Application of PBFDO membrane in CDI desalination system
By using a PBFDO membrane as the cathode in a CDI system and assembling it with polyaniline@graphene or activated carbon, the problems of poor stability of n-type conductive polymers and low desalination capacity of traditional materials are solved, achieving a highly efficient and stable desalination effect.
Patent Information
- Application Number
- CN202511676144.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-01-23
AI Technical Summary
In existing CDI technologies, n-type conductive polymers have poor stability in aqueous solutions, which limits their application in capacitive deionization. Furthermore, traditional carbon materials have low desalination capacity, and Faraday materials suffer from environmental pollution and slow reaction kinetics, making it difficult to achieve efficient and stable desalination effects.
Using PBFDO membranes as the cathode of a CDI system, PBFDO membranes are prepared by a blade coating method and assembled with polyaniline@graphene or activated carbon to form all-organic or hybrid CDI devices. The conjugated structure and carbonyl groups of PBFDO are used to achieve efficient Na+ insertion/deintercalation reactions.
It achieves high desalination capacity (78.8 mg/g), high desalination rate (2.6 mg/g/min) and low energy consumption (0.34 Wh g−1), and has excellent cycling stability, demonstrating the highest desalination performance of current all-organic CDI devices.
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Figure CN121377231A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of water treatment technology, and in particular to the application of a PBFDO membrane in a CDI desalination system. Background Technology
[0002] Freshwater scarcity is one of the major global challenges facing the 21st century. As an emerging seawater desalination technology, capacitive deionization (CDI) has attracted widespread attention for its advantages in alleviating freshwater shortages due to its low energy consumption, low operating costs, and lack of secondary pollution. Electrode materials, as the core component of the CDI system, largely determine the overall desalination performance. In recent years, the development of electrode materials has gradually shifted from traditional electric double-layer (EDL) carbon materials to Faraday materials. Carbon materials, limited by their specific surface area, typically have a desalination capacity of less than 20 mg / g. In contrast, Faraday materials achieve ion capture through ion intercalation / deintercalation or reversible redox reactions, significantly improving desalination capacity to 30–60 mg / g, with some systems even exceeding 100 mg·g⁻¹, opening up new directions for the development of CDI technology. However, most current Faraday materials are inorganic compounds, which often face problems such as environmental pollution, low conductivity, slow reaction kinetics, and significant volume expansion during cycling, limiting their long-term stable operation.
[0003] Against this backdrop, conjugated polymers have become a strong alternative to inorganic and carbon-based materials due to their low cost, readily available raw materials, environmental friendliness, and ease of large-scale production. However, most conductive polymers exhibit p-type characteristics dominated by hole transport (applicable only to anodes for anion capture), while n-type polymers (used as cathodes for cation capture) are rarely reported. This is because n-type polymers have relatively poor conductivity and are difficult to stabilize in aqueous solutions, thus severely limiting their application in CDI. Therefore, all-organic CDI devices with advantages such as ultra-high desalination performance and environmental friendliness currently exist only in the theoretical development stage.
[0004] Poly(benzodifurandione) polymers (PBFDOs) possess excellent electrical conductivity and optical transparency. Their unique conjugated structure, good solution processability, and flexibility have made them a core component of next-generation organic functional materials and organic electronics research. Conjugated polymers endow materials with unique optical, electrical, and magnetic properties through delocalized π-electron systems, leading to their widespread application in organic solar cells (OPVs), organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), organic thermoelectric devices (OTEs), and organic electrochemical transistors (OECTs). However, there has been no research on their application in capacitive deionization (CDI) technology. Summary of the Invention
[0005] To address the problems existing in the prior art, this invention provides an application of PBFDO membrane in a CDI desalination system. This invention utilizes PBFDO membrane as the cathode of the CDI system, which has high desalination capacity, desalination rate, low energy consumption, and excellent cycle stability.
[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0007] This invention provides an application of a PBFDO membrane in a CDI desalination system. The PBFDO membrane, prepared by a blade coating method, is used as the cathode in the CDI desalination system; specifically as follows:
[0008] (1) Preparation of PBFDO membrane:
[0009] (11) Preparation of PBFDO solution: H-BFDO crystals (200 mg) and durquinone (259 mg) were dissolved in 12 mL of dimethyl sulfoxide (99.7%). The reaction solution was heated to 100 °C under a nitrogen atmosphere and stirred vigorously for 1 hour. During the process, the color of the solution gradually changed from light yellow to dark brown, and the solution gradually became viscous. The reaction solution was then allowed to cool naturally to room temperature, placed in a dialysis bag, and immersed in dimethyl sulfoxide for dialysis for two weeks. The external dimethyl sulfoxide was replaced every three days. The polymer solution in the dialysis bag was then collected and filtered to obtain the PBFDO solution.
[0010] (12) Adjust the concentration of the prepared PBFDO solution to 10 mg / mL;
[0011] (13) PBFDO film was prepared by a blade coating method: 1 mL of 10 mg / mL PBFDO was added to 2.8 mg of acetylene black and 1.4 mg of PVDF that had been ground evenly. After mixing evenly, the mixture was coated onto a 4×4 cm film. 2 The PBFDO film electrode can be obtained by drying the surface of the titanium sheet in an oven at 70°C overnight.
[0012] (2) Preparation of polyaniline@graphene:
[0013] (21) Synthesis of polyaniline: 0.05 mol of aniline was poured into 50 mL of 1 mol / L hydrochloric acid solution, and the pH of the solution was adjusted to 1.0 with hydrochloric acid. Then, 26 mL of 2.4 mmol / L ammonium persulfate solution was added dropwise to the above solution and stirred at 0℃ for 24 hours. The precipitate was centrifuged and washed with deionized water. Then, the sample was deprotonated in ammonia solution for 24 hours, filtered, washed with deionized water and ethanol, and vacuum dried at 60℃ for 24 h to obtain polyaniline powder sample.
[0014] (22) Preparation of polyaniline@graphene: 2 mg·L −1 Graphene oxide with 5 mg·L −1 The polyaniline solution was mixed at a mass ratio of 4:1, sonicated for 30 min, dispensed into 5 mL glass bottles, and freeze-dried. The resulting solid was then treated with 200 W plasma power for 1 s to obtain polyaniline@graphene.
[0015] (23) Preparation of polyaniline@graphene electrode: 20 mg of polyaniline@graphene, 2.5 mg of acetylene black, and 2.5 mg of PVDF were ground evenly in a mortar, and then NMP was added to grind it into a slurry and coated onto a 4×4 cm electrode. 2 On the titanium sheet, dry it overnight in an oven at 70°C.
[0016] (3) Assembly of CDI desalination system: The CDI system mainly consists of a pair of parallel cathodes (PBFDO) and anodes (activated carbon or polyaniline@graphene), with a cation exchange membrane and an anion exchange membrane (0.4 cm apart) placed between the two electrodes, and then encapsulated with plexiglass; a peristaltic pump is used to introduce brine into the CDI system at a flow rate of 25 mL / min; and an external power supply is connected to the cathode / anode, and the power supply voltage is controlled at 0.6~1.4 V, thereby realizing the desalination process of brine.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] This invention provides an n-type conjugated polymer, namely poly(benzodifurandione) (PBFDO), as a cathode for use in CDI desalination systems.
[0019] This invention utilizes PBFDO, which possesses an ultrathin two-dimensional layered structure and excellent dispersibility in dimethyl sulfoxide. PBFDO films can be prepared using a blade coating method and used as cathodes in CDI systems. These films can then be assembled with polyaniline@graphene or activated carbon to obtain either an all-organic CDI (PBFDO‖polyaniline@graphene) or a traditional hybrid CDI (PBFDO‖activated carbon). Notably, the former exhibits the highest desalination performance currently available in all-organic CDI devices, with a salt adsorption capacity of 78.8 mg / g, a desalination rate of 2.6 mg / g / min, and an energy consumption of 0.34 Wh g at 1.4 V. −1 It also exhibits excellent cycle stability. Na + The insertion / deintercalation process of ions in PBFDO is mainly based on the reversible redox reaction between quinone / hydroquinone groups, which endows PBFDO with excellent structural stability and electrochemical sustainability. Attached Figure Description
[0020] Figure 1This is a schematic diagram of the PBFDO‖polyaniline@graphene system prepared in Example 1 of the present invention;
[0021] Figure 2 The conductivity response of PBFDO‖polyaniline@graphene prepared in Example 1 of this invention at an initial NaCl concentration of 500 mg·L⁻¹ is shown in the figure.
[0022] Figure 3 This is a pH change graph of PBFDO‖polyaniline@graphene prepared in Example 1 of the present invention when the initial NaCl concentration is 500 mg·L⁻¹.
[0023] Figure 4 The graph shows the change of cathode potential over time for PBFDO‖polyaniline@graphene prepared in Example 1 of this invention when the initial NaCl concentration is 500 mg·L⁻¹.
[0024] Figure 5 Ragone diagram of PBFDO‖polyaniline@graphene prepared in Example 1 of this invention at an initial NaCl concentration of 500 mg·L⁻¹;
[0025] Figure 6 The current response of PBFDO‖polyaniline@graphene prepared in Example 1 of this invention as a function of time when the initial NaCl concentration is 500 mg·L⁻¹ (inset shows energy consumption);
[0026] Figure 7 The graph shows the change of SAC over time for PBFDO‖polyaniline@graphene prepared in Example 1 of this invention under different initial NaCl concentrations.
[0027] Figure 8 The graph shows the cycle stability test results of PBFDO‖polyaniline@graphene prepared in Example 1 of this invention.
[0028] Figure 9 for Figure 8 Photographs of PBFDO after cyclic stability testing (a), O 1s XPS data (b), and XRD patterns (c).
[0029] Figure 10 (a) Schematic diagram of PBFDO||AC; (b) Conductivity of PBFDO||AC under different applied voltages; (c) Relationship between solution pH and cathode potential with CDI time; (d) Performance relationship graph under different voltages; (e) Energy consumption comparison; (f) Salt adsorption capacity curves with time corresponding to different initial NaCl concentrations under ±1.4 V voltage conditions. Detailed Implementation
[0030] To make the technical problem to be solved, the technical solution and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments. Graphene oxide is a commercially available product.
[0031] Unless otherwise specified, all materials and reagents used in this invention are commercially available.
[0032] This invention provides an application of PBFDO membrane in a CDI desalination system, and specific embodiments are as follows.
[0033] Example 1
[0034] An application of a PBFDO membrane in a CDI desalination system: the PBFDO membrane, prepared by a blade coating method, is used as the cathode in the CDI desalination system; details are as follows:
[0035] (1) Preparation of PBFDO membrane:
[0036] (11) Preparation of PBFDO solution: H-BFDO crystals (200 mg) and durquinone (259 mg) were dissolved in 12 mL of dimethyl sulfoxide (99.7%). The reaction solution was heated to 100 °C under a nitrogen atmosphere and stirred vigorously for 1 hour. During the process, the color of the solution gradually changed from light yellow to dark brown, and the solution gradually became viscous. The reaction solution was then allowed to cool naturally to room temperature, placed in a dialysis bag, and immersed in dimethyl sulfoxide for dialysis for two weeks. The external dimethyl sulfoxide was replaced every three days. The polymer solution in the dialysis bag was then collected and filtered to obtain the PBFDO solution.
[0037] (12) Adjust the concentration of the prepared PBFDO solution to 10 mg / mL;
[0038] (13) PBFDO film was prepared by a blade coating method: 1 ml of 10 mg / mL PBFDO was added to 2.8 mg of acetylene black and 1.4 mg of PVDF that had been ground evenly. After mixing evenly, the mixture was coated onto a 4×4 cm film. 2 The PBFDO film electrode can be obtained by drying the surface of the titanium sheet in an oven at 70°C overnight.
[0039] (2) Preparation of polyaniline@graphene:
[0040] (21) Synthesis of polyaniline: 0.05 mol of aniline was poured into 50 mL of 1 mol / L hydrochloric acid solution, and the pH of the solution was adjusted to 1.0 with hydrochloric acid. Then, 26 mL of 2.4 mmol / L ammonium persulfate solution was added dropwise to the above solution and stirred at 0℃ for 24 hours. The precipitate was centrifuged and washed with deionized water. Then, the sample was deprotonated in ammonia solution for 24 hours, filtered, washed with deionized water and ethanol, and vacuum dried at 60℃ for 24 h to obtain polyaniline powder sample.
[0041] (22) Preparation of polyaniline@graphene: 2 mg·L −1 Graphene oxide with 5 mg·L −1 The polyaniline solution was mixed at a mass ratio of 4:1, sonicated for 30 min, dispensed into 5 mL glass bottles, and freeze-dried. The resulting solid was then treated with 200 W plasma power for 1 s to obtain polyaniline@graphene.
[0042] (23) Preparation of polyaniline@graphene electrode: 20 mg of polyaniline@graphene, 2.5 mg of acetylene black, and 2.5 mg of PVDF were ground evenly in a mortar, and then 0.6 g of NMP was added to grind it into a slurry and coated onto a 4×4 cm electrode. 2 On the titanium sheet, dry it overnight in an oven at 70°C.
[0043] (3) Assembly of CDI desalination system: The CDI system consists of a cathode (PBFDO), a cation exchange membrane, an anion exchange membrane, and an anode (polyaniline@graphene) placed in parallel in sequence. A gasket is also provided between the cation exchange membrane and the anion exchange membrane to separate the anion / cation exchange membrane. The thickness of the gasket is 0.4 cm. Then, rubber gaskets are placed on the outside of the cathode and the anode respectively, and then they are encapsulated with plexiglass. A peristaltic pump is used to introduce brine into the CDI system at a flow rate of 25 mL / min. An external power supply is connected to the cathode / anode, and the power supply voltage is controlled at 0.6~1.4 V to realize the desalination process of brine.
[0044] A schematic diagram of the CDI system prepared in this embodiment is shown below. Figure 1 As shown. This invention also investigated the CDI response behavior of PBFDO‖polyaniline@graphene in a 500 mg·L⁻¹ NaCl feed solution with an applied battery voltage ranging from 0.6 to 1.4 V. The results are shown in [Figure number missing]. Figure 2 As the battery voltage increases, the solution conductivity gradually decreases; upon voltage reversal, the conductivity rapidly recovers to its initial value, indicating that the CDI process has excellent reversibility. The real-time pH response exhibits a fluctuation trend that is completely opposite to that of the conductivity-time plot, and the amplitude is negligible (less than ±0.2). Figure 3The cathode potential stabilizes within a potential window (-0.8 to 0.8 V). Figure 4 This indicates that no side reactions occurred during the entire desalination process. Calculations show that the desalination capacity, desalination rate, and energy consumption of the PBFDO‖polyaniline@graphene system increase with increasing voltage. For example, at 0.6 V, these are 40.3 mg / g, 1.34 mg / g / min, and 0.11 Wh / g, respectively; when the voltage increases to 1.4 V, they are 74.1 mg / g, 2.47 mg / g / min, and 0.34 Wh / g, respectively. Figure 5 and Figure 6 ).
[0045] This invention also investigated the effect of different initial NaCl solution concentrations on the desalination performance of PBFDO‖polyaniline@graphene, with initial NaCl solution concentrations ranging from 500 to 3500 mg·L⁻¹. The results are shown in [Figure number missing]. Figure 7 When the concentration is ≤1000 mg / L, the desalination capacity is positively correlated with the initial NaCl concentration; above this concentration, the desalination capacity hardly increases, with a maximum desalination capacity of 78.8 mg / g (desalination rate of 2.6 mg / g / min), indicating that the electrochemical active sites of the PBFDO electrode are fully utilized under high salinity. Furthermore, the desalination performance of PBFDO‖polyaniline@graphene is the highest reported for an all-organic CDI system to date.
[0046] Cyclic stability is a key parameter for evaluating the practical application of n-type polymer cathodes. PBFDO exhibits excellent adsorption-desorption cyclic stability, with a capacity retention of >88.6% after 50 consecutive cycles. Figure 8 After cycle testing, the battery was disassembled, and no visible discoloration or dissolution was observed on the PBFDO electrode. Figure 9 (a) The almost unchanged O 1s and C 1s XPS spectra before and after cycling further confirm the robustness and insolubility of PBFDO. Figure 9 (b)). At the same time, ( Figure 9 (c) XRD analysis showed that the (001) peak of PBFDO moved from 8.12° before cycling to 7.21° after cycling, and the peak intensity decreased significantly, indicating that the interlayer spacing increased and the lattice order decreased.
[0047] To verify the universality of the PBFDO cathode, it was further assembled with an activated carbon anode to obtain the traditional hybrid PBFDO‖ activated carbon CDI system, as detailed below.
[0048] Example 2
[0049] An application of a PBFDO membrane in a CDI desalination system: the PBFDO membrane, prepared by a blade coating method, is used as the cathode in the CDI desalination system; details are as follows:
[0050] (1) The preparation of the PBFDO membrane is the same as step (1) in Example 1;
[0051] (2) Preparation of activated carbon electrode: 20 mg of activated carbon, 2.5 mg of acetylene black, and 2.5 mg of PVDF were ground evenly in a mortar, and then NMP was added to grind it into a slurry and coated on a 4×4 cm plate. 2 Activated carbon electrodes can be obtained by drying titanium sheets overnight in an oven at 70°C.
[0052] (3) Assembly of PBFDO‖ activated carbon system: replace polyaniline@graphene with activated carbon electrode, and the other conditions are the same as step (3) in Example 1.
[0053] Consistent with the behavior observed in the PBFDO‖polyaniline@graphene system, the desalination capacity and rate of PBFDO‖AC are correlated with the applied voltage and the initial NaCl concentration. The desalination capacity and rate reach their maximum values at 1.4 V and 1000 mg / L NaCl solution, respectively, at 52.8 mg / g and 1.76 mg / g / min, with an energy consumption of 0.31 Wh g⁻¹. Figure 10 Compared with the all-organic PBFDO‖polyaniline@graphene system, the PBFDO‖activated carbon system has slightly lower desalination performance. This is because the activated carbon anode is limited by the EDL desalination mechanism, which affects the overall performance of the CDI system.
[0054] In summary, this invention is the first to propose the use of PBFDO in a CDI desalination system, utilizing its stable conjugated framework and abundant carbonyl functional groups to achieve desalination of Na+. + The efficient capture of these materials provides a new research direction for the development of high-performance, sustainable organic cathode materials.
[0055] The above description is a preferred embodiment of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.
Claims
1. The application of a poly(benzodifurandione) (PBFDO) membrane in a capacitive deionization (CDI) desalination system, characterized in that, The PBFDO membrane was prepared by a blade coating method and used as a cathode in a CDI desalination system.
2. The application according to claim 1, characterized in that, The method for preparing the PBFDO membrane includes the following steps: Step 1: Prepare PBFDO solution using dimethyl sulfoxide as solvent; Step 2: Adjust the concentration of the prepared PBFDO solution to 10 mg / mL. −1 ; Step 3: Grind PBFDO, acetylene black and polyvinylidene fluoride evenly in a mass ratio of 50:14:7, coat the mixture onto the surface of a titanium sheet, and dry to obtain a PBFDO film.
3. The application according to claim 2, characterized in that, The CDI desalination system also includes an anode arranged parallel to the PBFDO membrane, the anode being made of activated carbon or polyaniline@graphene.
4. The application according to claim 3, characterized in that, The preparation method of the polyaniline@graphene anode includes the following steps: (1) Synthesis of polyaniline; (2) Preparation of polyaniline@graphene; (3) Preparation of polyaniline@graphene electrode: Polyaniline@graphene, acetylene black and polyvinylidene fluoride are ground evenly in a mortar at a mass ratio of 8:1:
1. Then N-methylpyrrolidone is added and ground into a slurry, which is then coated on a titanium sheet and dried to obtain polyaniline@graphene electrode.
5. The application according to claim 4, characterized in that, The CDI desalination system consists of a cathode, a cation exchange membrane, an anion exchange membrane, and an anode arranged in parallel in sequence, and is externally encapsulated using plexiglass. An external power supply is then connected to the cathode and anode.
6. The application according to claim 5, characterized in that, The voltage of the external power supply is 0.6~1.4 V.
7. The application according to claim 6, characterized in that, When using the CDI desalination system, a peristaltic pump is used to introduce the solution to be desalinated into the CDI system, and the power is turned on to achieve desalination of the solution; the sodium ion concentration in the solution to be desalinated is 50~1000 mg / L.
8. The application according to claim 2, characterized in that, In step 1, the PBFDO solution is prepared by the following method: 200 mg of 3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione (H-BFDO) and 259 mg of durquinone are dissolved in 12 mL of dimethyl sulfoxide. The reaction solution is heated to 100°C under a nitrogen atmosphere and stirred vigorously for 1 hour. The reaction solution is then allowed to cool naturally to room temperature, placed in a dialysis bag, and immersed in dimethyl sulfoxide for dialyzing. The polymer solution in the dialysis bag is then collected and filtered to obtain the PBFDO solution.
9. The application according to claim 4, characterized in that, In (1), polyaniline is prepared by the following method: 0.05 mol of aniline is poured into 50 mL of 1 mol / L hydrochloric acid solution, the pH of the solution is adjusted to 1.0 with hydrochloric acid, and then 26 mL of 2.4 mmol / L ammonium persulfate solution is added dropwise to the above solution and stirred at 0°C for 24 hours. The precipitate is centrifuged and washed with deionized water. Then the sample is deprotonated in ammonia solution for 24 hours, filtered, washed with deionized water and ethanol, and vacuum dried at 60°C for 24 hours to obtain polyaniline powder sample.
10. The application according to claim 5, characterized in that, In (2), polyaniline@graphene is prepared by the following method: N-methylpyrrolidone is used as a solvent to dissolve polyaniline powder and adjust its concentration to 50 mg / mL; 0.16 mL of polyaniline solution is added to 20 mL of 2 mg / mL graphene oxide solution, sonicated for 30 min, and then freeze-dried; the resulting solid is placed in a plasma radio frequency instrument and treated at a plasma power of 200 W for 1 s to obtain polyaniline@graphene.