Solid-solid phase change composite material for solar interface water evaporation and preparation method and application thereof

Abstract

The application discloses a solid-solid phase change composite material for water evaporation on a solar interface and a preparation method and application thereof. The preparation method of the solid-solid phase change composite material for water evaporation on the solar interface comprises the following steps: (1) lauric acid is subjected to acyl chloride treatment; (2) anhydrous triethylamine, anhydrous dichloromethane and graphene oxide are uniformly mixed, then the acyl chloride treated lauric acid is added, and stirring reaction is carried out; after the reaction is completed, rotary evaporation, centrifugal washing and drying are carried out to obtain GO-g-LA; and (3) bacterial cellulose, GO-g-LA and polyvinyl alcohol are uniformly mixed, then freezing treatment is carried out, and then soaking and washing are carried out to obtain the solid-solid phase change composite material. The solid-solid phase change composite material for water evaporation on the solar interface and the preparation method and application thereof chemically graft phase change material lauric acid and graphene oxide, and polyvinyl alcohol is used to modify the substrate material bacterial cellulose, so that the obtained material can prevent leakage and has excellent desalination performance in simulated seawater and real saline-alkali water with different concentrations.

Description

Technical Field

[0001] This invention belongs to the field of interfacial evaporation materials, specifically relating to a solid-solid phase change composite material for solar interfacial water evaporation, its preparation method, and its application. Background Technology

[0002] Global population growth, rapid industrialization, climate change, and severe environmental pollution have exacerbated the shortage of clean water, making water scarcity a global ecological challenge facing humanity. Currently, industrialized seawater desalination technologies include distillation, multi-stage flash evaporation, reverse osmosis, electrodialysis, and condensation. However, these desalination processes suffer from high costs, high energy consumption during equipment operation, and environmental pollution, limiting their large-scale application in rural and remote areas and thus restricting their practical use. In contrast, solar-driven interfacial photothermal conversion water evaporation is considered a low-cost method for obtaining clean water. Currently, solar-driven water evaporation directly converts solar energy into heat energy for water evaporation, thereby obtaining clean water resources with minimal environmental impact and addressing the water scarcity problem.

[0003] Because of the intermittent nature of solar radiation, traditional photothermal conversion materials cannot operate continuously around the clock. Therefore, researchers have proposed a bifunctional phase change composite material (PCCS) that integrates a phase change material (PCM) and a photothermal conversion material, capable of simultaneously converting, storing, and releasing solar energy. To prevent leakage of PCMs, methods such as encapsulation, porous adsorption, sintering, and spinning are employed to address this issue. However, even with these physically blended PCMs, leakage still occurs during long-term use, causing secondary water pollution.

[0004] In contrast, integrating solid-state phase change materials (SPCMs) into a polymer backbone via permanent chemical bonding is a more promising method for preparing solid-solid phase change materials (SSPCMs). In recent years, solid-solid chemical grafting of PCCs has attracted increasing attention from researchers. Chemical grafting involves connecting high-melting-point polymers with low-melting-point polymers through chemical bonds to form copolymers. When the low-melting-point polymer transitions from a crystalline to an amorphous state, the backbone of the high-melting-point polymer remains undissolved, restricting the flow of the low-melting-point polymer. Therefore, the overall material remains robust, effectively solving the leakage problem. According to the literature, chemically grafted PCCs are mainly used in solar thermoelectric integration, photovoltaic systems, and wearable temperature sensors. These materials are less commonly used in seawater desalination and water purification technologies. Therefore, it is essential to develop a leak-free, efficient, economical, and low-energy-consumption SSPCM for application in seawater desalination and water purification technologies.

[0005] Based on this, the present invention proposes a new solid-solid phase change composite material for solar interface water evaporation, its preparation method and application. This material has the advantages of leak prevention, low cost and simple preparation process, and can be promoted on a large scale. Summary of the Invention

[0006] The purpose of this invention is to provide a simple method for preparing a solid-solid phase change composite material for water evaporation at a solar interface.

[0007] To achieve the above objectives, the technical solution adopted is as follows:

[0008] A method for preparing a solid-solid phase change composite material for solar interface water evaporation, characterized by comprising the following steps:

[0009] (1) Lauroyl chloride

[0010] Phosphorus chloride was added to liquid lauric acid to react. After the reaction was completed, the mixture was allowed to stand and separate into layers. The supernatant was taken and distilled under reduced pressure to obtain acyl-chlorinated lauric acid.

[0011] (2) Esterification reaction

[0012] Anhydrous triethylamine, anhydrous dichloromethane and graphene oxide were mixed in an ice-water bath, and then the acyl-chlorinated lauric acid was added and stirred to react. After the reaction was completed, rotary evaporation was performed until a black emulsion was obtained. The emulsion was then centrifuged, washed and dried to obtain GO-g-LA.

[0013] (3)Synthetic materials:

[0014] After mixing bacterial cellulose, GO-g-LA and polyvinyl alcohol, the mixture was frozen, then immersed in a soaking solution and washed to obtain the solid-solid phase change composite material for solar interface water evaporation.

[0015] Furthermore, in step (1), the molar ratio of lauric acid to phosphorus chloride is 2.5 to 3.5:1;

[0016] The reaction temperature is 65–75℃, and the reaction time is 1.5–2.5 h.

[0017] The temperature for vacuum distillation is 65–75℃, and the time is 1.5–2.5 h.

[0018] Furthermore, in step (1), the molar ratio of lauric acid to phosphorus chloride is 3:1;

[0019] The reaction temperature was 70℃, and the reaction time was 2 hours.

[0020] The vacuum distillation was carried out at a temperature of 70℃ for 2 hours.

[0021] Furthermore, in step (2), the mass-to-volume ratio of anhydrous triethylamine, anhydrous dichloromethane, graphene oxide, and the acyl-chlorinated lauric acid is 7-9 mL: 26-34 mL: 90-110 mg: 10 mL.

[0022] Wash with ethanol by centrifugation at 7000–9000 r / min for 6–10 min;

[0023] Vacuum dry at 55–65℃ for 10–14 hours.

[0024] Furthermore, in step (2), the mass-to-volume ratio of anhydrous triethylamine, anhydrous dichloromethane, graphene oxide, and the acyl-chlorinated lauric acid is 8 mL: 30 mL: 100 mg: 10 mL.

[0025] Centrifuge and wash at 8000 r / min for 8 min;

[0026] Vacuum dried at 60℃ for 12 hours.

[0027] Furthermore, in step (3), the mass ratio of bacterial cellulose to GO-g-LA is 30g:400-600mg;

[0028] The mass of PVA is 1 to 2% of the total mass of bacterial cellulin, GO-g-LA and PVA;

[0029] The freezing temperature is -26 to -22°C, and the time is 10 to 14 hours;

[0030] The soaking solution contains glutaraldehyde, hydrochloric acid, and anhydrous ethanol in a volume ratio of 70–90:1:1.

[0031] Wash with deionized water 3 to 4 times.

[0032] Furthermore, in step (3), the mass ratio of bacterial cellulose to GO-g-LA is 30g:500mg;

[0033] The mass of PVA is 1% of the total mass of bacterial cellulin, GO-g-LA and PVA;

[0034] The freezing process was carried out at -24°C for 12 hours.

[0035] The soaking solution contains glutaraldehyde, hydrochloric acid, and anhydrous ethanol in a volume ratio of 80:1:1.

[0036] Another objective of this invention is to provide a solid-solid phase change composite material for solar interface water evaporation, which is prepared by the above-described preparation method. This material is leak-proof and exhibits excellent desalination performance in simulated seawater and real saline water of different concentrations.

[0037] Another object of the present invention is to provide the application of the above-mentioned solid-solid phase change composite material.

[0038] The above-mentioned solid-solid phase change composite material is used in materials for interfacial water evaporation.

[0039] Furthermore, the material is a material for solar interface water evaporation.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. The technical solution of the present invention involves chlorinating LA to lauroyl chloride, and then reacting lauroyl chloride and GO with esterification to generate GO-g-LA, which becomes a PCCS composite. The size of the BC pores is adjusted by modifying with PVA, and a solid-solid phase change composite material capable of continuous evaporation is prepared by low-temperature crosslinking method, which shows effective integration of solar thermal conversion and storage.

[0042] 2. The technical solution of the present invention synthesizes a material that integrates a solid-solid phase change composite material and a solar absorber through chemical grafting. It can prevent leakage and has the advantages of low cost and simple preparation process, thus enabling large-scale promotion.

[0043] 3. The technical solution of the present invention provides a material with high light absorption across the entire spectrum. It exhibits efficient and stable evaporation performance in both cyclic experiments and harsh environments (high-concentration brine, acidic solutions, alkaline solutions, and dye wastewater), demonstrating great application potential in efficient and large-scale solar-powered seawater desalination. Attached Figure Description

[0044] Figure 1 This invention relates to a solar interface water evaporation solid-solid phase change composite material that evaporates clean water and stores heat when there is light, and releases the stored heat to evaporate clean water when there is no light.

[0045] Figure 2 : Schematic diagram of the preparation of the solid-solid phase change composite material of the present invention.

[0046] Figure 3 Photographs of (a) BC aerogel, (b) BC / GO-g-LA-SSPCMs and (c) BC / PVA / GO-g-LA-SSPCMs prepared in Example 1; SEM images of (d, g) BC aerogel, (e, h) BC / GO-g-LA-SSPCMs and (f, i) BC / PVA / GO-g-LA-SSPCMs at different magnifications.

[0047] Figure 4TEM images of (a) GO and (b) GO-g-LA.

[0048] Figure 5 FTIR spectra of different materials; Figure (a) shows C 11 H 23 COOH and C 11 H 23 COCl, (b) are GO and GO-g-LA.

[0049] Figure 6 : Representative spectral detection of different materials; Figure (a) is FTIR spectrum, Figure (b) is FTIR spectrum before and after evaporation, Figure (c) is Raman spectrum, and Figure (d) is XRD spectrum.

[0050] Figure 7 The thermal reliability and phase transition properties of lauric acid (LA) and BC / GO-g-LA-SSPCMs prepared in Example 1 were tested; Figure (a) shows the TG, Figure (b) shows the DTG, Figure (c) shows the UV-Vis-NIR absorption spectrum, and Figure (d) shows the DSC thermal analysis diagram.

[0051] Figure 8 POMs of different materials; (a) is LA, (b) is a solid-solid phase change composite material.

[0052] Figure 9 Hydrophilicity test of BC, BC / GO-g-LA and BC / GO-g-LA-SSPCMs prepared in Example 1.

[0053] Figure 10 Leakage tests of different materials at 80℃, representing different materials.

[0054] Figure 11 The solid-solid phase change composite materials prepared in Example 1 are shown in (a) as mass change curves and (b) as corresponding surface temperature change curves under different masses of light irradiation for 1 hour and light-off for 1 hour. GO-g-LA is shown in (c) as mass change curves and (d) as corresponding surface temperature change curves under different proportions of light irradiation for 1 hour and light-off for 1 hour.

[0055] Figure 12 The following figures illustrate the mass change curves (a) and surface temperature change curves (b) of GO-g-LA with different masses prepared in this invention under 1 hour of illumination and 1 hour of darkness. The figures also show the mass change curves (c) and corresponding surface temperature change curves (d) of different PVA dosages under 1 hour of illumination and 1 hour of darkness.

[0056] Figure 13 The surface temperature changes of representative materials prepared in this invention under 1 hour of light exposure and 1 hour of light-off conditions, along with corresponding infrared photographs.

[0057] Figure 14 The mass change curves and temperature change curves of the four different materials prepared in this invention under 1 hour of light and 1 hour of darkness are shown in (a) and (b) respectively. The evaporation rate and photothermal conversion efficiency of the four different materials under 1 hour of light and 1 hour of darkness are shown in (c) and (d) respectively.

[0058] Figure 15 The following are the evaporation rate curves and temperature change curves of representative acid, base and salt solutions prepared in this invention under 1 hour of light and 1 hour of darkness: (a) evaporation rate curves and (b) temperature change curves; (c) BC / PVA / GO-g-LA-SSPCMs under 15 cycles of 1 hour of light and 1 hour of darkness; (d) temperature and humidity change graphs.

[0059] Figure 16 Outdoor evaporation performance test of the solid-solid phase change composite material prepared in Example 1 of this invention; (a) Evaporation performance of BC / PVA / GO-g-LA-SSPCMs and BC / PVA / GO composite material in outdoor evaporation experiment; (b) Conductivity-salinity curve; (c) Salinity change before and after desalination at three different levels of salinity; (d) Change in ion content before and after desalination of actual saline-alkali water.

[0060] Figure 17 Examples of the present invention: Salinity changes of solid-solid phase change composite materials prepared in Example 1 of the present invention before and after desalination in salt solutions of different salinities; (a) Photographs and UV-Vis absorption spectra of methylene blue solution before and after purification; (b) Photographs and UV-Vis absorption spectra of Congo red solution before and after purification; (c) Photographs of pH test strips tested in acidic solution, alkaline solution and collected distilled water.

[0061] Figure 18-19 The infrared images are for comparison examples 1-5. Detailed Implementation

[0062] To further illustrate the solid-solid phase change composite material for solar interface water evaporation, its preparation method, and its application, and to achieve the intended purpose of the invention, the following detailed description, in conjunction with preferred embodiments, details the specific implementation methods, structures, features, and effects of the solid-solid phase change composite material for solar interface water evaporation, its preparation method, and its application. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0063] The following will provide a detailed description of the solid-solid phase change composite material for solar interface water evaporation, its preparation method, and its applications, with reference to specific embodiments:

[0064] Solar-driven interfacial evaporation materials are widely used in seawater desalination. However, solar energy is intermittent. To address this issue, phase change materials (PCMs) and interfacial evaporation materials are combined. Many PCMs are physically blended and loaded onto interfacial evaporation matrix materials, which may lead to leakage problems and secondary water pollution during long-term use. To solve these problems, this invention develops a novel interfacial evaporation material that can continuously and efficiently evaporate clean water under intermittent sunlight irradiation. The material is obtained by chemically grafting PCMs with lauric acid (LA) and graphene oxide (GO), and modifying the matrix material bacterial cellulose (BC) with polyvinyl alcohol (PVA). This solid-solid PCM composite material exhibits high light absorption across the entire spectrum and demonstrates efficient and stable evaporation performance in cyclic experiments and harsh environments (high-concentration brine, acidic solutions, alkaline solutions, and dye wastewater). It can also be used to treat acidic solutions, alkaline solutions, and dye wastewater to achieve water purification.

[0065] To achieve the above objectives, the technical solution adopted is as follows:

[0066] A method for preparing a solid-solid phase change composite material for solar interface water evaporation, characterized by comprising the following steps:

[0067] (1) Lauroyl chloride

[0068] Phosphorus chloride was added to liquid lauric acid (LA) to carry out the reaction. After the reaction was completed, the mixture was allowed to stand and separate into layers. The supernatant was taken and distilled under reduced pressure to obtain acyl-chlorinated lauric acid.

[0069] (2) Esterification reaction

[0070] Anhydrous triethylamine, anhydrous dichloromethane and graphene oxide were mixed in an ice-water bath, and then the acyl-chlorinated lauric acid was added and stirred to react. After the reaction was completed, rotary evaporation was performed until a black emulsion was obtained. The emulsion was then centrifuged, washed and dried to obtain GO-g-LA.

[0071] (3)Synthetic materials:

[0072] After mixing bacterial cellulose (BC), GO-g-LA and polyvinyl alcohol (PVA), the mixture is frozen, then immersed in a soaking solution and washed to obtain the solid-solid phase change composite material for solar interface water evaporation.

[0073] Preferably, in step (1), the molar ratio of lauric acid to phosphorus chloride is 2.5 to 3.5:1;

[0074] The reaction temperature is 65–75℃, and the reaction time is 1.5–2.5 h.

[0075] The temperature for vacuum distillation is 65–75℃, and the time is 1.5–2.5 h.

[0076] More preferably, in step (1), the molar ratio of lauric acid to phosphorus chloride is 3:1;

[0077] The reaction temperature was 70℃, and the reaction time was 2 hours.

[0078] The vacuum distillation was carried out at a temperature of 70℃ for 2 hours.

[0079] Preferably, in step (2), the mass-to-volume ratio of anhydrous triethylamine, anhydrous dichloromethane, graphene oxide, and the acyl-chlorinated lauric acid is 7-9 mL: 26-34 mL: 90-110 mg: 10 mL.

[0080] Wash with ethanol by centrifugation at 7000–9000 r / min for 6–10 min;

[0081] Vacuum dry at 55–65℃ for 10–14 hours.

[0082] More preferably, in step (2), the mass-to-volume ratio of anhydrous triethylamine, anhydrous dichloromethane, graphene oxide and the acyl-chlorinated lauric acid is 8 mL: 30 mL: 100 mg: 10 mL.

[0083] Centrifuge and wash at 8000 r / min for 8 min;

[0084] Vacuum dried at 60℃ for 12 hours.

[0085] Preferably, in step (3), the mass ratio of bacterial cellulose to GO-g-LA is 30g:400-600mg;

[0086] The mass of PVA is 1 to 2% of the total mass of bacterial cellulin, GO-g-LA and PVA;

[0087] The freezing temperature is -26 to -22°C, and the time is 10 to 14 hours;

[0088] The soaking solution contains glutaraldehyde, hydrochloric acid, and anhydrous ethanol in a volume ratio of 70–90:1:1.

[0089] Wash with deionized water 3 to 4 times.

[0090] More preferably, in step (3), the mass ratio of bacterial cellulose to GO-g-LA is 30g:500mg;

[0091] The mass of PVA is 1% of the total mass of bacterial cellulin, GO-g-LA and PVA;

[0092] The freezing process was carried out at -24°C for 12 hours.

[0093] The soaking solution contains glutaraldehyde, hydrochloric acid, and anhydrous ethanol in a volume ratio of 80:1:1.

[0094] Example 1.

[0095] Synthesis process as follows Figure 2 As shown, the specific operation steps are as follows:

[0096] (1) Lauroyl chloride

[0097] Lauric acid (3 mol) was added to a reaction vessel, and the temperature was controlled at 70℃. After the lauric acid was completely dissolved, PCl3 (1 mol) was added dropwise through a separatory funnel, and the reaction was carried out at 70℃ for 2 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours to separate into two layers, with the lower layer being H3PO3. The supernatant was collected and distilled under reduced pressure at 70℃ for 2 hours to remove H3PO3, yielding lauroyl chloride, i.e., lauric acid chloride.

[0098] (2) Esterification reaction

[0099] The reaction vessel was placed in an ice-water bath (4°C), and anhydrous triethylamine (8 mL), anhydrous dichloromethane (30 mL), and GO (100 mg) were added and stirred for 20 min. Then, lauroyl chloride (10 mL) was added dropwise using a separatory funnel; white fumes were produced in the reaction vessel during this process. After the lauroyl chloride was completely added, the mixture was stirred at room temperature (1000 rpm) for 12 h. The resulting mixture was then rotary evaporated to form a black emulsion, centrifuged (8000 rpm) for 8 min, washed three times with ethanol, and dried under vacuum at 60°C for 12 h. Finally, GO-g-LA was obtained.

[0100] (3)Synthetic materials:

[0101] BC (30g), GO-g-LA (500mg), and PVA (308mg) were mechanically stirred at room temperature for 1 hour (1000rpm) to obtain a dispersion. Then, 6g of the dispersion was weighed and placed into a mold, and frozen at -24℃ for 12 hours. Next, the frozen dispersion was immersed in a soaking solution containing glutaraldehyde (GA), hydrochloric acid, and anhydrous ethanol in a volume ratio of 80:1:1 for 12 hours. Finally, it was washed three times with deionized water to obtain the solid-solid phase change composite material (BC / PVA / GO-g-LA-SSPCMs).

[0102] Comparative Example 1: DA-gR-COOH

[0103] The specific steps are as follows:

[0104] First, dopamine (1 mol), lauric acid (2 mol), N,N-dimethylformamide (10 mL), and N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC, 0.001 mol) were added to the reaction vessel and reacted for 20 min. Then, N-hydroxysuccinimide (NHS, 0.001 mol) was added and reacted for 6 h.

[0105] Then, the above mixed solution was centrifuged (8000 rpm) for 8 min and dried under vacuum at 60 °C for 12 h. Finally, 50 mL of Tris-HCl buffer solution and 100 mg of the above dried substance were added to a 250 mL beaker, stirred, and reacted at room temperature for 24 h, during which time it remained as a white flocculent precipitate. After centrifugation at 8000 rpm for 8 min and drying under vacuum at 60 °C for 24 h, a white powder was obtained.

[0106] The experiment failed; dopamine did not polymerize and no black substance was formed, which did not meet the initial assumption that the material was both a phase change material and a solar absorber.

[0107] Comparative Example 2: DA-gR-COCI

[0108] The specific steps are as follows:

[0109] First, dopamine hydrochloride (1 mol), N,N-dimethylformamide (10 mL), and N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC, 0.001 mol) were added to an ice-water bath reactor and reacted for 20 min. Then, N-hydroxysuccinimide (NHS, 0.001 mol) was added, and lauroyl chloride (2 mol) was added dropwise using a separatory funnel and reacted for 6 h.

[0110] Then, the above mixed solution was centrifuged (8000 rpm) for 8 min and dried under vacuum at 60 °C for 12 h. Finally, 50 mL of Tris-HCl buffer solution and 100 mg of the above dried substance were added to a 250 mL beaker, stirred, and reacted at room temperature for 24 h, during which time it remained as a white flocculent precipitate. After centrifugation at 8000 rpm for 8 min and drying under vacuum at 60 °C for 24 h, a white powder was obtained.

[0111] The experiment failed because the hydroxyl and carboxyl groups were esterified, preventing dopamine from polymerizing and forming a black substance. This did not meet the initial design requirement of being both a phase change material and a solar absorber.

[0112] Comparative Example 3: PDA-gR-COOH

[0113] The specific steps are as follows:

[0114] First, add 100 mg of dopamine hydrochloride and 50 mL of Tris-HCl buffer solution to the reaction vessel, stir at room temperature for 24 h, centrifuge at 8000 rpm / min for 8 min, and vacuum dry at 60 °C for 24 h to obtain polydopamine.

[0115] Next, polydopamine (1 mol), lauric acid (2 mol), N,N-dimethylformamide (10 mL), and N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC, 0.001 mol) were added to a round-bottom flask and reacted for 20 min. Then, N-hydroxysuccinimide (NHS, 0.001 mol) was added and reacted for 6 h.

[0116] Finally, the above mixed solution was centrifuged (8000 r / min) for 8 min and dried under vacuum at 60℃ for 12 h.

[0117] pass Figure 18 Infrared spectroscopy reveals that the hydroxyl groups in polydopamine are difficult to graft onto the carboxyl groups in lauric acid, which does not conform to the original design that the material is both a phase change material and a solar absorber.

[0118] Comparative Example 4: PDA-gR-COCI

[0119] The specific steps are as follows:

[0120] First, add 100 mg of dopamine hydrochloride and 50 mL of Tris-HCl buffer solution to the reaction vessel, stir at room temperature for 24 h, centrifuge at 8000 rpm / min for 8 min, and vacuum dry at 60 °C for 24 h to obtain polydopamine.

[0121] Next, polydopamine (1 mol), N,N-dimethylformamide (10 mL), and N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC, 0.001 mol) were added to an ice-water bath reactor. Lauroyl chloride (2 mol) was added dropwise using a separatory funnel. The reaction was carried out for 20 min, followed by the addition of N-hydroxysuccinimide (NHS, 0.001 mol), and the reaction was carried out for 6 h.

[0122] Finally, the above mixed solution was centrifuged (8000 r / min) for 8 min and dried under vacuum at 60℃ for 12 h.

[0123] pass Figure 18 Infrared spectroscopy reveals that there are no ester groups. It is difficult for the hydroxyl groups in polydopamine to graft onto the carboxyl groups in lauric acid, which does not conform to the original design that the material is both a phase change material and a solar absorber.

[0124] Comparative Example 5: GO-gR-COOH

[0125] The specific steps are as follows:

[0126] First, add graphene oxide (100 mg) to the reaction vessel and sonicate for 30 min.

[0127] Next, add lauric acid (300 mg), N,N-dimethylformamide (10 mL) and concentrated sulfuric acid (2 mL), and react at 120 °C for 12 h.

[0128] Finally, the above mixed solution was centrifuged (8000 r / min) for 8 min and dried under vacuum at 60℃ for 12 h.

[0129] The experiment revealed that the precipitate and black substance separated into layers after centrifugation, and the grafting yields of graphene oxide and lauric acid were relatively low. Figure 19 Infrared spectroscopy reveals the absence of ester groups. This contradicts the initial assumption that the material should function as both a phase change material and a solar absorber.

[0130] Example 2.

[0131] The specific steps are as follows:

[0132] (1) Lauroyl chloride

[0133] Lauric acid (2.5 mol) was added to a reaction vessel, and the temperature was controlled at 70℃. After the lauric acid was completely dissolved, PCl3 (1 mol) was added dropwise through a separatory funnel, and the reaction was carried out at 65℃ for 2.5 h. After the reaction was completed, the mixture was allowed to stand for 12 h to separate into two layers, with the lower layer being H3PO3. The supernatant was taken and distilled under reduced pressure at 65℃ for 2.5 h to remove H3PO3, yielding lauroyl chloride, i.e., lauric acid chloride.

[0134] (2) Esterification reaction

[0135] The reaction vessel was placed in an ice-water bath (4°C), and anhydrous triethylamine (7 mL), anhydrous dichloromethane (26 mL), and GO (90 mg) were added and stirred for 20 min. Then, lauroyl chloride (10 mL) was added dropwise using a separatory funnel; white fumes were produced in the reaction vessel during this process. After the lauroyl chloride was completely added, the mixture was stirred at room temperature (1000 rpm) for 12 h. The resulting mixture was then rotary evaporated to form a black emulsion, centrifuged (7000 rpm) for 10 min, washed three times with ethanol, and dried under vacuum at 55°C for 14 h. Finally, GO-g-LA was obtained.

[0136] (3)Synthetic materials:

[0137] BC (30g), GO-g-LA (400mg), and PVA (620mg) were mechanically stirred at room temperature for 1 hour (1000rpm) to obtain a dispersion. Then, 6g of the dispersion was weighed and placed into a mold, and frozen at -26℃ for 10 hours. Next, the frozen dispersion was immersed in a soaking solution containing glutaraldehyde (GA), hydrochloric acid, and anhydrous ethanol in a volume ratio of 70:1:1 for 12 hours. Finally, it was washed three times with deionized water to obtain a solid-solid phase change composite material.

[0138] Example 3.

[0139] The specific steps are as follows:

[0140] (1) Lauroyl chloride

[0141] Lauric acid (3.5 mol) was added to a reaction vessel, and the temperature was controlled at 70℃. After the lauric acid was completely dissolved, PCl3 (1 mol) was added dropwise through a separatory funnel, and the reaction was carried out at 75℃ for 1.5 h. After the reaction was completed, the mixture was allowed to stand for 12 h to separate into two layers, with the lower layer being H3PO3. The supernatant was taken and distilled under reduced pressure at 75℃ for 1.5 h to remove H3PO3, yielding lauroyl chloride, i.e., lauric acid chloride.

[0142] (2) Esterification reaction

[0143] The reaction vessel was placed in an ice-water bath (4°C), and anhydrous triethylamine (9 mL), anhydrous dichloromethane (34 mL), and GO (110 mg) were added and stirred for 20 min. Then, lauroyl chloride (10 mL) was added dropwise using a separatory funnel; white fumes were produced in the reaction vessel during this process. After the lauroyl chloride was completely added, the mixture was stirred at room temperature (1000 rpm) for 12 h. The resulting mixture was then rotary evaporated to form a black emulsion, centrifuged (9000 rpm) for 6 min, washed three times with ethanol, and dried under vacuum at 65°C for 10 h. Finally, GO-g-LA was obtained.

[0144] (3)Synthetic materials:

[0145] BC (30g), GO-g-LA (600mg), and PVA (500mg) were mechanically stirred at room temperature for 1 hour (1000rpm) to obtain a dispersion. Then, 6g of the dispersion was weighed and placed into a mold, and frozen at -22℃ for 14 hours. Next, the frozen dispersion was immersed in a soaking solution containing glutaraldehyde (GA), hydrochloric acid, and anhydrous ethanol in a volume ratio of 90:1:1 for 12 hours. Finally, it was washed four times with deionized water to obtain the solid-solid phase change composite material.

[0146] Example 4.

[0147] The specific steps are as follows:

[0148] (1) Lauroyl chloride

[0149] Lauric acid (3.0 mol) was added to a reaction vessel, and the temperature was controlled at 75℃. After the lauric acid was completely dissolved, PCl3 (1 mol) was added dropwise through a separatory funnel, and the reaction was carried out at 72℃ for 2 hours. After the reaction was completed, the mixture was allowed to stand for 12 hours to separate into two layers, with the lower layer being H3PO3. The supernatant was collected and distilled under reduced pressure at 68℃ for 2 hours to remove H3PO3, yielding lauroyl chloride, i.e., lauric acid chloride.

[0150] (2) Esterification reaction

[0151] The reaction vessel was placed in an ice-water bath (4°C), and anhydrous triethylamine (8 mL), anhydrous dichloromethane (30 mL), and GO (105 mg) were added and stirred for 20 min. Then, lauroyl chloride (10 mL) was added dropwise using a separatory funnel; white fumes were produced in the reaction vessel during this process. After the lauroyl chloride was completely added, the mixture was stirred at room temperature (1000 rpm) for 12 h. The resulting mixture was then rotary evaporated to form a black emulsion, centrifuged (8000 rpm) for 9 min, washed four times with ethanol, and dried under vacuum at 60°C for 10 h. Finally, GO-g-LA was obtained.

[0152] (3)Synthetic materials:

[0153] BC (30g), GO-g-LA (500mg), and PVA (500mg) were mechanically stirred at room temperature for 1 hour (1000rpm) to obtain a dispersion. Then, 6g of the dispersion was weighed and placed into a mold, and frozen at -24℃ for 14 hours. Next, the frozen dispersion was immersed in an soaking solution containing glutaraldehyde (GA), hydrochloric acid, and anhydrous ethanol in a volume ratio of 82:1:1 for 12 hours. Finally, it was washed four times with deionized water to obtain the solid-solid phase change composite material.

[0154] Example 5.

[0155] The morphology of the prepared solid-solid phase change composite material was analyzed.

[0156] (1) BC / GO-g-LA-SSPCMs: BC / GO-g-LA-SSPCMs were prepared using the preparation method of Example 1, except that PVA was not used in the grafting process.

[0157] SEM was used to detect bacterial cellulose (BC) aerogels, BC / GO-g-LA-SSPCMs, and BC / PVA / GO-g-LA-SSPCMs prepared in Example 1.

[0158] The results are as follows Figure 3 As shown, Figure 3 SEM images of representative materials are shown.

[0159] (2) Figure 4 TEM images show the sheet-like structure and morphology of graphene oxide (GO) and GO-g-LA prepared in Example 1, demonstrating that GO-g-LA does not affect the sheet-like structure and morphology of GO.

[0160] (3) Detection based on chemical structure and crystallization properties:

[0161] Lauric acid (C) in Example 1 11 H 23 COOH) and lauric acid (C) chloride 11 H 23 FTIR spectroscopy was performed on COCl, graphene oxide, and GO-g-LA, and the results are as follows: Figure 5 As shown.

[0162] FTIR spectroscopy was performed on lauric acid (LA), graphene oxide (GO), BC, GO-g-LA, PVA, and BC / GO-g-LA-SSPCMs in Example 1; FTIR spectroscopy was performed on BC / GO-g-LA-SSPCMs before and after evaporation; Raman spectroscopy was performed on graphene oxide (GO) and GO-g-LA; and XRD spectroscopy was performed on lauric acid (LA) and GO-g-LA. The results are as follows: Figure 6 As shown.

[0163] From the perspective of chemical structure and crystallization properties, Figure 5 and Figure 6 Representative spectroscopic detection of different prepared materials; through infrared, Raman, and XRD patterns, it can be seen that C 11 H 23 COOH acyl chloride successfully converted to C 11 H 23 COCl and GO-g-LA were successfully grafted.

[0164] The functional groups of the materials were characterized by FTIR, and the FTIR spectra of GO and GO-g-LA were obtained. GO and GO-g-LA showed the FTIR spectrum at 2924 cm⁻¹. -1 and 2859cm -1 The peak at 1633 cm⁻¹ is caused by the stretching CH vibration, corresponding to the presence of CH bonds, and is located at 1633 cm⁻¹. -1 The absorption peak at 3445 cm⁻¹ is attributed to C=O stretching. The most prominent feature of the GO spectrum is at 3445 cm⁻¹. -1 The peak at 1717 cm⁻¹ originates from the stretching vibration of the OH group, which may be due to adsorbed water. Compared to GO, the OH peak in the infrared spectrum of GO-g-LA is elevated, which is due to the substitution of the OH group in the carboxyl group by an ester group. -1 The peak at this point can be attributed to the tensile vibration of C=O. Another peak appears at 1172 cm⁻¹.-1 At this point, the CO stretching vibration in the carboxyl group is observed; another stronger peak appears at 1040 cm⁻¹. -1 This is the OC in GO-g-LA. 11 H 23 The CO stretching vibration in the CO group also provides clear evidence that the LA chain was successfully grafted onto the GO chip.

[0165] (4) To demonstrate thermal reliability and phase change performance, the TG, DTG, UV-Vis-NIR absorption spectra and DSC thermal analysis diagrams of different materials were tested. Lauric acid (LA) and the BC / GO-g-LA-SSPCMs prepared in Example 1 were subjected to TG, DTG, UV-Vis-NIR absorption spectra and DSC thermal analysis.

[0166] The results are as follows Figure 7 As shown, solid-solid phase change composite materials have excellent shape stability, light absorption rate of up to 88.8%, and high phase change enthalpy, which is sufficient to meet the thermal energy storage requirements of seawater desalination and can effectively and continuously evaporate.

[0167] (5) The phase transition process was monitored using POM (Polymer Oxide Membrane) to further investigate the thermal energy storage mechanism. The POM of the LA and the solid-solid phase change composite materials prepared in Example 1 was tested. The results are as follows: Figure 8 As shown, the hydrophilicity of the material affects the water supply during the evaporation process and is crucial to ensuring continuous evaporation.

[0168] (6) The hydrophilicity of BC, BC / GO-g-LA (i.e., the above-mentioned BC / GO-g-LA-SSPCMs) and BC / GO-g-LA-SSPCMs prepared in Example 1 was tested.

[0169] The results are as follows Figure 9 As shown, the three materials have good hydrophilicity, which is beneficial for water supply during the evaporation process.

[0170] (7) To investigate the leak-proof performance of solid-solid phase change composites, morphological qualitative and leak-proof performance tests were conducted on BC, GO-g-LA prepared in Example 1, and BC / GO-g-LA-SSPCMs prepared in Example 1 at 80°C. The results are as follows: Figure 10 As shown, no leakage was observed around GO-g-LA and solid-solid phase change composites (BC / GO-g-LA-SSPCMs), which proves that the grafting of GO and LA was successful and that there was no significant change in morphology.

[0171] Example 6.

[0172] The evaporation performance of the prepared solid-solid phase change composite material was analyzed.

[0173] (1) The mass change curves and corresponding surface temperature change curves of the solid-solid phase change composite material prepared in Example 1 under different light irradiation times (1 h) and light-off times (1 h) were tested. GO-g-LA with different molar ratios of LA and PCl3 (3:1, 1:1, 1:3, 1:5, 1:7) were prepared using the method of Example 1. The mass change curves and corresponding surface temperature change curves of GO-g-LA with different molar ratios under light irradiation times (1 h) and light-off times (1 h) were tested. The results are as follows: Figure 11 As shown.

[0174] The mass change curves and surface temperature change curves of GO-g-LA with different dosages prepared using the method of Example 1 under 1 hour of illumination and 1 hour of darkness-off conditions are shown. (c) Mass change curves and (d) corresponding surface temperature change curves for different PVA dosages under 1 hour of illumination and 1 hour of darkness-off conditions are also shown. The percentage of PVA dosage was calculated as PVA mass / (bacterial cellulose mass + GO-g-LA mass + PVA mass). Results are as follows... Figure 12 As shown.

[0175] from Figure 11 and 12 As shown, the performance of the prepared representative solid-solid phase change composite material was optimized, and the highest performance evaporation rate was finally obtained. That is, the best performance was achieved when the molar ratio of lauric acid and phosphorus chloride in GO-g-LA was 3:1 and the amount of PVA was 1wt%.

[0176] (2) In order to verify the photothermal conversion performance and energy storage performance of solid-solid phase change composite material, the photothermal conversion performance and energy storage performance of solid-solid phase change composite material were tested.

[0177] The surface temperature changes of water, bacterial cellulose (BC), BC / PVA / GO composite material (a phase change-free composite material), and BC / GO-g-LA-SSPCMs prepared in Example 1 were detected under 1 hour of illumination and 1 hour of illumination with the lights off, and the corresponding infrared images were obtained. Figure 13 As shown, the results indicate that solid-solid phase change composite materials possess excellent photothermal conversion and heat storage capabilities.

[0178] (3) To verify the sustained evaporation performance of the solid-solid phase change composite material, optimized evaporation performance tests were conducted on water, bacterial cellulose (BC), BC / PVA / GO composite material (non-phase change composite material), and BC / GO-g-LA-SSPCMs prepared in Example 1. Specifically, the mass change curves and temperature change curves of these four different materials were tested under 1 hour of light and 1 hour of darkness. The evaporation rate and photothermal conversion efficiency of these four different materials were also tested under 1 hour of light and 1 hour of darkness.

[0179] The results are as follows Figure 14As shown, evaporation performance tests were conducted, and the results showed that the solid-solid phase change composite material extended the evaporation time and improved the photothermal conversion efficiency, laying the foundation for overcoming the limitations of light conditions.

[0180] (4) Different acid, alkali, and salt solutions exist in real life. In order to study the practical application of solid-solid phase change composite materials in different acid, alkali, and salt solutions, the solid-solid phase change composite materials prepared in Example 1 were tested in acidic solution (0.1M HCl, pH=1), alkaline solution (0.1M NaOH, pH=13), 1.0wt% NaCl, 5.0wt% NaCl, 10wt% NaCl, and 1g·mL⁻¹ solution. -1 Evaporation performance test in simulated saline water.

[0181] The results are as follows Figure 15 As shown, the evaporation rate and surface temperature curves show no difference from those in tap water, and the evaporation rate remains high in the cyclic experiment.

[0182] Example 7.

[0183] Outdoor evaporation experiments, such as Figure 1 As shown in the figure, the outdoor evaporation experiment proved that the desired effect was achieved.

[0184] (1) To verify the seawater desalination performance of the solid-solid phase change composite material, the solid-solid phase change composite material prepared in Example 1 was tested for outdoor evaporation performance using actual seawater from the Bohai Sea as a sample. This included: the evaporation performance of the BC / PVA / GO-g-LA-SSPCMs and BC / PVA / GO composite material prepared in Example 1 in outdoor evaporation experiments; the conductivity-salinity curve of the BC / PVA / GO-g-LA-SSPCMs prepared in Example 1; the salinity changes of the BC / PVA / GO-g-LA-SSPCMs prepared in Example 1 before and after desalination at three different salinity levels; and the changes in ion content of the BC / PVA / GO-g-LA-SSPCMs prepared in Example 1 before and after desalination in actual saline-alkali water.

[0185] The results are as follows Figure 16 As shown, the results indicate that solid-solid phase change composite materials can provide a higher total water output than those without phase change materials.

[0186] (2) The solid-solid phase change composite material of the present invention can address the challenge of low solar energy intensity in seawater desalination technology due to climate change. To determine the salinity change of the solid-solid phase change composite material prepared in Example 1 before and after desalination in salt solutions of different salinities, a linear fitting curve was performed using the conductivity of NaCl solution and salinity. The results are as follows... Figure 17 As shown, the solid-solid phase change composite material prepared in Example 1 has excellent potential for saline-alkali water desalination.

[0187] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a solid-solid phase change composite material for solar interface water evaporation, characterized in that, Includes the following steps: (1) Lauroyl chloride Phosphorus chloride was added to liquid lauric acid to react. After the reaction was completed, the mixture was allowed to stand and separate into layers. The supernatant was taken and distilled under reduced pressure to obtain acyl-chlorinated lauric acid. (2) Esterification reaction Anhydrous triethylamine, anhydrous dichloromethane and graphene oxide were mixed in an ice-water bath, and then the acyl-chlorinated lauric acid was added and stirred to react. After the reaction was completed, rotary evaporation was performed until a black emulsion was obtained. The emulsion was then centrifuged, washed and dried to obtain GO-g-LA. (3)Synthetic materials: After stirring and mixing bacterial cellulose, GO-g-LA and polyvinyl alcohol, the mixture was frozen and then immersed in a soaking solution and washed to obtain the solid-solid phase change composite material for solar interface water evaporation. The soaking solution contains glutaraldehyde, hydrochloric acid, and anhydrous ethanol in a volume ratio of 70-90:1:

1.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of lauric acid to phosphorus chloride is 2.5 to 3.5:1; The reaction temperature is 65–75℃, and the reaction time is 1.5–2.5 h. The temperature for vacuum distillation is 65–75℃, and the time is 1.5–2.5 h.

3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of lauric acid to phosphorus chloride is 3:1; The reaction temperature was 70℃, and the reaction time was 2 hours. The vacuum distillation was carried out at a temperature of 70℃ for 2 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass-to-volume ratio of anhydrous triethylamine, anhydrous dichloromethane, graphene oxide, and the acyl-chlorinated lauric acid is 7-9 mL: 26-34 mL: 90-110 mg: 10 mL. Wash with ethanol by centrifugation at 7000–9000 r / min for 6–10 min; Vacuum dry at 55–65℃ for 10–14 hours.

5. The preparation method according to claim 4, characterized in that, In step (2), the mass-volume ratio of anhydrous triethylamine, anhydrous dichloromethane, graphene oxide and the acyl-chlorinated lauric acid is 8 mL: 30 mL: 100 mg: 10 mL. Centrifuge and wash at 8000 r / min for 8 min; Vacuum dried at 60℃ for 12 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of bacterial cellulose to GO-g-LA is 30g:400-600mg; The mass of PVA is 1-2% of the total mass of bacterial cellulin, GO-g-LA and PVA; The freezing temperature is -26 to -22°C, and the time is 10 to 14 hours; Wash with deionized water 3 to 4 times.

7. The preparation method according to claim 6, characterized in that, In step (3), the mass ratio of bacterial cellulose and GO-g-LA is 30g:500mg; The mass of PVA is 1% of the total mass of bacterial cellulin, GO-g-LA, and PVA. The freezing process was carried out at -24°C for 12 hours. The soaking solution contains glutaraldehyde, hydrochloric acid, and anhydrous ethanol in a volume ratio of 80:1:

1.

8. A solid-solid 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 7.

9. The application of the solid-solid phase change composite material according to claim 8 in materials for interfacial water evaporation.

10. The application according to claim 9, characterized in that, The material described is a material for solar interface water evaporation.

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