A three-dimensional seawater desalination evaporator with a sunflower bionic structure and its preparation technology

Abstract

The present invention belongs to the field of photothermal conversion and solar desalination, and particularly relates to a three-dimensional seawater desalination evaporator with a sunflower bionic structure and its preparation technology. After cleaning and drying the polyester fiber, it is soaked in ferric chloride hexahydrate solution and pyrrole solution respectively, and finally washed with deionized water and dried to obtain polypyrrole-modified fiber. A composite hydrogel with full-angle, high-precision and fast-response characteristics, and the response process does not require human intervention is utilized, and a two-dimensional water-absorbing material and polypyrrole-modified fiber with high photothermal conversion efficiency are introduced into the center of the hydrogel. The polypyrrole-modified fiber has good photothermal performance and stability, and has the advantages of being cheap, large-area preparable, sewable and washable. It forms a new type of fiber composite material with the two-dimensional water-absorbing material, and integrating it into the center of the composite hydrogel can obtain a three-dimensional seawater desalination evaporator with a sunflower bionic structure. In addition, the evaporator has characteristics such as shape memory, omnidirectional light tracking, self-healing and photothermal response, and has great application potential in the fields of seawater desalination, energy conservation and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the fields of photothermal conversion and solar desalination, and particularly relates to a three-dimensional seawater desalination evaporator with a sunflower bionic structure and a preparation technology thereof. Background Art

[0002] On the earth's surface, 70% of the area is covered by water. Among them, fresh water resources only account for 2.5% of the total water. And in this extremely small amount of fresh water resources, about 70% of the fresh water is frozen in the ice sheets of Antarctica and the Arctic. Coupled with soil moisture and deep groundwater, 87% of the fresh water resources are difficult to be directly utilized by humans. On the earth, the fresh water resources that humans can truly utilize are part of the rivers, lakes and groundwater, accounting for about 0.26% of the total water volume of the earth. It is estimated that by 2025, 3 billion people in the world will face water shortage, and the fresh water supply in more than 40 countries and regions will be seriously insufficient. At present, seawater desalination technology is one of the main ways to solve the shortage of water resources. Seawater desalination technology can also be extended to applications such as brackish water desalination, wastewater resource utilization, water ecological restoration, water environment governance and drinking water safety guarantee, etc., and has good social, economic and ecological benefits.

[0003] The most commonly used seawater desalination technologies are: multi-effect flash evaporation, multi-effect seawater desalination, vapor compression, reverse osmosis membrane and electrodialysis. However, traditional seawater desalination technologies need to rely on burning fossil fuels to drive. Among all renewable energy sources, solar energy is the most promising choice to meet the future energy needs of mankind. Solar-driven interfacial photothermal evaporation has attracted increasing attention in the past few years because it can desalinate seawater by generating steam at a temperature far below the boiling point of water. However, most current photothermal materials mainly focus on improving energy efficiency and multifunctional applications, lacking the characteristics of scalability, low cost, flexibility and cleanability, which severely limits the application of materials from the laboratory to industrialization. At the same time, most current photothermal evaporations focus on a fixed two-dimensional interfacial vaporization platform, with problems such as low space utilization efficiency and low solar light utilization rate. Therefore, in a restricted system, constructing a two-dimensional light absorber unit into a three-dimensional framework is considered to be one of the most direct and effective methods to improve the purified water collection capacity. In addition, traditional evaporators mainly float on the surface of seawater and can only exhibit the maximum evaporation capacity under vertically incident sunlight. The performance of solar-driven interfacial water evaporation is also limited by the reduction of photothermal evaporation caused by oblique irradiation of incident light. Therefore, automatically tracking the incident light from three-dimensional space to keep the evaporator always under vertically incident sunlight can make the evaporator always exhibit the maximum evaporation efficiency. Summary of the Invention

[0004] Objectives of the present invention: The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention aims to design a device for three-dimensional interfacial vaporization. Another objective of the present invention is to design a seawater desalination evaporator with a sunflower bionic structure that integrates artificial phototropism, solar interfacial evaporation, thermal responsiveness, and self-repairability.

[0005] Technical solution of the present invention: To solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A three-dimensional seawater desalination evaporator with a sunflower bionic structure and its preparation technology. First, prepare a photothermal evaporator by attaching polypyrrole with photothermal responsiveness to polyester fiber to obtain a cheap, large-area preparable, highly stable, washable, and sewable photothermal evaporator. Then, use a hydrogel (CNT@PDA / PNIPAM) composite of polydopamine-modified carbon nanotubes and poly(N-isopropylacrylamide) as a sunlight tracker. Finally, a two-dimensional water-absorbing material is composited in the center of the hydrogel, and a polypyrrole photothermal evaporator is composited at the upper end to obtain a three-dimensional seawater desalination evaporator with a sunflower bionic structure. The specific steps are as follows:

[0007] (1) Ultrasonically clean the polyester fiber with an organic solvent first, then repeatedly wash it with deionized water, and finally place it in an oven for drying.

[0008] (2) Immerse the dried polyester fiber in a ferric chloride hexahydrate (FeCl3·6H2O) solution and then take it out to obtain polyester fiber modified with iron ions.

[0009] (3) Immerse the polyester fiber modified with iron ions in a pyrrole solution and then take it out, and wash it three times with deionized water to remove the unstable Fe 3+ / Fe 2+ polymer. After washing and drying, a polypyrrole photothermal evaporator (PMC) with good water absorbency is obtained.

[0010] (4) Use a hydrogel with full-angle phototropism as a sunlight tracker, introduce a two-dimensional water-absorbing material and a polypyrrole photothermal evaporator into the center of the hydrogel to obtain the target product.

[0011] Furthermore, in step (1), the organic solvents used are acetone and ethanol, and their purpose is to remove oil stains and dirt.

[0012] Furthermore, in step (2), the concentration of the FeCl3·6H2O solution is 1-4 mol / L, and the soaking time is 1 h.

[0013] Preferably, the optimal concentration of the FeCl3·6H2O solution is 2 mol / L.

[0014] Further, in step (3), the concentration of the pyrrole solution is 0.2 mol / L, and the soaking time is 1 h.

[0015] Further, in step (3), the drying temperature is 60 °C, and the drying time is 2 h.

[0016] Further, in step (4), the hydrogel used is CNT@PDA / PNIPAM, with specific dimensions of a diameter of 4.5 mm and a height of 5 cm.

[0017] Further, in step (4), the PMC used is made into a cone with a diameter of 2 cm, a height of 1 cm, and a vertex angle of 90°.

[0018] Further, in step (4), more than 5 cm of two-dimensional water-absorbing material is reserved at the bottom of the hydrogel.

[0019] The present invention provides a three-dimensional seawater desalination evaporator with a sunflower bionic structure and its preparation technology. First, a polypyrrole-modified fiber with high-efficiency photothermal conversion characteristics, low cost, large-area preparation, high stability, sewability, and washability is prepared as a photothermal evaporator; a hydrogel with all-angle phototropism is used as a sunlight tracker, and a two-dimensional material with high-efficiency water absorption is introduced into the center of the hydrogel, and the photothermal evaporator is compounded at the upper end. Finally, a three-dimensional seawater desalination evaporator with a sunflower bionic structure is obtained, and relevant tests and studies are carried out on it.

[0020] Beneficial effects:

[0021] (1) The present invention provides a three-dimensional seawater desalination evaporator with a sunflower bionic structure and its preparation technology.

[0022] (2) Excellent performance: The light-responsive hydrogel can automatically align with the incident light, enabling the evaporator to maintain a high evaporation rate and effectively improving the utilization rate of sunlight. The polypyrrole-modified polyester fiber has high stability and sewability and can be made into a three-dimensional evaporation interface, effectively improving the space utilization rate.

[0023] (3) Compared with other evaporators, this evaporator has the following advantages:

[0024] ① The evaporator is washable, sewable, and has high stability;

[0025] ② The three-dimensional interface evaporator greatly improves the space utilization rate;

[0026] ③ It can track light in all directions and automatically align, always maintaining a high utilization rate of sunlight;

[0027] ④ It has a low cost, strong practicability, and good industrial application prospects. Description of the drawings

[0028] Figure 1 Ultraviolet-visible-near-infrared absorption spectra of Examples 1, 2, and 3.

[0029] Figure 2 Schematic diagram of the test device for the products of Examples 4 and 5.

[0030] Figure 3 is the evaporation rate test chart of the products of Examples 4 and 5.

[0031] Figure 4 is the seawater desalination efficiency test chart of the products of Examples 4 and 5

[0032] Figure 5 is the evaporation rate and seawater desalination efficiency test chart of the product of Example 4 under different sunlight intensities. Detailed implementation manners

[0033] The detailed implementation manners of preparing the materials in the present invention are as follows:

[0034] Example 1

[0035] The polyester fiber was ultrasonically cleaned with acetone and ethanol to remove oil stains and dirt, then repeatedly washed with deionized water and placed in an oven for drying. The cleaned polyester fiber was immersed in a 2 mol / L FeCl3·6H2O solution for 1 h to obtain iron ion-modified polyester fiber; the iron ion-modified polyester fiber was immersed in a 0.2 mol / L pyrrole solution for 1 h, then taken out and washed three times with deionized water to remove the unstable Fe 3+ / Fe 2+ polymer. After cleaning, it was placed in an oven at 60 °C for drying for 2 h, and finally a polypyrrole solar thermal evaporator (PMC-2M) with good water absorption and photothermal conversion characteristics was obtained.

[0036] Example 2

[0037] The concentration of the FeCl3·6H2O solution was 1 mol / L, and other conditions were the same as those in Example 1, to obtain PMC-1M.

[0038] Example 3

[0039] The concentration of the FeCl3·6H2O solution was 4 mol / L, and other conditions were the same as those in Example 1, to obtain PMC-4M.

[0040] Figure 1It is the ultraviolet-visible-near-infrared absorption spectrogram of the products of Example 1, Example 2 and Example 3. The specific steps are as follows: make the polyester fiber modified by polypyrrole into a sample with a size of 5 cm × 5 cm, and the test range is 300 - 2500 nm. It can be seen that the light absorption rates of PMC-1M, PMC-2M, and PMC-4M are 97.81%, 98.68%, and 98.79% respectively, all showing high absorption performance.

[0041] Example 4

[0042] Make PMC-2M into a cone with a diameter of 2 cm, a height of 1 cm, and a vertex angle of 90°. Compound a two-dimensional water-absorbing material at the vertex of the cone. Finally, pass the two-dimensional water-absorbing material through the center of the CNT@PDA / PNIPAM hydrogel, and leave more than 5 cm of the two-dimensional water-absorbing material at the bottom of the hydrogel to facilitate efficient water absorption and transmission to the polyester fiber interface for water evaporation, and finally obtain a three-dimensional bionic sunflower seawater desalination evaporator, namely the CNT@PDA / PNIPAM-PMC evaporator. Fix the bottom of the evaporator on a self-made polystyrene foam, make the foam float on the water surface, adjust the light intensity and light angle of the solar simulator AM1.5G, and conduct desalination tests.

[0043] Example 5

[0044] Pass the two-dimensional water-absorbing material through the center of the hydrogel (PNIPAM) without full-angle phototropism, and compound PMC-2M at the upper end. Other conditions are the same as those in Example 4, and finally obtain the PNIPAM-PMC evaporator.

[0045] Figure 2 It is a schematic diagram of the test device for the products of Example 4 and Example 5.

[0046] Figure 3(a) and Figure 3(b) are respectively the evaporation rate test diagrams of the products of Example 4 and Example 5 at different solar illumination angles. The specific steps are as follows: float the CNT@PDA / PNIPAM-PMC evaporator and the PNIPAM-PMC evaporator in a beaker filled with water, place the beaker on an analytical balance, adjust the illumination angles of the solar simulator AM1.5G to 0°, 45°, 90°, 135°, and 180° respectively, and conduct desalination tests; connect the balance to a computer terminal to monitor the weight loss data of the seawater in real time. It can be seen that when the illumination angle is 90°, the evaporation rates of the CNT@PDA / PNIPAM-PMC evaporator and the PNIPAM-PMC evaporator are basically the same, which are 1.52 kg·m -2 ·h -1 and 1.40 kg·m -2 ·h -1, at this time, the utilization rate of solar energy is the highest, and its water evaporation rate is the fastest. The evaporation rates of the CNT@PDA / PNIPAM-PMC evaporator tend to be consistent at oblique incident light angles (0°, 45°, 135°, and 180°) and vertical incident light angle (90°), and its evaporation rates at oblique incident light angles are higher than those of the PNIPAM-PMC evaporator.

[0047] Figures 4(a) and 4(b) are the test diagrams of the seawater desalination efficiency of the products in Example 4 and Example 5 at different solar light angles respectively. The specific steps are as follows: Float the CNT@PDA / PNIPAM-PMC evaporator and the PNIPAM-PMC evaporator in a beaker filled with water, place the beaker on an analytical balance, adjust the light angles of the solar simulator AM1.5G to 0°, 45°, 90°, 135°, and 180° respectively, and conduct desalination tests; Connect the balance to a computer terminal to monitor the weight loss data of the seawater in real time. It can be calculated that when the light angle is 45°, the seawater desalination efficiency of the PNIPAM-PMC evaporator is only 27.15%, while the seawater desalination efficiency of the CNT@PDA / PNIPAM-PMC evaporator is 87.79%, and the seawater desalination efficiency of the bionic sunflower evaporator has increased by 3 times.

[0048] Figures 5(a) and 5(b) are the test result diagrams of the evaporation rate and seawater desalination efficiency of the product in Example 4 at different solar light intensities. The specific steps are as follows: Float the CNT@PDA / PNIPAM-PMC evaporator in a beaker filled with water, place the beaker on an analytical balance, adjust the light angle of the solar simulator AM1.5G to 45°, and the intensities are successively 100 mW / cm 2 , 200 mW / cm 2 , 400 mW / cm 2 , 600 mW / cm 2 , and conduct desalination tests; Connect the balance to a computer terminal to monitor the weight loss data of the seawater in real time. It can be calculated that its seawater desalination efficiencies are 16.85%, 53.42%, 87.79%, and 102.09% respectively.

Claims

1. A preparation method of a three-dimensional seawater desalination evaporator with a sunflower bionic structure, characterized in that, It includes the following steps: (1) Prepare polypyrrole-modified fiber PMC-2M. Ultrasonically clean the polyester fiber with acetone and ethanol to remove oil stains and dirt, then repeatedly wash it with deionized water and place it in an oven for drying. Immerse the cleaned polyester fiber in a ferric chloride hexahydrate FeCl3·6H2O solution for 1 h to obtain iron ion-modified polyester fiber. Immerse the iron ion-modified polyester fiber in a pyrrole solution with a concentration of 0.2 mol / L, take it out after 1 h, and wash it three times with deionized water to remove unstable Fe 3+ / Fe 2+ polymers. After cleaning, place it in an oven at 60 °C for drying for 2 h to obtain PMC-2M with good water absorption; (2) Use a phototropic hydrogel as a sunlight tracker, and make PMC-2M into a conical structure with specific dimensions of 2 cm in diameter, 1 cm in height, and a cone angle of 90°. Composite a two-dimensional water-absorbing material at its vertex. Finally, pass the two-dimensional water-absorbing material through the center of the hydrogel to finally obtain a three-dimensional seawater desalination evaporator with a sunflower bionic structure. Among them, the hydrogel material is a hydrogel CNT@PDA / PNIPAM composite of polydopamine-modified carbon nanotubes and poly(N-isopropylacrylamide).

2. The preparation method of a three-dimensional seawater desalination evaporator with a sunflower bionic structure according to claim 1, characterized in that, In step (1), the concentration of the FeCl3·6H2O solution used is 2 mol / L.

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