Ion selective adsorption electrode, micro-electric field adsorption system and application thereof in water softening and sterilization and algae removal

Abstract

This invention belongs to the field of water softening and sterilization technology, and discloses an ion-selective adsorption electrode, a micro-electric field adsorption system, and their application in water softening and sterilization / algae removal. An ion-selective adsorption electrode comprises polypolycarboxylate ion exchange fibers, activated carbon, a conductive agent, and a binder, wherein the mass percentage of the polypolycarboxylate ion exchange fibers is 5-20%. This invention uses CCEF-modified activated carbon as the cathode, and at the optimal doping level, it effectively removes Ca... 2+ and Mg 2+ The selectivity coefficients were 15.0 and 13.5, respectively, for Ca 2+ The electroadsorption capacity of the electrode is 311 μmol / g, which is much higher than that of the AC electrode. After 50 cycles of stability testing, the Ca... 2+ The electroadsorption capacity remained above 85%, demonstrating good regeneration ability. Activated carbon modified with nano-silver was used as the anode, and under electric field enhancement, the inhibition rates against bacteria and microalgae reached over 99% and 90%, respectively, exhibiting excellent antimicrobial contamination capabilities.

Description

Technical Field

[0001] This invention belongs to the field of water softening and sterilization technology, specifically relating to an ion-selective adsorption electrode, a micro-electric field adsorption system, and their application in water softening, sterilization, and algae removal. Background Technology

[0002] Water hardness is a common water quality problem worldwide, and the development of water softening technology is a fundamental solution to the hazards of hard water. Currently, traditional methods for hard water softening mainly include chemical precipitation, membrane separation, and ion exchange. Chemical precipitation, however, can affect water quality and generate large amounts of potentially polluting waste; incomplete treatment can also pose safety hazards. Water softened using cation exchange resins contains high levels of sodium salts, which can be destructive to some environments after discharge, and it also suffers from high swelling rates, leading to clogging in industrial applications. Membrane separation technology requires specific inlet water pressure, has high construction and operating costs, and carries the risk of scaling and clogging; therefore, it is rarely used specifically for hard water softening in practical engineering projects.

[0003] Compared to traditional technologies, micro-electric field adsorption (MEFB) technology is a novel water treatment technology that uses the concentration of dissolved salts and other charged substances in water on the surface of an electrode to purify and desalinate the water. Currently, this technology is mainly used for seawater desalination, with limited research on its application in freshwater softening. Carbon-based electrode materials in MEFB technology can utilize their electric double-layer effect to broadly adsorb ions in water. However, both surface water and tap water are complex systems with multiple ions coexisting. Traditional activated carbon electrodes suffer from low adsorption capacity and lack of ion selectivity, making them difficult to apply practically in the softening of hard water in complex systems. For daily drinking water, sodium and potassium are essential macroelements for maintaining human health. Therefore, drinking water contains a certain amount of sodium (Na). + and K + This is what we expect. Furthermore, when softening hard water in a multi-ion system, due to the common ion effect, non-target ions such as Na+... + and K + It will react with the target ion Ca 2+ and Mg 2+Due to competition for adsorption sites, ordinary carbon-based electrode materials have low adsorption capacity for hardness ions, resulting in unsatisfactory softening effects on hard water. Recently, Chinese patent CN106395814B disclosed a capacitive deionization activated carbon electrode block for water desalination or hardness ion removal. This electrode exhibits good conductivity, high mechanical strength, and an adsorption capacity of 3.39 mg / g. However, the electrode prepared by this method lacks selectivity for ion adsorption and has a low adsorption capacity for hardness ions. Surface water not only faces the problem of high hardness but also poses serious microbial safety hazards. Common microorganisms in water bodies, such as bacteria and algae, often coexist with metal ions, which can impose significant economic costs on the safe use of these surface freshwater sources. However, there are few reports on the use of micro-electric field adsorption technology for microbial suppression, and its application in selectively removing hardness ions while simultaneously suppressing microorganisms is yet to be reported. Importantly, the application of micro-electric field adsorption technology in killing microorganisms serves two purposes: firstly, to purify drinking water, and secondly, to prevent microorganisms from attaching and multiplying on the surface of active materials, thereby reducing the adsorption performance of the electrode material.

[0004] Therefore, developing an electrode material and its preparation method that can selectively and efficiently remove hardness ions and simultaneously inhibit microorganisms, and providing a micro-electric field deionization system assembled from this electrode, has broad application prospects. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide an ion-selective adsorption electrode and a microbial inhibition electrode, comprising a carbon-based composite electrode modified with polycarboxylic acid ion exchange fiber (CCEF) and a carbon-based composite electrode modified with nano-silver. The composite material is readily available, has a simple preparation method, high adsorption capacity, high selectivity, and can simultaneously inhibit microorganisms. After being modified with CCEF, the activated carbon electrode can significantly improve its hydrophilicity, reduce the mass transfer resistance of the solution, and improve its electrochemical performance.

[0006] Another object of the present invention is to provide a micro-electric field adsorption MEFB unit cell.

[0007] Another object of the present invention is to provide a micro-electric field adsorption MEFB system.

[0008] Another objective of this invention is to provide the application of the above-mentioned system in water softening and sterilization / algae removal. It can selectively remove hardness ions under different salt concentration conditions, effectively resist microbial contamination and delay scale formation on electrode surfaces, thus possessing practical application prospects for water softening. It is suitable for water softening and microbial sterilization of natural freshwater such as tap water and surface water.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] An ion-selective adsorption electrode, the ion-selective adsorption electrode comprising polypolycarboxylic acid ion exchange fibers, activated carbon, a conductive agent, and a binder;

[0011] The mass percentage of the polycarboxylic acid ion exchange fiber is 5-20%.

[0012] Preferably, the activated carbon accounts for 60%-80% by mass, the conductive agent accounts for 5-10% by mass, and the binder accounts for 5-10% by mass.

[0013] Preferably, the ion-selective adsorption electrode is prepared by a coating method: polypolycarboxylic acid ion exchange fiber, activated carbon, conductive agent, and binder are added to an appropriate amount of water to disperse into a slurry, which is then coated onto a current collector and dried under vacuum.

[0014] Preferably, the vacuum drying is performed at 80–100°C for 1–3 hours.

[0015] Preferably, the dispersion involves sequentially ultrasonically dispersing the binder, polypolycarboxylic acid ion-exchange fiber, conductive agent, and activated carbon.

[0016] Preferably, the amount of coating is 20mg to 1000mg for a single electrode.

[0017] Preferably, the conductive agent is Ketjen Black or acetylene black;

[0018] The adhesive is PTFE, PVDF, or Nafion;

[0019] The current collector is made of titanium foil, copper foil, aluminum foil, carbon paper, graphite paper, or titanium plate.

[0020] A micro-electric field adsorption unit cell includes a cathode and an anode, wherein the cathode is the ion-selective adsorption electrode according to any one of claims 1 to 4;

[0021] The anode is the same as the cathode, or the anode is an activated carbon anode doped with nano-silver.

[0022] Preferably, the unit cell includes the following electrode combination:

[0023] (-)CCEF-10-ACIICCEF-10-AC

[0024] (-)CCEF-5-ACIIAC

[0025] (-)CCEF-10-ACIIAC

[0026] (-)CCEF-15-ACIIAC

[0027] (-)CCEF-20-ACIIAC

[0028] (-)CCEF-10-ACIIAC-Ag;

[0029] More preferably, it is (-)CCEF-10-ACIIAC or (-)CCEF-10-ACIIAC-Ag.

[0030] Preferably, the amount of silver doping in the nanoparticles is 0–1 wt%.

[0031] Preferably, the activated carbon anode doped with nano-silver is prepared by a coating method, in which activated carbon, conductive agent, binder, and nano-silver are added to an appropriate amount of water to disperse into a slurry, which is then coated onto a current collector and dried under vacuum.

[0032] A micro-electric field adsorption system includes the aforementioned micro-electric field adsorption MEFB unit cell, and also includes a conductivity meter, a peristaltic pump, a circulating adsorption-desorption tank, a desorption tank, and a constant voltage DC power supply.

[0033] The above-mentioned micro-electric field adsorption system is used in water softening and / or sterilization and algae removal.

[0034] Preferably, the cations in the water include calcium ions, magnesium ions, potassium ions, and sodium ions, wherein the molar ratio of calcium ions, magnesium ions, potassium ions, and sodium ions is 1:1:4:4 to 4:4:1:1, and the cation concentration is 2.5 mM to 10 mM.

[0035] The bacteria are Gram-negative Escherichia coli and / or Gram-positive Staphylococcus aureus;

[0036] The voltage is 1.0 to 2.0 V, more preferably 1.2 V.

[0037] Preferably, before use, the electrode is first circulated and cleaned by passing deionized water through the MEFB unit cell. The conductivity is tested every 5 minutes. When the change in solution conductivity is less than 0.5 μs / cm, the electrode purification process is completed.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] (1) In the field of MEFB, the application of CCEF in this invention is rarely reported, and there is no research on the selective removal of hardness ions and simultaneous microbial inhibition.

[0040] (2) The preparation process of the electrode for water softening and simultaneous microbial inhibition described in this invention adopts the doping method. The preparation process is simple and can effectively improve the hydrophilicity of traditional activated carbon electrodes, reduce the mass transfer resistance of the solution, and improve the electrochemical performance of the material. At the same time, the raw materials used are low in cost, non-toxic and harmless, easy to dispose of after disposal, and easy to industrialize and mass-produce.

[0041] (3) For uncontaminated hard water, thanks to the polycarboxylic acid structure of CCEF, which has high electronegativity in hard water, the MEFB system composed of the asymmetric electrode (-)CCEF-10-ACIIAC exhibits high adsorption capacity and high selectivity for hardness ions in multi-salt mixture solutions, particularly for Ca2+. 2+ The adsorption capacity reaches 311 μmol / g, which is much higher than the electroadsorption capacity of the AC electrode (188 μmol / g), and is effective for Ca. 2+ and Mg 2+ The selectivity coefficients are 15.0 and 13.5, respectively, which overcomes the shortcomings of existing similar materials that have no selectivity or low selectivity for hardness ions and have a good hard water softening effect.

[0042] (4) A stability test of 50 cycles demonstrated that the CCEF-10-AC electrode has good stability and regeneration capability, and is effective against Ca2+. 2+ Its adsorption capacity remains above 85%, and it can effectively alleviate electrode scaling.

[0043] (5) For surface water, the MEFB system composed of asymmetric electrode (-)CCEF-10-ACIIAC-Ag not only has good hard water softening ability, but also effectively inhibits microorganisms that coexist with hardness ions. The kill rate of bacteria is over 99% and the inhibition rate of microalgae is over 90% in 30 minutes, which has good anti-microbial pollution ability.

[0044] (6) This invention provides a simple and feasible method for achieving efficient water softening and simultaneous microbial killing using MEFB technology, which is of great significance for the application of MEFB in the energy and environmental fields and for enriching the selection range of MEFB electrode materials.

[0045] (7) The water softening system of the present invention has low operating energy consumption and can be controlled by portable energy sources such as lithium batteries, making it highly operable. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the MEFB water softening system.

[0047] Figure 2 This is a standard curve showing the change in calcium chloride solution concentration with conductivity.

[0048] Figure 3 For the analysis of electrode adsorption performance, A to C are respectively: A is the adsorption-desorption curve, adsorption efficiency curve and adsorption capacity curve of calcium ions for electrodes with different CCEF ratios; B is the adsorption-desorption curve, electrode water contact angle and electrode Zeta potential of calcium ions for different electrode combinations; C is the adsorption-desorption capacity of calcium ions for different electrode combinations.

[0049] Figure 4For the adsorption selectivity analysis of hardness ions by the electrodes, A to E are respectively: A is the adsorption capacity of different electrodes for ions when the molar concentrations of calcium, magnesium, potassium, and sodium ions are 1:1:1:1; B is the adsorption capacity of the CCEF-10-AC electrode for ions when the molar concentrations of calcium, magnesium, potassium, and sodium ions are 4:4:1:1; C is the adsorption capacity of the CCEF-10-AC electrode for ions when the molar concentrations of calcium, magnesium, potassium, and sodium ions are 1:1:4:4; D is the selective adsorption coefficient of different electrodes for ions when the molar concentrations of calcium, magnesium, potassium, and sodium ions are 1:1:1:1; and E is the selective adsorption coefficient of the CCEF-10-AC electrode for ions at different molar concentrations of calcium, magnesium, potassium, and sodium ions.

[0050] Figure 5 After 50 cycles of adsorption-desorption, the desalination tank and concentration tank contain Ca. 2+ Concentration changes.

[0051] Figure 6 This is a diagram of a scale inhibition evaporation experiment.

[0052] Figure 7 For the analysis of the selective adsorption mechanism of hardness ions by the electrode, A to C are respectively: A is the XRD pattern of pure CCEF before and after electroadsorption; B is the change of calcium and sodium content of CCEF-10-AC electrode before and after electroadsorption; C is the XRD pattern of CCEF-10-AC electrode before and after electroadsorption.

[0053] Figure 8 The graph shows the electrode stability test and the adsorption-desorption cycles of different electrodes over 50 cycles. A represents the Ca values ​​of different electrodes over 50 cycles of adsorption-desorption. 2+ Concentration changes and it curves; B represents a comparison of the calcium content at the cathode after different adsorption-desorption cycles.

[0054] Figure 9 This is a graph showing the bactericidal effect of MEFB. AF corresponds to the growth of bacterial colonies under experimental conditions ① to ⑥ in Test Example 2, with the top graph showing Escherichia coli and the bottom graph showing Staphylococcus aureus.

[0055] Figure 10 To investigate the antibacterial mechanism and the effect of bacteria on the adsorption of hardness ions by the active material, A to E represent the following: A: the bactericidal effect of different experimental conditions on Escherichia coli; B: the bactericidal effect of different experimental conditions on Staphylococcus aureus; C: the effect of Escherichia coli on the adsorption of calcium ions by CCEF-10-AC; D: the effect of Staphylococcus aureus on the adsorption of calcium ions by CCEF-10-AC; E: the conductivity change curve of the CCEF-10-AC electrode after 10 cycles of adsorption after the addition of bacteria.

[0056] Figure 11 The effect of bacteria on the adsorption performance of active materials.

[0057] Figure 12This study aimed to investigate the killing effect and algae-inhibiting mechanism of MEFB on microalgae.

[0058] Figure 13 The change in conductivity of the algae solution during the algae removal process.

[0059] Figure 14 SEM images of different electrodes and scale are shown. A to K are CCEF-5-AC (A), CCEF-10-AC (B), CCEF-15-AC (C), CCEF-20-AC (D), CCEF-10-AC after 50 adsorption-desorption tests (E), AC after 50 adsorption-desorption tests (F), scale without any treatment (G), scale after evaporation experiment after 50 cycles of ACIIAC MEFB unit cell treatment (H), scale after evaporation experiment after 50 cycles of (-)CCEF-10-ACIIAC MEFB unit cell treatment (I), corresponding surface scan elemental spectrum of AC after 50 MEFB unit cell treatment (J), and corresponding surface scan elemental spectrum of CCEF-10-AC after 50 MEFB unit cell treatment (K).

[0060] Figure 15 SEM images of bacteria and microalgae before and after MEFB treatment: (A)-(B) are algal cells before treatment, (C) are algal cells after treatment, (D)-(E) are Staphylococcus aureus cells before treatment, (F)-(I) are Staphylococcus aureus cells after treatment, (J) are Escherichia coli cells before treatment, and (K)-(L) are Escherichia coli cells after treatment.

[0061] Figure 16 The images show the infrared spectra of pure CCEF before and after electroadsorption.

[0062] Figure 17 The figures show the CV, specific capacitance, GCD, and EIS of the electrode in 1M CaCl2.

[0063] Figure 18 This is a voltage drop graph for electrode GCD testing.

[0064] Figure 19 The figures show the CV, specific capacitance, and GCD of the electrode in 1M CaCl2 or NaCl. Detailed Implementation

[0065] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0066] Polycarboxylic acid ion exchange fiber (CCEF), purchased from Guangzhou Rushang Industrial Co., Ltd.;

[0067] Polytetrafluoroethylene (PTFE) was purchased from Daikin Fluorochemicals (China) Co., Ltd., Japan.

[0068] Activated carbon (AC) was purchased from Kuraray (China) Co., Ltd., Japan.

[0069] Kotjen Black, purchased from Lion Corporation, Japan;

[0070] Nano silver, purchased from Guangzhou Rushang Industrial Co., Ltd.;

[0071] A constant voltage DC power supply (Shanghai Chenhua CHI660E), MEFB cell composed of the prepared electrodes, a conductivity meter (Mettler FE38), a peristaltic pump (Kamoer NKCP-C-B08), and a circulating adsorption-desorption tank.

[0072] Solution preparation:

[0073] Single ion system:

[0074] 1M CaCl2, 1M NaCl, 10mM CaCl2

[0075] Multi-ion system:

[0076] Ca 2+ Mg 2+ :K + Na + =2.5mM:2.5mM:2.5mM:2.5mM

[0077] Ca 2+ Mg 2+ :K + Na + = 4mM: 4mM: 1mM: 1mM

[0078] Ca 2+ Mg 2+ :K + Na + = 1mM: 1mM: 4mM: 4mM

[0079] Example 1 (-) Preparation of CCEF-10-ACIIAC electrode

[0080] First, activated carbon, CCEF, Ketjen black, and PTFE were dispersed in an appropriate amount of deionized water at a mass ratio of 7:1:1:1 to form a CCEF-10-AC slurry. Then, activated carbon, Ketjen black, and PTFE were dispersed in an appropriate amount of deionized water at a mass ratio of 8:1:1 to form an AC slurry. Finally, the two electrode slurries were coated onto a titanium plate current collector, with a coating amount of 45 mg per electrode. The electrodes were then vacuum dried at 80°C for 3 hours to obtain the CCEF-10-AC cathode and AC anode.

[0081] The electrode slurry dispersion method is as follows: first, PTFE is ultrasonically dispersed in an appropriate amount of deionized water for 1 minute with an ultrasonic power of 300W, then CCEF is added and ultrasonically dispersed for 1 minute, then Ketjen Black is added and ultrasonically dispersed for 1 minute, and finally AC is added and ultrasonically dispersed for 3 minutes, with stirring as an auxiliary process while adding the materials.

[0082] Example 2(-) Preparation of CCEF-10-ACIIAC-Ag electrode

[0083] The CCEF-10-AC cathode was prepared in the same way as in Example 1, and the AC-Ag anode was prepared in the same way as the AC anode in Example 1. The difference is that 1% by mass of nano-silver was added to the AC electrode. This mass ratio is 1% relative to the mass of the materials (activated carbon, conductive agent, binder) before water was added.

[0084] The dispersion method of AC-Ag electrode slurry is as follows: First, PTFE is ultrasonically dispersed in an appropriate amount of deionized water for 1 minute with an ultrasonic power of 300W. Then, nano-silver is added and ultrasonically dispersed for 1 minute. Next, Ketjen black is added and ultrasonically dispersed for 1 minute. Finally, AC is added and ultrasonically dispersed for 3 minutes, with stirring as needed.

[0085] Example 3: Construction of the MEFB water softening system

[0086] The MEFB water softening system constructed in this invention mainly consists of a constant voltage DC power supply (Shanghai Chenhua CHI660E), MEFB unit cells composed of the prepared electrodes, a conductivity meter (Mettler FE38), a peristaltic pump (Kamoer NKCP-C-B08), a circulating adsorption-desorption tank, and a desorption tank. A schematic diagram of the MEFB water softening system is attached. Figure 1 .

[0087] Comparative Example 1: Preparation of ACIIAC Electrode

[0088] The AC electrode was prepared in the same manner as in Example 1, except that AC was both the cathode and the anode.

[0089] Comparative Example 2: Preparation of CCEF-10-AC electrode

[0090] The CCEF-10-AC electrode was prepared in the same manner as in Example 1, except that CCEF-10-AC is both the cathode and the anode.

[0091] Preparation of Comparative Example 3(+)CCEF-10-ACIIAC Electrode

[0092] The preparation of the CCEF-10-AC electrode and the AC electrode is the same as in Example 1, except that CCEF-10-AC is used as the anode and AC is used as the cathode.

[0093] Preparation of Comparative Example 4 (-) CCEF-5-ACIIAC Electrode

[0094] Comparative Example 4 adjusts the mass ratio of CCEF in Example 1 from 10% to 5%, with the conductive agent and binder in a fixed ratio. The only difference is the ratio of AC to CCEF, and all other conditions are the same as in Example 1.

[0095] Preparation of Comparative Example 5(-) CCEF-15-ACIIAC Electrode

[0096] The preparation method of Comparative Example 5 is the same as that of Comparative Example 4, except that the mass percentage of CCEF is adjusted from 5% to 15%.

[0097] Preparation of Comparative Example 6(-) CCEF-20-ACIIAC Electrode

[0098] The preparation method of Comparative Example 6 is the same as that of Comparative Example 4, except that the mass ratio of CCEF is adjusted from 5% to 20%.

[0099] Preparation of Comparative Example 7(-) CCEF-10-AC-AgIIAC Electrode

[0100] The AC anode was prepared in the same way as in Example 1, and the CCEF-10-AC-Ag cathode was prepared in the same way as the CCEF-10-AC cathode in Example 1. The difference was that 1% by mass of nano-silver was added to the CCEF-10-AC electrode. All other conditions were the same as in Example 1.

[0101] Test Example 1

[0102] Purification materials:

[0103] Before performing the hardness ion removal test, the prepared electrode was first circulated with deionized water in the MEFB cell to clean it. The conductivity was tested every 5 minutes. When the change in solution conductivity was less than 0.5 μs / cm, the material purification process was considered to be complete.

[0104] Physical adsorption equilibrium:

[0105] Before the electroadsorption test, 10 mM CaCl2 was first introduced into the MEFB cell using a peristaltic pump to make the electrodes in the MEFB cell more compatible with CaCl2. 2+ Physical adsorption equilibrium is reached when the change in solution conductivity is less than 0.5 μS / cm.

[0106] 1. Hardness ion removal performance test

[0107] 1) The electrodes prepared in Examples 1-2 and Comparative Examples 1-7 were applied to hardness ion removal tests. The test method is as follows: the test solution was 10 mM CaCl2, the solution flow rate was 15 mL / min, a constant voltage of 1.2 V was applied to the MEFB cell for hardness ion adsorption, and short-circuit discharge was used for hardness ion desorption. The conductivity in the solution was measured every 2 minutes, and the change in conductivity was used to evaluate the adsorption-desorption effect of the MEFB cell on hardness ion. Furthermore, the CaCl2 in the solution... 2+ The concentration change was calculated using a standard curve showing the change in calcium chloride solution concentration versus conductivity. The standard curve for the change in calcium chloride solution concentration versus conductivity is attached. Figure 2 The removal efficiency of hardness ions by the MEFB cell is shown in the appendix. Figure 3 ,Depend on Figure 3 (A)~(C) and Figure 3 (A) As shown in the second illustration from the top, when the doping concentration of CCEF is 10%, CCEF-10-AC is the cathode, and AC or AC-Ag is the anode, MEFB has a certain effect on Ca. 2+ The adsorption effect is the best for Ca 2+ The adsorption capacities are as high as 311 μmol / g and 300 μmol / g, respectively. (-)CCEF-10-ACIIAC or (-)CCEF-10-ACIIAC-Ag is the optimal electrode combination. Moreover, the active material has good adsorption and regeneration capabilities for hardness ions. Figure 3 In (A), the first inset from top to bottom shows the Ragone curve of MEFB, which generally reflects the advantages of MEFB unit cells in terms of fast adsorption rate and high adsorption capacity for hardness ions.

[0108] 2) The selective adsorption of hardness ions by the electrodes prepared in Example 1 and Comparative Example 1 was studied, and the test results are shown in the appendix. Figure 4 .Depend on Figure 4 (A) It can be seen that Ca 2+ Mg 2+ K + Na + At the same ion molar concentration, the asymmetric target electrode exhibits higher adsorption capacity for all four ions compared to the AC symmetric electrode, especially showing high selectivity for hardness ions; in natural hard water, the concentration of hardness ions is higher than that of K. + Na + Ion concentration, by Figure 4 (B) It can be seen that under the conditions of simulating natural hard water, that is, when Ca 2 + Mg 2+ K + Na +When the ion molar concentration is 4:4:1:1, the high selectivity of the target electrode for hardness ions shows promising prospects for practical applications; furthermore, due to Figure 4 (C) indicates that under high salinity conditions, i.e., when Ca... 2+ Mg 2+ K + Na + When the ion molar concentration is 1:1:4:4, the adsorption capacity of the target electrode for hardness ions is lower than that of K. + Na + While it contains ions, it still exhibits good selectivity for hardness ions, demonstrating excellent salt resistance and stability; Figure 4 (D) and Figure 4 (E) It can be seen that, compared with the AC symmetric electrode, the asymmetric target electrode (-)CCEF-10-ACIIAC exhibits excellent selectivity for the adsorption of hardness ions, in Ca... 2+ Mg 2+ K + Na + When the ion molar concentration is 4:4:1:1, for Ca 2+ Mg 2+ The selective adsorption coefficients were as high as 15.0 and 13.5, respectively.

[0109] 3) Investigation into the application of the electrodes prepared in Example 1 and Comparative Example 1 in hard water softening:

[0110] The adsorption-desorption experiment steps and results are as follows:

[0111] Adsorption stage: Close the desorption stage pipeline switch, open the adsorption stage pipeline switch, apply a 1.2V voltage to the MEFB unit cell, and apply the voltage to the Ca in the hard water in the circulating adsorption-desorption tank. 2+ Ions are removed by adsorption;

[0112] Desorption stage: Close the switch of the adsorption stage pipeline and open the switch of the desorption stage pipeline. Remove the Ca adsorbed on the electrode by short-circuiting or reversing the electrode connection. 2+ Ion removal is performed in a desorption tank, and this cycle is repeated for testing.

[0113] The test results are attached. Figures 5-6 ,Depend on Figure 6 As shown in the upper left illustration, after hard water undergoes 50 cycles of cyclic electroadsorption treatment via an ACIIAC electrode, the Ca in the solution... 2+ The decreasing trend of Ca concentration gradually leveled off, and after 50 cycles of cyclic electroadsorption treatment via a (-)CCEF-10-ACIIAC electrode, the Ca concentration in the solution... 2+ The decreasing concentration maintained a good linear relationship, indicating that the target electrode possesses good stability and regeneration capability. Figure 5 It can be seen that, by comparing the Ca in the desiccant and the concentration tank after 50 cycles of adsorption and desorption, 2+ The concentration changes show that, compared to the ACIIAC symmetrical electrode, the (-)CCEF-10-ACIIAC electrode exhibits better hard water softening ability.

[0114] Scale inhibition experiment: Hard water that had undergone 50 cycles of adsorption (softening) in both the AC cathode experimental group and the CCEF-10-AC cathode experimental group was heated and evaporated using a heating rod. Before heating, 100 mL of 10 mM NaHCO3 solution was added to 100 mL of softened hard water. After heating, the turbidity of the solutions in both groups was observed, and the mass of scale collected was compared. Figure 6 The scale inhibition evaporation experiment showed that when heated for 151 seconds (i.e., the solution evaporation rate was 10%), the solution treated by the ACIIAC electrode became turbid, indicating the appearance of a large amount of scale. When heated for 700 seconds (i.e., the solution evaporation rate was 62.5%), the solution treated by the (-)CCEF-10-ACIIAC electrode became turbid, with a small amount of scale appearing. Finally, the scale deposited in the heating rod and solution was collected and weighed. The scale mass in the ACIIAC group was 0.5790 g, which was significantly higher than the scale mass in the (-)CCEF-10-ACIIAC group (0.2467 g). This also indicates that the target electrode (-)CCEF-10-ACIIAC has a good water softening effect.

[0115] 2. Electrode stability test

[0116] The stability experiments of the electrodes prepared in Example 1 and Comparative Example 1 are conducted, and the specific steps and results are as follows:

[0117] Dynamic conditions: In a 10 mM CaCl2 solution within a circulating adsorption-desorption tank, an electroadsorption test was performed on the MEFB cell by applying a voltage of 1.2 V. Once the conductivity in the solution stopped decreasing (electroadsorption equilibrium was reached), the MEFB cell was short-circuited or reversed to perform a desorption test. Once the conductivity in the solution stopped increasing (desorption equilibrium was reached), the next cycle began. This process was repeated for 50 cycles of adsorption-desorption testing, all within the circulating adsorption-desorption tank. Static conditions: After 50 cycles of adsorption-desorption under dynamic conditions, the electrode was detached from the current collector, rinsed three times with deionized water, and the calcium content in the electrode was tested using ICP-OES. Test results are attached. Figure 7 (B) and Figure 8 . Figure 7 (B) and Figure 8 (B) is a stability test under static conditions. Figure 8 (A) is a stability experiment under dynamic conditions, by Figure 7(B) It can be seen that by comparing the Ca and Na content in the CCEF-10-AC electrode before and after electroadsorption, the Na content in the target electrode decreases significantly after electroadsorption, while the Ca content increases significantly. This indicates that ion exchange occurred during the electroadsorption process. Figure 8 (B) It can be seen that by comparing the Ca content in the AC cathode and CCEF-10-AC cathode after different adsorption-desorption cycles, it was found that after long-term use, the Ca content in the target electrode CCEF-10-AC was significantly lower than that in AC. This indicates that the target electrode has good stability and regeneration capability, and can effectively alleviate scaling on the electrode surface. Figure 8 (A) It can be seen that, compared with the ACIIAC electrode, the (-)CCEF-10-ACIIAC electrode exhibits good stability and regeneration ability when softening hard water for 50 long-term cycles. In practical applications, it can continuously and effectively soften hard water.

[0118] Test Example 2

[0119] 1. Electrode bactericidal performance test

[0120] 1) The electrodes prepared in Examples 1-2 and Comparative Example 7 were applied to a microbial inhibition test. The test method was as follows: Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were used as model pathogens to conduct an antibacterial activity experiment. A concentration of 10... 7 -10 8 100 μL of bacterial sample with CFU / mL was added to the MEFB water softening system. Reaction times were set to 0 minutes and 30 minutes. A series of control experiments were established: Under no-electricity conditions, ① 100 μL of a 10 mM CaCl2 solution with a concentration of 10... 7 -10 8① Bacteria at CFU / mL (the same below); ② Add bacteria to CaCl2 solution and run the MEFB unit cell composed of (-)CCEF-10-ACIIAC electrode; ③ Add bacteria to CaCl2 solution and run the MEFB unit cell composed of (-)CCEF-10-ACIIAC-Ag electrode. Under energized conditions, ④ Add bacteria to CaCl2 solution and apply a voltage of 1.2V to the MEFB unit cell composed of (-)CCEF-10-ACIIAC electrode; ⑤ Add bacteria to CaCl2 solution and apply a voltage of 1.2V to the MEFB unit cell composed of (-)CCEF-10-AC-AgIIAC electrode; ⑥ Add bacteria to CaCl2 solution and apply a voltage of 1.2V to the MEFB unit cell composed of (-)CCEF-10-ACIIAC-Ag electrode. At 0 min and 30 min of MEFB treatment, colonies under different experimental conditions were cultured in LB solid medium, and the effect of different experimental conditions on colonies was observed by plate colony counting method. Each bacterial sample was tested three times. Test results are attached. Figure 9 and Figure 10 (A)~(B), from Figure 9 and Figure 10 As shown in (A) to (B), the voltage applied to the MEFB system is a key factor in killing the target bacteria. More importantly, the applied voltage to the MEFB system can enhance the microbial killing effect of the AC-Ag anode. When a voltage of 1.2V is applied, the MEFB cell composed of (-)CCEF-10-ACIIAC-Ag electrodes achieves a kill rate of over 99% for both Escherichia coli and Staphylococcus aureus after 30 minutes of sterilization treatment.

[0121] 2) The effect of bacteria on the adsorption of ions by the electrode active materials prepared in Examples 1-2 and Comparative Example 7 is shown in the appendix. Figure 10 (C)~(E) and Figure 11 .Depend on Figure 10 (C)~(E) and Figure 11 The results of the change in electrical conductivity over time show that during the MEFB sterilization process, the electroadsorption performance of the active material is basically consistent with that before the introduction of bacteria, still exhibiting good water softening performance. The MEFB unit cell assembled from (-)CCEF-10-ACIIAC-Ag combines good hardness ion removal performance with excellent sterilization effect. Figure 10 (E) It can be seen that when Escherichia coli was introduced into the MEFB system, after 10 electroadsorption cycles, the change in conductivity was basically the same as that without the introduction of bacteria. However, after the introduction of Staphylococcus aureus, the conductivity did not change significantly, and the water softening effect remained stable. This indicates that the prepared active material has good antimicrobial contamination ability and has practical application prospects.

[0122] 2. Electrode performance test on algal cell inhibition

[0123] 1) The electrodes prepared in Examples 1-2 and Comparative Example 7 were applied to a microbial inhibition test. The test method was as follows: the concentrated algal solution was diluted with 10 mM CaCl2 to a concentration of 1.2 x 10⁻⁶ m³ / h. 7 With a cell / mL concentration of approximately [value missing], 100 ml of water sample was taken for MEFB testing, and samples were taken every 5 minutes for observation and counting. The reaction time was set from 0 to 300 minutes. A series of control experiments were established: Under no-electricity conditions, ① the inhibition rate of 10 mM CaCl2 on microalgae (the same below); ② the inhibition rate of MEFB unit cells composed of (-)CCEF-10-ACIIAC electrodes on microalgae; ③ the inhibition rate of MEFB unit cells composed of (-)CCEF-10-ACIIAC-Ag electrodes on microalgae. Under a 1.2V voltage, ④ the inhibition rate of MEFB unit cells composed of (-)CCEF-10-ACIIAC electrodes on microalgae; ⑤ the inhibition rate of MEFB unit cells composed of (-)CCEF-10-AC-AgIIAC electrodes on microalgae; ⑥ the inhibition rate of MEFB unit cells composed of (-)CCEF-10-ACIIAC-Ag electrodes on microalgae. During MEFB treatment from 0 min to 300 min, algal solutions under different experimental conditions were counted by flow cytometry to observe the effects of different experimental conditions on algal cells. The test results are shown in the appendix. Figures 12-13 . Figure 12 and Figure 12 The results illustrated in the figures show that, without applied voltage, CCEF, AC, and CaCl2 have poor algicidal effects, and under dynamic conditions, the inhibitory effect of nano-silver on algae is very limited. Similarly, applying an external voltage is a key factor in inhibiting algal growth, and importantly, the electric field can enhance the inhibitory effect of the AC-Ag anode on algal cells in the MEFB system. Figure 13 The results showed that the conductivity of the solution increased during the treatment of algal cells using the MEFB system, which was due to the dissolution of intracellular electrolytes after algal cell death. This further demonstrates that the prepared active material has good resistance to microbial contamination.

[0124] Test Example 3

[0125] Electrode structural characterization, surface chemical analysis, and electrochemical performance testing

[0126] (1) Surface structure analysis was performed on the electrodes, scale, and microorganisms prepared in Examples 1-2 and Comparative Examples 1-7, as well as in Test Example 2. The results are shown in […]. Figures 14-15 .Depend on Figure 14It can be seen that when the CCEF content increases from 5% to 20%, CCEF gradually accumulates around the AC particles. When its doping amount is 10%, CCEF effectively and uniformly fills the gaps between large AC particles like a "conductive network," which is beneficial for ion diffusion and mass transfer along the electrode. The scale crystal forms of the blank group and the experimental group are stable calcite and metastable aragonite, respectively, while the scale morphology after treatment with (-)CCEF-10-ACIIAC electrode is more loose, because current density affects the microstructure and composition of the scale. After 50 cycles, the Ca element content on the AC cathode surface is significantly higher than that on the CCEF-10-AC cathode, which indirectly indicates that the target electrode CCEF-10-AC has good stability and regeneration ability, and can effectively alleviate scale formation on the electrode surface. Figure 15 It can be seen that after treatment by the MEFB unit cell composed of the target electrode, the cell walls of microalgae and bacteria are damaged and shrunken, and the cell contents are leaked, resulting in the death of microorganisms. This shows that the (-)CCEF-10-ACIIAC-Ag electrode has good killing ability and antimicrobial contamination ability against microorganisms.

[0127] (2) Surface chemical analysis was performed on the electrodes prepared in Examples 1-2 and Comparative Examples 1-7. The results are shown in […]. Figure 3 Chinese illustrations Figure 7 (A) and (C) and Figure 16 Activated carbon (AC) has poor hydrophilicity and exhibits significant mass transfer resistance, while CCEF is rich in hydrophilic groups, which can improve the hydrophilicity of the composite material. Figure 3 As shown in the first illustration, the hydrophilicity of the electrode is significantly improved with the increase of CCEF doping, which is beneficial for ion diffusion and mass transfer along the electrode. Figure 3 The second illustration examines the Zeta potentials of CCEF and silver nanoparticles in weakly acidic and weakly alkaline environments. The results show that CCEF has a negatively charged surface, and thanks to its polycarboxylic acid structure, it exhibits high electronegativity in hard water. This is closely related to its high selectivity and adsorption capacity for hardness ions. Silver nanoparticles, on the other hand, have a positively charged surface, providing a basis for the optimal combination of electrodes in the MEFB unit cell. Figure 7 (A) It can be seen that the electro-adsorption of Ca 2+ Before and after, the XRD diffraction peaks of pure CCEF matched well with the standard card PDF#20-1149, and showed no change, indicating its good crystal stability. Figure 7 (B) It can be seen that before and after electroadsorption, CCEF-10-AC exhibits XRD diffraction peaks similar to those of sodium carboxylate type fibers, indicating that the ion exchange process has no significant effect on the crystal structure of CCEF. Figure 16 It can be seen that adsorbing Ca 2+Before and after, characteristic peaks of Na-O and Ca-O bonds were observed at the characteristic peaks of the corresponding carboxylate in the infrared spectrum of pure CCEF, indicating that ion exchange occurred, which is consistent with the results of ICP-OES.

[0128] (3) The electrochemical performance of the electrodes prepared in Example 1, Comparative Example 1, Comparative Example 4, Comparative Example 5 and Comparative Example 6 was tested, and the results are shown in the figure. Figures 17-19 . Figure 17 The results in (A) to (B) show that as the doping amount of CCEF increases, the capacitance current first increases and then decreases. CCEF-10-AC exhibits the largest specific capacitance and maintains 44% specific capacitance at a scan rate of 50 mV / s. Figure 17 The results in (C) show that the GCD curve of CCEF-10-AC is close to an isosceles triangle, indicating the longest discharge time, which means it has a larger specific capacitance, consistent with the CV results. Figure 18 The results of the IR drop show that an appropriate amount of CCEF can reduce the internal resistance of the battery. Figure 17 The EIS results in (D) show that CCEF-10-AC exhibits the lowest interfacial charge transfer resistance Rct (1.64 Ω) in the high-frequency region, and the steep slope in the low-frequency region indicates good ion diffusion behavior. Figure 19 As shown in (A) to (B), the ideal rectangular CV curves indicate that the target electrode MEFB exhibits typical double-layer electric field behavior, showing greater current and specific capacitance in CaCl2 solution. At different scan rates, its specific capacitance in NaCl solution decreases more rapidly, eventually retaining only 7% of the original capacitance. This is attributed to the free Na+ in the target electrode. + With Ca 2+ An exchange occurred, for Ca 2+ It provides more active sites, which is beneficial for Ca 2+ Diffusion and transportation. By Figure 19 From (C) to (D), it can be seen that the GCD curves indicate the effect of the target electrode on Ca. 2+ The specific capacitance is significantly higher than that of Na. + Consistent with the CV results, the GCD curves are almost symmetrical under different current densities, and the target electrode exhibits excellent double-layer electric field behavior and reversibility. Figure 8 (A) The it curve on the right shows that after 50 charge-discharge cycles of the MEFB cell, the current decrease of the (-)CCEF-10-ACIIAC electrode is much smaller compared to the ACIIAC symmetrical electrode. This indicates that the interfacial resistance of the electrode does not increase significantly under long-term operation, reflecting the good stability and regeneration capability of the target electrode. By comparing the electrochemical performance of the target electrode in CaCl2 and NaCl solutions, the potential for selective adsorption of hardness ions by the target electrode can be reflected.

[0129] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An ion-selective adsorption electrode, characterized in that, The ion-selective adsorption electrode comprises polypolycarboxylic acid ion exchange fibers, activated carbon, a conductive agent, and a binder; The polycarboxylic acid ion exchange fiber has a mass percentage of 10%, the activated carbon has a mass percentage of 60%-80%, the conductive agent has a mass percentage of 5%-10%, the binder has a mass percentage of 5%-10%, and the sum of the mass percentages of the above components is 100%. The ion-selective adsorption electrode is prepared by a coating method: polypolycarboxylic acid ion exchange fiber, activated carbon, conductive agent, and binder are added to an appropriate amount of water to disperse into a slurry, which is then coated onto a current collector and dried under vacuum.

2. The ion-selective adsorption electrode according to claim 1, characterized in that, The conductive agent is Ketjen Black or acetylene black; The adhesive is PTFE, PVDF, or Nafion; The current collector is made of titanium foil, copper foil, aluminum foil, carbon paper, graphite paper, or titanium plate.

3. A micro-electric field adsorption MEFB unit cell, characterized in that, It includes a cathode and an anode, wherein the cathode is the ion-selective adsorption electrode according to any one of claims 1 to 2; The anode is the same as the cathode, or the anode is an activated carbon anode doped with nano-silver.

4. The micro-electric field adsorption MEFB unit cell according to claim 3, characterized in that, The amount of silver doping in nanoparticles is 0~1wt%.

5. The micro-electric field adsorption MEFB unit cell according to claim 4, characterized in that, The activated carbon anode doped with nano-silver was prepared by a coating method, in which activated carbon, conductive agent, binder, and nano-silver were added to an appropriate amount of water to disperse into a slurry, which was then coated onto a current collector and dried under vacuum.

6. A micro-electric field adsorption MEFB system, characterized in that, The unit cell includes any one of claims 3 to 5, and further includes a conductivity meter, a peristaltic pump, a circulating suction-desorption tank, a desorption tank, and a constant voltage DC power supply.

7. The application of the micro-electric field adsorption MEFB system according to claim 6 in water softening and / or sterilization and algae removal.

8. The application according to claim 7, characterized in that, The cations in the water include calcium ions, magnesium ions, potassium ions, and sodium ions; The bacteria are Escherichia coli and / or Staphylococcus aureus; The system applies a voltage of 1.0V to 2.0V.

Images