Self-supporting composite electrode for CDI as well as preparation method and application of self-supporting composite electrode

Abstract

The invention discloses a self-supporting composite electrode for CDI and a preparation method and application of the self-supporting composite electrode, and belongs to the technical field of capacitive deionization. The preparation method of the self-supporting composite electrode for CDI provided by the invention comprises the following steps: S1, mixing hypha suspension and preparation raw materials of an MOF material, and then carrying out solvothermal reaction; the preparation raw materials of the MOF material comprise a metal precursor and a ligand; s2, pyrolyzing and carbonizing the solid product obtained in the step S1. According to the preparation method provided by the invention, the self-supporting composite electrode with a good capacitive deionization effect can be obtained. The invention further provides the self-supporting composite electrode for the CDI prepared by the preparation method and application of the self-supporting composite electrode for the CDI.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitive deionization, and in particular to a self-supporting composite electrode for CDI, a preparation method thereof, and an application thereof. Background Art

[0002] Capacitive deionization (CDI) is a water treatment technology based on electrochemical principles, primarily used to remove ions (such as salt and heavy metals) from water. It boasts high efficiency, low energy consumption, and is environmentally friendly and pollution-free. CDI has become a research hotspot in recent years, with promising applications in brackish water desalination, seawater desalination, and pollutant ion removal. The primary component of CDI is a capacitor, which consists of two electrodes. When voltage is applied, ions are adsorbed onto the electrode surfaces, removing them from the water. When the electrodes become saturated, discharge or reverse voltage releases the ions, regenerating the electrodes for recycling.

[0003] The performance requirements for CDI capacitor electrode materials differ from those for other types of electrode materials. For example, in the catalytic field, electrode materials are required to be highly conductive and to catalyze oxidation and / or reduction reactions, primarily involving Faraday processes. However, electrode materials used in CDI require higher ion adsorption for specific ions, primarily relying on the effects of the double layer, and require longer cycle times. The performance of the electrode material determines the desalination capacity of capacitive deionization (CDI). Currently, commonly used electrode materials include activated carbon, carbon nanotubes, graphene, carbon fiber, MOF-derived carbon, and biochar. However, the desalination capacity and desalination rate of most carbon-based electrodes in CDI are suboptimal.

[0004] In summary, how to improve the performance of electrode materials for capacitive deionization has become an important research topic to improve the effect of capacitive deionization. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing a self-supporting composite electrode for CDI, which can obtain a composite electrode with good capacitive deionization effect.

[0006] The present invention also provides a self-supporting composite electrode for CDI prepared by the above preparation method.

[0007] The present invention also provides applications of the self-supporting composite electrode for CDI.

[0008] According to an embodiment of the first aspect of the present invention, a method for preparing a self-supporting composite electrode for CDI is provided, the preparation method comprising the following steps:

[0009] S1. The mycelial suspension and the raw materials for preparing the MOF material are mixed and subjected to a solvent thermal reaction; the raw materials for preparing the MOF material include a metal precursor and a ligand;

[0010] S2. The solid product obtained in step S1 is subjected to pyrolysis and carbonization.

[0011] The preparation method according to the embodiment of the present invention has at least the following beneficial effects:

[0012] MOF materials are a type of crystalline material with a periodic network structure constructed by self-assembly of metal ions or metal clusters and multidentate organic ligands through coordination bond bridges. They have a high surface area and a well-developed pore system, making them an important research target for capacitive deionization electrode materials. However, after carbonization, most MOF materials are powdery and have poor conductivity. The electrode preparation requires the use of adhesives, which are non-conductive and often hinder electron transfer between MOF carbon particles, affecting the desalination effect. Furthermore, MOF crystals are prone to self-aggregation during growth, affecting the surface area, pore size, and pore structure of the MOF particles. This, in turn, affects electron transfer and ion migration and diffusion during the desalination process when used as capacitive deionization electrodes.

[0013] In the preparation method provided by the present invention, what is obtained is a self-supporting composite electrode, which can be used directly as an electrode without adding additional adhesives, and essentially overcomes the adverse effects of adhesives. Compared with the traditional method of directly using carbon cloth as a self-supporting carrier to prepare a composite electrode (i.e., replacing mycelium with carbon cloth, etc.), in the preparation method provided by the present invention, the mycelium before carbonization contains richer and more diverse functional groups, which are more likely to combine with metal precursors and ligands in a solvent thermal environment (under solvent thermal conditions), provide MOF material crystal growth sites, promote MOF directional growth, and avoid MOF particle agglomeration. Therefore, the obtained self-supporting composite electrode has better uniformity (including overall uniformity and uniformity of the load on the surface of the self-supporting carrier); and this uniformity is more conducive to the occurrence of synergistic effects. In addition, the carbonized mycelium fiber, as a self-supporting carrier, has high conductivity and can quickly transfer electrons to the MOF carbon material, promoting ion adsorption.

[0014] Compared with the traditional preparation method without solvent thermal method (i.e., no heating and closed environment in step S1), the self-supporting composite electrode obtained by the preparation method provided by the present invention has a higher bonding strength between the self-supporting carrier and the load, which is more conducive to the formation of a multi-level pore structure; it is also more conducive to the physical and chemical reactions between the self-supporting carrier and the load, resulting in a synergistic effect.

[0015] In summary, in the preparation method provided by the present invention, by selecting suitable preparation raw materials and suitable preparation conditions, a significant synergistic effect can be produced between the self-supporting carrier and the load of the obtained self-supporting composite electrode, greatly improving the effect of capacitive deionization; in addition, the preparation method provided by the present invention has a simple process flow and is easy to replicate and mass-produce.

[0016] According to some embodiments of the present invention, in step S1, the mixing includes:

[0017] The mycelium suspension, the metal precursor solution A, and the ligand solution B are mixed.

[0018] More specifically, the mixing includes:

[0019] The mycelium suspension is sequentially mixed with Solution A and Solution B. Solution A is added first to allow the metal ions to fully dissolve in the solvent, forming a uniform solution. This allows the metal ions to more easily contact the ligands when Solution B is added, promoting coordination reactions. This addition method effectively avoids the occurrence of intermediate side reactions and avoids uneven distribution of metal ions and subsequent MOF materials due to uneven distribution of ligands.

[0020] More specifically, the mixing includes:

[0021] The solution A and the mycelium suspension are stirred and mixed for the first time and ultrasonically dispersed; and then the resulting mixture is stirred and mixed for the second time with the solution B.

[0022] The duration of the ultrasonic dispersion is 25 to 35 minutes; for example, it can be about 30 minutes.

[0023] The temperature of the ultrasonic dispersion is 15-25°C; for example, it can be about 20°C.

[0024] The power of the ultrasonic dispersion is 700-900W; for example, it can be about 800W.

[0025] The second stirring and mixing time is 25 to 35 minutes; for example, it can be about 30 minutes.

[0026] According to some embodiments of the present invention, in step S1, the solid content of the mycelial suspension is 4-20 g / L, for example, about 5 g / L, 7 g / L, 7.6 g / L, 8 g / L, 10 g / L, 12 g / L, 15 g / L, or about 18 g / L.

[0027] According to some embodiments of the present invention, in step S1, the method for obtaining the mycelial suspension comprises culturing the fungus in a culture medium, followed by washing and redispersing.

[0028] The fungus includes at least one of Aspergillus niger, Aspergillus flavus and Rhizopus.

[0029] The culture medium includes a hot hydrolyzed liquid of kitchen waste or a glucose-peptone culture medium.

[0030] The culture duration is 2 to 5 days, for example, about 3 days or about 4 days.

[0031] The culture temperature is 25-35°C, for example, about 28°C, 30°C or about 32°C.

[0032] The culture is carried out under stirring at a speed of 50 to 300 rpm, for example, about 100 rpm, 150 rpm, 200 rpm or about 250 rpm.

[0033] The cleaning method includes solid-liquid separation followed by redispersion in water, which is repeated 3 to 8 times. For example, it can be 5 times. The solid-liquid separation method is to collect the mycelium using a filter.

[0034] According to some embodiments of the present invention, in step S1, the metal precursor includes at least one of a zinc salt and a cobalt salt.

[0035] According to some embodiments of the present invention, in step S1, the metal precursor comprises a metal nitrate. Specifically, it can be at least one of cobalt nitrate, zinc nitrate, or a crystalline hydrate thereof. More specifically, the metal precursor comprises zinc nitrate hexahydrate.

[0036] According to some embodiments of the present invention, in step S1, the ligand includes at least one of 2-methylimidazole (CAS: 693-98-1), terephthalic acid (CAS: 100-21-0), trimesic acid (CAS: 554-95-0), benzimidazole (CAS: 51-17-2) and 2-ethylimidazole (CAS: 1072-62-4).

[0037] According to some embodiments of the present invention, the concentration of solution A is 5 to 50 g / L, for example, about 10 g / L, 15 g / L, 20 g / L, 22.3 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L or about 45 g / L.

[0038] According to some embodiments of the present invention, the solvent of the solution A includes at least one of methanol, dimethylformamide (CAS: 68-12-2) and dimethyl sulfoxide (CAS: 67-68-5).

[0039] According to some embodiments of the present invention, the concentration of solution B is 5 to 50 g / L, for example, about 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 32.8 g / L, 35 g / L, 40 g / L or about 45 g / L.

[0040] According to some embodiments of the present invention, the solvent of the solution B includes at least one of methanol, dimethylformamide (CAS: 68-12-2) and dimethyl sulfoxide (CAS: 67-68-5).

[0041] According to some embodiments of the present invention, the volume ratio of the mycelial suspension, solution A, and solution B is 100:6-12:4-10. The volume ratio of the mycelial suspension to solution A is 100:8 or approximately 100:10; and the volume ratio of the mycelial suspension to solution B is 100:5, 100:6, or approximately 100:8.

[0042] According to some embodiments of the present invention, in step S1, the temperature of the solvothermal reaction is 60-90°C, for example, about 70°C, 75°C, 80°C or about 85°C.

[0043] According to some embodiments of the present invention, in step S1, the temperature of the solvothermal reaction is 8 to 20 hours, for example, about 10 hours, 12 hours, 15 hours, or about 18 hours.

[0044] According to some embodiments of the present invention, step S1 further comprises cooling, washing, shaping and drying the obtained mixture after the solvent thermal reaction.

[0045] The cooling method is natural cooling, that is, no additional means are used to interfere with the cooling process. The end point of the cooling is room temperature.

[0046] The water washing method includes dispersing in water after solid-liquid separation and circulating the operation. The number of cycles is ≥ 3 times, thereby fully removing the unreacted metal precursor, ligand and non-aqueous solvent.

[0047] The shaping method includes at least one of filtration and molding; specifically, the mycelium in the aqueous dispersion is prepared into a suitable shape. Since the self-supporting composite electrode for CDI will basically inherit the macroscopic shape after shaping, in actual production, the shaping method and the resulting shape are determined by the desired self-supporting composite electrode for CDI. When the shaping method is filtration, the shaped shape is a cake (depending on the shape of the filter and filter paper). The filtration method includes at least one of suction filtration and filter press. In the suction filtration, the volume of the aqueous dispersion used is 150 to 500 mL; for example, it can be about 200 mL, 250 mL, 300 mL, 350 mL, 400 mL, or about 450 mL; the duration used is 30 to 150 seconds; for example, it can be about 50 seconds, 80 seconds, 100 seconds, or about 120 seconds.

[0048] The drying method includes freeze drying, thereby preserving the macro and micro structures of the shaped shape as much as possible. The freeze drying time is ≤ 48 hours. For example, it can be about 5 hours, 8 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, or about 45 hours.

[0049] According to some embodiments of the present invention, in step S2, the temperature of the pyrolysis carbonization is 400-1000°C, for example, about 500°C, 600°C, 700°C, 800°C or about 900°C.

[0050] According to some embodiments of the present invention, in step S2, the pyrolysis carbonization time is 0.5 to 5 hours, for example, about 1.0 hours, 1.5 hours, 2 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4.0 hours, or about 4.5 hours.

[0051] According to an embodiment of the second aspect of the present invention, a self-supporting composite electrode for CDI is provided. The self-supporting composite electrode for CDI is prepared by the preparation method described in the embodiment of the first aspect of the present invention.

[0052] Because the self-supporting composite electrode for CDI utilizes all the technical solutions of the preparation method described in the aforementioned embodiment, it exhibits at least all the beneficial effects of the technical solutions of the aforementioned embodiment. Specifically, the present invention utilizes the high specific surface area and rich pore structure of MOF-derived carbon materials and combines them with the excellent conductivity of mycelium pyrolyzed carbon fibers to form a three-dimensional network structure with high conductivity and high specific surface area. The resulting self-supporting composite electrode for CDI exhibits excellent electrochemical properties, demonstrates high desalination capacity and rate, and exhibits stability in capacitive deionization.

[0053] According to some embodiments of the present invention, the self-supporting composite electrode for CDI includes a self-supporting carrier, and MOF-derived carbon supported on the surface of the self-supporting carrier; the self-supporting carrier includes mycelium pyrolysis carbon.

[0054] According to some embodiments of the present invention, the self-supporting composite electrode for CDI has a three-dimensional network structure.

[0055] According to an embodiment of the third aspect of the present invention, there is provided a use of the self-supporting composite electrode for CDI according to an embodiment of the second aspect of the present invention in water desalination and pollutant ion removal.

[0056] Since the application adopts all the technical solutions of the self-supporting composite electrode for CDI of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0057] According to some embodiments of the present invention, the NaCl concentration in the influent treated by the water desalination is 100-1000 mg / L.

[0058] According to some embodiments of the present invention, the influent water treated by the water desalination includes at least one of brackish water and seawater.

[0059] Unless otherwise specified, the term “about” in the present invention actually means that the error is allowed to be within the range of ±2%, for example, about 100 actually means 100±2%×100.

[0060] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values 2 and 3.

[0061] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0063] Figure 1 It is a flow chart of important steps in Example 1 of the present invention.

[0064] Figure 2 This is the morphology of the mycelium used in Example 1 of the present invention.

[0065] Figure 3 This is the local morphology of the self-supporting composite electrode obtained in Example 1 of the present invention.

[0066] Figure 4 This is the local morphology of the self-supporting composite electrode obtained in Comparative Example 3 of the present invention.

[0067] Figure 5 CV curves of the products obtained in Example 1 of the present invention, Comparative Examples 1-2, and commercial activated carbon powder.

[0068] Figure 6 It is the EIS spectrum of the products obtained in Example 1 of the present invention, Comparative Examples 1-2, and commercial activated carbon powder.

[0069] Figure 7 It is the CDI desalination capacity of the products obtained in Example 1 of the present invention, Comparative Examples 1-2 and commercial activated carbon powder.

[0070] Figure 8 The graph shows the change of the ion concentration of the effluent water during the electrosorption and desorption process of the products obtained in Example 1 and Comparative Example 3 of the present invention over time.

[0071] Figure 9 This is the CDI cycle adsorption test result of the self-supporting composite electrode obtained in Example 1 of the present invention.

[0072] Figure 10 This is a statistical diagram of the adsorption capacity of the self-supporting composite electrode obtained in Example 1 of the present invention during CDI cycle adsorption. DETAILED DESCRIPTION

[0073] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0074] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0075] The hot hydrolyzed liquid of food waste used in the present invention is obtained by the method described in Example 1 of reference patent CN116116882A.

[0076] Example 1

[0077] In this example, a self-supporting composite electrode for CDI was prepared. The specific steps are as follows:

[0078] S1.

[0079] S1a. All suspensions were obtained: filamentous fungal species (Aspergillus niger) were cultured in a culture medium (hot hydrolyzed food waste) for 5 days at 28°C and 150 rpm to obtain fermentation mycelium. The mycelium was then collected with a filter, washed five times with deionized water, and dispersed in pure water to obtain a mycelial suspension with a solid content of 7.4 g / L.

[0080] S1b. Solvothermal reaction: A 22.3 g / L methanol solution of Zn(NO3)2·6H2O was added to the mycelial suspension, stirred, and then ultrasonicated for 30 min at a temperature of 20°C and an ultrasonic power of 800 W.

[0081] Then add 32.8 g / L 2-methylimidazole methanol solution and stir for 30 minutes;

[0082] The volume ratio of mycelial suspension, zinc nitrate methanol solution and 2-methylimidazole solution is 100:8:6.

[0083] The reaction was carried out at 75°C for 12 hours, and the mixture was cooled to room temperature. The MOF-loaded composite mycelium precursor obtained by the reaction was collected by filtration, washed three times with deionized water, and then dispersed in deionized water to prepare a MOF-loaded composite mycelium precursor suspension.

[0084] 300 mL of MOF-loaded composite mycelium precursor suspension was vacuum filtered for 100 s and freeze-dried for 12 h;

[0085] S2. pyrolysis and carbonization of the product obtained in step S1;

[0086] The temperature of pyrolysis carbonization is 800°C and the duration is 2h.

[0087] The thickness of the self-supporting composite electrode for CDI obtained in this example is about 300 μm.

[0088] The flowchart of the important steps in this example is as follows Figure 1 shown.

[0089] Comparative Example 1

[0090] This example prepares a composite electrode material for CDI, which differs from Example 1 in that:

[0091] (1) does not include step S1a;

[0092] (2) No mycelial suspension was added in step S1b.

[0093] (3) Adaptability: filtration is selected as the solid-liquid separation method in the subsequent steps.

[0094] That is, a MOF carbon is actually prepared.

[0095] Comparative Example 2

[0096] This example prepared a self-supporting composite electrode for CDI, which differs from Example 1 in that:

[0097] (1) In step S1b, neither the metal precursor solution nor the ligand solution is added.

[0098] That is, a composite electrode having the same shape as that of Example 1 and made of mycelium pyrolytic carbon was actually prepared.

[0099] Comparative Example 3

[0100] This example prepared a self-supporting composite electrode for CDI, which differs from Example 1 in that:

[0101] Step S1b does not include "solvothermal reaction at 75°C for 12 hours and natural cooling to room temperature".

[0102] Test Example 1

[0103] This example tests the morphology of the mycelium in the mycelium dispersion used in Example 1, the obtained self-supporting composite electrode, and the self-supporting composite electrode obtained in Comparative Example 3, and the testing method is SEM. The test results show that the self-supporting composite electrode obtained in Example 1 forms a dense granular load on the surface of the mycelium, and the load density and particle size are uniform; thus confirming that a combination occurs between the MOF material-derived carbon and the mycelium pyrolysis carbon. In addition, compared with the morphology of the product obtained in Example 1, in the product obtained in Comparative Example 3, the granular material loaded on the surface of the mycelium is relatively sparsely dispersed, and the particle size is larger and the shape is uneven; thus, it can be seen that the present invention uses a solvent thermal method to achieve in situ growth of MOF materials, which is more conducive to the formation of functional group binding between the mycelium and the MOF material (or its preparation raw materials), thereby producing a more uniform and effective anchoring effect on the generation of the MOF material. The above specific test results are as follows. Figures 2-4 shown.

[0104] Test Example 2

[0105] This example tests the pore characteristics and specific surface area of the products obtained in Example 1, Comparative Example 1, and Comparative Example 2 using the BET method. The test results are shown in Table 1.

[0106] Table 1 Pore structure of the products obtained in Example 1 and Comparative Examples 1-2

[0107] Hole feature Example 1 Comparative Example 2 Comparative Example 1 <![CDATA[Total pore volume (cm 3 / g)]]> 0.33 0.02 0.03 <![CDATA[Specific surface area (cm 2 / g)]]> 573.0 20.7 78.1 Average pore size (nm) 3.5 4.3 1.7

[0108] The results show that the pore volume and specific surface area of the self-supporting composite electrode provided by the embodiment of the present invention are greater than the sum of the products of Comparative Examples 1 and 2. Therefore, from the perspective of pore structure characteristics, a synergistic effect occurs between the mycelium and the MOF material in the preparation method provided by the present invention.

[0109] Test Example 3

[0110] This example tests the products obtained in Example 1, Comparative Examples 1-2, and commercial activated carbon powder (specific surface area 2000m 2 / kg, Nanjing Pioneer Nanotechnology Co., Ltd., XFP06) were used for electrochemical performance; specifically, CV and EIS tests were performed; the scan rate for the CV test was 2 mV / s. The process for preparing electrodes from the product obtained in Comparative Example 1 and commercial activated carbon powder was as follows:

[0111] Active material (the product from Comparative Example 1 or commercial activated carbon powder) and water were added to a glutaraldehyde-crosslinked polyvinyl alcohol (PVA) binder to ensure a final solids content of approximately 30%; the mass ratio of active material to PVA was 9:1. After the mixture was slurried for 12 hours, a uniform slurry was applied to a graphite sheet using a spatula. The mixture was dried in a vacuum oven at 80°C for 12 hours and cooled to room temperature to obtain an electrode.

[0112] The results show that in a two-electrode system with 1M NaCl solution, the CV curve of the product obtained in Example 1 at 2mV / s has no obvious redox peak, indicating that no Faradaic reaction occurs and ions are mainly adsorbed on the electrode surface through capacitive behavior. According to the integrated area of the CV curve, the specific capacitance of the product obtained in Example 1 is 81.0F / g, which is more than four times that of the products obtained in Comparative Example 2 (16.7F / g) and Comparative Example 1 (4.9F / g). The specific test results are as follows: Figure 5 shown.

[0113] In the EIS spectrum, the overall resistance of the product obtained in Example 1 is lower than that of the product obtained in Comparative Example 1, and the conductivity of the product obtained in Example 1 is higher. Compared with the product obtained in Comparative Example 1, the product obtained in Comparative Example 1 has lower charge transfer resistance and ion diffusion resistance. Specifically, the real axis intercept in the EIS spectrum (represents the overall device resistance, which mainly includes the intrinsic resistance of the electrode and the current collector and the ionic resistance of the electrolyte solution. The overall resistance of the self-supporting composite electrode for CDI provided in Example 1 (3.8Ω) is obviously lower than that of the composite electrode material obtained in Comparative Example 1 (5.3Ω); the diameter of the semicircle in the EIS spectrum represents the charge transfer resistance at the electrode / electrolyte interface; compared with Comparative Example 1 and commercial activated carbon powder, the self-supporting composite electrode for CDI obtained in Example 1 exhibits a lower charge transfer resistance, which may be related to its porous structure and hydrophilic characteristics, which are conducive to charge transfer at the interface between the electrode and the electrolyte; the nearly vertical line in the low-frequency region represents the diffusion resistance of the electrolyte in the porous structure of the electrode. The product obtained in Example 1 shows a steeper line, indicating that the ion diffusion resistance is low, which is related to its open-pore network structure and mesopore-dominated structure. In view of its superior properties, such as hierarchical porous structure, high specific surface area, high conductivity, low charge transfer resistance and low ion diffusion resistance, the self-supporting composite electrode for CDI provided by the present invention is expected to become an excellent electrode material for CDI desalination. The specific test results are as follows Figure 6 shown.

[0114] Test Example 3

[0115] This example tests the performance of the products obtained in Example 1 and Comparative Examples 1 to 3 in the CDI test, with a test voltage of 1.2V and an influent concentration of 585mg / L NaCl aqueous solution. The test device in this example is based on the patent CN 115231665 A. Figure 2 conduct.

[0116] The first-week adsorption desalination capacity of the product obtained in Example 1 is 40.8 mg / g, which is higher than the electrosorption desalination capacity of Comparative Example 2 (17.9 mg / g) and Comparative Example 1 (7.4 mg / g). Comparing the results of Example 1 and Comparative Examples 1-2, it can be seen from the performance of CDI that in the self-supporting composite electrode for CDI provided by the present invention, there is a significant synergistic effect between the mycelium pyrolysis carbon and the MOF material-derived carbon. The specific test results are as follows Figure 7 shown.

[0117] The first-week electrosorption desalination capacity of the product obtained in Comparative Example 3 is 31.4 mg / g, compared with 40.8 mg / g of the product obtained in Example 1. This shows that the solvothermal method used in the present invention significantly improves the bonding strength between the MOF material-derived carbon and the mycelium pyrolysis carbon. During the solvothermal reaction, subtle physical and chemical reactions occur between the two, significantly improving the performance of the obtained product in CDI. The specific test results are as follows: Figure 8 As shown; Figure 8 Starting from about 30 minutes, it is the stage of desorption during the discharge phase after adsorption.

[0118] This example also tests the long-term CDI cycle adsorption experiment of the self-supporting composite electrode obtained in Example 1. The test conditions are the same as those of the single test above, except that the test is repeated multiple times. The results show that the self-supporting composite electrode provided in Example 1 shows almost the same performance in terms of effluent salt ion concentration during the 5th and 30th cycles; the average salt adsorption capacity during the continuous cycle adsorption and desorption operation is about 36.8 mg / g, and the self-supporting composite electrode still maintains a relatively high CDI adsorption capacity after the long-term cycle test. The specific test results are as follows: Figures 9-10 shown.

[0119] In summary, the self-supporting composite electrode for CDI prepared by the method provided herein exhibits a significant synergistic effect between the raw materials and preparation conditions. These combined features result in a more rational pore structure and improved conductivity, significantly enhancing its performance in CDI. These advantages make the self-supporting composite electrode for CDI obtained by the present invention promising for widespread application in water desalination and pollutant ion removal.

[0120] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing a self-supporting composite electrode for CDI, characterized in that: The preparation method comprises the following steps: S1. The mycelial suspension and the raw materials for preparing the MOF material are mixed and subjected to a solvent thermal reaction; the raw materials for preparing the MOF material include a metal precursor and a ligand; S2. The solid product obtained in step S1 is subjected to pyrolysis and carbonization.

2. The preparation method according to claim 1, characterized in that In step S1, the mixing includes: The mycelium suspension, the metal precursor solution A, and the ligand solution B are mixed.

3. The preparation method according to claim 2, characterized in that The concentration of the solution A is 5 to 50 g / L; preferably, the concentration of the solution B is 5 to 50 g / L; preferably, in step S1, the solid content of the mycelium suspension is 4 to 20 g / L.

4. The preparation method according to claim 3, characterized in that The volume ratio of the mycelium suspension, solution A and solution B is 100:6-12:4-10.

5. The preparation method according to claim 1, characterized in that In step S1, the metal precursor includes at least one of a zinc salt and a cobalt salt; and / or the ligand includes at least one of 2-methylimidazole, terephthalic acid, trimesic acid, benzimidazole and 2-ethylimidazole.

6. The preparation method according to claim 1, characterized in that In step S1, the temperature of the solvent thermal reaction is 60-90°C; and / or, in step S1, the temperature of the solvent thermal reaction is 8-20h.

7. The preparation method according to any one of claims 1 to 6, characterized in that In step S2, the temperature of the pyrolysis carbonization is 400-1000°C; preferably, in step S2, the duration of the pyrolysis carbonization is 0.5-5h.

8. A self-supporting composite electrode for CDI, characterized in that: The self-supporting composite electrode for CDI is prepared by the preparation method according to any one of claims 1 to 7.

9. The self-supporting composite electrode for CDI according to claim 8, characterized in that: The self-supporting composite electrode for CDI includes a self-supporting carrier and MOF-derived carbon supported on the surface of the self-supporting carrier; the self-supporting carrier includes mycelium pyrolysis carbon.

10. Use of the self-supporting composite electrode for CDI according to claim 8 or 9 in water desalination and pollutant ion removal.

Images