A core-shell structure solar evaporator and a preparation method and application thereof

Abstract

The application belongs to the technical field of photothermal interface evaporation, and particularly relates to a core-shell structure solar evaporator and a preparation method and application thereof. The core-shell structure solar evaporator comprises a hydrophilic inner core and a hydrophobic shell; the hydrophilic inner core and the hydrophobic shell both use Co-doped MoS2 as a photothermal conversion material. The unique three-dimensional macrostructure of the core-shell structure solar evaporator not only enlarges the evaporation area, but also enhances the light absorption capacity through multiple reflections of incident light. In addition, because the hydrophobic layer is the shell, the problem of surface salt deposition of the existing solar evaporator during seawater desalination can be solved, the core-shell structure solar evaporator has excellent salt resistance, and can stably perform seawater desalination for a long time.

Description

Technical Field

[0001] This invention belongs to the field of photothermal interface evaporation technology, specifically relating to a core-shell structure solar evaporator, its preparation method, and its application. Background Technology

[0002] With the rapid growth of the global population, the demand for water resources is also increasing, making water scarcity a global problem. Since most of the Earth's water is seawater, seawater desalination has become an important means of addressing water scarcity.

[0003] The most commonly used seawater desalination methods can be divided into three main categories: biological treatment, chemical treatment, and physical / mechanical treatment. However, existing technologies are insufficient to meet the enormous demand for low-cost freshwater. The main problems include: high temperature sensitivity of microorganisms, significant risks to secondary ecosystems, low yield, and high energy consumption. This not only increases the environmental burden and wastes resources but also severely limits the long-term effectiveness of these methods. Traditional absorbents are often ineffective in harsh environments. While photothermal absorbents can greatly improve seawater desalination performance, their practical application is still limited due to complex preparation processes and secondary pollution. Utilizing solar evaporators for water evaporation-condensation under new energy sources is a low-cost and efficient seawater desalination method. Although traditional solar evaporators have the advantage of high porosity, their single-component characteristics lead to significant functional limitations.

[0004] Therefore, developing a new core-shell structure solar evaporator is of great significance. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of existing technologies by providing a core-shell solar evaporator with tunable hydrophilicity and hydrophobicity, using Co-doped MoS2 as the photothermal conversion material. The photothermal performance of Co-doped MoS2 and the seawater desalination efficiency of the tunable hydrophilicity and hydrophobicity core-shell solar evaporator are investigated. Using this tunable hydrophilicity and hydrophobicity core-shell solar evaporator for seawater desalination or wastewater treatment not only avoids the environmental pollution caused by traditional methods but also alleviates the pressure of insufficient traditional energy resources.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a core-shell structure solar evaporator, the core-shell structure solar evaporator comprising a hydrophilic core and a hydrophobic shell; wherein the hydrophilic core and the hydrophobic shell are made of Co-doped MoS2 as photothermal conversion materials.

[0008] The hydrophilic core is prepared by solidification of a chitosan solution containing Co-doped MoS2; the hydrophobic shell is prepared by solidification of a mixed solution of poly(1,4-butanediol)bis(4-aminobenzoic acid) / carbodiimide modified 4,4'-diphenylmethane diisocyanate containing Co-doped MoS2.

[0009] A second aspect of this invention provides a method for preparing a core-shell structured solar evaporator, comprising the following steps:

[0010] S1. Chitosan and Co-doped MoS2 are mixed evenly in a solvent to obtain a mixed solution. The mixed solution is injected into a mold, freeze-dried and then solidified to obtain a hydrophilic core.

[0011] S2. Mix poly(1,4-butanediol)bis(4-aminobenzoic acid), carbodiimide-modified 4,4'-diphenylmethane diisocyanate, deionized water and Co-doped MoS2 evenly, and pour the mixture into a mold. Before the slurry is completely solidified, transfer the hydrophilic core to the hydrophobic outer shell mold. After the whole is completely solidified, the hydrophobic outer shell is obtained, and a complete core-shell structure solar evaporator is obtained.

[0012] The preparation method of the Co-doped MoS2 includes the following steps: (NH4)6Mo7O 24 ·4H2O, CH4N2S and Co(No3)2·6H2O were dissolved in deionized water to obtain a mixed solution. The solution was kept at 180~220 °C for 18 h. The reaction product was collected by centrifugation, washed and dried to obtain Co-doped MoS2.

[0013] Among them, (NH4)6Mo7O 24 The mass ratio of ·4H2O, CH4N2S and Co(No3)2·6H2O is 25:50:1.

[0014] In some embodiments of the present invention, the washing is a process involving distilled water and ethanol, and the specific washing methods include, but are not limited to, centrifugal washing and / or vacuum filtration washing.

[0015] In S1, the chitosan has a mass-volume concentration of 10-50 mg / mL in the mixed solution; the Co-doped MoS2 has a mass-volume concentration of 1-5 mg / mL in the mixed solution; and the solvent in the mixed solution is an aqueous acetic acid solution with a volume percentage concentration of 1-5%.

[0016] In some embodiments of the present invention, in S1, the mixing conditions are: stirring at 80 °C for 1-2 h.

[0017] In S1, the freeze-drying conditions are: temperature -40~-50 °C, time 72 h; the curing conditions are: immersing the freeze-dried sample in a 2 M NaOH solution for curing.

[0018] In S2, the mass ratio of poly(1,4-butanediol)bis(4-aminobenzoic acid), carbodiimide-modified 4,4'-diphenylmethane diisocyanate, deionized water, and Co-doped MoS2 is 70:30:10:3.

[0019] A third aspect of the present invention provides an application of a core-shell structure solar evaporator in seawater desalination or sewage / wastewater treatment.

[0020] In some embodiments of the present invention, by using 1kW m -2 The evaporation rates and salt precipitation processes of a fully hydrophilic solar evaporator, a fully hydrophobic solar evaporator, and a core-shell structure solar evaporator were tested under sunlight irradiation. The results showed that the core-shell structure solar evaporator possesses better evaporation performance at 1kW m³ / s. -2 Under high light intensity, the water evaporation rate of a 4cm×4cm core-shell solar evaporator reaches as high as 2.14 kg m³. -2 h -1 Furthermore, it maintains stable continuous evaporation in a 20wt% NaCl solution for extended periods, overcoming the poor salt tolerance problem of existing solar evaporators. This demonstrates that the core-shell structure solar evaporator provided by this invention has promising applications in seawater desalination or sewage and wastewater treatment.

[0021] Beneficial effects:

[0022] 1. The core-shell structure solar evaporator prepared by this invention scatters incident light multiple times, effectively reducing the energy loss of reflected light and achieving efficient thermal conversion of sunlight.

[0023] 2. The hydrophilic core layer of the core-shell structure solar evaporator prepared by this invention is conducive to rapid water absorption through capillary force, which establishes an effective channel for water transport and is beneficial to water transport.

[0024] 3. The shell of the core-shell structure solar evaporator prepared by the present invention effectively prevents salt deposition on the surface during the evaporation process based on the hydrophobic effect.

[0025] 4. The core-shell structure solar evaporator preferably prepared by this invention can desalinate seawater, purify rainwater, snowmelt, and lake water, and treat sewage and wastewater. By utilizing solar energy, it provides a sustainable green strategy for producing clean, potable freshwater and alleviating water scarcity.

[0026] 5. The core-shell structure solar evaporator prepared by this invention has excellent recyclability. After continuous testing in 20 wt% NaCl for 10 h, the evaporation rate can still remain stable.

[0027] 6. The core-shell structure solar evaporator prepared by this invention uses a hydrophobic layer as the outer shell, thus solving the problem of surface salt deposition during seawater desalination in existing solar evaporators. Simultaneously, because the salt is blocked within the outer shell, the reduced efficiency caused by salt obstructing water transport channels during evaporation is eliminated, achieving excellent cycle stability. Attached Figure Description

[0028] The present invention will be further described in detail below with reference to the accompanying drawings, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0029] Figure 1 This is a SEM image of Co-MoS2 prepared in an embodiment of the present invention.

[0030] Figure 2 The image shows the XRD pattern of Co-MoS2 prepared in this embodiment of the invention.

[0031] Figure 3 This is a schematic diagram of the structure and operation of the core-shell structure solar evaporator in an embodiment of the present invention.

[0032] Figure 4 These are test diagrams of the contact angle and wetting process of water for fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators in the embodiments of the present invention.

[0033] Figure 5 The figures show the water evaporation rate test results for fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators in the embodiments of the present invention.

[0034] Figure 6 This is a graph showing the evaporation rate over 8 hours for the fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators in the embodiments of the present invention.

[0035] Figure 7 This diagram shows the continuous 8-hour surface salt precipitation process of fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators in the embodiments of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0037] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0038] Example 1:

[0039] This embodiment provides a method for preparing a fully hydrophilic solar evaporator, including the following steps:

[0040] S1: Synthesis of Co-MoS2: 1 g of (NH4)6Mo7O 24 ·4H2O and 2 g CH4N2S were added to beakers containing 30 mL of deionized water and stirred for 30 min. Then, 0.04 g Co(No3)2·6H2O was added to obtain a mixed solution. The mixed solution was transferred to an autoclave reactor and kept at 220 °C for 18 h. The reaction solution was collected by centrifugation, washed several times with distilled water and ethanol, and dried at 60 °C for 12 h to obtain Co-doped MoS2, denoted as Co-MoS2.

[0041] The microstructure of Co-MoS2 was characterized using scanning electron microscopy and X-ray diffraction. Figure 1 The SEM image of Co-MoS2 is provided by [source missing]. Figure 1 It can be seen that the microstructure of the prepared Co-doped MoS2 material is a three-dimensional flower-like structure. Figure 2 The XRD pattern of Co-MoS2 is shown below. Figure 2 It can be seen that obvious diffraction peaks appear at 14.2°, 33.8°, 39.6°, 43.3°, 49.4° and 58.8° in the XRD pattern, which correspond to the (002), (100), (102), (106) and (110) crystal planes of MoS2, respectively, indicating that the 2H phase MoS2 was synthesized.

[0042] S2: Dissolve 0.7 g of chitosan completely in 20 mL of acetic acid solution (100 mL of deionized water plus 1 mL of acetic acid) to obtain a clear and transparent viscous liquid. Dissolve 0.06 g of the prepared Co-MoS2 in the above viscous liquid and stir at 80 °C for 1 h to obtain a mixed solution. Pour the mixed solution into a mold and allow it to cool to room temperature. Pre-freeze at -40~-50 °C for 12 h, and then freeze-dry at -40~-50 °C for 72 h. After demolding the sample, immerse it in NaOH solution (2 M) to solidify it, and then rinse it with a large amount of deionized water until neutral to obtain a fully hydrophilic solar evaporator.

[0043] Example 2:

[0044] This embodiment provides a method for preparing a fully hydrophobic solar evaporator, including the following steps:

[0045] S1: Synthesis of Co-MoS2: 1 g of (NH4)6Mo7O 24·4H2O and 2 g CH4N2S were added to beakers containing 30 mL of deionized water and stirred for 30 min. Then, 0.04 g Co(No3)2·6H2O was added to obtain a mixed solution. The mixed solution was transferred to an autoclave reactor and kept at 220 °C for 18 h. The reaction solution was collected by centrifugation, washed several times with distilled water and ethanol, and dried at 60 °C for 12 h to obtain Co-doped MoS2, denoted as Co-MoS2.

[0046] S2: 4,4'-diphenylmethane diisocyanate (Wannate) modified with poly(1,4-butanediol)bis(4-aminobenzoic acid) and carbodiimide. ® CDMDI-100L and deionized water are mixed in a weight ratio of 14:6:2, and the total system mass is controlled to be 22g. After stirring vigorously for 45s, 0.6g of Co-MoS2 (which has been ultrasonically homogenized in a small amount of deionized water before addition) is added, and then stirred vigorously for another 45s. The mixture is then quickly poured into a mold and allowed to solidify completely to obtain a fully hydrophobic solar evaporator.

[0047] Example 3:

[0048] This embodiment provides a core-shell structure solar evaporator. Figure 3 The diagram shows the structure and operation of a core-shell solar evaporator. Figure 3 In the diagram, 'a' represents the hydrophilic core, 'b' represents the hydrophobic outer shell, 'c' represents the assembled core-shell solar evaporator, and 'd' is a schematic diagram of the core-shell solar evaporator in operation. The specific fabrication method includes the following steps:

[0049] S1: Prepare a hydrophilic core according to the preparation method of the fully hydrophilic solar evaporator in Example 1;

[0050] S2: Prepare a hydrophobic shell using the preparation method of the fully hydrophobic solar evaporator in Example 2. After the corresponding slurry is quickly poured into the mold, transfer the hydrophilic core into the hydrophobic shell. Once the whole structure is completely solidified, the core-shell structure solar evaporator is obtained.

[0051] Testing and Analysis:

[0052] The performance of the fully hydrophilic solar evaporator, the fully hydrophobic solar evaporator, and the core-shell structure solar evaporator obtained in Examples 1-3 were tested, and the specific details are as follows:

[0053] 1. Wetting test

[0054] The fabricated fully hydrophilic solar evaporator, fully hydrophobic solar evaporator, and core-shell structure solar evaporator were placed horizontally on a contact angle measuring instrument, and 10 μL of water was taken for measurement. Figure 4The test diagrams show the contact angle and wetting process of water for fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators. Figure 4 It can be seen that in the fully hydrophilic solar evaporator, water droplets just contact the surface at 0 ms, and by 40 ms, they have completely spread out, forming an extremely thin water film with almost no visible droplet outline. This confirms the extremely strong hydrophilicity of the fully hydrophilic type. In contrast, in the fully hydrophobic solar evaporator, water droplets just contact the surface at 0 ms, and after 4 s, they remain almost perfectly spherical (or hemispherical) on the surface with a very large contact angle. This confirms the superhydrophobicity of the fully hydrophobic solar evaporator. In the core-shell structure solar evaporator, water droplets just contact the surface at 0 ms, and after 3 s, the droplet shape is between fully hydrophilic and fully hydrophobic. The droplets do not spread out completely like on a fully hydrophilic surface, nor do they remain perfectly spherical; they begin to widen at the edges, indirectly reflecting the characteristics of the core-shell structure solar evaporator: the outer shell is superhydrophobic, and the core is superhydrophilic.

[0055] 2. Evaporation performance test

[0056] All-hydrophilic, all-hydrophobic, and core-shell structure solar evaporators were placed in beakers filled with water. A solar simulator was used to irradiate the water, a power meter was used to measure the simulated solar intensity, and an electronic balance was used to monitor changes in water quality in real time. The test results are as follows: Figure 5 As shown. At 1kW m -2 Under sunlight, the evaporation rates of the fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators were 2.40 kg m³. -2 h -1 1.85 kg m -2 h -1 and 2.14 kg m -2 h -1 .

[0057] 3. Seawater desalination efficiency test

[0058] At 1kW m -2 Under sunlight irradiation, fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators were subjected to continuous evaporation experiments in a 20wt% NaCl solution for 8 hours. Figure 6 The graphs show the evaporation rates of fully hydrophilic, fully hydrophobic, and core-shell structure solar evaporators over a continuous 8-hour period. Figure 7 This diagram illustrates the continuous 8-hour surface salt deposition process for fully hydrophilic, fully hydrophobic, and core-shell structured solar evaporators. Figure 6 and 7 As shown, at 1kW m -2Under harsh conditions of sunlight exposure and a 20 wt% high-concentration NaCl solution, the salt resistance and long-term stability of the three types of evaporators showed significant differences. The fully hydrophilic evaporator experienced rapid and significant salt crystallization on its surface due to the continuous migration of salt to the evaporation interface with water, which accumulated over time, resulting in a stepwise decrease in its evaporation rate, confirming its susceptibility to clogging and instability. In stark contrast, the fully hydrophobic and core-shell structure evaporators effectively blocked the salt deposition path due to their hydrophobic surface properties. No salt crystal precipitation was observed on the surface throughout the entire test period, and the evaporation performance remained highly stable. The core-shell structure, in particular, achieved a high evaporation rate by relying on the synergistic mechanism of the hydrophobic outer shell resisting salt and the hydrophilic inner core conducting water, fully verifying its excellent salt clogging resistance and long-term seawater desalination application potential.

[0059] This invention provides a core-shell structure solar evaporator, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A core-shell structure solar evaporator, characterized in that, The core-shell structure solar evaporator includes a hydrophilic core and a hydrophobic shell; wherein the hydrophilic core and the hydrophobic shell use Co-doped MoS2 as photothermal conversion materials.

2. The core-shell structure solar evaporator according to claim 1, characterized in that, The hydrophilic core is obtained by solidification of a chitosan solution containing Co-doped MoS2; the hydrophobic shell is obtained by solidification of a mixed solution of poly(1,4-butanediol)bis(4-aminobenzoic acid) / carbodiimide modified 4,4'-diphenylmethane diisocyanate containing Co-doped MoS2.

3. The method for preparing the core-shell structure solar evaporator according to claim 1 or 2, characterized in that, Includes the following steps: S1. Chitosan and Co-doped MoS2 are mixed evenly in a solvent to obtain a mixed solution. The mixed solution is injected into a mold, freeze-dried and then solidified to obtain a hydrophilic core. S2. Mix poly(1,4-butanediol)bis(4-aminobenzoic acid), carbodiimide-modified 4,4'-diphenylmethane diisocyanate, deionized water and Co-doped MoS2 evenly, and pour the mixture into a mold. Before the slurry is completely solidified, transfer the hydrophilic core to the hydrophobic outer shell mold. After the whole is completely solidified, the hydrophobic outer shell is obtained, and a complete core-shell structure solar evaporator is obtained.

4. The preparation method according to claim 3, characterized in that, The preparation method of the Co-doped MoS2 includes the following steps: (NH4)6Mo7O 24 ·4H2O, CH4N2S and Co(No3)2·6H2O were dissolved in deionized water to obtain a mixed solution. The solution was kept at 180~220 °C for 18 h. The reaction product was collected by centrifugation, washed and dried to obtain Co-doped MoS2.

5. The preparation method according to claim 4, characterized in that, The (NH4)6Mo7O 24 The mass ratio of ·4H2O, CH4N2S and Co(No3)2·6H2O is 25:50:

1.

6. The preparation method according to claim 3, characterized in that, In S1, the chitosan has a mass-volume concentration of 10-50 mg / mL in the mixed solution; the Co-doped MoS2 has a mass-volume concentration of 1-5 mg / mL in the mixed solution; and the solvent in the mixed solution is an aqueous acetic acid solution with a volume percentage concentration of 1-5%.

7. The preparation method according to claim 3, characterized in that, In S1, the freeze-drying conditions are: temperature -40~-50 °C, time 72 h; the curing conditions are: immersing the freeze-dried sample in a 2 M NaOH solution for curing.

8. The preparation method according to claim 3, characterized in that, In S2, the mass ratio of poly(1,4-butanediol)bis(4-aminobenzoic acid), carbodiimide-modified 4,4'-diphenylmethane diisocyanate, deionized water, and Co-doped MoS2 is 70:30:10:

3.

9. The application of the core-shell structure solar evaporator according to claim 1 or 2 in seawater desalination or sewage / wastewater treatment.

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