Sponge-based phase change composites for solar interface evaporation of water and methods of making

Abstract

The application discloses a sponge-based phase change composite material for solar interface evaporation of water and a preparation method thereof, and steps are as follows: step 1, pretreating waste PU sponge to obtain activated PU sponge; step 2, preparing PU / PDA / CNTs sponge through the activated PU sponge, dopamine hydrochloride and carbon nanotubes; and step 3, loading polyethylene glycol on the PU / PDA / CNTs sponge through a vacuum-assisted melt impregnation method to obtain a PU / PDA / CNTs / PEG composite material. The PU / PDA / CNTs / PEG composite material obtained by the application has good cycle stability and is not prone to leakage of PEG.

Description

Technical Field

[0001] This invention belongs to the field of phase change composite material technology, specifically relating to a sponge-based phase change composite material for solar energy interface water evaporation, and also relating to a method for preparing the sponge-based phase change composite material for solar energy interface water evaporation. Background Technology

[0002] Solar-driven interfacial water evaporation technology, due to its low-carbon and high-efficiency characteristics, is a promising solution to the problem of freshwater scarcity. However, the practical application of this technology is severely limited by the intermittent nature of solar radiation, making it difficult to achieve continuous operation around the clock.

[0003] Introducing phase change materials (PCMs) and utilizing their heat storage and release properties to achieve energy "peak shifting and valley filling" is an important way to break through the limitations of continuous operation in all weather conditions. However, the current PCM composite materials are generally prepared by simply impregnating PCM into a conventional porous matrix, but the PCM composite materials obtained by this method have problems such as easy leakage of PCM and poor cycle stability. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing sponge-based phase change composite materials for solar interface water evaporation, which solves the problems of easy PCM leakage and poor cycle stability of composite materials obtained by existing preparation methods.

[0005] Another object of the present invention is to provide a sponge-based phase change composite material for solar interface water evaporation.

[0006] The technical solution adopted in this invention is a method for preparing a sponge-based phase change composite material for solar interface water evaporation, the steps of which are as follows: Step 1: Pre-treat the waste PU (polyurethane) sponge to obtain activated PU sponge; Step 2: Prepare PU / PDA / CNTs sponge using activated PU sponge, dopamine hydrochloride (DA), and carbon nanotubes (CNTs); Step 3: Polyethylene glycol (PEG) is loaded onto PU / PDA / CNTs sponge by vacuum-assisted melt impregnation to obtain PU / PDA / CNTs / PEG composite material.

[0007] The invention is further characterized by: The specific process of step 1 is as follows: the PU sponge is ultrasonically cleaned and dried in anhydrous ethanol, then the dried PU sponge is soaked in NaOH solution for activation treatment, ultrasonically treated after activation treatment, and then washed with pure water until the washing solution is neutral. The PU sponge is then taken out and dried in an oven to obtain activated PU sponge.

[0008] The ultrasonic cleaning time is 20 min to 60 min; the drying temperature after cleaning is 50℃ to 70℃; the ultrasonic treatment time is 1 h to 2 h; and the concentration of NaOH solution is 1 mol / L to 3 mol / L.

[0009] The specific process of step 2 is as follows: Step 2.1: Dissolve dopamine hydrochloride (DA) in Tris buffer solution at pH 8.5 to obtain a dopamine solution; Step 2.2: Add CNTs to dopamine solution and sonicate to fully disperse CNTs in dopamine solution to obtain PDA / CNTs dispersion; Step 2.3: Immerse the activated PU sponge in the PDA / CNTs dispersion and stir magnetically to carry out the reaction. After the reaction is completed, rinse with pure water several times and dry after rinsing to obtain the PU / PDA / CNTs sponge.

[0010] In step 2.1, the concentration of the dopamine solution is 2 mg / mL to 10 mg / mL.

[0011] In step 2.2, the ultrasonic treatment temperature is 30 min to 90 min; the mass ratio of CNTs to DA is 0.04 to 2:1.

[0012] In step 2.3, the magnetic stirring temperature is 20℃~30℃, the magnetic stirring time is 10h~14h, and the drying temperature is 60℃~100℃.

[0013] The specific process of step 3 is as follows: melt PEG, then immerse the PU / PDA / CNTs sponge in the molten PEG, transfer the impregnated PU / PDA / CNTs sponge to a vacuum oven for vacuum adsorption, and after adsorption, dry it in a forced-air drying oven until no PEG seeps out from the surface to obtain the PU / PDA / CNTs / PEG composite material.

[0014] The PEG melting temperature is 60℃~80℃, the vacuum adsorption temperature is 50℃~80℃, the vacuum degree of vacuum adsorption is -0.08MPa~-0.1MPa, the vacuum adsorption time is 2h~6h, the drying temperature is 60℃~80℃, and the drying time is 4h~12h.

[0015] Another technical solution adopted in this invention is a sponge-based phase change composite material for solar interface water evaporation, which is prepared by the above-mentioned preparation method.

[0016] The beneficial effects of this invention are: (1) The preparation method of the present invention uses polydopamine (PDA) as an adhesive. It not only has photothermal properties, but also firmly binds carbon nanotubes (CNTs) and PU sponge skeleton through strong adhesion, and provides more binding sites for subsequent PEG loading. At the same time, PDA and PEG can form hydrogen bonds and other interactions, which significantly enhances the encapsulation stability of PEG in the three-dimensional porous network, thereby avoiding PEG leakage. (2) The preparation method of the present invention uses CNTs and PDA as efficient photothermal conversion agents, which endows the composite material with excellent broad-spectrum light absorption ability. PEG, as a phase change material, absorbs and stores excess heat during the light stage and releases heat through solidification during the dark stage, thereby realizing the time and air control of thermal energy and realizing the all-weather utilization of solar energy. (3) The PU / PDA / CNTs / PEG composite material prepared by the method of the present invention has excellent hydrophilicity, high efficiency photothermal conversion and heat storage capacity, and the evaporation rate and photothermal efficiency remain stable after multiple cycles, showing great potential for all-weather seawater desalination and water purification. (4) The preparation method of the present invention uses waste polyurethane sponge as the main matrix, realizes the high-value utilization of waste, has low cost, and the preparation process is simple, mild and easy to scale up. Attached Figure Description

[0017] Figure 1 This is a SEM image of the PU / PDA / CNTs / PEG composite material obtained in Example 1 of this invention; Figure 2 This is a SEM image of the PU sponge in Comparative Example 1 of the present invention; Figure 3 This is a SEM image of the PU / PDA / PEG composite material of Comparative Example 2 of the present invention; Figure 4 This is a SEM image of the PU / CNTs / PEG composite material of Comparative Example 3 of the present invention; Figure 5 SEM image of the PU / PDA / CNTs sponge in Comparative Example 4 of this invention; Figure 6 Leakage rate comparison curves of the PU / PDA / CNTs / PEG composite material obtained in Example 1 of the present invention, the PU / PDA / PEG composite material in Comparative Example 2, and the PU / CNTs / PEG composite material in Comparative Example 3; Figure 7The photothermal conversion temperature-time curves of the PU / PDA / CNTs / PEG composite material obtained in Example 1 of the present invention, the PU sponge of Comparative Example 1, the PU / PDA / PEG composite material of Comparative Example 2, the PU / CNTs / PEG composite material of Comparative Example 3, and the PU / PDA / CNTs sponge of Comparative Example 4 are shown. Figure 8 The interfacial evaporation rates at 1 SUN are shown for the PU / PDA / CNTs / PEG composite material obtained in Example 1 of the present invention, the PU sponge of Comparative Example 1, the PU / PDA / PEG composite material of Comparative Example 2, the PU / CNTs / PEG composite material of Comparative Example 3, and the PU / PDA / CNTs sponge of Comparative Example 4. Figure 9 This is a photograph of the salt crystallization on the surface of the PU / PDA / CNTs / PEG composite material obtained in Example 1 of the present invention after evaporating 3% sodium chloride in simulated seawater outdoors for 10 hours; Figure 10 This is a photograph of the salt crystallization on the surface of the PU / PDA / CNTs sponge (Comparative Example 4 of this invention) after evaporating 3% sodium chloride in simulated seawater outdoors for 10 hours. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] The present invention relates to a method for preparing a sponge-based phase change composite material for solar interface water evaporation, comprising the following steps: Step 1: Pre-treat the waste PU (polyurethane) sponge to obtain activated PU sponge; The specific process is as follows: A PU (polyurethane) sponge measuring 2 cm × 2 cm × 1 cm was ultrasonically cleaned in anhydrous ethanol for 20 min to 60 min. After removal, it was dried at 50℃ to 70℃. The dried PU sponge was then immersed in a NaOH solution with a concentration of 1 mol / L to 3 mol / L for activation treatment. During the immersion process, the PU sponge was squeezed repeatedly to allow the NaOH solution to be absorbed into the pores of the PU sponge. After activation treatment, it was ultrasonically treated for 1 h to 2 h. Then, it was washed with pure water until the washing solution was neutral. The PU sponge was removed and dried in an oven to obtain the activated PU sponge. Step 2: Prepare PU / PDA / CNTs sponge using activated PU sponge, dopamine hydrochloride (DA), and carbon nanotubes (CNTs); The specific process is as follows: Step 2.1: Dissolve dopamine hydrochloride (DA) in Tris-HCl (tris(hydroxymethyl)aminomethane) buffer solution at pH 8.5 to obtain a dopamine solution with a concentration of 2 mg / mL to 10 mg / mL. Step 2.2: Add carbon nanotubes (CNTs) to a dopamine solution and sonicate for 30 min to 90 min to fully disperse the CNTs in the dopamine solution to obtain a PDA / CNTs dispersion. The mass ratio of CNTs to DA is 0.04 to 2:1; the CNTs are multi-walled carbon nanotubes. Step 2.3: Immerse the activated PU sponge in the PDA / CNTs dispersion and magnetically stir at 20℃~30℃ for 10h~14h. During the stirring process, squeeze the activated PU sponge multiple times to allow the PDA / CNTs dispersion to fully penetrate into the pores of the activated PU sponge. After the reaction is complete, rinse with pure water multiple times and dry at 60℃~100℃ to obtain the PU / PDA / CNTs sponge. Step 3: Polyethylene glycol (PEG) is loaded onto PU / PDA / CNTs sponge using a vacuum-assisted melt impregnation method to obtain a PU / PDA / CNTs / PEG composite material; The specific process is as follows: PEG was melted at 60℃~80℃, and then PU / PDA / CNTs sponge was immersed in the molten PEG. During the immersion process, the PU / PDA / CNTs sponge was squeezed repeatedly to ensure that the PEG fully penetrated into the pores of the PU / PDA / CNTs sponge. The impregnated PU / PDA / CNTs sponge was transferred to a vacuum oven at 50℃~80℃ and adsorbed at a vacuum of -0.08MPa~-0.1MPa for 2h~6h. After adsorption, it was dried in a forced-air drying oven at 60℃~80℃ for 4h~12h until no PEG seepage was observed on the surface, thus obtaining the PU / PDA / CNTs / PEG composite material. The PEG used is PEG-2000, which has a phase transition temperature of approximately 45℃.

[0020] The specific roles of each raw material and step in the preparation method of the sponge-based phase change composite material for solar interface evaporation water of the present invention are as follows: Polyurethane (PU) sponge: As a porous support matrix, its three-dimensional interconnected macroporous structure provides ample space for loading PPDA / CNTs photothermal layer and adsorbing PEG, while also facilitating moisture transport and vapor escape; Polydopamine (PDA): (1) As a green adhesive, it forms a strong interaction with the amino groups of the PU skeleton through its catechol group, and adheres firmly to the skeleton; (2) It has a certain photothermal conversion ability; (3) Its abundant functional groups on the surface provide active sites for the adhesion of CNTs and the hydrogen bonding of PEG, which is the key to preventing PEG leakage; if its content is too low, the adhesion and leakage prevention effect will be poor, and if it is too high, it may block the pores and affect water transmission.

[0021] Carbon nanotubes (CNTs): As a photothermal agent, they have broad-spectrum strong absorption characteristics, which can efficiently convert solar energy into heat energy and improve the evaporation rate. They can form an effective heat conduction and photothermal network on the surface of the sponge skeleton, while avoiding pore blockage due to agglomeration.

[0022] Polyethylene glycol (PEG): As a phase change thermal storage material, it absorbs or releases a large amount of latent heat during the solid-liquid phase transition. It stores excess heat under sunlight to mitigate interface overheating and releases heat to maintain evaporation when there is no sunlight, which is key to achieving all-weather operation. The phase change temperature of PEG-2000 (about 45°C) matches the working temperature of solar evaporation well. At the same time, the superhydrophilicity of PEG can ensure water transfer and reduce salt crystallization. Therefore, it can provide significant thermal storage effect and can be effectively encapsulated by a porous framework to prevent leakage.

[0023] Step 1: Used to remove impurities from the surface of PU sponge and treat with sodium hydroxide alkali to give the PU sponge more active groups such as hydroxyl groups, providing reaction sites for the robust loading of PDA, CNTs and PEG.

[0024] Step 2: Constructing a high-efficiency and stable photothermal conversion layer. The principle is as follows: Dopamine undergoes oxidative self-polymerization in a weakly alkaline Tris-HCl buffer to form polydopamine (PDA). PDA has extremely strong adhesive properties, tightly encapsulating the PU sponge skeleton and CNTs. The CNTs are adhered and fixed to the sponge skeleton by the PDA, preventing them from detaching, and simultaneously forming a highly light-absorbing network. This step is fundamental to the subsequent successful loading of PEG and leak-proof operation.

[0025] Step 3: Introducing phase change thermal storage functionality. The principle is as follows: Under vacuum assistance, molten PEG is drawn into the pores of the PU / PDA / CNTs sponge via capillary force. The phenolic hydroxyl and amino functional groups abundant on the PDA molecular chain can form hydrogen bonds with the hydroxyl groups at the PEG chain ends. Simultaneously, the physical entanglement effect of CNTs and PDA synergistically fix the PEG. This multi-scale interfacial interaction significantly enhances the anchoring effect of PEG in the three-dimensional porous network, thereby effectively preventing leakage during the phase change melting state.

[0026] The preparation method of this invention utilizes the dual functions of polydopamine (PDA) in adhesion and photothermal properties to construct a stable and highly active photothermal interface layer on an inexpensive waste PU sponge skeleton. By utilizing the interaction between this layer and the phase change material PEG, long-term, high-load, and leak-proof encapsulation of PEG in a high-porosity matrix is ​​achieved. This results in the preparation of a multifunctional composite material with highly efficient and synergistic photothermal conversion, heat storage and release, and moisture transport performance, which significantly improves the evaporation performance, stability, and all-weather working potential of the solar interface evaporation system.

[0027] Example 1 Step 1: Pre-treat the waste PU (polyurethane) sponge to obtain activated PU sponge; The specific process is as follows: A PU (polyurethane) sponge measuring 2 cm × 2 cm × 1 cm was ultrasonically cleaned in anhydrous ethanol for 30 min. After removal, it was dried at 60℃. The dried PU sponge was then immersed in a 2 mol / L NaOH solution for activation treatment. During the immersion process, the PU sponge was squeezed repeatedly to allow the NaOH solution to be absorbed into the pores of the PU sponge. After activation treatment, it was ultrasonically treated for 1.5 h, and then washed with pure water until the washing solution was neutral. The PU sponge was then removed and dried in a 60℃ forced-air oven for 6 h to obtain the activated PU sponge. Step 2: Prepare PU / PDA / CNTs sponge using activated PU sponge, dopamine hydrochloride (DA), and carbon nanotubes (CNTs); The specific process is as follows: Step 2.1: Dissolve 0.1 g of dopamine hydrochloride (DA) in 20 mL of Tris-HCl buffer solution with pH 8.5 to obtain a dopamine solution with a concentration of 5 mg / mL; Step 2.2: Add 0.02g of carbon nanotubes (CNTs) to a dopamine solution and sonicate for 30min to fully disperse the CNTs in the dopamine solution, thus obtaining a PDA / CNTs dispersion. CNTs utilize multi-walled carbon nanotubes; Step 2.3: Immerse the activated PU sponge in the PDA / CNTs dispersion and magnetically stir at 200 rpm for 12 hours at 25°C. During the stirring process, squeeze the activated PU sponge every 2 hours to allow the PDA / CNTs dispersion to fully penetrate the pores of the activated PU sponge. After the reaction is complete, rinse with pure water several times and dry at 60°C for 12 hours to obtain the PU / PDA / CNTs sponge. Step 3: Load PEG-2000 onto PU / PDA / CNTs sponge using vacuum-assisted melt impregnation method to obtain PU / PDA / CNTs / PEG composite material; The specific process is as follows: PEG-2000 was melted in a water bath at 70°C. PU / PDA / CNTs sponge was then immersed in the molten PEG-2000. During the immersion process, the PU / PDA / CNTs sponge was repeatedly squeezed to ensure that PEG-2000 fully penetrated into the pores of the PU / PDA / CNTs sponge. The impregnated PU / PDA / CNTs sponge was then transferred to a vacuum oven at 70°C and adsorbed under a vacuum of -0.09 MPa for 4 hours. After adsorption, the sponge was dried in a forced-air drying oven at 70°C for 12 hours until no PEG-2000 leached from the surface, thus obtaining the PU / PDA / CNTs / PEG composite material.

[0028] Example 2 Step 1: Pre-treat the waste PU (polyurethane) sponge to obtain activated PU sponge; The specific process is as follows: A PU (polyurethane) sponge measuring 2 cm × 2 cm × 1 cm was ultrasonically cleaned in anhydrous ethanol for 20 min. After removal, it was dried at 50℃. The dried PU sponge was then immersed in a 3 mol / L NaOH solution for activation treatment. During the immersion process, the PU sponge was squeezed repeatedly to allow the NaOH solution to be absorbed into the pores of the PU sponge. After activation treatment, it was ultrasonically treated for 1 h, and then washed with pure water until the washing solution was neutral. The PU sponge was then removed and dried in a 60℃ forced-air oven for 6 h to obtain the activated PU sponge. Step 2: Prepare PU / PDA / CNTs sponge using activated PU sponge, dopamine hydrochloride (DA), and carbon nanotubes (CNTs); The specific process is as follows: Step 2.1: Dissolve 0.1 g of dopamine hydrochloride (DA) in 10 mL of Tris-HCl buffer solution with pH 8.5 to obtain a dopamine solution with a concentration of 10 mg / mL; Step 2.2: Add 0.2g of carbon nanotubes (CNTs) to a dopamine solution and sonicate for 90min to fully disperse the CNTs in the dopamine solution, thus obtaining a PDA / CNTs dispersion. CNTs utilize multi-walled carbon nanotubes; Step 2.3: Immerse the activated PU sponge in the PDA / CNTs dispersion and magnetically stir at 200 rpm for 10 hours at 35°C. During the stirring process, squeeze the activated PU sponge every 2 hours to allow the PDA / CNTs dispersion to fully penetrate the pores of the activated PU sponge. After the reaction is complete, rinse with pure water several times and dry at 100°C for 9 hours to obtain the PU / PDA / CNTs sponge. Step 3: Load PEG-2000 onto PU / PDA / CNTs sponge using vacuum-assisted melt impregnation method to obtain PU / PDA / CNTs / PEG composite material; The specific process is as follows: PEG-2000 was melted in a water bath at 80°C. PU / PDA / CNTs sponge was then immersed in the molten PEG-2000. During the immersion process, the PU / PDA / CNTs sponge was repeatedly squeezed to ensure that PEG-2000 fully penetrated into the pores of the PU / PDA / CNTs sponge. The impregnated PU / PDA / CNTs sponge was then transferred to a vacuum oven at 80°C and adsorbed under a vacuum of -0.1 MPa for 2 hours. After adsorption, the sponge was dried in a forced-air drying oven at 80°C for 4 hours until no PEG-2000 leached from the surface, thus obtaining the PU / PDA / CNTs / PEG composite material.

[0029] Example 3 Step 1: Pre-treat the waste PU (polyurethane) sponge to obtain activated PU sponge; The specific process is as follows: A PU (polyurethane) sponge measuring 2 cm × 2 cm × 1 cm was ultrasonically cleaned in anhydrous ethanol for 60 min. After removal, it was dried at 70℃. The dried PU sponge was then immersed in a 1 mol / L NaOH solution for activation treatment. During the immersion process, the PU sponge was squeezed multiple times to allow the NaOH solution to be absorbed into the pores of the PU sponge. After activation treatment, it was ultrasonically treated for 2 h, and then washed with pure water until the washing solution was neutral. The PU sponge was then removed and dried in a 60℃ forced-air oven for 6 h to obtain the activated PU sponge. Step 2: Prepare PU / PDA / CNTs sponge using activated PU sponge, dopamine hydrochloride (DA), and carbon nanotubes (CNTs); The specific process is as follows: Step 2.1: Dissolve 0.1 g of dopamine hydrochloride (DA) in 50 mL of Tris-HCl (tris(hydroxymethyl)aminomethane) buffer solution with pH 8.5 to obtain a dopamine solution with a concentration of 2 mg / mL. Step 2.2: Add 0.02g of carbon nanotubes (CNTs) to a dopamine solution and sonicate for 60min to fully disperse the CNTs in the dopamine solution and obtain a PDA / CNTs dispersion. CNTs utilize multi-walled carbon nanotubes; Step 2.3: Immerse the activated PU sponge in the PDA / CNTs dispersion and magnetically stir at 200 rpm for 14 hours at 20°C. During the stirring process, squeeze the activated PU sponge every 2 hours to allow the PDA / CNTs dispersion to fully penetrate the pores of the activated PU sponge. After the reaction is complete, rinse with pure water several times and dry at 80°C for 10 hours to obtain the PU / PDA / CNTs sponge. Step 3: Load PEG-2000 onto PU / PDA / CNTs sponge using vacuum-assisted melt impregnation method to obtain PU / PDA / CNTs / PEG composite material; The specific process is as follows: PEG-2000 was melted in a water bath at 60°C. PU / PDA / CNTs sponge was then immersed in the molten PEG-2000. During the immersion process, the PU / PDA / CNTs sponge was repeatedly squeezed to ensure that PEG-2000 fully penetrated into the pores of the sponge. The impregnated PU / PDA / CNTs sponge was then transferred to a vacuum oven at 50°C and adsorbed under a vacuum of -0.08 MPa for 6 hours. After adsorption, the sponge was dried in a forced-air drying oven at 60°C for 10 hours until no PEG-2000 leached from the surface, thus obtaining the PU / PDA / CNTs / PEG composite material.

[0030] Example 4 The difference from Example 1 is that in step 2.1, the mass of dopamine hydrochloride (DA) is 0.5g; and in step 2.2, the mass of carbon nanotubes (CNTs) is 0.02g.

[0031] Example 5 The difference from Example 1 is that in step 2.1, the mass of dopamine hydrochloride (DA) is 0.5g; and in step 2.2, the mass of carbon nanotubes (CNTs) is 0.1g.

[0032] Example 6 The difference from Example 1 is that in step 2.1, the mass of dopamine hydrochloride (DA) is 0.5g; and in step 2.2, the mass of carbon nanotubes (CNTs) is 0.2g.

[0033] Comparative Example 1 Only PU foam is used.

[0034] Comparative Example 2 Prepare PU / PDA / PEG composite materials.

[0035] The difference from Example 1 is that step 2.2 is omitted; step 2.3 is as follows: the activated PU sponge is immersed in a dopamine solution and magnetically stirred at 200 rpm for 12 hours at 25°C. During stirring, the activated PU sponge is squeezed every 2 hours to allow the dopamine solution to fully penetrate the pores of the activated PU sponge. After the reaction is complete, it is rinsed multiple times with pure water and then dried at 60°C for 12 hours to obtain a PU / PDA sponge; step 3 is as follows: PEG-2000 is loaded onto the PU / PDA sponge using a vacuum-assisted melt impregnation method to obtain a PU / PDA / PEG composite material. The remaining steps are the same as in Example 1.

[0036] Comparative Example 3 Prepare PU / CNTs / PEG composite materials.

[0037] The difference from Example 1 is as follows: Step 2 involves dispersing 0.02 g of carbon nanotubes (CNTs) in 50 mL of Tris-HCl buffer solution with a pH of 8.5 to obtain a CNTs dispersion. An activated PU sponge is then immersed in the CNTs dispersion and magnetically stirred at 200 rpm for 12 hours at 25°C. During stirring, the activated PU sponge is squeezed every 2 hours to ensure the CNTs dispersion fully penetrates the pores of the activated PU sponge. After the reaction is complete, the sponge is rinsed multiple times with pure water and then dried at 60°C for 12 hours to obtain a PU / CNTs sponge. The remaining steps are the same as in Example 1.

[0038] Comparative Example 4 Prepare PU / PDA / CNTs composite materials.

[0039] The difference from Example 1 is that step 3 is omitted. The remaining steps are the same as in Example 1.

[0040] The performance of the PU / PDA / CNTs / PEG composite material prepared in Example 1 of this invention and the composite materials (PU, PU / PDA / PEG, PU / CNTs / PEG, PU / PDA / CNTs) obtained in Comparative Examples 1 to 4 were tested, and the results are as follows: Depend on Figure 1 As can be seen from the example, the PU / PDA / CNTs / PEG composite material obtained in Example 1 retains the three-dimensional porous structure of the PU sponge. Its skeleton surface becomes rougher than the original PU sponge, and the attachment of PDA and CNTs is visible. Furthermore, the surface is covered with a smooth PEG film, indicating that PEG has been successfully loaded and formed an encapsulation layer.

[0041] Depend on Figure 2 As can be seen from the data, the PU sponge substrate used in Comparative Example 1 has a complete three-dimensional porous structure, and its skeleton surface is flat and smooth.

[0042] Depend on Figure 3 As can be seen from the data, the PU / PDA / PEG composite material obtained in Comparative Example 2 retains the three-dimensional porous structure of the PU sponge. Compared with the original PU sponge, its skeleton surface has blocky crystals (PEG) with a smooth surface and a small number of protruding particles (PDA), indicating that PDA and PEG have been successfully loaded and formed an encapsulation layer.

[0043] Depend on Figure 4 As can be seen from the comparison sample PU / CNTs / PEG composite material obtained in Comparative Example 3, the three-dimensional porous structure of PU sponge is retained. The surface of its skeleton becomes rougher than that of the original PU sponge. The embedded attachment of linear CNTs and PEG film layers is visible, indicating that CNTs and PDA were successfully loaded and formed an encapsulation layer.

[0044] Depend on Figure 5 As can be seen, the PU / PDA / CNTs composite material obtained in Comparative Example 4 retains the three-dimensional porous structure of the PU sponge. Its skeleton surface is rougher than the original PU sponge, revealing the embedded attachment of PDA polymer particles and linear CNTs. Figure 1 The comparison of the obtained PU / PDA / CNTs / PEG samples shows that PDA, CNTs and PEG were successfully loaded on the PU skeleton, and PDA and CNTs synergistically enhanced the loading strength of PEG.

[0045] Depend on Figure 6 As can be seen, the prepared PEG-containing composite material was placed at 70℃ and its mass change was recorded. Calculations showed that the leakage rate of PU / PDA / CNTs / PEG was lower than that of other control groups (PU / PDA / PEG, PU / CNTs / PEG), proving that the synergistic effect of PDA and CNTs enhanced the encapsulation stability of PEG.

[0046] Depend on Figure 7 As can be seen, the PU / PDA / CNTs / PEG composite material exhibits significant performance advantages under 1 solar irradiance (1 kW / m²). Its photothermal conversion and heat storage functions have a synergistic enhancement effect, achieving a maximum equilibrium temperature of approximately 78°C under illumination. More importantly, in the absence of sunlight, thanks to the release of the latent heat of phase change of PEG, the material demonstrates excellent heat retention capabilities, with a significantly slowed cooling rate. This indicates that the composite material successfully achieves spatiotemporal management of thermal energy, providing crucial support for its all-weather stable operation in solar interface evaporation.

[0047] Depend on Figure 8As can be seen, under 1 sun irradiation in the indoor simulation, the water evaporation rate of PU / PDA / CNTs / PEG is as high as 2.4 kg / (m²·h), and it remains higher than the evaporation rate of the control sample, especially after the light is turned off for 60 min.

[0048] Depend on Figure 9 and Figure 10 As can be seen from the photographic record of NaCl crystallization on the sample surface after evaporating 3.5% NaCl solution for 10 hours under outdoor natural light conditions, the PU / PDA / CNTs / PEG surface showed no NaCl crystallization at all, while the PU / PDA / CNTs surface without PEG showed a large amount of NaCl crystallization, indicating that PU / PDA / CNTs / PEG has good salt resistance.

Claims

1. A method for the preparation of a sponge-based phase change composite for solar interface evaporation of water, characterized by, The steps are as follows: Step 1: Pre-treat the waste PU sponge to obtain activated PU sponge; Step 2: Prepare PU / PDA / CNTs sponge using activated PU sponge, DA, and CNTs; Step 3: Load PEG onto PU / PDA / CNTs sponge using vacuum-assisted melt impregnation method to obtain PU / PDA / CNTs / PEG composite material.

2. The method for preparing sponge-based phase change composite material for solar interface water evaporation according to claim 1, characterized in that, The specific process of step 1 is as follows: the PU sponge is ultrasonically cleaned and dried in anhydrous ethanol, then the dried PU sponge is soaked in NaOH solution for activation treatment, ultrasonically treated after activation treatment, and then washed with pure water until the washing solution is neutral. The PU sponge is then taken out and dried in an oven to obtain activated PU sponge.

3. The method for preparing sponge-based phase change composite materials for solar interface water evaporation according to claim 2, characterized in that, The ultrasonic cleaning time is 20 min to 60 min; the drying temperature after cleaning is 50℃ to 70℃; the ultrasonic treatment time is 1 h to 2 h; and the concentration of NaOH solution is 1 mol / L to 3 mol / L.

4. The method for preparing sponge-based phase change composite material for solar interface water evaporation according to claim 1, characterized in that, The specific process of step 2 is as follows: Step 2.1: Dissolve DA in Tris-HCl buffer solution at pH 8.5 to obtain dopamine solution; Step 2.2: Add CNTs to dopamine solution and sonicate to fully disperse CNTs in dopamine solution to obtain PDA / CNTs dispersion; Step 2.3: Immerse the activated PU sponge in the PDA / CNTs dispersion and stir magnetically to carry out the reaction. After the reaction is completed, rinse with pure water several times and dry after rinsing to obtain the PU / PDA / CNTs sponge.

5. The method for preparing sponge-based phase change composite material for solar interface evaporation water according to claim 4, characterized in that, In step 2.1, the concentration of the dopamine solution is 2 mg / mL to 10 mg / mL.

6. The method for preparing sponge-based phase change composite material for solar interface evaporation water according to claim 4, characterized in that, In step 2.2, the ultrasonic treatment temperature is 30 min to 90 min; the mass ratio of CNTs to DA is 0.04 to 2:

1.

7. The method for preparing sponge-based phase change composite material for solar interface evaporation water according to claim 4, characterized in that, In step 2.3, the magnetic stirring temperature is 20℃~30℃, the magnetic stirring time is 10h~14h, and the drying temperature is 60℃~100℃.

8. The method for preparing sponge-based phase change composite material for solar interface evaporation water according to claim 1, characterized in that, The specific process of step 3 is as follows: melt PEG, then immerse the PU / PDA / CNTs sponge in the molten PEG, transfer the impregnated PU / PDA / CNTs sponge to a vacuum oven for vacuum adsorption, and after adsorption, dry it in a forced-air drying oven until no PEG seeps out from the surface to obtain the PU / PDA / CNTs / PEG composite material.

9. The method for preparing sponge-based phase change composite material for solar interface evaporation water according to claim 8, characterized in that, The PEG melting temperature is 60℃~80℃, the vacuum adsorption temperature is 50℃~80℃, the vacuum degree of vacuum adsorption is -0.08MPa~-0.1MPa, the vacuum adsorption time is 2h~6h, the drying temperature is 60℃~80℃, and the drying time is 4h~12h.

10. A sponge-based phase change composite material for solar interface water evaporation, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

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