Three-dimensional aerogel, manufacturing method therefor, and solar and wind power-based interfacial evaporation desalination method using same

Abstract

Three-dimensional aerogel, a manufacturing method thereof, and a solar and wind power-based interfacial evaporation desalination method using same are disclosed. Specifically, provided is the three-dimensional aerogel comprising chitosan and carbon nanomaterials. The three-dimensional aerogel-based desalination technique of the present invention can use sunlight and wind power energy as a power source, and obtains fresh water through a condensation process after only water molecules are evaporated from seawater or contaminated water through a photothermal conversion effect of the carbon materials.

Description

3D aerogel, its manufacturing method, and solar and wind power-based interfacial evaporation desalination method using the same

[0001] The present invention relates to a three-dimensional aerogel, a method for manufacturing the same, and a solar and wind power-based interfacial evaporation desalination method using the same.

[0002] Water shortage is a global issue that is accelerating due to population growth and industrialization. Seawater desalination technology is being actively researched as a solution. Solar-based desalination technology can be used to address water shortages in mountainous islands, poor regions, and drought-stricken areas where large-scale water treatment facilities are difficult to build.

[0003] Existing seawater desalination technologies are dominated by reverse osmosis (RO), and their production costs have advanced to the point where they rival those of groundwater and contaminated water treatment processes. However, RO, which extracts fresh water by passing it through an RO membrane at high pressure, suffers from drawbacks such as excessive energy consumption, high installation costs, geographical restrictions, complex processes, and fouling issues. While these drawbacks need to be addressed and production costs and efficiency improved, insurmountable limitations remain, necessitating the development of new seawater desalination technologies.

[0004] Two prior art technologies closely related to the invention are as follows. The first is the existing evaporative freshwater harvesting technology (solar still system), a traditional technology that heats a surface coated with a black photothermal material close to a blackbody to evaporate water. This is an existing technology that has been widely utilized as an appropriate technology and is widely used in salt farms in Korea. The second related technology is membrane distillation (MD), which combines solar energy harvesting with a heat transfer collector. This technology passes only evaporated bubbles through a hydrophobic membrane, filtering out other impurities. The bubbles that pass through the membrane are condensed at low temperatures on the other side to produce freshwater. However, this technology has the disadvantage of being relatively complex and equipment-intensive, and losing its hydrophobicity over time due to continuous use while submerged in water.

[0005] Recently, existing, outdated seawater desalination technologies are emerging as new alternatives, complementing their shortcomings. For example, hybrid methods combining membrane-based desalination with electroosmosis and solar energy maximize the strengths of each technology and enhance efficiency. However, these hybrid methods also require additional processes to utilize renewable energy. The increased energy consumption, coupled with increased CO2 emissions and environmental pollution, runs counter to the environmentally friendly nature of desalination and necessitates appropriate complementary measures.

[0006] Therefore, there is a need to develop an eco-friendly and sustainable technology that can solve the problems of conventional technologies and desalinate polluted water and seawater through inexpensive and easy installation.

[0007] The purpose of the present invention is to provide a desalination technology for obtaining fresh water from groundwater, salt water or seawater by manufacturing a three-dimensional aerogel-based photothermal membrane by optimizing a polymer structure and manufacturing a desalination device based on the membrane.

[0008] Another object of the present invention is to provide a desalination device that is manufactured as a small, portable device, thus reducing costs and providing convenience, and that can be manufactured using a 3D printing method or a simple mold.

[0009] Another object of the present invention is to provide a desalination technology based on renewable energy that evaporates seawater or contaminated water using an interfacial evaporation membrane, solar energy, and wind, and condenses the vapor to obtain drinking water and industrial water.

[0010] According to one aspect of the present invention, an aerogel structure is provided, which comprises a porous skeleton; and pores within the skeleton, and comprises chitosan and carbon nanomaterials.

[0011] In addition, the carbon nanomaterial may include at least one selected from the group consisting of graphene nanoplatelets, graphene, nanographite, carbon nanotubes, and reduced graphene oxide, polypyrrole, activated carbon, ink, and carbon black.

[0012] Additionally, the shape of the aerogel structure may include at least one shape selected from the group consisting of a cylinder, a polygonal cylinder, a sphere, a triangular pyramid, a polygonal pyramid, and a combination thereof.

[0013] Additionally, the shape of the aerogel structure may be a cylinder or a polygonal cylinder, and the aspect ratio of the aerogel structure may be 2 to 10.

[0014] Additionally, the aerogel structure may include 1 to 3 wt% of the chitosan and 1 to 10 wt% of the carbon nanomaterial.

[0015] According to another aspect of the present invention, a double-layer aerogel structure is provided, comprising: the aerogel structure; and a second aerogel structure formed on the first aerogel structure.

[0016] Additionally, the shape of the first aerogel structure may include at least one shape selected from the group consisting of a cylinder, a polygonal cylinder, a sphere, a triangular pyramid, a polygonal pyramid, and combinations thereof.

[0017] Additionally, the second aerogel structure may be laminated on part or all of the surface of the first aerogel structure.

[0018] Additionally, the density of the first aerogel and the density of the second aerogel may be different.

[0019] Additionally, the pore size of the first aerogel and the pore size of the second aerogel may be different from each other.

[0020] Additionally, the second aerogel structure may be laminated parallel to the longitudinal direction of the first aerogel structure, or may be laminated perpendicular to the longitudinal direction of the first aerogel.

[0021] Additionally, the pore size of the second aerogel structure may be larger than the pore size of the first aerogel.

[0022] According to another aspect of the present invention, a method for producing a double-layered aerogel structure is provided, comprising: (a) preparing a first mixture comprising a first chitosan, a second carbon nanomaterial, and a first solvent, and a second mixture comprising a second chitosan, a second carbon nanomaterial, and a second solvent, respectively; (b) placing the first mixture into a first mold having a predetermined first shape and freezing it; (c) separating the frozen first mixture from the first mold to obtain a first frozen mixture; (d) placing the first frozen mixture into a second mold having a predetermined second shape, and placing the second mixture into a void of the second mold and freezing it to form a second frozen mixture on the first frozen mixture; and (e) separating the first frozen mixture and the second frozen mixture formed on the first frozen mixture from the second mold and freeze-drying them to produce a double-layered aerogel structure.

[0023] According to another aspect of the present invention, a method for desalinating seawater or contaminated water is provided, comprising: (1) preparing an aerogel structure according to claim 1; (2) immersing a lower portion of the aerogel structure in seawater or contaminated water and exposing an upper portion of the aerogel structure to the outside of the seawater or contaminated water; and (3) irradiating the aerogel structure with sunlight to produce fresh water from the seawater or contaminated water in the upper portion of the aerogel structure using an interfacial evaporation desalination method.

[0024] In addition, the step (3) may be a step of irradiating the aerogel structure with sunlight to evaporate water molecules of seawater or contaminated water at the interface between the aerogel structure and the seawater or contaminated water on the upper part of the aerogel structure, evaporating them to the outside through the aerogel structure, and condensing them to produce fresh water.

[0025] Additionally, in the above step (3), blowing wind on the aerogel structure may be added.

[0026] The three-dimensional aerogel-based desalination technique of the present invention can use solar and wind energy as a power source, and has the effect of obtaining fresh water by evaporating only water molecules from seawater or polluted water through the photothermal conversion effect of carbon materials and then going through a condensation process.

[0027] In addition, the present invention is a non-power-free desalination technique that is simple to install and can be applied to various porous materials.

[0028] In addition, it is possible to create a solar distillation device or a portable desalination device including the three-dimensional aerogel of the present invention, or to design a compact device by combining it with existing technologies in a hybrid manner, so that it can be widely used in the desalination field in the future.

[0029] These drawings are for reference in explaining exemplary embodiments of the present invention, and therefore, the technical idea of ​​the present invention should not be interpreted as being limited to the attached drawings.

[0030] Figure 1 is a schematic diagram showing a process for manufacturing a photothermal conversion type interfacial evaporator based on a double-layer three-dimensional aerogel of the present invention.

[0031] Figure 2 shows the morphological analysis of the synthesized chitosan / graphene nanoplatelet aerogel.

[0032] Figure 3 shows the XPS structural analysis of a three-dimensional aerogel according to an embodiment of the present invention.

[0033] Figure 4 shows the photothermal conversion effect and evaporation amount analysis of a three-dimensional aerogel according to a wind speed change in an embodiment of the present invention.

[0034] Figure 5 shows the analysis of the desalination performance and ion concentration change of the three-dimensional aerogel-based evaporator of the present invention measured for seawater.

[0035] Figure 6 shows the photothermal conversion effect and evaporation amount analysis of the three-dimensional aerogel of the present invention according to the aspect ratio.

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention.

[0037] However, the following description is not intended to limit the present invention to a specific embodiment, and when explaining the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description is omitted.

[0038] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, or combinations thereof.

[0039] Additionally, terms including ordinal numbers, such as "first," "second," etc., which will be used hereinafter, may be used to describe various components, but these components are not limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component could be referred to as a second component, and similarly, a second component could also be referred to as a first component.

[0040] Additionally, when it is said that a component is "formed on" or "laminated on" another component, it should be understood that it may be formed or laminated directly on the entire surface or one side of the other component, but there may also be other components present in between.

[0041] Hereinafter, the three-dimensional aerogel of the present invention, its manufacturing method, and the interfacial evaporation desalination method utilizing it based on solar and wind power will be described in detail. However, these examples are provided by way of example only and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0042] Figure 1 is a schematic diagram showing a process for manufacturing a photothermal conversion type interfacial evaporator based on a double-layer three-dimensional aerogel of the present invention.

[0043] Referring to FIG. 1, the present invention provides an aerogel structure comprising a porous framework; and pores within the framework, and comprising chitosan and carbon nanomaterials.

[0044] In addition, the carbon nanomaterial may include at least one selected from the group consisting of graphene nanoplatelets, graphene, nanographite, carbon nanotubes, and reduced graphene oxide, polypyrrole, activated carbon, ink, and carbon black, preferably graphene nanoplatelets, but this is only an example, and any material having a photothermal conversion effect may be used without limitation.

[0045] Additionally, the shape of the aerogel structure may include at least one shape selected from the group consisting of a cylinder, a polygonal cylinder, a sphere, a triangular pyramid, a polygonal pyramid, and a combination thereof.

[0046] In addition, the shape of the aerogel structure may be a cylinder or a polygonal cylinder, and the aspect ratio of the aerogel structure may be 2 to 10. If the aspect ratio is less than 2, it is difficult to view it as a three-dimensional shape, and it is not preferable in terms of water absorption using the capillary effect and evaporation through heat integration, and if it exceeds 10, the mechanical strength of the porous structure is lowered and it is difficult to support it straight, which is not preferable.

[0047] In addition, the shape of the aerogel structure may be cylindrical, but this is only a preferred example and is not limited thereto. If an aerogel with excellent performance is manufactured in a three-dimensional shape and used, the area of ​​sunlight irradiation can be expanded, which can significantly increase the amount of evaporation, and evaporation can be accelerated using wind from the outside. In the case of a three-dimensional evaporator, the area of ​​irradiation can vary depending on the angle of the sun, but the contact area with seawater is reduced and the evaporation area is increased, which is a great advantage. In this case, a cylindrical structure is preferable for a gel with an appropriate aspect ratio by optimizing the diameter / height ratio of the three-dimensionally manufactured aerogel.

[0048] Furthermore, as the aspect ratio (AR) of the aerogel structure increases, the amount of evaporation can increase. Evaporation varies depending on the amount of sunlight, the angle of irradiance, and changes in light intensity. Furthermore, since the area of ​​sunlight irradiation and the amount of light at each site vary depending on the structure of the aerogel structure, i.e., the height-to-diameter ratio, the aspect ratio of the three-dimensional structure was optimized to maximize evaporation performance.

[0049] In addition, the aerogel structure may include 1 to 3 wt% of the chitosan and 1 to 10 wt% of the carbon nanomaterial. When the chitosan is included in an amount of less than 1 wt%, the proportion of the skeleton constituting the structure is too low, resulting in weak mechanical strength, which is undesirable. When the chitosan is included in an amount of more than 3 wt%, the viscosity is too high, resulting in too small a pore size and poor water absorption, which is undesirable. When the carbon nanomaterial is included in an amount of less than 1 wt%, the ability to absorb sunlight is insufficient, which is undesirable. When the carbon nanomaterial is included in an amount of more than 10 wt%, the concentration is too high, resulting in poor dispersion in the polymer network structure and agglomeration, and unnecessary overuse increases the manufacturing cost, which is undesirable.

[0050] According to another aspect of the present invention, a double-layer aerogel structure is provided, comprising: the aerogel structure; and a second aerogel structure formed on the first aerogel structure.

[0051] In addition, the shape of the first aerogel structure may be at least one shape selected from the group consisting of a cylinder, a polygonal cylinder, a sphere, a triangular pyramid, a polygonal pyramid, and a combination thereof, preferably a cylindrical shape, but this is only a preferred example and is not limited thereto.

[0052] Additionally, the second aerogel structure may be laminated on part or all of the surface of the first aerogel structure.

[0053] Additionally, the density of the first aerogel and the density of the second aerogel may be different.

[0054] Additionally, the pore size of the first aerogel and the pore size of the second aerogel may be different from each other.

[0055] Additionally, the second aerogel structure may be laminated parallel to the longitudinal direction of the first aerogel structure, or may be laminated perpendicular to the longitudinal direction of the first aerogel.

[0056] Additionally, the pore size of the second aerogel structure may be larger than the pore size of the first aerogel.

[0057] Referring to FIGS. 2 and 5, it can be confirmed that the evaporation amount is significantly improved by using a double-layer aerogel having large pores in the outer layer and small pores in the inner layer. The first aerogel structure corresponding to the inner layer has small and dense pores, and the second aerogel structure corresponding to the outer layer may have relatively large pores, and may include a double layer including the first aerogel structure and the second aerogel structure. When a higher evaporation amount is required, a double-layer aerogel structure with increased evaporation amount can be provided by including the double layer.

[0058] According to another aspect of the present invention, a method for producing a double-layered aerogel structure is provided, comprising: (a) preparing a first mixture comprising a first chitosan, a second carbon nanomaterial, and a first solvent, and a second mixture comprising a second chitosan, a second carbon nanomaterial, and a second solvent, respectively; (b) placing the first mixture into a first mold having a predetermined first shape and freezing it; (c) separating the frozen first mixture from the first mold to obtain a first frozen mixture; (d) placing the first frozen mixture into a second mold having a predetermined second shape, and placing the second mixture into a void of the second mold and freezing it to form a second frozen mixture on the first frozen mixture; and (e) separating the first frozen mixture and the second frozen mixture formed on the first frozen mixture from the second mold and freeze-drying them to produce a double-layered aerogel structure.

[0059] Additionally, the freezing of steps (b) and (d) may be performed at -30 to -10°C, respectively. When the freezing temperature is lower than -30°C, the network structure is rough and not sufficiently cross-linked due to rapid freezing bonding, which is undesirable. When the freezing temperature exceeds -10°C, the time required for freezing is long, and the first frozen mixture in step (d) is melted and stirred, which is undesirable because the characteristics of the layered structure are not formed.

[0060] Additionally, the freeze-drying in step (e) can be performed at -80 to -40°C. If it exceeds -40°C, the relatively high drying temperature causes the movement of water molecules to become active, which lowers the stability of the structure, which is not desirable.

[0061] In addition, the method for manufacturing the double-layer aerogel structure may additionally include a step (f) of washing the double-layer aerogel structure after step (e).

[0062] In addition, the first solvent of step (a) may include an organic acid, and the step (f) may include (f-1) a step of contacting the double-layer aerogel structure with an alkaline solution to neutralize the hydrogen ion concentration index (pH) of the double-layer aerogel structure; and (f-2) a step of washing the neutralized double-layer aerogel structure with a mixed solution of distilled water and water.

[0063] Additionally, the organic acid may include at least one selected from the group consisting of acetic acid and C3 to C10 carboxylic acids.

[0064] According to another aspect of the present invention, a method for desalinating seawater or contaminated water is provided, comprising: (1) preparing an aerogel structure according to claim 1; (2) immersing a lower portion of the aerogel structure in seawater or contaminated water and exposing an upper portion of the aerogel structure to the outside of the seawater or contaminated water; and (3) irradiating the aerogel structure with sunlight to produce fresh water from the seawater or contaminated water in the upper portion of the aerogel structure using an interfacial evaporation desalination method.

[0065] In addition, the step (3) may be a step of irradiating the aerogel structure with sunlight to evaporate water molecules of seawater or contaminated water at the interface between the aerogel structure and the seawater or contaminated water on the upper part of the aerogel structure, evaporating them to the outside through the aerogel structure, and condensing them to produce fresh water.

[0066] Additionally, in the above step (3), blowing wind on the aerogel structure may be added.

[0067] Aerogels can be created by freezing and drying the moisture within a cryogenically swollen hydrogel, creating a void within it. Aerogels possess similar properties, making them ideal for use in interfacial evaporative desalination technology to enhance desalination performance and functional properties.

[0068] Evaporation via natural convection can be utilized to harness wind energy, in addition to solar energy. Accordingly, we compared evaporation performance according to the number and arrangement of 3D aerogels. This study also considered the evaporation rate based on the area exposed to the wind and economic factors.

[0069] Solar-based interfacial evaporative desalination technology offers many advantages, including cost-effectiveness, environmental friendliness, and the potential for integration with other technologies. This patent applies a photothermal membrane synthesized from a polymer to interfacial evaporative desalination technology to enhance evaporation and salt suppression performance. Specifically, a three-dimensional aerogel-based evaporator with high photothermal conversion performance is fabricated and used to expand the solar irradiation area, significantly increasing evaporation. Furthermore, wind can be applied to the porous evaporator to accelerate evaporation. While the irradiation area of ​​a three-dimensional evaporator can vary depending on the solar irradiation angle, the reduced contact area with seawater reduces heat loss and increases the evaporation area, significantly increasing the overall evaporation amount. The aspect ratio (diameter / height) of the three-dimensionally fabricated aerogel was optimized to produce a cylindrical evaporator with excellent evaporation performance.

[0070] Accordingly, the present invention relates to a technology for obtaining fresh water from groundwater, brine, or seawater by fabricating a three-dimensional aerogel-based photothermal membrane to enhance the evaporation performance of an interfacial evaporative desalination device and developing a solar-powered desalination device using the membrane. The goal is to contribute to the development of a solar-powered interfacial evaporative desalination technique and device with superior evaporation performance.

[0071] [Example]

[0072] Hereinafter, preferred embodiments of the present invention will be described. However, these are provided for illustrative purposes only and the scope of the present invention is not limited thereby.

[0073] Example: Synthesis of chitosan / graphene nanoplatelets (C / G) 3D aerogel

[0074] Example 1: Single-layer 3D aerogel according to concentration change

[0075] Example 1-1: Single-layer 3D aerogel with a concentration of 1.5%

[0076] Chitosan powder was mixed with an acetic acid solution and stirred with a magnetic stirrer at 60°C for approximately 16 hours to produce a chitosan solution. Graphene nanoplatelets, either in solution or powder form, were mixed with the solution and stirred with a magnetic stirrer at room temperature for approximately 12 hours to produce a chitosan / graphene nanoplatelet solution. The solution was poured into a mold of the desired shape and frozen at -20°C for approximately 12 hours. The frozen solution was separated from the mold and dried at -60°C for approximately 72 hours to remove any moisture inside. The aerogel was immersed in a sodium hydroxide solution and gently washed to neutralize its pH. The sufficiently neutralized aerogel was washed at least three times with distilled water and ethanol solutions to completely remove any residual solutions.

[0077] Example 1-2: Single-layer 3D aerogel with a concentration of 3%

[0078] A single-layer three-dimensional aerogel was manufactured in the same manner as in Example 1-1, except that a chitosan concentration of 3% was used instead of a chitosan concentration of 1.5%.

[0079] Example 1-3: Single-layer 3D aerogel with a concentration of 2.5%

[0080] A single-layer three-dimensional aerogel was manufactured in the same manner as in Example 1-1, except that instead of using a chitosan concentration of 1.5%, the concentration was 2.5%.

[0081] Example 2: Double-layer 3D aerogel according to concentration change

[0082] Example 2-1: Inner layer concentration 3%, outer layer concentration 1.5%

[0083] The method used in Example 1-2 was the same, but a solution with a concentration of 1.5% was poured once more into the frozen three-dimensional aerogel during the molding process, and freezing and molding were performed to produce a bi-layered aerogel having different components or densities.

[0084] Example 2-2: Inner layer concentration 1.5%, outer layer concentration 3%

[0085] A double-layered three-dimensional aerogel was manufactured in the same manner as in Example 2-1, except that instead of using chitosan having an inner layer concentration of 3% and an outer layer concentration of 1.5%, chitosan having an inner layer concentration of 1.5% (as in Example 1-1) and an outer layer concentration of 3% was used.

[0086] Comparative example

[0087] A single-layer three-dimensional aerogel was manufactured in the same manner as in Example 1-1, except that instead of using a chitosan having a concentration of 3%, a chitosan having a concentration of less than 1% was used.

[0088] [Example Exam]

[0089] Test Example 1: Confirmation of the 3D structural properties of chitosan / graphene nanoplatelet aerogels.

[0090] Test Example 1-1: Morphological analysis of chitosan / graphene nanoplatelet aerogel

[0091] Figure 2 shows the morphological analysis of the synthesized chitosan / graphene nanoplatelet aerogel.

[0092] Referring to Fig. 2a, the synthesized aerogel can be synthesized into a desired shape through a mold, and it was confirmed that it has a porous structure according to the characteristics of chitosan, a natural polymer.

[0093] Referring to Figures 2b to 2d, it was confirmed that the density and porosity characteristics of the synthesized aerogel could be changed by controlling the concentration in the solution state before gelation. Graphene nanoplatelets, which are formed by stacking graphene layers, are manufactured on a very small scale, making it difficult to properly confirm the morphology. Surface images acquired using FE-SEM confirmed that the synthesized chitosan / graphene nanoplatelet aerogel was well synthesized on the microscale.

[0094] Through this, it was confirmed that pores of various sizes were formed along the surface of the chitosan / graphene nanoplatelets.

[0095] Test Example 1-2: XPS Structural Analysis of Chitosan / Graphene Nanoplatelet (CG) Aerogel

[0096] Figure 3 shows the XPS structural analysis of a three-dimensional aerogel according to an embodiment of the present invention.

[0097] Referring to Fig. 3, the composition and chemical bonding state of the synthesized polymer were confirmed through X-ray photoelectron spectroscopy (XPS) analysis. As a result, in the case of CG aerogel, several peaks overlapped in C1s and N1s, which are the main peaks of graphene components and chitosan. The C1s peak is formed by bonds such as CN, C-OH, OCO, etc., and not only chitosan that constitutes carbon, but also nitrogen and oxygen atoms are involved to form two distinct and complex peaks. The N1s peak is largely composed of NH2, C-NH2 group, NH3 + It is formed by groups such as NH, and mainly represents chitosan deacetylation by the formation of NH groups. The position and intensity of these peaks may vary depending on the sample preparation process, but the results of this experiment are in good agreement with those reported in previous studies, confirming the successful synthesis of the desired material.

[0098] Test Example 2: Analysis of evaporation amount and heating characteristics of aerogel under conditions of sunlight and wind.

[0099] Figure 4 shows the photothermal conversion effect and evaporation amount analysis of a three-dimensional aerogel according to a wind speed change in an embodiment of the present invention.

[0100] Referring to Fig. 4, the evaporation amount and heating characteristics of aerogel under solar and convective conditions are shown using a wind tunnel facility capable of applying a uniform flow rate. Aerogels with different densities were produced using a molding technique that is simple in the process of producing the desired shape of the solution concentration, and evaporation experiments were performed. The experimental results showed that the evaporation performance of aerogels with low density and large pores was high, and 1 kW m -2 Under solar irradiation conditions, the wind speed is maximum (6 ms -1 ) the highest evaporation amount of 5.9 kg m -2 h -1 was achieved.

[0101] In addition, as the aspect ratio (AR) of the aerogel increases, the specific surface area where convective energy exchange occurs increases, resulting in higher evaporation performance. When examining the thermal characteristics in an environment where convective heat transfer by sunlight and wind occurs simultaneously, the temperature of the evaporator decreases overall due to the cooling effect by convection despite the presence of the photothermal conversion material, and as a result, the side temperature is maintained at a low value of about 19 ℃ even when sunlight is shining. Since this is a lower temperature than the surrounding air temperature, latent heat energy can be obtained from the surrounding air and used for evaporation. The energy exchange effect at the side of the evaporator due to the wind also affects the evaporation amount. Referring to Fig. 4e, even in the absence of sunlight, the evaporator of AR7 can obtain 5.9 kg m at a wind speed of 6 m / s. -2 h -1 It can be seen that it shows a high evaporation rate.

[0102] Test Example 3: Analysis of desalination performance and ion residue of aerogel in seawater solution.

[0103] Figure 5 shows the analysis of the desalination performance and ion concentration change of the three-dimensional aerogel-based evaporator of the present invention measured for seawater.

[0104] Referring to Fig. 5, aerogels basically have a porous structure, and the porosity and pore size vary depending on the density. If one aerogel structure is manufactured into two regions with different densities, water can be rapidly transported in the low-density region with relatively large pores, and in the high-density region with small pores, the transported moisture can be retained for a long time based on strong mechanical strength and high water retention capacity, and the flame retardant properties of the aerogel can be enhanced. In addition, it was confirmed through optical images and internal X-ray images that the aerogel's excellent water transport and retention capacity can naturally dissolve salt placed on top of the evaporator. The evaporation amounts measured for artificial seawater composed of a concentration of 3.5 wt.%, as well as sodium chloride (NaCl) solutions of 5 wt.%, 15 wt.%, and 20 wt.%, are lower for seawater and contaminated water than for distilled water due to the increased vapor pressure caused by the impurities contained in these solutions. However, the evaporation amount for the 20 wt.% high-concentration brine was maintained at 70% of the evaporation amount for distilled water.

[0105] Through this, when comparing the ion concentrations of the NaCl solutions before and after desalination, it was confirmed that the major ions of seawater were hardly detected in the water obtained through desalination treatment and that it met the WHO drinking water standards, so it could be used as freshwater.

[0106] Experimental Example 4: Analysis of Evaporation and Heating Characteristics of Thermoresponsive Chitosan / Graphene Nanoplatelet Aerogels Under Solar Irradiation

[0107] Figure 6 shows the photothermal conversion effect and evaporation amount analysis of the three-dimensional aerogel of the present invention according to the aspect ratio.

[0108] Referring to Fig. 6, the evaporation characteristics according to sunlight irradiation were analyzed while changing the aspect ratio (height / radius) (AR), weight % density composition, and internal density composition of the double-layer aerogel of the chitosan / graphene nanoplatelet aerogel. After preparing 3D single aerogels and double-layer aerogels with aspect ratios of 5 and 7 with different density compositions, the change in evaporation due to the photothermal conversion effect according to sunlight irradiation was measured (Fig. 6). As a result, the evaporation amount of the single aerogel with an aspect ratio of 5 decreased as the density of the structure increased, and the evaporation amount was increased from a maximum of 2.34 kg m to a maximum of 1.5% aerogel with a weight ratio of 1.5%. -2 h -1 The evaporation amount was obtained. In the case of double-layer aerogels, a higher evaporation amount (up to 2.17 kg m) was obtained when the density of the outer part was lower. -2 h -1 ) was obtained (Fig. 6a). The aerogel with an aspect ratio of 7 has a relatively larger lateral area than the aerogel with an aspect ratio of 5, resulting in an evaporation amount of at least 0.3 kg m -2 h -1 This indicates that evaporation increases with the increased aspect ratio. In the case of double-layer aerogels, if the density of the outer layer exposed to the atmosphere is low, the pore size increases, providing more space for water molecules to evaporate and escape, thereby promoting evaporation compared to the opposite case.

[0109] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. Porous skeleton; and Contains pores inside the above skeleton, Containing chitosan and carbon nanomaterials, Aerogel structure.

2. In paragraph 1, An aerogel structure characterized in that the carbon nanomaterial comprises at least one selected from the group consisting of graphene nanoplatelets, graphene, nanographite, carbon nanotubes, reduced graphene oxide, polypyrrole, activated carbon, ink, and carbon black.

3. In paragraph 1, An aerogel structure characterized in that the shape of the aerogel structure includes at least one shape selected from the group consisting of a cylinder, a polygonal cylinder, a sphere, a triangular pyramid, a polygonal pyramid, and combinations thereof.

4. In paragraph 3, The shape of the above aerogel structure is a cylinder or a polygonal cylinder, An aerogel structure characterized in that the aspect ratio of the aerogel structure is 2 to 10.

5. In paragraph 1, An aerogel structure characterized in that the aerogel structure comprises 1 to 3 wt% of the chitosan and 1 to 10 wt% of the carbon nanomaterial.

6. The above aerogel structure; and A second aerogel structure formed on the first aerogel structure: A double-layer aerogel structure comprising:

7. In paragraph 6, A double-layer aerogel structure characterized in that the shape of the first aerogel structure includes at least one shape selected from the group consisting of a cylinder, a polygonal cylinder, a sphere, a triangular pyramid, a polygonal pyramid, and combinations thereof.

8. In paragraph 6, A double-layer aerogel structure characterized in that the second aerogel structure is laminated on part or all of the surface of the first aerogel structure.

9. In paragraph 6, A double-layer aerogel structure characterized in that the density of the first aerogel and the density of the second aerogel are different.

10. In paragraph 6, A double-layer aerogel structure characterized in that the second aerogel structure is laminated parallel to the longitudinal direction of the first aerogel structure or perpendicular to the longitudinal direction of the first aerogel. 11.(a) A step of preparing a first mixture comprising a first chitosan, a second carbon nanomaterial, and a first solvent, and a second mixture comprising a second chitosan, a second carbon nanomaterial, and a second solvent, respectively; (b) a step of putting the first mixture into a first mold having a predetermined first shape and freezing it; (c) a step of separating the frozen first mixture from the first mold to obtain a first frozen mixture; (d) placing the first frozen mixture in a second mold having a predetermined second shape, injecting the second mixture into the empty space of the second mold, and freezing it to form a second frozen mixture on the first frozen mixture; and (e) a step of separating the first frozen mixture and the second frozen mixture formed on the first frozen mixture from the second mold and freeze-drying them to produce a double-layer aerogel structure; A method for manufacturing a double-layer aerogel structure comprising:

12. In paragraph 11, The first solvent of step (a) contains an organic acid, The method for manufacturing the above double-layer aerogel structure is after step (e). (f-1) A step of neutralizing the hydrogen ion concentration index (pH) of the double-layer aerogel structure by contacting the double-layer aerogel structure with an alkaline solution; (f-2) A method for manufacturing a double-layer aerogel structure, characterized by comprising the step of washing the neutralized double-layer aerogel structure with a mixed solution of distilled water and water.

13. In paragraph 12, A method for producing a double-layer aerogel structure, characterized in that the organic acid comprises at least one selected from the group consisting of acetic acid and C3 to C10 carboxylic acids. 14.(1) A step of preparing an aerogel structure according to paragraph 1; (2) a step of immersing the lower part of the aerogel structure in seawater or contaminated water and exposing the upper part of the aerogel structure to the outside of the seawater or contaminated water; and (3) A step of producing fresh water by irradiating sunlight on the aerogel structure and using an interface evaporation desalination method from seawater or contaminated water on the upper part of the aerogel structure; A method for desalinating seawater or polluted water.

15. In paragraph 14, The above step (3) A method for desalinating seawater or contaminated water, characterized in that the method comprises a step of irradiating the aerogel structure with sunlight to evaporate water molecules of seawater or contaminated water at the interface between the aerogel structure and the seawater or contaminated water, thereby evaporating them to the outside through the aerogel structure and condensing them to produce fresh water.

16. In paragraph 14, A method for desalinating seawater or contaminated water, characterized in that in the above step (3), blowing wind on the aerogel structure is added.

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