Electrode capable of selectively adsorbing ions, and micro-electric field adsorption system and use thereof in water softening, sterilization and algae removal

Abstract

The present invention belongs to the technical fields of water softening and sterilization. Disclosed are an electrode capable of selectively adsorbing ions, and a micro-electric field adsorption system and the use thereof in water softening, sterilization and algae removal. The electrode capable of selectively adsorbing ions comprises polycarboxylic acid ion exchange fibers, activated carbon, a conductive agent and a binder, wherein the mass percent of the polycarboxylic acid ion exchange fibers is 5-20%. In the present invention, CCEF-modified activated carbon is used as a cathode; and in the case of the optimal doping amount of the cathode, the selectivity coefficients of Ca2+ and Mg2+ are 15.0 and 13.5, respectively, and the electro-adsorption capacity of Ca2+ is 311 μmol / g, which are far higher than those of an AC electrode. After a stability test in which 50 cycles are conducted, the electro-adsorption capacity of Ca2+ is maintained at 85% or higher, indicating that the electrode has a good regeneration capability. With nano-silver-modified activated carbon as an anode, under the reinforcement of an electric field, the killing rates with respect to bacteria and microalgae are up to 99% and 90% or higher, respectively, exhibiting good resistance to microbial pollution.

Description

An ion-selective adsorption electrode, a micro-electric field adsorption system, and its application in water softening and sterilization and algae removal

[0001] Technology Neighborhood

[0002] The present invention belongs to the technical field of water softening and sterilization, and in particular relates to an ion selective adsorption electrode, a micro-electric field adsorption system and applications thereof in water softening and sterilization and algae removal. Background Art

[0003] Water hardness is a common water quality problem worldwide, and the development of water softening technology is a fundamental measure to address the hazards of hard water. Currently, traditional methods for softening hard water mainly include chemical precipitation, membrane separation, and ion exchange. Among them, chemical precipitation affects water quality and produces a large amount of waste that may pollute the environment. Incomplete treatment can also easily pose safety hazards. Water softened using cation exchange resins contains large amounts of sodium salts, which can be destructive to some environments upon discharge. In addition, it has the industrial application problem of high swelling rate and easy water blockage. Membrane separation technology has certain requirements for water inlet pressure, high construction and operating costs, and the risk of scaling and clogging. In actual projects, it is generally rarely used specifically for hard water softening treatment.

[0004] Compared with traditional technologies, a new water treatment technology that uses micro electric field adsorption technology (MEFB) to enrich and concentrate dissolved salts and other charged substances in water on the surface of the electrode to achieve water purification and desalination. At present, this technology is mainly used for seawater desalination, and there are fewer studies on its application in fresh water softening. The carbon-based electrode materials of micro electric field adsorption technology can use their double layer effect to adsorb ions in water in a broad spectrum. However, both surface water and tap water are complex systems with multiple ions coexisting. Traditional activated carbon electrodes have the disadvantages of low adsorption capacity and no ion selectivity, making it difficult to be used in the softening of hard water in complex systems. For daily drinking water, sodium and potassium are essential constant elements to maintain human health. Therefore, drinking water contains a certain amount of Na + and K + In addition, when softening hard water in a multi-ion system, non-target ions such as Na + and K + Will react with the target ion Ca 2+ and Mg 2+Competition for adsorption sites causes ordinary carbon-based electrode materials to have a low adsorption capacity for hardness ions, resulting in an unsatisfactory softening effect on hard water. In recent years, Chinese patent CN106395814B has disclosed a capacitive deionized activated carbon electrode block for water desalination or removal of hardness ions. The electrode has good conductivity, high mechanical strength, and an adsorption capacity of 3.39 mg / g. However, the electrode prepared by this method is not selective for ion adsorption and has a low adsorption capacity for hardness ions. For surface water, there is not only the problem of high hardness, but also a serious microbial safety hazard. Common microorganisms in water bodies, such as bacteria and algae, often coexist with metal ions, which will impose a large economic cost on the safe use of these surface freshwaters by humans. However, there are currently few reports on the use of micro-field adsorption technology in the inhibition of microorganisms, and its application in selectively removing hardness ions and achieving simultaneous inhibition of microorganisms has not been reported. Importantly, micro-field adsorption technology is used to kill microorganisms, on the one hand to purify drinking water, and on the other hand to prevent microorganisms from attaching and multiplying on the surface of active materials, thereby reducing the adsorption performance of electrode materials.

[0005] Therefore, developing an electrode material and a preparation method thereof that can selectively and efficiently remove hardness ions and simultaneously inhibit microorganisms, and providing a micro-electric field deionization system assembled by the electrode, has broad application prospects.

[0006] Summary of the Invention

[0007] In order to address the shortcomings of the existing technology, the primary purpose of the present invention is to provide an ion-selective adsorption electrode and a microbial inhibition electrode, which are composed of a carbon-based composite electrode modified with polycarboxylic acid ion exchange fiber (CCEF) and a carbon-based composite electrode modified with nanosilver. The raw materials of the composite material are easy to obtain, the preparation method is simple, the adsorption capacity is high, the selectivity is high, and microorganisms can be inhibited simultaneously. After the activated carbon electrode is modified with CCEF, its hydrophilicity can be significantly improved, the mass transfer resistance of the solution can be reduced, and its electrochemical performance can be improved.

[0008] Another object of the present invention is to provide a micro-electric field adsorption MEFB unit cell.

[0009] Another object of the present invention is to provide a micro-electric field adsorption MEFB system.

[0010] Another object of the present invention is to provide the application of the above-mentioned system for water softening and sterilization and algae removal. The system can selectively remove hardness ions under varying salt concentrations, effectively resist microbial contamination, and slow down electrode surface scaling, demonstrating its practical application in water softening. The system is suitable for softening and sterilizing natural freshwater, such as tap water and surface water.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] An ion selective adsorption electrode, comprising polycarboxylic acid ion exchange fiber, activated carbon, a conductive agent, and a binder;

[0013] The mass percentage of the polycarboxylic acid ion exchange fiber is 5-20%.

[0014] Preferably, the mass percentage of the activated carbon is 60%-80%, the mass percentage of the conductive agent is 5-10%, and the mass percentage of the binder is 5-10%.

[0015] Preferably, the ion selective adsorption electrode is prepared by a coating method: polycarboxylic acid ion exchange fiber, activated carbon, a conductive agent, and a binder are added to an appropriate amount of water to form a slurry, which is then coated on a current collector and vacuum dried to obtain the slurry.

[0016] Preferably, the vacuum drying is performed at 80-100° C. for 1-3 hours.

[0017] Preferably, the dispersion is carried out by ultrasonically dispersing the binder, polycarboxylic acid ion exchange fiber, conductive agent and activated carbon in sequence.

[0018] Preferably, the coating amount is 20 mg to 1000 mg for a single electrode.

[0019] Preferably, the conductive agent is Ketjen black or acetylene black;

[0020] The binder is PTFE, PVDF or Nafion;

[0021] The current collector is titanium foil, copper foil, aluminum foil, carbon paper, graphite paper or titanium plate.

[0022] A micro-electric field adsorption unit cell, comprising a cathode and an anode, wherein the cathode is the ion selective adsorption electrode according to any one of claims 1 to 4;

[0023] The anode is the same as the cathode, or the anode is an activated carbon anode doped with nanosilver.

[0024] Preferably, the unit cell comprises the following electrode combination:

[0025] (-)CCEF-10-ACIICCEF-10-AC

[0026] (-)CCEF-5-ACIIAC

[0027] (-)CCEF-10-ACIIAC

[0028] (-)CCEF-15-ACIIAC

[0029] (-)CCEF-20-ACIIAC

[0030] (-)CCEF-10-ACIIAC-Ag;

[0031] More preferred is (-)CCEF-10-ACIIAC or (-)CCEF-10-ACIIAC-Ag.

[0032] Preferably, the doping amount of the nanosilver is 0-1 wt%.

[0033] Preferably, the nanosilver-doped activated carbon anode is prepared by a coating method, wherein activated carbon, a conductive agent, a binder, and nanosilver are added with an appropriate amount of water to form a slurry, which is then coated on a current collector and vacuum dried to obtain the slurry.

[0034] A micro-electric field adsorption system comprises the above-mentioned micro-electric field adsorption MEFB unit cell, a conductivity meter, a peristaltic pump, a circulating adsorption-desorption tank, a desorption tank and a constant voltage DC power supply.

[0035] Application of the above-mentioned micro-electric field adsorption system in water softening and / or sterilization and algae removal.

[0036] 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;

[0037] The bacteria are Gram-negative Escherichia coli and / or Gram-positive Staphylococcus aureus;

[0038] The voltage is 1.0 to 2.0 V, more preferably 1.2 V.

[0039] Preferably, before use, deionized water is passed through the MEFB unit cell to circulate and clean the electrode, and 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.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] (1) In the field of MEFB, the application of CCEF in the present invention has rarely been reported, and research on the selective removal of hardness ions and simultaneous microbial inhibition has not been reported.

[0042] (2) The preparation process of the electrode for water softening and simultaneous microbial inhibition described in the present invention adopts a 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 properties of the material. At the same time, the raw materials used are low in cost, non-toxic and harmless, and are easy to dispose of after waste, making them easy to industrialize and mass-produce.

[0043] (3) For unpolluted hard water, thanks to the polycarboxyl structure of CCEF, which has a 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 a multi-salt mixture solution, especially for Ca 2+ The adsorption capacity of Ca2+ is 311 μmol / g, which is much higher than the adsorption capacity of AC electrode (188 μmol / g). 2+ and Mg 2+ The selectivity coefficients are 15.0 and 13.5 respectively, which overcome the shortcomings of existing similar materials with no selectivity or low selectivity for hardness ions and have good hard water softening effect.

[0044] (4) The stability test of 50 cycles proved that CCEF-10-AC electrode has good stability and regeneration ability. 2+ The adsorption capacity is maintained above 85%, and the electrode scaling can be effectively alleviated.

[0045] (5) For surface water, the MEFB system composed of the asymmetric electrode (-)CCEF-10-ACIIAC-Ag not only has good hard water softening ability, but also can effectively inhibit microorganisms that coexist with hardness ions. The killing rate of bacteria in 30 minutes is more than 99%, and the killing rate of microalgae is more than 90%, which has good anti-microbial contamination ability.

[0046] (6) The present 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 fields of energy and environment and for enriching the selection range of MEFB electrode materials.

[0047] (7) The water softening system of the present invention has low operating energy consumption and can be controlled by portable energy such as lithium batteries, and has strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a schematic diagram of the MEFB water softening system.

[0049] Figure 2 is a standard curve showing the change of calcium chloride solution concentration with conductivity.

[0050] Figure 3 is an analysis of the electrode adsorption performance, where A to C are the adsorption and desorption curves, adsorption efficiency curves, and adsorption capacity curves of calcium ions at electrodes with different CCEF ratios; B is the adsorption and desorption curves, electrode water contact angles, and electrode Zeta potentials of calcium ions at different electrode combinations; and C is the adsorption and desorption capacity of calcium ions at different electrode combinations.

[0051] Figure 4 is an analysis of the adsorption selectivity of the electrode for hardness ions, where A to E are respectively: A is the adsorption capacity of different electrodes for ions when the molar concentration of calcium, magnesium, potassium and sodium ions is 1:1:1:1; B is the adsorption capacity of the CCEF-10-AC electrode for ions when the molar concentration of calcium, magnesium, potassium and sodium ions is 4:4:1:1; C is the adsorption capacity of the CCEF-10-AC electrode for ions when the molar concentration of calcium, magnesium, potassium and sodium ions is 1:1:4:4; D is the selective adsorption coefficient of different electrodes for ions when the molar concentration of calcium, magnesium, potassium and sodium ions is 1:1:1:1; E is the selective adsorption coefficient of the CCEF-10-AC electrode for ions under different molar concentrations of calcium, magnesium, potassium and sodium ions.

[0052] Figure 5 shows the Ca content of the desalination tank and the concentration tank after 50 cycles of adsorption and desorption. 2+ Concentration changes.

[0053] Figure 6 is a diagram of scale inhibition and evaporation experiment.

[0054] Figure 7 is an analysis of the selective mechanism of electrode adsorption of hardness ions. A to C are the XRD spectra of pure CCEF before and after electrosorption; B is the change of calcium and sodium content of CCEF-10-AC electrode before and after electrosorption; C is the XRD spectrum of CCEF-10-AC electrode before and after electrosorption.

[0055] Figure 8 is the electrode stability test and the it diagram of 50 cycles of adsorption-desorption of different electrodes. A is the Ca adsorption-desorption of different electrodes for 50 cycles. 2+ Concentration change and it curve; B is the comparison of cathode calcium content after different adsorption and desorption cycles.

[0056] Figure 9 shows the killing effect of MEFB on bacteria. Figures AF correspond to the growth of bacterial colonies under experimental conditions ① to ⑥ in Test Example 2, respectively. The upper figure shows Escherichia coli, and the lower figure shows Staphylococcus aureus.

[0057] Figure 10 shows the investigation of the antibacterial mechanism and the influence of bacteria on the adsorption of hardness ions by active materials. A to E are respectively: A is the killing effect of Escherichia coli under different experimental conditions; B is the killing effect of Staphylococcus aureus under different experimental conditions; C is the effect of Escherichia coli on the adsorption of calcium ions by CCEF-10-AC; D is the effect of Staphylococcus aureus on the adsorption of calcium ions by CCEF-10-AC; E is the conductivity change curve of the CCEF-10-AC electrode after 10 cycles of adsorption after the addition of bacteria.

[0058] Figure 11 shows the effect of bacteria on the adsorption performance of active materials.

[0059] Figure 12 shows the killing effect and mechanism of MEFB on microalgae.

[0060] Figure 13 shows the changes in conductivity of the algae solution during the algaecide process.

[0061] Figure 14 is the SEM images of different electrodes and scales, 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 treatments (F), scale without any treatment (G), scale after 50 cycles of evaporation experiment in ACIIAC MEFB unit cell (H), scale after 50 cycles of evaporation experiment in (-)CCEF-10-ACIIAC MEFB unit cell (I), the corresponding surface scanning elemental spectrum of AC after 50 MEFB unit cell treatments (J), and the corresponding surface scanning elemental spectrum of CCEF-10-AC after 50 MEFB unit cell treatments (K).

[0062] Figure 15 is SEM images of bacteria and microalgae before and after MEFB treatment, (A) to (B) are algal cells before killing treatment, (C) is algal cells after killing treatment, (D) to (E) are Staphylococcus aureus cells before killing treatment, (F) to (I) are Staphylococcus aureus cells after killing treatment, (J) is Escherichia coli cells before killing treatment, and (K) to (L) are Escherichia coli cells after killing treatment.

[0063] Figure 16 shows the infrared spectra of pure CCEF before and after electrosorption.

[0064] Figure 17 shows the CV, specific capacitance, GCD, and EIS graphs of the electrode in 1 M CaCl2.

[0065] Figure 18 is a voltage drop diagram of the electrode GCD test.

[0066] Figure 19 shows the CV, specific capacitance, and GCD graphs of the electrode in 1M CaCl2 or NaCl. DETAILED DESCRIPTION

[0067] The present invention will be described in further detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto. For process parameters not particularly noted, conventional techniques may be used.

[0068] Polycarboxylic acid ion exchange fiber (CCEF) was purchased from Guangzhou Rushang Industrial Co., Ltd.

[0069] Polytetrafluoroethylene (PTFE) was purchased from Daikin Fluorochemical (China) Co., Ltd., Japan;

[0070] Activated carbon (AC) was purchased from Kuraray (China) Co., Ltd.

[0071] Ketjen black was purchased from Lion Corporation of Japan;

[0072] Nanosilver was purchased from Guangzhou Rushang Industrial Co., Ltd.

[0073] Constant voltage DC power supply (Shanghai Chenhua CHI660E), MEFB unit cell composed of prepared electrodes, conductivity meter (Mettler FE38), peristaltic pump (Kamoer NKCP-C-B08), circulating adsorption-desorption tank

[0074] Solution preparation:

[0075] Single ion system:

[0076] 1M CaCl2, 1M NaCl, 10mM CaCl2

[0077] Multi-ion system:

[0078] Ca 2+ :Mg 2+ :K + :Na + =2.5mM:2.5mM:2.5mM:2.5mM

[0079] Ca 2+ :Mg 2+ :K + :Na + =4mM:4mM:1mM:1mM

[0080] Ca 2+ :Mg 2+ :K + :Na + =1mM:1mM:4mM:4mM

[0081] Example 1 Preparation of (-)CCEF-10-ACIIAC Electrode

[0082] 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 respectively coated on the titanium plate current collector. The coating amount of a single electrode was 45 mg. The electrodes were vacuum dried at 80°C for 3 hours to obtain a CCEF-10-AC cathode and AC anode.

[0083] The electrode slurry dispersion method is as follows: first ultrasonically disperse PTFE in an appropriate amount of deionized water for 1 minute with an ultrasonic power of 300W, then add CCEF and ultrasonically disperse for 1 minute, then add Ketjen black and ultrasonically disperse for 1 minute, and finally add AC and ultrasonically disperse for 3 minutes, stirring while adding the materials.

[0084] Example 2 Preparation of (-)CCEF-10-ACIIAC-Ag Electrode

[0085] The preparation method of CCEF-10-AC cathode is the same as that of Example 1. The preparation method of AC-Ag anode is the same as that of AC anode in Example 1, except that 1% by weight of nanosilver is additionally added to the AC electrode. This mass ratio is 1% relative to the mass of the materials (activated carbon, conductive agent, binder) before water is added.

[0086] The dispersion method of AC-Ag electrode slurry is as follows: first ultrasonically disperse PTFE in an appropriate amount of deionized water for 1 minute with an ultrasonic power of 300W, then add nanosilver and ultrasonically disperse for 1 minute, then add Ketjen black and ultrasonically disperse for 1 minute, and finally add AC and ultrasonically disperse for 3 minutes, stirring while adding the materials.

[0087] Example 3 Construction of MEFB water softening system

[0088] The MEFB water softening system constructed in the present invention mainly consists of a constant voltage DC power supply (Shanghai Chenhua CHI660E), a MEFB unit cell composed of prepared electrodes, a conductivity meter (Mettler FE38), a peristaltic pump (Kamoer NKCP-C-B08), a circulating adsorption-desorption tank and a desorption tank. The schematic diagram of the MEFB water softening system is shown in Figure 1.

[0089] Comparative Example 1 Preparation of ACIIAC Electrode

[0090] The preparation of the AC electrode is the same as in Example 1, except that the AC serves as both the cathode and the anode.

[0091] Comparative Example 2 Preparation of CCEF-10-AC II CCEF-10-AC Electrode

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

[0093] Comparative Example 3 Preparation of (+)CCEF-10-ACIIAC Electrode

[0094] The preparation of CCEF-10-AC electrode and AC electrode was the same as in Example 1, except that CCEF-10-AC was used as the anode and AC was used as the cathode.

[0095] Comparative Example 4 Preparation of (-)CCEF-5-ACIIAC Electrode

[0096] In this comparative example 4, the mass proportion of CCEF in Example 1 is adjusted from 10% to 5%, wherein the conductive agent and the binder are fixed in proportion, and the proportion of AC and CCEF is changed. The other conditions are the same as those in Example 1.

[0097] Comparative Example 5 Preparation of (-)CCEF-15-ACIIAC Electrode

[0098] The preparation method of Comparative Example 5 is the same as that of Comparative Example 4, except that the mass proportion of CCEF is adjusted from 5% to 15%.

[0099] Comparative Example 6 Preparation of (-)CCEF-20-ACIIAC Electrode

[0100] The preparation method of Comparative Example 6 is the same as that of Comparative Example 4, except that the mass proportion of CCEF is adjusted from 5% to 20%.

[0101] Comparative Example 7 Preparation of (-)CCEF-10-AC-AgIIAC Electrode

[0102] The AC anode was prepared in the same manner as in Example 1, and the CCEF-10-AC-Ag cathode was prepared in the same manner as in Example 1, except that 1% by mass of nanosilver was additionally added to the CCEF-10-AC electrode. The other conditions were the same as in Example 1.

[0103] Test Example 1

[0104] Purification materials:

[0105] Before the hardness ion removal test, the prepared electrode was first cleaned by circulating deionized water into the MEFB unit cell. The conductivity was tested every 5 minutes. When the change in solution conductivity was less than 0.5μs / cm, the material purification process was considered to be completed.

[0106] Physical adsorption equilibrium:

[0107] Before the electrosorption test, 10 mM CaCl2 was passed into the MEFB cell through a peristaltic pump to make the electrodes in the MEFB cell sensitive to CaCl2. 2+ When the change in solution conductivity is less than 0.5 μs / cm, the material is considered to have reached physical adsorption equilibrium.

[0108] 1. Hardness ion removal performance test

[0109] 1) The electrodes prepared in Examples 1 to 2 and Comparative Examples 1 to 7 were applied to the hardness ion removal test. The test method is as follows: the test solution is 10 mM CaCl2, the solution flow rate is 15 mL / min, a constant voltage of 1.2 V is applied to the MEFB unit cell to adsorb the hardness ions, and a short-circuit discharge is performed to desorb the hardness ions. The conductivity of the solution is tested every 2 minutes, and the change in conductivity is used to evaluate the adsorption-desorption effect of the MEFB unit cell on the hardness ions. Furthermore, the CaCl2 in the solution 2+The concentration change is calculated using a standard curve of calcium chloride solution concentration versus conductivity. See Figure 2 for a standard curve of calcium chloride solution concentration versus conductivity. The removal effect of the MEFB unit cell on hardness ions is shown in Figure 3. As can be seen from Figures 3(A) to (C) and the second illustration from the top of Figure 3(A), when the CCEF doping level is 10%, CCEF-10-AC is the cathode, and AC or AC-Ag is the anode, MEFB has a significant effect on Ca removal. 2+ The adsorption effect is the best for Ca 2+ The adsorption capacity is as high as 311μmol / g and 300μmol / g respectively. (-)CCEF-10-ACIIAC or (-)CCEF-10-ACIIAC-Ag is the best electrode combination, and the active material has good adsorption and regeneration ability for hardness ions. The Ragone curve of the first illustration from top to bottom in Figure 3(A) generally reflects that the MEFB unit cell has the advantages of fast adsorption rate and high adsorption capacity for hardness ions.

[0110] 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 Figure 4. As shown in Figure 4(A), Ca 2+ , Mg 2+ , K + , Na + When the ion molar concentration is the same, the asymmetric target electrode has a higher adsorption capacity for the four ions than the AC symmetric electrode, especially showing high selectivity for the adsorption of hardness ions. In natural hard water, the concentration of hardness ions is higher than that of K. + , Na + As shown in Figure 4(B), under the conditions of simulating natural hard water, 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 good practical application prospects; in addition, as shown in Figure 4(C), under high salt conditions, that is, 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 + ions, but it still has good selectivity for hardness ions, showing good salt tolerance and stability; as shown in Figure 4 (D) and Figure 4 (E), compared with the AC symmetric electrode, the asymmetric target electrode (-)CCEF-10-ACIIAC shows excellent selectivity for the adsorption of hardness ions. 2+ , Mg 2+, K + , Na + When the ion molar concentration is 4:4:1:1, the Ca 2+ , Mg 2+ The selective adsorption coefficients are as high as 15.0 and 13.5 respectively.

[0111] 3) Application of the electrodes prepared in Example 1 and Comparative Example 1 to soften hard water:

[0112] The adsorption and desorption experimental steps and results are as follows:

[0113] Adsorption stage: turn off the switch of the desorption stage pipeline, turn on the switch of the adsorption stage pipeline, apply 1.2V voltage to the MEFB unit cell, and adjust the Ca in the hard water in the circulating adsorption-desorption tank. 2+ Ions are removed by adsorption;

[0114] Desorption stage: turn off the switch of the adsorption stage pipeline, turn on the switch of the desorption stage pipeline, and remove the Ca adsorbed on the electrode by short-circuiting or reverse-connecting the electrode. 2+ Ions are removed in the desorption tank, and the cycle test is repeated.

[0115] The test results are shown in Figures 5 and 6. As shown in the illustration in the upper left corner of Figure 6, after hard water has been subjected to 50 cycles of cyclic electrosorption treatment through the ACIIAC electrode, the Ca 2+ The decreasing trend of the concentration gradually became flat, and after 50 cycles of cyclic electrosorption treatment by (-)CCEF-10-ACIIAC electrode, the Ca 2+ The decreasing trend of the concentration still maintains a good linear relationship, which shows that the target electrode has good stability and regeneration ability. As shown in Figure 5, by comparing the Ca content of the desalination tank and the concentration tank after 50 cycles of adsorption and desorption, the concentration of Ca 2+ From the concentration changes, it can be seen that compared with the ACIIAC symmetrical electrode, the (-)CCEF-10-ACIIAC electrode exhibits good hard water softening ability.

[0116] Scale inhibition experiment: Hard water softened by 50 adsorption cycles in 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. The turbidity of the two solutions after heating was observed, and the mass of the scale collected was compared. The scale inhibition and evaporation experiment in Figure 6 shows that when heated for 151 seconds, that is, the solution evaporation rate is 10%, the solution treated with the ACIIAC electrode becomes turbid, that is, a large amount of scale appears. When heated for 700 seconds, that is, the solution evaporation rate is 62.5%, the solution treated with the (-)CCEF-10-ACIIAC electrode becomes turbid, and a small amount of scale appears. Finally, the scale deposited on the heating rod and the solution are collected and weighed. The mass of scale in the ACIIAC group is 0.5790g, which is significantly higher than the mass of scale in the (-)CCEF-10-ACIIAC group of 0.2467g. This also shows that the target electrode (-)CCEF-10-ACIIAC has a good water softening application effect.

[0117] 2. Electrode stability test

[0118] The specific steps and results of the stability experiments of the electrodes prepared in Example 1 and Comparative Example 1 are as follows:

[0119] Dynamic conditions: Electrosorption testing was performed by applying a voltage of 1.2V to the MEFB unit cell in a 10mM CaCl2 solution in a cyclic adsorption-desorption tank. When the conductivity of the solution stopped decreasing, i.e., when adsorption equilibrium was reached, the MEFB unit cell was short-circuited or reversed to perform a desorption test. When the conductivity of the solution stopped increasing, i.e., when desorption equilibrium was reached, the next cycle began. This adsorption-desorption test was repeated for 50 cycles, all within the cyclic adsorption-desorption tank. Static conditions: After 50 cycles of dynamic adsorption-desorption, the electrode was removed from the current collector, rinsed three times with deionized water, and the calcium content in the electrode was measured by ICP-OES. The test results are shown in Figures 7(B) and 8. Figures 7(B) and 8(B) show the stability experiments under static conditions, while Figure 8(A) shows the stability experiments under dynamic conditions. Figure 7(B) shows that a comparison of the Ca and Na content in the CCEF-10-AC electrode before and after electrosorption reveals that the Na content in the target electrode decreased significantly after electrosorption, while the Ca content increased significantly, indicating that ion exchange occurred during the electrosorption process. Figure 8(B) shows that a comparison of the Ca content in the AC and CCEF-10-AC cathodes after different adsorption-desorption cycles reveals that the Ca content in the target electrode CCEF-10-AC is significantly lower than that in the AC after long-term use. This indicates that the target electrode has excellent stability and regeneration ability, effectively mitigating scaling on the electrode surface. Figure 8(A) shows that, compared to the ACIIAC electrode, the (-)CCEF-10-ACIIAC electrode exhibits excellent stability and regeneration ability during 50 cycles of long-term softening of hard water, demonstrating its sustained and effective softening of hard water in practical applications.

[0120] Test Example 2

[0121] 1. Electrode bacteria killing performance test

[0122] 1) The electrodes prepared in Examples 1-2 and Comparative Example 7 were applied to microbial inhibition tests. The test method was as follows: Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were used as model pathogens for antibacterial activity experiments. 7 -10 8 100 μL of bacterial sample with a concentration of 10 CFU / mL was added to the MEFB water softening system. The reaction time was set to 0 min and 30 min. A series of control experiments were established: ① In the absence of power, 100 μL of 10 CFU / mL was added to the 10 mM CaCl2 solution. 7 -10 8CFU / mL of bacteria (the same below); ② Bacteria were added to a CaCl2 solution and operated on a MEFB cell composed of a (-)CCEF-10-ACIIAC electrode; ③ Bacteria were added to a CaCl2 solution and operated on a MEFB cell composed of a (-)CCEF-10-ACIIAC-Ag electrode. With power applied, ④ Bacteria were added to a CaCl2 solution and a voltage of 1.2V was applied to the MEFB cell composed of a (-)CCEF-10-ACIIAC electrode; ⑤ Bacteria were added to a CaCl2 solution and a voltage of 1.2V was applied to the MEFB cell composed of a (-)CCEF-10-AC-AgIIAC electrode; ⑥ Bacteria were added to a CaCl2 solution and a voltage of 1.2V was applied to the MEFB cell composed of a (-)CCEF-10-ACIIAC-Ag electrode. At 0 and 30 minutes of MEFB treatment, colonies grown under different experimental conditions were cultured on LB solid medium, and the effects of different experimental conditions on colony counts were observed using the plate colony counting method. Each bacterial sample was repeated three times. The test results are shown in Figures 9 and 10(A)-(B). As shown in Figures 9 and 10(A)-(B), the voltage applied to the MEFB system is a key factor in killing the target bacteria. More importantly, the voltage-applied MEFB system can enhance the killing effect of the AC-Ag anode on microorganisms. When a voltage of 1.2V was applied, the MEFB unit cell composed of (-)CCEF-10-ACIIAC-Ag electrodes achieved a kill rate of over 99% against both Escherichia coli and Staphylococcus aureus after 30 minutes of sterilization.

[0123] 2) The effect of bacteria on the adsorption of ions by the electrode active materials prepared in Examples 1-2 and Comparative Example 7. The test results are shown in Figures 10(C)-(E) and Figure 11. As shown in Figures 10(C)-(E) and 11, the conductivity changes over time during the MEFB sterilization process are basically the same as when no bacteria are introduced, and it still shows good water softening performance. The MEFB unit cell assembled from (-)CCEF-10-ACIIAC-Ag has both good hardness ion removal performance and excellent sterilization effect. As shown in Figure 10(E), when Escherichia coli was introduced into the MEFB system and the electrosorption cycle was repeated 10 times, the conductivity change was basically the same compared to when no bacteria were introduced. After the introduction of Staphylococcus aureus, the conductivity still did not change significantly, and the hard water softening effect remained stable, indicating that the prepared active material has good anti-microbial contamination ability and has practical application prospects.

[0124] 2. Test of the killing performance of electrodes on algae cells

[0125] 1) The electrodes prepared in Examples 1-2 and Comparative Example 7 were applied to the microbial killing test. The test method was as follows: the concentrated algae solution was diluted with 10 mM CaCl2 to 1.2 x 10 7 The MEFB assay was performed using a 100ml water sample with a concentration of approximately 10 cells / mL. Samples were collected every 5 minutes for observation and counting. The reaction time was set to 0 to 300 minutes. A series of control experiments were conducted: ① The killing rate of microalgae by 10mM CaCl2 (the same below) without power applied; ② The killing rate of microalgae by a MEFB cell composed of a (-)CCEF-10-ACIIAC electrode; ③ The killing rate of microalgae by a MEFB cell composed of a (-)CCEF-10-ACIIAC-Ag electrode; ④ The killing rate of microalgae by a MEFB cell composed of a (-)CCEF-10-ACIIAC electrode; ⑤ The killing rate of microalgae by a MEFB cell composed of a (-)CCEF-10-AC-AgIIAC electrode; and ⑥ The killing rate of microalgae by a MEFB cell composed of a (-)CCEF-10-ACIIAC-Ag electrode under an applied voltage of 1.2V. During MEFB treatment for 0 to 300 minutes, algal cells were counted using flow cytometry under different experimental conditions to observe the effects of different experimental conditions on algal cells. The test results are shown in Figures 12 and 13. Figure 12 and the accompanying insets demonstrate that CCEF, AC, and CaCl2 have very poor algae-killing effects when no voltage is applied. Furthermore, under dynamic conditions, nanosilver has limited algae-killing effects. Similarly, applying an external voltage is a key factor in suppressing algae growth, and importantly, the electric field enhances the algae-killing effect of the AC-Ag anode in the MEFB system. The results in Figure 13 demonstrate that during MEFB treatment of algal cells, the conductivity of the solution increases, due to the dissolution of intracellular electrolytes following algal cell death. This further demonstrates the excellent antimicrobial properties of the prepared active material.

[0126] Test Example 3

[0127] Electrode structural characterization, surface chemical analysis, and electrochemical performance testing

[0128] (1) The surface structure analysis of the relevant electrodes, scales prepared in Examples 1 to 2 and Comparative Examples 1 to 7, and the microorganisms in Test Example 2 was performed, and the results are shown in Figures 14 and 15. As shown in Figure 14, when the CCEF content increases from 5% to 20%, CCEF gradually gathers around the AC particles. When its doping amount is 10%, CCEF effectively and evenly fills the gaps between large AC particles like a "conductive network", which is conducive to ion diffusion and mass transfer along the electrode. The scale crystal forms of the blank group and the experimental group are stable calcite type and metastable aragonite type, respectively, while the scale morphology after (-)CCEF-10-ACIIAC electrode treatment is looser, because the current density affects the microscopic morphology 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 shows that the target electrode CCEF-10-AC has good stability and regeneration ability, and can effectively alleviate the scaling of the electrode surface. As shown in Figure 15, after being treated by the MEFB unit cell composed of the target electrodes, the cell walls of the microalgae and bacteria were damaged and shrunk, and the cell contents leaked, resulting in the death of the microorganisms. This shows that the (-)CCEF-10-ACIIAC-Ag electrode has good killing ability against microorganisms and anti-microbial contamination ability.

[0129] (2) The surface chemical analysis of the relevant electrodes prepared in Examples 1 to 2 and Comparative Examples 1 to 7 is performed, and the results are shown in the illustrations in Figure 3, Figures 7(A) and (C), and Figure 16. The hydrophilicity of activated carbon AC is poor, and there is a large mass transfer resistance, while CCEF is rich in hydrophilic groups, which can improve the hydrophilicity of the composite material. As can be seen from the first illustration in Figure 3, with the increase of the CCEF doping amount, the hydrophilicity of the electrode is significantly improved, which is conducive to the diffusion and mass transfer of ions along the electrode. The second illustration in Figure 3 detects the Zeta potential of CCEF and nanosilver in weakly acidic and weakly alkaline environments. The results show that the surface of CCEF is negatively charged. Thanks to its polycarboxyl structure, CCEF has a high electronegativity in hard water, which is closely related to its high selectivity and high adsorption capacity for hardness ions, while the surface of nanosilver is positively charged, which provides a basis for the optimal combination of electrodes in the MEFB unit cell. As can be seen from Figure 7(A), the electroadsorbed Ca 2+ Before and after electrosorption, the XRD diffraction peaks of pure CCEF match well with the standard card PDF#20-1149 and do not change, indicating that its crystal has good stability. As shown in Figure 7(B), before and after electrosorption, CCEF-10-AC presents 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. As shown in Figure 16, the adsorption of Ca 2+Before and after, characteristic peaks of Na-O bonds and Ca-O bonds were observed at the characteristic peaks of carboxylates in the infrared spectrum of pure CCEF, indicating that ion exchange occurred, which is consistent with the results of ICP-OES.

[0130] (3) The electrochemical performance tests of the relevant electrodes prepared in Example 1, Comparative Example 1, Comparative Example 4, Comparative Example 5 and Comparative Example 6 are shown in Figures 17 to 19. The results of Figures 17 (A) to (B) show that with the increase of the CCEF doping amount, the capacitance current first increases and then decreases. CCEF-10-AC presents the largest specific capacitance, maintaining a specific capacitance of 44% at a scan rate of 50 mv / s. The results of Figure 17 (C) show that the GCD curve of CCEF-10-AC is close to an isosceles triangle, showing the longest discharge time, which means that it has a larger specific capacitance, which is consistent with the CV results. The results of IR drop in Figure 18 show that an appropriate amount of CCEF can reduce the internal resistance of the battery. The results of EIS in Figure 17 (D) show that the high-frequency region of CCEF-10-AC exhibits the lowest interface charge transfer resistance Rct (1.64Ω), and the steep slope in the low-frequency region shows good ion diffusion behavior. As shown in Figures 19(A) and 19(B), the ideal rectangular CV curves indicate that the target electrode MEFB exhibits typical double-layer electric field behavior, showing a larger current and specific capacitance in CaCl2 solution. At different scan rates, its specific capacitance in NaCl solution decreases faster, and only 7% of the specific capacitance is retained at the end, which is attributed to the free Na in the target electrode. + With Ca 2+ An exchange occurs, for Ca 2+ Provides more active sites, which is beneficial for Ca 2+ Diffusion and transport. As shown in Figure 19 (C) to (D), the GCD curve shows that the target electrode has a strong affinity for Ca 2+ The specific capacitance is significantly higher than that of Na + Consistent with the CV results, the GCD curves are almost symmetrical at different current densities, and the target electrode exhibits excellent double-layer electric field behavior and reversibility. The IT curve on the right side of Figure 8(A) shows that after 50 cycles of charge and discharge of the MEFB unit cell, the current drop of the (-)CCEF-10-ACIIAC electrode is very small compared to the ACIIAC symmetrical electrode, indicating that the interface resistance of the electrode does not increase much when the electrode is running for a long time, reflecting the good stability and regeneration ability of the target electrode. By comparing the electrochemical performance of the target electrode in CaCl2 and NaCl solutions, the potential of the target electrode to selectively adsorb hardness ions can be reflected.

[0131] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. An ion selective adsorption electrode, characterized in that: The ion selective adsorption electrode comprises polycarboxylic acid ion exchange fiber, activated carbon, a conductive agent, and a binder; The mass percentage of the polycarboxylic acid ion exchange fiber is 5% to 20%.

2. An ion selective adsorption electrode according to claim 1, characterized in that: The mass percentage of the activated carbon is 60%-80%, the mass percentage of the conductive agent is 5%-10%, and the mass percentage of the binder is 5%-10%.

3. An ion selective adsorption electrode according to claim 2, characterized in that: The ion selective adsorption electrode is prepared by a coating method: polycarboxylic acid ion exchange fiber, activated carbon, conductive agent, and binder are added with a proper amount of water to be dispersed into slurry, which is then coated on a current collector and vacuum dried to obtain the ion selective adsorption electrode.

4. An ion selective adsorption electrode according to claim 3, characterized in that: The conductive agent is Ketjen black or acetylene black; The binder is PTFE, PVDF or Nafion; The current collector is titanium foil, copper foil, aluminum foil, carbon paper, graphite paper or titanium plate.

5. A micro-electric field adsorption MEFB unit cell, characterized in that: It comprises a cathode and an anode, wherein the cathode is the ion selective adsorption electrode according to any one of claims 1 to 4; The anode is the same as the cathode, or the anode is an activated carbon anode doped with nanosilver.

6. The micro-electric field adsorption MEFB unit cell according to claim 5, characterized in that: The doping amount of nano silver is 0-1wt%.

7. The micro-electric field adsorption MEFB unit cell according to claim 5, characterized in that: The nano-silver-doped activated carbon anode is prepared by a coating method, wherein activated carbon, a conductive agent, a binder, and nano-silver are dispersed into a slurry by adding a proper amount of water, and the slurry is coated on a current collector and vacuum dried to obtain the slurry.

8. A micro-electric field adsorption MEFB system, characterized in that: The invention comprises the unit cell as claimed in any one of claims 5 to 7, and further comprises a conductivity meter, a peristaltic pump, a circulating absorption-desorption tank, a desorption tank and a constant voltage DC power supply.

9. Use of the micro-electric field adsorption MEFB system according to any one of claims 4 to 8 in water softening and / or sterilization and algae removal.

10. The use according to claim 9, 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 applied voltage is 1.0v~2.0v.

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