Janus solar evaporator of self-floating sandwich structure and preparation method and application thereof

Abstract

The application provides a Janus solar energy evaporator with a self-floating sandwich structure and a preparation method thereof, and belongs to the technical field of solar energy interfacial evaporation, and solves the problems of high heat energy loss and poor interfacial adhesion of a traditional Janus solar energy evaporator. The Janus solar energy evaporator comprises, from top to bottom, a photo-thermal conversion layer, a thermal insulation layer and a porous sponge layer. The method is to use the upper carbon fiber cloth as the photo-thermal conversion layer, to use the foaming method to prepare the foamed epoxy resin thermal insulation layer, to use the closed pores in the foamed layer for heat insulation, to use the hydrophilic porous sponge as a water supply layer, and finally to obtain the sandwich-Janus solar energy evaporator through a simple assembly method. The material can be applied to the technical field of solar energy interfacial evaporation.

Description

Technical Field

[0001] This invention belongs to the field of solar interface evaporation technology, specifically relating to a self-floating sandwich structure Janus solar evaporator, its preparation method, and its application. Background Technology

[0002] Solar-driven interfacial evaporation (SDIE) uses solar energy to promote water evaporation and has wide applications in seawater desalination and wastewater treatment. The core of this technology lies in absorbing solar energy and converting it into heat energy to heat the water interface, thereby accelerating the evaporation process. Currently, there are three main structural designs for solar-driven interfacial evaporation: porous structures, nanocoatings, and Janus structures.

[0003] The Janus structure separates photothermal conversion from water management, and its bilayer design provides greater stability. Therefore, the Janus structure design has been widely used in solar-driven interfacial evaporation (SDIE). In the design of the Janus structure, materials with different functions are typically used to construct the upper and lower layers separately. The upper layer usually uses hydrophobic materials, such as photothermal conversion materials, mainly including metal nanoparticles (e.g., gold, silver) or carbon-based materials (e.g., carbon black, graphene). These materials can effectively absorb solar energy and convert it into heat energy, thereby accelerating water evaporation. The lower layer is usually composed of hydrophilic materials, which need to exhibit good water absorption, retention, and transport capabilities. Common materials for the lower layer include porous polymers, cellulose-based materials, or hydrogels. However, traditional Janus structures suffer from two problems: high heat loss and poor interfacial adhesion. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a self-floating sandwich structure Janus solar evaporator, its preparation method and application, which has excellent light absorption capacity and high evaporation rate, and can improve the application of solar-driven interfaces.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a self-floating sandwich structure Janus solar evaporator, comprising a photothermal conversion layer, an insulation layer, and a porous sponge layer from top to bottom;

[0007] The photothermal conversion layer is made of carbon fiber cloth;

[0008] The insulation layer includes a foaming agent and an adhesive.

[0009] Preferably, the porous sponge layer includes polyurethane sponge, polyvinyl alcohol sponge, or melamine sponge.

[0010] Preferably, the photothermal conversion layer is a plain or twill 1K carbon fiber cloth, 3K carbon fiber cloth, or 12K carbon fiber cloth.

[0011] Preferably, the insulation layer is a foamed epoxy resin layer.

[0012] This invention provides a method for preparing the Janus solar evaporator with the self-floating sandwich structure, comprising:

[0013] Step 1: Mix the foaming agent and thermosetting adhesive to obtain the foaming pretreatment solution;

[0014] Step 2: Apply the foaming pretreatment liquid from Step 1 between the porous sponge layer and the photothermal conversion layer;

[0015] Step 3: After heating and foaming to solidify, ultrasonic treatment is performed to obtain the Janus solar evaporator with a self-floating sandwich structure.

[0016] Preferably, the thermosetting adhesive is an epoxy resin mixture and the foaming agent is sodium bicarbonate.

[0017] Preferably, the mass ratio of the foaming agent to the thermosetting adhesive is (0.1-2):1.

[0018] Preferably, the curing temperature in step three is 70–130°C.

[0019] Preferably, the ultrasound time in step three is 2 min to 30 min.

[0020] This invention provides the application of the self-floating sandwich structure Janus solar evaporator described in the above technical solution or the Janus solar evaporator prepared by the preparation method described in the above technical solution in seawater desalination or high-salt wastewater treatment.

[0021] Beneficial effects of the present invention

[0022] This invention provides a self-floating sandwich structure Janus solar evaporator, comprising a photothermal conversion layer, an insulation layer, and a porous sponge layer. Combining the high light absorption rate of the photothermal conversion layer, the closed-cell insulation of the insulation layer, and the hydrophilicity of the porous sponge, the Janus solar evaporator, during evaporation, is kept at the upper layer due to the presence of the insulation layer, preventing downward heat conduction loss and improving the utilization rate of sunlight. Simultaneously, the different wettability of the upper and lower layers achieves self-floating and resistance to salt contamination, overcoming the problems of non-floating and salt contamination in traditional interfacial solar evaporators. The insulation layer ensures good interfacial bonding between the upper and lower layers, avoiding the interfacial separation problem present in traditional two-layer Janus evaporators and improving the evaporator's durability. The photothermal conversion layer of this invention can achieve rapid heating, exhibiting excellent photothermal conversion capabilities with a light absorption rate as high as 91.43%, and an evaporation rate of 3.56 kg·m³ under one times illumination. -2 ·h -1 .

[0023] The solar evaporator of this invention is a highly efficient solar interface evaporation system with extremely high photothermal conversion capacity. It is simple to prepare, has stable durability, and exhibits stable evaporation efficiency at normal temperature and pressure. It can be used in seawater desalination, high-salt wastewater and sewage treatment, and has good economic benefits and commercial prospects. Attached Figure Description

[0024] Figure 1 Scanning electron microscope (SEM) images and partial views of the self-floating sandwich structure Janus solar evaporator prepared in Example 1 of the present invention; wherein a is an overall SEM image of the three-layer structure of the Janus solar evaporator; b to h are SEM images of various parts of the Janus solar evaporator.

[0025] Figure 2 The above images show the temperature changes of the upper and lower surfaces of the Janus solar evaporator prepared in Example 1 and Comparative Example 1 of this invention over a period of 2 minutes.

[0026] Figure 3 This is a test diagram of the self-floating performance of the Janus solar evaporator with a self-floating sandwich structure prepared in Example 1 of the present invention;

[0027] Figure 4 These are comparative diagrams of the self-floating sandwich structure Janus solar evaporators in Embodiments 1 and 4 of the present invention;

[0028] Figure 5 Dynamic contact angle test of the melamine sponge layer of the self-floating sandwich structure Janus solar evaporator prepared in Example 1 of the present invention for superhydrophilicity;

[0029] Figure 6 The contact angle of the carbon fiber cloth surface of the self-floating sandwich structure Janus solar evaporator prepared in Example 1 of this invention;

[0030] Figure 7 The epoxy resin surface contact angle of the self-floating sandwich structure Janus solar evaporator prepared in Comparative Example 1 of this invention;

[0031] Figure 8 The temperature change curves of the upper and lower surfaces of the Janus solar evaporator prepared in Example 1 and Comparative Example 1 of this invention are shown in 2 minutes.

[0032] Figure 9 Photographs of the light absorption rate of Janus solar evaporators prepared in Examples 1, 2 and 3 of this invention in the range of 250 nm to 2500 nm.

[0033] Figure 10 The evaporation rate variation curves of the Janus solar evaporators prepared in Examples 1, 2, and 3 of this invention within 1 hour under 1 light intensity are shown.

[0034] Figure 11 The bar chart shows the evaporation rates of the Janus solar evaporators prepared in Example 1, Comparative Example 2, and Comparative Example 3 of this invention at one light intensity.

[0035] Figure 12 The temperature change curves of the upper surface of the Janus solar evaporator prepared in Examples 1, 2, and 3 of the present invention within 1 hour under 1 light intensity are shown. Detailed Implementation

[0036] This invention provides a self-floating sandwich structure Janus solar evaporator, comprising a photothermal conversion layer, an insulation layer, and a porous sponge layer from top to bottom;

[0037] According to the present invention, the photothermal conversion layer is a hydrophobic carbon fiber cloth layer. In this invention, the carbon fiber cloth layer preferably includes 1K plain weave carbon fiber cloth, 3K plain weave carbon fiber cloth, 12K plain weave carbon fiber cloth, 1K twill carbon fiber cloth, 3K twill carbon fiber cloth, or 12K twill carbon fiber cloth, more preferably 1K plain weave carbon fiber cloth; the diameter of the carbon fibers in the carbon fiber cloth is preferably 2 micrometers to 12 micrometers. The diameter of the carbon fibers in the 1K plain weave carbon fiber cloth is preferably 2 to 5 micrometers. The present invention does not specifically limit the source of the carbon fiber cloth; carbon fiber cloth from sources well known in the art can be used.

[0038] According to the present invention, the insulation layer has an adhesive effect. In the present invention, the insulation layer comprises a foaming agent and an adhesive; the adhesive preferably comprises a thermosetting resin, more preferably an epoxy resin mixture. The present invention does not specifically limit the source of the adhesive and the foaming agent; adhesives from sources well known in the art can be used. The foaming agent is preferably a carbonate, more preferably sodium bicarbonate. In the present invention, the mass ratio of the foaming agent to the adhesive in the insulation layer is preferably (0.1–2):1, more preferably (0.2–1):1.

[0039] According to the present invention, the porous sponge layer preferably comprises polyvinyl alcohol sponge, melamine sponge, or polyurethane sponge, more preferably melamine sponge; the porosity of the porous sponge is preferably 70-99.9%, more preferably 80-99.9%. The present invention does not specifically limit the source of the porous sponge; porous sponges from sources well known in the art can be used.

[0040] This invention provides a method for preparing the Janus solar evaporator with the self-floating sandwich structure described in the above technical solution, comprising the following steps:

[0041] Step 1: Mix the foaming agent and thermosetting adhesive to obtain the foaming pretreatment solution;

[0042] Step 2: Apply the foaming pretreatment liquid from Step 1 between the porous sponge layer and the photothermal conversion layer;

[0043] Step 3: After heating and foaming to solidify, ultrasonic treatment is performed to obtain the Janus solar evaporator with a self-floating sandwich structure.

[0044] In this invention, the preferred method is to mix the thermally decomposed foaming agent and the thermosetting resin adhesive:

[0045] The foaming agent and thermosetting resin binder are magnetically stirred to obtain a uniform solution. The stirring speed is preferably 500-800 rpm, more preferably 600 rpm; the stirring time is preferably 0.5-2 h, more preferably 1 h; and the mixing temperature is preferably 20-30℃, more preferably 25℃.

[0046] According to the present invention, heating causes the foaming agent to foam and the adhesive to cure, resulting in a denser sandwich structure.

[0047] In this invention, the heating and curing temperature is preferably 70-130°C, more preferably 90-120°C.

[0048] In this invention, the heating device is preferably an oven, a water bath, or an oil bath, and more preferably an oven.

[0049] After obtaining the primary product of the solar evaporator, the present invention places the primary product of the solar evaporator into deionized water and ultrasonically cleans it to remove sodium carbonate.

[0050] In this invention, the solution used for ultrasonic cleaning preferably includes anhydrous ethanol and deionized water, more preferably deionized water; the ultrasonic time is preferably 2 min to 30 min, more preferably 3 min to 10 min.

[0051] After obtaining the moistened Janus solar evaporator, the present invention places the moistened Janus solar evaporator into an oven for drying.

[0052] In this invention, the drying time is preferably 0.5h to 5h, more preferably 0.5h to 2h; the drying temperature is preferably 25℃ to 100℃, more preferably 40℃ to 80℃.

[0053] The method for preparing the self-floating sandwich structure Janus solar evaporator provided by this invention is simple, easy to operate, and low in cost, and can achieve large-scale preparation and installation.

[0054] This invention provides the application of the self-floating sandwich structure Janus solar evaporator described in the above technical solution or the Janus solar evaporator prepared by the preparation method described in the above technical solution in seawater desalination or high-salt wastewater treatment.

[0055] The present invention does not impose any particular limitation on the application of the self-floating sandwich structure Janus solar evaporator in seawater desalination and / or high-salt wastewater treatment; any application method known in the art can be used.

[0056] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1: Preparation of a self-floating sandwich structure Janus solar evaporator, carried out according to the following steps:

[0058] Step 1: Mix epoxy resin mixture at a mass ratio of A:B = 3:1 (the epoxy resin mixture is produced by Wenzhou Yichen Industrial Co., Ltd., China. Component A is mainly epoxy resin (90%) and diluent (10%). Component B is mainly polypropylene glycol bis(30%), alicyclic amine (28%), epoxy resin (7%), diluent (34.6%), and defoaming agent (0.4%). Model number: 7737). Then, add sodium bicarbonate at a mass ratio of epoxy resin mixture:sodium bicarbonate = 5:1. Stir the mixture magnetically for 1 hour. Finally, thoroughly stir the sodium bicarbonate in the solution to ensure it is evenly dispersed throughout the epoxy resin, obtaining the pre-foaming solution.

[0059] Step 2: Heat 1K plain weave carbon fiber cloth in a water bath at 80℃ with deionized water for 2 hours. Then dry the cleaned carbon fiber cloth in an oven. After drying, cut it into 1.5 cm x 1.5 cm pieces. Apply a thin layer of foaming pretreatment solution to melamine foam with a brush, then place the carbon fiber cloth on top to obtain the composite.

[0060] Step 3: Then, place the composite in an oven at 120℃ for 2 hours, and sonicate the foamed evaporator in deionized water for 5 minutes. After sonication, place it in an oven and dry at 80℃ for 1 hour to obtain the self-floating sandwich structure Janus solar evaporator.

[0061] Example 2

[0062] The difference from Example 1 is that the porous sponge used is polyurethane sponge, and the rest is the same as in Example 1.

[0063] Example 3

[0064] The difference from Example 1 is that the carbon fiber cloth used is 3K plain weave carbon fiber cloth, and the rest is the same as Example 1.

[0065] Example 4

[0066] The difference from Example 1 is that the carbon fiber cloth used is 12K plain weave carbon fiber cloth, and the rest is the same as Example 1.

[0067] Example 5

[0068] The difference from Example 1 is that the mass ratio of the foaming agent to the adhesive used is 1:10, and the rest is the same as in Example 1.

[0069] Example 6

[0070] The difference from Example 1 is that the ratio of foaming agent to adhesive used is 3:10, and the rest is the same as in Example 1.

[0071] Example 7

[0072] The difference from Example 1 is that the foaming temperature used is 90°C, but the rest is the same as Example 1.

[0073] Example 8

[0074] The difference from Example 1 is that the foaming temperature used is 100°C, but the rest is the same as Example 1.

[0075] Comparative Example 1

[0076] The difference from Example 1 is that there is no insulation layer between the melamine sponge and the carbon fiber cloth.

[0077] Comparative Example 2

[0078] The difference from Example 1 is that there is no photothermal conversion layer above the insulation layer.

[0079] Comparative Example 3

[0080] The difference from Example 1 is that there is no melamine sponge for water supply under the insulation layer.

[0081] Performance testing

[0082] Figure 1 The images shown are scanning electron microscope (SEM) images and partial views of the self-floating sandwich structure Janus solar evaporator prepared in Example 1 of this invention; where a is an overall SEM image of the three-layer structure of the Janus solar evaporator; and b to h are SEM images of various parts of the Janus solar evaporator.

[0083] Depend on Figure 1 Figure a shows the successful fabrication of the overall sandwich structure Janus evaporator; Figure b shows the presence of vertical water channels on the upper surface of the carbon fiber layer; Figure c shows 1000 carbon fibers in a bundle of carbon fibers impregnated with epoxy resin and tightly bonded together; Figures d and e show the strong interfacial bonding between layers; Figure f shows the melamine sponge mesh-like water delivery structure; Figure g shows the foaming process of the foamed layer; Figure h clearly shows the three-layer structure.

[0084] Figure 2 Thermal imaging images showing the temperature changes of the upper and lower surfaces of the Janus solar evaporators prepared in Example 1 and Comparative Example 1 over 2 minutes; where CF+MF represents Comparative Example 1 and CEM represents Example 1. Figure 2 It can be seen that the temperature increase rate of the carbon fiber surface in Example 1 is faster than that in Comparative Example 1 (without insulation layer). This indicates that the insulation layer does indeed play a role in heat preservation.

[0085] Figure 3It is a self-floating performance test diagram of the self-floating sandwich-structured Janus solar evaporator prepared in Example 1 of the present invention; Figure 3 illustrates the successful design of the Janus structure. The difference in wettability between the two layers enables the evaporator to float on the water surface, promotes interfacial evaporation and reduces heat loss.

[0086] Figure 4 It is a comparison diagram of the self-floating sandwich-structured Janus solar evaporator prepared in Example 1 ( Figure 4 A) and Example 4 ( Figure 4 B) of the present invention; from Figure 4 it can be found that the 1K plain-woven carbon fiber cloth has a denser arrangement, thus having more abundant vertical water transport channels.

[0087] Figure 5 It is the dynamic contact angle test of superhydrophilicity for the melamine sponge layer of the self-floating sandwich-structured Janus solar evaporator prepared in Example 1 of the present invention; from Figure 5 it can be seen that the melamine sponge layer can quickly absorb liquid droplets within 0.03 s, which verifies that it has superhydrophilicity and is a good choice for the water supply layer.

[0088] Figure 6 It is the surface contact angle of the carbon fiber cloth of the self-floating sandwich-structured Janus solar evaporator prepared in Example 1 of the present invention; from Figure 6 it can be seen that the surface contact angle of the carbon fiber cloth is 111°, which indicates that the carbon fiber cloth layer is hydrophobic.

[0089] Figure 7 It is the surface contact angle of epoxy resin of the self-floating sandwich-structured Janus solar evaporator prepared in Comparative Example 1 of the present invention; from Figure 7 it can be seen that the surface contact angle of the thermal insulation layer is 100°, which indicates that the thermal insulation layer is hydrophobic.

[0090] Figure 8 It is the temperature change curves of the upper and lower surfaces within 2 minutes of the Janus solar evaporators prepared in Example 1 and Comparative Example 1 of the present invention; wherein, CMLT represents the temperature change of the lower layer of Comparative Example 1, CEMLT represents the temperature change of the lower layer of Example 1, CMHT represents the temperature change of the upper layer of Comparative Example 1, and CEMHT represents the temperature change of the upper layer of Example 1. From Figure 8 it can be seen that the temperature difference between the upper layer and the lower layer in Example 1 can reach 9.4°C within 2 minutes, while that in Comparative Example 1 is only 4°C.

[0091] Figure 9These are photographs of the light absorption rate of the Janus solar evaporators prepared in the range of 250 nm to 2500 nm, as shown in Examples 1, 2, and 3 of this invention; where CEM represents Example 1, ER+MF represents Comparative Example 2, and CF+ER represents Comparative Example 3. Figure 9 It can be seen that the light absorption rates of Comparative Example 3, Comparative Example 2, and Example 1 are 89.56%, 84.26%, and 91.43%, respectively. The light absorption mainly comes from the contribution of the upper carbon fiber layer. The porous structure of the carbon fiber only meets the requirements for vapor release, while enhancing light absorption through multiple reflections within the pores, thus ensuring effective photothermal performance.

[0092] Figure 10 The figures show the evaporation rate changes of the Janus solar evaporators prepared in Examples 1, 2, and 3 of this invention over 1 hour under a given light intensity; where CEM represents Example 1, CFER represents Comparative Example 3, and ERMF represents Comparative Example 2. It can be observed that the evaporation rate of Example 1 per unit time is significantly greater than that of Comparative Examples 2 and 3, and tends to stabilize after 20 minutes.

[0093] Figure 11 The bar chart shows the evaporation rates of the Janus solar evaporators prepared in Example 1, Comparative Example 2, and Comparative Example 3 of this invention under one light intensity; where CEM represents Example 1, CF+ER represents Comparative Example 3, and ER+MF represents Comparative Example 2. Figure 11 Evaporation rates for different evaporators are presented. Due to heat loss, the evaporation rates of Comparative Example 3 and Comparative Example 2 are similar, both being 2.26 kg·m³. - 2·h -1 and 2.19 kg·m - 2·h -1 However, the evaporation rate in Example 1 was as high as 3.56 kg·m³. - 2·h -1 Although the light absorption rate is similar to that of Example 1 and Comparative Example 3, the evaporation rate of Example 1 is significantly higher. This is beneficial to the coefficient of the insulation layer and its self-floating properties, which direct heat to the carbon fiber layer and prevent downward heat conduction.

[0094] Figure 12 The figures show the temperature change curves of the upper surface of the Janus solar evaporators prepared in Example 1, Comparative Examples 2 and 3 of this invention, under one light intensity over 1 hour. CEM represents Example 1, CFER represents Comparative Example 3, and ERMF represents Comparative Example 2. It can be observed that the temperature of Example 1 is significantly higher than that of Comparative Examples 2 and 3, and tends to stabilize after 20 minutes.

Claims

1. A method for preparing a self-floating sandwich structure Janus solar evaporator, characterized in that, Step 1: Mix the foaming agent and thermosetting adhesive to obtain the foaming pretreatment solution; Step 2: Apply the foaming pretreatment liquid from Step 1 between the porous sponge layer and the photothermal conversion layer; Step 3: After heating and foaming to solidify, ultrasonic treatment is performed to obtain a self-floating sandwich structure Janus solar evaporator; The thermosetting adhesive is an epoxy resin mixture, and the foaming agent is sodium bicarbonate. The mass ratio of the foaming agent to the thermosetting adhesive is (0.1-2):1; The curing temperature in step three is 70–130°C; The solar evaporator comprises, from top to bottom, a photothermal conversion layer, an insulation layer, and a porous sponge layer; The photothermal conversion layer is made of carbon fiber cloth; The insulation layer is a foamed epoxy resin layer.

2. The method for preparing a self-floating sandwich structure Janus solar evaporator according to claim 1, characterized in that, The porous sponge layer includes polyurethane sponge, polyvinyl alcohol sponge, or melamine sponge.

3. The method for preparing a self-floating sandwich structure Janus solar evaporator according to claim 1, characterized in that, The photothermal conversion layer is a plain or twill 1K carbon fiber cloth, 3K carbon fiber cloth, or 12K carbon fiber cloth.

4. The method for preparing the Janus solar evaporator with a self-floating sandwich structure according to claim 1, characterized in that, The ultrasound time for step three is 2 to 30 minutes.

5. The application of the Janus solar evaporator prepared by the method of claim 1 (a self-floating sandwich structure) in seawater desalination or high-salinity wastewater treatment.

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