Visible light response catalytic electrode for wastewater treatment and preparation method thereof

Abstract

The invention relates to a visible-light response catalytic electrode for wastewater treatment and a preparation method of the visible-light response catalytic electrode, and belongs to the technical field of sewage treatment. The hollow iron oxide, the zinc oxide and the polypyrrole are compounded to obtain the visible light response catalytic material, the hollow iron oxide in the material can enable the conductive polymer polypyrrole to enter pores of the hollow iron oxide in a solution state and to be more tightly loaded on the iron oxide, and meanwhile, the conductive polymer polypyrrole can be more tightly loaded on the iron oxide. The zinc salt chemically bonded and grafted on the surface of the polypyrrole can be distributed in a molecular chain form, so that the zinc salt is more uniformly distributed on the surface of the polypyrrole, and when the polypyrrole grafted with the zinc salt is in contact with sodium hydroxide in a solution state, zinc in the zinc salt reacts with the sodium hydroxide to form a zinc oxide seed crystal; and finally, zinc oxide particles uniformly loaded on the surface of the polypyrrole are formed, and the grafted zinc salt is uniformly dispersed, so that the loaded zinc oxide can also be uniformly distributed on the surface of the polypyrrole, and the zinc oxide modified polypyrrole composite material is formed.

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 wastewater treatment. Background Art

[0002] Water is the most important resource on earth and the source of life. The total amount of water resources on earth is limited, and the fresh water resources available for direct drinking are even less. With the rapid development of the world economy and the sharp increase in population, water pollution is becoming increasingly serious, and water consumption is also increasing day by day. The water crisis caused by water pollution and water shortage is becoming a global problem. Carrying out sewage treatment and water utilization and recycling is one of the effective countermeasures to solve the water crisis.

[0003] Advanced oxidation technology is a new type of water treatment technology, which is characterized by the production of hydroxyl free radicals with strong oxidizing ability. Under the reaction conditions of high temperature and high pressure, electricity, sound, light irradiation, catalysts, etc., it oxidizes large molecular organic pollutants that are difficult to degrade into low-toxic or non-toxic small molecular substances, thereby effectively removing pollutants. Among them, photocatalytic oxidation technology does not require any external chemical reagents, but irradiates semiconductors with ultraviolet or visible light, uses light energy to convert into energy required for chemical reactions to produce catalytic effects, excite surrounding water molecules and oxygen, and produce highly oxidizing active oxides, thereby achieving the decomposition of most organic pollutants and some inorganic substances.

[0004] Currently, the main visible light catalytic materials are inorganic semiconductor materials such as zinc oxide and titanium oxide. When used, these solid materials are usually coated on the glass electrode in the form of a suspension. However, since the solid particles are in the form of a suspension during coating, the semiconductor material has a poor adhesion to the substrate, which is not conducive to large-scale use and promotion. In addition, the current visible light catalytic materials can only process a limited number of pollutants, which limits their scope of use. Summary of the invention

[0005] 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.

[0006] The technical scheme of the method for preparing the visible light responsive catalytic electrode for wastewater treatment of the present invention is as follows:

[0007] A method for preparing a visible light responsive catalytic electrode for wastewater treatment comprises the following steps:

[0008] (1) mixing polypyrrole and glycidyl methacrylate under the action of concentrated sulfuric acid as a catalyst to obtain double-bond grafted polypyrrole;

[0009] (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 the double-bond quaternary ammonium salt grafted polypyrrole;

[0010] (3) subjecting the double bond in the double-bond quaternary ammonium salt grafted polypyrrole to an addition reaction with the mercapto group in the zinc mercaptocarboxylate under the catalytic action of an organic base to obtain zinc salt grafted polypyrrole;

[0011] (4) reacting zinc salt grafted polypyrrole, porous nano-iron trioxide and sodium hydroxide in a solvent to generate zinc oxide in situ, thereby obtaining a dispersion containing a visible light responsive catalyst;

[0012] (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.

[0013] Preferably, in step (1), the number average molecular weight of the polypyrrole is 1500 to 3500.

[0014] Preferably, 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 3-4 hours.

[0015] 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.

[0016] 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.

[0017] Preferably, in step (4), the solvent is dimethyl sulfoxide.

[0018] Preferably, in step (4), the method for in-situ generation of zinc oxide is as follows: adding porous nano-iron trioxide to a dimethyl sulfoxide solution of zinc salt grafted polypyrrole to obtain a mixed solution A; dissolving sodium hydroxide in dimethyl sulfoxide to obtain a solution B; under stirring conditions, adding the mixed solution A to the solution B, and then heating to 55-60° C., stirring and reacting 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 trioxide to zinc salt grafted polypyrrole is 1:10-12.

[0019] Preferably, in step (5), the drying temperature is 75-85°C.

[0020] 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 to 0.55 mg / cm 2 .

[0021] The technical solution of the visible light responsive catalytic electrode for wastewater treatment of the present invention is as follows:

[0022] A visible light responsive catalytic electrode prepared by the method for preparing a visible light responsive catalytic electrode for wastewater treatment as described above.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0024] (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 grafted by chemical bonding 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 to form a zinc oxide modified polypyrrole filled hollow iron oxide composite material. When encountering visible light, iron oxide shows good photochemical response to both ultraviolet light and visible light, and has a relatively high utilization rate for visible light. Therefore, visible light energy can be effectively utilized, increasing the absorption of visible light, thereby increasing the yield of photogenerated electron-hole pairs, and then improving quantum yield. At the same time, the polypyrrole molecular chain has good transport capacity, which can transport electrons well, thereby broadening the spectral response range of zinc oxide with high redox potential and large exciton binding energy, and comprehensively improving the photochemical catalytic performance of visible light catalytic materials. Moreover, polypyrrole and zinc oxide can form internal pore doping for hollow iron oxide, reduce the recombination speed of photogenerated electrons and holes in the photocatalytic process, and doping elements can reduce the initial oxidation potential, increase photocurrent, reduce activation energy, and improve electrical conductivity. The visible light response catalytic material prepared by the present invention can form a composite structure, promote electron / hole separation, enhance charge transfer efficiency, and improve photocatalytic performance.

[0025] (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 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.

[0026] (3) The experimental results show that when non-grafted zinc salt is used to prepare zinc oxide-loaded polypyrrole, the zinc salt is non-chemically bonded to the surface of polypyrrole, and the distance between the two belongs to the intermolecular distance range, resulting in that zinc oxide cannot be well loaded on the surface of polypyrrole, and the loading is uneven, resulting in 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 iron oxide in the state 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; when iron 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.

[0027] (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

[0028] The following examples are intended to further illustrate the present invention rather than to limit the scope of protection of the present invention.

[0029] The porous nano-iron oxide (α-Fe 2 O 3 ) is prepared 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, calcined at 500°C for 2 hours, and sieved to obtain porous nano-iron trioxide (α-Fe 2 O 3 ) with a particle size of 30 to 50 nm. 2 O 3 ).

[0030] Specific embodiments of the visible light responsive catalytic electrode for wastewater treatment and the preparation method thereof of the present invention are as follows:

[0031] Example 1

[0032] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0033] (1) 10 g of polypyrrole (number average molecular weight: 2000) and 0.08 g of glycidyl methacrylate were added to a stirring kettle and stirred evenly. Then, 0.01 g of concentrated sulfuric acid as a catalyst was added, and the mixture was heated to 80° C. and stirred for 3 h. The mixture was cooled to room temperature, and the reaction solution was poured into ice water. After precipitation, the mixture was filtered and washed with water and ethanol, respectively, to obtain double-bond grafted polypyrrole.

[0034] (2) adding double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heating to 80° C., stirring until the double bond grafted polypyrrole is dissolved, and cooling to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 1%; dissolving 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%; and adding 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 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, and the reaction solution was poured into water. After precipitation, it was 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:

[0035]

[0036] (3) Add double-bond quaternary ammonium salt grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirred tank, heat to 80°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 5%; then add zinc mercaptocarboxylate and tetraethylamine to the double-bond quaternary ammonium salt grafted polypyrrole solution, heat to 60°C, stir to react for 8 hours, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, and obtain zinc salt grafted polypyrrole. The mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine is 40:50:0.05.

[0037] (4) Add zinc salt grafted polypyrrole and dimethyl sulfoxide into a stirred tank and stir until the zinc salt grafted polypyrrole is fully dissolved to obtain a zinc salt grafted polypyrrole solution with a mass fraction of 3%, and then add porous nano-iron trioxide (α-Fe 2 O 3), stir evenly to obtain a mixed solution A; dissolve sodium hydroxide in dimethyl sulfoxide to obtain a dimethyl sulfoxide solution with a mass fraction of 4% sodium hydroxide, named solution B; under stirring, add the mixed solution A to solution B, the mass ratio of zinc salt grafted polypyrrole and sodium hydroxide is 1:2, then heat to 55°C, stir to react for 3h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, to obtain a visible light responsive catalyst. Porous nano-iron trioxide (α-Fe 2 O 3 ) and zinc salt grafted polypyrrole have a mass ratio of 1:10.

[0038] (5) The visible light responsive catalyst and dimethyl sulfoxide were stirred evenly at a mass ratio of 5:100, and ultrasonically dispersed for 60 minutes to obtain a dispersion of the visible light responsive catalyst, which was then spin-coated on the pretreated FTO conductive glass at a speed of 1000 rpm, and then dried at 75°C for 24 hours 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 .

[0039] Example 2

[0040] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0041] (1) 10 g of polypyrrole (number average molecular weight: 2000) and 0.1 g of glycidyl methacrylate were added into a stirred tank and stirred evenly. Then, 0.015 g of concentrated sulfuric acid as a catalyst was added. The mixture was heated to 85° C. and stirred for 4 h. The mixture was cooled to room temperature. The reaction solution was poured into ice water. After precipitation, the mixture was filtered and washed with water and ethanol, respectively, to obtain double-bond grafted polypyrrole.

[0042] (2) adding double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heating to 100° C., stirring until the double bond grafted polypyrrole is dissolved, and cooling to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 3%; dissolving 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride in anhydrous N-methylpyrrolidone to obtain a 20% 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride solution; and stirring 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 and 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 and 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1.2:1). The reaction was continued to stir for 7 hours, and the reaction solution was poured into water. After precipitation, it was 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:

[0043]

[0044] (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 to react for 10 hours, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, and 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.

[0045] (4) Add zinc salt grafted polypyrrole and dimethyl sulfoxide into a stirred tank and stir until the zinc salt grafted polypyrrole is fully dissolved to obtain a zinc salt grafted polypyrrole solution with a mass fraction of 5%, and then add porous nano-iron trioxide (α-Fe 2 O 3 ), stir evenly to obtain a mixed solution A; dissolve sodium hydroxide in dimethyl sulfoxide to obtain a dimethyl sulfoxide solution with a mass fraction of 6% sodium hydroxide, named solution B; under stirring, add the mixed solution A to solution B, the mass ratio of zinc salt grafted polypyrrole and sodium hydroxide is 1:3, then heat to 60°C, stir to react for 5h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, and obtain a visible light responsive catalyst. Porous nano-iron trioxide (α-Fe 2 O 3) and zinc salt grafted polypyrrole have a mass ratio of 1:12.

[0046] (5) The visible light responsive catalyst and dimethyl sulfoxide were stirred evenly in a mass ratio of 5:100, and ultrasonically dispersed for 80 minutes to obtain a dispersion of the visible light responsive catalyst, which was then spin-coated on the pretreated FTO conductive glass at a speed of 1300 rpm, and then dried at 85°C for 24 hours 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 .

[0047] Example 3

[0048] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0049] (1) 10 g of polypyrrole (number average molecular weight: 2000) and 0.09 g of glycidyl methacrylate were added to a stirring kettle and stirred evenly. Then, 0.013 g of concentrated sulfuric acid as a catalyst was added, and the mixture was heated to 82° C. and stirred for reaction for 3.5 h. The mixture was cooled to room temperature, and the reaction solution was poured into ice water. After precipitation, the mixture was filtered and washed with water and ethanol, respectively, to obtain double-bond grafted polypyrrole.

[0050] (2) adding double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heating to 90° C., stirring until the double bond grafted polypyrrole is dissolved, and cooling to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 2%; dissolving 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%; and adding 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 the double-bond grafted polypyrrole and 2-chloro-N,N,N-trimethyl-2-oxo-1-ethylammonium chloride was 1:1.3). 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 1.1:1). The reaction was continued to stir for 6 hours, and the reaction solution was poured into water. After precipitation, it was 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:

[0051]

[0052] (3) Add double-bond quaternary ammonium salt grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirred tank, heat to 90°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 6%; then add zinc mercaptocarboxylate and tetraethylamine to the double-bond quaternary ammonium salt grafted polypyrrole solution, heat to 70°C, stir to react for 9 hours, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, and obtain zinc salt grafted polypyrrole. The mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine is 40:55:0.055.

[0053] (4) Add zinc salt grafted polypyrrole and dimethyl sulfoxide into a stirred tank and stir until the zinc salt grafted polypyrrole is fully dissolved to obtain a zinc salt grafted polypyrrole solution with a mass fraction of 4%, and then add porous nano-iron trioxide (α-Fe 2 O 3 ), stir evenly to obtain a mixed solution A; dissolve sodium hydroxide in dimethyl sulfoxide to obtain a dimethyl sulfoxide solution with a mass fraction of 5% sodium hydroxide, named solution B; under stirring, add the mixed solution A to solution B, the mass ratio of zinc salt grafted polypyrrole and sodium hydroxide is 1:2.5, then heat to 58°C, stir to react for 4h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, and obtain a visible light responsive catalyst. Porous nano-iron trioxide (α-Fe 2 O 3 ) and zinc salt grafted polypyrrole have a mass ratio of 1:11.

[0054] (5) The visible light responsive catalyst and dimethyl sulfoxide were stirred evenly in a mass ratio of 5:100, and ultrasonically dispersed for 70 minutes to obtain a dispersion of the visible light responsive catalyst, which was then spin-coated on the pretreated FTO conductive glass at a speed of 1200 rpm, and then dried at 80°C for 24 hours 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 .

[0055] Example 4

[0056] 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 polypyrrole in step (1) of the method for preparing a visible light responsive catalytic electrode for wastewater treatment in this embodiment is 1500.

[0057] Example 5

[0058] 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 polypyrrole in step (1) of the method for preparing a visible light responsive catalytic electrode for wastewater treatment in this embodiment is 3500.

[0059] Example 6

[0060] The method for preparing a visible light responsive catalytic electrode for wastewater treatment of this embodiment comprises the following steps:

[0061] (1) 10 g of polypyrrole (number average molecular weight: 2000) and 0.08 g of glycidyl methacrylate were added to a stirring kettle and stirred evenly. Then, 0.01 g of concentrated sulfuric acid as a catalyst was added, and the mixture was heated to 80° C. and stirred for 3 h. The mixture was cooled to room temperature, and the reaction solution was poured into ice water. After precipitation, the mixture was filtered and washed with water and ethanol, respectively, to obtain double-bond grafted polypyrrole.

[0062] (2) adding double bond grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirring kettle, heating to 80° C., stirring until the double bond grafted polypyrrole is dissolved, and cooling to room temperature to obtain a double bond grafted polypyrrole solution with a mass fraction of 1%; dissolving 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%; and adding 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 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 double-bond quaternary ammonium salt grafted polypyrrole.

[0063] (3) Add double-bond quaternary ammonium salt grafted polypyrrole and anhydrous N-methylpyrrolidone into a stirred tank, heat to 80°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 5%; then add zinc mercaptocarboxylate and tetraethylamine to the double-bond quaternary ammonium salt grafted polypyrrole solution, heat to 60°C, stir to react for 8 hours, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, and obtain zinc salt grafted polypyrrole. The mass ratio of double-bond quaternary ammonium salt grafted polypyrrole, zinc mercaptocarboxylate and tetraethylamine is 40:50:0.05.

[0064] (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%, and then add porous nano-iron trioxide (α-Fe 2 O 3 ), stir evenly to obtain a mixed solution A; dissolve sodium hydroxide in ethanol to obtain an ethanol solution of sodium hydroxide with a mass fraction of 4%, named solution B; under stirring conditions, add the mixed solution A to solution B, the mass ratio of zinc salt grafted polypyrrole and sodium hydroxide is 1:2, then heat to 55°C, stir to react for 3h, cool to room temperature, pour the reaction solution into ice water, filter after precipitation, wash with water and ethanol respectively, and obtain a visible light responsive catalyst. Porous nano-iron trioxide (α-Fe 2 O 3 ) and zinc salt grafted polypyrrole have a mass ratio of 1:10.

[0065] (5) The visible light responsive catalyst and dimethyl sulfoxide were stirred evenly at a mass ratio of 5:100, and ultrasonically dispersed for 60 minutes to obtain a dispersion of the visible light responsive catalyst, which was then spin-coated on the pretreated FTO conductive glass at a speed of 1000 rpm, and then dried at 75°C for 24 hours 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 .

[0066] Comparative Example 1

[0067] 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 catalyst dispersion in 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-Fe 2 O 3), stir evenly to obtain a mixed solution A, the mass ratio of polypyrrole and zinc mercaptocarboxylate is 40:50, and the sum of the mass fractions of polypyrrole and zinc mercaptocarboxylate in the mixed solution is 3%; dissolve sodium hydroxide in dimethyl sulfoxide to obtain a dimethyl sulfoxide solution of sodium hydroxide with a mass fraction of 4%, named solution B; under stirring conditions, add the mixed solution A to solution B, the mass ratio of the sum of polypyrrole and zinc mercaptocarboxylate to the mass ratio of sodium hydroxide is 1:2, then heat to 55°C, stir to react for 3h, cool to room temperature, filter, wash the filter cake with water and ethanol respectively to remove unreacted zinc mercaptocarboxylate, and then stir the washed solid and dimethyl sulfoxide at a mass ratio of 5:100, ultrasonically disperse for 60min, and obtain a dispersion of a visible light responsive catalyst. Porous nano-iron trioxide (α-Fe 2 O 3 ) to the sum of the masses of polypyrrole and zinc mercaptocarboxylate is 1:10.

[0068] Comparative Example 2

[0069] 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), thereby obtaining the zinc salt grafted polypyrrole.

[0070] Comparative Example 3

[0071] 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, porous nano-iron trioxide (α-Fe 2 O 3 ) is replaced by nonporous nano-iron oxide (α-Fe 2 O 3 ).

[0072] Comparative Example 4

[0073] 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 trioxide (α-Fe 2 O 3 ) is added in an amount of 0.

[0074] Comparative Example 5

[0075] 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 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-iron trioxide (α-Fe 2 O 3 ) and dimethyl sulfoxide were stirred evenly in a mass ratio of 5:100, and ultrasonically dispersed for 60 minutes to obtain a dispersion of a visible light responsive catalyst.

[0076] Effect example

[0077] 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 carry out 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 pollutants 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 2 During the reaction process, the test liquid in the electrolytic cell is removed at regular intervals for testing and analysis to determine the concentration of the target pollutant in the test liquid at different times. Then, according to the initial concentration of the target pollutant in the test liquid and the concentration after treatment, the removal rate of the target pollutant is calculated. 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 reaction kinetic constant of the visible photoelectrocatalytic reaction is calculated according to 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 reaction kinetic constant. The test calculation results of the removal rate of the target pollutant when the reaction time is 60min and the first-order reaction kinetic constant k of the target pollutant are shown in Table 1.

[0078] 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 off, or bubbling, the bonding strength test result was qualified; if there was falling off, peeling off, or bubbling, the bonding strength test result was unqualified.

[0079] Table 1 Concentration of target pollutants, first-order reaction kinetic constant k and binding strength of target pollutants when the reaction time is 60 min

[0080]

[0081] 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 make the conductive polymer polypyrrole enter the hollow iron oxide pores in the solution state, and be more tightly loaded on the iron oxide. At the same time, the zinc salt grafted by chemical bonding on the surface of the polypyrrole can be distributed in the form of molecular chains, so that the zinc salt is more evenly distributed on the surface of the polypyrrole. When the polypyrrole grafted with the zinc salt contacts sodium hydroxide in the 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. 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 to form a zinc oxide-modified polypyrrole-filled hollow iron oxide composite material. When encountering visible light, iron oxide shows good photochemical response to both ultraviolet light and visible light, and has a relatively high utilization rate of visible light. Therefore, visible light energy can be effectively utilized, increasing the absorption of visible light, thereby increasing the yield of photogenerated electron-hole pairs, and further increasing the quantum yield. At the same time, the polypyrrole molecular chain has good transport capacity and can transport electrons well, thereby broadening the spectral response range of zinc oxide with high redox potential and large exciton binding energy, and comprehensively improving the photochemical catalytic performance of visible light catalytic materials. Moreover, polypyrrole and zinc oxide can form internal pore doping of hollow iron oxide, reduce the recombination rate of photogenerated electrons and holes in the photocatalytic process, and doping elements can reduce 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.

[0082] 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 travel inside 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.

[0083] 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, since the polypyrrole is distributed in a granular form, 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, which in turn affects the loading amount of zinc oxide and the formation of the composite structure, thereby resulting in a decrease in the photocatalytic performance.

[0084] 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 non-chemically bonded to the surface of polypyrrole, the distance between the two belongs to the range of intermolecular distance, resulting in zinc oxide not being well loaded on the surface of polypyrrole, and the loading is uneven, resulting in deviation in photocatalytic performance.

[0085] 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.

[0086] It can be seen from Example 1 and Comparative Example 3 that when non-porous nano-iron oxide is used, during the in-situ generation of zinc oxide, polypyrrole cannot enter the interior of the iron oxide in the state 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.

[0087] 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.

[0088] 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.

[0089] 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 trioxide is used, and polypyrrole cannot enter its interior, resulting in poor affinity and compatibility between iron trioxide and the polymer matrix, and the iron trioxide particles affect 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) mixing polypyrrole and glycidyl methacrylate under the action 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 the double-bond quaternary ammonium salt grafted polypyrrole; (3) subjecting the double bond in the double-bond quaternary ammonium salt grafted polypyrrole to an addition reaction with the mercapto group in the zinc mercaptocarboxylate under the catalytic action 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, thereby obtaining a dispersion containing a visible light responsive catalyst; (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.

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

3. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1, characterized in that: 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 3-4 hours.

4. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to any one of claims 1 to 3, characterized in that: 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, characterized in that: 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, characterized in that: In step (4), the solvent is dimethyl sulfoxide.

7. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1 or 6, characterized in that: In step (4), the method for in-situ generation of zinc oxide is as follows: adding porous nano-iron oxide to a dimethyl sulfoxide solution of zinc salt grafted polypyrrole to obtain a mixed solution A; dissolving sodium hydroxide in dimethyl sulfoxide to obtain a solution B; adding the mixed solution A to the solution B under stirring conditions, and then heating to 55-60° C. and stirring 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.

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

9. The method for preparing a visible light responsive catalytic electrode for wastewater treatment according to claim 1 or 8, characterized in that: 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 .

10. 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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