 precursor was calcined to obtain triclinic FeVO4;

[0043] A reduction reaction is carried out by mixing a palladium source, a reducing agent, and water to obtain Pd. 0 ;

[0044] The CNTs are placed in an acid solution to be acidized to obtain acidized CNTs;

[0045] The acidized CNTs, triclinic FeVO4, Pd 0 and a solvent are mixed to obtain a mixed dispersion liquid.

[0046] The mixed dispersion liquid is suction-filtered onto a base film to obtain the cathode composite film.

[0047] In the present application, the iron source is preferably a trivalent iron source, and more preferably a trivalent iron salt. In specific embodiments of the present application, the iron source is Fe(NO3)3·9H2O or FeCl3·6H2O. In the present application, the vanadate source is preferably NH4VO3 or NaVO3. In the present application, the molar ratio of iron in the iron source to vanadium in the vanadate source is preferably 1:1-1.5, and more preferably 1:1. In the present application, the water is preferably deionized water.

[0048] In the present application, the mixing of the iron source, the vanadate source and the water preferably comprises: dissolving the iron source and the vanadate source in water respectively to obtain an iron source solution and a vanadate source solution; and then stirring the iron source solution and the vanadate source solution uniformly to obtain an iron source-vanadate source mixed solution. In the present application, the concentration of the iron source in the iron source-vanadate source mixed solution is preferably 0.07-0.25 mol / L, and more preferably 0.11-0.17 mol / L. In the present application, the stirring is preferably magnetic stirring; and the stirring time is preferably 30 min.

[0049] In the present application, the temperature of the hydrothermal reaction is preferably 170-190℃, and more preferably 180℃; and the time of the hydrothermal reaction is preferably 2-4 h, and more preferably 3 h.

[0050] In the present application, the obtained system is preferably subjected to centrifugation after the hydrothermal reaction to obtain the FeVO4 precursor. In the present application, the centrifugation time is preferably 5-10 min, and more preferably 5-7 min; and the centrifugation speed is preferably 6000-10000 r / min.

[0051] After obtaining the FeVO4 precursor, the FeVO4 precursor is calcined to obtain triclinic FeVO4. In the present application, the FeVO4 precursor preferably further comprises sequentially performed washing and drying before being calcined. In the present application, the washing preferably comprises centrifugal washing with deionized water and anhydrous ethanol for five times respectively. In the present application, the drying is preferably vacuum drying; the temperature of the vacuum drying is preferably 60-90℃, more preferably 70-80℃; the time of the vacuum drying is preferably 22-26h, more preferably 24h.

[0052] In the present application, the temperature of the calcination is preferably 300-600℃, more preferably 400-500℃; the time of the calcination is preferably 1-3h, more preferably 2h. In the present application, the atmosphere of the calcination is preferably air or N2, more preferably air. In the present application, the calcination is preferably performed in a muffle furnace.

[0053] In the present application, the Pd source, the reducing agent and water are mixed to perform a reduction reaction to obtain Pd 0 (elemental palladium). In the present application, the Pd source is preferably a palladium salt, more preferably palladium chloride (PdCl2) or palladium acetate (Pd(OAc)2). In the present application, the reducing agent is preferably sodium borohydride (NaBH4), sodium hypophosphite (NaH2PO2) or hydrazine hydrate (N2H4·H2O). In the present application, the mass ratio of the Pd source and the reducing agent is preferably 1:8-10, more preferably 1:9-9.5. In the present application, the water is preferably deionized water.

[0054] In the present application, the mixing of the Pd source, the reducing agent and water preferably comprises: dissolving the Pd source and the reducing agent in water respectively to obtain a Pd source solution and a reducing agent solution; adjusting the mixture to weak alkalinity after adding the reducing agent solution into the Pd source solution with dilute acid. In the present application, the concentration of the Pd source solution is preferably 0.1-0.3g / L, more preferably 0.2g / L; the concentration of the reducing agent solution is preferably 30-50g / L, more preferably 38g / L. In the present application, the dilute acid is preferably dilute hydrochloric acid; the concentration of the dilute hydrochloric acid is preferably 0.5-1.5mol / L, more preferably 1mol / L. In the present application, the pH of the weak alkalinity is preferably 7-8.

[0055] In the present application, the temperature of the reduction reaction is preferably room temperature; the time of the reduction reaction is preferably 5-10min.

[0056] In the present application, the Pd 2+ is reduced to Pd 0 by the reduction reaction.

[0057] The present application preferably carries out solid-liquid separation on the obtained reduction system after the reduction reaction to obtain solid substance; and carries out drying on the solid substance to obtain Pd 0 In the present application, the solid-liquid separation is preferably centrifugation; the centrifugation time is preferably 5-10 min, more preferably 6-7 min; and the centrifugation speed is preferably 6000-10000 r / min. In the present application, the drying is preferably vacuum drying; the vacuum drying temperature is preferably 60-90℃, more preferably 80℃; and the vacuum drying time is preferably 22-26 h, more preferably 24 h.

[0058] The present application places CNTs in an acidic solution to carry out acidification to obtain acidified CNTs. In the present application, the CNTs are preferably multi-walled CNTs; and the diameter of the CNTs is preferably 10-20 nm. In the present application, the acidic solution is preferably concentrated nitric acid, concentrated sulfuric acid or a mixed solution of concentrated nitric acid and concentrated sulfuric acid. In the present application, the concentration of the concentrated nitric acid is preferably 16 mol / L; the concentration of the concentrated sulfuric acid is preferably 18 mol / L; and the mixed solution of concentrated nitric acid and concentrated sulfuric acid is preferably prepared by mixing concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:1. In the present application, the dosage ratio of the CNTs to the acidic solution is preferably 0.1-0.3 g: 50-150 mL.

[0059] In the present application, the acidification temperature is preferably 60-80℃; and the acidification time is preferably 10-15 h, more preferably 12 h.

[0060] The present application preferably carries out washing and drying on the obtained CNTs in sequence after the acidification is completed to obtain acidified CNTs. In the present application, the washing is preferably washing with deionized water until neutral, and more preferably washing until the filtrate pH is 6.5-7.3. In the present application, the drying is preferably vacuum drying; the vacuum drying temperature is preferably 60-90℃, more preferably 80℃; and the vacuum drying time is preferably 22-26 h, more preferably 24 h.

[0061] to obtain triclinic FeVO4, Pd 0 After obtaining the acidified CNTs, triclinic FeVO4, Pd 0 and the solvent to obtain a mixed dispersion. In the present application, the acidified CNTs, triclinic FeVO4 and Pd 0The mass ratio of the Nafion, water and ethanol is preferably 1:1-2:1-3, and more preferably 1:1:1.25-1.75. In the present application, the solvent is preferably a mixture of 5wt% Nafion solution, water and anhydrous ethanol; the concentration of the Nafion solution is preferably 5wt%; and the volume ratio of the Nafion, water and anhydrous ethanol is preferably 1:5-10:10-20, and more preferably 1:5:15. In the present application, the water is preferably pure water. In the present application, the mixing is preferably performed under ultrasonic conditions; the power of the ultrasonic is preferably 160-200W; and the time of the ultrasonic is preferably 1-3h, and more preferably 2h.

[0062] After obtaining the mixed dispersion, the present application performs vacuum filtration on the mixed dispersion to obtain the cathode composite film. In the present application, the vacuum filtration is preferably vacuum suction filtration. In the present application, the material of the substrate film is consistent with the substrate film described above, and will not be repeated here.

[0063] After the filtration, the present application preferably performs drying on the obtained composite film to obtain the cathode composite film. In the present application, the drying is preferably vacuum drying; the temperature of the vacuum drying is preferably 60-90℃, and more preferably 80℃; and the time of the vacuum drying is preferably 6-8h.

[0064] The present application provides an application of the cathode composite film in the above technical solution or the cathode composite film prepared by the preparation method in the above technical solution in removing organic pollutants in wastewater in a continuous flow system. In the present application, the organic pollutants are preferably chlorobenzoic acid (CA).

[0065] In the present application, the application preferably includes: using the cathode composite film as a cathode, using a platinum mesh as an anode, and using Ag / AgCl as a reference electrode, and filtering and degrading the organic pollutants in the wastewater containing the organic pollutants through the continuous flow system.

[0066] In the present application, the concentration of the organic pollutants in the wastewater containing the organic pollutants is preferably 1-10mg / L. In the present application, the distance between the anode plate and the cathode plate is preferably 0.5-3cm. In the present application, the flow rate of the wastewater containing the organic pollutants through the continuous flow system is preferably 0.5-3mL / min.

[0067] In the present application, the cathode potential applied to the cathode composite film is preferably -0.6--1.2V. In the present application, the pH range of the wastewater containing the organic pollutants is preferably 3-9.

[0068] In the present application, the wastewater containing organic pollutants preferably further comprises an electrolyte. In the present application, the electrolyte is preferably Na2SO4. In the present application, the concentration of the electrolyte in the wastewater is preferably 20-100 mmol / L.

[0069] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0070] Embodiment 1

[0071] Step 1): 10 mmol Fe(NO3)3·9H2O and 10 mmol NH4VO3 were dissolved in 30 mL of deionized water respectively to obtain a Fe(NO3)3 solution and an NH4VO3 solution; the Fe(NO3)3 solution and the NH4VO3 solution were mixed and magnetically stirred for 30 min, then transferred to a reaction kettle, reacted at 180℃ for 3 h, and centrifuged for 5 min to obtain a FeVO4 precursor; the FeVO4 precursor was washed with deionized water and anhydrous ethanol by centrifugation for five times, vacuum dried at 80℃ for 24 h, and then transferred to a muffle furnace for calcination at 400℃ for 2 h to obtain triclinic FeVO4;

[0072] Step 2): 0.1 g of PdCl2 was dissolved in 500 mL of deionized water to prepare a 0.2 g / L PdCl2 solution, 25 mL of a NaBH4 solution with a concentration of 38 g / L was added, the pH value was adjusted to 7.5 with a 1 mol / L HCl solution, the precipitate was collected after centrifugation for 5 min, and vacuum dried at 80℃ for 24 h to obtain Pd 0 ;

[0073] Step 3): 0.2 g of CNTs was acidified in 100 mL of concentrated HNO3 (concentration of 16 mol / L) for 12 h, the acidification temperature was 70℃, and after acidification, the CNTs were washed to neutral with deionized water, and vacuum dried at 80℃ for 24 h to obtain acidified CNTs;

[0074] Step 4): 10 mg of the acidified CNTs, 10 mg of triclinic FeVO4 and 15 mg of Pd 0 were dissolved in a solvent (100 μL of a 5 wt% Nafion solution, 0.5 mL of pure water and 1.5 mL of anhydrous ethanol), and ultrasonically treated for 2 h to obtain a mixed dispersion; the mixed dispersion was vacuum filtered onto a PTFE membrane with a diameter of 50 mm and a pore size of 5 μm (effective area of 12.56 cm 2), and the obtained composite membrane material was vacuum dried at 80°C for 6h to obtain dried CNTs / FeVO4 / Pd 0 cathode composite membrane.

[0075] Example 2

[0076] Step 1): 8mmol Fe(NO3)3·9H2O and 8mmol NH4VO3 were respectively dissolved in 30mL deionized water to obtain Fe(NO3)3 solution and NH4VO3 solution; the Fe(NO3)3 solution and NH4VO3 solution were mixed and magnetically stirred for 30min, then transferred to a reaction kettle, reacted at 180°C for 3h, and centrifuged for 7min to obtain FeVO4 precursor; the above FeVO4 precursor was washed with deionized water and anhydrous ethanol by centrifugation for five times, vacuum dried at 70°C for 26h, and then transferred to a muffle furnace and calcined at 400°C for 2h to obtain triclinic FeVO4;

[0077] Step 2): 0.1g PdCl2 was dissolved in 500mL deionized water to prepare a 0.2g / L PdCl2 solution, 25mL of 38g / L NaBH4 solution was added, and the pH value was adjusted to 7.5 with 1mol / L HCl solution, the precipitate was collected after centrifugation for 5min, and vacuum dried at 70°C for 26h to obtain Pd 0 ;

[0078] Step 3): 0.1g CNTs was acidified in 60mL concentrated HNO3 (concentration of 16mol / L) for 12h, the acidification temperature was 70°C, and the acidification was washed with deionized water to neutral, and vacuum dried at 80°C for 26h to obtain acidified CNTs;

[0079] Step 4): 10mg acidified CNTs, 10mg triclinic FeVO4 and 12.5mg Pd 0 were dissolved in a solvent (100μL 5wt% Nafion solution, 0.5mL pure water and 1.5mL anhydrous ethanol), and ultrasonic treatment was performed for 2h to obtain a mixed dispersion liquid; the mixed dispersion liquid was vacuum filtered onto a PTFE membrane with a diameter of 50mm and a pore size of 5μm (effective area of 12.56cm 2 ), to obtain a composite membrane material, and the obtained composite membrane material was vacuum dried at 70°C for 8h to obtain dried CNTs / FeVO4 / Pd 0 cathode composite membrane.

[0080] Example 3

[0081] Step 1): 5 mmol Fe(NO3)3·9H2O and 5 mmol NH4VO3 were dissolved in 30 mL of deionized water respectively to obtain Fe(NO3)3 solution and NH4VO3 solution; the Fe(NO3)3 solution and NH4VO3 solution were mixed and magnetically stirred for 30 min, then transferred into a reaction kettle, reacted at 180 ℃ for 3 h, and centrifuged for 5 min to obtain FeVO4 precursor; the FeVO4 precursor was washed with deionized water and anhydrous ethanol by centrifugation for five times, vacuum dried at 60 ℃ for 26 h, then transferred into a muffle furnace and calcined at 400 ℃ for 2 h to obtain triclinic FeVO4;

[0082] Step 2): 0.1 g of PdCl2 was dissolved in 500 mL of deionized water to prepare a PdCl2 solution with a concentration of 0.2 g / L, 25 mL of NaBH4 solution with a concentration of 38 g / L was added, and then the pH value was adjusted to 7.5 with 1 mol / L HCl solution; the precipitate was collected after centrifugation for 6 min, and vacuum dried at 70 ℃ for 26 h to obtain Pd 0 ;

[0083] Step 3): 0.1 g of CNTs was acidified in 60 mL of concentrated HNO3 (concentration of 16 mol / L) for 12 h, the acidification temperature was 70 ℃, and after acidification, the solution was washed to neutral with deionized water, and vacuum dried at 80 ℃ for 26 h to obtain acidified CNTs;

[0084] Step 4): 10 mg of acidified CNTs, 10 mg of triclinic FeVO4 and 17.5 mg of Pd 0 were dissolved in a solvent (100 μL of 5 wt% Nafion solution, 0.5 mL of pure water and 1.5 mL of anhydrous ethanol), and ultrasonicated for 2 h to obtain a mixed dispersion; the mixed dispersion was vacuum filtered onto a PTFE membrane with a diameter of 50 mm and a pore size of 5 μm (effective area of 12.56 cm 2 ), to obtain a composite membrane material, and the obtained composite membrane material was vacuum dried at 80 ℃ for 8 h to obtain a dried CNTs / FeVO4 / Pd 0 cathode composite membrane.

[0085] Comparative Example 1

[0086] Step 1): 0.2 g of CNTs was acidified in 100 mL of concentrated HNO3 (concentration of 16 mol / L) for 12 h, the acidification temperature was 70 ℃, and after acidification, the solution was washed to neutral with deionized water, and vacuum dried at 80 ℃ for 24 h to obtain acidified CNTs;

[0087] Step 2): 10 mg of the acidized CNTs were dissolved in a solvent (100 μL of 5 wt% Nafion solution, 0.5 mL of pure water and 1.5 mL of anhydrous ethanol) and ultrasonicated for 2 h to obtain a mixed dispersion; the mixed dispersion was vacuum filtered onto a PTFE membrane with a diameter of 50 mm and a pore size of 5 μm (effective area 12.56 cm 2 ), to obtain a composite membrane material, which was vacuum dried at 80°C for 6 h to obtain a dried CNTs cathode membrane.

[0088] Comparative Example 2

[0089] Step 1): 10 mmol of Fe(NO3)3·9H2O and 10 mmol of NH4VO3 were respectively dissolved in 30 mL of deionized water to obtain a Fe(NO3)3 solution and an NH4VO3 solution; the Fe(NO3)3 solution and the NH4VO3 solution were mixed and magnetically stirred for 30 min, then transferred into a reaction kettle, and reacted at 180°C for 3 h; after centrifugation for 5 min, a FeVO4 precursor was obtained; the FeVO4 precursor was washed with deionized water and anhydrous ethanol by centrifugation for five times, vacuum dried at 80°C for 24 h, and then transferred into a muffle furnace and calcined at 400°C for 2 h to obtain triclinic FeVO4;

[0090] Step 2): 0.2 g of CNTs were acidized in 100 mL of concentrated HNO3 (concentration of 16 mol / L) by heating for 12 h, the acidizing temperature was 70°C, and after the acidizing was completed, the CNTs were washed to neutral with deionized water and vacuum dried at 80°C for 24 h to obtain acidized CNTs;

[0091] Step 3): 10 mg of the acidized CNTs and 10 mg of the triclinic FeVO4 were dissolved in a solvent (100 μL of 5 wt% Nafion solution, 0.5 mL of pure water and 1.5 mL of anhydrous ethanol) and ultrasonicated for 2 h to obtain a mixed dispersion; the mixed dispersion was vacuum filtered onto a PTFE membrane with a diameter of 50 mm and a pore size of 5 μm (effective area 12.56 cm 2 ), to obtain a composite membrane material, which was vacuum dried at 80°C for 6 h to obtain a dried CNTs / FeVO4 cathode membrane.

[0092] Application Example 1

[0093] As shown in Figure 6 , a system reactor was built, the anode 3 was a platinum mesh, the cathode 4 was a cathode membrane, the reference electrode 5 was an Ag / AgCl electrode, the upper side of the anode 3 was the water inlet 2, the lower side of the cathode 4 was the water outlet 6, the anode and the cathode were conductively connected to an electrochemical workstation 1 by a titanium wire, the water inlet utilized a peristaltic pump 9 to pass through the continuous flow system reactor, a gas flow meter 8 was used to control the aeration amount, and an air pump 7 was used to aerate in a water collecting tank 10 to maintain the continuous generation of H2O2.

[0094] Prepare 40 mL of a 10 mg / L CA solution with a pH of 5, and add 50 mmol / L Na₂SO₄ as an electrolyte; then prepare the CNTs / FeVO₄ / Pd solution obtained in Example 1. 0 A cathode composite membrane serves as the cathode, and a platinum mesh as the anode. The vertical distance between the two electrodes is 7 mm. An electrochemical workstation applies a potential of -1 V (vsAg / AgCl) to the cathode composite membrane, and a peristaltic pump provides a flow rate of 2 mL / min to permeate the CA solution through an effective area of ​​3.14 cm². 2 The electrode membrane enters the reactor.

[0095] In comparison, the cathode membranes prepared in Comparative Examples 1 and 2 were used as cathodes, and degradation was carried out according to the above application examples. The concentration of pollutants in the effluent was determined by HPLC, and the results are as follows. Figure 7 As shown, the cathode composite membrane prepared in Example 1 achieved a degradation rate of 85% after 50 minutes, while Comparative Examples 1 and 2 showed degradation rates of 9% and 36%, respectively.

[0096] Application Example 2

[0097] like Figure 6 The system reactor was constructed as shown. 40 mL of a 10 mg / L CA solution was prepared, with a pH of 5, and 50 mmol / L Na₂SO₄ was added as an electrolyte. The CNTs / FeVO₄ / Pd obtained in Example 1 was then used. 0 A cathode composite membrane serves as the cathode, and a platinum mesh as the anode. The vertical distance between the two electrodes is 7 mm. An electrochemical workstation applies a potential of -1 V (vsAg / AgCl) to the cathode composite membrane, and a peristaltic pump provides a flow rate of 2 mL / min to permeate the CA solution through an effective area of ​​3.14 cm². 2 The electrode membrane enters the reactor.

[0098] The cathode composite membranes prepared in Examples 2 and 3 were used as cathodes, and degradation was carried out according to the above application examples. The concentration of pollutants in the effluent was determined by HPLC, and the results are as follows. Figure 8 As shown, the cathode composite membrane prepared in Example 1 achieved a degradation rate of 85% after 50 minutes, while Examples 2 and 3 showed degradation rates of 74% and 70%, respectively.

[0099] Application Example 3

[0100] like Figure 6 The system reactor was constructed as shown. 40 mL of a 10 mg / L CA solution was prepared, with a pH of 5, and 50 mmol / L Na₂SO₄ was added as an electrolyte. The CNTs / FeVO₄ / Pd obtained in Example 1 was then used. 0A cathode composite membrane serves as the cathode, and a platinum mesh as the anode. The vertical distance between the two electrodes is 7 mm. An electrochemical workstation applies a potential of -1.0 V (vsAg / AgCl) to the cathode composite membrane, and a peristaltic pump provides a flow rate of 2 mL / min to permeate the CA solution through an effective area of ​​3.14 cm². 2 The electrode membrane enters the reactor.

[0101] The pH of the CA solution was adjusted to 3, 7, and 9 using 0.1 mol / L H₂SO₄ or 0.1 mol / L NaOH solution, respectively. Degradation was then carried out according to the application example described above. The concentration of pollutants in the effluent was determined by HPLC, and the results are as follows: Figure 9 As shown, the degradation rates of the cathode composite membrane prepared in Example 1 were 91%, 85%, 78%, and 73% at pH values ​​of 3, 5, 7, and 9, respectively.

[0102] Characterization tests:

[0103] CNTs / FeVO4 / Pd prepared in Example 1 0 SEM image of the cathode composite film as follows Figure 1 As shown, the catalyst (triclinic FeVO4, Pd) 0 The CNTs are uniformly loaded onto the surface of the membrane.

[0104] CNTs / FeVO4 / Pd prepared in Example 1 0 The EDS spectrum of the cathode composite film is as follows Figure 2 As shown, all elements (Fe, V, O, Pd, C) can be detected on the surface.

[0105] SEM image of the CNTs cathode film prepared in Comparative Example 1 is shown below. Figure 3 As shown, CNTs are uniformly loaded on the PTFE membrane.

[0106] SEM image of the CNTs / FeVO4 cathode film prepared in Comparative Example 2 is shown below. Figure 4 As shown, the catalyst (triclinic FeVO4) is uniformly loaded on the surface of the CNTs membrane.

[0107] CNTs / FeVO4 / Pd prepared in Example 1 0 Cathode composite membrane and CNTs, FeVO4, Pd 0 XRD pattern as shown Figure 5 As shown, CNTs, FeVO4, Pd 0 All crystalline phases are present.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cathode composite membrane, characterized by, A substrate film and acidized carbon nanotubes loaded on the surface of the substrate film; the surface of the acidized carbon nanotubes is loaded with triclinic FeVO4 and Pd 0 ; The acid-treated carbon nanotube, triclinic FeVO4 and Pd 0 are present in a total amount of 100%, the acid-treated carbon nanotube is present in an amount of 20 to 30%, the triclinic FeVO4 is present in an amount of 20 to 35%, and the Pd 0 is present in an amount of 30 to 50%.

2. The method for preparing the cathode composite membrane of claim 1, comprising the following steps: mixing an iron source, a vanadate source and water, and performing a hydrothermal reaction to obtain a FeVO4 precursor; calcining the FeVO4 precursor to obtain triclinic FeVO4; The palladium source, the reducing agent and water are mixed to carry out the reduction reaction to obtain Pd 0 ; placing carbon nanotubes in an acid solution to perform acidification to obtain acidified carbon nanotubes; The acidified carbon nanotubes, triclinic FeVO4, Pd 0 and solvent are mixed to obtain a mixed dispersion liquid; sucking the mixed dispersion liquid onto a base film to obtain the cathode composite membrane.

3. The preparation method according to claim 2, characterized in that, The temperature of the hydrothermal reaction is 170-190°C. The time of the hydrothermal reaction is 2-4h.

4. The production method according to claim 2, characterized by, The temperature of the calcination is 300-600°C; the time of the calcination is 1-3h.

5. The preparation method according to claim 2, characterized in that, The acidified carbon nanotubes, triclinic FeVO4 and Pd 0 The mass ratio of the acidified carbon nanotubes, triclinic FeVO4 and Pd is 1:1~2:1~3.

6. The preparation method according to claim 2, characterized in that, The base film comprises a polytetrafluoroethylene film or a polyvinylidene fluoride film.

7. The application of the cathode composite membrane of claim 1 or the cathode composite membrane prepared by the method of any one of claims 2-6 in removing organic pollutants in wastewater in a continuous flow system.

8. Use according to claim 7, characterized in that, The application comprises: using the cathode composite membrane as a cathode, using a platinum mesh as an anode, and using Ag / AgCl as a reference electrode, and passing wastewater containing organic pollutants through a continuous flow system to filter and degrade the organic pollutants in the wastewater.

9. Use according to claim 8, characterized in that, The wastewater containing organic pollutants also comprises an electrolyte.

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