Capacitive desalination flow electrode material and method of preparation, fcdi device and applications thereof

Abstract

The application discloses a capacitive desalination flow electrode material and a preparation method thereof, a FCDI device and application of the capacitive desalination flow electrode material. The preparation method of the capacitive desalination flow electrode material comprises the following steps: dispersing polypyrrole and polyvinylpyrrolidone into a methanol solution containing zinc nitrate hexahydrate and / or cobalt nitrate hexahydrate, stirring for the first time to obtain a solution A; adding 2-methylimidazole into methanol, stirring for the second time to obtain a solution B, and dropping the solution B into the solution A, stirring for the third time to obtain a mixed solution; and performing standing, suction filtration, washing, drying and grinding on the mixed solution to obtain a ZIF@PPy powder. The flow electrode material prepared by the preparation method has high adsorption capacity and high electron mobility, and is not prone to aggregation and settlement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flow electrode, and particularly relates to a flow electrode material for capacitive desalination, a preparation method thereof, an FCDI device and application thereof. BACKGROUND

[0002] With the growing global population and human's attention to health, the consumption and production of antibiotics have surged worldwide, which leads to an increase in the discharge of waste solutions containing antibiotics. Residual antibiotics cannot be fully eliminated and have potential ecological risks, causing serious environmental pollution. Traditional separation methods including evaporation, condensation, distillation, filtration, and electrodialysis, although have been proven to be effective for the separation of certain organic and salt mixtures under specific conditions, still have problems such as high energy consumption, low efficiency, high cost, and safety hazards. Various related technologies developed on the basis of capacitive deionization technology (CDI) have gradually attracted attention due to their low energy consumption, high efficiency, low cost, safety and reliability, and environmental friendliness. In the traditional CDI system, a fixed voltage is applied, and ions move directionally in the electric field, and finally cations and anions are adsorbed in the electric double layer (EDLs) formed by the electrode material and the liquid surface. However, the fixed electrode has a limited area, resulting in a limited ion storage capacity, which cannot solve the problem of continuous desalination, and therefore can only desalinate low salinity water in an intermittent manner, greatly increasing the cost and efficiency of desalination.

[0003] The invention patent application with publication number CN117535693A discloses a FCDI-based seawater desalination combined hydrogen production device, relating to the field of seawater electrolysis. The device includes a device main body, a power supply, a seawater container, and a flow electrode liquid container. The device main body includes a first end plate, a first graphite plate, an annular gasket, a second graphite plate, and a second end plate arranged in sequence. The annular gasket is sandwiched between the two graphite plates, and the inside of the annular gasket is provided with a water-permeable gas-separation membrane, forming a first electrolysis cavity and a second electrolysis cavity inside the annular gasket. The annular gasket is connected with a water inlet pipe and a water outlet pipe. The first graphite plate is provided with a first flow channel, and the second graphite plate is provided with a second flow channel. Ion exchange membranes are arranged between the two electrolysis cavities and the adjacent flow channels. The two ion exchange membranes are respectively provided with water electrolysis electrocatalytic selective electrode materials on the side facing the electrolysis cavities. The power supply is electrically connected with the two graphite plates, the seawater container is connected with the two electrolysis cavities, and the flow electrode liquid container is connected with the first liquid inlet / outlet pipe and the second liquid inlet / outlet pipe.

[0004] The patent application with the publication number CN117661001A discloses an electrolytic chlorine production device for enriching seawater by using an FCDI device, which comprises an electrolytic chlorine production device, a flow electrode mixing box, a water inlet pipeline, a water production and recycling pipeline, and an FCDI device.

[0005] The above two patents use a flow electrode slurry instead of a fixed electrode to realize continuous separation and purification of different ions, so as to achieve the purpose of continuous adsorption and desorption of ions. The performance of the electrode material is one of the key factors restricting the application of the FCDI method. The electrode material with low conductivity and low adsorption capacity limits its further application. The increase of the flow electrode material leads to the increase of the slurry viscosity, and the blockage phenomenon is easy to occur in the flow channel, which is not conducive to long-term stable operation. SUMMARY

[0006] The application provides a preparation method of a capacitive desalination flow electrode material.

[0007] The application provides a preparation method of a capacitive desalination flow electrode material, which comprises the following steps:

[0008] (1) disperse polypyrrole and polyvinylpyrrolidone into a methanol solution containing zinc nitrate hexahydrate and / or cobalt nitrate hexahydrate, and stir for the first time to obtain solution A;

[0009] (2) add 2-methylimidazole into methanol, stir for the second time to obtain solution B, drop solution B into solution A, stir for the third time to obtain a mixed solution, and perform standing, suction filtration, washing, drying and grinding on the mixed solution to obtain ZIF@PPy powder.

[0010] The polypyrrole is used as a substrate for supporting ZIF material in series, has high conductivity and toughness, improves the connectivity and regularity of the pore structure, and increases the ion transfer rate and charge density; the ZIF material provides a large specific surface area and a controllable pore size, so that the material has high adsorption capacity and is not easy to settle and block as a whole, and the difficulty that the traditional flow electrode material cannot be compatible with high conductivity and high specific surface area is solved, and the difficulty of easy settlement and poor stability is solved.

[0011] Preferably, the mass ratio of the zinc nitrate hexahydrate and the cobalt nitrate hexahydrate is 6.44-9.67:2.91-5.82.

[0012] The ratio of the added Zn and Co affects the specific surface area and pore size of the ZIF framework material grown on the polypyrrole. The larger the specific surface area, the larger the area that can contact the liquid, and the more active sites there are. A suitable pore size controls the actual effective area for adsorbing inorganic salt ions. Since inorganic salt ions form hydrated ions, the radius of the ions is increased. For example, the diameter of Na + is 1.16 angstroms, and the diameter of Cl - is 1.67 angstroms. However, in a NaCl solution, the hydrated diameters of Na + and Cl - are 3.58 angstroms and 3.31 angstroms, respectively. Therefore, too small a pore size channel is not conducive to the rapid transmission of ions inside the material, and too small a size micropore cannot accommodate hydrated ions. The structure of the Zn center has a stronger pore-forming ability, which greatly improves the specific surface area. The structure of the Co center can effectively adjust the pore size and improve the stability of the material, making the ZIF structure more stable.

[0013] Further preferably, the mass ratio of the zinc nitrate hexahydrate and the cobalt nitrate hexahydrate is 9.67 g:2.91 g.

[0014] When Co:Zn=3:1, the proportion of metal-nitrogen saturated bonds formed by coordination with the Co and Zn metal centers is the highest, so the ability of electron transfer is the highest, and the adsorption capacity for Cl- and Na+ embedded in the pore size is also the largest.

[0015] Preferably, the mass ratio of the polypyrrole, the zinc nitrate hexahydrate, and the cobalt nitrate hexahydrate is 0.8134:9.67 g:2.91 g, so that the ZIF can grow more uniformly on the PPy.

[0016] Preferably, the polypyrrole preparation method of step (1) comprises the following steps:

[0017] Dissolve FeCl3 in a methyl orange solution, stir uniformly in a nitrogen environment, obtain a mixed solution, then slowly add the pyrrole monomer after rotary evaporation to the mixed solution, stir at room temperature for 12-24 h, filter, wash, vacuum dry, and grind to obtain polypyrrole (PPy).

[0018] Further preferably, the concentration of the FeCl3 in the methyl orange solution is 6-10 g / L, the concentration of the methyl orange solution is 1-2 g / L, and the volume is 200-400 mL.

[0019] Further preferably, the volume of the pyrrole monomer in the methyl orange solution is 0.8-1.5 mL.

[0020] Further preferably, the flow rate of the nitrogen gas is 20-50 ml / min;

[0021] Further preferably, the washing is performed using deionized water or ethanol until the pH is 6-8.

[0022] Preferably, the mass ratio of the polyvinylpyrrolidone to the polypyrrole is 1:3-3:1.

[0023] In step (2), the solution B is added dropwise to the solution A.

[0024] Preferably, the volume of the methanol is 400-600 mL, and the mass of the 2-methylimidazole is 20-30 g.

[0025] Preferably, the dropping speed of the solution B is 1-3 ml / min, which allows the ZIF (Co / Zn) to grow uniformly on the PPy and form a suitable size of pore diameter.

[0026] Preferably, the stirring speed of the solution B is 1000-1200 r / min, which allows the ZIF (Co / Zn) to grow uniformly on the PPy and form a suitable size of pore diameter.

[0027] In another aspect, the present application also provides a capacitive desalination flow electrode material prepared by the preparation method of the capacitive desalination flow electrode material.

[0028] In another aspect, the present application also provides a FCDI device, which comprises:

[0029] An ion separation chamber connected with the feed tank, for receiving the high-salt solution of the cephalosporin antibiotic organic matter from the feed tank and inputting the desalinated cephalosporin antibiotic organic matter solution into the feed tank;

[0030] A cation exchange membrane and a modified anion exchange membrane oppositely arranged on two sides of the ion separation chamber, and a negative charge layer arranged on the surface of the modified anion exchange membrane for blocking the cephalosporin antibiotic organic anion;

[0031] An anode graphite current collector and a cathode graphite current collector, which are respectively and independently connected with the fluid electrode slurry cavity, so that the fluid electrode slurry can flow and circulate in the anode graphite current collector and the cathode graphite current collector, respectively, the cathode graphite current collector is arranged on the side of the cation exchange membrane away from the ion separation chamber for capturing inorganic positive ions, and the anode graphite current collector is arranged on the side of the modified anion exchange membrane away from the ion separation chamber for capturing inorganic negative ions, so as to desalinate the high-salt solution of the cephalosporin antibiotic organic matter by capturing the inorganic positive ions and the inorganic negative ions;

[0032] A power supply, two ends of which are connected with the anode graphite current collector and the cathode graphite current collector respectively, for supplying power to the anode graphite current collector and the cathode graphite current collector;

[0033] The fluid electrode slurry comprises sodium chloride, activated carbon and the capacitive deionization flow electrode material.

[0034] The FCDI device based on the modified anion exchange membrane can change the positive electric property and hydrophilic-lipophilic property of the surface layer of the anion exchange membrane, reduce the easy ionization of organic matters, such as cephalosporin antibiotic organic matters, and realize the separation of the easy ionization organic matters and inorganic salts under the migration of the organic ions in water under the action of the electric field force. However, the migration of inorganic anions in the electric field is not prevented, so that the separation efficiency of the high-salt solution containing cephalosporin antibiotic organic matters is improved.

[0035] Preferably, in the fluid electrode slurry, the content of the sodium chloride is 0.122-0.366 g, the content of the activated carbon is 4.872-6.090 g, and the content of the capacitive deionization flow electrode material is 0.305-1.523 g.

[0036] In order to maintain the stability of the electrode slurry and prevent the blockage of the flow channel, the proportioning of the electrode slurry needs to be adjusted. The suitable content of sodium chloride is added into the flow electrode slurry as an electrolyte to reduce the start-up time of the system to reach the optimal performance. Too low mass concentration will lead to an increase in the start-up time and uneven charge distribution, and too high mass concentration will greatly affect the separation performance of the ion exchange chamber. The suitable content of the flow electrode material is added into the flow electrode slurry to improve the overall conductivity and adsorption performance of the slurry. Although too high concentration can still improve the adsorption rate and upper limit, the improvement capacity is limited, and the risk of flow channel blockage is increased. Further preferably, the content of 2wt% is the most suitable.

[0037] Preferably, the flow rate of the fluid electrode slurry is 50-100 ml / min.

[0038] Preferably, in the high-salt solution of the cephalosporin antibiotic organic matter, the concentration of the cephalosporin antibiotic is 0.5-1.0 mmol / L.

[0039] The concentration of NaCl is 0.1-0.2 mol / L.

[0040] Preferably, the cephalosporin antibiotic organic matter is one or more of the following: cefazolin sodium, cefoperazone sodium, cephalothin sodium, ceftriaxone sodium, latamoxef sodium, cefuroxime sodium, etc.

[0041] Preferably, the preparation method of the modified anion exchange membrane comprises:

[0042] (1) sequentially cleaning the anion exchange membrane by NaOH solution, NaCl solution and deionized water, and vacuum drying;

[0043] (2) adding L-dopamine into a tris-hydroxymethyl aminomethane buffer solution with pH value of 7-9, stirring uniformly to obtain a first mixed solution, and adding the anion exchange membrane obtained in step (1) into the first mixed solution, so as to coat a dopamine layer on the anion exchange membrane;

[0044] (3) adding the anion exchange membrane with the surface coated with the dopamine layer obtained in step (2) into a 2-acrylamidododecane sulfonic acid solution, stirring and mixing, forming a negative charge layer on the anion exchange membrane through Michael addition reaction, and obtaining a modified anion exchange membrane.

[0045] Preferably, the model of the anion exchange membrane is G1204, and the thickness is 0.15-0.16 mm.

[0046] Preferably, the concentration of the NaOH and NaCl solution is 0.1-0.2 mol / L.

[0047] Preferably, the cleaning time of the NaOH, NaCl and deionized water is 15-30 min.

[0048] Preferably, the mass concentration of the tris-hydroxymethyl aminomethane buffer solution is 0.605-1.21 g / L.

[0049] Preferably, in the first mixed solution, the concentration of the L-dopamine is 0.2-0.4 g / L.

[0050] Preferably, in step (2), the stirring rate is 200-400 ml / min, and the soaking time is 12-24 h.

[0051] Preferably, in step (3), the concentration of the 2-acrylamidododecane sulfonic acid solution is 5-10 g / L.

[0052] Preferably, in step (3), the stirring rate is 200-400 ml / min, and the soaking time is 2 h.

[0053] In another aspect, the application further provides application of the modified membrane-based flow electrode capacitive deionization system in separation and purification of high-salt solution containing cephalosporin antibiotic organic matter.

[0054] Compared with the prior art, the application has the following beneficial effects:

[0055] The application constructs a conductive network through polypyrrole connection, increases the electron transfer efficiency between electrode particles, and supports as a base, and then improves the effective adsorption area of the electrode material by self-growing ZIF framework materials with different proportions of bimetal (Co & Zn) centers on the polypyrrole conductive network. Suitable Co and Zn proportions form more suitable pore sizes to accommodate hydrated ions; and the formed coordination environment provides a good path for electron transfer, thereby enhancing the ion adsorption capacity. The synthesized electrode material of the application has the advantages of high conductivity, high ion transmission channel, stable support skeleton of polypyrrole, and high specific surface area and controllable pore size of ZIF framework material. The particle size of the composite material is small, the wettability is also improved, and the dispersibility and stability in water become more excellent, thereby making up for the shortcomings of polypyrrole easy to aggregate and settle and the shortcomings of ZIF framework material high resistance.

[0056] The application modifies the anion exchange membrane, a core component of the FCDI device, to have negative charge. The negative charge layer of the modified anion exchange membrane has repulsion to anions, which will hinder the transport behavior of organic anions across the membrane, but since the molecular size of Cl - is small, the repulsion is small, and it can still pass through the anion exchange membrane.

[0057] The application is directed to the separation and purification of high-salt solutions containing cephalosporin antibiotic organic matter and other organic matter with recycling value in the medical health, agriculture, forestry, livestock and poultry industries. Cephalosporin antibiotics are broad-spectrum antibiotics of the beta-lactam class. High-salt solutions containing cephalosporin antibiotic organic matter contain toxic organic compounds, inorganic salts and active pharmaceutical ingredients, posing a potential threat to organisms in the environment. For this new type of pollutant, cephalosporin antibiotics, the improved device of the application can achieve rapid and continuous separation of cephalosporin antibiotic organic matter and inorganic salts, helping to reduce the chemical oxygen demand (COD) level and reduce the toxicity of the wastewater and the generation of cephalosporin antibiotic-resistant microorganisms. And the separated cephalosporin antibiotic-like organic matter with recycling value can be purified and recycled or treated uniformly, which is more clean, environmentally friendly, efficient and simple than traditional filtration and degradation, and has significant advantages. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 It is a synthesis flowchart of the new flow electrode material in Example 1;

[0059] Figure 2 It is a structure schematic diagram of the flow electrode capacitive deionization system based on the modified membrane provided in the specific embodiment of the application;

[0060] Figure 3 It is a structure schematic diagram of the flow electrode capacitive deionization system based on the modified membrane provided in the specific embodiment of the application;

[0061] Figure 4 Part structure and operation process schematic diagram of modified membrane based flow electrode capacitive deionization system provided for specific embodiments of the present application, wherein, Figure 4 (a) is a schematic diagram of anode or cathode graphite current collector structure, Figure 4 (b) is a schematic diagram of flow electrode slurry operation, Figure 4 (c) is a schematic diagram of modified anion exchange membrane;

[0062] Figure 5 Schematic diagram of separation mechanism of modified membrane based flow electrode capacitive deionization device in Example 1;

[0063] Figure 6 SEM characterization result diagram of flow electrode material prepared in Example 1, PPy alone and ZIF (Co:Zn=3:1) alone, wherein, Figure 6 (a) is a SEM characterization result diagram of polypyrrole (PPy), Figure 6 (b) is a SEM characterization result diagram of ZIF (Co:Zn=3:1), Figure 6 (c) is a SEM characterization result diagram of flow electrode material prepared in Example 1;

[0064] Figure 7 BET diagram and pore size distribution diagram of flow electrode material prepared in Example 1-5 and Comparative Example 1-3, wherein, Figure 7 (a) is a BET diagram of flow electrode material prepared in Example 1-5 and Comparative Example 1-3, Figure 7 (b)- Figure 7 (d) is a distribution diagram of flow electrode material prepared in Example 1-5 and Comparative Example 1-3 in different pore size ranges.

[0065] Figure 8 Model diagram of flow electrode material prepared in Example 1 and Comparative Example 3;

[0066] Figure 9 Desalination effect diagram of ZIF (Co:Zn=3:1) @PPy at different concentrations in Application Example 1, Figure 9 (a) is the change of Cl - In the FCDI separation process using flow electrode at different concentrations, Figure 9 (b) is the change of cefazolin sodium in the FCDI separation process using flow electrode at different concentrations, Figure 9 (c) is the separation factor of Cl - and cefazolin sodium in the FCDI separation using flow electrode at different concentrations;

[0067] Figure 10The diagram shows the desalination effect when using the flow electrode materials prepared in Examples 1-5 and Comparative Examples 1-3 as raw materials in Application Example 1. Figure 10 (a) For the separation of Cl during FCDI using different flow electrodes - The change graph Figure 10 (b) is a graph showing the changes in organic anions during FCDI separation using different flow electrodes. Figure 10 (c) Separation factor for FCDI using different flow electrodes;

[0068] Figure 11 The graph shows the desalting effect of ZIF (Co:Zn=3:1)@PPy at a content of 2 wt% on different cephalosporin antibiotics in Application Example 1. Figure 11 (a) Cl during the separation process - Changes, Figure 11 (b) shows the changes of different organic anions during the separation process. Figure 11 (c) is Cl - Separation factors of organic compounds from different cephalosporin antibiotics;

[0069] Figure 12 The diagram shows the water contact angle of the flow electrode materials prepared in Examples 1-5 and Comparative Examples 1-3.

[0070] Figure 13 EIS diagrams of the flow electrode materials prepared in Examples 1-5 and Comparative Examples 1-3;

[0071] Figure 14 The graph shows the resistance of the flow electrode materials prepared in Examples 1-5 and Comparative Examples 1-3.

[0072] Figure 15 XPS images of the flow electrode materials prepared in Examples 1-5 and Comparative Examples 1-3 are shown below. Figure 15 (a) shows the XPS images of various flow electrode materials. Figure 15 (b) shows the Co 2p peak of ZIF(Co)@PPy. Figure 15 (c) shows the Zn 2p peak of ZIF(Zn)@PPy. Figure 15 (d) shows the Co 2p peak of ZIF (Co:Zn=1:3)@PPy. Figure 15 (e) is the Co 2p peak of ZIF(Co:Zn=2:2)@PPy. Figure 15 (f) shows the Co 2p peak of ZIF (Co:Zn=3:1)@PPy. Figure 15 (g) is the Zn 2p peak of ZIF (Co:Zn=1:3)@PPy. Figure 1 (h) is the Zn 2p peak of ZIF(Co:Zn=2:2)@PPy.Figure 6 (i) Zn 2p peak of ZIF (Co:Zn = 1:3) @PPy.

[0073] Wherein, ion separation chamber 1, cation exchange membrane 2, modified anion exchange membrane 3, anode graphite current collector 4, cathode graphite current collector 5, first circulating pipeline 61, second circulating pipeline 62, third circulating pipeline 63, feed tank 7, fluid electrode slurry cavity 8, inlet channel B, flow electrode channel A, outlet channel C, anode membrane gasket 21, modified cathode membrane gasket 31, negatively charged layer 34, left side fixed plate 91, right side fixed plate 92, flow electrode slurry a, flow electrode material aa, Cl ion b, Na ion c, orientation d, cephalosporin antibiotic anion e, electrostatic repulsive force f, electric field force g. DETAILED DESCRIPTION

[0074] The present application will be further illustrated below in conjunction with the embodiments and drawings. It should be understood that the embodiments are implemented on the premise of the technical scheme of the present application, and give detailed implementation modes and specific operation processes. These embodiments are only used to illustrate the present application, and are not used to limit the scope of the present application.

[0075] The operation methods not specified in the following examples are usually carried out according to conventional conditions or according to the conditions recommended by the manufacturer; both the anion exchange membrane and the cation exchange membrane are purchased from Hangzhou Lvhe Environmental Protection Technology Co., Ltd.

[0076] Example 1: The present embodiment provides a preparation method of a capacitive desalination flow electrode material, as shown in Figure 6 , which comprises:

[0077] (1) Dissolve 2.43 g (1.5 mmol) of FeCl3 in 300 mL of methyl orange (5 mM), then add 1.05 mL of pyrrole monomer, and stir at room temperature under nitrogen atmosphere for 24 h. Wash the formed precipitate with deionized water / ethanol several times until the filtrate is colorless and neutral, and finally dry at 60 ℃ under vacuum atmosphere for 24 h.

[0078] (2) Disperse 1 g of the above-synthesized polypyrrole (PPy) into 500 mL of methanol solution, and degrade by ultrasonic wave for 1 h. Dissolve 2.85 g of zinc nitrate hexahydrate and 8.55 g of cobalt nitrate hexahydrate in the above solution completely by ultrasonic machine, and stir for 1 h.

[0079] (3) 29.94 g of 2-methylimidazole was dispersed into 500 mL of methanol. Then, the 2-methylimidazole-methanol solution was added dropwise into the above initial mixture at a dropwise rate of 5 mL / min, stirred vigorously for 0.5-1 h, and left at room temperature overnight. After vacuum filtration, washing with methanol until colorless, and drying at 70 °C under vacuum atmosphere for 24 h.

[0080] From Name (a)- PPy (c)It can be seen that ZIF (Co:Zn = 3:1) is successfully grown on PPy, and PPy presents a nanotube-like hollow structure with a diameter of about 150-250 nm, which is accumulated in an unordered manner, like a spider network interconnecting, interacting, and extending to form a three-dimensional network structure, acting as a blockchain in the entire composite system of the material, effectively connecting each ZIF cubic structure, and serving as a bridge for electron transfer.

[0081] Example 2-5: Compared with Example 1, the mass of zinc nitrate hexahydrate and cobalt nitrate hexahydrate is different, as shown in Table 1.

[0082] Comparative Example 1: Compared with Example 1, the difference is that the flow electrode material provided in this comparative example is AC (activated carbon), among all the electrode materials, although AC has the highest specific surface area of mesopores, its ion adsorption rate and adsorption capacity are still not ideal, which shows that simply increasing the number of mesopores cannot improve the adsorption rate. As for the composite material, although the specific surface area of ZIF (Co:Zn = 3:1) decreases slightly after self-growth on PPy, the addition of PPy not only significantly improves the electron transfer rate, but also increases the proportion and number of mesopores, so that more ion adsorption active sites are activated, and finally the adsorption rate and adsorption capacity of Cl - are greatly improved.

[0083] Comparative Example 2: Compared with Example 1, the flow electrode material provided in this comparative example is PPy, PPy contains fewer pore structures, and the pore size is mainly concentrated below 2 nm, mainly dominated by micropores, with a specific surface area of only 47.83 m 2 / g, while ZIF (Co:Zn = 3:1) @ PPy has a larger specific surface area, providing more abundant adsorption sites and more mesopores and micropores, forming micropore-mesopore connectivity, reducing ion adsorption resistance, and improving ion diffusion rate.

[0084] Comparative Example 3: Compared with Example 1, the difference is that step (1) is not performed to obtain synthetic polypyrrole (PPy), and in step (2), polypyrrole (PPy) is not added, but the flow electrode material ZIF (Co:Zn = 3:1) is directly synthesized.

[0085] Although ZIF (Co:Zn=3:1) has a huge specific surface area (1825.51 m2 / g), 99% of its specific surface area is microporous, with almost no mesoporous structure. ZIF (Co:Zn=3:1)@PPy, on the other hand, provides a richer array of adsorption sites and more mesopores and micropores, forming micropore-mesopore connectivity, reducing ion adsorption resistance, and increasing ion diffusion rate.

[0086] Table 1. Mass of zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and polypyrrole provided in Examples 1-5

[0087] Example 2 Zn(N03)2.6H20 Co(N03)2.6H20 ZIF (Co)@PPy Example 1 ZIF (Co:Zn = 3: 1)@PPy 0g 11.64g 0.8134g Example 3 ZIF (Co:Zn = 2:2)@PPy 2.85g 8.55g 0.8134g Example 4 ZIF (Co:Zn = 1:3)@PPy 6.44g 5.82g 0.8134g Example 5 ZIF (Zn)@PPy 9.67g 2.91g 0.8134g Figure 7 Figure 7 12.88g 0g 0.8134g

[0088] Table 2 shows the pore size and specific surface area of ​​the materials prepared from different proportions of bimetals provided in Examples 1-5.

[0089]

[0090] Depend on Figure 8 (a)- Figure 12 (d) and Table 2 show that the ZIF (Co:Zn=3:1) provided in Comparative Example 3 ( Figure 13 The electrode material of the first type (ZIF) has the largest specific surface area, the most micropores, and the smallest average pore size, with almost no mesopores. However, when ZIF material is grown on a polypyrrole network, the overall specific surface area decreases slightly, but the proportion of mesopores increases, the average pore size significantly increases, and the number of active sites for inorganic salt adsorption also increases. Furthermore, the micropore-mesopore linkage can accommodate more Cl... - Furthermore, it can be observed that Zn centers can enlarge pore size and effectively promote pore formation. Therefore, ZIF(Co:Zn=3:1)@PPy combines the advantages of large specific surface area and more suitable pore sizes as active sites. In contrast, pure polypyrrole has a very small specific surface area and very small pore size, but the largest average pore size, suggesting that it contains more mesopores and macropores.

[0091] Depend on Figure 14 It can be concluded that composite materials prepared with different proportions of bimetals have different wettability, and the magnitude of wettability is expressed by the size of the contact angle. The smaller the contact angle, the better the wettability. The flow electrode materials provided in Examples 1-5 have suitable contact angles.

[0092] Depend on Figure 14 , Figure 15It can be concluded that the EIS curves of all samples consist of a semicircle in the high-frequency region and a sloping line in the low-frequency region, corresponding to the charge transfer resistance and the ion transport process within the material, respectively. The semicircle is almost invisible in the high-frequency region for PPy, indicating that the charge transfer resistance within PPy is negligible. The steepest slope of the sloping line indicates that PPy material possesses optimal electronic conductivity and the most convenient ion transport channel, while the slope of the composite material is significantly greater than that of the ZIF material alone, further demonstrating that the conductivity of the composite material is optimized. Compared to AC and ZIF alone, the intersection point of the high-frequency region of the EIS curve of the ZIF@PPy composite material with the true impedance axis is significantly smaller, indicating a decrease in resistance. This is consistent with... Figure 15 The correlation between the resistivity of different materials further demonstrates that the addition of PPy significantly improves the electrical conductivity of the composite material and the electron transfer rate within the material.

[0093] Table 3. Proportion of coordination bonds formed around Co / Zn metal centers in materials prepared with different proportions of bimetals in Example 1.

[0094]

[0095] In composite materials, the slight difference in ionic radius of cations (Zn) is taken into account. 2+ It is 0.74 Å, Co 2+ The unit particle size of ZIF(Zn) and ZIF(Co) is very similar (0.72 Å), and Co... 2+ and Zn 2+ The different electronegativity and electronic configurations distinguish the properties of Co-N and Zn-N bonds. Figure 2 (a)- Figure 3 (i) and Table 3 show that, compared to ZIF(Zn), the nitrogen-stretching frequency MN of ZIF(Co) exhibits a blue shift, while the peak of ZIF(Zn / Co) shifts accordingly based on the Co / Zn ratio. Therefore, the connectivity of the Co-N bond is stronger than that of the Zn-N bond, resulting in higher electronegativity for Co-N. Furthermore, Co... 2+ The valence electrons of Zn may contribute to the formation of additional metallic coordination bonds, thus forming π bonds, while Zn 2+ Due to its 3d10 electronic configuration, it can only form σ bonds, thus its structural stability is not as good as ZIF(Co). ZIF(Co:Zn=3:1)@PPy has the highest Co-N4 ratio and the strongest ion adsorption capacity. Based on Table 2, ZIF(Co:Zn=3:1)@PPy is selected as the optimal flow electrode material in this example.

[0096] A specific embodiment of the present invention also provides a flow electrode capacitive deionization (FCDI) device based on a modified membrane, such as... Figure 4 andFigure 4 As shown, it comprises an ion separation chamber 1, a cation exchange membrane 2, a modified anion exchange membrane 3, an anode graphite current collector 4 and a cathode graphite current collector 5.

[0097] The ion separation chamber 1 provided by the embodiment of the present application is connected with a feed tank 7 through a first circulation pipeline 61, the feed tank 7 transports the high-salt solution of the cephalosporin antibiotic organic matter to the bottom of the ion separation chamber 1, and transports the desalted cephalosporin antibiotic organic matter solution from the top of the ion separation chamber 1 to the feed tank 7.

[0098] The cation exchange membrane 2 and the modified anion exchange membrane 3 provided by the embodiment of the present application are oppositely arranged on the two sides of the ion separation chamber 1, the inorganic cations of the high-salt solution of the cephalosporin antibiotic organic matter can pass through the cation exchange membrane 2, the modified anion exchange membrane 3 is provided with a negative charge layer 34 on the surface, which is used for blocking the cephalosporin antibiotic organic anions, so that the cephalosporin antibiotic organic anions cannot pass through the modified anion exchange membrane 3, and the inorganic anions can pass through the modified anion exchange membrane 3 due to the small size, so as to realize the separation.

[0099] In an embodiment, the preparation method of the modified anion exchange membrane 3 provided by the embodiment of the present application comprises:

[0100] A dopamine solution with a concentration of 2 g / L is prepared, a commercial anion exchange membrane is immersed in the dopamine solution, and a polydopamine layer is deposited on the anion exchange membrane through a self-polymerization reaction at a rotation speed of 400 r / min; a monomer solution of 2-acrylamidododecanesulfonic acid with a concentration of 1 wt% is prepared, and the anion exchange membrane with the polydopamine intermediate layer is immersed in the negative monomer solution, and a Michael addition reaction is carried out at a rotation speed of 400 r / min for 120 min, so as to obtain the modified anion exchange membrane 3.

[0101] As shown in FIG. Figure 4 As shown in FIG. (c), the modified anion exchange membrane 3 is obtained by modifying the surface of the anion exchange membrane, the pore size of the membrane is changed, and a negative charge layer 34 is grown, so that the hydrophilic-lipophilic property of the surface layer of the anion exchange membrane is changed and the electronegativity is presented, the migration d of the easily ionized organic matter (for example, the cephalosporin antibiotic anion e) through the membrane under the action of the electric field force is reduced through the charge repulsion force f, and the small-sized Cl - b can pass through, so as to enhance the separation effect of the organic anion and the inorganic ion.

[0102] The anode graphite current collector 4 and the cathode graphite current collector 5 provided by the embodiment of the present application are respectively connected with the fluid electrode slurry cavity 8 through the second circulating pipeline 62 and the third circulating pipeline 63, so that the fluid electrode slurry can flow in the anode graphite current collector 4 and the cathode graphite current collector 5 respectively, the anode graphite current collector 4 is arranged on the side of the modified anion exchange membrane 3 away from the ion separation chamber and is used for capturing inorganic negative ions, the cathode graphite current collector 5 is arranged on the side of the cation exchange membrane 2 away from the ion separation chamber and is used for capturing inorganic positive ions, the corresponding inorganic negative ions and inorganic positive ions are captured through the fluid electrode slurry with positive charges or negative charges, and the inorganic positive ions and the inorganic negative ions are bound through mesopores with a suitable size, so that the desalination of the high-salt solution of the cephalosporin antibiotic organic matter can be better realized, and the stability is higher.

[0103] In an embodiment, as shown in Figure 5 As shown in (a), the anode graphite current collector 4 and the cathode graphite current collector 5 provided by the embodiment of the present application both include an inlet channel A, a flow electrode channel B and an outlet channel C connected in sequence, and the inlet channel A and the outlet channel C are connected with the fluid electrode slurry cavity 8 through the circulating pipeline.

[0104] As shown in Figure 5 As shown in (b), the fluid electrode slurry provided by the embodiment of the present application flows into the flow electrode channel A from the inlet channel B, adsorbs the corresponding inorganic positive ions and negative ions in the flow electrode channel A, and outputs the fluid electrode slurry with the adsorbed positive ions and negative ions to the fluid electrode slurry cavity 8 from the outlet channel C.

[0105] The two ends of the power supply provided by the embodiment of the present application are respectively connected with the anode graphite current collector 4 and the cathode graphite current collector 5, so as to supply power to the anode graphite current collector 4 and the cathode graphite current collector 5, so that the flow electrode material slurry flowing into the anode graphite current collector 4 and the cathode graphite current collector 5 carries the corresponding positive charges or negative charges.

[0106] In an embodiment, the preparation method of the fluid electrode slurry provided by the embodiment of the present application includes:

[0107] 1.22 g of the flow electrode material powder prepared in the embodiment 1 is weighed, dispersed in 54.57 g of deionized water (the concentration in the deionized water is 2wt%), 0.24 g of NaCl (0.4wt%) is added as an electrolyte, and 4.87 g (7.6wt%) of activated carbon is added, so as to obtain the flow electrode slurry. The stirring is performed at a rotating speed of 400 r / min for more than 24 h.

[0108] The modified membrane-based flow electrode capacitive deionization system provided by the embodiment of the application further comprises an anode membrane gasket 21, a modified cathode membrane gasket 31, a left fixed plate 91 and a right fixed plate 92, the anode membrane gasket 21 is located between the ion separation chamber 1 and the cation exchange membrane 2, the modified cathode membrane gasket 31 is located between the ion separation chamber 1 and the modified anion exchange membrane 3, and the left fixed plate 91 and the right fixed plate 92 are respectively located outside the left fixed plate 91 and the right fixed plate 92, and are used for fixing the modified membrane flow electrode capacitive deionization system.

[0109] As shown in Figure 5 , the operation principle of the device for separating cephalosporin antibiotics organic matter and NaCl provided by the embodiment of the application is as shown in Figure 9 , the flow electrode slurry a runs along the flow electrode channel B on the anode graphite current collector 4 and the cathode graphite current collector 5, covers the corresponding anode graphite current collector 4 and cathode graphite current collector 5 through the cation exchange membrane 2 and the modified anion exchange membrane 3 respectively, and is in full contact with the flow electrode slurry a, and a certain voltage is applied at the same time. Under the action of the voltage, the anode graphite current collector 4 and the cathode graphite current collector 5 carry corresponding positive and negative charges, so that the flow electrode material aa carries corresponding charges of the anode graphite current collector 4 and the cathode graphite current collector 5. When Cl - b and Na + c in the ion separation chamber 1 are respectively oriented d through the modified anion exchange membrane 3 and the cation exchange membrane 2 under the electric field, and are embedded in the specific surface area formed in the micropores of the flow electrode material aa under the action of the Faraday reaction, while the cephalosporin antibiotic anion e cannot cross the membrane and is forced to accumulate in the ion separation chamber 1 due to the electrostatic repulsive force f of the negative charge layer on the modified cathode membrane, and finally the separation purpose is achieved.

[0110] Application Example 1: The application example provides a modified membrane-based flow electrode capacitive deionization system for separating and purifying a high-salt solution containing cephalosporin antibiotics, and the specific steps are as follows:

[0111] (1) The flow electrode slurry in the flow electrode slurry cavity 8 is driven by a peristaltic pump to be introduced into the anode graphite current collector and the cathode graphite current collector at a rate of 100 ml / min, and the flow electrode material in the flow electrode slurry used in the application example is prepared by the embodiment 1.

[0112] (2) The high-salt solution g containing cephalosporin antibiotic organic matter is introduced into the ion separation chamber at a rate of 20 ml / min from the feed tank.

[0113] (3) As shown in Figure 9As shown, the electric field generated by the constant voltage of the power supply drives the directional movement d of the cations and anions, on the one hand, the flow electrode material aa in the flow electrode material slurry a of the cathode graphite current collector 5 will capture the inorganic cations Na + + passing through the cation exchange membrane 2, and on the other hand, the flow electrode material aa of the flow electrode material slurry a in the anode graphite current collector 4 will capture the inorganic Cl - - passing through the modified anion exchange membrane 3, while the cefalosporin organic matter is easily ionized into cefalosporin anions e in water, which are repelled by the electrostatic repulsion f and cannot pass through the modified anion exchange membrane 3, so as to achieve the desalination of the high-salt solution of the cefalosporin organic matter.

[0114] (4) The desalted cefalosporin is transported back to the feed tank through the ion separation chamber.

[0115] As shown in Figure 9 (a) and Figure 11 (b), the application example makes the concentration of the flow electrode material be 2.0 wt%, the C t / C0of the cefalosporin anions e with an initial concentration of 1 mmol / L can still be kept above 0.85, and the C - / C0of the Cl t - can be reduced to 0.67, as shown in Figure 11 (c), the application example makes the concentration of the flow electrode material be 2.0 wt% and the separation coefficient be 7425.56, and when the concentration is 2.5 wt%, the separation coefficient can reach 7757.21 after 60 min of separation.

[0116] The flow electrode material prepared in the application example 1 is operated for 60 min, and the mass concentration of 2 wt% is the most suitable ratio. It can be seen that the separation efficiency is obviously increased when the mass fraction of the flow electrode material is increased from 0.5 wt% to 2.0 wt%. Although the separation performance can still be improved when the mass concentration is continuously increased, the improved performance is not high, so it is still considered that the mass concentration of 2 wt% is the most suitable ratio.

[0117] As shown in Figure 10 , the influence of the separation performance of the device applied to the high-salt solutions of different kinds of cefalosporin organic matter (for example, cefazolin sodium, cefoperazone sodium, ceftriaxone sodium, la oxycefalosporin sodium, and cefuroxime sodium) is tested, and the physical and chemical properties are shown in Table 4. After 60 min of operation, the separation of the cefalosporin anions e and the Cl - - can still be realized by the device, and the separation coefficients are all more than 7000.

[0118] Table 4 provides the physicochemical properties of different kinds of cefalosporin antibiotic organic anions provided by the application example 1

[0119]

[0120] The structural formula of different kinds of cefalosporin antibiotic organic anions is as follows:

[0121] The structural formula of cefoperazone sodium provided by the embodiment is as follows:

[0122]

[0123] The structural formula of ceftriaxone sodium provided by the embodiment is as follows:

[0124]

[0125] The structural formula of cefoperazone sodium provided by the embodiment is as follows:

[0126]

[0127] The structural formula of cefoperazone sodium provided by the embodiment is as follows:

[0128]

[0129] The structural formula of cefoperazone sodium provided by the embodiment is as follows:

[0130]

[0131] From table 4 and Figure 10 It can be concluded that the application example can be applied to the separation and purification of cefalosporin antibiotic organic matters with molecular weight less than 1000 in high salt solution.

[0132] Different from the application example 1, the flow electrode materials prepared by the embodiment 2 to embodiment 5 are used as raw materials of the flow electrode slurry used in the application example 1 to application example 5.

[0133] As shown in ​ (a) ​ (c), the separation effect of the flow electrode materials prepared by the application embodiment 1 to embodiment 5 is obviously better than that of the flow electrode materials prepared by the comparative example 1 to comparative example 3.

[0134] The above description of the embodiments is for the purpose of facilitating the understanding and use of the invention by the person skilled in the art. However, the invention is not limited to the above embodiments, and the person skilled in the art can obviously easily make various modifications to these embodiments, and apply the method described herein to other embodiments without creative labor. Therefore, the improvements and modifications made without departing from the scope of the invention should be within the protection scope of the invention.

Claims

1. A method of preparing a capacitive desalination flow electrode material, characterized by, The method comprises the following steps: (1) dispersing polypyrrole and polyvinylpyrrolidone into a methanol solution containing zinc nitrate hexahydrate and / or cobalt nitrate hexahydrate, stirring for the first time to obtain solution A; (2) adding 2-methylimidazole into methanol, stirring for the second time to obtain solution B, and adding solution B into solution A drop by drop, stirring for the third time to obtain a mixed solution, and subjecting the mixed solution to standing, suction filtration, washing, drying and grinding to obtain ZIF@PPy powder.

2. The method of claim 1, wherein the method further comprises: The mass ratio of the zinc nitrate hexahydrate and the cobalt nitrate hexahydrate is 6.44-9.67:2.91-5.

82.

3. The method of claim 1, wherein the method further comprises: The polypyrrole preparation method of step (1) comprises the following steps: dissolving FeCl3 in a methyl orange solution, stirring uniformly in a nitrogen environment to obtain a mixed solution, slowly adding pyrrole monomer after rotary evaporation into the mixed solution, stirring for 12-24 hours at room temperature, and filtering, washing, vacuum drying and grinding to obtain polypyrrole.

4. The method of claim 3, wherein the method further comprises: The concentration of FeCl3 in the methyl orange solution is 6-10 g / L, the concentration of the methyl orange solution is 1-2 g / L, and the volume of the methyl orange solution is 200-400 mL.

5. The method of claim 1, wherein the method further comprises: The mass ratio of the polyvinylpyrrolidone and the polypyrrole is 1:3-3:

1.

6. A capacitive desalination flow electrode material, characterized in that, The method is prepared by the preparation method of the capacitive desalination flow electrode material in any one of claims 1-5.

7. An FCDI apparatus, characterized by, The method comprises the following steps: an ion separation chamber connected with a feed tank, for receiving a high-salt solution of cephalosporin organic matter from the feed tank and inputting a desalinated cephalosporin solution into the feed tank; a cation exchange membrane and a modified anion exchange membrane oppositely arranged on two sides of the ion separation chamber, the modified anion exchange membrane being provided with a negative charge layer on the surface thereof for blocking cephalosporin organic anions; an anode graphite current collector and a cathode graphite current collector respectively and independently connected with a fluid electrode slurry cavity, so that the fluid electrode slurry can flow in the anode graphite current collector and the cathode graphite current collector respectively, the anode graphite current collector being arranged on the side of the modified anion exchange membrane away from the ion separation chamber for capturing inorganic negative ions, and the cathode graphite current collector being arranged on the side of the cation exchange membrane away from the ion separation chamber for capturing inorganic positive ions, so as to realize desalination of the high-salt solution of cephalosporin organic matter by capturing inorganic positive ions and inorganic negative ions; a power supply having two ends respectively connected with the anode graphite current collector and the cathode graphite current collector for supplying power to the anode graphite current collector and the cathode graphite current collector; the fluid electrode slurry comprising sodium chloride, activated carbon and the capacitive desalination flow electrode material in claim 6.

8. The FCDI apparatus of claim 7, wherein, In the fluid electrode slurry, the mass percentage of the sodium chloride is 0.2-0.6 wt%; the mass percentage of the activated carbon is 8-10 wt%; the mass percentage of the capacitive desalination flow electrode material is 0.5-2.5 wt%.

9. The FCDI apparatus of claim 7, wherein, The preparation method of the modified anion exchange membrane comprises the following steps: (1) cleaning the anion exchange membrane through NaOH solution, NaCl solution and deionized water, and vacuum drying; (2) adding L-dopamine into a tris-hydroxymethyl aminomethane buffer solution with pH value of 7-9, stirring to obtain a first mixed solution, and adding the anion exchange membrane obtained in step (1) into the first mixed solution to coat a layer of dopamine on the anion exchange membrane; (3) adding the anion exchange membrane coated with the dopamine layer obtained in step (2) into a 2-acrylamidyl dodecane sulfonic acid solution, stirring to mix, forming a negative charge layer on the anion exchange membrane through Michael addition reaction, and obtaining a modified anion exchange membrane.

10. Use of the FCDI device according to any one of claims 7-9 for separating and purifying a high-salt solution containing cephalosporin antibiotic organic matter.

Images