Preparation and application of cobalt-palladium bimetallic composite electro-Fenton catalytic membrane

Abstract

The invention relates to the technical field of electro-Fenton coupling membranes and water treatment, in particular to a preparation method and application of a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane. According to the preparation method, the electro-Fenton catalyst taking the carbon nano tube as a base material is loaded on the polytetrafluoroethylene substrate membrane, metal cobalt and the carbon nano tube are connected through a chemical bond, a metal bond bridge is constructed, then the electron transfer process is accelerated, the limitation that the cycle rate of variable valence metal in a Fenton-like reaction is limited is broken through, and the rate of the Fenton reaction is increased; meanwhile, Pd0 is loaded on the carbon nano tube, so that atomic hydrogen is easy to generate, and dehalogenation reaction is facilitated. Degradation is carried out under a continuous flow system through a coupled membrane separation technology, meanwhile, the contact efficiency of pollutants and a catalytic membrane interface is enhanced, the mass transfer rate of the pollutants is increased, and efficient mineralization detoxification of brominated aromatic compounds can be achieved through the cobalt-palladium bimetallic composite electro-Fenton catalytic membrane.

Description

Technical Field

[0001] The present invention relates to the technical field of electro-Fenton coupling membranes and water treatment, and in particular to a preparation method and application of a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane. Background Art

[0002] Halogenated aromatic compounds, a typical class of organic pollutants, are widely used in industrial preservatives, fungicides, and pesticides. They enter aquatic environments through surface runoff and subsurface infiltration, particularly at high concentrations in industrial wastewater. These compounds are extremely toxic and difficult to degrade, posing a serious threat to the ecological environment and hindering sustainable environmental protection. Therefore, the mineralization and detoxification of halogenated aromatic compounds has become a research hotspot in water treatment, with electrochemical advanced oxidation processes (EAOPs) being one of the main approaches.

[0003] As one of the most typical technologies in EAOP, electro-Fenton (E-Fenton) technology is particularly suitable for the treatment of refractory organic pollutants. However, during the E-Fenton reaction, the leaching of Fe element will form iron sludge precipitation as the pH increases, which limits its application range. In order to overcome this limitation, Fenton-like catalysts have been developed to replace the Fe in traditional Fenton reagents by utilizing the transition between different valence states of transition metals. 2+ , thus breaking the pH limitation on the application of E-Fenton technology. Furthermore, the preparation method of E-Fenton catalysts is also crucial. Traditional physical methods are prone to metal leaching, causing secondary pollution. Chemical methods, on the other hand, connect metals through chemical bonds, extending the catalyst's service life and reducing the risk of environmental pollution.

[0004] Furthermore, in order to improve the recovery efficiency and recycling performance of the E-Fenton catalyst, membrane coupling technology was introduced into the E-Fenton system. By fixing the E-Fenton catalyst on the membrane material, an electrocatalytic membrane is formed. This design not only promotes the recovery of the catalyst, but also precisely controls the catalytic reaction site so that the reaction occurs mainly on the membrane electrode surface. However, this also limits the reaction rate. To solve this problem, a flow-through reactor operation mode is adopted to force water to pass through the membrane electrode, increase the mass transfer rate, reduce the thickness of the diffusion layer, and thus improve the reaction efficiency. This method has significant advantages over traditional plate electrodes, especially in enhancing mass transfer.

[0005] Carbon nanotube membranes have been widely studied in the field of EAOP due to their excellent electrical conductivity and are usually used as ideal substrate materials for E-Fenton coupled membranes. Not only can it generate H2O2 through oxygen reduction reaction, provide sufficient E-Fenton reagents, and reduce the need for additional chemical reagents, but it can also accelerate the E-Fenton reaction through transition metal modification, broaden the pH application range, and thus improve the detoxification efficiency of organic pollutants. In order to enhance the stability between the transition metal and the carbon nanotubes, a chemical bond bridge is used to connect them, which not only enhances the stability between the metal source and the substrate, but also provides a channel for electron transfer in the E-Fenton reaction. In addition, zero-valent palladium (Pd 0 ), using its catalytic reaction to produce atomic hydrogen ([H*]), can significantly accelerate the dehalogenation process of halogenated aromatic compounds and further improve the mineralization and detoxification efficiency.

[0006] To further optimize the treatment of halogenated aromatic compounds, a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane was developed. Application of this bimetallic modified carbon nanotube membrane in a flow-through reactor not only overcomes the mass transfer limitations of traditional systems but also significantly enhances the contact oxidation efficiency between the catalytic membrane and the active material, accelerating the mineralization and detoxification of halogenated aromatic compounds, effectively addressing the problem of halogenated aromatic compound contamination in water. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method and application of a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention provides a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, comprising a base membrane and a carbon nanotube composite catalyst, wherein the surface of the carbon nanotube composite catalyst is connected with cobalt and loaded with Pd 0 .

[0010] Preferably, the carbon nanotubes are 10-30 μm long, 5-10 nm in inner diameter and 10-20 nm in outer diameter. The metal content in the carbon nanotube composite catalyst is 100%, the metal cobalt accounts for 30-50%, the Pd 0 It accounts for 50~70%.

[0011] The present invention also provides a method for preparing the cobalt-palladium bimetallic composite electro-Fenton catalytic film described in the above technical solution, comprising the following steps:

[0012] The carbon nanotubes were placed in concentrated acid solution for acidification, washed and dried after treatment, and used as the substrate of the bimetallic material, which was denoted as ACCNTs.

[0013] The ACCNTs are placed in a cobalt-based precursor solution, connected to metallic cobalt through a hydrothermal reaction, and then washed and dried after treatment, which is recorded as ACCNTs-O-Co;

[0014] Dissolve palladium salt in water to prepare a solution, add excess reducing agent, carry out reduction reaction, adjust pH environment, and obtain black precipitate. After vacuum drying, it is zero-valent palladium particles, recorded as Pd 0 ;

[0015] The ACCNTs-O-Co and Pd 0 Prepare a dispersed solution according to a certain ratio;

[0016] The dispersed solution was filtered onto the substrate membrane and vacuum dried to obtain a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, which was recorded as ACCNTs-O-Co / Pd 0 .

[0017] Preferably, the concentrated acid solution comprises concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:(1-5); the ultrasonic dispersion time before the concentrated acid treatment is 20-60 min; the temperature for the acidification treatment is 60-100°C, and the acidification treatment time is 2-6 h; deionized water is used for washing until the pH of the filtrate is 6-7.

[0018] Preferably, the cobalt-based precursor solution mainly comprises cobalt nitrate hexahydrate and water in a mass ratio of 1:(30-60); the amount of ACCNTs added to the reaction solution is 50-100 mg, and the ultrasonic dispersion time is 30-90 min; the hydrothermal reaction temperature is 180-220° C., and the reaction time is 12-36 h.

[0019] Preferably, the palladium salt includes palladium chloride and palladium acetate, and the mass ratio of palladium salt to water in its aqueous solution is 1: (3000~8000); the reducing agent is sodium borohydride and its derivatives, the solution concentration is 1~5 mol / L, and the addition amount is 5~50 mL; the pH adjuster is HCl, the concentration is 1~3 mol / L; the pH is 7~8.

[0020] Preferably, the Pd 0 The mixing ratio of ACCNTs-O-Co is 1: (1-3) by mass; the dispersion liquid mainly contains 5% by weight Nafion and ethanol in a volume ratio of 1: (200-1000), and the dispersion time is 30-90 min.

[0021] Preferably, the ultrasonic dispersion frequency is preferably 120~180W.

[0022] Preferably, the drying is carried out in a vacuum environment at a temperature of 60-80°C.

[0023] Preferably, the base film is mainly polytetrafluoroethylene film or polyvinylidene fluoride.

[0024] The present invention also provides the use of the cobalt-palladium bimetallic composite electro-Fenton catalytic membrane described in the above technical solution for degrading trace brominated aromatic compounds in water in a continuous flow system.

[0025] Preferably, the brominated aromatic compound is 2,4,6-tribromophenol; and the water body contains 0.05 mol / L sodium sulfate electrolyte.

[0026] The present invention provides a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, comprising a base membrane and a carbon nanotube composite catalyst, wherein the surface of the carbon nanotube composite catalyst is connected with cobalt and loaded with Pd 0 .

[0027] The connection of the metal cobalt in the carbon nanotube composite catalyst of the present invention makes the metal reaction sites more stable, overcoming the problem of easy detachment of the metal reaction sites caused by traditional loading forms; at the same time, the constructed chemical bonds can fully expose the reaction active sites, effectively avoiding the relatively small number of reaction active sites caused by the agglomeration of single atoms; in addition, by applying external electrical energy, electrons are rapidly transferred to the cobalt metal reaction center through the chemical bonds, accelerating the electron transfer rate in the E-Fenton reaction.

[0028] Pd loaded in the carbon nanotube composite catalyst of the present invention 0 , whose purpose is to produce atomic hydrogen ([H*]) through redox reaction, and then efficiently undergo dehalogenation reaction to accelerate the breaking of C-Br bond.

[0029] The carbon nanotube composite catalyst of the present invention uses a polytetrafluoroethylene membrane or a polyvinylidene fluoride membrane as a base membrane to realize the operation of the composite electro-Fenton catalytic membrane in a continuous flow reactor, thereby improving the contact oxidation efficiency of brominated aromatic compounds and active species on the surface of the catalytic membrane, and overcoming the mass transfer limitation problem of the flat-plate E-Fenton degradation system.

[0030] This invention overcomes the difficulty of recovering E-Fenton catalysts in water treatment by utilizing a polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) membrane as a substrate. The loaded carbon nanotube composite catalyst chemically bonds to cobalt metal, enhancing the stability of the metal element in the E-Fenton-like reaction. This also fully exposes the active reaction sites, and the resulting chemical bonds provide pathways for electron transfer, accelerating the redox reaction. The invention boasts a simple preparation process and mild reaction conditions. During the E-Fenton membrane water treatment process, it produces large amounts of ·OH and [H*], which attack C-Br bonds, breaking them and mineralizing 2,4,6-tribromophenol to CO2 and H2O. This is expected to improve the removal of trace, difficult-to-degrade organic pollutants in water using E-Fenton technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 FT-IR images of ACCNTs and ACCNTs-O-Co obtained in Example 1;

[0032] Figure 2 Raman images of ACCNTs and ACCNTs-O-Co obtained in Example 1;

[0033] Figure 3 ACCNTs-O-Co / Pd obtained in Example 1 0 Pd in ​​the catalytic film 0 XPS fine spectrum (Pd 3d);

[0034] Figure 4 ACCNTs and ACCNTs-O-Co / Pd obtained in Example 1 0 XRD pattern of

[0035] Figure 5 ACCNTs, ACCNTs-O-Co and ACCNTs-O-Co / Pd obtained in Example 1 0 Electrochemical impedance spectroscopy of

[0036] Figure 6 The electrocatalytic membrane obtained in Comparative Example 1 and the ACCNTs-O-Co / Pd obtained in Example 1 0 FT-IR image of the catalytic film;

[0037] Figure 7 ACCNTs, ACCNTs-O-Co and ACCNTs-O-Co / Pd obtained in Example 1 0 Degradation test results of 2,4,6-tribromophenol simulated organic wastewater by catalytic membrane;

[0038] Figure 8 ACCNTs-O-Co / Pd obtained in Example 10 Degradation test results of 2,4,6-tribromophenol simulated organic wastewater under different pH modes; DETAILED DESCRIPTION

[0039] The present invention provides a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, comprising a base membrane and a carbon nanotube composite catalyst, wherein the surface of the carbon nanotube composite catalyst is connected with cobalt and loaded with Pd 0 .

[0040] Preferably, the carbon nanotubes are 10-30 μm long, 5-10 nm in inner diameter and 10-20 nm in outer diameter. The metal content in the carbon nanotube composite catalyst is 100%, the metal cobalt accounts for 30-50%, the Pd 0 It accounts for 50~70%.

[0041] The present invention also provides a method for preparing the cobalt-palladium bimetallic composite electro-Fenton catalytic film described in the above technical solution, comprising the following steps:

[0042] The carbon nanotubes were placed in concentrated acid solution for acidification, washed and dried after treatment, and used as the substrate of the bimetallic material, which was denoted as ACCNTs.

[0043] The ACCNTs are placed in a cobalt-based precursor solution, connected to metallic cobalt through a hydrothermal reaction, and then washed and dried after treatment, which is recorded as ACCNTs-O-Co;

[0044] Dissolve palladium salt in water to prepare a solution, add excess reducing agent, carry out reduction reaction, adjust pH environment, and obtain black precipitate. After vacuum drying, it is zero-valent palladium particles, recorded as Pd 0 ;

[0045] The ACCNTs-O-Co and Pd 0 Prepare a dispersed solution according to a certain ratio;

[0046] The dispersed solution was filtered onto the substrate membrane and vacuum dried to obtain a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, which was recorded as ACCNTs-O-Co / Pd 0 .

[0047] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0048] The present invention acidifies commercially available CNTs in concentrated acid, fully disperses them in the concentrated acid solution by ultrasonication, heats them in a high-temperature oil bath, washes them with a large amount of deionized water, and vacuum-dries them to obtain metal-connected substrate ACCNTs.

[0049] In the present invention, the concentrated acid solution comprises concentrated sulfuric acid and concentrated nitric acid, preferably in a volume ratio of 1:(1-5), more preferably 1:(2-3); the ultrasonic dispersion time before the concentrated acid treatment is preferably 20-60 minutes, more preferably 30-50 minutes; the acidification temperature is preferably 60-100°C, more preferably 70-90°C, and even more preferably 80°C, and the acidification time is preferably 2-6 hours, more preferably 3-5 hours; the washing is preferably performed with deionized water until the filtrate pH reaches 6-7. In the present invention, the acidification treatment can increase the surface carboxyl content of CNTs, facilitating the production of H2O2 in the E-Fenton reaction.

[0050] In the present invention, the cobalt-based precursor solution mainly comprises cobalt nitrate hexahydrate and water, and the mass ratio thereof is preferably 1: (30-60), more preferably 1: (40-50); the amount of ACCNTs added to the reaction solution is preferably 50-100 mg, the ultrasonic dispersion time is preferably 30-90 min, more preferably 60-90 min, the hydrothermal reaction temperature is preferably 180-220°C, more preferably 180-200°C, the reaction time is preferably 12-36 h, more preferably 18-30 h, and even more preferably 24 h, to obtain ACCNTs-O-Co.

[0051] In the present invention, the palladium salt is mainly palladium chloride or palladium acetate, and the mass ratio of the palladium salt to water in the aqueous solution is preferably 1: (3000-8000), more preferably 1: (5000-7000); the reducing agent is preferably sodium borohydride and its derivatives, more preferably sodium borohydride, the solution concentration is preferably 1-5 mol / L, more preferably 1-2 mol / L, and the addition amount is preferably 5-50 mL; the pH is preferably adjusted to 1-3 mol / L of HCl, the concentration is more preferably 1-2 mol / L, more preferably 1 mol / L, and the pH environment is preferably 7-8. The obtained black solid is Pd 0 In the present invention, the pH of the solution is adjusted by HCl to remove excess sodium borohydride in the solution.

[0052] In the present invention, the Pd 0The mixing ratio of ACCNTs-O-Co and PdO-Co is preferably 1: (1-3); the dispersion liquid is mainly preferably 5% by weight Nafion and ethanol, and the volume ratio is preferably 1: (200-1000), more preferably 1: (400-800), more preferably 1: (500-600), and the dispersion time is preferably 30-90 min, more preferably 60-90 min, to obtain ACCNTs-O-Co / PdO-Co. 0 Catalytic membrane.

[0053] In the present invention, the ultrasonic dispersion frequency is preferably 120-180 W, more preferably 150-180 W.

[0054] In the present invention, the vacuum drying temperature is preferably 60-80° C., more preferably 80° C., and the vacuum drying time is preferably 12-24 h.

[0055] In the present invention, the base film is preferably mainly a polytetrafluoroethylene film or a polyvinylidene fluoride film.

[0056] The present invention also provides the use of the cobalt-palladium bimetallic composite electro-Fenton catalytic membrane described in the above technical solution or the cobalt-palladium bimetallic composite electro-Fenton catalytic membrane prepared by the preparation method described in the above technical solution in degrading trace brominated aromatic compounds in water.

[0057] In order to further illustrate the present invention, a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane provided by the present invention, its preparation method and application are described in detail below in combination with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] 300 mg of CNTs (10-30 μm in length, 10 nm in inner diameter, and 20 nm in outer diameter) were thoroughly dispersed in 150 mL of concentrated acid solution (concentrated sulfuric acid:concentrated nitric acid = 1:3). Ultrasonication was performed at 180 W for 30 min to ensure thorough contact between the CNTs and the concentrated acid. The mixture was placed in a round-bottom flask, connected to a spherical condenser, and heated in an oil bath at 80°C for 4 h. After acidification, the solution was cooled to room temperature and the CNTs were separated from the concentrated acid using vacuum filtration. The CNTs were then washed with copious amounts of deionized water until the pH of the washing solution was consistent with that of the deionized water. The CNT powder was collected and dried in a vacuum oven at 80°C for 12 h, ground, and stored for future use. This was designated as ACCNTs.

[0060] A precursor solution was prepared by dissolving 1.75 g of cobalt nitrate hexahydrate in 60 mL of deionized water. 100 mg of ACCNTs was added to the precursor solution and subjected to ultrasonic dispersion at 180 W for 1 h. The resulting reaction solution was transferred to a 100 mL autoclave and heated in a 200°C oven for 24 h. After the reaction, the mixture was cooled to room temperature, filtered, and washed with 100 mL of deionized water. The resulting solid was dried in a vacuum oven at 80°C for 12 h. The resulting product was ground and stored for future use, designated ACCNTs-O-Co.

[0061] Weigh 100 mg of palladium chloride and dissolve it fully in 500 mL of deionized water. Add 25 mL of 1 mol / L sodium borohydride solution while stirring. Observe that the brown solution turns black with the release of a large amount of gas. Add 1 mol / L HCl solution dropwise while stirring to adjust the pH of the solution until the pH is 7-8 and no bubbles are generated. A black precipitate is produced. Collect the black precipitate and dry it in a vacuum oven at 80°C for 12 hours. The resulting product is ground and stored for future use and is recorded as Pd 0 .

[0062] Measure 30 mL of anhydrous ethanol and add 50 μL of 5% wt Nafion to prepare a dispersion solution. Weigh 10 mg of Pd 0 20 mg of ACCNTs-O-Co and 20 mg of ACCNTs-O-Co were placed in the dispersion and ultrasonicated at 180 W for 1 h. The dispersion was filtered onto a 5 μm polytetrafluoroethylene membrane (hydrophilic) and vacuum dried for 12 h to obtain ACCNTs-O-Co / Pd 0 Catalytic membrane.

[0063] Comparative Example 1

[0064] 300 mg of CNTs (10-30 μm in length, 10 nm in inner diameter, and 20 nm in outer diameter) were thoroughly dispersed in 150 mL of concentrated acid solution (concentrated sulfuric acid:concentrated nitric acid = 1:3). Ultrasonication was performed at 180 W for 30 min to ensure thorough contact between the CNTs and the concentrated acid. The mixture was placed in a round-bottom flask, connected to a spherical condenser, and heated in an oil bath at 80°C for 4 h. After acidification, the solution was cooled to room temperature and the CNTs were separated from the concentrated acid using vacuum filtration. The CNTs were then washed with copious amounts of deionized water until the pH of the washing solution was consistent with that of the deionized water. The CNT powder was collected and dried in a vacuum oven at 80°C for 12 h, ground, and stored for future use. This was designated as ACCNTs.

[0065] 50 mg of palladium chloride was weighed and fully dispersed in 60 mL of deionized water to prepare a palladium chloride solution. 100 mg of ACCNTs was added and fully dispersed in the palladium chloride solution. Ultrasonication was performed to uniformly disperse the solution. The reaction was placed in a 100 mL autoclave and reacted at 80°C for 50 min. After cooling to room temperature, an excess of 1 mol / L sodium borohydride was added for reduction. While stirring, 1 mol / L HCl solution was added dropwise to adjust the pH of the solution until the pH was 7-8 and no bubbles were generated. A black precipitate was produced and washed with 100 mL of deionized water. The black precipitate was collected and dried in a vacuum oven at 80°C for 12 h. The resulting product was ground and stored for future use and was designated as ACCNTs / Pd 0 .

[0066] Weigh 1.75 g of cobalt nitrate hexahydrate and dissolve it in 60 mL of deionized water to prepare the precursor solution. Add 100 mg of ACCNTs / Pd 0 The precursor solution was subjected to ultrasonic dispersion at 180 W for 1 h. The resulting reaction solution was transferred to a 100 mL autoclave and heated in a 200°C oven for 24 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and washed with 100 mL of deionized water. The resulting solid was dried in a vacuum oven at 80°C for 12 h. The resulting product was ground and stored for later use, designated as ACCNTs-O-Co / Pd. 0 .

[0067] Measure 30 mL of anhydrous ethanol and add 50 μL of 5% wt Nafion to prepare a dispersion solution, weigh 30 mg of ACCNTs-O-Co / Pd 0 Place in the dispersion and ultrasonicate at 180 W for 1 h. Filter the dispersion onto a 5 μm polytetrafluoroethylene membrane (hydrophilic) and vacuum dry for 12 h to obtain ACCNTs-O-Co / Pd 0 Catalytic membrane.

[0068] Characterization and performance testing

[0069] Test Example 1

[0070] Figure 1 This is the FT-IR image of ACCNTs-O-Co prepared in Example 1. Figure 1 It can be seen that the prepared material has Co(Ⅱ)-O and Co(Ⅲ)-O chemical bonds.

[0071] Figure 2 The Raman diagram of ACCNTs-O-Co prepared in Example 1 is Figure 2 It can be seen that the defects in the CNTs structure in the prepared material are deeper, and it also has a CO-Co chemical bond structure.

[0072] Figure 3 ACCNTs-O-Co / Pd prepared in Example 1 0 Pd 3d fine spectrum of catalytic film XPS, by Figure 3 It can be seen that the palladium in the catalytic membrane is mainly Pd 0 For the main.

[0073] Figure 4 ACCNTs-O-Co / Pd prepared in Example 1 0 The XRD pattern of the catalytic film is Figure 4 It can be seen that the cobalt in the catalytic film exists in the form of Co3O4 and the palladium exists in the form of Pd 0 Form exists.

[0074] Figure 5 The electrochemical impedance spectrum of the electrocatalytic membrane prepared in Example 1 is shown in FIG. Figure 5 It can be seen that ACCNTs-O-Co / Pd 0 The charge transfer resistance of the catalytic film is smaller.

[0075] Figure 6 The FT-IR diagram of the material obtained in Comparative Example 1 is shown in FIG. Figure 6 It can be seen that Pd is added first 0 When Co is reconnected, the response of the Co(II)-O and Co(III)-O chemical bonds decreases compared with Example 1.

[0076] Test Example 2

[0077] A 10 mg / L 2,4,6-tribromophenol solution was prepared containing 0.05 mol / L Na2SO4 as an electrolyte and used as a simulated organic wastewater for degradation experiments.

[0078] The different catalytic membrane electrodes prepared in Example 1 were used as cathodes, and the platinum mesh was used as anodes. The cathode and anode were placed in opposite and perpendicular positions with a plate spacing of 6 mm in a flow-through reactor. The reactor volume was about 2 mL, and the effective area of ​​the catalytic membrane electrode was 3.14 cm 2 An aeration system was set up in the simulated organic wastewater with an aeration volume of 200 mL / min. The degradation system flow rate was set to 3 mL / min by a peristaltic pump. A voltage of 2.5 V was applied by a power supply to perform the degradation experiment. The volume of the degraded simulated organic wastewater was 50 mL.

[0079] During the test, 1 mL of the degradation solution was taken at different times to test the concentration of 2,4,6-tribromophenol. The test results were as follows: Figure 7 and Table 1

[0080] Table 1 Degradation effect of different catalytic membrane electrodes obtained in Example 1 on 2,4,6-tribromophenol

[0081] Different catalytic membrane materials 90 min degradation efficiency (%) <![CDATA[Degradation reaction rate constant k app (min -1 )]]> ACCNTs 62.90 0.0116 ACCNTs-O-Co 80.24 0.0187 <![CDATA[ACCNTs-O-Co / Pd 0 ]]> 91.19 0.0278

[0082] It can be seen from Table 1 that under the same degradation conditions, ACCNTs-O-Co / Pd 0 The electrode is optimal, higher than other membrane electrodes, and a degradation rate of 91.19% can be achieved in 90 minutes. At the same time, the reaction rate of the synthesized bimetallic composite electro-Fenton catalytic membrane is more than 2 times higher than that of the metal-free electro-Fenton catalytic membrane, and 1.5 times higher than that of the single metal electro-Fenton catalytic membrane.

[0083] Test Example 3

[0084] A 10 mg / L 2,4,6-tribromophenol solution was prepared containing 0.05 mol / L Na2SO4 as an electrolyte. The pH of the solution was adjusted with 1 mol / L H2SO4 and NaOH to create different pH environments for the simulated organic wastewater degradation experiments. The pH was adjusted to 3, 5, 7, and 9, respectively.

[0085] The ACCNTs-O-Co / Pd obtained in Example 1 0 The membrane electrode was used as the cathode and the platinum mesh was used as the anode. The cathode and anode were placed in opposite and perpendicular positions with a plate spacing of 6 mm in a flow-through reactor. The reactor volume was approximately 2 mL and the effective area of ​​the catalytic membrane electrode was 3.14 cm. 2 An aeration system was set up in the simulated organic wastewater with an aeration volume of 200 mL / min. The degradation system flow rate was set to 3 mL / min by a peristaltic pump. A voltage of 2.5 V was applied by a power supply to perform the degradation experiment. The volume of the degraded simulated organic wastewater was 50 mL.

[0086] During the test, 1 mL of the degradation solution was taken at different times to test the concentration of 2,4,6-tribromophenol. The test results were as follows: Figure 8 and Table 2

[0087] Table 2 ACCNTs-O-Co / Pd obtained in Example 1 0 Degradation effect of membrane on 2,4,6-tribromophenol

[0088] Degradation conditions Degradation efficiency in 30 min (%) <![CDATA[Degradation reaction rate constant k app (min -1 )]]> pH 3 99.60 0.1562 pH 5 90.13 0.0818 pH 7 72.19 0.0413 Ph 9 56.30 0.0312

[0089] From Table 2, we can see that ACCNTs-O-Co / Pd 0 The membrane electrode has differences under different pH conditions. When the pH is 3, the degradation efficiency of 2,4,6-tribromophenol is the highest, which can reach 99.6%. The degradation efficiency is relatively slow under other pH conditions, but still has a certain degradation effect. This shows that ACCNTs-O-Co / Pd 0The membrane electrode broadens the pH adaptability range during the degradation of 2,4,6-tribromophenol through the Fenton reaction.

[0090] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, characterized in that: The invention comprises a base film and a carbon nanotube composite catalyst, wherein the surface of the carbon nanotube composite catalyst is connected with cobalt and loaded with Pd 0 .

2. The cobalt-palladium bimetallic composite electro-Fenton catalytic membrane according to claim 1, characterized in that: The carbon nanotubes are 10-30 μm long, 5-10 nm in inner diameter and 10-20 nm in outer diameter. The metal content in the carbon nanotube composite catalyst is 100%, wherein the metal cobalt accounts for 30-50%, the Pd 0 It accounts for 50~70%.

3. A method for preparing a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, characterized in that: The preparation method comprises the following steps: The carbon nanotubes were placed in concentrated acid solution for acidification, washed and dried after treatment, and used as the substrate of the bimetallic material, which was denoted as ACCNTs. The ACCNTs are placed in a cobalt-based precursor solution, connected to metallic cobalt through a hydrothermal reaction, and then washed and dried after treatment, which is recorded as ACCNTs-O-Co; Dissolve palladium salt in water to prepare a solution, add excess reducing agent, carry out reduction reaction, adjust pH environment, and obtain black precipitate. After vacuum drying, it is zero-valent palladium particles, recorded as Pd 0 ; The ACCNTs-O-Co and Pd 0 Prepare a dispersed solution according to a certain ratio; The dispersed solution was filtered onto the substrate membrane and vacuum dried to obtain a cobalt-palladium bimetallic composite electro-Fenton catalytic membrane, which was recorded as ACCNTs-O-Co / Pd 0 .

4. The preparation method according to claim 3, characterized in that The concentrated acid solution comprises concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:(1-5), is fully dispersed by ultrasound, and is heated in a high-temperature oil bath; the temperature for the acidification treatment is 60-100°C, and the acidification treatment time is 2-6 hours; and deionized water is used for washing until the pH of the filtrate is 6-7.

5. The preparation method according to claim 3, characterized in that The cobalt-based precursor solution mainly comprises cobalt nitrate hexahydrate and water in a mass ratio of 1:(30-60); the amount of ACCNTs added to the reaction solution is 50-100 mg, and the ultrasonic dispersion time is 30-90 min; the hydrothermal reaction temperature is 180-220°C, and the reaction time is 12-36 h.

6. The preparation method according to claim 3, characterized in that The palladium salt is mainly palladium chloride and palladium acetate, and the mass ratio of palladium salt to water in its aqueous solution is 1: (3000-8000); the reducing agent is sodium borohydride and its derivatives, the solution concentration is 1-5 mol / L, and the addition amount is 5-50 mL; the pH adjuster is HCl, the concentration is 1-3 mol / L; the pH is 7-8.

7. The preparation method according to claim 3, characterized in that The Pd 0 The mixing ratio of ACCNTs-O-Co is 1: (1-3) by mass; the dispersion liquid mainly contains 5% by weight Nafion and ethanol in a volume ratio of 1: (200-1000), and the dispersion time is 30-90 min.

8. The preparation method according to claim 3, characterized in that The drying is carried out in a vacuum environment at a temperature of 60-80°C.

9. The preparation method according to claim 3, characterized in that The base film is mainly a polytetrafluoroethylene film or a polyvinylidene fluoride film.

10. Use of the cobalt-palladium bimetallic composite electro-Fenton catalytic membrane according to claim 1 or 2 in degrading trace brominated aromatic compounds in water in a continuous flow system.

11. The use according to claim 10, characterized in that The trace amount of brominated aromatic compound is 2,4,6-tribromophenol, and the water body contains 0.05 mol / L of sodium sulfate electrolyte.

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