Preparation method of electrochemical self-cleaning conductive composite membrane and water treatment application

Abstract

The present invention discloses a preparation method and water treatment application of an electrochemical self-cleaning conductive composite membrane, comprising the following steps: (1) preparation of a precursor: graphene quantum dots and carbon nanomaterials are dispersed in a solvent, aniline and concentrated hydrochloric acid are added under an ice bath, ammonium persulfate-hydrochloric acid solution is slowly added to the above solution, reacted under an ice bath, then separated, dried to obtain a precursor powder; (2) preparation of a conductive composite membrane: precursor powder and sodium dodecylbenzenesulfonate are dispersed in water to obtain a precursor dispersion; suction filtration is performed on the surface of an organic basement membrane, the precursor and a cross-linking agent are fixed on the basement membrane, the resulting membrane is then immersed in a glutaraldehyde-hydrochloric acid solution for cross-linking, and finally taken out and dried to obtain a conductive composite membrane. The conductive composite membrane of the present invention has a higher non-Faraday capacitance, is conducive to improving the electrostatic repulsion force to charged pollutants, and can be used for water treatment and other membrane separation / resource recovery applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane materials and water treatment, and specifically relates to a method for preparing a carbon nanomaterial-organic conductive composite membrane that can be self-cleaned by an electrochemical method and its application in water treatment using the membrane method. Background Art

[0002] Membrane fouling is the most critical challenge facing the application of membrane water treatment technology. Common methods for controlling membrane fouling currently include physical cleaning (such as hydraulic flushing and backwashing), chemical cleaning (such as the addition of oxidants, acids, and alkalis), and electrochemical anti-fouling techniques. Electrochemical membrane fouling control primarily relies on applying a certain electric field to the membrane surface, leveraging electrostatic repulsion to reduce the adsorption of membrane contaminants on the membrane surface or in situ degradation of membrane contaminants through the generation of active substances such as free radicals through electrochemical reactions. This method offers advantages such as ease of operation and environmental friendliness, and has broad development and application prospects. To reduce energy loss and enhance electrochemical anti-fouling effectiveness, a common approach currently involves adding a conductive layer composed of conductive materials such as carbon nanotubes (CNTs), polyaniline (PANI), and polypyrrole (PPy) to the organic substrate membrane, or directly incorporating conductive nanomaterials into the membrane to create a highly conductive composite membrane. The surface charge density of the conductive layer directly determines the electrostatic repulsion effect of the membrane. However, existing conductive membranes are generally modified with a single carbon nanomaterial or conductive polymer. Due to the structural and chemical properties of the material itself, the amount of surface charge they can carry is limited. In addition, the surface-modified conductive membranes generally have low mechanical strength and poor long-term operational stability. These shortcomings severely restrict the application of these electrochemical anti-fouling membranes. Summary of the Invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing an electrochemical self-cleaning conductive composite membrane and its water treatment application. The present invention first uses graphene quantum dots (GQDs) and other nanomaterials with high capacitance and PANI to surface modify conductive carbon nanomaterials such as CNT to prepare a precursor with excellent conductive properties and capacitance. Then, an organic polymer membrane such as polyethersulfone (PES) is used as a base membrane (support layer), and the precursor and polyvinyl alcohol (PVA) cross-linking agent (together as a conductive layer) are fixed on the base membrane by filtration; the conductive composite membrane prepared by the present invention has a higher surface charge density, and the conductive layer of the composite membrane not only has a higher conductivity (can reduce power loss), but also has a higher capacitance performance (can provide a higher charge density). The present invention uses a material with high capacitance to construct a conductive layer, and the prepared composite membrane has a strong electrostatic repulsion effect on negatively charged substances such as proteins and humus (common membrane pollutants in water). The conductive composite membrane can be used for water treatment and other membrane separation / resource recovery applications.

[0004] The technical solution of the present invention is:

[0005] The present invention relates to a method for preparing a conductive composite film, comprising the following steps:

[0006] (1) Preparation of precursor: Graphene quantum dots (GQDs) and carbon nanomaterials are dispersed in a solvent, aniline and concentrated hydrochloric acid are added under ice bath, and then ammonium persulfate-hydrochloric acid solution is slowly added to the above solution, reacted under ice bath, and then separated and dried to obtain precursor powder;

[0007] (2) Preparation of a conductive composite film: The precursor powder obtained in step (1) and sodium dodecylbenzenesulfonate are dispersed in water to obtain a precursor dispersion; the surface of the organic base film is filtered to fix the precursor and the cross-linking agent on the organic base film, and then the obtained film is immersed in a glutaraldehyde-hydrochloric acid solution for cross-linking, and finally taken out and dried to obtain a conductive composite film.

[0008] Preferably, the graphene quantum dots are prepared by electrochemically oxidizing a graphite electrode, followed by centrifugation and purification by dialysis to obtain a solution containing graphene quantum dots. The resulting graphene quantum dot-containing solution is freeze-dried to obtain a GQD powder, and the concentration of the solution can be further calculated based on the mass of the GQD powder.

[0009] Preferably, in the process of preparing graphene quantum dots, a graphite electrode is oxidized based on an electrochemical system, the electrochemical system uses 0.05-0.3 mol / L KH2PO4 as the electrolyte solution, the voltage is set to 2-5 V, and the oxidation treatment is 2-6 hours; the centrifugation conditions are centrifugation at 9000-12000 rpm for 0.5-1 hour; and the dialysis conditions are 2000-3500D pure water dialysis for 1-3 days.

[0010] The electrochemical system includes an electrochemical workstation and a three-electrode system, wherein a graphite electrode is used as a working electrode, a Ti sheet is used as a counter electrode, and Ag / AgCl is used as a reference electrode. The working electrode, the counter electrode, and the reference electrode are all connected to the electrochemical workstation via wires.

[0011] Preferably, in step (1), the graphene quantum dots are added in the form of a solution containing graphene quantum dots, and the concentration of the graphene quantum dots in the solution containing graphene quantum dots is 0.5-1.0 mg / mL;

[0012] The mass ratio of graphene quantum dots to carbon nanomaterials is 1:9 to 1:4, and the total mass of the dispersed graphene quantum dots and carbon nanomaterials per milliliter of solvent is 2-6 mg;

[0013] The graphene quantum dots and carbon nanomaterials are dispersed in a solvent, and aniline and concentrated hydrochloric acid are added in an ice bath, wherein the ratio of the added volume of concentrated hydrochloric acid to the volume of the solvent is 1:8 to 1:24, the concentration of HCl in the resulting solution is 0.5-1.5 mol / L, and the ratio of the added mass of aniline to the mass of the graphene quantum dots is 3:1 to 10:1;

[0014] The ammonium persulfate-hydrochloric acid solution is prepared by dispersing ammonium persulfate in 0.5-1.5 mol / L hydrochloric acid, wherein the mass of the ammonium persulfate dispersed in each milliliter of hydrochloric acid is 1-2 mg, and the mass ratio of the ammonium persulfate to the aniline is 61:200.

[0015] Preferably, in step (1), the solvent is ethanol, and the carbon nanomaterial is carbon nanotubes (CNTs); the graphene quantum dots and the carbon nanomaterial are ultrasonically dispersed in the solvent, and the ultrasonic dispersion time is 0.5-2 hours; the ammonium persulfate-hydrochloric acid solution is added at a rate of 1-3 mL / min, and the reaction time under ice bath conditions is 10-15 hours.

[0016] Preferably, in step (2), the mass ratio of the precursor powder to sodium dodecylbenzenesulfonate is 1:4-1:2, the total mass of the precursor powder and sodium dodecylbenzenesulfonate dispersed in each milliliter of water is 1-3 mg; the glutaraldehyde concentration in the glutaraldehyde-hydrochloric acid solution is 0.5-1.5 wt%, and the HCl concentration is 0.5-1.5 mol / L;

[0017] The cross-linking reaction temperature is 70-100°C and the time is 10-20 minutes.

[0018] Preferably, in step (2), the cross-linking agent is polyvinyl alcohol; during the filtration process, polyvinyl alcohol solution A, precursor dispersion, water, and polyvinyl alcohol (PVA) solution B are filtered sequentially on the surface of the organic base membrane; wherein the organic base membrane is a PES (polyethersulfone) membrane, and the amount of the precursor loaded is 40-100 mg / cm 2 The concentration of polyvinyl alcohol solution A used for filtration is 0.05-0.15wt%, and the concentration of polyvinyl alcohol solution B is 0.05-0.15wt%; during the filtration process, the volume ratio of polyvinyl alcohol solution A, water and polyvinyl alcohol solution B used is 0.5:10:0.5 to 1:10:1.

[0019] The present invention also relates to the application of the above-mentioned conductive composite membrane in the treatment of wastewater containing organic macromolecules. The wastewater treatment specifically involves separating and removing organic solvents, proteins, humic acid and other organic macromolecules in the wastewater. The conductive composite membrane can effectively intercept charged macromolecular substances, further change the membrane surface voltage, reduce the formation of the pollution layer and realize self-cleaning of the membrane surface.

[0020] The present invention also relates to an electrically driven cross-flow pressure cell device based on a conductive composite membrane, comprising a membrane cell, a conductive composite membrane disposed within the membrane cell, the membrane cell having an inlet and an outlet, a base membrane of the conductive composite membrane disposed near the outlet, a counter electrode disposed near the inlet, the conductive composite membrane and the counter electrode each connected to a DC power supply via a wire, the counter electrode being a titanium mesh, and a spacer disposed between the conductive composite membrane and the titanium mesh serving as the counter electrode. The conductive composite membrane serves as a working electrode, and the titanium mesh is disposed near the spacer.

[0021] The present invention also relates to a method for treating wastewater containing organic macromolecules, which uses the above-mentioned electrically driven cross-flow pressure cell device to apply alternating positive and negative voltages to the conductive composite membrane, specifically as follows: a salt solution containing organic macromolecules is introduced into the electrically driven cross-flow pressure cell device installed with the conductive composite membrane, and the water is treated in an energized state to obtain clean water. After treatment, the contamination layer on the membrane surface can be effectively removed by changing the voltage applied to the conductive composite membrane, thereby realizing an in-situ electrochemical cleaning process.

[0022] The beneficial effects of the present invention are:

[0023] 1) The present invention uses GQDs and PANI to modify the conductive carbon nanomaterial as the conductive layer, and CNT (53F·g at 0 to 1V) -1 , 38F·g at 0 to -1V -1 ), CNT-GQDs (109F·g at 0 to 1V -1 , 98F·g at 0 to -1V -1 ), CNT-PANI (161F·g at 0 to 1V -1 , 124F·g at 0 to -1V -1 ) conductive film, the conductive composite film provided by the present invention has a higher non-Faraday capacitance (338F·g at 0 to 1V). -1 , 158F·g at 0 to -1V -1 ), which is beneficial to improving the electrostatic repulsion of charged pollutants. Therefore, under negative pressure drive, it has a significant repulsive effect on negatively charged BSA pollutants, and the conductive composite membrane can stably maintain a water flux of more than 90% within 60 minutes.

[0024] 2) After the introduction of GQDs and PANI, the rich functional groups of both can enhance the cross-linking process, which reduces the pore size of the conductive membrane and improves the separation ability and mechanical strength. Compared with the CNT conductive membrane, the conductive composite membrane has a smaller pore size distribution and has no obvious changes after ultrasonic treatment in water, while the active layer of the CNT membrane obviously falls off.

[0025] 3) The present invention realizes the synergy of electrostatic repulsion and electrochemical oxidation cleaning by alternatingly applying positive and negative voltages, further improving the membrane fouling control effect; while significantly enhancing the electrostatic repulsion of common membrane pollutants in negatively charged water such as proteins and humus, the present invention can further remove membrane fouling caused by positively charged or uncharged pollutants in water, thereby making up for the shortcomings of a simple electrostatic repulsion anti-pollution system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0027] Figure 1 , the electrically driven cross-flow pressure cell device used in the present invention;

[0028] Figure 2 , structural schematics, TEM characterization and XPS N 1s patterns of different carbon nanomaterials prepared in the present invention;

[0029] Figure 3 , XPS O 1s patterns of different carbon nanomaterials;

[0030] Figure 4 , SEM, AFM and Raman imaging characterization of conductive films of different carbon nanomaterials;

[0031] Figure 5 , SEM and surface contact angle of the cross section of different carbon nanomaterial conductive films;

[0032] Figure 6 , the stability of conductive films made of different carbon nanomaterials;

[0033] Figure 7 , FTIR-ATR spectra (a), resistance and conductivity (b), flux (c) and retention of dextran with different molecular weights (d) of different carbon nanomaterial conductive films;

[0034] Figure 8 , the changes of normalized membrane flux when different carbon nanomaterial conductive membranes are filtering BSA with and without voltage;

[0035] Figure 9 , Normalized flux decrease (a) of electrically driven anti-pollution and electrochemical cleaning cycles and TOC removal rate (b) of different cycle periods when electrically driven conductive membranes of different carbon nanomaterials are used in actual wastewater filtration. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0037] Example 1: Preparation of CNT-PANI-GQDs Conductive Composite Film Using CNT as Carbon Nanomaterial

[0038] S1. Preparation of GQDs: Using a Shanghai Chenhua 660E electrochemical workstation and a three-electrode system, a graphite electrode was used as the working electrode, a Ti sheet was used as the counter electrode, and Ag / AgCl was used as the reference electrode. In 50mL of 0.1mol / LKH2PO4 electrolyte, the chronoamperometry was used, the voltage was set to 3V, and the oxidation was carried out for 250min to obtain a dark brown solution. The dark brown solution was centrifuged at 12000rpm for 0.5h, the supernatant was collected and dialyzed with pure water for 2d (3000D). After dialysis, a portion of the solution was freeze-dried and weighed to obtain GQDs powder (based on the mass of the GQDs powder, the solution concentration can be further calculated to be 1.0mg / mL), and the remaining solution was stored for later use.

[0039] S2. Preparation of CNT-PANI-GQDs powder: Measure the solution containing 0.03g GQDs prepared in step S1 and add it to 0.17g CNT, add 50mL ethanol, and ultrasonicate for 1h; add 0.2g aniline and 4.2mL concentrated hydrochloric acid to the stirred solution under an ice bath, and the HCl concentration in the resulting solution is 1mol / L; disperse 61mg ammonium persulfate in 50mL 1mol / L hydrochloric acid to obtain an ammonium persulfate-hydrochloric acid solution, and add the ammonium persulfate-hydrochloric acid solution dropwise to the above solution at a rate of 2mL / min; after reacting for 12h under ice bath, filter the solution, wash the precipitate with ethanol and water, and freeze-dry to obtain CNT-PANI-GQDs powder (precursor powder), and polyaniline is obtained by the reaction of ammonium persulfate and aniline added later.

[0040] S3. Preparation of CNT-PANI-GQDs conductive composite film: 5 mg of CNT-PANI-GQDs powder and 20 mg of SDBS obtained in step S2 were dispersed in 20 mL of water, and the CNT-PANI-GQDs solution was obtained after ultrasonic treatment for 20 min for standby use; a PES base membrane (4 cm in diameter) was placed on a filtration device, and 10 mL of PVA solution (concentration of 0.15 wt%), CNT-PANI-GQDs solution, 100 mL of water and 10 mL of PVA solution (concentration of 0.15 wt%) were filtered on its surface in sequence, and the PES membrane loaded with CNT-PANI-GQDs on the surface was immersed in glutaraldehyde-hydrochloric acid solution (glutaraldehyde concentration of 1 wt%, HCl concentration of 1 mol / L), reacted at 90 ° C for 15 min, and dried for standby use.

[0041] With reference to the preparation process of CNT-PANI-GQDs powder in step S2 above, control samples of CNT and GQDs mixed powder and CNT and PANI mixed powder were prepared. In addition, CNT powder was also selected as a control sample.

[0042] CNT and GQDs mixed powder: Measure the solution containing 0.03 g of GQDs prepared in step S1 and add it to 0.17 g of CNT, add 50 mL of ethanol, and sonicate for 1 hour; add 4.2 mL of concentrated hydrochloric acid to the stirred solution under an ice bath; add 50 mL of 1 mol / L hydrochloric acid dropwise to the above solution at a rate of 2 mL / min; after continuing to react under an ice bath for 12 hours, filter the solution, wash the precipitate with ethanol and water, and freeze-dry to obtain CNT and GQDs mixed powder.

[0043] CNT and PANI mixed powder: 0.17 g of CNT was added to 50 mL of ethanol and sonicated for 1 hour. 0.2 g of aniline and 4.2 mL of concentrated hydrochloric acid were added to the stirred solution under an ice bath. 61 mg of ammonium persulfate was dispersed in 50 mL of 1 mol / L hydrochloric acid to obtain an ammonium persulfate-hydrochloric acid solution, which was added dropwise to the above solution at a rate of 2 mL / min. After a further 12 hours of reaction under an ice bath, the solution was filtered, the precipitate was washed with ethanol and water, and freeze-dried to obtain a CNT and PANI mixed powder.

[0044] The CNT-PANI-GQDs powder in step S3 was replaced with CNT powder, CNT and GQDs mixed powder, and CNT and PANI mixed powder. CNT, CNT-GQDs, and CNT-PANI were loaded onto the PES support layer according to the method of step S3 to prepare CNT, CNT-GQDs, and CNT-PANI conductive films.

[0045] like Figure 1As shown, a CNT-PANI-GQDs conductive composite membrane is used in an electrically driven cross-flow pressure cell device. The conductive composite membrane is disposed within a membrane cell, which is provided with a feed inlet and a discharge inlet. The base membrane of the conductive composite membrane is disposed near the discharge inlet, and a counter electrode is disposed near the feed inlet. The conductive composite membrane and the counter electrode are each connected to a DC power supply via a wire. The counter electrode is a titanium mesh, and a spacer is disposed between the conductive composite membrane and the titanium mesh serving as the counter electrode. The conductive composite membrane serves as the working electrode, and a titanium mesh is also disposed on the side of the conductive composite membrane near the spacer. The applications in Examples 3-5 all utilize the above-described device.

[0046] The electrically driven cross-flow pressure cell device uses the CNT-PANI-GQDs conductive composite film prepared in step (3) of Example 1, which can also be replaced with CNT, CNT-GQDs, and CNT-PANI conductive films for comparison.

[0047] like Figure 2 As shown in Figure 2, GQDs with a diameter of 3-7 nm formed agglomerates and wrapped around CNTs. In addition, in CNT-PANI-GQDs, in addition to the same PANI-wrapped CNT structure, spherical substances composed of GQDs were observed connected to the CNT-PANI backbone. In this unique structure, the spherical substance containing GQDs can provide an effective spatial structure for electron transmission, while the wrapped PANI acts as a bridge for electron transmission between the external circuit and the spherical substance, making the transmission process faster and more stable. In addition, as Figure 2 and 3 As shown in the figure, quinone amine and aniline peaks belonging to PANI were observed in the CNT-PANI and CNT-PANI-GQDs materials. The O 1s spectrum results show that the C=O ratio in CNT-GQDs and CNT-PANI-GQDs increased, indicating that the carbonyl content increased after GQD modification. By introducing zero-dimensional GQDs into the one-dimensional CNT-PANI network, not only the nanostructure was changed, but the number of active functional groups was significantly increased.

[0048] Example 2: Hydrophilicity and mechanical stability test of CNT-PANI-GQDs conductive composite film

[0049] According to step S3, CNT, CNT-GQDs, CNT-PANI and CNT-PANI-GQDs were loaded onto the PES support layer to obtain four corresponding conductive films. Figure 4 As shown in the figure, after loading the conductive layer, a modified CNT active layer of 5-6 μm thick was formed on the top of the sponge-like PES membrane. The thickness of the active layer of the four materials is close. At the same time, AFM analysis shows that the surface roughness of the four conductive films is similar (Ra is 70-80 nm), and Raman test shows that I D / I GThe value increases, which is beneficial to improving the electrochemical activity of the conductive film. Figure 5 As shown in Figure 3, the contact angles of CNT-GQDs, CNT-PANI, and CNT-PANI-GQDs films decreased compared to unmodified CNTs, with the CNT-PANI-GQDs film having the smallest contact angle. This is because the presence of hydrophilic functional groups in PANI and GQDs increases the hydrophilicity of the film, which helps to reduce the adhesion of hydrophobic organic pollutants. Figure 6 As shown in the figure, these functional groups can also promote the cross-linking of the material with PVA and glutaraldehyde, enhance the mechanical stability of the membrane, and after 30 minutes of ultrasound in water, there is no obvious change in the active layer of the CNT-GQDs, CNT-PANI and CNT-PANI-GQDs conductive composite films.

[0050] This embodiment demonstrates that the CNT-PANI-GQDs conductive composite film of the present invention has good hydrophilicity and excellent mechanical stability.

[0051] Example 3: Application of CNT-PANI-GQDs conductive composite membrane in filtering dextran under electrically driven conditions

[0052] like Figure 7 As shown in the figure, the conductivity of CNT, CNT-GQDs, CNT-PANI and CNT-PANI-GQDs conductive composite films measured by the four-probe method is in the order of CNT-PANI-GQDs≈CNT-PANI>CNT-GQDs>CNT. Applying +2.5V and -2.5V voltages has no obvious effect on the pure water flux, which is comparable to the pure water flux of the unmodified CNT membrane (182L·m -2 ·h -1 bar -1 ), the pure water flux of the CNT-GQDs, CNT-PANI, and CNT-PANI-GQDs membranes decreased slightly compared to the CNT-GQDs membranes. However, in a homemade cross-flow pressure cell apparatus, the retention of 100 ppm 10 kDa, 100 kDa, and 300 kDa dextran solutions by the membrane electrode was tested, and the retention performance of the CNT-PANI and CNT-PANI-GQDs membranes was improved.

[0053] This embodiment shows that the CNT-PANI-GQDs conductive composite film of the present invention has excellent conductive properties. Under electric drive conditions, it can effectively retain polymers of different molecular weights, showing excellent electron utilization and stable water treatment performance.

[0054] Example 4: Anti-pollution application of CNT-PANI-GQDs conductive composite membrane in electrically driven filtration of BSA solution

[0055] In a self-made cross-flow pressure cell device, the electrically driven anti-fouling performance of CNT, CNT-GQDs, CNT-PANI, and CNT-PANI-GQDs conductive films was compared. Figure 8 As shown in the figure, applying a -2.5V voltage to the conductive membrane significantly increased its water flux compared to when no voltage was applied, and the magnitude of the water flux decrease was reduced, indicating that membrane fouling was suppressed. Specifically, the electrically driven CNT-PANI-GQDs conductive composite membrane maintained a water flux of over 90% for 60 minutes, and the surface contaminant content of the CNT-PANI-GQDs conductive composite membrane was minimal after use.

[0056] This embodiment shows that under electric driving conditions, the CNT-PANI-GQDs conductive composite film of the present invention has good and stable anti-pollution performance.

[0057] Example 5: Application of CNT-PANI-GQDs conductive composite membrane in treating actual wastewater under electrically driven conditions

[0058] In actual wastewater treatment, we first filter the wastewater at 1 bar and -2.5 V, then change the feed liquid to pure water, electrochemically clean the conductive membrane at +3.0 V for 15 minutes, and repeat the cycle. Figure 9 As shown, the normalized flux of the CNT-PANI-GQDs membrane electrode decreased slowly over four cycles. After 60 minutes of operation, electrochemical cleaning at +3.0 V restored the normalized flux of the CNT-PANI-GQDs membrane to 0.9-0.95, demonstrating that the combination of electrically driven antifouling and electrochemical cleaning can effectively suppress membrane flux decline and achieve self-cleaning of the membrane electrode in practical applications. Furthermore, the enhanced electrically driven repulsive force increased the TOC removal rate of the CNT-PANI-GQDs membrane.

[0059] This embodiment shows that the CNT-PANI-GQDs conductive composite membrane of the present invention can effectively intercept pollutants when used in membrane treatment processes, and at the same time, combine with electric drive to achieve membrane self-cleaning of contamination, so it has good water treatment capacity and renewability.

[0060] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for preparing a conductive composite film, characterized in that: The following steps are involved: (1) Preparation of a precursor: Graphene quantum dots and carbon nanomaterials are dispersed in a solvent, aniline and concentrated hydrochloric acid are added in an ice bath, and then ammonium persulfate-hydrochloric acid solution is slowly added to the above solution, reacted in an ice bath, and then separated and dried to obtain a precursor powder; wherein the carbon nanomaterial is carbon nanotubes; (2) Preparation of a conductive composite film: The precursor powder obtained in step (1) and sodium dodecylbenzenesulfonate are dispersed in water to obtain a precursor dispersion; the surface of the organic base film is filtered to fix the precursor and the cross-linking agent on the organic base film, and then the obtained film is immersed in a glutaraldehyde-hydrochloric acid solution for cross-linking, and finally taken out and dried to obtain a conductive composite film.

2. The method for preparing a conductive composite film according to claim 1, wherein: The preparation process of graphene quantum dots is as follows: using electrochemical oxidation of graphite electrodes, centrifugation and dialysis purification to obtain a solution containing graphene quantum dots.

3. The method for preparing a conductive composite film according to claim 2, wherein: In the process of preparing graphene quantum dots, a graphite electrode is oxidized based on an electrochemical system. The electrochemical system uses 0.05-0.3 mol / L KH2PO4 as the electrolyte solution, the voltage is set to 2-5V, and the oxidation treatment is performed for 2-6 hours; the centrifugation condition is centrifugation at 9000-12000 rpm for 0.5-1 hour; and the dialysis condition is dialysis with 2000-3500D pure water for 1-3 days.

4. The method for preparing a conductive composite film according to claim 1, wherein: In step (1), the graphene quantum dots are added in the form of a solution containing graphene quantum dots, and the concentration of the graphene quantum dots in the solution containing graphene quantum dots is 0.5-1.0 mg / mL; The mass ratio of graphene quantum dots to carbon nanomaterials is 1:9 to 1:4, and the total mass of the dispersed graphene quantum dots and carbon nanomaterials per milliliter of solvent is 2-6 mg; The graphene quantum dots and carbon nanomaterials are dispersed in a solvent, and aniline and concentrated hydrochloric acid are added in an ice bath, wherein the ratio of the added volume of concentrated hydrochloric acid to the volume of the solvent is 1:8 to 1:24, the concentration of HCl in the resulting solution is 0.5-1.5 mol / L, and the ratio of the added mass of aniline to the mass of the graphene quantum dots is 3:1 to 10:1; The ammonium persulfate-hydrochloric acid solution is prepared by dispersing ammonium persulfate in 0.5-1.5 mol / L hydrochloric acid, wherein the mass of the ammonium persulfate dispersed in each milliliter of hydrochloric acid is 1-2 mg, and the mass ratio of the ammonium persulfate to the aniline is 61:100 to 61:

200.

5. The method for preparing a conductive composite film according to claim 1, wherein: In step (1), the solvent is ethanol; the graphene quantum dots and carbon nanomaterials are ultrasonically dispersed in the solvent, and the ultrasonic dispersion time is 0.5-2h; the ammonium persulfate-hydrochloric acid solution dropwise acceleration rate is 1-3mL / min, and the reaction time under ice bath conditions is 10-15h.

6. The method for preparing a conductive composite film according to claim 1, wherein: In step (2), the mass ratio of the precursor powder to sodium dodecylbenzenesulfonate is 1:4-1:2, and the total mass of the precursor powder and sodium dodecylbenzenesulfonate dispersed in each milliliter of water is 1-3 mg; the glutaraldehyde concentration in the glutaraldehyde-hydrochloric acid solution is 0.5-1.5 wt%, and the HCl concentration is 0.5-1.5 mol / L; The cross-linking reaction temperature is 70-100°C and the time is 10-20 minutes.

7. The method for preparing a conductive composite film according to claim 1, wherein: In step (2), the cross-linking agent is polyvinyl alcohol; during the filtration process, polyvinyl alcohol solution A, precursor dispersion, water, and polyvinyl alcohol solution B are filtered sequentially on the surface of the organic base membrane; wherein the organic base membrane is a PES membrane, and the amount of the precursor loaded is 40-100 mg / cm 2 The concentration of polyvinyl alcohol solution A used for filtration is 0.05-0.15wt%, and the concentration of polyvinyl alcohol solution B is 0.05-0.15wt%; During the filtration process, the volume ratio of the polyvinyl alcohol solution A, water and polyvinyl alcohol solution B used is 0.5:10:0.5 to 1:10:

1.

8. Use of the conductive composite membrane prepared by the preparation method according to any one of claims 1 to 7 in treating wastewater containing organic macromolecules.

9. An electrically driven cross-flow pressure cell device, characterized in that: It comprises a membrane pool and a conductive composite membrane prepared by the preparation method according to any one of claims 1 to 7, wherein the conductive composite membrane is arranged in the membrane pool, the membrane pool is provided with a feed port and a discharge port, the base membrane of the conductive composite membrane is arranged on the side close to the discharge port, a counter electrode is provided on the side close to the feed port, the conductive composite membrane and the counter electrode are respectively connected to a DC power supply through a wire, the counter electrode adopts a titanium mesh, and a spacer is provided between the conductive composite membrane and the titanium mesh serving as the counter electrode.

10. A method for treating wastewater containing organic macromolecules, characterized in that: The electrically driven cross-flow pressure cell device according to claim 9 is used to apply alternating positive and negative voltages to the conductive composite membrane.

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