An electrode integrated unit, a multi-stage capacitive desalination device and a wastewater desalination system

Abstract

The application discloses an electrode integrated unit, which comprises a first positive electrode plate, a second positive electrode plate, a first negative electrode plate and a second negative electrode plate, the four electrode plates are arranged at the top, the bottom and the two side portions respectively, and are sequentially connected in a head-tail mode to form a square structure with a cavity in the interior, one end of the square structure is a water inlet side, and the other end is a water outlet side; two adjacent electrode plates are separated by an insulating gasket; the four electrode plates each comprise, from the outside to the inside, an insulating end plate, an outer silica gel gasket, a current collector plate, a modified electrode material layer, an activated carbon fiber layer and an inner silica gel gasket layer. The electrode integrated unit is further used for constructing a multi-stage capacitive desalination device and a wastewater desalination system; the contact area of wastewater and the capacitive module can be effectively increased, and the desalination efficiency of saline water is effectively improved in combination with the modified composite material and the water flow buffering arrangement; the process is short and compact, the operation is convenient and flexible, the treatment efficiency is high, the energy consumption is low, and the process is suitable for popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to an electrode integrated unit, a multi-stage capacitor desalination device, and a wastewater desalination system. Background Technology

[0002] Capacitive adsorption desalination (CDI) is a novel water treatment technology. It involves applying a voltage to two electrode plates, creating an electric field between them. When a salt-containing solution flows through the channel between the plates, it is adsorbed onto the plates by the electric field. Once adsorption saturation is reached, desorption is achieved by cutting off the power supply, short-circuiting, or reversing the voltage, causing the adsorbed ions to fall back into the solution. This allows the capacitive adsorption desalination module to be reused. Due to its advantages of low energy consumption, low cost, simple operation, high treatment efficiency, and environmental friendliness, capacitive adsorption desalination technology can be widely used in electronics, chemistry, and manufacturing industries.

[0003] Electrode materials are a key factor affecting the desalination performance and energy consumption of CDI systems. Generally, metal oxide electrode materials exhibit higher pseudocapacitive performance than carbon-based double-layer capacitors. However, metal oxides suffer from complex preparation, high cost, and significant environmental impact, hindering large-scale commercial applications. Therefore, CDI electrodes are typically made of porous carbon materials with high specific surface area and excellent conductivity. Currently reported high specific surface area carbon electrodes include carbon aerogel (CAS), activated carbon (AC), activated carbon fiber (ACF), carbon nanotubes (CNT), mesoporous carbon (OMC), carbon nanofibers, and graphene, but most suffer from high precursor costs, complex and time-consuming preparation processes, hindering large-scale production. Furthermore, the relatively low adsorption performance of single-component carbon materials limits the large-scale application of CDI. Summary of the Invention

[0004] The main objective of this invention is to provide an electrode integrated unit, a multi-stage capacitor desalination device, and a wastewater desalination system. The desalination process is short and compact, easy and flexible to operate, has high processing efficiency and low energy consumption, and is especially suitable for the resource utilization of saline-alkali water and other harsh environments.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An electrode integration unit includes a first positive electrode plate, a second positive electrode plate, a first negative electrode plate, and a second negative electrode plate. The four electrode plates are respectively disposed on the top, bottom, and sides, and are connected end to end to form a square structure with an internal cavity. One end of the square structure is the water inlet side, and the other end is the water outlet side. Adjacent electrode plates are separated by insulating gaskets.

[0007] The four electrode plates have the same structure, each including, from the outside to the inside, an insulating end plate, an outer silicone pad, a current collector plate, a modified electrode material layer, an activated carbon fiber layer, and an inner silicone pad layer; an electrode wiring port is provided on one end face of the current collector plate, and the electrode wiring port is connected to the power supply device through a wire.

[0008] Preferably, the modified electrode material layer and activated carbon fiber layer are prepared by processes such as slurry preparation, coating, and curing to form a modified activated carbon / activated carbon fiber composite layer. Specific steps include: using modified activated carbon, conductive carbon black, binder, and organic solvent as main raw materials, slurry preparation is performed; the obtained modified activated carbon slurry is coated (on a current collector), then covered with activated carbon fibers, and cured to obtain the modified activated carbon / activated carbon fiber composite layer; the modified activated carbon is obtained by mixing water with a strong alkali and activated carbon powder evenly, allowing it to react statically; filtering and drying, then high-temperature activation under a protective atmosphere, and naturally cooling to room temperature; acid washing, water washing until neutral; drying, and sieving (200 mesh) to obtain the final product.

[0009] In the above scheme, the slurry preparation step includes: dissolving modified activated carbon, conductive carbon black and binder in an organic solvent and stirring to obtain electrode slurry.

[0010] In the above scheme, the stirring treatment (magnetic stirring) time is 4 to 6 hours.

[0011] In the above scheme, the curing step includes: curing at room temperature for 20 to 24 hours.

[0012] Furthermore, the mass ratio of the modified activated carbon, conductive carbon black, and binder is 1::8~8.5:0.5~1.

[0013] Furthermore, the mass ratio of the modified activated carbon to activated carbon fiber is 0.5 to 1.5:1.

[0014] In the above scheme, the adhesive can be polyvinylidene fluoride (PVDF) or the like; the organic solvent can be N-methylpyrrolidone or the like.

[0015] In the above scheme, the mass ratio of the adhesive to the organic solvent is 1:1 to 3.

[0016] In the above scheme, the mass ratio of the strong alkali to the activated carbon powder is 1:8 to 8.5.

[0017] In the above scheme, the strong alkali can be one or more of NaOH, KOH, Ca(OH)2, etc.

[0018] In the above scheme, the static reaction time is 24-26 hours.

[0019] In the above scheme, the protective atmosphere can be nitrogen or the like.

[0020] In the above scheme, the high-temperature activation step includes: heating to 800-850°C at a rate of 5-10°C / min and holding the temperature for 1-2 hours.

[0021] Furthermore, the activated carbon fiber (ACF) is pretreated before use. The specific steps include cutting the activated carbon fiber, laying it flat in a water bath constant temperature shaker, boiling it in water to remove volatile impurities, then soaking it in room temperature water and drying it.

[0022] In the above scheme, the water boiling treatment step involves letting the wastewater stand for 2 to 4 hours.

[0023] In the above scheme, the soaking time in water is 24 to 48 hours.

[0024] In the above scheme, the diameter of the activated carbon fiber is 1.5-3 mm and the length is 1-2 m; by adding an activated carbon fiber layer to the surface of the electrode sheet, the adsorption performance of the capacitor deionization device for anions and cations in water can be effectively improved.

[0025] A multi-stage capacitor desalination device includes several electrode integration units as described above, which are aligned and spliced ​​together in a horizontal and vertical direction. The cavity of each electrode integration unit forms a channel, one end of which is the inlet of the multi-stage capacitor desalination device, and the other end of which is the outlet of the multi-stage capacitor desalination device.

[0026] In two horizontally adjacent electrode integration units, the two top electrode plates have the same polarity, the two bottom electrode plates have the same polarity, and the two attached side electrode plates have the same polarity.

[0027] In two vertically adjacent electrode integration units, the polarity of the bottom electrode plate of the upper electrode integration unit is the same as the polarity of the top electrode plate of the lower electrode integration unit.

[0028] A multi-stage capacitive desalination system includes a pretreatment system, a multi-stage capacitive desalination device as described above, a desalination tank, an effluent tank, and a high-salinity tank. The pretreatment system comprises a sedimentation tank, a chemical dosing and equalization tank, an anaerobic tank, and an aerobic tank, which are sequentially connected by pipes. The multi-stage capacitive desalination device is horizontally positioned within the desalination tank, dividing it into an inlet chamber and an effluent chamber. The inlet chamber is connected to the inlet of the multi-stage capacitive desalination device and to the effluent outlet of the aerobic tank via a pipe. The effluent chamber is connected to the effluent outlet of the multi-stage capacitive desalination device and is connected to both the effluent tank and the high-salinity tank via pipes.

[0029] According to the above scheme, the multi-stage capacitor desalination equipment is placed at an angle to form a water flow buffer device, and the outlet of the multi-stage capacitor desalination equipment is higher than the inlet.

[0030] In the above scheme, the raw water (wastewater) to be treated, after being treated by the pretreatment system, mainly comprises the following components and their contents: chemical oxygen demand (COD) of 15-40 mg / L, and salt content (calcium ions (Ca)). 2+ ), magnesium ions (Mg 2+ Sodium ions (Na) + ), potassium ions (K) + ), carbonate ions (CO3) 2- ), bicarbonate ions (HCO3) 3- ), sulfate ions (SO4) 2- ) and chloride ions (Cl - The total concentration of the drug is 500-30000 mg / L.

[0031] In the above scheme, the sedimentation tank removes suspended solids, temporary hardness, alkalinity, and color from the raw water; the chemical dosing tank adds a pH adjuster to adjust the pH value; and the anaerobic and aerobic tanks remove a large amount of organic matter and suspended solids from the water. The inlet of the water storage tank is connected to the inlet of the high-density sedimentation tank via a pipeline, and the outlet of the high-density sedimentation tank is connected to the inlet of the anaerobic tank via a pipeline; the outlet of the anaerobic tank is connected to the inlet of the aerobic tank via a pipeline, and the outlet of the aerobic tank is connected to the capacitor desalination system via a pipeline.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1) The multi-level capacitor structure introduced in this invention can effectively increase the contact area between wastewater (saline water, etc.) and the capacitor module, and combined with new composite electrode materials and water flow buffer settings, it can effectively improve the desalination efficiency of saline water.

[0034] 2) This process has the advantages of being short and compact, easy and flexible to operate, high processing efficiency, and low energy consumption. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the electrode sheet integration unit according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of the electrode plate in the electrode sheet integration unit according to one embodiment;

[0037] Figure 3 A schematic diagram of adsorption for a single electrode sheet integrated unit;

[0038] Figure 4 This is a schematic diagram of the structure of a multi-stage capacitor desalination device according to one embodiment;

[0039] Figure 5 This is a schematic diagram showing the polarity of two adjacent electrode plates in the multi-stage capacitor desalination device of the present invention.

[0040] Figure 6 This is a schematic diagram illustrating the overall application of the multi-stage capacitive wastewater desalination system described in this invention.

[0041] Figure 7 The surface morphology and structure characterization results of three electrode materials, AC, ACF, and AC / ACF, are shown. Among them, a and b are SEM images of AC material, c and d are SEM images of ACF material, and e and f are SEM images of AC / ACF, respectively.

[0042] Figure 8 The images show the BET, XRD, and FTIR spectra of three electrodes: AC, ACF, and AC / ACF. (a) is the nitrogen isothermal adsorption-desorption curve; (b) is the pore size distribution; (c) is the X-ray diffraction curve; and (d) is the Fourier transform infrared spectrum.

[0043] Figure 9 XPS images of three electrode materials, AC, ACF, and AC / ACF, are shown. (a) and (b) show the XPS surface elemental composition of AC, ACF, and AC / ACF; (c) shows the C1s spectrum of AC, ACF, and AC / ACF; and (d) shows the O1s spectrum of AC, ACF, and AC / ACF.

[0044] Figure 10 The graph shows the variation of adsorption amount and adsorption rate of the electrode integrated unit obtained by using three electrode materials, AC, ACF, and AC / ACF, under different voltages and flow rates. In the graph, a represents AC, b represents ACF, and c represents AC / ACF.

[0045] The components include: 1. Electrode integration unit; 1-1. Insulating end plate; 1-2. Outer silicone gasket; 1-3. Current collector plate; 1-4. Modified electrode material layer; 1-5. Activated carbon fiber layer; 1-6. Inner silicone gasket layer; 1-7. First positive electrode plate; 1-8. Second positive electrode plate; 1-9. First negative electrode plate; 1-10. Second negative electrode plate; 1-11. Insulating gasket; 2. Dosing and conditioning tank; 3. Anaerobic tank; 4. Aerobic tank; 5. Multi-stage capacitor desalination equipment; 6. Effluent tank; 7. High salinity tank; 8. Sedimentation tank; 9. Desalination tank; 9-1. Inlet chamber; 9-2. Effluent chamber. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to embodiments, so as to facilitate a clearer understanding of the present invention, but these embodiments do not constitute a limitation on the present invention.

[0047] Example

[0048] like Figure 1An electrode integration unit 1 is shown, comprising a first positive electrode plate 1-7, a second positive electrode plate 1-8, a first negative electrode plate 1-9, and a second negative electrode plate 1-10. The four electrode plates are respectively disposed at the top, bottom, and sides, and are connected end to end in sequence to form a square structure with an internal cavity. One end of the square structure is the water inlet side, and the other end is the water outlet side. Adjacent electrode plates are separated by insulating gaskets 1-11.

[0049] like Figure 2 As shown, the four electrode plates have the same structure, each including an insulating end plate 1-1, an outer silicone pad 1-2, a current collector plate 1-3, a modified electrode material layer 1-4, an activated carbon fiber layer 1-5, and an inner silicone pad layer 1-6 arranged sequentially from the outside to the inside; an electrode wiring port is provided on one end face of the current collector plate 1-3, and the electrode wiring port is connected to the power supply device through a wire.

[0050] In this embodiment, as Figure 3 As shown, two positive electrode plates and two negative electrode plates are arranged facing each other, with the first positive electrode plate 1-7 located at the top, the second positive electrode plate 1-8 located on the left side, the first negative electrode plate 1-9 located on the right side, and the second negative electrode plate 1-10 located at the bottom.

[0051] like Figure 3 and Figure 4 The multi-stage capacitor desalination device shown includes several electrode integration units 1 that are aligned and spliced ​​together in a horizontal and vertical direction; the cavity of each electrode integration unit 1 forms a channel, one end of the channel is the water inlet of the multi-stage capacitor desalination device, and the other end of the channel is the water outlet of the multi-stage capacitor desalination device.

[0052] In two horizontally adjacent electrode integration units 1, the two top electrode plates have the same polarity, the two bottom electrode plates have the same polarity, and the two attached side electrode plates have the same polarity.

[0053] In two vertically adjacent electrode integration units 1, the polarity of the bottom electrode plate of the upper electrode integration unit 1 is the same as the polarity of the top electrode plate of the lower electrode integration unit 1.

[0054] In this embodiment, the two attached electrode plates have the same polarity.

[0055] The capacitor desalination device includes 5 units arranged horizontally in each row and 3 units arranged vertically in each column, with the polarity of each electrode plate as follows: Figure 4 As shown.

[0056] like Figure 5The multi-stage capacitive desalination system shown includes a pretreatment system and a multi-stage capacitive desalination device 5 as described above. The pretreatment system includes a sedimentation tank 8, a chemical dosing and equalization tank 2, an anaerobic tank 3, and an aerobic tank 4, which are connected in sequence by pipes. The multi-stage capacitive desalination device 5 is horizontally arranged in the desalination tank, dividing the desalination tank 9 into an inlet chamber 9-1 and an outlet chamber 9-2. The inlet chamber 9-1 is connected to the inlet of the multi-stage capacitive desalination device 5 and is connected to the outlet of the aerobic tank 4 by pipes. The outlet chamber 9-2 is connected to the outlet of the multi-stage capacitive desalination device 5 and is connected to an outlet tank 6 and a high-salinity tank 7 by pipes.

[0057] In this invention, each pipe is equipped with a valve.

[0058] In this invention, raw water flows sequentially through a sedimentation tank 8, a chemical dosing tank 2, an anaerobic tank 3, and an aerobic tank 4. The sedimentation tank 8 removes suspended solids, temporary hardness, alkalinity, and color from the raw water. The chemical dosing tank 2 adds a pH adjuster to regulate the pH. The anaerobic tank 3 and aerobic tank 4 remove a large amount of organic matter and suspended solids from the water, forming pre-filtered saline-alkali water, which flows to the multi-stage capacitor desalination system 5 in the desalination tank 9. Voltage is applied to the positive and negative electrode plates of the multi-stage capacitor desalination system 5, and the anions and cations in the treated liquid are adsorbed and stored in the double layer of the positive and negative porous carbon electrodes, thus achieving desalination. The desalinated fresh water is discharged into the effluent chamber 9-2 and flows through a pipe into the effluent pool 6. As the saline-alkali water is continuously purified, the multi-stage capacitor... The purification capacity gradually decreases. When the salinity in the effluent chamber 9-2 of the desalination tank 9 reaches the set threshold (salt concentration at the effluent outlet is greater than 3g / L), the valve on the pipeline connecting the influent chamber 9-1 of the desalination tank 9 and the aerobic tank 4 is closed (water intake is stopped). When the water level in the effluent chamber 9-2 of the desalination tank 9 reaches the minimum high-salt water discharge level, the outlet of the multi-stage capacitor desalination device 5 to the effluent tank 6 is closed, and the voltage of the multi-stage capacitor desalination device 5 is turned off. At this time, the anions and cations originally adsorbed in the electrodes are released into the water, the electrodes are regenerated, the outlet of the desalination tank to the high-salt water tank 7 is opened, and the high-salt water flows to the high-salt water tank 7. After the high-salt water is collected, it returns to the initial state and repeats this multi-stage capacitor desalination process. During the process, the adsorption and release of anions and cations and the regeneration of electrodes are achieved by applying and removing the voltage of the multi-stage capacitor desalination equipment 5. The opening and closing of the pipeline valves and the application and removal of the multi-stage capacitor voltage are automatically controlled by the water level sensor (used to detect the water level in the outlet chamber) and the salinity sensor (used to detect the salinity in the outlet chamber). All electrical energy is directly or indirectly converted from solar energy.

[0059] In this embodiment, the multi-stage capacitor desalination device 5 is placed at an angle, with the outlet of the multi-stage capacitor desalination device 5 being higher than the inlet. The angle of inclination is calculated based on the water flow rate and the initial concentration of the solution. The multi-stage capacitor can increase the contact area between the saline water and the capacitor module.

[0060] In the embodiments of the present invention, the preparation steps of the modified electrode material layer and the activated carbon fiber layer include:

[0061] 1) Activated carbon modification (modified AC); Activated carbon powder is sieved through a 0.05 mm (300 mesh) sieve to remove large particles of activated carbon, washed with deionized water until the conductivity of the effluent drops below 10 μS / cm, and dried in a 120℃ constant temperature drying oven for later use; 20 g of the above activated carbon powder is placed in a 250 mL polytetrafluoroethylene bottle, a certain amount of 3 mol / L KOH solution is added, and the mixture is placed in a constant temperature shaking water bath at 80℃ and 60 r / min for 1 h; The treated activated carbon is washed with deionized water until neutral, and dried in a 120℃ constant temperature drying oven for 24 h; Modified activated carbon is obtained.

[0062] 2) Pretreatment of activated carbon fiber (ACF);

[0063] Commercially available activated carbon fiber (ACF) was cut into two rectangles with a length × width of 15cm × 15cm. The rectangles were laid flat in a SHA-82A digital display water bath constant temperature shaker and boiled in 100℃ deionized water for 2 hours to remove volatile impurities. After soaking in deionized water for 24 hours, the rectangles were dried in an electric heating constant temperature drying oven at 120℃ for 24 hours. After weighing, the rectangles were sealed in a self-sealing bag.

[0064] 3) Modified AC, conductive carbon black (CCB), and PVDF are mixed in a mass ratio of 85:10:5 and dissolved in 10-15 ml of NMP solvent (PVDF to NMP mass ratio of 1:2). The mixture is stirred with a magnetic stirrer for 6 hours to obtain an AC electrode slurry. Subsequently, the titanium plate used for electrode coating is pretreated by dust removal and degreasing, and then dried for later use. Finally, the uniformly mixed AC electrode slurry is coated onto the pretreated titanium plate using a coating machine to a thickness of 250 μm. A layer of ACF (controlling the mass ratio of modified AC to ACF to be 1:1) is uniformly covered on the coated electrode sheet. The resulting composite electrode is then compacted and cured at room temperature for 24 hours to obtain a modified activated carbon / activated carbon fiber composite layer (modified AC / ACF).

[0065] The characterization results of the modified electrode material in the modified electrode material layer include the following:

[0066] The surface morphology and structure of three materials, modified AC, ACF, and modified AC / ACF, were analyzed. The preparation methods of the modified AC and ACF layers were the same as those of the modified electrode material layers obtained by the above-mentioned slurry preparation, coating, and drying methods. Figure 7 a and b are SEM images of the obtained modified AC material. The images show that the activated carbon surface has a porous structure, with many porous channels and network structures between the particles, indicating that AC has good adsorption performance and a stable structure. Figure 7 c, d and Figure 7 e and f represent SEM images of ACF and AC / ACF, respectively. It is evident that AC / ACF and ACF have similar morphology and structural characteristics. The nanofibers in the ACF mesh exhibit a regular and curved fibrous morphology, indicating that AC / ACF has lower contact resistance than granular AC, making it more suitable as an electrode material. Furthermore, both ACF and AC / ACF materials are composed of numerous irregularly shaped and varying-sized fiber structures, forming a small number of longitudinal textured grooves of varying depths, discontinuous and irregular voids, and wedge-shaped axial cracks, indicating that AC / ACF possesses greater plasticity. In conclusion, compared to AC materials, ACF and AC / ACF exhibit superior surface morphology, making them more suitable as electrode materials.

[0067] Figure 8 (a) shows the N2 adsorption-desorption isotherms for AC, ACF, and AC / ACF. According to IUPAC, the nitrogen adsorption / desorption isotherms of the three materials are all Type I curves, indicating that the materials have microporous pore size characteristics. Figure 8 (b) The pore characteristics of the carbon samples were summarized. As shown in the figure, the pore size distribution of AC / ACF is concentrated between 0.2-2 nm and 2-10 nm, indicating the coexistence of micropores and mesopores. The presence of micropores can increase the adsorption capacity of the material, while the presence of mesopores can provide more adsorption channels, allowing the adsorbate to enter the micropores smoothly. Therefore, the synergistic effect between micropores and mesopores can further improve the adsorption performance of the material. The specific surface area and total pore volume of AC and ACF are both greater than those of AC / ACF (Table 1), with specific surface areas of AC, ACF, and AC / ACF being 1667.0448, 1294.3422, and 1076.7713 m², respectively. 2 ·g -1 The total pore volumes are 0.780331, 0.545107, and 0.492993 cm³. 3 ·g -1Studies have shown that the decrease in specific surface area after compositing activated carbon materials may be due to functional groups occupying some of the available pores. Therefore, the decrease in specific surface area of ​​the AC / ACF composite material in this paper may be due to the increase in the number of functional groups. In summary, the AC / ACF composite material has the characteristics of a large number of micropores and high adsorption performance, but its specific surface area and the number of total pores are smaller than those of AC material.

[0068] XRD analysis can be found in [link to XRD analysis]. Figure 8 (c) Compared with AC, the crystal planes of ACF and AC / ACF are shifted to the right, and the diffraction peaks of ACF and AC / ACF are significantly enhanced compared with the diffraction peaks of AC. This indicates that the cell parameters and interplanar spacing of the AC / ACF composite crystal are smaller, and the crystal stability is stronger, thus giving the composite material stable physical and chemical properties, making the adsorption process less susceptible to interference from side reactions.

[0069] Table 1. BET characterization results of AC, ACF, and AC / ACF materials.

[0070]

[0071] XPS and FTIR were used to detect the surface functional groups and elemental types and quantities of AC, ACF, and AC / ACF. Figure 9 As shown in (b) and (c), the surface C functional group content of the composite AC / ACF material is significantly reduced, while the surface oxygen functional group content is increased. Figure 9 Images (a) and (b) show that C and O elements are present in all three materials. The O element content significantly increases after composite formation, from 13.94% to 42.54%; the C element content decreases, from 85.75% to 36.69%. The C1 energy spectrum of AC / ACF is shown in the images. Figure 9 (c) with O1s energy spectrum Figure 9 (d) also confirms this phenomenon, indicating that the increased proportion of oxygen-containing functional groups improves the surface wettability of the composite material, thus making full use of the specific surface area of ​​the electrode material.

[0072] Further comparison was made of the adsorption capacity and adsorption rate variations of the resulting electrode integrated units under different voltages and flow rates when AC, ACF, and AC / ACF were used as electrode materials, respectively. The results are shown in [Figure number missing]. Figure 10 The results showed that the AC / ACF composite material described in this invention exhibited better adsorption performance than the single material at the same voltage and flow rate, with an influent flow rate of 65 ml / min. -1 When the operating voltage is 2V, the adsorption capacity and adsorption rate corresponding to AC / ACF are 130.81 mg·g⁻¹. -1 With 7.48 mg·g -1 ·min -1 ,

[0073] In summary, the AC / ACF composite material has better micropore count, crystal stability, and oxygen-containing functional groups than AC and ACF materials. Although the specific surface area of ​​the composite material is not as large as that of the single material, the increased oxygen-containing functional groups make full use of the specific surface area of ​​AC / ACF.

[0074] This invention addresses the shortcomings of traditional ACF electrode material preparation processes, which involve coating a current collector (titanium plate) with copper conductive adhesive to achieve ACF bonding and conductivity. However, uneven coating of the conductive adhesive leads to inconsistent current collector thickness and poor conductivity. This invention provides a novel composite material, activated carbon / activated carbon fiber (AC / ACF), which effectively improves upon the problems of unstable conductivity, pore blockage, difficulty in cleaning, and high cost associated with traditional copper conductive adhesive processes (e.g., during desalination, it can easily block some pores in the ACF, reducing adsorption capacity; and the difficulty in cleaning copper conductive adhesive can cause abrasion to the current collector, inevitably increasing costs when replacing materials).

[0075] In summary, the multi-stage capacitor-based wastewater desalination system of this invention features a rationally arranged positive and negative electrode plate, which significantly enhances the desalination effect. The positive and negative electrodes are arranged in a cross-shaped repeating pattern, with insulating material at the intersections. The multi-stage capacitor increases the contact area between the brine and the capacitor module, improving desalination efficiency. In actual water purification, the device is placed at an angle to further increase the contact area between the brine and the capacitor module, ensuring that the raw water remains in the multi-stage capacitor for a longer period, thus enhancing the desalination effect.

[0076] Furthermore, the cost and energy consumption of electrode materials directly impact the application value of CDI, and they typically require excellent adsorption properties, high specific surface area, and superior chemical stability. However, these high-performance materials are often expensive and energy-intensive, limiting the widespread application of CDI technology. Therefore, researching and developing low-cost, low-energy-consumption electrode materials is crucial for advancing CDI technology.

[0077] To explore the application value of the novel AC / ACF composite material, the adsorption cost (cost per gram of salt adsorbed) and energy consumption of AC / ACF and other composite materials were normalized and analyzed (cost of other materials source: Huayuan.com). Parameters such as specific surface area, adsorption capacity, cost, and energy consumption are shown in Table 3. AC / ACF has the lowest total cost, costing $0.11 per gram of salt adsorbed. This result is comparable to the $0.16·g for MnO2 / AC material. salt -1 The difference is not significant, but the SAC of AC / ACF material is 3.87 times greater than that of MnO2 / AC (36 mg·g). -1 / 9.3mg·g -1 =3.87). In terms of energy consumption, the AC / ACF material consumes 0.45 Wh·g.salt -1 Second only to Co-PBA@MXene / PPy material at 0.283 Wh·g salt -1 However, the material cost is 1 / 45.45 (0.11g) of Co-PBA@MXene / PPy. salt -1 / 5$·g salt -1 ≈45.45). Additionally, the specific surface area (S) of AC / ACF... BET ) and SAC up to 1089.01m 2 / g and 36.00mg·g -1 Second only to ZIF-8 / BA-a / PAN's 3066.29m 2 / g and 45.00mg·g -1 However, the cost of AC / ACF is 1 / 33.1 (3.65g) of that of ZIF-8 / BA-a / PAN. salt -1 / 0.11$·g salt -1 =33.18). By comparing AC / ACF with composite materials in other studies, it can be seen that the AC / ACF described in this invention has the advantages of large specific surface area, excellent desalination performance, low cost and low energy consumption, and has broad commercial application prospects.

[0078] Table 2 Cost Analysis of Different Composite Materials

[0079]

[0080]

[0081] The specific documents are as follows:

[0082] Literature 1T.Alfredy,J.Elisadiki,M.Dahbi,CKKing'ondu,YACJande,Electrosorption of paraquat pesticide on activated carbon modified byaluminium oxide(Al2O3)with capacitivedeionization,Desalination.572(2024)117116,https: / / doi.org / 10.1016 / j.desal.2023.117116.

[0083] Reference 2: R. Chen, X. Deng, C. Wang, J. Du, Z. Zhao, W. Shi, F. Cui, C. Zhang, "Enhanced desalination performances by using porous polyaniline-activated carbon composite flow-electrodes in capacitive deionization system", Desalination. 557 (2023) 116568, https: / / doi.org / 10.1016 / j.desal.2023.116568.

[0084] Reference 3: H.Z. Zhang, J.Y. Tian, X.K. Cui, J.S. Li, Z.G. Zhu, "Highly mesoporous carbon nanofiber electrodes with ultrahigh specific surface area for efficient capacitive deionization", Carbon. 201 (2023) 920 - 929, https: / / doi.org / 10.1016 / j.carbon.2022.10.002.

[0085] Reference 4: Y. Cai, W. Zhang, J. Zhao, Y. Wang, "Flexible structural construction of the ternary composite Ni,Co-Prussian blue analogue@MXene / polypyrrole for high-capacity capacitive deionization", Appl. Surf. Sci. 622 (2023) 156926, https: / / doi.org / 10.1016 / j.apsusc.2023.156926.

[0086] Reference 5 M. Beke, T. Velempini, E. Prabakaran, K. Pillay, Preparation of carbon-aerogel polypyrrole composite for desalination by hybrid capacitive desalination method, Arab. J. Chem. 16(2) (2023) 104412, https: / / doi.org / 10.1016 / j.arabjc.2022.104412.

[0087] Reference 6 Y. H. Liu, H. C. Hsi, K. C. Li, C. H. Hou, Electrodeposited Manganese Dioxide / Activated Carbon Composite As a High-Performance Electrode Material for Capacitive Deionization, Acs. Sustainable Chem. Eng. 4(9) (2016) 4762-4770, https: / / doi.org / 10.1021 / acssuschemeng.6b00974.

[0088] Reference 7 H. Zhang, Q. Wang, J. Zhang, G. Chen, Z. Wang, Z. Wu, Development of novel ZnZr-COOH / CNT composite electrode for selectively removing phosphate by capacitive deionization, Chem. Eng. J. 439 (2022) 135527, https: / / doi.org / 10.1016 / j.cej.2022.135527.

[0089] Reference 8: G. Tan, S. Wan, S.C. Mei, B. Gong, C. Qian, J.J. Chen, Boosted brackish water desalination and water softening by facilely designed MnO2 / hierarchical porous carbon as capacitive deionization electrode, Water Res. X 19 (2023) 100182, https: / / doi.org / 10.1016 / j.wroa.2023.100182.

[0090] Reference 9: D.M. El-Gendy, I.M. Maafa, N. Zouli, A. Abutaleb, A. Yousef, Synthesis of black TiO2 nanotubes decorated biomass-derived spongy carbon as an electrode material for producing deionized water through capacitive deionization technology, Ceram. Int. 50 (5) (2024) 7775-7788, https: / / doi.org / 10.1016 / j.ceramint.2023.12.104.

[0091] Reference 10: L. Men, C. Chen, A. Liu, S. Yu, J. Zhou, Y. Xie, D. Ju, N-doped porous carbon-based capacitive deionization electrode materials loaded with activated carbon fiber for water desalination applications, J. Environ. Chem. Eng. 10 (3) (2022) 107943, https: / / doi.org / 10.1016 / j.jece.2022.107943.

[0092] Literature 11X.Song,

[0093] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. An electrode integrated unit characterized by comprising: The application relates to a multi-stage capacitive desalination device, which comprises a first positive electrode plate, a second positive electrode plate, a first negative electrode plate and a second negative electrode plate. The four electrode plates are arranged in a square structure with cavities in the interiors, and the four electrode plates are sequentially and circularly connected. The modified active carbon / active carbon fiber composite layer is prepared by the following steps: mixing strong alkali and active carbon powder, standing and reacting, filtering and drying, high-temperature activation in a protective atmosphere, natural cooling to room temperature, acid washing and washing to neutral, drying and sieving. The modified active carbon is prepared by mixing strong alkali and active carbon powder, standing and reacting, filtering and drying, high-temperature activation in a protective atmosphere, natural cooling to room temperature, acid washing and washing to neutral, drying and sieving.

2. The electrode integrated unit according to claim 1, characterized by, The electrode connection port is connected with a power supply device through a wire.

3. The electrode integrated unit according to claim 1, characterized by, The diameter of the active carbon fiber is 1.5-3mm, and the length is 1-2m.

4. A multi-stage capacitive desalination apparatus, characterized by, The cavities of the electrode integrated units form channels, one end of the channels is the water inlet of the multi-stage capacitive desalination device, and the other end of the channels is the water outlet of the multi-stage capacitive desalination device. In the two electrode integrated units which are horizontally adjacent, the polarities of the two top electrode plates are the same, the polarities of the two bottom electrode plates are the same, and the polarities of the two side electrode plates which are in contact are the same. In the two electrode integrated units which are vertically adjacent, the polarity of the bottom electrode plate of the former electrode integrated unit is the same as the polarity of the top electrode plate of the latter electrode integrated unit.

5. A multi-stage capacitive wastewater desalination system, characterized by, The application further relates to a multi-stage capacitive desalination device and a pretreatment system. The multi-stage capacitive desalination device is horizontally arranged in the desalination tank, and the desalination tank is divided into a water inlet cavity and a water outlet cavity.

6. The multi-stage capacitive wastewater desalination system of claim 5, wherein, The multi-stage capacitive desalination device is arranged in a tilted manner, and the water outlet of the multi-stage capacitive desalination device is higher than the water inlet.

Images