Electric control ion exchange membrane material capable of adjusting oxygen vacancy concentration as well as preparation and application of electric control ion exchange membrane material

Abstract

The invention belongs to the technical field of electric control ion exchange materials, and discloses an electric control ion exchange membrane material with adjustable oxygen vacancy concentration and preparation and application thereof. The preparation method comprises the following steps: dispersing a Mn < 7 + > source and a pH regulator in a solvent A to obtain a solution A; dispersing a Mn < 2 + > source in a solvent B to obtain a solution B; dropwise adding the solution A into the solution B to obtain a solution C; the solution C is subjected to microwave treatment, so that Mn < 7 + > and Mn < 2 + > are subjected to a redox reaction, a manganese-based oxide is generated, and a mixed solution containing the manganese-based oxide is obtained; filtering, washing and drying the mixed solution to obtain a precursor material; and roasting the precursor material at 200-600 DEG C to obtain the electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration. According to the electrically-controlled ion exchange membrane material prepared by the method disclosed by the invention, the placement and release of valuable metals are realized by virtue of oxidation / reduction potential of a membrane electrode in a wastewater treatment process, and the whole process is free from secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of electrically controlled ion exchange materials technology, and particularly to electrically controlled ion exchange membrane materials with adjustable oxygen vacancy concentration, their preparation and application. Background Technology

[0002] With the accelerating pace of industrialization, wastewater treatment has become an indispensable part of production for various petrochemical, papermaking, and textile enterprises. Considering the cost and environmental issues of wastewater recycling, recovering valuable metal ions from wastewater for resource recovery is crucial. Traditional wastewater treatment methods, including precipitation, ion exchange, and extraction, suffer from drawbacks such as difficulty in recovery, low adsorption efficiency, poor selectivity, and susceptibility to secondary pollution, thus limiting large-scale wastewater recycling.

[0003] In recent years, electro-controlled ion exchange (ESIX) has attracted much attention from scholars at home and abroad as an ion separation and recovery technology with no secondary pollution, high selectivity, and high separation efficiency [ElectrochimicaActa, 2019, 306:35-44.DOI:10.1016 / j.electacta.2019.03.106]. By controlling the oxidation / reduction state of the membrane electrode, the insertion / release of target ions can be achieved, effectively avoiding the generation of secondary pollution. However, the membrane electrode materials prepared by electro-controlled ion exchange in existing technologies, i.e., electro-controlled ion exchange membranes, have low ion capacity and poor membrane electrode stability, which seriously limits the application of electro-controlled ion exchange membranes in the recovery of valuable metals from wastewater.

[0004] Therefore, the present invention provides an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration, its preparation and application. Summary of the Invention

[0005] To address the limitations of existing electro-controlled ion exchange membranes in recovering valuable metals from wastewater due to low separation capacity and poor stability, this invention provides an electro-controlled ion exchange membrane material with adjustable oxygen vacancy concentration, its preparation, and its application. This invention achieves its electro-controlled ion exchange membrane material with adjustable oxygen vacancy concentration, its preparation, and its application through the following technical solution:

[0006] The first objective of this invention is to provide a method for preparing an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration, comprising the following steps:

[0007] Mn 7+ The source and pH adjuster are uniformly dispersed in solvent A to obtain solution A; wherein the pH adjuster is used to adjust the pH of solution A to be 1-6;

[0008] Mn 2+ The source is uniformly dispersed in solvent B to obtain solution B;

[0009] Solution A was added dropwise to solution B to obtain solution C; subsequently, solution C was subjected to microwave treatment to reduce Mn content. 7+ With Mn 2+ A redox reaction occurs between them to generate manganese-based oxides, resulting in a mixed solution containing manganese-based oxides;

[0010] The mixed solution was filtered, washed, and dried to obtain the precursor material.

[0011] The precursor material is calcined at 200–600°C to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0012] Preferably, the Mn 7+ The source is any one of NaMnO4, KMnO4, and LiMnO4;

[0013] The Mn 2+ The source is any one of MnSO4, Mn(NO3)2, and Mn(CH3COO)2.

[0014] Preferably, the pH adjuster is any one of citric acid, oxalic acid, malic acid, and acetic acid.

[0015] Preferably, the Mn in solution A 7+ With Mn in solution B 2+ The molar ratio is 1-2:1-3.

[0016] Preferably, solvent A is one or both of water and ethanol;

[0017] Solvent B is one or both of ethanol.

[0018] Preferably, the microwave power of the microwave treatment is 20-450W, and the microwave time is 10-2000s;

[0019] The roasting process takes 1 to 5 hours and the heating rate is 2 to 15 °C / min.

[0020] The second objective of this invention is to provide an electrically controlled ion exchange membrane material prepared by the above-described preparation method.

[0021] The third objective of this invention is to provide an application of the above-mentioned electrically controlled ion exchange membrane material in the recovery of valuable metals from wastewater, which is achieved through the following steps:

[0022] The electronically controlled ion exchange membrane material, binder, and organic solvent are mixed to form a slurry;

[0023] The slurry is coated onto a conductive substrate and dried to obtain a membrane electrode.

[0024] Using the membrane electrode as the working electrode, the membrane electrode is placed in wastewater, and an oxidation / reduction potential is applied to the membrane electrode to achieve the electro-controlled separation and recovery of valuable cations in the wastewater.

[0025] The valuable metal ions in the wastewater are one or more of lithium ions, cobalt ions, nickel ions, manganese ions, copper ions, chromium ions, lead ions, and lithium ions.

[0026] Furthermore, when an oxidation / reduction potential is applied, the oxidation potential is 0–1.5V and the reduction potential is -1.2–0V.

[0027] Preferably, the adhesive is any one of starch, dextrin, animal glue, polyvinyl alcohol, carboxymethyl cellulose, vinyl acetate resin, acrylic resin, and chlorinated rubber;

[0028] The organic solvent is any one of acetone, N,N-dimethylformamide, N-methylacetamide, and isopropyl ketone;

[0029] The conductive substrate is any one of stainless steel plate, stainless steel mesh, carbon paper, platinum sheet, titanium plate, graphite paper, carbon cloth, and titanium mesh.

[0030] Preferably, the ratio of the amount of the electro-controlled ion exchange membrane material, the binder, and the organic solvent is 50 mg: 15-25 mg: 1 mL;

[0031] The coating thickness of the slurry on the conductive substrate is 10 nm to 10 μm.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] This invention utilizes Mn 2+ With Mn 7+ The oxidation-reduction reaction between the two processes generates manganese-based oxides. At the same time, a certain amount of pH adjuster is added during the oxidation-reduction process, and high-energy microwaves are used as an energy source for the generation of oxygen vacancies. Then, impurities are removed by calcination, which greatly improves the cleanliness of the electro-controlled ion exchange membrane material and thus improves the membrane structure stability of the electro-controlled ion exchange membrane material.

[0034] This invention uses Mn 7+ The source solution was added dropwise to Mn 2+ In the source solution, to ensure that the Mn in the solution system is within the range of the dropwise addition process. 7+ The content is relatively low, while Mn 2+ The content is relatively high, namely Mn 2+The presence of excess oxygen vacancies in the manganese oxides effectively controls the oxidation-reduction rate, regulates the structure of the oxides, and modulates the oxygen vacancy content to form structurally stable manganese oxides. Simultaneously, microwave treatment effectively increases the oxygen vacancy concentration in the manganese oxides. This increased concentration accelerates the response of the electrically controlled ion exchange membrane material to electrons, significantly improving the utilization rate of the applied current and thus enhancing the ion capacity of the electrically controlled ion exchange membrane material.

[0035] This invention combines the potential-driven nature of electro-controlled ion exchange technology in wastewater recovery with the characteristic of manganese oxide membrane materials that the electron-rich regions formed by oxygen vacancies easily capture cations. When a reduction potential is applied, the membrane material becomes negatively charged as a whole, and electrons accumulate near the oxygen vacancies, forming a high-density negatively charged region that can act as a cation probe in the wastewater, adsorbing valuable cations in the wastewater into the membrane material for recovery. When an oxidation potential is applied, the membrane material becomes positively charged as a whole, and the oxygen vacancies (negatively charged) in the electron-rich regions inside the material are replenished. The electron density around the oxygen vacancies decreases, and the adsorption between the vacancies and valuable cations weakens, causing the cations to be released back into the receiving liquid, significantly improving the capture-recovery efficiency of valuable cations in wastewater.

[0036] The manganese oxide membrane material prepared by this invention has high ion capacity, and the membrane electrode prepared by this invention can realize the insertion and release of valuable metals by relying on the oxidation / reduction potential of the membrane electrode during wastewater treatment. The membrane electrode has poor stability, the applied voltage is less than the standard industrial voltage, the energy consumption of the whole process is low, and there is no secondary pollution in the whole process. Attached Figure Description

[0037] Figure 1 This is a comparison chart of the EPR of oxygen vacancy concentration in the electrically controlled ion exchange membrane materials of Example 1 and Comparative Example 1.

[0038] Figure 2 The curves showing the change of lithium ion concentration in wastewater over time during the adsorption of lithium ions by the membrane electrodes prepared in Examples 4, 5, 6, and Comparative Example 2. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0040] This invention provides an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration. This invention utilizes Mn... 2+ With Mn 7+The oxidation-reduction reaction between the two processes generates manganese-based oxides. Simultaneously, a certain amount of pH adjuster is added during the oxidation-reduction process, and high-energy microwaves are used as the energy source for oxygen vacancy generation. Impurities are then removed through calcination, thereby obtaining an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration. The preparation method of this invention for an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration specifically involves the following steps:

[0041] Step 1, using Mn 2+ With Mn 7+ The redox reaction between them produces manganese-based oxides:

[0042] 1) Mn 7+ The source and pH adjuster are uniformly dispersed in solvent A to obtain solution A;

[0043] 2) Mn 2+ The source is uniformly dispersed in solvent B to obtain solution B;

[0044] 3) Solution A is added dropwise to solution B to obtain solution C; subsequently, solution C is subjected to microwave treatment to reduce Mn 7+ With Mn 2+ A redox reaction occurs between them to generate manganese-based oxides, resulting in a mixed solution containing manganese-based oxides.

[0045] It should be noted that, in this invention, when adding a pH adjuster, it is preferable to combine the pH adjuster with Mn. 7+ The source is dispersed in solvent A to form solution A, and the pH of the solution is adjusted to 1-6 by a pH adjuster so that Mn can exert its effect better under acidic conditions. 7+ It has strong oxidizing properties. In a preferred embodiment of the present invention, the pH adjuster used may be selected from any one of citric acid, oxalic acid, malic acid, and acetic acid.

[0046] Furthermore, the amount of pH adjuster, i.e., the amount of acid, needs to be sufficient to ensure the amount of Mn. 2+ With Mn 7+ After the redox reaction, the solution becomes weakly acidic overall, which has a certain corrosive effect on the generated manganese oxides and promotes the growth of Mn. 3+ The disproportionation effect effectively increases the average valence state of Mn in manganese oxides, thereby enhancing the ion adsorption capacity. Furthermore, to ensure this objective is achieved, in a preferred embodiment of the invention, the pH adjuster is limited to the interaction between the Mn and... 7+ The ratio of the source used is 0.5–1 mL: 0.02–0.05 mol to ensure that the pH of solution A can be adjusted to 1–6.

[0047] This invention aims to effectively control Mn 2+ With Mn 7+The present invention preferably uses Mn to control the rate of redox reactions between the two, thereby effectively regulating the structure of manganese oxides. 7+ Source and Mn 2+ After the sources form solutions, Mn is then added. 7+ The source solution and Mn 2+ The source solution is mixed so that Mn can be further processed during subsequent microwave treatment. 2+ With Mn 7+ The oxidation-reduction reaction between them produces manganese-based oxides.

[0048] This invention relates to the mixing of Mn 7+ The source solution and Mn 2+ When preparing a solution from a source, it is preferable to use Mn. 7+ The source solution was added dropwise to Mn 2+ In the source solution, to ensure that the Mn in the solution system is within the range of the dropwise addition process. 7+ The content is relatively low, while Mn 2+ The content is relatively high, namely Mn 2+ The presence of an excess of Mn allows for effective control of the redox rate, regulation of the oxide structure, and control of oxygen vacancy content. It is important to emphasize that the key to the formation of manganese-based oxides in this invention lies in the application of highly oxidizing Mn... 7+ Dropped onto Mn 2+ In this context, Mn cannot be directly... 7+ The source solution and Mn 2+ The source solution must be mixed; otherwise, the manganese oxide of this invention cannot be obtained. Furthermore, to ensure Mn... 2+ With Mn 7+ Manganese-based oxides can be generated through redox reactions. In a preferred embodiment of the present invention, the Mn in solution A... 7+ With Mn in solution B 2+ The molar ratio of Mn is 1-2:1-3, i.e., Mn 7+ The source solution and Mn 2+ Mn in the source solution 7+ With Mn 2+ The molar ratio is 1-2:1-3.

[0049] The Mn used in this invention 7+ As long as the source can provide Mn 7+ That is, for example, it can be selected from any one of NaMnO4, KMnO4, and LiMnO4. And in order to make Mn... 7+ To form a homogeneous solution, in a preferred embodiment of the invention, water is used as solvent A, and Mn is controlled... 7+ The amount of source and solvent A used is 0.02-0.05 mol: 100 mL, so that Mn 7+ The source is uniformly dispersed in solvent A.

[0050] The Mn used in this invention 2+ As long as the source can provide Mn 2+ That is, for example, it can be selected from any one of MnSO4, Mn(NO3)2, and Mn(CH3COO)2. And in order to make Mn 2+ To form a homogeneous solution, in a preferred embodiment of the invention, water is used as solvent B, and Mn is controlled... 2+ The amount of source and solvent B used is 0.02-0.06 mol: 100 mL, so that Mn 2+ The source is uniformly dispersed in solvent B.

[0051] This invention utilizes microwave processing to remove Mn from solution C. 2+ Source, Mn 7+ The microwave treatment generates instantaneous high energy within the material (the magnitude of this instantaneous high energy can be adjusted by regulating the duration and power of the microwave treatment; different durations and powers will produce different instantaneous high energies). This instantaneous high energy disrupts the material's internal crystal structure (i.e., the -O-Mn-O-Mn-O- structure), leading to oxygen deficiency and the formation of oxygen vacancies. The formation of oxygen vacancies helps to increase the material's adsorption capacity for target ions. Furthermore, to ensure that the present invention can obtain an electrically controlled ion exchange membrane material with high oxygen vacancy concentration through microwave treatment, in a preferred embodiment, the microwave power during microwave treatment is 20–450 W, and the microwave duration is 10–2000 s. This ensures that the instantaneous high energy provided by the microwave treatment effectively increases the oxygen vacancy concentration of manganese oxides, thereby ensuring the acquisition of an electrically controlled ion exchange membrane material with high oxygen vacancy concentration.

[0052] Step 2: Calcination treatment removes impurities to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0053] 1) The mixed solution is filtered, washed, and dried to obtain the precursor material;

[0054] 2) The precursor material is calcined at 200-600°C to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0055] It should be noted that the present invention further involves filtering, washing, and drying the microwave-treated mixed solution to obtain crude manganese oxides, followed by calcination to remove the bound water deep within the manganese oxides. Simultaneously, unoxidized Mn... 2+It can be oxidized by oxygen in the air, which greatly improves the cleanliness of the electro-controlled ion exchange membrane material, thereby enhancing the membrane structure stability. To ensure the removal of bound water deep within the manganese oxides in the crude manganese oxides, and simultaneously remove unoxidized Mn... 2+ In a preferred embodiment of the present invention, the calcination treatment takes 1 to 5 hours and the heating rate is 2 to 15 °C / min.

[0056] The present invention also provides an application of the above-mentioned electrically controlled ion exchange membrane material in the recovery of valuable metals from wastewater, and the recovery of valuable metals from wastewater is achieved through the following steps:

[0057] 1) The electronically controlled ion exchange membrane material, binder, and organic solvent are mixed to form a slurry;

[0058] 2) The slurry is coated onto a conductive substrate and dried to obtain a membrane electrode;

[0059] 3) Using the membrane electrode as the working electrode, the membrane electrode is placed in wastewater, and an oxidation / reduction potential is applied to the membrane electrode to achieve the electro-controlled separation and recovery of valuable cations in the wastewater.

[0060] It should be noted that the valuable metal ions in the wastewater mentioned above are one or more of lithium ions, cobalt ions, nickel ions, manganese ions, copper ions, chromium ions, lead ions, and lithium ions; and when an oxidation / reduction potential is applied, the oxidation potential is 0 to 1.5V and the reduction potential is -1.2 to 0V.

[0061] A slurry is formed by mixing an electrically controlled ion exchange membrane material, a binder, and an organic solvent. This slurry, under the binding action of the binder, allows the electrically controlled ion exchange membrane material to be coated onto a conductive substrate surface and cured to form a membrane layer, thereby obtaining a membrane electrode. In a preferred embodiment of the invention, the binder is any one of starch, dextrin, animal glue, polyvinyl alcohol, carboxymethyl cellulose, vinyl acetate resin, acrylic resin, and chlorinated rubber. In a preferred embodiment of the invention, the conductive substrate is any one of stainless steel plate, stainless steel mesh, carbon paper, platinum sheet, titanium plate, graphite paper, carbon cloth, and titanium mesh. In a preferred embodiment of the invention, the organic solvent is any one of acetone, N,N-dimethylformamide, N-methylacetamide, and isoacetone.

[0062] To ensure that the membrane electrode formed after coating the conductive substrate with slurry can achieve effective electro-controlled separation and recovery of valuable cations in wastewater, in a preferred embodiment of the present invention, the ratio of the electro-controlled ion exchange membrane material, binder and organic solvent is 50mg:15-25mg:1mL; and the coating thickness of the slurry on the conductive substrate is 10nm-10μm.

[0063] Example 1

[0064] This embodiment provides an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration, and its preparation method is as follows:

[0065] Step 1, using Mn 2+ With Mn 7+ The redox reaction between them produces manganese-based oxides:

[0066] 1) Using NaMnO4 as Mn 7+ The source uses oxalic acid as a pH adjuster and deionized water as solvent A.

[0067] Dissolve 3.1g NaMnO4 and 1mL oxalic acid in 100mL deionized water to obtain solution A;

[0068] 2) Using MnSO4 as Mn 2+ The source was prepared by using deionized water as solvent B, and dissolving 8.65g of MnSO4 in 100mL of deionized water to obtain solution B.

[0069] 3) Add the solution A obtained above to the solution B obtained above and mix well to obtain solution C;

[0070] Subsequently, the above solution C was placed in a microwave reactor and subjected to microwave treatment at a power of 200W for 500s. This was done to utilize the instantaneous high radiation characteristic of microwave treatment to induce Mn... 7+ With Mn 2+ A redox reaction occurs between them to generate manganese-based oxide MnOx, resulting in a mixed solution containing manganese-based oxide MnOx.

[0071] Step 2: Calcination treatment removes impurities to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0072] 1) After filtering the above mixed solution, solid manganese oxide MnOx particles were obtained. The manganese oxide MnOx particles were washed three times with deionized water and then dried in an oven at 100°C for 8 hours to obtain the precursor material.

[0073] 2) The above precursor material is calcined at 350°C for 5 hours to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0074] Example 2

[0075] This embodiment provides an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration, and its preparation method is as follows:

[0076] Step 1, using Mn 2+ With Mn 7+The redox reaction between them produces manganese-based oxides:

[0077] 1) Using KMnO4 as Mn 7+ The source uses glacial acetic acid as a pH adjuster and deionized water as solvent A.

[0078] Dissolve 7.9 g KMnO4 and 1 mL glacial acetic acid in 100 mL deionized water to obtain solution A;

[0079] 2) Using Mn(NO3)2 as Mn 2+ The source was prepared by using deionized water as solvent B, and dissolving 8.65g of Mn(NO3)2 in 100mL of deionized water to obtain solution B;

[0080] 3) Add the solution A obtained above to the solution B obtained above and mix well to obtain solution C;

[0081] Subsequently, the above solution C was placed in a microwave reactor and subjected to microwave treatment at a power of 100W for 300s. This was done to utilize the instantaneous high radiation characteristic of microwave treatment to induce Mn... 7+ With Mn 2+ A redox reaction occurs between them to generate manganese-based oxide MnOx, resulting in a mixed solution containing manganese-based oxide MnOx.

[0082] Step 2: Calcination treatment removes impurities to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0083] 1) After filtering the above mixed solution, solid manganese oxide MnOx particles were obtained. The manganese oxide MnOx particles were washed three times with deionized water and then dried in an oven at 100°C for 8 hours to obtain the precursor material.

[0084] 2) The above precursor material is calcined at 400°C for 3 hours to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0085] Example 3

[0086] This embodiment provides an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration, and its preparation method is as follows:

[0087] Step 1, using Mn 2+ With Mn 7+ The redox reaction between them produces manganese-based oxides:

[0088] 1) Using KMnO4 as Mn 7+ The source uses glacial acetic acid as a pH adjuster and deionized water as solvent A.

[0089] Dissolve 7.9 g KMnO4 and 0.5 mL glacial acetic acid in 100 mL deionized water to obtain solution A;

[0090] 2) Using Mn(NO3)2 as Mn 2+ The source was prepared by using deionized water as solvent B, and dissolving 4.21 g of Mn(NO3)2 in 100 mL of deionized water to obtain solution B;

[0091] 3) Add the solution A obtained above to the solution B obtained above and mix well to obtain solution C;

[0092] Subsequently, the above solution C was placed in a microwave reactor and microwaved for 50 seconds at a microwave power of 150W. This was done to utilize the instantaneous high radiation characteristic of microwave treatment to induce Mn... 7+ With Mn 2+ A redox reaction occurs between them to generate manganese-based oxide MnOx, resulting in a mixed solution containing manganese-based oxide MnOx.

[0093] Step 2: Calcination treatment removes impurities to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0094] 1) After filtering the above mixed solution, solid manganese oxide MnOx particles were obtained. The manganese oxide MnOx particles were washed three times with deionized water and then dried in an oven at 100°C for 8 hours to obtain the precursor material.

[0095] 2) The above precursor material is calcined at 350°C for 3 hours to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0096] Example 4

[0097] This embodiment provides a method for recovering valuable metals from wastewater using an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration:

[0098] 1) Mix 50 mg of the electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration prepared in Example 1 with 20 mg of binder PVDF, then add 1 mL of acetone and stir to mix evenly to obtain a slurry.

[0099] 2) Using a stainless steel wire mesh with a size of 4cm×4cm as a conductive substrate, the above slurry is coated onto the surface of the stainless steel wire mesh by coating method. After vacuum drying, a membrane electrode with a high concentration of oxygen vacancy manganese oxide is obtained.

[0100] 3) Using the membrane electrode obtained above as the working electrode, and a stainless steel sheet with a size of 4cm×4cm as the counter electrode;

[0101] In this embodiment, a solution containing 25 ppm lithium ions is used as simulated wastewater. The working electrode and the counter electrode are placed in 100 mL of the simulated wastewater to form a closed loop.

[0102] By treating the simulated wastewater with a voltage of -0.7V for 30 minutes, the lithium ion concentration was measured to be 12 ppm, indicating a lithium ion removal rate of 52%. After repeating the above process three times, the lithium ion concentration after treatment was found to be lower than the atomic absorption spectrometry standard, indicating that repeating the process three times can achieve 100% removal of lithium ions from the wastewater.

[0103] The membrane electrode was removed and placed in a 0.1M sodium sulfate regeneration solution. It was treated for 30 minutes under a voltage of 0.6V. The concentration of lithium ions in the regeneration solution was measured to be 22.5ppm, indicating that the lithium ion regeneration rate was 90% after treatment in this example.

[0104] Example 5

[0105] This embodiment provides a method for recovering valuable metals from wastewater using an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration:

[0106] 1) Mix 50 mg of the electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration prepared in Example 2 with 20 mg of binder PVDF, then add 1 mL of acetone and stir to mix evenly to obtain a slurry.

[0107] 2) Using a stainless steel wire mesh with a size of 4cm×4cm as a conductive substrate, the above slurry is coated onto the surface of the stainless steel wire mesh by coating method. After vacuum drying, a membrane electrode with a high concentration of oxygen vacancy manganese oxide is obtained.

[0108] 3) Use the membrane electrode obtained above as the working electrode and a stainless steel sheet with a size of 4cm×4cm as the counter electrode.

[0109] In this embodiment, a solution containing 21 ppm lithium ions is used as simulated wastewater. The working electrode and the counter electrode are placed in 100 mL of the simulated wastewater to form a closed loop.

[0110] By treating the simulated wastewater with a voltage of -0.8V for 25 minutes, the lithium ion concentration was measured to be 9 ppm, indicating a lithium ion removal rate of 57%. After repeating the above process three times, the lithium ion concentration after treatment was found to be lower than the atomic absorption spectrometry standard, indicating that repeating the process three times can achieve 100% removal of lithium ions from the wastewater.

[0111] The membrane electrode was removed and placed in 100 mL of 0.1 mol / L sodium sulfate regeneration solution. It was treated for 30 min under a voltage of 0.6 V. The concentration of lithium ions in the regeneration solution was measured to be 18.91 ppm, indicating that the lithium ion regeneration rate was 90.05% after treatment in this example.

[0112] Example 6

[0113] This embodiment provides a method for recovering valuable metals from wastewater using an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration:

[0114] 1) Mix 50 mg of the electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration prepared in Example 3 with 20 mg of binder PVDF, then add 1 mL of acetone and stir to mix evenly to obtain a slurry.

[0115] 2) Using a stainless steel wire mesh with a size of 4cm×4cmcm as a conductive substrate, the above slurry is coated onto the surface of the stainless steel wire mesh by coating method. After vacuum drying, a membrane electrode with a high concentration of oxygen vacancy manganese oxide is obtained.

[0116] 3) The membrane electrode obtained above is used as the working electrode, and a stainless steel sheet with a size of 4cm×4cm is used as the counter electrode.

[0117] In this embodiment, a solution containing 20 ppm lithium ions is used as simulated wastewater. The working electrode and the counter electrode are placed in 100 mL of the simulated wastewater to form a closed loop.

[0118] By treating the simulated wastewater with a voltage of -0.9V for 25 minutes, the lithium ion concentration was measured to be 8.5 ppm, indicating a lithium ion removal rate of 57.5%. After repeating the above process three times, the lithium ion concentration after treatment was found to be lower than the atomic absorption spectrometry standard, indicating that repeating the process three times can achieve 100% removal of lithium ions from the wastewater.

[0119] The membrane electrode was removed and placed in 100 mL of 0.1 mol / L sodium sulfate regeneration solution. It was treated for 30 min under a voltage of 0.5 V. The concentration of lithium ions in the regeneration solution was measured to be 18.25 ppm, indicating that the lithium ion regeneration rate was 91.25% after treatment in this example.

[0120] Comparative Example 1

[0121] This comparative example provides an electrically controlled ion exchange membrane material, and its preparation method is as follows:

[0122] Step 1, using Mn 2+ With Mn 7+ The redox reaction between them produces manganese-based oxides:

[0123] 1) Using NaMnO4 as Mn 7+ The source uses oxalic acid as a pH adjuster and deionized water as solvent A.

[0124] Dissolve 3.1g NaMnO4 and 1mL oxalic acid in 100mL deionized water to obtain solution A;

[0125] 2) Using MnSO4 as Mn 2+ The source was prepared by using deionized water as solvent B, and dissolving 8.65g of MnSO4 in 100mL of deionized water to obtain solution B.

[0126] 3) Add the solution A obtained above to the solution B obtained above and mix well to obtain solution C;

[0127] Subsequently, the above solution C was subjected to a hydrothermal reaction at 150°C for 6 hours to obtain a mixed solution.

[0128] Step 2: Calcination treatment removes impurities to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

[0129] 1) After filtering the above mixed solution, the obtained solid component was washed three times with deionized water and then dried in an oven at 100°C for 8 hours to obtain the precursor material.

[0130] 2) The above precursor material was calcined at 350°C for 5 hours to obtain the electro-controlled ion exchange membrane material.

[0131] The only difference between Comparative Example 1 and Example 1 is that:

[0132] In this comparative example, the microwave treatment in Example 1 is replaced by hydrothermal synthesis. The process parameters for hydrothermal synthesis are: hydrothermal reaction temperature of 150°C and hydrothermal treatment time of 6 hours.

[0133] Comparative Example 2

[0134] This embodiment provides a method for recovering valuable metals from wastewater using an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration:

[0135] 1) Mix 50 mg of the electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration prepared in Comparative Example 1 with 20 mg of binder PVDF, then add 1 mL of acetone and stir to mix well to obtain a slurry.

[0136] 2) Using a stainless steel wire mesh with a size of 4cm×4cm as a conductive substrate, the above slurry is coated onto the surface of the stainless steel wire mesh by coating method. After vacuum drying, a membrane electrode with a high concentration of oxygen vacancy manganese oxide is obtained.

[0137] 3) Using the membrane electrode obtained above as the working electrode, and a stainless steel sheet with a size of 4cm×4cm as the counter electrode;

[0138] In this embodiment, a solution containing 25 ppm lithium ions is used as simulated wastewater. The working electrode and the counter electrode are placed in 100 mL of the simulated wastewater to form a closed loop.

[0139] By treating the simulated wastewater with a voltage of -0.7V for 30 minutes, the lithium ion concentration was measured to be 12 ppm, indicating a lithium ion removal rate of 52%. After repeating the above process three times, the lithium ion concentration after treatment was found to be lower than the atomic absorption spectrometry standard, indicating that repeating the process three times can achieve 100% removal of lithium ions from the wastewater.

[0140] The membrane electrode was removed and placed in a 0.1M sodium sulfate regeneration solution. It was treated for 30 minutes under a voltage of 0.6V. The concentration of lithium ions in the regeneration solution was measured to be 22.5ppm, indicating that the lithium ion regeneration rate was 90% after treatment in this example.

[0141] The only difference between this comparative example and Example 4 is that:

[0142] In this comparative example, the electrically controlled ion exchange membrane material prepared in Comparative Example 1 is used instead of the electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration obtained in Example 1.

[0143] Experimental Section

[0144] (I) EPR Test

[0145] This invention uses the electrically controlled ion exchange membrane material prepared in Example 1 and the electrically controlled ion exchange membrane material prepared in Comparative Example 1 as examples. The g value of the EPR is controlled to be 2.003, and the oxygen vacancy concentration is measured using electron paramagnetic resonance (EPR) spectroscopy. The main focus is on testing the oxygen vacancy concentration of the sample; the higher the oxygen vacancy concentration, the greater the peak intensity, and the test results are as follows: Figure 1 As shown.

[0146] And by Figure 1 It can be seen that the oxygen vacancy concentration of the electrically controlled ion exchange membrane material prepared in Example 1 is significantly higher than that of the electrically controlled ion exchange membrane material prepared in Comparative Example 1, indicating that microwave treatment can effectively increase the oxygen vacancy concentration of manganese oxides.

[0147] (II) Adsorption capacity test

[0148] This invention uses the membrane electrodes prepared in Examples 4, 5, and 6, as well as Comparative Example 2, as examples. Atomic absorption spectroscopy (AAS) was used to test the changes in lithium ion concentration during the adsorption process, and the concentration changes were used to obtain... Figure 2 .

[0149] The test method is as follows: The test system is an electrochemical three-electrode system, with each of the above-mentioned membrane electrodes as the working electrode, a stainless steel sheet as the counter electrode, and Ag / AgCl as the reference electrode. A voltage of -0.8V is applied, and the results are obtained based on the concentration change. Figure 2 .

[0150] And from Figure 2 As can be seen, after applying a voltage of -0.8V, the membrane electrodes of Examples 4-6 exhibit an adsorption capacity of 15-20 mg / L for lithium ions, while the membrane electrode of Comparative Example 1 has an adsorption capacity of less than 5 mg / L for lithium ions. In other words, the manganese oxide membrane electrode prepared by this invention has an adsorption capacity for lithium ions that is 3-4 times that of manganese oxides prepared by conventional hydrothermal synthesis, representing a significant improvement.

[0151] Obviously, the above embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration, characterized in that, Includes the following steps: Mn 7+ The source and pH adjuster are uniformly dispersed in solvent A to obtain solution A; wherein the pH adjuster is used to adjust the pH of solution A to be 1-6; Mn 2+ The source is uniformly dispersed in solvent B to obtain solution B; Solution A was added dropwise to solution B to obtain solution C; subsequently, solution C was subjected to microwave treatment to reduce Mn content. 7+ With Mn 2+ A redox reaction occurs between them to generate manganese-based oxides, resulting in a mixed solution containing manganese-based oxides; The mixed solution was filtered, washed, and dried to obtain the precursor material. The precursor material is calcined at 200–600°C to obtain an electrically controlled ion exchange membrane material with adjustable oxygen vacancy concentration.

2. The preparation method according to claim 1, characterized in that, The Mn 7+ The source is any one of NaMnO4, KMnO4, and LiMnO4; The Mn 2+ The source is any one of MnSO4, Mn(NO3)2, and Mn(CH3COO)2.

3. The preparation method according to claim 1, characterized in that, The pH adjuster is any one of citric acid, oxalic acid, malic acid, and acetic acid.

4. The preparation method according to claim 1, characterized in that, Mn in solution A 7+ With Mn in solution B 2+ The molar ratio is 1-2:1-3.

5. The preparation method according to claim 1, characterized in that, Solvent A is one or both of water and ethanol; Solvent B is one or both of ethanol.

6. The preparation method according to claim 1, characterized in that, The microwave power of the microwave processing is 20-450W, and the microwave time is 10-2000s; The roasting process takes 1 to 5 hours and the heating rate is 2 to 15 °C / min.

7. An electrically controlled ion exchange membrane material prepared by the preparation method according to any one of claims 1-6.

8. The application of the electrically controlled ion exchange membrane material according to claim 7 in the recovery of valuable metals from wastewater, characterized in that, The following steps are used to recover valuable metals from wastewater: The electronically controlled ion exchange membrane material, binder, and organic solvent are mixed to form a slurry; The slurry is coated onto a conductive substrate and dried to obtain a membrane electrode. Using the membrane electrode as the working electrode, the membrane electrode is placed in wastewater, and an oxidation / reduction potential is applied to the membrane electrode to achieve the electro-controlled separation and recovery of valuable cations in the wastewater. The valuable metal ions in the wastewater are one or more of lithium ions, cobalt ions, nickel ions, manganese ions, copper ions, chromium ions, lead ions, and lithium ions. Furthermore, when an oxidation / reduction potential is applied, the oxidation potential is 0–1.5V and the reduction potential is -1.2–0V.

9. The application as described in claim 8, characterized in that, The adhesive is any one of starch, dextrin, animal glue, polyvinyl alcohol, carboxymethyl cellulose, vinyl acetate resin, acrylic resin, and chlorinated rubber; The organic solvent is any one of acetone, N,N-dimethylformamide, N-methylacetamide, and isopropyl ketone; The conductive substrate is any one of stainless steel plate, stainless steel mesh, carbon paper, platinum sheet, titanium plate, graphite paper, carbon cloth, and titanium mesh.

10. The application as described in claim 8, characterized in that, The ratio of the amount of the electrically controlled ion exchange membrane material, the binder, and the organic solvent is 50 mg: 15-25 mg: 1 mL; The coating thickness of the slurry on the conductive substrate is 10 nm to 10 μm.

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