Bi-based CDI active electrode material and preparation method and application thereof

Abstract

The invention belongs to the field of wastewater treatment, and particularly relates to a preparation method of a Bi-based CDI active electrode material, and the Bi-based CDI active electrode material is obtained by performing solvothermal reaction in a mixed solution containing a compound Bi source in a formula 1, DMF and alcohol, in the formula 1, R is-COOH or the invention also comprises the material prepared by the preparation method and application of the material in CDI. The material prepared by the preparation method disclosed by the invention can be sheeted, and has excellent CDI adsorption capacity and selectivity.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical deionization, specifically relating to materials for electrochemical deionization wastewater treatment. Background Technology

[0002] High-salinity, chlorine-containing wastewater is a major problem facing the green development of the iron and steel, non-ferrous metals, and other smelting industries. my country's metallurgical products are diverse, with various production processes, generating large amounts of chlorine-containing wastewater annually. This wastewater contains chloride ions (Cl-). - It has a high content of ) and high acidity, with a complex composition. If not properly treated, Cl... - This will cause significant environmental damage and economic losses, such as corroding industrial production equipment and endangering ecological and environmental safety. Currently, domestic and international technologies for treating high-salt, chlorine-containing wastewater can be broadly classified into four categories: chemical precipitation, adsorption, oxidation, and membrane separation. However, these technologies still suffer from problems such as low treatment efficiency, secondary pollution, and high costs.

[0003] Capacitive deionization (CDI) is considered a promising solution for chlorine-containing wastewater purification due to its advantages such as high efficiency, small environmental footprint, and low energy consumption. Generally, the performance of a CDI system largely depends on the electrochemical properties of the electrode materials. To date, carbon materials such as activated carbon, graphene, and porous carbon have been extensively studied as electrode materials. However, their effectiveness in treating Cl-... - Insufficient affinity for adsorption leads to problems such as low adsorption capacity and low desalination rate, which seriously restricts its practical application.

[0004] Current research on Cl - The current collection electrodes are mainly composed of conductive polymers, layered double hydroxides, FeOOH, MXene, Ag, etc. These materials suffer from problems such as poor stability, low desalination capacity, slow desalination rate, and high cost. Therefore, there is an urgent need to develop a novel chloride ion removal electrode with high desalination capacity and good charge transfer. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a method for preparing Bi-based CDI active electrode materials, aiming to prepare CDI active materials with excellent CDI processing capacity.

[0006] The second objective of this invention is to provide the Bi-based CDI active material prepared by the aforementioned method and its application in CDI electroadsorption.

[0007] A third objective of this invention is to provide a CDI electrode comprising the Bi-based CDI active material and its application in wastewater treatment.

[0008] To achieve the above objectives, the solution of the present invention is:

[0009] A method for preparing a Bi-based CDI active electrode material involves carrying out a solvothermal reaction of a mixed solution containing a compound of formula 1, a Bi source, DMF, and an alcohol to obtain the material.

[0010]

[0011] In Equation 1, R is -COOH or

[0012] This invention demonstrates that by performing solvothermal treatment of Formula 1 and a bismuth source in a DMF-alcohol composite solvent system, Formula 1-Bi coupling materials can be successfully constructed. This solves problems such as difficulty in forming the product into sheets, easy peeling of the electrode layer, and difficulty in utilizing the CDI adsorption capacity, and can significantly improve the capacity and selectivity of CDI.

[0013] In this invention, the combination of Formula 1, Bi, and the DMF-alcohol solvent is the key to the synergistic preparation of the material and to solving the problems of difficulty in forming sheets and the difficulty in realizing the capacity of CDI.

[0014] In this invention, the Bi source is Bi. 3+ The salt, taking into account the ease of sourcing commercial materials, may be further selected from at least one of bismuth nitrate, bismuth citrate, bismuth acetate, and potassium bismuth citrate.

[0015] In this invention, the molar ratio of the Bi source to the compound of formula 1 is 0.5 to 3:1; further, it is 0.9 to 2.1:1; and even further, it is 1 to 2:1.

[0016] In this invention, the combination of DMF and alcohol unexpectedly enables the preparation of the CDI active electrode material, which can be coated into sheets and has good stability of the coated electrode structure.

[0017] In this invention, the alcohol can be any alcohol solvent available in the industry, such as a C1 to C4 unit or polyol; preferably at least one of methanol and ethanol.

[0018] In this invention, the volume ratio of DMF to alcohol can be adjusted as needed, for example, it can be 1:5 to 50; further, it can be 1:10 to 20.

[0019] Preferably, the concentration of Bi element in the Bi source in the mixed solution is 0.001 to 0.01 M.

[0020] In this invention, a bismuth source can be pre-mixed with DMF to obtain solution 1; Formula 1 can be pre-mixed with an alcohol to obtain solution 2; solutions 1 and 2 can be mixed to obtain the mixed solution; and the mixed solution can be placed in a pressure-resistant container and heated to carry out a solvothermal reaction.

[0021] In this invention, the solvothermal temperature is above 100°C, more specifically 110–150°C, and more specifically 120–140°C;

[0022] Preferably, the solvothermal holding time is more than 6 hours, more preferably 9 to 20 hours, and more preferably 10 to 15 hours;

[0023] In this invention, after solvent heat treatment, a crude product is obtained through solid-liquid separation, and then the crude product is washed to obtain the Bi-based CDI active electrode material.

[0024] The present invention also provides a Bi-based CDI active electrode material prepared by the aforementioned preparation method.

[0025] The present invention demonstrates that the preparation method described herein can obtain materials with novel structures (as shown in Formulas 2 and 3 below), and the materials prepared by the method can solve the problem of Bi-based materials being difficult to form into sheets, and can also improve the capacity and selectivity of CDI based on multiple mechanisms.

[0026]

[0027] The present invention also provides an application of the Bi-based CDI active electrode material described above, using it as a CDI active material.

[0028] The present invention has found that the Bi-based CDI active electrode material exhibits excellent electroadsorption capacity and selectivity in CDI.

[0029] The application described in this invention uses it as a CDI active material for the electroadsorption of anions. Furthermore, it is used as a CDI active material for the electroadsorption of chlorine in chlorinated water.

[0030] The present invention also provides a CDI electrode material, comprising an active material, wherein the active material comprises the Bi-based CDI active electrode material of the present invention.

[0031] In this invention, the content of the Bi-based CDI active electrode material in the active material is above 70 wt.%; in order to further leverage the advantages of the material of this invention, its content in the active material can be further increased, for example, the active material is the Bi-based CDI active electrode material of this invention.

[0032] In this invention, the CDI electrode material may also contain binders and conductive agents.

[0033] The present invention also provides a CDI electrode, comprising a current collector and a CDI electrode material composite thereon, wherein the CDI electrode material is the CDI electrode material described in the present invention.

[0034] In this invention, the CDI electrode can be prepared by a coating method. The coating method includes, for example, the following steps: slurrying the CDI electrode material with a solvent, coating it onto a current collector, and then drying it.

[0035] The present invention shows that Bi-based materials often face problems such as difficulty in forming sheets and easy peeling during the coating electrode process. However, the Bi-based CDI active electrode material prepared by the method of the present invention can overcome these problems and can exhibit excellent CDI activity, capacity and selectivity.

[0036] The present invention also provides a CDI device comprising the aforementioned Bi-based CDI active electrode material.

[0037] It further comprises the CDI electrode material described in this invention. It even further comprises the CDI electrode described in this invention.

[0038] Beneficial effects

[0039] This invention involves solvothermal treatment of Formula 1 and a bismuth source in the DMF-alcohol, thereby successfully preparing Formula 1-Bi coordination coupling materials. The materials prepared by this method are unexpectedly suitable for sheet formation requirements, solving the problem of electrode peeling. Furthermore, they can effectively exert their CDI adsorption performance.

[0040] Specifically, in practical applications, the Bi-based CDI electrode prepared by this invention exhibits good performance in the presence of Cl in water. - Excellent electroadsorption performance; in a 1000 mg / L NaCl solution, at a voltage of 1.4 V, it exhibited a Cl- adsorption capacity of 107.20 mg / g. - The adsorption capacity and dechlorination rate are as high as 36.79 mg / g / min. Attached Figure Description

[0041] Figure 1 The images show the XRD patterns of the Bi-based CDI electrode material and the BulkBi material prepared in Example 1.

[0042] Figure 2 SEM image of the Bi-based CDI electrode material prepared in Example 1;

[0043] Figure 3 Cyclic voltammetry curves of the Bi-based CDI electrode material prepared in Example 1 in 1M NaCl solution;

[0044] Figure 4 The dechlorination performance of the Bi-based CDI electrode material prepared in Example 1, Bulk Bi and AC;

[0045] Figure 5The dechlorination performance of the Bi-based CDI electrode material prepared in Example 1 under different applied voltages.

[0046] In the above figures, Bulk Bi represents commercially purchased Bi powder (Shanghai Aladdin Biochemical Technology Co., Ltd., 99.9% metal content, 1μm particle size); AC represents commercially purchased activated carbon (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., specific surface area 1800m²). 2 / g). Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] This invention provides a novel Bi-based CDI active electrode material and a preparation method that utilizes a compound of Formula 1, a Bi source, and a DMF-alcohol system for a solvothermal reaction.

[0049] The preparation method of the Bi-based CDI active electrode material of the present invention typically includes the following steps:

[0050] S1, under stirring conditions, the Bi source is dissolved in N,N-dimethylformamide (DMF) solution to obtain solution one;

[0051] S2, dissolve Formula 1 in an alcohol solution to obtain Solution 2, then add Solution 1 to Solution 2 and stir to obtain Mixed Solution 3;

[0052] S3, transfer mixed solution three into a polytetrafluoroethylene stainless steel reactor and heat it at a certain temperature for a certain time to obtain mixed solution four;

[0053] S4. After the reaction vessel has cooled to room temperature, the above-obtained mixed solution is centrifuged four times, washed several times, and dried under vacuum at a certain temperature to obtain the final product.

[0054] The present invention also provides a Bi-based CDI active electrode, comprising a current collector and an electrode material layer composited on the surface of the current collector; the active material comprises a conductive agent, a binder, and the CDI electrode active material.

[0055] The current collector is made of carbon paper, graphite paper, carbon cloth, or titanium plate, with titanium plate being preferred.

[0056] The conductive agent is at least one of acetylene black and conductive carbon black.

[0057] The adhesive is at least one of PVDF and PTFE.

[0058] In the electrode material layer, the content of the conductive agent is 1-10 wt.%; the content of the binder is 1-10 wt.%.

[0059] The present invention also provides a method for preparing the CDI electrode, wherein the conductive agent, binder and CDI electrode active material are slurried with a solvent to obtain a slurry, which is then coated on the surface of the current collector and dried to obtain the final product.

[0060] The present invention also provides an application of the Bi-based CDI active electrode material as described in any one of the above claims in the electroadsorption of chloride ions.

[0061] The present invention also provides a method for electro-adsorption of chloride ions using a Bi-based CDI active electrode, wherein the Bi-based CDI active electrode material as described in any one of the above claims is used as the anode of a capacitive deionization device, and the capacitive deionization device is used to electrochemically adsorb chloride ions in a chloride-containing solution.

[0062] In this invention, the method for electroadsorption of chloride ions using a Bi-based CDI active electrode can be conventional. For example, there are no special requirements for the chloride content of the solution to be treated, such as it can be above 100 mg / L; there are also no special requirements for the voltage of the adsorption process, such as it can be above 1V, further can be 1 to 2V, and even further can be 1.3 to 1.8V.

[0063] The following is a more typical case:

[0064] Example 1

[0065] This embodiment describes a method for preparing Bi-based CDI active materials, which includes the following steps:

[0066] (1) Weigh 242.54 mg (0.5 mmol) of bismuth nitrate pentahydrate and dissolve it completely in 5 mL of LDMF solution to obtain solution one;

[0067] (2) Weigh out Equation 1 (Equation 1-A, (0.5 mmol) was dissolved in 60 mL of anhydrous methanol to obtain solution two. Then, solution one was added to solution two and stirred for 30 min to obtain mixed solution three.

[0068] (3) Transfer the mixed solution three to a polytetrafluoroethylene stainless steel reactor and heat it at 125℃ (solvent temperature) for 12 hours to obtain mixed solution four;

[0069] (4) After the reaction vessel is cooled to room temperature, the above-obtained mixed solution is centrifuged four times, washed several times with DMF and anhydrous ethanol, and dried at 60°C for 6 hours under vacuum to obtain Bi-based CDI active material (labeled as Bi-Fc).

[0070] Example 2

[0071] Compared with Example 1, the only difference is that Formula 1 is replaced with Formula 1-B. The molar ratio of Bi to Bi and other operating conditions are the same as in Example 1.

[0072] Example 3

[0073] Compared with Example 1, the only difference is that in step (3), the solvothermal temperature is 135°C and the time is 10h, while the other operating conditions are the same as in Example 1.

[0074] Example 4

[0075] Compared with Example 1, the only difference is that in step (1), the amount of bismuth nitrate is changed so that the molar ratio of bismuth nitrate to Formula 1 is 2:1, and all other operating conditions are the same as in Example 1.

[0076] Comparative Example 1

[0077] Compared with Example 1, the only difference is that the bismuth nitrate is replaced by an equimolar amount of the following groups of metal M nitrates:

[0078] Group A: Metal M is Al;

[0079] Group B: Metal M is Fe;

[0080] Group C: Metal M is Co;

[0081] Group D: Metal M is Ni;

[0082] All other operations and parameters are the same as in Example 1.

[0083] Comparative Example 2

[0084] Compared with Example 1, the only difference is that raw material A with the following structure is used to replace Formula 1 in equimolar form, while all other operations and parameters are the same as in Example 1. The specific groups are as follows:

[0085] Group A: Raw material A is...

[0086] Group B: Raw material A is

[0087] Group C: Raw material A is

[0088] All other operations and parameters are the same as in Example 1.

[0089] Comparative Example 3

[0090] Compared with Example 1, the only difference is that DMF is used to replace methanol by an equal volume, that is, the reaction solvent is DMF alone, and all other operations and parameters are the same as in Example 1.

[0091] <Experiment>

[0092] The following experiments were conducted on the products of Example 1 above.

[0093] <Experiment 1>

[0094] The purpose of this experiment is to characterize the crystal structure and morphology of the synthesized Bi-based CDI active material.

[0095] The XRD patterns of the Bi-based CDI active material and Bulk Bi material prepared according to the final step (4) of Example 1 above are shown in the following figures. Figure 1 The XRD diffraction peaks of Bulk Bi at 22.46°, 23.79°, 27.16°, 37.95°, 39.62°, 44.55°, 45.86°, 46.02°, 46.74°, 48.70°, 56.03°, 59.32°, 61.13°, 62.18°, 62.89°, 64.51°, 67.43°, 70.78°, 71.53°, 71.88°, 73.71°, 75.33°, 76.40°, and 81.14° correspond to the (0) ∠B ... The crystal planes (03), (101), (012), (104), (110), (015), (006), (113), (021), (202), (024), (107), (205), (116), (211), (122), (018), (214), (009), (300), (027), (125), (133), and (208) are almost identical to the standard peaks in the standard card PDF#04-007-5315 for rhombic metallic Bi, indicating that Bulk Bi has a metallic Bi crystal structure. No metallic Bi crystal structure was found in the XRD pattern of the Bi-based CDI active material prepared in Example 1, indicating that Bi in the Bi-based CDI active material exists in a coordination structure, not in the form of metallic Bi.

[0096] like Figure 2 As shown, the SEM image of the Bi-based CDI active material prepared according to the final step (4) of Example 1 above shows a spherical nanoflower-like structure with a size of 220 nm.

[0097] <Experiment 2>

[0098] The specific operation process is as follows: 8 mg of CDI active material (material prepared in each example or comparative example), 1 mg of conductive carbon black, and 1 mg of PVDF as binder are mixed and dissolved in 0.6 mL of NMP, then ultrasonically treated and stirred for 30 minutes to form a uniform slurry. Then, 50 μL of the mixed slurry is coated onto a 1×1 cm... 2 Carbon paper was vacuum dried at 120℃. The prepared electrode was placed in a 1 mol / L NaCl electrolyte, with a platinum sheet electrode as the counter electrode and silver / silver chloride as the reference electrode, and electrochemical tests were performed using a three-electrode method.

[0099] The cyclic voltammetry curve of the Bi-based CDI electrode material obtained in Example 1 was measured at a scan rate of 10 mV / s. Figure 3 The Bi-based CDI electrode material exhibited two sets of redox peaks at a scan rate of 10 mV / s. The oxidation peak at -0.34 V corresponds to Fe in Formula 1. 2+ Oxidized to Fe 3+ The reduction peak at -0.26V is Fe 3+ Reduced to Fe 2+ The oxidation peak at 0.027V is due to the reaction of Bi and Cl. - The reaction converts to BiOCl, and the reduction peak at -1.132 indicates the conversion of BiOCl to Bi.

[0100] Experiment 3

[0101] The purpose of this experiment is to investigate the dechlorination performance and dechlorination rate of Bi-based CDI electrode materials.

[0102] The Bi-based CDI electrode material prepared in Bulk Bi, AC, and Example 1 above was used as the active material and prepared using the following capacitive deionization electrode preparation method: 80 wt% of the active material, 10 wt% of acetylene black, and 10 wt% of PVDF were dissolved in 1 mL of NMP, then ultrasonically treated and stirred for 30 minutes to form a homogeneous slurry. 1 mL of the mixed slurry was coated onto a current collector and dried at 120 °C. The obtained CDI electrode was assembled into a CDI unit, a certain applied voltage was applied between the positive and negative electrodes, and the salt solution to be treated was delivered to the CDI unit by a peristaltic pump. The electrochemical performance of the CDI device was then tested.

[0103] like Figure 4 As shown, in an initial NaCl solution of 1000 mg / L at 1.4 V, the Cl content of the Bi-based CDI electrode material... - The removal capacity was 107.21 mg / g, significantly higher than that of Bulk Bi (64.38 mg / g) and AC (37.15 mg / g) for Cl. - Capacity removal. Cl-based CDI electrode material of Bi. -Removal rates up to 36.79 mg / g / min, Bulk Bi and AC Cl - The removal rates were 12.13 mg / g / min and 14.56 mg / g / min, respectively.

[0104] <Experiment 4>

[0105] The purpose of this experiment is to investigate the dechlorination performance and dechlorination rate of Bi-based CDI electrode materials under different voltages.

[0106] The Bi-based CDI electrode material prepared in Example 1 above was prepared using the following capacitive deionization electrode method: 80 wt% of the active material, 10 wt% of acetylene black, and 10 wt% of PVDF were dissolved in 1 mL of NMP, followed by ultrasonic treatment and stirring for 30 minutes to form a homogeneous slurry. 1 mL of the mixed slurry was coated onto a current collector and dried at 120°C. The resulting CDI electrode was assembled into a CDI unit. A certain applied voltage was applied between the positive and negative electrodes, and the salt solution to be treated was delivered to the CDI unit via a peristaltic pump. The electrochemical performance of the CDI device was then tested.

[0107] like Figure 5 As shown, in an initial 1000 mg / L NaCl solution, the Bi-based CDI electrode material exhibits Cl- content at voltages of 1.0, 1.2, 1.4, and 1.6 V. - The removal capacities were 47.27, 64.01, 107.21 and 133.57 mg / g, respectively, with corresponding maximum desalination rates of 12.63, 16.99, 31.71 and 35.34 mg / g / min.

[0108] <Experiment 5>

[0109] The purpose of this experiment was to investigate the dechlorination performance of the materials prepared in Examples 2, 3, 4, Comparative Example 1, and Comparative Example 2. In other words, the materials prepared in each case were used as active materials and tested according to the method described in Experiment 4.

[0110] The test conditions were a constant voltage of 1.4V, an initial NaCl solution of 1000 mg / L, and electroadsorption for 40 minutes. The test results are shown in Table 1.

[0111] Table 1

[0112]

[0113] <Experiment 6>

[0114] The purpose of this experiment is to investigate the dechlorination performance of the material prepared in Comparative Example 3.

[0115] The Bi-based CDI electrode material prepared in Comparative Example 3 was processed using the following capacitive deionization electrode preparation method: 80 wt% of the active material, 10 wt% of acetylene black, and 10 wt% of PVDF were dissolved in 1 mL of NMP, followed by ultrasonic treatment and stirring for 30 minutes to form a homogeneous slurry. 1 mL of the mixed slurry was coated onto a current collector and dried at 120 °C. After final drying, the active material cracked and detached from the electrode surface, indicating instability and unsuitability for testing.

[0116] The above description of the embodiments is intended to enable those skilled in the art to understand and use the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the principles of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A method for preparing a Bi-based CDI active electrode material, characterized in that, The mixture of compound 1, Bi source, DMF, and alcohol is subjected to a solvothermal reaction to obtain the product. In Equation 1, R is -COOH or 2. The method for preparing the Bi-based CDI active electrode material as described in claim 1, characterized in that, The Bi source is at least one of bismuth nitrate, bismuth citrate, bismuth acetate, and potassium bismuth citrate. Preferably, the molar ratio of the Bi source to the compound of formula 1 is 0.5 to 3:1; further, it is 0.9 to 2.1:1; and even further, it is 1 to 2:

1.

3. The method for preparing the Bi-based CDI active electrode material as described in claim 1, characterized in that, The alcohol is a C1-C4 unit or polyol; preferably at least one of methanol and ethanol.

4. The method for preparing the Bi-based CDI active electrode material as described in claim 1, characterized in that, The volume ratio of DMF to alcohol is 1:5 to 50; more specifically, 1:10 to 20. Preferably, the concentration of Bi element in the Bi source in the mixed solution is 0.001 to 0.01 M.

5. The method for preparing the Bi-based CDI active electrode material as described in claim 1, characterized in that, The solvothermal temperature is above 100℃, further to 110~150℃, and further to 120~140℃; Preferably, the solvothermal holding time is more than 6 hours, more preferably 9 to 20 hours, and more preferably 10 to 15 hours; Preferably, after solvent heat treatment, a crude product is obtained through solid-liquid separation, and then the crude product is washed to obtain the Bi-based CDI active electrode material.

6. A Bi-based CDI active electrode material prepared by the preparation method according to any one of claims 1 to 5.

7. The application of a Bi-based CDI active electrode material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, It can be used as a CDI active material; Preferably, it is used as a CDI active material for the electroadsorption of anions; Preferably, it is used as a CDI active material for the electro-adsorption of chlorine in chlorinated water.

8. A CDI electrode material, comprising an active material, characterized in that, The active material comprises the Bi-based CDI active electrode material prepared by the preparation method according to any one of claims 1 to 5; Preferably, the content of the Bi-based CDI active electrode material in the active material is above 70 wt.%. Preferably, the CDI electrode material may also contain a binder and a conductive agent.

9. A CDI electrode, comprising a current collector and a CDI electrode material composite thereon, characterized in that, The CDI electrode material is the CDI electrode material as described in claim 7.

10. A CDI device, characterized in that, It includes the Bi-based CDI active electrode material prepared by the preparation method according to any one of claims 1 to 5; Preferably, it comprises the CDI electrode material as described in claim 8; Further preferably, it includes the CDI electrode as described in claim 9.

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