Preparation method and application of self-template nitrogen-doped sugarcane bagasse biochar electrode material

Abstract

The application discloses a preparation method of a self-template nitrogen-doped sugarcane residue biochar electrode material and application thereof, and the preparation comprises the following steps: placing repeatedly cleaned sugarcane residue in a tubular furnace, and performing low-temperature carbonization under a nitrogen atmosphere. Then, the product after low-temperature carbonization is uniformly mixed with potassium hydroxide with a certain mass ratio in a mortar, and then the uniformly mixed sample is placed in the tubular furnace to perform activation under a nitrogen atmosphere. Finally, the obtained activated product is neutralized with hydrochloric acid to neutralize excessive alkali, then washed with deionized water until neutral, and vacuum dried to obtain the self-template nitrogen-doped sugarcane residue biochar electrode material. In the application, cheap and easily obtained sugarcane residue is used as a raw material to prepare a tubular structure biochar for electric adsorption, and no additional template is needed. Compared with similar technologies, the electrode is more excellent in effect and lower in cost, achieves the purpose of waste treatment with waste, and is an effective technical approach to realize the double carbon.

Description

Technical Field

[0001] This invention belongs to the field of waste biomass resource development and utilization and the preparation of capacitive deionization electrode materials, specifically involving a preparation method and application of a self-templated nitrogen-doped sugarcane bagasse biochar electrode material. Background Technology

[0002] Seawater and brackish water account for 98% of the Earth's total water volume. From the perspective of sustainable development, seawater desalination technology is receiving increasing attention and research. Capacitive deionization (CDI) is a novel seawater desalination technology. Compared with multi-stage flash evaporation, reverse osmosis, and electrodialysis, CDI has advantages such as low energy consumption, simple operation, easy regeneration, low cost, and no secondary pollution. It has broad application prospects in seawater desalination, ion separation, and ion recovery.

[0003] Since CDI technology relies on electro-adsorption on the electrode surface, the properties and design of the electrode material are crucial to CDI performance. However, the high cost and cumbersome preparation methods of CDI electrode materials limit the further development of CDI technology. Low-cost, high-performance electrode materials with simple preparation methods have always been a hot topic of research. Biomass, with its advantages of being renewable, having high carbon content, and being widely available, is an ideal precursor for preparing porous carbon materials and also the most promising capacitive deionization electrode material for large-scale applications.

[0004] Although biochar possesses a high specific surface area and abundant micropores, which are beneficial for improving the desalination performance of CDI technology, biochar electrode materials dominated by double-layer adsorption mechanisms still suffer from limited desalination capacity. This is mainly due to the less-than-ideal pore distribution and insufficient utilization of the specific surface area. Furthermore, heteroatom doping can alter the surface chemistry of carbon materials and regulate the electron distribution on the carbon plane, and is widely recognized as an effective strategy for improving the electrochemical performance of carbon materials. Compared with in-situ doping, post-treatment methods have limitations such as process complexity, poor stability, and higher cost.

[0005] A biomass-derived porous carbon electrode and its preparation method and application have been proposed in the prior art (CN2021116013660). Among them, a carbon electrode derived from the fruit of the Chinese parasol tree was prepared. However, its capacitance-deionization specific capacitance, salt adsorption rate (SAR), and salt adsorption capacity need to be further improved. In addition, the prior art has also reported the preparation of sugarcane bagasse electrodes by physical activation and chemical activation methods. The preparation process of this method is complicated, and the specific surface area of ​​the material is small, and the salt adsorption capacity is not ideal (Lado J J, Zornitta RL, Vázquez Rodríguez I, et al. Sugarcane Biowaste-Derived Biochars as Capacitive Deionization Electrodes for Brackish Water Desalination and Water-Softening Applications[J].ACS Sustainable Chemistry & Engineering, 2019, 7(23): 18992-19004).

[0006] Certain unique components and structures in biomass enable self-doping of heteroatoms and simplify the preparation of hierarchical porous carbon materials using template methods, thereby reducing the production cost of electrode materials and facilitating the large-scale industrial application of template methods. Therefore, combining template methods with biomass to develop a rational strategy for preparing biochar electrode materials with heteroatom-doped hierarchical porous structures for use in capacitive deionization is of great significance. Summary of the Invention

[0007] Objective: To address the problems existing in the prior art, this invention provides a method for preparing a biochar electrode based on self-templating nitrogen doping of sugarcane bagasse. The biochar electrode prepared by this invention improves the pore distribution of the biochar through a template method, weakens the "double-layer overlap" effect, shortens the ion transport path, and enhances the electroadsorption and desalination performance. This effectively solves the problems of insufficient specific surface area utilization, low salt adsorption capacity, and slow salt adsorption rate in existing biochar electrodes. Furthermore, the introduction of nitrogen atoms increases the conductivity and wettability of the material with the electrolyte, effectively improving the electrochemical performance of the carbon material, reducing raw material input costs, and expanding the application of biochar in the field of electroadsorption.

[0008] The present invention also provides the application of the self-templated nitrogen-doped bagasse biochar electrode.

[0009] Technical Solution: To achieve the above objectives, the present invention provides a method for preparing a self-templated nitrogen-doped sugarcane bagasse biochar electrode, comprising the following steps:

[0010] (1) Carbonization of sugarcane bagasse biochar: The washed sugarcane bagasse is carbonized at low temperature.

[0011] (2) Activation of sugarcane bagasse biochar: The product after low-temperature carbonization is uniformly mixed with an alkaline reagent, and then the uniformly mixed sample is activated by heating.

[0012] (3) The activated product was neutralized with acid and alkali, then washed until neutral, and then dried under vacuum to obtain the self-template nitrogen-doped bagasse biochar electrode material.

[0013] As a preferred option, in step (1), the bagasse is first crushed by a high-speed pulverizer at a speed of 2000 r / min for 2 min to 4 min.

[0014] In step (1), the carbonization temperature is 300-450℃, the heating rate is 5-10℃ / min, and the holding time is 1-2h.

[0015] In step (2), the mass ratio of the carbonized product to the alkaline reagent is 1:3.5 to 14.5. The two are ground evenly in a mortar for a time of not less than 15 minutes. The alkaline reagent is potassium hydroxide or sodium hydroxide.

[0016] Preferably, the mass ratio of the carbonized product to the alkaline reagent is 1:4.

[0017] In step (2), the activation temperature is 750-850℃, the heating rate is 5-10℃ / min, and the holding time is 1-2h.

[0018] Preferably, the activation temperature in step (2) is 800°C.

[0019] In step (3), hydrochloric acid is used to neutralize excess alkali. The concentration of hydrochloric acid is 1-2 mol / L. After neutralizing excess alkali with hydrochloric acid, the biochar is allowed to settle naturally and then washed repeatedly with deionized water 4-5 times.

[0020] The self-templated nitrogen-doped sugarcane bagasse biochar electrode material prepared by the preparation method described in this invention.

[0021] The application of the self-templated nitrogen-doped sugarcane bagasse biochar electrode material described in this invention in the preparation of capacitive deionization electrodes.

[0022] In this process, sugarcane bagasse biochar and polytetrafluoroethylene solution are mixed in a mass ratio of 1:3 to 1:1, and then uniformly mixed with anhydrous ethanol to obtain a slurry. The slurry is ultrasonicated for 30 minutes, uniformly coated on graphite paper, and dried at 80°C for 12 hours. After drying, the slurry is assembled into a capacitor deionization mold (CDI mold) electrode. The electrode is cleaned by circulating deionized water using a peristaltic pump. When the conductivity is less than or equal to 2 μS / cm, it can be used for desalination.

[0023] The application of the capacitive deion electrode prepared by the self-templated nitrogen-doped sugarcane bagasse biochar electrode material of the present invention in electroadsorption desalination.

[0024] The voltage applied for the electro-adsorption desalination is 1.0–1.6V, the influent flow rate is 5.7–17 mL / min, the volume of the sodium chloride solution is 50–100 mL, and the concentration of the sodium chloride solution is 50–300 mg / L.

[0025] Preferably, the voltage applied for the electro-adsorption desalination is 1.6V, the influent flow rate is 17mL / min, the sodium chloride solution volume is 100mL, and the sodium chloride solution concentration is 300mg / L.

[0026] This invention uses inexpensive and readily available sugarcane bagasse as raw material to prepare tubular biochar for electroadsorption without the need for additional templates. Compared with similar technologies, this electrode has superior performance and lower cost, achieving the goal of treating waste with waste and is an effective technical approach to realizing "dual carbon".

[0027] Existing traditional activated carbon typically has a large specific surface area (>2000 m²). 2 / g). However, the specific surface area is mainly composed of micropores. Since micropores are usually narrow and tortuous, they tend to lead to high ion diffusion resistance, resulting in a relatively small specific capacitance even at high current densities. Introducing mesopores (2-50 nm) can not only minimize ion diffusion resistance and improve ion migration rate, but also effectively improve the utilization rate of surface area. In current attempts to prepare hierarchical porous carbon (HPC) with interconnected micropores and mesopores, a combination of template and activation methods is often used in various approaches. In this method, the template method generates mesopores and the activation method generates micropores; however, it usually involves a complex hard template synthesis process. Therefore, it is necessary to simplify or eliminate the preparation process of hard templates. This invention successfully synthesizes a self-templated bagasse-derived carbon with high electrochemical performance by fixing the original tubular structure of bagasse at low temperature and generating a hierarchical porous structure through high temperature activation. This material has a three-dimensional interconnected hierarchical porous structure and a high specific surface area (2880.05 nm). 2 The material has abundant nitrogen doping ( / g) and low resistance, while also effectively improving the desalination effect of the electrode material.

[0028] This invention utilizes a specific method to prepare an electrode material using sugarcane bagasse biochar as raw material. The resulting material possesses a three-dimensionally interconnected hierarchical porous structure, composed of abundant micropores, mesopores, and macropores. Macropores provide a buffer for electrolyte ions, mesopores offer rapid ion transport channels, and micropores provide abundant ion adsorption sites. The presence of these three elements effectively enhances the ion diffusion rate and the double-layer specific capacitance. Nitrogen doping improves the wettability of the electrode material in the electrolyte, enhancing its adsorption of electrolyte ions. Therefore, this material exhibits excellent electrochemical performance. In a three-electrode system, at a scan rate of 10 mV / s, the specific capacitance reaches 134.22 F / g, and the charge transfer resistance is only 0.53 Ω. When the sodium chloride solution concentration is 100 mg / g, the salt adsorption capacity reaches 22.94 mg / g; when the sodium chloride solution concentration is 300 mg / L, the maximum salt adsorption capacity reaches as high as 28.10 mg / g, with an average salt adsorption rate of 0.94 mg / (g·min).

[0029] This invention is the first to prepare bagasse-derived biochar with excellent electrochemical performance via a self-templating method and activation method. This electrode material exhibits superior salt adsorption capacity (28.10 mg / g) and good cycling stability in the field of capacitive deionization. Not only does this invention show significantly better salt adsorption capacity than existing bagasse electrodes, but it also only requires chemical activation, avoiding the need for physical and chemical activation methods to prepare biochar in existing bagasse electrodes.

[0030] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0031] 1. This invention uses bagasse to prepare desalination electrodes. Bagasse is a complex lignocellulose material, mainly composed of cellulose (45%), hemicellulose (30%), and lignin (18%). It is also a major industrial byproduct of ethanol and sucrose production, generating approximately 280 kg of bagasse waste per ton of sugarcane. The usual method for treating bagasse waste is incineration to power boilers within sugar mills. However, the increasing production of bagasse waste and the growing demand for alternative waste management solutions make biomass conversion into biochar a low-cost solution to this problem. Waste resource utilization and waste-to-carbon conversion are effective technological approaches to achieving "dual carbon" (carbon reduction and carbon reduction).

[0032] 2. Traditional hollow tubular structures are typically prepared using a hard template method, requiring the addition of polystyrene, silica, metal compounds, and coatings, followed by etching or calcination to remove the template and obtain the hollow structure. However, these methods are cumbersome and often use environmentally unfriendly reagents (e.g., chloroform and hydrofluoric acid), causing related environmental problems. This invention utilizes the fine structure of sugarcane bagasse and employs a specific method to directly prepare hierarchical porous carbon via a self-templating method. This improves the pore distribution of biochar, reduces the "double-layer overlap" effect, shortens the ion transport path, and enhances electro-adsorption desalination performance.

[0033] 3. Heteroatom doping can alter the surface chemical properties of carbon materials and regulate the electron distribution in the carbon plane, and has been recognized as an effective strategy for improving the electrochemical performance of carbon materials. Compared with post-processing methods, biochar self-doping has advantages such as simple process, good stability, and low cost.

[0034] 4. Potassium hydroxide, phosphoric acid, and zinc chloride are the most commonly used chemical activators. Compared with potassium hydroxide, biochar prepared with phosphoric acid and zinc chloride has uneven pores and a small specific surface area, and zinc chloride is prone to environmental pollution. The activation principle of potassium hydroxide is that a gasification reaction occurs at high temperatures, promoting the development of porosity in carbon materials. The activation effect of potassium hydroxide expands the space between carbon atom layers, increasing the total pore volume and the number of adsorption active sites.

[0035] 5. The method of this invention successfully synthesizes self-templated bagasse-derived carbon with high electrochemical performance by fixing the original tubular structure of bagasse at low temperature and generating a hierarchical porous structure through high-temperature activation. This material has a three-dimensional interconnected hierarchical porous structure and a high specific surface area (2880.05 m²). 2 The abundant nitrogen doping and low resistance of the saturated nitrogen dopant effectively avoid the complex and time-consuming hard template synthesis process that is typically involved in hard template methods.

[0036] 6. The self-template nitrogen-doped sugarcane bagasse biochar electrode material prepared by this invention has the characteristics of being non-toxic and harmless during use, having excellent electrochemical performance, and having a long cycle life. It is an ideal capacitor deionization electrode material with good application prospects. Attached Figure Description

[0037] Figure 1 The results of cyclic voltammetry testing of the sugarcane bagasse biochar prepared in Example 1 of this invention;

[0038] Figure 2 The AC impedance test results are for the sugarcane bagasse biochar prepared in Example 1 of this invention.

[0039] Figure 3This is a graph showing the change in electrical conductivity over time of the sugarcane bagasse biochar prepared in Example 1 of this invention.

[0040] Figure 4 This is a scanning electron microscope image of the sugarcane bagasse biochar prepared in Example 1 of this invention;

[0041] Figure 5 The X-ray diffraction pattern of the sugarcane bagasse biochar prepared in Example 1 of this invention;

[0042] Figure 6 The image shows the Raman spectrum of the sugarcane bagasse biochar prepared in Example 1 of this invention.

[0043] Figure 7 This is a full scan X-ray photoelectron spectroscopy (XPS) image of the sugarcane bagasse biochar prepared in Example 1 of this invention.

[0044] Figure 8 The attached figure shows the nitrogen adsorption and desorption process of the sugarcane bagasse biochar prepared in Example 1 of this invention;

[0045] Figure 9 This is a pore size distribution diagram of the sugarcane bagasse biochar prepared in Example 1 of this invention. Detailed Implementation

[0046] The present invention will be further described below with reference to the embodiments.

[0047] Unless otherwise specified, the experimental methods described in the embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0048] Example 1

[0049] 1. Preparation of sugarcane bagasse biochar material:

[0050] Step 1: Washing of sugarcane bagasse biomass: Place 20g of sugarcane bagasse and 500mL of deionized water in a 1000mL beaker, soak for 1 hour, wash repeatedly four times, and then place in a forced-air drying oven at 80℃ for 12 hours. Grind the dried sugarcane bagasse using a high-speed grinder at 2000r / min for 3 minutes.

[0051] Step 2: Carbonization of sugarcane bagasse biochar: Weigh 3g of dried and pulverized sugarcane bagasse and place it in a corundum boat, then place it in the heating zone of a tube furnace and carbonize it at 450℃ under a nitrogen atmosphere. The heating rate is 5℃ / min and the holding time is 1h.

[0052] Step 3: Activation of sugarcane bagasse biochar: Grind 2.4g of the low-temperature carbonized product and 9.6g of potassium hydroxide in a mortar until uniform, grind for 15min, and then place the uniformly mixed sample in a tube furnace for activation at 800℃ under a nitrogen atmosphere, with a heating rate of 5℃ / min and a holding time of 1h.

[0053] Step 4: Neutralize the excess alkali in the obtained activated product with 1 mol / L hydrochloric acid (until no bubbles are produced), let the biochar stand to precipitate naturally, then wash it repeatedly with deionized water 4-5 times until neutral, and finally place it in a vacuum drying oven at 80℃ for 12 hours to obtain sugarcane bagasse biochar electrode material.

[0054] 2. Preparation of electrochemical characterization electrode sheets for sugarcane bagasse biochar:

[0055] Weigh 0.03 g of sugarcane bagasse biochar and 0.05 g of polytetrafluoroethylene (PTFE) solution (60 wt%) into a 25 mL beaker, then add 10 drops of anhydrous ethanol to mix the biochar and PTFE solution evenly. The resulting slurry is sonicated for 30 min. The slurry is then evenly coated onto 1 × 1.2 cm graphite paper, with approximately 0.01 g of material on each sheet. After drying, a biochar electrode is obtained. A three-electrode system is used for electrochemical characterization of the sugarcane bagasse biochar. The working electrode is the self-made biochar electrode, the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode. The experiment is conducted at room temperature. When the sodium chloride solution concentration is 0.5 mol / L, the sodium chloride solution volume is 40 mL, the potential window is -0.4–0.6 V, and the scan rate is 10 mV / s, the cyclic voltammetry results are as follows: Figure 1 As shown, the calculated specific capacitance of the electrode is 134.22 F / g. The AC impedance test results are as follows... Figure 2 As shown, the charge transfer resistance is calculated to be 0.53Ω using software fitting.

[0056] 3. Preparation of sugarcane bagasse biochar desalination electrode sheets:

[0057] Weigh 0.05g of sugarcane bagasse biochar and 0.0833g of polytetrafluoroethylene solution (60wt%) into a 25mL beaker, then add 20 drops of anhydrous ethanol to mix the biochar and polytetrafluoroethylene solution evenly, and sonicate the resulting slurry for 30 minutes. Coat the slurry evenly onto a 3×3cm graphite paper, ensuring a smooth surface and consistent thickness. After drying as described above, two desalination electrodes are prepared. The dried electrodes are then assembled into a desalination device, consisting of two transparent acrylic plates, two gasket diaphragms, and symmetrical 3cm x 3cm electrodes. The device is fixed in place with screws and connected to a water pipe. The solution flows through the electrode material via the water pipe. A peristaltic pump is used to circulate deionized water to clean the electrodes until the conductivity is less than or equal to 2μS / cm, at which point the device is ready for desalination. When the operating voltage is 1.6V, the flow rate is 17mL / min, the volume of the sodium chloride solution is 100mL, and the concentration of the sodium chloride solution is 100mg / L, the results are as follows: Figure 3 As shown, at adsorption equilibrium, the conductivity decreased from 196.81 μS / cm to 153.71 μS / cm, the maximum salt adsorption capacity was 22.94 mg / g, and the average salt adsorption rate was 0.72 mg / (g·min).

[0058] Example 2

[0059] The preparation method is the same as in Example 1, except for step 3 in the preparation of the sugarcane bagasse biochar electrode material. 2.4g of the low-temperature carbonized product is uniformly mixed with 9.6g of zinc chloride in a mortar. The uniformly mixed sample is then placed in a tube furnace and activated at 800℃ under a nitrogen atmosphere at a heating rate of 5℃ / min for 1 hour. The calculated specific capacitance of the electrode is 42.94 F / g, the charge transport resistance is 2.03 Ω, and the maximum salt adsorption capacity, determined according to the method in Example 1, is 5.09 mg / g.

[0060] Example 3

[0061] The preparation method is the same as in Example 1, except for step 3 of the sugarcane bagasse biochar preparation. 2.4g of the low-temperature carbonized product is uniformly mixed with 9.6g of phosphoric acid. The uniformly mixed sample is then placed in a tube furnace and activated at 800°C under a nitrogen atmosphere at a heating rate of 5°C / min for 1 hour. Calculations show that the electrode's specific capacitance is 59.89 F / g, the charge transfer resistance is 0.92 Ω, and the maximum salt adsorption capacity, determined according to the method in Example 1, is 6.81 mg / g.

[0062] As can be seen from Examples 2 and 3, when using different acids or salts for activation, the salt adsorption effect of the present invention using alkali activation is significantly better than the other two.

[0063] Example 4

[0064] The preparation method is the same as in Example 1, except for step 3 of the sugarcane bagasse biochar preparation. 2.4g of the low-temperature carbonized product is uniformly mixed with 7.2g of potassium hydroxide in a mortar. The uniformly mixed sample is then placed in a tube furnace and activated at 800℃ under a nitrogen atmosphere at a heating rate of 5℃ / min for 1 hour. The calculated specific capacitance of the electrode is 125.12 F / g, the charge transfer resistance is 0.64 Ω, and the maximum salt adsorption capacity, determined according to the method in Example 1, is 15.09 mg / g.

[0065] Example 5

[0066] The preparation method is the same as in Example 1, except for step 3 of the sugarcane bagasse biochar preparation. 2.4g of the low-temperature carbonized product is uniformly mixed with 12g of potassium hydroxide in a mortar. The uniformly mixed sample is then placed in a tube furnace and activated at 800℃ under a nitrogen atmosphere at a heating rate of 5℃ / min for 1 hour. The calculated specific capacitance of the electrode is 115.53 F / g, the charge transport resistance is 0.77 Ω, and the maximum salt adsorption capacity, determined according to the method in Example 1, is 13.08 mg / g.

[0067] As can be seen from Examples 4 and 5, when using different ratios of carbonized product to potassium hydroxide, the salt adsorption effect of the specific ratio of carbonized product to potassium hydroxide of the present invention is significantly better than other ratios.

[0068] Example 6

[0069] The preparation method is the same as in Example 1, except for step 3 of the sugarcane bagasse biochar preparation. 2.4g of the low-temperature carbonized product is uniformly mixed with 9.6g of potassium hydroxide in a mortar. The uniformly mixed sample is then placed in a tube furnace and activated at 700℃ under a nitrogen atmosphere at a heating rate of 5℃ / min for 1 hour. The calculated specific capacitance of the electrode is 110.16 F / g, the charge transfer resistance is 0.87 Ω, and the maximum salt adsorption capacity, determined according to the method in Example 1, is 16.25 mg / g.

[0070] Example 7

[0071] The preparation method is the same as in Example 1, except for step 3 of the sugarcane bagasse biochar preparation. 2.4g of the low-temperature carbonized product is uniformly mixed with 9.6g of potassium hydroxide in a mortar. The uniformly mixed sample is then placed in a tube furnace and activated at 900℃ under a nitrogen atmosphere at a heating rate of 5℃ / min for 1 hour. The calculated specific capacitance of the electrode is 126.88 F / g, the charge transfer resistance is 0.65 Ω, and the maximum salt adsorption capacity, determined according to the method in Example 1, is 16.59 mg / g.

[0072] As can be seen from Examples 6 and 7, using different activation temperatures, the salt adsorption effect at the specific temperature of the present invention is significantly better than at other temperatures.

[0073] Examples 1 to 7 show that the sugarcane bagasse biochar prepared in Example 1 has excellent electrochemical properties. Specifically, the activator is potassium hydroxide. When the mass ratio of carbonization product to potassium hydroxide is 1:4 and the activation temperature is 800°C, the material has the largest specific capacitance, the smallest specific resistance, and the best desalination performance.

[0074] Example 8

[0075] Specifically, the morphology and structure of the sugarcane bagasse biomass prepared in Example 1 of the present invention were characterized as follows:

[0076] 1. The morphology of sugarcane bagasse biochar was analyzed using scanning electron microscopy, such as... Figure 4 As shown, the activated biochar exhibits a distinct tubular structure and a three-dimensional porous structure. This tubular porous morphological structure is conducive to charge transfer and accumulation during electroadsorption. The rough surface and large pores can further improve the hydrophilicity of the carbon material, thereby enhancing the capacitive deionization performance of the material.

[0077] 2. X-ray diffraction was used to analyze the crystal structure of sugarcane bagasse biochar, such as... Figure 5 As shown, the X-ray diffraction pattern of the bagasse-derived carbon material shows two distinct diffraction peaks on the (002) and (100) crystal planes of the corresponding carbon material. The peak intensities are relatively large, indicating that the layered structure of the crystal is relatively complete and there are no obvious impurities after activation.

[0078] 3. Raman spectroscopy was used to analyze the degree of defects in sugarcane bagasse biochar, such as... Figure 6 As shown, at 1333cm -1 and 1584cm -1 Typical D and G peaks appear at this point. The D band corresponds to a defective or disordered carbon framework structure in carbon materials, while the G band represents ordered stretching vibrations within the sp2-bonded carbon atom plane. Generally, the intensity ratio of the D band to the G band (I) is... D / I G The value () represents the degree of disorder in carbon materials. The ID / IG value of bagasse biochar is close to 1, indicating that this carbon material has a rich porous defect structure.

[0079] 4. Elemental composition analysis of sugarcane bagasse biochar was performed using X-ray photoelectron spectroscopy, such as... Figure 7 As shown, characteristic peaks of C1s, N1s and O1s appeared in the full X-ray photoelectron spectrum, and the peak value of C1s was significantly higher than that of the other two, indicating that it has a high carbon content.

[0080] 5. Pore size analysis of sugarcane bagasse biochar was performed using nitrogen adsorption / desorption testing, such as... Figure 8 As shown, the nitrogen adsorption-desorption isotherm rises rapidly in the relative pressure (P / P0) < 0.01 range, then slowly climbs, reaching adsorption saturation at a certain relative pressure. This is a typical type I isotherm corresponding to the microporous structure, indicating that the carbon material possesses abundant micropores with a diameter of ≤2 nm and a specific surface area as high as 2880.05 m². 2 / g. For example... Figure 9 As shown in the pore size distribution diagram, the SBC-800 material possesses a large number of micropores, mesopores, and macropores. Micropores can increase adsorption active sites; mesopores can shorten ion transport distances; and macropores can serve as buffer sites for ion solutions.

[0081] Example 9

[0082] Example 9 is the same as Example 1 in terms of method, except that in the preparation method of the sugarcane bagasse biochar desalination electrode, when the working voltage is 0.8V, the flow rate is 17mL / min, the volume of sodium chloride solution is 100mL, and the concentration of sodium chloride solution is 100mg / L, the maximum salt adsorption capacity is 8.31mg / g, and the average salt adsorption rate is 0.28mg / (g·min).

[0083] Example 10

[0084] Example 10 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.2V, the flow rate is 17mL / min, the volume of sodium chloride solution is 100mL, and the concentration of sodium chloride solution is 100mg / L, the maximum salt adsorption capacity is 13.77mg / g, and the average salt adsorption rate is 0.46mg / (g·min).

[0085] Example 11

[0086] Example 11 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.6V, the flow rate is 5.7mL / min, the sodium chloride solution volume is 100mL, and the sodium chloride solution concentration is 100mg / L, the maximum salt adsorption capacity is 19.36mg / g, and the average salt adsorption rate is 0.65mg / (g·min).

[0087] Example 12

[0088] Example 12 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.6V, the flow rate is 11.3mL / min, the volume of sodium chloride solution is 100mL, and the concentration of sodium chloride solution is 100mg / L, the maximum salt adsorption capacity is 21.63mg / g, and the average salt adsorption rate is 0.72mg / (g·min).

[0089] Example 13

[0090] Example 13 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode sheet, when the working voltage is 1.6V, the flow rate is 17mL / min, the sodium chloride solution volume is 100mL, and the sodium chloride solution concentration is 50mg / L, the maximum salt adsorption capacity is 12.87mg / g, and the average salt adsorption rate is 0.43mg / (g·min).

[0091] Example 14

[0092] Example 14 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.6V, the flow rate is 17mL / min, the sodium chloride solution volume is 100mL, and the sodium chloride solution concentration is 75mg / L, the maximum salt adsorption capacity is 16.79mg / g, and the average salt adsorption rate is 0.56mg / (g·min).

[0093] Example 15

[0094] Example 15 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.6V, the flow rate is 17mL / min, the sodium chloride solution volume is 100mL, and the sodium chloride solution concentration is 125mg / L, the maximum salt adsorption capacity is 24.27mg / g, and the average salt adsorption rate is 0.81mg / (g·min).

[0095] Example 16

[0096] Example 16 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.6V, the flow rate is 17mL / min, the sodium chloride solution volume is 100mL, and the sodium chloride solution concentration is 150mg / L, the maximum salt adsorption capacity is 25.84mg / g, and the average salt adsorption rate is 0.86mg / (g·min).

[0097] Example 17

[0098] Example 17 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.6V, the flow rate is 17mL / min, the sodium chloride solution volume is 100mL, and the sodium chloride solution concentration is 200mg / L, the maximum salt adsorption capacity is 27.56mg / g, and the average salt adsorption rate is 0.92mg / (g·min).

[0099] Example 18

[0100] Example 18 is the same as Example 1 in method, except that in the preparation method of sugarcane bagasse biochar desalination electrode, when the working voltage is 1.6V, the flow rate is 17mL / min, the volume of sodium chloride solution is 100mL, and the concentration of sodium chloride solution is 300mg / L, the maximum salt adsorption capacity is 28.10mg / g, and the average salt adsorption rate is 0.94mg / (g·min).

[0101] In summary, the optimal conditions for desalination of the electrode material prepared by this invention are as follows: when the working voltage is 1.6V, the flow rate is 30r / min, and the sodium chloride solution concentration is 300mg / L, the maximum salt adsorption capacity is 28.10mg / g, and the average salt adsorption rate is 0.94mg / (g·min).

[0102] Example 19

[0103] The sugarcane bagasse biochar electrode prepared in Example 1 was subjected to a desalination cycle stability test. The conductivity curves of 10 cycles all showed an almost identical "V" shape. After 500 minutes of cycling, the desalination capacity of the sugarcane bagasse biochar did not decrease significantly, indicating that the prepared sugarcane bagasse-derived carbon material has good regeneration performance and can be used for a long time in actual capacitive deionization systems, which can extend the replacement cycle of desalination electrode materials.

[0104] Example 20

[0105] The desalination effects of the sugarcane bagasse biochar desalination electrode sheet prepared in Example 1 and the existing electrode are shown in Table 1 below:

[0106] Table 1 Desalination effect of different electrode materials

[0107]

[0108] [1]Lado J J,Zornitta R L,Vázquez Rodríguez I,et al.SugarcaneBiowaste-Derived Biochars as Capacitive Deionization Electrodes for BrackishWater Desalination and Water-Softening Applications[J].ACS SustainableChemistry&Engineering,2019,7(23):18992-19004.

[0109] [2]Bei Li,Xiaojing Liu,Ao Wang,et al.Biochar with inherited negativesurface charges derived from Enteromorpha prolifera as a promising cathodematerial for capacitive deionization technology[J].Desalination,2022,539(1):115955.

[0110] [3]Li Yun,Li Hongxiang,Zhou Tiantian,et al.Platanus acerifolia(Aiton)Willd.fruit-derived nitrogen-doped porous carbon as an electrode material forthe capacitive deionization of brackish water[J].Journal of EnvironmentalChemical Engineering,2023,11(3):109914.

[0111] [4]Jiao Chen, Kuichang Zuo, Bing Li, et al. Fungal hypha-derivedfreestanding porous carbon pad as a high-capacity electrode for waterdesalination in membrane capacitive deionization[J]. Chemical Engineering Journal, 2022, 433(3):133781.

[0112] [5]Dingfei Deng a, Mapesa K. Luhasile ac, Haonan Li, et al. A novel layered activated carbon with rapid ion transport through chemical activation of chestnut inner shell for capacitive deionization[J]. Desalination, 2022, 531(1):115685.

[0113] Furthermore, the SCBFA electrode material from Reference 1 was tested under the conditions of Example 18 of this invention. When the operating voltage was 1.6V, the flow rate was 17mL / min, the sodium chloride solution volume was 100mL, and the sodium chloride solution concentration was 300mg / L, the maximum salt adsorption capacity was 18.57mg / g. In fact, the desalination capacity (mg / g) proposed in the prior art are all optimal results under optimal conditions, while the desalination capacity and average salt adsorption rate results of this invention are significantly better than those of the prior art.

Claims

1. Application of a capacitive deion electrode prepared from a self-templated nitrogen-doped sugarcane bagasse biochar electrode material in electroadsorption desalination; The voltage applied for the electro-adsorption desalination is 1.6 V, the influent flow rate is 17 mL / min, the sodium chloride solution volume is 100 mL, and the sodium chloride solution concentration is 300 mg / L. By mass fraction, sugarcane bagasse biochar electrode material and polytetrafluoroethylene solution were mixed in a mass ratio of 1:3 to 1:1, and then uniformly mixed with anhydrous ethanol to obtain a slurry. After ultrasonication, the slurry was uniformly coated on graphite paper, dried, and assembled into a capacitor deion electrode. The electrode was then cleaned. The preparation method of the self-templated nitrogen-doped sugarcane bagasse biochar electrode material includes the following steps: (1) Carbonization of sugarcane bagasse biochar: The washed sugarcane bagasse is carbonized at low temperature; (2) Activation of sugarcane bagasse biochar: The product after low-temperature carbonization is uniformly mixed with an alkaline reagent, and then the uniformly mixed sample is activated by heating. (3) The activated product obtained is neutralized with acid and alkali, then washed until neutral, and vacuum dried to obtain the self-template nitrogen-doped sugarcane bagasse biochar electrode material. In step (2), the mass ratio of the carbonized product to the alkaline reagent is 1:4, and the alkaline reagent is potassium hydroxide or sodium hydroxide. In step (2), the activation temperature is 800 ℃, the heating rate is 5~10 ℃ / min, and the holding time is 1~2 h.

2. The application according to claim 1, characterized in that, In step (1), the carbonization temperature is 300~450 ℃, the heating rate is 5~10 ℃ / min, and the holding time is 1~2 h.

3. The application according to claim 1, characterized in that, In step (3), hydrochloric acid is used to neutralize excess alkali. The concentration of hydrochloric acid is 1-2 mol / L. After neutralizing excess alkali with hydrochloric acid, the biochar is allowed to settle naturally and then washed repeatedly with deionized water 4-5 times.

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