Composite two-dimensional biomimetic membrane with artificial water channel and preparation method of composite two-dimensional biomimetic membrane

Abstract

The 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 a preparation method thereof.The composite two-dimensional biomimetic membrane with the artificial water channels (AWCs) comprises the steps that firstly, MXene nanosheet aqueous dispersion liquid is prepared through an in-situ etching method, then ethyl alcohol / hydrocolloid dispersion liquid of hydroxyl and imidazole tetramer artificial water channels is prepared, and the composite two-dimensional biomimetic membrane with the artificial water channels is prepared. And then re-dispersing a certain amount of MXene nanosheet aqueous dispersion liquid into the artificial water channel colloidal dispersion liquid, embedding the artificial water channel into an interlayer confinement mass transfer space of the MXene two-dimensional membrane through a vacuum-assisted self-assembly method, and carrying out cleaning and drying processes to obtain the composite two-dimensional biomimetic membrane with the artificial water channel. An artificial water channel is embedded into an interlayer channel of the MXene two-dimensional membrane, so that the selectivity, the permeability and the long-term application stability of the membrane are further improved, and the obtained composite two-dimensional biomimetic membrane can be efficiently applied to the membrane processes of seawater desalination, nanofiltration desalination, organic solvent nanofiltration and the like.

Description

Technical Field The invention belongs to the field of two-dimensional bionic membrane materials and relates to an AWC-MXene composite two-dimensional bionic membrane and a preparation method and application thereof. Background Art Water shortage has become a major challenge facing the world, mainly due to the impact of population growth, industrialization and climate change. To alleviate this problem, seawater desalination methods that rely on reverse osmosis technology are increasingly being used. The membrane materials used in this technology can transport water and filter small molecular solutes or ions. At present, the reverse osmosis membrane process mainly uses polymer membranes such as polyamide, but there is a trade-off between its water flux and salt rejection rate. In the field of membrane separation, the preparation of membranes with nano- or sub-nano channels has a significant impact on the selective water transport performance. Layered membranes formed by face-to-face stacking of two-dimensional materials usually have uniformly spaced interlayer channels below the nanometer scale and show great potential in many separation applications because these intra-membrane channels enable controllable material transport. Usually, material transport occurs in the physical gap between layers, that is, 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 physical and chemical properties. Transition metal carbides / nitrides (MXene) are an emerging two-dimensional material with an extremely high aspect ratio, making it easy to prepare defect-free two-dimensional layered membranes, which are often used in ultrafiltration, nanofiltration and other applications. However, due to the hydrophilicity and high expansion of the MXene membrane itself, the interlayer spacing is easily expanded due to the insertion of water molecules, resulting in a significant decrease in performance in separation applications. At the same time, MXene membranes still perform poorly in pressure-driven desalination performance, especially their low desalination rate. Inspired by aquaporins, artificial water channels (AWCs) can achieve highly selective transport of water molecules in cell membranes and have stronger physical and chemical stability, making them potential for composite with most synthetic materials. Water channel molecules can self-assemble into lines or clusters with internal pores. Water molecules can form four hydrogen bonds with water channel molecules and transport in the channel in the form of water molecule lines. Increasing the hydrogen bond interaction with water molecules can form clusters, and the formation of clusters will increase the selectivity of water channel molecules. AWCs have a stable supramolecular structure, which can achieve selective rejection of salt ions and protons. Therefore, by embedding the superstructure of AWCs into the membrane matrix, the separation performance of the composite membrane can be greatly improved. The supramolecular structure of artificial water channels formed by monomer self-assembly is largely synergistically strengthened by the intrinsic properties of the matrix. Summary of the invention This paper proposes an effective strategy to combine artificial water channels that efficiently and selectively transport water at the sub-nanometer scale with the two-dimensional interlayer nanochannels of MXene membranes. Through this simple strategy, a precisely controllable artificial water channel composite two-dimensional biomimetic membrane is prepared, thereby achieving excellent separation performance in applications such as seawater desalination, nanofiltration desalination, and organic solvent nanofiltration. The technical solutions used in the present invention are as follows: An AWC-MXene composite two-dimensional bionic membrane and a preparation method thereof, wherein the preparation method comprises: (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 LiF was completely dissolved. 3 AlC 2 Slowly add it to the prepared solution and stir it at a constant temperature of 45°C for 36 hours. After the reaction is completed, the reaction product is repeatedly washed with deionized water to remove residual acid and by-products. During the washing process, the speed of the centrifuge is gradually increased from 3500rpm to 10000rpm to ensure that the nanosheets are fully washed. The washing step is repeated several times until the pH value of the supernatant reaches above 6. Next, the solution is centrifuged at 1500rpm for 15 minutes to remove the unpeeled residue and obtain pure Ti 3 C 2 T x Nanosheet dispersion. The Ti 3 C 2 T x The concentration of nanosheets. (2) Preparation of ethanol / water colloid dispersion for artificial water channels: A certain amount of AWC powder (1-10 mg) was weighed and dissolved in 15 mL of ethanol. After it was completely dissolved, 15 mL of water was added to prepare a mixed dispersion with a solvent ratio of ethanol: water = 1:1, and ultrasonic treatment was performed for 10 minutes. (3) Preparation of AWC-MXene composite two-dimensional biomimetic membrane: Take a certain amount of prepared Ti 3 C 2 T x Nanosheet dispersion (200-1500 μL, concentration 1.0 mg mL -1 ) was redispersed into the prepared AWC colloidal dispersion, and after being evenly dispersed, the Ti 3 C 2 T xThe nanosheets and artificial water channels were deposited onto the polyethersulfone substrate membrane, then rinsed with water and dried at 60°C under vacuum conditions for 10 minutes to obtain the AWC-MXene bionic composite two-dimensional membrane. Advantageously, according to the composite two-dimensional biomimetic membrane of the present invention, the at least one compound of formula I or formula II is an artificial water channel in the form of a hydroxyl or imidazole tetramer type supramolecular aggregate, which is uniformly distributed between the interlayer nanochannels formed by face-to-face stacking of MXene nanosheets. Furthermore, in step (4), in preparing the AWC-MXene composite two-dimensional biomimetic membrane, the mass ratio of AWC and MXene nanosheets is 1:1. An AWC-MXene composite two-dimensional bionic membrane, wherein the mass ratio of AWC to MXene nanosheets is 5:1. An AWC-MXene composite two-dimensional bionic membrane, wherein the mass ratio of AWC to MXene nanosheets is 10:1. An application of an AWC-MXene composite two-dimensional bionic membrane can be used as a separation membrane in the separation process of salt water. Separation tests are performed using different salt solutions, that is, the salt solution is passed through the AWC-MXene membrane under pressure, and the salt concentration in the solution after permeation through the AWC-MXene membrane is analyzed. An application of an AWC-MXene composite two-dimensional bionic membrane can be used as a separation membrane in the separation process of organic solvent dewaxing. A separation test is performed using an n-hexane solution of polyethylene wax, that is, the AWC-MXene membrane is passed under pressure, and the polyethylene wax concentration of the solution after permeating through the AWC-MXene membrane is analyzed. Advantageously, the AWC-MXene composite two-dimensional biomimetic membrane according to the present invention is characterized in that it comprises: -Ultrafiltration support membrane - at least one compound of formula I or II:

[0027] Wherein, R represents a C4 to C12 alkyl side chain (including butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl). AWC-MXene composite two-dimensional biomimetic membrane Furthermore, the at least one compound of Formula I or Formula II is an artificial water channel in the form of a hydroxyl or imidazole tetramer type supramolecular aggregate, which is uniformly distributed between the interlayer nanochannels formed by face-to-face stacking of MXene nanosheets. In the present application, "ultrafiltration support membrane" refers to any microporous support material compatible with the expected pressure and purpose. It can be made of microporous polysulfone (PSF), or a microporous material composed of polyethersulfone (PES) or polyvinylidene fluoride (PVDF), cast on a non-woven reinforced fabric, such as a support layer of polyethylene (PET), polypropylene (PP) or polyacrylonitrile (PAN 50 or PAN 450). The support membrane can be a commercial 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, wherein the MWCO point value is 20 kD. The thickness of the support membrane is about 20 to 200 μm, for example, the thickness of the PSF or PES porous support membrane is between 20 and 70 μm, and the thickness of the PET or PP support membrane is between 50 and 150 μm. The present invention has the following beneficial effects: (1) The present invention utilizes artificial water channels formed by aggregation of molecules with hydroxyl groups or imidazoles in Formula I or Formula II to modify the interlayer space of the MXene two-dimensional membrane and use them as the main mass transfer channel to improve the transmission rate and selectivity of water molecules. (2) Hydroxyl or imidazole tetramer artificial water channels serve as the main mass transfer channels, which improve the anti-swelling property and long-term application stability of the AWC-MXene composite two-dimensional bionic membrane. (3) The present invention has no significant changes compared to the commonly used process for preparing two-dimensional membranes, and the method is simple. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a surface scanning electron microscope image of the AWC-MXene composite two-dimensional bionic membrane prepared with a mass ratio of AWC and MXene nanosheets of 5:1. Figure 2 These are the water flux and NaCl retention rate of the composite two-dimensional biomimetic membrane of AWC-MXene with AWC loading of 0, 1, 5, and 10 mg when treating a NaCl solution with a concentration of 1000 ppm. Figure 3 The AWC-MXene composite two-dimensional biomimetic membrane prepared with a mass ratio of AWC to MXene nanosheets of 5:1 treated with 1000ppm NaCl and MgCl 2 、Na 2 SO 4 and MgSO 4 Water flux and salt retention in solution. Figure 4 This is a graph showing the changes in flux and retention rate over time when the AWC-MXene composite two-dimensional bionic membrane prepared with a mass ratio of AWC and MXene nanosheets of 5:1 treated a n-hexane solution of polyethylene wax. DETAILED DESCRIPTION The present invention is described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Comparative Example 1 (1) Preparation of MXene nanosheet aqueous dispersion: 1g LiF was added to 20ml HCl solution and stirred continuously until LiF was completely dissolved. 3 AlC 2 Slowly add it to the prepared solution and stir it at a constant temperature of 45°C for 36 hours. After the reaction is completed, the reaction product is repeatedly washed with deionized water to remove residual acid and by-products. During the washing process, the speed of the centrifuge is gradually increased from 3500rpm to 10000rpm to ensure that the nanosheets are fully washed. The washing step is repeated several times until the pH value of the supernatant reaches above 6. Next, the solution is centrifuged at 1500rpm for 15 minutes to remove the unpeeled residue and obtain pure Ti 3 C 2 T x Nanosheet dispersion. The Ti 3 C 2 T x The concentration of nanosheets. (2) Preparation of MXene 2D membranes Take 1000 μL of the prepared Ti 3 C 2 T x The MXene nanosheet aqueous dispersion was dispersed into 30 mL of water, and after being evenly dispersed, the Ti 3 C 2 T x The nanosheets were deposited on the polyethersulfone substrate membrane, then rinsed with water and dried at 60°C under vacuum conditions for 10 minutes to obtain a MXene two-dimensional membrane. The MXene two-dimensional membrane was used to treat a 1000 ppm NaCl solution at a pressure of 4 bar, and the water flux of the membrane was 2.87 Lm -2 h -1 bar -1 , the NaCl retention rate is 46.2%. Example 1 In this embodiment, the AWC-MXene composite two-dimensional biomimetic membrane is put into the preparation method, which specifically includes the following steps: (1) Preparation of Ti 3 C 2 T x The MXene nanosheet aqueous dispersion is the same as that in Comparative Example 1 and will not be described again herein. (2) Preparation of ethanol / water colloid dispersion for artificial water channels: 1 mg of AWC powder was weighed and dissolved in 15 mL of ethanol. After complete dissolution, 15 mL of water was added to prepare a mixed dispersion with a solvent ratio of ethanol: water = 1:1, and ultrasonic treatment was performed for 10 minutes. (3) Preparation of AWC-MXene composite two-dimensional biomimetic membrane: Take 1000 μL of the prepared Ti 3 C 2 T x The MXene nanosheet dispersion was redispersed into the prepared AWC colloidal dispersion, and after uniform dispersion, the Ti was assembled by vacuum-assisted self-assembly. 3 C 2 T x The nanosheets and artificial water channels were deposited on the polyethersulfone substrate membrane, then rinsed with water and dried at 60°C under vacuum conditions for 10 minutes to obtain the AWC-MXene composite two-dimensional bionic membrane. The AWC-MXene composite two-dimensional biomimetic membrane was used to treat a 1000 ppm NaCl solution at a pressure of 4 bar, and the water flux of the membrane was 3.42 L m -2 h -1 bar -1 , the NaCl retention rate is 54.8%. Example 2 In this embodiment, the AWC-MXene composite two-dimensional biomimetic membrane is put into the preparation method, which specifically includes the following steps: (1) The preparation of MXene nanosheet aqueous dispersion is the same as that in Comparative Example 1 and will not be repeated here. (2) Preparation of ethanol / water colloid dispersion for artificial water channels: 5 mg of AWC powder was weighed and dissolved in 15 mL of ethanol. After complete dissolution, 15 mL of water was added to prepare a mixed dispersion with a solvent ratio of ethanol: water = 1:1, and ultrasonic treatment was performed for 10 minutes. (3) The preparation of AWC-MXene composite two-dimensional biomimetic membrane is the same as in Example 1 and will not be repeated here. The AWC-MXene composite two-dimensional biomimetic membrane was used to treat a 1000 ppm NaCl solution at a pressure of 4 bar, and the water flux of the membrane was 5.95 L m -2 h -1 bar -1, the NaCl retention rate is 82.5%. Example 3 In this embodiment, the AWC-MXene composite two-dimensional biomimetic membrane is put into the preparation method, which specifically includes the following steps: (1) The preparation of MXene nanosheet aqueous dispersion is the same as that in Comparative Example 1 and will not be repeated here. (2) Preparation of ethanol / water colloid dispersion for artificial water channels: 10 mg of AWC powder was weighed and dissolved in 15 mL of ethanol. After complete dissolution, 15 mL of water was added to prepare a mixed dispersion with a solvent ratio of ethanol: water = 1:1, and ultrasonic treatment was performed for 10 minutes. (3) The preparation of AWC-MXene composite two-dimensional biomimetic membrane is the same as in Example 1 and will not be repeated here. The AWC-MXene composite two-dimensional biomimetic membrane was used to treat a 1000 ppm NaCl solution at a pressure of 4 bar, and the water flux of the membrane was 9.88 L m -2 h -1 bar -1 , the NaCl retention rate is 63.9%. Example 4 In this embodiment, the AWC-MXene composite two-dimensional biomimetic membrane is put into the preparation method, which specifically includes the following steps: (1) The preparation of MXene nanosheet aqueous dispersion is the same as that in Comparative Example 1 and will not be repeated here. (2) The ethanol / water colloid dispersion for configuring the artificial water channel is the same as that in Example 2 and will not be described in detail here. (3) The preparation of AWC-MXene composite two-dimensional biomimetic membrane is the same as in Example 1 and will not be repeated here. The AWC-MXene composite two-dimensional biomimetic membrane was used to treat NaCl and MgCl with a concentration of 1000 ppm at a pressure of 4 bar. 2 、Na 2 SO 4 and MgSO 4 The membrane treated NaCl solution with a water flux of 5.95 L m -2 h -1 bar -1 The NaCl rejection rate is 82.5%. The membrane can process MgCl 2 The water flux of the solution was 6.39 L m -2 h -1 bar -1 , MgCl 2 The rejection rate was 89.6%. 2 SO 4 The water flux of the solution was 7.83 L m-2 h -1 bar -1 , Na 2 SO 4 The rejection rate was 92.2%. The membrane treated MgSO 4 The water flux of the solution was 7.43 L m -2 h -1 bar -1 , MgSO 4 The retention rate was 93.5%. Example 5 In this embodiment, the AWC-MXene composite two-dimensional biomimetic membrane is put into the preparation method, which specifically includes the following steps: (1) The preparation of MXene nanosheet aqueous dispersion is the same as that in Comparative Example 1 and will not be repeated here. (2) The ethanol / water colloid dispersion for configuring the artificial water channel is the same as that in Example 2 and will not be described in detail here. (3) The preparation of AWC-MXene composite two-dimensional biomimetic membrane is the same as in Example 1 and will not be repeated here. The AWC-MXene composite two-dimensional biomimetic membrane was used to treat a 2000 ppm polyethylene wax n-hexane solution at a pressure of 6 bar. The initial flux was 42.61 L m -2 h -1 bar -1 , the retention rate of polyethylene wax was 87.6%. And during the 246-hour operation, the flux remained almost stable and increased, and the retention rate decayed slightly. Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

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

2. The AWCs-MXene composite two-dimensional biomimetic membrane according to claim 1, characterized in that: The ultrafiltration support membrane is made of microporous polysulfone (PSF), or is made of microporous materials composed of polyethersulfone (PES) or polyvinylidene fluoride (PVDF) cast on non-woven reinforced fabric.

3. The method for preparing the AWCs-MXene composite two-dimensional biomimetic membrane according to claim 1 or 2, characterized in that: The following steps are involved: (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 stirred at a constant temperature of 45 ° C for 36 hours; after the reaction, the reaction product was repeatedly washed with deionized water to remove residual acid and by-products; the washing step was repeated several times until the pH value of the supernatant reached 6 or above; the reaction product solution was centrifuged at a speed of 1500 rpm for 15 minutes to remove the unpeeled residues to obtain pure Ti3C2T x Nanosheet dispersion; (2) Preparation of AWCs ethanol / water colloid dispersion: Weigh a certain amount of AWC powder, dissolve it in 15 mL of ethanol, add 15 mL of water after it is completely dissolved, prepare a mixed dispersion with a solvent ratio of ethanol: water = 1:1, and ultrasonically treat it for 10 minutes; (3) Preparation of AWC-MXene composite two-dimensional biomimetic membrane: Take a certain amount of prepared Ti3C2T x The nanosheet dispersion was redispersed into the prepared AWCs ethanol / water colloid dispersion, and after uniform dispersion, the Ti3C2T x The nanosheets and artificial water channels were deposited onto the ultrafiltration support membrane, then rinsed with water and dried at 60°C under vacuum conditions for 10 minutes to obtain the AWC-MXene bionic composite two-dimensional membrane.

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

1.

5. The use of the AWCs-MXene composite two-dimensional biomimetic membrane as claimed in claim 1 or 2, characterized in that: Used as a separation membrane for the separation of salt water.

6. The use of the AWCs-MXene composite two-dimensional biomimetic membrane as claimed in claim 1 or 2, characterized in that: Used as separation membrane for organic solvent dewaxing.

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