Electrode for electrochemical degradation of biomass wastewater and preparation method and application thereof

Abstract

The application discloses an electrode for electrochemical degradation of biomass wastewater and a preparation method and application thereof, and the preparation method of the electrode comprises the following steps: performing surface oxidation pretreatment on a planar boron-doped diamond electrode; adding a mixed solution of a metal salt and a precipitant into a reaction kettle to perform a hydrothermal reaction on the pretreated boron-doped diamond electrode, so that a metal layer is uniformly grown on the surface of the electrode; placing the metal / boron-doped diamond electrode into a tube furnace, introducing hydrogen gas, and performing high-temperature etching under the catalysis of the metal, so that a metal / porous boron-doped diamond electrode is obtained after cooling; and soaking the metal / porous boron-doped diamond electrode in strong acid to obtain a porous boron-doped diamond electrode. The planar boron-doped diamond electrode is used as a basis, a metal layer is grown on the surface of the boron-doped diamond electrode by using a hydrothermal method, and a porous boron-doped diamond electrode with excellent performance is prepared through high-temperature hydrogen etching technology, so that the active area of the electrode is effectively increased, the anodic oxidation efficiency is improved, and biomass chemical wastewater can be efficiently degraded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electro-catalysis biomass, and particularly relates to an electrode for electrochemical degradation of biomass wastewater and a manufacturing method and application thereof. BACKGROUND

[0002] With the increasing demand for green environmental protection, new biomass materials gradually attract people's attention, and the biomass chemical industry develops rapidly. Biomass resources can be converted into various high-value biomass compounds, such as 5-hydroxymethylfurfural (HMF) and 2,5-furan dicarboxylic acid (FDCA), through catalytic conversion processes such as hydrolysis and isomerization. However, the rapid rise of the industry and the expansion of the industrial production line can also lead to environmental problems. Biomass products are usually extracted during the production process, but the extraction rate cannot reach 100%, and a part of the biomass chemicals are still dissolved in the wastewater. These organic matters in the chemical wastewater enter the aquatic system, causing serious water pollution, and ultimately endangering human life safety. Therefore, the research on effective degradation of biomass chemical wastewater is of great significance.

[0003] As a clean, effective and environmentally friendly water treatment technology, the anodic oxidation method in electrochemical oxidation technology can realize the complete conversion of organic matter into CO2, H2O and other substances under the action of electric current. The efficiency and selectivity of anodic oxidation are greatly influenced by the properties of the anode material. Boron-doped diamond (BDD) electrode has excellent mechanical properties, high oxygen evolution potential, wide potential window, extremely low background current, good stability, corrosion resistance and no metal pollution, and is an ideal anode material. However, the surface of the existing boron-doped diamond electrode is mostly smooth and planar, and the active area of the electrode is limited, which also limits the efficiency of anodic oxidation. SUMMARY

[0004] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is how to increase the active area of the boron-doped diamond electrode and improve the efficiency of anodic oxidation.

[0005] To solve the above technical problems, the present application provides a preparation method of an electrode for electrochemical degradation of biomass wastewater, comprising the following steps:

[0006] S1, performing surface oxidation pretreatment on a planar boron-doped diamond electrode;

[0007] S2, adding a mixed solution of the pretreated boron-doped diamond electrode, metal salt and precipitant into a reaction kettle for hydrothermal reaction, so as to uniformly grow a metal layer on the surface of the electrode;

[0008] S3, placing the metal / boron-doped diamond electrode into a tube furnace, introducing hydrogen gas for high-temperature etching, and cooling to obtain a metal / porous boron-doped diamond electrode;

[0009] S4, soaking the metal / porous boron-doped diamond electrode in strong acid to obtain the porous boron-doped diamond electrode.

[0010] The present application takes a planar boron-doped diamond electrode as a basis, grows a metal layer on the surface of the boron-doped diamond electrode by using a hydrothermal method, and then prepares a porous boron-doped diamond electrode with excellent performance by using a high-temperature hydrogen etching technology, thereby effectively increasing the active area of the electrode, improving the anodic oxidation efficiency, and efficiently degrading biomass chemical wastewater.

[0011] In the preferred or optional embodiment, the heating temperature in step S2 is 90-140 DEG C, and the heating time is 8-16 h. Limiting the temperature and time of the hydrothermal reaction can obtain a metal layer with small and uniformly distributed crystal grains, which is convenient for subsequent etching.

[0012] In the preferred or optional embodiment, in step S2, the concentration of the metal salt in the mixed solution of the metal salt and the precipitant is 10-40 mM, the concentration of the precipitant is 10-40 mM, and the concentration ratio of the metal salt to the precipitant is 1:1-2. The precipitant promotes the formation of a complex of metal ions and is precipitated onto the surface of the electrode. Then, the complex is converted into metal hydroxide or oxide by hydrothermal conversion. Generally, the ratio of the metal ion to the organic ligand when forming the complex is 1:1, and therefore, the concentration of the precipitant is excessive or equal to that of the metal salt.

[0013] In the preferred or optional embodiment, the metal salt is selected from one or more of ferric nitrate, ferric sulfate, ferric chloride, ferric acetate, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, nickel nitrate, nickel sulfate, nickel chloride, and nickel acetate, and the precipitant is selected from one or more of hexamethylenetetramine, urea, and ethylenediaminetetraacetic acid.

[0014] In the preferred or optional embodiment, step S3 specifically comprises the following steps: placing the metal / boron-doped diamond electrode into a tube furnace, introducing an inert gas, and heating at a temperature increasing rate of 5-15 DEG C / min to 850-950 DEG C, and maintaining the temperature for 10-60 min. Hydrogen gas is introduced at the beginning of the temperature maintaining process, the flow rate of the inert gas remains unchanged, the hydrogen gas flow is cut off after the temperature maintaining process is completed, and the electrode is naturally cooled. In the case of pure inert gas, etching reaction also occurs, although the reaction is very slow. A too slow temperature increasing rate leads to a too long heating time, which may increase the etching degree and cause damage to the surface of the electrode. The temperature maintaining temperature and time are important conditions for the etching reaction. A too low temperature cannot perform etching, a too high temperature causes excessive etching, a too short temperature maintaining time causes a shallow etching degree and a small performance improvement, and a long temperature maintaining time causes a deep etching degree and serious damage to the surface of the electrode, which seriously affects the performance.

[0015] In the preferred or optional embodiment, in step S3, the flow rate of the inert gas is 20-60 mL·min -1, hydrogen flow rate is 20~60mL·min -1 The flow rate ratio of inert gas to hydrogen is 1 to 2:1. Hydrogen is a reactant in the diamond etching reaction. Surface metal hydroxides or oxides are reduced by hydrogen to form metal particles, which catalyze hydrogen etching of the electrode surface. The gas flow rate can control the sufficient amount of hydrogen in the reaction. The inert gas mainly assists in etching and isolates oxygen, and its flow rate is coordinated with the hydrogen.

[0016] In a preferred or optional embodiment, in step S4, the strong acid is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and concentrated nitric acid, and the soaking time is 12 to 24 hours. The soaking time is limited to ensure that the metal is completely reacted with the strong acid.

[0017] In a preferred or optional embodiment, step S1 specifically includes:

[0018] S11, the planar boron-doped diamond electrode was subjected to constant current oxidation in the electrolyte for 20 to 60 minutes at a current of 50 to 70 mA;

[0019] S12, ultrasonically cleaning the oxidized electrode sheet with water and ethanol in sequence;

[0020] S13. Soak the cleaned electrode sheets in concentrated nitric acid for 20 to 40 minutes.

[0021] The surface of commercial boron-doped diamond electrodes usually has an attached carbon deposit layer, which is removed by constant current oxidation; water and ethanol cleaning removes residual inorganic and organic pollutants on the surface; concentrated nitric acid treatment can change the hydrophobicity of the electrode surface, making the electrode surface hydrophilic, which facilitates better growth of the metal layer.

[0022] A second aspect of the present invention provides an electrode for electrochemical degradation of biomass wastewater, produced by the aforementioned preparation method. The electrode surface is provided with a plurality of pores, each 50 to 500 nm in size. The method of the present invention forms a large number of pores on the surface of the boron-doped diamond electrode, thereby increasing the active area of ​​the electrode and significantly improving its electrical conductivity while retaining its other excellent properties.

[0023] A second aspect of the present invention provides the use of the aforementioned electrode to degrade biomass wastewater containing furanic compounds under the oxidative action of the electrode, mineralizing the organic matter into carbon dioxide. The electrode prepared by the present invention can be used for electrochemical degradation of biomass wastewater, thereby improving degradation efficiency and reducing energy consumption.

[0024] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention uses a hydrothermal method combined with a thermal etching method to process a planar boron-doped diamond electrode. The operation is simple and repeatable. The metal particle size and pore size are controllable, and a porous boron-doped diamond electrode with a large number of nanoscale pores distributed on the surface can be prepared.

[0026] (2) The preparation method of the present invention etches only the surface of the boron-doped diamond electrode, thereby increasing the active area of ​​the electrode and retaining the excellent performance of the boron-doped diamond electrode.

[0027] (3) The electrical conductivity of porous boron-doped diamond electrodes has been significantly improved, which can improve the degradation efficiency of biomass wastewater while reducing energy consumption, and has good prospects for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a microscopic morphology of the planar boron-doped diamond electrode in Example 1 of the present invention.

[0029] Figure 2 This is a microscopic morphology of the nickel / boron-doped diamond electrode in Example 1 of the present invention.

[0030] Figure 3 This is a microscopic morphology of the nickel / porous boron-doped diamond electrode in Example 1 of the present invention.

[0031] Figure 4 This is a microscopic morphology of the porous boron-doped diamond electrode in Example 1 of the present invention.

[0032] Figure 5 4 is an LSV curve diagram of the electrodes of Example 1 and Comparative Example 1 in Example 4 of the present invention.

[0033] Figure 6 This is a statistical curve diagram of the substrate removal rate and the chemical oxygen demand removal rate during the electrolysis process using the electrode prepared in Example 1 as the anode in Example 5 of the present invention.

[0034] Figure 7 This is a statistical curve diagram of the chemical oxygen demand removal rate in the electrolysis process using the electrodes of Example 1 and Comparative Example 1 as anodes in Example 6 of the present invention.

[0035] Figure 8 This is a statistical curve diagram of the chemical oxygen demand removal rate in the electrolysis process using the electrode of Example 2 as the anode in Example 7 of the present invention. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The present description and examples are intended to be illustrative only.

[0039] A specific embodiment of the present invention provides an electrode for electrochemical degradation of biomass wastewater, which is prepared by the following method:

[0040] S1. Pre-treating the surface of the planar boron-doped diamond electrode by surface oxidation.

[0041] The specific steps of pretreatment include: constant current oxidation of the planar boron-doped diamond electrode in an electrolyte with a current of 50 to 70 mA for 20 to 60 minutes, and the electrolyte is sulfuric acid and / or sodium sulfate, and the carbon deposit layer attached to the surface of the boron-doped diamond electrode is removed by constant current oxidation; the oxidized electrode sheet is ultrasonically cleaned with water and ethanol in turn to remove inorganic and organic pollutants remaining on the surface; the cleaned electrode sheet is soaked in concentrated nitric acid for 20 to 40 minutes. The concentrated nitric acid treatment can change the hydrophobicity of the electrode surface, making the electrode surface hydrophilic, which facilitates the subsequent better growth of the metal layer.

[0042] S2. Adding the boron-doped diamond electrode pretreated in step S1 and a mixed solution of metal salt and precipitant into a reactor to carry out a hydrothermal reaction, thereby uniformly growing a metal layer on the surface of the electrode.

[0043] In a specific embodiment, in the mixed solution of metal salt and precipitant, the concentration of metal salt is 10-40 mM, the concentration of precipitant is 10-40 mM, and the concentration ratio of metal salt to precipitant is 1:1-2; the metal salt is ferric nitrate, ferric sulfate, ferric chloride, ferric acetate, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, nickel nitrate, nickel sulfate, nickel chloride, nickel acetate, etc., and the precipitant is hexamethylenetetramine, urea, ethylenediaminetetraacetic acid, etc. The precipitant can promote the metal ions to form a complex and precipitate on the electrode surface, and then the complex is converted into a metal hydroxide or oxide by hydrothermal conversion, and a metal layer is uniformly grown on the electrode surface.

[0044] In specific embodiments, the heating temperature of the hydrothermal reaction is 90-140 DEG C, the heating time is 8-16 h, and a metal layer with small and uniformly distributed crystal grains is obtained, facilitating subsequent etching.

[0045] S3, the metal / boron-doped diamond electrode prepared in step S2 is placed in a tube furnace, hydrogen gas is introduced for high-temperature etching, and a metal / porous boron-doped diamond electrode is obtained after cooling.

[0046] The high-temperature hydrogen etching step specifically comprises the following steps: the metal / boron-doped diamond electrode is placed in a tube furnace, inert gas is introduced, and the temperature is raised to 850-950 DEG C at a temperature raising rate of 5-15 DEG C / min, the temperature is kept for 10-60 min, hydrogen gas is introduced at the beginning of the temperature keeping, the flow rate of the inert gas remains unchanged, the hydrogen gas flow is cut off after the temperature keeping ends, and natural cooling is performed.

[0047] In specific embodiments, the flow rate of the inert gas is 20-60 mL·min -1 , the flow rate of the hydrogen gas is 20-60 mL·min -1 , the flow rate ratio of the inert gas to the hydrogen gas is 1-2:1, and the flow rate of the gas is controlled to ensure sufficient hydrogen gas in the reaction.

[0048] S4, the metal / porous boron-doped diamond electrode prepared in step S3 is soaked in strong acid to obtain a porous boron-doped diamond electrode.

[0049] In specific embodiments, the strong acid is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid and concentrated nitric acid, and the soaking time is 12-24 h, so that the metal is completely reacted with the strong acid.

[0050] The above method uses a planar boron-doped diamond electrode as a basis, grows a metal layer on the surface of the boron-doped diamond electrode by using a hydrothermal method, and combines a high-temperature hydrogen etching technology to prepare a porous boron-doped diamond electrode with excellent performance. The porous boron-doped diamond electrode has multiple pores on the surface, the size of the pores is 50-500 nm, the active area of the electrode is effectively increased, the anodic oxidation efficiency is improved, and the biomass chemical wastewater can be efficiently degraded.

[0051] The above preparation method is simple in operation, high in repeatability, controllable in the particle size of the metal particles and the size of the pores, and can etch the surface of the electrode while retaining the excellent performance of the boron-doped diamond electrode.

[0052] Another embodiment of the present application provides an application of the above porous boron-doped diamond electrode. Biomass wastewater containing furan compounds is used as a solution, and the porous boron-doped diamond electrode is used as a working electrode to perform a constant-voltage electrolysis reaction.

[0053] In specific embodiments, the constant-voltage electrolysis reaction conditions are as follows: the reaction voltage is 5-6 V, and the reaction time is 2.5 h-7 h.

[0054] In some embodiments, the furan compound is selected from one or more of furan, furfural, 2,5-furan dimethanol, 5-hydroxymethylfurfural, 5-hydroxymethyl-2-furancarboxylic acid, 2,5-furan dicarboxylic acid, 5-formyl-2-furancarboxylic acid.

[0055] Compared with the flat boron-doped diamond electrode, the porous boron-doped diamond electrode has obvious improvement in conductivity, can improve the degradation efficiency of biomass wastewater, reduce energy consumption, and has good industrial popularization prospect.

[0056] The technical effects of the present application are described below in combination with specific embodiments.

[0057] Embodiment 1

[0058] (1) The micro-morphology of the flat boron-doped diamond electrode as a raw material is as shown in FIG. 1. The flat boron-doped diamond electrode was subjected to constant current oxidation in sulfuric acid for 30 min, with a current of 50 mA; and then sequentially ultrasonically cleaned with water and ethanol for 10 min; and then immersed in concentrated nitric acid for 40 min, washed with deionized water, and naturally air-dried. Figure 1

[0059] (2) A 50 mL mixed solution of 20 mM nickel sulfate and 40 mM hexamethylenetetramine was prepared, and the flat boron-doped diamond electrode and the solution were placed in a 100 mL hydrothermal reactor, and reacted at 120℃ for 10 h. The electrode was taken out, washed with ethanol and deionized water, and naturally dried to obtain a nickel / boron-doped diamond electrode. The micro-morphology of the nickel / boron-doped diamond electrode after hydrothermal treatment is as shown in FIG. 2, and a nickel layer uniformly grew on the surface of the electrode. Figure 2

[0060] (3) The nickel / boron-doped diamond electrode was placed in a tube furnace, the nitrogen flow rate was adjusted to 40 mL·min -1 , the tube furnace was set to have a temperature rising rate of 10℃·min -1 to rise to 850℃, and was kept at this temperature for 0.5 h. Hydrogen gas was introduced at a flow rate of 40 mL·min -1 at the beginning of the heat preservation, the nitrogen flow rate remained unchanged, the hydrogen flow was cut off after the heat preservation ended, and then the nickel / multi-porous boron-doped diamond electrode was obtained by natural cooling. The micro-morphology of the nickel / multi-porous boron-doped diamond electrode is as shown in FIG. 3, and a large number of pores were formed on the surface of the electrode. Figure 3

[0061] (4) The nickel / multi-porous boron-doped diamond electrode was immersed in concentrated hydrochloric acid for 12 h, washed with ethanol and deionized water, and dried to obtain a multi-porous boron-doped diamond electrode. The micro-morphology of the multi-porous boron-doped diamond electrode is as shown in FIG. 4. Figure 4

[0062] Embodiment 2

[0063] ​​​​(1) The planar boron-doped diamond electrode was subjected to constant current oxidation in sodium sulfate for 60 min at a current of 50 mA; sequentially washed with water and ethanol for 10 min by ultrasonic cleaning; then soaked in concentrated nitric acid for 40 min, washed with deionized water, and naturally air-dried.

[0064] (2) A 50 mL mixed solution of 40 mM cobalt sulfate and 40 mM urea was prepared, and the planar boron-doped diamond electrode and the solution were placed in a 100 mL hydrothermal reactor, and reacted at 90℃ for 8 h. After the electrode was taken out, it was washed with ethanol and deionized water and naturally dried to obtain a cobalt / boron-doped diamond electrode.

[0065] (3) The cobalt / boron-doped diamond electrode was placed in a tube furnace, the nitrogen flow rate was adjusted to 20 mL·min -1 , the tube furnace was set to a temperature rising rate of 10℃·min -1 to 900℃, and was kept for 1 h. Hydrogen gas was introduced at a flow rate of 20 mL·min -1 at the beginning of the heat preservation, the nitrogen flow remained unchanged, the hydrogen flow was cut off after the heat preservation ended, and then the natural cooling was performed to obtain a cobalt / porous boron-doped diamond electrode.

[0066] (4) The cobalt / porous boron-doped diamond electrode was soaked in concentrated hydrochloric acid for 12 h, washed with ethanol and deionized water, and dried to obtain a porous boron-doped diamond electrode.

[0067] Example 3

[0068] (1) The planar boron-doped diamond electrode was subjected to constant current oxidation in sodium sulfate for 20 min at a current of 70 mA; sequentially washed with water and ethanol for 10 min by ultrasonic cleaning; then soaked in concentrated nitric acid for 40 min, washed with deionized water, and naturally air-dried.

[0069] (2) A 50 mL mixed solution of 20 mM iron sulfate and 20 mM ethylenediaminetetraacetic acid was prepared, and the planar boron-doped diamond electrode and the solution were placed in a 100 mL hydrothermal reactor, and reacted at 140℃ for 16 h. After the electrode was taken out, it was washed with ethanol and deionized water and naturally dried to obtain an iron / boron-doped diamond electrode.

[0070] (3) The iron / boron-doped diamond electrode was placed in a tube furnace, the nitrogen flow rate was adjusted to 40 mL·min -1 , the tube furnace was set to a temperature rising rate of 10℃·min -1 to 950℃, and was kept for 0.5 h. Hydrogen gas was introduced at a flow rate of 40 mL·min -1 at the beginning of the heat preservation, the nitrogen flow remained unchanged, the hydrogen flow was cut off after the heat preservation ended, and then the natural cooling was performed to obtain an iron / porous boron-doped diamond electrode.

[0071] (4) The iron / porous boron-doped diamond electrode was immersed in concentrated hydrochloric acid for 12 hours, rinsed with ethanol and deionized water, and then dried to obtain a porous boron-doped diamond electrode.

[0072] Comparative Example 1

[0073] A planar boron-doped diamond electrode was used as a comparative example.

[0074] Example 4

[0075] (1) The porous boron-doped diamond electrode prepared in Example 1 and the planar boron-doped diamond electrode prepared in Comparative Example 1 were respectively installed on an electrochemical workstation as anodes. 20 mL of 0.1 M Na2SO4 solution was used as the electrolyte. A titanium sheet was used as the counter electrode, and a silver-silver chloride electrode was used as the reference electrode. The area of ​​the catalyst immersed in the electrolyte was 2 × 1 cm 2 and stirred with a magnetic stirrer at a speed of 200 rpm.

[0076] (2) The LSV curve was obtained using the linear scanning method of the electrochemical workstation with a scanning rate of 5 mV / s and a scanning range of 1.0 to 3.0 V. Figure 5 As shown, it can be seen that the conductive performance of the porous boron-doped diamond electrode is significantly improved compared with the planar boron-doped diamond electrode.

[0077] Example 5

[0078] (1) 5-HMF was added to 150 mL of 0.1 M Na2SO4 electrolyte as a model pollutant. The concentration of 5-HMF was 500 mg·L -1 .

[0079] (2) Take a piece of porous boron-doped diamond electrode prepared in Example 1 as the anode and a titanium sheet as the cathode, and assemble them into a two-electrode system without a diaphragm with the above electrolyte. The area of ​​the electrodes immersed in the electrolyte is 2×2 cm 2 , using magnetic stirring at a speed of 200 rpm.

[0080] (3) The working voltage was set to 6V, and the electrolysis was carried out for 2.5 hours. The removal rate of 5-hydroxymethylfurfural and chemical oxygen demand during the electrolysis process were calculated. The results are as follows: Figure 6 As shown in the figure, the final 5-HMF removal rate was 94.20% and the chemical oxygen demand removal rate was 55.57%.

[0081] Example 6

[0082] (1) 5-HMF was added to 150 mL of 0.1 M Na2SO4 electrolyte as a model pollutant. The concentration of 5-HMF was 1000 mg·L -1 .

[0083] (2) Take a porous boron-doped diamond electrode prepared in Example 1 and a planar boron-doped diamond electrode prepared in Comparative Example 1 as the anode, and a titanium sheet as the cathode, and assemble them into a diaphragm-free double-electrode system with the above electrolyte. The area of ​​the electrodes immersed in the electrolyte is 2×2 cm 2 , using magnetic stirring at a speed of 200 rpm.

[0084] (3) The working voltage was set to 6V and the electrolysis was carried out for 4 hours. During the process, the chemical oxygen demand removal rate curves of the two electrodes as anodic oxidation were calculated. The results are as follows: Figure 7 As shown, the chemical oxygen demand removal rate corresponding to the electrode of Example 1 reaches 68.43%, and the chemical oxygen demand removal rate corresponding to the electrode of Comparative Example 1 is 62.99%. It can be seen that the porous boron-doped diamond electrode has a higher biomass wastewater degradation efficiency.

[0085] Example 7

[0086] (1) 5-HMF was added to 150 mL of 0.1 M Na2SO4 electrolyte as a model pollutant. The concentration of 5-HMF was 500 mg·L -1 .

[0087] (2) A porous boron-doped diamond electrode prepared in Example 2 was used as the anode, and a titanium sheet was used as the cathode. The electrodes were assembled into a two-electrode system without a diaphragm and the electrolyte was prepared. The area of ​​the catalyst immersed in the electrolyte was 2 × 2 cm. 2 , using magnetic stirring at a speed of 200 rpm.

[0088] (3) The working voltage is set to 6V and the electrolysis is performed for 7 hours. The chemical oxygen demand removal rate curve during the electrolysis process is as follows: Figure 8 As shown, 94.87% was reached at the end of electrolysis.

[0089] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing an electrode for electrochemical degradation of biomass wastewater, characterized in that: The following steps are involved: S1, pre-treating the planar boron-doped diamond electrode by electrochemical constant current surface oxidation; S2. Adding the pretreated boron-doped diamond electrode and a mixed solution of a metal salt and a precipitant into a reactor for hydrothermal reaction to uniformly grow a metal layer on the electrode surface, the heating temperature is 90-140° C., and the heating time is 8-16 hours. The metal salt is selected from one or more of ferric nitrate, ferric sulfate, ferric chloride, ferric acetate, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate, nickel nitrate, nickel sulfate, nickel chloride, and nickel acetate. The precipitant is selected from one or more of hexamethylenetetramine, urea, and ethylenediaminetetraacetic acid. S3. Place the metal / boron-doped diamond electrode in a tube furnace, introduce inert gas, and heat the furnace to 850-950° C. at a heating rate of 5-15° C. / min, and keep the temperature for 10-60 min. At the beginning of the heat preservation, introduce hydrogen flow for high-temperature etching. After the heat preservation is completed, cut off the hydrogen flow, and cool the furnace to obtain a metal / porous boron-doped diamond electrode; S4. Immersing the metal / porous boron-doped diamond electrode in a strong acid to prepare a porous boron-doped diamond electrode.

2. The method for preparing an electrode for electrochemical degradation of biomass wastewater according to claim 1, characterized in that: In step S2, in the mixed solution of metal salt and precipitant, the concentration of metal salt is 10-40 mM, the concentration of precipitant is 10-40 mM, and the concentration ratio of metal salt to precipitant is 1:1-2.

3. The method for preparing an electrode for electrochemical degradation of biomass wastewater according to claim 1, characterized in that: In step S3, hydrogen flow is introduced at the beginning of heat preservation, and the flow rate of the inert gas flow remains unchanged. After the heat preservation is completed, the hydrogen flow is cut off and the mixture is cooled naturally.

4. The method for preparing an electrode for electrochemical degradation of biomass wastewater according to claim 3, characterized in that: In step S3, the inert gas flow rate is 20-60 mL min -1 , hydrogen flow rate is 20~60mL·min -1 , the flow rate ratio of the inert gas flow and the hydrogen gas is 1 to 2:

1.

5. The method for preparing an electrode for electrochemical degradation of biomass wastewater according to claim 1, characterized in that: In step S4, the strong acid is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and concentrated nitric acid, and the soaking time is 12 to 24 hours.

6. The method for preparing an electrode for electrochemical degradation of biomass wastewater according to claim 1, characterized in that: The step S1 specifically includes: S11, the planar boron-doped diamond electrode was subjected to constant current oxidation in the electrolyte for 20 to 60 minutes at a current of 50 to 70 mA; S12, ultrasonically cleaning the oxidized electrode sheet with water and ethanol in sequence; S13. Soak the cleaned electrode in concentrated nitric acid for 20 to 40 minutes.

7. An electrode for electrochemical degradation of biomass wastewater, characterized in that: The electrode is prepared by the preparation method according to any one of claims 1 to 6, wherein a plurality of pores are distributed on the surface of the electrode, and the size of the pores is 50 to 500 nm.

8. Use of the electrode according to claim 7, characterized in that: Biomass wastewater containing furan compounds is degraded under the oxidation action of the electrodes, and organic matter is mineralized into carbon dioxide.

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