A photothermal conversion aerogel and a preparation method and application thereof

Abstract

The application provides a photothermal conversion aerogel and a preparation method and application thereof. The application takes tea residue as raw material, and obtains tea residue fiber through alkali treatment; the tea residue fiber is calcined at high temperature to obtain carbonized tea residue; the tea residue fiber and the carbonized tea residue are added into a sodium alginate solution, and are freeze-dried through liquid nitrogen to obtain tea residue fiber and carbonized tea residue aerogel; the aerogel is soaked in a CaCl2 solution for crosslinking, and is freeze-dried through liquid nitrogen to obtain a full-biomass-waste-based photothermal conversion aerogel; the photothermal conversion aerogel has the following advantages: 1) the photothermal conversion aerogel has vertically oriented water-conducting channels, can realize stable seawater desalination, and can effectively alleviate the shortage of fresh water resources; 2) the photothermal conversion aerogel can stably desalinate 10wt% of salt water, and the efficiency is 1.5kg m –2 h –1 ; 3) the photothermal conversion aerogel can effectively reduce the pollution of tea residue to the environment.

Description

Technical Field

[0001] This invention relates to the field of aerogel technology, and in particular to a photothermal conversion aerogel, its preparation method, and its application. Background Technology

[0002] Freshwater scarcity, energy crisis, and environmental pollution are pressing challenges facing humanity. Seawater accounts for 97% of the Earth's water resources, and desalination technology can effectively alleviate the global water shortage. However, traditional desalination methods, such as thermal distillation and reverse osmosis, consume vast amounts of energy, further exacerbating the energy crisis. In 2014, interfacial solar-driven desalination was proposed as a promising solution to this problem, attracting widespread attention due to its high evaporation rate and environmental friendliness. Interfacial solar-driven desalination systems typically include photothermal materials, an insulation layer, and a water transporter. The photothermal materials absorb sunlight and convert it into heat energy, while the insulation layer restricts heat loss to the large volume of water at the water vapor interface. The water transporter delivers water to the surface of the photothermal materials for evaporation. Photothermal materials are mainly classified into four categories: plasma, semiconductor, polymer, and carbon materials.

[0003] Carbon materials, especially biochar, have attracted widespread attention due to their abundant availability and broad solar energy absorption capacity. Furthermore, the evaporation mechanism of interfacial solar-driven desalination is similar to transpiration in plants, where roots supply water to leaves for evaporation, just as a water transporter delivers water to a photothermal material to generate steam. Many all-biomass-based solar evaporators have been developed, which can be divided into two types. The first type is based on carbonized biomass, which retains the natural porous structure of the biomass for interfacial solar-driven desalination, such as carbonized mushrooms and wood. While this method allows for convenient fabrication of solar evaporators, carbonized biomass is prone to cracking due to water loss. The second type is based on photothermal conversion membranes made entirely of biological waste. Although the fabrication of these membranes is relatively simple, their desalination performance can be affected by salt crystal deposition on their surface during the desalination process.

[0004] Given the current shortcomings of photothermal conversion materials based on biological waste, it is necessary to improve them. Summary of the Invention

[0005] In view of this, the present invention provides a photothermal conversion aerogel, its preparation method and application, to overcome the defects existing in the prior art.

[0006] In a first aspect, the present invention provides a method for preparing photothermal conversion aerogel, comprising the following steps:

[0007] Tea leaves are added to an alkaline solution and reacted at 150–170°C. The mixture is then filtered, washed, and tea leaves fiber is obtained.

[0008] Tea residue fibers are placed in a tube furnace and calcined at 500-700℃ to obtain carbonized tea residue.

[0009] Carbonized tea residue is ground into powder, added to acid solution, soaked, and washed to obtain tea residue carbon powder.

[0010] Sodium alginate was added to water, followed by tea dregs fiber, then tea dregs carbon powder, and stirred. After freezing and solidification, the mixture was freeze-dried in a freeze dryer to obtain an aerogel.

[0011] The aerogel was then soaked in CaCl2 solution, washed, and freeze-dried in a freeze dryer to obtain photothermal conversion aerogel.

[0012] Preferably, in the method for preparing the photothermal conversion aerogel, the alkaline solution includes at least one of NaOH solution and KOH solution.

[0013] Preferably, in the method for preparing the photothermal conversion aerogel, the concentration of the alkaline solution is 0.5–2 mol / L.

[0014] Preferably, the method for preparing the photothermal conversion aerogel involves adding tea residue to an alkaline solution, reacting at 150–170°C for 4–8 hours, filtering, and washing until neutral to obtain tea residue fiber; wherein the mass-to-volume ratio of the tea residue to the alkaline solution is (3–7) g:(50–100) mL.

[0015] Preferably, in the preparation method of the photothermal conversion aerogel, the step of placing tea residue fibers in a tube furnace and calcining them at 500-700°C for 1-3 hours is described.

[0016] Preferably, the method for preparing the photothermal conversion aerogel involves grinding carbonized tea residue into powder, adding it to an acid solution, soaking it for 1-3 hours, and washing it until neutral to obtain tea residue carbon powder; wherein the acid solution used includes at least one of HCl solution, H2SO4 solution, and HNO3 solution, and the mass concentration of the acid solution is 2-20%.

[0017] Preferably, in the preparation method of the photothermal conversion aerogel, in the steps of adding sodium alginate to water, then adding tea residue fiber, and then adding tea residue carbon powder and stirring, the mass ratio of sodium alginate, water, tea residue fiber, and tea residue carbon powder is (0.3-0.7):(20-30):(2-6):(0.03-0.07).

[0018] Preferably, in the method for preparing the photothermal conversion aerogel, the step of immersing the aerogel in a CaCl2 solution has a mass concentration of 3-7% and an immersion time of 10-15 hours.

[0019] Secondly, the present invention also provides a photothermal conversion aerogel, which is prepared by the preparation method described above.

[0020] Thirdly, the present invention also provides a photothermal conversion aerogel prepared by the preparation method described above, or the application of the photothermal conversion aerogel in the preparation of solar evaporators and seawater desalination.

[0021] The photothermal conversion aerogel of the present invention, its preparation method, and its application have the following advantages over the prior art:

[0022] Beneficial effects:

[0023] The preparation method of the photothermal conversion aerogel of the present invention uses tea residue as raw material and obtains tea residue fiber by alkaline treatment; then, the tea residue fiber is calcined at high temperature to obtain a light-absorbing material, namely carbonized tea residue; then, the tea residue fiber and carbonized tea residue are added to sodium alginate solution and obtained by liquid nitrogen freeze-drying to obtain tea residue fiber and carbonized tea residue aerogel; it is then soaked in CaCl2 solution for cross-linking treatment and prepared by liquid nitrogen freeze-drying to prepare a photothermal conversion aerogel based on all biomass waste, which has vertical directional water-guiding channels; the photothermal conversion aerogel of the present invention has the following advantages: 1) The tea residue-based photothermal conversion aerogel has vertical directional water-guiding channels, which can achieve stable seawater desalination performance and effectively alleviate the problem of freshwater shortage; 2) The tea residue-based photothermal conversion aerogel can stably desalinate 10wt% brine with an efficiency of 1.5 kg m –2 h –1 3) Tea residue-based photothermal conversion aerogel can effectively reduce the environmental pollution caused by tea residue. Based on the concept of "turning waste into treasure", this invention uses tea residue as raw material to design a photothermal conversion aerogel with stable seawater desalination performance, which can stably desalinate 10wt% brine. The tea residue-based photothermal conversion aerogel of this invention provides a promising solution to the global freshwater shortage, energy crisis and environmental pollution problems. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The images are electron microscope images of the photothermal conversion aerogel (sample 3) obtained in Example 1 and the photothermal conversion aerogel (sample 1) obtained in Example 2.

[0026] Figure 2 The graph shows the light absorption performance of photothermal conversion aerogel samples 1-4 containing different tea residue carbon powders in Examples 1-2.

[0027] Figure 3 The evaporation rate diagrams are shown for the photothermal conversion aerogel samples 1-4 containing different tea residue carbon powder in Examples 1-2, representing the evaporation rate of groundwater.

[0028] Figure 4 The graph shows the evaporation efficiency of photothermal conversion aerogel (sample 3) in Example 1 when diluting salt water of different concentrations.

[0029] Figure 5 This is an outdoor image of the photothermal conversion aerogel (sample 3) in Example 1 diluting 10wt% saline solution. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0032] This application provides a method for preparing photothermal conversion aerogel, comprising the following steps:

[0033] S1. Add tea leaves to an alkaline solution, react at 150-170°C, filter, wash, and obtain tea leaves fiber.

[0034] S2. Place the tea residue fiber in a tube furnace and calcine it at 500-700℃ to obtain carbonized tea residue;

[0035] S3. Grind the carbonized tea residue into powder, add it to the acid solution, soak and wash it to obtain tea residue carbon powder;

[0036] S4. Add sodium alginate to water, then add tea dregs fiber, then add tea dregs carbon powder and stir. After freezing and solidification, place it in a freeze dryer to freeze dry to obtain aerogel.

[0037] S5. The aerogel is then soaked in CaCl2 solution, washed, and freeze-dried in a freeze dryer to obtain photothermal conversion aerogel.

[0038] Specifically, the tea residue of this invention refers to the tea residue produced after tea drinking, which is currently rarely utilized and mostly discarded. This invention uses tea residue as raw material and obtains tea residue fiber through alkaline treatment. Subsequently, the tea residue fiber is calcined at high temperature to obtain a light-absorbing material, namely carbonized tea residue. Then, the tea residue fiber and carbonized tea residue are added to a sodium alginate solution and freeze-dried with liquid nitrogen to obtain tea residue fiber and carbonized tea residue aerogel. This aerogel is then soaked in CaCl2 solution for cross-linking treatment and freeze-dried with liquid nitrogen to prepare a photothermal conversion aerogel based entirely on biomass waste. This photothermal conversion aerogel has vertically directional water-guiding channels. The photothermal conversion aerogel of this invention has the following advantages: 1) The tea residue-based photothermal conversion aerogel has vertically directional water-guiding channels, which can achieve stable seawater desalination performance and effectively alleviate the problem of freshwater shortage; 2) The tea residue-based photothermal conversion aerogel can stably desalinate 10wt% brine with an efficiency of 1.5 kg m³ / h. –2 h –1 3) Tea residue-based photothermal conversion aerogel can effectively reduce the environmental pollution caused by tea residue. Based on the concept of "turning waste into treasure", this invention uses tea residue as raw material to design a photothermal conversion aerogel with stable seawater desalination performance, which can stably desalinate 10wt% brine. The tea residue-based photothermal conversion aerogel of this invention provides a promising solution to the global freshwater shortage, energy crisis and environmental pollution problems.

[0039] In some embodiments, the alkaline solution used in step S1 includes at least one of NaOH solution and KOH solution.

[0040] In some embodiments, the concentration of the alkaline solution used in step S1 is 0.5 to 2 mol / L.

[0041] In some embodiments, tea residue is added to an alkaline solution and reacted at 150–170°C for 4–8 hours. The mixture is then filtered and washed until neutral to obtain tea residue fiber. The mass-to-volume ratio of tea residue to alkaline solution is (3–7) g:(50–100) mL.

[0042] In some embodiments, in the step of placing tea residue fibers in a tube furnace and calcining them at 500–700°C, the calcination time is 1–3 hours.

[0043] In some embodiments, carbonized tea residue is ground into powder, added to an acid solution, soaked for 1 to 3 hours, and washed until neutral to obtain tea residue carbon powder; wherein the acid solution used includes at least one of HCl solution, H2SO4 solution, and HNO3 solution, and the mass concentration of the acid solution is 2 to 20%.

[0044] In some embodiments, in the steps of adding sodium alginate to water, then adding tea residue fiber, and then adding tea residue carbon powder and stirring, the mass ratio of sodium alginate, water, tea residue fiber, and tea residue carbon powder is (0.3-0.7):(20-30):(2-6):(0.03-0.07).

[0045] In some embodiments, in the step of immersing the aerogel in a CaCl2 solution, the mass concentration of the CaCl2 solution (CaCl2 aqueous solution) is 3-7%, and the immersion time is 10-15 hours.

[0046] In some embodiments, step S1 specifically involves: adding tea dregs to an alkaline solution, reacting at 150–170°C, filtering, washing the obtained fibers multiple times until the waste liquid becomes lighter in color, then placing the fibers with added deionized water in an ultrasonic instrument and ultrasonically cleaning them at 53 kHz for 30 minutes until the fibers are neutral, thus obtaining tea dregs fibers.

[0047] In some embodiments, step S3 specifically involves: grinding carbonized tea residue into powder, adding it to an HCl solution (mass concentration of 2-20%), soaking for 2 hours, filtering, and then washing with HNO3 solution (mass concentration of 2-20%) and deionized water until neutral to obtain tea residue carbon powder.

[0048] In some embodiments, step S4 specifically involves: adding sodium alginate to water and stirring, then adding crushed tea dregs fiber and continuing to stir, then adding tea dregs carbon powder and stirring, freezing and solidifying with liquid nitrogen, and then freeze-drying in a vacuum freeze dryer for 40-60 hours to obtain an aerogel.

[0049] In some embodiments, step S5 specifically involves: soaking the aerogel in a CaCl2 solution for 10–15 h, washing it three times with deionized water after removal, and then freeze-drying it in a vacuum freeze dryer for 40–60 h to obtain a photothermal conversion aerogel.

[0050] Specifically, in step S4, sodium alginate is added to water, followed by tea residue fiber, then tea residue carbon powder, and stirred. After freezing and solidification, the mixture is freeze-dried in a freeze dryer to obtain an aerogel. The tea residue fiber is prepared using the method in step S1, which involves adding tea residue to an alkaline solution, reacting at 150–170°C, filtering, washing with water, and then air-drying. The tea residue fiber cannot be dried in an oven at 80°C for an extended period, as prolonged oven drying will make the tea residue fiber less hydrophilic, which is detrimental to the preparation of the aerogel. Therefore, the tea residue fiber must be kept moist by natural air drying.

[0051] Based on the same inventive concept, the present invention also provides a photothermal conversion aerogel, which is prepared by the above-described preparation method.

[0052] Based on the same inventive concept, the present invention also provides a photothermal conversion aerogel prepared by the above-described preparation method or the application of the above-described photothermal conversion aerogel in the preparation of solar evaporators and seawater desalination.

[0053] The following detailed embodiments further illustrate the photothermal conversion aerogel, its preparation method, and its application. This section further explains the invention in conjunction with specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the techniques used in the embodiments are conventional methods well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in the art.

[0054] Example 1

[0055] This application provides a method for preparing photothermal conversion aerogel, comprising the following steps:

[0056] S1. Add 5g of tea residue to 70mL of 1mol / L NaOH solution and react in a 160℃ drying oven for 6h to obtain fibers. Wash the obtained fibers several times until the color of the waste liquid becomes lighter. Then place the fibers with added deionized water in an ultrasonic instrument and clean them by ultrasonication at 53KHz for 30min until the fibers are neutral. Let them air dry naturally to obtain tea residue fibers.

[0057] S2. Place the tea residue fiber from S1 in a tube furnace and calcine it at 600℃ for 2 hours to obtain carbonized tea residue.

[0058] S3. Grind the carbonized tea residue from S2 into powder, add it to HCl solution (mass concentration of 5%), soak for 2 hours, filter, and then wash with HNO3 solution (mass concentration of 5%) and deionized water until neutral to obtain tea residue carbon powder.

[0059] S4. Add 0.5g sodium alginate to 25mL deionized water, stir evenly, then add 2g of crushed tea residue fiber from S1 and continue stirring. Then add 50mg of tea residue carbon powder and stir. After freezing and solidifying with liquid nitrogen, freeze-dry in a vacuum freeze dryer for 48h to obtain aerogel.

[0060] S5. The aerogel from S4 was then soaked in a 5% CaCl2 solution for 12 hours, washed three times with deionized water, and then freeze-dried in a freeze dryer for 48 hours to obtain the photothermal conversion aerogel (i.e., sample 3 below).

[0061] Example 2

[0062] This application provides a method for preparing photothermal conversion aerogel, which is the same as in Example 1, except that the mass of tea residue carbon powder added in step S4 is 0 mg, 10 mg, and 100 mg, respectively, and the other process conditions are the same as in Example 1. Among them, the photothermal conversion aerogel finally prepared by adding 0 mg of tea residue carbon powder corresponds to Sample 1 below, the photothermal conversion aerogel finally prepared by adding 10 mg of tea residue carbon powder corresponds to Sample 2 below, and the photothermal conversion aerogel finally prepared by adding 100 mg of tea residue carbon powder corresponds to Sample 4 below.

[0063] Performance testing

[0064] Figure 1 The images are electron microscope images of the photothermal conversion aerogel (sample 3) obtained in Example 1 and the photothermal conversion aerogel (sample 1) obtained in Example 2. Figure 1 (a) is a photograph of the photothermal conversion aerogel (sample 1) obtained in Example 2, and (b) and (c) are scanning electron microscope images of the photothermal conversion aerogel (sample 1) obtained in Example 2 at different magnifications. Figure 1 (d) is a photograph of the photothermal conversion aerogel (sample 3) prepared in Example 1, and (e) and (f) are scanning electron microscope images of the photothermal conversion aerogel (sample 3) prepared in Example 1 at different magnifications. Figure 1 (g) is a cross-sectional photograph of the photothermal conversion aerogel (sample 3) prepared in Example 1, and (h) and (i) are cross-sectional electron microscope images of the photothermal conversion aerogel (sample 3) prepared in Example 1 at different magnifications.

[0065] from Figure 1As can be seen from the figures, the photothermal conversion aerogel without tea residue carbon powder obtained in Example 2 has a rich pore structure on its surface; the photothermal conversion aerogel containing tea residue carbon powder prepared in Example 1 also has a rich pore structure on its surface; and further from Figures (h) and (i), it can be seen that the photothermal conversion aerogel containing tea residue carbon powder prepared in Example 1 has vertical water-conducting channels inside, which is beneficial for the material to achieve salt self-cleaning performance.

[0066] Furthermore, the light absorption properties of photothermal conversion aerogel samples 1-4 containing different tea residue carbon powders in Examples 1-2 were tested as follows: Figure 2 As shown.

[0067] To preliminarily assess the photothermal conversion capability of the material, the ultraviolet-visible-near-infrared spectrum of the thermally converted aerogel was measured. Figure 2 ),from Figure 2 It can be seen that the carbon powder content of tea residue gradually increases in samples 1, 2, 3, and 4. It was found that with the increase of tea residue carbon powder content, the light absorption and energy absorption of the material gradually increase, reaching 97%. Figure 2 It can be found that samples 3 and 4 have the best light absorption properties, therefore sample 3 is the optimal photothermal conversion aerogel material.

[0068] The evaporation rate of groundwater in photothermal conversion aerogel samples 1-4 containing different tea residue carbon powder in Examples 1-2 was tested, and the results are as follows: Figure 3 As shown.

[0069] The specific method for testing the evaporation rate is as follows: Place the photothermal conversion aerogel sample in groundwater. The photothermal conversion aerogel absorbs heat, causing the brine to evaporate. The evaporation rate is then measured, and the calculation formula is: ν =

[0070] dm / (S·dt);

[0071] Where ν is the evaporation rate, m is the change in groundwater mass before and after evaporation, S is the light-illuminated area at the top of the photothermal conversion aerogel, and t is the illumination time.

[0072] Figure 3 This shows the change in groundwater quality with the duration of sunlight.

[0073] Figure 3 The mass change curves of photothermal conversion aerogel samples with different tea residue carbon powders under one solar intensity are shown. It was found that the evaporation efficiency increases with increasing tea residue carbon powder mass, but the evaporation rate reaches its maximum value of 1.63 kg m³ when the tea residue carbon powder mass reaches a certain level. –2 h –1 The evaporation rates of samples 3 and 4 are the same.

[0074] Figure 4 The graph shows the evaporation efficiency of the photothermal conversion aerogel (sample 3) in Example 1 when desalinated with different concentrations of brine. The 3.5 wt% brine was prepared by dissolving NaCl (13.37 g), KCl (0.36 g), MgCl2 (3.19 g), and CaCl2 (0.58 g) in 500 mL of deionized water. The 10 wt% brine was prepared by dissolving NaCl (38.24 g), KCl (1.03 g), MgCl2 (9.12 g), and CaCl2 (1.66 g) in 500 mL of deionized water. The 20 wt% brine was prepared by dissolving NaCl (76.34 g), KCl (2.06 g), MgCl2 (18.21 g), and CaCl2 (3.31 g) in 500 mL of deionized water.

[0075] from Figure 4 It can be seen that the photothermal conversion aerogel maintains a stable evaporation efficiency in 3.5 wt% and 10 wt% brine, but the desalination efficiency gradually decreases with increasing brine concentration, reaching 20 wt%. This indicates that the photothermal conversion aerogel can stably desalinate 10 wt% brine with a desalination efficiency of 1.50 kg m³. –2 h –1 .

[0076] Figure 5 An outdoor image of the photothermal conversion aerogel (sample 3) obtained in Example 1 desalinated with 10 wt% saline solution, wherein... Figure 5 (a) and (b) show the apparatus before and after one hour of photothermal conversion aerogel desalination of 10 wt% brine; (c) shows the solid volume fraction of the collected water; (d) shows the comparison of cation concentrations before and after desalination of 10 wt% brine. Figure 5 In the text, "Before desalination" refers to the ion concentration of the brine before desalination, and "After desalination" refers to the ion concentration of the evaporated water obtained after desalination.

[0077] Figure 5 (a) An outdoor device for desalinating 10 wt% brine using photothermal conversion aerogel. After one hour of light exposure, water droplets can be observed on the top of the device, such as... Figure 5 As shown in (b). Figure 5 (c) is the solids volume fraction of the desalinated water, which is 84 ppm, meeting the standards for daily use. Figure 5 (d) is a comparison chart of cation concentration before and after desalination with 10wt% brine. It shows that the cation concentration in the collected desalinated water decreased sharply, reaching the drinking water standards of the World Health Organization (WHO). Figure 5 As shown in (d).

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing photothermal conversion aerogel, characterized in that, Includes the following steps: Tea leaves are added to an alkaline solution and reacted at 150-170℃ for 4-8 hours. The mixture is then filtered and washed until neutral to obtain tea leaf fiber. The mass-to-volume ratio of the tea leaves to the alkaline solution is (3-7) g:(50-100) mL. The alkaline solution includes at least one of NaOH solution and KOH solution. The concentration of the alkaline solution is 0.5-2 mol / L. The tea residue fiber is placed in a tube furnace and calcined at 500~700℃ for 1~3 hours to obtain carbonized tea residue. Carbonized tea residue is ground into powder, added to an acidic solution, soaked for 1-3 hours, and washed until neutral to obtain tea residue carbon powder; wherein the acidic solution used includes at least one of HCl solution, H2SO4 solution, and HNO3 solution, and the mass concentration of the acidic solution is 2-20%; Sodium alginate was added to water, followed by tea dregs fiber and then tea dregs carbon powder. After freezing and solidification, the mixture was freeze-dried in a freeze dryer to obtain an aerogel. The mass ratio of sodium alginate, water, tea dregs fiber, and tea dregs carbon powder was (0.3~0.7):(20~30):(2~6):0.

05. The aerogel is then immersed in CaCl2 solution, washed, and freeze-dried in a freeze dryer to obtain photothermal conversion aerogel; the mass concentration of the CaCl2 solution is 3~7%, and the immersion time is 10~15h.

2. A photothermal conversion aerogel, characterized in that, It was prepared using the preparation method described in claim 1.

3. The application of a photothermal conversion aerogel prepared by the method described in claim 1 in the preparation of solar evaporators and seawater desalination.

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