A nano-confined membrane reactor, preparation method and application thereof

Abstract

The present invention relates to the technical field of nanofiltration membrane preparation, and specifically to a nano-confined membrane reactor, a preparation method and applications thereof, in which nano-palladium particles are confined to the surface of boron nitride nanosheets and assembled into a membrane, and the boron nitride nanosheet membrane is synergistically utilized to efficiently separate dye molecules. At the same time, the abundant nanopores and efficient catalytic active sites introduced by the nano-palladium particles confined in the boron nitride nanosheets are utilized to achieve rapid degradation of the dye and efficient separation effects. The method is simple and easy to operate, and does not require complex chemical treatment of the boron nitride nanosheet raw materials. It has good guiding significance for separation applications in the field of nano-membranes.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofiltration membrane preparation, and in particular to a nanoconfined membrane reactor, a preparation method and applications thereof. Background Art

[0002] Membrane separation technology is often used in food, environmental protection, chemical industry, energy, water treatment and other fields due to its advantages such as high selectivity, low energy consumption, simple process and intermittent operation. It has higher social and economic benefits than traditional distillation, adsorption and extraction technologies. The development of membrane separation technology mainly focuses on two directions: solvent flux and solute selectivity, that is, exploring fast and efficient separation membranes. However, during the application of membrane separation, solute enrichment will inevitably occur on the membrane surface, which is the concentration polarization phenomenon. It not only causes a double reduction in membrane flux and selectivity, but also increases the operating costs of enterprises. Therefore, there is an urgent need to develop high-performance membrane materials to effectively improve the concentration polarization problem in the application of membrane separation.

[0003] In recent years, the rich nanoporous membranes constructed by assembling membranes of two-dimensional nanosheets such as graphene oxide, transition metal chalcogenides, covalent organic framework compounds, and metal carbonitrides have been able to overcome the mutual constraints between flux and selectivity of traditional organic membrane materials, providing technical support for effectively improving the industrial application of membrane separation technology. Among them, boron nitride nanosheet assembled membranes have excellent physical and chemical properties and can stably screen ions in the pH range of 1 to 14 and the temperature range of 5 to 95°C, providing a material basis for future membrane separation applications in extreme environments. However, the concentration of pollutants will significantly cause concentration polarization on the membrane surface, significantly interfering with the selectivity of boron nitride nanomembranes. In addition, the pursuit of selectivity at the expense of flux by boron nitride nanomembranes will increase the operating costs of enterprises.

[0004] In view of the above-mentioned defects, the inventors of the present invention finally obtained the present invention after a long period of research and practice. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that in separation applications of boron nitride nanomembranes, the concentration of pollutants will obviously cause concentration polarization on the membrane surface, which significantly interferes with the selectivity of the boron nitride nanomembrane. A nanomembrane reactor, a preparation method and its application are provided.

[0006] In order to achieve the above object, the present invention discloses a method for preparing a nano-membrane reactor, comprising the following steps:

[0007] S1, preparing a boron nitride nanosheet colloidal solution: mixing boron nitride and urea by ball milling, and dialysis-washing the urea to obtain a boron nitride nanosheet colloidal aqueous dispersion;

[0008] S2, preparing a nanoconfined membrane reactor: mixing the boron nitride nanosheet colloidal solution obtained in step S1 with the palladium salt solution, and assembling the resulting mixture into a nanoconfined membrane reactor under positive pressure;

[0009] S3, the nanoconfined membrane reactor prepared by positive pressure in step S2 is allowed to stand at a constant pressure under air pressure.

[0010] In step S1, the mass ratio of boron nitride to urea is 1:10 to 1:20.

[0011] In step S2, the mass ratio of boron nitride to palladium is 1:100 to 16:100.

[0012] The thickness of the nanofilm reactor in step S2 is 1 to 6 μm.

[0013] The stirring time in step S2 is 10 to 30 minutes.

[0014] The air pressure in step S3 is 0.1-1 bar.

[0015] The present invention also discloses a nanomembrane reactor prepared using the above-mentioned preparation method and its application in alleviating concentration polarization during membrane separation. In this application, the probe contaminant is methylene blue, the concentration of which is 1 to 40 ppm, and the pH of the solution in the application environment is 1 to 13. This invention fully utilizes boron nitride nanosheets to confine palladium nanoparticles, giving full play to their in-situ catalytic degradation of methylene blue. This not only effectively resolves the concentration polarization problem of pollutant molecules during membrane separation, but also provides abundant nanochannels, significantly enhancing the flux of the nanoconfined composite membrane.

[0016] Compared with existing technologies, the present invention offers a simple and easy-to-use method for enhancing the performance of boron nitride nanomembranes. This method leverages the advantages of boron nitride nanosheets, which are loaded with confined nanopalladium particles, to enhance the separation performance of boron nitride nanomembranes by in-situ catalytic degradation of methylene blue, eliminating concentration polarization issues, and the abundant nanoscale water channels created in situ. This method offers valuable insights into the application of boron nitride nanomembranes in removing high-concentration pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Transmission electron microscope images of the boron nitride nanosheets and the boron nitride nanosheet-confined nanopalladium particles of the present invention;

[0018] Figure 2Scanning electron microscope images of cross-sections of the boron nitride nanosheets and palladium nanoparticles confined in boron nitride nanosheets of different thicknesses of the present invention. In the figure, the boron nitride stacked film represents the film extracted from boron nitride, and the confined composite film-2 represents the boron nitride nanosheets confined palladium nanoparticles with a thickness of 2 μm.

[0019] Figure 3 is the X-ray photoelectron spectrum of the boron nitride nanosheets of the present invention;

[0020] Figure 4 The X-ray photoelectron spectrum of the boron nitride nanosheet confined nanopalladium particles of the present invention;

[0021] Figure 5 X-ray diffraction patterns of the boron nitride nanosheets and the boron nitride nanosheet-confined palladium nanoparticles of the present invention;

[0022] Figure 6 The Raman and infrared images of the boron nitride and boron nitride nanosheet confined nanopalladium particles of the present invention are shown;

[0023] Figure 7 is the absorbance of the boron nitride nanosheets containing sodium borohydride and the boron nitride nanosheets to methylene blue;

[0024] Figure 8 The absorbance of methylene blue by the boron nitride nanosheets containing sodium borohydride of different thicknesses of the present invention confined nano-palladium particles;

[0025] Figure 9 The figure shows the comparison of the flux and retention rate of methylene blue of boron nitride nanosheets of different thicknesses and boron nitride nanosheets containing sodium borohydride of different thicknesses.

[0026] Figure 10 The absorbance of methylene blue by the boron nitride nanosheet confined palladium particles with different palladium nanoparticle contents containing sodium borohydride of the present invention;

[0027] Figure 11 Comparison of the flux and retention rate of methylene blue by boron nitride nanosheet confined palladium particles with different palladium nanoparticle contents containing sodium borohydride of the present invention;

[0028] Figure 12 The absorbance of methylene blue by the boron nitride nanosheet confined nanopalladium particles containing sodium borohydride at different pH values ​​of the present invention;

[0029] Figure 13 The present invention compares the flux and retention rate of methylene blue by boron nitride nanosheet confined nanopalladium particles containing sodium borohydride at different pH values. DETAILED DESCRIPTION

[0030] The above and other technical features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

[0031] Example 1

[0032] (1) Preparation of amino-functionalized boron nitride nanosheet aqueous dispersion

[0033] 0.5 g of commercial boron nitride was mixed with 10 g of urea, milled at 600 rpm for 20 h using a planetary high-energy ball mill, and dialyzed for 14 days to remove excess urea to obtain a milky white aqueous dispersion of amino-functionalized boron nitride nanosheets.

[0034] (2) Preparation of Boron Nitride Nanosheet Confined Nanopalladium Particle Nanofiltration Membrane

[0035] To control the total mass of the mixed solution, amino-functionalized boron nitride nanosheets and palladium salt solution were mixed at a 16% mass ratio. 10 mL of ethylene glycol was then added and the three solutions were thoroughly stirred. Half the volume of the mixed solution was taken and made up to 50 mL with water. The mixed boron nitride nanosheet-confined palladium nanoparticles mixture was assembled onto a nylon substrate using a positive pressure device to form a boron nitride nanosheet-confined palladium nanoparticle nanofiltration membrane.

[0036] (3) The boron nitride nanosheet confined nanopalladium particle nanofiltration membrane prepared by positive pressure was statically pressurized under an air pressure of 0.4 bar.

[0037] (4) Testing the separation performance of methylene blue in water by boron nitride nanosheet confined nanopalladium particle nanofiltration membrane

[0038] Methylene blue was selected as the probe dye molecule. 20 mL (100 ppm methylene blue dye) was taken, 2 mL (0.1 mol / L sodium borohydride) was added, and water was added to make 100 mL of dye aqueous dispersion. During the test, 40 mL of filtrate was collected and the concentration of the original solution, the concentration of the filtrate, and the absorbance intensity of the retained solution were tested using a UV-visible spectrophotometer. Figure 1 Transmission electron microscope images of boron nitride nanosheets and palladium nanoparticles confined by boron nitride nanosheets. Figure 2 Scanning cross-section diagram of nanoconfined films with different thicknesses. Figure 3 and Figure 4 The X-ray photoelectron spectra of pure boron nitride and the nanoconfined composite membrane are shown. The above comparative tests and results confirm from a microstructural perspective that boron nitride nanosheets can confine palladium nanoparticles, providing a membrane material foundation for in-situ catalytic separation applications.

[0039] Example 2

[0040] (1) Preparation of amino-functionalized boron nitride nanosheet aqueous dispersion

[0041] 0.5 g of commercial boron nitride was mixed with 10 g of urea, milled at 600 rpm for 20 h using a planetary high-energy ball mill, and dialyzed for 14 days to remove excess urea to obtain a milky white aqueous dispersion of amino-functionalized boron nitride nanosheets.

[0042] (2) Preparation of nanofiltration membranes with confined nanopalladium particles using boron nitride nanosheets of different thicknesses

[0043] To control the total mass of the mixed solution, amino-functionalized boron nitride nanosheets and palladium salt solution were mixed at a 16% mass ratio. 10 mL of ethylene glycol was then added and thoroughly stirred. 3 mL, 6 mL, 8 mL, 9 mL, 10 mL, and 12 mL of the mixed solution were taken, each made up to 50 mL with water. The mixed boron nitride nanosheet-confined palladium nanoparticles mixture was then assembled onto a nylon substrate using a positive pressure device to form a boron nitride nanosheet-confined palladium nanofiltration membrane.

[0044] (3) The boron nitride nanosheet confined nanopalladium particle nanofiltration membrane prepared by positive pressure is statically pressed under an air pressure of 0.9 bar.

[0045] (4) Testing the separation performance of methylene blue in water by boron nitride nanosheet confined nanopalladium particle nanofiltration membranes of different thicknesses

[0046] Methylene blue was selected as the probe dye molecule. 20 mL (100 ppm methylene blue dye) was taken, 2 mL (0.1 mol / L sodium borohydride) was added, and water was added to make 100 mL of dye aqueous dispersion. During the test, 40 mL of filtrate was collected and the concentration of the original solution, the concentration of the filtrate, and the absorbance intensity of the retained solution were tested using a UV-visible spectrophotometer. Figure 5 and Figure 6 The X-ray diffraction, infrared, and Raman patterns of the nanoconfined membrane are shown. The comparative tests and results above confirm that the palladium nanoparticles are uniformly dispersed in the nanocomposite membrane composed of boron nitride nanosheets, providing a stable membrane material for the catalytic separation of methylene blue.

[0047] Example 3

[0048] (1) Preparation of amino-functionalized boron nitride nanosheet aqueous dispersion

[0049] 0.5 g of commercial boron nitride was mixed with 10 g of urea, milled at 600 rpm for 20 h using a planetary high-energy ball mill, and dialyzed for 14 days to remove excess urea to obtain a milky white aqueous dispersion of amino-functionalized boron nitride nanosheets.

[0050] (2) Preparation of Boron Nitride Nanosheets Confined Nanopalladium Particle Nanofiltration Membranes with Different Palladium Nanoparticle Contents

[0051] The total mass of the mixed solution nanosheets was controlled by mixing amino-functionalized boron nitride nanosheets with a palladium salt solution at a mass ratio of 16%, 8%, 5.3%, and 4%. Ethylene glycol and water were then added at a 5% ratio and thoroughly stirred. The mixed boron nitride nanosheet-confined palladium nanoparticle mixtures with varying palladium nanoparticle contents were assembled on a nylon substrate using a positive pressure device to form a boron nitride nanosheet-confined palladium nanoparticle nanofiltration membrane.

[0052] (3) The boron nitride nanosheet confined nanopalladium particle nanofiltration membrane prepared by positive pressure is statically pressed under an air pressure of 0.5 bar.

[0053] (4) Test the separation performance of methylene blue in water system by boron nitride nanosheet confined nanopalladium particle nanofiltration membrane with different palladium nanoparticle contents.

[0054] Methylene blue was selected as the probe dye molecule. 20 mL (100 ppm methylene blue dye) was taken, 2 mL (0.1 mol / L sodium borohydride) was added, and water was added to make 100 mL of dye aqueous dispersion. During the test, 40 mL of filtrate was collected and the concentration of the original solution, the concentration of the filtrate, and the absorbance intensity of the retained solution were tested using a UV-visible spectrophotometer. Figure 7 It is the absorbance of the boron nitride nanosheets containing sodium borohydride and the boron nitride nanosheets to methylene blue. Figures 8 to 11 This study compares the catalytic separation performance of methylene blue using nanoconfined membranes of varying thicknesses and precious metal contents. These comparative tests and results are intended to optimize the optimal parameters for the catalytic separation of methylene blue. These parameters, which determine the optimal precious metal content and membrane thickness, provide a nanomembrane reactor with both catalytic and separation performance.

[0055] Example 4

[0056] (1) Preparation of amino-functionalized boron nitride nanosheet aqueous dispersion

[0057] 0.5 g of commercial boron nitride was mixed with 10 g of urea, milled at 600 rpm for 20 h using a planetary high-energy ball mill, and dialyzed for 14 days to remove excess urea to obtain a milky white aqueous dispersion of amino-functionalized boron nitride nanosheets.

[0058] (2) Preparation of Boron Nitride Nanosheet Confined Nanopalladium Particle Nanofiltration Membrane

[0059] To control the total mass of the mixed solution, amino-functionalized boron nitride nanosheets and palladium salt solution were mixed at a 16% by mass ratio. 10 mL of ethylene glycol was then added and the three solutions were thoroughly stirred. Half of the mixed solution was taken and made up to 50 mL with water. The mixed boron nitride nanosheet-confined palladium nanoparticles mixture was assembled onto a nylon substrate using a positive pressure device to form a boron nitride nanosheet-confined palladium nanoparticle nanofiltration membrane.

[0060] (3) The boron nitride nanosheet confined nanopalladium particle nanofiltration membrane prepared by positive pressure is statically pressed under an air pressure of 0.8 bar.

[0061] (4) Test the effect of different pH on the separation performance of boron nitride nanosheet confined nanopalladium particles nanofiltration membrane in water system.

[0062] Prepare 100 mL of solution at pH 1, pH 3, pH 5, pH 7, pH 9, pH 11, and pH 13, respectively, and pour them into the above-assembled boron nitride nanosheet confined nanopalladium particle nanofiltration membrane. After filtration, select methylene blue as the probe dye molecule, take 20 mL (100 ppm methylene blue dye), add 2 mL (0.1 mol / L sodium borohydride), and then add water to 100 mL of dye aqueous dispersion. Collect 40 mL of filtrate during the test, and use a UV-visible spectrophotometer to test the concentration of the original solution, the concentration of the filtrate, and the absorbance intensity of the retained solution. Figure 12 and Figure 13 The above experiments and results demonstrate that the nano-membrane reactor of the present invention can stably catalytically separate high concentrations of methylene blue molecules within a pH range of 1 to 13.

[0063] The above description is merely a preferred embodiment of the present invention and is intended to be illustrative rather than restrictive of the present invention. Those skilled in the art will appreciate that many changes, modifications, and even equivalents may be made to the present invention within the spirit and scope of the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A method for preparing a nanoconfined membrane reactor, characterized in that: The following steps are involved: S1, preparing a boron nitride nanosheet colloidal solution: mixing boron nitride and urea by ball milling, and dialysis-washing the urea to obtain a boron nitride nanosheet colloidal aqueous dispersion; S2, preparing a nanoconfined membrane reactor: mixing the boron nitride nanosheet colloidal solution obtained in step S1 with the palladium salt solution, and assembling the resulting mixture into a nanoconfined membrane reactor under positive pressure; S3, placing the nanoconfined membrane reactor prepared under positive pressure in step S2 at a constant pressure under air pressure; In step S1, the mass ratio of boron nitride to urea is 1:10 to 1:20; In step S2, the mass ratio of boron nitride to palladium is 1:100 to 16:100; The thickness of the nanofilm reactor in step S2 is 1 to 6 μm.

2. The method for preparing a nanoconfined membrane reactor according to claim 1, wherein: The stirring time in step S2 is 10 to 30 minutes.

3. The method for preparing a nanoconfined membrane reactor according to claim 1, wherein: The air pressure in step S3 is 0.1-1 bar.

4. A nanoconfined membrane reactor prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the nanoconfined membrane reactor according to claim 4 in alleviating the concentration polarization problem in a membrane separation process.

6. Use of a nanoconfined membrane reactor according to claim 5 in alleviating the concentration polarization problem in a membrane separation process, characterized in that: The probe contaminant is methylene blue, and the concentration of the methylene blue is 1 to 40 ppm.

7. The use of a nanoconfined membrane reactor according to claim 5 in alleviating the concentration polarization problem in a membrane separation process, characterized in that: The solution pH of the application environment is 1-13.

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