3D-printed porous Janus biochar flow electrodes, methods of making and using the same

Abstract

The application discloses a 3D-printed porous Janus biochar flow electrode and a preparation method and application thereof, and the preparation steps comprise the following steps: treating dry sludge to obtain deashed biochar, then performing modification treatment and pyrrole polymerization to obtain a biochar catalyst, mixing the biochar catalyst and other substances to obtain 3D printing ink I, and forming a hydrophilic biochar catalyst layer with a "rice character type" network porous structure through a light curing printing technology; mixing and stirring a binder and a dispersing agent to obtain 3D printing ink II, and printing an area-equivalent "prism square type" network hydrophobic oxygen storage layer on the hydrophilic biochar catalyst layer through a direct ink writing printing technology to obtain a double-layer network structure printing body, and freezing and drying the double-layer network structure printing body to obtain the 3D-printed porous Janus biochar flow electrode, and the 3D-printed porous Janus biochar flow electrode is used for efficiently degrading PPCPs in a heterogeneous electro-Fenton system. The application provides a new solution to the problem that the biochar electrode has low catalytic removal efficiency on PPCPs pollutants.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pollutant treatment, in particular to a 3D-printed porous Janus biochar flow electrode and a preparation method and application thereof. BACKGROUND

[0002] In recent years, pharmaceutical and personal care products (PPCPs) as a new pollutant have attracted widespread attention since the 21st century. They enter the environment through different ways such as human excretion, production process waste, medical process waste, and even illegal and expired drugs entering the market. As a new pollutant, it has attracted widespread attention. The daily use of PPCPs leads to their frequent detection and high concentration in the influent and effluent of wastewater treatment plants and sludge. However, traditional wastewater treatment processes are difficult to effectively remove them. The research on the removal of PPCPs by microorganism degradation, photodegradation and ozone oxidation is still in the laboratory stage, and the removal effect is not ideal when applied to actual wastewater treatment.

[0003] Sludge biochar electrodes exhibit excellent catalytic activation performance in heterogeneous electro-Fenton advanced oxidation processes and have great potential in removing new pollutants PPCPs in water. However, they still face problems such as poor conductivity of the electrode, serious catalyst shedding and agglomeration, and low oxygen transfer rate of the electrolyte solution, which slow down the catalytic degradation rate of pollutants in the system.

[0004] Therefore, it is necessary to develop a preparation method of 3D-printed porous Janus biochar flow electrode to solve the problems of poor conductivity of existing biochar electrodes, catalyst shedding, serious agglomeration, and low oxygen transfer rate of electrolyte solution. SUMMARY

[0005] The present application aims to: in view of the shortcomings of the prior art, provide a preparation method of 3D-printed porous Janus biochar flow electrode, which solves the problems of poor conductivity of existing biochar electrodes, catalyst shedding, serious agglomeration, and low oxygen transfer rate of electrolyte solution.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a 3D-printed porous Janus biochar flow electrode, comprising the following steps:

[0008] Step S1, after acidizing dry sludge particles, pyrolyzing them under an inert atmosphere to obtain sludge biochar, and then performing acid washing, centrifugation and washing until the pH is neutral, and drying to obtain deashed biochar;

[0009] Step S2, after mixing the deashing biochar and metal salt, the modified treatment is carried out to obtain the magnetic biochar, after using the pyrrole solution to polymerize the magnetic biochar to obtain the polypyrrole loaded magnetic biochar, grinding to obtain the biochar catalyst;

[0010] Step S3, mixing the biochar catalyst, aqueous crosslinking agent, active monomer, photoinitiator, gelatin and deionized water to obtain 3D printing ink I, forming a network porous structure of the hydrophilic biochar catalyst layer by the light curing printing technology in the "millet type" path;

[0011] Step S4, mixing and stirring the adhesive and dispersant to obtain 3D printing ink II, printing the network porous hydrophobic oxygen storage layer formed in the "prism type" path with equal area on the hydrophilic biochar catalyst layer by the direct ink writing printing technology, to obtain a double-layer network structure printing body;

[0012] Step S5, freezing and drying the double-layer network structure printing body to obtain the 3D printed porous Janus biochar flow electrode.

[0013] Preferably, the volume ratio of the porous hydrophobic oxygen storage layer to the hydrophilic biochar catalyst layer is (1-2):(3-6).

[0014] Preferably, in step S1, the acid solvent for acidification and pickling is at least one of hydrochloric acid, nitric acid, acetic acid, phosphoric acid and hydrofluoric acid, and the volume ratio of the sludge biochar to the acid solution during pickling is (1-2):(5-10).

[0015] Preferably, in step S2, the metal salt is at least one of ferric chloride, manganese chloride, copper chloride, zinc chloride and cobalt chloride, and the modification treatment is at least one of ultrasonic treatment, immersion treatment and hydrothermal treatment.

[0016] Preferably, in step S3, the mass ratio of the biochar catalyst, aqueous crosslinking agent, active monomer, photoinitiator, gelatin and deionized water is (5-20):(6-12):(5-15):(0.5-2):(5-10):(90-110).

[0017] The aqueous crosslinking agent is at least one of N,N-methylenebisacrylamide, polyethylene glycol-2-acrylate and diisocyanate, the active monomer is at least one of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid, and the photoinitiator is at least one of LAP photoinitiator, Irgacure 2100 photoinitiator and EY photoinitiator.

[0018] Preferably, in step S3, the printing nozzle diameter in the light-curing printing technology is 0.58-1.20 mm, the extrusion pressure is 10-40 kPa, the temperature of the extrusion head and the substrate is 20-30 DEG C, the printing structure is designed as a 3D grid, the length-width-height ratio of the printing body is (4-8):(4-8):(1-2), the printing line width is 2-4 mm, the printing layer number is 15-45, the printing height of each layer is 0.5-1.5 mm, the printing speed is 3-7 mm / s, the wavelength of the ultraviolet light is 400-450 nm, and the ultraviolet light crosslinking time is 10-60 s.

[0019] The specific printing path of the "rice-shaped" structure is that square grid structures are alternately printed in an S-shaped path first, and then the square vertexes are crossed to form the "rice-shaped" structure.

[0020] Preferably, in step S4, the dispersing agent is at least one of N-methyl pyrrolidone solvent and deionized water, and the use ratio of the dispersing agent to the binder is (10-30) ml:(5-10) g.

[0021] In the direct ink writing printing technology, the printing nozzle diameter is 0.58-1.20 mm, the extrusion pressure is 20-60 kPa, the temperature of the extrusion head and the substrate is 20-30 DEG C, the length-width-height ratio of the printing body is (4-8):(4-8):(1-2), the printing layer number is 5-15, the printing height of each layer is 0.5-1.5 mm, and the printing speed is 3-7 mm / s.

[0022] The specific printing path of the "prism square-shaped" structure is that square grid structures are alternately printed in an S-shaped path first, and then the square center points are crossed to form the "prism square-shaped" structure.

[0023] Preferably, in step S5, the temperature of the freeze-drying is -80--70 DEG C, and the time is 20-40 h.

[0024] In addition, the application further provides a 3D-printed porous Janus biochar flow electrode prepared by the above method.

[0025] Preferably, the 3D-printed porous Janus biochar flow electrode is applied to wastewater treatment containing typical PPCPs pollutants sulfamethoxazole.

[0026] In addition, the application further provides an application of the above 3D-printed porous Janus biochar flow electrode in wastewater treatment, which comprises the following steps:

[0027] Step S1, a 3D-printed porous Janus biochar flow electrode is used as a cathode, a platinum sheet is used as an anode, the anode is opposite to the cathode and has an equal area, a silver-silver chloride electrode is a reference electrode, and wastewater containing typical PPCPs pollutants sulfamethoxazole is used as an electrolyte to form a heterogeneous electro-Fenton system;

[0028] Step S2, the heterogeneous electro-Fenton system is connected to an external power source, the solution is taken after reaction, the H2O2 concentration in the reaction process is determined by a potassium titanium oxalate spectrophotometric method, quantitative analysis is performed by liquid chromatography UPLC, and the removal rate of sulfamethoxazole is calculated.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] 1) The present application is targeted at the efficient catalytic degradation of PPCPs based on the construction of a heterogeneous electro-Fenton system using a porous Janus biochar flow electrode, aiming at the problems of poor conductivity of the biochar electrode, serious catalyst agglomeration and shedding, and limited H2O2 production rate of the system. The hydrophobic material PTFE with stable oxygen storage capacity and the hydrophilic biochar catalyst with high adsorption and conductivity are combined to develop a porous cross-grid Janus biochar flow electrode by using 3D printing technology, which is applied to the degradation of typical PPCPs in a heterogeneous electro-Fenton system. This method not only realizes the green resource utilization of sludge, but also effectively enhances the gas / liquid / solid mass transfer process and electro-Fenton performance of the system, providing a new solution to the low efficiency of biochar electrodes in catalytic removal of PPCPs pollutants.

[0031] 2) The doped polypyrrole used in the present application has good adsorption capacity and conductivity, and is mainly used in electrode materials, display materials, electromagnetic wave stealth, sensors and other fields. It can fully utilize the good coupling effect of mineral ash of sludge biochar and polypyrrole, and realize in-situ polymerization of polypyrrole on the surface of sludge biochar by chemical synthesis method, which can greatly improve the conductivity of sludge-based biochar electrode.

[0032] 3) The 3D-printed porous cross-grid Janus biochar flow electrode with hydrophobic oxygen storage layer and hydrophilic catalyst layer in the present application is used for efficient oxygen reduction and H2O2 production in a heterogeneous electro-Fenton system, which can effectively solve the problem of catalyst agglomeration and promote the gas-liquid-solid three-phase mass transfer process, further improving the efficiency of catalytic removal of pollutants PPCPs in water. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The figure is a flow chart for the preparation process of the 3D-printed porous Janus biochar flow electrode.

[0034] Figure 2A flow chart of printing process of the "herringbone" path and the "prism square" path of the 3D-printed porous Janus biochar flow electrode.

[0035] Figure 3 A schematic diagram of the 3D-printed porous Janus biochar flow electrode.

[0036] Figure 4 A diagram of H2O2 production rate of the hydrophilic catalyst layer biochar loadings of the 3D-printed porous Janus biochar flow electrode.

[0037] Figure 5 A diagram of treatment effect on simulated SMX-containing wastewater of the hydrophilic catalyst layer biochar loadings of the 3D-printed porous Janus biochar flow electrode.

[0038] Figure 6 A diagram of treatment effect on simulated SMX-containing wastewater under different pH conditions.

[0039] Figure 7 A diagram of treatment effect on simulated SMX-containing wastewater of Example 1 and Comparative Examples 1-2.

[0040] Figure 8 A diagram of treatment effect on simulated SMX-containing wastewater under different voltage conditions.

[0041] Wherein, A is a hydrophilic biochar catalyst layer, B is a hydrophobic oxygen storage layer, and C is a 3D-printed porous Janus biochar flow electrode. DETAILED DESCRIPTION

[0042] In order to make the technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below in combination with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0043] According to a first aspect of the present application, the present application provides a preparation method of a 3D-printed porous Janus biochar flow electrode, comprising the following steps:

[0044] Step S1, after acidizing dry sludge particles, pyrolyzing the sludge biochar under an inert atmosphere, and then performing acid washing, centrifugation and washing to neutral pH and drying to obtain deashed biochar;

[0045] Step S2, mixing the deashed biochar and metal salt, and then performing modification treatment to obtain magnetic biochar, using a pyrrole solution to polymerize the magnetic biochar to obtain polypyrrole loaded magnetic biochar, and then grinding to obtain a biochar catalyst;

[0046] Step S3, mixing biochar catalyst, aqueous crosslinking agent, active monomer, photoinitiator, gelatin and deionized water to obtain 3D printing ink I, and forming a hydrophilic biochar catalyst layer with a network porous structure in a "millet-shaped" path by a light-curing printing technology;

[0047] Step S4, mixing and stirring the adhesive and dispersant to obtain 3D printing ink II, and printing a reticular porous hydrophobic oxygen storage layer formed in a "prism square" path on the hydrophilic biochar catalyst layer by a direct ink writing printing technology to obtain a double-layer network structure printed body.

[0048] Step S5, freeze-drying the double-layer network structure printed body to obtain the 3D printed porous Janus biochar flow electrode.

[0049] The preparation of polypyrrole in-situ polymerization magnetic sludge biochar realizes a substantial increase in the conductivity and effective adsorption sites of the sludge biochar electrode, and realizes the green resource utilization of sludge. On the other hand, the 3D printed porous cross-grid Janus biochar flow electrode with a hydrophobic oxygen storage layer and a hydrophilic catalyst layer is developed for efficient oxygen reduction to produce H2O2 in a heterogeneous electro-Fenton system, effectively solving the problem of catalyst agglomeration and promoting the gas-liquid-solid three-phase mass transfer process, and further improving the efficiency of catalytic removal of pollutants PPCPs in water. The reticular porous hydrophobic oxygen storage layer maintains stable oxygen storage to provide abundant oxygen supply, effectively improving the solution dissolved oxygen transmission rate. The hydrophilic biochar catalyst layer provides efficient active sites while overcoming the problems of catalyst material agglomeration and shedding.

[0050] In some embodiments, the volume ratio of the porous hydrophobic oxygen storage layer to the hydrophilic biochar catalyst layer is (1-2):(3-6), for example, it can be 1:3, 1:4, 1:5, 1:6, 2:3, 2:4, 2:5 or 2:6.

[0051] When the volume ratio exceeds the preset range, the hydrophilic catalyst layer has fewer catalytic sites, the hydrophobic oxygen storage layer has low oxygen utilization efficiency, and the efficiency is reduced.

[0052] In some embodiments, in step S1, the acid solvent for acidification and pickling is at least one of hydrochloric acid, nitric acid, acetic acid, phosphoric acid and hydrofluoric acid, and the volume ratio of sludge biochar to acid solution during pickling is (1-2):(5-10), for example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 2:5, 2:6, 2:7, 2:8, 2:9 or 2:10.

[0053] In some embodiments, in step S2, the metal salt is selected from at least one of iron chloride, manganese chloride, copper chloride, zinc chloride and cobalt chloride, and the modification treatment is at least one of ultrasonic treatment, immersion treatment and hydrothermal treatment.

[0054] In some embodiments, in step S3, the mass ratio of the biochar catalyst, the aqueous crosslinking agent, the active monomer, the photoinitiator, the gelatin and the deionized water is (5-20):(6-12):(5-15):(0.5-2):(5-10):(90-110), for example, it can be 10:8:10:2:8:100, 10:8:10:2:8:100, 20:8:10:2:8:100, 10:12:10:2:8:100, 10:6:10:2:8:100, 5:8:15:2:8:100, 10:8:10:2:8:110, 10:8:10:2:8:90, 10:8:10:0.5:8:100, 10:8:10:2:5:100, 10:8:10:2:10:100 or 15:8:15:2:8:110;

[0055] The aqueous crosslinking agent is selected from at least one of N,N-methylenebisacrylamide, polyethylene glycol-2-acrylate and diisocyanate, the active monomer is selected from at least one of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid, and the photoinitiator is selected from at least one of LAP photoinitiator, Irgacure 2100 photoinitiator and EY photoinitiator.

[0056] In some embodiments, in step S3, in the light-curing printing technology, the printing nozzle diameter is 0.58-1.20 mm, for example, it can be 0.58 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.1 mm or 1.2 mm; the extrusion pressure is 10-40 kPa, for example, it can be 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa, 35 kPa or 40 kPa; the extrusion head and substrate temperature is 20-30°C, for example, it can be 20°C, 22°C, 24°C, 26°C, 28°C or 30°C; the printing structure design is a 3D grid, the printing body length-width-height ratio is (4-8):(4-8):(1-2), for example, it can be 4:4:1, 4:8:1, 8:4:1, 4:4:2, 4:8:2 or 8:4:2; the printing line width is 2-4 mm, for example, it can be 2 mm, 3 mm or 4 mm; the printing layer number is 15-45 layers, for example, it can be 15 layers, 20 layers, 25 layers, 30 layers, 35 layers, 40 layers or 45 layers; the printing height per layer is 0.5-1.5 mm, for example, it can be 0.5 mm, 1.0 mm or 1.5 mm; the printing speed is 3-7 mm / s, for example, it can be 3 mm / s, 4 mm / s, 5 mm / s, 6 mm / s or 7 mm / s; the ultraviolet light wavelength is 400-450 nm, for example, it can be 400 nm, 405 nm, 410 nm, 420 nm, 430 nm, 440 nm or 450 nm; the ultraviolet light crosslinking time is 10-60 s, for example, it can be 10 s, 20 s, 30 s, 40 s, 50 s or 60 s.

[0057] The specific printing path of the "rice-shaped" structure is: first, alternately print a square grid structure with an S-shaped path, and then cross the square vertices to form a "rice-shaped" structure.

[0058] The "rice-shaped" structure is coupled with the "prism-shaped" structure of the hydrophobic oxygen storage layer to form a cross-grid structure, which can accelerate the gas / liquid / solid mass transfer process of the system, improve the mass transfer efficiency, and thus enhance the pollutant degradation efficiency of the electro-Fenton process.

[0059] In some embodiments, in step S4, the dispersant is at least one of N-methyl pyrrolidone solvent and deionized water, and the ratio of the amount of the dispersant to the amount of the binder is (10-30) ml:(5-10) g, for example, it can be 10 ml:5 g, 15 ml:5 g, 20 ml:5 g, 30 ml:5 g, 10 ml:10 g, 15 ml:10 g, 20 ml:10 g or 30 ml:10 g. When the ratio of the amount of the dispersant to the amount of the binder is less than the preset range, the viscosity and mechanical properties of the printing ink will be too large, and the pressure provided by the printer cannot extrude the ink. When the ratio of the amount of the dispersant to the amount of the binder is greater than the preset range, the viscosity and mechanical properties of the printing ink will be too low, and the extruded printing body is prone to collapse and is not easy to be shaped.

[0060] In the direct ink writing printing technology, the printing nozzle diameter is 0.58-1.20 mm, for example, it can be 0.58 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.1 mm or 1.2 mm; the extrusion pressure is 20-60 kPa, for example, it can be 20 kPa, 25 kPa, 30 kPa, 40 kPa, 50 kPa or 65 kPa; the extrusion head and substrate temperature is 20-30℃, for example, it can be 20℃, 22℃, 24℃, 26℃, 28℃ or 30℃; the printing body length-width-height ratio is (4-8):(4-8):(1-2), for example, it can be 4:4:1, 4:8:1, 8:4:1, 4:4:2, 4:8:2 or 8:4:2; the printing layer number is 5-15 layers, for example, it can be 15 layers, 20 layers, 25 layers, 30 layers, 35 layers, 40 layers or 45 layers; the printing height of each layer is 0.5-1.5 mm, for example, it can be 0.5 mm, 1.0 mm or 1.5 mm; the printing speed is 3-7 mm / s, for example, it can be 3 mm / s, 4 mm / s, 5 mm / s, 6 mm / s or 7 mm / s;

[0061] The specific printing path of the "prism square type" is: first, alternately print a square grid structure in an S-shaped path, and then cross the center points of the squares to form a "prism square type" structure.

[0062] The "prism square type" structure is coupled with the "cross type" structure to form a cross grid structure, which can speed up the gas / liquid / solid mass transfer process of the system, improve the mass transfer efficiency, and thus enhance the pollutant degradation efficiency of the electro-Fenton process.

[0063] In some embodiments, in step S5, the temperature of the freeze-drying is -80 to -70℃, for example, it can be -80℃, -79℃, -78℃, -76℃, -75℃, -74℃, -73℃, -72℃, -71℃ or -70℃; the time is 20-40 h, for example, it can be 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h or 40 h.

[0064] According to the second aspect of the present application, the present application provides a 3D printed porous Janus biochar flow electrode prepared by the above steps.

[0065] According to the third aspect of the present application, the present application provides an application of the above 3D printed porous Janus biochar flow electrode in wastewater treatment containing typical PPCPs pollutants sulfamethoxazole.

[0066] Step S1, a 3D-printed porous Janus biochar flow electrode is used as a cathode, a platinum plate is used as an anode, the anode is opposite to the cathode and has an equal area, a silver-silver chloride electrode is used as a reference electrode, and a wastewater containing a typical PPCP contaminant, sulfamethoxazole, is used as an electrolyte to form a heterogeneous electro-Fenton system;

[0067] Step S2, the heterogeneous electro-Fenton system is connected to an external power source, the solution is taken after reaction, the concentration of H2O2 in the reaction process is determined by a potassium titanium oxalate spectrophotometric method, and quantitative analysis is performed by liquid chromatography UPLC to calculate the removal rate of sulfamethoxazole.

[0068] In some embodiments, the voltage of the heterogeneous electro-Fenton system connected to the external power source is -0.2 to -0.8 V, for example, it can be -0.2 V, -0.4 V, -0.6 V or -0.8 V; the external oxygen flow rate is 10 to 20 mL / min, for example, it can be 10 mL / min, 12 mL / min, 14 mL / min, 16 mL / min, 18 mL / min or 20 mL / min; the system volume is 50 to 100 mL, for example, it can be 50 mL, 60 mL, 70 mL, 80 mL, 90 mL or 100 mL; and the wastewater flow rate is 0.5 to 2.0 mL / min, for example, it can be 0.5 mL / min, 1.0 mL / min, 1.5 mL / min or 2 mL / min.

[0069] In some embodiments, the concentration of the contaminant sulfamethoxazole in the wastewater is 5 to 20 ppm, for example, it can be 5 ppm, 10 ppm, 15 ppm or 20 ppm; the pH value is 3.0 to 9.0, for example, it can be 3, 4, 5, 6, 7, 8 or 9; the electrolyte is a sodium sulfate solution, and the electrolyte concentration is 0.05 to 0.25 M, for example, it can be 0.05 M, 0.10 M, 0.15 M, 0.20 M or 0.25 M.

[0070] In order to make the technical solutions and advantages of the present application clearer, the following will combine specific embodiments and the drawings of the specification to make a further detailed description of the present application and its beneficial effects, but the embodiments of the present application are not limited thereto.

[0071] Example 1

[0072] (1) Preparation of 3D-printed porous Janus biochar flow electrode

[0073] Step S1, the dewatered sludge in the sewage treatment plant was dried, ground and sieved (200 mesh sieve) to obtain dry sludge particles. 10 g of dry sludge particles were immersed in 40 mL of 20% nitric acid at room temperature for 24 h with stirring, and the precipitate was completely dried in an oven at 80°C after centrifugation. The sludge biochar was obtained by pyrolysis in a tube furnace under N2 atmosphere at 800°C with a heating rate of 10°C / min for 2 h; the sludge biochar was acid washed (volume ratio 1:5) with 3 mol / L hydrochloric acid solution, centrifuged and washed to neutral pH, and dried to obtain the deashed biochar;

[0074] Step S2, iron chloride and manganese chloride (molar ratio 2:1) were dissolved in 30 mL of ethylene glycol, 0.2 g of deashed biochar was added and ultrasonicated for 3 h, 3 g of sodium acetate was added and stirred thoroughly, and then the solution was transferred to an autoclave and hydrothermal treated at 200°C for 10 h. After hydrothermal treatment, the precipitate was obtained by centrifugation and washed alternately with deionized water and ethanol, dried in an oven at 60°C overnight, and ground thoroughly to obtain magnetic biochar; 1.2 g of magnetic biochar was added to 25 mL of 1 mol / L pyrrole monomer solution and stirred at 500 r / min for 30 min, then 50 mL of 1 mol / L iron chloride solution was added as an oxidizing agent, and the stirring was continued for 12 h. The precipitate was washed alternately with deionized water and ethanol, dried to obtain polypyrrole loaded magnetic biochar, and ground to obtain the biochar catalyst;

[0075] Step S3, the mass ratio of biochar catalyst, aqueous crosslinking agent (N,N-methylene bisacrylamide), active monomer (acrylamide), photoinitiator (LAP photoinitiator), gelatin and deionized water was 10:8:10:2:8:100 to prepare printing ink raw material I. The printing ink raw material I was transferred to a syringe, centrifuged to remove air bubbles, and then a hydrophilic biochar catalyst layer with a network porous structure was formed by light curing printing technology in a "rice character" path;

[0076] The light curing printing technology (SLA) printing structure was designed to be printed in an alternating cycle in a "rice character" path, and the specific printing path was: first, a square grid structure was printed in an S-shaped path, and then a "rice character" structure was formed by crossing the square vertices. The printing technology parameters were set as follows: substrate temperature 25°C, extrusion pressure 300 kPa, printing body size 2×2×0.5 cm, printing layer number 30, printing height per layer 1.5 mm, printing speed 7 mm / s, and printing nozzle diameter 1.20 mm. The wavelength of the ultraviolet light was 405 nm, and the in-situ crosslinking time under the ultraviolet light was 40 s.

[0077] Step S4, the dispersant (N-methyl pyrrolidone solvent) is mixed with the binder (PTFE) and fully stirred using a high-speed blender to obtain a printing ink raw material II, and the amount ratio of the two is 20 mL:5 g. The printing ink raw material is transferred to a syringe, centrifuged to remove air bubbles to obtain a 3D printing ink II. The hydrophilic biochar catalyst layer is printed with an equal area of the mesh porous hydrophobic oxygen storage layer formed in a "prism square type" path by a direct ink writing printing technology (DIW) to obtain a double-layer network structure printing body;

[0078] wherein the DIW printing structure is designed to be printed in an alternating cycle with a "prism square type" path, and the specific printing path is: first, an S-shaped path is used to alternately print a square grid structure, and then the center points of the squares are crossed to form a "prism square type" structure. The printing technology parameters are set as follows: the printing structure is designed to be printed in an alternating cycle with a "prism square type" structure, the substrate temperature is 20-30°C, the extrusion pressure is 300 kPa, the printing layer number is 10, the printing height of each layer is 1.5 mm, the printing speed is 7 mm / s, and the printing nozzle diameter is 1.20 mm.

[0079] Step S5, the double-layer network structure printing body is taken out after being refrigerated at a temperature of -20°C for 12 h, and is placed in a freeze dryer and dried at a temperature of -80°C for 24 h to obtain the 3D printed porous Janus biochar flow electrode.

[0080] (2) Application of 3D printed porous Janus biochar flow electrode material in wastewater treatment

[0081] Step S1, the 3D printed porous Janus biochar flow electrode is used as a cathode, a platinum sheet is used as an anode, the anode and the cathode are opposite and have equal areas, a silver-silver chloride electrode is used as a reference electrode, and simulated wastewater containing typical PPCPs pollutants sulfamethoxazole is used as an electrolyte to form a heterogeneous electro-Fenton system;

[0082] The 3D printed porous Janus biochar flow electrode is used as a cathode, a silver-silver chloride electrode is used as a reference electrode, and a platinum sheet electrode is used as an anode. The SMX simulated wastewater with a concentration of pH=7.0 and 10 ppm is taken in a beaker, the electrolyte is 0.1M Na2SO4, the oxygen flow rate is 20 mL / min, the system solution volume is 100 mL, and the wastewater flow rate is 0.5 mL / min.

[0083] Step S2, the reactor is connected to a stabilized DC power supply, the voltage is set to -0.8V, and two parallel settings are set. The different loadings of the hydrophilic catalyst layer biochar are 1.25 g / cm 2 , 2.50 g / cm 2 , 5.00 g / cm 2 , and 7.50 g / cm2 After 30 min adsorption, the power was turned on, and the reaction solution was taken after 60 min reaction. The concentration of H2O2 in the reaction process was determined by the potassium titanium oxalate spectrophotometric method, and the results are shown in Table 1. Figure 4 2 mL of the solution was filtered through a 0.22 μm filter membrane, and quantitative analysis was performed by liquid chromatography UPLC. The removal rate of SMX was calculated, and the results are shown in Table 1. Figure 5

[0084] Example 2

[0085] Different from Example 1, the volume ratio of the porous hydrophobic oxygen storage layer to the hydrophilic biochar catalyst layer in the 3D-printed porous Janus biochar flow electrode of this embodiment is 1:4.

[0086] The rest is the same as Example 1, which will not be repeated here.

[0087] Example 3

[0088] Different from Example 1, the volume ratio of the porous hydrophobic oxygen storage layer to the hydrophilic biochar catalyst layer in the 3D-printed porous Janus biochar flow electrode of this embodiment is 2:5.

[0089] The rest is the same as Example 1, which will not be repeated here.

[0090] Example 4

[0091] Different from Example 1, in the preparation step S3 of the 3D-printed porous Janus biochar flow electrode of this embodiment, the mass ratio of the biochar catalyst, the aqueous crosslinking agent, the active monomer, the photoinitiator, the gelatin and the deionized water is 15:10:5:1:8:110.

[0092] The rest is the same as Example 1, which will not be repeated here.

[0093] Example 5

[0094] Different from Example 1, in the preparation step S4 of the 3D-printed porous Janus biochar flow electrode of this embodiment, the amount ratio of the dispersant to the binder is 20 mL:10 g.

[0095] The rest is the same as Example 1, which will not be repeated here.

[0096] Example 6

[0097] Different from Example 1, in the preparation step S4 of the 3D-printed porous Janus biochar flow electrode of this embodiment, the temperature of freeze-drying is-70℃, and the time is 40 h.

[0098] The rest is the same as Example 1, which will not be repeated here. ​

[0099] Example 7

[0100] Unlike Example 1, the pH of the SMX wastewater was set to 3.0, 5.0, 7.0, and 9.0 for degradation treatment. The results were obtained from... Figure 6 As shown.

[0101] The rest is the same as in Example 1, and will not be repeated here.

[0102] Comparative Example 1

[0103] Unlike Example 1, the 3D-printed porous Janus biochar flow cytometer in this comparative example does not contain a hydrophilic biochar catalyst layer. Results were obtained from... Figure 7 As shown.

[0104] The rest is the same as in Example 1, and will not be repeated here.

[0105] Comparative Example 2

[0106] Unlike Example 1, the 3D-printed porous Janus biochar flow cytometer in this comparative example does not contain a porous hydrophobic oxygen storage layer. Results were obtained from... Figure 7 As shown.

[0107] The rest is the same as in Example 1, and will not be repeated here.

[0108] Comparative Example 3

[0109] Unlike Example 1, this comparative example used applied voltages of 0, -0.2, -0.4, -0.6, and -0.8V for degradation treatment. The results were obtained from... Figure 8 As shown.

[0110] The rest is the same as in Example 1, and will not be repeated here.

[0111] Depend on Figures 4-8 Data comparison shows that when the porous Janus biochar flow cytometer electrode prepared in this application is used as the cathode for wastewater treatment, it can effectively solve the problems of poor conductivity of biochar electrode, serious catalyst shedding and agglomeration, and low dissolved oxygen transport rate of electrolyte solution.

[0112] Among them, by Figure 4 It can be seen that when the biochar loading in the hydrophilic catalyst layer is 5.00 g / cm³, 2 At that time, the H2O2 production was the highest, reaching 368.3 μmol / L, indicating that the porous Janus biochar flow cytometer of this invention can significantly increase the H2O2 production. Figure 5 It can be seen that when the biochar loading in the hydrophilic catalyst layer is 5 g / cm³, 2At this time, the removal rate of SMX is as high as 86.3%, which indicates that the porous Janus biochar flow electrode can promote the efficient removal of PPCPs pollutants. Figure 6 It can be seen that when the pH is 3.0-9.0, the removal rate of SMX is maintained at 73.8-88.3%, which indicates that the double-layer electrode has a wide pH application range. Figure 7 It can be seen that when the simple hydrophilic catalyst layer flow electrode is used as the working electrode, the removal rate of SMX is 62.8%, and when the simple hydrophobic oxygen storage layer is used as the working electrode, the removal rate of SMX is only 11.3%, which verifies that the porous cross-network structure with the hydrophobic oxygen storage layer and the hydrophilic catalyst layer cooperatively formed by 3D printing is important for improving the gas / liquid / solid three-phase interface mass transfer process and promoting the heterogeneous electro-Fenton reaction, and is more conducive to the efficient removal of SMX pollutants. Figure 8 It can be seen that when the voltage is-0.6V and-0.8V, the removal rate of SMX is as high as 88% or more, and when no voltage is applied, the removal rate of SMX is only 19.6%, which indicates that the applied voltage is conducive to promoting the efficient removal of SMX pollutants.

[0113] According to the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art on the basis of the present application all belong to the protection scope of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of description and do not constitute any limitation on the present application.

Claims

1. A method for the preparation of a 3D-printed porous Janus biochar flow electrode, characterized in that, The method comprises the following steps: Step S1, after the dry sludge particles are acidized, pyrolysis is carried out under an inert atmosphere to obtain sludge biochar, and then the sludge biochar is subjected to acid washing, centrifugation and washing until the pH is neutral, and then drying to obtain deashed biochar; Step S2, the deashed biochar and metal salt are mixed to obtain modified magnetic biochar, and then polypyrrole is used to polymerize the magnetic biochar to obtain polypyrrole-loaded magnetic biochar, and then the magnetic biochar is ground to obtain a biochar catalyst; Step S3, the biochar catalyst, aqueous crosslinking agent, active monomer, photoinitiator, gelatin and deionized water are mixed to obtain 3D printing ink I, and a hydrophilic biochar catalyst layer with a network porous structure is formed by a "rice character type” path through a photocuring printing technology; Step S4, the binder and dispersant are mixed and stirred to obtain 3D printing ink II, and a network porous hydrophobic oxygen storage layer with an equal area and a "prism square type” path is printed on the hydrophilic biochar catalyst layer by a direct ink writing printing technology to obtain a double-layer network structure printing body; Step S5, the double-layer network structure printing body is freeze-dried to obtain the 3D printed porous Janus biochar flow electrode.

2. The method of claim 1, wherein the 3D-printed porous Janus biochar flow electrode is prepared by a process comprising: The volume ratio of the porous hydrophobic oxygen storage layer to the hydrophilic biochar catalyst layer is (1-2):(3-6).

3. The method of claim 1, wherein the 3D-printed porous Janus biochar flow electrode is prepared by a process comprising: In step S1, the acid solvent for acidification and acid washing is at least one of hydrochloric acid, nitric acid, hydrofluoric acid, acetic acid and phosphoric acid, and the volume ratio of sludge biochar to acid solution during acid washing is (1-2):(5-10).

4. The method of claim 1, wherein the 3D-printed porous Janus biochar flow electrode is prepared by, In step S2, the metal salt is at least one of iron chloride, manganese chloride, copper chloride, zinc chloride and cobalt chloride, and the modification treatment is at least one of ultrasonic treatment, immersion treatment and hydrothermal treatment.

5. The method of claim 1, wherein the 3D-printed porous Janus biochar flow-by- electrode is prepared by, In step S3, the mass ratio of the biochar catalyst, aqueous crosslinking agent, active monomer, photoinitiator, gelatin and deionized water is (5-20):(6-12):(5-15):(0.5-2):(5-10):(90-110); The aqueous crosslinking agent is at least one of N,N-methylenebisacrylamide, polyethylene glycol-2-acrylate and diisocyanate, the active monomer is at least one of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid, and the photoinitiator is at least one of LAP photoinitiator, Irgacure 2100 photoinitiator and EY photoinitiator; In the photocuring printing technology, the printing nozzle diameter is 0.58-1.20 mm, the extrusion pressure is 10-40 kPa, the extrusion head and substrate temperature is 20-30℃, the printing structure design is a 3D grid, the printing body length-width-height ratio is (4-8):(4-8):(1-2), the printing line width is 2-4 mm, the printing layer number is 15-45 layers, the printing height of each layer is 0.5-1.5 mm, the printing speed is 3-7 mm / s, the ultraviolet light wavelength is 400-450 nm, and the ultraviolet light crosslinking time is 10-60 s; The specific printing path of the "rice character type” is that a square grid structure is printed alternately in an S-shaped path, and then the square vertexes are crossed to form a "rice character type” structure.

6. The method of claim 1, wherein the 3D-printed porous Janus biochar flow electrode is prepared by, In step S4, the dispersant is at least one of N-methyl pyrrolidone solvent and deionized water, and the ratio of the dispersant to the binder is (10-30) ml:(5-10) g; In the direct ink writing printing technology, the printing nozzle diameter is 0.58-1.20 mm, the extrusion pressure is 20-60 kPa, the extrusion head and the substrate temperature are 20-30 DEG C, the printing body length-width-height ratio is (4-8):(4-8):(1-2), the printing layer number is 5-15, the printing height of each layer is 0.5-1.5 mm, and the printing speed is 3-7 mm / s. The specific printing path of the "prism square type" is: first, an S-shaped path is used to alternately print a square grid structure, and then the square center points are crossed to form a "prism square type" structure.

7. The method of claim 1, wherein the 3D-printed porous Janus biochar flow electrode is prepared by, In step S5, the temperature of the freeze-drying is -80 to -70 DEG C, and the time is 20-40 h.

8. A 3D printed porous Janus biochar flow electrode, characterized in that, The 3D-printed porous Janus biochar flow electrode is prepared by the method of any one of claims 1-7.

9. Use of a 3D-printed porous Janus biochar flow electrode, characterized in that, The 3D-printed porous Janus biochar flow electrode is applied to wastewater treatment containing typical PPCPs pollutants sulfamethoxazole.

10. Use of a 3D-printed porous Janus biochar flow-by electrode according to claim 9, characterized in that, The method comprises the following steps: In step S1, the 3D-printed porous Janus biochar flow electrode is used as a cathode, a platinum sheet is used as an anode, the anode and the cathode are opposite and have equal areas, a silver-silver chloride electrode is used as a reference electrode, and simulated wastewater containing typical PPCPs pollutants sulfamethoxazole is used as an electrolyte to form a heterogeneous electro-Fenton system. In step S2, the heterogeneous electro-Fenton system is connected to an external power source, the solution after reaction is taken, the H2O2 concentration in the reaction process is determined by a potassium titanium oxalate spectrophotometric method, quantitative analysis is performed by liquid chromatography UPLC, and the removal rate of sulfamethoxazole is calculated.

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