Preparation method and application of a biochar self-cleaning chlorine evolution electrode

Abstract

The application discloses a preparation method of a biochar self-cleaning chlorine electrode, and comprises the following steps: carbonizing biomass washed by deionized water under an inert atmosphere at 600 DEG C to 900 DEG C to obtain biochar powder; adding the biochar powder, RuCl3.3H2O or H2IrCl6.6H2O into anhydrous methanol, mixing thoroughly, ultrasonicating the mixture at 30 DEG C to 60 DEG C for 15 min to 60 min, filtering and drying the solid; then, treating the solid under an inert atmosphere at 500 DEG C to 800 DEG C for 30 min to 60 min, grinding and sieving, adding the sieved substance and 5% Nafion solution into anhydrous ethanol, mixing, ultrasonicating the mixture at 40 DEG C to 60 DEG C for 20 min to 50 min, dropping the mixture on the surface of a piezoelectric ceramic electrode plate, and drying to obtain the biochar self-cleaning chlorine electrode.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy and electrochemistry, and particularly relates to a preparation and application of a biochar self-cleaning chlorine evolution electrode. BACKGROUND

[0002] High salt content in aquaculture wastewater has always been an important issue in the field of aquaculture wastewater treatment. With the continuous development of aquaculture industry, a large amount of wastewater discharge may have a serious impact on the environment. Direct discharge of untreated wastewater into farmland may cause soil void blockage, resulting in a decrease in soil aeration and water permeability, and even cause salinization, which has a serious impact on soil quality, and further leads to crop yield reduction and death. Therefore, developing an efficient and environmentally friendly aquaculture wastewater treatment technology has become the focus of current aquaculture environmental governance research. Traditional aquaculture wastewater treatment methods have low efficiency and long treatment cycle, so there is an urgent need for an innovative method to solve these challenges.

[0003] Chinese patent application CN113072138A discloses a reverse electrode DSA electrode prepared using iridium, tantalum, rhodium and other noble metals. Although this invention can improve the service life of the electrode under frequent reverse electrode use, it uses a lot of iridium, rhodium and other noble metals in the material, which makes the electrode very expensive. CN202023248883.8 provides a salt-containing wastewater zero-discharge pretreatment system and a wastewater zero-discharge system, which mainly uses two sedimentation devices to reduce the hardness, alkalinity and silicon content of the salt-containing wastewater. CN201010111515.0 provides a high-salt wastewater treatment method, which filters high-salt wastewater by using a sodium ion exchanger, a weak acid ion exchanger and a reverse osmosis device, thereby improving water recovery rate. Therefore, it is crucial to seek an electrode that can effectively remove salt, stably operate and is affordable. SUMMARY

[0004] In view of the problems of complex composition, high salt content and difficult disposal of aquaculture wastewater in aquaculture farms, the present application provides a preparation method of a biochar self-cleaning chlorine evolution electrode suitable for aquaculture wastewater treatment in aquaculture farms, aiming to reduce energy consumption, improve environmental performance and increase production efficiency, etc.

[0005] To solve the above technical problems, the technical scheme of the present application is as follows:

[0006] 1. The biochar self-cleaning chlorine electrode is prepared by carbonizing biomass after washing with deionized water under an inert atmosphere at 600℃~900℃. The carbonization product is then pulverized and sieved to obtain biochar powder. The biochar powder, RuCl3·3H2O or H2IrCl6·6H2O are added to anhydrous methanol and thoroughly mixed. The mixture is then sonicated at 30℃~60℃ for 15min~60min, filtered, and the solid is dried. The solid is then placed under an inert atmosphere at 500℃~800℃ for 30min~60min, ground, and sieved. The sieved material and 5% Nafion solution are added to anhydrous ethanol, mixed, and sonicated at 40℃~60℃ for 20min~50min. The mixture is then dropped onto the surface of a piezoelectric ceramic electrode and dried to obtain the final product.

[0007] The biomass is selected from wheat straw and rice straw; the mass ratio of biochar powder, RuCl3·3H2O or H2IrCl6·6H2O is 10~20:1.

[0008] The sieved material has a mass-volume concentration of 1-10% in anhydrous ethanol, and the volume ratio of 5% Nafion solution to anhydrous ethanol is 1:10-20.

[0009] 2. The biochar self-cleaning chlorine-electrode prepared by the above method is applied in the treatment of wastewater from livestock farms;

[0010] Several biochar self-cleaning chlorine-electrode electrodes and several inert electrode plates are arranged in parallel on the front and back sides of the wastewater tank and connected to the power supply. The distance between the electrodes is 10cm to 30cm.

[0011] In wastewater treatment, the voltage applied to the electrodes is 2V~4V, and the current is 10kA / m. 2 ~15kA / m 2 The operating temperature is room temperature. A 15 kA / m pressure is applied to the electrode plates. 2 ~20kA / m 2 A pulsed current of 10-30 minutes can remove impurities loaded on the chlorine electrode, achieving a self-cleaning effect.

[0012] The advantages and technical effects of this invention are as follows:

[0013] The electrode preparation method of this invention is simple and uses low-cost raw materials, showing potential for large-scale industrial application; the chlorine-electrode of this invention has been calculated to operate stably for more than 30,000 hours; and it can effectively treat salt, antibiotics and heavy metals in aquaculture wastewater.

[0014] The application takes a commercial piezoelectric ceramic sheet as a substrate, which can generate vibration when a pulse current is applied, so that the electrode sheet has a self-cleaning function; the application uses biochar as a metal loading site, and by virtue of the porous structure and adsorption properties of the biochar, the chlorine evolution function of the electrode can be enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Results of treating wastewater by the chlorine evolution electrode of the application. DETAILED DESCRIPTION

[0016] The advantages and features of the application will become more apparent with the description of specific embodiments, which are only exemplary and intended to explain the application, and should not be construed as limiting the application: those skilled in the art should understand that the details and forms of the technical solutions of the application can be modified and replaced without departing from the spirit and scope of the application, and such modifications and replacements all fall within the protection scope of the application.

[0017] Example 1: treating the wastewater from a livestock farm, the wastewater contains as much as 8000 mg / L of salt

[0018] 1. The wheat straw is cleaned with deionized water for 3 times to effectively remove impurities on the surface of the wheat straw;

[0019] 2. The biomass is carbonized at 650℃ for 35 min under N2 atmosphere, the heating rate is 10℃ / min, the carbonized product is crushed through a 100-mesh sieve to obtain biochar powder;

[0020] 3. 20g of the biochar powder and 1g of RuCl3·3H2O are added into 1L of anhydrous methanol and mixed well, the mixture is ultrasonicated (30kHz) at 35℃ for 30 min, filtered, and the solid is dried at 120℃, the dried product is kept at 500℃ under N2 atmosphere for 45 min, ground through a 100-mesh sieve, 10g of the sieved product and 100mL of Nafion (5%) are placed in 1L of anhydrous ethanol and mixed well, the mixture is ultrasonicated (30kHz) at 40℃ for 40 min, the mixture is dropped on the surface of a commercial piezoelectric ceramic electrode plate, and dried at 55℃ for 12h to obtain a biochar self-cleaning chlorine evolution electrode;

[0021] 4. The biochar self-cleaning chlorine evolution electrode is used for treating aquaculture wastewater

[0022] 10 biochar self-cleaning chlorine evolution electrodes and 10 graphite electrode plates are respectively arranged in parallel on the front and back sides of the wastewater tank, the distance between the electrode sheets is 15cm, the voltage of the electrode is 2.8V, and the current is 11kA / m 2 ; every 10h of operation, the electrode is applied with 15 kA / m 2pulse current of 17 kA / m2, and the pulse time is 18 min; meanwhile, the commercial DSA electrode is used as a control.

[0023] After detection, as Figure 1 , the Tafel slope of the Ru / biochar electrode in this embodiment is 66.16 mV·dec −1 , which is less than 123.45 mV·dec −1 of the DSA electrode, indicating that the prepared Ru / biochar electrode has better performance than the DSA electrode, and the electrode can be stably operated for more than 30,000 hours; after treatment, the salt content of the wastewater is reduced to 834 mg / L. Example 2

[0024] 1. The wheat straw is washed with deionized water for 4 times to effectively remove impurities on the surface of the wheat straw;

[0025] 2. The biomass is carbonized at 700°C for 30 min under Ar atmosphere, the heating rate is 12°C / min, the carbonized product is crushed to pass through a 150-mesh sieve to obtain biochar powder;

[0026] 3. 25 g of biochar powder and 1.2 g of H2IrCl6·6H2O are added to 1.2 L of anhydrous methanol and mixed well, the mixture is ultrasonicated (35 kHz) at 40°C for 20 min, filtered, and the solid is dried at 115°C, the dried material is kept at 600°C under Ar atmosphere for 40 min, ground to pass through a 150-mesh sieve, 15 g of the sieved material and 120 mL of Nafion (5%) are placed in 1.5 L of anhydrous ethanol and mixed well, the mixture is ultrasonicated (30 kHz) at 45°C for 30 min, the mixture is dropped on the surface of a commercial piezoelectric ceramic electrode plate, and dried at 55°C for 12 h to obtain a biochar self-cleaning chlorine evolution electrode;

[0027] 4. The biochar self-cleaning chlorine evolution electrode is used for treating aquaculture wastewater

[0028] 10 biochar self-cleaning chlorine evolution electrodes and 10 graphite electrode plates are respectively and parallelly arranged on the front and back sides of the wastewater tank, the distance between the electrode plates is 18 cm, the voltage of the electrode is 3.1 V, and the current is 11.8 kA / m 2 ; every 11 h, a pulse current of 17 kA / m 2 is applied to the electrode, and the pulse time is 18 min; meanwhile, the commercial DSA electrode is used as a control.

[0029] After detection, as Figure 1 , the Tafel slope of the Ir / biochar electrode in this embodiment is 108.91 mV·dec −1 , which is less than 123.45 mV·dec −1, indicating that the prepared Ru / biochar electrode has better performance than the DSA electrode, and the electrode can be stably operated for more than 30000 hours; after treatment, the contents of Cu, Cr and Pb in the wastewater are reduced to 0.01 mg / L, 0.08 mg / L and 0.13 mg / L, respectively, which meet the national standards.

[0030] Example 3: In a certain aquaculture farm, the oxytetracycline content in the aquaculture wastewater is 2 mg / kg, the salt content is 3500 mg / L, which exceeds the standard and is difficult to treat

[0031] 1. The wheat straw is cleaned with deionized water for 5 times to effectively remove the impurities on the surface of the wheat straw;

[0032] 2. The biomass is carbonized at 750℃ for 40 min under N2 atmosphere, the heating rate is 15℃ / min, the carbonized product is crushed through a 180 mesh sieve to obtain biochar powder;

[0033] 3. 30g of biochar powder and 2g of H2IrCl6·6H2O are added to 2L of anhydrous methanol and mixed well, the mixture is ultrasonicated (40kHz) at 50℃ for 30 min, filtered, and the solid is dried at 125℃, the dried material is kept at 700℃ under N2 atmosphere for 60 min, ground through a 180 mesh sieve, 25g of the sieved material and 180mL of Nafion (5%) are placed in 2L of anhydrous ethanol and mixed well, the mixture is ultrasonicated (40kHz) at 50℃ for 45 min, the mixture is dropped on the surface of a commercial piezoelectric ceramic electrode plate, and dried at 65℃ for 18h to prepare a biochar self-cleaning chlorine evolution electrode;

[0034] 4. The biochar self-cleaning chlorine evolution electrode is used for treating aquaculture wastewater

[0035] 8 biochar self-cleaning chlorine evolution electrodes and 8 graphite electrode plates are respectively and parallelly arranged on the front and back sides of the wastewater tank, the distance between the electrode plates is 25cm, the voltage of the electrode is 3.3V, and the current is 13.8kA / m 2 ; every 11.5h, a pulse current of 18kA / m 2 is applied to the electrode for 15min;

[0036] The electrode can be stably operated for more than 30000 hours; after treatment, the oxytetracycline content in the wastewater is reduced to 0.06mg / kg, and the salt content is reduced to 790mg / L.

Claims

1. A method for preparing a biochar self-cleaning chlorine evolution electrode, characterized by: The biomass after deionized water cleaning is carbonized at 600-900 ℃ under inert atmosphere, and a biochar powder is prepared by crushing and sieving the carbonization product; the biochar powder, RuCl3·3H2O or H2IrCl6·6H2O is added into anhydrous methanol, mixed thoroughly, and the mixture is ultrasonicated at 30-60 ℃ for 15-60 min, filtered, and the solid is dried; then the solid is treated at 500-800 ℃ under inert atmosphere for 30-60 min, ground and sieved, the sieved product and 5% Nafion solution are added into anhydrous ethanol, mixed, ultrasonicated at 40-60 ℃ for 20-50 min, the mixture is dropped on the surface of a piezoelectric ceramic electrode plate, and dried to obtain a biochar self-cleaning chlorine evolution electrode.

2. The method for preparing the biochar self-cleaning chlorine-precipitating electrode according to claim 1, characterized in that: The mass ratio of the biochar powder, RuCl3·3H2O or H2IrCl6·6H2O is 10-20:

1.

3. The method for preparing the biochar self-cleaning chlorine-precipitating electrode according to claim 1, characterized in that: The mass-volume concentration of the sieved product in anhydrous ethanol is 1-10%, and the volume ratio of 5% Nafion solution to anhydrous ethanol is 1:10-20.

4. The method for preparing the biochar self-cleaning chlorine extraction electrode according to claim 1, characterized in that: The biomass is selected from the group consisting of wheat straw and rice straw.

5. Application of the biochar self-cleaning chlorine evolution electrode prepared by the preparation method of the biochar self-cleaning chlorine evolution electrode according to any one of claims 1-4 in treatment of wastewater in a farm.

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