Preparation method and application of a capacitive deionization anode applied to phosphate adsorption and desorption

Abstract

A method for preparing a capacitive deionization anode for phosphate adsorption and desorption, and its application, belong to the field of inorganic phosphorus wastewater adsorption and enrichment. This invention aims to solve the problems of existing adsorption materials, such as low phosphate adsorption capacity, difficulty in reusing the adsorbent, or poor conductivity. Method: 1. Preparation of a PEDOT / YMOF-NH2 composite material; 2. Preparation of a capacitive deionization anode. Application: It is used for the adsorption and desorption of phosphates in phosphate-containing water. This invention is used for the preparation of a capacitive deionization anode for phosphate adsorption and desorption.

Description

Technical Field

[0001] This invention belongs to the field of wastewater adsorption and enrichment of inorganic phosphorus. Background Technology

[0002] With accelerated industrialization and rapid population growth, the global demand for efficient, low-cost, and sustainable water treatment technologies is increasing. Electrochemical processes, due to their ability to precisely regulate current and voltage, modular design, and good scalability, are gradually becoming a key technology in environmental remediation. Particularly in the removal and enrichment of phosphates, electrochemical technology demonstrates significant advantages due to its controllability and high efficiency. Phosphorus (P), an essential element for life, relies heavily on non-renewable phosphate rock reserves globally, which are projected to face severe depletion within the next century, triggering a phosphorus crisis, threatening food security, and disrupting the phosphorus cycle in ecosystems. To address the challenge of phosphorus resource depletion, widely adopted phosphorus removal technologies include precipitation, ion exchange, membrane separation, and capacitive deionization (CDI) technology.

[0003] Capacitive deionization (CDI) technology, due to its advantages of low energy consumption, high stability, and no secondary pollution, has yielded numerous patent publications in phosphorus adsorption research. Electrochemical technology offers advantages such as precise control (e.g., current, voltage), low chemical reagent consumption, and high long-term stability. As an emerging electro-assisted technology, CDI shows significant potential in phosphorus enrichment.

[0004] Although current CDI technology mainly relies on carbon-based adsorbents such as activated carbon and graphene, these materials typically have low adsorption capacity and poor stability, making reusability difficult and limiting their widespread application. To improve adsorption performance, researchers are increasingly turning to composite materials with multifunctional properties, particularly metal-organic frameworks (MOFs). Their high porosity, tunable pore size, and excellent physicochemical properties make them promising candidates for phosphorus adsorption. However, the poor conductivity of MOFs limits their use as electrode materials in electrochemical applications. Summary of the Invention

[0005] This invention aims to address the problems of existing adsorption materials having low phosphate adsorption capacity and difficulty in reusing adsorbents, or poor conductivity, and thus provides a method for preparing and applying a capacitive deionization anode for phosphate adsorption and desorption.

[0006] A method for preparing a capacitive deionization anode for phosphate adsorption and desorption comprises the following steps:

[0007] I. Preparation of PEDOT / YMOF-NH2 composite material:

[0008] ① Dissolve YCl3 in a mixed solution of deionized water and glacial acetic acid, then add 3,4-ethylenedioxythiophene liquid and mix by sonication to obtain solution I;

[0009] ② Dissolve 2-aminoterephthalic acid in deionized water, then add sodium hydroxide to carry out a deprotonation reaction to obtain solution II;

[0010] ③ Mix solution I with solution II and react at room temperature for 10-12 hours to obtain solution III;

[0011] ④ Add the ethanol solution of FeCl3 dropwise to solution III, and react for 4 to 8 hours at room temperature and stirring speed of 450 to 600 rpm to obtain black crystals;

[0012] ⑤ The black crystals were washed and dried to obtain the PEDOT / YMOF-NH2 composite material;

[0013] II. Preparation of capacitor deionization anode:

[0014] The PEDOT / YMOF-NH2 composite material, carbon black, and polyvinylidene fluoride were dispersed in ethanol and then stirred to obtain a slurry. The slurry was uniformly coated on the surface of a carbon felt and then dried to obtain a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode, thus completing the preparation method of a capacitive deionization anode for phosphate adsorption and desorption.

[0015] An application of a capacitive deionization anode for phosphate adsorption and desorption, used for the adsorption and desorption of phosphates in phosphate-containing saline solutions.

[0016] The beneficial effects of this invention are:

[0017] This invention provides a method for preparing an anode based on a PEDOT / YMOF-NH2 composite material and its application in capacitive deionization. By introducing poly(3,4-ethylenedioxythiophene) (PEDOT) into the porous structure of an amino-functionalized yttrium-based metal-organic framework (YMOF-NH2), a composite material with a large specific surface area and high conductivity is prepared, named PEDOT / YMOF-NH2. Its synthesis process utilizes 3,4-ethylenedioxythiophene, yttrium trichloride, 2-aminoterephthalic acid, and a solvent, involving multiple chemical reactions such as monomer assembly, oxidative polymerization, and topological intercalation. Using this composite material, PEDOT / YMOF-NH2, carbon black (to improve conductivity), and polyvinylidene fluoride (to improve adhesion) are mixed in ethanol and coated onto the surface of a carbon felt to prepare a carbon felt-supported PEDOT / YMOF-NH2 electrode. This electrode serves as the anode for capacitive deionization, constructing a capacitive deionization device for the efficient adsorption and enrichment of phosphates under electrochemical control. Meanwhile, the electrode exhibits excellent stability during phosphate adsorption and desorption cycles, effectively overcoming the shortcomings of traditional carbon-based electrodes in terms of capacity and regeneration performance. The specific principle is as follows:

[0018] PEDOT possesses excellent electrical conductivity, significantly improving the overall conductivity of YMOF-NH2. YMOF-NH2 exhibits a favorable pore structure and large specific surface area, providing ample adsorption sites; while PEDOT's superior conductivity ensures efficient electron transport during capacitive deionization, thus significantly enhancing the composite material's performance in electrochemical reactions. Under electrochemical action, the PEDOT / YMOF-NH2 composite material effectively adsorbs phosphate ions from water. When a voltage is applied, the charges in the composite material interact with phosphate ions in the water, causing phosphate to adsorb onto the electrode surface. When a reverse voltage is applied, the phosphate ions rapidly desorb from the electrode surface, achieving a cyclic process of adsorption and desorption. Compared to traditional chemisorption methods, this process offers higher controllability and lower energy consumption. Attached Figure Description

[0019] Figure 1 The images show the XRD patterns of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of Comparative Experiment 1.

[0020] Figure 2 FT-IR images of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of Comparative Experiment 1;

[0021] Figure 3XPS spectra of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of Comparative Experiment 1, (a) is the full spectrum and (b) is the characteristic peak spectrum.

[0022] Figure 4 EPR images of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of Comparative Experiment 1;

[0023] Figure 5 The conductivity test curves are shown for the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of the comparative experiment.

[0024] Figure 6 TEM images of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of Comparative Experiment 1;

[0025] Figure 7 SEM images of the carbon felt-supported PEDOT / YMOF-NH2 composite electrode prepared in step two of Example 1 and the carbon felt-supported YMOF-NH2 composite electrode prepared in step two of Comparative Experiment 1.

[0026] Figure 8 Cyclic voltammetry (CV) and constant current charge-discharge (GCD) plots of the carbon felt-loaded PEDOT / YMOF-NH2 composite electrode prepared in step two of Example 1 or the carbon felt-loaded YMOF-NH2 composite electrode prepared in step two of Comparative Experiment 1 are shown. (a) is the CV plot at a test rate of 10 mV / s, and (b) is the GCD plot at a current density of 1 A / g.

[0027] Figure 9 The diagrams and physical images of the capacitor deionization device in step one of Example 2 are shown below. (a) is a schematic diagram of the connection between the capacitor deionization device and the peristaltic pump, the electrochemical workstation and the container. (b) is a physical image of the capacitor deionization device. (c) is an internal structural diagram of the capacitor deionization device.

[0028] Figure 10For Example 2 and Comparative Experiment 2, the changes in phosphate concentration during electro-assisted adsorption and desorption using carbon felt-loaded PEDOT / YMOF-NH2 composite electrodes and carbon felt-loaded YMOF-NH2 composite electrodes under different external electric field conditions are shown in the following figures: (a) phosphate concentration change under 0V conditions, (b) phosphate concentration change under 0.8V adsorption and -0.8V desorption conditions, (c) phosphate concentration change under 1.2V adsorption and -1.2V desorption conditions, and (d) phosphate concentration change under 1.6V adsorption and -1.6V desorption conditions.

[0029] Figure 11 Example 2 shows the changes in adsorption capacity of phosphate using a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode under different applied voltage conditions, as well as the changes in adsorption capacity during five cycles of adsorption and desorption. (a) is a bar chart of adsorption capacity under applied voltage conditions from 0V to 1.6V, and (b) is a graph showing the changes in adsorption capacity during five cycles of adsorption and desorption.

[0030] Figure 12 Example 2 shows the changes in phosphate adsorption mass of the carbon felt-loaded PEDOT / YMOF-NH2 composite electrode under different external electric field conditions, as well as the changes in adsorption mass during five cycles of adsorption and desorption. (a) is a bar chart of adsorption and desorption mass under the applied voltage conditions from 0V to 1.6V, and (b) is a graph showing the changes in adsorption and desorption mass during five cycles of adsorption and desorption.

[0031] Figure 13 The comprehensive evaluation indexes for Example 2 and Comparative Experiment 2 using carbon felt-supported PEDOT / YMOF-NH2 composite electrodes and carbon felt-supported YMOF-NH2 composite electrodes are as follows: (a) phosphate enrichment rate, (b) energy consumption, (c) phosphate recovery rate, and (d) concentration factor. Detailed Implementation

[0032] Specific Implementation Method 1: This implementation method describes a method for preparing a capacitive deionization anode used in phosphate adsorption and desorption, which is carried out according to the following steps:

[0033] I. Preparation of PEDOT / YMOF-NH2 composite material:

[0034] ① Dissolve YCl3 in a mixed solution of deionized water and glacial acetic acid, then add 3,4-ethylenedioxythiophene liquid and mix by sonication to obtain solution I;

[0035] ② Dissolve 2-aminoterephthalic acid in deionized water, then add sodium hydroxide to carry out a deprotonation reaction to obtain solution II;

[0036] ③ Mix solution I with solution II and react at room temperature for 10-12 hours to obtain solution III;

[0037] ④ Add the ethanol solution of FeCl3 dropwise to solution III, and react for 4 to 8 hours at room temperature and stirring speed of 450 to 600 rpm to obtain black crystals;

[0038] ⑤ The black crystals were washed and dried to obtain the PEDOT / YMOF-NH2 composite material;

[0039] II. Preparation of capacitor deionization anode:

[0040] The PEDOT / YMOF-NH2 composite material, carbon black, and polyvinylidene fluoride were dispersed in ethanol and then stirred to obtain a slurry. The slurry was uniformly coated on the surface of a carbon felt and then dried to obtain a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode, thus completing the preparation method of a capacitive deionization anode for phosphate adsorption and desorption.

[0041] The beneficial effects of this embodiment are:

[0042] This embodiment provides a method for preparing an anode based on a PEDOT / YMOF-NH2 composite material and its application in capacitive deionization. By introducing poly(3,4-ethylenedioxythiophene) (PEDOT) into the porous structure of an amino-functionalized yttrium-based metal-organic framework (YMOF-NH2), a composite material with a large specific surface area and high conductivity is prepared, named PEDOT / YMOF-NH2. Its synthesis process utilizes 3,4-ethylenedioxythiophene, yttrium trichloride, 2-aminoterephthalic acid, and a solvent, involving multiple chemical reactions such as monomer assembly, oxidative polymerization, and topological intercalation. Using this composite material, PEDOT / YMOF-NH2, carbon black (to improve conductivity), and polyvinylidene fluoride (to improve adhesion) are mixed in ethanol and coated onto the surface of a carbon felt to prepare a carbon felt-supported PEDOT / YMOF-NH2 electrode. This electrode serves as the anode for capacitive deionization, constructing a capacitive deionization device for the efficient adsorption and enrichment of phosphates under electrochemical control. Meanwhile, the electrode exhibits excellent stability during phosphate adsorption and desorption cycles, effectively overcoming the shortcomings of traditional carbon-based electrodes in terms of capacity and regeneration performance. The specific principle is as follows:

[0043] PEDOT possesses excellent electrical conductivity, significantly improving the overall conductivity of YMOF-NH2. YMOF-NH2 exhibits a favorable pore structure and large specific surface area, providing ample adsorption sites; while PEDOT's superior conductivity ensures efficient electron transport during capacitive deionization, thus significantly enhancing the composite material's performance in electrochemical reactions. Under electrochemical action, the PEDOT / YMOF-NH2 composite material effectively adsorbs phosphate ions from water. When a voltage is applied, the charges in the composite material interact with phosphate ions in the water, causing phosphate to adsorb onto the electrode surface. When a reverse voltage is applied, the phosphate ions rapidly desorb from the electrode surface, achieving a cyclic process of adsorption and desorption. Compared to traditional chemisorption methods, this process offers higher controllability and lower energy consumption.

[0044] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in the following ways: In step one ①, the mass ratio of YCl3 to the volume of the mixed solution of deionized water and glacial acetic acid is 1 g:(15-18) mL; the volume ratio of deionized water to glacial acetic acid in the mixed solution of deionized water and glacial acetic acid in step one ① is 1:(0.07-0.1); the mass ratio of YCl3 to 3,4-ethylenedioxythiophene liquid in step one ① is 1:(2.0-2.3); the ultrasonic mixing in step one ① is specifically performed under a power of 450W-600W for 25-30 minutes. Everything else is the same as in Specific Implementation Method One.

[0045] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the mass ratio of 2-aminoterephthalic acid to deionized water in step one ② is 1 g:(38-40) mL; the mass ratio of 2-aminoterephthalic acid to sodium hydroxide in step one ② is 1:(0.4-0.5); the deprotonation reaction in step one ② is specifically carried out at room temperature and a stirring speed of 450 rpm to 600 rpm for 25 min to 30 min. Everything else is the same as in Specific Implementation Method One or Two.

[0046] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the volume ratio of solution I to solution II in step one ③ is 1:(2.3~2.5). Everything else is the same as in Specific Implementation Method Three.

[0047] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the volume ratio of the FeCl3 ethanol solution to Solution III in step one (④) is 1:(3.35-3.5); the concentration of the FeCl3 ethanol solution in step one (④) is 0.5 mol / L to 1 mol / L. Everything else is the same as in Specific Implementation Methods One to Four.

[0048] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the washing and drying described in step one (⑤) are specifically carried out as follows: Wash repeatedly with alternating deionized water and anhydrous ethanol solution until the washing liquid is colorless, then vacuum dry at a temperature of 60℃~70℃ for 10h~14h. Everything else is the same as in Specific Implementation Methods One to Five.

[0049] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in the following ways: the mass ratio of the PEDOT / YMOF-NH2 composite material to carbon black in step two is (8-8.5):1; the mass ratio of carbon black to polyvinylidene fluoride in step two is 1:(1-1.5); the mass ratio of the PEDOT / YMOF-NH2 composite material to ethanol in step two is 1g:(400-500)mL; the coating thickness of the slurry in step two is 0.02mm-0.05mm; the drying in step two is specifically vacuum drying at a temperature of 60℃-70℃ for 10-14 hours. Everything else is the same as in Specific Implementation Methods One to Six.

[0050] Specific Implementation Method 8: This implementation method is an application of a capacitive deionization anode for phosphate adsorption and desorption, which is used to adsorb and desorb phosphate in phosphate-containing saline solutions.

[0051] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Eight in that the adsorption and desorption of phosphate in phosphate-containing saline solution is carried out specifically according to the following steps:

[0052] 1. Using a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode as the capacitive deionization anode and a carbon felt-loaded carboxylated activated carbon electrode as the capacitive deionization cathode, the sealing plate, capacitive deionization anode, anion exchange membrane, gasket, capacitive deionization cathode and sealing plate are assembled sequentially from one side to the other. The distance between the anion exchange membrane and the capacitive deionization cathode is controlled to be 2mm to 5mm by the gasket. The water inlet is set on the sealing plate on the capacitive deionization anode side and the water outlet is set on the sealing plate on the capacitive deionization cathode side to obtain the capacitive deionization device.

[0053] 2. Connect the capacitor deionization anode and capacitor deionization cathode to the positive and negative terminals of the power supply, respectively. Use phosphate-containing water as the water to be treated. Pass the water to be treated into the capacitor deionization device through the inlet and circulate it. Adsorption is carried out under the conditions of applying a voltage of 0.8V to 1.6V and an outlet flow rate of 12mL / min to 15mL / min.

[0054] The concentration of phosphate in the phosphate-containing saline solution is 10 mg / L to 500 mg / L, and the pH value is 6 to 10.

[0055] 3. Connect the capacitor deionization anode and cathode to the negative and positive terminals of the power supply, respectively, to reverse the electrode polarity. Use a sodium hydroxide solution with a concentration of 0.01 mol / L to 0.02 mol / L as the eluent. Circulate the eluent into the capacitor deionization device through the inlet. Under conditions of an applied voltage of -0.8V to -1.6V and an outlet water flow rate of 12 mL / min to 15 mL / min, desorption is carried out for 0.5 h to 2 h. Other procedures are the same as in specific implementation method eight.

[0056] In this specific embodiment, the inlet is located on the sealing plate on the anode side, so that the phosphate-containing water body is first treated by the anode; while the outlet is located on the sealing plate on the cathode, so that the water body is discharged after being treated by the cathode.

[0057] The specific implementation of this adsorption process includes: storing the phosphate-containing water body in a container, transporting the solution to a capacitor deionization device through a peristaltic pump, adsorbing the phosphate at the anode, and then returning the treated solution to the container, thereby completing the adsorption process of phosphorus in the phosphorus-containing water body.

[0058] The desorption process in this specific embodiment includes: replacing the container with a new container containing sodium hydroxide solution, delivering the solution to the capacitor deionization device via a peristaltic pump, and under the action of a reverse electric field, desorbing the previously adsorbed phosphate and enriching it in the sodium hydroxide solution, and finally returning the treated solution to the container to complete the phosphate enrichment process.

[0059] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Eight or Nine in that the carboxylated activated carbon electrode supported on carbon felt in step one is specifically prepared according to the following steps:

[0060] ① Activated carbon is dispersed in deionized water and stirred for 20-30 minutes at room temperature and a stirring speed of 450-600 rpm. The mixture is then filtered, and the dispersion and filtration are repeated until the conductivity of the filtrate is below 10 μS / cm. The filtrate is then vacuum-dried at 60-70℃ for 6-12 hours to obtain pretreated activated carbon. Nitric acid solution is added to the pretreated activated carbon, and the mixture is stirred and heated at 60-80℃ and a stirring speed of 450-600 rpm for 65-70 hours. After the reaction, the mixture is filtered and repeatedly washed with deionized water until the washings are neutral. Finally, the mixture is vacuum-dried at 60-70℃ for 5-10 hours to obtain carboxylated activated carbon. The concentration of the nitric acid solution is 7.6 mol / L-8 mol / L, and the mass ratio of the pretreated activated carbon to the volume of the nitric acid solution is 1 g:(8-10) mL.

[0061] ② Disperse carboxylated activated carbon, carbon black, and polyvinylidene fluoride in ethanol, then stir to obtain a slurry. Coat the slurry evenly onto the surface of a carbon felt with a coating thickness of 0.02 mm to 0.05 mm. Finally, vacuum dry at 65℃ to 80℃ for 5 h to 12 h to obtain a carbon felt-supported carboxylated activated carbon electrode. The mass ratio of carboxylated activated carbon to carbon black is (8 to 8.5):1; the mass ratio of carbon black to polyvinylidene fluoride is 1:(1 to 1.5); and the mass ratio of carboxylated activated carbon to ethanol is 1 g:(66 to 70) mL. Other steps are the same as in specific embodiments eight or nine.

[0062] The beneficial effects of the present invention are verified using the following embodiments:

[0063] Example 1:

[0064] A method for preparing a capacitive deionization anode for phosphate adsorption and desorption comprises the following steps:

[0065] I. Preparation of PEDOT / YMOF-NH2 composite material:

[0066] ① Dissolve 0.976g YCl3 in a mixed solution of deionized water and glacial acetic acid, then add 2.18g 3,4-ethylenedioxythiophene liquid, and sonicate for 30min at a power of 450W to obtain solution I;

[0067] The aforementioned mixed solution of deionized water and glacial acetic acid is prepared by mixing 14 mL of deionized water and 1 mL of glacial acetic acid.

[0068] ② Dissolve 0.906 g of 2-aminoterephthalic acid in 35 mL of deionized water, then add 0.4 g of sodium hydroxide, and deprotonate the solution for 30 min at room temperature and stirring speed of 600 rpm to obtain solution II;

[0069] ③ Mix 15 mL of solution I with 35 mL of solution II, and then react at room temperature for 10 h to obtain solution III;

[0070] ④ Add 15 mL of FeCl3 ethanol solution dropwise to 50 mL of solution III, and react for 8 h at room temperature and 600 rpm to obtain black crystals;

[0071] The concentration of the FeCl3 ethanol solution is 0.5 mol / L;

[0072] ⑤ The black crystals were repeatedly washed with deionized water and anhydrous ethanol solution alternately until the washing solution was colorless. Then, the crystals were vacuum dried at 60℃ for 14 hours to obtain the PEDOT / YMOF-NH2 composite material.

[0073] II. Preparation of capacitor deionization anode:

[0074] 0.06 g of PEDOT / YMOF-NH2 composite material, carbon black and polyvinylidene fluoride were dispersed in ethanol and stirred for 30 min at a stirring speed of 600 rpm to obtain a slurry. The slurry was uniformly coated on the surface of carbon felt (3 cm × 3 cm × 2 mm) with a coating thickness of 0.02 mm. Finally, it was vacuum dried at a temperature of 60 °C for 10 h to obtain carbon felt-loaded PEDOT / YMOF-NH2 composite electrode.

[0075] The mass ratio of the PEDOT / YMOF-NH2 composite material to carbon black is 8:1; the mass ratio of carbon black to polyvinylidene fluoride is 1:1; and the mass ratio of the PEDOT / YMOF-NH2 composite material to ethanol is 1g:400mL.

[0076] Comparative Experiment 1: This comparative experiment differs from Example 1 in that: the addition of 3,4-ethylenedioxythiophene liquid is omitted in step 1①; the YMOF-NH2 composite material is obtained in step 1⑤; and the carbon felt-supported YMOF-NH2 composite electrode is obtained in step 2. Everything else is the same as in Example 1.

[0077] Figure 1The figures show the XRD patterns of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of the comparative experiment. The simulated YMOF-NH2 in the figures was obtained by simulating crystal data from a crystal database using Materials Studio software to verify the crystal data of standard YMOF-NH2, thus proving the accuracy of the materials prepared in the example. As shown in the figures, its diffraction peaks are consistent with the spectra of PEDOT and YMOF-NH2, indicating that PEDOT / YMOF-NH2 maintains its main crystal structure. This is comparable to Fe-MOF (CCDC card number: 640536) or Y3Fe5O4. 12 The structure mismatch (ICDD card number: 01-070-0953) indicates that Fe 3+ It exists only as an oxidant during in-situ polymerization and does not form a coordination compound with 2-aminoterephthalic acid (C8H7NO4).

[0078] Figure 2 The images show the FT-IR spectra of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of the comparative experiment; at 1550 cm⁻¹. -1 and 3300cm -1 ~3481cm -1 The HOH vibrations attributed to adsorbed water molecules were observed at [a specific location]. PEDOT / YMOF-NH2 exhibits the characteristic absorption peaks of YMOF-NH2, located at 1255 cm⁻¹. -1 CN stretching vibration in amino (-NH2), 702 cm⁻¹ -1 Out-of-plane bending vibration of CH in aromatic rings, and 1432 cm⁻¹ -1 and 1382cm -1 The CO stretching vibration in the carboxyl group (-COOH). PEDOT / YMOF-NH2 also exhibits characteristic peaks of PEDOT, including 1087 cm⁻¹. -1 COC stretching vibration in methyldioxy (-O-CH2-O-), 485 cm⁻¹ -1 CS stretching vibration in thiophene ring and 407 cm -1 CSC bending vibration.

[0079] Figure 3The XPS spectra of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of the comparative experiment are shown in Figure (a) as the full spectrum and (b) as the characteristic peak diagram. As can be seen from the figures, the full spectrum of PEDOT / YMOF-NH2 has characteristic peaks for C1s, O1s, N1s, and S2p, indicating successful composite material preparation. Figure (b) shows that the obvious N1s and S2p characteristic peaks in the PEDOT / YMOF-NH2 composite material indicate that PEDOT has been successfully embedded in the pore structure of YMOF-NH2.

[0080] Figure 4 The images show the EPR spectra of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of the comparative experiment. YMOF-NH2 shows a strong signal at a g factor of 2.005, indicating that it has a high concentration of oxygen vacancies. In contrast, the signal intensity of PEDOT / YMOF-NH2 at the same g factor is significantly reduced, indicating a decrease in oxygen vacancy concentration. The results also show that PEDOT has been successfully embedded in the pore structure of YMOF-NH2.

[0081] Figure 5 The electrical conductivity test curves are shown for the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of the comparative experiment. The electrical conductivity test shows that YMOF-NH2 itself has insulating properties, and its electrical conductivity is approximately 10. -8 S / cm, while the conductivity of bulk PEDOT is approximately 10. -5 The electrical conductivity of the PEDOT / YMOF-NH2 composite material was significantly improved by 3 to 4 orders of magnitude, reaching 10 S / cm. -4 The S / cm ratio is particularly significant under high pressure (25-30 MPa) conditions.

[0082] Figure 6 Figure 1 shows TEM images of the PEDOT / YMOF-NH2 composite material prepared in step one of Example 1 and the YMOF-NH2 composite material prepared in step one of the comparative experiment. Figure (a) shows a TEM image of the YMOF-NH2 composite material, revealing its lamellar structure with clear edges, composed of stacked multilayer lamellar structures with a size of approximately 150 nm. Figure (b) shows a TEM image of the PEDOT / YMOF-NH2 composite material, where arrows indicate the fibrous structures with dark contrast in the YMOF-NH2 matrix.

[0083] Figure 7SEM images show the carbon felt-loaded PEDOT / YMOF-NH2 composite electrode prepared in step two of Example 1 and the carbon felt-loaded YMOF-NH2 composite electrode prepared in step two of Comparative Experiment 1. Observations show that the CF surface is relatively smooth, and YMOF-NH2 forms a multilayered sheet-like structure on the CF, but does not completely cover the fibers. At higher magnification, it can be seen that YMOF-NH2 covers a larger area of ​​the CF; the arrows indicate the interfaces where YMOF-NH2 adheres to the CF surface, indicating that it is deposited in thin film form. Compared to YMOF-NH2, PEDOT / YMOF-NH2 forms a thicker film on the CF, with rounded and smooth edges. Further magnification reveals that the PEDOT / YMOF-NH2 coating is more uniform and has a higher degree of coverage on the CF surface; the arrows indicate the adhesion areas.

[0084] In the electrochemical tests, the carbon felt-supported PEDOT / YMOF-NH2 composite electrode prepared in step two of Example 1, or the carbon felt-supported YMOF-NH2 composite electrode prepared in step two of Comparative Experiment 1, was used as the working electrode. The reference electrode was a saturated calomel electrode (SCE), and the counter electrode was a carboxylated activated carbon electrode (prepared as in step one of Example 2). Tests were conducted at room temperature, in air, and in 1M H2SO4 electrolyte. The potential window for cyclic voltammetry (CV) was set to 0.1V to 0.8V, and the scan rate range was 5mV / s to 100mV / s. The potential window for galvanostatic charge-discharge (GCD) testing was 0V to 1V, and the current density range was 0.5A / g to 5A / g. All electrochemical tests were independently repeated three times to ensure the reproducibility of the results.

[0085] Figure 8 The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) curves of the carbon felt-supported PEDOT / YMOF-NH2 composite electrode prepared in step two of Example 1, or the carbon felt-supported YMOF-NH2 composite electrode prepared in step two of Comparative Experiment 1, are shown. (a) is the CV curve at a test rate of 10 mV / s, and (b) is the GCD curve at a current density of 1 A / g. The area under the CV curve of PEDOT / YMOF-NH2 is significantly larger than that of YMOF-NH2, highlighting the important role of the electroactive polymer PEDOT in improving the performance of MOFs with poor conductivity. Figure (b) shows that compared with pure YMOF-NH2 (whose charge-discharge time at 1 A / g is 16 seconds), the charge-discharge time of the PEDOT / YMOF-NH2 composite material is extended to 27.5 seconds at the same current density, significantly improving its energy storage capacity. These results further demonstrate that the introduction of PEDOT effectively improves the electrochemical performance of the composite material, especially its advantages in capacitive deionization applications.

[0086] Example 2:

[0087] An application of a capacitive deionization anode for phosphate adsorption and desorption is described. It is used to adsorb and desorb phosphates in phosphate-containing aqueous solutions, specifically through the following steps:

[0088] 1. Using a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode as the capacitive deionization anode and a carbon felt-loaded carboxylated activated carbon electrode as the capacitive deionization cathode, the acrylic sealing plate, capacitive deionization anode, anion exchange membrane, polymethyl methacrylate gasket, capacitive deionization cathode, and acrylic sealing plate are assembled sequentially from one side to the other. The distance between the anion exchange membrane and the capacitive deionization cathode is controlled to be 2mm by the gasket. The water inlet is set on the sealing plate on the capacitive deionization anode side, and the water outlet is set on the sealing plate on the capacitive deionization cathode side to obtain the capacitive deionization device.

[0089] The anion exchange membrane mentioned is an AMI-7001S anion exchange membrane, purchased from Hangzhou Huamo Technology Co., Ltd.

[0090] 2. Connect the capacitor deionization anode and capacitor deionization cathode to the positive and negative terminals of the power supply, respectively. Use 250 mL of phosphate-containing water as the water to be treated. Pass the water to be treated into the capacitor deionization device through the inlet and circulate it. Under the conditions of applying a voltage of 0V to 1.6V and an outlet flow rate of 12 mL / min, adsorption is carried out for 60 min.

[0091] The phosphate-containing saline solution has a phosphate concentration of 50 mg / L and a pH value of 7.

[0092] 3. Connect the capacitor deionization anode and cathode to the negative and positive terminals of the power supply, respectively, so that the electrode polarity is reversed. Use 50 mL of 0.01 mol / L sodium hydroxide solution as the eluent. Pass the eluent into the capacitor deionization device through the inlet and circulate it. Under the conditions of applying a voltage of 0V to -1.6V and an outlet water flow rate of 12 mL / min, desorption is carried out for 2 hours.

[0093] The carboxylated activated carbon electrode supported on carbon felt as described in step one is specifically prepared according to the following steps:

[0094] ① Disperse 10g of activated carbon in 300mL of deionized water and stir for 20min at room temperature and 600rpm. Then filter, repeat dispersion and filtration until the conductivity of the filtrate is lower than 10μS / cm. Then vacuum dry at 70℃ for 6h to obtain pretreated activated carbon. Add 80mL of nitric acid solution to 10g of pretreated activated carbon and stir and heat at 60℃ and 600rpm for 65h. After reaction, filter and wash repeatedly with deionized water until the washing solution is neutral. Finally, vacuum dry at 60℃ for 5h to obtain carboxylated activated carbon. The concentration of the nitric acid solution is 7.6mol / L.

[0095] ② Disperse carboxylated activated carbon, carbon black, and polyvinylidene fluoride in ethanol, and then stir for 30 minutes at a stirring speed of 600 rpm to obtain a slurry. Coat the slurry evenly on the surface of a carbon felt (3cm×3cm×2mm) with a coating thickness of 0.02mm. Finally, vacuum dry at a temperature of 60℃ for 5 hours to obtain a carbon felt-supported carboxylated activated carbon electrode. The mass ratio of carboxylated activated carbon to carbon black is 8:1; the mass ratio of carbon black to polyvinylidene fluoride is 1:1; and the mass ratio of carboxylated activated carbon to ethanol is 1g:66mL.

[0096] Comparative Experiment 2: This comparative experiment differs from Example 2 in that the carbon felt-supported PEDOT / YMOF-NH2 composite electrode in step 1 is replaced with the carbon felt-supported YMOF-NH2 composite electrode prepared in Comparative Experiment 1. Everything else is the same as in Example 2.

[0097] Figure 9 The diagrams and physical images of the capacitive deionization device in step one of Example 2 are shown below. (a) is a schematic diagram of the connection between the capacitive deionization device and the peristaltic pump, electrochemical workstation, and container. (b) is a physical image of the capacitive deionization device. (c) is an internal structural diagram of the capacitive deionization device. (a) shows the overall design of the system, including electrode positions, fluid channels, and power supply connection methods. (b) shows in detail the installation of the carbon felt-loaded PEDOT / YMOF-NH2 composite electrode and its connection method with the reactor. (c) focuses on the design of the electric field distribution and liquid flow path to optimize the adsorption and desorption process of phosphorus.

[0098] The adsorption and desorption performance of carbon felt-supported PEDOT / YMOF-NH2 composite electrode and carbon felt-supported YMOF-NH2 composite electrode for phosphate under different voltage conditions was evaluated using the capacitive deionization device assembled in Example 2.

[0099] (1) Baseline testing under 0V flow system:

[0100] Without an external electric field (0V), a phosphate solution (50mg / L, pH 7) was used as the treatment solution and the system was run continuously for 60min. The concentration of residual phosphate in the system after 60min of adsorption was recorded.

[0101] Without an external electric field (0V), a 0.01M NaOH solution was used as the eluent, and the process was run continuously for 120 minutes. The changes in the phosphate concentration in the eluent were recorded.

[0102] (2) Positive electric field assisted adsorption test:

[0103] Under positive voltage electric fields (0.8V, 1.2V and 1.6V), phosphate solution (50mg / L, pH 7) was used as the treatment solution and the process was run continuously for 60min. The residual phosphate concentration in the solution at the end of adsorption was recorded at each test point, and the adsorption capacity was fitted based on the residual concentration data.

[0104] (3) Negative electric field assisted adsorption test:

[0105] Under negative voltage electric fields (-0.8V, -1.2V, and -1.6V), 0.01M NaOH solution was used as the eluent, and the operation was carried out continuously for 120 minutes, recording the changes in phosphate concentration in the eluent solution.

[0106] Figure 10 The following figures illustrate the changes in phosphate concentration during electro-assisted adsorption and desorption processes using carbon felt-loaded PEDOT / YMOF-NH2 composite electrodes and carbon felt-loaded YMOF-NH2 composite electrodes under different external electric field conditions in Example 2 and Comparative Experiment 2: (a) Phosphate concentration change at 0V, (b) Phosphate concentration change at 0.8V adsorption and -0.8V desorption, (c) Phosphate concentration change at 1.2V adsorption and -1.2V desorption, and (d) Phosphate concentration change at 1.6V adsorption and -1.6V desorption.

[0107] Figure 10 (a) As shown, after 60 min of adsorption, the residual phosphate concentration of the PEDOT / YMOF-NH2-based electrode was 19.40 mg / L, while that of the YMOF-NH2 electrode was 18.70 mg / L. Furthermore, under the same conditions, phosphate desorption was performed using 0.01 M NaOH for 120 min, and only 4.07 mg / L of phosphate was eluted from the PEDOT / YMOF-NH2 electrode.

[0108] Figure 10(b) shows that when the voltage is 0.8V, after 60 min of adsorption, the residual phosphate concentration of the PEDOT / YMOF-NH2 electrode is 16.70 mg / L, while that of the YMOF-NH2 electrode is 19.38 mg / L; Figure 10 (c) shows that when the voltage was increased to 1.2V, the residual phosphate concentration decreased to 14.12 mg / L (PEDOT / YMOF-NH2) and 16.67 mg / L (YMOF-NH2), respectively; Figure 10 (d) shows that when the voltage is set to 1.6V, the adsorption effect reaches its peak and the residual phosphate concentration is further reduced, with the PEDOT / YMOF-NH2 electrode system decreasing to 10.00 mg / L and the YMOF-NH2 electrode system decreasing to 14.71 mg / L.

[0109] Figure 10 (b) shows that when the voltage is -0.8V, after 120 min of desorption, the phosphate concentrations in the eluents of the PEDOT / YMOF-NH2 and YMOF-NH2 electrodes are 11.22 mg / L and 11.59 mg / L, respectively. Figure 10 (c) shows that when the voltage was increased to -1.2V, the phosphate concentration in the eluent increased to 31.97 mg / L (PEDOT / YMOF-NH2) and 22.16 mg / L (YMOF-NH2), respectively; Figure 10 (d) shows that the desorption effect reached its maximum at -1.6V, with phosphate concentrations in the eluent of 76.82 mg / L (PEDOT / YMOF-NH2) and 58.92 mg / L (YMOF-NH2), respectively.

[0110] (4) Cyclic adsorption-desorption test:

[0111] To evaluate the cyclic regeneration capability of the PEDOT / YMOF-NH2 composite electrode, the mass of the PEDOT / YMOF-NH2 composite material in step two of Example 1 was reduced from 0.06g to 0.03g; five adsorption-desorption cycles were continuously performed under adsorption conditions of 0.8V and desorption conditions of -1.6V; the adsorption capacity and desorption performance of the electrode were recorded after each cycle.

[0112] Figure 11 Example 2 shows the changes in adsorption capacity of phosphate using a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode under different applied voltage conditions, as well as the changes in adsorption capacity during five cycles of adsorption and desorption. (a) is a bar chart of adsorption capacity under applied voltage conditions from 0V to 1.6V, and (b) is a graph showing the changes in adsorption capacity during five cycles of adsorption and desorption.

[0113] Figure 12Example 2 shows the changes in phosphate adsorption mass of the carbon felt-loaded PEDOT / YMOF-NH2 composite electrode under different external electric field conditions, as well as the changes in adsorption mass during five cycles of adsorption and desorption. (a) is a bar chart of adsorption and desorption mass under the applied voltage conditions from 0V to 1.6V, and (b) is a graph showing the changes in adsorption and desorption mass during five cycles of adsorption and desorption.

[0114] Figure 11 (a) shows that as the applied positive electric field increases from 0V to 1.6V, the phosphate adsorption capacity of the PEDOT / YMOF-NH2 composite electrode increases significantly from 130.42 mg P / g to 166.67 mg P / g. Meanwhile, Figure 12 (a) shows that the amount of phosphate captured increased from 7.82 mg to 10 mg, and the amount of phosphate desorbed increased from 0.20 mg to 3.84 mg. Excess adsorption (greater than 7.82 mg) and weaker phosphate release (less than 3.84 mg) may affect the electrode's regeneration capacity. Excess adsorption may lead to saturation of active sites on the electrode surface, thus affecting desorption efficiency; weaker phosphate release may indicate that the desorption efficiency of the electrode material is limited, thereby reducing the electrode's regeneration performance.

[0115] Figure 11 (b) shows that in the first cycle, the adsorption capacity of the PEDOT / YMOF-NH2 composite electrode was approximately 120 mg P / g. After five consecutive adsorption-desorption cycles, the adsorption capacity decreased to 88.5 mg P / g, indicating that the electrode's adsorption capacity weakened after multiple cycles. In the fourth and fifth cycles, the electrode adsorbed 2.55 mg of phosphate and desorbed 2.56 mg of phosphate, indicating that the electrode reached a dynamic equilibrium between adsorption and desorption after five cycles and possessed good regeneration performance.

[0116] The above tests show that under an applied positive electric field, the PEDOT / YMOF-NH2 composite electrode significantly enhances the adsorption capacity for phosphate, exhibiting superior adsorption performance compared to the YMOF-NH2 composite electrode. Simultaneously, under an appropriate negative voltage, the desorption performance of the electrode is also significantly improved. Cyclic testing further demonstrates the electrode's excellent regeneration stability during repeated adsorption-desorption processes. These results fully validate the superior performance of the PEDOT / YMOF-NH2 composite material for phosphate adsorption and enrichment, and its application potential in water treatment and phosphorus resource recovery.

[0117] (5) A comprehensive evaluation of the performance of the electric-assisted technology was conducted, focusing on key indicators such as phosphate enrichment rate, energy consumption, recovery efficiency, and concentration factor. The calculation formulas for each indicator are as follows:

[0118] Phosphate enrichment rate:

[0119] Energy consumption:

[0120] Phosphate recovery rate:

[0121] Concentration factor:

[0122] Performance metrics in electrically driven systems include phosphate enrichment rate (R, unit: mmol / (m²)). 2 •h), energy consumption (EC, unit: kWh / kgP), phosphate recovery rate (Pre, unit: %) and concentration factor (CF).

[0123] The amount of enriched phosphate is denoted as n. p The unit is millimoles (mmol). This value is affected by several factors, including the effective electrode area A (unit: m²). 2 ) and total enrichment time t total (Unit: h). These parameters determine the efficiency of the phosphorus enrichment process over time. The system performance is also affected by the applied voltage U (V) and current I (A). Furthermore, the total mass of enriched phosphate is denoted as m (kg). To evaluate the system's effectiveness, two important phosphate concentration values ​​are used: the initial phosphorus concentration C in the feed. P,in (mg / L) and the final phosphorus concentration C in the effluent P,eff (mg / L). The phosphorus concentration of phosphate in the concentrated product is denoted as C. P,con (mg / L). These values ​​are used to quantify the efficiency of the system in the phosphorus enrichment process.

[0124] ① Effect of voltage on phosphate enrichment rate:

[0125] Under positive electric field assisted conditions, voltages of 0.8V, 1.2V, and 1.6V were applied to conduct adsorption tests on carbon felt-loaded PEDOT / YMOF-NH2 composite electrodes, with each test lasting 60 minutes.

[0126] ② Energy consumption test:

[0127] a) Perform adsorption under a positive voltage of 0.8V and record the energy consumption;

[0128] b) After adsorption is completed at a positive voltage of 0.8V, the process switches to desorption, which is performed at a negative voltage of -1.6V. Desorption tests are conducted using 0.01M NaOH eluent, and energy consumption is recorded.

[0129] ③ Phosphate recovery rate and concentration factor:

[0130] The phosphate recovery rate and concentration factor of the carbon felt-loaded PEDOT / YMOF-NH2 composite electrode and the carbon felt-loaded YMOF-NH2 composite electrode were tested under applied voltages of 0V, 0.8V, 1.2V and 1.6V respectively.

[0131] Figure 13 The comprehensive evaluation indicators for Example 2 and Comparative Experiment 2 using the carbon felt-supported PEDOT / YMOF-NH2 composite electrode and the carbon felt-supported YMOF-NH2 composite electrode are as follows: (a) phosphate enrichment rate, (b) energy consumption, (c) phosphate recovery rate, and (d) concentration factor. Figure 13 As shown in (a), the phosphorus enrichment rate gradually increases with increasing applied voltage. Specifically, at 1.6V, the phosphorus enrichment rate of the PEDOT / YMOF-NH2 electrode reaches 22.21 mmol / (m²). 2 The phosphorus enrichment rate (·h) was significantly higher than that of other typical CDI systems (6.36 to 17.0 mmol / (m³)). 2 ·h)). For example Figure 13 As shown in (b), the energy consumption of the adsorption phase is 0.15 kWh / kgP at 0.8 V, while the energy consumption of the desorption phase is 0.71 kWh / kgP at -1.6 V, resulting in a total energy consumption of 0.86 kWh / kgP per cycle. This energy consumption is significantly lower than that of other typical capacitive deionization systems (typically 3.0 to 29.2 kWh / kgP), indicating a significant advantage in energy efficiency for this system. Although higher voltages lead to increased energy consumption, the overall energy consumption remains low, particularly demonstrating high efficiency under medium voltage conditions (0.8 V). Figure 13 As shown in (c), under all test conditions, the phosphate recovery rate of the PEDOT / YMOF-NH2 composite electrode was consistently higher than that of the pure YMOF-NH2 electrode. This result is attributed to the introduction of PEDOT, which improves the overall charge distribution of the electrode, thereby more effectively promoting the capture of phosphate ions. Figure 13 As shown in (d), the PEDOT / YMOF-NH2 composite electrode exhibits a high concentration factor under various operating conditions, with a maximum value of 1.54, indicating its excellent ability in phosphorus concentration.

Claims

1. A method for preparing a capacitive deionization anode for phosphate adsorption and desorption, characterized in that... It is done in the following steps: I. Preparation of PEDOT / YMOF-NH2 composite material: ① Dissolve YCl3 in a mixed solution of deionized water and glacial acetic acid, then add 3,4-ethylenedioxythiophene liquid and mix by sonication to obtain solution I; ② Dissolve 2-aminoterephthalic acid in deionized water, then add sodium hydroxide to carry out a deprotonation reaction to obtain solution II; ③ Mix solution I with solution II and react at room temperature for 10-12 hours to obtain solution III; ④ Add the ethanol solution of FeCl3 dropwise to solution III, and react for 4 to 8 hours at room temperature and a stirring speed of 450 to 600 rpm to obtain black crystals; ⑤ The black crystals were washed and dried to obtain the PEDOT / YMOF-NH2 composite material; II. Preparation of capacitor deionization anode: The PEDOT / YMOF-NH2 composite material, carbon black, and polyvinylidene fluoride were dispersed in ethanol and then stirred to obtain a slurry. The slurry was uniformly coated on the surface of a carbon felt and then dried to obtain a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode, thus completing the preparation method of a capacitive deionization anode for phosphate adsorption and desorption.

2. The method for preparing a capacitive deionization anode for phosphate adsorption and desorption according to claim 1, characterized in that... In step 1①, the mass ratio of YCl3 to the volume ratio of the mixed solution of deionized water and glacial acetic acid is 1 g:(15~18) mL; the volume ratio of deionized water to glacial acetic acid in the mixed solution of deionized water and glacial acetic acid in step 1① is 1:(0.07~0.1); the mass ratio of YCl3 to 3,4-ethylenedioxythiophene liquid in step 1① is 1:(2.0~2.3); the ultrasonic mixing in step 1① is specifically performed under a power of 450W~600W for 25min~30min.

3. The method for preparing a capacitive deionization anode for phosphate adsorption and desorption according to claim 1, characterized in that... The mass ratio of 2-aminoterephthalic acid to deionized water in step 1② is 1 g:(38~40) mL; the mass ratio of 2-aminoterephthalic acid to sodium hydroxide in step 1② is 1:(0.4~0.5); the deprotonation reaction in step 1② is specifically carried out at room temperature and a stirring speed of 450 rpm~600 rpm for 25 min~30 min.

4. The method for preparing a capacitive deionizing anode for phosphate adsorption and desorption according to claim 1, characterized in that... The volume ratio of solution I to solution II in step 1③ is 1:(2.3~2.5).

5. The method for preparing a capacitive deionizing anode for phosphate adsorption and desorption according to claim 1, characterized in that... The volume ratio of the FeCl3 ethanol solution to solution III in step 1, ④ is 1:(3.35~3.5); the concentration of the FeCl3 ethanol solution in step 1, ④ is 0.5mol / L~1mol / L.

6. The method for preparing a capacitive deionizing anode for phosphate adsorption and desorption according to claim 1, characterized in that... The washing and drying described in step 1.5 are carried out in the following steps: repeatedly wash with deionized water and anhydrous ethanol solution until the washing solution is colorless, and then vacuum dry at a temperature of 60℃~70℃ for 10h~14h.

7. The method for preparing a capacitive deionization anode for phosphate adsorption and desorption according to claim 1, characterized in that... The mass ratio of PEDOT / YMOF-NH2 composite material to carbon black in step two is (8~8.5):1; the mass ratio of carbon black to polyvinylidene fluoride in step two is 1:(1~1.5); the mass ratio of PEDOT / YMOF-NH2 composite material to ethanol in step two is 1g:(400~500)mL; the coating thickness of the slurry in step two is 0.02mm~0.05mm; the drying in step two is specifically vacuum drying at a temperature of 60℃~70℃ for 10h~14h.

8. The application of a capacitive deionization anode prepared by the preparation method according to claim 1 for use in phosphate adsorption and desorption, characterized in that... It is used for the adsorption and desorption of phosphates in phosphate-containing saline solutions.

9. The application of the capacitive deionization anode for phosphate adsorption and desorption according to claim 8, characterized in that... The adsorption and desorption of phosphates in phosphate-containing saline solutions are carried out specifically according to the following steps:

1. Using a carbon felt-loaded PEDOT / YMOF-NH2 composite electrode as the capacitive deionization anode and a carbon felt-loaded carboxylated activated carbon electrode as the capacitive deionization cathode, the sealing plate, capacitive deionization anode, anion exchange membrane, gasket, capacitive deionization cathode, and sealing plate are assembled sequentially from one side to the other. The distance between the anion exchange membrane and the capacitive deionization cathode is controlled to be 2mm~5mm by the gasket. The water inlet is set on the sealing plate on the capacitive deionization anode side, and the water outlet is set on the sealing plate on the capacitive deionization cathode side to obtain the capacitive deionization device.

2. Connect the capacitor deionization anode and capacitor deionization cathode to the positive and negative terminals of the power supply, respectively. Use phosphate-containing water as the water to be treated. Pass the water to be treated into the capacitor deionization device through the inlet and circulate it. Adsorption is carried out under the conditions of applying a voltage of 0.8V~1.6V and an outlet flow rate of 12mL / min~15mL / min. The concentration of phosphate in the phosphate-containing saline solution is 10 mg / L to 500 mg / L, and the pH value is 6 to 10.

3. Connect the capacitor deionization anode and cathode to the negative and positive terminals of the power supply, respectively, so that the electrode polarity is reversed. Use a sodium hydroxide solution with a concentration of 0.01mol / L to 0.02mol / L as the eluent. Pass the eluent into the capacitor deionization device through the inlet and circulate it. Under the conditions of applying a voltage of -0.8V to -1.6V and an outlet water flow rate of 12mL / min to 15mL / min, desorption is carried out for 0.5h to 2h.

10. The application of the capacitive deionization anode for phosphate adsorption and desorption according to claim 9, characterized in that... The carboxylated activated carbon electrode supported on carbon felt as described in step one is specifically prepared according to the following steps: ① Activated carbon is dispersed in deionized water and stirred for 20-30 minutes at room temperature and a stirring speed of 450-600 rpm. The mixture is then filtered, and the dispersion and filtration are repeated until the conductivity of the filtrate is below 10 μS / cm. The filtrate is then vacuum-dried at 60-70℃ for 6-12 hours to obtain pretreated activated carbon. Nitric acid solution is added to the pretreated activated carbon, and the mixture is stirred and heated at 60-80℃ and a stirring speed of 450-600 rpm for 65-70 hours. After the reaction, the mixture is filtered and repeatedly washed with deionized water until the washings are neutral. Finally, the mixture is vacuum-dried at 60-70℃ for 5-10 hours to obtain carboxylated activated carbon. The concentration of the nitric acid solution is 7.6 mol / L-8 mol / L, and the mass ratio of the pretreated activated carbon to the volume of the nitric acid solution is 1 g:(8-10) mL. ② Disperse carboxylated activated carbon, carbon black, and polyvinylidene fluoride in ethanol, then stir to obtain a slurry. Coat the slurry evenly on the surface of carbon felt with a coating thickness of 0.02 mm to 0.05 mm. Finally, vacuum dry at a temperature of 65℃ to 80℃ for 5 h to 12 h to obtain a carbon felt-supported carboxylated activated carbon electrode. The mass ratio of carboxylated activated carbon to carbon black is (8 to 8.5):1; the mass ratio of carbon black to polyvinylidene fluoride is 1:(1 to 1.5); and the mass ratio of carboxylated activated carbon to ethanol is 1 g:(66 to 70) mL.

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