Highly efficient salt-resistant and evaporation photothermal material for high-concentration brine and preparation method and application thereof

Abstract

The application provides a high-efficiency salt-resistant and evaporation photothermal material for high-concentration brine and a preparation method and application thereof, and the preparation method specifically comprises the following steps: preparing a MOF precursor solution; placing the fiber fabric and the prepared MOF precursor solution in a reactor together, and performing a hydrothermal reaction to obtain a MOF@fiber fabric; and performing carbonization treatment on the obtained MOF@fiber fabric to obtain the high-efficiency salt-resistant and evaporation photothermal material for high-concentration brine. The special structure of the MOF is utilized to reduce the evaporation enthalpy of water, improve the utilization rate of solar energy, and further improve the evaporation efficiency. Furthermore, the high water absorption property of the MOF is utilized to strengthen the convection and diffusion of the salt water on the surface of the photothermal material, and the precipitation of salt ions on the surface of the material is avoided. Meanwhile, the application provides a very promising strategy for improving the high-efficiency evaporation of the current solar desalination system for high-concentration brine based on interfacial evaporation and inhibiting the generation of salt crystals.

Description

Technical Field

[0001] The present invention relates to the field of photothermal conversion technology, and in particular to a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, and a preparation method and application thereof. Background Art

[0002] With the continued growth of the global population and the deepening of industrialization, freshwater consumption is increasing worldwide, while freshwater resources on Earth are relatively scarce. Therefore, providing a sustainable method for producing freshwater has important practical value. As a stable freshwater resource increment technology, seawater desalination has gradually become an important way to replenish freshwater resources.

[0003] Solar energy offers advantages over traditional heat sources, such as safety and environmental friendliness. Consequently, solar interfacial evaporation technology has been recognized in recent years as a low-cost, sustainable desalination strategy for producing fresh water. However, during the long-term desalination process of current solar interfacial evaporation materials, salts in the seawater tend to crystallize as the water evaporates. These precipitated salts clog the water transport channels of the evaporation material and prevent sunlight from reaching the surface, significantly slowing the evaporation rate.

[0004] In order to solve the problem of salt deposition, there are usually two methods: the first method is local salt crystallization, which causes salt to crystallize at a specific location and then be physically removed. Since this method requires a subsequent cleaning step, it will interrupt the evaporation process, reduce the evaporation efficiency, and increase the additional system maintenance cost, so it is difficult to apply it on a large scale. The second method is salt circulation, which mainly involves the following three salt removal mechanisms: (1) Salt rejection based on diffusion and advection, that is, continuously adding water to the evaporator so that the salt dissolution rate is greater than its crystallization rate, thereby causing the salt crystals to dissolve again. However, this will bring about a large heat loss, thereby reducing the evaporation rate and ultimately failing to achieve the purpose of efficiently treating concentrated brine. (2) Performing hydrophobic treatment on the evaporator surface to directly prevent salt formation from the source. (3) Using the Donan effect to inhibit salt crystallization, through electrostatic attraction and repulsion, reducing the diffusion of salt ions into the evaporator, achieving the effect of inhibiting salt crystallization. Although the above three salt resistance methods have made significant progress in salt resistance strategies, the evaporation rate is still not ideal, and the salt resistance effect needs to be improved. Therefore, on the basis of treating high-concentration brine, further improving the evaporation rate is a major challenge in the field of interfacial evaporation today.

[0005] In view of this, it is necessary to design an improved photothermal material with high efficiency, salt resistance and evaporation resistance for highly concentrated brine, as well as its preparation method and application, to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, as well as a preparation method and application thereof. A dense MOF nanolayer is formed on the surface of a fabric through a hydrothermal reaction, and the fabric is then carbonized through a carbonization treatment. The special structure of MOF is utilized to reduce the evaporation enthalpy of water, while increasing the utilization rate of solar energy and thereby improving the evaporation efficiency. Furthermore, the high water absorption properties of MOF are utilized to enhance the convection and diffusion of brine on the surface of the photothermal material, thereby avoiding the precipitation of salt ions on the material surface.

[0007] To achieve the above-mentioned object of the invention, the present invention provides a method for preparing a highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, comprising the following steps:

[0008] S1. Preparation of MOF precursor solution;

[0009] S2. placing the fiber fabric and the MOF precursor solution prepared in step S1 together in a reactor and performing a hydrothermal reaction to obtain MOF@fiber fabric;

[0010] S3. The MOF@fiber fabric prepared in step S2 is carbonized to obtain a highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine.

[0011] As a further improvement of the present invention, in step S3, the temperature of the carbonization treatment is 500-600° C., and the treatment time is 2-4 hours.

[0012] As a further improvement of the present invention, in step S2, the temperature of the hydrothermal reaction is 150-200° C., and the reaction time is 10-20 h.

[0013] As a further improvement of the present invention, the MOF precursor solution is prepared by adding organic ligands and metal salts to deionized water and ultrasonically mixing them; the molar ratio of the organic ligands to the metal salts is 1:(0.8~1.3), and the total concentration of the organic ligands and the metal salts in the MOF precursor solution is 7wt%~15wt%.

[0014] As a further improvement of the present invention, the fiber fabric includes one of polyimide fiber fabric, polytetrafluoroethylene fiber fabric or aromatic polyamide fiber fabric.

[0015] As a further improvement of the present invention, in step S1, the MOF precursor solution includes one of a Fe-MOF precursor solution, a Cr-MOF precursor solution or a Cu-MOF precursor solution.

[0016] As a further improvement of the present invention, in step S2, before the hydrothermal reaction, the fiber fabric needs to be immersed in alcohol and ultrasonically treated for 30 to 40 minutes, and then washed and dried.

[0017] To achieve the above-mentioned purpose of the invention, the present invention also provides a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, which is prepared using the above-mentioned method for preparing the high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine.

[0018] As a further improvement of the present invention, the highly efficient salt-resistant and evaporative photothermal material for highly concentrated brine has a power output of 1kW / m 2 The evaporation rate in pure water is as high as 1.63 kg·m -2 ·h -1 The evaporation efficiency in 10wt% concentrated brine is as high as 1.46kg·m -2 ·h -1 , and no salt crystals will appear after working outdoors for 7 days.

[0019] To achieve the above-mentioned purpose of the invention, the present invention also provides a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine prepared by the above-mentioned method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, or the application of the above-mentioned high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, wherein the high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine is used for seawater desalination.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention provides a highly efficient, salt-resistant and evaporation-resistant photothermal material for highly concentrated brine. By regulating the ratio of organic ligands and metal salts, a MOF precursor solution of a specific concentration is obtained. The fiber fabric and the MOF precursor solution are then subjected to a hydrothermal reaction. The reaction temperature, i.e., time, is controlled so that the organic ligands and metal salts are self-assembled into a porous crystalline material of a special structure through coordination, and are evenly loaded on the surface and internal pores of the fiber fabric, with a dense MOF nanolayer loaded on the surface of the fiber fabric. Finally, by carbonizing the fabric, not only the light absorption of the photothermal material is improved, but also its efficiency in absorbing sunlight is increased, thereby increasing the photothermal conversion efficiency of the material and thereby increasing the evaporation efficiency of water. At the same time, the bonding structure between the organic ligands, metals, and fiber fabrics is further changed in the process, forming a more stable bonded body, thereby increasing the service life of the material.

[0022] At the same time, the special structure of MOF absorbs water faster than the evaporation rate of water, which means that it provides a continuous source of water, making it difficult for salt crystals to precipitate.

[0023] (2) The highly efficient salt-resistant and evaporation-resistant photothermal material prepared by the present invention forms a nano-load layer on the surface of the fabric, improving the fabric's hydrophilicity and enabling it to absorb more water. Simultaneously, the MOF, due to its unique porous structure, can absorb more water and confine water through its own pore structure, destroying the microstructure of water molecules and reducing the heat energy required for their evaporation, thereby lowering the enthalpy of evaporation. Simultaneously, the photothermal material can absorb more solar energy, converting it into heat energy, accelerating water escape and improving water evaporation efficiency.

[0024] The special structure of MOF absorbs water faster than its evaporation rate, which means it provides a continuous supply of water, enhances the convection and diffusion of brine on the evaporator surface, and avoids the precipitation of salt ions on the evaporator surface.

[0025] (3) The highly efficient salt-resistant and evaporation-resistant photothermal material provided by the present invention for high-concentration brine provides a promising strategy for improving the efficient evaporation and inhibiting salt crystal formation of the current solar desalination high-concentration brine system based on interfacial evaporation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 These are optical photographs of the polyimide fiber fabric in Example 1 of the present invention before and after the reaction.

[0027] Figure 2 These are scanning electron microscope images of the polyimide fiber fabric in Example 1 of the present invention before and after the reaction, with a scale of 10 μm.

[0028] Figure 3 This is a diagram showing the salt evaporation resistance performance of the high-efficiency salt and evaporation-resistant photothermal material for highly concentrated brine prepared in Example 1 when working outdoors.

[0029] Figure 4 This is a graph showing the water absorption performance test results of the high-efficiency salt-resistant and evaporation-resistant photothermal materials for highly concentrated brine prepared in Example 1 and Comparative Example 8 of the present invention.

[0030] Figure 5 This is a graph showing the light absorption performance test results of the high-efficiency salt-resistant and evaporation-resistant photothermal materials for highly concentrated brine prepared in Example 1 and Comparative Example 8 of the present invention.

[0031] Figure 6 This is a graph showing the evaporation performance test results of the high-efficiency salt-resistant and evaporation-resistant photothermal materials for highly concentrated brine prepared in Example 1 and Comparative Example 8 of the present invention in 10 wt% concentrated brine (NaCl). DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0034] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0035] The present invention provides a method for preparing a highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, comprising the following steps:

[0036] S1. Preparation of MOF precursor solution:

[0037] The organic ligand and the metal salt in a preset ratio are added to deionized water, stirred and mixed, and then ultrasonically treated for 10 to 50 minutes to obtain a uniform MOF precursor solution.

[0038] The molar ratio of the organic ligand to the metal salt is 1:(0.8-1.3), and the total concentration of the organic ligand and the metal salt in the MOF precursor solution is 7wt%-15wt%.

[0039] The organic ligand is an amino-substituted terephthalic acid, preferably 2-aminoterephthalic acid; the metal salt is one of the corresponding metal nitrate, sulfate, and hydrochloride, preferably the corresponding metal nitrate. The MOF includes one of Fe-MOF, Cr-MOF, or Cu-MOF. Different MOF precursor solutions are obtained by selecting different metal salt solutions.

[0040] S2. Hydrothermal reaction

[0041] The fiber fabric is immersed in alcohol and ultrasonically treated for 10 to 40 minutes, preferably 30 to 40 minutes, to remove impurities such as oil stains on the surface of the fabric, and then dried.

[0042] The fiber fabric and the MOF precursor solution prepared in step S1 are placed together in a reactor and subjected to a hydrothermal reaction to obtain MOF@fiber fabric.

[0043] The hydrothermal reaction temperature is 150-200°C, and the reaction time is 10-20 hours. During this process, the organic ligands and metal salts coordinate and self-assemble into a porous crystalline material with a unique structure. This porous crystalline material is evenly loaded on the surface and internal pores of the fiber fabric. The organic ligands, metal, and fiber fabric are chemically bonded to form a stable inclusion, and a dense MOF nanolayer is loaded on the fiber fabric surface.

[0044] The fiber fabric includes one of polyimide fiber fabric, polytetrafluoroethylene fiber fabric or aromatic polyamide fiber fabric.

[0045] S3. Carbonization treatment

[0046] The MOF@fiber fabric prepared in step S2 is placed in a tubular furnace filled with N2 and carbonized at 500-600°C for 2-4 hours to obtain a highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine.

[0047] During this process, the fiber fabric carbonizes and turns black, improving the light absorption of the photothermal material and increasing its efficiency in absorbing sunlight, thereby increasing the material's photothermal conversion efficiency and, in turn, the water evaporation efficiency. Simultaneously, this process further alters the bonding structure between the organic ligand, metal, and fiber fabric, forming a more stable bond.

[0048] Furthermore, MOFs, due to their unique porous structure, can absorb more water and confine it through their pores, disrupting the microstructure of water molecules and reducing the heat required for their evaporation, thereby lowering the enthalpy of evaporation. This photothermal material can first absorb more solar energy, converting it into thermal energy while simultaneously reducing the amount of heat required for water evaporation. Even with the large amount of water absorbed within the MOF, it can still improve water evaporation efficiency. Furthermore, the MOF's unique structure absorbs water faster than its evaporation rate, providing a continuous water supply and preventing salt crystallization.

[0049] The present invention also provides a photothermal material with high efficiency and salt resistance and evaporation for high concentration brine, which is prepared by the above-mentioned preparation method of the photothermal material with high efficiency and salt resistance and evaporation for high concentration brine. The photothermal material with high efficiency and salt resistance and evaporation for high concentration brine has a heat transfer rate of 1kW / m 2 The evaporation rate in pure water is as high as 1.63 kg·m -2 ·h -1 The evaporation efficiency in 10wt% concentrated brine is as high as 1.46kg·m -2 ·h -1 , and no salt crystals will occur, making it suitable for the treatment of high-concentration brine.

[0050] The present invention also provides an application of a highly efficient, salt-resistant, and evaporation-resistant photothermal material for highly concentrated brine, which is used for seawater desalination. During desalination, the prepared photothermal material is placed on a foamed polystyrene surface (the polyethylene foam acts as a floating element, allowing the photothermal material to float on the water). Several polyester columns are then placed beneath the foamed polystyrene to form a water supply channel.

[0051] The present invention is described in detail below through a number of embodiments:

[0052] Example 1

[0053] A highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, comprising the following steps:

[0054] S1. Preparation of MOF precursor solution:

[0055] 6 mmol of 2-aminoterephthalic acid and 6 mmol of chromium (III) nitrate nonahydrate were added to 30 mL of deionized water, stirred and mixed, and then ultrasonically treated for 30 minutes to obtain a MOF precursor solution with a concentration of 10 wt%.

[0056] S2. Hydrothermal reaction

[0057] The polyimide fiber fabric was immersed in alcohol and ultrasonicated for 30 minutes to remove impurities such as oil stains on the surface of the fabric, and then dried.

[0058] The cleaned polyimide fiber fabric and the MOF precursor solution prepared in step S1 are placed together in a reactor and subjected to a hydrothermal reaction to obtain MOF@fiber fabric.

[0059] The temperature of the hydrothermal reaction was 180°C, and the reaction time was 15 h.

[0060] S3. Carbonization treatment

[0061] The MOF@fiber fabric prepared in step S2 was placed in a tubular furnace filled with N2 and carbonized at 550°C for 3 hours to obtain a highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine.

[0062] like Figure 1 The following are optical photos of polyimide fiber fabrics before and after the reaction. Figure 1 It can be seen that the carbonization and blackening of the fiber fabric improves the light absorption of the photothermal material and increases its efficiency in absorbing sunlight, thereby improving the photothermal conversion efficiency of the material and further improving the evaporation efficiency of water.

[0063] like Figure 2 The following are scanning electron microscope images of polyimide fiber fabrics before and after the reaction. Figure 2 It can be seen that a dense MOF nanolayer is formed on the surface of the polyimide fiber fabric.

[0064] The photothermal material prepared in Example 1 was assembled with expanded polystyrene and several polyester columns into an evaporation device for desalination of water and seawater. Evaporation tests of pure water and 10 wt% salt water were carried out under one sun. The test results are shown in Table 1. The evaporation rate of pure water by the evaporation material can reach 1.63 kg·m -2 ·h -1 , a stable and efficient steam generation rate of 1.46 kg·m -2 ·h -1 , without salt crystallization ( Figure 3 )

[0065] The evaporation device was placed outdoors for a 7-day evaporation performance test. The results are as follows Figure 3 As shown. Figure 3 It can be seen that the salt content in the photothermal layer is basically in a stable state. At the same time, no salt crystals appear on the surface of the photothermal layer. It can be seen that the photothermal material provided by the present invention can be used for the evaporation of outdoor seawater for a long time and stably, and has very excellent anti-salting ability.

[0066] In addition, the evaporation device is used to desalinate seawater from Qingdao waters, and the condensed water obtained by desalination, Na + 、B 3+ , K + Mg 2+ , Ca 2+ The removal rate of major impurity ions is close to 100%.

[0067] Examples 2-5 and Comparative Examples 1-4

[0068] A highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine. Compared with Example 1, the difference lies in that in step S1, the molar ratio of the organic ligand and the metal salt and the concentration of the MOF precursor solution are different. The other steps are roughly the same as Example 1 and are not repeated here.

[0069] The photothermal materials prepared in Examples 1-5 and Comparative Examples 1-4 were assembled with expanded polystyrene and several polyester columns into an evaporation device for desalination of water and seawater. Evaporation tests of pure water and 10 wt% concentrated brine were carried out under one sunlight. The test results are shown in Table 1.

[0070] Table 1 Performance test of photothermal materials prepared in Examples 1-5 and Comparative Examples 1-4

[0071]

[0072]

[0073] It can be seen from Table 1 that with the increase of the proportion of metal salt, the evaporation rate of the obtained photothermal material first increases and then decreases, which shows that the molar ratio of organic ligand and metal salt affects the bonding between organic ligand and metal salt, thereby affecting the structure of the generated MOF layer, and then affecting the performance of the photothermal material.

[0074] Under the same molar ratio of organic ligand to metal salt, the evaporation rate of the resulting photothermal material decreases with increasing concentration of the MOF precursor solution. This is likely because, as the concentration of the MOF precursor solution increases, an overly dense MOF nanolayer forms on the surface of the fiber fabric after the hydrothermal reaction, affecting the subsequent carbonization process and the bonding between the organic ligand, metal, and fiber fabric, thus affecting the performance of the photothermal material. However, when the concentration of the MOF precursor solution is low, the resulting photothermal material has poor salt resistance.

[0075] When the content of metal salt is too high or too low, or the concentration of MOF precursor solution is too high or too low, it will have a great impact on the performance of photothermal materials.

[0076] Examples 6-7 and Comparative Examples 5-6

[0077] A highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, which differs from Example 1 in that the temperature of the hydrothermal reaction in step S2 is different, and the rest is substantially the same as Example 1 and will not be repeated here.

[0078] The photothermal materials prepared in Examples 6-7 and Comparative Examples 5-6 were assembled with expanded polystyrene and several polyester columns into an evaporation device for desalination of seawater with water. Evaporation tests of pure water and 10 wt% concentrated brine were carried out under one sunlight. The test results are shown in Table 2.

[0079] Table 2 Performance test of photothermal materials prepared in Examples 6-7 and Comparative Examples 5-6

[0080]

[0081]

[0082] As shown in Table 2, the evaporation performance of the resulting photothermal material remains essentially stable when the hydrothermal reaction temperature varies within a certain range. This is primarily because as the carbonization temperature increases, the carbonization reaction proceeds more thoroughly, allowing the fabric to absorb sunlight more fully. Simultaneously, as the temperature changes, the bonding structure between the organic ligands, metal, and fiber fabric changes, further enhancing the performance of the photothermal material. However, excessively high carbonization temperatures can damage the fabric structure and the bonds between the organic ligands, metal, and fiber fabric, compromising the performance of the photothermal material.

[0083] If the temperature of the carbonization treatment is too low, the performance of the resulting photothermal material will still be poor even if the reaction time is extended.

[0084] Examples 8-10 and Comparative Examples 7-8

[0085] A highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, which differs from Example 1 in that the temperature and time of the carbonization treatment in step S3 are different, and the rest are substantially the same as Example 1 and will not be repeated here.

[0086] The photothermal materials prepared in Examples 8-10 and Comparative Examples 7-8 were assembled with expanded polystyrene and several polyester columns into an evaporation device for desalination of seawater with water. Evaporation tests of pure water and 10 wt% concentrated brine were carried out under one sunlight. The test results are shown in Table 3.

[0087] Table 3 Performance test of photothermal materials prepared in Examples 8-10 and Comparative Examples 7-8

[0088]

[0089]

[0090] As shown in Table 3, the evaporation performance of the resulting photothermal material initially improves but then decreases as the carbonization temperature increases. This is primarily because the carbonization reaction proceeds more thoroughly with increasing temperature, allowing the fabric to absorb sunlight more fully. Simultaneously, as the temperature changes, the bonding structure between the organic ligands, metal, and fiber fabric changes, further promoting the improvement of the photothermal material's performance. However, excessively high carbonization temperatures can damage the fabric structure and the bonds between the organic ligands, metal, and fiber fabric, compromising the performance of the photothermal material.

[0091] If the temperature of the carbonization treatment is too low, the performance of the resulting photothermal material will still be poor even if the reaction time is extended.

[0092] Examples 11-12

[0093] A highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, which differs from Example 1 in that the type of fiber fabric is different in step S2, and the rest is substantially the same as Example 1 and will not be repeated here.

[0094] The photothermal materials prepared in Examples 11-12 were assembled with expanded polystyrene and several polyester columns into an evaporation device for desalination of seawater with water. Evaporation tests of pure water and 10 wt% concentrated brine were carried out under one sunlight. The test results are shown in Table 4.

[0095] Table 4 Performance test of photothermal materials prepared in Examples 11-12

[0096]

[0097] It can be seen from Table 4 that when the fabric is changed to a different type, the evaporation rate and salt resistance of the obtained photothermal material are changed, but the overall performance is better.

[0098] Comparative Example 8

[0099] A high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine. Compared with Example 1, the difference is that the polyimide fiber fabric is directly carbonized, that is, a MOF nanolayer is not attached to the surface of the polyimide fiber fabric.

[0100] The photothermal materials prepared in Example 1 and Comparative Example 8 were tested for water absorption performance. The results are as follows: Figure 4 The specific test process is: inject water from the upper surface through the test instrument, and test the water content and water absorption speed of the lower surface after 1 minute. Figure 4 It can be seen from the test structure that the water content of the upper and lower surfaces of the polyimide fiber fabric of Comparative Example 8 is basically the same, and the water transmission speed is slow; while the moisture content of the lower surface of the photothermal material prepared in Example 1 is higher than that of the upper surface, indicating that the photothermal material prepared in Example 1 has strong water absorption and a fast water absorption rate, further indicating that the presence of the MOF nanolayer improves the water absorption performance of the fiber fabric.

[0101] The photothermal materials prepared in Example 1 and Comparative Example 8 were tested for their ultraviolet spectrum absorption performance. The results are as follows: Figure 5 As shown. Figure 5 It can be seen that the presence of the MOF nanolayer on the surface and in the pores of the polyimide fiber fabric basically does not affect the carbonization process of the fiber fabric, and the light absorption rate of the photothermal material prepared in Example 1 is as high as over 90%.

[0102] The photothermal materials prepared in Example 1 and Comparative Example 8 were placed in 10 wt% concentrated brine to test their evaporation performance. The results are as follows: Figure 6 As shown. Figure 6 It can be seen that the evaporation rate of the polyimide fiber fabric prepared in Comparative Example 8 is significantly lower than that of the photothermal material prepared in Example 1. This shows that under the conditions of roughly the same sunlight absorption in Example 1 and Comparative Example 8, the evaporation rate of Example 1 is actually higher when it absorbs more water, further demonstrating that the presence of the MOF nanolayer reduces the evaporation enthalpy of water.

[0103] Comparative Example 9

[0104] A highly efficient salt-resistant and evaporative photothermal material for highly concentrated brine. Compared with Example 1, the difference is that the carbonization treatment is not performed. The evaporation rate of the obtained photothermal material in 10wt% concentrated brine is 0.88kg·m -2 ·h -1 , which is significantly lower than the result of Example 1.

[0105] In summary, the present invention provides a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, as well as its preparation method and application. A dense MOF nanolayer is formed on the surface of a fabric through a hydrothermal reaction, and the fabric is then carbonized through a carbonization treatment. The special structure of MOF is utilized to reduce the evaporation enthalpy of water, while improving the utilization rate of solar energy, thereby improving the evaporation efficiency. Furthermore, the high water absorption characteristics of MOF are utilized to enhance the convection and diffusion of brine on the surface of the photothermal material, thereby avoiding the precipitation of salt ions on the surface of the material. This provides a promising strategy for improving the efficient evaporation of the current solar desalination system for high-concentration brine based on interfacial evaporation and inhibiting the formation of salt crystals.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, characterized in that: The steps include: S1. Preparation of MOF precursor solution; S2. placing the fiber fabric and the MOF precursor solution prepared in step S1 in a reactor together and performing a hydrothermal reaction to obtain a MOF@fiber fabric; the fiber fabric comprises one of a polyimide fiber fabric, a polytetrafluoroethylene fiber fabric or an aromatic polyamide fiber fabric; S3. The MOF@fiber fabric prepared in step S2 is carbonized to obtain a highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine.

2. The method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to claim 1, characterized in that: In step S3, the temperature of the carbonization treatment is 500-600° C., and the treatment time is 2-4 hours.

3. The method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to claim 1, characterized in that: In step S2, the temperature of the hydrothermal reaction is 150-200° C., and the reaction time is 10-20 h.

4. The method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to claim 1, characterized in that: The MOF precursor solution is prepared by adding an organic ligand and a metal salt to deionized water and ultrasonically mixing them; the molar ratio of the organic ligand to the metal salt is 1:(0.8-1.3), and the total concentration of the organic ligand and the metal salt in the MOF precursor solution is 7wt%-15wt%.

5. The method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to claim 1, characterized in that: In step S1, the MOF precursor solution includes one of a Fe-MOF precursor solution, a Cr-MOF precursor solution or a Cu-MOF precursor solution.

6. The method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to claim 3, characterized in that: In step S2, before the hydrothermal reaction, the fiber fabric needs to be immersed in alcohol and ultrasonically treated for 30 to 40 minutes, and then washed and dried.

7. A highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine, characterized in that: The photothermal material is prepared by the method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to any one of claims 1 to 6.

8. The high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to claim 7, characterized in that: The highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine has a capacity of 1 kW / m 2 The evaporation rate in pure water is as high as 1.63 kg·m -2 ·h -1 The evaporation efficiency in 10wt% concentrated brine is as high as 1.46kg·m -2 ·h -1 , and no salt crystals will appear after working outdoors for 7 days.

9. A use of a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine prepared by the method for preparing a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to any one of claims 1 to 6, or a high-efficiency salt-resistant and evaporation-resistant photothermal material for highly concentrated brine according to any one of claims 7 to 8, characterized in that: The highly efficient salt-resistant and evaporation-resistant photothermal material for highly concentrated brine is used for seawater desalination.

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