Preparation and application of ceramic-based MXene composite membrane modified by carbon nanotube transition layer

Abstract

The application relates to a preparation method and application of a carbon nanotube modified ceramic-based MXene composite membrane, and belongs to the technical field of environmental membrane separation. The preparation method improves the stability of a carrier and a MXene membrane layer by taking carbon nanotubes, which are modified by hexadecyl trimethyl ammonium bromide through ceramic carrier suction filtration, as a transition layer, adjusts the structure of the composite membrane by changing the suction filtration time and drying temperature of the MXene solution, and obtains a ceramic-based MXene composite membrane with high stability. The prepared ceramic-based MXene composite membrane has good separation effect and stability in the removal and separation of micro-pollutants by using a pressure driving method.

Description

Technical Field

[0001] This invention relates to the preparation and application of a ceramic-based MXene composite membrane modified with a carbon nanotube transition layer, belonging to the field of environmental membrane separation technology. Background Technology

[0002] Traditional methods for removing micropollutants, such as physical treatments (adsorption, flotation, coagulation, etc.), while effective, suffer from low removal rates, high costs, and low water flux. Biological methods are limited by antibiotic toxicity, and antibiotic wastewater typically has high concentrations, classifying it as high-concentration organic wastewater. Aerobic methods combined with anaerobic pretreatment to reduce COD can achieve good results, but are costly and relatively complex. Chemical methods also have drawbacks in treating wastewater containing micropollutants, such as the potential generation of more toxic intermediates, causing secondary pollution. Membrane separation technology, as a modern and highly efficient separation technology, can be categorized based on membrane pore size into microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. Ultrafiltration, nanofiltration, and reverse osmosis can all effectively remove micropollutants from water.

[0003] Membrane separation is a materials-based separation process, with membrane materials being the core of membrane technology. The physicochemical structure of the material and the interaction between the material and the separated components are crucial for achieving separation. Since its discovery in 2011, the novel two-dimensional nanomaterial transition metal carbonitrides (MXenes) have shown great promise due to their high mechanical strength, abundant functional groups on the surface, hydrophilicity, unique nanostructure, and excellent electrical properties. However, research reports on ceramic-based MXene composite membranes are still relatively scarce in the field of membrane separation. This is mainly because the poor adhesion between the MXene membrane layer and the ceramic support during the preparation of ceramic-based MXene composite membranes makes it impossible to obtain defect-free and highly stable membranes. Furthermore, research on the removal of micro-pollutants by MXene composite membranes is also relatively limited. Therefore, research on the preparation of highly stable ceramic-based MXene composite membranes and their effect on the removal of micro-pollutants is of paramount importance. Summary of the Invention

[0004] In light of the above background and problems, and addressing the key issues of poor adhesion between the ceramic substrate and the MXene membrane layer and contaminant removal, this invention provides a method for preparing a highly stable ceramic-based MXene composite membrane and its application in the removal of micro-pollutants. This ceramic-based composite membrane improves the adhesion between the membrane layer and the carrier by filtering carbon nanotubes into the ceramic substrate as a transition layer, and then obtains the MXene composite membrane by vacuum-assisted filtration of the MXene solution. Furthermore, a highly stable ceramic-based MXene composite membrane is obtained by heat treatment under vacuum conditions.

[0005] The technical solution of this invention: A method for preparing a carbon nanotube-modified ceramic-based MXene composite membrane, wherein the composite membrane uses ceramic as a carrier, a carbon nanotube intermediate transition layer is introduced on the surface of the carrier, and then an MXene separation layer is loaded on the carrier by vacuum-assisted filtration to obtain a highly stable ceramic-based MXene composite membrane; the preparation steps of the composite membrane are as follows:

[0006] (1) Preparation of intermediate transition layer of carbon nanotubes: Mix hexadecyltrimethylammonium bromide and deionized water and stir until completely dissolved; then add carbon nanotubes and stir again for 10-20 min; finally, sonicate the mixed solution to make it fully mixed and uniform to obtain CTAB modified carbon nanotube suspension.

[0007] The carbon nanotubes are multi-walled or single-walled carbon nanotubes, and the mass ratio of hexadecyltrimethylammonium bromide to carbon nanotubes is 1:0.5~3.

[0008] The CTAB-modified carbon nanotube suspension was filtered onto a ceramic support using vacuum-assisted filtration, thereby obtaining an alumina ceramic support with a carbon nanotube intermediate transition layer.

[0009] (2) Preparation of MXene solution: Lithium fluoride, deionized water, and concentrated hydrochloric acid were added sequentially to a polytetrafluoroethylene reactor. Aluminum carbide was slowly added to the reactor. The reaction temperature was 30-50℃, and the mixture was stirred for 18-30 h. The resulting solution was placed in a centrifuge tube, water was added, and the mixture was centrifuged. The supernatant was then poured off, leaving a precipitate. The precipitate was dissolved in deionized water and sonicated for 10-20 min. It was then centrifuged again for 45-70 min. The resulting supernatant was the MXene solution with a concentration range of 0.8-1.5 mg / mL. The mass ratio of lithium fluoride to concentrated hydrochloric acid was 1-1.6:5. The mass ratio of lithium fluoride to aluminum carbide was 1-1.6:1.

[0010] (3) Preparation of ceramic-based MXene composite membrane: The MXene solution was filtered onto an alumina ceramic support with a carbon nanotube intermediate transition layer using vacuum-assisted filtration. Different filtration times were adjusted to 30 s, 1 min, 3 min and 6 min. The resulting MXene composite membrane was then placed in a vacuum drying oven to obtain the ceramic-based MXene composite membrane.

[0011] The ceramic carrier is sheet-like or tubular alumina or titanium oxide;

[0012] The ceramic-based MXene composite membrane is used for the removal of micro-pollutants.

[0013] The micro-contaminants are tetracycline, amoxicillin, oxytetracycline, chloramphenicol, or levofloxacin.

[0014] Furthermore, carbon nanotube-modified alumina ceramic support was selected as an intermediate transition layer. MXene nanosheets were uniformly loaded onto the support using vacuum-assisted filtration, followed by vacuum drying to prepare a highly stable ceramic-based MXene composite membrane. The specific steps are as follows:

[0015] (1) Preparation of intermediate transition layer of multi-walled carbon nanotubes (MWCNTs)

[0016] (1.1) Immerse the alumina ceramic support with a pore size of ~1 μm in deionized water and evacuate for 20 min.

[0017] (1.2) Weigh 1 g of cetyltrimethylammonium bromide (CTAB) and place it in a beaker. Add 250 mL of deionized water and place it on a magnetic stirrer and stir for 10-20 min to completely dissolve it. Then weigh 0.125 g of multi-walled carbon nanotubes (MWCNTs) and add them to the beaker containing CTAB. Stir again for 10-20 min. Finally, sonicate the mixed solution for 2 h to ensure that it is fully mixed and homogeneous to obtain a CTAB-MWCNT suspension.

[0018] (1.3) Place the alumina ceramic support in the vacuum filtration device assembly, take 1 mL of CTAB-MWCNT suspension, dilute it with deionized water to 25 mL, add it into the vacuum filtration cup, and use vacuum-assisted filtration to filter it onto the alumina ceramic support, thereby obtaining an alumina ceramic support with an intermediate MWCNT transition layer.

[0019] (2) Preparation of ceramic-based MXene composite membrane

[0020] (2.1) MXene (Ti3C2T) x Preparation of solution

[0021] Lithium fluoride (LiF), deionized water, and concentrated hydrochloric acid (HCl) were added sequentially to a polytetrafluoroethylene reactor. After stirring for 1-3 minutes, aluminum carbide (Ti3AlC2) was slowly added. After the reaction was completed, the reactor was placed in a constant temperature water bath and the temperature was adjusted to 30-50℃. The reaction was stirred for 18-30 hours. The solution after the reaction was placed in a centrifuge tube, water was added, and the pH was washed. Finally, the supernatant was poured off, leaving the precipitate. The precipitate was dissolved in deionized water and sonicated for 10-20 minutes. It was then centrifuged again for 45-70 minutes. The resulting supernatant was the desired MXene solution with a concentration range of 0.8-1.5 mg / mL.

[0022] (2.2) Preparation of ceramic-based MXene composite membrane

[0023] The alumina ceramic support with the MWCNT intermediate transition layer prepared above was placed in a vacuum-assisted filtration assembly. 1 mL of MXene solution was placed in a 50 mL centrifuge tube and diluted with deionized water to 40-45 mL. The solution was then poured into a filtration cup. Different filtration times were adjusted to 30 s, 1 min, 3 min, and 6 min. The resulting MXene composite membrane was then placed in a vacuum drying oven at 140℃. After 12 h, the membrane was removed, and the ceramic-based MXene composite membrane was successfully prepared.

[0024] (3) Stability test of ceramic-based MXene composite membrane

[0025] Ceramic-based sub-nanoporous MXene composite membranes with and without MWCNT intermediate transition layers were placed in glass dishes filled with deionized water, and their morphology was recorded daily to compare the stability of the composite membranes with and without the transition layer. The ceramic-based sub-nanoporous MXene composite membrane with the MWCNT intermediate transition layer showed no significant changes after immersion in water for 10 days. However, the composite membrane without the intermediate transition layer showed surface protrusions immediately upon placement in the glass dish with deionized water, and obvious cracking occurred on the second day. After 7 days, the composite membrane layer was almost completely detached. This indicates that the ceramic-based sub-nanoporous MXene composite membrane with MWCNT as an intermediate transition layer exhibits good stability.

[0026] (4) Application of ceramic-based MXene composite membrane in the treatment of micro-pollutants in wastewater under different filtration times

[0027] By varying the filtration time of the MXene solution, MXene composite membranes with different membrane thicknesses were obtained. These composite membranes were then assembled into a pressure-driven testing device. The feed solution was a 50 ppm tetracycline (TC) solution prepared with deionized water, and the pressure was 1 bar. As the filtration time increased, the thickness of the MXene composite membrane also increased, while the water flux decreased from 8.94 Lm to 3.69 Lm. -2 h -1 bar -1 The tetracycline removal rate increased from 95.02% to 98.85%. Considering water flux and removal rate, an MXene composite membrane with a filtration time of 3 min was selected for subsequent experiments to ensure both high water flux and excellent removal rate.

[0028] (5) Application of ceramic-based MXene composite membrane in antibiotic wastewater treatment under different pressure conditions

[0029] The composite membrane was assembled into a pressure-driven testing device. The feed solution was a 50 ppm tetracycline (TC) solution, and the pressure was adjusted from 1 to 5 bar. The tetracycline removal rate and water flux under different pressure conditions were tested. With increasing pressure, the water flux of the MXene composite membrane showed an increasing trend, increasing from 4.13 to 19.71 L / m³. -2 h -1 bar -1 The removal rate decreased from 98.23% to 92.04%, but still remained above 90%. This indicates that the MXene composite membrane still maintains high micropollutant removal performance under high pressure. Under 1 bar conditions, the continuous operation performance of the MXene composite membrane for micropollutants was tested. After 10 h of operation, the water flux decreased from 4.54 L / m³ to 3.04 L / m³. -2 h -1 bar -1 The removal rate only decreased from 98.34% to 96.27%, indicating that the MXene composite membrane has good long-term stability.

[0030] (6) Application of ceramic-based MXene composite membrane in wastewater treatment of different micro-pollutants.

[0031] The composite membrane was assembled into a pressure-driven testing device. The feed solution consisted of 50 ppm tetracycline (TC), amoxicillin (AMX), oxytetracycline (OTC), and chloramphenicol (CAP) solutions, and the pressure was 1 bar. The removal performance of the MXene composite membrane for different pollutants was tested. It can be seen that the MXene composite membrane achieved a removal efficiency of over 95% for all four micropollutants, with a water flux ranging from 3.83 to 5.09 L / m³. -2 h -1 bar -1 This indicates that the MXene composite membrane has a good removal effect on various micro-pollutants.

[0032] The beneficial effects of this invention are as follows: By introducing a one-dimensional nanomaterial intermediate transition layer with positive charge and multiple binding sites on the surface of the macroporous alumina carrier, the bonding force between the carrier and the MXene membrane layer is enhanced. The thickness and pore size of the composite membrane can be controlled by changing the filtration time of the MXene solution and the vacuum drying temperature.

[0033] 1. Using MWCNT as an intermediate transition layer, the bonding force between the composite film and the alumina ceramic carrier is enhanced through electrostatic interaction and heat treatment. Compared with the intermediate transition layer introduced by the TiO2 and γ-Al2O3 dip-coating and sintering process, this method is simpler, eliminates the need for secondary high-temperature sintering, saves time and cost, and the composite film exhibits extremely high stability. This method has significant reference value for the preparation of highly stable two-dimensional films using inorganic carriers.

[0034] 2. Using inorganic alumina ceramic as a carrier, this composite membrane exhibits high mechanical strength, long service life, and acid and alkali resistance. The composite membrane thickness ranges from 100 to 600 nm, possessing nanometer and sub-nanometer-scale channels, enabling effective removal of micro-pollutants through a pressure-driven process.

[0035] 3. The highly stable ceramic-based sub-nanoporous MXene composite membrane prepared by this method achieves superior performance (high rejection rate, high stability, and high flux) in micropollutant removal tests. It exhibits excellent removal performance under different pressure conditions and with different types of micropollutants. Attached Figure Description

[0036] Figure 1 This is a comparison chart of the zeta potential changes and dispersibility of the MWCNT solution in Example 1.

[0037] Figure 2 These are scanning electron microscope (SEM) images of the surface and cross-section of the intermediate transition layer of MWCNT in Example 1.

[0038] Figure 3 This is a comparison chart of the stability of the composite membrane with and without the MWCNT intermediate transition layer in Example 2.

[0039] Figure 4 The images shown are cross-sectional scanning electron microscope (SEM) images of the MXene composite membrane under different filtration time conditions in Example 2.

[0040] Figure 5 Tetracycline removal performance of MXene composite membrane under different filtration time conditions in Example 3.

[0041] Figure 6 Example 4 illustrates the removal performance of the MXene composite membrane for tetracycline under different pressure conditions.

[0042] Figure 7 The removal performance of the MXene composite membrane in Example 5 for different micro-pollutants is shown. Detailed Implementation

[0043] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0044] Example 1: Preparation of MWCNT intermediate transition layer on alumina ceramic substrate

[0045] (1) Weigh 1 g of cetyltrimethylammonium bromide (CTAB) and place it in a beaker. Add 250 mL of deionized water and place it on a magnetic stirrer and stir for 10 min to completely dissolve it. Then weigh 0.125 g of multi-walled carbon nanotubes (MWCNTs) and add them to the beaker containing CTAB. Stir again for 10-20 min. Finally, sonicate the mixed solution for 2 h to ensure that it is fully mixed and homogeneous to obtain a CTAB-MWCNT suspension. Figure 1 The zeta potential changes and dispersibility of MWCNT solutions are compared. MWCNT itself is negatively charged and has a low potential, resulting in poor dispersibility and easy aggregation in water. In contrast, CTAB-MWCNT modified with CTAB is positively charged and has a high potential, resulting in better dispersibility in solution.

[0046] (2) The alumina ceramic support was placed in the vacuum filtration apparatus assembly. 1 mL of a 0.5 mg / mL CTAB-MWCNT suspension was taken, diluted to 25 mL with deionized water, and poured into the vacuum filtration cup. Vacuum-assisted filtration was then used to load the suspension onto the alumina ceramic support, thus obtaining an alumina ceramic support with a MWCNT intermediate transition layer. Scanning electron microscopy images of the surface and cross-section of the MWCNT intermediate transition layer are shown below. Figure 2 The upper part is the MWCNT transition layer, and the lower part is the alumina ceramic carrier.

[0047] Example 2: Preparation of Highly Stable Ceramic-Based Subnanoporous MXene Composite Membranes

[0048] (1) MXene (Ti3C2T) xSolution preparation: Weigh 1.6 g of lithium fluoride (LiF) and add it to a polytetrafluoroethylene reactor. Then, add 5 mL of deionized water and 15 mL of 12 mol concentrated hydrochloric acid (HCl) in sequence. After stirring magnetically for 3 min, slowly add 1.0 g of aluminum carbide (Ti3AlC2). After the aluminum carbide is completely added, place the reactor in a constant temperature water bath and adjust the temperature to 35℃. Stir and react for 24 h. Take the solution after the reaction and place it in a centrifuge tube. Add water and centrifuge 12 times (speed 5000 rpm). After the last centrifugation, pour off the supernatant and retain the precipitate. The purpose of this centrifugation process is to adjust the pH value of the etched solution to neutral and to wash away the fluoride generated during the etching process. The precipitate was then dissolved in 100 mL of deionized water and sonicated for 15 min, followed by centrifugation for 60 min (3500 rpm). After sonication, the multilayered MXene nanosheets were separated into single layers. During centrifugation, due to the low speed, the single-layer MXene nanosheets could not precipitate, while the unseparated multilayered MXene nanosheets, due to their larger mass, would precipitate. The supernatant was the single-layer MXene nanosheet solution. The supernatant was poured into a wide-mouth bottle for storage and later use. The concentration of the MXene solution was approximately 1.5 mg / mL.

[0049] (2) Preparation of ceramic-based MXene composite membrane: The alumina ceramic support with the MWCNT intermediate transition layer prepared above was placed in a vacuum-assisted filtration assembly. 1 mL of MXene solution was placed in a 50 mL centrifuge tube and diluted with deionized water to 40-45 mL. The solution was then poured into a filtration cup. The filtration time of the MXene solution was changed (30 s, 1 min, 3 min and 5 min). The membrane was vacuum dried at 140℃ for 12 h to obtain ceramic-based MXene composite membranes with different membrane thicknesses. The obtained MXene composite membranes were then placed in a vacuum drying oven with the temperature adjusted to 140℃. After 12 h, the membranes were removed, and the ceramic-based MXene composite membrane was successfully prepared. Figure 3 To compare the stability of composite membranes with and without the MWCNT intermediate transition layer, compared to the composite membrane without the MWCNT intermediate transition layer (which has extremely poor stability in water and the composite membrane layer falls off quickly), the composite membrane with the MWCNT intermediate transition layer remained stable and defect-free after being immersed in water for 10 days. Figure 4 The images show scanning electron microscope (SEM) images of ceramic-based MXene composite membranes under different filtration times. The thickness of the MXene composite membrane increases with increasing filtration time.

[0050] Example 3: Application of ceramic-based MXene composite membrane in the treatment of micro-pollutant wastewater under different filtration times

[0051] The MXene composite membranes obtained at different filtration times (30 s, 1 min, 3 min, and 5 min) in Example 2 were assembled into a pressure-driven testing device. The feed solution was a 50 ppm tetracycline (TC) solution prepared with deionized water, and the pressure was 1 bar to test the removal performance of micropollutants. Figure 5 Tetracycline removal rate and water flux of the MXene composite membrane at different filtration times. As the filtration time increased, the water flux increased from 8.94 L / m³. -2 h -1 bar -1 Reduced to 3.69 L m -2 h -1 bar -1 The tetracycline rejection rate increased from 95.02% to 98.85%. Considering both water flux and rejection rate, an MXene composite membrane with a filtration time of 3 min was selected for subsequent experiments to ensure both high water flux and excellent removal rate.

[0052] Example 4: Application of ceramic-based MXene composite membrane in antibiotic wastewater treatment under different pressure conditions

[0053] The test used the MXene solution from Example 3, which was filtered for 3 minutes and then vacuum dried at 140°C for 12 hours to obtain a ceramic-based MXene composite membrane. The composite membrane was assembled into a pressure-driven testing device, with a feed solution of 50 ppm tetracycline (TC) solution. The pressure was adjusted from 1 to 5 bar, and the tetracycline removal rate and water flux were tested under different pressure conditions. Figure 6 The removal rate and water flux of the MXene composite membrane for tetracycline were compared under different pressure conditions. The water flux of the MXene composite membrane showed an increasing trend with increasing pressure, from 4.13 L / m³. -2 h -1 bar -1 Increased to 19.71 L m -2 h -1 bar -1 The rejection rate decreased from 98.23% to 92.04%, but still remained above 90%. This indicates that the MXene composite membrane still exhibits high micro-pollutant removal performance under high pressure.

[0054] Example 5: Application of ceramic-based MXene composite membrane in wastewater treatment of different micro-pollutants.

[0055] The test used the MXene solution from Example 3, which was filtered for 3 minutes and then vacuum dried at 140°C for 12 hours to obtain a ceramic-based MXene composite membrane. The composite membrane was assembled into a pressure-driven test device assembly, with a feed solution of 50 ppm tetracycline (TC), amoxicillin (AMX), oxytetracycline (OTC), and chloramphenicol (CAP) at a pressure of 1 bar, to test the removal performance of the MXene composite membrane for different pollutants. Figure 7 The removal rates and water fluxes of the MXene composite membrane for different micropollutants are shown. It can be seen that the MXene composite membrane achieves a retention rate of over 95% for all four micropollutants, with water fluxes ranging from 3.83 to 5.09 L / m³. -2 h -1 bar -1 This indicates that the MXene composite membrane has a good removal effect on various micro-pollutants.

Claims

1. A method for preparing a ceramic-based MXene composite film modified with a carbon nanotube transition layer, characterized in that: This composite membrane uses ceramic as a carrier, with a carbon nanotube intermediate transition layer introduced on the carrier surface. Then, an MXene separation layer is loaded onto the carrier via vacuum-assisted filtration to obtain a highly stable ceramic-based MXene composite membrane. The preparation steps of the composite membrane are as follows: (1) Preparation of carbon nanotube transition layer: Mix hexadecyltrimethylammonium bromide and deionized water and stir until completely dissolved; then add carbon nanotubes and stir again for 10-20 min; finally, sonicate the mixed solution to make it fully mixed and uniform to obtain CTAB modified carbon nanotube suspension. The carbon nanotubes are multi-walled or single-walled carbon nanotubes; hexadecyltrimethylammonium bromide and carbon nanotubes Mass ratio 1: 0.5~3; The CTAB-modified carbon nanotube suspension was filtered onto a ceramic support using vacuum-assisted filtration, thereby obtaining a ceramic support with a carbon nanotube intermediate transition layer. (2) Preparation of MXene solution: Lithium fluoride, deionized water and concentrated hydrochloric acid were added to a polytetrafluoroethylene reactor in sequence, and aluminum carbide was slowly added to it. The reaction temperature was 30-50℃ and the mixture was stirred for 18-30 h. The solution after the reaction was placed in a centrifuge tube, water was added and centrifuged. Finally, the supernatant was poured out and the precipitate was left. The precipitate was dissolved in deionized water and sonicated for 10-20 min. It was centrifuged again for 45-70 min. The supernatant obtained was the MXene solution with a concentration range of 0.8-1.5 mg / mL. The mass ratio of lithium fluoride to concentrated hydrochloric acid is (1~1.6):5, and the mass ratio of lithium fluoride to aluminum carbide is 1~1.6:1; (3) Preparation of ceramic-based MXene composite membrane: The MXene solution was filtered onto a ceramic carrier with a carbon nanotube intermediate transition layer by vacuum-assisted filtration. The filtration time was adjusted to be 30 s to 350 s. The resulting MXene composite membrane was then placed in a vacuum drying oven to obtain the ceramic-based MXene composite membrane.

2. The method for preparing a carbon nanotube-modified ceramic-based MXene composite film according to claim 1, characterized in that: The ceramic carrier is sheet-like or tubular alumina or titanium oxide.

3. The application of the ceramic-based MXene composite film prepared by the method according to claim 1, characterized in that: The ceramic-based MXene composite membrane is used for the removal of micro-pollutants.

4. The application according to claim 3, characterized in that: The micro-contaminants are tetracycline, amoxicillin, oxytetracycline, chloramphenicol, or levofloxacin.

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