Preparation method of layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane

Abstract

The present invention relates to a preparation method of a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane, comprising the steps of: exfoliating and dispersing layered double hydroxide nanosheets in a first polar aprotic solvent to obtain a layered double hydroxide nanosheet dispersion; dissolving the quaternized phenolphthalein polyarylethersulfone membrane material in a second polar aprotic solvent, and fully stirring to obtain a first casting liquid L-1; adding the layered double hydroxide nanosheet dispersion to the first casting liquid L-1, heating and ultrasonically obtaining a second casting liquid L-2; filtering, vacuum or ultrasonically degassing the second casting liquid L-2 to obtain a third casting liquid L-3; coating the third casting liquid L-3 on a substrate, evaporating the solvent at a suitable temperature, and soaking the membrane in water to obtain a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane. The membrane has good mechanical properties, thermal stability, chemical stability, and ion conductivity, and has potential application prospects in the fields of electrodialysis desalination or concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of membranes, and in particular relates to a method for preparing a layered double metal hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane. Background Art

[0002] As a highly efficient membrane separation technology for separation and purification, electrodialysis holds great promise in brackish wastewater treatment, seawater desalination, and resource recovery due to its advantages, including low energy consumption, low cost, simple operation, high separation efficiency, and environmental friendliness. As the core component of electrodialysis, the performance of ion exchange membranes (particularly their ion conductivity) has a decisive influence on the entire electrodialysis process.

[0003] In recent years, organic-inorganic hybrid membranes are regarded as an effective means to improve the performance of anion exchange membranes, especially ion conductivity. For example, the document (ACS Appied Materials & Interfaces, 2013, 5, 1414-1422) directly doped different proportions of zirconium dioxide into quaternized polyethersulfone to prepare an organic-inorganic composite membrane. The addition of zirconium dioxide not only enhanced the mechanical strength of the quaternized polyethersulfone membrane, but also improved the ion conductivity of the composite membrane. Document (Journal OF Materials Chemistry A, 2018, 6, 24728-24739) Szekely et al. reported a series of highly selective graphene oxide-polybenzimidazole (GO-PBI) nanocomposite anion exchange membranes. Wang Baoguo et al. (Chinese patent application, publication number: CN114181426 A) invented an organic-inorganic composite membrane and its preparation method. Through a solvothermal reaction, a hydrophilic, ordered, and vertically oriented inorganic nanosheet network is in situ grown within the hydrophobic pores of an alkali-resistant membrane. This creates structurally ordered hydroxide ion transport channels, endowing the membrane with high ion conductivity. Yang Jianhua et al. (Chinese patent application, publication number: CN112999890 A) disclosed a flat organic-inorganic hybrid SiO2 composite membrane and its preparation method. This membrane exhibits advantages such as high flux and selectivity in pervaporation and seawater desalination applications.

[0004] Layered double hydroxide (LDH) is an inorganic two-dimensional layered anion exchange material with a positively charged main plate structure, exchangeable anions between the layers, and a surface rich in hydroxyl groups. The hydroxyl groups on the metal hydroxide layers of this material and the water molecules attached between the two layers can provide a good ion transport hydrogen bond network through hydrogen bonding, thereby relying on rapid hydrogen bond cleavage / reconstruction to achieve high anion conductivity. Based on the above, the invention utilizes the advantages of LDH in polar aprotic solvents, such as easy peeling and high dispersion, high anion conductivity, layer surface charge, and rich hydrogen bond network, while combining the good solubility, unique self-assembled microphase separation structure, and high anion conductivity of quaternized phenolphthalein polyarylethersulfone in polar aprotic solvents to prepare layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membranes, and then further improves its ion conductivity and electrodialysis performance through the synergistic effects of hydrogen bonding, electrostatics, etc. between LDH nanosheets and quaternized phenolphthalein polyarylethersulfone hybrid membranes. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane. The obtained layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane is used in the field of electrodialysis.

[0006] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0007] A method for preparing a layered double metal hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane is characterized by the following steps:

[0008] 1) exfoliating and dispersing the layered double hydroxide nanosheets in a first polar aprotic solvent to obtain a layered double hydroxide nanosheet dispersion having a concentration of 0.1 g / L to 80 g / L;

[0009] 2) dissolving the quaternized phenolphthalein polyarylethersulfone membrane material in a second polar aprotic solvent and stirring thoroughly to obtain a first casting solution L-1;

[0010] 3) adding the layered bimetallic hydroxide nanosheet dispersion described in step 1) to the first casting solution L-1, heating and ultrasonicating to obtain a second casting solution L-2;

[0011] 4) filtering, vacuum or ultrasonically degassing the second casting solution L-2 to obtain a third casting solution L-3;

[0012] 5) coating the third L-3 on the substrate, evaporating the solvent at 60° C. to 180° C., and finally soaking in water for 1 h to 48 h to obtain a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane.

[0013] According to the present invention, the general structural formula of the layered double hydroxide is:

[0014] [M n+ 1-x M x 3+ (OH)2] x+ Y n- x / n mH2O;

[0015] Where M n+ Mg 2+ 、Zn 2+ 、Co 2+ 、Mn 2+ 、Li + 、Cu 2+ Equivalent monovalent or divalent ions; M 3+ Al 3+ Cr 3+ 、Co 3 + 、Fe 3+ Sc 3+ Trivalent metal ions, such as Y n- is an anion intercalated between layers, the anion being OH - 、Cl - 、NO3 - 、CO3 2- or SO4 2- Inorganic and organic anions, x is M 2+ / (Mg 2+ +M 3+ ), x is usually between 0.2-0.33, n is an integer greater than 1, and m is the number of interlayer crystalline water.

[0016] Specifically, the first polar aprotic solvent is selected from one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0017] Furthermore, the quaternized phenolphthalein polyarylethersulfone membrane material is composed of a main chain containing a Cardo group and a side chain functional group, and its chemical structure is:

[0018]

[0019] Where R + Represents different cationic functional groups, which are one or more of the above-mentioned quaternary ammonium and heterocyclic cations.

[0020] Specifically, the second polar aprotic solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0021] The concentration of the first casting solution L-1 is 3wt% to 40wt%, and the mass percentage of the layered double hydroxide nanosheets and the quaternized phenolphthalein polyarylethersulfone membrane material is 0.1% to 50%.

[0022] The substrate is a metal plate, a glass plate, a ceramic, a polymer plate or a fabric.

[0023] The time for evaporating the solvent is 5 minutes to 48 hours.

[0024] The method for preparing a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane of the present invention utilizes the electrostatic and hydrogen bonding interactions between the layered double hydroxide and the quaternized phenolphthalein polyarylethersulfone in a polar aprotic solvent. The layered double hydroxide is peeled and then blended with the quaternized phenolphthalein polyarylethersulfone to prepare a dense and uniform organic-inorganic hybrid membrane.

[0025] Compared with existing technologies, the technological innovations brought about are:

[0026] This method combines the characteristics of layered double hydroxide, such as high surface charge density, high ion conductivity, and extensive hydrogen bond network on the surface, with the advantages of quaternized phenolphthalein polyarylethersulfone anion exchange material, such as unique microphase separation structure, good chemical stability, excellent ion conductivity, low membrane surface resistance and excellent electrodialysis performance, to provide a new preparation method for layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid anion exchange membrane.

[0027] 2. The hybrid membrane preparation method is simple to operate and easy to apply on a large scale in industrial applications;

[0028] 3. The obtained layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane has good mechanical properties, thermal stability, chemical stability, high ion conductivity and excellent electrodialysis performance, and has potential application prospects in the field of electrodialysis desalination or concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are morphology diagrams of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane prepared in Example 1, wherein (a) shows the surface morphology of the membrane, and (b) shows the overall cross-sectional morphology of the membrane.

[0030] Figure 2These are morphology images of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in Example 2, where (a) shows the surface morphology of the membrane and (b) shows the overall cross-sectional morphology of the membrane.

[0031] Figure 3 These are morphology images of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in Example 3, where (a) shows the surface morphology of the membrane and (b) shows the overall cross-sectional morphology of the membrane.

[0032] Figure 4 These are morphology images of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane prepared in Example 4, where (a) shows the surface morphology of the membrane and (b) shows the overall cross-sectional morphology of the membrane.

[0033] Figure 5 These are morphology images of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in Example 5, where (a) shows the surface morphology of the membrane and (b) shows the overall cross-sectional morphology of the membrane.

[0034] Figure 6 These are morphology images of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in Example 6, where (a) shows the surface morphology of the membrane and (b) shows the overall cross-sectional morphology of the membrane.

[0035] Figure 7 These are morphology diagrams of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in Example 7, where (a) shows the surface morphology of the membrane and (b) shows the overall cross-sectional morphology of the membrane.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0037] The research idea of ​​this application is to utilize the good chemical stability and excellent ion conductivity of two-dimensional layered double hydroxide (LDH) itself to prepare organic-inorganic hybrid membranes by blending quaternized phenolphthalein polyarylethersulfone anion exchange materials, and then utilize the synergistic effect between LDH and quaternized phenolphthalein polyarylethersulfone to further improve the ion conductivity and electrodialysis performance of the corresponding ion exchange membrane.

[0038] This embodiment provides a method for preparing a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane, which is prepared according to the following steps:

[0039] 1) Layered double hydroxide nanosheets (hereinafter referred to as LDH) are dispersed in a first polar aprotic solvent by exfoliation to obtain a layered double hydroxide nanosheet dispersion having a concentration of 0.1 g / L-80 g / L; in the following examples, the concentration is preferably 0.5-30 g / L.

[0040] 2) stirring and fully dissolving the quaternized phenolphthalein polyarylethersulfone in a second polar aprotic solvent to obtain a first casting solution L-1 having a mass fraction of 3 wt% to 40 wt%, preferably 5 wt% to 25 wt%;

[0041] 3) adding the layered double hydroxide nanosheet dispersion described in step 1) to the first casting solution L-1, heating and ultrasonicating to obtain a second casting solution L-2;

[0042] 4) filtering, vacuum or ultrasonically degassing the second casting solution L-2 for 1 minute to 24 hours to obtain a third casting solution L-3;

[0043] 5) coating the third L-3 on a substrate, wherein the substrate is any one of a metal plate, a glass plate, a ceramic, a polymer plate or a fabric, evaporating the solvent at 60°C to 180°C, preferably 60°C to 100°C, for 5 minutes to 48 hours, and finally soaking in water for 1 hour to 48 hours to obtain a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane.

[0044] In this embodiment, the step 1) of preparing the layered double hydroxide nanosheet dispersion is as follows:

[0045] Layered double hydroxide nanosheets (LDH) were dispersed in a polar aprotic solvent, and a single layered double hydroxide nanosheet dispersion was prepared by a heating and ultrasonic method under nitrogen protection.

[0046] The general structural formula of the layered double hydroxide is:

[0047] [M n+ 1-x M x 3+ (OH)2] x+ Y n- x / n mH2O;

[0048] Where M n+ Mg 2+ 、Zn 2+ 、Co 2+ 、Mn 2+ 、Li + 、Cu 2+ Equivalent monovalent or divalent ions; M 3+ Al 3+ Cr 3+ 、Co 3 + 、Fe 3+ Sc 3+ Trivalent metal ions, such as Y n-is an anion intercalated between layers, the anion being OH - 、Cl - 、NO3 - 、CO3 2- or SO4 2- Inorganic and organic anions x is M 2+ / (Mg 2+ +M 3+ ), x is usually between 0.2-0.33, n is an integer greater than 1, and m is the number of interlayer crystalline water.

[0049] In the following examples, MgAl-Cl-LDH, MgAl-NO3-LDH, ZnAl-Cl-LDH, and LiAl-Cl-LDH are preferred.

[0050] The first polar aprotic solvent is selected from N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO), and has the following characteristics:

[0051] (1) LDH can be exfoliated into single-layer nanosheets in a solvent by stirring / ultrasound methods;

[0052] (2) It has good solubility for quaternized phenolphthalein poly(arylether sulfone);

[0053] (3) LDH and quaternized phenolphthalein poly(arylethersulfone) can form a uniform dispersion system in the solvent;

[0054] In the following examples, N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are preferred.

[0055] The chemical structure of the quaternized phenolphthalein polyarylethersulfone membrane material in step 2) is:

[0056]

[0057] Where R + Represents different cationic functional groups, which are one or more of the above-mentioned quaternary ammonium and heterocyclic cations.

[0058] In the following embodiments, the functional group is preferably a pyrrolidine cyclic ammonium group, a morpholine cyclic ammonium group, a piperidine cyclic ammonium group, a piperazine cyclic ammonium group, a thiomorpholine cyclic ammonium group, and a trimethylamine-based quaternary ammonium cationic group;

[0059] The mass percentage of the LDH nanosheets and the quaternized phenolphthalein poly(arylethersulfone) is 0.1%-50%, and preferably 0.2%-15% in the following embodiments.

[0060] In this embodiment, the first organic solvent used in the first casting liquid L-1 is selected from one or more polar aprotic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0061] In this embodiment, the concentration of the first casting solution L-1 is 3 wt% to 40 wt%, and the mass percentage of LDH nanosheets and quaternized phenolphthalein polyarylethersulfone is 0.1% to 50%.

[0062] The substrate is a metal plate, a glass plate, a ceramic, a polymer plate or a fabric.

[0063] The evaporation time is 5 minutes to 48 hours, and the soaking time in water is 1 hour to 48 hours.

[0064] In the following embodiments, pyrrolidine cyclic ammonium groups, morpholine cyclic ammonium groups, piperidine cyclic ammonium groups, piperazine cyclic ammonium groups, thiomorpholine cyclic ammonium groups and trimethylamine-based quaternary ammonium cationic groups are preferred;

[0065] The following are specific embodiments given by the inventor.

[0066] Example 1:

[0067] This example provides a preparation of a layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane (Mor / 3% LDH). The quaternized polymer used contains morpholine cyclic ammonium groups, and its specific structural formula is:

[0068]

[0069] Under nitrogen protection, 0.015 g of MgAl-Cl-LDH was dispersed in 3 mL of N,N-dimethylformamide (DMF) and ultrasonicated at 60°C for 3 h to obtain a layered double hydroxide nanosheet dispersion, which was named LDH nanosheet dispersion.

[0070] 0.5 g of the above polymer was dissolved in 5 mL of DMF and stirred at room temperature for 6 h to obtain the first casting solution L-1.

[0071] A LDH nanosheet dispersion with a concentration of 7.5 g / L was mixed with the casting solution L-1 to obtain a second casting solution L-2, in which the mass percentage of LDH nanosheets and quaternized phenolphthalein polyarylethersulfone was 3%.

[0072] The second casting liquid L-2 is filtered and subjected to vacuum or ultrasonic degassing for 30 minutes to obtain a third casting liquid L-3.

[0073] The third casting solution L-3 was evenly coated on a glass plate and evaporated at 100°C for 2 hours. After the solvent evaporation step, the substrate membrane was immersed in RO water or UP water at room temperature for 1 hour to obtain a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane.

[0074] Morphology test of layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane: The morphology of the membrane was observed using a scanning electron microscope.

[0075] Electrodialysis desalination performance test of layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane: The test was carried out using a homemade four-chamber device.

[0076] The layered double hydroxide / quaternized phenolphthalein polyethersulfone hybrid membrane (Mor / 3% LDH) prepared in this example has a surface morphology as shown in FIG. Figure 1 As shown in (a), Figure 1 (b) is the overall cross-sectional morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane (Mor / 3% LDH). It can be seen that LDH nanosheets are evenly distributed on the surface and cross-section of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane (Mor / 3% LDH). In the electrodialysis desalination experiment, the salt flux reached 88.7 (mg m -2 s -1 ), current efficiency is as high as 99%, energy consumption is 5.8kWh kg -1 .

[0077] Example 2:

[0078] This example uses the same quaternized polymer as in Example 1. The difference is that the concentration of the added LDH nanosheet dispersion is 20 g / L, the mass percentage of the LDH nanosheet and the quaternized phenolphthalein polyarylethersulfone is 8%, and the other conditions are the same as in Example 1. The morphology characterization method and electrodialysis desalination performance test method of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane (Mor / 8% LDH) prepared in this example are the same as in Example 1. The measured salt flux of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane in the electrodialysis desalination experiment reached 92.5 (mg m -2 s -1 ), current efficiency is as high as 98%, energy consumption is 6.0kWh kg -1 .

[0079] The surface morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in this example is as follows: Figure 2 As shown in (a), Figure 2 (b) is the overall cross-sectional morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane.

[0080] Example 3:

[0081] This example uses the same quaternized polymer as in Example 1. The difference is that the concentration of the added LDH nanosheet dispersion is 30 g / L, the mass percentage of the LDH nanosheet and the quaternized phenolphthalein polyarylethersulfone is 12%, and the other conditions are the same as in Example 1. The morphology characterization method and electrodialysis desalination performance test method of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane (Mor / 12% LDH) prepared in this example are the same as in Example 1. The measured salt flux of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane in the electrodialysis desalination experiment reached 88.5 (mg m -2 s -1 ), current efficiency is as high as 98%, energy consumption is 5.2kWh kg -1 .

[0082] The surface morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in this example is as follows: Figure 3 As shown in (a), Figure 3 (b) is the overall cross-sectional morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane.

[0083] Example 4:

[0084] The difference between this embodiment and embodiment 3 is that the quaternized polymer used in this embodiment contains a pyrrolidine cyclic ammonium group, and its specific structural formula is:

[0085]

[0086] The concentration of the added LDH nanosheet dispersion was 20 g / L, the mass percentage of LDH nanosheets and quaternized phenolphthalein poly(arylethersulfone) was 8%, and the other conditions were the same as those in Example 1. The morphology characterization method and electrodialysis desalination performance test method of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane (Py / 12% LDH) prepared in this example were the same as those in Example 1. The measured salt flux of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane in the electrodialysis desalination experiment reached 89.5 (mg m -2 s -1 ), current efficiency up to 97%, energy consumption of 5.0kWh kg -1 .

[0087] The surface morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in this example is as follows: Figure 4 As shown in (a), Figure 4 (b) is the overall cross-sectional morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane.

[0088] Example 5:

[0089] The difference between this embodiment and embodiment 3 is that the quaternized polymer used in this embodiment contains a piperidine cyclic ammonium group, and its specific structural formula is:

[0090]

[0091] The concentration of the added LDH nanosheet dispersion was 20 g / L, the mass percentage of LDH nanosheets and quaternized phenolphthalein poly(arylethersulfone) was 8%, and the other conditions were the same as those in Example 1. The morphology characterization method and electrodialysis desalination performance test method of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane (Pi / 12% LDH) prepared in this example were the same as those in Example 1. The measured salt flux of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane in the electrodialysis desalination experiment reached 88.5 (mg m -2 s -1 ), current efficiency is as high as 98%, energy consumption is 4.9kWh kg -1 .

[0092] The surface morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in this example is as follows: Figure 5 As shown in (a), Figure 5 (b) is the overall cross-sectional morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane.

[0093] Example 6:

[0094] The difference between this embodiment and embodiment 3 is that the quaternized polymer used in this embodiment contains trimethylammonium groups, and its specific structural formula is:

[0095]

[0096] The concentration of the added LDH nanosheet dispersion was 20 g / L, the mass percentage of LDH nanosheets and quaternized phenolphthalein polyarylethersulfone was 8%, and the other conditions were the same as those in Example 1. The morphology characterization method and electrodialysis desalination performance test method of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane prepared in this example were the same as those in Example 1. The measured salt flux of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane in the electrodialysis desalination experiment reached 77.4 (mgm -2 s -1 ), current efficiency is 85%, energy consumption is 6.5kWh kg -1 .

[0097] The surface morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in this example is as follows: Figure 6 As shown in (a), Figure 6(b) is the overall cross-sectional morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane.

[0098] Example 7:

[0099] The difference between this embodiment and embodiment 3 is that the quaternized polymer used in this embodiment contains a piperazine group, and its specific structural formula is:

[0100]

[0101] The concentration of the added LDH nanosheet dispersion was 20 g / L, the mass percentage of the LDH nanosheets and the quaternized phenolphthalein polyarylethersulfone was 8%, and the other conditions were the same as those in Example 1. The morphology characterization method and electrodialysis desalination performance test method of the layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane prepared in this example were the same as those in Example 1. The measured layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane had a salt flux of 96.2 (mgm -2 s -1 ), current efficiency is 82%, energy consumption is 4.5 (kWh kg -1 ).

[0102] The surface morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane prepared in this example is as follows: Figure 7 As shown in (a), Figure 7 (b) is the overall cross-sectional morphology of the layered double hydroxide / quaternized phenolphthalein poly(arylethersulfone) hybrid membrane.

Claims

1. A method for preparing a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane, characterized in that: Prepare as follows: 1) exfoliating and dispersing the layered double hydroxide nanosheets in a first polar aprotic solvent to obtain a layered double hydroxide nanosheet dispersion having a concentration of 5 g / L to 30 g / L; 2) dissolving the quaternized phenolphthalein polyarylethersulfone membrane material in a second polar aprotic solvent and stirring thoroughly to obtain a first membrane casting solution L-1; 3) adding the layered bimetallic hydroxide nanosheet dispersion described in step 1) to the first casting solution L-1, heating and ultrasonicating to obtain a second casting solution L-2; 4) filtering, vacuuming or ultrasonically degassing the second casting solution L-2 to obtain a third casting solution L-3; 5) coating the third L-3 on the substrate, evaporating the solvent at 60°C to 180°C, and finally soaking in water for 1 hour to 48 hours to obtain a layered double hydroxide / quaternized phenolphthalein polyarylethersulfone hybrid membrane; The general structural formula of the layered double hydroxide is: [M n+ 1-x M x 3+ (OH)2] x+ Y n- x / n ·mH2O; Where M n+ Mg 2+ 、Zn 2+ 、Co 2+ 、Mn 2+ 、Li + 、Cu 2+ Equivalent monovalent or divalent ions; M 3+ A1 3+ Cr 3+ 、Co 3+ 、Fe 3 + Sc 3+ Trivalent metal ions, such as Y n- is an anion intercalated between layers, the anion being OH - 、C1 - 、NO3 - 、CO3 2- or SO4 2- Inorganic and organic anions, x is M 2+ / (Mg 2+ +M 3+ ), x is between 0.2 and 0.33, n is an integer greater than 1, and m is the number of interlayer crystalline water; The first polar aprotic solvent is selected from one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO); The chemical structure of the quaternized phenolphthalein polyarylethersulfone membrane material is: Where R + Represents different cationic functional groups, which are one or more of the above-mentioned quaternary ammonium and heterocyclic cations; The second polar aprotic solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO); The concentration of the first casting solution L-1 is 3 wt% to 40 wt%, and the mass percentage of the layered double hydroxide nanosheets and the quaternized phenolphthalein polyarylethersulfone membrane material is 0.1% to 50%; The substrate is a metal plate, a glass plate, a ceramic, a polymer plate or a fabric; The time for evaporating the solvent is 5 minutes to 48 hours.

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