A visible light responsive catalytic electrode for wastewater treatment and preparation method thereof

Abstract

The present invention relates to a visible light responsive catalytic electrode for wastewater treatment and a preparation method thereof, belonging to the technical field of sewage treatment. The present invention obtains a visible light responsive catalytic material by compounding hollow iron oxide, zinc oxide, and polypyrrole. The hollow iron oxide in the material can enable the conductive polymer polypyrrole to enter the pores of the hollow iron oxide in a solution state, and be more tightly loaded on the iron oxide. At the same time, the zinc salt chemically bonded and grafted on the surface of the polypyrrole can be distributed in the form of molecular chains, thereby making the zinc salt more evenly distributed on the surface of the polypyrrole. When the polypyrrole grafted with the zinc salt contacts sodium hydroxide in a solution state, the zinc in the zinc salt reacts with the sodium hydroxide to form zinc oxide seed crystals, ultimately forming zinc oxide particles evenly loaded on the surface of the polypyrrole. Since the grafted zinc salt is evenly dispersed, the loaded zinc oxide can also be evenly distributed on the surface of the polypyrrole, thereby forming a zinc oxide-modified polypyrrole composite material.

Description

Technical Field

[0001] The invention relates to a visible light responsive catalytic electrode for wastewater treatment and a preparation method thereof, belonging to the technical field of sewage treatment. Background Art

[0002] Advanced oxidation technology is a new type of water treatment technology characterized by the production of hydroxyl radicals with strong oxidizing power. Under reaction conditions such as high temperature and pressure, electricity, sound, light irradiation, and catalysts, it oxidizes large, difficult-to-degrade organic pollutants into small, low- or non-toxic molecules, thereby effectively removing pollutants. Photocatalytic oxidation technology, among other technologies, does not require the addition of any external chemical reagents. Instead, it irradiates semiconductors with ultraviolet or visible light, converting light energy into the energy required for chemical reactions to generate a catalytic effect, stimulating surrounding water molecules and oxygen to produce highly oxidizing active oxides, effectively decomposing most organic pollutants and some inorganic substances.

[0003] Currently, the main visible light photocatalytic materials used are inorganic semiconductor materials such as zinc oxide and titanium oxide. These solid materials are typically applied as a suspension onto a glass electrode. However, the suspension of solid particles during coating results in poor adhesion of the semiconductor material to the substrate, hindering large-scale application. Furthermore, current visible light photocatalytic materials are limited in the amount of pollutants they can treat, limiting their scope of application. Summary of the Invention

[0004] The purpose of the present invention is to provide a visible light responsive catalytic electrode for wastewater treatment and a preparation method thereof, so as to solve the problems of low binding strength of visible light responsive catalytic materials and limited types of pollutants that can be treated in the current visible light responsive catalytic electrode.

[0005] The technical solution of the method for preparing the visible light responsive catalytic electrode for wastewater treatment of the present invention is as follows:

[0006] A method for preparing a visible light responsive catalytic electrode for wastewater treatment comprises the following steps:

[0007] (1) Polypyrrole and glycidyl methacrylate are mixed and reacted in the presence of concentrated sulfuric acid as a catalyst to obtain double-bond grafted polypyrrole;

[0008] (2) reacting the hydroxyl group in the double-bond grafted polypyrrole with 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride to obtain a double-bond quaternary ammonium salt grafted polypyrrole;

[0009] (3) The double bond in the double-bond quaternary ammonium salt grafted polypyrrole and the mercapto group in the mercaptocarboxylate zinc are subjected to an addition reaction under the catalysis of an organic base to obtain zinc salt grafted polypyrrole;

[0010] (4) reacting zinc salt grafted polypyrrole, porous nano-iron trioxide and sodium hydroxide in a solvent to generate zinc oxide in situ and obtain a dispersion containing a visible light responsive catalyst;

[0011] (5) A dispersion containing a visible light responsive catalyst is coated on an electrode substrate, and after drying, a visible light responsive catalytic electrode for wastewater treatment is obtained.

[0012] Preferably, in step (1), the number average molecular weight of the polypyrrole is 1500-3500.

[0013] Preferably, in step (1), the mass ratio of polypyrrole, glycidyl methacrylate and concentrated sulfuric acid as the catalyst is 10:0.08-0.1:0.01-0.015; the temperature of the mixed reaction is 80-85°C, and the time is 3-4 hours.

[0014] Preferably, in step (2), the mass ratio of the double-bond grafted polypyrrole to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride is 1:1.2-1.5, and the reaction time is 5-7 hours.

[0015] Preferably, in step (3), the organic base is tetraethylamine, the temperature of the addition reaction is 60-80°C, the time is 8-10 hours, and the mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine is 40:50-60:0.05-0.06.

[0016] Preferably, in step (4), the solvent is dimethyl sulfoxide.

[0017] Preferably, in step (4), the method for in-situ generation of zinc oxide is as follows: porous nano-iron oxide is added to a dimethyl sulfoxide solution of zinc salt grafted polypyrrole to obtain a mixed solution A; sodium hydroxide is dissolved in dimethyl sulfoxide to obtain a solution B; under stirring conditions, the mixed solution A is added to the solution B, and then heated to 55-60° C. and stirred for reaction for 3-5 hours; the mass ratio of zinc salt grafted polypyrrole to sodium hydroxide is 1:2-3, and the mass ratio of porous nano-iron oxide to zinc salt grafted polypyrrole is 1:10-12.

[0018] Preferably, in step (5), the drying temperature is 75-85°C.

[0019] Preferably, in step (5), the electrode substrate is FTO conductive glass; the loading amount of the visible light responsive catalyst on the electrode substrate is 0.45-0.55 mg / cm 2 .

[0020] The technical solution of the visible light responsive catalytic electrode for wastewater treatment of the present invention is as follows:

[0021] A visible light responsive catalytic electrode prepared by the method for preparing a visible light responsive catalytic electrode for wastewater treatment as described above.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0023] (1) The present invention obtains a visible light responsive catalytic material by compounding hollow iron oxide, zinc oxide and polypyrrole. The hollow iron oxide in the material can make the conductive polymer polypyrrole enter the pores of the hollow iron oxide in a solution state and be more tightly loaded on the iron oxide. At the same time, the zinc salt chemically bonded and grafted on the surface of the polypyrrole can be distributed in the form of molecular chains, thereby making the zinc salt more evenly distributed on the surface of the polypyrrole. When the polypyrrole grafted with zinc salt contacts sodium hydroxide in a solution state, the zinc in the zinc salt reacts with the sodium hydroxide to form zinc oxide seeds, and finally forms zinc oxide particles evenly loaded on the surface of the polypyrrole. Since the grafted zinc salt is evenly dispersed, the loaded zinc oxide can also be evenly distributed on the surface of the polypyrrole, thereby forming a zinc oxide modified polypyrrole composite material. In addition, since the reaction of in situ synthesis of zinc oxide is carried out in the presence of hollow iron oxide, part of the zinc oxide modified polypyrrole composite material can be filled in the pores of the hollow iron oxide, forming a zinc oxide modified polypyrrole filled hollow iron oxide composite material. When exposed to visible light, iron oxide exhibits a strong photochemical response to both ultraviolet and visible light, with a relatively high visible light utilization rate. Consequently, visible light energy can be effectively utilized, increasing visible light absorption, thereby increasing the yield of photogenerated electron-hole pairs and, consequently, the quantum yield. Furthermore, the polypyrrole molecular chain possesses excellent transport capacity, effectively transporting electrons. This broadens the spectral response range of zinc oxide, which has a high redox potential and large exciton binding energy, thereby comprehensively improving the photochemical catalytic performance of the visible light-sensitive photocatalytic material. Furthermore, polypyrrole and zinc oxide can form internal pores in the hollow iron oxide, reducing the recombination rate of photogenerated electrons and holes during the photocatalytic process. The doping elements can lower the initial oxidation potential, increase the photocurrent, reduce the activation energy, and improve the electrical conductivity. The visible light-responsive catalytic material prepared by the present invention can form a composite structure, promoting electron / hole separation, enhancing charge transfer efficiency, and improving photocatalytic performance.

[0024] (2) The present invention introduces quaternary ammonium salt groups on the surface of polypyrrole to increase the affinity between pollutants in water and electrode materials, thereby increasing the adsorption capacity, increasing the amount of pollutants entering the surface of the electrode material, and reducing the resistance of pollutants approaching the electrode material, thereby improving the photocatalytic performance.

[0025] (3) The experimental results show that when non-grafted zinc salt is used to prepare zinc oxide loaded polypyrrole, the zinc salt is not chemically bonded to the surface of polypyrrole, and the distance between the two is in the range of intermolecular distance, resulting in the inability of zinc oxide to be well loaded on the surface of polypyrrole, uneven loading, and deviation in photocatalytic performance; when non-porous nano-iron oxide is used, during the in-situ generation of zinc oxide, polypyrrole cannot enter the interior of ferric oxide in the form of a molecular chain, but can only be loaded on its surface, with a low loading amount and a remote distance, resulting in limited formation of the composite structure and deviation in the composite tightness, which affects the photocatalytic performance of the visible light responsive catalytic material; when ferric oxide is not used, polypyrrole and zinc oxide cannot form the composite structure in Example 1, resulting in reduced visible light absorption rate and quantum yield, thereby reducing the photochemical catalytic performance of the visible light responsive catalytic material.

[0026] (4) The visible light responsive catalytic electrode for wastewater treatment prepared by the present invention has good decomposition and degradation performance for common pollutants in water, can effectively remove common pollutants in water, and has a faster degradation rate. DETAILED DESCRIPTION

[0027] The following examples are intended to further illustrate the present invention, but are not intended to limit the scope of protection of the present invention.

[0028] The preparation method of porous nano-iron trioxide (α-Fe2O3) used in the embodiments and comparative examples of the present invention is as follows: 1.2 g of urea is dissolved in 75 mL of ethylene glycol methyl ether to obtain a urea solution, and then 5 mmol of ferric nitrate is added to the urea solution, heated to 190°C, kept warm for 24 hours, cooled to room temperature, filtered, washed with ethanol, dried, and calcined at 500°C for 2 hours. After screening, porous nano-iron trioxide (α-Fe2O3) with a particle size of 30 to 50 nm is obtained.

[0029] Specific embodiments of the visible light responsive catalytic electrode for wastewater treatment and the preparation method thereof of the present invention are as follows: Example

[0030] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0031] (1) Add 10 g of polypyrrole (number average molecular weight of 2000) and 0.08 g of glycidyl methacrylate into a stirring kettle and stir evenly. Then add 0.01 g of concentrated sulfuric acid as a catalyst, heat to 80 °C, stir and react for 3 h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, and wash with water and ethanol respectively to obtain double-bond grafted polypyrrole.

[0032] (2) Add double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heat to 80 ° C, stir until the double bond grafted polypyrrole is dissolved, and cool to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 1%; dissolve 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride in anhydrous N-methylpyrrolidone to obtain a 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution with a mass fraction of 15%; under stirring, add 2-chloro-N,N,N-trimethyl The 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution was added dropwise to the double-bond grafted polypyrrole solution (the mass ratio of double-bond grafted polypyrrole to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1:1.2). After the addition was completed, triethylamine was added (the mass ratio of triethylamine to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1:1). The reaction was stirred and continued for 5 hours. The reaction solution was poured into water, precipitated, filtered, and washed with acetone, water, and ethanol, respectively, to obtain double-bond quaternary ammonium salt grafted polypyrrole. The structural formula of 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride is as follows:

[0033] .

[0034] (3) Double-bond quaternary ammonium salt grafted polypyrrole and anhydrous N-methylpyrrolidone were added to a stirred tank, heated to 80°C, stirred until the double-bond quaternary ammonium salt grafted polypyrrole was dissolved, and cooled to room temperature to obtain a double-bond quaternary ammonium salt grafted polypyrrole solution with a mass fraction of 5%. Then, zinc mercaptocarboxylate and tetraethylamine were added to the double-bond quaternary ammonium salt grafted polypyrrole solution, heated to 60°C, stirred for 8 hours, cooled to room temperature, and the reaction solution was poured into ice water. After precipitation, it was filtered and washed with water and ethanol respectively to obtain zinc salt grafted polypyrrole. The mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine was 40:50:0.05.

[0035] (4) Zinc salt grafted polypyrrole and dimethyl sulfoxide were added to a stirring kettle and stirred until the zinc salt grafted polypyrrole was fully dissolved to obtain a zinc salt grafted polypyrrole solution with a mass fraction of 3%. Then, porous nano-iron oxide (α-Fe2O3) was added and stirred evenly to obtain a mixed solution A. Sodium hydroxide was dissolved in dimethyl sulfoxide to obtain a dimethyl sulfoxide solution with a mass fraction of 4%, named solution B. Under stirring conditions, the mixed solution A was added to solution B with a mass ratio of zinc salt grafted polypyrrole and sodium hydroxide of 1:2. Then, the mixture was heated to 55°C and stirred for 3 hours. After cooling to room temperature, the reaction solution was poured into ice water, filtered after precipitation, and washed with water and ethanol respectively to obtain a visible light responsive catalyst. The mass ratio of porous nano-iron oxide (α-Fe2O3) and zinc salt grafted polypyrrole was 1:10.

[0036] (5) The visible light responsive catalyst and dimethyl sulfoxide were stirred evenly in a mass ratio of 5:100, and ultrasonically dispersed for 60 min to obtain a dispersion of the visible light responsive catalyst. The dispersion was then spin-coated on the pretreated FTO conductive glass at a speed of 1000 rpm, and then dried at 75 °C for 24 h to obtain a visible light responsive catalytic electrode for wastewater treatment. The loading amount of the visible light responsive catalyst on the FTO conductive glass was 0.45 mg / cm 2 . Example

[0037] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0038] (1) Add 10 g of polypyrrole (number average molecular weight of 2000) and 0.1 g of glycidyl methacrylate into a stirring kettle and stir evenly. Then add 0.015 g of concentrated sulfuric acid as a catalyst, heat to 85 °C, stir and react for 4 h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, and wash with water and ethanol respectively to obtain double-bond grafted polypyrrole.

[0039] (2) Add double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heat to 100 ° C, stir until the double bond grafted polypyrrole is dissolved, and cool to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 3%; dissolve 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride in anhydrous N-methylpyrrolidone to obtain a 20% mass fraction of 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution; under stirring, add 2-chloro-N,N,N-trimethyl The 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution was added dropwise to the double-bond grafted polypyrrole solution (the mass ratio of double-bond grafted polypyrrole to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1:1.5). After the addition was completed, triethylamine was added (the mass ratio of triethylamine to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1.2:1). The reaction was stirred and continued for 7 hours. The reaction solution was poured into water, precipitated, filtered, and washed with acetone, water, and ethanol, respectively, to obtain double-bond quaternary ammonium salt grafted polypyrrole. The structural formula of 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride is as follows:

[0040] .

[0041] (3) Add double-bond quaternary ammonium salt grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirred tank, heat to 100°C, stir until the double-bond quaternary ammonium salt grafted polypyrrole is dissolved, and cool to room temperature to obtain a double-bond quaternary ammonium salt grafted polypyrrole solution with a mass fraction of 7%. Then, add zinc mercaptocarboxylate and tetraethylamine to the double-bond quaternary ammonium salt grafted polypyrrole solution, heat to 80°C, stir and react for 10 hours, cool to room temperature, pour the reaction solution into ice water, precipitate, filter, and wash with water and ethanol respectively to obtain zinc salt grafted polypyrrole. The mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine is 40:60:0.06.

[0042] (4) Zinc salt grafted polypyrrole and dimethyl sulfoxide were added to a stirring kettle and stirred until the zinc salt grafted polypyrrole was fully dissolved to obtain a zinc salt grafted polypyrrole solution with a mass fraction of 5%. Then, porous nano-iron oxide (α-Fe2O3) was added and stirred evenly to obtain a mixed solution A. Sodium hydroxide was dissolved in dimethyl sulfoxide to obtain a dimethyl sulfoxide solution with a mass fraction of 6%, which was named solution B. Under stirring conditions, the mixed solution A was added to solution B with a mass ratio of zinc salt grafted polypyrrole and sodium hydroxide of 1:3. Then, the mixture was heated to 60°C and stirred for 5 hours. After cooling to room temperature, the reaction solution was poured into ice water, filtered after precipitation, and washed with water and ethanol respectively to obtain a visible light responsive catalyst. The mass ratio of porous nano-iron oxide (α-Fe2O3) and zinc salt grafted polypyrrole was 1:12.

[0043] (5) The visible light responsive catalyst and dimethyl sulfoxide were stirred evenly in a mass ratio of 5:100, and ultrasonically dispersed for 80 min to obtain a dispersion of the visible light responsive catalyst. The dispersion was then spin-coated on the pretreated FTO conductive glass at a speed of 1300 rpm, and then dried at 85°C for 24 h to obtain a visible light responsive catalytic electrode for wastewater treatment. The loading amount of the visible light responsive catalyst on the FTO conductive glass was 0.55 mg / cm 2 . Example

[0044] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0045] (1) 10 g of polypyrrole (number average molecular weight of 2000) and 0.09 g of glycidyl methacrylate were added to a stirred tank and stirred evenly. Then, 0.013 g of concentrated sulfuric acid as a catalyst was added. The mixture was heated to 82 °C and stirred for 3.5 h. The mixture was cooled to room temperature and poured into ice water. After precipitation, the mixture was filtered and washed with water and ethanol respectively to obtain double-bond grafted polypyrrole.

[0046] (2) Add double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heat to 90 ° C, stir until the double bond grafted polypyrrole is dissolved, and cool to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 2%; dissolve 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride in anhydrous N-methylpyrrolidone to obtain a 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution with a mass fraction of 18%; under stirring, add 2-chloro-N,N,N-trimethyl- The 2-oxo-1-ethylammonium chloride solution was added dropwise to the double-bond grafted polypyrrole solution (the mass ratio of double-bond grafted polypyrrole to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1:1.3). After the addition was complete, triethylamine was added (the mass ratio of triethylamine to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1.1:1). The reaction was stirred and continued for 6 hours. The reaction solution was poured into water, precipitated, filtered, and washed with acetone, water, and ethanol, respectively, to obtain double-bond quaternary ammonium salt grafted polypyrrole. The structural formula of 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride is as follows:

[0047] .

[0048] (3) Double-bond quaternary ammonium salt grafted polypyrrole and anhydrous N-methylpyrrolidone were added to a stirred tank, heated to 90°C, stirred until the double-bond quaternary ammonium salt grafted polypyrrole was dissolved, and cooled to room temperature to obtain a double-bond quaternary ammonium salt grafted polypyrrole solution with a mass fraction of 6%. Then, zinc mercaptocarboxylate and tetraethylamine were added to the double-bond quaternary ammonium salt grafted polypyrrole solution, heated to 70°C, stirred for 9 hours, cooled to room temperature, and the reaction solution was poured into ice water. After precipitation, it was filtered and washed with water and ethanol respectively to obtain zinc salt grafted polypyrrole. The mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine was 40:55:0.055.

[0049] (4) Zinc salt grafted polypyrrole and dimethyl sulfoxide were added to a stirring kettle and stirred until the zinc salt grafted polypyrrole was fully dissolved to obtain a zinc salt grafted polypyrrole solution with a mass fraction of 4%. Then, porous nano-iron oxide (α-Fe2O3) was added and stirred evenly to obtain a mixed solution A. Sodium hydroxide was dissolved in dimethyl sulfoxide to obtain a dimethyl sulfoxide solution with a mass fraction of 5%, named solution B. Under stirring conditions, the mixed solution A was added to solution B with a mass ratio of zinc salt grafted polypyrrole and sodium hydroxide of 1:2.5. Then, the mixture was heated to 58°C and stirred for 4 hours. After cooling to room temperature, the reaction solution was poured into ice water, filtered after precipitation, and washed with water and ethanol respectively to obtain a visible light responsive catalyst. The mass ratio of porous nano-iron oxide (α-Fe2O3) and zinc salt grafted polypyrrole was 1:11.

[0050] (5) The visible light responsive catalyst and dimethyl sulfoxide were mixed in a mass ratio of 5:100 and ultrasonically dispersed for 70 min to obtain a dispersion of the visible light responsive catalyst. The dispersion was then spin-coated on the pretreated FTO conductive glass at a speed of 1200 rpm. The dispersion was then dried at 80 °C for 24 h to obtain a visible light responsive catalytic electrode for wastewater treatment. The loading amount of the visible light responsive catalyst on the FTO conductive glass was 0.5 mg / cm 2 . Example

[0051] The only difference between the method for preparing a visible light responsive catalytic electrode for wastewater treatment in this embodiment and the method for preparing a visible light responsive catalytic electrode for wastewater treatment in Example 1 is that the number average molecular weight of the polypyrrole in step (1) of the method for preparing a visible light responsive catalytic electrode for wastewater treatment in this embodiment is 1500. Example

[0052] The only difference between the method for preparing a visible light responsive catalytic electrode for wastewater treatment in this embodiment and the method for preparing a visible light responsive catalytic electrode for wastewater treatment in Example 1 is that the number average molecular weight of the polypyrrole in step (1) of the method for preparing a visible light responsive catalytic electrode for wastewater treatment in this embodiment is 3500. Example

[0053] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0054] (1) Add 10 g of polypyrrole (number average molecular weight of 2000) and 0.08 g of glycidyl methacrylate into a stirring kettle and stir evenly. Then add 0.01 g of concentrated sulfuric acid as a catalyst, heat to 80 °C, stir and react for 3 h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, and wash with water and ethanol respectively to obtain double-bond grafted polypyrrole.

[0055] (2) Add double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heat to 80 ° C, stir until the double bond grafted polypyrrole is dissolved, and cool to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 1%; dissolve 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride in anhydrous N-methylpyrrolidone to obtain a 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution with a mass fraction of 15%; under stirring, add 2-chloro-N,N,N-trimethyl The 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution was added dropwise to the double-bond grafted polypyrrole solution (the mass ratio of the double-bond grafted polypyrrole and 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1:1.2). After the addition was completed, triethylamine was added (the mass ratio of triethylamine and 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1:1). The reaction was continued to stir for 5 hours. The reaction solution was poured into water, filtered after precipitation, and washed with acetone, water and ethanol, respectively, to obtain a double-bond quaternary ammonium salt grafted polypyrrole.

[0056] (3) Double-bond quaternary ammonium salt grafted polypyrrole and anhydrous N-methylpyrrolidone were added to a stirred tank, heated to 80°C, stirred until the double-bond quaternary ammonium salt grafted polypyrrole was dissolved, and cooled to room temperature to obtain a double-bond quaternary ammonium salt grafted polypyrrole solution with a mass fraction of 5%. Then, zinc mercaptocarboxylate and tetraethylamine were added to the double-bond quaternary ammonium salt grafted polypyrrole solution, heated to 60°C, stirred for 8 hours, cooled to room temperature, and the reaction solution was poured into ice water. After precipitation, it was filtered and washed with water and ethanol respectively to obtain zinc salt grafted polypyrrole. The mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine was 40:50:0.05.

[0057] (4) Add zinc salt grafted polypyrrole and ethanol into a stirring tank and stir evenly to obtain a zinc salt grafted polypyrrole dispersion with a mass fraction of 3%. Then add porous nano-iron trioxide (α-Fe2O3) and stir evenly to obtain a mixed solution A. Dissolve sodium hydroxide in ethanol to obtain an ethanol solution with a mass fraction of 4%, named solution B. Under stirring conditions, the mixed solution A is added to solution B with a mass ratio of zinc salt grafted polypyrrole and sodium hydroxide of 1:2. Then heat to 55℃, stir and react for 3h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, and wash with water and ethanol respectively to obtain a visible light responsive catalyst. The mass ratio of porous nano-iron trioxide (α-Fe2O3) and zinc salt grafted polypyrrole is 1:10.

[0058] (5) The visible light responsive catalyst and dimethyl sulfoxide were stirred evenly in a mass ratio of 5:100, and ultrasonically dispersed for 60 min to obtain a dispersion of the visible light responsive catalyst. The dispersion was then spin-coated on the pretreated FTO conductive glass at a speed of 1000 rpm, and then dried at 75 °C for 24 h to obtain a visible light responsive catalytic electrode for wastewater treatment. The loading amount of the visible light responsive catalyst on the FTO conductive glass was 0.45 mg / cm 2 .

[0059] Comparative Example 1

[0060] The difference between the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example and the preparation method of the visible light responsive catalytic electrode for wastewater treatment in Example 1 is that the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example is as follows: polypyrrole, zinc mercaptocarboxylate and dimethyl sulfoxide are added to a stirring kettle, stirred until the polypyrrole is fully dissolved to obtain a mixed solution, and then porous nano-iron trioxide (α-Fe2O3) is added and stirred to obtain a mixed solution A, wherein the mass ratio of polypyrrole to zinc mercaptocarboxylate is 40:50, and the polypyrrole and zinc mercaptocarboxylate in the mixed solution are 40:50. The total mass fraction of zinc mercaptocarboxylate is 3%. Sodium hydroxide is dissolved in dimethyl sulfoxide to obtain a 4% sodium hydroxide in dimethyl sulfoxide solution, designated Solution B. Mixture A is added to Solution B under stirring, with the mass ratio of the combined mass of polypyrrole and zinc mercaptocarboxylate to the mass of sodium hydroxide being 1:2. The mixture is then heated to 55°C, stirred for 3 hours, cooled to room temperature, and filtered. The filter cake is washed with water and ethanol to remove unreacted zinc mercaptocarboxylate. The washed solid is then mixed with dimethyl sulfoxide at a mass ratio of 5:100 and ultrasonically dispersed for 60 minutes to obtain a dispersion of the visible light-responsive catalyst. The mass ratio of the porous nano-iron oxide (α-Fe2O3) to the combined mass of polypyrrole and zinc mercaptocarboxylate is 1:10.

[0061] Comparative Example 2

[0062] The difference between the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example and the preparation method of the visible light responsive catalytic electrode for wastewater treatment in Example 1 is that step (2) is omitted in the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example, and the double bond grafted polypyrrole obtained in step (1) is directly replaced with the double bond quaternary ammonium salt grafted polypyrrole in step (3) to obtain the zinc salt grafted polypyrrole.

[0063] Comparative Example 3

[0064] The difference between the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example and the preparation method of the visible light responsive catalytic electrode for wastewater treatment in Example 1 is that in step (4) of the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example, the porous nano-iron oxide (α-Fe2O3) is replaced by non-porous nano-iron oxide (α-Fe2O3).

[0065] Comparative Example 4

[0066] The difference between the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example and the preparation method of the visible light responsive catalytic electrode for wastewater treatment in Example 1 is that the amount of porous nano-iron trioxide (α-Fe2O3) added in step (4) of the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example is 0.

[0067] Comparative Example 5

[0068] The only difference between the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example and the preparation method of the visible light responsive catalytic electrode for wastewater treatment in Example 1 is that the preparation method of the visible light responsive catalyst dispersion in the preparation method of the visible light responsive catalytic electrode for wastewater treatment in this comparative example is as follows: porous nano-ferric oxide (α-Fe2O3) and dimethyl sulfoxide are stirred evenly in a mass ratio of 5:100, and ultrasonically dispersed for 60 minutes to obtain a dispersion of the visible light responsive catalyst.

[0069] Effect Examples

[0070] In order to investigate the photoelectrocatalytic performance of the visible light responsive catalytic electrodes prepared in each embodiment and comparative example, a three-electrode electrolysis system was used to conduct a photoelectrocatalytic reaction test. During the test, the visible light responsive catalytic electrode was used as the working electrode, the Pt electrode was used as the counter electrode, the saturated calomel electrode was used as the reference electrode, the quartz cell was used as the electrolytic cell, the sodium sulfate solution with a concentration of 0.12 mol / L was used as the electrolyte, and a xenon lamp equipped with an ultraviolet filter (the ultraviolet filter can filter out light with a wavelength less than 420 nm) was used as the visible light source. The light intensity of the xenon lamp was 8 mW / cm 2 , and its distance from the working electrode is 12 cm. The photoelectrocatalytic reaction test was carried out at room temperature. Rhodamine B, glucose, phenol and methylene blue were used as target pollutants. The target pollutants and sodium sulfate solution were stirred evenly to obtain a test solution. The concentration of the target pollutant in the test solution was 8 mg / L, the concentration of sodium sulfate was 0.12 mol / L, and the initial pH of the test solution was 7. The test solution was placed in an electrolytic cell for visible photoelectrocatalytic reaction. The working voltage was 0.8 V and the light intensity was 8 mW / cm 2During the reaction, the test liquid in the electrolytic cell is removed at regular intervals for testing and analysis. The concentration of the target pollutant in the test liquid at different times is determined. The removal rate of the target pollutant is then calculated based on the initial concentration and the concentration after treatment. The removal rate is equal to (initial concentration of the target pollutant - concentration after treatment) / initial concentration of the target pollutant. Finally, the first-order kinetic constant of the visible photoelectrocatalytic reaction is calculated based on the removal rate at different times or the concentration of the target pollutant at different times. The calculation formula is as follows: ln(Ct / C0)=−kt, where Ct is the concentration of the target pollutant at different times, C0 is the initial concentration of the target pollutant, t is the reaction time, and k is the first-order kinetic constant. The test results for the removal rate of the target pollutant and the first-order kinetic constant k for the target pollutant with a reaction time of 60 minutes are shown in Table 1.

[0071] In addition, in order to examine the bonding strength of the visible light responsive catalytic material on the FTO conductive glass, the visible light responsive catalytic electrode prepared in each embodiment and comparative example was immersed in 50°C water for 36 hours, and then the visible light responsive catalytic material loaded on the electrode was observed to see whether it fell off, peeled off, or bubbled. If there was no falling off, peeling, or bubbling, the bonding strength test result was qualified; if there was falling off, peeling, or bubbling, the bonding strength test result was unqualified.

[0072] Table 1 Target pollutants when the reaction time is 60 min

[0073] concentration, the first-order reaction kinetic constant k of the target pollutant, and the binding strength

[0074]

[0075]

[0076]

[0077] As shown in the test results of Table 1, the visible light responsive catalytic electrode for wastewater treatment prepared by the present invention has good decomposition and degradation performance for common pollutants in water, can effectively remove common pollutants in water, and has a faster degradation rate. The hollow iron oxide in the visible light responsive catalytic material can allow the conductive polymer polypyrrole to enter the hollow iron oxide pores in a solution state, and be more tightly loaded on the iron oxide. At the same time, the zinc salt chemically bonded to the surface of the polypyrrole can be distributed in the form of molecular chains, thereby making the zinc salt more evenly distributed on the surface of the polypyrrole. When the polypyrrole grafted with the zinc salt contacts sodium hydroxide in a solution state, the zinc in the zinc salt reacts with the sodium hydroxide to form zinc oxide seeds, and finally forms zinc oxide particles uniformly loaded on the surface of the polypyrrole. Since the grafted zinc salt is evenly dispersed, the loaded zinc oxide can also be evenly distributed on the surface of the polypyrrole, thereby forming a zinc oxide modified polypyrrole composite material. Furthermore, because the in situ synthesis of zinc oxide occurs in the presence of hollow iron oxide, a portion of the zinc oxide-modified polypyrrole composite can fill the pores of the hollow iron oxide, forming a zinc oxide-modified polypyrrole-filled hollow iron oxide composite. When exposed to visible light, the iron oxide exhibits a strong photochemical response to both ultraviolet and visible light, with a relatively high visible light utilization rate. Consequently, visible light energy can be effectively utilized, increasing visible light absorption and thereby boosting the yield of photogenerated electron-hole pairs, thereby increasing the quantum yield. Furthermore, the polypyrrole molecular chain possesses excellent electron transport capacity, broadening the spectral response range of zinc oxide, which has a high redox potential and large exciton binding energy, thereby comprehensively improving the photochemical catalytic performance of the visible light photocatalytic material. Furthermore, polypyrrole and zinc oxide can form internal pores in the hollow iron oxide, reducing the recombination rate of photogenerated electrons and holes during the photocatalytic process. The doping elements can lower the initial oxidation potential, increase the photocurrent, reduce the activation energy, and improve the electrical conductivity. The visible light responsive catalytic material prepared by the present invention can form a composite structure, promote electron / hole separation, enhance charge transfer efficiency, and improve photocatalytic performance.

[0078] It can be seen from Examples 1 and 4-5 that with the number average molecular weight of polypyrrole, the photocatalytic performance of the visible light responsive catalytic material shows a trend of first increasing and then decreasing. This may be because the number average molecular weight of polypyrrole is too large, and it cannot effectively load and pass through the interior of the hollow iron oxide, and cannot form a better composite structure; the number average molecular weight of polypyrrole is too small, and the amount of zinc salt grafted on its surface is reduced, which in turn affects the loading amount of zinc oxide, thereby affecting the photocatalytic performance.

[0079] It can be seen from Examples 1 and 6 that when a poor solvent for polypyrrole is used to prepare a visible light responsive catalytic material, due to the granular distribution of polypyrrole, zinc oxide cannot be grown in situ on its surface to a large extent, and polypyrrole is not easy to be loaded inside the hollow iron oxide, thereby affecting the loading amount of zinc oxide and the formation of the composite structure, thereby leading to a decrease in photocatalytic performance.

[0080] It can be seen from Example 1 and Comparative Example 1 that when non-grafted zinc salt is used to prepare zinc oxide-loaded polypyrrole, since the zinc salt is not chemically bonded to the surface of polypyrrole, the distance between the two belongs to the intermolecular distance range, resulting in zinc oxide not being well loaded on the surface of polypyrrole, and the loading is uneven, resulting in deviation in photocatalytic performance.

[0081] It can be seen from Example 1 and Comparative Example 2 that when quaternary ammonium salt groups are not introduced into the polypyrrole molecular chain, the photocatalytic performance of the composite material deteriorates. This may be due to the poor hydrophilicity of polypyrrole. The quaternary ammonium salt groups can increase the affinity between pollutants in water and electrode materials, thereby increasing the adsorption amount, increasing the amount of pollutants entering the surface of the electrode material, and reducing the resistance of pollutants approaching the electrode material, thereby improving the photocatalytic performance.

[0082] It can be seen from Example 1 and Comparative Example 3 that when non-porous nano-iron sesquioxide is used, during the in-situ generation of zinc oxide, polypyrrole cannot enter the interior of the iron sesquioxide in the form of a molecular chain, but can only be loaded on its surface. The loading amount is low and the distance is remote, resulting in limited formation of the composite structure and deviation in the composite tightness, which affects the photocatalytic performance of the visible light responsive catalytic material.

[0083] It can be seen from Example 1 and Comparative Example 4 that when ferric oxide is not used, polypyrrole and zinc oxide cannot form the composite structure in Example 1, resulting in reduced visible light absorption rate and quantum yield, thereby reducing the photochemical catalytic performance of the visible light catalytic material.

[0084] It can be seen from Example 1 and Comparative Example 4 that when ferric oxide is used alone, the pores lack the modification of polypyrrole molecular chains, resulting in a decrease in photochemical catalytic performance and a significant decrease in the bonding strength to the electrode substrate.

[0085] Finally, since a poor solvent for polypyrrole is used in Example 6, polypyrrole cannot be completely dissolved and cannot be spread on the surface of the electrode matrix in molecular form, resulting in a deviation in the bonding strength between the two. In Comparative Example 1, no grafted zinc salt is used, and the in-situ grown zinc oxide is poorly dispersed, resulting in a deviation in the bonding strength. In Comparative Example 3, non-porous nano-iron sesquioxide is used, and polypyrrole cannot enter its interior, resulting in poor affinity between iron sesquioxide and the polymer matrix, poor compatibility, and iron sesquioxide particles affecting the bonding strength between the material and the electrode matrix.

Claims

1. A method for preparing a visible light responsive catalytic electrode for wastewater treatment, characterized in that: The following steps are involved: (1) Polypyrrole and glycidyl methacrylate are mixed and reacted in the presence of concentrated sulfuric acid as a catalyst to obtain double-bond grafted polypyrrole; (2) reacting the hydroxyl group in the double-bond grafted polypyrrole with 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride to obtain a double-bond quaternary ammonium salt grafted polypyrrole; (3) The double bond in the double-bond quaternary ammonium salt grafted polypyrrole and the mercapto group in the mercaptocarboxylate zinc are subjected to an addition reaction under the catalysis of an organic base to obtain zinc salt grafted polypyrrole; (4) reacting zinc salt grafted polypyrrole, porous nano-iron trioxide and sodium hydroxide in a solvent to generate zinc oxide in situ and obtain a dispersion containing a visible light responsive catalyst; (5) coating a dispersion containing a visible light responsive catalyst on an electrode substrate, and drying the dispersion to obtain a visible light responsive catalytic electrode for wastewater treatment; In step (4), the solvent is dimethyl sulfoxide.

2. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1, wherein: In step (1), the number average molecular weight of the polypyrrole is 1500-3500.

3. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1, wherein: In step (1), the mass ratio of polypyrrole, glycidyl methacrylate and concentrated sulfuric acid as a catalyst is 10:0.08~0.1:0.01~0.015; the temperature of the mixed reaction is 80~85°C, and the time is 3~4h.

4. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to any one of claims 1 to 3, wherein: In step (2), the mass ratio of double-bond grafted polypyrrole to 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride is 1:1.2-1.5, and the reaction time is 5-7 hours.

5. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1, wherein: In step (3), the organic base is tetraethylamine, the temperature of the addition reaction is 60-80°C, the time is 8-10 hours, and the mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine is 40:50-60:0.05-0.

06.

6. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1, wherein: In step (4), the method for in-situ generation of zinc oxide is as follows: porous nano-iron oxide is added to a dimethyl sulfoxide solution of zinc salt grafted polypyrrole to obtain a mixed solution A; sodium hydroxide is dissolved in dimethyl sulfoxide to obtain a solution B; under stirring conditions, the mixed solution A is added to the solution B, and then heated to 55-60° C. and stirred for reaction for 3-5 hours; the mass ratio of zinc salt grafted polypyrrole and sodium hydroxide is 1:2-3, and the mass ratio of porous nano-iron oxide to zinc salt grafted polypyrrole is 1:10-12.

7. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1, wherein: In step (5), the drying temperature is 75-85°C.

8. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1 or 7, wherein: In step (5), the electrode substrate is FTO conductive glass; the loading amount of the visible light responsive catalyst on the electrode substrate is 0.45~0.55mg / cm 2 .

9. A visible light responsive catalytic electrode prepared by the method for preparing a visible light responsive catalytic electrode for wastewater treatment as claimed in claim 1.

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