Capacitive desalination flowing electrode material and preparation method thereof, FCDI device and application thereof

Abstract

The invention discloses a capacitive desalination flowing electrode material and a preparation method thereof, and an FCDI device and application thereof, the preparation method of the capacitive desalination flowing electrode material comprises the following steps: dispersing polypyrrole and polyvinylpyrrolidone into a methanol solution containing zinc nitrate hexahydrate and / or cobalt nitrate hexahydrate, and 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, dropwise adding the solution B into the solution A, stirring for the third time to obtain a mixed solution, standing the mixed solution, performing suction filtration, washing, drying and grinding to obtain ZIF-coated PPy powder. The flowing electrode material prepared by the preparation method is relatively high in adsorption capacity, relatively high in electron mobility and not easy to aggregate and settle.

Description

Technical Field

[0001] The invention belongs to the technical field of flow electrodes, and in particular relates to a capacitive desalination flow electrode material and a preparation method, an FCDI device and applications thereof. Background Art

[0002] With the continuous growth of the global population and the emphasis on health, the consumption and production of antibiotics have surged worldwide, which has led to an increase in the discharge of waste solutions containing antibiotics. Residual antibiotics cannot be fully eliminated, which has potential ecological risks and causes serious environmental pollution. Traditional separation methods include evaporation, condensation, distillation, filtration, and electrodialysis. Although they have been proven to be effective in separating certain organic matter and salt mixtures under specific conditions, they still have problems such as high energy consumption, low efficiency, high cost, and potential safety hazards. Various related technologies developed based on capacitive deionization technology (CDI) have gradually attracted attention due to their many advantages such as low energy consumption, high efficiency, low cost, safety and reliability, and environmental friendliness. In traditional CDI systems, a fixed voltage is applied, and ions move in a directional manner in the electric field, and finally cations and anions are adsorbed in the electric double layers (EDLs) formed by the electrode material and the liquid surface. However, due to the limited area of ​​the fixed electrode, its limited ion storage capacity cannot solve the problem of continuous desalination. Therefore, low-salinity water can only be desalinated in an intermittent manner, which greatly increases the desalination cost and efficiency.

[0003] The invention patent application with publication number CN117535693A discloses a combined hydrogen production device based on FCD I seawater desalination, which relates to the field of seawater electrolysis. The device includes a device body, a power supply, a seawater container and a flowing electrode liquid container. The device body includes a first end plate, a first graphite plate, an annular gasket, a second graphite plate and a second end plate stacked in sequence; the annular gasket is sandwiched between two graphite plates, a water-permeable air-isolating membrane is provided inside the annular gasket, a first electrolysis chamber and a second electrolysis chamber are formed inside the annular gasket, and 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; an ion exchange membrane is provided between the two electrolysis chambers and the adjacent flow channels, and the two ion exchange membranes are respectively provided with water electrolysis electrocatalytic selective electrode materials facing the electrolysis chamber side; the power supply is electrically connected to the two graphite plates respectively, the seawater container is connected to the two electrolysis chambers respectively, and the flowing electrode liquid container is respectively connected to the first liquid inlet / liquid outlet pipe and the second liquid inlet / liquid outlet pipe.

[0004] The invention patent application with publication number CN117661001A discloses an electrolytic chlorine-making device for enriching seawater using an FCDI device, comprising an electrolytic chlorine-making device, a mobile electrode mixing box, a water inlet pipeline, a produced water reuse pipeline and an FCDI device. The FCDI device comprises a shell and a cathode plate and two anode plates arranged in the shell. The cathode plate is located between the two anode plates. A cation exchange membrane and an anion exchange membrane are arranged between the cathode plate and the anode plate. The anode plate, the anion exchange membrane, the cation exchange membrane and the cathode plate are distributed in sequence. A first channel is formed between the anode plate and the anion exchange membrane, a second channel is formed between the anion exchange membrane and the cation exchange membrane, and a third channel is formed between the cation exchange membrane and the cathode plate. The device can realize seawater desalination, and at the same time, the salt content of the wastewater is low and the investment cost is low.

[0005] In order to achieve continuous separation and purification of different ions, the above two patents use mobile electrode slurry instead of fixed electrodes to achieve the purpose of continuous adsorption and desorption of ions. The performance of electrode materials is one of the key factors restricting the application of FCDI method. Electrode materials with low conductivity and low adsorption capacity limit its further application. The increase of mobile electrode materials leads to an increase in slurry viscosity, which is prone to blockage in the flow channel, which is not conducive to long-term stable operation. Summary of the invention

[0006] The invention provides a method for preparing a capacitive desalination mobile electrode material. The mobile electrode material prepared by the preparation method has high adsorption capacity and high electron mobility and is not easy to aggregate and settle.

[0007] The present invention provides a method for preparing a capacitive desalination flow electrode material, comprising:

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

[0009] (2) adding 2-methylimidazole to methanol and stirring for a second time to obtain solution B, adding solution B dropwise to solution A and stirring for a third time to obtain a mixed solution, and allowing the mixed solution to stand, filter, wash, dry, and grind to obtain ZIF@PPy powder.

[0010] The present invention uses polypyrrole as a substrate for supporting the ZIF material in series, which 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 huge specific surface area and an adjustable pore size, which not only makes the material have a high adsorption capacity, but also makes the material as a whole not easy to settle and clog, solving the difficulties of the traditional mobile electrode material that the high conductivity and high specific surface area are incompatible, as well as the difficulties of easy sedimentation and poor stability.

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

[0012] Different ratios of added Zn and Co will affect the specific surface area and pore size of the ZIF framework material grown on polypyrrole. The larger the specific surface area, the larger the area that can contact the liquid and the more active sites. The appropriate pore size controls the actual effective area for adsorbing inorganic salt ions. Since inorganic salt ions will form hydrated ions, the radius of the ions is increased, for example: Na + The diameter is The diameter of Cl- is However, in NaCl solution, Na + and Cl - The hydrated diameters are and Therefore, too small an aperture channel is not conducive to the rapid transmission of ions inside the material, so too small a micropore cannot accommodate hydrated ions. The Zn-centered structure has a stronger pore-forming ability and can greatly increase the specific surface area; the Co-centered structure 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 to the cobalt nitrate hexahydrate is 9.67 g:2.91 g.

[0014] When Co:Zn=3:1, the ratio 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 pores is also the greatest.

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

[0016] Preferably, the method for preparing polypyrrole in step (1) comprises the following steps:

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

[0018] Further preferably, 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 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 is 20-50 ml / min;

[0021] More preferably, deionized water or ethanol is used for washing until the pH is 6-8.

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

[0023] In step (2):

[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 dripping speed of adding solution B to solution A is 1-3 ml / min, so that ZIF (Co / Zn) grows uniformly on PPy and forms pores of appropriate size.

[0026] Preferably, during the process of dropwise addition of solution B to solution A, the stirring speed of solution A is 1000-1200 r / min.

[0027] On the other hand, the present invention also provides a capacitive desalination flow electrode material, which is prepared by the preparation method of the capacitive desalination flow electrode material.

[0028] On the other hand, the present invention also provides a FCDI device, comprising:

[0029] An ion separation chamber, the ion separation chamber is connected to the feed tank, and is used to receive the high-salt solution of cephalosporin antibiotic organic matter from the feed tank, and input the desalted cephalosporin antibiotic organic matter solution into the feed tank;

[0030] A cation exchange membrane and a modified anion exchange membrane, wherein the cation exchange membrane and the modified anion exchange membrane are arranged on both sides of the ion separation chamber, and a negatively charged layer is provided on the surface of the modified anion exchange membrane to block organic anions of cephalosporin antibiotics;

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

[0032] A power supply, wherein two ends of the power supply are respectively connected to the anode graphite current collector and the cathode graphite current collector, and are used to supply power to the anode graphite current collector and the cathode graphite current collector;

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

[0034] The FCDI device based on the modified anion exchange membrane proposed by the present invention performs negative charge grafting modification on the surface of the anion exchange membrane, which can change the positive charge and hydrophilicity and lipophilicity of the surface layer of the anion exchange membrane, reduce the easily ionized organic matter, such as cephalosporin antibiotic organic matter, which is easily ionized into organic ions in water, and thus migrates through the membrane under the action of the electric field force, thereby achieving the technical effect of separating the easily ionized organic matter from the inorganic salt. However, it does not prevent the migration of inorganic anions in the electric field, thereby improving the efficiency of separating the high-salt solution containing cephalosporin antibiotic organic matter.

[0035] Preferably, in the fluid electrode slurry, the content of sodium chloride is 0.122-0.366 g, the content of activated carbon is 4.872-6.090 g, and the content of the capacitive desalination 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 present invention needs to adjust the ratio of the electrode slurry. Adding an appropriate amount of sodium chloride as an electrolyte to the flowing electrode slurry can reduce the startup time for the system to reach optimal performance. Too low a mass concentration will increase the startup time and cause uneven charge distribution, while too high a mass concentration will greatly affect the separation performance of the ion exchange chamber. Adding an appropriate amount of flowing electrode material to the flowing electrode slurry can improve the overall conductivity and adsorption performance of the slurry. Although too high a concentration can still increase the adsorption rate and upper limit, the improvement capacity is limited and increases the risk of blockage of the flow channel. It is further preferred that a content of 2wt% is selected as the most appropriate.

[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 substance is one or more of the following: cefazolin sodium, cefoperazone sodium, ceftriaxone sodium, cefuroxime sodium, latamoxef sodium, cefuroxime sodium, etc.

[0041] Preferably, the method for preparing the modified anion exchange membrane comprises:

[0042] (1) The anion exchange membrane is cleaned with NaOH solution, NaCl solution, and deionized water in sequence, and then vacuum dried;

[0043] (2) adding levodopamine to a tris(hydroxymethylformamide) buffer solution with a pH value of 7-9, stirring evenly to obtain a first mixed solution, and adding the anion exchange membrane obtained in step (1) to the first mixed solution, thereby coating a dopamine layer on the anion exchange membrane;

[0044] (3) Adding the 2-acrylamidododecanesulfonic acid solution to the anion exchange membrane with a dopamine layer on the surface obtained in step (2), stirring and mixing, and forming a negatively charged layer on the anion exchange membrane through Michael addition reaction to obtain a modified anion exchange membrane.

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

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

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

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

[0049] Preferably, in the first mixed solution, the concentration of levodopa 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-acrylamidododecanesulfonic 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] On the other hand, the present invention also provides the use of the modified membrane-based mobile electrode capacitive deionization system in separating and purifying a high-salt solution containing cephalosporin antibiotic organic matter.

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

[0055] The present invention connects through polypyrrole, constructs a conductive network, increases the electron transfer efficiency between electrode particles, and serves as a substrate support, and then self-grows a ZIF framework material with bimetallic (Co & Zn) centers in different proportions on the polypyrrole conductive network to increase the effective adsorption area of ​​the electrode material. The appropriate Co and Zn ratios form more pores of appropriate size to accommodate hydrated ions; and the formed coordination environment provides a good path for electron transfer, thereby enhancing the ion adsorption capacity. The electrode material synthesized by the present invention has the advantages of high conductivity, high ion transmission channel, and 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 becomes smaller, the wettability is also improved, and the dispersibility and stability in water become more excellent, thereby making up for the shortcomings of easy aggregation and sedimentation of polypyrrole and the shortcomings of high resistance of ZIF framework material.

[0056] The present invention specifically modifies the anion exchange membrane, the core component of the FCDI device, to make it negatively charged. The negative charge layer of the modified anion exchange membrane has a repulsive force on anions, which will hinder the transport of organic anions across the membrane. However, due to Cl - The molecular size is small, the repulsion force is small, and it can still pass through the anion exchange membrane.

[0057] The present invention is aimed at the separation and purification of high-salt solutions containing organic matter with recycling value such as cephalosporin antibiotic organic matter in the medical health, agriculture, forestry and animal husbandry industries. Cephalosporin antibiotics are broad-spectrum β-lactam antibiotics. The high-salt solution containing cephalosporin antibiotic organic matter contains toxic organic compounds, inorganic salts and active pharmaceutical ingredients, which pose a potential threat to organisms in the environment. For cephalosporin antibiotics, a new type of pollutant, the improved device of the present invention can achieve rapid and continuous separation of cephalosporin antibiotic organic matter and inorganic salts, which helps to reduce the level of chemical oxygen demand (COD), reduce the toxicity of wastewater and the production of cephalosporin antibiotic-resistant microorganisms. In addition, the separated organic matter with recycling value similar to cephalosporin antibiotic organic matter can be purified, recovered or uniformly treated, which is cleaner, more environmentally friendly, more efficient and simple than traditional filtration and degradation, and has significant advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the synthesis process of the new mobile electrode material in Example 1;

[0059] Figure 2 A schematic diagram of the structure of a mobile electrode capacitive deionization system based on a modified membrane provided in a specific embodiment of the present invention;

[0060] Figure 3 A schematic diagram of the structure of a mobile electrode capacitive deionization system based on a modified membrane provided in a specific embodiment of the present invention;

[0061] Figure 4 A schematic diagram of the partial structure and operation process of a mobile electrode capacitive deionization system based on a modified membrane provided in a specific embodiment of the present invention, wherein: Figure 4 (a) is a schematic diagram of the structure of the anode or cathode graphite collector. Figure 4 (b) is a schematic diagram of the operation of the flowing electrode slurry. Figure 4 (c) is a schematic diagram of the principle of the modified anion exchange membrane;

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

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

[0064] Figure 7 The BET diagram and pore size distribution diagram of the mobile electrode materials prepared in Examples 1-5 and Comparative Examples 1-3, wherein: Figure 7 (a) is the BET diagram of the flow electrode materials obtained in Examples 1-5 and Comparative Examples 1-3, Figure 7 (b)- Figure 7 (d) is a distribution diagram of different pore size ranges of the mobile electrode materials prepared in Examples 1-5 and Comparative Examples 1-3.

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

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

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

[0068] Fig.11 This is the desalination effect diagram of different cephalosporin antibiotic organic matter using 2wt% ZIF (Co: Zn = 3: 1) @ PPy in Application Example 1. Fig.11 (a) is Cl in the separation process - changes, Fig.11 (b) is the change of different organic anions during the separation process. Fig.11 (c) is Cl - and separation factors of different cephalosporin antibiotic organics;

[0069] Fig.12 The water contact angle diagram of the mobile electrode materials prepared in Examples 1-5 and Comparative Examples 1-3;

[0070] Fig.13 The EIS graphs of the flow electrode materials prepared in Examples 1-5 and Comparative Examples 1-3;

[0071] Fig.14 The resistance size diagram of the mobile electrode materials prepared in Examples 1-5 and Comparative Examples 1-3;

[0072] Fig.15 The XPS graphs of the flow electrode materials obtained in Examples 1-5 and Comparative Examples 1-3 are shown in FIG. Fig.15 (a) is the XPS graph of various flow electrode materials. Fig.15 (b) is the Co 2p peak of ZIF(Co)@PPy. Fig.15 (c) is the Zn 2p peak of ZIF(Zn)@PPy, Fig.15(d) is the Co 2p peak of ZIF(Co:Zn=1:3)@PPy, Fig.15 (e) is the Co 2p peak of ZIF(Co:Zn=2:2)@PPy, Fig.15 (f) is the Co 2p peak of ZIF (Co: Zn = 3: 1) @ PPy, Fig.15 (g) is the Zn 2p peak of ZIF(Co:Zn=1:3)@PPy, Fig.15 (h) is the Zn 2p peak of ZIF(Co:Zn=2:2)@PPy, Fig.15 (i) is the Zn 2p peak of ZIF(Co:Zn=1:3)@PPy.

[0073] Among them, there are ion separation chamber 1, cation exchange membrane 2, modified anion exchange membrane 3, anode graphite collector 4, cathode graphite collector 5, circulation pipe 61, circulation pipe 62, circulation pipe 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, left fixed plate 91, right fixed plate 92, flow electrode slurry a, flow electrode material aa, Cl ion b, Na ion c, orientation d, cephalosporin antibiotic anion e, electrostatic repulsion f, electric field force g. DETAILED DESCRIPTION

[0074] The present invention is further explained below in conjunction with the embodiments and drawings. It should be understood that this embodiment is implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. These embodiments are only used to illustrate the present invention, and are not used to limit the scope of the present invention.

[0075] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or conditions recommended by the manufacturers; the anion exchange membranes and cation exchange membranes were purchased from Hangzhou Lvhe Environmental Protection Technology Co., Ltd.

[0076] Example 1

[0077] This embodiment provides a method for preparing a capacitive desalination flow electrode material, such as Figure 1 As shown, including:

[0078] (1) 2.43 g (1.5 mmol) of FeCl3 (35) was dissolved in 300 mL of methyl orange (5 mM), and then 1.05 mL of pyrrole monomer was added and stirred at room temperature for 24 h under nitrogen atmosphere. The formed precipitate was washed several times with deionized water / ethanol until the filtrate was colorless and neutral, and finally dried at 60 °C in a vacuum atmosphere for 24 h.

[0079] (2) Disperse 1 g of the synthesized polypyrrole (PPy) in 500 mL of methanol solution and perform ultrasonic degradation for 1 h. Use an ultrasonic machine to completely dissolve 2.85 g of zinc nitrate hexahydrate and 8.55 g of cobalt nitrate hexahydrate in the solution and stir for 1 h.

[0080] (3) Disperse 29.94 g of 2-methylimidazole in 500 mL of methanol. Then, add the 2-methylimidazole-methanol solution to the initial mixed solution at a drop rate of 5 mL / min, stir vigorously for 0.5-1 h, and leave at room temperature overnight. After vacuum filtration, wash with methanol until colorless, and dry at 70°C in a vacuum atmosphere for 24 h.

[0081] Depend on Figure 6 (a)- Figure 6 (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 150-250nm. They are stacked in a disordered manner, interconnected and interacted with each other like a spider web, and extend to form a three-dimensional network structure, acting as a blockchain in the composite system of the entire material, effectively connecting each ZIF cubic structure and serving as a bridge for electron transfer.

[0082] Embodiment 2-5

[0083] Compared with Example 1, the masses of zinc nitrate hexahydrate and cobalt nitrate hexahydrate are different, as shown in Table 1.

[0084] Comparative Example 1

[0085] Compared with Example 1, the difference is that the flow electrode material provided in this comparative example is AC (activated carbon). Among all electrode materials, although AC has the highest mesoporous specific surface area, 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. 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 greatly improves the adsorption of Cl - adsorption rate and adsorption capacity.

[0086] Comparative Example 2

[0087] Compared with Example 1, the flow electrode material provided in this comparative example is PPy, which has a relatively small pore structure, and the pore size is mainly concentrated below 2nm, mainly micropores, and the specific surface area is only 47.83m 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 the ion adsorption resistance and increasing the ion diffusion rate.

[0088] Comparative Example 3

[0089] The difference compared with Example 1 is that step (1) is not performed to obtain synthesized polypyrrole (PPy), and polypyrrole (PPy) is not added in step (2), but the mobile electrode material ZIF (Co:Zn=3:1) is directly synthesized.

[0090] Although ZIF (Co: Zn = 3: 1) has a huge specific surface area (1825.51 m2 / g), the micropore specific surface area accounts for 99% of it, and there is almost no mesoporous structure. ZIF (Co: Zn = 3: 1) @ PPy provides more abundant adsorption sites and more mesopores and micropores, forming micropore-mesopore connectivity, reducing ion adsorption resistance and increasing ion diffusion rate.

[0091] Table 1 Mass of zinc nitrate hexahydrate, cobalt nitrate hexahydrate and polypyrrole provided in Examples 1-5

[0092]

[0093] Table 2 Pore size and specific surface area of ​​materials prepared by bimetallic materials with different ratios provided in Examples 1-5

[0094]

[0095]

[0096] Depend on Figure 7 (a)- Figure 7 (d) and Table 2 show that the ZIF (Co: Zn = 3: 1) provided in Example 1 ( Figure 8 ) has the largest specific surface area, the largest number of micropores, a small average pore size, and almost no mesopores. When the ZIF material is grown on the polypyrrole network, the overall specific surface area decreases slightly, but the proportion of mesopores increases, the average pore size increases significantly, and the number of active sites that can serve as inorganic salt adsorption increases. The linkage between micropores and mesopores can accommodate more Cl - It can be seen that the Zn center can enlarge the pore size and effectively promote the formation of channels. Therefore, ZIF (Co: Zn = 3: 1) @ PPy has the advantages of large specific surface area and more suitable pore sizes as active sites. The specific surface area of ​​pure polypyrrole is very small, and the pore size is also very small, but the average pore size is the largest, which is speculated to have more mesopores and macropores.

[0097] Depend on Fig.12 It can be concluded that composite materials prepared from bimetallic materials of different proportions have different wettability, and the wettability is shown by the contact angle. The smaller the contact angle, the better the wettability. The mobile electrode materials provided in Examples 1-5 have suitable contact angles.

[0098] Depend on Fig.13 , Fig.14 It can be concluded that the EIS curves of all samples are composed of semicircles in the high-frequency region and oblique lines in the low-frequency region, which correspond to the charge transfer resistance and the ion transport process inside the material, respectively. The semicircle of PPy is almost invisible in the high-frequency region, which indicates that the charge transfer resistance inside PPy is negligible. The largest slope of the oblique line part also shows that the PPy material has the best electronic conductivity and the most convenient ion transport channel, and the slope of the composite material is significantly greater than that of the single ZIF material, further indicating that the conductivity of the composite material is optimized. Compared with AC and single ZIF, the intersection value of the high-frequency region of the EIS curve of the ZIF@PPy composite material with the true impedance axis is significantly smaller. This change also indicates a decrease in resistance. This is also consistent with Fig.14 The regularity of the resistivity of different materials in the composite material once again proves that the addition of PPy significantly improves the conductive properties of the composite material and the electron transfer rate within the material.

[0099] Table 3 Ratio of coordination bonds formed with Co / Zn metal center in materials prepared with different ratios of bimetal in Example 1

[0100]

[0101] In the composite material, considering the small difference in cation ion radius (Zn 2+ for Co 2+ for The unit particle sizes of ZIF(Zn) and ZIF(Co) are very similar. 2+ and Zn 2+ The different electronegativity and electron configuration between them distinguish the properties of Co-N bond and Zn-N bond. Fig.15 (a)- Fig.15 (i) and Table 3 show that the metal nitrogen stretching frequency MN of ZIF(Co) is blue-shifted compared to ZIF(Zn), while the peak of ZIF(Zn / Co) moves accordingly according to the Co / Zn ratio. Therefore, the connectivity of Co-N bonds is stronger than that of Zn-N bonds, resulting in a higher electronegativity of Co-N. 2+ The valence electrons of Zn may contribute to the formation of additional metal coordination bonds, thereby forming π bonds, while 2+Due to its 3d10 electronic configuration, it can only form σ bonds, so the 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. Combined with Table 2, this example selects ZIF(Co:Zn=3:1)@PPy as the optimal mobile electrode material.

[0102] The specific embodiment of the present invention also provides a flow electrode capacitive deionization (FCDI) device based on the modified membrane, such as Figure 2 and Figure 3 As shown, it includes an ion separation chamber 1, a cation exchange membrane 2, a modified anion exchange membrane 3, an anode graphite collector 4 and a cathode graphite collector 5.

[0103] The ion separation chamber 1 provided in a specific embodiment of the present invention is connected to the feed pool 7 through a circulation pipe 61, and the feed pool 7 transports a high-salt solution of 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 pool 7.

[0104] The cation exchange membrane 2 and the modified anion exchange membrane 3 provided in the specific embodiment of the present invention are relatively arranged on both 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 surface of the modified anion exchange membrane 3 is provided with a negatively charged layer 34, which is used to block the cephalosporin antibiotic organic anions, so that the cephalosporin antibiotic organic anions cannot pass through the modified anion exchange membrane 3, while the inorganic anions can pass through the modified anion exchange membrane 3 due to their smaller size to achieve separation.

[0105] In a specific embodiment, the method for preparing the modified anion exchange membrane 3 provided in the specific embodiment of the present invention comprises:

[0106] A dopamine solution with a concentration of 2 g / L was prepared, and a commercial anion exchange membrane was immersed in the above dopamine solution. At a rotation speed of 400 r / min, an anion exchange membrane with a polydopamine layer deposited thereon was obtained through a self-polymerization reaction. Then, a 1 wt % monomer solution of 2-acrylamidododecanesulfonic acid was prepared, and the above anion exchange membrane with a polydopamine intermediate layer deposited thereon was immersed in the negatively charged monomer solution. The Michael addition reaction was carried out at a rotation speed of 400 r / min for 120 min to obtain the negatively charged anion exchange membrane 3.

[0107] like Figure 4As shown in (c), the specific embodiment of the present invention obtains a modified anion exchange membrane 3 by modifying the surface of the anion exchange membrane, changing the pore size of the membrane and growing a negatively charged layer 34, which can change the hydrophilicity and lipophilicity of the surface of the anion exchange membrane and present electronegativity, and reduce the migration d of easily ionized organic matter (such as cephalosporin antibiotic anions e) under the action of the electric field force through the membrane through the charge repulsion force f. - b can pass through, thereby enhancing the separation effect of organic anions and inorganic ions.

[0108] The anode graphite collector 4 and the cathode graphite collector 5 provided in the specific embodiment of the present invention are connected to the fluid electrode slurry cavity 8 through the circulation pipe 62 and the circulation pipe 63 respectively, so that the fluid electrode slurry can circulate in the anode graphite collector 4 and the cathode graphite collector 5 respectively. The anode graphite collector 4 is arranged on the side of the cation exchange membrane 2 away from the ion separation chamber, and is used to capture inorganic positive ions. The cathode graphite collector 5 is arranged on the side of the modified anion exchange membrane 3 away from the ion separation chamber, and is used to capture inorganic negative ions. The corresponding inorganic positive ions and inorganic negative ions are captured by the fluid electrode slurry with positive or negative charge, and the inorganic positive ions and inorganic negative ions are bound by mesopores of suitable size, which can better realize the desalination of high-salt solutions of cephalosporin antibiotic organic matter with high stability.

[0109] In a specific embodiment, if Figure 4 As shown in (a), the anode graphite collector 4 and the cathode graphite collector 5 provided in this embodiment 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 respectively connected to the fluid electrode slurry cavity 8 through a circulation pipeline.

[0110] like Figure 4 As shown in (b), the fluid electrode slurry provided in this embodiment flows from the inlet channel B into the flow electrode channel A, where the corresponding inorganic positive and negative ions are adsorbed, and the fluid electrode slurry with the adsorbed positive and negative ions is output from the outlet channel C to the fluid electrode slurry cavity 8.

[0111] The two ends of the power supply provided in the specific embodiment of the present invention are respectively connected to the anode graphite collector 2 and the cathode graphite collector 3, and are used to supply power to the anode graphite collector 2 and the cathode graphite collector 3, so that the flowing electrode material slurry flowing into the anode graphite collector 2 and the cathode graphite collector 3 carries the corresponding positive charge or negative charge.

[0112] In a specific embodiment, the method for preparing the fluid electrode slurry provided in this embodiment includes:

[0113] 1.22 g of the mobile electrode material powder prepared in Example 1 was weighed and dispersed in 54.57 g of deionized water (the concentration in deionized water was (2 wt%)), 0.24 g of NaCl (0.4 wt%) was added as an electrolyte, and 4.87 g (7.6 wt%) of activated carbon was added to obtain a mobile electrode slurry. The mixture was stirred at a speed of 400 r / min for more than 24 h.

[0114] The modified membrane-based flowing electrode capacitive deionization system provided in a specific embodiment of the present invention also includes an anode membrane gasket 21, a modified cathode membrane gasket 31, a left fixed plate 91 and a right fixed plate 92, wherein the anode membrane gasket 21 is located between the ion separation chamber 1 and the cation exchange membrane 2, and the modified cathode membrane gasket 31 is located between the ion separation chamber 1 and the modified anion exchange membrane 3, and is respectively located on the outside of the left fixed plate 91 and the right fixed plate 92 through the left fixed plate 91 and the right fixed plate 92, for fixing the modified membrane flowing electrode capacitive deionization system.

[0115] like Figure 5 As shown, the operating principle of the device provided in the specific embodiment of the present invention for separating cephalosporin antibiotic organic matter from NaCl is as follows Figure 5 As shown, the flowing electrode slurry a runs along the flowing electrode channel B on the anode graphite collector 4 and the cathode graphite collector 5, and covers the corresponding anode graphite collector 4 and cathode graphite collector 5 respectively through the cation exchange membrane 2 and the modified anion exchange membrane 3, and is in full contact with the flowing electrode slurry a, and a certain voltage is applied at the same time. Under the action of this voltage, the anode graphite collector 4 and the cathode graphite collector 5 carry corresponding positive and negative charges, so the flowing electrode material aa carries the corresponding charges with the anode graphite collector 4 and the cathode graphite collector 5. When the Cl in the ion separation chamber 1 - b and Na + c is directed d through the modified anion exchange membrane 3 and the cation exchange membrane 2 under the electric field, and is embedded in the specific surface area formed in the micropores of the mobile electrode material aa under the action of the Faraday reaction, while the cephalosporin antibiotic anions e receive the electrostatic repulsion f of the negative charge layer on the modified cathode membrane and cannot be transferred across the membrane, and are forced to accumulate in the ion separation chamber 1, ultimately achieving the purpose of separation.

[0116] Application Example 1

[0117] This application example provides a flow electrode capacitive deionization system based on a modified membrane to separate and purify a high-salt solution containing cephalosporin antibiotics. The specific steps are as follows:

[0118] (1) The flowing electrode slurry in the fluid electrode slurry cavity 8 is driven by a peristaltic pump to be introduced into the anode graphite collector and the cathode graphite collector at a rate of 100 ml / min. The flowing electrode material in the flowing electrode slurry used in this application example is prepared by Example 1.

[0119] (2) A high-salt solution containing cephalosporin antibiotic organic matter is introduced into the ion separation chamber at a rate of 20 ml / min from the feed tank.

[0120] (3) Figure 5 As shown, the electric field generated by the constant voltage of the power supply drives the directional movement of anions and cations d, on the one hand, so that the flowing electrode material aa in the flowing electrode material slurry a of the anode graphite collector 5 will pass through the cation exchange membrane 3. + c capture, on the other hand, so that the flowing electrode material aa of the flowing electrode material slurry a in the cathode graphite current collector 4 will pass through the inorganic anion of the modified anion membrane 2, Cl - b is captured, while cephalosporin antibiotic organic matter is easily ionized into cephalosporin antibiotic anion e in water, and cephalosporin antibiotic anion e is repelled by electrostatic repulsion f and cannot pass through the modified cathode ion membrane 2, so as to realize the desalination of the high salt solution of cephalosporin antibiotic organic matter.

[0121] (4) The desalted cephalosporin antibiotics are transported back to the feed tank through the ion separation chamber.

[0122] like Fig. 9 (a) and Fig. 9 As shown in (b), in this application example, when the concentration of the mobile electrode material is 2.0wt%, the C of the cephalosporin antibiotic anion e with a starting concentration of 1mmol / L t / C0 can still be kept above 0.85, 0.2mol / L Cl - b of C t / C0 can be reduced to 0.67, such as Fig. 9 As shown in (c), the concentration of the mobile electrode material in this application example is 2.0wt%, and the separation factor is 7425.56. When the concentration is 2.5wt%, after 60 minutes of separation, the separation factor can reach 7757.21.

[0123] After 60 minutes of operation, the mobile electrode material prepared in Example 1 has a mass concentration of 2wt% as the most suitable ratio. The mass fraction of the mobile electrode material is increased from 0.5wt% to 2.0wt%, and it can be seen that the separation efficiency is significantly improved. Although the separation performance can still be improved after further increasing the mass concentration, the improved performance is not high, so it is still considered that the mass concentration of 2wt% is the most suitable ratio.

[0124] like Fig.11As shown in Table 4, the test was applied to the separation performance of high salt solution of different types of cephalosporin antibiotic organic matter (such as cefazolin sodium, cefoperazone sodium, ceftriaxone sodium, latamoxef sodium, cefuroxime sodium), and the physicochemical properties are shown in Table 4. After 60 minutes of operation, the cephalosporin antibiotic anion e and Cl can still be separated by this device. - b, and the separation factors all exceeded 7000.

[0125] Table 4 Physicochemical properties of organic anions of different types of cephalosporin antibiotics provided in Application Example 1

[0126]

[0127] The structural formulas of organic anions of different types of cephalosporin antibiotics are as follows: The structural formula of cefoperazone sodium provided in this embodiment is:

[0128]

[0129] The structural formula of ceftriaxone sodium provided in this embodiment is:

[0130]

[0131] The structural formula of latamoxef sodium provided in this embodiment is:

[0132] The structural formula of cefazolin sodium provided in this embodiment is:

[0133]

[0134] The structural formula of cefuroxime sodium provided in this embodiment is:

[0135]

[0136] From Table 4 and Fig.11 It can be concluded that this application example can be applied to the separation and purification of cephalosporin antibiotic organic matter with a molecular weight less than 1000 in a high salt solution.

[0137] Application Example 2-5

[0138] Different from Application Example 1, the flowing electrode materials prepared in Examples 2 to 5 are used as raw materials for the flowing electrode slurries used in Application Examples 1 to 5, respectively.

[0139] like Fig.10 (a)- Fig.10 As shown in (c), the separation effect of the flowing electrode material prepared by using Examples 1 to 5 is significantly better than that of the flowing electrode material prepared by Comparative Examples 1 to 3.

[0140] The above description of the embodiments in conjunction with the accompanying drawings is to facilitate those skilled in the art to understand and use the invention. However, the present invention is not limited to the above embodiments. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the methods described herein to other embodiments without creative work. Therefore, improvements and modifications made without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a capacitive desalination flow electrode material, characterized in that: include: (1) dispersing polypyrrole and polyvinyl pyrrolidone into a methanol solution containing zinc nitrate hexahydrate and / or cobalt nitrate hexahydrate, and stirring for the first time to obtain solution A; (2) adding 2-methylimidazole to methanol and stirring for a second time to obtain solution B, adding solution B dropwise to solution A and stirring for a third time to obtain a mixed solution, and allowing the mixed solution to stand, filter, wash, dry, and grind to obtain ZIF@PPy powder.

2. The method for preparing a capacitive desalination flow electrode material according to claim 1, characterized in that: The mass ratio of the zinc nitrate hexahydrate to the cobalt nitrate hexahydrate is 6.44-9.67:2.91-5.

82.

3. The method for preparing a capacitive desalination flow electrode material according to claim 1, characterized in that: The polypyrrole preparation method of step (1) comprises the following steps: Dissolve FeCl3 in methyl orange solution, stir evenly in a nitrogen environment to obtain a mixed solution, slowly drop the pyrrole monomer after rotary evaporation into the mixed solution, stir at room temperature for 12-24 hours, filter, wash, vacuum dry and grind to obtain polypyrrole.

4. The method for preparing the capacitive desalination flow electrode material according to claim 3, characterized in that: 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 is 200-400 mL.

5. The method for preparing a capacitive desalination flow electrode material according to claim 1, characterized in that: The mass ratio of the polyvinyl pyrrolidone to polypyrrole is 1:3-3:

1.

6. A capacitive desalination flow electrode material, characterized in that: The material is prepared by the method for preparing the capacitive desalination flow electrode material.

7. A FCDI device, characterized in that: include: An ion separation chamber, the ion separation chamber is connected to the feed pool, and is used to receive a high-salt solution of cephalosporin antibiotic organic matter from the feed pool, and input the desalted cephalosporin antibiotic solution into the feed pool; A cation exchange membrane and a modified anion exchange membrane, wherein the cation exchange membrane and the modified anion exchange membrane are arranged on both sides of the ion separation chamber, and a negatively charged layer is provided on the surface of the modified anion exchange membrane to block organic anions of cephalosporin antibiotics; An anode graphite collector and a cathode graphite collector, the anode graphite collector and the cathode graphite collector are respectively connected to the fluid electrode slurry cavity, so that the fluid electrode slurry can circulate in the anode graphite collector and the cathode graphite collector respectively, the anode graphite collector is arranged on the side of the cation exchange membrane away from the ion separation chamber, and is used to capture inorganic positive ions, and the cathode graphite collector is arranged on the side of the modified anion exchange membrane away from the ion separation chamber, and is used to capture inorganic negative ions, and the desalination of the high-salt solution of cephalosporin antibiotic organic matter is achieved by capturing inorganic positive ions and inorganic negative ions; A power supply, wherein two ends of the power supply are respectively connected to the anode graphite current collector and the cathode graphite current collector, and are used to supply power to the anode graphite current collector and the cathode graphite current collector; The fluid electrode slurry comprises sodium chloride, activated carbon and the capacitive desalination flow electrode material as claimed in claim 6.

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

9. The FCDI device according to claim 7, characterized in that The method for preparing the modified anion exchange membrane comprises: (1) cleaning the anion exchange membrane with NaOH solution, NaCl solution, and deionized water, and vacuum drying; (2) adding levodopamine to a tris(hydroxymethylformamide) buffer solution with a pH value of 7-9, stirring evenly to obtain a first mixed solution, and adding the anion exchange membrane obtained in step (1) to the first mixed solution, thereby coating a dopamine layer on the anion exchange membrane; (3) Adding the 2-acrylamidododecanesulfonic acid solution to the anion exchange membrane with a dopamine layer on the surface obtained in step (2), stirring and mixing, and forming a negatively charged layer on the anion exchange membrane through Michael addition reaction to obtain a modified anion exchange membrane.

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

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