Preparation method of composite electrode for electro-Fenton-biological adsorption coupling system

Abstract

The invention discloses a preparation method of a composite electrode for an electro-Fenton-biosorption coupling system, which comprises the following steps: by taking foam metal as a current collector matrix, firstly coating aspergillus niger spores in Fe3O4 solid powder by a water-based magnetic fluid method to prepare core-shell structure aspergillus niger spore coated Fe3O4, and then coating the Fe3O4 solid powder with the aspergillus niger spores coated Fe3O4 to prepare the composite electrode for the electro-Fenton-biosorption coupling system. And uniformly distributing the aspergillus niger spores coated with Fe3O4 in the three-dimensional porous structure of the foam metal by using a binder to obtain the novel aspergillus niger spores coated with Fe3O4 / foam metal composite electrode. The preparation is simple, convenient and controllable, the reaction system is stable, the catalyst is not required to be recycled, the subsequent pollution problem is avoided, the organic pollutant wastewater can be well degraded under the neutral condition, and the method has a good application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical water treatment, and in particular to a method for preparing a composite electrode for an electro-Fenton-biosorption coupling system. Background Art

[0002] Antibiotic-metal complexes (AMCs) are a new type of difficult-to-degrade complex organic pollutants that are widely present in various water bodies. After sewage is treated in the biochemical stage, trace amounts of antibiotics and heavy metals still remain. The structure of antibiotics contains ionizable groups (hydroxyl, amino and carboxyl, etc.) and heteroatoms such as N, O, and S that can complex with a variety of heavy metal ions. Therefore, the two can easily form chelates, which in turn causes framework delocalization and reduces the polarity of the entire chelate system, making them usually insoluble or insoluble in aqueous media, and presenting variable forms and structures under different aqueous media conditions.

[0003] At present, the treatment of AMCs mainly adopts the adsorption method. However, the molecular weight becomes larger after the combination of antibiotics and heavy metals, which brings great difficulties to physical adsorption. At the same time, there are many combinations of antibiotics and heavy metals, and the adsorption method is often selective. More importantly, AMCs are not degraded during the adsorption process, thus producing secondary pollutant materials. Advanced oxidation methods can mineralize organic macromolecules, especially the electro-Fenton method, which is driven by electricity and belongs to the "carbon neutral" green water treatment technology system. Its core is that the H2O2 generated on the electrode can indiscriminately attack organic matter to mineralize it.

[0004] The core of improving the ability of electrochemical cathode oxygen reduction to produce H2O2 is the electrode material. At present, the most studied materials are mainly carbon materials (graphite, carbon nanotubes and biomass), precious metals and transition metals and their compounds. Precious metal and transition metal materials have certain limitations due to high cost, stability and ion leaching problems. Therefore, carbon electrodes as non-metallic electrode materials have the advantages of high efficiency, greenness and environmental friendliness. At the same time, compared with materials such as graphite, carbon nanotubes or carbon fibers, biomass electrode materials are easier to prepare and cheap and easy to obtain. The core of the adsorption method to improve the adsorption efficiency lies in the adsorption material. Among many adsorption materials such as zeolite and bentonite, biomass materials have a large number of negative charges on their surfaces and functional groups that can complex heavy metals, and they are environmentally friendly and have low comprehensive costs. They have good application prospects in the treatment of large-volume and low-concentration heavy metal wastewater.

[0005] In view of the above problems, the present invention provides a method for preparing a composite electrode for an electro-Fenton-biosorption coupling system. Summary of the invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a method for preparing a composite electrode for an electro-Fenton-biosorption coupling system.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a composite electrode for an electro-Fenton-biosorption coupling system, comprising the following steps:

[0009] S1, solid phase fermentation to culture Aspergillus niger spores;

[0010] S2, encapsulating the Aspergillus niger spores in Fe3O4 solid powder by a water-based flow magnet method to prepare an Aspergillus niger spore@Fe3O4 core-shell structure;

[0011] S3. Use a binder to evenly distribute the prepared Aspergillus niger spore@Fe3O4 core-shell structure in the three-dimensional porous structure of the foam metal to obtain an Aspergillus niger spore@Fe3O4 / foam metal composite electrode.

[0012] Furthermore, the S1 specifically includes the following steps:

[0013] S11, activating the Aspergillus niger strain into a modified Martin liquid medium and coating the plate with the seed liquid;

[0014] S12. After the seed solution is applied to the plate, it is inverted and cultured in a biochemical incubator at 28°C. Spores are harvested after five days.

[0015] Furthermore, in step S11, the modified Martin liquid culture medium includes 5g of peptone, 1g of yeast powder, 20g of glucose, 1g of KH2PO4 and 0.5g of MgSO4, and 2% of agar powder is added to the modified Martin liquid culture medium to prepare a seed liquid coating plate.

[0016] Furthermore, the S2 specifically includes the following steps:

[0017] S21. Dissolve 6.1 g of ferric chloride FeCl3·6H2O and 4.2 g of ferrous sulfate FeSO4·7H2O in 100 ml of ultrapure water, then quickly add 10 mL of 25% NH3·H2O to the solution, heat to 90°C and stir continuously for 30 min, and cool to room temperature;

[0018] S22, collecting the generated black precipitate by filtering, washing and drying, preparing a 5% water-based magnetic fluid, dropping it into a glacial acetic acid solution to form a uniform dispersion system, adding 0.1 g of spores to the magnetic Fe3O4 particle dispersion solution, and then shaking at 30°C for 24 hours;

[0019] S23, magnetic Fe3O4 particles and spores form black solid particles under the action of polar solvents, which are collected through magnetic separation, washing and drying processes, and the obtained black particles are Aspergillus niger spores@Fe3O4.

[0020] Furthermore, the Aspergillus niger spores are small spheres with a diameter of 2 μm, a large specific surface area, and ordered micro-mesopores on the surface. The contents of C, N, O and P in the Aspergillus niger spores are 62%, 10.5%, 22.8% and 3% respectively, and the spores also contain a large number of oxygen-containing functional groups and CN bonds.

[0021] Furthermore, the S3 specifically includes the following steps:

[0022] S31, ultrasonically treating the foamed metal in acetone for 30 min, and then washing with distilled water and drying for later use;

[0023] S32. Weigh 2.5 g of biomass and 2 mL of binder and disperse them in 20 mL of ethanol. After ultrasonic dispersion for 20 min, heat at 80° C. to form a uniform paste, and then press it onto a 10 cm×5 cm foam metal with a roller press to obtain an Aspergillus niger spore@Fe3O4 / foam metal cathode.

[0024] Furthermore, in step S31, the foam metal is foam nickel, foam copper or foam iron, the thickness of the foam metal is 4 mm, and the porosity is 98%.

[0025] Furthermore, in step S32, the binder is polytetrafluoroethylene, sodium carboxymethyl cellulose or polyacrylic acid.

[0026] Based on the above technical solution, the embodiments of the present invention can at least produce the following technical effects:

[0027] (1) The preparation method of the composite electrode provided by the present invention utilizes the natural properties of microorganisms to construct a highly active 2e-ORR electrode material. The micropores (0-4nm) on the surface of Aspergillus niger spores can enhance the mass transfer of oxygen, and the self-doping properties of heteroatoms (N, P) can improve the selectivity of 2e-ORR, thereby enhancing the production of ·OH by the active material from the perspectives of mass transfer and reaction. The Aspergillus niger spores@Fe3O4 / foam metal synthesized after being composited with Fe3O4 / foam metal is a heterogeneous electro-Fenton composite cathode, which can effectively produce H2O2.

[0028] (2) The preparation method of the composite electrode provided by the present invention can realize Fe 2+ with Fe 3+ The redox of Fe 2+As an electron donor, it can effectively catalyze the electro-Fenton reaction. In addition, if solid Fe3O4 is prepared into a water-based magnetic fluid to wrap the Aspergillus niger spores, it can not only serve as a protective layer to reduce the impact of gas, water and current on the Aspergillus niger spore clusters, but also become a "bond" between the current collector and the Aspergillus niger spores, directing the current to the spore surface. In addition, foamed metal (iron, copper, nickel, etc.) materials are ideal current collectors that can reduce the resistance of current and electrons during the transmission process. Their three-dimensional open structure and porosity not only provide a large specific surface area to increase active sites, but also facilitate the transmission of O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0030] Figure 1 This is a schematic diagram of the Aspergillus niger spore preparation process of the present invention;

[0031] Figure 2 This is a schematic diagram of the nano- and micro-scale structure of Aspergillus niger spores, a highly active 2e-ORR electrode material of the present invention;

[0032] Figure 3 This is a schematic diagram of the spore preparation method / spore structure analysis process of the present invention;

[0033] Figure 4 It is a schematic diagram of the process of producing H2O2 at the anode and cathode of Aspergillus niger spores of the present invention. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] The present invention provides a method for preparing a composite electrode for an electro-Fenton-biosorption coupling system. Figure 1 As shown, the following steps are included:

[0036] S1, solid phase fermentation to culture Aspergillus niger spores;

[0037] The Aspergillus niger strain (strain number: Aspergillus niger CMCC98003) purchased from the China Medical Culture Collection Center (CMCC) was activated into a modified Martin liquid medium (formula: 5g peptone, 1g yeast powder, 20g glucose, 1g KH2PO4, 0.5g MgSO4) as a seed solution for coating plates. The plate was prepared by adding agar powder (2% addition) to the modified Martin liquid medium. After 2ml of the seed solution was applied to the plate, it was inverted and cultured in a biochemical incubator at 28°C, and spores were harvested after five days.

[0038] S2, encapsulating the Aspergillus niger spores in Fe3O4 solid powder by a water-based flow magnet method to prepare an Aspergillus niger spore@Fe3O4 core-shell structure;

[0039] The specific method is as follows: ferric chloride FeCl3·6H2O (6.1 g) and ferrous sulfate FeSO4·7H2O (4.2 g) are dissolved in 100 ml of ultrapure water, and then 10 mL of NH3·H2O (25%) is quickly added to the solution, heated to 90°C and stirred continuously for 30 min, cooled to room temperature, and the generated black precipitate is collected by filtration, washing and drying to prepare a 5% water-based magnetic fluid, which is dropped into a glacial acetic acid solution to form a uniform dispersion system (6 ml), and then 0.1 g of spores are added to the magnetic Fe3O4 particle dispersion solution, and then shaken at 30°C for 24 h. The magnetic Fe3O4 particles and spores form black solid particles under the action of a polar solvent (HAc), which are collected through a magnetic separation, washing and drying process, and the obtained black particles are Fe3O4@Aspergillus niger spores.

[0040] S3, using a binder to evenly distribute the prepared Aspergillus niger spore@Fe3O4 core-shell structure in the three-dimensional porous structure of the foam metal to obtain an Aspergillus niger spore@Fe3O4 / foam metal composite electrode;

[0041] Taking the roller pressing method and the preferred foam metal as an example, an Aspergillus niger spore composite cathode is constructed: foam nickel, foam copper, and foam iron (thickness 4 mm, porosity 98%) are ultrasonically treated in acetone for 30 minutes, respectively, and then washed with distilled water and dried for standby use to remove grease and organic matter on the surface; 2.5 g of biomass and 2 mL of PTFE (60%, wt) are weighed and dispersed in 20 mL of ethanol, and after ultrasonic dispersion for 20 minutes, the mixture is heated at 80°C to form a uniform paste, and then pressed onto a 10 cm×5 cm foam metal with a roller press to obtain a Fe3O4@Aspergillus niger spore / foam metal cathode, and the dosage of a binder such as polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC) or polyacrylic acid (PAA) is similar.

[0042] Compared with the prior art, the present invention utilizes the natural properties of microorganisms to construct a highly active 2e-ORR electrode material. The schematic diagram of the nano-microscale structure of the highly active 2e-ORR electrode material-Aspergillus niger spores is shown in FIG. Figure 2 As shown in the figure, the micropores (0-4nm) on the surface of Aspergillus niger spores can enhance the mass transfer of oxygen, and the self-doping properties of heteroatoms (N, P) can improve the selectivity of 2e-ORR, and enhance the production of ·OH from the two perspectives of mass transfer and reaction. The Aspergillus niger spores@Fe3O4 / foam metal synthesized after being composited with Fe3O4 / foam metal belongs to a heterogeneous electro-Fenton composite cathode, which can effectively produce H2O2.

[0043] like Figure 3 As shown, the Aspergillus niger spores prepared by the above steps are small spheres with a diameter of 2 μm, a large specific surface area, and ordered micro-mesopores on the surface; the contents of C, N, O and P in the Aspergillus niger spores are 62%, 10.5%, 22.8% and 3%, respectively, which can effectively realize self-doping of elements with high N content, and the spores contain a large number of oxygen-containing functional groups such as -OH, -COOH, CO and CN bonds.

[0044] like Figure 4 As shown, the electron transfer number of Aspergillus niger spores catalyzing the cathode is 2.8, and the H2O2 selectivity is 80%, indicating that Aspergillus niger spores are more inclined to catalyze the 2e-ORR process. In addition, Aspergillus niger spores can also be used as anodes to produce H2O2.

[0045] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a composite electrode for an electro-Fenton-biosorption coupling system, characterized in that: The following steps are involved: S1, solid phase fermentation to culture Aspergillus niger spores; S2, encapsulating the Aspergillus niger spores in Fe3O4 solid powder by a water-based flow magnet method to prepare an Aspergillus niger spore@Fe3O4 core-shell structure; S3. Use a binder to evenly distribute the prepared Aspergillus niger spore@Fe3O4 core-shell structure in the three-dimensional porous structure of the foam metal to obtain an Aspergillus niger spore@Fe3O4 / foam metal composite electrode.

2. The method for preparing a composite electrode for an electro-Fenton-biosorption coupling system according to claim 1, characterized in that: The S1 specifically includes the following steps: S11, activating the Aspergillus niger strain into a modified Martin liquid medium and coating the plate with the seed liquid; S12. After the seed solution is applied to the plate, it is inverted and cultured in a biochemical incubator at 28°C. After five days, Aspergillus niger spores are harvested.

3. The method for preparing a composite electrode for an electro-Fenton-biosorption coupling system according to claim 2, characterized in that: In step S11, the modified Martin liquid culture medium includes 5g of peptone, 1g of yeast powder, 20g of glucose, 1g of KH2PO4 and 0.5g of MgSO4, and 2% of agar powder is added to the modified Martin liquid culture medium to prepare a seed solution for coating a plate.

4. The method for preparing a composite electrode for an electro-Fenton-biosorption coupling system according to claim 2, characterized in that: The Aspergillus niger spore is a small ball with a diameter of 2 μm, a large specific surface area, and ordered micro-mesopores on the surface. The contents of C, N, O and P in the Aspergillus niger spore are 62%, 10.5%, 22.8% and 3% respectively, and the spore also contains a large number of oxygen-containing functional groups and CN bonds.

5. The method for preparing a composite electrode for an electro-Fenton-biosorption coupling system according to claim 1, characterized in that: The S2 specifically includes the following steps: S21. Dissolve 6.1 g of ferric chloride FeCl3·6H2O and 4.2 g of ferrous sulfate FeSO4·7H2O in 100 ml of ultrapure water, then quickly add 10 mL of 25% NH3·H2O to the solution, heat to 90°C and stir continuously for 30 min, and cool to room temperature; S22, collecting the generated black precipitate by filtering, washing and drying, preparing a 5% water-based magnetic fluid, dropping it into a glacial acetic acid solution to form a uniform dispersion system, adding 0.1 g of spores to the magnetic Fe3O4 particle dispersion solution, and then shaking at 30°C for 24 hours; S23, magnetic Fe3O4 particles and spores form black solid particles under the action of polar solvents, which are collected through magnetic separation, washing and drying processes, and the obtained black particles are Aspergillus niger spores@Fe3O4.

6. The method for preparing a composite electrode for an electro-Fenton-biosorption coupling system according to claim 1, characterized in that: The S3 specifically includes the following steps: S31, ultrasonically treating the foamed metal in acetone for 30 min, and then washing with distilled water and drying for later use; S32. Weigh 2.5 g of biomass and 2 mL of binder and disperse them in 20 mL of ethanol. After ultrasonic dispersion for 20 min, heat at 80° C. to form a uniform paste, and then press it onto a 10 cm×5 cm foam metal with a roller press to obtain an Aspergillus niger spore@Fe3O4 / foam metal cathode.

7. The method for preparing a composite electrode for an electro-Fenton-biosorption coupling system according to claim 6, characterized in that: In step S31, the foam metal is foam nickel, foam copper or foam iron, the thickness of the foam metal is 4 mm, and the porosity is 98%.

8. The method for preparing a composite electrode for an electro-Fenton-biosorption coupling system according to claim 6, characterized in that: In step S32, the binder is polytetrafluoroethylene, sodium carboxymethyl cellulose or polyacrylic acid.

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