Preparation method of MXene composite membrane for efficiently removing dye rhodamine B

Abstract

The invention relates to a preparation method of an MXene composite film capable of efficiently removing dye rhodamine B. The method comprises the following steps: stripping from MAX-phase TiAlC through an HCL and LiF etching method to obtain a few-layer MXene nanosheet; sPH is prepared from 5, 5-dimethyl hydantoin and sodium hydroxide particles; the SPH and an ethanol solution are subjected to a heating reaction, and a polymerization product PSPH is obtained; dissolving MXene and PSPH in an ethanol solution, carrying out ultrasonic treatment, and then carrying out heating reaction; washing the product with absolute ethyl alcohol to obtain the PSPH grafted MXene nanosheet; and carrying out ultrasonic treatment on the PSPH grafted MXene nanosheet and a TBO solution, and carrying out suction filtration to form a membrane, so as to prepare the MX-TBO-PSPH composite membrane. The removal rate of the MXene composite film on rhodamine B dye can reach 97% or above, and the MXene composite film has good mechanical strength and stability and strong self-cleaning capability.

Description

Technical Field

[0001] The present invention relates to a method for preparing a composite membrane, in particular to a method for preparing a MXene composite membrane for efficiently removing the dye Rhodamine B. Background Art

[0002] Recent research has used graphene oxide (GO) membranes for dye removal. GO membranes, composed of stacked two-dimensional nanosheets, form two-dimensional channels that restrict the passage of dye molecules through pore size sieving, while also relying on their high surface area and π-π interactions to adsorb dye molecules. However, their main drawbacks include: the complex and costly preparation process for graphene oxide; the tendency for interlayer stacking to occur after long-term operation, leading to a decrease in flux; and unstable adsorption efficiency for cationic dyes such as rhodamine B.

[0003] Existing technologies also utilize molybdenum disulfide (MoS2) for dye removal, owing to its unique pore structure and adjustable interlayer distance. Dye molecules can be adsorbed on the surface of the MoS2 membrane through physical forces such as van der Waals forces. However, its main drawbacks are: the MoS2 membrane's interlayer height is relatively narrow, accommodating only one layer of water molecules, resulting in low water permeability and flux; MoS2 easily aggregates in aqueous solutions, reducing its specific surface area and pore structure; and the high production cost and low yield of MoS2 and its composite nanomaterials, which may increase the overall cost of dye wastewater treatment. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a MXene composite membrane based on a MXene composite membrane for removing the dye Rhodamine B with high efficiency, stability and low cost, in response to the problems of low dye removal efficiency, high cost and serious membrane pollution in the prior art.

[0005] The technical problem to be solved by the present invention is achieved by the following technical solution. The present invention is a method for preparing a MXene composite membrane that can efficiently remove the dye Rhodamine B, which is characterized by the following steps: (1) Few-layer MXene nanosheets were obtained by exfoliation from MAX phase Ti3AlC2 by HCL and LiF etching; (2) Using 5,5-dimethylhydantoin and sodium hydroxide particles to obtain a milky white product 5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin monomer SPH; the obtained SPH is heated and reacted with an ethanol solution to obtain a polymer product PSPH; (3) MXene and PSPH at a mass ratio of 1:1 to 2 are dissolved in an ethanol solution and subjected to ultrasonic treatment, followed by heating reaction; the product is washed with anhydrous ethanol to finally obtain a grafted product of a MXene-based silane halamine polymer precursor, namely, PSPH-grafted MXene nanosheets; (4) The PSPH-grafted MXene nanosheets were ultrasonically treated with TBO solution and vacuum filtration was used to form a membrane to prepare the MX-TBO-PSPH composite membrane.

[0006] The method for preparing the MXene composite film of the present invention has a further preferred technical solution: in step (2), the volume concentration of the ethanol solution is 60% to 70%; in step (3), the volume concentration of the ethanol solution is 30% to 40%.

[0007] The method for preparing the MXene composite film of the present invention further comprises the following preferred technical solutions: in step (2), SPH is heated to react with an ethanol solution prepared by mixing water and anhydrous ethanol in a volume ratio of 1:2 to obtain a polymer product PSPH; in step (3), MXene and PSPH are dissolved in an ethanol solution prepared by mixing water and ethanol in a volume ratio of 1:2 and subjected to ultrasonic treatment.

[0008] The preparation method of the MXene composite film of the present invention is further preferably provided as follows: the specific operation method of step (1) is as follows: LiF is dissolved in HCl solution, and rapidly stirred at 35°C for 30 min to form a mixed solution of LiF and HCl, and then the precursor ternary phase raw material Ti3AlC2 is etched in the mixed solution of LiF and HCl to convert it into a multilayer Ti3C2T x That is, MXene, wherein the temperature is 40°C and the mixture is stirred continuously for 48 h. The multilayer MXene in the mixed solution is then separated multiple times by centrifugation at 4000 rpm, rinsed with deionized water until the pH of the solution is neutral, and then dispersed in deionized water. Finally, the MXene generated by the above reaction is ultrasonically peeled off for 30 minutes, and then the upper dark purple liquid is collected again by centrifugation at 5000 rpm for 15 minutes to obtain a single layer of MXene.

[0009] The preparation method of the MXene composite film of the present invention is further preferred in the technical scheme as follows: the specific operation method of step (2) is as follows: add 5,5-dimethylhydantoin and sodium hydroxide particles in anhydrous ethanol in an equal molar amount, and stir at room temperature until completely dissolved; after rotary evaporation to remove the ethanol solvent, place the obtained sodium hydantoin salt in a vacuum drying oven at 45°C for 2 days to finally obtain foamy sodium hydantoin salt; dissolve the obtained sodium salt in N,N-dimethylformamide (DMF), and add 3-chloropropyltriethoxysilane in an equal molar amount thereto, and keep the temperature at 95°C for 16 hours; after the reaction is completed, remove the by-product NaCl by filtration; remove the solvent by vacuum distillation to finally obtain a milky white product 5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin monomer (SPH); put the obtained SPH into a mixed solution of water and anhydrous ethanol in a volume ratio of 1:2 and adjust the pH of the solution to between 3.5 and 5.5 with dilute hydrochloric acid; react at 85°C for 5 hours After that, the solvent is evaporated by heating until a viscous liquid appears; the transparent solid obtained after cooling is the final polymerization product, poly[5,5-dimethyl-3-(30-triethoxysilylpropyl)hydantoin], namely PSPH.

[0010] The method for preparing the MXene composite film of the present invention has a further preferred technical solution: the specific operation method of step (3) is as follows: MXene and PSPH with a mass ratio of 1:1 to 2 are dissolved in a mixed solution of water and ethanol with a volume ratio of 2:1; after ultrasonic treatment with an ultrasonic cleaner for 30 minutes, the mixture is reacted at 80°C for 6 hours; the product is separated by centrifugation and the supernatant is removed; the residue is repeatedly washed with ethanol, and the PSPH-grafted MXene nanosheets obtained by centrifugation are obtained.

[0011] The method for preparing the MXene composite film of the present invention has a further preferred technical solution: the ultrasonic cleaner has an operating frequency of 53 kHz and a power of 150 W.

[0012] The method for preparing the MXene composite membrane of the present invention has a further preferred technical solution: the centrifugal operation speed is 10,000 rpm, and the separation time is 15 min.

[0013] The preparation method of the MXene composite membrane described in the present invention has a further preferred technical solution: the specific operation method of step (4) is as follows: take the PSPH-grafted MXene nanosheets and TBO solution and mix them by ultrasonication for 15 minutes to form a composite water suspension, and load the MXene mixed water suspension onto the PES membrane carrier by vacuum-assisted assembly under a pressure of 0.1 MPa to form a MX-TBO-PSPH composite membrane.

[0014] The present invention also discloses a method for removing dyes using a MXene composite membrane for efficiently removing the dye Rhodamine B, which is prepared by the preparation method described in the above technical solution. The method is characterized in that the steps are as follows: wastewater containing Rhodamine B is passed through an MX-TBO-PSPH composite membrane at an operating pressure of 0.1 MPa, and the operating device is a low-pressure membrane separation device; the negative charge on the surface of the MX-TBO-PSPH composite membrane is combined with the Rhodamine B cation through electrostatic adsorption, and the membrane pore size is used to achieve size screening.

[0015] In the present invention, the description of each raw material is as follows: MXene: A two-dimensional transition metal carbide / nitride material with the chemical formula Ti3C2T x (T x is a surface functional group), wherein X is carbon or nitrogen, and T represents a surface functional group (such as -OH, -O, -F, etc.).

[0016] Rhodamine B: a cationic fluorescent dye with the molecular formula C 28 H 31 ClN2O3, often used in wastewater treatment research; TBO (Toluidine Blue): A versatile stain that can specifically bind to biomolecules or material surfaces; PSPH (Poly[5,5-dimethyl-3-(30-triethoxysilylpropyl)hydantoin]): A polymeric N-halamine antimicrobial material. The functional groups on the N-halamine compound can be converted to oxidized N-Cl or N-Br antimicrobial moieties upon halogenation. The halogenated moieties can be directly transferred into cells, where they inactivate the cellular system.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Efficient dye removal: The removal rate of Rhodamine B dye by MXene composite membrane can reach over 97%, which is much higher than that of traditional adsorption materials.

[0018] 2. Good mechanical strength and stability: By introducing the polymer matrix, the composite membrane has good mechanical strength and long-term stability.

[0019] 3. Strong self-cleaning ability: PSPH, a high molecular weight N-halamine antibacterial material, is grafted onto the surface of the MXene composite membrane, which enables the composite membrane to achieve antibacterial and self-cleaning effects during the dye removal process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1Surface and cross-sectional images of the MXene composite membrane prepared in the present invention; (ab) surface images of a 1:2 MX-TBO-PSPH composite membrane; (cd) cross-sectional images of a 1:2 MX-TBO-PSPH composite membrane; Figure 2 The flux and rejection performance bar graph of MX-TBO-PSPH composite membranes with different ratios at 1 bar using 15 ppm Rhodamine B solution as feed; Figure 3 The flux and rejection performance bar graph of 1:2MX-TBO-PSPH composite membrane at 1 bar using Rhodamine B solution with different concentrations as feed. DETAILED DESCRIPTION

[0021] The specific technical solutions of the present invention are further described below to facilitate further understanding of the present invention by those skilled in the art, but do not constitute a limitation to their rights.

[0022] Example 1, a method for preparing a MXene composite membrane for efficiently removing the dye Rhodamine B, the steps of which are as follows: (1) Few-layer MXene nanosheets were obtained by exfoliation from MAX phase Ti3AlC2 by HCL and LiF etching; (2) Using 5,5-dimethylhydantoin and sodium hydroxide particles to obtain a milky white product 5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin monomer SPH; the obtained SPH is heated and reacted with an ethanol solution to obtain a polymer product PSPH; (3) MXene and PSPH at a mass ratio of 1:1 to 2 are dissolved in an ethanol solution and subjected to ultrasonic treatment, followed by heating reaction; the product is washed with anhydrous ethanol to finally obtain a grafted product of a MXene-based silane halamine polymer precursor, namely, PSPH-grafted MXene nanosheets; (4) The PSPH-grafted MXene nanosheets were ultrasonically treated with TBO solution and vacuum filtration was used to form a membrane to prepare the MX-TBO-PSPH composite membrane.

[0023] Example 2, reference Figure 1 -3. Experimental preparation of MXene composite membrane for efficient removal of dye Rhodamine B: (1) Dissolve 1.6 g of LiF in 20 ml of HCl solution (9 mol·L -1 ) and rapidly stirred at 35 ° C for 30 min to form a mixed solution of LiF and HCl. Then, 1 g of the precursor ternary phase raw material Ti3AlC2 was etched in the mixed solution of LiF and HCl to convert it into multilayer Ti3C2T x(MXene), wherein the temperature is 40 ° C, and the mixture is stirred continuously for 48 hours. The multilayer MXene in the mixed solution is separated multiple times by centrifugation at 4000 rpm, rinsed with deionized water until the pH of the solution is neutral, and then dispersed in deionized water. Finally, the MXene generated by the above reaction is ultrasonically peeled off for 30 minutes, and then the upper dark purple liquid is collected again by centrifugation at 5000 rpm for 15 minutes to obtain a single layer of MXene; (2) Add 5,5-dimethylhydantoin and sodium hydroxide particles in anhydrous ethanol in an equal molar amount (0.1 mol) and stir at room temperature until completely dissolved. After removing the ethanol solvent by rotary evaporation, the obtained sodium hydantoin salt was placed in a vacuum drying oven at 45°C for 2 days to finally obtain foamy sodium hydantoin salt. The obtained sodium salt was dissolved in N,N-dimethylformamide (DMF), and an equal molar amount of 3-chloropropyltriethoxysilane was added thereto. The temperature was maintained at 95°C for 16 hours. After the reaction was completed, the by-product NaCl was removed by filtration. The solvent was removed by vacuum distillation to finally obtain a milky white product 5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin monomer (SPH). The obtained SPH was added to a mixed solvent of water and ethanol with a volume ratio of 1:2 (total volume of 54 mL) and the pH of the solution was adjusted to between 3.5 and 5.5 with dilute hydrochloric acid. After reacting at 85°C for 5 hours, the solvent was evaporated on a hot plate until a viscous liquid appeared. The resulting transparent solid upon cooling was the final polymerization product, poly[5,5-dimethyl-3-(30-triethoxysilylpropyl)hydantoin] (PSPH). (3) MXene and PSPH at mass ratios of 1:1, 1:2, and 1:3 were dissolved in a mixed solvent of water and ethanol (150 mL, v / v, 2:1). After ultrasonic treatment for 30 min using an ultrasonic cleaner (operating frequency 53 kHz, power 150 W), the mixture was reacted at 80°C for 6 h. The product was separated by centrifugation (10,000 rpm, 15 min), and the supernatant was removed. The residue was repeatedly washed with ethanol and centrifuged to obtain a colloidal solution of the MXene-based silane haloamine precursor grafted product.

[0024] (4) 2 mg of PSPH-grafted MXene nanosheets with different proportions were mixed with TBO solution and ultrasonicated for 15 min to form a composite water suspension. Under a pressure of 0.1 MPa, the MXene mixed water suspensions with different proportions were loaded onto the PES membrane carrier by vacuum-assisted assembly to form three MX-TBO-PSPH composite membranes with different proportions.

[0025] Dye removal process: (1) A 15 ppm Rhodamine B dye solution was prepared with deionized water and passed through three MX-TBO-PSPH composite membranes in a cross-flow filtration manner. The resulting composite membranes were installed in a membrane separation cross-flow device (Hangzhou Saifei SF-SA membrane performance evaluation instrument). The membranes were pre-pressed at 2 bar for 15 minutes until the composite membranes were stable. The pressure was adjusted to 1 bar, and the flux and dye retention performance were tested at room temperature. RhB solutions with concentrations of 5, 10, 15, 20, 25, and 30 ppm were prepared, and the flux and retention rate of the composite membranes for RhB dye under different initial concentration conditions were measured. (2) The dye solution before and after filtration was collected, and the membrane flux was calculated by the volume of the filtrate and the sampling time. The concentration of the raw liquid and the permeate was tested using an ultraviolet-visible spectrophotometer (UV-vis) to investigate the flux and retention rate of the composite membrane for rhodamine B dye; (3) The MX-TBO-PSPH composite membrane significantly improves the retention rate of Rhodamine B dye through electrostatic repulsion, the steric effect of the two-dimensional space caused by the rigid two-dimensional polycyclic skeleton structure of the conjugated polycyclic cations, and the precise control of the MXene interlayer spacing; (4) The MX-TBO-PSPH composite membrane prepared by dissolving MXene and PSPH in a mixed solvent of water and ethanol (150 mL, v / v, 2:1) with a mass ratio of 1:2 showed the best dye removal efficiency of 97.20%.

Claims

1. A method for preparing a MXene composite membrane for efficiently removing the dye Rhodamine B, characterized in that: The steps are as follows: (1) Few-layer MXene nanosheets were obtained by exfoliation from MAX phase Ti3AlC2 by HCL and LiF etching; (2) Using 5,5-dimethylhydantoin and sodium hydroxide particles to obtain a milky white product 5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin monomer SPH; the obtained SPH is heated and reacted with an ethanol solution to obtain a polymer product PSPH; (3) MXene and PSPH at a mass ratio of 1:1 to 2 are dissolved in an ethanol solution and subjected to ultrasonic treatment, followed by heating reaction; the product is washed with anhydrous ethanol to finally obtain a grafted product of a MXene-based silane halamine polymer precursor, namely, PSPH-grafted MXene nanosheets; (4) The PSPH-grafted MXene nanosheets were ultrasonically treated with TBO solution and vacuum filtration was used to form a membrane to prepare the MX-TBO-PSPH composite membrane.

2. The method for preparing a MXene composite film according to claim 1, wherein: The volume concentration of the ethanol solution in step (2) is 60% to 70%; in step (3), the volume concentration of the ethanol solution is 30% to 40%.

3. The method for preparing a MXene composite film according to claim 2, wherein: In step (2), SPH is heated to react with an ethanol solution prepared by mixing water and anhydrous ethanol in a volume ratio of 1:2 to obtain a polymer product PSPH; in step (3), MXene and PSPH are dissolved in an ethanol solution prepared by mixing water and ethanol in a volume ratio of 1:2 and subjected to ultrasonic treatment.

4. The method for preparing a MXene composite film according to claim 1, wherein: The specific operation method of step (1) is as follows: LiF is dissolved in HCl solution and rapidly stirred at 35 ° C for 30 min to form a mixed solution of LiF and HCl, and then the precursor ternary phase raw material Ti3AlC2 is etched in the mixed solution of LiF and HCl to convert it into multilayer Ti3C2T x That is, MXene, wherein the temperature is 40°C and the mixture is stirred continuously for 48 h. The multilayer MXene in the mixed solution is separated multiple times by centrifugation at 4000 rpm, rinsed with deionized water until the pH of the solution is neutral, and then dispersed in deionized water. Finally, the MXene generated by the above reaction is ultrasonically peeled off for 30 minutes, and then the upper dark purple liquid is collected again by centrifugation at 5000 rpm for 15 minutes to obtain a single layer of MXene.

5. The method for preparing a MXene composite film according to claim 1, wherein: The specific operation method of step (2) is as follows: add 5,5-dimethylhydantoin and sodium hydroxide particles in anhydrous ethanol in equal molar amounts, and stir at room temperature until completely dissolved; after rotary evaporation to remove the ethanol solvent, place the obtained sodium hydantoin salt in a vacuum drying oven at 45°C for 2 days to finally obtain foamy sodium hydantoin salt; dissolve the obtained sodium salt in N,N-dimethylformamide (DMF), and add 3-chloropropyltriethoxysilane in equal molar amounts thereto, and keep the temperature at 95°C for 16 hours; after the reaction is completed, remove the by-product NaCl by filtration; remove the solvent by vacuum distillation to finally obtain a milky white product 5,5-dimethyl-3-(3'-triethoxysilylpropyl)hydantoin monomer (SPH); put the obtained SPH into a mixed solution of water and anhydrous ethanol in a volume ratio of 1:2 and adjust the pH of the solution to between 3.5 and 5.5 with dilute hydrochloric acid; react at 85°C for 5 hours After that, the solvent is evaporated by heating until a viscous liquid appears; the transparent solid obtained after cooling is the final polymerization product, poly[5,5-dimethyl-3-(30-triethoxysilylpropyl)hydantoin], namely PSPH.

6. The method for preparing a MXene composite film according to claim 1, wherein: The specific operation method of step (3) is as follows: MXene and PSPH with a mass ratio of 1:1 to 2 are dissolved in a mixed solution of water and ethanol with a volume ratio of 2:1; after ultrasonic treatment with an ultrasonic cleaner for 30 minutes, the mixture is reacted at 80°C for 6 hours; the product is separated by centrifugation and the supernatant is removed; the residue is repeatedly washed with ethanol and the PSPH-grafted MXene nanosheets are obtained by centrifugation.

7. The method for preparing a MXene composite film according to claim 6, wherein: The operating frequency of the ultrasonic cleaner is 53kHz and the power is 150W.

8. The method for preparing a MXene composite film according to claim 6, wherein: The centrifugation speed was 10,000 rpm and the separation time was 15 min.

9. The method for preparing a MXene composite film according to claim 1, wherein: The specific operation method of step (4) is as follows: take the PSPH-grafted MXene nanosheets and TBO solution and mix them with ultrasound for 15 minutes to form a composite water suspension. Under a pressure of 0.1 MPa, the MXene mixed water suspension is loaded onto the PES membrane carrier by vacuum-assisted assembly to form a MX-TBO-PSPH composite membrane.

10. A method for removing dyes using a MXene composite membrane for efficiently removing the dye Rhodamine B obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The steps are as follows: wastewater containing rhodamine B is passed through an MX-TBO-PSPH composite membrane at an operating pressure of 0.1 MPa, and the operating device is a low-pressure membrane separation device; the negative charge on the surface of the MX-TBO-PSPH composite membrane is combined with the rhodamine B cation through electrostatic adsorption, and the membrane pore size realizes size screening.

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