An electrode for capacitor deionization and its preparation method
By preparing a mixture of electrode material containing DHPZ with carbon material and binder, the problem of low desalination capacity in capacitive deionization technology was solved, and a highly efficient ammonium ion removal effect was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-06
- Publication Date
- 2026-03-10
AI Technical Summary
Capacitive deionization technology has low desalination capacity, low adsorption capacity, and low removal efficiency.
DHPZ was used as the electrode material and mixed with carbon materials and binders to prepare the electrode. DHPZ was formed by grinding and mixing 2,5-dihydroxy-1,4-benzoquinone and 2,3-diaminophenazine and then acidifying it. The electrode was then prepared by combining it with NMP.
It improves the desalination capacity and removal efficiency of capacitive deionization, especially significantly enhancing the removal effect of ammonium ions.
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Figure CN119528283B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of capacitive deionization, in particular to an electrode for capacitive deionization and a preparation method thereof. BACKGROUND
[0002] Ammonium ions can cause water eutrophication, promote the massive reproduction of aquatic plants such as algae, form water bloom or red tide, consume a large amount of dissolved oxygen in water, cause the death of aquatic organisms such as fish due to lack of oxygen, and destroy the balance of aquatic ecology.
[0003] At present, the common methods for removing ammonium ions in water include chemical precipitation method, ion exchange method and biological treatment method, but the chemical precipitation method needs to add a large amount of chemical agents to the water, which will produce a large amount of sludge, has high treatment cost, and will introduce new impurities; the ion exchange method uses ion exchange resin to exchange with ammonium ions in water, adsorbs ammonium ions on the resin, so as to remove ammonium ions, but the ion exchange resin needs to be regenerated regularly, and a large amount of regeneration wastewater will be produced in the regeneration process, which is difficult to handle; the biological treatment method uses the metabolic action of microorganisms to convert ammonium ions into harmless substances such as nitrogen, so as to remove ammonium ions, but this method needs a long reaction time, and has high requirements for environmental conditions such as temperature and pH value.
[0004] Capacitive deionization technology (CDI) is a new type of water treatment technology based on electrochemical principle, compared with the above traditional water treatment methods, CDI technology does not need to add chemical agents in the process of removing ions, only a small amount of electric energy is consumed in the process of charging and discharging of electrode, therefore, CDI technology has low energy consumption and does not produce secondary pollution, which is a green and environmental protection water treatment technology.
[0005] The electrode in CDI technology usually uses activated carbon or graphene, but in practical application, it is found that the desalination capacity is low, and the adsorption capacity and removal efficiency are not high. SUMMARY
[0006] The present application provides an electrode for capacitive deionization and a preparation method thereof, to solve the problems of low desalination capacity, low adsorption capacity and low removal efficiency in the related technology of capacitive deionization.
[0007] In a first aspect, an electrode for capacitive deionization is provided, which comprises an electrode material, a carbon material and a binder:
[0008] The electrode material is DHPZ, the structural formula of which is as follows:
[0009]
[0010] The preparation method of the DHPZ comprises the following steps:
[0011] S1. Preliminary reaction: 2,5-dihydroxy-1,4-benzoquinone and 2,3-diaminophenazine are ground and mixed in a molar ratio of 1:3 to 1:5, and heated in an inert gas at 180 to 220°C for 5 to 7 hours. After cooling, the mixture is filtered, washed, and vacuum dried to obtain the initial product.
[0012] S2. Acidification treatment of the primary product: The primary product is mixed with 2 mol / L nitric acid at a mass-volume ratio of 1:1 and magnetically stirred for 5 hours. After filtration, it is washed with deionized water, centrifuged multiple times, and then vacuum dried at 60°C for 15 hours to obtain the DHPZ.
[0013] Preferably, in step S1, the cleaning includes washing with deionized water and washing with ethanol 3 to 4 times in sequence.
[0014] Preferably, the vacuum drying conditions in S1 are vacuum drying at 60°C for 15-20 hours.
[0015] Preferably, the carbon material is selected from carbon black and activated carbon.
[0016] Preferably, the mass ratio of DHPZ, carbon material, and adhesive is 7:2:1.
[0017] Preferably, it further includes NMP, wherein the volume mass ratio of NMP to DHPZ, carbon material and binder is 1:5 to 1:10.
[0018] Preferably, the inert gas includes nitrogen or argon.
[0019] Preferably, the adhesive is selected from carboxymethyl cellulose and polytetrafluoroethylene.
[0020] Secondly, a method for preparing an electrode for capacitive deionization is provided, which is used to prepare an electrode for capacitive deionization as described above, comprising the following steps:
[0021] DHPZ, carbon materials and binders are mixed evenly in a ratio of 7:2:1 to obtain a mixture. NMP is added dropwise and the mixture is ground for 1 to 5 minutes to obtain a slurry. The mass-volume ratio of NMP to the mixture is 1:5 to 1:10.
[0022] The slurry is applied to the electrode sheet to a thickness of 80~300μm to obtain the electrode.
[0023] The beneficial effects of the technical solution provided in this application include:
[0024] This application provides an electrode for capacitive deionization and its preparation method. DHPZ is obtained by grinding and mixing 2,5-dihydroxy-1,4-benzoquinone and 2,3-diaminophenazine, followed by acidification. DHPZ is then used as part of the electrode, prepared together with carbon materials and a binder. This enhances the desalination capacity, especially the removal of ammonium ions, in capacitive deionization applications, resulting in higher desalination capacity and removal efficiency. Therefore, it solves the problems of low desalination capacity, low adsorption capacity, and low removal efficiency in capacitive deionization technologies. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 This is a schematic diagram of the DHPZ preparation process provided in this application;
[0027] Figure 2 The Gaussian plot of Embodiment 1 provided in this application;
[0028] Figure 3 A schematic diagram of the electrochemical performance of Example 1 provided in this application;
[0029] Figure 4 A schematic diagram of the deionization capability of Example 1 provided in this application;
[0030] Figure 5 A schematic diagram of the deionization long-cycle capability of Example 1 provided in this application. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0032] See Figure 1 As shown, this application provides an electrode for capacitive deionization, which can solve the problems of low desalination capacity, low adsorption capacity and low removal efficiency in capacitive deionization related technologies.
[0033] The electrode for capacitive deionization comprises an electrode material, a carbon material, and a binder, wherein the structural formula of the electrode material is shown below:
[0034]
[0035] The preparation method of DHPZ includes the following steps:
[0036] S1. Preliminary reaction: 2,5-dihydroxy-1,4-benzoquinone (DHBQ) and 2,3-diaminophenazine (TTFQ) are ground and mixed in a molar ratio of 1:3 to 1:5, and heated in an inert gas atmosphere at 180 to 220°C for 5 to 7 hours. After cooling, the mixture is filtered, washed, and dried to obtain the initial product.
[0037] The chemical formula of the primary product is:
[0038]
[0039] S2. Acidification treatment of the primary product: The primary product is mixed with 2 mol / L nitric acid at a mass-to-volume ratio of 1:1 and magnetically stirred for 5 hours. After filtration, it is washed with deionized water, centrifuged multiple times, and then vacuum dried at 60°C for 15 hours to obtain DHPZ. Specifically, the mass-to-volume ratio is mg:mL. "Multiple times" in "multiple centrifugations" refers to 3-6 times.
[0040] Furthermore, the reaction formula for the primary product is as follows:
[0041]
[0042] After acidification, the final product DHPZ is obtained:
[0043]
[0044] In some embodiments, in step S1, the cleaning includes washing with deionized water and washing with ethanol 3 to 4 times in sequence.
[0045] In some embodiments, the vacuum drying conditions in S1 are vacuum drying at 60°C for 15-20 hours.
[0046] In some embodiments, the carbon material is selected from carbon black and activated carbon.
[0047] In some embodiments, the ratio of DHPZ, carbon material, and binder is 7:2:1;
[0048] In some embodiments, the electrode of the capacitive deionization further includes N-methylpyrrolidone (NMP), wherein the volume-to-mass ratio of NMP to DHPZ, carbon material, and binder is 1:5 to 1:10. It should be noted that the NMP used is a pure substance, and the volume-to-mass ratio is expressed in mL and g.
[0049] In some embodiments, the inert gas includes nitrogen or argon.
[0050] In some embodiments, the adhesive is selected from carboxymethyl cellulose and polytetrafluoroethylene.
[0051] Example 1
[0052] In this embodiment, the electrode used for capacitor deionization includes an electrode material, activated carbon, and carboxymethyl cellulose. The preparation method of the electrode material includes the following steps:
[0053] S1. Grind and mix 1 mmol of 2,5-dihydroxy-1,4-benzoquinone and 4 mmol of 2,3-diaminophenazine, heat at 200°C in nitrogen for 6 h, cool and filter, wash the product three times with deionized water, wash three times with ethanol, and dry under vacuum at 60°C for 16 h to obtain the initial product.
[0054] S2. Acidification treatment of the primary product: Mix 50 mg of the primary product with 50 mL of 2 mol / L nitric acid and stir magnetically for 5 h. After filtration, wash with deionized water, centrifuge 3 times, and then vacuum dry at 60 °C for 15 h to obtain the electrode material, denoted as DHPZ.
[0055] The mass ratio of DHPZ: activated carbon: carboxymethyl cellulose is 7:2:1. In this example, 7 mg of DHPZ, 2 mg of activated carbon, and 1 mg of carboxymethyl cellulose are used.
[0056] After mixing DHPZ, activated carbon, and carboxymethyl cellulose, 1 mL of NMP was added dropwise. The mixture was then ground and coated onto an electrode sheet to a thickness of 150 μm. The electrode sheet had a diameter of 1 cm. 2 Round carbon paper.
[0057] Example 2
[0058] In this embodiment, the electrode used for capacitor deionization includes an electrode material, carbon black, and carboxymethyl cellulose. The preparation method of the electrode material includes the following steps:
[0059] S1. Grind and mix 1 mmol of 2,5-dihydroxy-1,4-benzoquinone and 3 mmol of 2,3-diaminophenazine, heat at 180 °C in nitrogen for 5 h, cool and filter, wash the product 4 times with deionized water, wash 4 times with ethanol, and dry under vacuum at 60 °C for 15 h to obtain the initial product.
[0060] S2. Acidification treatment of the primary product: Mix 50 mg of the primary product with 50 mL of 2 mol / L nitric acid and stir magnetically for 5 h. After filtration, wash with deionized water, centrifuge 5 times, and then vacuum dry at 60 °C for 15 h to obtain the electrode material, denoted as DHPZ.
[0061] The mass ratio of DHPZ to carbon black and carboxymethyl cellulose is 7:2:1. In this example, 7 mg of DHPZ, 2 mg of carbon black, and 1 mg of carboxymethyl cellulose are used.
[0062] After mixing DHPZ, carbon black, and carboxymethyl cellulose, 0.5 mL of NMP was added dropwise. The mixture was then ground and coated onto an electrode sheet to a thickness of 80 μm. The electrode sheet had a diameter of 1 cm. 2 Round carbon paper.
[0063] Example 3
[0064] In this embodiment, the electrode used for capacitor deionization includes an electrode material, carbon black, and polytetrafluoroethylene. The preparation method of the electrode material includes the following steps:
[0065] S1. Grind and mix 1 mmol of 2,5-dihydroxy-1,4-benzoquinone and 5 mmol of 2,3-diaminophenazine, heat at 220°C in an inert gas atmosphere for 7 h, cool and filter, wash the product 4 times with deionized water, wash 3 times with ethanol, and dry under vacuum at 60°C for 20 h to obtain the initial product.
[0066] S2. Acidification treatment of the primary product: Mix 50 mg of the primary product with 50 mL of 2 mol / L nitric acid and stir magnetically for 5 h. After filtration, wash with deionized water, centrifuge 6 times, and then vacuum dry at 60 °C for 15 h to obtain the electrode material, denoted as DHPZ.
[0067] The mass ratio of DHPZ, carbon black and polytetrafluoroethylene is 7:2:1. In this example, 7 mg of DHPZ, 2 mg of activated carbon and 1 mg of polytetrafluoroethylene are used.
[0068] After mixing DHPZ, activated carbon, and polytetrafluoroethylene, 0.8 mL of NMP was added dropwise. The mixture was then ground and coated onto an electrode sheet to a thickness of 300 μm. The electrode sheet had a diameter of 1 cm. 2 Round carbon paper.
[0069] Comparative Example 1
[0070] In this comparative example, the electrode used for capacitor deionization includes an electrode material, carbon black, and carboxymethyl cellulose. The preparation method of the electrode material DHPZ includes the following steps:
[0071] 1 mmol of 2,5-dihydroxy-1,4-benzoquinone and 4 mmol of 2,3-diaminophenazine were ground and mixed, heated at 180 °C in nitrogen for 5 h, cooled and filtered, the product was washed three times with deionized water and then three times with ethanol, and dried under vacuum at 60 °C for 16 h to obtain DHPZ.
[0072] The mass ratio of DHPZ, carbon black and carboxymethyl cellulose is 7:2:1. In this example, 7 mg of DHPZ, 2 mg of carbon black and 1 mg of carboxymethyl cellulose are used.
[0073] After mixing DHPZ, carbon black, and carboxymethyl cellulose, 1 mL of NMP was added dropwise. The mixture was then ground and coated onto an electrode sheet to obtain an electrode. The electrode sheet had a diameter of 1 cm. 2 Round carbon paper.
[0074] Comparative Example 2
[0075] In this comparative example, the electrodes used for capacitive deionization are activated carbon, carbon black, and carboxymethyl cellulose, with a mass ratio of activated carbon:carbon black:carboxymethyl cellulose of 7:2:1, specifically 7 mg of activated carbon, 2 mg of carbon black, and 1 mg of carboxymethyl cellulose.
[0076] Comparative Example 3
[0077] In this comparative example, the electrode used for capacitor deionization is activated carbon.
[0078] The deionization performance of the electrodes for capacitor deionization manufactured in the above embodiments and comparative examples was tested.
[0079] Gaussian diagram:
[0080] See Figure 2 The figure shows the Gaussian plot of the electrode prepared in Example 1.
[0081] As can be seen, the energy level difference of the prepared product DHPZ is lower than that of 2,5-dihydroxy-1,4-benzoquinone (DHBQ) and 2,3-diaminophenazine (TTFQ), so the reaction can occur and it is relatively more stable in electronic structure. That is, as an electrode material, it can have a longer service life and higher stability.
[0082] Electrochemical performance testing:
[0083] The electrodes prepared in Examples 1-3 and Comparative Examples 1-3 were connected to an electrochemical workstation, and cyclic voltammetry tests were performed at different scan rates (1 mV / s, 2 mV / s, 5 mV / s, 10 mV / s, 20 mV / s, 50 mV / s), and the current-potential curves were recorded. Figure 3 This is a schematic diagram of the electrochemical performance of the electrode prepared in Example 1. As the scan rate increases, the adsorption and desorption rates of ammonium ions on the electrode surface accelerate; and the electrode maintains a good rectangular shape even at higher scan rates, indicating that it has high capacitance stability and fast response capability.
[0084] Deionization performance test:
[0085] Two electrodes prepared in Example 1 were prepared and tested separately. Taking Example 1 as an example, the two prepared electrodes were connected to the positive and negative terminals of the power supply, separated by an ion exchange membrane, placed in a sealed container, and then a certain volume of 0.01 mol / L NH4Cl solution was injected to ensure that the solution completely submerged the electrodes.
[0086] The conductivity of a 0.01 mol / L NH4Cl solution in its initial state was measured using a conductivity meter, and the volume of the NH4Cl solution V0 (in L) was recorded.
[0087] Apply voltages (0.8V, 1V, 1.2V) to start the capacitor deionization process and start timing simultaneously, recording the time t (unit: min).
[0088] The conductivity κ of the solution was measured every 5 minutes. t The time was recorded. Based on the relationship between conductivity and concentration, the ion concentration c at different time points was calculated. t The calculation method is as follows:
[0089]
[0090] Where κ is the conductivity of the solution, k is the proportionality coefficient, and c is the concentration of ions in the NH4Cl solution (unit: mol / L).
[0091] Given that the initial conductivity of the NH4Cl solution is κ0 and the initial concentration is c0 of 0.01 mol / L, the proportionality coefficient can be obtained. .
[0092] During the deionization process, the conductivity κ of the solution was measured every 5 minutes. t And according to the formula The concentration c of ions in the solution at the corresponding time was obtained. t .
[0093] Calculate the desalination amount q based on the change in ion concentration. t :
[0094]
[0095] Where c0 is the initial concentration of the NH4Cl solution, 0.01 mol / L, c t Let V0 be the ion concentration in the NH4Cl solution at a certain time, M be the molar mass of NH4Cl, and m0 be the electrode mass.
[0096] Plot the deionization performance curve with time on the x-axis and desalination amount (mg / g) on the y-axis.
[0097] Figure 4 The deionization performance curve of the electrode prepared in Example 1 is shown.
[0098] As can be seen, the slope is relatively large in the initial stage, indicating a fast desalination rate; as time goes on, the slope gradually decreases, and the desalination rate decreases. Within 30 minutes, it can reach 80~90mg / g, which is a relatively fast desalination rate.
[0099] Deionization long-cycle capability test:
[0100] Two electrodes were prepared for each of Examples 1-3 and Comparative Examples 1-3, and tested separately. Taking Example 1 as an example, the two prepared electrodes were connected to the positive and negative terminals of a power source, separated by an ion exchange membrane, placed in a sealed container, and then a certain volume of 0.01 mol / L NH4Cl solution was injected to ensure that the solution completely submerged the electrodes.
[0101] The conductivity σ0 of a 0.01 mol / L NH4Cl solution in its initial state was measured using a conductivity meter.
[0102] The deionization performance test was repeated, with the deionization process lasting 30 minutes and the voltage at 1.2V. The conductivity σ of the solution was measured after each test. n (n represents the number of cycles), perform 50 cycles, and calculate the ion removal rate after each cycle based on the change in conductivity:
[0103]
[0104] Figure 5 This is a schematic diagram of the deionization long-cycle capability of the electrode prepared in Example 1.
[0105] During 50 cycles, the removal capacity of ammonium ions showed relatively small fluctuations with the increase in the number of cycles, indicating relatively stable performance. The specific energy consumption (SEC) also remained stable at an average value. In long-term use, the energy consumed to remove each mole of ammonium ions was relatively stable, making it suitable for long-term use.
[0106] As can be seen, the performance indicators do not fluctuate much with the increase in the number of cycles, indicating that the electrode has good long-cycle capability.
[0107] This application also provides a method for preparing an electrode for capacitor deionization, the preparation method of which is described in the above embodiments.
[0108] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. An electrode for capacitive deionization, characterized by, It comprises electrode material, carbon material and binder: The electrode material is DHPZ, whose structural formula is shown as follows: The preparation method of the DHPZ comprises the following steps: S1, preliminary reaction: 2,5-dihydroxy-1,4-benzoquinone and 2,3-diaminophenazine are mixed in a ratio of 1:3-1:5 by molar ratio, and heated at 180-220°C in an inert gas for 5-7h, filtered after cooling, washed and vacuum dried to obtain a primary product; S2, acidification treatment of the primary product: the primary product is mixed with 2mol / L nitric acid in a ratio of 1:1 by mass volume ratio, and magnetically stirred for 5h, washed with deionized water after filtration, centrifuged for several times, and vacuum dried at 60°C for 15h to obtain the DHPZ.
2. The electrode for capacitive deionization according to claim 1, wherein: In S1, the washing comprises deionized water washing and ethanol washing for 3-4 times respectively.
3. The electrode for capacitive deionization according to claim 1, wherein: In S1, the vacuum drying condition is vacuum drying at 60°C for 15-20h.
4. The electrode for capacitive deionization according to claim 1, wherein: The carbon material is selected from one of carbon black and activated carbon.
5. The electrode for capacitive deionization according to claim 1, wherein: The mass ratio of the DHPZ, carbon material and binder is 7:2:
1.
6. The electrode for capacitive deionization according to claim 5, wherein: It further comprises NMP, and the volume mass ratio of the NMP to the total amount of DHPZ, carbon material and binder is 1:5-1:
10.
7. The electrode for capacitive deionization according to claim 1, wherein: The inert gas comprises nitrogen or argon.
8. The electrode for capacitive deionization according to claim 1, wherein: The binder is selected from one of carboxymethyl cellulose and polytetrafluoroethylene.
9. A method for the production of an electrode for capacitive deionization, for the production of an electrode for capacitive deionization as claimed in claim 6, characterized in that It comprises the following steps: DHPZ, carbon material and binder are mixed in a ratio of 7:2:1 to obtain a mixture, NMP is added dropwise, and the mixture is ground for 1-5min to obtain a slurry, and the mass volume ratio of the NMP to the mixture is 1:5-1:10; The slurry is applied to the electrode sheet with a thickness of 80-300μm to obtain the electrode.