Octadecane-loaded cellulose-based composite phase change material evaporator, preparation method thereof and application of octadecane-loaded cellulose-based composite phase change material evaporator in seawater desalination

Abstract

The invention provides an octadecane-loaded cellulose-based composite phase change material evaporator as well as a preparation method and application thereof in seawater desalination, and belongs to the field of photo-thermal conversion materials and the technical field of separation. Nano cellulose and polyvinyl alcohol are mixed to prepare aerogel, octadecane is packaged in pores of the aerogel through a vacuum impregnation method to obtain composite phase change material aerogel, the composite phase change material aerogel is coated with polypyrrole-loaded non-woven fabric, and the octadecane-loaded cellulose-based composite phase change material evaporator is obtained. The evaporator is a composite phase change material evaporator based on interface evaporation and phase change energy storage coupling, solves the problems of discontinuous evaporation, low solar energy utilization rate and the like caused by day and night replacement, has the characteristics of excellent light absorption performance, good heat insulation performance, sufficient water supply and the like, can be used for seawater desalination, and has a wide application prospect. And the device has the advantages of high evaporation rate, high energy conversion efficiency, salting-out prevention and the like.

Description

Technical Field

[0001] The present invention belongs to the field of photothermal conversion materials and separation technology, and in particular relates to an octadecane-loaded cellulose-based composite phase change material evaporator, a preparation method thereof, and application in seawater desalination. Background Art

[0002] Solar interfacial evaporation technology has shown great application potential in the fields of seawater desalination and sewage treatment due to its advantages such as zero carbon emissions and low cost. In recent years, with the deepening of research in this field, researchers have carried out fine-tuning and optimization of the core elements of solar interfacial evaporation technology, such as light absorption, water transmission and thermal insulation performance, and have innovatively proposed a series of strategies such as thermal management and cold evaporation to increase the evaporation rate. However, this technology is still constrained by natural factors such as unstable sunlight, day and night alternation and weather changes, which makes it impossible to achieve continuous evaporation around the clock, and the efficiency of solar energy utilization needs to be further improved. Therefore, it is urgent to develop a solar evaporator with continuous evaporation function to achieve continuous water evaporation.

[0003] In order to overcome this limitation, efficiently storing the heat from solar radiation and releasing it when there is no light or little light is an effective way to solve the problem of the solar evaporator not being able to work continuously. In solar thermal storage, phase change energy storage uses phase change materials to efficiently store or release heat energy during the solid-liquid phase change process, thereby realizing the continuous use of solar energy. By coupling interfacial evaporation with phase change energy storage, the current problem of discontinuous evaporation caused by the alternation of day and night can be solved, and the continuous interfacial water evaporation can be enhanced while improving the utilization rate of solar energy. In addition, aerogel, as a unique material with a multi-level porous structure, stands out as an ideal candidate matrix for encapsulating phase change materials due to its ultra-light weight and extremely high specific surface area.

[0004] Although exciting progress has been made in phase change energy storage by utilizing aerogels to encapsulate phase change materials, coupling interfacial evaporation with phase change energy storage to achieve enhanced continuous interfacial water evaporation still faces many challenges. For example, integrating thermal management and sufficient and stable water supply into a single solar evaporator to prevent salt accumulation while maintaining high evaporation rates and energy conversion efficiency remains a significant challenge. Therefore, the design and fabrication of solar evaporators that couple interfacial evaporation with phase change energy storage and enhance thermal management and sufficient water supply still require further exploration. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes an octadecane-loaded cellulose-based composite phase change material evaporator, a preparation method thereof, and an application thereof in seawater desalination.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

[0008] A method for preparing an octadecane-loaded cellulose-based composite phase change material evaporator comprises the following steps:

[0009] Nanocellulose and polyvinyl alcohol are mixed to obtain a nanocellulose / polyvinyl alcohol suspension, a catalyst and a cross-linking agent are added and stirred, the obtained product is poured into a mold and heated to form, and then freeze-dried to obtain an aerogel;

[0010] In situ growth of polypyrrole on the pretreated non-woven fabric to obtain a polypyrrole-loaded non-woven fabric;

[0011] Encapsulating a phase change material in the pores of the aerogel by a vacuum impregnation method to obtain a composite phase change material aerogel, wherein the phase change material is octadecane;

[0012] The composite phase change material aerogel is coated with the polypyrrole-loaded non-woven fabric to obtain the cellulose-based composite phase change material evaporator loaded with octadecane.

[0013] Furthermore, the mass ratio of nanocellulose to polyvinyl alcohol in the nanocellulose / polyvinyl alcohol suspension is (1-2): (1-2);

[0014] And / or, the catalyst is sulfuric acid, and the cross-linking agent is glutaraldehyde.

[0015] Furthermore, the amount of the catalyst added to the nanocellulose / polyvinyl alcohol suspension was 7.5 mg·mL -1 The amount of the crosslinking agent added to the nanocellulose / polyvinyl alcohol suspension is 15 mg·mL -1 .

[0016] Furthermore, the original non-woven fabric is washed with deionized water and anhydrous ethanol in succession to obtain the pretreated non-woven fabric.

[0017] Furthermore, in situ growth of pyrrole on the pretreated non-woven fabric comprises the following steps:

[0018] Pyrrole is dissolved in water, and then ferric chloride hexahydrate is added to obtain a pyrrole mixed solution. Subsequently, the pretreated non-woven fabric is added to the pyrrole mixed solution and stirred. After the stirring is completed, the non-woven fabric with in-situ polypyrrole growth is taken out, washed, and dried to obtain the polypyrrole-loaded non-woven fabric.

[0019] Furthermore, the ratio of pyrrole, ferric chloride hexahydrate and water in the pyrrole mixture is 0.25 mL: 0.075 mol: 150 mL;

[0020] And / or, the pretreated non-woven fabric is stirred in the pyrrole mixture for 6 hours.

[0021] Furthermore, the vacuum degree of the vacuum impregnation method is 0.07 MPa, and the processing time is 1 hour.

[0022] Furthermore, the composite phase change material aerogel is coated with the non-woven fabric loaded with polypyrrole, which specifically includes the following steps: according to the size and shape of the aerogel, the non-woven fabric loaded with polypyrrole is cut with scissors. During the cutting process, a certain margin should be reserved so that the non-woven fabric can completely wrap the aerogel and there is a certain operating space when wrapping, which is convenient for close fitting and fixing. Then, starting from the top of the aerogel, the non-woven fabric is slowly laminated to the surface of the aerogel, while gently pressing the non-woven fabric with the hand so that it is in full contact with the surface of the aerogel and the air between them is excluded. During the laminating process, the other edges of the non-woven fabric are wrapped to the surface of the aerogel in turn to ensure that each part can fit closely. For the corners of the aerogel, special attention should be paid to the wrapping method of the non-woven fabric. The edges of the non-woven fabric can be appropriately folded or overlapped to enhance the coating effect at the corners to prevent leakage or lax coating. After the non-woven fabric completely wraps the aerogel, an adhesive is used to fix the bottom of the non-woven fabric to avoid loosening or falling off.

[0023] For example, the method for preparing an octadecane-loaded cellulose-based composite phase change material evaporator proposed in the present invention specifically comprises the following steps:

[0024] (1) 2.5 g of polyvinyl alcohol was added to 50 mL of deionized water and heated to 90° C. and stirred for 2 h to obtain a 5 wt% polyvinyl alcohol solution. Then, a nanocellulose solution with a concentration of 4.5 wt% was stirred in a homogenizer at a speed of 12,000 rpm for 10 min. After stirring, the nanocellulose solution was heated to 85° C. and the prepared polyvinyl alcohol solution was slowly added dropwise to the nanocellulose solution. The mass ratio of nanocellulose to polyvinyl alcohol was controlled to be (1-2): (1-2), and stirred at 85° C. for 1 h to prepare a nanocellulose / polyvinyl alcohol suspension. Then, a crosslinking agent glutaraldehyde was added to the nanocellulose / polyvinyl alcohol suspension (the amount added to the nanocellulose / polyvinyl alcohol suspension was 15 mg·mL -1 ) and the catalyst sulfuric acid (added in the nanocellulose / polyvinyl alcohol suspension at a concentration of 7.5 mg mL -1 ) and stirred at room temperature for 6 h, after which the resulting mixed solution was poured into a mold and heated at 80 ° C for 3 h to obtain a cross-linked gel, which was then freeze-dried to obtain a vertically aligned aerogel;

[0025] (2) The original non-woven fabric was washed with deionized water and anhydrous ethanol to obtain a pretreated non-woven fabric, 0.25 mL of pyrrole was dissolved in 150 mL of deionized water, and then 0.075 mol of ferric chloride hexahydrate was added to the above solution, and stirred in an ice-water bath for 30 minutes to obtain a pyrrole mixture. The pretreated non-woven fabric was added to the pyrrole mixture and stirred for 6 hours. The non-woven fabric with in-situ polypyrrole growth was taken out and repeatedly washed with deionized water and dried at 60°C to obtain a non-woven fabric loaded with polypyrrole;

[0026] (3) By vacuum impregnation, under vacuum conditions (vacuum degree of 0.07 MPa), the phase change material octadecane was introduced into the pores of the aerogel prepared above by capillary action, and the impregnation treatment was performed for 1 h to form a composite phase change material aerogel, and the composite phase change material aerogel sample was placed on filter paper to remove excess octadecane on the surface;

[0027] (4) The composite phase change material aerogel is coated with a non-woven fabric loaded with polypyrrole to obtain a cellulose-based composite phase change material evaporator loaded with octadecane.

[0028] The second technical solution of the present invention:

[0029] An octadecane-loaded cellulose-based composite phase change material evaporator prepared by the preparation method.

[0030] The third technical solution of the present invention:

[0031] An application of the octadecane-loaded cellulose-based composite phase change material evaporator in seawater desalination.

[0032] Compared with the prior art, the present invention has the following advantages and technical effects:

[0033] (1) The evaporator of the present invention uses nanocellulose as a matrix material and combines it with polyvinyl alcohol to prepare a porous aerogel with excellent mechanical properties. The phase change material octadecane is encapsulated by a vacuum impregnation method, and is tightly wrapped with a non-woven fabric loaded with polypyrrole as a light-to-heat conversion layer and a two-dimensional moisture transmission channel. Finally, a cellulose-based composite phase change material evaporator is prepared. The prepared evaporator is a composite phase change material evaporator based on the coupling of interface evaporation and phase change energy storage, which solves the problems of discontinuous evaporation caused by the alternation of day and night and low solar energy utilization.

[0034] (2) The evaporator of the present invention has excellent light absorption performance, good thermal insulation performance, and sufficient water supply, and can be used for seawater desalination. It also has advantages such as high evaporation rate, high energy conversion efficiency, and prevention of salt precipitation. In addition, the evaporator has a simple preparation process, inexpensive and environmentally friendly raw materials, easy scalable production, and environmentally friendly features, providing a new and effective approach for the long-term, efficient, and stable operation of seawater desalination, especially high-concentration seawater desalination. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 The figures are SEM images of the aerogels obtained in steps (1) of Examples 1-3 and EDS images of the cellulose-based composite phase change material evaporator, wherein (a)-(c) represent SEM images of the aerogels cross-linked at different nanocellulose / polyvinyl alcohol ratios in Examples 2, 1, and 3, respectively, (d) represents a low-magnification SEM image of the cross-linked gel in step (1) of Example 1, (e) is an SEM image of the composite phase change material aerogel obtained in step (3) of Example 1, (f) represents an SEM image of the vertically arranged aerogel in step (1) of Example 1, (g) is an SEM image of the original non-woven fabric in step (2) of Example 1, (h) is an SEM image of the polypyrrole-loaded non-woven fabric in step (2) of Example 1, and (i) is an EDS spectrum of the polypyrrole-loaded non-woven fabric in step (2) of Example 1;

[0037] Figure 2 The stability test results of the cellulose-based composite phase change material evaporator loaded with octadecane prepared in Example 1 are shown in Figures 1 and 2. (a) shows the photos before and after drying, and (b) shows the photos before and after ultrasonic treatment.

[0038] Figure 3 The wettability test results of the polypyrrole-loaded non-woven fabric and the pretreated non-woven fabric in Example 1 are shown;

[0039] Figure 4 The light absorption performance test results of the polypyrrole-loaded non-woven fabric in Example 1;

[0040] Figure 5 Energy storage test results for pure water, the evaporator of Example 1 (with phase change), Comparative Example 1 (without phase change), Comparative Example 2 (without load), and the control group;

[0041] Figure 6 These are the evaporation performance test results of the octadecane-loaded cellulose-based composite phase change material evaporator prepared in Example 1. (a) is the steam generation rate at different salinities within 60 minutes, (b) is the evaporation rate and energy conversion efficiency at different salinities within 60 minutes, and (c) is the ion concentration in the water vapor before and after simulated seawater evaporation.

[0042] Figure 7 These are the test results of the evaporation and separation performance of the octadecane-loaded cellulose-based composite phase change material evaporator prepared in Example 1.

[0043] Figure 8This is a schematic diagram of the day and night alternating evaporation principle of the cellulose-based composite phase change material evaporator loaded with octadecane according to the present invention. DETAILED DESCRIPTION

[0044] 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.

[0045] 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.

[0046] 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.

[0047] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0048] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0049] The embodiment of the present invention provides a method for preparing an octadecane-loaded cellulose-based composite phase change material evaporator, comprising the following steps:

[0050] Nanocellulose and polyvinyl alcohol are mixed to obtain a nanocellulose / polyvinyl alcohol suspension, a catalyst and a cross-linking agent are added and stirred, the obtained product is poured into a mold and heated to form, and then freeze-dried to obtain an aerogel;

[0051] In situ growth of polypyrrole on the pretreated non-woven fabric to obtain a polypyrrole-loaded non-woven fabric;

[0052] A phase change material is encapsulated in the pores of the aerogel by a vacuum impregnation method to obtain a composite phase change material aerogel, wherein the phase change material is octadecane;

[0053] A composite phase change material aerogel is coated with a non-woven fabric loaded with polypyrrole to obtain a cellulose-based composite phase change material evaporator loaded with octadecane.

[0054] In a preferred embodiment of the present invention, the mass ratio of nanocellulose to polyvinyl alcohol in the nanocellulose / polyvinyl alcohol suspension is (1-2):(1-2), such as 1:2, 1:1 or 2:1.

[0055] In a preferred embodiment of the present invention, the catalyst is sulfuric acid and the cross-linking agent is glutaraldehyde.

[0056] In a preferred embodiment of the present invention, the amount of catalyst added to the nanocellulose / polyvinyl alcohol suspension is 7.5 mg·mL -1 The amount of crosslinker added to the nanocellulose / polyvinyl alcohol suspension was 15 mg·mL -1 .

[0057] In a preferred embodiment of the present invention, the original non-woven fabric is washed with deionized water and anhydrous ethanol in sequence to obtain the pretreated non-woven fabric.

[0058] In a preferred embodiment of the present invention, the in-situ growth of pyrrole on the pretreated non-woven fabric comprises the following steps:

[0059] Pyrrole is dissolved in water, and then ferric chloride hexahydrate is added to obtain a pyrrole mixture. Subsequently, the pretreated non-woven fabric is added to the pyrrole mixture and stirred. After the stirring is completed, the non-woven fabric with polypyrrole grown in situ is taken out, washed, and dried to obtain a non-woven fabric loaded with polypyrrole, wherein the amount ratio of pyrrole, ferric chloride hexahydrate, and water in the pyrrole mixture is 0.25 mL: 0.075 mol: 150 mL, and the pretreated non-woven fabric is stirred in the pyrrole mixture for 6 hours.

[0060] In a preferred embodiment of the present invention, the vacuum degree of the vacuum impregnation method is 0.07 MPa, and the processing time is 1 hour.

[0061] During the vacuum impregnation process, the high porosity and porous structure of the aerogel provide channels and space for the penetration of octadecane. Driven by the pressure difference, octadecane actively fills into the interior of the aerogel through capillary action. The two work together to achieve efficient filling of octadecane in the pores of the aerogel.

[0062] In a preferred embodiment of the present invention, wrapping the composite phase change material aerogel with a non-woven fabric loaded with polypyrrole specifically includes the following steps: according to the size and shape of the aerogel, use scissors to cut the non-woven fabric loaded with polypyrrole. During the cutting process, a certain margin should be reserved so that the non-woven fabric can completely wrap the aerogel and there is a certain operating space when wrapping, which is convenient for close fitting and fixing. Then, starting from the top of the aerogel, slowly fit the non-woven fabric to the surface of the aerogel, and gently press the non-woven fabric with your hands to make it fully contact with the surface of the aerogel and eliminate the air between the two. During the fitting process, the other edges of the non-woven fabric are wrapped to the surface of the aerogel in turn to ensure that each part can fit tightly. For the corners of the aerogel, special attention should be paid to the wrapping method of the non-woven fabric. The edges of the non-woven fabric can be appropriately folded or overlapped to enhance the wrapping effect at the corners to prevent leakage or loose wrapping. After the non-woven fabric completely wraps the aerogel, use an adhesive to fix the bottom of the non-woven fabric to avoid loosening or falling off.

[0063] The cellulose-based composite phase change material evaporator loaded with octadecane proposed in the embodiment of the present invention achieves efficient utilization of solar energy and evaporation continuity through coordinated optimization of material selection and structure. Specifically, due to its high specific surface area, degradability and excellent mechanical properties, nanocellulose is cross-linked with polyvinyl alcohol through glutaraldehyde to form a three-dimensional network skeleton, which enhances the covalent bond between molecular chains under sulfuric acid catalysis, giving the aerogel excellent mechanical stability and porous properties. The hierarchical pore structure formed after freeze-drying not only provides a high-load space for the phase change material, but also enhances the encapsulation efficiency through capillary action, while reducing the negative impact of volume changes during the phase change process.

[0064] Octadecane is encapsulated within the pores of the aerogel using a vacuum impregnation method, utilizing its high latent heat of phase change to achieve thermal energy storage and release. During the day, the solar energy absorbed by the photothermal layer is used for immediate evaporation, while the remaining heat is stored in the octadecane as latent heat. At night, the phase change material solidifies and releases heat, continuously driving evaporation and effectively resolving the intermittent nature of the aerogel. Furthermore, the aerogel's low thermal conductivity inhibits heat loss to the environment, improving energy efficiency.

[0065] The polypyrrole-loaded nonwoven fabric serves a dual purpose as a functional layer: First, polypyrrole achieves efficient photothermal conversion across a wide spectral range (especially in the near-infrared region) through its π-π conjugated structure. Its in-situ growth process ensures a tight bond with the nonwoven fibers, preventing them from falling off. Second, the hydrophilic modification of the nonwoven fabric creates two-dimensional water transport channels, enabling rapid water transport through capillary forces within the micron-scale pores between fibers. Meanwhile, the increased surface roughness helps expand the evaporation interface. This dual-layer structure spatially separates the photothermal conversion region from the evaporation surface, reducing heat convection losses and achieving localized heat focus.

[0066] Therefore, the cellulose-based composite phase change material evaporator loaded with octadecane prepared in the embodiment of the present invention synergizes the phase change energy storage of aerogel, the photothermal conversion of polypyrrole, and the moisture transmission of non-woven fabric, and provides an innovative solution for all-weather solar-driven water treatment through the coupling strategy of interfacial evaporation and phase change energy storage.

[0067] The room temperature in the embodiments of the present invention refers to "25°C".

[0068] The technical solution of the present invention is further illustrated by the following examples.

[0069] Example 1

[0070] A method for preparing an octadecane-loaded cellulose-based composite phase change material evaporator specifically comprises the following steps:

[0071] (1) 2.5 g of polyvinyl alcohol (Mw is 75000) was added to 50 mL of deionized water and heated to 90 ° C and stirred for 2 h to obtain a 5 wt% polyvinyl alcohol solution. Then, a 4.5 wt% nanocellulose solution (manufacturer: Guangdong Zhongshan Nanotechnology Co., Ltd.) was stirred in a homogenizer at a speed of 12000 rpm for 10 min. After stirring, the nanocellulose solution was heated to 85 ° C, and the prepared polyvinyl alcohol solution was slowly added dropwise to the nanocellulose solution. The mass ratio of nanocellulose and polyvinyl alcohol was controlled to be 1:1, and stirred at 85 ° C for 1 h to prepare a nanocellulose / polyvinyl alcohol suspension. Then, a crosslinking agent glutaraldehyde was added to the nanocellulose / polyvinyl alcohol suspension (the amount added to the nanocellulose / polyvinyl alcohol suspension was 15 mg·mL -1 ) and the catalyst sulfuric acid (concentration of 18 mol / L) (the amount added to the nanocellulose / polyvinyl alcohol suspension was 7.5 mg·mL -1 ) and stirred at room temperature for 6 h, after which the resulting mixed solution was poured into a mold and heated at 80 ° C for 3 h to obtain a cross-linked gel, which was then freeze-dried to obtain a vertically aligned aerogel;

[0072] (2) The original non-woven fabric was washed with deionized water and anhydrous ethanol to obtain a pretreated non-woven fabric, 0.25 mL of pyrrole was dissolved in 150 mL of deionized water, and then 0.075 mol of ferric chloride hexahydrate was added to the above solution, and stirred in an ice-water bath for 30 minutes to obtain a pyrrole mixture. The pretreated non-woven fabric was added to the pyrrole mixture and stirred for 6 hours. The non-woven fabric with in-situ polypyrrole growth was taken out and repeatedly washed with deionized water and dried at 60°C to obtain a non-woven fabric loaded with polypyrrole;

[0073] (3) By vacuum impregnation, under a vacuum degree of 0.07 MPa, the phase change material octadecane is introduced into the pores of the aerogel prepared above by capillary action. After impregnation treatment for 1 hour, a composite phase change material aerogel is formed, and the composite phase change material aerogel sample is placed on filter paper to remove excess octadecane on the surface;

[0074] (4) The composite phase change material aerogel is coated with a non-woven fabric loaded with polypyrrole to obtain a cellulose-based composite phase change material evaporator loaded with octadecane.

[0075] Example 2

[0076] The same as Example 1, except that the mass ratio of nanocellulose to polyvinyl alcohol is controlled to be 1:2.

[0077] Example 3

[0078] The same as Example 1, except that the mass ratio of nanocellulose to polyvinyl alcohol is controlled to be 2:1.

[0079] Comparative Example 1

[0080] The same as Example 1, except that the step of loading the phase change material on the non-woven fabric is omitted. Specifically, the following steps are performed:

[0081] (1) 2.5 g of polyvinyl alcohol was added to 50 mL of deionized water and heated to 90° C. and stirred for 2 h to obtain a 5 wt% polyvinyl alcohol solution. Then, a nanocellulose solution with a concentration of 4.5 wt% was stirred at a speed of 12,000 rpm in a homogenizer for 10 min. After stirring, the nanocellulose solution was heated to 85° C. and the prepared polyvinyl alcohol solution was slowly added dropwise to the nanocellulose solution. The mass ratio of nanocellulose to polyvinyl alcohol was controlled to be 1:1, and the solution was stirred at 85° C. for 1 h to prepare a nanocellulose / polyvinyl alcohol suspension. Then, a crosslinking agent glutaraldehyde was added to the nanocellulose / polyvinyl alcohol suspension (the amount added to the nanocellulose / polyvinyl alcohol suspension was 15 mg·mL -1 ) and the catalyst sulfuric acid (added in the nanocellulose / polyvinyl alcohol suspension at a concentration of 7.5 mg mL -1 ) and stirred at room temperature for 6 h, after which the resulting mixed solution was poured into a mold and heated at 80 ° C for 3 h to obtain a cross-linked gel, which was then freeze-dried to obtain a vertically aligned aerogel;

[0082] (2) The original non-woven fabric was washed with deionized water and anhydrous ethanol to obtain a pretreated non-woven fabric, 0.25 mL of pyrrole was dissolved in 150 mL of deionized water, and then 0.075 mol of ferric chloride hexahydrate was added to the above solution, and stirred in an ice-water bath for 30 minutes to obtain a pyrrole mixture. The pretreated non-woven fabric was added to the pyrrole mixture and stirred for 6 hours. The non-woven fabric with in-situ polypyrrole growth was taken out and repeatedly washed with deionized water and dried at 60°C to obtain a non-woven fabric loaded with polypyrrole;

[0083] (3) Wrapping the aerogel prepared in step (1) with a non-woven fabric loaded with polypyrrole to obtain a cellulose-based evaporator.

[0084] Comparative Example 2

[0085] The same as Example 1, except that the step of loading polypyrrole on the non-woven fabric is omitted, specifically:

[0086] (1) 2.5 g of polyvinyl alcohol (Mw is 75000) was added to 50 mL of deionized water and heated to 90 ° C and stirred for 2 h to obtain a 5 wt% polyvinyl alcohol solution. Then, a 4.5 wt% nanocellulose solution (manufacturer: Guangdong Zhongshan Nanotechnology Co., Ltd.) was stirred in a homogenizer at a speed of 12000 rpm for 10 min. After stirring, the nanocellulose solution was heated to 85 ° C, and the prepared polyvinyl alcohol solution was slowly added dropwise to the nanocellulose solution. The mass ratio of nanocellulose and polyvinyl alcohol was controlled to be 1:1, and stirred at 85 ° C for 1 h to prepare a nanocellulose / polyvinyl alcohol suspension. Then, a crosslinking agent glutaraldehyde was added to the nanocellulose / polyvinyl alcohol suspension (the amount added to the nanocellulose / polyvinyl alcohol suspension was 15 mg·mL -1 ) and the catalyst sulfuric acid (concentration of 18 mol / L) (the amount added to the nanocellulose / polyvinyl alcohol suspension was 7.5 mg·mL -1 ) and stirred at room temperature for 6 h, after which the resulting mixed solution was poured into a mold and heated at 80 ° C for 3 h to obtain a cross-linked gel, which was then freeze-dried to obtain a vertically aligned aerogel;

[0087] (2) washing the original non-woven fabric with deionized water and anhydrous ethanol to obtain a pretreated non-woven fabric;

[0088] (3) By vacuum impregnation, under a vacuum degree of 0.07 MPa, the phase change material octadecane is introduced into the pores of the aerogel prepared above by capillary action. After impregnation treatment for 1 hour, a composite phase change material aerogel is formed, and the composite phase change material aerogel sample is placed on filter paper to remove excess octadecane on the surface;

[0089] (4) The composite phase change material aerogel is wrapped with the pretreated non-woven fabric to obtain a cellulose-based composite phase change material evaporator loaded with octadecane.

[0090] Performance Testing

[0091] 1. SEM and EDS testing

[0092] The scanning electron microscope (SEM) image of the aerogel obtained in step (1) of Example 1-3 and the element distribution (EDS) image of the cellulose-based composite phase change material evaporator are shown in FIG. Figure 1 , where (a)-(c) represent the surface SEM images of aerogels formed by crosslinking at different nanocellulose / polyvinyl alcohol ratios in Examples 2, 1, and 3, respectively. It can be seen that the aerogel with a mass ratio of 1:1 (Example 1) exhibits a highly interconnected network structure with uniformly distributed pores. In contrast, the aerogel with a mass ratio of 2:1 (Example 3) has a looser network structure, and while the aerogel with a mass ratio of 1:2 (Example 2) also has a porous network structure, its homogeneity is reduced, exhibiting a non-uniform network structure. Figure 1 (d) shows a low-magnification SEM image of the cross-linked gel in step (1) of Example 1, and (f) shows an SEM image of the vertically aligned aerogel in step (1) of Example 1. The uniform porous network structure of the 1:1 aerogel (Example 1) is further confirmed, and has vertically aligned pores ( Figure 1 (f)), therefore, the optimal mass ratio of nanocellulose / polyvinyl alcohol is 1:1. In addition, Figure 1 (e) is an SEM image of the composite phase change material aerogel obtained in step (3) of Example 1. Rough pore walls and evenly distributed protrusions and blocky substances can be observed, indicating that octadecane is successfully loaded into the aerogel skeleton. Figure 1 (g) is the SEM image of the original non-woven fabric in step (2) of Example 1, from which it can be clearly seen that the original non-woven fabric has a smooth surface, and after polypyrrole loading, the non-woven fabric is covered with polypyrrole nanoparticles ( Figure 1 In addition, Figure 1 (i) is the EDS spectrum of the non-woven fabric loaded with polypyrrole in step (2) of Example 1. The figure shows the presence of C, O, and N elements, and these elements show a uniform distribution in the image, further confirming that polypyrrole is successfully loaded on the non-woven fabric.

[0093] 2. Evaporation performance

[0094] 1. Stability test

[0095] The cellulose-based composite phase change material evaporator loaded with octadecane prepared in Example 1 was heated in an oven at 60° C. for 5 h and then placed on filter paper to observe whether there was any octadecane leakage. The photos before and after treatment are shown in FIG. Figure 2(a) in the.

[0096] The cellulose-based composite phase change material evaporator loaded with octadecane prepared in Example 1 was added to water and ultrasonicated continuously for 30 minutes to observe whether there was any shedding phenomenon. The photos before and after treatment are shown in FIG. Figure 2 (b) in the.

[0097] according to Figure 2 It can be seen that after the cellulose-based composite phase change material evaporator loaded with octadecane was heated in an oven at 60°C for 5 hours, no leakage of liquid octadecane was observed on the filter paper of the watch glass; comparing the optical photographs of the evaporator before and after treatment, there was no shedding of the polypyrrole coating and no signs of damage to the sample.

[0098] 2. Wettability test

[0099] Contact angle test of water in air: The polypyrrole-loaded nonwoven fabric prepared in Example 1 and the nonwoven fabric pretreated in Example 1 were placed horizontally on a contact angle measuring instrument, and 4 μL of water was taken for measurement. The results are shown in FIG. Figure 3 , the non-woven fabric in the figure represents the pre-treated non-woven fabric. Figure 3 From the comparison in the figure, it can be seen that both the non-woven fabric and the non-woven fabric loaded with polypyrrole can achieve complete penetration of water droplets within 0.08s, showing super strong hydrophilicity, indicating that loading polypyrrole has no effect on the hydrophilicity of the non-woven fabric.

[0100] 3. Light absorption performance test

[0101] The polypyrrole-loaded nonwoven fabric prepared in Example 1 was cut into a size of 3 cm × 3 cm, and the light absorption performance within the wavelength range of 200-2500 nm was tested using a UV-VIS-NIR spectrometer. The test results are as follows: Figure 4 As shown: the photothermal conversion material of the non-woven fabric loaded with polypyrrole has excellent light absorption in the wavelength range of 200-2500nm, with a light absorption rate of 97.3%.

[0102] 4. Energy storage test

[0103] The cellulose-based composite phase change material evaporator loaded with octadecane prepared in Example 1, the cellulose-based evaporators prepared in Comparative Example 1 and Comparative Example 2 were placed in open containers (30 mm × 30 mm × 80 mm), and a xenon lamp was used to simulate the sunlight source for illumination experiments. The temperature change of the evaporation surface was monitored in real time using an infrared thermal imager. A pure water group was set as a control. The energy storage performance test results are shown in FIG. Figure 5, where no phase change represents comparative example 1, phase change represents embodiment 1, and no load represents comparative example 2. It can be seen that the surface temperature of the cellulose-based composite phase change material evaporator of embodiment 1 reached 40.8°C after 1 hour of continuous illumination, showing a strong light-to-heat conversion capability. In addition, after 1 hour of simulated sunlight irradiation, the light source was turned off, and the stored heat was effectively released through the crystallization of the phase change material. After the light source was turned off for 1 hour, the surface temperature of the cellulose-based composite phase change material evaporator was still 25.7°C, which was higher than the room temperature. The cellulose-based evaporator without composite phase change material in comparative example 1 returned to room temperature within 10 minutes of turning off the light, which shows that the cellulose-based composite phase change material evaporator prepared by the embodiment of the present invention has excellent energy storage capacity.

[0104] 5. Evaporation performance test

[0105] The cellulose-based composite phase change material evaporator loaded with octadecane prepared in Example 1 was placed in an open container (30 mm × 30 mm × 80 mm). A xenon lamp was used to simulate the sunlight to conduct an illumination experiment. An electronic balance was used to monitor the change in evaporation mass of the water body in real time. An infrared thermal imager was used to monitor the change in evaporation surface temperature in real time. The illumination distance was adjusted so that the light power density was 1 kW / m -2 The test was conducted under the conditions of 3.5wt%, 5wt%, 10wt%, 15wt% and 20wt% (concentration) of sodium chloride solution. The steam generation rate, evaporation rate and energy conversion efficiency of the evaporator within 60 minutes were tested. Pure water was used as a control (pure water). The ion concentrations in the water vapor before and after evaporation were measured when the test solution was simulated seawater (sodium ion, magnesium ion, potassium ion and calcium ion concentrations were 10000mg / L, 6969mg / L, 382mg / L and 393mg / L respectively). The results are shown in the figure. Figure 6 , where (a) is the steam generation rate under different salinities within 60 minutes, (b) is the evaporation rate and energy conversion efficiency under different salinities within 60 minutes, and (c) is the ion concentration in the water vapor before and after the simulated seawater evaporation. It can be seen that the steam generation rate of the cellulose-based composite phase change material evaporator has basically not changed, and it can maintain a high evaporation rate (2.22 kg·m -2 ·h -1 ,2.18kg·m -2 ·h -1 ,2.17kg·m -2 ·h -1 ,2.10kg·m -2 ·h -1 ,2.03kg·m -2 ·h -1 ,1.99kg·m -2 ·h -1), with corresponding conversion rates of (96.04%, 94.14%, 93.60%, 90.62%, 87.47%, and 85.28%). This demonstrates that the integrated steam generator maintains high evaporation rates not only with low seawater concentrations (pure water, 3.5wt%), but also with high seawater concentrations (5wt%, 10wt%, 15wt%, and 20wt%), significantly expanding the application range of interfacial evaporation. Furthermore, ion concentration measurements before and after ion evaporation indicate that the ion concentrations in the collected water vapor after evaporation are all below the World Health Organization (WHO) drinking water ion concentration standard.

[0106] 6. Evaporation separation performance test

[0107] The cellulose-based composite phase change material evaporator loaded with octadecane prepared in Example 1 was placed in an open container (30 mm × 30 mm × 80 mm). A xenon lamp was used to simulate the sunlight source for illumination experiments. An electronic balance was used to monitor the changes in the evaporation mass of the water in real time. The illumination distance was adjusted so that the light power density was 1 kW / m -2 The test liquid is 3.5wt% sodium chloride solution, the test time is 1 hour per day, and the test is repeated 10 times. The test results are shown in Figure 7 , it can be seen that during the 10 cycle tests, the evaporator of Example 1 can always maintain a high steam generation rate, which provides a basis for the practical application of interfacial evaporation.

[0108] Figure 8 This is a schematic diagram of the day-night evaporation principle of the cellulose-based composite phase change material evaporator loaded with octadecane of the present invention. The evaporator of the present invention solves the problems of discontinuous evaporation and low solar energy utilization caused by day-night alternation.

[0109] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing an octadecane-loaded cellulose-based composite phase change material evaporator, characterized in that: The following steps are involved: Nanocellulose and polyvinyl alcohol are mixed to obtain a nanocellulose / polyvinyl alcohol suspension, a catalyst and a cross-linking agent are added and stirred, the obtained product is heated and formed, and then freeze-dried to obtain an aerogel; In situ growth of polypyrrole on the pretreated non-woven fabric to obtain a polypyrrole-loaded non-woven fabric; Encapsulating a phase change material in the pores of the aerogel by a vacuum impregnation method to obtain a composite phase change material aerogel, wherein the phase change material is octadecane; The composite phase change material aerogel is coated with the polypyrrole-loaded non-woven fabric to obtain the cellulose-based composite phase change material evaporator loaded with octadecane.

2. The method for preparing the cellulose-based composite phase change material evaporator loaded with octadecane according to claim 1, characterized in that: The mass ratio of nanocellulose to polyvinyl alcohol in the nanocellulose / polyvinyl alcohol suspension is 1:(0.5-2); And / or, the catalyst is sulfuric acid, and the cross-linking agent is glutaraldehyde.

3. The method for preparing the cellulose-based composite phase change material evaporator loaded with octadecane according to claim 2, characterized in that: The amount of the catalyst added to the nanocellulose / polyvinyl alcohol suspension was 7.5 mg·mL -1 The amount of the crosslinking agent added to the nanocellulose / polyvinyl alcohol suspension is 15 mg·mL -1 .

4. The method for preparing the cellulose-based composite phase change material evaporator loaded with octadecane according to claim 1, characterized in that: The original non-woven fabric is washed with deionized water and anhydrous ethanol in sequence to obtain the pretreated non-woven fabric.

5. The method for preparing the cellulose-based composite phase change material evaporator loaded with octadecane according to claim 1, characterized in that: The in-situ growth of pyrrole on the pretreated non-woven fabric specifically comprises the following steps: Pyrrole is dissolved in water, and then ferric chloride hexahydrate is added to obtain a pyrrole mixed solution. Subsequently, the pretreated non-woven fabric is added to the pyrrole mixed solution and stirred. After stirring, the non-woven fabric is taken out and washed and dried to obtain the polypyrrole-loaded non-woven fabric.

6. The method for preparing the cellulose-based composite phase change material evaporator loaded with octadecane according to claim 5, characterized in that: The usage ratio of pyrrole, ferric chloride hexahydrate and water in the pyrrole mixture is 0.25 mL: 0.075 mol: 150 mL.

7. The method for preparing the cellulose-based composite phase change material evaporator loaded with octadecane according to claim 5, characterized in that: The pretreated non-woven fabric was stirred in the pyrrole mixture for 6 hours.

8. The method for preparing the cellulose-based composite phase change material evaporator loaded with octadecane according to claim 1, characterized in that: The vacuum degree of the vacuum impregnation method is 0.07 MPa, and the processing time is 1 hour.

9. An octadecane-loaded cellulose-based composite phase change material evaporator prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the cellulose-based composite phase change material evaporator loaded with octadecane as claimed in claim 9 in seawater desalination.

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