A double-sided electrocatalytic film for directional degradation regulation and a preparation method and application thereof

Abstract

The application belongs to the technical field of perfluorinated compound degradation, and particularly relates to a double-sided electrocatalytic membrane for directional degradation regulation and a preparation method and application thereof. The double-sided electrocatalytic membrane comprises a ceramic membrane substrate, a Pd-rGO composite membrane cathode layer and a Re-Ti4O7 composite membrane anode layer arranged on two sides of the ceramic membrane substrate respectively. The Re-Ti4O7 in the Re-Ti4O7 composite membrane anode layer is a rare earth element modified Magnéli phase Ti4O7. The electrochemical reduction-oxidation relay degradation system with the Janus electrocatalytic ceramic membrane as the core is constructed, so that the perfluorinated compound successively undergoes reduction defluorination and oxidation degradation reaction, thereby directional regulation of the PFASs degradation path can be realized, and deep / complete dehalogenation and mineralization of the PFASs are beneficial.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perfluorinated compound degradation, and particularly relates to a double-sided electrocatalytic membrane for directional degradation regulation and a preparation method and application thereof. BACKGROUND

[0002] Perfluorinated compounds (PFASs) are a class of persistent organic pollutants, which are widely used in various industrial products due to their good chemical stability, high temperature resistance, corrosion resistance, hydrophobicity and oleophobicity. However, PFASs have been confirmed to have problems such as liver toxicity, developmental toxicity, neurotoxicity, immunotoxicity and potential carcinogenicity.

[0003] The C-F bond of PFASs is the strongest bond among all covalent bonds, with a bond energy of 440.99 kJ / mol. The fluorine ion has three unpaired electrons, resulting in a very stable structure that is difficult to oxidize and lose electrons. Conventional biological methods are difficult to achieve defluorination degradation of PFASs. Currently, physical adsorption and membrane filtration remove PFASs through adsorption and separation, respectively, which are the most common methods for treating PFASs in water. However, these two methods only transfer phases and cannot completely remove PFASs, and have the disadvantages of high treatment cost and secondary pollution. Advanced oxidation methods usually use hydroxyl radicals (·OH) and persulfate radicals (SO4 - ·) as active substances to break the C-C bond by stealing the electrons of the C atom in the structure of PFASs, but have the problems of low defluorination efficiency and high toxicity of degradation intermediates. Advanced reduction technology based on hydrated electrons can efficiently achieve defluorination of PFASs due to its high reduction potential. However, as the number of defluorinated atoms increases, the reduction performance of the defluorinated product of PFASs changes, making it difficult to be further reduced, resulting in a single reduction method that still cannot balance high defluorination efficiency and mineralization efficiency. Therefore, it is urgent to find an efficient, low-cost and safe method to degrade PFASs.

[0004] Janus electrocatalytic membrane has a double-sided electrochemical reaction surface, and the unique structure is beneficial to improve the pollution removal performance of the electrocatalytic membrane. Compared with electrocatalytic membranes that only provide single-sided cathode reduction or anode oxidation, double-sided electrocatalytically active membranes can fully utilize the electrode oxidation-reduction reactions within the membrane matrix, with enhanced Faraday efficiency. Compared with electrocatalytic membranes, due to the electrical insulation properties of the substrate, double-sided electrocatalytically active ceramic membranes avoid the distance limitation between the electrodes, and allow a short diffusion distance to achieve rapid electrochemical oxidation.

[0005] Compared with the electrocatalytic membrane only providing single-face cathode reduction or anode oxidation, the Janus electrocatalytic membrane can fully utilize the electrode redox reaction inside the membrane matrix, and is conducive to improving the electron utilization efficiency. Moreover, the extremely small anode-cathode spacing and the micro-nano aperture inside the filter membrane can effectively solve the problems of “adding electrolyte” and “low mass transfer rate of low-concentration pollutants” in the process of treating PFASs by electrochemical technology.

[0006] Chinese invention patent application CN108543423A discloses an electrocatalytic membrane filter device and a preparation method of an electrocatalytic filter membrane thereof. An electrocatalytic membrane filter device is provided, which can couple membrane filtration with electrocatalytic mechanism and be applied to degrade organic matter and other wastewater. A preparation method of a hot-reduced graphene / carbon nanotube electrocatalytic filter membrane loaded with titanium dioxide is also provided. In actual application, compared with existing membrane filtration and electrocatalytic technology, the electrocatalytic membrane filter device can remove difficult-to-degrade small molecular pollutants in water in real time, has low energy consumption, high efficiency, and has potential industrial application value. However, the membrane described above is a flexible membrane, which lacks mechanical strength in actual application.

[0007] The invention of Chinese invention patent application CN202210717325.6 provides a double-face electrocatalytically active ceramic membrane and a preparation method thereof, the surface of which is sputtered with Magnéli phase Ti4O7 as an anode of the electrocatalytic membrane and deposited with CuFe2O4 prepared by the sol-gel-sintering method as a cathode of the electrocatalytic membrane. The double-face electrocatalytically active ceramic membrane can quickly remove organic pollutants in water, but only utilizes direct oxidation at the anode and indirect oxidation at the cathode to degrade the pollutants, and cannot realize directional degradation and regulation of the pollutants by reduction and then oxidation on the anode and the cathode of the double-face electrocatalytically active ceramic membrane. SUMMARY

[0008] In view of the deficiencies of the prior art, the technical problem actually solved by the present application is to provide a double-face electrocatalytic membrane for directional degradation and regulation, and a preparation method and application thereof. The present application couples the cathode and the anode in a membrane matrix to form a Janus electrocatalytic membrane with a cathode and an anode, and constructs an electrochemical reduction-oxidation relay degradation system based on the structural characteristics of perfluorinated compounds, so that the perfluorinated compounds undergo reduction defluorination and oxidation degradation reactions in sequence, which is conducive to realizing directional regulation of PFASs degradation path, deep / complete dehalogenation of PFASs, and mineralization.

[0009] In order to achieve the above-mentioned purposes of the present application, the specific technical solutions adopted by the present application are as follows:

[0010] The application provides a double-sided electrocatalytic film for directional degradation regulation, which comprises a ceramic film substrate, a Pd-rGO composite film cathode layer and a Re-Ti4O7 composite film anode layer arranged on two sides of the ceramic film substrate respectively; and the Re-Ti4O7 in the Re-Ti4O7 composite film anode layer is a Magnéli phase Ti4O7 modified by a rare earth element.

[0011] Preferably, the rare earth element is cerium or lanthanum; and the Pd-rGO in the Pd-rGO composite film cathode layer is reduced graphene oxide modified by Pd.

[0012] Preferably, the preparation method of the Pd-rGO in the Pd-rGO composite film cathode layer comprises:

[0013] (1) adding rGO into a hexane solution, adding 3-aminopropyltrimethoxysilane, centrifuging, drying to obtain rGO-NH2;

[0014] (2) adding rGO-NH2 into water, adding PdCl2, then irradiating with ultraviolet light, centrifuging, washing, drying to obtain Pd-rGO.

[0015] Further preferably, the mass concentration of the rGO in the hexane solution in step (1) is 1-3 g / L; the volume-mass ratio of the 3-aminopropyltrimethoxysilane to the rGO is 1.5-10 mL / g; and the drying temperature is 60-80 ℃, and the drying time is 10-14 h.

[0016] Further preferably, the mass concentration of the rGO-NH2 in water in step (2) is 0.5-1.25 g / L; the mass ratio of the PdCl2 to the rGO-NH2 is 7-10:1; the intensity of the ultraviolet light is 6-10 mW / cm 2 ; and the irradiation time of the ultraviolet light is 50-70 min.

[0017] Preferably, the preparation method of the Re-Ti4O7 in the Re-Ti4O7 composite film anode layer comprises: adding Ti4O7 into acetone, adding a rare earth element compound, dispersing, stirring, drying to obtain Re-Ti4O7.

[0018] Further preferably, the mass concentration of the Ti4O7 in the acetone is 100-150 g / L; the rare earth element compound is selected from one or both of a rare earth element chloride and a rare earth element nitrate; the molar concentration of the rare earth element compound in the acetone is 50-80 mM / L; the stirring temperature is 40-55 ℃, the drying temperature is 60-100 ℃, and the drying time is 20-28 h.

[0019] Preferably, the ceramic membrane substrate has a pore size of 0.1-1.0 μm, a thickness of 2-6 mm, and a diameter of 3-10 cm, and the Re-Ti4O7 composite membrane anode layer has a thickness of 10-20 μm.

[0020] The application also relates to a preparation method of the double-sided electrocatalytic membrane.

[0021] (1) Pd-rGO is dispersed in dimethyl sulfoxide, loaded on one side of the ceramic membrane substrate, washed, and dried to obtain a Pd-rGO composite membrane cathode layer;

[0022] (2) Re-Ti4O7 is sprayed on the other surface of the ceramic membrane substrate after being melted, and then annealed to obtain the double-sided electrocatalytic membrane.

[0023] Preferably, the mass concentration of the Pd-rGO after dispersion in step (1) is 0.4-0.6 g / L, and the content of Pd-rGO in the Pd-rGO composite membrane cathode layer is 1.5-2.5 mg / cm 2 ; and the annealing condition in step (2) is vacuum or H2 atmosphere, and the annealing temperature is 1000-1200℃.

[0024] The application also relates to application of the double-sided electrocatalytic membrane or the double-sided electrocatalytic membrane prepared by the preparation method in the field of directional degradation of perfluorinated compounds.

[0025] Preferably, the directional degradation comprises feeding a solution to be treated from a supply side, sequentially passing through the Pd-rGO composite membrane cathode layer and the Re-Ti4O7 composite anode layer, and finally discharging from a discharge side; and the concentration of the perfluorinated compound is 0.5-25 mg / L.

[0026] Preferably, the supply side is located on the anode layer side, and the discharge side is located on the cathode layer side, the supply side and the discharge side are two sides formed by the double-sided electrocatalytic membrane and not directly connected; the anode layer is connected to the positive electrode of the power supply, and the cathode layer is connected to the negative electrode of the power supply; and the voltage of the power supply is 1.5-8.0 V.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] (1) The Janus electrocatalytic ceramic membrane is used as the core of the electrochemical reduction-oxidation relay degradation system, the perfluorinated compound is subjected to reduction defluorination and oxidation degradation in sequence, the degradation path of PFASs can be directionally regulated, and the deep / complete dehalogenation and mineralization of PFASs are facilitated.

[0029] (2) The application can make full use of the film structure of the porous substrate to limit the reactants and charged active sites in the micron / nanometer scale, and maximize the compression of the diffusion layer thickness, thereby effectively solving the problem of limited mass transfer efficiency of conventional electrochemical methods in treating low-concentration PFASs;

[0030] (3) The Janus electro-catalytic ceramic membrane anode-cathode distance designed in the application is about 1-2 orders of magnitude lower than that of the traditional electrochemical system (about cm), which can compensate for the high resistance caused by low conductivity, and effectively solve the problem of adding electrolyte for treating low-conductivity wastewater by conventional electrochemical method;

[0031] (4) The application combines the advantages of high defluorination rate of the reduction method and high mineralization efficiency of the oxidation method, which is conducive to realizing deep / complete dehalogenation and mineralization of PFASs, and greatly reducing the toxicity of reaction products;

[0032] (5) The reactor in the application has small footprint, short process and does not produce secondary pollution. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is the electrochemical reaction device for implementing the application; Figure (a) is a Janus electro-catalytic membrane filtration system circulating flow experimental device, and figure (b) is a Janus electro-catalytic membrane filtration system continuous flow experimental device;

[0034] Among them: 1. Lifting pump; 2. Ceramic membrane; 3. Cathode; 4. Anode; 5. Power supply; 6. Water inlet and outlet tank; 7. Water inlet tank; 8. Water outlet tank;

[0035] Figure 2 is a double-sided electro-catalytic membrane filtration reactor schematic diagram. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application are further described in detail, and the described embodiments are only a part of the application, which are used to explain the application, but not to limit the application, so other embodiments obtained by other skilled persons in the art without creative labor are all within the protection scope of the application.

[0037] The raw materials used in the embodiments of the application are all industrial products and can be commercially available.

[0038] Example 1

[0039] A double-sided electro-catalytic membrane for directional degradation regulation comprises a ceramic membrane substrate, a Pd-rGO composite membrane cathode layer and a Ce-Ti4O7 composite membrane anode layer.

[0040] 1. Preparation method of Pd-rGO composite membrane cathode layer:

[0041] (1) Pd-rGO powder preparation: 0.5 g of rGO powder was first dispersed in 220 mL of hexane solution under ultrasonic action, and then 2 mL of 3-aminopropyltrimethoxysilane (APTMS) was added after 30 minutes to obtain amine-functionalized rGO (rGO-NH2); the obtained rGO-NH2 was separated by centrifugation, washed with ethanol and deionized water for 3 times, and then dried in an oven at 80°C; 80 mg of rGO-NH2 was dispersed in 100 mL of deionized water and ultrasonically treated for 30 minutes, and then 1.2 g of PdCl2 powder was added and ultrasonically treated for another 30 minutes to obtain a mixed solution of rGO-NH2 and PdCl2; the mixed solution was irradiated with UV light (wavelength 254 nm, intensity 7.5 mW / cm2) for 60 minutes to photoreduce the Pd precursor, and then the Pd-rGO composite product was collected by centrifugation, washed with deionized water, and dried in an oven at 80°C. 2 ) irradiation for 60 minutes, and then the Pd-rGO composite product was collected by centrifugation, washed with deionized water, and dried in an oven at 80°C.

[0042] (2) Pd-rGO composite membrane cathode layer preparation: a circular ceramic membrane with a pore size of 100 nm, a thickness of 4 mm, and a diameter of 4 cm was used as a substrate, 15 mg of the Pd-rGO powder obtained above was dispersed in 30 mL of dimethyl sulfoxide (DMSO) solution and ultrasonically treated for 2.0 hours, and then the catalyst was loaded onto one surface of the ceramic membrane by vacuum suction filtration; the membrane was washed with 60 mL of ethanol, 60 mL of 1:1 (V:V) deionized water / ethanol, and 120 mL of deionized water in sequence to remove residual DMSO, and then the ceramic membrane was placed for drying at 70°C for 12 h.

[0043] 2. Preparation method of Ce-Ti4O7 composite membrane anode layer

[0044] (1) Ce-Ti4O7 powder preparation: 12 g of Ti4O7 powder was added to 100 mL of acetone, and then 5 mM of rare earth element cerium chloride (CeCl3) was added after ultrasonic treatment for 30 minutes to obtain a suspension; the slurry was concentrated under stirring at 50°C, and then the slurry was completely dried in a vacuum oven at 80°C for 24 hours to prepare Ti4O7 powder loaded with rare earth element cerium (Ce).

[0045] (2) Preparation of Ce-Ti4O7 composite membrane anode layer

[0046] A vacuum plasma spraying method was used, and a direct current driven plasma arc was used as a heat source to heat the ceramic powder to a molten state, and then the Ce-Ti4O7 powder was uniformly sprayed on the other surface of the ceramic membrane substrate after melting; then the Ce-Ti4O7 composite membrane coating layer with a thickness of 10 μm was formed by annealing treatment at a high temperature of 1000°C in a H2 atmosphere; thereby obtaining a double-sided electrocatalytic membrane.

[0047] 3. Treating typical perfluorinated compound PFOA simulated wastewater

[0048] Using Figure 1 (a) the circulating flow experimental device shown in the figure, Figure 2 The double-sided electro-catalytic membrane filtration reactor shown in the figure; the supply side and the outflow side are two sides formed by the double-sided electro-catalytic membrane and are not directly connected; the anode layer is connected to the positive pole of the power supply, and the cathode layer is connected to the negative pole of the power supply.

[0049] First, the PFOA simulated wastewater reaches the Pd-rGO composite membrane cathode layer through the lifting pump to undergo a reduction reaction, and then reaches the Re-Ti4O7 composite anode layer through the gravity of the wastewater itself to undergo an oxidation reaction, and finally the effluent reaches the water tank, and so on. The experimental parameters are: the anode and cathode membrane areas are both 12.56 cm 2 , the reaction solution is 100 mL, the constant voltage is 2.0 V; the initial concentration of PFOA is 5 mg / L; the electrolyte Na2SO4 concentration is 10 mmol / L; the membrane flux is 25 mL / min.

[0050] Example 2

[0051] A double-sided electro-catalytic membrane for directional degradation regulation, comprising a ceramic membrane substrate, a Pd-rGO composite membrane cathode layer, and a La-Ti4O7 composite membrane anode layer.

[0052] 1. Preparation method of Pd-rGO composite membrane cathode layer:

[0053] (1) Pd-rGO powder preparation: first, 0.6 g of rGO powder is dispersed in 300 mL of hexane solution under ultrasonic action, and then 3 mL of 3-aminopropyltrimethoxysilane (APTMS) is added after 30 minutes to obtain amine-functionalized rGO (rGO-NH2); The obtained rGO-NH2 is separated by centrifugation, washed with ethanol and deionized water for 5 times, and then dried in an oven at 85°C; 100 mg of rGO-NH2 is dispersed in 120 mL of deionized water and ultrasonically treated for 40 minutes, then 1 g of PdCl2 powder is added and ultrasonically treated for another 30 minutes to obtain a mixture of rGO-NH2 and PdCl2; The mixture is irradiated with UV light (wavelength 254 nm, intensity 10 mW / cm 2 ) for 50 minutes to reduce the Pd precursor by light, then the Pd-rGO composite product is collected by centrifugation and washed with deionized water, and dried in an oven at 85°C.

[0054] (2) Pd-rGO composite membrane cathode layer preparation: a circular ceramic membrane with a pore size of 100 nm, a thickness of 4 mm, and a diameter of 4 cm was used as a substrate. 18 mg of the Pd-rGO powder obtained above was dispersed in 30 mL of dimethyl sulfoxide (DMSO) solution and ultrasonically treated for 2.0 hours. Then, the catalyst was loaded onto one surface of the ceramic membrane by vacuum filtration. The membrane was then washed with 80 mL of ethanol, 80 mL of 1:1 (V:V) deionized water / ethanol, and 120 mL of deionized water to remove residual DMSO. Finally, the ceramic membrane was dried at 80°C for 10 hours.

[0055] 2. Preparation method of La-Ti4O7 composite membrane anode layer:

[0056] (1) La-Ti4O7 powder preparation: 15 g of Ti4O7 powder was added to 100 mL of acetone, followed by the addition of 8 mM of lanthanum nitrate (La(NO3)3) and ultrasonic treatment for 45 minutes to obtain a suspension. The slurry was then concentrated at 55°C under stirring, and then completely dried in a vacuum oven at 100°C for 20 hours to prepare Ti4O7 powder loaded with rare earth element lanthanum (La).

[0057] (2) La-Ti4O7 composite membrane anode layer preparation

[0058] The La-Ti4O7 powder was heated to a molten state using vacuum plasma spraying, with a direct current driven plasma arc as the heat source. The molten La-Ti4O7 powder was then uniformly sprayed onto the other surface of the ceramic membrane substrate. Then, the La-Ti4O7 composite membrane coating was formed by annealing at 1200°C under vacuum conditions, with a thickness of 20 μm, thereby obtaining a double-sided electrocatalytic membrane.

[0059] 3. Treatment of typical perfluorinated compound PFOA simulated wastewater

[0060] Using Figure 1 (a) the circulating flow experimental device shown in the figure, Figure 2 the double-sided electrocatalytic membrane filtration reactor shown in the figure; the supply side and the outflow side are two sides formed by the double-sided electrocatalytic membrane without direct communication; the anode layer is connected to the positive electrode of the power supply, and the cathode layer is connected to the negative electrode of the power supply.

[0061] The PFOA simulated wastewater first reaches the membrane cathode layer to undergo a reduction reaction, and then reaches the anode layer using the gravity of the wastewater itself to undergo an oxidation reaction, and finally the effluent reaches the water tank, and this process is repeated. The experimental parameters are as follows: the anode and cathode membrane areas are both 19.63 cm 2 , the reaction solution is 100 mL, the constant voltage is 2.5 V; the initial concentration of PFOA is 25 mg / L; the electrolyte Na2SO4 concentration is 10 mmol / L; and the membrane flux is 25 mL / min.

[0062] Example 3

[0063] A dual-sided electrocatalytic membrane for directional degradation regulation, comprising a ceramic membrane substrate, a Pd-rGO composite membrane cathode layer, and a Ce-Ti4O7 composite membrane anode layer.

[0064] 1. A method for preparing the Pd-rGO composite membrane cathode layer, comprising:

[0065] (1) Pd-rGO powder preparation: 0.3 g of rGO powder was first dispersed in 200 mL of hexane solution under ultrasonic action, and then 1 mL of 3-aminopropyltrimethoxysilane (APTMS) was added after 30 minutes to obtain amine-functionalized rGO (rGO-NH2); the obtained rGO-NH2 was separated by centrifugation, washed with ethanol and deionized water for 3 times, and then dried in an oven at 75°C; 70 mg of rGO-NH2 was dispersed in 80 mL of deionized water and ultrasonically treated for 25 minutes, and then 0.5 g of PdCl2 powder was added and ultrasonically treated for 20 minutes to obtain a mixed solution of rGO-NH2 and PdCl2; the mixed solution was irradiated with UV light (wavelength 254 nm, intensity 6 mW / cm 2 ) for 70 minutes to reduce the Pd precursor by light, and then the Pd-rGO composite product was collected by centrifugation, washed with deionized water, and dried in an oven at 75°C.

[0066] (2) Pd-rGO composite membrane cathode layer preparation: a circular ceramic membrane with a pore size of 100 nm, a thickness of 4 mm, and a diameter of 4 cm was used as a substrate, 12 mg of the Pd-rGO powder obtained above was dispersed in 30 mL of dimethyl sulfoxide (DMSO) solution and ultrasonically treated for 1.5 hours, and then the catalyst was loaded onto one surface of the ceramic membrane by vacuum filtration; the membrane was washed with 40 mL of ethanol, 40 mL of 1:1 (V:V) deionized water / ethanol, and 80 mL of deionized water to remove residual DMSO, and then the ceramic membrane was placed in a drying oven at 60°C for 14 hours.

[0067] 2. A method for preparing the Ce-Ti4O7 composite membrane anode layer, comprising:

[0068] (1) Ce-Ti4O7 powder preparation: 10 g of Ti4O7 powder was added to 100 mL of acetone, and then 5 mM of rare earth element cerium chloride (CeCl3) was added and ultrasonically treated for 30 minutes to obtain a suspension; the suspension was concentrated into a slurry under stirring at 40°C, and then the slurry was completely dried in a vacuum oven at 60°C for 28 hours to prepare Ti4O7 powder loaded with rare earth element cerium (Ce).

[0069] (2) Ce-Ti4O7 composite membrane anode layer preparation

[0070] The ceramic powder is heated to a molten state by vacuum plasma spraying method using a direct current driven plasma arc as a heat source, and then the Ce-Ti4O7 powder is uniformly sprayed on the other surface of the ceramic membrane substrate after melting; then annealing treatment is carried out at 1200℃ under H2 atmosphere, to form a firmly attached Ce-Ti4O7 composite membrane coating with a thickness of 10μm; thereby obtaining a double-sided electrocatalytic membrane.

[0071] 3. Treating typical perfluorinated compound PFOA simulated wastewater

[0072] The Pd-rGO composite membrane cathode layer is prepared by the following method: Figure 1 (b) a continuous flow experimental device, Figure 2 The double-sided electrocatalytic membrane filter reactor is shown in the figure; the supply side and the outflow side are two sides formed by the double-sided electrocatalytic membrane without direct communication; the anode layer is connected to the positive electrode of the power supply, and the cathode layer is connected to the negative electrode of the power supply.

[0073] The PFOA simulated wastewater reaches the membrane cathode layer first to occur a reduction reaction by the lifting pump from the water inlet tank, and then reaches the anode to occur an oxidation reaction by the gravity of the wastewater itself, and finally the effluent reaches the water outlet tank; the experimental parameters are: the anode and cathode membrane areas are both 12.56cm 2 , the reaction solution is 100mL, the constant voltage is 2.0V; the initial concentration of PFOA is 0.5mg / L; the electrolyte Na2SO4 concentration is 10mmol / L; the membrane flux is 15mL / min.

[0074] Example 4

[0075] A directional degradation regulated double-sided electrocatalytic membrane, comprising a ceramic membrane substrate, a Pd-rGO composite membrane cathode layer, and a Ce-Ti4O7 composite membrane anode layer.

[0076] 1. A preparation method of the Pd-rGO composite membrane cathode layer:

[0077] (1) Preparation of Pd-rGO powder: first, 0.5g of rGO powder is dispersed in 220mL of hexane solution under ultrasonic action, and then 2mL of 3-aminopropyltrimethoxysilane (APTMS) is added after 30 minutes to obtain amine-functionalized rGO (rGO-NH2); the obtained rGO-NH2 is separated by centrifugation, washed with ethanol and deionized water for 3 times, and then dried in an oven at 80℃; 80mg of rGO-NH2 is dispersed in 100mL of deionized water and ultrasonically treated for 30 minutes, and then 1.2g of PdCl2 powder is added and ultrasonically treated for another 30 minutes to obtain a mixed solution of rGO-NH2 and PdCl2; the mixed solution is irradiated with UV light (wavelength 254nm, intensity 7.5mW / cm 2) The mixed solution was irradiated for 60 minutes to photoreduce the Pd precursor, and then the Pd-rGO composite product was collected by centrifugation, washed with deionized water, and dried in an oven at 80°C.

[0078] (2) Preparation of Pd-rGO composite membrane cathode layer: A circular ceramic membrane with a pore size of 100 nm, a thickness of 4 mm, and a diameter of 4 cm was used as a substrate. 15 mg of the Pd-rGO powder obtained above was dispersed in 30 mL of dimethyl sulfoxide (DMSO) solution and ultrasonically treated for 2.0 hours. Then, the catalyst was loaded onto one surface of the ceramic membrane by vacuum filtration. The membrane was washed with 60 mL of ethanol, 60 mL of 1:1 (V:V) deionized water / ethanol, and 120 mL of deionized water to remove residual DMSO, and then the ceramic membrane was placed in a drying oven at 70°C for 12 hours.

[0079] 2. Preparation method of Ce-Ti4O7 composite membrane anode layer:

[0080] (1) Preparation of Ce-Ti4O7 powder: 12 g of Ti4O7 powder was added to 100 mL of acetone, and then 5 mM of rare earth element cerium chloride (CeCl3) was added after ultrasonic treatment for 30 minutes to obtain a suspension. The slurry was concentrated at 50°C under stirring, and then the slurry was completely dried in a vacuum oven at 80°C for 24 hours, thereby preparing Ti4O7 powder loaded with rare earth element cerium (Ce).

[0081] (2) Preparation of Ce-Ti4O7 composite membrane anode layer

[0082] Vacuum plasma spraying method was used, and a direct current driven plasma arc was used as a heat source to heat the ceramic powder to a molten state. Then, the Ce-Ti4O7 powder was uniformly sprayed on the other surface of the ceramic membrane substrate after melting. Then, the Ce-Ti4O7 composite membrane coating with a thickness of 12 μm was formed by annealing at a high temperature of 1000°C under vacuum conditions, thereby obtaining a double-sided electrocatalytic membrane.

[0083] 3. Treatment of typical perfluorinated compound PFOS simulated wastewater

[0084] The double-sided electrocatalytic membrane filter reactor shown in Figure 1 (a) The circulating flow experimental device shown in, Figure 2 The double-sided electrocatalytic membrane filter reactor; the supply side and the outflow side are two sides formed by the double-sided electrocatalytic membrane without direct communication; the anode layer is connected to the positive electrode of the power supply, and the cathode layer is connected to the negative electrode of the power supply.

[0085] First, PFOS-simulated wastewater is pumped to the Pd-rGO composite membrane cathode layer for a reduction reaction. Then, using gravity, it reaches the Re-Ti4O7 composite anode layer for an oxidation reaction. Finally, the wastewater exits into a water tank, and this process is repeated. The experimental parameters are: both the anode and cathode membrane areas are 12.56 cm². 2 The reaction solution was 100 mL, the constant voltage was 3.0 V, the initial concentration of PFOS was 5 mg / L, the concentration of electrolyte Na2SO4 was 10 mmol / L, and the membrane flux was 25 mL / min.

[0086] Comparative Example 1

[0087] use Figure 1 The circulating flow experimental setup shown in (a) uses the Pd-rGO composite film prepared in Example 1 as the cathode and replaces the anode with a platinum-titanium mesh. The operation process is the same as in Example 1. The experimental parameters are: anode and cathode film area of ​​12.56 cm². 2 The reaction solution was 100 mL, the constant voltage was 2.0 V, the initial concentration of PFOA was 5 mg / L, the concentration of electrolyte Na2SO4 was 10 mmol / L, and the membrane flux was 25 mL / min.

[0088] Comparative Example 2

[0089] use Figure 1 (a) shows the experimental setup for the circulating flow experiment. The cathode was replaced with a platinum-titanium mesh, and the anode was the Ce-Ti4O7 composite film prepared in Example 1. The operation process was the same as in Example 1. The experimental parameters were: the anode and cathode film area was 12.56 cm². 2 The reaction solution was 100 mL, the constant voltage was 2.0 V, the initial concentration of PFOA was 5 mg / L, the concentration of electrolyte Na2SO4 was 10 mmol / L, and the membrane flux was 25 mL / min.

[0090] Comparative Example 3

[0091] use Figure 1 (a) shows the experimental setup for the circulating flow. Figure 2 The double-sided electrocatalytic membrane filtration reactor shown was assembled and tested using the Pd-rGO composite membrane cathode layer and Ce-Ti4O7 composite membrane anode layer prepared in Example 1. Unlike Example 1, the test was conducted without power supply to test the adsorption effect of the Janus electrocatalytic membrane on PFOA. The experimental parameters were: anode and cathode membrane area of ​​12.56 cm². 2 The reaction solution was 100 mL; the initial concentration of PFOA was 5 mg / L, and no current was applied.

[0092] Comparative Example 4

[0093] A copper ferrite gel-like precursor is prepared and deposited on a substrate by a sol-gel-sintering method; first, copper nitrate, iron nitrate, citric acid and ethylene glycol are dissolved in deionized water according to a ratio to form a sol, and the concentrations of the solutes in the sol are respectively 0.02 mol / L of copper nitrate, 0.04 mol / L of iron nitrate, 0.072 mol / L of citric acid and 0.144 mol / L of ethylene glycol. The sol is stirred at 90°C for 5 hours to form a gel-like precursor. 0.7 mL of the precursor is placed on one surface of a ceramic membrane substrate, and then a spin coater is used to spin coat at a speed of 1500 rpm for 30 s; then, the ceramic membrane substrate is spin coated twice with the same amount of precursor and spin coating parameters. Then, the spin-coated coating layer is gradually heated to 450°C for calcination by temperature programming at a heating rate of 3.5°C / min, to form a conductive coating layer as an anode layer. In the calcination process by gradient heating, the gradient heating is performed at a heating rate of 3°C / min, and the calcination is completed by maintaining at 100°C, 300°C and 450°C for 1.5 hours respectively, to prepare a copper ferrite cathode layer.

[0094] The Ce-Ti4O7 powder prepared in Example 1 is uniformly sprayed on the other surface of the ceramic membrane substrate after melting, and the treatment method is consistent with that of Example 1, to prepare a double-sided electrocatalytic membrane. Figure 1 (a) shows a circulating flow experimental device, Figure 2 (b) shows a Figure 2 (c) shows a double-sided electrocatalytic membrane filter reactor, which is used to treat perfluorinated compound PFOA simulated wastewater. The experimental process is consistent with that of Example 1. The experimental parameters are as follows: the anode and cathode membrane area is 12.56 cm 2 , the reaction solution is 100 mL, the constant voltage is 2.0 V; the initial concentration of PFOA is 1 mg / L; the electrolyte Na2SO4 concentration is 10 mmol / L; and the membrane flux is 25 mL / min.

[0095] The electrocatalytic membranes in Examples 1-4 and Comparative Examples 1-4 above are tested for effects, and the results are shown in Table 1.

[0096] Table 1 Test results

[0097]

[0098]

[0099] The test results of examples 1-4 and comparative examples 1-4 show that, in the present application, the Janus electrocatalytic ceramic membrane with a Pd and rGO composite film layer as the cathode and a rare earth element modified Ti4O7 film layer as the anode, the construction of the Janus electrocatalytic ceramic membrane as the core of the electrochemical reduction-oxidation relay degradation system, makes the PFASs undergo reduction defluorination and oxidation degradation reactions in turn, can realize the directional regulation of the PFASs degradation path, is conducive to the deep / complete dehalogenation and mineralization of PFASs. The efficient mineralization of pollutants is basically achieved, and no metal ions such as Pd, Ti and Ce are detected in the solution, which confirms the stability and safety of the Janus electrocatalytic membrane.

[0100] The above detailed description is a specific description of one of the feasible embodiments of the present application, which is not used to limit the patent scope of the present application, and any equivalent implementation or change without departing from the present application shall be included in the scope of the technical solutions of the present application.

Claims

1. A dual-sided electrocatalytic membrane for directional degradation modulation, characterized in that, The double-sided electro-catalytic membrane comprises a ceramic membrane substrate and a Pd-rGO composite membrane cathode layer and a Re-Ti4O7 composite membrane anode layer arranged on two sides of the ceramic membrane substrate respectively; the Re-Ti4O7 in the Re-Ti4O7 composite membrane anode layer is Magnéli phase Ti4O7 modified by a rare earth element; the rare earth element is cerium or lanthanum; The Pd-rGO in the Pd-rGO composite membrane cathode layer is reduced graphene oxide modified by Pd; The preparation method of the Pd-rGO in the Pd-rGO composite membrane cathode layer comprises: (1) adding rGO into a hexane solution, adding 3-aminopropyltrimethoxysilane, centrifuging, drying to obtain rGO-NH2; (2) adding rGO-NH2 into water, adding PdCl2, then irradiating with ultraviolet light, centrifuging, washing, drying to obtain Pd-rGO; The preparation method of the Re-Ti4O7 in the Re-Ti4O7 composite membrane anode layer comprises: adding Ti4O7 into acetone, adding a rare earth element compound, dispersing, stirring, drying to obtain Re-Ti4O7; The double-sided electro-catalytic membrane is used for directional degradation of perfluorinated compounds.

2. The dual-sided electrocatalytic membrane of claim 1, wherein, The mass concentration of the rGO in the hexane solution in step (1) is 1-3 g / L; the volume-mass ratio of the 3-aminopropyltrimethoxysilane to the rGO is 1.5-10 mL / g; the drying temperature is 60-80 o C, and the drying time is 10-14 h.

3. The dual-sided electrocatalytic membrane of claim 1, wherein, The mass concentration of the rGO-NH2 in water in step (2) is 0.5-1.25 g / L; the mass ratio of the PdCl2 to the rGO-NH2 is 7-10:1; the intensity of the ultraviolet light is 6-10 mW / cm 2 ; and the time of ultraviolet light irradiation is 50-70 min.

4. The dual-sided electrocatalytic membrane of claim 1, wherein, The mass concentration of the Ti4O7 in acetone is 100-150 g / L; the rare earth element compound is selected from one or both of a rare earth element chloride and a rare earth element nitrate; the molar concentration of the rare earth element compound in acetone is 50-80 mM / L; the temperature of the stirring is 40-55 °C, the temperature of the drying is 60-100 °C, and the time of the drying is 20-28 h.

5. The dual-sided electrocatalytic membrane of any one of claims 1-4, wherein, The pore size of the ceramic membrane substrate is 0.1-1.0 μm, the thickness is 2-6 mm, and the diameter is 3-10 cm; the thickness of the Re-Ti4O7 composite membrane anode layer is 10-20 μm.

6. A method of producing a double-sided electrocatalytic film according to any one of claims 1-5, characterized by, The method comprises the following steps: (1) dispersing Pd-rGO in dimethyl sulfoxide, loading the Pd-rGO into one side of the ceramic membrane substrate, flushing, drying to obtain a Pd-rGO composite membrane cathode layer; (2) spraying Re-Ti4O7 melted on the other surface of the ceramic membrane substrate, annealing to obtain a double-sided electro-catalytic membrane.

7. The preparation method according to claim 6, characterized in that, The mass concentration of the Pd-rGO after dispersion in step (1) is 0.4-0.6 g / L, and the content of Pd-rGO in the cathode layer of the Pd-rGO composite film is 1.5-2.5 mg / cm 2 ; the annealing conditions in step (2) are vacuum or H2 atmosphere, and the annealing temperature is 1000-1200℃.

8. Use of the double-sided electro-catalytic membrane according to any one of claims 1-5 or prepared by the preparation method of claim 6 or 7 in the field of directional degradation of perfluorinated compounds.

9. Use according to claim 8, characterized in that, The directional degradation comprises passing a solution to be treated from a supply side, sequentially through the Pd-rGO composite membrane cathode layer and the Re-Ti4O7 composite anode layer, and finally discharging from a discharge side; the concentration of the perfluorinated compounds is 0.5-25 mg / L.

10. Use according to claim 9, characterized in that, The supply side is located on the anode layer side, and the discharge side is located on the cathode layer side; the supply side and the discharge side are two sides formed by the double-sided electro-catalytic membrane without direct communication; the anode layer is connected to the positive pole of a power supply, and the cathode layer is connected to the negative pole of the power supply; the voltage of the power supply is 1.5-8.0 V.

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