A bimetallic MOFs derived LDHs / activated carbon three-dimensional particle electrode and a preparation method and application thereof

Abstract

The application discloses a preparation method of a bimetallic MOFs derived LDHs / activated carbon three-dimensional particle electrode, and comprises the following steps: (1) taking a coordination control organic reagent and a metal salt containing an iron series element as raw materials, taking a mixed solution of ethanol and N, N-dimethylformamide or methanol as a solvent, and synthesizing a bimetallic MOFs material through a solvothermal method; (2) dispersing the bimetallic MOFs material in an alkaline solution, reacting under a heating condition, then centrifuging and repeatedly washing with deionized water and ethanol, and drying to obtain a bimetallic MOFs derived LDHs powder; (3) mixing the bimetallic MOFs derived LDHs powder and an activated carbon powder to obtain a bimetallic MOFs derived LDHs / activated carbon composite powder, adding a sodium carboxymethyl cellulose solution to the composite powder to prepare uniform particles, and fully drying the prepared particles to obtain the bimetallic MOFs derived LDHs / activated carbon three-dimensional particle electrode; the three-dimensional particle electrode prepared by the application can be used for electrolysis of nitrogen-containing disinfection by-products, and has excellent performance.

Description

Technical Field

[0001] This invention relates to a bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode, its preparation method and application, belonging to the field of electrochemical technology. Background Technology

[0002] The safety of drinking water is directly related to human health, social stability, and economic development. Disinfection is a crucial step in drinking water treatment, effectively killing pathogenic microorganisms in the water. During the disinfection process, disinfectants react with natural organic matter in the water to generate disinfection byproducts (DBPs). Nitrosamines (NAs), as novel nitrogen-containing disinfection byproducts (N-DBPs), have attracted widespread attention due to their strong carcinogenicity, making research into their control and removal technologies extremely important.

[0003] Electrocatalytic oxidation technology is a type of advanced oxidation technology. Its principle involves applying a specific voltage to electrodes located within the reactor using an external power source, causing the electrodes to undergo a redox reaction with organic pollutants, or generating highly oxidizing substances to oxidize organic matter. Electrocatalytic oxidation technology offers advantages such as being green, environmentally friendly, highly efficient, producing minimal pollution, and simple to operate, making it highly suitable for water treatment.

[0004] Conventional electrochemical reactions typically employ two-dimensional electrodes, relying primarily on the cathode and anode. This results in a limited effective reaction area and insufficient active sites, leading to low throughput. Three-dimensional particle electrodes, on the other hand, are novel electrochemical reactors constructed by filling the spaces between electrodes in a traditional two-dimensional electrolytic cell with granular electrode material. Under an applied electric field, the filled particle electrodes are polarized into independent micro-electrodes (the third stage), where electrochemical reactions occur. This further increases the specific surface area of ​​the reaction and improves the space utilization rate. Therefore, compared to traditional two-dimensional electrodes, three-dimensional particle electrodes offer higher current efficiency and spatiotemporal efficiency, resulting in better processing performance.

[0005] The core of a three-dimensional particle electrode electrochemical reactor is the particle electrode material, whose performance determines the treatment efficiency and operating cost of the electrocatalytic reaction. Traditional electrode materials have high resistance and poor conductivity, resulting in low current efficiency and poor stability in practical electrochemical water treatment applications, leading to short electrode lifespans. Therefore, designing and developing novel three-dimensional particle electrode materials is a pressing problem to be solved in this field. Activated carbon is a commonly used supported material for preparing three-dimensional particle electrodes. Chinese patent application CN201310665223.5, "A Three-Dimensional Particle Electrode with Activated Carbon Supported Catalyst and Its Preparation Method," discloses a three-dimensional particle electrode composed of granular activated carbon and a TiO2 solid solution composite catalyst doped with Sn and Sb elements supported on the granular activated carbon. This electrode, when applied in a three-dimensional electrode reactor, can efficiently treat recalcitrant organic wastewater. Chinese patent application CN201910357822.8, "A Three-Dimensional Particle Electrode with F-Doped Modified Metal Oxide as Catalyst and Its Preparation Method," discloses an electrode composed of columnar activated carbon and an F-doped modified metal oxide composite catalyst supported on the activated carbon. The metal oxide is F-doped modified manganese oxide, copper oxide, zinc oxide, nickel oxide, or tin oxide. However, the materials prepared according to the above schemes only rely on activated carbon as the supporting material to achieve the specific surface area for the reaction. With increasing application demands, a new type of electrode material is needed to optimize electrocatalytic performance.

[0006] Metal-organic frameworks (MOFs) are crystalline porous materials with specific network topologies formed by the coordination of metal ions or metal clusters with organic ligands. The uniform pore structure and well-distributed metal active sites of MOFs facilitate the construction of morphology-controllable three-dimensional derivatives. Furthermore, derivatives synthesized using MOFs as templates or supports not only possess their own morphology and size but also achieve high surface area and pore volume. Layered double hydroxides (LDHs) are three-dimensional crystalline materials formed by parallel arrangement of nanosheet-like layers. The proportions of metal atoms in these materials are adjustable and highly dispersed, with a uniform distribution. Their structure and chemical properties are easily modulated, making them ideal electrocatalytic materials. Under certain conditions, MOFs can be converted into LDHs in situ through chemical etching. LDHs materials derived from MOFs can provide a large number of active centers, sufficient space, and reaction interfaces for electrocatalytic reactions, making them an ideal novel electrode material. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a three-dimensional particle electrode of LDH / activated carbon derived from bimetallic MOFs, its preparation method, and its application. First, LDHs materials are synthesized by in-situ alkaline etching of bimetallic MOFs, and then further combined with activated carbon to prepare a three-dimensional particle electrode with excellent electrocatalytic performance.

[0008] One objective of this invention is to provide a method for preparing a bimetallic MOF-derived LDHs / activated carbon three-dimensional particle electrode, comprising the following steps:

[0009] (1) Preparation of bimetallic MOFs materials: Bimetallic MOFs materials are synthesized by solvothermal method using coordination-regulating organic reagents and iron-containing metal salts as raw materials and a mixed solution of ethanol and N,N-dimethylformamide or methanol as solvent.

[0010] (2) Preparation of bimetallic MOFs-derived LDHs materials: Bimetallic MOFs materials were dispersed in an alkaline solution and reacted under heating conditions. Then, the mixture was centrifuged and repeatedly washed with deionized water and ethanol. Finally, it was dried to obtain bimetallic MOFs-derived LDHs powder.

[0011] (3) Preparation of bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode: Bimetallic MOFs-derived LDHs powder and activated carbon powder are mixed to obtain bimetallic MOFs-derived LDHs / activated carbon composite powder. Sodium carboxymethyl cellulose solution is added to the bimetallic MOFs-derived LDHs / activated carbon composite powder to prepare uniform particles. The prepared particles are thoroughly dried to obtain bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode.

[0012] Preferably, the iron-containing metal salts are FeCl2·4H2O and Ni(NO3)2·6H2O, or Fe(NO3)3·9H2O and Co(NO3)2·6H2O.

[0013] Preferably, in step (1), when the iron-containing metal salts are FeCl2·4H2O and Ni(NO3)2·6H2O, the coordination-regulating organic reagent is 2,5-dihydroxyterephthalic acid; when the iron-containing metal salts are Fe(NO3)3·9H2O and Co(NO3)2·6H2O, the coordination-regulating organic reagent is 2-methylimidazole.

[0014] Preferably, when FeCl2·4H2O and Ni(NO3)2·6H2O are selected as raw materials, the molar ratio of FeCl2·4H2O to Ni(NO3)2·6H2O is (1-3):1, the molar ratio of the total amount of iron-containing metal salts to 2,5-dihydroxyterephthalic acid is (0.2-0.7):1, and deionized water is added to the mixed solvent, wherein the volume ratio of deionized water, ethanol and N,N-dimethylformamide in the mixed solvent is (1-4):(1-4):1.

[0015] Preferably, when Fe(NO3)3·9H2O and Co(NO3)2·6H2O are selected as raw materials, the molar ratio of Fe(NO3)3·9H2O to Co(NO3)2·6H2O is (1-5):1, the molar ratio of the total amount of iron-containing metal salts to 2-methylimidazole is (0.1-0.8):1, and the volume ratio of ethanol to methanol in the mixed solvent is (3-10):1.

[0016] Preferably, in step (2), the alkaline solution is at least one of NaOH, KOH, and Ba(OH)2 aqueous solution, and the concentration of the alkaline solution is 0.3-2M; the reaction time under the heating conditions is 3-12h, and the temperature is 40-80℃.

[0017] Preferably, in step (3), bimetallic MOFs-derived LDHs powder and activated carbon powder are mixed in a mass ratio of (10-2):1 to obtain bimetallic MOFs-derived LDHs / activated carbon composite powder; the concentration of the binder sodium carboxymethyl cellulose solution is 0.026-0.057 g / mL.

[0018] A second objective of this invention is to provide a bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode prepared according to the above preparation method.

[0019] The third objective of this invention is to provide an application of a bimetallic MOF-derived LDHs / activated carbon three-dimensional particle electrode in the catalytic degradation of nitrogen-containing disinfection byproducts.

[0020] Preferably, a bimetallic MOF-derived LDHs / activated carbon electrode is used as a three-dimensional particle electrode, a graphite carbon plate is used as the working electrode, and an anhydrous sodium sulfate electrolyte is used to assemble a three-dimensional particle electrode system to achieve electrocatalytic degradation of nitrogen-containing disinfection byproducts.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) This invention provides a method for synthesizing LDHs materials by in-situ alkaline etching of bimetallic MOFs. In this method, MOFs are converted into LDHs in situ through chemical etching. The LDHs grown on the surface can effectively improve the stability, conductivity and mass transfer capacity of MOFs materials. The latter, as a three-dimensional structural support, overcomes the uncontrollable aggregation of traditional LDHs materials. At the same time, as LDHs replace the organic framework structure of MOFs, the vulnerability of MOFs materials to strong current, acid and alkaline environments and chemical reagents will be improved, and the catalytic performance will be more stable. In addition, since the nucleation and growth of MOFs is relatively simple, they can be used as a medium to grow LDHs on other substrates and establish a stronger coordination connection. Therefore, compared with traditional LDHs materials as electrodes, LDHs materials derived from bimetallic MOFs can be further combined with activated carbon to prepare three-dimensional particle electrodes with excellent electrocatalytic performance.

[0023] (2) The bimetallic MOF-derived LDHs / activated carbon three-dimensional particle electrode prepared according to the preparation method provided by the present invention can efficiently electrocatalytically degrade nitrogen-containing disinfection byproducts. It is green, non-toxic, and environmentally friendly. Compared with the traditional two-dimensional electrode, the three-dimensional particle electrode obtained by this method has a larger contact area, higher efficiency, and lower energy consumption. Because the bimetallic MOF-derived LDHs contain a large amount of Fe 3+ Ni 2+ or Co 2+ In the electrocatalytic process, Fe ions 3+ While Ni ions exhibit the Fenton effect, 2+ or Co 2 + Co-catalysis can promote regeneration and additional Fe production. 2+ The presence of ·OH enhances the yield of ·OH, which is the main active species in the electro-Fenton, thus achieving highly efficient catalytic performance. Furthermore, comparative experiments show that, thanks to the bimetallic MOF precursor structure, which provides more uniform and dispersed catalytic sites for LDHs, LDHs derived from bimetallic MOFs exhibit better electrocatalytic performance than three-dimensional particle electrodes prepared using LDHs synthesized by the traditional co-precipitation method.

[0024] (3) Electrochemical experiments showed that the three-dimensional particle electrode prepared in this invention had a mass of 5g, a flow rate of 3mL / min, and a current density of 15mA / cm². 2 When the initial concentration of pollutants was 30 mg / L, after 100 min of electrolysis, the removal rate of nitrosopyrrolidine by the catalytic system remained stable at over 80%, which once again proved the excellent electrocatalytic performance of the three-dimensional particle electrode material prepared in this invention. Attached Figure Description

[0025] Figure 1 This is a powder X-ray diffraction pattern of the bimetallic MOF material FeNi-MOF in Example 1 of the present invention;

[0026] Figure 2 The image shows a scanning electron microscope (SEM) image of the bimetallic MOF material FeNi-MOF in Example 1 of this invention, along with its elemental distribution of Fe and Ni.

[0027] Figure 3 This is a powder X-ray diffraction pattern of FeNi-LDH prepared by FeNi-MOF derivatization in Example 1 of the present invention;

[0028] Figure 4 The X-ray photoelectron spectrum of FeNi-LDH prepared by FeNi-MOF derivatization in Example 1 of this invention is shown.

[0029] Figure 5 This is a scanning electron microscope image of FeNi-LDH prepared by FeNi-MOF derivatization in Example 1 of the present invention;

[0030] Figure 6 This is a powder X-ray diffraction pattern of the bimetallic MOF material FeCo-MOF in Example 4 of the present invention;

[0031] Figure 7 The image shows a scanning electron microscope (SEM) image of the bimetallic MOF material FeCo-MOF in Example 4 of this invention, along with its elemental distribution of Fe and Co.

[0032] Figure 8 This is a powder X-ray diffraction pattern of FeCo-LDH prepared by FeCo-MOF derivatization in Example 4 of the present invention;

[0033] Figure 9 The X-ray photoelectron spectrum of FeCo-LDH prepared by FeCo-MOF derivatization in Example 4 of this invention is shown.

[0034] Figure 10 This is a scanning electron microscope image of FeCo-LDH prepared by FeCo-MOF derivatization in Example 5 of the present invention;

[0035] Figure 11 Example 9 of this invention compares the electrocatalytic performance of three-dimensional particle electrodes prepared with five different materials (FeNi-LDH, FeNi-LDH-2, FeNi-LDH-3, FeCo-LDH, and FeCo-LDH-2) and activated carbon.

[0036] Figure 12The electrocatalytic removal performance of the FeNi-LDH / activated carbon three-dimensional particle electrode prepared by bimetallic FeNi-MOF derivatization in Example 1 of this invention is shown under (a) different electrolyte concentrations, (b) different current densities, (c) different flow rates, and (d) different initial pollutant concentrations. Detailed Implementation

[0037] The present invention will be further described below with reference to preferred embodiments. The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values. These ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges. These numerical ranges should be considered as specifically disclosed herein.

[0038] Unless otherwise specified, the experimental methods in the following examples are conventional methods, performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions; the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0039] Example 1

[0040] The method for preparing FeNi-MOF-derived LDH / activated carbon three-dimensional particle electrodes includes the following steps:

[0041] (1) Preparation of bimetallic MOF material FeNi-MOF

[0042] 0.32 mmol FeCl2·4H2O, 0.16 mmol Ni(NO3)2·6H2O and 0.8 mmol 2,5-dihydroxyterephthalic acid were added to a mixed solution of 3 mL deionized water, 3 mL ethanol and 1 mL N,N-dimethylformamide. The mixture was stirred at room temperature for 30 min to ensure complete dissolution. The mixture was then transferred to a 20 mL reactor and heated at 120 °C for 24 h. After the reaction was completed, the mixture was allowed to cool to room temperature, centrifuged to obtain a solid powder, and washed three times with ethanol. Finally, the powder was dried in a vacuum oven at 60 °C for 12 h to obtain FeNi-MOF.

[0043] X-ray diffraction pattern of FeNi-MOF material as follows Figure 1 As shown, its characteristic peak signal is strong, and bimetallic MOF crystals have been successfully synthesized; Figure 2 The image shows a scanning electron microscope (SEM) image of FeNi-MOF and an elemental distribution diagram of Fe and Ni. The image shows that the MOF is composed of spindle-shaped crystals with uniform particle size, and contains two metallic elements, Fe and Ni.

[0044] (2) FeNi-MOF derivatization to prepare FeNi-LDH

[0045] 0.3 g of FeNi-MOF was dispersed in 10 mL of 0.5 M NaOH solution and stirred slowly at 65 °C for 5 h. After stirring, the solid was separated by centrifugation. The obtained solid was washed three times with deionized water and three times with ethanol, and finally dried in a vacuum oven at 60 °C for 12 h to obtain FeNi-LDH. The X-ray diffraction pattern of FeNi-LDH is shown below. Figure 3 As shown, the signal peaks corresponding to the crystal planes (003), (006), and (101) are displayed, which are consistent with the characteristic peaks of the typical FeNi-LDH standard card JSPDS No.40-0215, indicating that we successfully synthesized FeNi-LDH by etching.

[0046] The X-ray photoelectron spectrum of FeNi-LDH is as follows: Figure 4 As shown, this indicates the coexistence of Fe, Ni, C, and O elements in the material, indirectly proving that we have obtained FeNi-LDH; the scanning electron microscope image of FeNi-LDH is shown below. Figure 5 As shown, FeNi-LDH is a polygonal layered crystal. The pore structure formed by the stacking of the layers can effectively adsorb nitrogen-containing disinfection byproducts in water, while also allowing the metal active sites to be fully exposed during the electrocatalytic process.

[0047] (3) Preparation of FeNi-MOF-derived LDH / activated carbon three-dimensional particle electrode

[0048] FeNi-LDH powder and activated carbon powder were mixed at a mass ratio of 4:1 to obtain FeNi-LDH / activated carbon composite powder. The mixed powder was added to a 0.3 g / mL sodium carboxymethyl cellulose solution to prepare uniform particles. The prepared particles were dried at 70 °C for 10 h to obtain FeNi-MOF-derived LDH activated carbon three-dimensional particle electrode, which is FeNi-LDH.

[0049] Example 2

[0050] The method for preparing FeNi-MOF-derived LDH / activated carbon three-dimensional particle electrodes includes the following steps:

[0051] (1) Preparation of bimetallic MOF material FeNi-MOF

[0052] 0.40 mmol FeCl2·4H2O, 0.40 mmol Ni(NO3)2·6H2O and 4.0 mmol 2,5-dihydroxyterephthalic acid were added to a mixed solution of 6 mL deionized water, 6 mL ethanol and 1.5 mL N,N-dimethylformamide. The mixture was stirred at room temperature for 1 h to ensure complete dissolution. The mixture was then transferred to a 20 mL reaction vessel and heated at 120 °C for 24 h. After the reaction was completed, the mixture was allowed to cool to room temperature, centrifuged to obtain a solid powder, and washed three times with ethanol. Finally, the powder was dried in a vacuum oven at 60 °C for 12 h to obtain FeNi-MOF.

[0053] (2) FeNi-MOF derivatization to prepare FeNi-LDH

[0054] 0.3 g FeNi-MOF was dispersed in 10 mL of 0.3 M KOH solution and stirred slowly at 80 °C for 3 h. After the stirring was completed, the solid was separated by centrifugation. The obtained solid was washed three times with deionized water and ethanol respectively, and finally dried in a vacuum oven at 80 °C for 12 h to obtain FeNi-LDH.

[0055] (3) Preparation of FeNi-MOF-derived LDH / activated carbon three-dimensional particle electrode

[0056] FeNi-LDH powder and activated carbon powder were mixed at a mass ratio of 2:1 to obtain FeNi-LDH / activated carbon composite powder. The mixed powder was added to a 0.026 g / mL sodium carboxymethyl cellulose solution to prepare uniform particles. The prepared particles were dried at 60 °C for 14 h to obtain FeNi-MOF-derived LDHs activated carbon three-dimensional particle electrode, which is FeNi-LDH-2.

[0057] Example 3

[0058] The method for preparing FeNi-MOF-derived LDH / activated carbon three-dimensional particle electrodes includes the following steps:

[0059] (1) Preparation of bimetallic MOF material FeNi-MOF

[0060] 0.30 mmol FeCl2·4H2O, 0.10 mmol Ni(NO3)2·6H2O and 0.54 mmol 2,5-dihydroxyterephthalic acid were added to a mixed solution of 2 mL deionized water, 2 mL ethanol and 2 mL N,N-dimethylformamide. The mixture was stirred at room temperature for 30 min to ensure complete dissolution. The mixture was then transferred to a 20 mL reactor and heated at 120 °C for 24 h. After the reaction was completed, the mixture was allowed to cool to room temperature, centrifuged to obtain a solid powder, and washed three times with ethanol. Finally, the powder was dried in a vacuum oven at 60 °C for 12 h to obtain FeNi-MOF.

[0061] (2) FeNi-MOF derivatization to prepare FeNi-LDH

[0062] 0.3 g FeNi-MOF was dispersed in 10 mL of 2.0 M Ba(OH)2 solution and stirred slowly at 40 °C for 12 h. After the stirring was completed, the solid was separated by centrifugation. The obtained solid was washed three times with deionized water and ethanol respectively, and finally dried in a vacuum oven at 100 °C for 12 h to obtain FeNi-LDH.

[0063] (3) Preparation of FeNi-MOF-derived LDH / activated carbon three-dimensional particle electrode

[0064] FeNi-LDH powder and activated carbon powder were mixed at a mass ratio of 10:1 to obtain FeNi-LDH / activated carbon composite powder. The mixed powder was added to a 0.057 g / mL sodium carboxymethyl cellulose solution to prepare uniform particles. The prepared particles were dried at 100 °C for 8 h to obtain FeNi-MOF-derived LDH activated carbon three-dimensional particle electrode.

[0065] Example 4

[0066] The method for preparing FeCo-MOF-derived LDH / activated carbon three-dimensional particle electrodes includes the following steps:

[0067] (1) Preparation of bimetallic MOF material FeCo-MOF

[0068] 3 mmol Fe(NO3)3·9H2O and 1 mmol Co(NO3)2·6H2O were dissolved in 40 mL of methanol solution, and this solution was designated as solution A. 8 mmol 2-methylimidazole was dissolved in 10 mL of ethanol solution, and this solution was designated as solution B. Solution B was slowly added dropwise to solution A, stirred at room temperature for 2 h, and then allowed to stand for 24 h to precipitate. After centrifugation, the obtained solid was washed repeatedly with methanol 5 times, and finally dried in a vacuum oven at 100 °C for 12 h to obtain FeCo-MOF.

[0069] The X-ray diffraction pattern of the bimetallic MOF material FeCo-MOF is shown below. Figure 6 As shown, the main diffraction peak signals are obvious, indicating that the bimetallic MOF crystal was successfully synthesized; its scanning electron microscope image is shown below. Figure 7 As shown, the MOF has a polyhedral crystalline structure and uniform particle size;

[0070] (2) FeCo-MOF derivatization of bimetallic MOF material FeCo-MOF to prepare FeCo-LDH

[0071] 0.5 g of FeCo-MOF was dispersed in 20 mL of 1 M Ba(OH)₂ solution and stirred slowly at 80 °C for 3 h. After stirring, the solid was separated by centrifugation. The obtained solid was washed three times each with deionized water and ethanol, and finally dried in a vacuum oven at 80 °C for 12 h to obtain FeCo-LDH. The X-ray diffraction pattern of this material is shown below. Figure 8 As shown, the signal peaks corresponding to the crystal planes (003), (006), and (012) are displayed, which are consistent with the characteristic peaks of the typical FeCo-LDH standard card JSPDS No. 50-0235, indicating that we have successfully synthesized FeCo-LDH by etching.

[0072] The X-ray photoelectron spectrum of FeCo-LDH is as follows: Figure 9 As shown, this indicates the coexistence of Fe, Co, C, and O elements in the material, indirectly proving that we have obtained FeCo-LDH; its scanning electron microscope image is shown below. Figure 10 As shown, FeCo-LDH is also a polygonal layered crystal, which is beneficial for electrocatalysis;

[0073] (3) Preparation of FeCo-MOF-derived LDHs / activated carbon three-dimensional particle electrode

[0074] FeCo-MOF powder and activated carbon powder were mixed at a mass ratio of 4:1 to obtain FeCo-LDH / activated carbon composite powder. The mixed powder was added to a 0.3 g / mL sodium carboxymethyl cellulose solution to prepare uniform particles. The prepared particles were dried at 70 °C for 10 h to obtain FeCo-MOF-derived LDH activated carbon three-dimensional particle electrode, which is FeCo-LDH.

[0075] Example 5

[0076] The method for preparing FeCo-MOF-derived LDH / activated carbon three-dimensional particle electrodes includes the following steps:

[0077] (1) Preparation of bimetallic MOF material FeCo-MOF

[0078] 1 mmol Fe(NO3)3·9H2O and 1 mmol Co(NO3)2·6H2O were dissolved in 30 mL of methanol solution, and this solution was designated as solution A. 20 mmol 2-methylimidazole was dissolved in 10 mL of ethanol solution, and this solution was designated as solution B. Solution B was slowly added dropwise to solution A, stirred at room temperature for 1 h, and then allowed to stand for 12 h to precipitate. After centrifugation, the obtained solid was washed repeatedly with methanol 5 times, and finally dried in a vacuum oven at 100 °C for 12 h to obtain FeCo-MOF.

[0079] (2) FeCo-MOF derivatization of bimetallic MOF material FeCo-MOF to prepare FeCo-LDH

[0080] 0.5 g FeCo-MOF was dispersed in 20 mL of 2 M NaOH solution and stirred slowly at 40 °C for 12 h. After the stirring was completed, the solid was separated by centrifugation. The obtained solid was washed three times with deionized water and ethanol respectively, and finally dried in a vacuum oven at 80 °C for 12 h to obtain FeCo-LDH.

[0081] (3) Preparation of FeCo-MOF-derived LDHs / activated carbon three-dimensional particle electrode

[0082] FeCo-MOF powder and activated carbon powder were mixed at a mass ratio of 10:1 to obtain FeCo-LDHs / activated carbon composite powder. The mixed powder was added to a 0.057 g / mL sodium carboxymethyl cellulose solution to prepare uniform particles. The prepared particles were dried at 100 °C for 8 h to obtain FeCo-MOF-derived LDH activated carbon three-dimensional particle electrode.

[0083] Example 6

[0084] The method for preparing FeCo-MOF-derived LDH / activated carbon three-dimensional particle electrodes includes the following steps:

[0085] (1) Preparation of bimetallic MOF material FeCo-MOF

[0086] 10 mmol Fe(NO3)3·9H2O and 2 mmol Co(NO3)2·6H2O were dissolved in 100 mL of methanol solution, and this solution was designated as solution A. 20 mmol 2-methylimidazole was dissolved in 10 mL of ethanol solution, and this solution was designated as solution B. Solution B was slowly added dropwise to solution A, stirred at room temperature for 6 h, and then allowed to stand for 48 h to precipitate. After centrifugation, the obtained solid was washed repeatedly with methanol 5 times, and finally dried in a vacuum oven at 100 °C for 12 h to obtain FeCo-MOF.

[0087] (2) FeCo-MOF derivatization of bimetallic MOF material FeCo-MOF to prepare FeCo-LDH

[0088] 0.5 g FeCo-MOF was dispersed in 20 mL of 0.3 M KOH solution and stirred slowly at 60 °C for 8 h. After the stirring was completed, the solid was separated by centrifugation. The obtained solid was washed three times with deionized water and ethanol respectively, and finally dried in a vacuum oven at 100 °C for 12 h to obtain FeCo-LDH.

[0089] (3) Preparation of FeCo-MOF-derived LDHs / activated carbon three-dimensional particle electrode

[0090] FeNi-LDH powder and activated carbon powder were mixed at a mass ratio of 2:1 to obtain FeCo-LDH / activated carbon composite powder. The mixed powder was added to a 0.026 g / mL sodium carboxymethyl cellulose solution to prepare uniform particles. The prepared particles were dried at 60 °C for 14 h to obtain FeCo-MOF-derived LDH activated carbon three-dimensional particle electrode.

[0091] Comparative Example 7: FeNi-LDH-3 prepared by coprecipitation method

[0092] 0.02 mol Ni(NO3)2·6H2O and 0.04 mol Fe(NO3)3·9H2O were dissolved in 90 mL of deionized water to form a salt solution. Then, 0.085 mol NaOH and 0.03 mol Na2CO3 were dissolved in 90 mL of deionized water to form an alkaline solution. After the salt and alkaline solutions were completely dissolved, the alkaline solution was slowly added to the salt solution to obtain a mixed solution. The mixed solution was placed in a constant temperature water bath at 60℃ and stirred for 7 hours. After that, it was taken out and washed several times by centrifugation with water and ethanol until the pH value reached 7. The obtained material was dried in a vacuum oven at 80℃ to obtain FeNi-LDH-3.

[0093] Comparative Example 8: Preparation of FeCo-LDH-2 using coprecipitation method

[0094] 0.02 mol Co(NO3)2·6H2O and 0.04 mol Fe(NO3)3·9H2O were dissolved in 90 mL of deionized water to form a salt solution. Then, 0.085 mol NaOH and 0.03 mol Na2CO3 were dissolved in 90 mL of deionized water to form an alkaline solution. After the salt and alkaline solutions were completely dissolved, the alkaline solution was slowly added to the salt solution to obtain a mixed solution. The mixed solution was placed in a constant temperature water bath at 60 °C and stirred for 7 h. After that, it was taken out and washed several times by centrifugation with water and ethanol until the pH value reached 7. The obtained material was dried in a vacuum oven at 80 °C to obtain FeCo-LDH-2.

[0095] Example 9: Electrocatalytic degradation of nitrosopyrrolidine using a three-dimensional particle electrode

[0096] The FeNi-LDH three-dimensional particle electrode prepared in Example 1, the FeNi-LDH-2 three-dimensional particle electrode prepared in Example 2, the FeCo-LDH-3 three-dimensional particle electrode prepared in Example 4, the FeNi-LDH-3 prepared in Comparative Example 7, and the FeCo-LDH-2 prepared in Comparative Example 8 were used as three-dimensional particle electrodes for the electrocatalytic degradation of nitrosopyrrolidine. Carbon plates were used as the positive and negative electrodes, and a three-dimensional particle electrode system was assembled for electrochemical catalytic oxidation testing. Figure 11 Electrochemical experiments show that at a current density of 15 mA / cm², 2 When the flow rate is 3 mL / min, the electrolyte concentration is 20 g / L, and the initial pollutant concentration is 30 mg / L, after 100 min of electrolysis, the removal rate of nitrosopyrrolidine by the three-dimensional mobile phase electrocatalytic system of LDHs / activated carbon three-dimensional particle electrode derived from bimetallic MOFs is stable at over 80%. In contrast, the removal rate of nitrosopyrrolidine by the LDHs / activated carbon particle electrode prepared by the traditional co-precipitation method under the same conditions can only be maintained at around 55%. This demonstrates that the electrode material prepared by the present invention has superior electrocatalytic performance.

[0097] Furthermore, this invention supplements some control experiments to explore the factors affecting the catalytic performance of the material; the material properties of the FeNi-LDH / activated carbon three-dimensional particle electrode prepared by bimetallic FeNi-MOF derivatization are as follows: Figure 12 The results show that the removal efficiency of the electrochemical reactor is directly affected by the electrolyte concentration and current density. With increasing electrolyte concentration and current density, the degradation rate increases slightly, but the corresponding energy consumption and economic costs also increase significantly. Hydraulic retention time is also one of the indicators for studying continuous flow reactors. At a flow rate of 0.5 mL / min for 100 min, nitrosopyrrolidine can be almost completely degraded, but the solution treatment volume at this point is too small, and the reactor is almost static. Further control experiments show that the reactor achieves the best removal efficiency for nitrosopyrrolidine when the flow rate is controlled at 3 mL / min, which may be the result of balancing mass transfer efficiency and the residence time of active species. The initial concentration of nitrosopyrrolidine also directly affects the removal rate. As the initial concentration increases from 10 to 20 mg / L, the removal rate of nitrosopyrrolidine increases; however, when the concentration is further increased to 25 and 30 mg / L, the removal rate does not change significantly, which may be related to the presence of sufficient ·OH active species in the reaction system.

[0098] The above embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

Claims

1. A method for preparing a bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode, characterized in that, Includes the following steps: (1) Preparation of bimetallic MOF materials: using coordination-controlled organic reagents and iron-containing metal salts. Using FeCl2·4H2O and Ni(NO3)2·6H2O, or Fe(NO3)3·9H2O and Co(NO3)2·6H2O as raw materials, and a mixed solution of ethanol and N,N-dimethylformamide or methanol as solvent, bimetallic MOF materials are synthesized by a solvothermal method; wherein the bimetallic MOF materials can be chemically etched and transformed in situ into LDHs structures; (2) Preparation of bimetallic MOFs-derived LDHs materials: Bimetallic MOFs materials are dispersed in an alkaline solution, wherein the alkaline solution is at least one of NaOH, KOH, and Ba(OH)2 aqueous solution, and the concentration of the alkaline solution is 0.3~2 M; the reaction is carried out at 40~80℃ for 3~12 h, then centrifuged and repeatedly washed with deionized water and ethanol, and finally dried to obtain bimetallic MOFs-derived LDHs powder. The MOFs are converted into LDHs in situ by chemical etching. (3) Preparation of bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode: Bimetallic MOFs-derived LDHs powder and activated carbon powder are mixed to obtain bimetallic MOFs-derived LDHs / activated carbon composite powder. Sodium carboxymethyl cellulose solution is added to the bimetallic MOFs-derived LDHs / activated carbon composite powder to prepare uniform particles. The prepared particles are thoroughly dried to obtain bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode. Activated carbon provides a conductive network, and LDHs provide catalytic active centers. The two work together to improve the electrocatalytic degradation efficiency.

2. The method for preparing a bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode according to claim 1, characterized in that, In step (1), when the iron-containing metal salts are FeCl2·4H2O and Ni(NO3)2·6H2O, the coordination-regulating organic reagent is 2,5-dihydroxyterephthalic acid; when the iron-containing metal salts are Fe(NO3)3·9H2O and Co(NO3)2·6H2O, the coordination-regulating organic reagent is 2-methylimidazole.

3. The method for preparing a bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode according to claim 2, characterized in that, When FeCl2·4H2O and Ni(NO3)2·6H2O are selected as raw materials, the molar ratio of FeCl2·4H2O and Ni(NO3)2·6H2O is (1~3):1, the molar ratio of the total amount of iron-containing metal salts to 2,5-dihydroxyterephthalic acid is (0.2~0.7):1, and deionized water is added to the mixed solvent, wherein the volume ratio of deionized water, ethanol and N,N-dimethylformamide in the mixed solvent is (1~4):(1~4):

1.

4. The method for preparing a bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode according to claim 2, characterized in that, When Fe(NO3)3·9H2O and Co(NO3)2·6H2O are selected as raw materials, the molar ratio of Fe(NO3)3·9H2O and Co(NO3)2·6H2O is (1~5):1, the molar ratio of the total amount of iron-containing metal salts to 2-methylimidazole is (0.1~0.8):1, and the volume ratio of ethanol to methanol in the mixed solvent is (3~10):

1.

5. The method for preparing a bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode according to claim 1, characterized in that, In step (3), bimetallic MOFs-derived LDHs powder and activated carbon powder are mixed at a mass ratio of (10~2):1 to obtain bimetallic MOFs-derived LDHs / activated carbon composite powder; the concentration of the binder sodium carboxymethyl cellulose solution is 0.026~0.057 g / mL.

6. A bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode prepared according to the preparation method described in claim 1.

7. The application of the bimetallic MOFs-derived LDHs / activated carbon three-dimensional particle electrode according to claim 6 in the catalytic degradation of nitrogen-containing disinfection byproducts.

8. The application according to claim 7, characterized in that, A bimetallic MOF-derived LDHs / activated carbon electrode is used as a three-dimensional particle electrode, a graphite carbon plate is used as the working electrode, and anhydrous sodium sulfate electrolyte is used to assemble a three-dimensional particle electrode system to achieve electrocatalytic degradation of nitrogen-containing disinfection byproducts.

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