Composite two-dimensional biomimetic membrane with artificial water channels and preparation method thereof

Abstract

This invention belongs to the field of two-dimensional biomimetic membrane materials and discloses a composite two-dimensional biomimetic membrane with artificial water channels (AWCs) and its preparation method. First, an aqueous dispersion of MXene nanosheets is prepared by in-situ etching. Then, an ethanol / water colloidal dispersion of hydroxyl and imidazole tetramer artificial water channels is prepared. Next, a certain amount of the MXene nanosheet aqueous dispersion is redispersed into the artificial water channel colloidal dispersion. The artificial water channels are then embedded into the interlayer confined mass transfer space of the MXene two-dimensional membrane using a vacuum-assisted self-assembly method. After cleaning and drying, the composite two-dimensional biomimetic membrane with artificial water channels is obtained. This invention, by embedding artificial water channels into the interlayer channels of the MXene two-dimensional membrane, further improves the membrane's selectivity, permeability, and long-term application stability. The resulting composite two-dimensional biomimetic membrane can be efficiently applied to membrane processes such as seawater desalination, nanofiltration desalination, and organic solvent nanofiltration.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional biomimetic membrane materials, and relates to an AWCs-MXene composite two-dimensional biomimetic membrane, its preparation method and application. Background Technology

[0002] Water scarcity has become a major global challenge, primarily stemming from the effects of population growth, industrialization, and climate change. To alleviate this problem, seawater desalination methods relying on reverse osmosis technology are increasingly being used. This technology utilizes membrane materials capable of transporting water and filtering small molecule solutes or ions. Currently, reverse osmosis membrane processes mainly use membranes based on polymers such as polyamides, but there is a trade-off between their water flux and salt rejection rate.

[0003] In the field of membrane separation, the fabrication of membranes with nano- or sub-nanometer channels significantly impacts their selective water transport performance. Layered membranes, formed by face-to-face stacking of two-dimensional materials, typically possess uniformly spaced sub-nanometer interlayer channels, demonstrating great potential in many separation applications because these intramembrane channels enable controllable mass transport. Generally, mass transport occurs within the physical interlayer gaps, i.e., the interlayer spacing. Therefore, designing regular artificial water channels at the nano- and sub-nanometer scales can enable membranes to exhibit highly selective separation performance between solutes with similar physicochemical properties.

[0004] Transition metal carbides / nitrides (MXenes) are an emerging type of two-dimensional material with extremely high aspect ratios, making them easy to fabricate into defect-free two-dimensional layered membranes, which are commonly used in ultrafiltration, nanofiltration, and other applications. However, due to the hydrophilicity and high expansibility of MXene membranes, the interlayer spacing easily expands due to the insertion of water molecules, leading to a significant decrease in performance in separation applications. Furthermore, MXene membranes still exhibit poor performance in pressure-driven desalination, particularly with low desalination rates.

[0005] Inspired by aquaporins, artificial water channels (AWCs) can achieve highly selective transport of water molecules within cell membranes and possess enhanced physical and chemical stability, making them potential composites with most synthetic materials. Aquaporin molecules can self-assemble into lines or clusters with internal pores. Water molecules can form four hydrogen bonds with water channel molecules and be transported within the channels as water molecule lines. Increasing hydrogen bond interactions with water molecules can lead to cluster formation, which enhances the selectivity of the water channel molecules. AWCs possess a stable supramolecular structure, enabling selective repulsion of salt ions and protons. Therefore, embedding the supramolecular structure of AWCs into the membrane matrix can significantly improve the separation performance of composite membranes. The supramolecular structure of artificial water channels, formed by monomer self-assembly, is largely enhanced by the intrinsic properties of the matrix. Summary of the Invention

[0006] This invention proposes an effective strategy to combine artificial water channels for highly efficient and selective water transport at the sub-nanometer scale with two-dimensional interlayer nanochannels in MXene membranes. This simple strategy enables the fabrication of precisely controllable artificial water channel composite two-dimensional biomimetic membranes, thereby achieving excellent separation performance in applications such as seawater desalination, nanofiltration desalination, and organic solvent nanofiltration.

[0007] The technical solution used in this invention is as follows:

[0008] An AWCs-MXene composite two-dimensional biomimetic membrane and its preparation method, the preparation method including:

[0009] (1) Preparation of MXene nanosheet aqueous dispersion:

[0010] 1 g of lithium fluoride (LiF) was added to 20 mL of hydrochloric acid (HCl) solution and stirred continuously until the LiF was completely dissolved. Then, 1 g of Ti3AlC2 was slowly added to the prepared solution, and the mixture was stirred at a constant temperature of 45°C for 36 hours. After the reaction was complete, the reaction product was repeatedly washed with deionized water to remove residual acid and byproducts. During the washing process, the centrifuge speed was gradually increased from 3500 rpm to 10000 rpm to ensure thorough washing of the nanosheets. The washing step was repeated multiple times until the pH of the supernatant reached above 6. Next, the solution was centrifuged at 1500 rpm for 15 minutes to remove any unremoved residues, yielding pure Ti3C2T. x Nanosheet dispersion. The obtained Ti3C2T was accurately determined using a freeze-drying method. x Concentration of nanosheets.

[0011] (2) Preparation of ethanol / water colloidal dispersion with artificial water channels:

[0012] Weigh a certain amount of AWCs powder (1-10 mg), dissolve it in 15 mL of ethanol, and after it is completely dissolved, add 15 mL of water to prepare a mixed dispersion with a solvent ratio of ethanol:water = 1:1, and sonicate for 10 minutes.

[0013] (3) Preparation of AWCs-MXene composite two-dimensional biomimetic membrane:

[0014] Take a certain amount of the prepared Ti3C2T x Nanosheet dispersion (200–1500 μL, concentration 1.0 mg / mL) -1 The Ti3C2T was redispersed into the prepared AWCs colloidal dispersion. After uniform dispersion, the Ti3C2T was assembled using a vacuum-assisted self-assembly method. xNanosheets and artificial water channels are deposited onto a polyethersulfone substrate membrane, then rinsed with water and dried under vacuum at 60°C for 10 minutes to obtain an AWCs-MXene biomimetic composite two-dimensional membrane.

[0015] Advantageously, in the composite two-dimensional biomimetic membrane according to the invention, the at least one compound of formula I or formula II is an artificial water channel in the form of a supramolecular aggregate of hydroxyl or imidazole tetramer type, which is uniformly distributed between the interlayer nanochannels formed by face-to-face stacking of MXene nanosheets.

[0016] Furthermore, in step (4), the mass ratio of AWCs to MXene nanosheets in the preparation of the AWCs-MXene composite two-dimensional biomimetic membrane is 1:1.

[0017] An AWCs-MXene composite two-dimensional biomimetic membrane, wherein the mass ratio of AWCs to MXene nanosheets is 5:1.

[0018] An AWCs-MXene composite two-dimensional biomimetic membrane, wherein the mass ratio of AWCs to MXene nanosheets is 10:1.

[0019] An application of an AWCs-MXene composite two-dimensional biomimetic membrane is disclosed. As a separation membrane, it can be used in the separation process of saline solution. Separation tests are conducted using different salt solutions, that is, the salt solution is passed through the AWCs-MXene membrane under pressure and the salt concentration in the solution after permeation through the AWCs-MXene membrane is analyzed.

[0020] An application of an AWCs-MXene composite two-dimensional biomimetic membrane is disclosed. As a separation membrane, it can be used in the separation process of organic solvent dewaxing. The separation test is performed using a hexane solution of polyethylene wax, that is, the solution is passed through the AWCs-MXene membrane under pressure, and the concentration of polyethylene wax in the solution after passing through the AWCs-MXene membrane is analyzed.

[0021] Advantageously, the AWCs-MXene composite two-dimensional biomimetic membrane according to the invention is characterized in that it comprises:

[0022] -Ultrafiltration Support Membrane

[0023] -At least one compound of formula I or formula II:

[0024]

[0025] Wherein, R represents an alkyl side chain from C4 to C12 (including butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl).

[0026] AWCs-MXene composite two-dimensional biomimetic membrane

[0027] Furthermore, the at least one compound of Formula I or Formula II is an artificial water channel in the form of a supramolecular aggregate of hydroxyl or imidazole tetramer type, which is uniformly distributed between the interlayer nanochannels formed by face-to-face stacking of MXene nanosheets.

[0028] In this application, "ultrafiltration support membrane" refers to any microporous support material compatible with the intended pressure and application. It can be made of microporous polysulfone (PSF), or a microporous material composed of polyethersulfone (PES) or polyvinylidene fluoride (PVDF), cast onto a nonwoven reinforcing fabric, such as a support layer of polyethylene (PET), polypropylene (PP), or polyacrylonitrile (PAN 50 or PAN 450). The support membrane can be a commercially available type of membrane, such as M-PS20-GPET and M-PS35-GPP. The molecular weight cutoff (MWCO) of the support layer ranges from 10 to 250 kD, preferably from 10 to 40 kD, more preferably from 20 to 35 kD, with a MWCO point value of 20 kD. The thickness of the support membrane is approximately 20 to 200 μm, for example, the thickness of a PSF or PES porous support membrane is between 20 and 70 μm, while the thickness of a PET or PP support membrane is between 50 and 150 μm.

[0029] The present invention has the following beneficial effects:

[0030] (1) The present invention utilizes artificial water channels formed by the aggregation of molecules with hydroxyl or imidazole in Formula I or Formula II to modify the interlayer space of MXene two-dimensional membranes, and uses them as the main mass transfer channels to improve the transport rate and selectivity of water molecules.

[0031] (2) Hydroxyl or imidazole tetramer artificial water channels serve as the main mass transfer channels, which improves the swelling resistance and long-term application stability of AWCs-MXene composite two-dimensional biomimetic membranes.

[0032] (3) The present invention does not significantly change the commonly used process for preparing two-dimensional membranes, and the method is simple. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image of the surface of an AWCs-MXene composite two-dimensional biomimetic film prepared with an AWCs-MXene nanosheet mass ratio of 5:1.

[0034] Figure 2 The values ​​represent the water flux and NaCl rejection rate of AWCs-MXene composite two-dimensional biomimetic membranes with AWCs loadings of 0, 1, 5, and 10 mg, respectively, when treating a NaCl solution with a concentration of 1000 ppm.

[0035] Figure 3The values ​​represent the water flux and salt rejection rate of the AWCs-MXene composite two-dimensional biomimetic membrane prepared with an AWCs-MXene nanosheet mass ratio of 5:1 when treating NaCl, MgCl2, Na2SO4 and MgSO4 solutions with a concentration of 1000ppm.

[0036] Figure 4 The graph shows the changes in flux and rejection rate over time when an AWCs-MXene composite two-dimensional biomimetic membrane, prepared with a mass ratio of AWCs and MXene nanosheets of 5:1, is used to treat a hexane solution of polyethylene wax. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0038] Comparative Example 1

[0039] (1) Preparation of Ti3C2T x Nanosheet aqueous dispersion:

[0040] 1 g of LiF was added to 20 ml of HCl solution and stirred continuously until the LiF was completely dissolved. Then, 1 g of Ti3AlC2 was slowly added to the prepared solution, and the mixture was stirred at a constant temperature of 45°C for 36 hours. After the reaction was complete, the reaction product was repeatedly washed with deionized water to remove residual acid and byproducts. During the washing process, the centrifuge speed was gradually increased from 3500 rpm to 10000 rpm to ensure thorough washing of the nanosheets. The washing step was repeated multiple times until the pH of the supernatant reached above 6. Next, the solution was centrifuged at 1500 rpm for 15 minutes to remove any unremoved residues, yielding pure Ti3C2T. x Nanosheet dispersion. The obtained Ti3C2T was accurately determined using a freeze-drying method. x Concentration of nanosheets.

[0041] (2) Preparation of MXene two-dimensional membranes

[0042] Take 1000 μL of the prepared Ti3C2T x The nanosheet aqueous dispersion was dispersed in 30 mL of water. After uniform dispersion, Ti3C2T was assembled using a vacuum-assisted self-assembly method. x Nanosheets are deposited onto a polyethersulfone substrate film, then rinsed with water, and dried under vacuum at 60°C for 10 minutes to obtain an MXene two-dimensional film.

[0043] Using this MXene two-dimensional membrane to treat a 1000 ppm NaCl solution at 4 bar pressure, the membrane's water flux was 2.87 Lm. -2 h -1 bar -1 The NaCl retention rate was 46.2%.

[0044] Example 1

[0045] In this embodiment, the preparation method of the AWCs-MXene composite two-dimensional biomimetic membrane specifically includes the following steps:

[0046] (1) Preparation of Ti3C2T x The aqueous dispersion of nanosheets is the same as that of Comparative Example 1, and will not be described again here.

[0047] (2) Preparation of ethanol / water colloidal dispersion with artificial water channels:

[0048] Weigh 1 mg of AWCs powder and dissolve it in 15 mL of ethanol. After it is completely dissolved, add 15 mL of water to prepare a mixed dispersion with a solvent ratio of ethanol:water = 1:1. Then, sonicate the mixture for 10 minutes.

[0049] (3) Preparation of AWCs-MXene composite two-dimensional biomimetic membrane:

[0050] Take 1000 μL of the prepared Ti3C2T x The nanosheet dispersion was redispersed into the prepared AWCs colloidal dispersion. After uniform dispersion, Ti3C2T was assembled using a vacuum-assisted self-assembly method. x Nanosheets and artificial water channels are deposited onto a polyethersulfone substrate membrane, then rinsed with water and dried under vacuum at 60°C for 10 minutes to obtain an AWCs-MXene composite two-dimensional biomimetic membrane.

[0051] Using this AWCs-MXene composite two-dimensional biomimetic membrane, a NaCl solution with a concentration of 1000 ppm was treated at a pressure of 4 bar, and the water flux of the membrane was 3.42 L / m³. -2 h -1 bar -1 The NaCl retention rate was 54.8%.

[0052] Example 2

[0053] In this embodiment, the preparation method of the AWCs-MXene composite two-dimensional biomimetic membrane specifically includes the following steps:

[0054] (1) Preparation of Ti3C2T x The aqueous dispersion of nanosheets is the same as that of Comparative Example 1, and will not be described again here.

[0055] (2) Preparation of ethanol / water colloidal dispersion with artificial water channels:

[0056] Weigh 5 mg of AWCs powder, dissolve it in 15 mL of ethanol, and after it is completely dissolved, add 15 mL of water to prepare a mixed dispersion with a solvent ratio of ethanol:water = 1:1, and sonicate for 10 minutes.

[0057] (3) The preparation of AWCs-MXene composite two-dimensional biomimetic membrane is the same as in Example 1, and will not be repeated here.

[0058] Using this AWCs-MXene composite two-dimensional biomimetic membrane, a NaCl solution with a concentration of 1000 ppm was treated at a pressure of 4 bar, and the water flux of the membrane was 5.95 L / m³. -2 h -1 bar -1 The NaCl retention rate was 82.5%.

[0059] Example 3

[0060] In this embodiment, the preparation method of the AWCs-MXene composite two-dimensional biomimetic membrane specifically includes the following steps:

[0061] (1) Preparation of Ti3C2T x The aqueous dispersion of nanosheets is the same as that of Comparative Example 1, and will not be described again here.

[0062] (2) Preparation of ethanol / water colloidal dispersion with artificial water channels:

[0063] Weigh 10 mg of AWCs powder, dissolve it in 15 mL of ethanol, and after it is completely dissolved, add 15 mL of water to prepare a mixed dispersion with a solvent ratio of ethanol:water = 1:1, and sonicate for 10 minutes.

[0064] (3) The preparation of AWCs-MXene composite two-dimensional biomimetic membrane is the same as in Example 1, and will not be repeated here.

[0065] Using this AWCs-MXene composite two-dimensional biomimetic membrane, a NaCl solution with a concentration of 1000 ppm was treated at a pressure of 4 bar, and the water flux of the membrane was 9.88 L / m³. -2 h -1 bar -1 The NaCl retention rate was 63.9%.

[0066] Example 4

[0067] In this embodiment, the preparation method of the AWCs-MXene composite two-dimensional biomimetic membrane specifically includes the following steps:

[0068] (1) Preparation of Ti3C2Tx The aqueous dispersion of nanosheets is the same as that of Comparative Example 1, and will not be described again here.

[0069] (2) The ethanol / water colloidal dispersion for preparing the artificial water channel is the same as in Example 2, and will not be described in detail here.

[0070] (3) The preparation of AWCs-MXene composite two-dimensional biomimetic membrane is the same as in Example 1, and will not be repeated here.

[0071] The AWCs-MXene composite two-dimensional biomimetic membrane was used to treat NaCl, MgCl2, Na2SO4, and MgSO4 solutions with a concentration of 1000 ppm at a pressure of 4 bar. The water flux of the membrane was 5.95 Lm when treating the NaCl solution. -2 h -1 bar -1 The NaCl rejection rate was 82.5%. The water flux of this membrane when treating MgCl2 solution was 6.39 L / m³. -2 h -1 bar -1 The MgCl2 rejection rate was 89.6%. The water flux of this membrane when treating Na2SO4 solution was 7.83 L / m³. -2 h -1 bar -1 The Na₂SO₄ rejection rate was 92.2%. The water flux for treating MgSO₄ solution using this membrane was 7.43 L / m². -2 h -1 bar -1 The MgSO4 rejection rate was 93.5%.

[0072] Example 5

[0073] In this embodiment, the preparation method of the AWCs-MXene composite two-dimensional biomimetic membrane specifically includes the following steps:

[0074] (1) Preparation of Ti3C2T x The aqueous dispersion of nanosheets is the same as that of Comparative Example 1, and will not be described again here.

[0075] (2) The ethanol / water colloidal dispersion for preparing the artificial water channel is the same as in Example 2, and will not be described in detail here.

[0076] (3) The preparation of AWCs-MXene composite two-dimensional biomimetic membrane is the same as in Example 1, and will not be repeated here.

[0077] The AWCs-MXene composite two-dimensional biomimetic membrane was used to treat a hexane solution with a polyethylene wax concentration of 2000 ppm at 6 bar pressure. The initial flux was 42.61 L / m³. -2 h -1 bar -1The rejection rate of polyethylene wax was 87.6%. Furthermore, the flux remained almost stable and even increased during the 246-hour operation, with minimal decline in the rejection rate.

[0078] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. An AWCs-MXene composite two-dimensional biomimetic membrane, characterized in that: The mixture includes an ultrafiltration support membrane and at least one compound of formula (I) or formula (II) in the form of a supramolecular aggregate of hydroxyl or imidazole tetramer type as AWCs, which are uniformly distributed between the interlayer nanochannels formed by face-to-face stacking of MXene nanosheets. Wherein, R represents an alkyl side chain from C4 to C12.

2. The AWCs-MXene composite two-dimensional biomimetic membrane as described in claim 1, characterized in that: The ultrafiltration support membrane is made of microporous polysulfone, or is made of microporous material composed of polyethersulfone or polyvinylidene fluoride cast onto a nonwoven reinforcing fabric.

3. The method for preparing the AWCs-MXene composite two-dimensional biomimetic membrane as described in claim 1 or 2, characterized in that: Includes the following steps: (1) Preparation of MXene nanosheet aqueous dispersion: 1 g of lithium fluoride was added to 20 mL of hydrochloric acid solution and stirred continuously until LiF was completely dissolved. Then, 1 g of Ti3AlC2 was slowly added to the hydrochloric acid solution, and the mixture was stirred at a constant temperature of 45°C for 36 hours. After the reaction was complete, the reaction product was repeatedly washed with deionized water to remove residual acid and byproducts. This washing step was repeated multiple times until the pH of the supernatant reached above 6. The reaction product solution was centrifuged at 1500 rpm for 15 minutes to remove any unremoved residues, yielding pure Ti3C2T. x Nanosheet dispersion; (2) Preparation of AWCs ethanol / water colloidal dispersion: Weigh a certain amount of AWCs powder, dissolve it in 15 mL of ethanol, and after it is completely dissolved, add 15 mL of water to prepare a mixed dispersion with a solvent ratio of ethanol:water = 1:1, and sonicate for 10 minutes. (3) Preparation of AWCs-MXene composite two-dimensional biomimetic membrane: Take a certain amount of the prepared Ti3C2T x The nanosheet dispersion was redispersed into the prepared AWCs ethanol / water colloidal dispersion. After uniform dispersion, Ti3C2T was assembled using a vacuum-assisted self-assembly method. x Nanosheets and artificial water channels are deposited onto an ultrafiltration support membrane, then rinsed with water and dried under vacuum at 60°C for 10 minutes to obtain an AWCs-MXene biomimetic composite two-dimensional membrane.

4. The preparation method according to claim 3, characterized in that: In step (3), the mass ratio of AWCs to MXene nanosheets in the AWCs-MXene composite two-dimensional biomimetic membrane is 1 to 10:

1.

5. The application of the AWCs-MXene composite two-dimensional biomimetic membrane as described in claim 1 or 2, characterized in that: It is used as a separation membrane for the separation of saline solutions.

6. The application of the AWCs-MXene composite two-dimensional biomimetic membrane as described in claim 1 or 2, characterized in that: It is used as a separation membrane for dewaxing organic solvents.

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