Preparation method and application of solar driven interface evaporator based on polyimide

Abstract

The invention relates to a preparation method and application of a polyimide-based solar driven interface evaporator, and belongs to the technical field of high polymer materials. A polyimide nanofiber aerogel skeleton is prepared through an electrostatic spinning technology, and the three-dimensional porous structure of the polyimide nanofiber aerogel skeleton can promote backflow and absorption of salt and prevent the salt crystallization phenomenon. The two-dimensional photo-thermal material MXene is introduced into the skeleton, so that the hydrophilic performance of the composite aerogel is improved, and solar energy can be efficiently utilized and rapid water transmission can be realized by virtue of the high-broadband light absorption capability of the composite aerogel. Under one sunlight intensity, the photothermal conversion efficiency of the composite aerogel can reach 95.6%. The prepared solar-driven interface evaporator based on polyimide is applied to the field of seawater desalination, has good cycling stability, salt resistance and structural stability, and provides a new way for efficiently and stably obtaining fresh water driven by solar energy.

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 polyimide-based solar-driven interface evaporator. Background Art

[0002] The lack of clean fresh water is one of the prevalent global problems in recent years. With the rapid development of economy and industry and the improvement of people's quality of life, the deterioration of water quality and the uneven distribution of fresh water resources will pose a great threat to human survival. Seawater, as the most abundant water source on the earth, accounts for 97.5% of the water resources on the earth, so seawater desalination is the most direct and effective strategy to solve the existing problems. Traditional seawater desalination technology consumes a lot of fossil resources and inevitably causes air pollution. Therefore, the development and utilization of sustainable energy for seawater desalination has become an urgent desire. In the past decade, the research on interfacial solar steam generation has achieved remarkable results in improving water production efficiency and achieving salt resistance for long-term use, further increasing the possibility of this technology towards practical application. Polyimide nanofibers, as an emerging material, have a significant nanoscale structure with a large aspect ratio and specific surface area, excellent mechanical, thermal durability and chemical properties. PI nanofiber aerogel was selected as the substrate of the composite aerogel evaporator due to its high porosity, ultra-low thermal conductivity and excellent wettability, which are crucial to promote water transfer and reduce heat loss. In addition, the presence of a large number of porous structures makes it possible to become a skeleton structure supporting MXene, enhancing the light absorption and photothermal conversion of MXene, and ultimately enhancing the ability of seawater desalination. Therefore, it is meaningful to prepare a solar-driven interfacial evaporator based on polyimide nanofiber aerogel. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing a polyimide 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 polyimide solar-driven interface evaporator comprises the following steps:

[0005] Step 1: Obtain a single-layer MXene nanosheet by etching the Al layer in the MAX phase with hydrofluoric acid;

[0006] Step 2: electrospinning a polyamic acid nanofiber membrane, cutting it into pieces and dispersing it in water to evenly disperse it, and adding a certain amount of triethylamine to the dispersion for cross-linking;

[0007] Step 3: Ultrasonicate the MXene nanosheets obtained in step 1 into a uniform dispersion, mix with the polyamic acid dispersion obtained in step 2, and then freeze-dry. The obtained aerogel is thermally imidized under nitrogen to obtain a polyimide / MXene composite aerogel.

[0008] Beneficial effects:

[0009] The aerogel prepared by electrospinning in the present invention has light-to-heat conversion performance;

[0010] Based on the above technical solution, the present invention can also be improved as follows.

[0011] Preferably, the etching temperature in step 1 is 25-35°C.

[0012] Preferably, the etching time in step 1 is 24-36 hours.

[0013] Preferably, the electrospinning parameter in step 2 is a voltage of 26-32 kV.

[0014] Preferably, the receiving distance in step 2 is 15-17 cm.

[0015] Preferably, the feeding amount in step 2 is 0.5-1.0 mL / h.

[0016] Preferably, the air humidity in step 2 is controlled at 20-30% RH.

[0017] Preferably, the receiving roller in step 2 rotates at a speed of 10-20 rpm.

[0018] Preferably, the concentration of the polyamic acid dispersion in step 2 is 0.5wt%-1.5wt%.

[0019] Preferably, the mass ratio of triethylamine in step 2 is 50%-70% of the mass of the polyamic acid.

[0020] Preferably, the concentration of the Mxene dispersion in step three is 1wt%-10wt%.

[0021] The purpose of the present invention is to provide an application of a polyimide-based solar-driven interface evaporator, wherein the polyimide-based solar-driven interface evaporator is prepared by the preparation method of the polyimide-based solar-driven interface evaporator.

[0022] Beneficial effects: The prepared polyimide-based solar-driven interfacial 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

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a SEM picture of the polyimide solar-driven interface evaporator obtained in Example 1 of the present invention;

[0025] Figure 2 This is an infrared imaging diagram of the temperature change of the polyimide-based solar-driven interface evaporator prepared in Example 1 in a dry state under a sunlight irradiation intensity;

[0026] Figure 3 The evaporation rate and photothermal conversion efficiency of the polyimide solar-driven interface evaporator at one sunlight intensity of Example 1;

[0027] Figure 4 The comparison of ion concentration in water before and after desalination by the polyimide solar-driven interface evaporator in Example 1; DETAILED DESCRIPTION

[0028] 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.

[0029] Example 1

[0030] A method for preparing a polyimide solar-driven interface evaporator comprises the following steps:

[0031] Step 1: Obtain a single-layer MXene nanosheet by etching the Al layer in the MAX phase with hydrofluoric acid;

[0032] Step 2: electrospinning a polyamic acid nanofiber membrane, cutting it into pieces and dispersing it in water to evenly disperse it, and adding a certain amount of triethylamine to the dispersion for cross-linking;

[0033] Step 3: Ultrasonicate the MXene nanosheets obtained in step 1 into a uniform dispersion, mix with the polyamic acid dispersion obtained in step 2, and then freeze-dry. The obtained aerogel is thermally imidized under nitrogen to obtain a polyimide / MXene composite aerogel.

[0034] The polyimide solar-driven interface evaporator prepared in Example 1 was observed by electron microscope. Figure 1As shown in the figure, the prepared polyimide-based solar-driven interfacial evaporator has a very obvious pore structure, which is mainly attributed to the following two aspects: first, the intermolecular interaction between the polyimide macromolecular skeletons can counteract the capillary force of ice crystal growth during freezing; second, the introduction of MXene nanosheets with large specific surface area can effectively reduce the shrinkage of aerogel during thermal imidization, making the aerogel have a stable three-dimensional porous structure, which makes the water transport distance shorter and the resistance smaller.

[0035] The polyimide-based solar-driven interface evaporator prepared in Example 1 responded very quickly to the temperature change under the radiation of one sun in the air, and increased from 20.1°C to 109.8°C within 35 minutes. Its excellent photothermal effect is mainly attributed to the excellent light absorption capacity and good photothermal conversion efficiency of MXene.

[0036] The photothermal conversion capability of the polyimide 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 3 As shown in Figure 2, the water evaporation rate of the polyimide solar-driven interfacial evaporator in air under one sun radiation is 1.438 kg m -2 h -1 , which is 5.45 times the evaporation rate of seawater, and its photothermal conversion efficiency is 94.3%.

[0037] The desalination capacity of the polyimide solar-driven interface evaporator prepared in Example 1 was investigated. In order to detect 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, from 8582.357, 328.409, 375.284, and 1477.339 mg / L to 219.165, 8.492, 7.381, and 27.964 mg / L, respectively, which are far below the drinking water standards set by the World Health Organization (WHO).

[0038] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a polyimide solar-driven interface evaporator, characterized in that: The following steps are involved: Step 1: Obtain a single-layer MXene nanosheet by etching the Al layer in the MAX phase with hydrofluoric acid; Step 2: electrospinning a polyamic acid nanofiber membrane, cutting it into pieces and dispersing it in water to evenly disperse it, and adding a certain amount of triethylamine to the dispersion for cross-linking; Step 3: Ultrasonicate the MXene nanosheets obtained in step 1 into a uniform dispersion, mix with the polyamic acid dispersion obtained in step 2, and then freeze-dry. The obtained aerogel is thermally imidized under nitrogen to obtain a polyimide / MXene composite aerogel.

2. The method for preparing a polyimide solar-driven interface evaporator according to claim 1, characterized in that: The hydrofluoric acid in step 1 is synthesized from lithium fluoride and hydrochloric acid, the etching temperature is 25-35° C., and the etching time is 24-36 hours.

3. The method for preparing a polyimide 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 volume of 0.5-1.0 mL / h, air humidity controlled at 20-30% RH, and the receiving roller collecting the nanofiber membrane at a rotation speed of 10-20 rpm.

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

5. The method for preparing a polyimide 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 polyimide solar-driven interface evaporator according to claim 1, characterized in that: The concentration of the Mxene dispersion in step three is 1wt%-10wt%.

7. The method for preparing a polyimide solar-driven interface evaporator according to claim 1, characterized in that: The volume ratio of the polyamic acid dispersion and the MXene dispersion in the composite aerogel in step three is 3:2.

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