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

Abstract

The invention discloses a method for removing lead in water by using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, the method is characterized in that lead-containing wastewater is treated by using the mesoporous hollow carbon sphere / covalent organic framework composite electrode material, and the mesoporous hollow carbon sphere / covalent organic framework composite electrode material is prepared from mesoporous hollow carbon spheres, 2, 4, 5, 6, 7, 7, 8, 8, 9, 10, 11, 12, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13 The flame retardant is prepared by taking 2, 3, 6-triformyl phloroglucinol and melamine as raw materials through solvothermal reaction. The mesoporous hollow carbon sphere / covalent organic framework composite electrode material adopted by the invention has the advantages of high specific surface area, multiple active sites, good conductivity, good structural stability, excellent long cycle performance, high removal rate, high selectivity and the like; the composite material still shows excellent selective adsorption performance on lead ions in a wide voltage range, can remove lead in wastewater with high selectivity, and has good regeneration capacity and recycling effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal lead ion water pollution treatment, and specifically relates to a method for removing lead from water by utilizing a mesoporous hollow carbon sphere / covalent organic framework composite electrode material. Background Art

[0002] Currently, the main technologies for removing lead ions from wastewater include adsorption, chemical precipitation, and ion exchange. However, these methods have limitations for removing low-concentration lead ions, are complex processes, and can produce 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 utilizes an electric field to transport ions from a solution into the double layer at the electrode / solution interface, thereby accumulating further capture capacity. CDI has not only become an environmentally friendly, energy-efficient, and economical desalination strategy, but some studies have also utilized CDI to remove heavy metal ions from wastewater. The development of 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 excellent chemical / mechanical durability, high conductivity, and high specific surface area. Porous carbons encompass hierarchical porous structures, including macropores, mesopores, and micropores. Mesoporous materials, also known as mesoporous carbons, exhibit highly uniform pores, large specific surface area, narrow area distribution, and a wide range of tunable pore sizes. These excellent properties are crucial for improving electrochemical signals, enhancing capacitive performance, and increasing the number of charge transfer sites. Mesoporous carbon materials have a certain adsorption capacity for lead ions. However, when other ions coexist in water, especially sodium ions, calcium ions, magnesium ions, etc., they will interfere with the removal efficiency of lead ions and have very poor selectivity for lead ions. Therefore, how to improve the adsorption of Pb 2+ Selectivity is one of the key issues that need to be solved in practical applications.

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

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a method for removing lead in water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material with high selectivity for lead ions, good removal effect, and green environmental protection.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material. The method comprises treating lead-containing wastewater using the mesoporous hollow carbon sphere / covalent organic framework composite electrode material. The mesoporous hollow carbon sphere / covalent organic framework composite electrode material is prepared by solvent thermal reaction using mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol, and melamine as raw materials. The ratio of the mesoporous hollow carbon spheres to 2,4,6-triformylphloroglucinol is less than 200 mg:0.75 mmol.

[0008] The above method is further improved in that the mass molar ratio of the mesoporous hollow carbon spheres to 2,4,6-triformylphloroglucinol is 10 mg to 30 mg: 0.15 mmol, and the molar ratio of the 2,4,6-triformylphloroglucinol to melamine is 1:0.9 to 1.5.

[0009] The above method is further improved in that the mass molar ratio of the mesoporous hollow carbon spheres to 2,4,6-triformylphloroglucinol is 17 mg to 23 mg: 0.15 mmol.

[0010] The above method is further improved, and 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 performing a solvothermal reaction to obtain a mesoporous hollow carbon sphere / covalent organic framework composite electrode material.

[0011] The above method is further improved, wherein the organic solvent is dimethyl sulfoxide, the mixing is carried out under ultrasonic conditions, the ultrasonic time is 30 minutes to 60 minutes, the temperature of the solvent thermal reaction is 110°C to 150°C, the solvent thermal reaction time is 10 hours to 15 hours, and the following treatment is performed after the solvent thermal reaction: the reaction product is washed and dried; the washing is performed using acetone, and the drying temperature is 60°C.

[0012] The above method is further improved, and the preparation method of the mesoporous hollow carbon spheres comprises the following steps: S1. Mix ethanol, water and ammonia water, stir, add tetrapropylaminosilane, and stir to obtain a mixed solution B; S2, mixing the mixed solution B obtained in S1, resorcinol and formaldehyde aqueous solution, stirring, washing, and drying to obtain a mixture; S3. The mixture obtained in S2 is calcined and alkali-etched to obtain mesoporous hollow carbon spheres.

[0013] The above method is further improved, wherein the ratio of ethanol, water, ammonia water, tetrapropylaminosilane, resorcinol and formaldehyde aqueous solution 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 using ethanol and water in sequence; the specific process of the centrifugation is: centrifugation at a speed of 4000 rpm to 5000 rpm for 4 to 6 times, each centrifugation for 5 minutes; In step S3, the calcination temperature is 700° C., the calcination time is 5 hours, and the specific process of the alkaline etching is: mixing the calcined product with an alkaline solution and etching; the mass ratio of the calcined product to the alkaline solution is 1:6-10, the alkaline solution is a sodium hydroxide solution, the mass fraction of the sodium hydroxide solution is 20%, the etching temperature is 60° C. to 80° C., and the etching time is 2 days to 3 days.

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

[0015] The above method is further improved, and the treatment is: a capacitive deionization electrode is made using a mesoporous hollow carbon ball / covalent organic framework composite electrode material as a raw material, and a capacitive deionization device is constructed using the capacitive deionization electrode as a cathode and an activated carbon electrode as an anode to perform adsorption treatment on lead-containing wastewater to achieve the removal of lead from the wastewater.

[0016] The above method is further improved, wherein 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 to be 0.6 V to 1.2 V during the adsorption treatment process, and the adsorption treatment time is ≥60 min. The above method is further improved, wherein the raw materials of the capacitor deionization electrode also include conductive carbon black and a binder; the preparation method of the capacitor deionization electrode includes the following steps: mixing a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, conductive carbon black and a binder, adding a solvent to form a colloid, coating the colloid on a conductive carrier, and drying to obtain a capacitor deionization electrode; the mass ratio of the mesoporous hollow carbon sphere / 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: (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, the present invention creatively proposes a method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, and uses the mesoporous hollow carbon sphere / covalent organic framework composite electrode material to treat lead-containing wastewater, wherein the mesoporous hollow carbon sphere / covalent organic framework composite electrode material is prepared by solvent thermal reaction using mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol and melamine as raw materials, and the ratio of mesoporous hollow carbon spheres to 2,4,6-triformylphloroglucinol is less than 200 mg:0.75 mmol. In the present invention, mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol and melamine are used as raw materials and the ratio of the raw materials is optimized to prepare 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. As a new type of composite electrode material, it still exhibits excellent selective adsorption performance for lead ions within a wide voltage and pH range in the presence of multiple competing ions, and has good regeneration ability and recycling effect. Therefore, when it is 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 skeleton network and rich nitrogen and oxygen atoms, and its unique The hollow structure and the strong coordination effect of specific nitrogen and oxygen functional groups can improve its selectivity and removal efficiency for lead ions in water. More importantly, the carbon support / scaffold material with mesoporous hollow carbon spheres as active sites, and then covalent organic skeletons grown on the inner and outer walls of the mesoporous hollow carbon spheres to form a double-layer structure, improve the conductive network and fast ion transport channels, thereby quickly adsorbing lead ions near the electrode 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 agglomeration of strip-shaped covalent organic skeletons to a certain extent, and the hollow structure can buffer the volume expansion / contraction caused by the embedding / ex-embedding of ions during the cycle of the electrode material, thereby improving its long-cycle performance. The present invention utilizes a mesoporous hollow carbon sphere / covalent organic framework composite electrode material to remove lead from water. The method has the advantages of 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 when multiple ions coexist, it can selectively remove lead ions from wastewater. It has high use value and good application prospects. It also meets the requirements of sustainable development and helps to reduce the negative impact on the environment. In addition, the preparation method of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material adopted by the present invention also has the advantages of simple process, cheap and readily available materials, convenient and stable storage, etc., is suitable for large-scale production, and has broad application prospects.

[0017] (2) In the present invention, the mesoporous hollow carbon sphere / covalent organic framework composite electrode material is optimized to have a mass molar ratio of mesoporous hollow carbon spheres to 2,4,6-triformyl phloroglucinol of 17mg to 23mg:0.15mmol and a molar ratio of 2,4,6-triformyl phloroglucinol to melamine of 1:0.9 to 1.5, which can not only improve the forming 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, not only the conductivity of the composite electrode material will be weakened, but also the specific surface area of ​​the material will be reduced, thereby reducing the effective utilization rate of the composite electrode material.

[0018] (3) In the present invention, the preparation method of mesoporous hollow carbon spheres adopts 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 contaminated water sample during the capacitive deionization process, making it easier for lead ions in the water to contact the electrode, thereby improving the removal efficiency.

[0019] (4) In the present invention, a capacitive deionization electrode is prepared using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, conductive carbon black, and a binder as raw materials, which has better cycle stability and lower energy consumption. When used for selective removal of lead ions, the capacitive deionization electrode has higher selectivity, better lead ion removal effect, and excellent long-term cycle stability, which not only ensures the reliability and durability of the system, but also reduces operating costs and improves the economic efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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 sphere (MCHS) in Example 1 of the present invention.

[0021] Figure 2 TEM images of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and mesoporous hollow carbon sphere (MCHS) in Example 1 of the present invention.

[0022] Figure 3 This is the Fourier infrared spectrum 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 Example 1 of the present invention.

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

[0024] Figure 5 This is a comparative chart of the selectivity of 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 sphere (MCHS), and activated carbon (AC) for lead ions in water in Example 1 of the present invention.

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

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

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

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

[0029] Figure 10 This is a diagram showing the removal effect of lead ions in water by the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in Example 6 of the present invention when different heavy metal ions coexist.

[0030] Figure 11 This is a diagram showing 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. DETAILED DESCRIPTION

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

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

[0033] (2) Assembling a capacitor deionization device using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrodes as anodes. 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 gasket, an activated carbon anode, a silicone gasket, a diaphragm, a capacitor deionization electrode cathode, a silicone gasket, and an acrylic plate stacked in sequence 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) The capacitive deionization device in step (2) was used to conduct a selective lead ion removal experiment. Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. + The concentration is 100mg / L, Pb 2+ The concentration of lead ions was 10 mg / L, the initial pH value 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 achieve selective removal of lead ions in 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 aqueous ammonia, and stir for 15 minutes to fully mix the solution. Add 3.46 mL of tetrapropoxysilane, continue stirring for 15 minutes, then add 0.4 g of resorcinol and 0.56 mL of formaldehyde aqueous solution (the concentration of the solution is 37 wt%), and continue stirring for 24 hours to obtain a mixed solution. Wash the obtained mixed solution with anhydrous ethanol and water by centrifugation at 5000 rpm four times, each time for 5 minutes. Dry the obtained precipitate in vacuum at 60°C for 12 hours to obtain a mixture. S1-2. The mixture obtained in step S1-1 was calcined at 700° C. for 5 h, and the calcined product was immersed in a 20 wt% sodium hydroxide solution with a mass ratio of the calcined product to the sodium hydroxide solution being 1:8. The product was etched at 80° C. for 48 h to remove silica, thereby obtaining mesoporous hollow carbon spheres, which were recorded as MCHS.

[0036] S2. Preparation of mesoporous hollow carbon sphere / covalent organic framework composite electrode materials S2-1, taking 100 mg of the mesoporous hollow carbon spheres obtained in step S1-2, 0.75 mmol of 2,4,6-triformylphloroglucinol, 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 mixed solution; S2-2. The mixed solution obtained in step S2-1 was heated at 120° C. for 12 h to react. After cooling, the reaction product was washed with acetone and dried at 60° C. for 12 h to obtain a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, which was recorded 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, and the covalent organic framework grows 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 thereof was basically the same as the preparation method of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1), with the only difference being that in step S2-1, the amounts of mesoporous hollow carbon spheres used were 200 mg and 50 mg, respectively; the corresponding mesoporous hollow carbon sphere / covalent organic framework composite electrode materials were named MCHS@COF-0.5 and MCHS@COF-2, respectively.

[0039] In this embodiment, the preparation method of the covalent organic framework (COF) used includes the following steps: (a) 0.75 mmol of 2,4,6-triformylphloroglucinol and 0.75 mmol of melamine were mixed uniformly, dispersed in 50 ml of dimethyl sulfoxide, and sonicated for 30 min to obtain a mixed solution; (b) The mixture obtained in (a) was heated at 120°C for 12 h to react. 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 The 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 sphere (MCHS) in Example 1 of the present invention are shown. 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 larger than the diameter, and it has a significant aspect ratio, which is conducive to building a conductive network and enhancing signal response. The mesoporous hollow carbon spheres (MCHS) synthesized by the hard template method present uniform and regular spherical particles (diameter approximately 450-530 nm) with good dispersion and no obvious adhesion or breakage. After the COF and MCHS are combined, that is, the mesoporous hollow carbon sphere / covalent organic framework composite electrode materials (MCHS@COF-0.5, MCHS@COF-1, MCHS@COF-2), it can effectively reduce aggregation and increase more active sites.

[0041] Figure 2 TEM images of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) and mesoporous hollow carbon sphere (MCHS) in Example 1 of the present invention. Figure 2 Among them, (a) is MCHS, and (b) is MCHS@COF-1. Figure 2 The contrast in brightness reveals that MCHS has a hollow spherical structure. The MCHS carbon layer is approximately 50 nm thick, and the shell contains mesoporous channels. MCHS@COF-1 is approximately 70 nm thick and darker than MCHS, indicating that COF is tightly bonded to the carbon sphere surface and grows more uniformly vertically on the surface. This further demonstrates the relatively uniform synthesis of COF on the MCHS surface.

[0042] Figure 3 The following is a Fourier transform infrared spectrum 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 Example 1 of the present invention. Figure 3 It can be seen that the Fourier infrared spectra of the three materials all show an obvious absorption peak at about 3410 cm-1 , corresponding to the stretching vibration of the OH bond. In contrast, the characteristic peak of the CO stretching vibration and MCHS is significantly weaker, indicating that the COF and MCHS are connected through an ether bond. In addition, the results of Fourier transform infrared spectroscopy also confirmed the successful loading of the covalent organic framework on the mesoporous hollow carbon spheres.

[0043] In this example, continuous sampling was performed at set times during the treatment process. 0.3 mL of sample was taken from the solution at regular intervals, mixed and diluted with deionized water, filtered through a 0.22 μm membrane, and the lead ion concentration and sodium ion concentration were determined by inductively coupled plasma chromatography. The selectivity and removal effect of different electrode materials on lead ions in water were calculated. The results are shown in FIG. Figure 4 and Figure 5 In this embodiment, at 120 min, 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.

[0044] Figure 4 This figure shows the removal efficiency of lead and sodium ions from water using the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in Example 1 of the present 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%, and the lead ion removal rate reaches approximately 96%. This demonstrates that the mesoporous hollow carbon sphere / covalent organic framework composite electrode material of the present invention can achieve highly selective removal of lead ions from water.

[0045] Figure 5 This is a comparative chart of the selectivity of 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 sphere (MCHS), and activated carbon (AC) for lead ions in water in Example 1 of the present invention. Adsorption experiments were carried out using AC, MCHS, MCHS@COF-0.5, MCHS@COF-1, and MCHS@COF-2 as cathodes and AC as anode. Figure 5 As shown, the selectivity coefficient of MCHS@COF-1 (Pb 2+ / Na +) is the largest, with the selectivity of MCHS@COF-2 being lower than that of MCHS@COF-1. This is likely due to the increased surface roughness of the MCHS due to the presence of more COF encapsulating it, which provides more defects and active sites, enhancing the adsorption capacity of sodium ions and thus affecting the selectivity. After 90 minutes of operation, the capacitive deionization system gradually reached saturation for lead ion adsorption, which may be 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 of the present invention comprises 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 them evenly. Then slowly add N-methylpyrrolidone (NMP) dropwise and stir to form a uniform colloid. Use a pestle to spread the colloid on a graphite plate (5 cm × 5 cm) and vacuum dry it for 12 h to obtain a capacitive deionization electrode.

[0047] (2) Assembling a capacitor deionization device using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrodes as anodes. 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 gasket, an activated carbon anode, a silicone gasket, a diaphragm, a capacitor deionization electrode cathode, a silicone gasket, and an acrylic plate stacked in sequence 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) The capacitive deionization device in step (2) was used to conduct a selective lead ion removal experiment. Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. + The concentration is 100mg / L, Pb 2+ The concentration of lead ions was 10 mg / L, and the initial pH value of the polluted water was 6. The adsorption treatment was carried out for 120 minutes under the conditions of applied voltages of 0.6 V, 0.9 V, 1.2 V, and 1.5 V, respectively, to achieve selective removal of lead ions in the water.

[0049] In this example, continuous sampling was performed at set times during the reaction process. 0.3 mL of sample was taken from the solution at regular intervals, mixed and diluted with deionized water, filtered through a 0.22 μm membrane, and the lead ion concentration and sodium ion concentration were determined by inductively coupled plasma chromatography. The selective removal effect of the electrode material on lead ions in water was calculated. The results are shown in FIG. Figure 6shown. Figure 6 This is a comparison chart of the selectivity of mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) to lead ions in water at different voltages in Example 2 of the present invention. Figure 6 It can be seen that in the present invention, when the voltage is 1.2 V, the selectivity of MCHS@COF-1 for lead ions is the highest; at 0.6 V, the selectivity of MCHS@COF-1 is relatively high, which may be due to the low ability of the double-layer capacitor to adsorb sodium ions at low voltage; the selectivity is lowest at 1.5 V, which may be due to the electrochemical decomposition of water molecules at this potential to produce hydrogen ions, which compete with lead ions for adsorption, resulting in a decrease in the lead ion adsorption efficiency. At the same time, as the voltage increases, the adsorption capacity for sodium ions is enhanced.

[0050] In addition, in this embodiment, at 120 min, the capacitive deionization electrode prepared with MCHS@COF-1 as raw material had lead ion removal rates of 96.0%, 93.9%, 95.7%, and 92.1% at applied voltages of 0.6 V, 0.9 V, 1.2 V, and 1.5 V, respectively.

[0051] Example 3: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material of the present invention comprises 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 them evenly. Then slowly add N-methylpyrrolidone (NMP) dropwise and stir to form a uniform colloid. Use a pestle to spread the colloid on a graphite plate (5 cm × 5 cm) and vacuum dry it for 12 h to obtain a capacitive deionization electrode.

[0052] (2) Assembling a capacitor deionization device using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrodes as anodes. 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 gasket, an activated carbon anode, a silicone gasket, a diaphragm, a capacitor deionization electrode cathode, a silicone gasket, and an acrylic plate stacked in sequence 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) The capacitive deionization device in step (2) was used to conduct a selective lead ion removal experiment. Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 with different concentrations was used as the polluted water body. +The concentration of Pb in the polluted water is 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 minutes to achieve selective removal of lead ions in the water.

[0054] In this embodiment, continuous sampling was performed at set times during the treatment process. 0.3 mL of sample was taken from the solution at regular intervals, mixed and diluted with deionized water, filtered through a 0.22 μm membrane, and the lead ion concentration and sodium ion concentration were determined by inductively coupled plasma chromatography. The selectivity and removal effect of the electrode material on lead ions in water were calculated. The results are shown in FIG. Figure 7 shown.

[0055] Figure 7 This is a comparison chart of the selectivity of mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) to lead ions in water at different concentrations in Example 3 of the present invention. Figure 7 It can be seen that in the present 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, that is, the lead ion concentration is low, the selectivity of MCHS@COF-1 for lead ions is low, which 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, which 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 capacitor deionization electrode prepared with MCHS@COF-1 as raw material was 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 of the present invention comprises 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 them evenly. Then slowly add N-methylpyrrolidone (NMP) dropwise and stir to form a uniform colloid. Use a pestle to spread the colloid on a graphite plate (5 cm × 5 cm) and vacuum dry it for 12 h to obtain a capacitive deionization electrode.

[0058] (2) Assembling a capacitor deionization device using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrodes as anodes. 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 gasket, an activated carbon anode, a silicone gasket, a diaphragm, a capacitor deionization electrode cathode, a silicone gasket, and an acrylic plate stacked in sequence 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) The capacitive deionization device in step (2) was used to conduct a selective lead ion removal experiment. Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. + The concentration is 100mg / L, Pb 2+ The concentration of lead ions was 10 mg / L, and the pH value of the contaminated water was adjusted with 0.01 M HNO3 and 0.01 M NH3·H2O, that is, the pH value of the contaminated 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 in the water.

[0060] In this embodiment, continuous sampling was performed at set times during the treatment process. 0.3 mL of sample was taken from the solution at regular intervals, mixed and diluted with deionized water, filtered through a 0.22 μm membrane, and the lead ion concentration and sodium ion concentration were determined by inductively coupled plasma chromatography. The selectivity and removal effect of the electrode material on lead ions in water were calculated. The results are shown in FIG. Figure 8 shown.

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

[0062] In addition, in this embodiment, within 120 minutes, the capacitive deionization electrode prepared with MCHS@COF-1 as raw material had a lead ion removal rate of 93.8%, 96.0%, 98.0%, 95.7%, and 97.9% when the pH values ​​of the contaminated water were 3, 4, 5, 6, and 7, respectively.

[0063] Example 5: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material of the present invention comprises 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 them evenly. Then slowly add N-methylpyrrolidone (NMP) dropwise and stir to form a uniform colloid. Use a pestle to spread the colloid on a graphite plate (5 cm × 5 cm) and vacuum dry it for 12 h to obtain a capacitive deionization electrode.

[0064] (2) Assembling a capacitor deionization device using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrodes as anodes. 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 gasket, an activated carbon anode, a silicone gasket, a diaphragm, a capacitor deionization electrode cathode, a silicone gasket, and an acrylic plate stacked in sequence 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) The capacitive deionization device in step (2) was used to conduct a selective lead ion removal experiment. 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 concentration is 100mg / L, Mg 2+ The concentration is 100 mg / L, Ca 2+ The concentration is 100 mg / L, K + The concentration is 100mg / L, Pb 2+ The concentration of lead ions was 10 mg / L, the initial pH value 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 achieve selective removal of lead ions in the water.

[0066] In this embodiment, continuous sampling was performed at set times during the reaction process. 0.3 mL of sample was taken from the solution at regular intervals, deionized water was added to mix and dilute, and the sample was filtered through a 0.22 μm membrane. The sodium ion concentration, magnesium ion concentration, calcium ion concentration, potassium ion concentration, and lead ion concentration were determined by inductively coupled plasma chromatography. The selective removal effect of the electrode material on lead ions in water was calculated. The results are shown in FIG. Figure 9 shown.

[0067] Figure 9 This is a comparative diagram of the selectivity of mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) to lead ions in water under the coexistence of different ions in Example 5 of the present invention. Figure 9 It can be seen that in this embodiment, the effects of different electrolyte solutions on the selective adsorption of lead ions are compared. + , Ca 2+ Mg 2+ 、Na + The adsorption of lead is relatively small, and the adsorption selectivity of lead is higher. This is because: the electrode shows different trends for ions with different hydration radii. The size of the hydration radius: Na + >K + >Ca 2+ >Mg 2+ >Pb 2+ The larger the hydration radius, the lower the electrical adsorption of ions, the higher the electrode microporosity, and the better the fit between ions and the electrode surface. When the hydration radius of the ions is equivalent to the pore size, the micropores will adsorb more ions with a smaller hydration radius, that is, the electrode has the highest adsorption selectivity for lead ions.

[0068] In addition, in this embodiment, within 120 minutes, the capacitive deionization electrode prepared with MCHS@COF-1 as raw material had 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.

[0069] Example 6: A method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material of the present invention comprises 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 them evenly. Then slowly add N-methylpyrrolidone (NMP) dropwise and stir to form a uniform colloid. Use a pestle to spread the colloid on a graphite plate (5 cm × 5 cm) and vacuum dry it for 12 h to obtain a capacitive deionization electrode.

[0070] (2) Assembling a capacitor deionization device using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrodes as anodes. 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 gasket, an activated carbon anode, a silicone gasket, a diaphragm, a capacitor deionization electrode cathode, a silicone gasket, and an acrylic plate stacked in sequence 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) The capacitive deionization device in step (2) was used to conduct a selective lead ion removal experiment. 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 concentration is 100mg / L, Pb 2+ The concentration is 10mg / L, Ni 2+ The concentration is 10mg / L, Fe 3+ The concentration of lead ions was 10 mg / L, the initial pH value 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 achieve selective removal of lead ions in the water.

[0072] In this example, continuous sampling was performed at set times during the reaction process. 0.3 mL of sample was taken from the solution at regular intervals, mixed and diluted with deionized water, filtered with a 0.22 μm membrane, and the lead ion concentration, sodium ion concentration, nickel ion concentration, and iron ion concentration were determined by inductively coupled plasma chromatography. The selective removal effect of the electrode material on lead ions in water was calculated. The results are shown in FIG. Figure 10 shown.

[0073] Figure 10 This is a diagram showing the removal effect of lead ions in water by the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) in Example 6 of the present invention when different heavy metal ions coexist. Figure 10A comparison of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material (MCHS@COF-1) revealed the best lead ion removal performance when different heavy metal ions coexisted. This is attributed to the specific adsorption of the covalent organic framework within the composite electrode material. Iron ions showed lower selectivity than nickel ions. This is likely due to the fact that iron ions, existing in a trivalent state and possessing a higher charge, experience stronger attraction in an electric field, resulting in the presence of a large number of electrically adsorbed ions. Furthermore, since iron ions have a smaller radius than nickel ions, they 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 of the present invention comprises 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 them evenly. Then slowly add N-methylpyrrolidone (NMP) dropwise and stir to form a uniform colloid. Use a pestle to spread the colloid on a graphite plate (5 cm × 5 cm) and vacuum dry it for 12 h to obtain a capacitive deionization electrode.

[0075] (2) Assembling a capacitor deionization device using the capacitor deionization electrodes obtained in step (1) as cathodes and the activated carbon electrodes as anodes. 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 gasket, an activated carbon anode, a silicone gasket, a diaphragm, a capacitor deionization electrode cathode, a silicone gasket, and an acrylic plate stacked in sequence 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) The capacitive deionization device in step (2) was used to conduct a selective lead ion removal experiment. Specifically, 50 mL of a mixed aqueous solution of NaNO3 and Pb(NO3)2 was used as the polluted water body. + The concentration is 100mg / L, Pb 2+ The concentration is 10 mg / L, the initial pH value of the polluted water is 6, and the adsorption treatment is 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 was added to desorb the capacitor deionization electrode, and then ultrapure water was added to rinse to obtain a regenerated capacitor deionization electrode.

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

[0079] In this example, continuous sampling was performed at set times during the reaction process. 0.3 mL of sample was taken from the solution at regular intervals, mixed and diluted with deionized water, filtered through a 0.22 μm membrane, and the lead ion concentration and sodium ion concentration were determined by inductively coupled plasma chromatography. The selective removal effect of the electrode material on lead ions in water was calculated. The results are shown in FIG. Figure 11 shown.

[0080] Figure 11 This is a diagram showing 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 can be seen that the mesoporous hollow carbon sphere / covalent organic framework composite electrode material exhibits excellent stability and regeneration ability in the adsorption-desorption cycle. After 50 consecutive adsorption-desorption cycles, the adsorption efficiency of the material for lead ions is about 90% or more, and the selectivity coefficient remains at around 8. This shows that the material structure of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material of the present invention is stable, and there is no obvious loss of active sites. Its 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 skeleton composite electrode material used in the present invention is a new type of composite electrode material with the advantages of high specific surface area, many active sites, good conductivity, good structural stability, excellent long cycle performance, high removal rate, high selectivity, etc. In the presence of multiple competing ions, it still exhibits excellent selective adsorption performance for lead ions within a wide voltage and pH range, and has good regeneration ability and recycling effect. The method of removing lead from water using a mesoporous hollow carbon sphere / covalent organic skeleton composite electrode material of the present invention has the advantages of simple operation, green environmental protection, low processing cost, high processing efficiency, good selective removal effect, good reusability, high use value, good application prospects, can meet the needs of lead-containing wastewater treatment, and also meets the requirements of sustainable development, helping to reduce the negative impact on the environment.

[0082] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution 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 utilizes a 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 solvent thermal reaction using mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol and melamine as raw materials; the ratio of the mesoporous hollow carbon spheres to 2,4,6-triformylphloroglucinol is less than 200 mg:0.75 mmol.

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 mass molar ratio of the mesoporous hollow carbon spheres to 2,4,6-triformyl phloroglucinol is 10 mg to 30 mg: 0.15 mmol, and the molar ratio of the 2,4,6-triformyl phloroglucinol to melamine is 1: 0.9 to 1.

5.

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 mass molar ratio of the mesoporous hollow carbon spheres to 2,4,6-triformylphloroglucinol is 17 mg to 23 mg: 0.15 mmol.

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 preparation method of the mesoporous hollow carbon sphere / covalent organic framework composite electrode material comprises the following steps: mixing mesoporous hollow carbon spheres, 2,4,6-triformylphloroglucinol, melamine and an organic solvent, and performing a solvothermal reaction to obtain the mesoporous hollow carbon sphere / covalent organic framework composite electrode material.

5. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 4, characterized in that: The organic solvent is dimethyl sulfoxide, the mixing is carried out under ultrasonic conditions, the ultrasonic time is 30 minutes to 60 minutes, the temperature of the solvent thermal reaction is 110°C to 150°C, the solvent thermal reaction time is 10 hours to 15 hours, and the following treatments are also performed after the solvent thermal reaction: the reaction product is washed and dried; the washing is performed using acetone, and the drying temperature is 60°C.

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

7. 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 covalent organic frameworks. The covalent organic frameworks grow on the inner and outer walls of the mesoporous hollow carbon spheres to form a double-layer structure. The covalent organic frameworks contain oxygen-containing functional groups and nitrogen-containing functional groups. The covalent organic frameworks are strip-shaped structures. The covalent organic frameworks are TpTt-COF.

8. 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 7, characterized in that: The treatment method is as follows: a capacitive deionization electrode is made from a mesoporous hollow carbon ball / covalent organic framework composite electrode material as a raw material, the capacitive deionization electrode is used as a cathode, and an activated carbon electrode is used as an anode to construct a capacitive deionization device to perform adsorption treatment on lead-containing wastewater to achieve lead removal from the wastewater.

9. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 8, 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, 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 external voltage is controlled to be 0.6 V to 1.2 V during the adsorption treatment process, and the time of the adsorption treatment is ≥60 min.

10. The method for removing lead from water using a mesoporous hollow carbon sphere / covalent organic framework composite electrode material according to claim 9, characterized in that: The raw materials of the capacitor deionization electrode also include conductive carbon black and a binder; the preparation method of the capacitor deionization electrode includes the following steps: mixing a mesoporous hollow carbon sphere / covalent organic framework composite electrode material, conductive carbon black and a binder, adding a solvent to form a colloid, coating the colloid on a conductive carrier, and drying to obtain a capacitor deionization electrode; the mass ratio of the mesoporous hollow carbon sphere / 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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