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

Abstract

The application provides an octadecane-loaded cellulose-based composite phase change material evaporator and a preparation method and application thereof in seawater desalination, and belongs to the fields of photo-thermal conversion materials and separation technologies. Nanocellulose and polyvinyl alcohol are mixed to prepare an aerogel, octadecane is encapsulated in the pores of the aerogel by a vacuum impregnation method to obtain a composite phase change material aerogel, and the composite phase change material aerogel is coated with a non-woven fabric loaded with polypyrrole to obtain the octadecane-loaded cellulose-based composite phase change material evaporator. The evaporator is a composite phase change material evaporator based on the coupling of interfacial evaporation and phase change energy storage, solves the problems of discontinuous evaporation and low solar energy utilization rate caused by day and night alternation, has excellent light absorption performance, good heat insulation performance and sufficient water supply and the like, can be used for seawater desalination, and has the advantages of high evaporation rate, high energy conversion efficiency, salt precipitation prevention and the like.

Description

TECHNICAL FIELD

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

[0002] Solar interface evaporation technology has shown great application potential in seawater desalination and wastewater treatment due to its zero carbon emission and low cost. In recent years, with the in-depth research in this field, researchers have carried out fine regulation and optimization for the core elements of solar interface evaporation technology, such as light absorption, water transport and heat insulation performance, and have innovatively proposed a series of strategies such as heat management and cold evaporation to improve the evaporation rate. However, this technology still faces the constraints of unstable sunlight, day and night alternation and weather changes, which leads to the inability to achieve continuous evaporation all day long, and the utilization efficiency of solar energy needs to be further improved. Therefore, it is urgent to develop a solar evaporator with continuous evaporation function to realize continuous water evaporation.

[0003] In order to overcome this limitation, efficient storage of solar radiation heat and release in the absence or less of light is an effective way to solve the problem that the solar evaporator cannot work continuously. In solar heat storage, phase change energy storage utilizes the ability of phase change materials to store or release heat energy efficiently during the solid-liquid phase change, so as to realize the continuous utilization of solar energy. By coupling interface evaporation with phase change energy storage, the problem of discontinuous evaporation caused by day and night alternation can be solved, which can improve the utilization rate of solar energy and realize continuous interface water evaporation. In addition, aerogel, as a unique material with multi-level and porous structure, has become an ideal candidate for encapsulating phase change materials due to its ultra-light weight and high specific surface area.

[0004] At present, although exciting progress has been made in phase change energy storage by using aerogel to encapsulate phase change materials, coupling interface evaporation with phase change energy storage to realize continuous interface water evaporation still faces many challenges, such as how to integrate heat management function and sufficient and stable water supply function into a single solar evaporator to prevent salt accumulation while maintaining high evaporation rate and energy conversion efficiency. Therefore, the design and manufacture of a solar evaporator for coupling interface evaporation with phase change energy storage and enhancing heat management and sufficient water supply still need further exploration. SUMMARY

[0005] To solve the above technical problems, the present application provides a cellulose-based composite phase change material evaporator loaded with octadecane and a preparation method and application thereof in seawater desalination.

[0006] To achieve the above object, the present application provides the following technical solutions:

[0007] One of the technical solutions of the present application is:

[0008] A preparation method of a cellulose-based composite phase change material evaporator loaded with octadecane, comprising the following steps:

[0009] Mixing nanocellulose and polyvinyl alcohol to obtain a nanocellulose / polyvinyl alcohol suspension, adding a catalyst and a crosslinking agent for stirring, pouring the obtained product into a mold for heating and molding, and then freeze-drying to obtain an aerogel;

[0010] In-situ growing 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, the phase change material being octadecane;

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

[0013] Further, 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 crosslinking agent is glutaraldehyde.

[0015] Further, the amount of the catalyst added in the nanocellulose / polyvinyl alcohol suspension is 7.5 mg·mL -1 , and the amount of the crosslinking agent added in the nanocellulose / polyvinyl alcohol suspension is 15 mg·mL -1 .

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

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

[0018] Dissolving polypyrrole in water, then adding ferric chloride hexahydrate to obtain a polypyrrole mixture, then adding the pretreated non-woven fabric into the polypyrrole mixture for stirring, taking out the non-woven fabric with in-situ grown polypyrrole after the stirring is completed, washing and drying to obtain the polypyrrole-loaded non-woven fabric.

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

[0020] and / or, the non-woven fabric after the pretreatment is stirred in the pyrrole mixed solution for 6h.

[0021] Further, the vacuum degree of the vacuum impregnation method is 0.07 MPa, and the treatment time is 1h.

[0022] Further, the step of coating the composite phase change material aerogel with the polypyrrole-loaded non-woven fabric specifically includes the following steps: according to the size and shape of the aerogel, the polypyrrole-loaded non-woven fabric is cut using scissors, and a certain amount of excess is reserved during the cutting process, so that the non-woven fabric can completely wrap the aerogel, and there is a certain operation space during the coating process, 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 at the same time, gently press the non-woven fabric with your hand to make it fully contact with the surface of the aerogel and exclude the air between them. 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 every part can be closely fitted. For the corner parts 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 folded or overlapped appropriately to enhance the wrapping effect of the corner parts and prevent the occurrence of leakage or loose wrapping. When the non-woven fabric completely wraps the aerogel, the bottom of the non-woven fabric is fixed using an adhesive to avoid the phenomenon of loosening or falling off.

[0023] For example, the preparation method of the octadecane-loaded cellulose-based composite phase change material evaporator proposed by the present application specifically includes the following steps:

[0024] (1) 2.5g of polyvinyl alcohol is added to 50mL of deionized water and heated to 90℃ and stirred for 2h to obtain a 5wt% polyvinyl alcohol solution, then a 4.5wt% nanocellulose solution is stirred in a homogenizer at a speed of 12000rpm for 10min, after stirring is completed, the nanocellulose solution is heated to 85℃, and the prepared polyvinyl alcohol solution is slowly added to the nanocellulose solution, the mass ratio of nanocellulose and polyvinyl alcohol is controlled to be (1-2):(1-2), and stirring is carried out at 85℃ for 1h to prepare a nanocellulose / polyvinyl alcohol suspension, then crosslinking agent glutaraldehyde (the amount added to the nanocellulose / polyvinyl alcohol suspension is 15mg·mL -1 ) and catalyst sulfuric acid (the amount added to the nanocellulose / polyvinyl alcohol suspension is 7.5mg·mL -1 ) are added, and stirring is carried out at room temperature for 6h, then the obtained mixed solution is poured into a mold, heated at 80℃ for 3h to obtain a crosslinked gel, and the gel is freeze-dried to obtain a vertically arranged aerogel;

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

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

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

[0028] The second technical scheme of the present application:

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

[0030] The third technical scheme of the present application:

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

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

[0033] (1) The evaporator of the present application uses nanocellulose as a matrix material and combines polyvinyl alcohol to prepare a porous aerogel with excellent mechanical properties, encapsulates the phase change material octadecane by a vacuum impregnation method, and tightly wraps the non-woven fabric loaded with polypyrrole as a light-heat conversion layer and a two-dimensional water transport channel, finally preparing a cellulose-based composite phase change material evaporator, which is a composite phase change material evaporator based on the coupling of interfacial evaporation and phase change energy storage, solving the problems of discontinuous evaporation and low solar energy utilization rate caused by day-night alternation.

[0034] (2) The evaporator of the present application has excellent light absorption performance, good heat insulation performance, and sufficient water supply, and can be used for seawater desalination, and has the advantages of high evaporation rate, high energy conversion efficiency, and prevention of salting-out. In addition, the preparation process of the evaporator is simple, the raw materials are cheap, environmentally friendly and easy to obtain, easy to scale up production, and environmentally friendly, which provides a new effective way for long-term, efficient and stable operation of seawater desalination, especially high-concentration seawater desalination. Attached Figure Description

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

[0036] Figure 1 The images are SEM images of the aerogels obtained in step (1) of Examples 1-3 and EDS images of the cellulose-based composite phase change material evaporator. (a)-(c) represent SEM images of aerogels formed by crosslinking under different nanocellulose / polyvinyl alcohol ratios in Examples 2, 1, and 3, respectively. (d) represents a low-magnification SEM image of the crosslinked gel in step (1) of Example 1. (e) represents a SEM image of the composite phase change material aerogel obtained in step (3) of Example 1. (f) represents a SEM image of the vertically arranged aerogels in step (1) of Example 1. (g) represents a SEM image of the original nonwoven fabric in step (2) of Example 1. (h) represents a SEM image of the nonwoven fabric loaded with polypyrrole in step (2) of Example 1. (i) represents the EDS spectrum of the nonwoven fabric loaded with polypyrrole in step (2) of Example 1.

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

[0038] Figure 3 The results of the wettability test of the nonwoven fabric loaded with polypyrrole and the pretreated nonwoven fabric in Example 1 are shown.

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

[0040] Figure 5 The energy storage test results are for the evaporators of pure water, Example 1 (with phase change), Comparative Example 1 (without phase change), Comparative Example 2 (without load), and the control group.

[0041] Figure 6 The evaporation performance test results of the evaporator of the cellulose-based composite phase change material loaded with octadecane prepared in Example 1 are as follows: (a) Steam generation rate under different salinities within 60 min; (b) Evaporation rate and energy conversion efficiency under different salinities within 60 min; (c) Ion concentration in water vapor before and after simulated seawater evaporation.

[0042] Figure 7 The results show the evaporation separation performance of the evaporator of the cellulose-based composite phase change material loaded with octadecane prepared in Example 1.

[0043] Figure 8Schematic diagram of day and night alternation evaporation principle of the octadecane-loaded cellulose-based composite phase change material evaporator of the present application. DETAILED DESCRIPTION

[0044] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be illustrative of certain aspects, features and embodiments of the present application and are not intended to limit the present application, which should be understood in its broader aspects.

[0045] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, where particular ranges of values are given, understand that each intervening value, to the upper or lower limit of the ranges is also specifically included. Each smaller range that falls within the broader ranges is also specifically included in the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0046] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in further detail the methods and / or materials associated with the documents. In the event of conflict between the present specification and any incorporated document, the present specification controls.

[0047] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0048] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0049] The embodiment of the present application provides a preparation method of an octadecane-loaded cellulose-based composite phase change material evaporator, which comprises the following steps:

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

[0051] The polypyrrole is in-situ grown on the pretreated non-woven fabric to obtain a polypyrrole-loaded non-woven fabric;

[0052] The phase change material is octadecane.

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

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

[0055] In the preferred embodiment of the present application, the catalyst is sulfuric acid and the crosslinking agent is glutaraldehyde.

[0056] In the preferred embodiment of the present application, the catalyst is added to the nanocellulose / polyvinyl alcohol suspension in an amount of 7.5 mg·mL -1 , and the crosslinking agent is added to the nanocellulose / polyvinyl alcohol suspension in an amount of 15 mg·mL -1 .

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

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

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

[0060] In the preferred embodiment of the present application, the vacuum degree of the vacuum impregnation method is 0.07 MPa, and the treatment time is 1 h.

[0061] During the vacuum impregnation process, the high porosity and porous structure of the aerogel provide channels and spaces for the penetration of octadecane, which, under the driving of pressure difference, promotes the active filling of octadecane into the interior of the aerogel by capillary action, and the two cooperate to realize the efficient filling of octadecane in the pores of the aerogel.

[0062] In the preferred embodiment of the present application, the composite phase change material aerogel is coated with polypyrrole-loaded non-woven fabric, which specifically includes the following steps: according to the size and shape of the aerogel, polypyrrole-loaded non-woven fabric is cut using scissors. During the cutting process, a certain amount of excess material is reserved, so that the non-woven fabric can completely wrap the aerogel, and there is a certain operating space during the coating process, which facilitates 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 hand to make it fully contact with the surface of the aerogel and eliminate the air between them. During the fitting process, the other edges of the non-woven fabric are wrapped around the surface of the aerogel in turn to ensure that each part is tightly fitted. For the corner parts 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 folded or overlapped appropriately to enhance the coating effect at the corners and prevent leakage or poor coating. When the non-woven fabric completely wraps the aerogel, the bottom of the non-woven fabric is fixed using adhesive to avoid loosening or falling off.

[0063] The octadecane-loaded cellulose-based composite phase change material evaporator proposed in the embodiments of the present application realizes efficient utilization of solar energy and evaporation continuity through material selection and structure optimization. Specifically, nanocellulose, due to its high specific surface area, biodegradability and excellent mechanical properties, forms a three-dimensional network skeleton with polyvinyl alcohol through glutaraldehyde crosslinking, and 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 high loading space for the phase change material, but also enhances the encapsulation efficiency through capillary action, while reducing the negative effects of volume change during the phase change.

[0064] The vacuum impregnation method encapsulates octadecane in the pores of the aerogel, and uses its high phase change latent heat to realize heat storage and release. During the day, part of the solar energy absorbed by the photothermal layer is used for immediate evaporation, and the remaining heat is stored in the form of latent heat by octadecane; at night, the phase change material solidifies and releases heat, continuously driving evaporation, effectively solving the problem of discontinuity between day and night. In addition, the low thermal conductivity of the aerogel can inhibit the loss of heat to the environment, improving energy utilization efficiency.

[0065] The polypyrrole-loaded non-woven fabric as a functional layer has a dual role: on the one hand, polypyrrole realizes efficient photo-thermal conversion in a wide spectral range (especially in the near-infrared region) through π-π conjugated structure, and its in-situ growth process ensures close combination with non-woven fabric fibers, avoiding falling off; on the other hand, the non-woven fabric forms a two-dimensional water transport channel after hydrophilic modification, and the capillary force of the micron-sized pores between the fibers realizes rapid transport of water, while the increased surface roughness helps to expand the evaporation interface. This double-layer structure separates the photo-thermal conversion region and the evaporation surface in space, reduces heat convection loss, and realizes local heat focusing.

[0066] Therefore, the octadecane-loaded cellulose-based composite phase change material evaporator prepared in the embodiment of the present application synergizes phase change energy storage of aerogel, light-heat conversion of polypyrrole and 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 embodiment of the present application refers to 25 DEG C.

[0068] The technical solutions of the present application are further described below through examples.

[0069] Example 1

[0070] The preparation method of the octadecane-loaded cellulose-based composite phase change material evaporator specifically includes the following steps:

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

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

[0073] (3) The phase change material octadecane is introduced into the pores of the aerogel prepared above by capillary action under vacuum at a vacuum degree of 0.07 MPa, and a composite phase change material aerogel is formed after 1 h of impregnation treatment. 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 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 and polyvinyl alcohol is controlled to be 1:2.

[0077] Example 3

[0078] The same as Example 1, except that the mass ratio of nanocellulose and 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:

[0081] (1) 2.5 g of polyvinyl alcohol is added to 50 mL of deionized water and heated to 90°C for 2 h to obtain a 5 wt% polyvinyl alcohol solution. Then, a 4.5 wt% nanocellulose solution is stirred in a homogenizer at a speed of 12000 rpm for 10 min. After stirring, the nanocellulose solution is heated to 85°C, and the prepared polyvinyl alcohol solution is slowly added to the nanocellulose solution, with the mass ratio of nanocellulose and polyvinyl alcohol controlled to be 1:1. The mixture is stirred at 85°C for 1 h to prepare a nanocellulose / polyvinyl alcohol suspension. Then, a crosslinking agent glutaraldehyde (added in an amount of 15 mg·mL -1 ) and a catalyst sulfuric acid (added in an amount of 7.5 mg·mL -1 ) are added to the nanocellulose / polyvinyl alcohol suspension, and the mixture is stirred at room temperature for 6 h. Then, the obtained mixture is poured into a mold and heated at 80°C for 3 h to obtain a crosslinked gel. The gel is freeze-dried to obtain a vertically aligned aerogel.

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

[0083] (3) The aerogel prepared in step (1) is coated with the 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 75000) is 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.) is stirred in a homogenizer at a speed of 12000 rpm for 10 min. After stirring is completed, the nanocellulose solution is heated to 85°C, and the prepared polyvinyl alcohol solution is slowly added dropwise to the nanocellulose solution. The mass ratio of nanocellulose to polyvinyl alcohol is controlled to be 1:1, and stirring is carried out at 85°C for 1 h to prepare a nanocellulose / polyvinyl alcohol suspension. Then, a crosslinking agent glutaraldehyde (added amount in the nanocellulose / polyvinyl alcohol suspension is 15 mg·mL -1 ) and a catalyst sulfuric acid (concentration is 18 mol / L) (added amount in the nanocellulose / polyvinyl alcohol suspension is 7.5 mg·mL -1 ) are added to the nanocellulose / polyvinyl alcohol suspension, and stirring is carried out at room temperature for 6 h. Then, the obtained mixed solution is poured into a mold, heated at 80°C for 3 h to obtain a crosslinked gel, and the gel is freeze-dried to obtain a vertically arranged aerogel;

[0087] (2) The original non-woven fabric is washed with deionized water and anhydrous ethanol to obtain a pretreated non-woven fabric.

[0088] (3) By vacuum impregnation method, under the vacuum state of 0.07 MPa, the phase change material octadecane is introduced into the pores of the prepared aerogel by capillary action. After 1 h of impregnation treatment, 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 non-woven fabric after pretreatment is used to coat the composite phase change material aerogel to obtain a cellulose-based composite phase change material evaporator loaded with octadecane.

[0090] Performance test

[0091] I. SEM and EDS test

[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 Figure 1 , in which (a)-(c) respectively represent the SEM images of the surface of the aerogel cross-linked at different ratios of nanocellulose / polyvinyl alcohol in Examples 2, 1, 3, respectively. It can be seen that the aerogel with a mass ratio of 1:1 (Example 1) presents a highly interconnected and uniformly distributed network structure. In contrast, the network structure of the aerogel with a ratio of 2:1 (Example 3) is relatively loose, while the aerogel with a ratio of 1:2 (Example 2) also has a porous network structure, but its homogeneity has decreased, showing an uneven network structure. Figure 1 , in which (d) represents the low magnification SEM image of the gel cross-linked in step (1) of Example 1, and (f) represents the SEM image of the vertically arranged aerogel in step (1) of Example. The uniform porous network structure of the aerogel with a ratio of 1:1 (Example 1) is further confirmed, and it has vertically arranged pores Figure 1 , (f)). Therefore, the optimal mass ratio of nanocellulose / polyvinyl alcohol is 1:1. In addition, Figure 1 , (e) is the SEM image of the composite phase change material aerogel obtained in step (3) of Example 1. It can be observed that the rough pore walls, as well as the uniformly distributed protrusions and blocky substances, indicate that octadecane has been 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 exhibits a smooth surface, while after loading of polypyrrole, the non-woven fabric is covered with polypyrrole nanoparticles Figure 1 , (h)). In addition, Figure 1 , (i) is the EDS spectrum of the non-woven fabric loaded with polypyrrole in step (2) of Example 1. The presence of C, O, and N elements is shown in the figure, and these elements exhibit a uniform distribution in the image, further confirming that polypyrrole has been successfully loaded on the non-woven fabric.

[0093] II. 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 5h, and then placed on filter paper to observe whether there was leakage of octadecane. The photos before and after the treatment are shown in Figure 2(a) in the middle.

[0096] The evaporator of the cellulose-based composite phase change material loaded with octadecane prepared in Example 1 was added to water and continuously sonicated for 30 minutes. The presence of any detachment was then observed. Photos before and after treatment are shown below. Figure 2 (b) in the middle.

[0097] according to Figure 2 It can be seen that after the evaporator of cellulose-based composite phase change material 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 petri dish; comparing the optical photographs before and after the evaporator treatment, no peeling of the polypyrrole coating occurred, and there were no signs of damage to the sample.

[0098] 2. Wetting test

[0099] Contact angle test of water in air: The nonwoven fabric loaded with polypyrrole prepared in Example 1 and the pretreated nonwoven fabric in Example 1 were placed horizontally on the contact angle measuring instrument, and 4 μL of water was taken for measurement. The results are shown in the figure. Figure 3 In the diagram, the nonwoven fabric represents the pre-treated nonwoven fabric. According to... Figure 3 The comparison shows that both the nonwoven fabric and the nonwoven fabric loaded with polypyrrole achieved complete water penetration within 0.08s, exhibiting super hydrophilicity, indicating that the loading of polypyrrole has no effect on the hydrophilicity of the nonwoven fabric.

[0100] 3. Light absorption performance test

[0101] The polypyrrole-loaded nonwoven fabric prepared in Example 1 was cut into 3cm × 3cm pieces, and its light absorption performance in the wavelength range of 200-2500nm was tested using a UV-VIS-NIR ultraviolet spectrometer. The test results are as follows. Figure 4 As shown, nonwoven photothermal conversion materials loaded with polypyrrole exhibit 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, and the cellulose-based evaporators prepared in Comparative Examples 1 and 2 were respectively placed in open containers (30mm × 30mm × 80mm). Irradiation experiments were conducted using a xenon lamp to simulate sunlight, and the temperature change of the evaporation surface was monitored in real time using an infrared thermal imager. A pure water group was set up as a control. The energy storage performance test results are shown in […]. Figure 5, where no phase change represents Comparative Example 1, phase change represents Example 1, and no loading represents Comparative Example 2. It can be seen that the surface temperature of the cellulose-based composite phase change material evaporator of Example 1 reached 40.8℃ after 1h of continuous light, showing a strong light-heat conversion capability. In addition, after 1h 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 1h of turning off the light source, the surface temperature of the cellulose-based composite phase change material evaporator was still 25.7℃, which was higher than the room temperature. The cellulose-based evaporator without composite phase change material of Comparative Example 1 returned to room temperature within 10min of turning off the light, which indicates that the cellulose-based composite phase change material evaporator prepared in the present application has excellent energy storage capacity.

[0104] 5. Evaporation performance test

[0105] The octadecane-loaded cellulose-based composite phase change material evaporator prepared in Example 1 was placed in an open container (30mm x 30mm x 80mm), and a xenon lamp was used to simulate a sunlight source for light irradiation experiments. An electronic balance was used to monitor the real-time change in water evaporation mass, and an infrared thermal imager was used to monitor the real-time change in evaporation surface temperature. The irradiation distance was adjusted so that the light power density was 1kw / m -2 The steam generation rate, evaporation rate and energy conversion efficiency of the evaporator within 60min were tested under the conditions of a sodium chloride solution with a concentration of 3.5wt%, 5wt%, 10wt%, 15wt% and 20wt% respectively, and pure water was used as a control (pure water). The ion concentration in the water vapor before and after evaporation of the simulated seawater (sodium ion, magnesium ion, potassium ion, calcium ion concentrations: 10000mg / L, 6969mg / L, 382mg / L, 393mg / L) was determined, and the results are shown in Figure 6 , where (a) is the steam generation rate under different salinities within 60min, (b) is the evaporation rate and energy conversion efficiency under different salinities within 60min, and (c) is the ion concentration in the water vapor before and after evaporation of the simulated seawater. It can be seen that the steam generation rate of the cellulose-based composite phase change material evaporator did not change significantly, and a relatively high evaporation rate (2.22kg·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 -1The corresponding conversion rates were (96.04%, 94.14%, 93.60%, 90.62%, 87.47%, 85.28%). This demonstrates that the integrated steam generator maintains a high evaporation rate not only in low-concentration seawater (pure water, 3.5 wt%) but also in high-concentration seawater (5 wt%, 10 wt%, 15 wt%, 20 wt%) conditions, greatly expanding the application range of interfacial evaporation. Furthermore, ion concentration measurements before and after ion evaporation showed that the ion concentration in the collected water vapor after evaporation was lower than the World Health Organization (WHO) drinking water ion concentration standards.

[0106] 6. Evaporation separation performance test

[0107] The evaporator of the cellulose-based composite phase change material loaded with octadecane prepared in Example 1 was placed in an open container (30mm×30mm×80mm). A light irradiation experiment was conducted using a xenon lamp to simulate sunlight. The change in water evaporation mass was monitored in real time using an electronic balance. The irradiation distance was adjusted to achieve a light power density of 1 kW / m². -2 The test solution was a 3.5 wt% sodium chloride solution. The test time was 1 hour per day, with 10 consecutive measurements. The test results are shown below. Figure 7 As can be seen, the evaporator of Example 1 was able to maintain a high steam generation rate throughout the 10-cycle test, which provides a basis for the practical application of interfacial evaporation.

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

[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 variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a cellulose-based composite phase change material evaporator loaded with octadecane, characterized by, comprising the following steps: mixing nanocellulose and polyvinyl alcohol to obtain a nanocellulose / polyvinyl alcohol suspension, adding a catalyst and a crosslinking agent to stir, heating the obtained product to form, and then freeze-drying to obtain an aerogel; dissolving pyrrole in water, then adding ferric chloride hexahydrate to obtain a pyrrole mixture, then adding the pretreated non-woven fabric into the pyrrole mixture to stir, taking out the non-woven fabric after stirring and washing and drying 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, the phase change material being octadecane; coating the composite phase change material aerogel with the polypyrrole-loaded non-woven fabric to obtain the octadecane-loaded cellulose-based composite phase change material evaporator.

2. The method for preparing the cellulose-based composite phase change material evaporator supported on 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 crosslinking agent is glutaraldehyde.

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

4. The method for preparing the cellulose-based composite phase change material evaporator supported on 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 supported on octadecane according to claim 1, characterized in that, The amount ratio of pyrrole, ferric chloride hexahydrate and water in the pyrrole mixture is 0.25 mL:0.075 mol:150 mL.

6. The method for preparing the cellulose-based composite phase change material evaporator supported on octadecane according to claim 1, characterized in that, The pretreated non-woven fabric is stirred in the pyrrole mixture for 6 h.

7. The method for preparing the cellulose-based composite phase change material evaporator supported on octadecane according to claim 1, characterized in that, The vacuum degree of the vacuum impregnation method is 0.07 MPa, and the treatment time is 1 h.

8. An octadecane-loaded cellulose-based composite phase change material evaporator prepared by the preparation method of any one of claims 1-7.

9. Use of the octadecane-loaded cellulose-based composite phase change material evaporator of claim 8 in seawater desalination.

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