An in-situ intercalation preparation method of a sandwich type TpHz@MXene composite film

Abstract

The application discloses an in-situ intercalation preparation method of a sandwich type TpHz@MXene composite film, relates to the technical field of ultrafiltration separation of dye and salt aqueous solution, and discloses the following steps: an MXene nanosheet dispersion is taken as a base and is subjected to negative pressure suction filtration to prepare an MXene / organic film composite film; TP is dissolved in n-hexane and is uniformly dispersed; a hydrazine hydrate solution and p-toluenesulfonamide are dissolved in deionized water and are uniformly dispersed; the composite film is arranged between interface polymerization devices, the two solutions are arranged on the two sides of the interface polymerization devices, and an interface polymerization reaction is performed to obtain a TpHz@MXene composite film, which is continuous, rough and thin in surface morphology, and has high surface area, with MXene and TpHz layers being stacked between the film layers. The composite film has high permeation capacity, high retention rate, high separation efficiency and superior performance for the ultrafiltration separation of dye and salt aqueous solution, and has outstanding durability and high-temperature stability.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ultrafiltration separation of dyes and salt aqueous solutions, in particular to an in-situ intercalation preparation method of a sandwich type TpHz@MXene composite membrane. BACKGROUND

[0002] Textile printing and dyeing wastewater has the characteristics of large water quantity, high content of organic pollutants, strong alkalinity, and large water quality variation, and is one of the industrial wastewaters that are difficult to treat. At present, the main methods for treating printing and dyeing wastewater include adsorption, biological method, chemical method and the like. The pretreatment in the wastewater treatment is mainly to improve the wastewater quality, remove suspended solids, adjust the wastewater quality, reduce the wastewater temperature and the like, improve the overall effect of the wastewater treatment, and ensure the stability of the entire treatment system, so that the pretreatment has an extremely important position in the printing and dyeing wastewater treatment.

[0003] With the continuous development of membrane separation technology, the membrane technology has become an important research direction for the treatment and reuse of industrial wastewater. The ultrafiltration membrane technology is a physical treatment technology for realizing the treatment of wastewater by using the screening and penetration characteristics of a filter membrane under the action of the self-pressure of a solution, so that low-molecular solutes in water penetrate the filter membrane. Through the ultrafiltration technology, lignin and slurry in the wastewater can be completely separated, and the filtered lignin and slurry can be collected again, so that the utilization rate is greatly improved. The membrane separation ultrafiltration technology has the advantages of low energy consumption, low labor intensity and production cost, high production efficiency, excellent water quality, large membrane specific surface area, small occupation area, convenience for technical improvement and expansion, and the like, and can reduce the production cost and investment. The textile printing and dyeing wastewater is reused by using the ultrafiltration technology, the use amount of fresh water is reduced, the consumption of water resources is reduced, and the development of the textile printing and dyeing industry has important significance.

[0004] As a new type of nanomaterial, MXene not only has a regular and uniform edge structure, an ultrathin monatomic layer structure and a large lateral size, but also has the advantages of large specific surface area, good mechanical property and good film forming property, and is an ideal separation membrane material. Covalent organic framework (COFS) is a kind of porous organic polymer with crystallinity, and the building blocks are connected into a two-dimensional or three-dimensional structure through covalent bonds. COFS has the advantages of large specific surface area, low density, good stability and ordered structure. However, the interlayer of the MXene film is mainly the relatively weak van der Waals force and electrostatic force interaction, water molecules or hydrated ions in the aqueous solution will enter the interlayer of the layered film to cause swelling phenomenon and increase the interlayer spacing, and further cause the disintegration and dissolution of the film. Moreover, the MXene film cannot meet the separation application requirements of long-time printing and dyeing wastewater in reality, which seriously limits the development process of the industry.

[0005] Therefore, it is of great significance to develop a new type of TpHz@MXene composite film preparation method with low cost, low energy consumption, high separation efficiency, high surface area, high stability, high durability, superior performance, and meeting the requirements of industrial production. SUMMARY

[0006] In order to solve the problems that the current MXene composite film is easy to disintegrate and dissolve, which leads to the fact that it cannot meet the long-time separation requirements in industrial production and is difficult to be mass-produced, the application provides an in-situ intercalation preparation method of a sandwich type TpHz@MXene composite film, which has the advantages of low cost, low energy consumption, high separation efficiency, high surface area, high stability, high durability, superior performance, and meeting the requirements of industrial production.

[0007] In order to achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows:

[0008] The in-situ intercalation preparation method of the sandwich type TpHz@MXene composite film is to synthesize TpHz with COF structure between the MXene layers on the basis of MXene / organic film, so as to realize the structure of layer-by-layer growth, and significantly improve the stability, separation efficiency and separation performance of the TpHz@MXene composite film. The specific steps are as follows:

[0009] (1) LiF and TiAlC2 are used as raw materials to prepare a MXene nanosheet dispersion with a concentration of 0.1-100 mg / mL; then the MXene nanosheet dispersion is used as a substrate to prepare a film by negative pressure suction filtration, i.e. a MXene / organic film composite film, which is stored under an inert gas atmosphere for standby;

[0010] (2) 0.1-100 mg of 1,3,5-triformylphloroglucinol (Tp) is dissolved in 10-500 mL of n-hexane to disperse uniformly, which is denoted as solution A. Solution A includes an aldehyde monomer in an organic phase, i.e. an organic phase solution of a substance capable of Schiff base reaction with an aldehyde monomer. 0.1-100 mmol of hydrazine hydrate (Hz·H2O) and 0.1-10 g of p-toluenesulfonamide (PTSA·H2O) are dissolved in 10-500 mL of deionized water to disperse uniformly, which is denoted as solution B. Solution B includes an amine monomer in an aqueous phase, i.e. an aqueous phase solution of a substance capable of Schiff base reaction with an amine monomer;

[0011] (3) The MXene / organic film composite film prepared in step (1) is placed between the interfacial polymerization devices and fixed by a clamp. Solutions A and B are respectively placed on the two sides of the interfacial polymerization devices. After interfacial polymerization, the composite film is taken out from the interfacial polymerization mold, dried, and washed with ethanol and water for several times, so as to obtain a TpHz@MXene composite film, which is stored in water for standby.

[0012] As a further preferred technical solution of the present application, in the preparation method:

[0013] The organic film in step (1) is selected from nylon-66, polypropylene, polyethylene, polyacrylonitrile, polysulfone, aromatic polyamide or polyvinylidene fluoride. The inert gas is one or a mixed gas atmosphere of nitrogen, argon, helium.

[0014] The uniform dispersion method in step (2) includes mechanical stirring, ultrasonic, shaking or manual stirring.

[0015] In step (3), the interfacial polymerization is carried out at room temperature for 1-24 hours. The drying method includes normal pressure drying, freeze drying or vacuum drying.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] (1) The interlayer type TpHz@MXene composite film prepared by the present application has a continuous surface without cracks, is relatively rough, and has a thin thickness. The MXene and COF layer (TpHz) are stacked between the film layers, and the film has a high surface area.

[0018] (2) The TpHz@MXene composite film prepared by the present application has high permeation capacity, high retention rate, high separation efficiency and superior performance for the ultrafiltration separation of dye and salt aqueous solution, and has outstanding durability and high temperature stability.

[0019] (3) The raw materials used in the present application are cheap, the reaction is simple and easy to control, and the industrial production is easy. The application in the ultrafiltration separation of dye and salt aqueous solution can greatly reduce the energy consumption in the separation and treatment of printing and dyeing industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 X-ray powder diffraction pattern of Ti3AlC2 and MXene in the preparation process of Example 1.

[0021] Figure 2 X-ray powder diffraction pattern of TpHz@MXene composite film prepared in Example 3 and related materials thereof.

[0022] Figure 3 Fourier transform infrared spectrum of TpHz@MXene composite film prepared in Example 3 and related materials thereof.

[0023] Figure 4 Scanning electron microscope images of the surface and section of MXene / nylon-66 composite film prepared in Example 2, wherein a and c represent low magnification, and b and d represent high magnification.

[0024] Figure 5Scanning electron microscope images of the surface and cross-section of the TpHz@MXene composite film prepared in Example 3, wherein a, c represent low magnification, b, d represent high magnification.

[0025] Figure 6 Thermogravimetric analysis chart of the TpHz@MXene composite film prepared in Example 3.

[0026] Figure 7 Surface streaming potential chart of the TpHz@MXene composite film described in Example 3 and its control group.

[0027] Figure 8 Permeability and rejection rate chart of the TpHz@MXene composite film in Example 4 to different dye solutions.

[0028] Figure 9 Permeability and rejection rate chart of the TpHz@MXene composite film in Example 5 to different salt ion solutions.

[0029] Figure 10 Permeability and rejection rate chart of the TpHz@MXene composite film in Example 6 to Congo red solution for 80h.

[0030] Figure 11 Surface and cross-section scanning electron microscope images of the TpHz@MXene composite film in Example 6 after being intercepted by Congo red solution for 80h, wherein a, c represent low magnification, b, d represent high magnification.

[0031] Figure 12 Ultraviolet spectrum curve of the Congo red solution intercepted by the TpHz@MXene composite film in Example 6. DETAILED DESCRIPTION

[0032] The present application will be further described in conjunction with the examples and the accompanying drawings.

[0033] Example 1

[0034] Preparation of MXene nanoplate powder:

[0035] First, 1g of LiF was dissolved in 20mL of 6mol / L HCl solution, and then 1g of Ti3AlC2 was added. After stirring at 35℃ for 24h, the precipitate was collected by centrifugation and washed with water several times until the pH value of the supernatant reached neutral. Then, the MXene powder was dispersed in water by ultrasonic treatment in an ice bath for 1h under flowing nitrogen to delaminate the MXene nanoplate. Then, centrifugation was performed at 3500rpm for 40min to remove the undetached bulk material, and then a MXene nanoplate dispersion with a concentration of 1.8mg / mL was obtained.

[0036] AsFigure 1 As shown, the diffraction peak positions of Ti3C2 at 6.7°, 13.5°, and 19.7° perfectly match the XRD diffraction peaks in the data. The 6.7° peak corresponds to its (002) lattice, proving the successful synthesis of Ti3C2. Among these, the following method was used... Figure 1 The Ti3AlC2 crystal form described herein is used as a raw material.

[0037] like Figure 3 As shown, Ti3C2 at 680 cm⁻¹ -1 1202cm -1 1625cm -1 The peaks at the positions represent the positions of Ti-O, CF, and -OH functional groups, respectively, demonstrating the successful preparation of Ti3C2. Figure 1 The results shown are saved consistently.

[0038] Example 2

[0039] Preparation of an MXene / Nylon-66 composite membrane:

[0040] Take 110 mL of the 1.8 mg / mL MXene dispersion synthesized in Example 1, disperse it thoroughly in 200 mL of deionized water, and then place it in a sintered glass funnel. Place the nylon-66 base membrane at the bottom of the funnel and filter it using a vacuum filtration device. Compress the MXene powder into a powder filter cake film under a negative pressure of approximately 0.1 MPa to obtain the MXene / nylon-66 composite membrane. Store the composite membrane in an argon atmosphere for later use to prevent oxidation. Use a Zeta potentiometer to measure the flow charge on the surface of the MXene / nylon-66 composite membrane.

[0041] like Figure 4 As shown in a and b, the surface of the MXene / Nylon-66 composite film is continuous and crack-free, but its surface is relatively rough in detail, which is beneficial to its hydrophilicity. Figure 4 As shown in Figure c, thin films are present on both sides of the surface of nylon-66. MXene is mainly distributed on the outer side of nylon-66, while a small amount of aggregated MXene exists inside nylon-66. Figure 4 As shown in d, MXene has uniformly distributed strip-shaped fibers inside and an extremely thin surface layer, which is beneficial to increasing the water flux for separating fuel or salt ions.

[0042] like Figure 7 As shown, the surface flow of negative charge in the MXene / Nylon-66 composite membrane increases with increasing pH. Compared with the Nylon-66 base membrane, the increased number of negative charges is beneficial to improving the performance of separating anionic dyes.

[0043] Example 3

[0044] An in-situ intercalation preparation method of a sandwich type COF@MXene composite film

[0045] The MXene / nylon-66 composite film prepared in Example 2 was placed between the interfacial polymerization devices and fixed using a clamp. 12.6 mg of 1,3,5-triformylphloroglucinol (Tp) was dissolved in 80 mL of n-hexane, denoted as solution A (organic phase, aldehyde monomer), and 9 mmol (98 wt%, 440 μL) of hydrazine hydrate solution (Hz·H2O) and 1.712 g of p-toluenesulfonamide (PTSA·H2O) were dissolved in 80 mL of deionized water, denoted as solution B (aqueous phase, amine monomer). The A and B solutions were both dispersed in ultrasonic for 30 min. The A and B solutions were placed on both sides of the interfacial polymerization device, and after interfacial polymerization at room temperature for 6 h, the composite film was taken out of the interfacial polymerization mold, dried at 60°C for 12 h, and washed with ethanol and water several times to obtain the TpHz@MXene composite film, which was stored in water for standby. The streaming charge of the surface of the TpHz@MXene composite film was measured using a related Zeta potential instrument.

[0046] As shown in Figure 2 , the XRD of the TpHz@MXene composite film was compared with the XRD of the nylon-66-based film, and it was found that the peaks of MXene and TpHz were combined inside the TpHz@MXene composite film, which proved the successful synthesis of the TpHz@MXene composite film.

[0047] As shown in Figure 3 , the FTIR curve of the TpHz@MXene composite film was compared with the MXene and TpHz powders, and it was found that almost all the diffraction peaks of the two materials were combined, which proved that the synthesized TpHz@MXene composite film had the components of MXene and TpHz, and that the stretching vibration of -NH2 between 3360 cm -1 -3474 cm -1 was not captured, and the peak value of -CHO at 1698 cm -1 was not captured, which indicated that Tp and hydrazine hydrate had successfully synthesized TpHz, and that the TpHz@MXene composite film was successfully prepared.

[0048] As shown in Figure 5 a, b, the surface of the TpHz@MXene composite film was continuous and had no cracks, and the MXene / nylon-66 composite film in Figure 4 a, b was compared, and the surface details of the TpHz@MXene composite film were rougher, which indicated that the hydrophilicity was improved. As shown in Figure 5 c, the surface of the nylon-66 had a thin film on both sides, and the film thickness was Figure 4The MXene / nylon-66 composite film in c is similar, but there are a large number of layer-by-layer aggregated MXenes or TpHz inside the nylon-66 in the TpHz@MXene composite film. As shown in Figure 4 It is known that MXenes are uniformly distributed inside the strip fibers, and the surface is an extremely thin layer of surface, and as shown in Figure 5 The inside of TpHz@MXene is more complex than MXene, as shown in c, there are many extra fine stripes and flocculation on the surface, which shows that TpHz is successfully compounded on the surface of MXene fiber, and MXene is wrapped up. Since MXene is a sheet structure, it forms a layer-by-layer composite effect of TpHz and MXene, which greatly improves the efficiency and flux of separating dye or salt ions.

[0049] As shown in Figure 6 The weight of the TpHz@MXene composite film is about 95% before 300°C, which proves the good high temperature resistance of the TpHz@MXene composite film, and the evaporation should be water and part of the residual organic solvent. Between 300-800°C, the weight of the TpHz@MXene composite film starts to decrease uniformly, to 41%, indicating that the proportion of MXene in the TpHz@MXene composite film is about 40%.

[0050] As shown in Figure 7 The surface of the TpHz@MXene composite film flows negative charges, which increases with the increase of pH. Compared with the nylon-66 base film and the MXene / nylon-66 composite film, the number of negative charges increases, which is beneficial to the performance improvement of separating anionic dyes.

[0051] Example 4

[0052] Test of permeation performance and retention rate of sandwich type COF@MXene composite film on various dye solutions:

[0053] The dye retention rate of TpHz@MXene composite film (prepared in Example 3, same below) was tested by nanofiltration method. The test device is a related separation membrane performance test device. First, configure 50 μM of dye raw material solution (as shown in Table 1), according to its molar mass, calculate its concentration. Use ultraviolet spectrophotometer to test the absorbance value, get the corresponding standard curve. The composite film is installed in the membrane module, and a certain amount of dye raw material solution is added to the membrane module cavity, and a certain amount of pressure is applied to the membrane module cavity using nitrogen. The permeate side collects permeate liquid every 30 min. The membrane module cavity is placed with a magnetic stirring paddle to avoid concentration polarization of the raw material solution. The collected permeate liquid is weighed, the solution absorbance is measured, and the dye concentration is calculated.

[0054] Table 1: Dye type table

[0055]

[0056] Note: The pH of all raw material solutions is the initial pH of the solution.

[0057] like Figure 8 As shown, the TpHz@MXene composite membrane exhibits high permeability and rejection rate for both cationic and neutral ionic dyes, while showing lower rejection rate for anionic dyes but higher permeability.

[0058] Example 5

[0059] Tests on the permeation performance and rejection rate of sandwich-type COF@MXene composite membranes for various dye and salt ion solutions:

[0060] The salt solution to be tested, prepared according to the proportions in Table 2, was used as the feed solution. The rejection rate and permeation performance of the TpHz@MXene composite membrane were tested using a membrane performance testing device. At room temperature, the cut composite membrane sheet was placed at the bottom of the feed tank, with the test solution used as the filtration solution. Nitrogen gas was introduced, and the operating pressure was adjusted to 8 bar for pre-pressurization for 10 minutes. Then, the operating pressure was adjusted to 6 bar, and after the test system stabilized, the permeate was collected using a tray, and the mass of the permeate was measured using a measuring balance over a certain period. Then, the salt concentrations of the original solution and the permeate were measured using a conductivity meter, and the permeation performance and rejection rate of the membrane for the test solution were calculated according to relevant formulas.

[0061] Table 2. Types of Salt Solutions

[0062]

[0063] Note: The pH of all raw material solutions is the initial pH of the solution.

[0064] like Figure 9 As shown, the TpHz@MXene composite membrane exhibits high permeability and high rejection rate for common salt ions such as MgSO4, Na2SO4, MgCl2, CaCl2, and NaCl. While the rejection rates for CaCl2 and NaCl salt ions are lower than those for other salt ions, they are still far higher than the industrial level.

[0065] Example 6

[0066] Ultra-long-term permeation performance and retention rate of sandwich-type COF@MXene composite membrane for Congo red dye solution:

[0067] The dye rejection rate of the TpHz@MXene composite film is tested by using the method of nanofiltration. The test device is a related separation membrane performance test device. First, configure 50 muM of the congo red dye raw material solution, calculate its concentration and standard curve. The composite film is installed in the membrane module, and an appropriate amount of congo red dye raw material solution is added to the membrane module cavity. Nitrogen is used to apply a certain amount of pressure to the membrane module cavity, and the permeate is collected on the permeation side. Sampling is taken every 3 hours, and the process is continuously continued for 80 hours. Then, data processing is performed.

[0068] As shown in Figure 10 , the flux and rejection rate of the TpHz@MXene composite film remain at 450 L·m -2 ·h -1 ·bar -1 and above 90% during the 80h process of intercepting the congo red solution, indicating that it has high separation efficiency and stability.

[0069] As shown in Figure 11 a, b, the TpHz@MXene composite film surface increases many congo red fine particles, but observation Figure 11 c, d can be seen that the separation layer of TpHz@MXene is heavily contaminated by congo red particles, and the picture is relatively clean, which corresponds to Figure 10 the stability shown in the stability, indicating that the composite film has great potential in separating the congo red solution.

[0070] Figure 12 As shown in the UV spectrum curve of the solution after intercepting the congo red, the peak of the congo red almost disappears, indicating that the TpHz@MXene composite film intercepts the congo red solution completely, and its industrialization potential is great.

[0071] The above content is only an example and description of the concept of the present application. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the concept of the present application or exceed the scope defined by the present claims, and should belong to the protection scope of the present application.

Claims

1. A method for in-situ intercalation preparation of a sandwich-type TpHz@MXene composite film, characterized in that, Based on MXene / organic membranes, COF-structured TpHz was synthesized between MXene layers, achieving a layer-by-layer growth structure. The specific steps are as follows: (1) MXene nanosheet dispersions with concentrations of 0.1-100 mg / mL were prepared using LiF and TiAlC2 as raw materials; then, the dispersions were prepared into membranes by negative pressure filtration using an organic membrane as a substrate, i.e., MXene / organic membrane composite membranes, which were stored in an inert gas atmosphere for later use. (2) Dissolve 0.1-100 mg of 1,3,5-tricarboxymethyl phloroglucinol (Tp) in 10-500 mL of n-hexane and disperse evenly, and record as solution A; dissolve 0.1-100 mmol of hydrazine hydrate solution (Hz·H2O) and 0.1-10 g of p-toluenesulfonamide (PTSA·H2O) in 10-500 mL of deionized water and disperse evenly, and record as solution B; (3) Place the MXene / organic membrane composite membrane prepared in step (1) between the interfacial polymerization devices and fix it with a clamp; place solutions A and B on both sides of the interfacial polymerization device respectively. After the interfacial polymerization reaction, take the composite membrane out of the interfacial polymerization mold, dry it, and wash it with ethanol and water several times to obtain the TpHz@MXene composite membrane, and store it in water for later use.

2. The in-situ intercalation preparation method as described in claim 1, characterized in that, The organic membrane mentioned in step (1) is selected from nylon-66, polypropylene, polyethylene, polyacrylonitrile, polysulfone, aromatic polyamide or polyvinylidene fluoride.

3. The in-situ intercalation preparation method as described in claim 1, characterized in that, In step (1), the inert gas is one or more of nitrogen, argon, and helium mixed gas atmosphere.

4. The in-situ intercalation preparation method as described in claim 1, characterized in that, The methods for achieving uniform dispersion in step (2) include mechanical stirring, ultrasonication, vibration, or manual stirring.

5. The in-situ intercalation preparation method as described in claim 1, characterized in that, In step (3), interfacial polymerization is carried out at room temperature for 1-24 hours.

6. The in-situ intercalation preparation method according to claim 1, characterized in that, The drying methods in step (3) include atmospheric pressure drying, freeze drying, or vacuum drying.

7. The sandwich-type TpHz@MXene composite membrane prepared by the in-situ intercalation preparation method according to any one of claims 1-6.

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