Preparation method and application of photothermal fiber membrane material with multi-scale structure

Abstract

The application belongs to the technical field of solar seawater desalination, and relates to a preparation method and application of a photothermal fiber membrane material with a multi-scale structure. The preparation method comprises the following steps: mixing a photothermal nanomaterial, a polymer and glutaraldehyde, and heating and reacting; then coating the mixture on a fabric infiltrated with a cross-linking solution, standing and reacting, repeatedly freezing and thawing at low temperature, drying, and engraving a channel array on the surface to obtain the photothermal fiber membrane material with the multi-scale structure; and the material can be used for solar seawater desalination. Compared with the prior art, the application has the advantages of wide raw material sources, simple preparation process, low cost and the like, and the prepared multi-scale photothermal fiber membrane material has sensitive and powerful solar light absorption and photothermal conversion performance: the material shows a solar light absorption rate of up to 96.1%, and the surface temperature of the wet material can be increased to about 40.0 DEG C within 200s, so that an efficient way for obtaining environment-friendly fresh water can be provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar seawater desalination, and relates to a preparation method and application of a photothermal fiber membrane material with a multi-scale structure. BACKGROUND

[0002] With urbanization, industrial development and population growth, energy crisis and water shortage have become serious global problems. Since there is abundant seawater on the earth, solar-driven seawater evaporation is considered as a sustainable method to alleviate freshwater shortage. Solar seawater evaporation can greatly reduce the energy consumption of existing seawater desalination technology, reduce greenhouse gas emissions in the production and engineering application process, and focus on solving the needs of the national economy and people's livelihood such as freshwater supply in China, and has indispensable ecological benefits. The key to this technology is photothermal materials with wide spectral response and high-efficiency photothermal conversion. In recent years, photothermal materials for solar seawater evaporation technology include photothermal nanoparticles, membrane materials, carbonized natural materials, hydrogels, aerogels and fiber materials. Among them, photothermal fiber membrane materials stand out due to their good flexibility, abundant sources, easy functionalization and other remarkable characteristics.

[0003] So far, a variety of photothermal fiber membrane materials and solar evaporators with them as the core have been reported. However, due to the problems of poor hydrophilicity, limited two-dimensional plane evaporation efficiency, single structure, complex preparation process and high cost of photothermal fiber membranes (such as carbon fiber materials, etc.), the photothermal seawater evaporation efficiency of photothermal fiber membrane materials is low. In view of this situation, the macro / micro structure design of photothermal fiber membranes has attracted widespread attention, and is expected to be widely used in the field of high-efficiency solar seawater desalination. At present, there is a blank in the domestic photothermal fiber membrane market, and the cost of traditional carbon fiber materials is very high, which is difficult to be applied in large scale in the solar seawater desalination industry. Therefore, it is urgent to develop multi-scale photothermal fiber membrane materials to build high-efficiency solar seawater evaporators.

[0004] Chinese patent application CN201910633916.3 discloses a kind of polyvinyl alcohol carbon nanotube gel material for photo-thermal water vapor conversion, with polyvinyl alcohol particle heating dissolved in deionized water to obtain A solution, carbon nanotube dispersion liquid is diluted with deionized water, and A solution, B solution, C solution and deionized water are mixed at room temperature after stirring and completely uniform mixing Pour into mold loading;The solution loaded with mold is frozen, thawed and repeated several times;Finally, the frozen gel is completely freeze-dried to obtain polyvinyl alcohol carbon nanotube composite gel.The beneficial effects of the present application are that the prepared polyvinyl alcohol / carbon nanotube gel material can realize efficient photo-thermal water vapor conversion.However, the macrostructure of the polyvinyl alcohol carbon nanotube gel material in the present application is seriously dependent on the mold, and it is difficult to expand in large area;In addition, the gel material only has a single microporous structure, and the steam generated inside the material is difficult to diffuse outward, and the evaporation rate is limited.Therefore, how to obtain a large-area industrial preparation, low-cost and high-evaporation-rate photo-thermal evaporation material has become a major research direction. SUMMARY

[0005] The purpose of the present application is to provide a preparation method and application of a photo-thermal fiber membrane material with a multi-scale structure, which has the advantages of wide raw material sources, simple preparation process, low cost, etc.The prepared photo-thermal fiber membrane material has sensitive and powerful solar light absorption and photo-thermal conversion performance: the material shows a solar light absorption rate as high as 96.1%, and the surface temperature of the wet material can be raised to about 40.0 °C (1.0 kW m -2 light intensity) within 200 s, which can be expected to provide an efficient way to obtain environmentally friendly freshwater.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The first aspect of the present application provides a preparation method of a photo-thermal fiber membrane material with a multi-scale structure, comprising:

[0008] Mixing photo-thermal nanomaterials with polymers and glutaraldehyde, and heating to obtain a photo-thermal hydrogel precursor solution;

[0009] Coating the photo-thermal hydrogel precursor solution on the fabric infiltrated with the cross-linking solution, standing for reaction, and then repeatedly freezing and thawing at low temperature to obtain the photo-thermal fiber membrane material after drying;

[0010] Engraving channel array on the surface of the photo-thermal fiber membrane material to obtain the photo-thermal fiber membrane material with a multi-scale structure.

[0011] Further, the mixing and heating reaction process of the photo-thermal nanomaterials, the polymers and the glutaraldehyde comprises:

[0012] The photo-thermal nanomaterial is dispersed in water at room temperature by ultrasonic, then a polymer is added and stirred at 30-100 DEG C, then glutaraldehyde is added and stirred at 30-100 DEG C, to obtain a photo-thermal hydrogel precursor solution.

[0013] Further, in the photo-thermal hydrogel precursor solution, the mass content of the polymer is 0.1-15 %, the mass content of the photo-thermal nanomaterial is 0.1-15 %, and the volume content of the glutaraldehyde is 0.1-10 %.

[0014] Further, the photo-thermal nanomaterial is selected from one or more of graphene, carbon black, carbon nanotube, polyaniline, polydopamine and polypyrrole, and the average particle size of the photo-thermal nanomaterial is 20-500 nm.

[0015] Further, the polymer is selected from one or more of polyvinyl alcohol, hydroxyethyl cellulose, sodium alginate and chitosan.

[0016] Further, during the ultrasonic dispersion, the ultrasonic power is 1-100 W, and the ultrasonic time is 1-60 min.

[0017] Further, the fabric has a layered structure, sequentially comprising a tight fabric layer, a coarse fiber supporting air layer and a tight fabric layer; and the fabric material is selected from one or more of polyester, polyamide, polyacrylonitrile, polyurethane, cotton and regenerated fiber.

[0018] Further, the cross-linking solution is selected from one or more of hydrochloric acid, boric acid and calcium chloride aqueous solution, and the concentration is 0.1-2 mol / L.

[0019] Further, the coating thickness of the photo-thermal hydrogel precursor solution on the fabric is 1-1000 µm.

[0020] Further, the channel array is obtained by laser engraving, the laser intensity is 1-80 W, the laser engraving environment is air atmosphere, and the channel diameter is 1-10 mm.

[0021] The second aspect of the application provides a use of the photo-thermal fiber membrane material with a multi-scale structure prepared by the above method in solar seawater desalination.

[0022] The main materials (commercial 3D fabric, photothermal material and synthetic polymer polymer, etc.) involved in the present application are easy to obtain in large quantities and have low cost, and the forming process of the porous gel component is free from the size limitation of the mold. The industrial application of the surface coating technology, freeze-drying technology and laser engraving technology involved in the preparation process is mature, so the material can be easily prepared on an industrial scale. This is very beneficial to the industrialization of photothermal fiber membrane materials in solar seawater desalination. On the other hand, the photothermal fiber membrane proposed in the present application has a multi-scale structure, including nanoscale hydrogel pores, micrometer-scale fiber networks and millimeter-scale vapor channel arrays. The presence of pores and fiber networks increases the photothermal evaporation interface area, which is beneficial to the generation of more steam; and the millimeter-scale vapor channel array allows the generated steam to diffuse quickly, avoiding internal steam accumulation, which can increase the evaporation rate of the photothermal fiber membrane by nearly 20%.

[0023] Compared with the prior art, the present application has the following characteristics:

[0024] 1) The present application takes advantage of the multi-scale structure to improve the internal scattering and absorption of sunlight, increase the evaporation area and enhance the steam escape, and designs a photothermal fiber membrane material with sensitive and strong sunlight absorption and photothermal conversion performance, solving the problem of low evaporation rate and evaporation efficiency of two-dimensional photothermal fiber membranes in traditional solar seawater evaporation:

[0025] The surface coating modification enhances the sunlight absorption and photothermal performance of the material, and the obtained material has a stable solar spectrum response in the range of 250-2500 nm and a sunlight absorption rate as high as 96.1%. Under the simulation of 1.0 kW m -2 of simulated sunlight, the surface temperature of the dry material can be raised to 78.1 °C within 200 s, and the surface temperature of the wet material can be raised to about 40.0 °C within 200 s.

[0026] At the same time, the multi-scale structure design greatly increases the evaporation surface area and enhances the steam diffusion, and when applied to a light-hanging type solar seawater evaporator, the evaporation rate is 2.58 kg m -2 h -1 , and the evaporation efficiency is as high as 97%, which is higher than most of the photothermal fiber membrane materials. It has important application value in promoting the development of high-efficiency solar seawater desalination. The development of this photothermal fiber membrane material can enhance China's international competitiveness in clean solar energy utilization and freshwater resource acquisition, promote major breakthroughs in solar seawater evaporation technology and related industries in China, and make important contributions to improving people's health level and quality of life.

[0027] 2) The preparation process of the present application is simple, the raw materials are widely available, and the cost is low, which can be suitable for mass production. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A structural schematic diagram of a light-heat fiber membrane material with a multi-scale structure prepared in Example 1;

[0029] Figure 2 A physical object and a scanning electron microscope image of a light-heat fiber membrane material with a multi-scale structure prepared in Example 1;

[0030] Figure 3 A solar light absorption spectrum of a light-heat fiber membrane material with a multi-scale structure prepared in Example 1;

[0031] Figure 4 A light-heat temperature rising curve of a light-heat fiber membrane material with a multi-scale structure prepared in Example 1 under simulated sunlight with an intensity of 1.0 kW m-2; -2 A light-heat temperature rising curve under simulated sunlight;

[0032] Figure 5 A front view structural schematic diagram of a solar evaporator constructed by taking a light-heat fiber membrane material with a multi-scale structure prepared in Example 1 as a core;

[0033] Figure 6 A top view structural schematic diagram of a solar evaporator constructed by taking a light-heat fiber membrane material with a multi-scale structure prepared in Example 1 as a core;

[0034] Figure 7 Evaporation efficiency and evaporation rate of a light-heat fiber membrane material with a multi-scale structure applied to solar seawater evaporation;

[0035] Marking explanation in the figure:

[0036] 1-a hydrogel coating, 2-a fabric structure, 3-a channel array, 4-a seawater tank, 5-a light-heat fiber membrane, 6-a brine collection tank. DETAILED DESCRIPTION

[0037] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0038] A preparation method of a light-heat fiber membrane material with a multi-scale structure, comprising:

[0039] The light-heat fiber membrane material is obtained by mixing light-heat nanoparticles and a polyvinyl alcohol matrix to obtain a hydrogel precursor solution, cross-linking the hydrogel precursor solution on a micron-level fiber network surface to form a nano-level pore structure, and then constructing a millimeter-level vapor channel array by laser engraving to prepare the light-heat fiber membrane material with a multi-scale structure;

[0040] Specifically, the following steps are included:

[0041] 1) Disperse the nanomaterial as a photothermal component into an aqueous solution, uniformly distribute it at room temperature by ultrasonic treatment at 1-100 W for 1-60 minutes, and obtain a photothermal nanomaterial aqueous dispersion;

[0042] Add a high-molecular polymer powder into the above dispersion, and obtain a mixed solution by stirring at 30-100 °C;

[0043] Add glutaraldehyde into the above mixed solution, and continue to stir at 30-100 °C for several hours to obtain a hydrogel coating precursor solution;

[0044] In the precursor solution, the mass fraction of the high-molecular polymer powder is 0.1-15 %, and the mass fraction of the photothermal nanomaterial is 0.1-15 %; the volume ratio of glutaraldehyde to the mixed solution is 0.1-10 %;

[0045] The photothermal nanomaterial is selected from one or more of graphene, carbon black, carbon nanotube, polyaniline, polydopamine, and polypyrrole, and has an average particle size of 20-500 nm;

[0046] The high-molecular polymer powder is selected from one or more of polyvinyl alcohol, hydroxyethyl cellulose, sodium alginate, and chitosan;

[0047] 2) Prepare a mixed solution of acetone and ethanol at a volume ratio of 1:1, and ultrasonically clean the surface of the three-dimensional structure fabric at room temperature for 1-60 minutes, and then wash with clean water and dry;

[0048] Prepare a crosslinking solution, immerse the three-dimensional structure fabric washed and dried in the crosslinking solution, take it out, wait for the excess crosslinking solution to naturally drip off, and then brush the hydrogel precursor solution on the surface of the fabric, and stand at room temperature for several minutes to allow the precursor solution to be preliminarily crosslinked on the surface of the fabric;

[0049] Further crosslink the treated sample by repeated freezing and thawing at -18 °C for 5-10 times, and finally obtain the sample by using freeze-drying technology;

[0050] The fabric has a layered structure, and sequentially comprises a tight fabric layer, a coarse fiber air support layer, and a tight fabric layer; and the fabric material is selected from one or more of polyester, polyamide, polyacrylonitrile, polyurethane, cotton, and regenerated fiber;

[0051] The crosslinking solution is selected from one or more of hydrochloric acid, boric acid, and calcium chloride aqueous solution, and has a concentration of 0.1-2 mol / L;

[0052] The coating thickness of the photothermal hydrogel precursor solution on the fabric is 1-1000 µm;

[0053] 3) Millimeter-scale vapor channel array is engraved on the surface of the photo-thermal fiber membrane by laser engraving, and a photo-thermal fiber membrane material with a multi-scale structure is obtained.

[0054] During the laser engraving process, the laser intensity is 1-80 W, the laser engraving environment is air atmosphere, and the channel diameter is 1-10 mm.

[0055] The photo-thermal fiber membrane material with a multi-scale structure prepared by the above method can be used for solar seawater desalination.

[0056] The following examples are implemented on the basis of the above technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0057] The experimental light conditions in the following examples include 1.0 kW m -2 The simulated sunlight is used, and the three-dimensional structure polyester fabric is a 3D mesh fabric product purchased from Shanghai Jet Yingtu New Material Technology Co., Ltd.

[0058] Example 1:

[0059] A photo-thermal fiber membrane material with a multi-scale structure, the preparation method thereof comprises the following steps:

[0060] S1: Preparation of photo-thermal hydrogel precursor solution:

[0061] 84 mg of carbon nanotube powder (6 wt% relative to polyvinyl alcohol) was dissolved in 20 mL of distilled water, and ultrasonic dispersion was performed at a power of 50 W for 20 minutes. 1.4 g of polyvinyl alcohol powder was added to the dispersion, and the mixture was stirred at 95 °C until the powder was completely dissolved. Then, 250 μL of glutaraldehyde was added and the mixture was continuously stirred for 6 hours to obtain a photo-thermal hydrogel precursor solution.

[0062] S2: Preparation of photo-thermal fiber membrane material:

[0063] A mixed solution was prepared by using 100 mL of acetone and 100 mL of ethanol, and the surface of the commercial three-dimensional structure polyester fabric was immersed in the mixed solution and ultrasonically cleaned at a power of 50 W for 25 minutes. After washing with clean water, the fabric was dried.

[0064] A 0.5 mol / L hydrochloric acid solution was prepared, and the above-mentioned water-washed and dried commercial three-dimensional structured polyester fabric was immersed in the hydrochloric acid solution for 10 minutes. After being taken out, the excess hydrochloric acid solution was allowed to naturally drip until no water droplets were formed. Then, a light-heat hydrogel precursor solution was brushed on the surface of the fabric, with a coating thickness of about 300-500 μm. The fabric was allowed to stand at room temperature for 15 minutes to allow the precursor solution to be preliminarily crosslinked on the surface of the fabric, and then immersed in water for 10 minutes. Then, the material was repeatedly frozen and thawed 10 times in an environment with a temperature of -18 °C, and finally freeze-dried to obtain a light-heat fiber membrane material;

[0065] S3: Construction of surface vapor channel array:

[0066] Using a laser engraving machine in an air atmosphere, the laser intensity was adjusted to 30 W, and a channel array with a diameter of 3 mm was engraved on the surface of the light-heat fiber membrane to obtain a light-heat fiber membrane material with a multi-scale structure.

[0067] As shown in Figure 1 , the light-heat fiber membrane material with a multi-scale structure of the present embodiment is composed of a hydrogel coating layer 1 and a fabric structure 2, forming a multi-scale structure of nanoscale hydrogel pores, micrometer-scale fiber networks, and millimeter-scale channel arrays 3.

[0068] As can be seen from Figure 2 a, due to the presence of carbon nanotubes in the hydrogel coating layer, the light-heat fiber membrane material with a multi-scale structure appears black, and a clear 3 mm circular channel array is visible on the surface. The SEM photos Figure 2 b-d) show that the light-heat fiber membrane material with a multi-scale structure is composed of a 400-500 μm fiber bundle network (a single polyester fiber has a size of 15-20 μm). There is porous hydrogel between the fibers, and the pore size ranges from about 500-900 nm.

[0069] In order to evaluate the light absorption performance of the light-heat fiber membrane material with a multi-scale structure, the ultraviolet-visible-near infrared diffuse reflectance absorption spectrum of the sample was tested, as shown in Figure 3 . The solar absorption rate of the material was calculated by integrating the standard solar spectrum (AM 1.5 G). The untreated 3D polyester fabric exhibits very low solar absorption performance, with a solar absorption efficiency of only 11.8% in the range of 250-2500 nm. When the surface of the 3D polyester fabric is covered with light-heat hydrogel, the light absorption performance of the material is greatly improved, with a solar absorption rate of about 97.1% in the full wavelength range of 250-2500 nm. After the surface is punched to construct vapor channels, the light-heat fiber membrane material with a multi-scale structure still exhibits a high solar absorption rate of 96.1%.

[0070] In order to test the light-heat conversion performance of the sample, a solar simulator (1.0 kW m-2 ) irradiation while recording the surface temperature of the sample with a near-infrared imager, and the results are shown in FIG. 27. The untreated 3D polyester fabric has almost no photothermal performance, with a surface temperature of 27 °C. The photothermal fiber film rapidly heats up under light irradiation, with the surface temperature reaching equilibrium at 40.6 °C within 200 s. The photothermal fiber film with a multi-scale structure has a slow increase in surface temperature at the beginning of light irradiation due to the vapor channels on the surface, which allow rapid vapor diffusion. However, the surface temperature can still increase to about 40.0 °C after 200 s. Figure 4

[0071] The photothermal fiber film with a multi-scale structure can be used to construct a light-tilted hanging seawater evaporator for solar seawater desalination. The front view of the constructed light-tilted hanging seawater evaporator is shown in FIG. 28, and the top view is shown in FIG. 29, which consists of a high water tank 4, a low water tank 6, and a photothermal fiber film 5 with a multi-scale structure. The two ends of the photothermal fiber film with a multi-scale structure are fixed to the inner wall of the water tank by a magnet, and the middle is flattened. The two water tanks are placed at different heights, with the higher tank filled with seawater and the lower tank kept empty to collect high-concentration brine during the evaporation process. Due to the combined action of capillary force, hydrophilicity, and gravity between the two water tanks, seawater is first absorbed into the photothermal fiber film with a multi-scale structure and then permeates and transfers along the fiber film, flowing from high to low. In the process of flowing, the photothermal fiber film with a multi-scale structure absorbs sunlight to generate heat and evaporate seawater, and the water vapor is condensed and collected to obtain clean freshwater, achieving the purpose of seawater desalination. Figure 5 Figure 6

[0072] To test the photothermal evaporation performance of the samples, a simulated sunlight (1.0 kW m -2 ) was used to irradiate the light-tilted hanging seawater evaporator, and the evaporation rate and corresponding evaporation efficiency of the material are shown in FIG. 30. The evaporation rate and evaporation efficiency of the 3D polyester fabric are 1.14 kg m -2 h -1 and 45.6%, respectively; the evaporation rate and evaporation efficiency of the photothermal fiber film are 2.15 kg m -2 h -1 and 94.6%, respectively; while the photothermal fiber film with a multi-scale structure exhibits an excellent evaporation rate of 2.58 kg m -2 h -1 and a high evaporation efficiency of 97.8%, which is higher than most of the current photothermal fiber film materials. Figure 7

[0073] ​​​​The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of the preferred embodiments as a number of alternatives. It is not intended to limit the application to the precise form described.

Claims

1. A method for preparing a photothermal fiber film material having a multiscale structure, characterized by, The application relates to a light-heat water gel precursor solution and a light-heat fiber membrane material. The light-heat water gel precursor solution is prepared by dispersing carbon nanotubes in water at room temperature, adding polyvinyl alcohol and stirring at 30-100 DEG C, and then adding glutaraldehyde and stirring at 30-100 DEG C. The cross-linking solution is an aqueous hydrochloric acid solution, The light-heat fiber membrane material is obtained by coating the light-heat water gel precursor solution on the fabric infiltrated with the cross-linking solution, allowing reaction, repeatedly freezing and thawing at low temperature, and drying. The cross-linking solution is an aqueous hydrochloric acid solution, 2. The method of claim 1, wherein the method further comprises the step of: The light-heat fiber membrane material with a multi-scale structure is obtained by engraving a channel array on the surface of the light-heat fiber membrane material.

3. The method of claim 2, wherein the method further comprises the step of: The channel array is obtained by laser engraving, the laser intensity is 1-80 W, the laser engraving environment is air, and the channel diameter is 1-10 mm.

4. The method of claim 1, wherein the method further comprises the step of: The mass content of the polymer in the light-heat water gel precursor solution is 0.1-15 %, the mass content of the light-heat nanomaterial is 0.1-15 %, and the volume content of the glutaraldehyde is 0.1-10 %.

5. The method of claim 1, wherein the method further comprises the step of: The average particle size of the light-heat nanomaterial is 20-500 nm.

6. The method of claim 1, wherein the method further comprises the step of: During the ultrasonic dispersion process, the ultrasonic power is 1-100 W, and the ultrasonic time is 1-60 min.

7. The method of claim 1, wherein the method further comprises the step of: The fabric has a layered structure and comprises a tight fabric layer, a coarse fiber air support layer and a tight fabric layer in sequence.

8. Use of the photothermal fiber membrane material having a multi-scale structure prepared by the method according to any one of claims 1 to 7, characterized in that, The fabric is made of one or more of polyester, polyamide, polyacrylonitrile, polyurethane, cotton and regenerated fiber. The concentration of the cross-linking solution is 0.1-2 mol / L. The coating thickness of the light-heat water gel precursor solution on the fabric is 1-1000 microns. The light-heat fiber membrane material with a multi-scale structure is used for solar seawater desalination.

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