Method for removing lead in water by using mesoporous hollow carbon sphere / covalent organic framework composite electrode material

Abstract

The application discloses a method for removing lead in water by using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, and the method is to treat lead-containing wastewater by using the mesoporous hollow carbon sphere / covalent organic framework composite electrode material, wherein the mesoporous hollow carbon sphere / covalent organic framework composite electrode material is prepared by using mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol and melamine as raw materials and through a solvothermal reaction. The mesoporous hollow carbon sphere / covalent organic framework composite electrode material has the advantages of high specific surface area, many active sites, good conductivity, good structural stability, excellent long cycle performance, high removal rate, high selectivity and the like, and in the presence of various competitive ions, the mesoporous hollow carbon sphere / covalent organic framework composite electrode material still has excellent selective adsorption performance on lead ions within a wide voltage range, can selectively remove lead in wastewater, and has good regeneration capacity and recycling effect.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal lead ion water pollution treatment technology, specifically relating to a method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material. Background Technology

[0002] Currently, the main technologies for removing lead ions from wastewater include adsorption, chemical precipitation, and ion exchange. However, these methods have limitations in removing low concentrations of lead ions, involve complex processes, and generate secondary pollution such as sludge. Therefore, it is necessary to select new methods to remove lead ions from industrial wastewater.

[0003] Capacitive deionization (CDI) is an electrochemically controlled adsorption process that uses an electric field to transport ions from solution to the electric double layer at the electrode / solution interface, further accumulating capture capacity. CDI has become an environmentally friendly, energy-saving, and economical seawater desalination strategy; some studies have also utilized CDI technology to remove heavy metal ions from wastewater. Exploring electrode materials with excellent adsorption / desorption capabilities is crucial for CDI performance. Carbon materials such as activated carbon, porous carbon, carbon aerogels, and carbon nanotubes are widely used as electrode materials due to their good chemical / mechanical durability, high conductivity, and specific surface area. Porous carbon includes hierarchical porous structures such as macropores, mesopores, and micropores. Mesoporous materials, also known as mesoporous carbon materials, exhibit highly uniform pore size, large specific surface area, narrow area distribution, and a wide range of tunable pore sizes. These superior properties have a significant impact on improving electrochemical signals, enhancing capacitance performance, and increasing charge transfer sites. Mesoporous carbon materials possess a certain adsorption capacity for lead ions. However, the presence of other ions in water, particularly sodium, calcium, and magnesium ions, interferes with lead ion removal efficiency, and the selectivity for lead ions is very poor. Therefore, how to improve the removal efficiency of lead ions is a crucial issue. 2+ The selectivity of selection is one of the key issues that needs to be addressed in practical applications.

[0004] In recent years, covalent organic frameworks (COFs), due to their unique structural properties, have become highly competitive adsorbents in water purification and pollutant removal. However, COFs suffer from drawbacks such as poor conductivity and easy aggregation in aquatic environments, which limits their application in electrochemical ion separation. Therefore, there is an urgent need to develop a method for removing lead from water using mesoporous hollow carbon spheres / covalent organic framework composite electrode materials that offers high selectivity, good removal efficiency, and is environmentally friendly. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material that is highly selective for lead ions, has a good removal effect, and is environmentally friendly.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, wherein the method utilizes the mesoporous hollow carbon sphere / covalent organic framework composite electrode material to treat lead-containing wastewater; the mesoporous hollow carbon sphere / covalent organic framework composite electrode material is prepared by solvothermal reaction of mesoporous hollow carbon spheres, 2,4,6-triformylresorcinol and melamine as raw materials; the ratio of mesoporous hollow carbon spheres to 2,4,6-triformylresorcinol is <200mg:0.75mmol.

[0008] In a further improvement to the above method, the mass molar ratio of the mesoporous hollow carbon spheres to 2,4,6-tricarboxymethyl phloroglucinol is 10 mg to 30 mg : 0.15 mmol, and the molar ratio of 2,4,6-tricarboxymethyl phloroglucinol to melamine is 1 : 0.9 to 1.5.

[0009] In a further improvement to the above method, the mass molar ratio of the mesoporous hollow carbon spheres to 2,4,6-tricarboxymethyl phloroglucinol is 17 mg to 23 mg: 0.15 mmol.

[0010] A further improvement to the above method is that the preparation method of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material includes the following steps: mixing mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol, melamine and an organic solvent, and carrying out a solvothermal reaction to obtain the mesoporous hollow carbon sphere / covalent organic framework composite electrode material.

[0011] In a further improvement to the above method, the organic solvent is dimethyl sulfoxide, the mixing is carried out under ultrasonic conditions for 30 to 60 minutes, the solvothermal reaction temperature is 110°C to 150°C, the solvothermal reaction time is 10 to 15 hours, and the reaction product is further treated after the solvothermal reaction by washing and drying the product with acetone and drying at 60°C.

[0012] A further improvement to the above method, the preparation method of the mesoporous hollow carbon spheres includes the following steps: S1. Mix ethanol, water and ammonia, stir, add tetrapropoxysilane, stir, and obtain mixed solution B; S2. Mix the mixed solution B obtained in S1 with resorcinol and formaldehyde aqueous solution, stir, wash, and dry to obtain a mixture; S3. The mixture obtained in S2 is calcined and then etched with alkali to obtain mesoporous hollow carbon spheres.

[0013] In a further improvement to the above method, the ratio of the aqueous solution of ethanol, water, ammonia, tetrapropoxysilane, resorcinol, and formaldehyde is 70 mL: 10 mL: 3 mL: 3.46 mL: 0.4 g: 0.56 mL. In step S1, the stirring time is 15 minutes. In step S2, the stirring time is 24 hours, and the washing is performed by centrifugation with ethanol and water in sequence; the specific centrifugation process is as follows: centrifuge 4 to 6 times at a speed of 4000 rpm to 5000 rpm, each time for 5 minutes; In step S3, the calcination temperature is 700℃, the calcination time is 5h, and the specific process of alkaline etching is as follows: the calcined product is mixed with an alkaline solution and etched; the mass ratio of the calcined product to the alkaline solution is 1:6 to 10, the alkaline solution is a sodium hydroxide solution with a mass fraction of 20%, the etching temperature is 60℃ to 80℃, and the etching time is 2d to 3d.

[0014] In a further improvement to the above method, the mesoporous hollow carbon sphere / covalent organic framework composite electrode material includes mesoporous hollow carbon spheres and a covalent organic framework. The covalent organic framework grows on the inner and outer walls of the mesoporous hollow carbon spheres to form an electric double layer structure. The covalent organic framework contains oxygen-containing functional groups and nitrogen-containing functional groups. The covalent organic framework has a strip-like structure and is TpTt-COF.

[0015] A further improvement to the above method is that the treatment involves: using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material as raw material to prepare a capacitive deionization electrode; using the capacitive deionization electrode as the cathode and an activated carbon electrode as the anode to construct a capacitive deionization device for adsorption treatment of lead-containing wastewater, thereby achieving the removal of lead from the wastewater.

[0016] In a further improvement to the above method, the initial concentration of lead in the lead-containing wastewater is 10 mg / L to 20 mg / L, the lead-containing wastewater also contains sodium ions, the initial concentration of sodium ions in the lead-containing wastewater is 100 mg / L, the initial pH value of the lead-containing wastewater is 5.5 to 6.5, the applied voltage is controlled at 0.6V to 1.2V during the adsorption treatment process, and the adsorption treatment time is ≥60 min. In a further improvement to the above method, the raw materials for the capacitive deionization electrode also include conductive carbon black and a binder; the preparation method of the capacitive deionization electrode includes the following steps: mixing mesoporous hollow carbon spheres / covalent organic framework composite electrode material, conductive carbon black and binder, adding solvent to form a colloid, coating the colloid on a conductive carrier, and drying to obtain the capacitive deionization electrode; the mass ratio of the mesoporous hollow carbon spheres / covalent organic framework composite electrode material, conductive carbon black and binder is 8-9:0.8-1:0.8-1, the binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol and polypropylene, the solvent is N-methylpyrrolidone, and the conductive carrier is a graphite plate. Compared with the prior art, the advantages of the present invention are as follows: (1) In view of the defects of existing capacitive deionization electrode materials in adsorbing lead ions in water, such as poor stability, low removal rate and poor selectivity, this invention creatively proposes a method for removing lead from water using mesoporous hollow carbon spheres / covalent organic framework composite electrode materials. The mesoporous hollow carbon spheres / covalent organic framework composite electrode materials are used to treat lead-containing wastewater. The mesoporous hollow carbon spheres / covalent organic framework composite electrode materials are prepared by solvothermal reaction of mesoporous hollow carbon spheres, 2,4,6-triformylresorcinol and melamine. The ratio of mesoporous hollow carbon spheres to 2,4,6-triformylresorcinol is <200mg:0.75mmol. In this invention, by using mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol, and melamine as raw materials and optimizing the proportions of the raw materials, a mesoporous hollow carbon sphere / covalent organic framework composite electrode material with high specific surface area, multiple active sites, good conductivity, good structural stability, excellent long-cycle performance, high removal rate, and high selectivity for lead ions can be prepared. As a novel composite electrode material, it exhibits excellent selective adsorption performance for lead ions over a wide voltage and pH range even in the presence of multiple competing ions, and also has good regeneration capacity and recycling effect. Therefore, when used to treat lead-containing wastewater, it can bring the following unexpected technical effects: On the one hand, the covalent organic framework has an aromatic framework network and abundant nitrogen and oxygen atoms, its unique... The hollow structure and strong coordination of specific nitrogen and oxygen functional groups can improve the selectivity and removal efficiency of lead ions in water. More importantly, the carbon support / scaffold material with mesoporous hollow carbon spheres as active sites, and the covalent organic framework grown on the inner and outer walls of the mesoporous hollow carbon spheres to form an electric double layer structure, improves the conductive network and fast ion transport channels. Thus, lead ions near the electrode are quickly adsorbed through the electronic conductive network and ion transport channels, thereby achieving highly selective adsorption and efficient removal of lead ions in water. On the other hand, the spherical structure of the mesoporous hollow carbon spheres can alleviate the aggregation of strip-shaped covalent organic frameworks to a certain extent, and the hollow structure can buffer the volume expansion / contraction caused by ion insertion / extraction during the cycling of the electrode material, thereby improving its long-cycle performance. This invention discloses a method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material. This method offers advantages such as simple operation, environmental friendliness, low processing cost, high processing efficiency, good selective removal effect, and good reusability. It can meet the needs of lead-containing wastewater treatment, especially in the case of multiple coexisting ions, where it can selectively remove lead ions from wastewater. It has high practical value and promising application prospects, while also aligning with sustainable development requirements and helping to reduce negative environmental impacts. Furthermore, the preparation method of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material used in this invention also has advantages such as simple process, inexpensive and readily available materials, convenient and stable storage, and suitability for large-scale production, demonstrating broad application prospects.

[0017] (2) In this invention, the mesoporous hollow carbon sphere / covalent organic framework composite electrode material, by optimizing the mass molar ratio of mesoporous hollow carbon spheres to 2,4,6-tricarboxymethyl phloroglucinol to 17mg~23mg∶0.15mmol and the molar ratio of 2,4,6-tricarboxymethyl phloroglucinol to melamine to 1∶0.9~1.5, can not only improve the molding rate and firmness of the composite electrode material, but also further improve the selectivity and adsorption efficiency of the composite electrode material for lead ions. If the amount of mesoporous hollow carbon spheres is too large, the excessive amount of mesoporous hollow carbon spheres will block the microporous channels of the covalent organic framework and reduce the active sites, thereby reducing the adsorption activity of the composite electrode material; if the amount of mesoporous hollow carbon spheres is too small, it will not only weaken the conductivity of the composite electrode material, but also reduce the specific surface area of ​​the material, thus reducing the effective utilization rate of the composite electrode material.

[0018] (3) In this invention, the method for preparing mesoporous hollow carbon spheres uses sodium hydroxide solution as an etchant instead of the commonly used hydrofluoric acid, which can make the mesoporous hollow carbon spheres exhibit better hydrophilic properties, thereby increasing the contact area between the mesoporous hollow carbon sphere / covalent organic framework composite electrode material and the polluted water sample during the capacitive deionization process, making it easier for lead ions in the water to contact the electrode and improve the removal efficiency.

[0019] (4) In this invention, a capacitive deionization electrode is made from mesoporous hollow carbon spheres / covalent organic framework composite electrode material, conductive carbon black, and binder, which has better cycle stability and lower energy consumption. When this capacitive deionization electrode is used for selective removal of lead ions, it has higher selectivity, better lead ion removal effect, and excellent long-term cycle stability. This not only ensures the reliability and durability of the system, but also reduces operating costs and improves the economic efficiency of the system. Attached Figure Description

[0020] Figure 1 The images show SEM images of the mesoporous hollow carbon sphere / covalent organic framework composite electrode materials (MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2), covalent organic framework (COF), and mesoporous hollow carbon spheres (MCHS) in Embodiment 1 of the present invention.

[0021] Figure 2 The image shows a TEM image of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and mesoporous hollow carbon spheres (MCHS) in Example 1 of this invention.

[0022] Figure 3 The Fourier transform infrared spectra of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1), covalent organic framework (COF), and mesoporous hollow carbon sphere (MCHS) in Embodiment 1 of the present invention are shown.

[0023] Figure 4 This image shows the removal effect of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) on lead and sodium ions in water in Example 1 of the present invention.

[0024] Figure 5 This is a comparative diagram showing the selectivity of lead ions in water for the mesoporous hollow carbon sphere / covalent organic framework composite electrode materials (MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2), covalent organic framework (COF), mesoporous hollow carbon spheres (MCHS), and activated carbon (AC) in Example 1 of the present invention.

[0025] Figure 6 This is a comparison diagram of the selectivity of lead ions in water for the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in Example 2 of the present invention under different voltages.

[0026] Figure 7 This is a comparison of the selectivity of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) for lead ions in water at different concentrations in Example 3 of the present invention.

[0027] Figure 8 This is a comparison of the selectivity of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) for lead ions in water at different pH values ​​in Example 4 of the present invention.

[0028] Figure 9 This is a comparison diagram of the selectivity of lead ions in water for the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in Example 5 of the present invention under different ion coexistence conditions.

[0029] Figure 10 This image shows the effect of the medium-porous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in removing lead ions from water when different heavy metal ions coexist. (Example 6 of this invention)

[0030] Figure 11 This image shows the effect of lead ion cyclic removal by the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in Example 7 of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0032] Example 1: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to the present invention includes the following steps: (1) Weigh out 50 mg each of mesoporous hollow carbon spheres / covalent organic framework composite electrode materials (MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2), covalent organic framework (COF), mesoporous hollow carbon spheres (MCHS), and activated carbon (AC). Add 6.25 mg of conductive carbon black and 6.25 mg of polyvinylidene fluoride (PVDF) and mix evenly. Then slowly add N-methylpyrrolidone (NMP) and stir to form a uniform colloid. Use a trowel to spread the colloid on a graphite plate (5cm×5cm) and vacuum dry for 12h to obtain a capacitor deionization electrode.

[0033] (2) Using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrode as anode, assemble the capacitor deionization device. In this step, the capacitor deionization device includes an activated carbon anode and a capacitor deionization electrode cathode, and its structure is as follows: The capacitor deionization device includes an acrylic plate, a silicone pad, an activated carbon anode, a silicone pad, a diaphragm, a capacitor deionization electrode cathode, a silicone pad, and an acrylic plate stacked sequentially along the water inlet direction, wherein the activated carbon anode and the capacitor deionization electrode cathode are connected to a DC power supply.

[0034] (3) Selective removal of lead ions was carried out using the capacitor deionization device in step (2). Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. The NaNO3 content in this polluted water body was... + The concentration of Pb was 100 mg / L. 2+ The concentration of lead was 10 mg / L, and the initial pH of the polluted water was 6. Under the condition of an applied voltage of 1.2 V, the adsorption treatment was carried out for 120 min to achieve selective removal of lead ions from the water.

[0035] In this embodiment, the preparation method of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) includes the following steps: S1. Preparation of mesoporous hollow carbon spheres S1-1. Mix 70 mL of anhydrous ethanol, 10 mL of deionized water, and 3 mL of ammonia water, and stir for 15 min to ensure the solution is thoroughly homogeneous. Add 3.46 mL of tetrapropoxysilane and continue stirring for 15 min. Then add 0.4 g of resorcinol and 0.56 mL of formaldehyde aqueous solution (concentration of 37 wt%), and continue stirring for 24 h to obtain a mixed solution. Wash the obtained mixed solution four times by centrifugation with anhydrous ethanol and water at 5000 rpm for 5 min each time. Dry the obtained precipitate under vacuum at 60 °C for 12 h to obtain the mixture. S1-2. The mixture obtained in step S1-1 is calcined at 700°C for 5 h. The calcined product is then immersed in a 20 wt% sodium hydroxide solution with a mass ratio of 1:8. The mixture is then etched at 80°C for 48 h to remove silica, resulting in mesoporous hollow carbon spheres, denoted as MCHS.

[0036] S2. Preparation of mesoporous hollow carbon sphere / covalent organic framework composite electrode materials S2-1: Take 100 mg of mesoporous hollow carbon spheres obtained in step S1-2, 0.75 mmol of 2,4,6-tricarboxymethyl phloroglucinol, and 0.75 mmol of melamine, mix them evenly, disperse them in 50 mL of dimethyl sulfoxide, and sonicate for 30 min to obtain a mixture. S2-2. The mixture obtained in step S2-1 is heated at 120℃ for 12h to carry out the reaction. After cooling, the reaction product is washed with acetone and dried at 60℃ for 12h to obtain a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, denoted as MCHS@COF-1.

[0037] The mesoporous hollow carbon sphere / covalent organic framework composite electrode material prepared in Example 1 includes a covalent organic framework and mesoporous hollow carbon spheres, with the covalent organic framework growing on the inner and outer walls of the mesoporous hollow carbon spheres.

[0038] In this embodiment, different mesoporous hollow carbon sphere / covalent organic framework composite electrode materials were also prepared. The preparation method was basically the same as that of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1), except that in step S2-1, the amount of mesoporous hollow carbon spheres used was 200 mg and 50 mg, respectively. The corresponding mesoporous hollow carbon sphere / covalent organic framework composite electrode materials were named as follows: MCHS@COF-0.5 and MCHS@COF-2.

[0039] In this embodiment, the method for preparing the covalent organic framework (COF) includes the following steps: (a) Take 0.75 mmol of 2,4,6-tricarboxymethyl phloroglucinol and 0.75 mmol of melamine, mix them evenly, disperse them in 50 ml of dimethyl sulfoxide, and sonicate for 30 min to obtain a mixture; (b) The mixture obtained in (a) was heated at 120°C for 12 h to carry out the reaction. After cooling, the reaction product was washed with acetone several times and dried at 60°C for 12 h to obtain a covalent organic framework, denoted as COF.

[0040] Figure 1 These are SEM images of the mesoporous hollow carbon sphere / covalent organic framework composite electrode materials (MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2), covalent organic framework (COF), and mesoporous hollow carbon spheres (MCHS) of Embodiment 1 of the present invention. Figure 1 It can be seen that the pure covalent organic framework (COF) exhibits an irregular strip-like alternating morphology, with a length of approximately 200-400 nm and a diameter of approximately 10-20 nm. The length is much greater than the diameter, and it has a significant aspect ratio, which is beneficial for constructing a conductive network and enhancing signal response. The mesoporous hollow carbon spheres (MCHS) synthesized by the hard template method exhibit uniform and regular spherical particles (diameter of approximately 450-530 nm), with good dispersibility and no obvious adhesion or breakage. Combining COF and MCHS, i.e., mesoporous hollow carbon sphere / covalent organic framework composite electrode materials (MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2), can effectively reduce aggregation and increase more active sites.

[0041] Figure 2 The image shows a TEM image of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and mesoporous hollow carbon spheres (MCHS) in Example 1 of this invention. Figure 2 In the diagram, (a) represents MCHS, and (b) represents MCHS@COF-1. From... Figure 2 The difference in brightness reveals that MCHS has a hollow spherical structure, with a carbon layer thickness of approximately 50 nm and a shell containing mesoporous channels. MCHS@COF-1, with a thickness of approximately 70 nm, is darker in color than MCHS, indicating that COF is tightly bonded to the carbon sphere surface and grows more uniformly vertically on the surface. This further proves that COF synthesis on the MCHS surface is relatively uniform.

[0042] Figure 3 The Fourier transform infrared (FTIR) spectra of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1), the covalent organic framework (COF), and the mesoporous hollow carbon spheres (MCHS) in Embodiment 1 of the present invention are shown below. Figure 3 As can be seen, the Fourier transform infrared spectra of all three materials show a distinct absorption peak at approximately 3410 cm⁻¹.-1 This corresponds to the stretching vibration of the OH bond. In contrast, the stretching vibration of CO, and the characteristic peak of MCHS, are significantly weaker, indicating that COF and MCHS are linked through ether bonds. Furthermore, Fourier transform infrared spectroscopy results also confirm the successful loading of the covalent organic framework onto mesoporous hollow carbon spheres.

[0043] In this embodiment, samples were continuously taken at set times during the processing. 0.3 mL of sample was taken from the solution at regular intervals, diluted with deionized water, filtered through a 0.22 μm membrane, and the concentrations of lead and sodium ions were determined using inductively coupled plasma chromatography (ICP-C). The selectivity and removal efficiency of different electrode materials for lead ions in the water were calculated, and the results are as follows: Figure 4 and Figure 5 As shown. In this embodiment, the lead ion removal rates of the capacitive deionization electrodes prepared using MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2, MCHS, COF, and AC as raw materials were 97.0%, 95.7%, 93.8%, 90.4%, 96.0%, and 42.1% respectively after 120 min.

[0044] Figure 4 This figure shows the removal effect of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) on lead and sodium ions in water in Example 1 of this invention. As can be seen from the figure, the removal rates of sodium and lead ions gradually increase with increasing treatment time. After 120 minutes of treatment, the sodium ion removal rate of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) is approximately 10%, while the lead ion removal rate reaches approximately 96%. Therefore, the mesoporous hollow carbon sphere / covalent organic framework composite electrode material of this invention can achieve highly selective removal of lead ions from water.

[0045] Figure 5 This is a comparative diagram showing the selectivity of mesoporous hollow carbon spheres / covalent organic framework composite electrode materials (MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2), covalent organic framework (COF), mesoporous hollow carbon spheres (MCHS), and activated carbon (AC) for lead ions in water in Example 1 of the present invention. Adsorption experiments were conducted using AC, MCHS, MCHS@COF-0.5, MCHS@COF-1, and MCHS@COF-2 as cathodes and AC as the anode. Figure 5 As shown, the selectivity coefficient (Pb) of MCHS@COF-1 2+ / Na +The selectivity of MCHS@COF-2 was the highest, lower than that of MCHS@COF-1. This may be because more COFs encapsulate MCHS, increasing the surface roughness of the material and providing more defects and active sites, thus enhancing the adsorption capacity of sodium ions and affecting the selectivity. After 90 minutes of operation, the adsorption of lead ions in each system gradually reached saturation, which is one of the reasons for the decrease in selectivity over time.

[0046] Example 2: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to the present invention includes the following steps: (1) Weigh 50 mg each of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and activated carbon (AC) prepared in Example 1, add 6.25 mg of conductive carbon black and 6.25 mg of polyvinylidene fluoride (PVDF) and mix evenly. Then slowly add N-methylpyrrolidone (NMP) and stir to form a uniform colloid. Use a trowel to spread the colloid on a graphite plate (5cm×5cm) and vacuum dry for 12h to obtain a capacitor deionization electrode.

[0047] (2) Using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrode as anode, assemble the capacitor deionization device. In this step, the capacitor deionization device includes an activated carbon anode and a capacitor deionization electrode cathode, and its structure is as follows: The capacitor deionization device includes an acrylic plate, a silicone pad, an activated carbon anode, a silicone pad, a diaphragm, a capacitor deionization electrode cathode, a silicone pad, and an acrylic plate stacked sequentially along the water inlet direction, wherein the activated carbon anode and the capacitor deionization electrode cathode are connected to a DC power supply.

[0048] (3) Selective removal of lead ions was carried out using the capacitor deionization device in step (2). Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. The NaNO3 content in this polluted water body was... + The concentration of Pb was 100 mg / L. 2+ The concentration of lead was 10 mg / L, and the initial pH of the polluted water was 6. Adsorption treatment was carried out for 120 min under the conditions of applied voltage of 0.6 V, 0.9 V, 1.2 V, and 1.5 V, respectively, to achieve selective removal of lead ions from the water.

[0049] In this embodiment, samples were continuously taken at set times during the reaction process. 0.3 mL of sample was taken from the solution at regular intervals, diluted with deionized water, filtered through a 0.22 μm membrane, and the concentrations of lead and sodium ions were determined using inductively coupled plasma chromatography (ICP-C). The selective removal efficiency of the electrode material for lead ions in the water was calculated, and the results are as follows: Figure 6As shown. Figure 6 This is a comparison of the selectivity of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) for lead ions in water under different voltages in Example 2 of the present invention. Figure 6 It can be seen that in this invention, MCHS@COF-1 exhibits the highest selectivity for lead ions at a voltage of 1.2V; at 0.6V, MCHS@COF-1 also shows relatively high selectivity, which may be due to the lower adsorption capacity of the double-layer capacitance for sodium ions at lower voltages; and at 1.5V, the selectivity is the lowest, which may be because water molecules undergo electrochemical decomposition at this potential, producing hydrogen ions that compete with lead ions for adsorption, leading to a decrease in lead ion adsorption efficiency. At the same time, the adsorption capacity for sodium ions is enhanced due to the increase in voltage.

[0050] In addition, in this embodiment, the capacitive deionization electrode made from MCHS@COF-1 achieved lead ion removal rates of 96.0%, 93.9%, 95.7%, and 92.1% at applied voltages of 0.6V, 0.9V, 1.2V, and 1.5V, respectively, after 120 minutes.

[0051] Example 3: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to the present invention includes the following steps: (1) Weigh 50 mg each of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and activated carbon (AC) prepared in Example 1, add 6.25 mg of conductive carbon black and 6.25 mg of polyvinylidene fluoride (PVDF) and mix evenly. Then slowly add N-methylpyrrolidone (NMP) and stir to form a uniform colloid. Use a trowel to spread the colloid on a graphite plate (5cm×5cm) and vacuum dry for 12h to obtain a capacitor deionization electrode.

[0052] (2) Using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrode as anode, assemble the capacitor deionization device. In this step, the capacitor deionization device includes an activated carbon anode and a capacitor deionization electrode cathode, and its structure is as follows: The capacitor deionization device includes an acrylic plate, a silicone pad, an activated carbon anode, a silicone pad, a diaphragm, a capacitor deionization electrode cathode, a silicone pad, and an acrylic plate stacked sequentially along the water inlet direction, wherein the activated carbon anode and the capacitor deionization electrode cathode are connected to a DC power supply.

[0053] (3) Selective removal of lead ions was carried out using the capacitor deionization device in step (2). Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 at different concentrations was used as the polluted water body. The NaNO3 concentration in the polluted water body was... +The concentration of Pb in the polluted water was 100 mg / L. 2+ The concentrations of lead ions were 5 mg / L, 10 mg / L, 15 mg / L, and 20 mg / L, respectively. The initial pH value of the polluted water was 6. Under the condition of an applied voltage of 1.2 V, the adsorption treatment was carried out for 120 min to achieve selective removal of lead ions from the water.

[0054] In this embodiment, samples were continuously taken at set times during the processing. 0.3 mL of sample was taken from the solution at regular intervals, diluted with deionized water, filtered through a 0.22 μm membrane, and the concentrations of lead and sodium ions were determined using inductively coupled plasma chromatography (ICP-C). The selectivity and removal efficiency of the electrode material for lead ions in the water were calculated, and the results are as follows: Figure 7 As shown.

[0055] Figure 7 This is a comparison of the selectivity of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) for lead ions in water at different concentrations in Example 3 of the present invention. Figure 7 It can be seen that in this invention, the Pb of the control electrode system 2+ The selectivity changes are as follows: when the lead ion concentration in the wastewater is 5 mg / L, i.e., the lead ion concentration is low, the selectivity of MCHS@COF-1 for lead ions is low. This may be due to less competition from sodium ions and more adsorption of sodium ions. When the lead ion concentration is 20 mg / L, the selectivity increases at the beginning of adsorption and then decreases. This may be due to the high initial lead concentration and strong adsorption capacity for lead ions. As time increases, the adsorption gradually reaches saturation and the selectivity decreases.

[0056] In addition, in this embodiment, the capacitive deionization electrode prepared using MCHS@COF-1 as raw material was subjected to a reaction time of 120 min in Pb. 2+ When the initial concentrations were 5 mg / L, 10 mg / L, 15 mg / L, and 20 mg / L, the removal rates of lead ions were 91.8%, 95.7%, 93.0%, and 96.1%, respectively.

[0057] Example 4: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to the present invention includes the following steps: (1) Weigh 50 mg each of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and activated carbon (AC) prepared in Example 1, add 6.25 mg of conductive carbon black and 6.25 mg of polyvinylidene fluoride (PVDF) and mix evenly. Then slowly add N-methylpyrrolidone (NMP) and stir to form a uniform colloid. Use a trowel to spread the colloid on a graphite plate (5cm×5cm) and vacuum dry for 12h to obtain a capacitor deionization electrode.

[0058] (2) Using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrode as anode, assemble the capacitor deionization device. In this step, the capacitor deionization device includes an activated carbon anode and a capacitor deionization electrode cathode, and its structure is as follows: The capacitor deionization device includes an acrylic plate, a silicone pad, an activated carbon anode, a silicone pad, a diaphragm, a capacitor deionization electrode cathode, a silicone pad, and an acrylic plate stacked sequentially along the water inlet direction, wherein the activated carbon anode and the capacitor deionization electrode cathode are connected to a DC power supply.

[0059] (3) Selective removal of lead ions was carried out using the capacitor deionization device in step (2). Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. The NaNO3 content in this polluted water body was... + The concentration of Pb was 100 mg / L. 2+ The concentration of lead was 10 mg / L. The pH of the polluted water was adjusted with 0.01 M HNO3 and 0.01 M NH3·H2O, that is, the pH of the polluted water was adjusted to 3, 4, 5, 6 and 7 respectively. Under the condition of an applied voltage of 1.2 V, the adsorption treatment was carried out for 120 min to achieve selective removal of lead ions from the water.

[0060] In this embodiment, samples were continuously taken at set times during the processing. 0.3 mL of sample was taken from the solution at regular intervals, diluted with deionized water, filtered through a 0.22 μm membrane, and the concentrations of lead and sodium ions were determined using inductively coupled plasma chromatography (ICP-C). The selectivity and removal efficiency of the electrode material for lead ions in the water were calculated, and the results are as follows: Figure 8 As shown.

[0061] Figure 8 This is a comparison of the selectivity of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) for lead ions in water at different pH values ​​in Example 4 of this invention. Figure 8 It can be seen that in this invention, when experiments were conducted under different pH conditions, the lead ion selectivity reached its maximum at pH=6. This is because: at low pH values, the hydrogen ion concentration is higher than that of Pb. 2+At high concentrations, most active sites on the electrode surface are occupied by hydrogen ions. As the pH value increases, the hydrogen ion concentration decreases, and the number of negatively charged metal binding sites increases, thereby adsorbing more Pb. 2+ .

[0062] In addition, in this embodiment, the capacitive deionization electrode made from MCHS@COF-1 achieved lead ion removal rates of 93.8%, 96.0%, 98.0%, 95.7%, and 97.9% respectively at pH values ​​of 3, 4, 5, 6, and 7 in the polluted water body after 120 min.

[0063] Example 5: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to the present invention includes the following steps: (1) Weigh 50 mg each of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and activated carbon (AC) prepared in Example 1, add 6.25 mg of conductive carbon black and 6.25 mg of polyvinylidene fluoride (PVDF) and mix evenly. Then slowly add N-methylpyrrolidone (NMP) and stir to form a uniform colloid. Use a trowel to spread the colloid on a graphite plate (5cm×5cm) and vacuum dry for 12h to obtain a capacitor deionization electrode.

[0064] (2) Using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrode as anode, assemble the capacitor deionization device. In this step, the capacitor deionization device includes an activated carbon anode and a capacitor deionization electrode cathode, and its structure is as follows: The capacitor deionization device includes an acrylic plate, a silicone pad, an activated carbon anode, a silicone pad, a diaphragm, a capacitor deionization electrode cathode, a silicone pad, and an acrylic plate stacked sequentially along the water inlet direction, wherein the activated carbon anode and the capacitor deionization electrode cathode are connected to a DC power supply.

[0065] (3) Selective removal of lead ions was carried out using the capacitor deionization device in step (2). Specifically, 50 mL of a mixed aqueous solution of NaNO3, Mg(NO3)2, Ca(NO3)2, KNO3, and Pb(NO3)2 was used as the polluted water body. The Na in the polluted water body was... + The concentration is 100 mg / L, Mg 2+ The concentration was 100 mg / L, Ca 2+ The concentration was 100 mg / L, K + The concentration of Pb was 100 mg / L. 2+ The concentration of lead was 10 mg / L, and the initial pH of the polluted water was 6. Under the condition of an applied voltage of 1.2 V, the adsorption treatment was carried out for 120 min to achieve selective removal of lead ions from the water.

[0066] In this embodiment, samples were continuously taken at set times during the reaction process. 0.3 mL of sample was taken from the solution at regular intervals, diluted with deionized water, filtered through a 0.22 μm membrane, and the concentrations of sodium, magnesium, calcium, potassium, and lead ions were determined using inductively coupled plasma chromatography (ICP-C). The selective removal efficiency of the electrode material for lead ions in the water was calculated, and the results are as follows: Figure 9 As shown.

[0067] Figure 9 This is a comparative graph showing the selectivity of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in water under different ion coexistence conditions, as described in Example 5 of the present invention. Figure 9 As can be seen, in this embodiment, the effects of different electrolyte solutions on the selective adsorption of lead ions were compared. The K in the mixed solution... + Ca 2+ Mg 2+ Na + The adsorption of Na is relatively small, while the adsorption selectivity of lead is relatively high. This is because the electrode exhibits different trends for ions with different hydration radii. The hydration radius is: Na + >K + >Ca 2+ >Mg 2+ >Pb 2+ The larger the hydration radius, the lower the electroadsorption of ions, the higher the electrode microporosity, and the better the adhesion between ions and the electrode surface. When the hydration radius of ions is comparable to the pore size, the micropores will adsorb more ions with smaller hydration radii, meaning that the electrode has the highest adsorption selectivity for lead ions.

[0068] In addition, in this embodiment, the capacitive deionization electrode made from MCHS@COF-1 as raw material achieved removal rates of 7.2%, 9.3%, 12.5%, 11.5%, and 85.6% for sodium ions, magnesium ions, calcium ions, potassium ions, and lead ions, respectively, after 120 min.

[0069] Example 6: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to the present invention includes the following steps: (1) Weigh 50 mg each of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and activated carbon (AC) prepared in Example 1, add 6.25 mg of conductive carbon black and 6.25 mg of polyvinylidene fluoride (PVDF) and mix evenly. Then slowly add N-methylpyrrolidone (NMP) and stir to form a uniform colloid. Use a trowel to spread the colloid on a graphite plate (5cm×5cm) and vacuum dry for 12h to obtain a capacitor deionization electrode.

[0070] (2) Using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrode as anode, assemble the capacitor deionization device. In this step, the capacitor deionization device includes an activated carbon anode and a capacitor deionization electrode cathode, and its structure is as follows: The capacitor deionization device includes an acrylic plate, a silicone pad, an activated carbon anode, a silicone pad, a diaphragm, a capacitor deionization electrode cathode, a silicone pad, and an acrylic plate stacked sequentially along the water inlet direction, wherein the activated carbon anode and the capacitor deionization electrode cathode are connected to a DC power supply.

[0071] (3) Selective removal of lead ions was carried out using the capacitor deionization device in step (2). Specifically, 50 mL of a mixed aqueous solution of NaNO3, Pb(NO3)2, Ni(NO3)2, and Fe(NO3)3 was used as the polluted water body. The Na in the polluted water body was... + The concentration of Pb was 100 mg / L. 2+ The concentration was 10 mg / L, Ni 2+ The concentration was 10 mg / L, Fe 3+ The concentration of lead was 10 mg / L, and the initial pH of the polluted water was 6. Under the condition of an applied voltage of 1.2 V, the adsorption treatment was carried out for 120 min to achieve selective removal of lead ions from the water.

[0072] In this embodiment, samples were continuously taken at set times during the reaction process. 0.3 mL samples were taken from the solution at regular intervals, diluted with deionized water, filtered through a 0.22 μm membrane, and the concentrations of lead, sodium, nickel, and iron ions were determined using inductively coupled plasma chromatography (ICP-C). The selective removal efficiency of the electrode material for lead ions in the water was calculated, and the results are as follows: Figure 10 As shown.

[0073] Figure 10 This image shows the removal effect of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) from water under different heavy metal ion coexistence conditions, as described in Example 6 of this invention. Figure 10It was found that when different heavy metal ions coexisted, the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) showed the best removal effect for lead ions, which is attributed to the specific adsorption of the covalent organic framework in the composite electrode material. Compared with nickel ions, the selectivity of iron ions was lower. This may be because iron ions exist in a trivalent state, have a higher charge, and are more strongly attracted in an electric field, resulting in a large number of electro-adsorbed ions. At the same time, since the radius of iron ions is smaller than that of nickel ions, they can more easily enter the pores of the material.

[0074] Example 7: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to the present invention includes the following steps: (1) Weigh 50 mg each of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and activated carbon (AC) prepared in Example 1, add 6.25 mg of conductive carbon black and 6.25 mg of polyvinylidene fluoride (PVDF) and mix evenly. Then slowly add N-methylpyrrolidone (NMP) and stir to form a uniform colloid. Use a trowel to spread the colloid on a graphite plate (5cm×5cm) and vacuum dry for 12h to obtain a capacitor deionization electrode.

[0075] (2) Using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrode as anode, assemble the capacitor deionization device. In this step, the capacitor deionization device includes an activated carbon anode and a capacitor deionization electrode cathode, and its structure is as follows: The capacitor deionization device includes an acrylic plate, a silicone pad, an activated carbon anode, a silicone pad, a diaphragm, a capacitor deionization electrode cathode, a silicone pad, and an acrylic plate stacked sequentially along the water inlet direction, wherein the activated carbon anode and the capacitor deionization electrode cathode are connected to a DC power supply.

[0076] (3) Selective removal of lead ions was carried out using the capacitor deionization device in step (2). Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. The NaNO3 content in this polluted water body was... + The concentration of Pb was 100 mg / L. 2+ The concentration of the substance was 10 mg / L, the initial pH of the polluted water was 6, and the adsorption treatment was carried out for 120 minutes under the condition of an applied voltage of 1.2 V to complete one cycle.

[0077] (4) After the adsorption treatment in step (3), 0.05M HCl is added to desorb the capacitor deionization electrode, and then ultrapure water is added to rinse it to obtain the regenerated capacitor deionization electrode.

[0078] (5) Repeat steps (3) and (4) to conduct a cyclic experiment for a total of 50 times to achieve selective removal of lead ions in water.

[0079] In this embodiment, samples were continuously taken at set times during the reaction process. 0.3 mL of sample was taken from the solution at regular intervals, diluted with deionized water, filtered through a 0.22 μm membrane, and the concentrations of lead and sodium ions were determined using inductively coupled plasma chromatography (ICP-C). The selective removal efficiency of the electrode material for lead ions in the water was calculated, and the results are as follows: Figure 11 As shown.

[0080] Figure 11 This image shows the cyclic removal effect of lead ions by the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in Example 7 of the present invention. Figure 11 It is evident that the mesoporous hollow carbon sphere / covalent organic framework composite electrode material exhibits excellent stability and regeneration capability during adsorption-desorption cycles. After 50 consecutive adsorption-desorption cycles, the adsorption efficiency of the material for lead ions is approximately 90% or higher, and the selectivity remains around 8. This indicates that the material structure of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material of this invention is stable, with no significant loss of active sites. Its highly efficient regeneration performance has practical application potential in the treatment of heavy metal lead ion wastewater.

[0081] In summary, the mesoporous hollow carbon sphere / covalent organic framework composite electrode material used in this invention is a novel composite electrode material with advantages such as high specific surface area, numerous active sites, good conductivity, good structural stability, excellent long-term cycling performance, high removal rate, and high selectivity. Even in the presence of multiple competing ions, it still exhibits excellent selective adsorption performance for lead ions over a wide voltage and pH range, and also possesses good regeneration capacity and recycling efficiency. The method for removing lead from water using the mesoporous hollow carbon sphere / covalent organic framework composite electrode material of this invention has advantages such as simple operation, environmental friendliness, low treatment cost, high treatment efficiency, good selective removal effect, and good reusability. It has high practical value and promising application prospects, can meet the needs of lead-containing wastewater treatment, and also conforms to the requirements of sustainable development, helping to reduce negative environmental impacts.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, characterized in that, The method describes the treatment of lead-containing wastewater using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material. This material is prepared by a solvothermal reaction of mesoporous hollow carbon spheres, 2,4,6-triformylresorcinol, and melamine. The molar ratio of the mesoporous hollow carbon spheres to 2,4,6-triformylresorcinol is 17 mg–23 mg:0.15 mmol, and the molar ratio of 2,4,6-triformylresorcinol to melamine is 1:0.9–1.

5. The solvothermal reaction temperature is 110°C–150°C. The treatment of lead-containing wastewater involves: using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material as raw material to prepare a capacitive deionization electrode; using the capacitive deionization electrode as the cathode and an activated carbon electrode as the anode to construct a capacitive deionization device for adsorption treatment of lead-containing wastewater, thereby achieving the removal of lead from the wastewater.

2. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 1, characterized in that, The preparation method of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material includes the following steps: mixing mesoporous hollow carbon spheres, 2,4,6-tricarboxymethyl phloroglucinol, melamine and organic solvent, and carrying out a solvothermal reaction to obtain the mesoporous hollow carbon sphere / covalent organic framework composite electrode material.

3. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 2, characterized in that, The organic solvent is dimethyl sulfoxide, the mixing is carried out under ultrasonic conditions, the ultrasonic time is 30 min to 60 min, the solvothermal reaction time is 10 h to 15 h, and the reaction product is washed and dried after the solvothermal reaction; the washing is done with acetone, and the drying temperature is 60 °C.

4. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 3, characterized in that, The method for preparing the mesoporous hollow carbon spheres includes the following steps: S1. Mix ethanol, water and ammonia, stir for 15 min, add tetrapropoxysilane, stir for 15 min, and obtain a mixed solution; S2. Mix the mixed solution obtained in S1, resorcinol and formaldehyde aqueous solution, stir, wash and dry to obtain a mixture; the stirring time is 24 hours, and the washing is performed by centrifugation with ethanol and water in sequence; the specific centrifugation process is as follows: centrifuge 4 to 6 times at a speed of 4000 rpm to 5000 rpm, each time for 5 minutes; S3. The mixture obtained in S2 is calcined and then etched with an alkali to obtain mesoporous hollow carbon spheres. The calcination temperature is 700℃, the calcination time is 5 hours, and the specific process of the alkali etching is as follows: the calcined product is mixed with an alkaline solution and etched. The mass ratio of the calcined product to the alkaline solution is 1:6 to 10, the alkaline solution is a sodium hydroxide solution with a mass fraction of 20%, the etching temperature is 60℃ to 80℃, and the etching time is 2 days to 3 days. The ratio of ethanol, water, ammonia, tetrapropoxysilane, resorcinol, and formaldehyde aqueous solution is 70mL:10mL:3mL:3.46mL:0.4g:0.56mL, and the mass percentage of the formaldehyde aqueous solution is 37%.

5. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 1, characterized in that, The mesoporous hollow carbon sphere / covalent organic framework composite electrode material includes mesoporous hollow carbon spheres and a covalent organic framework. The covalent organic framework is grown on the inner and outer walls of the mesoporous hollow carbon spheres. The covalent organic framework contains oxygen-containing functional groups and nitrogen-containing functional groups. The covalent organic framework has a strip-like structure and is TpTt-COF.

6. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to any one of claims 1 to 5, characterized in that, The initial concentration of lead in the lead-containing wastewater is 10 mg / L to 20 mg / L. The lead-containing wastewater also contains sodium ions, with an initial concentration of sodium ions of 100 mg / L. The initial pH value of the lead-containing wastewater is 5.5 to 6.

5. The applied voltage during the adsorption treatment is controlled at 0.6V to 1.2V, and the adsorption treatment time is ≥60 min.

7. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 6, characterized in that, The raw materials for the capacitive deionization electrode also include conductive carbon black and a binder; the preparation method of the capacitive deionization electrode includes the following steps: mixing mesoporous hollow carbon spheres / covalent organic framework composite electrode material, conductive carbon black and binder, adding solvent to form a colloid, coating the colloid on a conductive carrier, and drying to obtain the capacitive deionization electrode; the mass ratio of the mesoporous hollow carbon spheres / covalent organic framework composite electrode material, conductive carbon black and binder is 8-9:0.8-1:0.8-1, the binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol and polypropylene, the solvent is N-methylpyrrolidone, and the conductive carrier is a graphite plate.

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