Method for treating heavy metal wastewater by using double-metal MOFs derived carbon-porous carbon composite electrode material

Abstract

The application discloses a method for treating heavy metal wastewater by using a bimetallic MOFs derived carbon-porous carbon composite electrode material, which comprises the following steps: preparing the bimetallic MOFs derived carbon-porous carbon into a composite electrode material and assembling the composite electrode material into a capacitive deionization device as a working electrode; and performing electric adsorption treatment on the heavy metal wastewater by using the capacitive deionization device to complete the treatment of the heavy metal wastewater. In the application, the capacitive deionization device assembled by the bimetallic MOFs derived carbon-porous carbon is used to treat the heavy metal wastewater, which can not only efficiently and quickly remove heavy metal ions, but also has the characteristics of high adsorption and selective adsorption, can realize efficient removal of heavy metals in wastewater, can selectively recover toxic and harmful metals, and has the advantages of low cost, simple process, convenient operation, high treatment efficiency, good removal effect, green environmental protection and the like, and has high application value and wide application prospect in the treatment of heavy metal contaminated water bodies.

Description

Technical Field

[0001] This invention belongs to the field of capacitive deionization and electroadsorption, and relates to a method for treating heavy metal wastewater, specifically a method for treating heavy metal wastewater using bimetallic MOFs-derived carbon-porous carbon composite electrode materials. Background Technology

[0002] Heavy metals, whether in elemental form or as metal ions, can cause serious damage to aquatic environments when they enter the water supply through rainwater or surface water. For example, large amounts of lead and manganese entering water bodies not only affect aquatic ecosystems and water quality but also pose toxic risks to human health. Therefore, effectively removing heavy metals from wastewater is of great importance.

[0003] Capacitive deionization (CDI) technology is a water treatment technology developed in the late 20th century. It features low energy consumption, no secondary pollution, recyclability, and fast treatment rates, making it a promising technology with broad application prospects. Theoretically, CDI can treat any electron-carrying pollutant. However, most research on CDI devices has been limited to seawater desalination, primarily focusing on the removal of alkali metals and valuable metals, with limited research on the removal of heavy metal ions. The electrode is the most crucial component of CDI technology, determining its application direction and effectiveness. Currently, carbon-based materials used to prepare CDI electrodes mainly include activated carbon, graphene, carbon nanotubes, and biochar. However, they still have the following drawbacks: for example, activated carbon has low conductivity, affecting its charge transfer rate and deionization efficiency; graphene is relatively expensive; carbon nanotubes have complex preparation methods and high costs; and biochar has relatively low pore structure and controllability, with disordered functional characteristics, making it unsuitable for complex treatment environments. To address the aforementioned shortcomings, some researchers have proposed using metal-organic frameworks (MOFs) to prepare capacitive deionization electrodes. However, in order to improve the adsorption capacity of the capacitive deionization electrode, acid washing is required during the preparation of MOF-derived carbon. This results in CDI electrode materials prepared from MOF-derived carbon only having electroadsorption capabilities and lacking redox capabilities. Consequently, they cannot achieve the conversion of heavy metal ions and are difficult to selectively adsorb heavy metal ions. This greatly limits the widespread application of MOF-derived carbon in capacitive deionization technology. In addition, some researchers have proposed to composite metal-organic framework (MOF)-derived carbon with graphene to create CDI electrode materials, utilizing the high conductivity of graphene to improve the conductivity of the CDI electrode material. However, the CDI electrode material constructed in this way still only has electroadsorption function and lacks redox function, thus failing to achieve the conversion of heavy metal ions. At the same time, this CDI electrode material still has defects such as small specific surface area, few adsorption sites, and small adsorption capacity, resulting in poor adsorption and removal capacity for heavy metals, ultimately making it difficult to effectively remove heavy metals from water. Therefore, obtaining a bimetallic MOF-derived carbon-porous carbon composite electrode material with large specific surface area, many adsorption sites, large adsorption capacity, good conductivity, strong redox ability, and good chemical stability is of great significance for realizing the effective treatment of heavy metal wastewater using capacitive deionization technology. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for treating heavy metal wastewater using bimetallic MOFs-derived carbon-porous carbon composite electrode materials that is simple in process, convenient in operation, low in cost, high in treatment efficiency, good in removal effect, and environmentally friendly.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A method for treating heavy metal wastewater using bimetallic MOF-derived carbon-porous carbon composite electrode materials includes the following steps:

[0007] S1. Prepare a bimetallic MOFs-derived carbon-porous carbon composite electrode material by processing bimetallic MOFs-derived carbon-porous carbon as a composite material of bimetallic MOFs and porous carbon.

[0008] S2. A capacitive deionization device is assembled using bimetallic MOFs-derived carbon-porous carbon composite electrode material as the working electrode.

[0009] S3. Use a capacitor deionization device to electro-adsorb heavy metal wastewater to complete the treatment of heavy metal wastewater.

[0010] A further improvement to the above method is the preparation method of bimetallic MOFs-derived carbon-porous carbon, which includes the following steps: heating the composite material of bimetallic MOFs and porous carbon to 450℃~600℃ for carbonization to obtain bimetallic MOFs-derived carbon-porous carbon; the carbonization is carried out under an inert atmosphere and / or a nitrogen atmosphere; the inert atmosphere is argon and / or helium; the heating rate during the carbonization process is 5℃ / min~15℃ / min; and the carbonization time is 30min~120min.

[0011] A further improvement to the above method, the preparation method of the composite material of bimetallic MOFs and porous carbon includes the following steps:

[0012] (a) Zinc salt and cobalt salt were mixed with methanol to obtain a metal template solution; organic ligands were mixed with methanol and porous carbon was added to obtain an organic ligand solution containing porous carbon.

[0013] (b) An organic ligand solution containing porous carbon was added to a metal template solution and stirred to obtain a composite material of bimetallic MOFs and porous carbon.

[0014] In a further improvement to the above method, in step (a), the molar ratio of the zinc salt to the cobalt salt is 1:1 to 3; in the metal template solution, the ratio of the total molar amount of zinc salt and cobalt salt to methanol is 0.01 mol: 100 mL to 200 mL; in the organic ligand solution containing porous carbon, the ratio of the organic ligand to methanol is 3.5 g: 50 mL to 100 mL; the mass ratio of the porous carbon to the total mass of the zinc salt and cobalt salt is 1:1 to 3; the zinc salt is at least one of zinc chloride, zinc nitrate, and zinc acetate; the cobalt salt is at least one of cobalt chloride, cobalt nitrate, and cobalt acetate; the organic ligand is at least one of 1-methylimidazole, 2-methylimidazole, 4,5-dimethylimidazole, 2-ethylimidazole, and 2-isopropylimidazole; the porous carbon is porous biochar and / or activated carbon; and the particle size of the porous carbon is less than 30 mesh.

[0015] In a further improvement to the above method, in step (b), the stirring is carried out at a temperature of 25℃ to 40℃; the stirring time is 1h to 2h; after the stirring is completed, the method further includes: centrifuging the stirred product at 8000 to 12000 r / min, washing the centrifuged solid product with a washing solution, and drying it at 60 to 90℃; the washing solution is water, an organic solvent, and an acidic solution; the organic solvent is at least one of ether, alcohol, and ketone; the acidic solution is hydrochloric acid and / or dilute nitric acid.

[0016] A further improvement to the above method is that, in step S1, the preparation method of the bimetallic MOFs-derived carbon-porous carbon composite electrode material includes the following steps:

[0017] (1) Mix bimetallic MOFs-derived carbon-porous carbon, binder and solvent, stir to prepare electrode slurry;

[0018] (2) The electrode slurry is mixed with carbon felt, ultrasonicated, and dried to obtain a carbon felt electrode loaded with the material;

[0019] (3) The carbon felt electrode loaded with the material is attached to the current collector to obtain a bimetallic MOFs-derived carbon-porous carbon composite electrode material.

[0020] In a further improvement to the above method, in step (1), the mass ratio of the bimetallic MOFs-derived carbon-porous carbon to the binder is 4 to 9:1; the ratio of the total mass of the bimetallic MOFs-derived carbon-porous carbon and the binder to the volume of the solvent is 1 mg: 1 mL to 2 mL; the binder is at least one of polyvinyl alcohol and polyvinylidene fluoride; the solvent is N-methylpyrrolidone; and the stirring time is ≥4 h.

[0021] The above method is further improved in step (2), in which the carbon felt is further treated as follows before use: the carbon felt is cut into sheet material with a length and width of 5cm×5cm, ultrasonically cleaned in ethanol for more than 2 hours, ultrasonically cleaned in water for more than 2 hours, and then dried.

[0022] In a further improvement to the above method, in step (3), a conductive carbon adhesive is used to attach the carbon felt electrode to the current collector; the current collector is one of titanium plate, copper foil, aluminum foil, graphite paper, and graphite plate; before use, the current collector is further treated as follows: the current collector is placed in an oxalic acid solution and heated to 85℃~100℃, maintained for 1.5 hours~3 hours, and then washed with water and ethanol in sequence, and dried; the mass fraction of the oxalic acid solution is 5%~20%.

[0023] In a further improvement to the above method, in step S3, the flow rate of the heavy metal wastewater in the capacitive deionization device is controlled to be 15 mL / min during the electro-adsorption treatment process. -1 ~20mL min -1 .

[0024] In a further improvement to the above method, in step S3, the residence time of the heavy metal wastewater in the capacitor deionization device is 1 to 3 hours.

[0025] In a further improvement to the above method, in step S3, the voltage of the capacitor deionization device is controlled to be 1V to 1.2V during the electro-adsorption treatment process.

[0026] In a further improvement to the above method, in step S3, the heavy metal in the heavy metal wastewater is at least one of lead, cadmium, manganese, and copper; and the initial concentration of the heavy metal in the heavy metal wastewater is ≤100 mg / L. -1 The initial pH value of the heavy metal wastewater is <7.5.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] (1) In view of the shortcomings of existing MOFs-derived carbon-based capacitive deionization electrode materials, such as small specific surface area, few adsorption sites, small adsorption capacity, and poor redox ability, and the resulting defects such as only having desalination function, difficulty in quickly and thoroughly removing heavy metal ions, and difficulty in selectively adsorbing heavy metal ions, this invention creatively proposes a method for treating heavy metal wastewater using bimetallic MOFs-derived carbon-porous carbon composite electrode material. The bimetallic MOFs-derived carbon-porous carbon composite electrode material is used as the working electrode, assembled into a capacitive deionization device, and the capacitive deionization device is used to perform electro-adsorption treatment on heavy metal wastewater. The bimetallic MOFs-derived carbon-porous carbon is prepared by carbonization treatment of a composite material of bimetallic MOFs and porous carbon. In this invention, a composite material of bimetallic MOFs and porous carbon is used as the raw material. This material is a porous material with a bimetallic organic framework loaded onto porous carbon as a carrier. On one hand, using porous carbon as a carrier improves the dispersibility of the bimetallic organic framework, allowing it to be uniformly dispersed and stably loaded onto biochar. This facilitates the formation of a structurally stable bimetallic MOF-derived carbon-porous carbon with a large specific surface area, abundant mesopores, numerous adsorption sites, and excellent conductivity during carbonization. Therefore, using this material to prepare bimetallic MOF-derived carbon-porous carbon composite electrode materials is beneficial for achieving efficient removal of heavy metals from water. On the other hand, during carbonization, the organic ligands in the bimetallic organic framework carbonize to form a carbon framework. Simultaneously, the metal ions in the bimetallic organic framework are converted into metal oxides and embedded in the carbon framework. In this material, due to the excellent semiconductor properties, electrocatalytic ability, and redox ability of metal oxides, bimetallic MOFs-derived carbon-porous carbon has the ability to change the valence state or form of heavy metals, exhibiting excellent selective adsorption performance. Moreover, under the promoting effect of the carbon skeleton, the conductivity of bimetallic MOFs-derived carbon-porous carbon can also be significantly improved, exhibiting excellent conductivity. Thus, bimetallic MOFs-derived carbon-porous carbon with excellent electroadsorption performance and strong redox ability can be formed. Using it to prepare bimetallic MOFs-derived carbon-porous carbon composite electrode materials can not only greatly improve the ability of bimetallic MOFs-derived carbon-porous carbon composite electrode materials to remove heavy metals, but also greatly improve the rate of heavy metal removal, ultimately achieving selective adsorption and recovery of heavy metals in water.Therefore, in this invention, when a capacitive deionization device assembled using a bimetallic MOFs-derived carbon-porous carbon composite electrode material as the working electrode is used to treat heavy metal wastewater, it not only efficiently and rapidly removes heavy metal ions but also possesses high adsorption capacity and selective adsorption characteristics. It can not only achieve efficient removal of heavy metals from wastewater but also selectively recover toxic and harmful metals. It has advantages such as low cost, simple process, convenient operation, high treatment efficiency, good removal effect, and green environmental protection. It has high application value and broad application prospects in the treatment of heavy metal polluted water bodies.

[0029] (2) In this invention, the composite material of bimetallic MOFs and porous carbon is prepared using porous carbon as raw material and zinc salt and cobalt salt as metal templates under the action of organic ligands. Compared with conventional preparation methods, the present invention uses porous carbon as raw material and zinc salt and cobalt salt as metal templates, which has the following advantages: (a) Porous carbon has high electrical conductivity and capacitance performance, which can enhance electrochemical performance and make the capacitive deionization material have better energy storage capacity, thereby further improving the conductivity of the capacitive deionization material. (b) Porous carbon has a porous structure, which can provide more active surface area for the capacitive deionization material, increase the adsorption and storage capacity in the deionization process, and improve the efficiency of the capacitive deionization material. (c) Organometallic frameworks and porous carbon can compensate for each other's shortcomings. Biochar provides good electrical conductivity and promotes electron conduction, while organometallic frameworks provide porous structure and regulatory functions. Therefore, combining these two materials can form a composite material with excellent conductivity and high tunability. Further, through calcination, a zinc-cobalt bimetallic MOFs-derived carbon-porous carbon with a large specific surface area, abundant mesopores, numerous adsorption sites, good conductivity, and strong catalytic performance is formed. This not only improves the adsorption capacity of the bimetallic MOFs-derived carbon-porous carbon composite electrode material but also enhances its adsorption rate, resulting in excellent electroadsorption performance. Furthermore, the method for preparing the bimetallic MOFs-porous carbon composite material of this invention has advantages such as simple process, convenient operation, wide availability of raw materials, simple preparation conditions, low production cost, high economic benefits, short production cycle, and environmental friendliness, making it suitable for large-scale preparation and industrial application. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0031] Figure 1This is a SEM image of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention.

[0032] Figure 2 The image shows the full XRD pattern of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention.

[0033] Figure 3 This is the full FTIR spectrum of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention.

[0034] Figure 4 This is the XPS full spectrum of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention.

[0035] Figure 5 This is the nitrogen adsorption-desorption isotherm of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of the present invention.

[0036] Figure 6 This is a pore size distribution diagram of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of the present invention.

[0037] Figure 7 The image shows the CV diagram of the bimetallic MOFs-derived carbon-porous carbon composite electrode material prepared in Example 1 of this invention.

[0038] Figure 8 This is a graph showing the removal rate of lead and manganese wastewater with a concentration of 100 mg / L treated using bimetallic MOFs-derived carbon-porous carbon composite electrode material in Example 1 of the present invention.

[0039] Figure 9 This is a diagram showing the selective adsorption effect of different ions when using bimetallic MOFs-derived carbon-porous carbon composite electrode material to treat lead ions with a concentration of 100 mg / L in Example 1 of the present invention.

[0040] Figure 10 This is a diagram showing the selective adsorption effect of different ions when using bimetallic MOFs-derived carbon-porous carbon composite electrode material to treat manganese ions at a concentration of 100 mg / L in Example 1 of the present invention.

[0041] Figure 11 This is a comparison chart of the highest adsorption capacity of the bimetallic MOFs-derived carbon-porous carbon composite electrode material and the pure biochar electrode in Example 1 of the present invention. Detailed Implementation

[0042] 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.

[0043] Example 1:

[0044] A method for treating heavy metal wastewater using bimetallic MOF-derived carbon-porous carbon composite electrode materials, specifically using a capacitor deionization device assembled from bimetallic MOF-derived carbon-porous carbon composite electrode materials to treat heavy metal lead wastewater and heavy metal manganese wastewater, includes the following steps:

[0045] S1. A bimetallic MOF-derived carbon-porous carbon composite electrode material is prepared by fabricating a bimetallic MOF-derived carbon-porous carbon composite electrode material, specifically as follows:

[0046] S1-1. Weigh 25mg of bimetallic MOFs-derived carbon-porous carbon and 5mg of polyvinyl alcohol, mix them evenly, add 30mL of N-methylpyrrolidone (NMP), stir for 4h to form a paste slurry, and obtain the electrode slurry.

[0047] In this step, the bimetallic MOF-derived carbon-porous carbon is prepared by carbonization of a composite material of bimetallic MOFs and porous carbon, including the following steps:

[0048] (1.1) Add 0.01 mol of zinc salt (3 g of zinc nitrate hexahydrate) and 0.01 mol of cobalt salt (3 g of cobalt nitrate hexahydrate) to methanol in an equimolar ratio. Stir at 25°C for 2 h (stirring at 25–40°C for 2 h–4 h is also acceptable) to dissolve the zinc and cobalt salts in the methanol, thus obtaining a metal template solution. The ratio of the total molar amount of zinc and cobalt salts to methanol in this metal template solution is 0.01 mol: 100 mL.

[0049] (1.2) Add 7g of 2-methylimidazole to 200mL of methanol and stir at 25℃ for 2h (stirring at 25~40℃ for 2h~4h is also acceptable) to dissolve 2-methylimidazole in methanol and obtain an organic ligand solution (a solution containing 2-methylimidazole).

[0050] (1.3) Following a mass ratio of porous biochar to the total mass of zinc and cobalt salts of 1:3 (the mass ratio should not be too high or too low; if the ratio is too low, the MOFs material will not be fully loaded on the biochar surface, and if the ratio is too high, the MOFs will be unevenly dispersed, resulting in unstable material performance), 2g of porous biochar is added to a solution containing 2-methylimidazole and stirred at 25℃ for 2h (stirring at 25-40℃ for 2h-4h is also acceptable) to obtain an organic ligand solution containing porous biochar. In this step, the porous biochar used is a carbon material obtained by pyrolysis of biomass under anaerobic conditions. The sources of the biomass include: plant residues, agricultural waste, or animal manure, etc.; the porous biochar particle size is less than 30 mesh.

[0051] (1.4) The organic ligand solution containing porous biochar was quickly added to the metal template solution and stirred at 25°C for 2 hours (stirring at 25-40°C for 1-2 hours is acceptable, but it should not be too short. If the time is too short, the metal template will not be able to mix evenly with the organic ligand, thus failing to form a precursor with high dispersion and purity). Finally, the product was centrifuged at 8000 r / min, the solid product was collected, and then washed three times with methanol. The product was then dried in an oven at 60°C to obtain a composite material of bimetallic MOFs and porous carbon.

[0052] (1.5) The composite material of bimetallic MOFs and porous carbon was placed in a tube furnace, nitrogen was introduced, and carbonization was carried out at a heating rate of 10℃ / min until it reached 600℃. The temperature was maintained for 30min to obtain bimetallic MOFs-derived carbon-porous carbon.

[0053] S1-2. The electrode slurry is mixed with carbon felt (purchased from Tianjin Carbon Plant, high-purity graphite fiber felt, 20cm x 30cm in length and width), and ultrasonicated for 6 hours to ensure thorough mixing of the slurry and carbon felt. The mixture is then dried in an oven at 80℃ for 12 hours to obtain the carbon felt electrode. Before use, the carbon felt undergoes the following treatment: it is cut into sheets 5cm x 5cm in length and width, ultrasonically cleaned in ethanol for 2 hours, then ultrasonically cleaned in water for 2 hours, and finally dried in an oven at 80℃.

[0054] S1-3. A conductive carbon adhesive (purchased from Shunsheng Electronics Technology Co., Ltd., SEM double-sided carbon conductive tape, 5mm*20m; other similar conductive double-sided carbon adhesives used for SEM and EDS experiments are also applicable) is used to attach the carbon felt electrode to the titanium plate, obtaining a bimetallic MOFs-derived carbon-porous carbon composite electrode material. Before use, the titanium plate undergoes the following treatment: a 5cm×5cm titanium plate is placed in a 10% oxalic acid solution (an oxalic acid solution with a mass fraction of 5%–20% can be used, but excessively high concentrations may generate vapors that can damage the respiratory tract) and heated to 100°C, maintaining a boiling state for 2 hours to etch the titanium plate. It is then cleaned sequentially with water and ethanol to remove residual impurities and dried.

[0055] S2. A capacitive deionization device is assembled using bimetallic MOFs-derived carbon-porous carbon composite electrode material as the working electrode.

[0056] S3. Using a capacitor deionization device, the heavy metal lead wastewater (pH value 7, concentration 100 mg / L) was treated. -1 ) and heavy metal manganese wastewater (the wastewater has a pH of 7 and a concentration of 100 mg / L) -1 Electroadsorption treatment is performed, specifically as follows:

[0057] S3-1. The heavy metal wastewater to be treated is introduced into the capacitor deionization device. Before energizing, the flow rate is set at 15 mL / min. -1 First, circulate the solution for 60 minutes to eliminate the influence of physical adsorption on the deionization performance of the capacitor.

[0058] S3-2. Connect the power supply and provide a constant voltage. Under the condition of 1.2V, use the capacitor deionization device to perform electro-adsorption treatment on heavy metal wastewater. Metal ions in the solution flowing through the capacitor deionization device are transferred to the electrode with opposite charge under the action of electric field force. The treated solution flows back to the water tank. This cycle is repeated. After 2 hours of power supply, disconnect the power supply to complete the treatment of heavy metal wastewater.

[0059] Control group: Unmodified biochar was used as the electrode material to replace bimetallic MOFs-biochar, and it was used to treat lead and manganese wastewater with a concentration of 100 mg / L, under the same conditions. The preparation method of unmodified biochar was basically the same as that of bimetallic MOFs-biochar, the only difference being that the MOFs material was not modified in the preparation method of unmodified biochar.

[0060] Figure 1 This is a SEM image of the bimetallic MOF-derived carbon-porous carbon prepared in Example 1 of this invention. Figure 1 It can be seen that after modification, bimetallic MOF-derived carbon-porous carbon exhibits a very regular and smooth dodecahedral crystal structure on the surface of biochar, forming a number of sites on the surface of biochar that are conducive to charge transfer and catalysis.

[0061] Figure 2 The image shows the full XRD pattern of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention.

[0062] Figure 3 This is the full FTIR spectrum of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention.

[0063] Depend on Figure 2 It can be seen that the peak distribution of the bimetallic MOFs-derived carbon-porous carbon prepared in this invention shows the ZIF-8 arrangement, indicating that through the modification step, the organometallic framework composed of Zn and Co has been successfully loaded into biochar and simultaneously possesses the basic structure of MOFs. Meanwhile, through... Figure 3 FTIR testing revealed that, through the introduction of ligands, amino functional groups that facilitate the adsorption of metal ions appeared in the spectrum of biochar.

[0064] Figure 4 This is the XPS full spectrum of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention. Figure 4 It can be seen that the peak binding energies of Zn and Co elements in the bimetallic MOFs-derived carbon-porous carbon prepared by this invention are very obvious, indicating that Zn and Co have been loaded into biochar in a very stable state.

[0065] Figure 5 This is the nitrogen adsorption-desorption isotherm diagram of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention. Figure 5 It can be seen that this isotherm belongs to type IV adsorption isotherm, meaning that pressure and adsorption capacity are basically linearly and uniformly distributed. Further analysis reveals that the adsorption capacity steadily increases within the pressure range of 0.2-0.8, indicating that the bimetallic MOFs-derived carbon-porous carbon of this invention has a predominantly mesoporous structure, which is more conducive to ion transport and charge conduction. Simultaneously, the sample's specific surface area exceeds 1200 m². 2 The specific surface area of ​​the bimetallic MOF-derived carbon-porous carbon prepared in this invention is ·g, indicating that it possesses excellent adsorption performance. In contrast, the specific surface area of ​​conventional bimetallic MOF-derived carbon-graphene is only 639.1 m². 2 In contrast, the highest adsorption capacity of the bimetallic MOFs-derived carbon-porous carbon prepared in this invention reaches 245.03 mg / g, while the highest adsorption capacity of conventional bimetallic MOFs-derived carbon-graphene is only 7.92 mg / g.

[0066] Figure 6 This is a pore size distribution diagram of the bimetallic MOFs-derived carbon-porous carbon prepared in Example 1 of this invention. Figure 6 It can be seen that the maximum pore volume of the bimetallic MOF-derived carbon-porous carbon prepared by this invention exceeds 0.324 cm³. 3 The pore size distribution ranges from 0 to 150 nm, indicating that the sample has a relatively dense pore formation area and a wide pore size distribution range. Meanwhile, from... Figure 6 It can be seen that the bimetallic MOFs-derived carbon-porous carbon prepared by this invention has a relatively uniform pore size distribution and a relatively symmetrical curve, mainly consisting of mesopores (2-50 nm).

[0067] Figure 7 This is a CV diagram of the bimetallic MOFs-derived carbon-porous carbon composite electrode material prepared in Example 1 of this invention. Figure 7 It can be seen that the CV diagram of the bimetallic MOFs-derived carbon-porous carbon composite electrode material prepared in this invention presents a spindle-shaped region, and the closed image formed is not symmetrical. This indicates that the electrochemical reaction should be mainly adsorption, and the ion diffusion is relatively dense and uniform, indicating that the electrode is relatively stable in the reaction.

[0068] In this embodiment, during the electroadsorption treatment process, samples were taken under different treatment time conditions to detect the concentration of heavy metals in the wastewater, and the removal rate of heavy metals by different electrode materials was calculated. The results are as follows: Figures 8-10 As shown.

[0069] Figure 8 This is a graph showing the removal rate of lead and manganese wastewater with a concentration of 100 mg / L treated using a bimetallic MOF-derived carbon-porous carbon composite electrode material in Example 1 of this invention. Figure 8 It can be seen that bimetallic MOF-derived carbon-porous carbon has a very good removal effect on lead and manganese ions in capacitive deionization. After a complete power-on operation, both metal ions reach adsorption equilibrium in about 120 minutes. The results of metal ion concentration tests by extracting sample solutions at different time periods show that the removal efficiency of lead and manganese ions using bimetallic MOF-derived carbon-porous carbon is close to 100%, and the effluent concentration has reached the national discharge standard (National Wastewater Discharge Standard (<1mg / L) (GB8978-1996)).

[0070] Figure 9 This is a diagram showing the selective adsorption effect of different ions when using bimetallic MOFs-derived carbon-porous carbon composite electrode material to treat lead ions with a concentration of 100 mg / L in Example 1 of the present invention.

[0071] Figure 10 This is a diagram showing the selective adsorption effect of different ions when using bimetallic MOFs-derived carbon-porous carbon composite electrode material to treat manganese ions at a concentration of 100 mg / L in Example 1 of the present invention.

[0072] Depend on Figure 9 Figure 10 It is evident that bimetallic MOF-derived carbon-porous carbon achieves selective removal of heavy metal ions in capacitive deionization, thereby avoiding the removal of essential and beneficial elements required by the environment. This indicates that the material can bring more innovative solutions to the separation technology and environmental fields.

[0073] Figure 11 This is a comparison chart of the highest adsorption capacities of the bimetallic MOFs-derived carbon-porous carbon composite electrode material and the pure biochar electrode in Example 1 of this invention. Figure 11 It is evident that the adsorption capacity of biochar increases exponentially after modification with MOF-derived carbon, and the improved removal efficiency is not limited to a single metal element, indicating that the method of this invention has universality and is conducive to promotion. By modifying MOF-derived carbon, biochar acquires high adsorption performance, making it an effective tool for solving ion pollution problems. It can provide water purification and resource recovery solutions for various industries, and achieve resource recovery and utilization in a sustainable manner.

[0074] In summary, the method for treating heavy metal wastewater using bimetallic MOFs-derived carbon-porous carbon composite electrode materials can rapidly and thoroughly adsorb heavy metals in water, thereby achieving effective removal of heavy metals from wastewater. This method boasts advantages such as simple process, convenient operation, low cost, high treatment efficiency, good removal effect, and environmental friendliness, demonstrating high application value and broad application prospects in the treatment of heavy metal-polluted water bodies.

[0075] 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 treating heavy metal wastewater using bimetallic MOFs-derived carbon-porous carbon composite electrode materials, characterized in that, Includes the following steps: S1. Prepare a bimetallic MOFs-derived carbon-porous carbon composite electrode material by processing bimetallic MOFs-derived carbon-porous carbon; the bimetallic MOFs-derived carbon-porous carbon is obtained by carbonization treatment of a composite material of bimetallic MOFs and porous carbon; the preparation method of the composite material of bimetallic MOFs and porous carbon includes the following steps: (a) Zinc salt and cobalt salt are mixed with methanol to obtain a metal template solution; organic ligands are mixed with methanol and porous carbon is added to obtain an organic ligand solution containing porous carbon; (b) Add the organic ligand solution containing porous carbon to the metal template solution and stir to obtain a composite material of bimetallic MOFs and porous carbon. S2. A capacitive deionization device is assembled using bimetallic MOFs-derived carbon-porous carbon composite electrode material as the working electrode. S3. Electro-adsorption treatment of heavy metal wastewater is performed using a capacitor deionization device to complete the treatment of heavy metal wastewater; the heavy metal in the heavy metal wastewater is at least one of lead, cadmium and manganese.

2. The method according to claim 1, characterized in that, The preparation method of the bimetallic MOFs-derived carbon-porous carbon includes the following steps: heating the composite material of bimetallic MOFs and porous carbon to 450℃~600℃ for carbonization to obtain bimetallic MOFs-derived carbon-porous carbon; the carbonization is carried out under an inert atmosphere and / or a nitrogen atmosphere; the inert atmosphere is argon and / or helium; the heating rate during the carbonization process is 5℃ / min~15℃ / min; the carbonization time is 30min~120min.

3. The method according to claim 2, characterized in that, In step (a), the molar ratio of the zinc salt to the cobalt salt is 1:1 to 3; in the metal template solution, the ratio of the total molar amount of zinc salt and cobalt salt to methanol is 0.01 mol: 100 mL to 200 mL; in the organic ligand solution containing porous carbon, the ratio of the organic ligand to methanol is 3.5 g: 50 mL to 100 mL; the mass ratio of the porous carbon to the total mass of the zinc salt and cobalt salt is 1:1 to 3; the zinc salt is at least one of zinc chloride, zinc nitrate, and zinc acetate; the cobalt salt is at least one of cobalt chloride, cobalt nitrate, and cobalt acetate; the organic ligand is at least one of 1-methylimidazole, 2-methylimidazole, 4,5-dimethylimidazole, 2-ethylimidazole, and 2-isopropylimidazole; the porous carbon is porous biochar and / or activated carbon; the particle size of the porous carbon is less than 30 mesh. In step (b), the stirring is carried out at a temperature of 25°C to 40°C; the stirring time is 1 hour to 2 hours. After the stirring is completed, the process further includes: centrifuging the stirred product at 8000 r / min to 12000 r / min, washing the solid product after centrifugation with a washing solution, and drying it at 60℃ to 90℃; the washing solution is water, an organic solvent, or an acidic solution; the organic solvent is at least one of ether, alcohol, and ketone; the acidic solution is hydrochloric acid and / or dilute nitric acid.

4. The method according to any one of claims 1 to 3, characterized in that, In step S1, the preparation method of the bimetallic MOFs-derived carbon-porous carbon composite electrode material includes the following steps: (1) Mix bimetallic MOFs-derived carbon-porous carbon, binder and solvent, stir to prepare electrode slurry; (2) The electrode slurry is mixed with carbon felt, ultrasonicated, and dried to obtain a carbon felt electrode loaded with the material; (3) The carbon felt electrode loaded with the material is attached to the current collector to obtain a bimetallic MOFs-derived carbon-porous carbon composite electrode material.

5. The method according to claim 4, characterized in that, In step (1), the mass ratio of the bimetallic MOFs-derived carbon-porous carbon to the binder is 4 to 9:1; the ratio of the total mass of the bimetallic MOFs-derived carbon-porous carbon and the binder to the volume of the solvent is 1 mg: 1 mL to 2 mL; the binder is at least one of polyvinyl alcohol and polyvinylidene fluoride; the solvent is N-methylpyrrolidone; and the stirring time is ≥4 h. In step (2), the carbon felt is further treated as follows before use: the carbon felt is cut into sheet material with a length and width of 5cm×5cm, ultrasonically cleaned in ethanol for more than 2 hours, ultrasonically cleaned in water for more than 2 hours, and then dried. In step (3), a carbon felt electrode is attached to the current collector using conductive carbon adhesive; the current collector is one of titanium plate, copper foil, aluminum foil, graphite paper, and graphite plate; before use, the current collector is further treated as follows: the current collector is placed in an oxalic acid solution and heated to 85℃~100℃, kept for 1.5 hours~3 hours, and then washed with water and ethanol in sequence, and dried; the mass fraction of the oxalic acid solution is 5%~20%.

6. The method according to any one of claims 1 to 3, characterized in that, In step S3, during the electro-adsorption treatment process, the flow rate of the heavy metal wastewater in the capacitive deionization device is controlled at 15 mL / min. -1 ~20 mL min -1 .

7. The method according to claim 6, characterized in that, In step S3, the residence time of the heavy metal wastewater in the capacitor deionization device is 1 hour to 3 hours.

8. The method according to claim 6, characterized in that, In step S3, the voltage of the capacitor deionization device is controlled to be 1V to 1.2V during the electro-adsorption process.

9. The method according to claim 6, characterized in that, In step S3, the initial concentration of heavy metals in the heavy metal wastewater is ≤100 mg / L. -1 The initial pH value of the heavy metal wastewater is <7.5.

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