Flow-through capacitive deionization device for removal of cobalt ions using coated composite materials

Abstract

The present invention discloses a flow-through capacitor deionization device for removing cobalt ions by using a coated composite material, comprising an upper end plate, an upper gasket, an upper current collecting plate, an upper insulating gasket, a PTFE diaphragm, a lower insulating gasket, a lower current collecting plate, a lower gasket and a lower end plate which are stacked in sequence; a water outlet chamber is formed between the upper end plate, the upper gasket and the upper current collecting plate, and a water inlet chamber is formed between the lower current collecting plate, the lower gasket and the lower end plate; a water inlet is provided on the lower end plate, and a water outlet is provided on the upper end plate. The present invention changes the water inlet direction of the traditional capacitor deionization system, so that the water flows vertically through the positive and negative current collecting plates, the porous cathode current collecting plate is connected to the negative electrode of the external power supply, and the activated carbon coated porous current collecting plate as the anode is connected to the positive electrode to form an electric field in the capacitor deionization component, assisting the cathode material in capturing the target charged body, strengthening the system ion removal effect, and improving the effective utilization rate of the electrode material.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a flow-through capacitor deionization device for removing cobalt ions by utilizing a coated composite material. Background Art

[0002] Heavy metal pollution is one of the current global environmental problems. As an important transition metal material, cobalt is widely used in industries such as ternary batteries, cemented carbide, glass, pigments, and electroplating, and a large amount of cobalt-containing wastewater is produced. The direct discharge of untreated cobalt wastewater not only causes a waste of industrial resources, but also the excessive heavy metal ions in the environment will accumulate in organisms and cause a variety of diseases. Therefore, the effective treatment of wastewater containing cobalt ions becomes very important.

[0003] Traditional cobalt ion wastewater treatment methods include chemical precipitation, ion exchange resin, adsorption, and biological methods. The process is complicated and requires the addition of multiple reaction reagents, which is inefficient and costly. Therefore, it is of great significance to develop a high-efficiency, low-cost cobalt ion wastewater treatment process. Summary of the invention

[0004] Based on the above technical problems, the present invention provides a flow-through capacitive deionization device that utilizes a coated composite material to remove cobalt ions, thereby solving the problems of low removal efficiency, slow migration and diffusion speed, and easy detachment of electrode materials in the existing cobalt ion wastewater treatment technology.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A flow-through capacitive deionization device for removing cobalt ions using a coated composite material comprises an upper end plate, an upper gasket, an upper current collecting plate, an upper insulating gasket, a PTFE diaphragm, a lower insulating gasket, a lower current collecting plate, a lower gasket and a lower end plate which are stacked in sequence;

[0007] A water outlet chamber is formed between the upper end plate, the upper gasket and the upper current collecting plate, and a water inlet chamber is formed between the lower current collecting plate, the lower gasket and the lower end plate; a water inlet is provided on the lower end plate, and a water outlet is provided on the upper end plate;

[0008] The upper current collecting plate and the lower current collecting plate are both porous titanium plates;

[0009] The upper current collecting plate is located on one side of the PTFE diaphragm and is coated with a positive electrode material coating, wherein the positive electrode material is conductive activated carbon;

[0010] The lower current collecting plate is located on one side of the PTFE diaphragm and is coated with a negative electrode material coating, wherein the negative electrode material is a composite material formed by ZIF-67 coated with rod-shaped MnO2 powder;

[0011] The upper current collecting plate and the lower current collecting plate are respectively connected to the positive and negative electrodes of the power source.

[0012] The present invention also discloses a flow-through capacitive deionization device for removing cobalt ions using a coated composite material. In addition to the device described above, the device also includes a power supply, a conductivity meter, a water storage container for storing a solution to be treated, and a peristaltic pump; the water outlet of the upper end plate is connected to the water storage container, the water inlet of the lower end plate is connected to the peristaltic pump, and the peristaltic pump is connected to the water storage container.

[0013] Preferably, an ultrafiltration membrane is provided between the lower collecting plate and the lower end plate.

[0014] Preferably, the diameter of the holes on the titanium plate is 200-500 um; the thickness of the titanium plate is 0.4-0.7 mm.

[0015] Preferably, the positive electrode material coating preparation method is:

[0016] Step 1, after activating PVDF powder at 60-70° C. for 36-48 hours, disperse it in DMF, heat and stir at 70-80° C. for 30-60 minutes to obtain a colloidal solution;

[0017] Step 2, mixing the colloidal solution of step 1 with activated carbon, acetylene black and PVDF to obtain a uniform activated carbon mixed slurry; the mass ratio of the activated carbon, acetylene black and PVDF is 8:1:1;

[0018] Step 3, brushing the mixed slurry obtained in step 2 onto the current collecting plate, drying at 40-60° C. for 4-8 hours, and then soaking in deionized water for 12-15 hours. After drying, a positive electrode material coating is formed on the current collecting plate.

[0019] Preferably, the negative electrode material coating preparation method is:

[0020] Step 1, mixing MnSO4 solution, KMnO4 solution and polyvinyl pyrrolidone to obtain a mixed solution; the mass ratio of MnSO4, KMnO4 and polyvinyl pyrrolidone is 2.5:1.5-1.6:1;

[0021] Step 2, reacting the mixed solution in a reactor at 120-140° C. for 2-3 hours, cooling to room temperature to obtain a solid, washing, drying, and grinding the obtained solid to obtain a rod-shaped MnO2 powder, recorded as MO;

[0022] Step 3, dispersing the MO obtained in step 2 in methanol, and then adding cobalt nitrate hexahydrate; then adding a methanol solution of 2-methylimidazole under stirring, stirring for 10 to 12 hours, and centrifuging to obtain a precipitate;

[0023] Step 4, washing the precipitate obtained in step 3, drying, and grinding to obtain a MOF-encapsulated composite pseudocapacitor material, recorded as MO@ZIF-67;

[0024] Step 5, after activating the PVDF powder at 60-70° C. for 36-48 hours, dispersing the powder in DMF, heating and stirring at 70-80° C. for 30-60 minutes to obtain a colloidal solution;

[0025] Step 6, mixing the colloidal solution of step 5 with the MO@ZIF-67, acetylene black and PVDF of step 4 to obtain a uniform mixed slurry; the mass ratio of the activated carbon, acetylene black and PVDF is 8:1:1;

[0026] Step 7, brushing the mixed slurry of step 6 on the current collecting plate, drying at 40-60° C. for 4-8 hours, and then soaking in deionized water for 12-15 hours. After drying, a negative electrode material coating is formed on the current collecting plate.

[0027] Preferably, the coating amount of the positive electrode material coating on the upper current collector is 2-5 mg / cm according to the activated carbon content on the upper current collector. 2 Apply the coating.

[0028] Preferably, the coating amount of the negative electrode material coating on the lower current collector is about 2 to 5 mg / cm according to the content of MO@ZIF-67 on the lower current collector. 2 Apply the coating.

[0029] Preferably, the distance between the upper current collecting plate and the lower current collecting plate is 1 to 3 mm.

[0030] Preferably, the power supply is a tributary pulse power supply.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention changes the water inlet direction of the traditional capacitor deionization system, so that the water flows vertically through the positive and negative current collectors, the porous cathode current collector is connected to the negative electrode of the external power supply, and the activated carbon coated porous current collector as the anode is connected to the positive electrode to form an electric field in the capacitor deionization component, assisting the cathode material to capture the target charged body, strengthening the system ion removal effect, and improving the effective utilization rate of the electrode material; the water flow parallel to the electric field direction increases the migration speed of the charged body toward the electrode direction, and at the same time slows down the impact of the water flow on the side of the electrode material, improves the electrode stability, and stabilizes the system operation effect. In addition, the present invention utilizes the pseudocapacitor characteristics of the MOF-coated composite material. Under the action of the electric field, the cobalt ions move toward the electrode plate and react electrochemically with the composite electrode material, thereby achieving the purpose of removing cobalt ions from wastewater.

[0033] In addition, the present invention also has the following advantages:

[0034] (2) The water inlet and outlet of the device of the present invention are respectively provided with water storage chambers, which have a certain water distribution effect, and an ultrafiltration membrane is added between the water inlet and water storage chambers and the electrode plates to improve the uniformity of the water distribution of the system and pre-screen the raw water, thereby ensuring the stability of the system operation;

[0035] (3) A PTFE diaphragm is added in the middle of the device of the present invention to ensure water flux while preventing short circuit;

[0036] (4) The upper and lower current collecting plates of the present invention are made of titanium foil, which has improved electrode stability compared with carbon plates, and can be replaced with different electrode materials after multiple cleanings, and has good recyclability; a number of uniform columnar holes are reserved on the current collecting plates for the treated liquid to pass through, effectively ensuring the water flow rate;

[0037] (5) The MOF-coated composite material of the present invention retains the pseudocapacitive properties of the material. At the same time, during the cyclic capacitive deionization process, the porous MOF layer reduces the effect of the volume change of the active electrode material on the electrode stability, alleviating the cracking problem to a certain extent;

[0038] (6) The external power supply of the present invention is a pulse power supply, which provides a reverse electric field for the capacitive deionization process at intervals. Compared with the continuous electric field of the DC power supply, it can alleviate the concentration polarization near the electrode plate and weaken the adverse effects caused by excessive pH changes;

[0039] (7) The present invention can set the number of capacitor deionization units in series and parallel, adjust the electric field strength and pulse electric field frequency according to the raw water volume and water quality, and effectively control the processing capacity;

[0040] (8) The device provided by the present invention also has the advantages of easy operation, simple structure, compact unit and small footprint. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the structure of the flow-through capacitive deionization device described in Example 1 of the present invention.

[0042] Figure 2 It is a schematic diagram of the structure of the flow-through capacitive deionization device described in Example 2 of the present invention.

[0043] Figure 3 It is a schematic structural diagram of an upper current collecting plate (a) and a lower current collecting plate (b) of a flow-through capacitive deionization device of the present invention.

[0044] Figure 4 It is a microscopic morphology picture of rod-shaped MnO2 powder prepared by the negative electrode material coating preparation method of the present invention.

[0045] The meaning of the symbols in the figure:

[0046] 1-upper end plate, 2-upper gasket, 3-upper current collecting plate, 4-upper insulating gasket, 5-PTFE diaphragm, 6-lower insulating gasket, 7-lower current collecting plate, 8-ultrafiltration membrane, 9-lower gasket, 10-lower end plate, 11-power supply, 12-conductivity meter, 13-water storage container, 14-peristaltic pump. DETAILED DESCRIPTION

[0047] The migration and diffusion of ions to the electrodes is an important part of the ion removal process. In addition to adjusting the operating parameters and modifying the electrode materials, changing the fluid state in the flow channel is also an important way to increase the migration and diffusion speed of ions. In a flow-through capacitive deionization system, the direction of ion migration is parallel to the flow direction of the solution. When the solution passes through the electrode plate vertically, the cations and anions are attracted and bound to the electrodes with opposite charges, weakening the lateral impact of the water flow on the electrode material, improving the stability of the electrode plate, and achieving the purpose of desalination or separation of target ions. At the same time, by utilizing the pseudocapacitive properties of the MOF-coated composite material, under the action of the electric field, the cobalt ions move toward the electrode plate and undergo an electrochemical reaction with the composite electrode material, thereby achieving the purpose of removing cobalt ions from wastewater. Based on the above principles, the present invention proposes a flow-through capacitive deionization device that uses a coated composite material to remove cobalt ions.

[0048] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0049] In the description of the present invention, unless otherwise clearly specified and limited, the terms such as "set" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a direct connection or an indirect connection, etc. For ordinary technicians in this field, the specific meanings of the above terms in this technical solution can be understood according to the specific circumstances. In the absence of any contrary instructions, the directional words used, such as "upper, lower, bottom, top", are generally defined based on the drawings of the corresponding drawings, and "inside and outside" are defined based on the outline of the corresponding drawings.

[0050] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, or product that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or equipment.

[0051] Example 1

[0052] The present embodiment discloses a flow-through capacitive deionization device for removing cobalt ions using a coated composite material, such as Figure 1 As shown, the device includes an upper end plate 1, an upper gasket 2, an upper current collecting plate 3, an upper insulating gasket 4, a PTFE diaphragm 5, a lower insulating gasket 6, a lower current collecting plate 7, a lower gasket 9 and a lower end plate 10 which are stacked in sequence.

[0053] The upper and lower gaskets 2 and 9 are made of silicone and are used to seal the water storage chamber; the PTFE diaphragm 5 is used to prevent short circuits while allowing ions to pass through; the upper and lower insulating washers 4 and 6 are used to fix the spacing between the upper and lower current collecting plates 3 and 7. The spacing between the upper and lower current collecting plates 3 and 7 is 1 to 3 mm. If the spacing is too close, short circuits are likely to occur, which is not conducive to the capacitor deionization process; if the spacing is too far, the ion movement distance increases and the removal effect decreases. The upper and lower gaskets 2 and 9, the upper and lower insulating washers 4 and 6 are all hollow structures, and the upper end plate 1 and the lower end plate 10 are both made of organic glass.

[0054] A water outlet chamber is formed between the upper end plate 1, the upper gasket 2, and the upper current collecting plate 3, and a water inlet chamber is formed between the lower current collecting plate 7, the lower gasket 9, and the lower end plate 10. Specifically, a groove is provided on one side of the upper end plate 1 and the lower end plate 10, and after the lower current collecting plate 7 and the upper current collecting plate 3 are connected to the lower end plate 10 and the upper end plate 1, a water inlet chamber and a water outlet chamber are formed between them, and the function of the water inlet chamber is to evenly replenish water, and the function of the water outlet chamber is to stabilize water discharge.

[0055] The lower end plate 10 is provided with a water inlet, and the upper end plate 1 is provided with a water outlet, which are connected to the water storage container via a water inlet pipe and a water outlet pipe. The water inlet direction is from bottom to top, so that the chamber is easily filled with water to maintain the stable operation of the system.

[0056] The upper collector plate 3 and the lower collector plate 7 are both porous titanium plates. Compared with carbon plates, the electrode stability is improved, and different electrode materials can be replaced after multiple cleanings, and the recycling is good; the porous structure on the titanium plate allows the treated liquid to pass through, effectively ensuring the water flow rate. The diameter of the holes on the titanium plate of this embodiment is 200-500um; the thickness of the titanium plate is 0.4-0.7mm.

[0057] A positive electrode material coating is coated on one side of the upper current collecting plate 3 located at the PTFE diaphragm 5, and the positive electrode material is conductive activated carbon. Specifically, the positive electrode material coating is prepared by:

[0058] Step 1, weigh 250 mg of PVDF powder, activate it at 60°C for 48 hours, disperse it in 10 mL of DMF, heat and stir at 80°C for 30 minutes to obtain a uniform colloidal solution;

[0059] Step 2, take 2 mL of the solution prepared in step 1, add 80% activated carbon, 10% acetylene black and 10% PVDF in a small glass bottle, mix and stir for 24 hours to obtain a uniform activated carbon mixed slurry;

[0060] Step 3: evenly brush the mixed slurry obtained in step 2 onto the collector plate, where the activated carbon content is about 2-5 mg / cm 2 , dried at 60°C for 4h;

[0061] Step 4, soaking the coated electrode plate obtained in step 3 in deionized water for 12 hours, and drying at room temperature to obtain a current collector coated with a conductive activated carbon coating.

[0062] A negative electrode material coating is coated on one side of the lower current collecting plate 7 located at the PTFE diaphragm 5. The negative electrode material is a composite material formed by ZIF-67 coated with rod-shaped MnO2 powder. The specific preparation method is as follows:

[0063] Step 1, weigh 2.535 g of MnSO4 and dissolve it in 20 mL of deionized water, which is referred to as solution A; weigh 1.58 g of KMnO4 and dissolve it in 50 mL of deionized water, which is referred to as solution B; mix solution A and solution B under continuous stirring, and add 1 g of polyvinyl pyrrolidone to the mixed solution to obtain a mixed solution;

[0064] Step 2, after the liquid is mixed evenly, it is transferred into a polytetrafluoroethylene reactor, reacted at 140°C for 2 hours, cooled to room temperature and centrifuged to obtain a brown-black solid; after cross-cleaning with deionized water and anhydrous ethanol for at least three times, it is dried in a vacuum drying oven at 60°C for 24 hours; the brown-black solid is ground with an agate mortar to obtain a rod-shaped MnO2 powder, recorded as MO; Figure 4 Shown is the morphology of rod-shaped MnO2 powder.

[0065] Step 3, weigh 0.18g of MO prepared in step 2, and ultrasonically disperse it in 20mL of methanol; weigh 0.2910g of cobalt nitrate hexahydrate and add it to the above solution, and stir it magnetically for 2h, which is recorded as solution C; weigh 0.4926g of 2-methylimidazole and dissolve it in 20mL of methanol, which is recorded as solution D; mix solution C and solution D under magnetic stirring, maintain 300r / min, and stir for 10h; centrifuge to obtain a precipitate;

[0066] Step 4, washing the precipitate obtained in step 3 with methanol, drying at 60° C. for 6 h, and grinding the solid with an agate mortar to obtain a MOF-encapsulated composite pseudocapacitor material, recorded as MO@ZIF-67;

[0067] Step 5, weigh 250 mg of PVDF powder, activate it at 60° C. for 48 hours, disperse it in 10 mL of DMF, heat and stir at 80° C. for 30 minutes to obtain a uniform colloidal solution;

[0068] Step 6, take 2 mL of the colloidal solution of step 5, add 80% of the MO@ZIF-67 obtained in step 4, 10% of acetylene black and 10% of PVDF in a small glass bottle, mix and stir for 24 hours to obtain a uniform mixed slurry;

[0069] Step 7: Apply the mixed slurry of step 6 on the collector plate, where the content of MO@ZIF-67 on the collector plate is about 2-5 mg / cm 2 , dried at 60°C for 4 hours; then immersed in deionized water for 12 to 15 hours, and dried at room temperature to form a negative electrode material coating on the current collecting plate.

[0070] Preferably, an ultrafiltration membrane 8 is provided between the lower current collecting plate 7 and the lower end plate 10, which improves the uniformity of water distribution in the system and pre-screens the raw water, thereby ensuring the stability of system operation. The ultrafiltration membrane 8 of this embodiment is a polysulfone ultrafiltration membrane, a PVDF ultrafiltration membrane or a PS ultrafiltration membrane, preferably a polysulfone ultrafiltration membrane.

[0071] The power supply 11 of this embodiment is a DC pulse power supply, which provides a reverse electric field for the capacitive deionization process at intervals. Compared with the continuous electric field of the DC power supply, it can alleviate the concentration polarization near the electrode plate and weaken the adverse effects caused by excessive pH changes.

[0072] Bolt holes are arranged around the upper end plate 1, the upper gasket 2, the upper current collecting plate 3, the upper insulating gasket 4, the PTFE diaphragm 5, the lower insulating gasket 6, the lower current collecting plate 7, the ultrafiltration membrane 8, the lower gasket 9 and the lower end plate 10. The bolt holes are located in corresponding positions and are equal in size, and are fixed as a whole by bolts.

[0073] The above structure of this embodiment forms a group of capacitor deionization units. The present invention can set the number of capacitor deionization units in series and parallel, adjust the electric field strength and pulse electric field frequency according to the raw water volume and water quality, and effectively control the processing capacity.

[0074] Example 2

[0075] This embodiment discloses a flow-through capacitive deionization device that utilizes a coated composite material to remove cobalt ions. Figure 2 As shown, the device includes a group of capacitive deionization units described in the embodiment, a power supply 11, a conductivity meter 12, a water storage container 13 for storing a solution to be treated, and a peristaltic pump 14.

[0076] The conductivity meter 12 is inserted into the water storage container 13 to monitor the water quality of the system in a timely manner. The peristaltic pump 14 is used to control the water flow rate and provide power for the water to flow through the capacitive deionization device.

[0077] The water outlet of the upper end plate 1 is connected to the water storage container 13 , the water inlet of the lower end plate 10 is connected to the peristaltic pump 14 , and the peristaltic pump 14 is connected to the water storage container 13 .

[0078] Example 3

[0079] This embodiment discloses a method for removing cobalt ions from water using the flow-through capacitive deionization device described in the above embodiment, which specifically includes the following steps:

[0080] Step 1, placing wastewater containing cobalt ions in a water storage container 13, and adjusting the pH value to 4-5;

[0081] Step 2, connect the upper current collecting plate 3 to the positive electrode of the power supply, and connect the lower current collecting plate 7 to the negative electrode of the power supply with a wire;

[0082] Step 3, using a peristaltic pump 14 to pump the wastewater in the water storage container 13 into the assembled device at a flow rate of 20 mL / min;

[0083] Step 4, adjust the power supply voltage to 1.2V, set the conductivity meter to measure the conductivity, measure once every 30s, the reverse pulse voltage is 3V, the pulse interval time is 5min, the pulse duration is 5s, sample once every 10min, and measure the cobalt ion concentration.

[0084] Step 5, when the conductivity data tends to be stable, remove the upper and lower current collecting plates, put them into deionized water, connect the two current collecting plates with a wire, and short-circuit desorption;

[0085] Step 6, discharge the solution treated in step 5 into the water storage container 13, collect and treat it, and then discharge it.

[0086] Material adsorption capacity (SAC, mg g -1 ) is calculated as follows:

[0087]

[0088] Where C0 and V are the initial solution of cobalt chloride solution (mg·L -1 ) and volume (L); m (g) represents the mass of active components of the current collecting plate electrode in the device (the mass of the titanium plate is 1.5 g); C t (mg·L -1 ) is the cobalt ion concentration at t(min).

[0089] The following Examples 4 to 8 show the changes in the concentration of cobalt ions before and after the treatment according to the steps of Example 3. The difference between Examples 4 to 8 and Example 3 is that the initial concentration of cobalt ions in the wastewater is different.

[0090] Table 1 Cobalt ion treatment effects at different initial concentrations

[0091]

[0092] It can be seen from the data in Table 1 that solutions containing cobalt ions of different concentrations can be pumped at a flow rate of 20 mL min using the method of the present invention. -1 (The wastewater volume at this flow rate is 500 mL) After 2 hours of treatment, the concentration of cobalt ions can be significantly reduced, but when the cobalt ion concentration is too high (greater than 40 mg·L -1 ), the adsorption capacity did not increase significantly, indicating that when using MOF-encapsulated composite pseudocapacitive materials as electrical adsorption materials, it is necessary to select an appropriate treatment load (80 mg·g -1 ) to ensure the circulation operation of the system.

[0093] Example 9

[0094] The flow-through capacitive deionization device of this embodiment is the same as that of embodiment 2, and the method for removing cobalt ions from water is the same as that of embodiment 3. The influent water has a cobalt ion concentration of 40 mg L -1 The cobalt chloride solution was run for 2 h, and the MO@ZIF-67 content on the cathode current collector was 3.07 mg / cm 2 , the effective area of ​​a single collector plate is 16cm 2 , flow rate is 20mL·min -1 , working voltage 1.2V, reverse pulse voltage 3V, pulse interval time 10s.

[0095] After running for a period of time, the test found that the cobalt ion removal capacity of the device in this embodiment was 82.48 mg·g -1 .

[0096] Example 10

[0097] The water inlet parameters of this embodiment are the same as those of embodiment 9, except that: this embodiment is a conventional flow-through capacitive deionization device, and the MO@ZIF-67 content of the cathode current collector is 4.01 mg / cm 2 , the effective area of ​​a single collector plate is 16cm 2 , no pulsed electric field was applied.

[0098] After running for a period of time, the cobalt ion removal capacity was 74.70 mg g -1 .

[0099] It can be seen from Example 9 and Example 10 that the flow-through capacitive deionization system device of the present invention can enhance the ion removal effect and improve the effective utilization rate of electrode materials.

[0100] Embodiment 11

[0101] The water inlet parameters of this embodiment are the same as those of embodiment 9, except that no DC pulse electric field is applied. The MO@ZIF-67 content of the cathode current collector is 3.76 mg / cm 2 .

[0102] After running for a period of time, the cobalt ion removal capacity was 79.94 mg g -1 .

[0103] It can be seen from Examples 9 and 11 that the application of a DC pulse electric field in the present invention can alleviate the ion concentration polarization on the surface of the collector plate electrode material, and improve the ability of the flow-through capacitive deionization system to remove cobalt ions to a certain extent.

[0104] Example 12

[0105] The water inlet parameters of this embodiment are the same as those of embodiment 9, except that: the negative electrode of the current collector is coated with activated carbon, and the activated carbon content of the negative current collector is 4.79 mg / cm 2 .

[0106] After running for a period of time, the cobalt ion removal capacity was 10.93 mg g -1 .

[0107] It can be seen from Examples 9 and 12 that the coated composite material of the present invention can significantly improve the effect of removing cobalt ions.

Claims

1. A flow-through capacitive deionization device for removing cobalt ions using a coated composite material, characterized in that: It comprises an upper end plate (1), an upper gasket (2), an upper current collecting plate (3), an upper insulating gasket (4), a PTFE diaphragm (5), a lower insulating gasket (6), a lower current collecting plate (7), a lower gasket (9) and a lower end plate (10) which are stacked in sequence; A water outlet chamber is formed between the upper end plate (1), the upper gasket (2) and the upper current collecting plate (3), and a water inlet chamber is formed between the lower current collecting plate (7), the lower gasket (9) and the lower end plate (10); a water inlet is provided on the lower end plate (10), and a water outlet is provided on the upper end plate (1); The upper current collecting plate (3) and the lower current collecting plate (7) are both porous titanium plates; The upper current collecting plate (3) is located on one side of the PTFE diaphragm (5) and is coated with a positive electrode material coating, wherein the positive electrode material is conductive activated carbon; The lower current collecting plate (7) is located on one side of the PTFE diaphragm (5) and is coated with a negative electrode material coating, wherein the negative electrode material is a composite material formed by ZIF-67 coated with rod-shaped MnO2 powder; The upper current collecting plate (3) and the lower current collecting plate (7) are respectively connected to the positive and negative electrodes of a power source (11); An ultrafiltration membrane (8) is provided between the lower current collecting plate (7) and the lower end plate (10); The negative electrode material coating preparation method is: Step 1, mixing MnSO4 solution, KMnO4 solution and polyvinyl pyrrolidone to obtain a mixed solution; the mass ratio of MnSO4, KMnO4 and polyvinyl pyrrolidone is 2.5:1.5-1.6:1; Step 2, reacting the mixed solution in a reactor at 120-140° C. for 2-3 hours, cooling to room temperature to obtain a solid, washing, drying, and grinding the obtained solid to obtain a rod-shaped MnO2 powder, recorded as MO; Step 3, dispersing the MO obtained in step 2 in methanol, and then adding cobalt nitrate hexahydrate; then adding a methanol solution of 2-methylimidazole under stirring, stirring for 10 to 12 hours, and centrifuging to obtain a precipitate; Step 4, washing the precipitate obtained in step 3, drying, and grinding to obtain a MOF-encapsulated composite pseudocapacitor material, recorded as MO@ZIF-67; Step 5, after activating the PVDF powder at 60-70° C. for 36-48 hours, dispersing the powder in DMF, heating and stirring at 70-80° C. for 30-60 minutes, to obtain a colloidal solution; Step 6, mixing the colloidal solution of step 5 with the MO@ZIF-67, acetylene black and PVDF of step 4 to obtain a uniform mixed slurry; the mass ratio of the MO@ZIF-67, acetylene black and PVDF is 8:1:1; Step 7, brushing the mixed slurry of step 6 on the current collecting plate, drying at 40-60° C. for 4-8 hours, and then soaking in deionized water for 12-15 hours. After drying, a negative electrode material coating is formed on the current collecting plate.

2. The flow-through capacitive deionization device for removing cobalt ions using a coated composite material as claimed in claim 1, characterized in that: It comprises a power supply (11), a conductivity meter (12), a water storage container (13) for storing a solution to be treated, and a peristaltic pump (14); The water outlet of the upper end plate (1) is connected to the water storage container (13), the water inlet of the lower end plate (10) is connected to the peristaltic pump (14), and the peristaltic pump (14) is connected to the water storage container (13).

3. The flow-through capacitive deionization device for removing cobalt ions using a coated composite material as claimed in claim 1 or 2, characterized in that: The diameter of the holes on the titanium plate is 200-500um; the thickness of the titanium plate is 0.4-0.7mm.

4. The flow-through capacitive deionization device for removing cobalt ions using a coated composite material as claimed in claim 1 or 2, characterized in that: The positive electrode material coating preparation method is: Step 1, after activating PVDF powder at 60-70°C for 36-48h, disperse it in DMF, heat and stir at 70-80°C for 30-60min to obtain a colloidal solution; Step 2, mixing the colloidal solution of step 1 with activated carbon, acetylene black and PVDF to obtain a uniform activated carbon mixed slurry; the mass ratio of the activated carbon, acetylene black and PVDF is 8:1:1; Step 3, brushing the mixed slurry obtained in step 2 onto the current collecting plate, drying at 40-60° C. for 4-8 hours, and then soaking in deionized water for 12-15 hours. After drying, a positive electrode material coating is formed on the current collecting plate.

5. The flow-through capacitive deionization device for removing cobalt ions using a coated composite material as claimed in claim 1 or 2, characterized in that: The coating amount of the positive electrode material coating on the upper current collecting plate (3) is 2-5 mg / cm according to the activated carbon content on the upper current collecting plate (3). 2 Apply the coating.

6. The flow-through capacitive deionization device for removing cobalt ions using a coated composite material as claimed in claim 1 or 2, characterized in that: The coating amount of the negative electrode material coating on the lower current collecting plate (7) is 2-5 mg / cm according to the content of MO@ZIF-67 on the lower current collecting plate (7). 2 Apply the coating.

7. The flow-through capacitive deionization device for removing cobalt ions using a coated composite material as claimed in claim 1 or 2, characterized in that: The distance between the upper current collecting plate (3) and the lower current collecting plate (7) is 1 to 3 mm.

8. The flow-through capacitive deionization device for removing cobalt ions using a coated composite material as claimed in claim 1 or 2, characterized in that: The power supply (11) is a direct current pulse power supply.

Images