Hierarchical composite membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polymer composite membrane materials and interface photo-thermal water purification, in particular to a hierarchical composite membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing a solution containing diatomite and a solution containing an aniline monomer, then applying the mixture to a porous membrane substrate, then applying an initiator, and carrying out a polymerization reaction, so that the surface of the porous membrane substrate is loaded with diatomite and polyaniline to obtain a polyaniline / diatomite / porous composite membrane; a solution containing bismuth chloride is applied to the surface of the polyaniline / diatomite / porous membrane composite material, water is applied after fumigation, a hydrolysis reaction is carried out, and the hierarchical composite membrane is obtained. The hierarchical composite material disclosed by the invention has double functions of solar interface water evaporation and photocatalytic dye degradation, is high in evaporation rate, high in photocatalytic degradation removal efficiency and good in evaporation cycle and degradation cycle stability, and has a wide application value in the fields of wastewater purification and purified water recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite membrane materials and interface light-heat water purification technology, and in particular to a hierarchical composite membrane and a preparation method and application thereof. Background Art

[0002] Using renewable energy to treat wastewater and recover clean water from it can achieve a sustainable freshwater supply. Solar interfacial water evaporation is the most direct method currently available. It converts solar energy directly into heat and concentrates the energy on the surface of a material, effectively producing freshwater by continuously evaporating various water sources (including seawater and wastewater) at relatively low temperatures. This method minimizes heat loss and achieves higher energy conversion efficiency and water productivity.

[0003] Organic dyes are widely used in industries such as leather, printing, papermaking, and food, often generating large amounts of wastewater containing these dyes during industrial production. Organic dyes are characterized by high production volumes, strong toxicity, and difficulty in biodegrading. However, when it comes to treating organic dye wastewater, interfacial solar evaporation technology can only concentrate the organic pollutants in the bulk water while simultaneously evaporating and collecting the condensed water vapor, failing to effectively treat and degrade the organic pollutants in the wastewater. This not only shortens the service life of the evaporator, but improper treatment of the residual wastewater after evaporation can also lead to new environmental problems.

[0004] Therefore, how to provide a dual-functional layered composite membrane that can be used for solar interfacial water evaporation and photocatalytic dye degradation to alleviate the shortage of freshwater resources and water pollution has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a hierarchical composite membrane and a preparation method and application thereof, so as to solve the problems existing in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a hierarchical composite membrane, comprising the following steps:

[0008] (1) mixing a solution containing diatomaceous earth and a solution containing aniline monomer and applying the mixture to a porous membrane substrate, then applying an initiator to carry out a polymerization reaction, so that the surface of the porous membrane substrate is loaded with diatomaceous earth and polyaniline, thereby obtaining a polyaniline / diatomaceous earth / porous composite membrane;

[0009] (2) applying a solution containing bismuth chloride to the surface of the polyaniline / diatomaceous earth / porous membrane composite material, fumigating, and then applying water to perform a hydrolysis reaction, so that the surface of the polyaniline / diatomaceous earth / porous membrane composite material is loaded with bismuth oxychloride to obtain a hierarchical composite membrane.

[0010] Optionally, the porous membrane substrate comprises sponge, polyethylene foam or aerogel.

[0011] Optionally, the solution containing diatomaceous earth comprises: diatomaceous earth, sodium carboxymethyl cellulose and an acidic solution.

[0012] Optionally, the mass ratio of the diatomaceous earth to sodium carboxymethyl cellulose is 3-5:1; the acidic solution includes a hydrochloric acid solution; the concentration of the acidic solution is 1-5 mol / L; and the dosage ratio of the diatomaceous earth to the acidic solution is 0.03-0.05 g / mL.

[0013] Optionally, the solution containing aniline monomer comprises: aniline monomer and ethanol; the volume ratio of the aniline monomer to ethanol is 0.01 to 0.1:1;

[0014] The volume ratio of the solution containing diatomaceous earth to the solution containing aniline monomer is 1 to 5:1.

[0015] Optionally, the initiator comprises an ammonium persulfate solution; the concentration of the initiator is 0.2 to 0.5 g / mL; the volume ratio of the initiator to the aniline monomer is 8 to 12:1; the polymerization reaction temperature is 0 to 10° C., and the reaction time is 8 to 12 hours.

[0016] Optionally, the solution containing bismuth chloride comprises: bismuth chloride and hydrochloric acid solution; the dosage ratio of the bismuth chloride to the hydrochloric acid solution is 0.06 to 0.13 g / mL; and the concentration of the hydrochloric acid solution is 1 to 5 mol / L.

[0017] Optionally, the fumigation is to fumigate the surface containing the bismuth chloride solution with water vapor, and the fumigation time is 1 to 1.5 hours; the dosage ratio of the bismuth chloride to water is 0.0024 to 0.006 g / mL; the temperature of the hydrolysis reaction is 18 to 25° C., and the time is 20 to 30 minutes.

[0018] The present invention also provides a hierarchical composite membrane prepared by the above preparation method.

[0019] The present invention also provides the application of the hierarchical composite film in solar interface water evaporation and photocatalytic dye degradation.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention adopts a multi-level assembly strategy to prepare a dual-functional layered composite membrane. The efficient water transport capacity is due to the diatomaceous earth filling the gaps in the porous membrane substrate, the excellent photothermal conversion capacity is due to the polyaniline in the middle layer, and the efficient photocatalytic degradation capacity of rhodamine B comes from the bismuth oxychloride photocatalyst in the surface layer.

[0022] (2) The present invention combines interfacial solar evaporation with photocatalytic technology. The photothermal effect improves the conversion of light into water vapor, and the generated local heat accelerates the charge transfer during the catalytic reaction. This enables the sustainable generation of clean water and the effective removal of pollutants in wastewater. The prepared hierarchical composite membrane material can achieve an evaporation rate of 1.11 kg m under low-energy visible light LED irradiation. -2 h -1 The excellent photocatalytic degradation and removal efficiency of Rhodamine B can reach 95.9%.

[0023] (3) The hierarchical composite membrane material prepared by the present invention exhibits good catalytic degradation performance in periodic cyclic degradation and a wide range of rhodamine B concentrations, has potential for recycling organic dye wastewater, and has good evaporation cycle stability. The evaporation performance remains unchanged after 10 cycles, and the degradation efficiency is still above 80% after 3 cycles. It has broad application value in the fields of wastewater purification and clean water recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the preparation of the bismuth oxychloride / polyaniline / diatomaceous earth / sponge hierarchical composite membrane of Example 1;

[0025] Figure 2 SEM images of the hierarchical composite membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 3, and a blank control sponge, wherein (a) is a blank control sponge, (b) is a composite membrane of Comparative Example 1, (c) is a composite membrane of Comparative Example 2, (d) is a cross-section of the composite membrane of Example 1, (e) is an enlarged cross-section of the composite membrane of Example 1, (f) is a composite membrane of Example 1, (g) is a composite membrane of Comparative Example 3, (h) is a composite membrane of Example 2, and (i) is a composite membrane of Example 3;

[0026] Figure 3 XRD patterns (a) and FT-IR patterns (b) of the hierarchical composite films prepared in Examples 1 to 3 and Comparative Examples 1 to 3, as well as a blank control sponge;

[0027] Figure 4 The water contact angle test graphs of the hierarchical composite films prepared in Example 1 and Comparative Examples 1-2 and the blank control sponge;

[0028] Figure 5 (a) Graph showing the water evaporation rate of the hierarchical composite membranes prepared in Examples 1 to 3, Comparative Examples 1 to 3, and a blank control sponge under one sunlight, and (b) a graph showing the evaporation cycle of the hierarchical composite membrane of Example 1;

[0029] Figure 6The photocatalytic degradation efficiency diagram of Rhodamine B for the hierarchical composite membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 3 and the blank control sponge (a), the cyclic stability test of the hierarchical composite membrane prepared in Example 1 (b) and the degradation efficiency diagram under different initial concentrations of Rhodamine B (c). DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0032] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0033] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present description and examples are intended to be illustrative only.

[0034] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0035] The raw materials used in the present invention can be obtained commercially or prepared using existing technologies.

[0036] The present invention provides a method for preparing a hierarchical composite membrane, comprising the following steps:

[0037] (1) mixing a solution containing diatomaceous earth and a solution containing aniline monomer and applying the mixture to a porous membrane substrate, then applying an initiator to carry out a polymerization reaction, so that the surface of the porous membrane substrate is loaded with diatomaceous earth and polyaniline, thereby obtaining a polyaniline / diatomaceous earth / porous composite membrane;

[0038] (2) applying a solution containing bismuth chloride to the surface of the polyaniline / diatomaceous earth / porous membrane composite material, fumigating, and then applying water to perform a hydrolysis reaction, so that the surface of the polyaniline / diatomaceous earth / porous membrane composite material is loaded with bismuth oxychloride to obtain a hierarchical composite membrane.

[0039] The present invention is a method for preparing a hierarchical composite membrane, wherein the composite membrane is a bismuth oxychloride / polyaniline / diatomite / porous membrane, wherein a solution containing diatomite and a solution containing aniline monomer are dropwise added to a three-dimensional porous membrane substrate material, the hydrophobic porous membrane is modified, and then polyaniline is condensed to form polyaniline. A photocatalytic material bismuth oxychloride is grown on the surface of the loaded polyaniline by a hydrothermal method, and finally bismuth oxychloride / polyaniline / diatomite / porous membrane is obtained. In order to ensure the bifunctionalization of the hierarchical composite membrane, the hydrophobic material diatomite is first uniformly filled in the porous base membrane based on a layer-by-layer assembly technique, and then polyaniline is in-situ condensed on the surface layer to serve as a light-to-heat conversion layer. Finally, bismuth oxychloride is embedded in the polyaniline surface layer by a hydrothermal method, and bismuth oxychloride serves as a photocatalytic degradation layer. The various functional areas are hierarchically constructed to ensure that the hierarchical composite membrane has excellent degradation performance while performing efficient water evaporation, and exhibits significant stability in tests of 10 water evaporation cycles and 3 degradation cycles.

[0040] Step 1) first adding diatomaceous earth and sodium carboxymethyl cellulose to an acidic solution, stirring and mixing uniformly to obtain a solution containing diatomaceous earth; mixing aniline monomer and ethanol, stirring uniformly to obtain a solution containing aniline monomer; then dropping the solution containing diatomaceous earth and the solution of aniline monomer onto a porous membrane substrate, applying an initiator, and performing a polymerization reaction to load diatomaceous earth and polyaniline on the surface of the porous membrane substrate, and then washing and drying to obtain a polyaniline / diatomaceous earth / porous composite membrane.

[0041] In the present invention, the diatomaceous earth needs to be purified before use. In an embodiment of the present invention, the purification method is as follows: dissolving the diatomaceous earth in a hydrochloric acid solution, stirring uniformly, and then repeatedly washing with ethanol and deionized water, centrifuging, and drying to obtain purified diatomaceous earth for subsequent experiments.

[0042] The usage ratio of the diatomaceous earth and the hydrochloric acid solution is 20 g:60 mL; the volume concentration of the hydrochloric acid solution is 8%; the stirring temperature is 90° C. and the time is 30 min; and the drying temperature is 105° C.

[0043] In the present invention, the porous membrane substrate comprises sponge, polyethylene foam or aerogel, preferably sponge, and more preferably polyurethane sponge.

[0044] In the present invention, the porous membrane substrate needs to be pretreated before use. In an embodiment of the present invention, the pretreatment method is: ultrasonically washing the porous membrane substrate three times with ethanol and deionized water respectively, and then drying to complete the pretreatment.

[0045] In the present invention, the mass ratio of the diatomaceous earth to sodium carboxymethyl cellulose is 3 to 5:1, preferably 4:1; the acidic solution includes a hydrochloric acid solution; the concentration of the acidic solution is 1 to 5 mol / L, preferably 2 to 4 mol / L, and more preferably 2.5 to 3 mol / L; the amount ratio of the diatomaceous earth to the acidic solution is 0.03 to 0.05 g / mL, preferably 0.04 g / mL.

[0046] In the present invention, washing is performed with ethanol and deionized water three times each to remove APS and oligoaniline; and drying is performed at 40°C.

[0047] In the present invention, the volume ratio of the aniline monomer to ethanol is 0.01 to 0.1:1, preferably 0.02 to 0.0975:1, and more preferably 0.05 to 0.06:1; the volume ratio of the solution containing diatomaceous earth to the solution containing aniline monomer is 1 to 5:1, preferably 2 to 4:1, and more preferably 2.5 to 3:1.

[0048] In the present invention, the initiator comprises an ammonium persulfate solution; the solvent of the ammonium persulfate solution is water; the concentration of the initiator is 0.2 to 0.5 g / mL, preferably 0.3125 to 0.45 g / mL, and more preferably 0.35 to 0.4 g / mL; the volume ratio of the initiator to the aniline monomer is 8 to 12:1, preferably 9 to 11:1, and more preferably 10:1; the polymerization reaction temperature is 0 to 10°C, preferably 1 to 8°C, more preferably 2 to 6°C, and more preferably 4 to 5°C, and the time is 8 to 12 hours, preferably 9 to 11 hours, and more preferably 10 hours.

[0049] Step (2) comprises mixing bismuth chloride and hydrochloric acid solution uniformly, stirring until the solution becomes transparent and clear, thereby obtaining a solution containing bismuth chloride; then applying the solution containing bismuth chloride to the surface of the polyaniline / diatomaceous earth / porous membrane composite material, fumigating, and then applying water to carry out a hydrolysis reaction, wherein the bismuth chloride is hydrolyzed into bismuth oxychloride, so that the surface of the polyaniline / diatomaceous earth / porous membrane composite material is loaded with bismuth oxychloride, and drying in an oven, thereby obtaining a hierarchical composite membrane.

[0050] In the present invention, the dosage ratio of the bismuth chloride and the hydrochloric acid solution is 0.06 to 0.13 g / mL, preferably 0.08 to 0.12 g / mL, and more preferably 0.09 to 0.1 g / mL; the concentration of the hydrochloric acid solution is 1 to 5 mol / L, preferably 1.5 to 3 mol / L.

[0051] In the present invention, the fumigation is to fumigate the surface containing bismuth chloride solution with water vapor, and the fumigation time is 1 to 1.5 hours, preferably 1 hour; the dosage ratio of bismuth chloride to water is 0.0024 to 0.006 g / mL, preferably 0.003 to 0.005 g / mL, and more preferably 0.0035 to 0.0.04 g / mL; the temperature of the hydrolysis reaction is 18 to 25°C, preferably 20 to 24°C, and the time is 20 to 30 minutes, preferably 25 to 26 minutes.

[0052] In the present invention, the purpose of fumigation is to hydrolyze part of the bismuth chloride into bismuth oxychloride, and the subsequent addition of deionized water is to ensure that all the bismuth chloride is completely hydrolyzed into bismuth oxychloride.

[0053] In the present invention, the drying temperature is 40°C.

[0054] The present invention also provides a hierarchical composite membrane material prepared by the above preparation method.

[0055] The present invention also provides the use of the hierarchical composite film material in solar interface water evaporation and photocatalytic dye degradation.

[0056] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0057] In the examples and comparative examples of the present invention, diatomaceous earth and sponge were pretreated before use;

[0058] The diatomite pretreatment method is as follows: 20 g of raw diatomite was dispersed in 60 mL of 8% hydrochloric acid solution, stirred in a constant temperature magnetic stirrer at 90°C for 30 min, then repeatedly washed with ethanol and deionized water and centrifuged, and dried at 105°C to obtain purified diatomite (labeled as Dp) for subsequent experiments;

[0059] The specific method of sponge pretreatment is: cutting 4.5×4.5cm 2 The polyurethane sponge (MF) was ultrasonically washed three times with ethanol and deionized water respectively, and dried in an oven at 40°C. The treated sponge was used as a blank control.

[0060] Example 1

[0061] like Figure 1Schematic diagram of the preparation of the bismuth oxychloride / polyaniline / diatomaceous earth / sponge hierarchical composite membrane of the present invention is shown.

[0062] (1) Add 0.05g sodium carboxymethyl cellulose and 0.2g Dp to 5mL 1M hydrochloric acid, stir and dissolve at room temperature to form a solution containing diatomaceous earth; mix 0.195mL aniline monomer and 2mL ethanol to obtain a solution containing aniline monomer; dissolve 0.625g ammonium persulfate in 2mL deionized water to obtain an ammonium persulfate solution; mix the solution containing diatomaceous earth and the solution containing aniline monomer and stir them evenly, then add them dropwise to the treated sponge base, and then add the ammonium persulfate solution dropwise. After the treated sponge is refrigerated at 4℃ for 10 hours, it is washed with ethanol and deionized water three times each to remove APS and oligoaniline. Finally, the sample is dried in an oven at 40℃ to obtain a polyaniline / diatomaceous earth / sponge composite material;

[0063] (2) Under magnetic stirring, 0.182 g of bismuth chloride was added to 2 mL of 1.5 M hydrochloric acid solution and stirred until the solution became transparent and clear to obtain a clear solution. The clear solution was dripped dropwise onto the surface of the treated polyaniline / diatomaceous earth / sponge composite material (this surface is the front side) and evenly dripped until it was completely dripped. The surface containing the bismuth chloride solution, polyaniline and diatomaceous earth was then directly exposed to water vapor for fumigation. After fumigation for 1 hour, 40 mL of deionized water was dripped dropwise onto the composite membrane material at 25°C and waited for 20 minutes to allow the bismuth chloride to be fully hydrolyzed into bismuth oxychloride. Finally, the bismuth oxychloride / polyaniline / diatomaceous earth / sponge hierarchical composite material was dried in an oven at 40°C to obtain a bismuth oxychloride / polyaniline / diatomaceous earth / sponge hierarchical composite material. This sample was recorded as DpM / PANI-3.

[0064] Example 2

[0065] The only difference from Example 1 is that the added amount of bismuth chloride is 0.121 g, which is recorded as DpM / PANI-2.

[0066] Example 3

[0067] The only difference from Example 1 is that the added amount of bismuth chloride is 0.242 g, which is recorded as DpM / PANI-4.

[0068] Comparative Example 1

[0069] 0.05 g of sodium carboxymethyl cellulose and 0.2 g of Dp were added to 5 mL of 1 M hydrochloric acid and stirred at room temperature to dissolve to form a uniform suspension. The suspension was added dropwise to a cleaned sponge to obtain a diatomaceous earth / sponge composite material, which was recorded as a DpM sample.

[0070] Comparative Example 2

[0071] 0.05g of sodium carboxymethylcellulose and 0.2g of Dp were added to 5mL of 1M hydrochloric acid and stirred at room temperature to dissolve to form a diatomite solution. 0.195mL of aniline monomer was mixed with 2mL of ethanol to obtain an aniline monomer solution. 0.625g of ammonium persulfate was dissolved in 2mL of deionized water to obtain an ammonium persulfate solution. The diatomite solution and the aniline monomer solution were mixed and stirred until uniform, then added dropwise to the treated sponge substrate. The ammonium persulfate solution was then added dropwise. The treated sponge was then refrigerated at 4°C for 10 hours and then washed three times with ethanol and three times with deionized water to remove APS and oligoaniline. Finally, the sample was dried in an oven at 40°C to obtain a polyaniline / diatomite / sponge composite, designated DpM / PANI.

[0072] Comparative Example 3

[0073] The only difference from Example 1 is that the added amount of bismuth chloride is 0.061 g, which is recorded as DpM / PANI-1.

[0074] Test Case

[0075] The morphologies of the composite membrane materials of different layers prepared in Example 1, Comparative Example 1 and Comparative Example 2 and the blank control sponge were analyzed by SEM. Figure 2 The SEM image of MF shows its three-dimensional porous sponge structure ( Figure 2 a). Typical diatomaceous earth disc shapes can be seen in the DPM composite membrane material ( Figure 2 b). Figure 2 As shown in Figure c, spherical or ellipsoidal polyaniline particles can be clearly seen on the surface of the DpM / PANI composite membrane material, and many coral-like protrusions form a large area of ​​polyaniline fiber network, which indicates that polyaniline and diatomaceous earth are successfully anchored on the sponge skeleton. Figure 2 d and magnification Figure 2 As shown in e, the DpM / PANI-3 hierarchical composite membrane exhibits a distinct hierarchical structure, with a three-dimensional porous polyurethane sponge as the bottom layer, diatomaceous earth filled in it, and polyaniline and bismuth oxychloride loaded layer by layer on the sponge. Bismuth oxychloride is in the form of nanoflower microspheres composed of many irregular lamellar structures of different shapes and sizes. These microspheres give bismuth oxychloride a large specific surface area. Figure 2 As shown in Figure f, it can be seen that the three-dimensional flower-like bismuth oxychloride on the surface of the DpM / PANI-3 layered composite membrane is tightly embedded in the gaps between DpM / PANI. This growth method makes the bismuth oxychloride loading more firm and not easy to fall off.

[0076] The loading amount of bismuth oxychloride also has a significant effect on the growth state and position distribution of bismuth oxychloride microspheres. The bismuth oxychloride nanosheets attached to the surface of the DpM / PANI-1 hierarchical composite film are disordered and loose ( Figure 2 g). Bismuth oxychloride microspheres on the surface of DpM / PANI-2 hierarchical composite membrane are densely distributed in multiple layers and irregular patterns ( Figure 2 h). As the content of bismuth oxychloride nanoparticles gradually increased, the number of bismuth oxychloride microspheres formed also gradually increased. Interestingly, the number of self-assembled nanosheets in the microspheres on the surface of the DpM / PANI-3 layered composite membrane decreased, the dispersion of the bismuth oxychloride microspheres remained more uniform, and more pores on the bismuth oxychloride surface were exposed. The bismuth oxychloride microspheres on the surface of the DpM / PANI-4 layered composite membrane were more dispersed ( Figure 2 i).

[0077] The XRD ( Figure 3 a) and FT-IR spectra ( Figure 3 b) Characterization to analyze its crystal form and chemical bond structure. This demonstrated the successful growth of bismuth oxychloride nanoflower structures on the DpM / PANI sample film. Diatomaceous earth, polyaniline, and bismuth oxychloride were stably bonded together through chemical bonding, forming a structurally stable hierarchical structure. This further confirmed the successful preparation of the bismuth oxychloride / polyaniline / diatomaceous earth / sponge hierarchical composite material.

[0078] The hydrophilicity and hydrophobicity of the sample films were evaluated by testing the water contact angles of the composite membrane materials of different layers prepared in Examples 1-3 and the surface of the blank control sponge. Figure 4 As shown, the contact angle of the original blank sponge (MF) is 104.05°. After loading MF with diatomaceous earth, the contact angle reaches 31.71°, significantly improving its hydrophilicity and supporting efficient water transport and evaporation. DpM / PANI and DpM / PANI-3 exhibit excellent hydrophilicity, absorbing water droplets within 0.15 seconds of contact. This excellent hydrophilicity enables efficient and stable water evaporation and facilitates contact between pollutants and catalytically active components, accelerating their degradation.

[0079] The water evaporation performance of the different layered composite membrane materials prepared in Examples 1-3 and Comparative Examples 1-3 and the blank control sponge and the evaporation cycle stability of the layered composite membrane prepared in Example 1 were tested. Figure 5 As shown. Figure 5 As shown in a, the evaporation rate of water under one sun is 0.73 kg m -2 h -1 , 0.75kg m -2 h -1 , 1.22kg m -2 h -1 , 1.18kg m -2 h -1 , 1.16kg m -2 h-1 , 1.11kg m -2 h -1 , 1.08kg m -2 h -1 After ten cycles of light-heat water evaporation, the evaporation performance of the DpM / PANI-3 composite film remained basically unchanged (e.g. Figure 5 b), indicating that the DpM / PANI-3 composite membrane has good stability.

[0080] The photocatalytic degradation performance of the different layered composite membrane materials prepared in Examples 1-3 and Comparative Examples 1-3 and the blank control sponge were tested, and the stability of the layered composite membrane prepared in Example 1 under cyclic degradation and different initial concentrations of Rhodamine B was tested. The photocatalytic degradation test was carried out using Rhodamine B as the target pollutant and a 30W LED as the light source to characterize the photocatalytic performance of the composite membrane, such as Figure 6 As shown in Figure a, when the dosage of bismuth chloride was 0.182 g, the hierarchical composite membrane DpM / PANI-3 composite membrane had the highest Rhodamine B degradation efficiency of 95.9% within 60 min. Subsequent experiments selected the DpM / PANI-3 hierarchical composite membrane with the best performance. Figure 6 As shown in Figure b, after three degradation cycles, the degradation efficiency of the DpM / PANI-3 composite membrane can always be maintained above 80%. Figure 6 As shown in Figure c, the effect of target pollutant concentration on degradation efficiency was investigated by varying the concentration of rhodamine B to 15, 20, 25, and 30 mg / L. The DpM / PANI-3 composite membrane nearly completely degraded 15 mg / L of rhodamine B within 30 minutes of exposure. The degradation efficiencies for the other concentrations were 95.9%, 82.2%, and 57.8%, respectively, after 60 minutes of exposure. This demonstrates the excellent stability and reusability of the prepared hierarchical composite membrane.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a hierarchical composite membrane, characterized in that: The following steps are involved: (1) mixing a solution containing diatomaceous earth and a solution containing aniline monomer and applying the mixture to a porous membrane substrate, then applying an initiator to carry out a polymerization reaction, so that the surface of the porous membrane substrate is loaded with diatomaceous earth and polyaniline, thereby obtaining a polyaniline / diatomaceous earth / porous composite membrane; (2) applying a solution containing bismuth chloride to the surface of the polyaniline / diatomaceous earth / porous membrane composite material, fumigating, and then applying water to perform a hydrolysis reaction, so that the surface of the polyaniline / diatomaceous earth / porous membrane composite material is loaded with bismuth oxychloride to obtain a hierarchical composite membrane.

2. The preparation method according to claim 1, characterized in that The porous membrane substrate includes sponge, polyethylene foam or aerogel.

3. The preparation method according to claim 1, characterized in that The diatomaceous earth-containing solution comprises diatomaceous earth, sodium carboxymethyl cellulose and an acidic solution.

4. The preparation method according to claim 3, characterized in that The mass ratio of the diatomaceous earth to sodium carboxymethyl cellulose is 3-5:1; the acidic solution includes a hydrochloric acid solution; the concentration of the acidic solution is 1-5 mol / L; and the dosage ratio of the diatomaceous earth to the acidic solution is 0.03-0.05 g / mL.

5. The preparation method according to claim 1, characterized in that The solution containing aniline monomer comprises: aniline monomer and ethanol; the volume ratio of the aniline monomer to ethanol is 0.01 to 0.1:1; The volume ratio of the solution containing diatomaceous earth to the solution containing aniline monomer is 1 to 5:

1.

6. The preparation method according to claim 1, characterized in that The initiator comprises an ammonium persulfate solution; the concentration of the initiator is 0.2 to 0.5 g / mL; the volume ratio of the initiator to the aniline monomer is 8 to 12:1; the temperature of the polymerization reaction is 0 to 10° C., and the time is 8 to 12 hours.

7. The preparation method according to claim 1, characterized in that The solution containing bismuth chloride comprises: bismuth chloride and hydrochloric acid solution; the dosage ratio of the bismuth chloride to the hydrochloric acid solution is 0.06-0.13 g / mL; and the concentration of the hydrochloric acid solution is 1-5 mol / L.

8. The preparation method according to claim 1, characterized in that The fumigation is to fumigate the surface containing the bismuth chloride solution with water vapor for 1 to 1.5 hours; the dosage ratio of the bismuth chloride to water is 0.0024 to 0.006 g / mL; the temperature of the hydrolysis reaction is 18 to 25° C., and the time is 20 to 30 minutes.

9. The hierarchical composite membrane prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the hierarchical composite film according to claim 9 in solar interfacial water evaporation and photocatalytic dye degradation.

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