A particle electrode for enhancing the electrocatalytic degradation of pollutants in industrial wastewater, its preparation method and application

Abstract

The present invention discloses a particle electrode for enhancing the electrocatalytic degradation of pollutants in industrial wastewater, its preparation method and application, belonging to the technical fields of electrochemistry and sewage treatment. The particle electrode is a TiO2 / Fe-g-C3N4 / BC particle electrode, wherein BC is porous biochar, Fe-g-C3N4 is loaded on BC, and TiO2 is loaded on Fe-g-C3N4 / BC. Using the TiO2 / Fe-g-C3N4 / BC particles as the particle electrode for electrocatalytic degradation of pollutants, a three-dimensional electrocatalytic oxidation system is formed for the degradation treatment of wastewater. Since the particle electrode is loaded with a photocatalytic material, it can not only improve the stability of the particle electrode, but also effectively combine photocatalysis and electrocatalysis, thereby improving the degradation effect of pollutants in industrial wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemistry and sewage treatment, and specifically relates to a particle electrode for enhancing the electrocatalytic degradation of pollutants in industrial wastewater, and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Although great progress has been made in the field of wastewater treatment with the continuous development of science and technology, the overall volume of industrial water consumption is still large, and the industry still faces a large demand for industrial wastewater treatment. Problems such as substandard industrial wastewater discharge still exist widely. Industrial wastewater has complex components, unstable water quality and water volume, and high concentrations of chemical oxygen demand (COD). Since industrial wastewater often contains a variety of toxic substances, most of which have "three-cause" toxicity, wanton discharge will cause great harm to the water ecological environment and threaten human health and safety. Therefore, it is becoming more and more urgent to develop a new and efficient method to treat industrial wastewater, which has become a hot topic of concern.

[0004] At present, traditional biological treatment, Fenton oxidation, membrane separation and other methods are all applicable to industrial wastewater treatment, but they are not targeted, have low efficiency or high energy consumption, produce more by-products, or react with non-target oxides after oxidation to produce many unknown or more toxic substances. Among them, the emerging electrocatalytic oxidation technology has the advantages of high pollutant degradation efficiency, no secondary pollution, and simple operation. It provides a new way for industrial wastewater treatment, especially for difficult-to-degrade wastewater with high salt or high organic content. It has great potential.

[0005] Electrocatalytic oxidation is to apply a certain voltage to wastewater, so that pollutants undergo oxidation reaction under the action of the electric field, degrade into small molecules that are easily degradable pollutants or directly mineralize into water and carbon dioxide, and then remove them from the wastewater. Electrocatalytic oxidation technology provides a promising method for the field of industrial wastewater treatment, with advantages such as environmental compatibility, small footprint, and rapid reaction; compared with biochemical treatment processes, electrocatalytic oxidation technology has a fast reaction rate, can degrade organic matter that is difficult to biodegrade, and improve the biodegradability of wastewater; compared with advanced oxidation technologies such as photocatalysis and Fenton, electrocatalytic oxidation technology has the advantages of mild reaction conditions and low operating conditions.

[0006] Common electrocatalytic oxidation technologies generally use a two-dimensional electrode system, but in practical applications, there are defects such as short electrode material life and high price, limited electrode reaction area, low current efficiency and degradation efficiency. Therefore, researchers have proposed a three-dimensional electrocatalytic reaction system to improve the electro-chemical reaction efficiency and reduce the cost of pollutant removal. The three-dimensional electrocatalytic system is to fill powder or granular materials (i.e., particle electrodes, also known as the third electrode) between the electrodes in the two-dimensional electrode system. Under the action of an electric field, the particle electrode becomes a microelectrode, which increases the active area of the electrode and the surface-to-volume ratio of the reactor, enhances the mass transfer efficiency, and thus improves the degradation effect of pollutants. Moreover, the particle electrode has a large specific surface area, and thus it is easy to combine with the reaction medium, can adsorb a large amount of pollutants, provides more reaction sites for the catalytic reaction, and thus improves the degradation efficiency. The particle electrode can also improve the current distribution and effectiveness of electrochemical oxidation. Therefore, the performance of the particle electrode plays a crucial role in the three-dimensional electrode system, and people often focus on the particle electrode in the three-dimensional electrocatalytic technology.

[0007] Common particle electrodes include activated carbon, metal particles, and nickel foam, etc. Among them, activated carbon is widely used as a particle electrode due to its excellent electrode properties such as high adsorption, good conductivity, and high chemical stability. Although the activated carbon particle electrode has a strong adsorption capacity, its catalytic ability is limited. After adsorbing pollutants, it cannot degrade them, and the micropores on the surface of the activated carbon are blocked, which will cause the catalytic performance of the activated carbon particle electrode to gradually decline and affect the treatment effect of wastewater. Therefore, the preparation of particle electrodes with high catalytic activity has become a current research hotspot. To solve the above problems, how to improve the electrocatalytic oxidation performance of particle electrodes by loading metal and its oxides and composite oxide materials with high catalytic activity on the surface of activated carbon is an important research hotspot at present. Summary of the Invention

[0008] To solve the problems existing in electrocatalysis when degrading refractory pollutants in industrial wastewater, the purpose of the present invention is to provide a particle electrode for enhancing the electrocatalytic degradation of pollutants in industrial wastewater, its preparation method and application. The particle electrode for enhancing the electrocatalytic degradation of pollutants in industrial wastewater provided by the present invention is loaded with a photocatalytic material, which can not only improve the stability of the particle electrode, but also effectively combine photocatalysis and electrocatalysis, thereby improving the degradation effect.

[0009] To achieve the above purpose, the technical solution of the present invention is as follows:

[0010] In the first aspect, the present invention provides a particle electrode for enhancing the electrocatalytic degradation of pollutants in industrial wastewater, and the particle electrode is TiO 2 / Fe-g-C 3 N 4 / BC particle electrode, where BC is porous biochar, and Fe-g-C 3 N 4 is loaded on BC, and TiO 2 is loaded on Fe-g-C 3 N 4 / BC.

[0011] The Fe-g-C 3 N 4 is metal Fe-doped modified g-C 3 N 4 .

[0012] In one or more embodiments, the mass of the iron source is 5-10% of the mass of g-C 3 N 4 , the mass of Fe-g-C 3 N 4 is 5%-10% of the mass of BC, and the mass of TiO 2 is 10%-15% of the mass of Fe-g-C 3 N 4 / BC.

[0013] In a second aspect, the present invention provides the above method for preparing a particle electrode for enhancing electrocatalytic degradation of pollutants in industrial wastewater, comprising the following steps:

[0014] Pyrolyzing a biomass raw material to prepare biochar;

[0015] Using g-C 3 N 4 and an iron source to prepare Fe-g-C 3 N 4 ;

[0016] Using biochar and Fe-g-C 3 N 4 to prepare Fe-g-C 3 N 4 / BC;

[0017] Using Fe-g-C 3 N 4 / BC and TiO 2 to prepare TiO 2 / Fe-g-C 3 N 4 / BC particle electrode.

[0018] In one or more embodiments, the biomass raw material is wood or straw. Considering the concept of low cost and sustainable development, the solid waste resource - straw is preferably selected. The straw includes reed straw, corn straw, wheat straw, etc.

[0019] In one or more embodiments, the biomass raw material is crushed and sieved. The crushing is to use a crusher to mechanically crush the biomass, and sieve to obtain 100-300 mesh for standby use, preferably 200 mesh.

[0020] In one or more embodiments, the biomass raw materials obtained by crushing and screening are dried or sprayed with water so that the moisture content of the biomass raw materials is maintained at 15% to 20%.

[0021] In one or more embodiments, the pyrolysis temperature is 400-600°C, the pyrolysis time is 2-6h, and the heating rate is 3-8°C / min. Preferably, the pyrolysis temperature is 500°C, and the pyrolysis time is maintained for 4h, and the heating rate of the tubular furnace is 5°C / min.

[0022] In one or more embodiments, biochar (BC) is pretreated by soaking in acid and alkali to remove its ash and modify it. The purpose of the modification is to increase the surface functional group content of biochar, improve its adsorption performance and enhance its chemical reaction activity. Specifically, it is soaked and shaken in an alkaline solution and an acid solution respectively. The alkaline solution is a 1-3 mol / L sodium hydroxide (NaOH) solution, and the acid solution is a 1-3 mol / L dilute hydrochloric acid (HCL) solution. The shaking conditions are a rotation speed of 100-300 r / min and an shaking time of 1-2 h.

[0023] After the soaking, the process also includes water washing to adjust the pH to neutral, ultrasonic cleaning, and drying. Specifically, it is washed with deionized water until the pH of the cleaning solution is neutral (pH=6.5-7.2), and finally ultrasonic cleaning is used. After the cleaning, it is dried at 80-110°C.

[0024] In one or more embodiments, the use of gC 3 N 4 Preparation of Fe-gC with iron source 3 N 4 The preparation process is as follows: gC 3 N 4 After the iron source is dissolved in water and mixed and stirred, it is separated, washed and dried to obtain Fe-gC 3 N 4 .

[0025] Furthermore, the gC 3 N 4 It is made by calcining melamine as raw material and grinding it. The calcination temperature is 400-600℃, the calcination time is 2-6h, the heating rate is 4-6℃ / min, and after cooling to room temperature, it is taken out and fully ground with an agate mortar to obtain powdered gC 3 N 4(Graphitic carbon nitride). A tube furnace can be used for calcination during the process.

[0026] Further, the iron source includes ferric nitrate nonahydrate (Fe(NO 3 ) 3 ∙9H 2 O) or ferric chloride hexahydrate.

[0027] The mass of the iron source is 5-10% of the mass of g-C 3 N 4

[0028] Further, during stirring, an alcohol solution of sodium borohydride with a concentration of 4-8 mg / mL is also added. Specifically: After the g-C 3 N 4 powder is dissolved in deionized water at 10-60 °C, Fe(NO 3 ) 3 ∙9H 2 O is used as the supported iron source for mechanical stirring for 20-40 min, and 1-2 mL of the alcohol solution of sodium borohydride with a concentration of 4-8 mg / mL is added during the stirring and continued to stir for 20-40 min, followed by centrifugal separation, and the precipitate is washed and dried to obtain Fe-g-C 3 N 4 .

[0029] Among them, the sodium borohydride added during the stirring process is used as a reducing agent, and its function is to reduce iron ions to iron nanoparticles. Alcohol is used as a solvent, which helps the uniform dispersion of sodium borohydride and the full reaction with iron ions.

[0030] In one or more embodiments, the process of preparing Fe-g-C 3 N 4 / BC using biochar and Fe-g-C 3 N 4 is as follows: The pretreated biochar and Fe-g-C 3 N 4 are dissolved in water, stirred, dried, and calcined to obtain Fe-g-C 3 N 4 / BC.

[0031] Further, the stirring time is 6-14 h, the drying temperature is 100-110 °C, the calcination temperature is 400-500 °C, the calcination time is 2-4 h, and the heating rate is 2-6 °C / min.

[0032] The mass of Fe-g-C 3 N 4 is 5%-10% of the mass of BC. If the loading amount is too large and the amount of BC becomes smaller, the adsorption and other properties of BC will deteriorate; if the loading amount is too small, Fe-g-C​3 N 4 If the amount is small, then Fe-g-C 3 N 4 has poor photocatalytic performance.

[0033] Specifically: The pretreated biochar and water are mixed for 2 - 3 h. After that, Fe-g-C 3 N 4 is dissolved in the suspension and mechanically stirred for 6 - 14 h to allow sufficient adsorption. After that, it is dried at 80 - 110 °C and then calcined in a tube furnace under a nitrogen atmosphere at 400 - 500 °C for 2 - 4 h, heating at a rate of 2 - 6 °C / min. After cooling to room temperature, it is taken out to obtain Fe-g-C 3 N 4 / BC.

[0034] In one or more embodiments, using Fe-g-C 3 N 4 / BC and TiO 2 to prepare TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes, the preparation process is as follows: Add an adhesive and a dispersant to the TiO 2 powder to obtain a TiO 2 mixture. Then mix, dry, and calcine Fe-g-C 3 N 4 / BC and the TiO 2 mixture.

[0035] Furthermore, the preparation method of the TiO 2 powder includes sol-gel hydrothermal method, sol-gel method, etc. Preferably, it is the sol-gel hydrothermal method, which can overcome the defects in the calcination process of the sol-gel method and enhance the dissolution effect of the formed gel under high temperature and high pressure conditions.

[0036] Preferably, the preparation method of the TiO 2 powder is to use tetrabutyl titanate as the raw material and obtain it by sol-gel hydrothermal method, calcination, and grinding. That is, first prepare TiO 2 sol, then carry out hydrothermal reaction, and finally calcine and grind to obtain titanium dioxide (TiO 2 ).

[0037] Specifically: Anhydrous ethanol and tetrabutyl titanate are fully stirred and mixed at a ratio of (2 - 3):1 to obtain solution A; Anhydrous ethanol and water are mixed at a ratio of (3 - 4):1, and 0.1 - 2 mL of HNO 3 (70%) solution is added and stirred to obtain solution B; Solution A is slowly added to solution B and mixed and stirred for 0.5 - 2 h to obtain TiO 2Sol. Hydrothermal reaction was carried out on TiO 2 sol, the hydrothermal temperature was 150 - 200 °C, and the hydrothermal time was 4 - 6 h. After the reaction, the reaction solution was dried at 80 - 110 °C, calcined in a nitrogen atmosphere for 1 - 3 h, the calcination temperature was 400 - 600 °C, the heating rate was 4 - 6 °C / min, and the calcination environment was an inert gas atmosphere to obtain TiO 2 solid material, which was ground into powder for standby after cooling to room temperature.

[0038] Furthermore, the binder is 10 wt% polytetrafluoroethylene or polyether ketone (PEEK).

[0039] The dispersant is anhydrous ethanol.

[0040] In the TiO 2 mixture, the ratio of TiO 2 , binder and dispersant is 1:(1.5 - 3):(1.5 - 3), g / mL / mL.

[0041] In order to better load TiO 2 onto Fe - g - C 3 N 4 / BC, first add the binder and dispersant to the TiO 2 powder to obtain the TiO 2 mixture. The specific preparation process is as follows: the binder and dispersant are mixed, and then added dropwise to the TiO 2 powder and heated and ultrasonicated to obtain the TiO 2 mixture. Among them, the ultrasonic time is 1 - 2 h.

[0042] Furthermore, in the preparation process of mixing, drying and calcining Fe - g - C 3 N 4 / BC and the TiO 2 mixture, the drying temperature is 80 - 110 °C, the drying time is 0.5 - 2 h, the calcination temperature is 300 - 500 °C, the heating rate is 2 - 6 °C / min, the calcination time is 4 - 5 h, and the calcination environment is an inert gas atmosphere.

[0043] Among them, the mass of TiO 2 is 10% - 15% of the mass of Fe - g - C 3 N 4 / BC.

[0044] Thirdly, the present invention provides the application of the above - mentioned particle electrode for enhancing the electro - catalytic degradation of pollutants in industrial wastewater in the electro - catalytic degradation of pollutants in industrial wastewater.

[0045] The wastewater includes wastewater containing tetrahydrofuran (THF) and / or N,N-dimethylformamide (DMF), chemical industrial wastewater, pharmaceutical wastewater, pesticide wastewater, etc.

[0046] Fourthly, the present invention provides a method for enhancing the electrocatalytic degradation of pollutants in industrial wastewater, comprising the following steps:

[0047] (1) Construct a three-dimensional electrocatalytic oxidation system in an electrolytic cell, the system including an anode, a cathode, an electrolyte solution, and particle electrodes suspended in the electrolyte solution; the particle electrodes are the particle electrodes for enhancing the electrocatalytic degradation of pollutants in industrial wastewater prepared by the above method; (2) Mix the industrial wastewater with the electrolyte solution; (3) Apply a voltage in the three-dimensional electrocatalytic oxidation system to perform electrocatalytic oxidation treatment on the industrial wastewater.

[0048] Specifically, the above-mentioned TiO 2 / Fe-g-C 3 N 4 / BC particles are used as particle electrodes for electrocatalytic degradation of pollutants. Two pairs of working electrodes are adopted, the working electrodes including two anodes and three cathodes. The cathodes are made of titanium plates, and the anodes are DSA electrodes (titanium-based oxide-coated electrodes) or BDD electrodes (boron-doped diamond electrodes), and the power supply is a DC regulated power supply.

[0049] Among them, the DSA electrode is a DSA ruthenium-iridium electrode.

[0050] Furthermore, the dosage of the TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes is 1-5 g / L, preferably 1-2 g / L.

[0051] Furthermore, the electrolyte solution is 10-30 mmol / L of Na 2 SO 4 , preferably 15-25 mmol / L.

[0052] Furthermore, the electrode spacing is 1-3 cm.

[0053] Furthermore, the current density of the electrocatalytic oxidation system is 10-30 mA / cm 2 , preferably 15-25 mA / cm 2 .

[0054] The beneficial effects of the present invention are as follows:

[0055] (1) The TiO 2 / Fe-g-C 3 N 4The / BC particle electrode material has a rich pore structure, good electrocatalytic oxidation ability, and the particle electrode is loaded with photocatalytic material, which can not only improve the stability of the particle electrode, but also effectively combine photocatalysis and electrocatalysis, thus improving the degradation effect of electrocatalytic oxidation technology on typical pollutants in industrial wastewater.

[0056] (2)Using TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes form a three-dimensional electrocatalytic oxidation system. Compared with the two-dimensional electrocatalytic oxidation system, the removal effect of typical pollutants in industrial wastewater has been greatly improved. Brief Description of the Drawings

[0057] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0058] Figure 1 It is the degradation effect diagram of tetrahydrofuran as the target pollutant in Example 1 and Comparative Example 1 of the present invention;

[0059] Figure 2 It is the degradation effect diagram of N,N-dimethylformamide as the target pollutant in Example 3 and Comparative Example 2 of the present invention;

[0060] Figure 3 It is the degradation effect diagram of the wastewater from a certain chemical plant as the target pollutant in Example 4 and Comparative Example 3 of the present invention;

[0061] Figure 4 It is the degradation effect diagram of the pharmaceutical wastewater from a certain pharmaceutical factory as the target pollutant in Example 5 and Comparative Example 4 of the present invention;

[0062] Figure 5 It is the degradation effect diagram of the wastewater from a certain pesticide factory as the target pollutant in Example 6 and Comparative Example 5 of the present invention. Detailed Description of the Invention

[0063] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0064] Example 1

[0065] (1)Biochar preparation

[0066] The reed straw is crushed by a crusher and then screened through a 200-mesh sieve for standby. The moisture content of the straw is maintained at 15% - 20% by drying or spraying water. It is pyrolytically carbonized in a tubular furnace under a nitrogen atmosphere at a temperature of 500 °C for 4 h with a heating rate of 5 °C / min to obtain biochar denoted as BC. After BC is screened (150-mesh), the surface impurities are washed with deionized water. Then BC is first soaked in a 1 mol / L sodium hydroxide (NaOH) solution and oscillated (100 r / min) at room temperature for 1 h. After the soaking, it is transferred to a 1 mol / L dilute hydrochloric acid (HCl) solution for soaking and oscillation (100 r / min) for 1 h. After the soaking, it is washed with deionized water until the pH of the washing solution is neutral (pH = 6.5 - 7.2), and finally ultrasonic cleaning is carried out. After the cleaning, it is dried in an oven at 105 °C.

[0067] (2)g-C 3 N 4 Preparation

[0068] Using melamine as the raw material, it is calcined at a calcination temperature of 550 °C for 4 h with a heating rate of 5 °C / min. After cooling to room temperature, it is sufficiently ground with an agate mortar to obtain a powdery g-C 3 N 4 material.

[0069] (3)Fe-g-C 3 N 4 Preparation

[0070] Take 4 g of powdery g-C 3 N 4 Stir it in 20 mL of deionized water at 50 °C for 10 min, then add 0.3 g of Fe(NO 3 ) 3 ∙9H 2 O and mechanically stir for 30 min, then dropwise add 1 mL of an alcohol solution of sodium borohydride with a concentration of 6 mg / mL, continue to stir for 30 min and then centrifuge. The obtained precipitate is washed with deionized water and absolute ethanol respectively, and placed in an oven to dry, obtaining a sample denoted as Fe-g-C 3 N 4 .

[0071] (4)Fe-g-C 3 N 4 / BC Preparation

[0072] Take 20 g of pretreated BC and ultrasonically mix it with deionized water for 2 h to make a suspension, and then add 2 g of Fe-g-C 3 N 4Dissolve it in it and stir it mechanically for 12 hours to allow it to be fully adsorbed. After that, move it to an oven and dry it at 105°C. After that, calcine it in a tubular furnace under a nitrogen atmosphere at 450°C for 4 hours, increase the temperature at a rate of 5°C / min, and take it out after cooling to room temperature to obtain Fe-gC 3 N 4 / BC.

[0073] (5) TiO 2 Preparation

[0074] Take 40 mL of anhydrous ethanol and slowly add 20 mL of tetrabutyl titanate under magnetic stirring to obtain solution A. Take 30 mL of anhydrous ethanol and add 10 mL of distilled water and 0.12 mL of HNO 3 (70%) and stirred thoroughly to obtain solution B. Solution A was slowly added to solution B and stirred for 1 h to obtain TiO 2 The sol was transferred to a hydrothermal reactor and heated at 180 °C for 5 h. After the reaction, it was dried in an oven at 105 °C. The dried material was then calcined in a tubular furnace at 450 °C for 2 h to obtain TiO 2 Solid material.

[0075] (6) TiO 2 / Fe-gC 3 N 4 Preparation of BC

[0076] Take 1.5g TiO 2 Powder, 2 mL 10% PTFE and 2 mL anhydrous ethanol were stirred and added dropwise thereto and heated with ultrasound for 1 h to obtain TiO 2 Mixture. Then mix it with 10gFe-gC 3 N 4 After being stirred evenly, the mixture was moved to an oven and dried at 105°C. After drying, the mixture was calcined in a tubular furnace at 400°C for 4 h under a nitrogen atmosphere at a heating rate of 5°C / min to obtain TiO 2 / Fe-gC 3 N 4 / BC particle electrode.

[0077] Fe-gC 3 N 4 Metal Fe doped modified gC 3 N 4 ;Fe-gC 3 N 4 Uniformly loaded on the surface and pores of BC, TiO 2 Uniformly loaded on Fe-gC 3 N 4 / on the surface or in the pores of BC.

[0078] In this example, a three-dimensional electrocatalytic oxidation system is used to remove the industrial organic solvent tetrahydrofuran (THF). The prepared TiO 2 / Fe-g-C 3 N 4 / BC particles are used as particle electrodes for electrocatalytic degradation of pollutants. Two pairs of working electrodes (two anodes and three cathodes) are adopted. The cathode is made of titanium plate, and the anode is made of DSA ruthenium-iridium electrode. The power supply is a DC regulated power supply. A three-dimensional electrocatalytic oxidation system is assembled for electrochemical catalytic oxidation testing.

[0079] Using tetrahydrofuran (THF) as the target pollutant, experimental water with a COD of 1500 mg / L is prepared. The electrolyte is 20 mmol / L of Na 2 SO 4 , the dosage of the particle electrode TiO 2 / Fe-g-C 3 N 4 / BC is 1 g / L, the electrode spacing is 2 cm, and the current density of the electrocatalytic oxidation system is regulated to 20 mA / cm 2 . As Figure 1 shown, the removal rate of the three-dimensional electrocatalytic oxidation system for tetrahydrofuran (THF) reaches more than 85.23%; through the above experiments, it is proved that the TiO 2 / Fe-g-C 3 N 4 / BC particle electrode prepared by the present invention can efficiently degrade pollutants.

[0080] Example 2

[0081] (1) Preparation of biochar

[0082] Use a crusher to crush reed straw and sieve it through a 200-mesh sieve for standby. Keep the moisture content of the straw at 15% - 20% by drying or spraying water. Pyrolyze and carbonize it in a tubular furnace under a nitrogen atmosphere at a temperature of 500 °C for 4 h, with a heating rate of 5 °C / min, to obtain biochar denoted as BC. After screening BC (150 mesh), wash the surface impurities with deionized water, then soak BC in a 1 mol / L sodium hydroxide (NaOH) solution and oscillate (100 r / min) at room temperature for 1 h. After the soaking, transfer it to a 1 mol / L dilute hydrochloric acid (HCl) solution for soaking and oscillation (100 r / min) for 1 h. After the soaking, wash it with deionized water until the pH of the washing solution is neutral (pH = 6.5 - 7.2), and finally perform ultrasonic cleaning. After the cleaning, dry it in an oven at 105 °C.

[0083] (2) Preparation of g-C 3 N 4

[0084] Using melamine as raw material, calcined at a calcination temperature of 550 °C for 4 h, with a heating rate of 5 °C / min. After cooling to room temperature, it was thoroughly ground with an agate mortar to obtain powdered g-C 3 N 4 material.

[0085] (3)Preparation of Fe-g-C 3 N 4 Take 4 g of powdered g-C

[0086] and stir it in 20 mL of deionized water at 50 °C for 10 min. Then add 0.3 g of Fe(NO 3 N 4 ) 3 ∙9H 3 O and stir mechanically for 30 min. Then add 1 mL of an alcohol solution of sodium borohydride with a concentration of 6 mg / mL, and continue to stir for 30 min. After that, centrifuge and separate. The obtained precipitate was washed with deionized water and absolute ethanol respectively, and then dried in an oven to obtain the sample denoted as Fe-g-C 2 N 3 . 4

[0087] (4)Preparation of Fe-g-C 3 N 4 / BC

[0088] Take 20 g of pretreated BC and ultrasonically mix it with deionized water for 2 h to make a suspension. Then dissolve 2 g of Fe-g-C 3 N 4 in it and stir mechanically for 12 h to make it fully adsorbed. After that, transfer it to an oven and dry it at 105 °C. Then calcine it in a tube furnace under a nitrogen atmosphere at 450 °C for 4 h, with a heating rate of 5 °C / min. After cooling to room temperature, take it out to obtain Fe-g-C 3 N 4 / BC.

[0089] (5)Preparation of TiO 2 Slowly add 40 mL of absolute ethanol to 20 mL of tetrabutyl titanate under magnetic stirring and stir thoroughly to obtain solution A; take 30 mL of absolute ethanol, add 10 mL of distilled water and 0.12 mL of HNO

[0090] (70%)and stir thoroughly to obtain solution B. Slowly add solution A to solution B and stir for 1 h. The obtained TiO 3 sol was transferred to a hydrothermal reaction kettle and heated at 180 °C for 5 h. After the reaction, it was dried in an oven at 105 °C. The dried material was then calcined in a tube furnace at 450 °C for 2 h to obtain TiO 2 ​2 Solid material.

[0091] (6)TiO 2 / Fe-g-C 3 N 4 / BC Preparation

[0092] Take 1 g of TiO 2 powder, add 2 mL of 10% PTFE and 2 mL of absolute ethanol and stir and mix them, then add dropwise into it and heat and ultrasonicate for 1 h to obtain TiO 2 mixture. Then mix it evenly with 10 g of Fe-g-C 3 N 4 / BC, transfer it to an oven and dry it at a temperature of 105 °C. After drying, calcine it in a tubular furnace under a nitrogen atmosphere at 400 °C for 4 h, with a heating rate of 5 °C / min, to obtain TiO 2 / Fe-g-C 3 N 4 / BC particle electrode.

[0093] In this example, a three-dimensional electrocatalytic oxidation system is used to remove the industrial organic solvent tetrahydrofuran (THF). The prepared TiO 2 / Fe-g-C 3 N 4 / BC particles are used as particle electrodes for electrocatalytic degradation of pollutants. Two pairs of working electrodes (two anodes and three cathodes) are used. The cathode is made of titanium plate, the anode is made of DSA ruthenium-iridium electrode, and the power supply is a DC regulated power supply. Assemble a three-dimensional electrocatalytic oxidation system for electrochemical catalytic oxidation testing.

[0094] Use tetrahydrofuran (THF) as the target pollutant to prepare experimental water with a COD of 1500 mg / L. The electrolyte is 20 mmol / L of Na 2 SO 4 , the dosage of the particle electrode TiO 2 / Fe-g-C 3 N 4 / BC is 1 g / L, the electrode spacing is 2 cm, and the current density of the electrocatalytic oxidation system is regulated to 20 mA / cm 2 . As Figure 1 shown, the removal rate of the three-dimensional electrocatalytic oxidation system for tetrahydrofuran (THF) reaches more than 81.15%; through the above experiments, it is proved that the TiO 2 / Fe-g-C 3 N 4 / BC particle electrode prepared by the present invention can efficiently degrade pollutants.

[0095] Comparative Example 1

[0096] In this comparative example, the same device as in Example 1 was used, but the prepared TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes were not added. Two pairs of working electrodes (two anodes and three cathodes) were still used. The cathode was made of titanium plate, the anode was made of DSA ruthenium-iridium electrode, and the power supply was a DC regulated power supply. A two-dimensional electrocatalytic oxidation system was assembled.

[0097] Consistent with Example 1, tetrahydrofuran (THF) was used as the target pollutant, and experimental water with a COD of 1500 mg / L was prepared. The electrolyte was 20 mmol / L of Na 2 SO 4 , the electrode spacing was 2 cm, and the current density of the electrocatalytic oxidation system was adjusted to 20 mA / cm 2 . As Figure 1 shown, the removal rate of tetrahydrofuran (THF) by the two-dimensional electrocatalytic oxidation system reached 77.27%.

[0098] By comparing the treatment effects of Example 1 and Comparative Example 1, it can be seen that the addition of TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes significantly improved the degradation of the pollutant THF by the electrocatalytic oxidation system.

[0099] Example 3

[0100] In this example, the production methods of the electrolytic cell and particle electrodes were the same as those in Example 1. The cathode was made of titanium plate, the anode was a DSA electrode, two pairs of working electrodes were used, and a DC regulated power supply was used as the output power supply. The prepared TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes were added to assemble a three-dimensional electrocatalytic oxidation system.

[0101] Using N,N-dimethylformamide (DMF) as the target pollutant, wastewater with a COD of about 1500 mg / L was prepared. The electrolyte was 20 mmol / L of Na 2 SO 4 , the dosage of the particle electrode TiO 2 / Fe-g-C 3 N 4 / BC was 1 g / L, the electrode spacing was 2 cm, and the current density of the electrocatalytic oxidation system was adjusted to 20 mA / cm 2 . As Figure 2 shown, the removal rate of DMF by the three-dimensional electrocatalytic oxidation system reached 37.63%.

[0102] Comparative Example 2

[0103] The device in this comparative example is the same as that in Example 3, but the prepared particle electrodes are not added, and only a two-dimensional electrocatalytic oxidation system is constructed. The experimental water is the same as that in Example 3. DMF is used as the target pollutant, and wastewater with a COD of 1500 mg / L is prepared. The electrolyte is 20 mmol / L of Na 2 SO 4 , the electrode spacing is 2 cm, and the current density of the electrocatalytic oxidation system is adjusted to 20 mA / cm 2 . As Figure 2 shown, after 4 h of treatment, the removal rate of wastewater COD by the two-dimensional electrocatalytic oxidation system is only 25.13%.

[0104] Comparing the treatment effects of Example 3 and Comparative Example 2, it can be seen that the addition of TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes significantly improves the degradation of the pollutant DMF by the electrocatalytic oxidation system.

[0105] Example 4

[0106] The method for fabricating the particle electrodes in this example is the same as that in Example 1. Two pairs of working electrodes are used. The cathode is a titanium plate, and the anode is changed to a BDD electrode. A DC regulated power supply is used as the output power supply. The prepared TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes are added to form a three-dimensional electrocatalytic oxidation system.

[0107] The experimental water is the wastewater from a chemical plant with a COD of 31750 mg / L. The dosage of the particle electrode TiO 2 / Fe-g-C 3 N 4 / BC is 1 g / L, the electrode spacing is 2 cm, and the current density of the electrocatalytic oxidation system is adjusted to 50 mA / cm 2 . As Figure 3 shown, after 4 h of treatment, the removal rate of wastewater COD by the three-dimensional electrocatalytic oxidation system reaches 32.54%.

[0108] Comparative Example 3

[0109] The device in this comparative example is the same as that in Example 4. The cathode is a titanium plate, and the anode is a BDD electrode. However, no particle electrodes are added, and a two-dimensional electrocatalytic oxidation system is used to treat the wastewater from the chemical plant (the same as that in Example 4) with a COD of 31750 mg / L. The electrode spacing is 2 cm, and the current density of the electrocatalytic oxidation system is adjusted to 50 mA / cm 2 . As Figure 3As shown, after 4 hours of treatment, the removal rate of COD in the wastewater by the two-dimensional electrocatalytic oxidation system was only 22.74%.

[0110] Comparing the treatment effects of Example 4 and Comparative Example 3, it can be seen that the addition of the TiO 2 / Fe-g-C 3 N 4 / BC particle electrode significantly improved the degradation of COD in this chemical wastewater by the electrocatalytic oxidation system.

[0111] Example 5

[0112] In this example, the production methods of the electrolytic cell and the particle electrode were the same as those in Example 4. The cathode was made of titanium plate, the anode was a BDD electrode, two pairs of working electrodes were used, and a DC regulated power supply was used as the output power supply. The prepared TiO 2 / Fe-g-C 3 N 4 / BC particle electrode was added to assemble a three-dimensional electrocatalytic oxidation system.

[0113] The experimental water was the pharmaceutical wastewater from a certain pharmaceutical factory, with a COD of 27800 mg / L. The dosage of the particle electrode TiO 2 / Fe-g-C 3 N 4 / BC was 1 g / L, the electrode spacing was 2 cm, and the current density of the electrocatalytic oxidation system was adjusted to 50 mA / cm 2 . As Figure 4 shown, after 4 hours of treatment, the removal rate of COD in the wastewater by the three-dimensional electrocatalytic oxidation system reached 39.39%.

[0114] Comparative Example 4

[0115] The device in this comparative example was the same as that in Example 5, but the prepared particle electrode was not added. A two-dimensional electrocatalytic oxidation system was used to treat the pharmaceutical wastewater from a certain pharmaceutical factory, with a COD of 27800 mg / L, an electrode spacing of 2 cm, and the current density of the electrocatalytic oxidation system was adjusted to 50 mA / cm 2 . As Figure 4 shown, after 4 hours of treatment, the removal rate of COD in the wastewater by the two-dimensional electrocatalytic oxidation system was only 28.13%.

[0116] Comparing the treatment effects of Example 5 and Comparative Example 4, it can be seen that the addition of the TiO 2 / Fe-g-C 3 N 4 / BC particle electrode significantly improved the degradation of COD in this pharmaceutical wastewater by the electrocatalytic oxidation system.

[0117] Example 6

[0118] The manufacturing methods of the electrolytic cell and the particle electrode in this embodiment are the same as those in Embodiment 4. The cathode uses a titanium plate, the anode is a BDD electrode, two pairs of working electrodes are used, a DC regulated power supply is used as the output power supply, and the prepared TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes are added to construct a three-dimensional electrocatalytic oxidation system.

[0119] Wastewater from a pesticide factory is treated. The COD is 30700 mg / L, the electrode distance is 2 cm, and the current density of the electrocatalytic oxidation system is regulated to 50 mA / cm 2 . As Figure 5 shown, after 4 hours of treatment, the removal rate of COD in the wastewater by the three-dimensional electrocatalytic oxidation system is 40.36%.

[0120] Comparative Example 5

[0121] The device in this comparative example is the same as that in Embodiment 6. The cathode uses a titanium plate, the anode is a BDD electrode, but no particle electrode is added to construct a two-dimensional electrocatalytic oxidation system. Wastewater from a pesticide factory is treated. The COD is 30700 mg / L, the electrode distance is 2 cm, and the current density of the electrocatalytic oxidation system is regulated to 50 mA / cm 2 . As Figure 5 shown, after 4 hours of treatment, the removal rate of COD in the wastewater by the two-dimensional electrocatalytic oxidation system is only 28.63%.

[0122] By comparing the treatment effects of Embodiment 6 and Comparative Example 5, it can be seen that the addition of TiO 2 / Fe-g-C 3 N 4 / BC particle electrodes significantly improves the degradation of COD in the wastewater from this pesticide factory by the electrocatalytic oxidation system.

[0123] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for enhancing electrocatalytic degradation of pollutants in industrial wastewater, characterized in that: The steps include: (1) constructing a three-dimensional electrocatalytic oxidation system in an electrolytic cell, wherein the system comprises an anode, a cathode, an electrolyte solution, and a particle electrode suspended in the electrolyte solution; (2) mixing industrial wastewater with the electrolyte solution; (3) applying voltage in the three-dimensional electrocatalytic oxidation system to electrocatalytically oxidize the industrial wastewater; The industrial wastewater includes wastewater containing tetrahydrofuran and / or N,N-dimethylformamide, chemical wastewater, pharmaceutical wastewater or pesticide wastewater; The particle electrode is a TiO2 / Fe-g-C3N4 / BC particle electrode, wherein BC is porous biochar, and Fe-g-C3N4 is g-C3N4 doped with metal Fe and modified; Fe-g-C3N4 is uniformly loaded on the surface and pores of BC, and TiO2 is uniformly loaded on the surface or pores of Fe-g-C3N4 / BC; The method for preparing the particle electrode for enhancing the electrocatalytic degradation of pollutants in industrial wastewater comprises the following steps: Preparation of biochar by pyrolysis of biomass raw materials; Preparation of Fe-g-C3N4 using g-C3N4 and iron source; Fe-g-C3N4 / BC was prepared using biochar and Fe-g-C3N4; TiO2 / Fe-g-C3N4 / BC particle electrode was prepared by using Fe-g-C3N4 / BC and TiO2; The biomass raw material is wood or straw; the biochar is pretreated by immersing in an acid-base solution; the pyrolysis temperature is 400-600°C, the pyrolysis time is 2-6h, and the heating rate is 3-8°C / min; The preparation process of TiO2 / Fe-g-C3N4 / BC particle electrode prepared by mixing Fe-g-C3N4 / BC and TiO2 is as follows: adding a binder and a dispersant to TiO2 powder to obtain a TiO2 mixture, and then mixing, drying and calcining the Fe-g-C3N4 / BC and TiO2 mixture; The mass of the iron source is 5%-10% of the mass of g-C3N4, the mass of Fe-g-C3N4 is 5%-10% of the mass of BC, and the mass of TiO2 is 10%-15% of the mass of Fe-g-C3N4 / BC.

2. The method according to claim 1, characterized in that The biomass raw materials are crushed and sieved; the moisture content of the biomass raw materials is maintained at 15%-20%.

3. The method according to claim 1, characterized in that The preparation process of Fe-g-C3N4 using g-C3N4 and an iron source is as follows: g-C3N4 and an iron source are dissolved in water, mixed and stirred, and then separated, washed, and dried to obtain Fe-g-C3N4; Or, the g-C3N4 is prepared by calcining and grinding melamine as a raw material; During stirring, an alcohol solution of sodium borohydride at a concentration of 4-8 mg / mL was also added; The iron source includes ferric nitrate nonahydrate or ferric chloride hexahydrate.

4. The method according to claim 1, characterized in that: The preparation process of Fe-g-C3N4 / BC using biochar and Fe-g-C3N4 is as follows: the pretreated biochar and Fe-g-C3N4 are dissolved in water, stirred, dried, and calcined to obtain Fe-g-C3N4 / BC; Or, the stirring time is 6-14h, the drying temperature is 100-110°C, the calcination temperature is 400-500°C, the calcination time is 2-4h, and the heating rate is 2-6°C / min.

5. The method according to claim 1, characterized in that The adhesive is 10wt% polytetrafluoroethylene or polyetherketone; The dispersant is anhydrous ethanol; In the TiO2 mixture, the ratio of TiO2, binder and dispersant is 1:(1.5-3):(1.5-3), g / mL / mL; In the preparation process of mixing, drying and calcining the Fe-g-C3N4 / BC and TiO2 mixture, the drying temperature is 80-110°C, the drying time is 0.5-2h, the calcination temperature is 300-500°C, the heating rate is 2-6°C / min, and the calcination time is 4-5h.

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