An efficient and recyclable electrosorption method and electrode material for removing perfluorinated compounds from water

Abstract

The present invention targets perfluorobutanesulfonic acid, the most widely distributed perfluorocompound, and provides a highly efficient and recyclable electrosorption method and electrode material for removing perfluorocompounds from water. The method uses chitosan and magnetic nano-ferroferric oxide as raw materials for modified activated carbon to prepare a nano-Fe3O4 / chitosan / activated carbon composite electrode. Using the nano-Fe3O4 / chitosan / activated carbon composite electrode as the anode and activated carbon as the cathode, an operating voltage of 0.8 to 5V is applied. The composite electrode electrically adsorbs and desorbs perfluorocompounds from water, achieving online adsorption, desorption, and concentration of perfluorocompounds, thereby achieving controllable and efficient removal, enrichment, and recovery of perfluorocompounds.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollutant treatment, and in particular relates to an efficient and recyclable electric adsorption method and electrode material for removing perfluorinated compounds in water. Background Art

[0002] Perfluorinated compounds are compounds formed when all hydrogen atoms on the carbon chain of a molecule are replaced by fluorine atoms. They are difficult to degrade and accumulate in the environment and the human body. Certain concentrations of perfluorinated compounds have been detected in most important water bodies in China, such as the Yangtze River and the Yellow River. Perfluorinated compounds also come from a wide range of sources, including fire extinguishers, clothing coatings, and paints in daily life. The U.S. Centers for Disease Control and Prevention evaluated blood samples from more than 16,000 people between 1999 and 2016 and found that per- and polyfluoroalkyl substances (PFAS) were detectable in the blood of almost all those tested. China is also facing serious PFAS pollution. PFAS testing in six water plants in central and eastern China found that perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) were the main PFAS in drinking water. A certain concentration of PFOA was still detected in treated drinking water, ranging from 0.38 to 51.0 ng·L -1 between.

[0003] Technologies such as photochemical oxidation, ultraviolet irradiation, electrochemical oxidation, ultrasonic irradiation, adsorption, coagulation, and zero-valent iron reduction have been developed for the removal of PFSA from aqueous solutions. However, these methods are not efficient or economical enough for the removal of low concentrations of PFSA. The development of an effective technology for the removal of PFSA under low energy consumption and mild experimental conditions remains a pressing need.

[0004] Capacitive deionization (CDI, also known as electrosorption) boasts excellent adsorption selectivity, low energy consumption, easy recycling, no secondary pollution, and low operating costs. Its promising application prospects have attracted the attention of numerous scholars and become a hot topic of current research. The key to CDI technology lies in the selection and modification of electrode materials. The selected electrode materials must possess high specific surface area, good hydrophilicity, a suitable pore size distribution, and high electrical conductivity.

[0005] Currently, there are few studies on the application of CDI in the field of perfluorinated compound removal, and the current research mainly focuses on reducing the common ion effect in the electrosorption process by adding ion exchange membranes, thereby increasing the adsorption capacity of electrosorbed perfluorinated anions.<Separation and Purification Technology> A research result published in (348(2024)127728) describes the effectiveness of an ACDI system with only CEV (cation exchange membrane) added to remove short-chain PFAS (PFBS) from aqueous solutions. The traditional CDI configuration does not include an ion exchange membrane between the electrodes, and it consists only of two 100μm nylon spacers. The MCDI device includes a cation exchange membrane (CMV, SelemionTM, AGC Engineering Co., Japan) behind the negative electrode and an anion exchange membrane (AMV, SelemionTM, AGC Engineering Co., Japan) near the positive electrode. The ACDI in this study modified the design of MCDI and omitted the anion exchange membrane. The results showed that the deionization capacity of the CDI system with the addition of anion exchange membrane was 28.75 mg / g, which was 2.7 times and 3.3 times that of CDI and MCDI (membrane CDI), respectively.

[0006] Directly modifying carbon materials as electrode materials offers a more convenient CDI system application solution. By modifying the activated carbon, the affinity for the target adsorbed ions is enhanced, thereby mitigating the common ion adsorption effect. Compared to CDI systems that incorporate ion exchange membranes, CDI systems using directly modified activated carbon as electrode materials are simpler to assemble and more convenient for application. Furthermore, membraneless CDI systems are more environmentally friendly, eliminating the risk of secondary contamination.

[0007] At present, the main problems of CDI technology for removing perfluorinated compounds using carbon electrodes are: easy detachment of electrode materials, small adsorption capacity, and difficulty in desorption. Therefore, it is of great significance to introduce new carbon composite materials with high efficiency and easy desorption to quickly remove perfluorinated compounds. Summary of the Invention

[0008] To address the above problems, the present invention targets perfluorobutanesulfonic acid, the most widely distributed perfluorochemical, and invents a method and electrode material for removing perfluorochemicals from water bodies by capacitive deionization based on a nano-Fe3O4 / chitosan / activated carbon composite electrode. The method can effectively adsorb perfluorobutanesulfonic acid in water. After desorption, the electrode material retains its high-efficiency adsorption capacity. The electrode material is reusable, green, safe and environmentally friendly, and perfluorochemicals can be recycled.

[0009] The technical solution adopted in the present invention is as follows:

[0010] An efficient and recyclable electrosorption method for removing perfluorinated compounds from water, characterized in that a nano-Fe3O4 / chitosan / activated carbon composite electrode is used as an anode and activated carbon is used as a cathode, a working voltage of 0.8 to 5V is applied, and the electrode is placed in water for electrosorption;

[0011] The nano-Fe3O4 / chitosan / activated carbon composite electrode is prepared by the following method:

[0012] (1) adding chitosan to an acetic acid solution to fully dissolve it, then adding nano-ferroferric oxide and mixing it thoroughly, and then adding activated carbon and a cross-linking agent to obtain a slurry;

[0013] (2) completely drying the slurry obtained in step (1) to obtain a block of carbon sheets, which is then ground into powder;

[0014] (3) The powder obtained in step (2) is mixed with the binder solution and fully dissolved to obtain a composite electrode slurry, which is evenly coated on a titanium plate to obtain a nano-Fe3O4 / chitosan / activated carbon composite electrode.

[0015] Preferably, in step (1), the mass ratio of chitosan to nano-ferroferric oxide is (0.8-1.2):1, and the mass ratio of chitosan to activated carbon is 1:(5-35).

[0016] Preferably, in step (1), the concentration of the acetic acid solution is 1% to 3%, the added mass of chitosan is 0.2% to 2% of the volume of the acetic acid solution, and the added amount of the cross-linking agent is 1 to 3 vol%.

[0017] Preferably, step (1) is specifically as follows: adding chitosan to the acetic acid solution, ultrasonicating at 20-50°C for 20-40 minutes, placing in a 20-40°C water bath and stirring for 20-40 minutes to fully dissolve, then adding nano-ferrosoferric oxide, stirring and mixing in a 60-90°C water bath for 1-3 hours, then adding activated carbon and continuing stirring for 1-2 hours, adding a cross-linking agent, and stirring at 60-90°C for 5-8 hours.

[0018] Preferably, in step (1), the cross-linking agent is at least one of methyltrimethoxysilane and glutaraldehyde; and the mass ratio of chitosan to activated carbon is 1:(14-18).

[0019] Preferably, the drying temperature in step (2) is 50-100° C., and the drying time is 15-24 hours; the powder is ground into powder and sieved to a mesh size of 40-200 meshes.

[0020] Preferably, in step (3), in the binder solution, the binder is at least one of propylene oxide and polyvinylidene fluoride, and the solvent is at least one of ethanol and dimethylacetamide.

[0021] Preferably, in step (3), the mass ratio of the binder to the powder obtained in step (2) is 1:(8-10); the mass ratio of the binder to the solvent is 1:(30-50).

[0022] Preferably, the operating voltage is 0.8-1.6V.

[0023] An electrode material is a nano-Fe3O4 / chitosan / activated carbon composite electrode used in the method of the present invention.

[0024] The present invention uses chitosan as the raw material for modified activated carbon because it will be positively charged after protonation, which can enhance the adsorption of anions by the anode. After the activated carbon is modified with chitosan, the hydrophilicity of the electrode becomes stronger, the surface properties are improved, and more adsorption sites are added, so that its adsorption capacity is improved. In addition, the hydroxyl and amino functional groups rich in chitosan can form hydrogen bonds with the sulfonic acid functional groups in perfluorosulfonic acid, thereby enhancing the selective adsorption ability of the electrode. Another modified raw material is magnetic nano-ferroferric oxide, which has high electrical conductivity, which can be attributed to the electrons in Fe 2+ with Fe 3+ It can be used as an anode material for supercapacitors and lithium-ion batteries, showing good electrochemical properties. Therefore, the modification of chitosan with magnetic Fe3O4 can effectively improve the electrochemical performance of chitosan on carbon-based electrode materials. The magnetic chitosan obtained by modifying chitosan with nanomagnetic materials has a stronger positive charge after protonation, and is more likely to adsorb negatively charged anions during electrosorption. There are cation-π interactions between the Fe=O and S=O bonds in ferroferric oxide, which can be beneficial for the selective adsorption of perfluorosulfonic acid anion groups.

[0025] Compared with the prior art, the advantages of the present invention are as follows:

[0026] 1. The present invention adopts the CDI method of novel carbon electrode materials to efficiently adsorb and desorb perfluorinated compounds, and recycles the carbon electrode materials. It can enrich and concentrate perfluorinated compounds and has the characteristics of being green, environmentally friendly, safe and controllable, low in energy consumption, recyclable, and basically emission-free.

[0027] 2. The magnetic ferroferric oxide selected in the present invention has high electrical conductivity, which can be attributed to the electrons in Fe 2+ with Fe 3 + It can be used as an anode material for supercapacitors and lithium-ion batteries, showing good electrochemical properties, and thus can effectively improve the electrochemical properties of electrode materials.

[0028] 3. After the present invention uses chitosan to modify the activated carbon, the hydrophilicity of the electrode becomes stronger, and water can more fully infiltrate the electrode surface, further improving the performance and efficiency of electrical adsorption.

[0029] 4. Chitosan and nano-Fe3O4 are positively charged. The present invention uses chitosan and nano-Fe3O4 to modify the activated carbon, which makes the positive charge of the anode stronger and adsorbs perfluorinated compounds as much as possible, which can effectively reduce the common ion adsorption effect and increase the adsorption capacity compared with the CDI system of the traditional unmodified carbon electrode system.

[0030] 5. The hydroxyl and amino functional groups rich in the activated carbon composite electrode of the present invention can form hydrogen bonds with the sulfonic acid functional groups in perfluorosulfonic acid, and the Fe=O bond and S=O also have a π-π conjugation effect, which further enhances the adsorption affinity of the electrode for perfluorosulfonic acid.

[0031] 6. Compared with the CDI system with the addition of ion exchange membrane, the CDI system of the present invention that directly modifies activated carbon as the electrode material is simpler to assemble and easier to use. It does not require regular replacement of the ion exchange membrane, thus avoiding the risk of group leakage on the exchange membrane and reducing costs.

[0032] 7. The present invention can be coated on different current collectors as needed to prepare flat, tubular and rolled membrane components, which are convenient for industrial production and large-scale application.

[0033] 8. The present invention can facilitate the removal and enrichment of perfluorinated compounds by controlling the voltage of 0-5 volts according to the specific perfluorinated compound pollution situation, and facilitates the optimization of the removal process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a comparison diagram of the adsorption capacity effect of the embodiment and the comparative example.

[0035] Figure 2 The figure is a comparison of the adsorption capacity of the embodiment and the comparative example over time.

[0036] Figure 3 This is a graph of the adsorption capacity of Example 1 within 10 cycles.

[0037] Figure 4 This is a comparison chart of the adsorption capacity of Example 1 at different operating voltages. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts are all within the scope of protection of the present invention.

[0039] The nano-ferroferric oxide used in the examples of the present invention was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; the activated carbon was purchased from Kuraray Co., Ltd. of Japan, model number YP-50F.

[0040] Example 1

[0041] A method for removing perfluorobutanesulfonic acid from water by capacitive deionization using a nano-Fe3O4 / chitosan / activated carbon composite electrode is described. The nano-Fe3O4 / chitosan / activated carbon composite electrode serves as the anode and activated carbon serves as the cathode to achieve electrical adsorption of perfluorobutanesulfonic acid in water. The following is the preparation process of the anode electrode material:

[0042] (1) Add 0.5 g of chitosan to 100 ml of 2% acetic acid solution, ultrasonicate at 30 ° C for half an hour, and then stir in a 30 ° C water bath for half an hour to fully dissolve. Then take 0.5 g of nano-ferroferric tetroxide and add it to the chitosan acetic acid solution. Stir and mix in an 80 ° C water bath for 2 hours. Then add 8 g of activated carbon and continue stirring for 1 hour. Then add 2.5 ml of glutaraldehyde and heat and stir at 80 ° C for 6 hours.

[0043] (2) Pour the slurry obtained in (1) into a flat container, place it in an oven, adjust the temperature to 80°C, and bake for 18 hours. After it is completely dried, grind the obtained block carbon sheet into a powder that can pass through a 100-mesh sieve for use.

[0044] (3) 0.05 g of PVDF was added to 2 g of DMAC and stirred thoroughly to dissolve. Then, 0.45 g of the powder obtained in step (2) was added to the PVDF-DMAC solution and mixed thoroughly. The mixture was evenly coated on a titanium plate to form the anode of the CDI device, which was designated as Fe3O4 / CS10.

[0045] Example 2

[0046] A method for removing perfluorobutanesulfonic acid from water based on nano-Fe3O4 / chitosan / activated carbon composite electrode capacitive deionization, with nano-Fe3O4 4 / Chitosan / activated carbon composite electrode is used as anode and activated carbon as cathode to achieve the electrical adsorption of perfluorobutanesulfonic acid in water. The following is the preparation process of the anode electrode material:

[0047] (1) Add 1 g of chitosan to 100 ml of 2% acetic acid solution, ultrasonicate at 30°C for half an hour, and then stir in a 30°C water bath for half an hour to fully dissolve. Then take 1 g of nano-ferroferric tetroxide and add it to the chitosan acetic acid solution. Stir and mix in an 80°C water bath for 2 hours. Then add 7 g of activated carbon and continue stirring for 1 hour. Then add 2.5 ml of glutaraldehyde and heat and stir at 80°C for 6 hours.

[0048] (2) Pour the slurry obtained in (1) into a flat container, place it in an oven, adjust the temperature to 80°C, and bake for 18 hours. After it is completely dried, grind the obtained block carbon sheet into a powder that passes through a 100-mesh sieve for use.

[0049] (3) 0.05 g of PVDF was added to 2 g of DMAC and stirred thoroughly to dissolve. Then, 0.45 g of the powder obtained in step (2) was added to the PVDF-DMAC solution and mixed thoroughly. The mixture was evenly coated on a titanium plate to form the anode of the CDI device, which was designated as Fe3O4 / CS20.

[0050] Example 3

[0051] A method for removing perfluorobutanesulfonic acid from water by capacitive deionization using a nano-Fe3O4 / chitosan / activated carbon composite electrode is described. The nano-Fe3O4 / chitosan / activated carbon composite electrode serves as the anode and activated carbon serves as the cathode to achieve electrical adsorption of perfluorobutanesulfonic acid in water. The following is the preparation process of the anode electrode material:

[0052] (1) Add 0.25 g of chitosan to 100 ml of 2% acetic acid solution, ultrasonicate at 30 ° C for half an hour, and then stir in a 30 ° C water bath for half an hour to fully dissolve. Then take 0.25 g of nano-ferroferric tetroxide and add it to the chitosan acetic acid solution. Stir and mix in an 80 ° C water bath for 2 hours. Then add 8.5 g of activated carbon and continue stirring for 1 hour. Then add 2.5 ml of glutaraldehyde and heat and stir at 80 ° C for 6 hours.

[0053] (2) Pour the slurry obtained in (1) into a flat container, place it in an oven, adjust the temperature to 80°C, and bake for 18 hours. After it is completely dried, grind the obtained block carbon sheet into a powder that passes through a 100-mesh sieve for use.

[0054] (3) 0.05 g of PVDF was added to 2 g of DMAC and stirred thoroughly to dissolve. Then, 0.45 g of the powder in step (2) was added to the PVDF DMAC solution and mixed thoroughly. The mixture was evenly coated on a titanium plate to form the anode of the CDI device, which was recorded as Fe3O4 / CS5.

[0055] Comparative Example 1

[0056] The difference from the embodiment is that both the anode and cathode of the CDI device use unmodified activated carbon as the electrode material, and the preparation method is as follows:

[0057] 0.05 g of PVDF was added to 2 g of DMAC and stirred thoroughly to dissolve. Then 0.45 g of activated carbon powder was added to the PVDF-DMAC solution and mixed thoroughly. The mixture was evenly coated on a titanium plate to form the anode of the CDI device, which was denoted as AC.

[0058] Comparative Example 2

[0059] The difference from the embodiment is that,

[0060] The anode of the CDI device uses only chitosan-modified activated carbon as the electrode material, and the preparation method is as follows:

[0061] (1) Add 1 g of chitosan to 100 ml of 2% acetic acid solution, ultrasonicate at 30°C for half an hour, then stir in a 30°C water bath for half an hour to fully dissolve, then add 8 g of activated carbon and continue stirring for 1 hour, then add 2.5 ml of glutaraldehyde, and heat and stir at 80°C for 6 hours.

[0062] (2) Pour the slurry obtained in (1) into a flat container, place it in an oven, adjust the temperature to 80°C, and bake for 18 hours. After it is completely dried, remove it and grind the obtained block carbon sheet into a powder that passes through a 100-mesh sieve for later use.

[0063] (3) 0.05 g of PVDF was added to 2 g of DMAC and stirred thoroughly to dissolve. 0.45 g of the powder obtained in step (2) was added to the PVDF-DMAC solution and mixed thoroughly. The mixture was evenly coated on a titanium plate to form the anode of the CDI device, which was designated as CS10.

[0064] Application Experiment Example 1

[0065] 1. The performance of Examples 1 to 3 in removing perfluorinated compounds was investigated. The specific results and process are as follows:

[0066] The composite electrodes of Examples 1-3 and Comparative Examples 1 and 2 served as anodes, and unmodified activated carbon served as cathodes. The electrodes measured 5×5 cm. A voltage of 1.2 V was applied between the anode and cathode to form a PFBS electrosorption assembly. 500 mg / L PFBS was used as the adsorption influent. The PFBS solution was adjusted to pH 6.5 with 0.1 mol / L sodium hydroxide solution. A treatment volume of 100 mL was used in a 150 mL beaker for adsorption. Power was applied for 15 minutes to complete capacitive removal of PFBS. Data for capacitive adsorption of PFBS were obtained.

[0067] like Figure 1 、 2 As shown in Figure 2, after 15 minutes of power application, the calculated adsorption capacities of Fe₃O₄ / CS₅, Fe₃O₄ / CS₁₀, and Fe₃O₄ / CS₂₀ were 21.32 mg / g, 30.24 mg / g, and 25.62 mg / g, respectively. The adsorption capacity of the unmodified activated carbon used as the anode in Comparative Example 1 was 6.21 mg / g, while the adsorption capacity of the chitosan-modified activated carbon used as the anode in Comparative Example 2 was 19.68 mg / g. This shows that the adsorption capacity of perfluorobutanesulfonic acid is significantly improved when the modification ratio of nano-Fe₃O₄ and chitosan is appropriate.

[0068] 2. Examining the regeneration process of the nano-Fe3O4 / chitosan / activated carbon composite electrode of Example 1: After the capacitor adsorbs PFBS, the adsorbed PFBS will automatically desorb into water after the voltage is disconnected. Figure 3 As shown in the figure, the Fe3O4 / CS10 electrode still has a high adsorption capacity after multiple cycles of adsorption and desorption.

[0069] 3. The performance of the nano-Fe3O4 / chitosan / activated carbon composite electrode of Example 1 in the field of adsorption of perfluorobutanesulfonic acid was investigated. The specific process and results are as follows:

[0070] 500 mg / L perfluorobutanesulfonic acid was used as the adsorption influent, the pH of the perfluorobutanesulfonic acid solution was adjusted to 6.5 with 0.1 mol / L sodium hydroxide solution, and the treatment volume was 100 mL.

[0071] Effect of operating voltage on adsorption of PFBS:

[0072] Voltages of 0.8V, 1.2V, and 1.6V were applied between the anode and cathode to electro-adsorb PFBS. The capacitive removal of PFBS was completed after 15 minutes of power application. Data on capacitive adsorption of PFBS at different voltages were obtained. Figure 4As shown in the figure, the adsorption capacities at voltages of 0.8V, 1.2V, and 1.6V are calculated to be 20.69 mg / g, 30.24 mg / g, and 38.89 mg / g, respectively. As the voltage increases, the electrical adsorption capacity of the CDI system gradually increases. However, when the voltage is greater than 1.23V, the ions in the water will gain or lose enough electrons, causing a chemical reaction to generate hydrogen and oxygen, resulting in water electrolysis, which is not conducive to its application in the field of water treatment in actual production.

Claims

1. An efficient and recyclable electrosorption method for removing perfluorinated compounds from water, characterized in that: With nano-Fe3O4 / chitosan / activated carbon composite electrode as anode and activated carbon as cathode, a working voltage of 0.8-5V was applied and placed in water for electrosorption. The nano-Fe3O4 / chitosan / activated carbon composite electrode is prepared by the following method: (1) adding chitosan to an acetic acid solution to fully dissolve it, then adding nano-ferroferric oxide and mixing it thoroughly, and then adding activated carbon and a cross-linking agent to obtain a slurry; (2) completely drying the slurry obtained in step (1) to obtain a block of carbon sheets, which is then ground into powder; (3) The powder obtained in step (2) is mixed with the binder solution and fully dissolved to obtain a composite electrode slurry, which is evenly coated on a titanium plate to obtain a nano-Fe3O4 / chitosan / activated carbon composite electrode.

2. The highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to claim 1, characterized in that: In step (1), the mass ratio of chitosan to nano-ferroferric oxide is (0.8-1.2):1, and the mass ratio of chitosan to activated carbon is 1:(5-35).

3. The highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to claim 2, characterized in that: In step (1), the concentration of the acetic acid solution is 1% to 3%, the added mass of chitosan is 0.2% to 2% of the volume of the acetic acid solution, and the added amount of the cross-linking agent is 1 to 3 vol%.

4. The highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to claim 3, characterized in that: Step (1) is specifically as follows: adding chitosan to the acetic acid solution, ultrasonicating at 20-50° C. for 20-40 minutes, placing in a 20-40° C. water bath and stirring for 20-40 minutes to fully dissolve, then adding nano-ferroferric tetroxide, stirring and mixing in a 60-90° C. water bath for 1-3 hours, then adding activated carbon and continuing stirring for 1-2 hours, adding a cross-linking agent, and stirring at 60-90° C. for 5-8 hours.

5. The highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to claim 4, characterized in that: In step (1), the cross-linking agent is at least one of methyltrimethoxysilane and glutaraldehyde; and the mass ratio of chitosan to activated carbon is 1:(14-18).

6. The highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to claim 1, characterized in that: The drying temperature in step (2) is 50-100° C. and the drying time is 15-24 hours; the powder is ground into powder and sieved to a mesh size of 40-200 meshes.

7. The highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to claim 1, characterized in that: In step (3), in the binder solution, the binder is at least one of propylene oxide and polyvinylidene fluoride, and the solvent is at least one of ethanol and dimethylacetamide.

8. The highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to claim 7, characterized in that: In step (3), the mass ratio of the binder to the powder obtained in step (2) is 1:(8-10); the mass ratio of the binder to the solvent is 1:(30-50).

9. A highly efficient and recyclable electrosorption method for removing perfluorinated compounds from water according to any one of claims 1 to 8, characterized in that: The operating voltage is 0.8-1.6V.

10. An electrode material, characterized in that: The nano-Fe3O4 / chitosan / activated carbon composite electrode is used in the method according to any one of claims 1 to 9.

Images