Photo-thermal moisture absorption gel and preparation method thereof

Abstract

The invention provides photo-thermal moisture absorption gel and a preparation method thereof, and belongs to the field of moisture absorption gel. The photo-thermal moisture absorption gel provided by the invention comprises an aerogel carrier and moisture absorption salt loaded on the aerogel carrier, the aerogel carrier comprises a first photo-thermal aerogel layer, a cellulose network aerogel layer and a second photo-thermal aerogel layer which are arranged in sequence; each of the first photo-thermal aerogel layer and the second photo-thermal aerogel layer comprises cellulose network aerogel and a photo-thermal conversion material loaded on the cellulose network aerogel; pore channels penetrating through the first photo-thermal aerogel layer, the cellulose network aerogel layer and the second photo-thermal aerogel layer are formed in the aerogel carrier. The photo-thermal moisture absorption gel provided by the invention is high in reproducibility, environment-friendly and pollution-free, and has high moisture absorption capacity and rapid moisture absorption capacity.

Description

Technical Field

[0001] The present invention relates to the field of hygroscopic aerogels, and in particular to a photothermal hygroscopic aerogel and a preparation method thereof. Background Art

[0002] Humidity control is crucial in areas such as food packaging, electronic product protection, and pharmaceutical storage. High humidity can cause items to become damp, deteriorate, become damaged, or even fail. Traditional hygroscopic materials include silica gel, montmorillonite, and hygroscopic salts. While silica gel has a certain ability to absorb moisture, its moisture absorption capacity is limited, and after reaching saturation, it requires complex regeneration processes. This typically involves heating and drying, which consumes energy and is inconvenient to operate. Furthermore, the hygroscopic performance of the regenerated silica gel desiccant is significantly reduced. Mineral hygroscopic materials such as montmorillonite also face similar issues and may cause certain environmental pollution.

[0003] With the continuous advancement of science and technology and people's increasing demands for the environment, the requirements for hygroscopic materials are also getting higher and higher. Therefore, providing a hygroscopic material that can efficiently absorb moisture from the air, has a high moisture absorption capacity, is highly recyclable, and is environmentally friendly and pollution-free has become a technical problem that needs to be solved in this field. Summary of the Invention

[0004] The present invention aims to provide a photothermal hygroscopic aerogel and a preparation method thereof. The photothermal hygroscopic aerogel provided by the present invention is highly regenerable, environmentally friendly and pollution-free, and has a high hygroscopic capacity and the ability to rapidly absorb moisture.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a photothermal hygroscopic aerogel, comprising an aerogel carrier and a hygroscopic salt loaded on the aerogel carrier;

[0007] The aerogel carrier comprises a first photothermal aerogel layer, a cellulose network aerogel layer, and a second photothermal aerogel layer arranged in sequence; the first photothermal aerogel layer and the second photothermal aerogel layer both comprise a cellulose network aerogel and a photothermal conversion material loaded on the cellulose network aerogel;

[0008] The aerogel carrier is provided with pores that penetrate the first photothermal aerogel layer, the cellulose network aerogel layer, and the second photothermal aerogel layer.

[0009] Preferably, the thickness of the first photothermal aerogel layer and the second photothermal aerogel layer are both 1 to 1.5 cm, and the thickness of the cellulose network matrix layer is 1.2 to 3.6 cm.

[0010] Preferably, the porosity of the aerogel carrier is 90-98%.

[0011] Preferably, the channel is a cylindrical hole, the diameter of the cylindrical hole is 3 to 5 mm, and the distance between two adjacent cylindrical holes is 0.3 to 0.6 cm.

[0012] Preferably, the light-to-heat conversion material includes one or more of carbon black, graphene, graphene oxide, polypyrrole and multi-walled carbon nanotubes.

[0013] The present invention also provides a method for preparing the photothermal hygroscopic aerogel described in the above technical solution, comprising:

[0014] mixing the first nanocellulose solution with the photothermal conversion material to obtain a dispersion;

[0015] Pour a portion of the dispersion into a container containing a pore-forming mold and perform a first freezing, then continue to pour the second nanocellulose solution into the container and perform a second freezing, and finally continue to pour the remaining dispersion into the container and perform a third freezing, and then remove the container to obtain a composite frozen layer containing the pore-forming mold;

[0016] The composite frozen layer containing the pore-forming mold is subjected to solvent replacement in a solvent to remove the pore-forming mold, and then dried to obtain an aerogel carrier;

[0017] The aerogel carrier is immersed in a hygroscopic salt solution and then dried to obtain a photothermal hygroscopic aerogel.

[0018] Preferably, the concentrations of the first nanocellulose solution and the second nanocellulose solution are both 0.5-1 wt%.

[0019] Preferably, the solvent replacement time is 15 to 20 hours.

[0020] Preferably, the concentration of the hygroscopic salt solution is 5-8 wt%.

[0021] Preferably, the immersion time is 10 to 12 hours.

[0022] The present invention provides a photothermal hygroscopic aerogel, comprising an aerogel carrier and a hygroscopic salt loaded on the aerogel carrier; the aerogel carrier comprises a first photothermal aerogel layer, a cellulose network aerogel layer, and a second photothermal aerogel layer arranged in sequence; the first photothermal aerogel layer and the second photothermal aerogel layer both comprise a cellulose network aerogel and a photothermal conversion material loaded on the cellulose network aerogel; the aerogel carrier is provided with a channel that passes through the first photothermal aerogel layer, the cellulose network aerogel layer, and the second photothermal aerogel layer. The present invention utilizes the pore structure on the aerogel carrier to increase the contact area between moisture and the aerogel carrier, shorten the diffusion path of moisture, reduce the diffusion resistance, and facilitate the rapid moisture absorption of the hygroscopic salt loaded on the aerogel carrier. At the same time, the pore structure can also improve the moisture absorption capacity of the photothermal hygroscopic aerogel; the first photothermal aerogel layer and the second photothermal aerogel layer in the aerogel carrier absorb solar energy through the photothermal conversion material loaded on the cellulose network aerogel, and perform photothermal conversion of the solar energy to generate heat to remove moisture from the photothermal hygroscopic aerogel after moisture absorption, thereby reducing the difficulty of regenerating the photothermal hygroscopic aerogel; and by adopting the cellulose network aerogel, environmental pollution is avoided. The results of the embodiments show that the photothermal hygroscopic aerogel provided by the present invention has a moisture absorption capacity of 1.3 g / g, 1.59 g / g, 2.09 g / g, 3.14 g / g and 4.7 g / g at a relative humidity of 25°C, 30%, 45%, 60%, 75% and 90%, respectively. In the first 30 minutes of moisture absorption, the moisture absorption rate can reach 1.54 g / g / h, 1.59 g / g / h, 2.20 g / g / h, 2.39 g / g / h and 3.55 g / g / h, respectively; at a temperature of 25°C and a relative humidity of 75%, after absorbing moisture for 12 hours and then evaporating for 12 hours in the sun as a cycle, the moisture absorption capacity of the photothermal hygroscopic aerogel can be maintained at 2.66 g / g after 30 cycles. It is highly recyclable, environmentally friendly and pollution-free, and has a high moisture absorption capacity and the ability to absorb moisture quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a macroscopic photograph of the photothermal hygroscopic aerogel in Example 1 of the present invention;

[0024] Figure 2 This is the UV-visible-near-infrared absorption spectrum of the photothermal hygroscopic aerogel in Example 1 of the present invention;

[0025] Figure 3 This is a curve diagram of the moisture absorption capacity of the photothermal moisture absorbing aerogel in Example 1 of the present invention;

[0026] Figure 4 This is a moisture absorption-dehumidification cycle curve of the photothermal moisture absorbing aerogel in Example 1 of the present invention;

[0027] Figure 5This is a curve diagram of the moisture absorption capacity of the photothermal moisture absorbing aerogel at different relative humidity in Comparative Example 1 of the present invention;

[0028] Figure 6 This is the UV-visible-near-infrared absorption spectrum of the hygroscopic aerogel in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The invention provides a photothermal hygroscopic aerogel, comprising an aerogel carrier and a hygroscopic salt loaded on the aerogel carrier.

[0030] The photothermal moisture absorbing aerogel provided by the present invention includes an aerogel carrier.

[0031] In the present invention, the aerogel carrier includes a first photothermal aerogel layer, a cellulose network aerogel layer and a second photothermal aerogel layer arranged in sequence; the first photothermal aerogel layer and the second photothermal aerogel layer both include cellulose network aerogel and a photothermal conversion material loaded on the cellulose network aerogel.

[0032] In the present invention, the photothermal conversion material preferably includes one or more of carbon black, graphene, graphene oxide, polypyrrole, and multi-walled carbon nanotubes, with carbon black being more preferred. The present invention limits the photothermal conversion material to the aforementioned materials, which can achieve photothermal conversion, facilitating the conversion of light energy into heat energy under illumination for the hygroscopic aerogel, thereby achieving drying of the photothermally hygroscopic aerogel.

[0033] In the present invention, the thickness of the first photothermal aerogel layer and the second photothermal aerogel layer is preferably 1 to 1.5 cm, more preferably 1.3 cm. As an embodiment of the present invention, the thickness of the cellulose network aerogel layer can be 1.2 to 3.6 cm, or 2 to 3 cm, or 2.5 cm. The present invention limits the thickness of the first photothermal aerogel layer, the second photothermal aerogel layer, and the cellulose network aerogel layer to the above range, which can be more conducive to improving the hygroscopic performance of the photothermal hygroscopic aerogel and better drying and regenerating the photothermal hygroscopic aerogel after absorbing moisture.

[0034] In the present invention, the aerogel carrier is provided with pores penetrating the first photothermal aerogel layer, the cellulose network aerogel layer and the second photothermal aerogel layer.

[0035] As an embodiment of the present invention, the porosity of the aerogel carrier can be 90-98%, 92-96%, or 94-96%. In the present invention, limiting the porosity of the aerogel carrier to the above range can further improve the moisture absorption rate of the photothermal hygroscopic aerogel.

[0036] As one embodiment of the present invention, the pores may be cylindrical; the diameter of the cylindrical pores is preferably 3 to 5 mm, more preferably 4 mm; the spacing between two adjacent cylindrical pores is preferably 0.3 to 0.6 cm, more preferably 0.4 to 0.5 cm, and even more preferably 0.5 cm. Limiting the pore diameter and pore spacing of the aerogel carrier to the above ranges can improve the hygroscopic properties of the photothermal hygroscopic aerogel.

[0037] The photothermal hygroscopic aerogel provided by the present invention includes a hygroscopic salt supported on the aerogel carrier; the hygroscopic salt preferably includes one or more of calcium chloride, lithium chloride, magnesium chloride, and magnesium sulfate. Limiting the type of hygroscopic salt to the aforementioned range enables the photothermal hygroscopic aerogel to have high hygroscopic properties.

[0038] As one embodiment of the present invention, the loading amount of the hygroscopic salt on the aerogel carrier can be 60-95% of the total mass of the photothermal hygroscopic aerogel, or can be 80-85wt%. Limiting the loading amount of the hygroscopic salt on the aerogel carrier to the above range can enable the photothermal hygroscopic aerogel to have good hygroscopic properties.

[0039] The present invention utilizes the pore structure on the aerogel carrier to increase the contact area between moisture and the aerogel carrier, shorten the diffusion path of moisture, reduce the diffusion resistance, and facilitate the rapid moisture absorption of the hygroscopic salt loaded on the aerogel carrier. At the same time, the pore structure can also improve the moisture absorption capacity of the photothermal hygroscopic aerogel; the first photothermal aerogel layer and the second photothermal aerogel layer in the aerogel carrier absorb solar energy through the photothermal conversion material loaded on the cellulose network aerogel, and perform photothermal conversion of the solar energy to generate heat to remove moisture from the photothermal hygroscopic aerogel after moisture absorption, thereby reducing the difficulty of regenerating the photothermal hygroscopic aerogel; and by adopting the cellulose network aerogel, environmental pollution is avoided.

[0040] The present invention also provides a method for preparing the photothermal hygroscopic aerogel described in the above technical solution, comprising:

[0041] mixing the first nanocellulose solution with the photothermal conversion material to obtain a dispersion;

[0042] Pour a portion of the dispersion into a container containing a pore-forming mold and perform a first freezing, then continue to pour the second nanocellulose solution into the container and perform a second freezing, and finally continue to pour the remaining dispersion into the container and perform a third freezing, and then remove the container to obtain a composite frozen layer containing the pore-forming mold;

[0043] The composite frozen layer containing the pore-forming mold is subjected to solvent replacement in a solvent to remove the pore-forming mold, and then dried to obtain an aerogel carrier;

[0044] The aerogel carrier is immersed in a hygroscopic salt solution and then dried to obtain a photothermal hygroscopic aerogel.

[0045] The present invention mixes a first nanocellulose solution with a photothermal conversion material to obtain a dispersion.

[0046] In the present invention, the concentration of the first nanocellulose solution is preferably 0.5-1 wt %, more preferably 0.8-1 wt %. The present invention limits the concentration of the first nanocellulose solution to the above range to ensure that the formed aerogel has a large porosity.

[0047] In the present invention, the first nanocellulose solution is preferably prepared by:

[0048] The lignin and hemicellulose in the poplar wood powder are removed by chemical treatment to obtain cellulose;

[0049] The cellulose is mixed with water and then subjected to a defibrillation treatment to obtain a nanocellulose solution.

[0050] In the present invention, lignin and hemicellulose in poplar wood powder are preferably removed by chemical treatment to obtain cellulose.

[0051] As an embodiment of the present invention, the specific operation of the chemical treatment method is:

[0052] 1) sodium chlorite is added to a 2 wt % aqueous dispersion of poplar wood flour to obtain a first mixed solution, and then glacial acetic acid is added to the first mixed solution to adjust the pH to 4. The mixture is reacted in a 75° C. water bath for 1 hour to obtain a first reaction solution; the concentration of sodium chlorite in the first mixed solution is 1 wt %;

[0053] 2) mixing the first reaction liquid obtained in step 1) with the same mass of sodium chlorite as in step 1), then adding the same mass of glacial acetic acid as in step 1), and reacting in a water bath at 75° C. for 1 hour to obtain a second reaction liquid, then adding the same mass of sodium chlorite to the second reaction liquid again, repeating the above operation three times, and filtering the obtained reaction liquid until it is neutral to obtain primary treated wood powder;

[0054] 3) The once-treated wood powder obtained in step 2) is mixed with a 5 wt % potassium hydroxide solution, reacted in a 90° C. water bath for 2 h, and filtered until neutral to obtain cellulose.

[0055] As an embodiment of the present invention, in order to obtain cellulose with higher purity, the once-treated wood powder is mixed with a 5wt% potassium hydroxide solution and reacted in a water bath at 90°C for 2 hours. The solid product obtained after filtration to neutrality can be further mixed with 1wt% sodium chlorite and then glacial acetic acid is added to adjust the pH to 4, and reacted in a water bath at 75°C for 2 hours. The solid product obtained after filtration to neutrality is mixed with a 5wt% potassium hydroxide solution and reacted in a water bath at 90°C for 2 hours, and filtered to neutrality to obtain cellulose.

[0056] After obtaining the cellulose, the present invention preferably mixes the cellulose with water and then performs a defibration treatment to obtain a nanocellulose solution.

[0057] As an embodiment of the present invention, the defibration treatment may be ultrasonic treatment; the ultrasonic treatment may be performed in an ultrasonic cell disruptor; the power of the ultrasonic treatment may be 600-800w; and the time of the ultrasonic treatment may be 30-40min.

[0058] The present invention adopts the above-mentioned method for preparing the nanocellulose solution to obtain a uniformly dispersed first nanocellulose solution, which is beneficial to the uniform loading of the subsequent photothermal conversion material in the cellulose network aerogel.

[0059] As one embodiment of the present invention, the mass ratio of the first nanocellulose solution to the photothermal conversion material can be 100:(0.03-0.06). By limiting the mass ratio of the first nanocellulose solution to the photothermal conversion material to the above range, the photothermal hygroscopic aerogel can have good hygroscopic properties while having photothermal conversion capabilities.

[0060] As one embodiment of the present invention, the mixing can be performed by stirring followed by ultrasonication; the stirring time can be 22 to 27 minutes, or even 25 minutes; and the ultrasonication time can be 3 to 7 minutes, or even 5 minutes. The present invention does not specifically limit the stirring speed and ultrasonication frequency; the stirring speed and ultrasonication frequency commonly used by those skilled in the art can be used. The present invention limits the mixing method to the above range so that the first nanocellulose and the photothermal conversion material in the dispersion can be evenly dispersed.

[0061] After obtaining the dispersion, the present invention pours a portion of the dispersion into a container containing a pore-forming mold for a first freezing, then continues to pour a second nanocellulose solution into the container for a second freezing, and finally continues to pour the remaining portion of the dispersion into the container for a third freezing, and then removes the container to obtain a composite frozen layer containing the pore-forming mold.

[0062] As one embodiment of the present invention, the pore-forming mold can be a cylindrical mold; the material of the cylindrical mold can be metal; the metal can be stainless steel; the diameter of the cylinder in the cylindrical mold can be 3 to 5 mm, and the spacing between adjacent cylinders in the cylindrical mold can be 0.3 to 0.6 cm; the container can be an acrylic box. In an embodiment of the present invention, the dimensions of the acrylic box are 7 cm × 7 cm × 7 cm; the cylindrical mold is a stainless steel cylindrical mold; the diameter of the stainless steel cylinder in the stainless steel cylindrical mold is 4 mm; and the spacing between adjacent cylinders in the stainless steel cylindrical mold is 0.5 cm. The present invention limits the size of the pore-forming mold to the above range so that the diameter of the hole in the channel can be 3 to 5 mm, and the spacing between adjacent holes can be 0.3 to 0.6 cm.

[0063] As an embodiment of the present invention, the partial dispersion may be 1 / 2 of the total volume of the dispersion.

[0064] The present invention has no particular limitation on the specific amount of the partial dispersion, as long as the thickness of the first photothermal aerogel layer is ensured to be 1 to 1.5 cm.

[0065] As an embodiment of the present invention, the temperature of the first freezing can be -20 to -10°C, or -10°C; the time of the first freezing can be 1 to 4 hours, or 2 to 3 hours. The present invention limits the temperature and time of the first freezing to the above ranges so that the liquid can be completely solidified.

[0066] As an embodiment of the present invention, the second nanocellulose solution is the same as the first nanocellulose solution used to prepare the dispersion, and will not be described in detail here.

[0067] As an embodiment of the present invention, the mass ratio of the second nanocellulose solution to the partial dispersion may be (2.5-3.5):1, or may be 3:1.

[0068] The present invention has no particular limitation on the specific amount of the second nanocellulose solution, as long as the amount can ensure that the thickness of the cellulose network aerogel layer is 1.2 to 3.6 cm.

[0069] As an embodiment of the present invention, the temperature range of the second freezing is set to be consistent with the temperature range of the first freezing, which will not be described in detail here; the second freezing time can be 4 to 8 hours, 5 to 7 hours, or even 6 hours. In the present invention, the temperature and time of the second freezing are limited to the above ranges so that the liquid can be completely solidified.

[0070] As an embodiment of the present invention, the mass ratio of the remaining dispersion to the second nanocellulose solution may be 1:(2.5-3.5), or 1:3.

[0071] As an embodiment of the present invention, the temperature and time range settings of the third freezing are consistent with the temperature and time range settings of the first freezing, and will not be described in detail here.

[0072] As an embodiment of the present invention, the operation of removing the container can be to place the third frozen container in water for thawing; the thawing time can be 15 minutes. The present invention removes the container, which is conducive to the subsequent solvent replacement.

[0073] After obtaining the composite freezing layer containing the pore-forming mold, the present invention performs solvent replacement on the composite freezing layer containing the pore-forming mold in a solvent to remove the pore-forming mold and then dries the layer to obtain an aerogel carrier.

[0074] As an embodiment of the present invention, the solvent may be an ethanol solution; the purity of the ethanol solution may be ≥90%; the solvent of the ethanol solution may be water; the time for the solvent replacement may be 15 to 20 hours, or 16 to 19 hours, or 17 to 18 hours. The present invention can form a hydrogel through solvent replacement, and can maintain pores to become an aerogel after drying; it can also separate the pore-forming mold in the composite freezing layer containing the pore-forming mold from the composite freezing layer, thereby removing the pore-forming mold. The present invention limits the type of solvent for solvent replacement to the above range to ensure sufficient volatilization of the solvent; limiting the time for solvent replacement to the above range can ensure sufficient solvent replacement and better removal of the pore-forming mold.

[0075] The present invention has no particular limitation on the amount of the solvent, as long as it can completely immerse the composite freezing layer.

[0076] As an embodiment of the present invention, the drying after the solvent replacement to remove the pore-making mold can be carried out in an oven. The present invention does not specifically limit the model of the oven, and an oven commonly used by those skilled in the art can be used. The temperature for drying after the solvent replacement can be 60-80°C, 65-75°C, or 70°C; the time for drying after the solvent replacement can be 3-5h, 3.5-4.5h, or 4h. The present invention limits the temperature and time for drying after the solvent replacement to the above range to ensure that the replaced solvent is fully volatilized.

[0077] After obtaining the aerogel carrier, the present invention immerses the aerogel carrier in a hygroscopic salt solution and then dries it to obtain the photothermal hygroscopic aerogel.

[0078] As one embodiment of the present invention, the concentration of the hygroscopic salt solution can be 5-8wt%, or 6-7wt%. The hygroscopic salt in the hygroscopic salt solution can include one or more of calcium chloride, lithium chloride, magnesium chloride, and magnesium sulfate. The solvent of the hygroscopic salt solution can be water or an ethanol solution. The concentration of the ethanol solution can be ≥90%. The solvent of the ethanol solution can be water. Limiting the concentration of the hygroscopic salt solution and the type of hygroscopic salt to the above ranges can improve the impregnation effect of the aerogel and ensure that the photothermal hygroscopic aerogel has good hygroscopic properties.

[0079] The present invention has no particular limitation on the amount of the hygroscopic salt solution, as long as it can completely immerse the aerogel carrier.

[0080] As one embodiment of the present invention, the impregnation is preferably performed under vacuum conditions; the vacuum degree of the vacuum conditions may be 0.5 to 0.8 kPa; the impregnation time may be 10 to 12 hours, 10.5 to 11.5 hours, or even 11 hours. By impregnating under vacuum and limiting the impregnation time to the above range, the present invention enables the hygroscopic salt to be loaded onto the aerogel carrier as much as possible, thereby improving the hygroscopic properties of the photothermal hygroscopic aerogel.

[0081] As an embodiment of the present invention, the drying after the impregnation can be carried out in an oven. The present invention does not specifically limit the model of the oven, and an oven commonly used by those skilled in the art can be used. The temperature for the drying after the impregnation can be 80-100°C, 85-95°C, or 90°C; the time for the drying after the impregnation can be 8-12 hours, 9-11 hours, or 10 hours. The present invention limits the temperature and time of the drying after the impregnation to the above ranges so that the photothermal hygroscopic aerogel can be fully dried.

[0082] As one embodiment of the present invention, after absorbing moisture, the photothermal hygroscopic aerogel is dried in sunlight. The photothermal conversion material loaded in the photothermal hygroscopic aerogel absorbs solar energy and generates heat to evaporate the moisture. The drying time can be 12 to 14 hours. In the present invention, drying the photothermal hygroscopic aerogel in sunlight for 12 to 14 hours can remove moisture from the photothermal hygroscopic aerogel after absorbing moisture.

[0083] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0084] Example 1

[0085] A photothermal hygroscopic aerogel, comprising an aerogel carrier and a hygroscopic salt (lithium chloride) loaded on the aerogel carrier;

[0086] The aerogel carrier is composed of a first photothermal aerogel layer, a cellulose network aerogel layer, and a second photothermal aerogel layer arranged in sequence; the thickness of the first photothermal aerogel layer and the second photothermal aerogel layer are both 1.2 cm; the thickness of the cellulose network aerogel layer is 3.5 cm; the first photothermal aerogel layer and the second photothermal aerogel layer both include cellulose network aerogel and a photothermal conversion material loaded on the cellulose network aerogel; the photothermal conversion material is carbon black;

[0087] The aerogel carrier is provided with a channel that penetrates the first photothermal aerogel layer, the cellulose network aerogel layer, and the second photothermal aerogel layer; the channel is a cylindrical hole; the diameter of the cylindrical hole is 4 mm, and the distance between two adjacent cylindrical holes is 0.5 cm;

[0088] The porosity of the aerogel carrier is 96%;

[0089] Preparation method of the photothermal hygroscopic aerogel:

[0090] A 1 wt% first nanocellulose solution and carbon black were mixed and stirred for 25 minutes, followed by ultrasonication for 5 minutes to obtain a dispersion; the mass ratio of the first nanocellulose solution to the carbon black was 100:0.05;

[0091] 50 g of the dispersion was poured into a container containing a cylindrical mold (an acrylic box measuring 7 cm × 7 cm × 7 cm, and the cylindrical mold was a stainless steel cylindrical mold; the diameter of the stainless steel cylinder in the stainless steel cylindrical mold was 4 mm; the interval between adjacent cylinders in the stainless steel cylindrical mold was 0.5 cm). The mixture was first frozen at -15°C for 2 h, and then 150 g of a 1 wt% second nanocellulose solution was poured into the container. The mixture was then secondly frozen at -15°C for 6 h. Finally, 50 g of the dispersion was poured into the container. The mixture was thirdly frozen at -15°C for 2 h, and then the container was thawed in water for 15 min and removed to obtain a composite frozen layer containing the cylindrical mold.

[0092] The composite frozen layer containing the cylindrical mold was subjected to solvent replacement in 600 mL of ethanol solution (purity of 98%) for 15 h to remove the cylindrical mold, and then dried in an oven at 60° C. for 4 h to obtain an aerogel carrier;

[0093] The aerogel carrier was immersed in an 8 wt % lithium chloride solution (the solvent of the lithium chloride solution was an ethanol solution; the concentration of the ethanol solution was 98%) for 12 h and then dried in an oven at 80° C. for 12 h to obtain a photothermal hygroscopic aerogel;

[0094] The preparation of the 1 wt% nanocellulose solution is as follows:

[0095] The lignin and hemicellulose in the poplar wood powder are removed by chemical treatment to obtain cellulose;

[0096] The cellulose was mixed with water to prepare a 1 wt% cellulose solution, and then subjected to a fibrillation treatment in an ultrasonic cell disruptor (ultrasonic treatment, the power of the ultrasonic treatment was 800 W; the ultrasonic treatment time was 30), to obtain a 1 wt% nanocellulose solution;

[0097] The specific operation of the chemical treatment method is:

[0098] 1) sodium chlorite is added to a 2 wt % aqueous dispersion of poplar wood flour to obtain a first mixed solution, and then glacial acetic acid is added to the first mixed solution to adjust the pH to 4. The mixture is reacted in a 75° C. water bath for 1 hour to obtain a first reaction solution; the concentration of sodium chlorite in the first mixed solution is 1 wt %;

[0099] 2) mixing the first reaction liquid obtained in step 1) with the same mass of sodium chlorite as in step 1), then adding the same mass of glacial acetic acid as in step 1), and reacting in a water bath at 75° C. for 1 hour to obtain a second reaction liquid, then adding the same mass of sodium chlorite to the second reaction liquid again, repeating the above operation three times, and filtering the obtained reaction liquid until it is neutral to obtain primary treated wood powder;

[0100] 3) The once-treated wood powder obtained in step 2) is mixed with a 5 wt % potassium hydroxide solution, reacted in a 90° C. water bath for 2 h, and filtered until neutral to obtain cellulose.

[0101] The macroscopic photo of the photothermal hygroscopic aerogel in Example 1 is shown in FIG. Figure 1 As shown, from Figure 1 It can be seen that the photothermal hygroscopic aerogel has a sandwich structure, with black at both ends and white in the middle, and there are a large number of directional channels inside the aerogel.

[0102] The light absorption performance of the photothermal hygroscopic aerogel in Example 1 was tested using a UV-VIS-NIR spectrophotometer, and the obtained UV-visible-near infrared absorption spectrum was as follows: Figure 2 As shown, from Figure 2 It can be seen that the light absorption rate of the photothermal hygroscopic aerogel in the wavelength range of 500-2500nm is greater than 94%, and it has good light absorption.

[0103] The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Example 1 was tested, and the mass of the aerogel before and after loading with salt was weighed using an electronic balance to calculate the loading rate. The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Example 1 was 80% of the total weight of the photothermal hygroscopic aerogel.

[0104] The moisture absorption capacity of the photothermal moisture absorbing aerogel in Example 1 was tested in a constant temperature and humidity chamber at 25°C. The moisture absorption capacity curves at different relative humidity were as shown in FIG. Figure 3 As shown, from Figure 3 It can be seen that at relative humidity of 30%, 45%, 60%, 75% and 90%, the moisture absorption capacity is 1.3g / g, 1.59g / g, 2.09g / g, 3.14g / g and 4.7g / g respectively. In the first 30 minutes of moisture absorption, the moisture absorption rate can reach 1.54g / g / h, 1.59g / g / h, 2.20g / g / h, 2.39g / g / h and 3.55g / g / h respectively, which has high moisture absorption capacity and the ability to absorb moisture quickly.

[0105] The moisture absorption cycle performance of the photothermal hygroscopic aerogel in Example 1 was tested using a constant temperature and humidity chamber at a temperature of 25°C and a relative humidity of 75%. After absorbing moisture for 24 hours and then evaporating it under the sun for 12 hours as a cycle, the moisture absorption-dehumidification cycle curve is shown in the figure below. Figure 4 As shown, from Figure 4 It can be seen that after 30 cycles, the moisture absorption capacity of the photothermal hygroscopic aerogel can be maintained at 2.66g / g, and it has strong reproducibility.

[0106] Example 2

[0107] The only difference between Example 2 and Example 1 is that the concentration of the lithium chloride solution in step (6) is 5wt%, and the rest is the same as Example 1.

[0108] The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Example 2 was tested, and the mass of the aerogel before and after loading with salt was weighed using an electronic balance to calculate the loading rate. The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Example 2 was 68% of the total weight of the photothermal hygroscopic aerogel.

[0109] The moisture absorption capacity of the photothermal hygroscopic aerogel in Example 2 was tested at 25°C using a constant temperature and humidity chamber. At relative humidities of 30%, 45%, 60%, 75% and 90%, the moisture absorption capacities were 0.91 g / g, 1.25 g / g, 1.82 g / g, 2.83 g / g and 3.77 g / g, respectively.

[0110] Example 3

[0111] The only difference between Example 3 and Example 1 is that the solvent of the lithium chloride solution in step (6) is water, and the rest is the same as Example 1.

[0112] The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Example 3 was tested, and the mass of the aerogel before and after loading with salt was weighed using an electronic balance to calculate the loading rate. The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Example 3 was 75% of the total weight of the photothermal hygroscopic aerogel.

[0113] The moisture absorption capacity of the photothermal hygroscopic aerogel in Example 3 was tested at 25°C using a constant temperature and humidity chamber. At relative humidities of 30%, 45%, 60%, 75% and 90%, the moisture absorption capacities were 0.93 g / g, 1.32 g / g, 1.95 g / g, 2.16 g / g and 3.25 g / g, respectively.

[0114] Example 4

[0115] The only difference between Example 4 and Example 1 is that the hygroscopic salt in the hygroscopic salt solution in step (6) is calcium chloride, and the rest is the same as Example 1.

[0116] The loading rate of calcium chloride in the photothermal hygroscopic aerogel in Example 4 was tested, and the mass of the aerogel before and after loading with salt was weighed using an electronic balance to calculate the loading rate. The loading rate of calcium chloride in the photothermal hygroscopic aerogel in Example 4 was 82% of the total weight of the photothermal hygroscopic aerogel.

[0117] The moisture absorption capacity of the photothermal hygroscopic aerogel in Example 4 was tested at 25°C using a constant temperature and humidity chamber. At relative humidities of 30%, 45%, 60%, 75% and 90%, the moisture absorption capacities were 0.52 g / g, 0.98 g / g, 1.34 g / g, 1.79 g / g and 2.55 g / g, respectively.

[0118] Comparative Example 1

[0119] The only difference between Comparative Example 1 and Example 1 is that the aerogel carrier does not have pores that penetrate the first photothermal aerogel layer, the cellulose network aerogel layer, and the second photothermal aerogel layer; the acrylic box with a size of 7 cm × 7 cm × 7 cm in step (2) of the photothermal hygroscopic aerogel preparation method does not contain a cylindrical mold, and the rest is the same as Example 1.

[0120] The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Comparative Example 1 was tested, and the mass of the aerogel before and after loading with salt was weighed using an electronic balance to calculate the loading rate. The loading rate of lithium chloride in the photothermal hygroscopic aerogel in Comparative Example 1 was 78% of the total weight of the photothermal hygroscopic aerogel.

[0121] The moisture absorption capacity of the photothermal moisture absorbing aerogel in Comparative Example 1 was tested in a constant temperature and humidity chamber at 25°C. The moisture absorption capacity curves at different relative humidity were as shown in FIG. Figure 5 As shown, from Figure 5 It can be seen that at relative humidities of 30%, 45%, 60%, 75% and 90%, the moisture absorption capacity is 0.8g / g, 1.05g / g, 1.34g / g, 2.23g / g and 3.14g / g, respectively, which is significantly lower than that in Example 1.

[0122] Comparative Example 2

[0123] A hygroscopic aerogel, comprising an aerogel carrier and a hygroscopic salt (lithium chloride) loaded on the aerogel carrier;

[0124] The aerogel carrier is a cellulose network aerogel; the thickness of the cellulose network aerogel is 6 cm;

[0125] The porosity of the aerogel carrier is 95%;

[0126] Preparation method of the hygroscopic aerogel:

[0127] 250 g of a 1 wt% nanocellulose solution was poured into a container (an acrylic box with a size of 7 cm × 7 cm × 7 cm), and after freezing at -15°C for 12 h, the container was placed in water for thawing for 15 min to obtain a frozen layer;

[0128] The frozen layer was subjected to solvent replacement in 600 mL of ethanol solution (purity of 98%) for 12 h and then dried in an oven at 60° C. for 4 h to obtain an aerogel carrier;

[0129] The aerogel carrier was immersed in an 8 wt % lithium chloride solution (the solvent of the lithium chloride solution was an ethanol solution; the concentration of the ethanol solution was 98%, and the solvent of the ethanol solution was water) for 12 h, and then dried in an oven at 80° C. for 12 h to obtain a hygroscopic aerogel;

[0130] The preparation method of the 1 wt % nanocellulose solution is the same as that in Example 1.

[0131] The light absorption properties of the hygroscopic aerogel in Comparative Example 2 were tested using a UV-VIS-NIR spectrophotometer, and the obtained UV-visible-near infrared absorption spectrum was as shown in FIG. Figure 6 As shown, from Figure 6 It can be seen that the light absorption rate of the hygroscopic aerogel in the range of 200-2500nm is greater than 95%, and can reach up to 98.4%.

[0132] The loading rate of lithium chloride in the hygroscopic aerogel in Comparative Example 2 was tested. The mass of the aerogel before and after loading with salt was weighed using an electronic balance to calculate the loading rate. The loading rate of lithium chloride in the hygroscopic aerogel in Comparative Example 2 was 79% of the total weight of the hygroscopic aerogel.

[0133] The moisture absorption capacity of the hygroscopic aerogel in Comparative Example 2 was tested at 25°C using a constant temperature and humidity chamber. At relative humidities of 30%, 45%, 60%, 75% and 90%, the moisture absorption capacities were 0.81 g / g, 1.08 g / g, 1.35 g / g, 2.22 g / g and 3.11 g / g, respectively.

[0134] From the data measured in Examples 1 to 4 and Comparative Examples 1 to 2, it can be seen that the photothermal hygroscopic aerogel provided by the present invention has a moisture absorption capacity of 1.3 g / g, 1.59 g / g, 2.09 g / g, 3.14 g / g and 4.7 g / g at a relative humidity of 25° C., 30%, 45%, 60%, 75% and 90%, respectively. In the first 30 minutes of moisture absorption, the moisture absorption rate can reach 1.54 g / g / h, 1.59 g / g / h, 2.20 g / g / h, 2.39 g / g / h and 3.55 g / g / h, respectively; at a temperature of 25° C. and a relative humidity of 75%, moisture absorption for 12 hours and evaporation for 12 hours in the sun is taken as a cycle. After 30 cycles, the moisture absorption capacity of the photothermal hygroscopic aerogel can be maintained at 2.66 g / g, which is highly recyclable, environmentally friendly and pollution-free, and has a high moisture absorption capacity and the ability to absorb moisture quickly.

[0135] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A photothermal hygroscopic aerogel comprising an aerogel carrier and a hygroscopic salt loaded on the aerogel carrier; The aerogel carrier comprises a first photothermal aerogel layer, a cellulose network aerogel layer, and a second photothermal aerogel layer arranged in sequence; the first photothermal aerogel layer and the second photothermal aerogel layer both comprise a cellulose network aerogel and a photothermal conversion material loaded on the cellulose network aerogel; The aerogel carrier is provided with pores that penetrate the first photothermal aerogel layer, the cellulose network aerogel layer, and the second photothermal aerogel layer.

2. The photothermal hygroscopic aerogel according to claim 1, characterized in that The thickness of the first photothermal aerogel layer and the second photothermal aerogel layer are both 1 to 1.5 cm, and the thickness of the cellulose network matrix layer is 1.2 to 3.6 cm.

3. The photothermal hygroscopic aerogel according to claim 1, characterized in that The porosity of the aerogel carrier is 90-98%.

4. The photothermal hygroscopic aerogel according to claim 1 or 3, characterized in that: The pores are cylindrical holes with a diameter of 3 to 5 mm and a distance between two adjacent cylindrical holes of 0.3 to 0.6 cm.

5. The photothermal hygroscopic aerogel according to claim 1, characterized in that The light-to-heat conversion material includes one or more of carbon black, graphene, graphene oxide, polypyrrole and multi-walled carbon nanotubes.

6. The method for preparing the photothermal hygroscopic aerogel according to any one of claims 1 to 5, comprising: mixing the first nanocellulose solution with the photothermal conversion material to obtain a dispersion; Pour a portion of the dispersion into a container containing a pore-forming mold and perform a first freezing, then continue to pour the second nanocellulose solution into the container and perform a second freezing, and finally continue to pour the remaining dispersion into the container and perform a third freezing, and then remove the container to obtain a composite frozen layer containing the pore-forming mold; The composite frozen layer containing the pore-forming mold is subjected to solvent replacement in a solvent to remove the pore-forming mold, and then dried to obtain an aerogel carrier; The aerogel carrier is immersed in a hygroscopic salt solution and then dried to obtain a photothermal hygroscopic aerogel.

7. The preparation method according to claim 6, characterized in that The concentrations of the first nanocellulose solution and the second nanocellulose solution are both 0.5-1 wt %.

8. The preparation method according to claim 6, characterized in that The time for the solvent replacement is 15 to 20 hours.

9. The preparation method according to claim 6, characterized in that The concentration of the hygroscopic salt solution is 5-8 wt%.

10. The preparation method according to claim 6, characterized in that The immersion time is 10 to 12 hours.

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