Preparation method and application of a sandwich-type solar-driven interface evaporator

Abstract

The present invention relates to a preparation method and application of a sandwich-type solar-driven interface evaporator, and belongs to the technical field of polymer materials. The present invention constructs a sandwich-type wetting gradient aerogel with hydrophilic-hydrophobic-hydrophilic properties, and sprays molybdenum disulfide, a two-dimensional material with high photothermal conversion effect, on the upper surface of the porous electrospun polyimide aerogel, and performs a hydrophilic treatment on the bottom surface of the super-hydrophobic three-dimensional polyimide aerogel, which is beneficial to the supply and transmission of water. Thanks to this reasonable design, the evaporator has excellent photothermal conversion efficiency, which can reach 98.8% under one sunlight intensity. The prepared sandwich-type solar-driven interface evaporator is applied to the field of seawater desalination. Its good cycle stability, salt resistance and structural stability provide a new way for solar-driven efficient and stable acquisition of fresh water.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a preparation method and application of a sandwich-type solar-driven interface evaporator. Background Art

[0002] With the global energy crisis and worsening water pollution, freshwater scarcity has become a global issue that cannot be ignored. As we all know, oceans account for over 97% of Earth's water resources. Therefore, desalination is an effective strategy to address this existing problem. Solar-driven evaporation technology offers a new solution to the desalination problem. Compared to traditional desalination technologies that rely heavily on fossil fuels, solar energy, a widely available, sustainable, and green energy source, has attracted widespread research attention. Currently, solar-driven interfacial evaporation technology is attracting significant attention. This involves placing a photothermal material at the gas-liquid interface for heating and evaporation. This method reduces heat loss into the water. Methods for achieving interfacial evaporation include exploiting the hydrophobicity and porous or hollow structures of the evaporator. However, over time, salt accumulation inevitably occurs due to a decrease in capillary forces, resulting in a decrease in evaporation efficiency. Therefore, the development of aerogel materials with diverse wettability structures, excellent photothermal conversion performance, and salt tolerance has become a research priority. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing a sandwich-type solar-driven interface evaporator.

[0004] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing a sandwich-type solar-driven interface evaporator, comprising the following steps:

[0005] Step 1: Preparation of MoS2 nanoflowers by hydrothermal method;

[0006] Step 2: preparing a polyamic acid nanofiber membrane by electrospinning, cutting it into pieces and dispersing it in water for homogeneous dispersion, adding a certain amount of triethylamine to the dispersion for cross-linking, freeze-drying and then thermal imidization to obtain a polyimide aerogel;

[0007] Step 3: The molybdenum disulfide nanoflowers obtained in step 1 are mixed with polyvinyl pyrrolidone to form a dispersion, a polyvinyl alcohol solution is prepared, the molybdenum disulfide / polyvinyl pyrrolidone dispersion is sprayed on the top surface of the polyimide aerogel prepared in step 2, and the polyvinyl alcohol solution is sprayed on the bottom surface of the polyimide aerogel prepared in step 2. After drying, a solar-driven interface evaporator with a sandwich-type wetting structure is obtained. Beneficial effects

[0008] The aerogel prepared by electrospinning in the present invention has light-to-heat conversion performance and salt resistance;

[0009] On the basis of the above technical solution, the present invention can also be improved as follows.

[0010] Preferably, the hydrothermal temperature in step 1 is 220-280°C.

[0011] Preferably, the hydrothermal time in step 1 is 6-10 hours.

[0012] Preferably, the electrospinning parameter in step 2 is a voltage of 26-32 kV.

[0013] Preferably, the receiving distance in step 2 is 15-17 cm.

[0014] Preferably, the feeding volume in step 2 is 0.5-1.0 mL / h.

[0015] Preferably, the air humidity in step 2 is controlled at 20-30% RH.

[0016] Preferably, the receiving roller in step 2 rotates at a speed of 10-20 rpm.

[0017] Preferably, the concentration of the polyamic acid dispersion in step 2 is 0.5 wt %-1.5 wt %.

[0018] Preferably, the mass ratio of triethylamine in step 2 is 50%-70% of the mass of the polyamic acid.

[0019] Preferably, the concentration of the molybdenum disulfide / polyvinyl pyrrolidone dispersion in step three is 5%-20%.

[0020] The purpose of the present invention is to provide an application of a sandwich-type solar-driven interface evaporator, wherein the sandwich-type solar-driven interface evaporator is prepared by the preparation method of the sandwich-type solar-driven interface evaporator.

[0021] Beneficial effects: The prepared sandwich-type solar-driven interface evaporator is applied to seawater desalination, and photothermal conversion is performed under light conditions, and clean fresh water resources are obtained based on this characteristic. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1This is a SEM image of the sandwich-type solar-driven interface evaporator obtained in Example 1 of the present invention;

[0024] Figure 2 The evaporation rate and photothermal conversion efficiency of the sandwich-type solar-driven interface evaporator of Example 1 at one sunlight intensity;

[0025] Figure 3 The evaporation rate and photothermal conversion efficiency of the sandwich-type solar-driven interface evaporator of Example 1 in water environments with different salinity contents under one sunlight intensity;

[0026] Figure 4 Comparison of ion concentrations in water before and after desalination by the sandwich-type solar-driven interface evaporator of Example 1; DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0028] Example 1, a method for preparing a sandwich-type solar-driven interface evaporator, comprising the following steps:

[0029] Step 1: Preparation of MoS2 nanoflowers by hydrothermal method;

[0030] Step 2: preparing a polyamic acid nanofiber membrane by electrospinning, cutting it into pieces and dispersing it in water for homogeneous dispersion, adding a certain amount of triethylamine to the dispersion for cross-linking, freeze-drying and then thermal imidization to obtain a polyimide aerogel;

[0031] Step 3: The molybdenum disulfide nanoflowers obtained in step 1 are mixed with polyvinyl pyrrolidone to form a dispersion, a polyvinyl alcohol solution is prepared, the molybdenum disulfide / polyvinyl pyrrolidone dispersion is sprayed on the top surface of the polyimide aerogel prepared in step 2, and the polyvinyl alcohol solution is sprayed on the bottom surface of the polyimide aerogel prepared in step 2. After drying, a solar-driven interface evaporator with a sandwich-type wetting structure is obtained.

[0032] The sandwich-type solar-driven interface evaporator prepared in Example 1 was observed under an electron microscope. Figure 1 As shown, the molybdenum disulfide / polyvinyl pyrrolidone dispersion sprayed on the top surface of the polyimide aerogel presents a uniform stacked coating. Polyvinyl pyrrolidone as a binder can make the coating not easy to fall off at high temperatures.

[0033] The photothermal conversion capability of the sandwich-type solar-driven interface evaporator prepared in Example 1 was investigated. First, a photothermal evaporation test was conducted on it and seawater. The test results are as follows: Figure 3As shown in Figure 2, the water evaporation rate of the sandwich-type solar-driven interface evaporator in air under one sun radiation is 1.46 kg m -2 h -1 , and its photothermal conversion efficiency is 93.6%.

[0034] The salt tolerance of the sandwich-type solar-driven interface evaporator prepared in Example 1 was tested, and the test results are as follows: Figure 3 As shown in Figure 2, the water evaporation rates of the sandwich-type solar-driven interface evaporator at salt concentrations of 5, 10, 15, and 20% are 1.541, 1.537, 1.488, and 1.481 kg m, respectively. -2 h -1 The photothermal conversion efficiencies are 96.8, 96.6, 93.2, and 92.8%, respectively. With the gradual increase in salt content, the evaporation rate decreases slightly, but still maintains a good evaporator effect.

[0035] The desalination capacity of the polyimide solar-driven interface evaporator prepared in Example 1 was investigated. In order to test its desalination performance, the evaporated water vapor was collected. The collection device was as follows: Figure 4 As shown in the figure. Under the radiation of one sun, obvious water vapor accumulation appeared on the glass cover after 20 minutes. The concentration changes of the four main ions before and after seawater desalination were detected by ICP. Compared with the simulated seawater before desalination, Na, K + , Ca 2+ Mg 2+ The four ions were significantly reduced by several orders of magnitude in the desalinated seawater, which is far below the drinking water standards set by the World Health Organization (WHO).

[0036] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a sandwich-type solar-driven interface evaporator, characterized in that: The following steps are involved: Step 1: Preparation of MoS2 nanoflowers by hydrothermal method; Step 2: preparing a polyamic acid nanofiber membrane by electrospinning, cutting it into pieces and dispersing it in water for homogeneous dispersion, adding a certain amount of triethylamine to the dispersion for cross-linking, freeze-drying and then thermal imidization to obtain a polyimide aerogel; Step 3: The molybdenum disulfide nanoflowers obtained in step 1 are mixed with polyvinyl pyrrolidone to form a dispersion, a polyvinyl alcohol solution is prepared, the molybdenum disulfide / polyvinyl pyrrolidone dispersion is sprayed on the top surface of the polyimide aerogel prepared in step 2, and the polyvinyl alcohol solution is sprayed on the bottom surface of the polyimide aerogel prepared in step 2. After drying, a sandwich-type solar-driven interface evaporator is obtained.

2. The method for preparing a sandwich-type solar-driven interface evaporator according to claim 1, characterized in that: The raw materials used in the step 1 are ammonium molybdate and thiourea, the hydrothermal temperature is 220-280° C., and the hydrothermal time is 6-10 h.

3. The method for preparing a sandwich-type solar-driven interface evaporator according to claim 1, characterized in that: The electrospinning parameters in step 2 are as follows: voltage of 26-32 kV, receiving distance of 15-17 cm, liquid feeding rate of 0.5-1.0 mL / h, air humidity controlled at 20-30% RH, and receiving roller collecting nanofiber membrane at a speed of 10-20 rpm.

4. The method for preparing a sandwich-type solar-driven interface evaporator according to claim 1, characterized in that: The concentration of the polyamic acid dispersion in step 2 is 0.5 wt % to 1.5 wt %.

5. The method for preparing a sandwich-type solar-driven interface evaporator according to claim 1, characterized in that: The mass ratio of triethylamine in the step 2 is 50%-70% of the mass of the polyamic acid.

6. The method for preparing a sandwich-type solar-driven interface evaporator according to claim 1, characterized in that: The concentration of the molybdenum disulfide / polyvinyl pyrrolidone dispersion in step 3 is 5%-20%.

7. The method for preparing a sandwich-type solar-driven interface evaporator according to claim 1, characterized in that: The concentration of the polyvinyl alcohol solution in step three is 2-4 wt %.

8. The method for preparing a sandwich-type solar-driven interface evaporator according to claim 1, characterized in that: The spraying distance in step 3 is 10-20 cm, and the spraying intensity is 15-25 psi.

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