A rattan-inspired solar-driven evaporator and its preparation method

Abstract

The present invention discloses a rattan biomimetic solar-driven evaporator and a preparation method thereof, and relates to the technical field of seawater desalination. The preparation method of the rattan biomimetic solar-driven evaporator of the present invention comprises the following steps: (1) dissolving thermoplastic polyurethane, black photothermal conversion material, and polyvinyl pyrrolidone in 1,4-dioxane to obtain a mixed solution; (2) introducing gas into the mixed solution to obtain a solution containing gas; (3) directionally freezing the solution containing gas; (4) freeze-drying the directionally frozen product to obtain a foam with vertical channels; (5) hydrophilically modifying the foam to obtain the rattan biomimetic solar-driven evaporator. The present invention designs the structure of the rattan biomimetic solar-driven evaporator so that the evaporator has a large evaporation area, can avoid salt accumulation, and can be used for a long time.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater desalination, and in particular to a rattan bionic solar-driven evaporator and a preparation method thereof. Background Art

[0002] With population growth and environmental changes, freshwater resources are in short supply. Although distillation desalination and reverse osmosis desalination technologies are well-developed, their high investment and energy consumption make them unsuitable for use in developing countries with limited infrastructure or remote rural areas. Recently, solar-driven desalination has been recognized as a promising technology due to its low cost. However, previously developed solar evaporators have long suffered from severe salt accumulation, limited evaporation area, and inefficient solar-to-steam conversion, severely restricting their practical application.

[0003] To break through the limitations of solar-to-steam conversion efficiency, researchers have previously developed 3D evaporators in the hope of collecting additional energy from the environment. However, their disordered pore structures can induce severe salt crystallization, leading to evaporator failure, which limits their practical application. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a rattan bionic solar-driven evaporator which can reduce salt crystallization and has good evaporation efficiency and a preparation method thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a rattan bionic solar-driven evaporator, the method comprising the following steps:

[0007] (1) dissolving thermoplastic polyurethane, black photothermal conversion material, and polyvinyl pyrrolidone in 1,4-dioxane to obtain a mixed solution;

[0008] (2) introducing gas into the mixed solution to obtain a gas-containing solution;

[0009] (3) continuously directional freezing the gas-containing solution, wherein during the directional freezing process, the height of the ice crystals is higher than the freezing liquid surface, and a frozen product is obtained after the freezing is completed;

[0010] (4) freeze-drying the frozen product to obtain a foam having vertically ordered channels;

[0011] (5) The foam is subjected to hydrophilic modification to obtain the rattan bionic solar-driven evaporator.

[0012] The present invention designs the structure of the rattan bionic solar-powered evaporator to provide it with vertically ordered water channels. This structure not only increases the evaporation area but also reduces the problem of salt crystallization and accumulation in the channels causing blockage, thus contributing to the long-term and efficient operation of the rattan bionic solar-powered evaporator.

[0013] Preferably, in step (1), the mass fraction of the thermoplastic polyurethane is 2% to 6%, the mass fraction of the carbon nanotubes is 0.2% to 2%, and the added amount of the polyvinyl pyrrolidone is 10 wt% of the mass of the carbon nanotubes.

[0014] By limiting the mass fractions of thermoplastic polyurethane, carbon nanotubes, and polyvinyl pyrrolidone as described above, an evaporator with optimal performance can be obtained. The rattan bionic solar-driven evaporator has both high evaporation efficiency and good mechanical properties.

[0015] Preferably, the black light-to-heat conversion material is at least one of multi-walled carbon nanotubes, carbon black, and graphite.

[0016] Preferably, in step (2), the gas is at least one of nitrogen, oxygen and carbon dioxide.

[0017] Preferably, in step (3), the directional freezing method is: loading the gas-containing solution into a freezing module, inserting the freezing module into a cryogen at a rate of 12 to 60 mm / h; the temperature of the cryogen is -30 to -40°C.

[0018] Preferably, in step (3), the freezing module is inserted into the refrigerant at a constant speed with the aid of a universal testing machine to perform continuous directional freezing. This technique can extend the freezing distance and greatly expand the size of products prepared using freezing technology. This method can produce large-scale samples, which is beneficial for improving the performance of the evaporator.

[0019] The present invention also discloses a rattan bionic solar-powered evaporator prepared using the above method. Further preferably, the rattan bionic solar-powered evaporator is cylindrical, with a diameter of 20 mm and a length of 110 mm. Furthermore, the present invention discloses an integrated solar-powered evaporator prepared using the above rattan bionic solar-powered evaporator.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a method for preparing a rattan bionic solar-driven evaporator. The vertically ordered water channels within the rattan bionic solar-driven evaporator can shorten the distance salt ions migrate to the main water, which helps prevent salt crystallization and ensures the long-term and efficient operation of the rattan bionic solar-driven evaporator. In addition, the present invention prepares rattan-shaped vertically ordered water channels through continuous directional freezing technology. This structure helps increase the vertical transport height of water, allowing the evaporator to obtain a large water surface exposure height. The large water surface exposure height helps to increase the evaporation area of the rattan bionic solar-driven evaporator and its ability to collect additional energy from the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a physical picture of the rattan bionic solar-driven evaporator described in Example 1;

[0023] Figure 2 This is a picture of the operation site of continuous directional freezing technology;

[0024] Figure 3 This is an optical image of the cross section of the rattan bionic solar-driven evaporator described in Example 1;

[0025] Figure 4 This is a SEM image of the cross section of the rattan bionic solar-driven evaporator described in Example 1;

[0026] Figure 5 This is a physical picture of the integrated rattan bionic solar-driven evaporator. DETAILED DESCRIPTION

[0027] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] An embodiment of the rattan bionic solar-driven evaporator of the present invention is provided. The preparation method of the rattan bionic solar-driven evaporator of this embodiment comprises the following steps:

[0030] (1) 20 g of thermoplastic polyurethane, 5 g of multi-walled carbon nanotubes, 474.5 g of 1,4-dioxane, and 0.5 g of polyvinylpyrrolidone were heated and stirred at 75° C. to dissolve to obtain a mixed solution;

[0031] (2) using an air pump to fill the mixed solution with dry air to obtain a mixed solution containing saturated air;

[0032] (3) Adding the mixed solution containing saturated air into a directional freezing module, wherein the diameter of the freezing module is 25 mm and the height of the solution is 150 mm, wherein the upper end of the freezing module is connected to the universal testing machine via a thin rope;

[0033] (4) Under the control of a universal testing machine, the entire freezing module is slowly inserted from top to bottom into -40°C ethanol at a rate of 12 mm / h for freezing. After the mixed solution containing saturated air is completely frozen, a frozen product is obtained;

[0034] (5) freeze-drying the frozen product to obtain a foam having pores and vertical channels; the parameters of the freeze dryer are: temperature -40°C, pressure 20Pa;

[0035] (6) Soaking the foam in a hydrophilic modification solution for five days to obtain the rattan biomimetic solar-driven evaporator; the hydrophilic modification solution is composed of 10 g / L DA and 10 g / L PEI, and the solvent is a mixed solution of water and ethanol with a mass ratio of 7:3.

[0036] Under one sun radiation, the rattan biomimetic solar-driven evaporator achieved a high energy density of 3.5 kg·m at an exposure height of 10 cm. -2 ·h -1 The evaporation flux was very low and almost no salt crystallization occurred during the test.

[0037] Example 2

[0038] An embodiment of the rattan bionic solar-driven evaporator of the present invention is provided. The rattan bionic solar-driven evaporator of this embodiment is different from that of Example 1 only in that, in step (1), the amount of thermoplastic polyurethane used is 60 g, the amount of multi-walled carbon nanotubes used is 10 g, the amount of 1,4-dioxane used is 429 g, and the amount of polyvinyl pyrrolidone used is 1 g.

[0039] Under one sun radiation, the rattan biomimetic solar-driven evaporator achieved a high energy density of 3.37 kg·m at an exposure height of 10 cm. -2 ·h -1 evaporation flux.

[0040] Example 3

[0041] An embodiment of the rattan biomimetic solar-driven evaporator of the present invention is provided. The difference between the rattan biomimetic solar-driven evaporator of this embodiment and that of Example 1 is that nitrogen is used instead of air in step (2). The rattan biomimetic solar-driven evaporator has a similar structure to that of Example 1.

[0042] Example 4

[0043] An embodiment of the rattan bionic solar-driven evaporator of the present invention is provided. The difference between the rattan bionic solar-driven evaporator of this embodiment and that of Example 1 is only that, in step (4), the rate at which the freezing module is inserted into -40°C ethanol is 60 mm / h.

[0044] Under one sun radiation, the rattan biomimetic solar-driven evaporator achieved a high energy density of 3.45 kg·m at an exposure height of 10 cm. -2 ·h -1 evaporation flux.

[0045] Comparative Example 1 (non-continuous directional freezing method)

[0046] A rattan bionic solar-driven evaporator. The preparation method of the rattan bionic solar-driven evaporator differs from that of Example 1 only in that, in step (3), the height of the solution is 15 cm; in step (4), the bottom of the directional freezing module is directly immersed in -40°C ethanol for discontinuous directional freezing, and the length of the frozen block is 2 cm, ultimately obtaining an evaporator with a height of only 1.6 cm.

[0047] Figure 1 This is a physical picture of the rattan bionic solar-driven evaporator described in Example 1. The rattan bionic solar-driven evaporator is cylindrical in shape, with a diameter of 20 mm and a length of 110 mm; Figure 2 This is a scene diagram of the continuous directional freezing technology in operation. With the help of a universal testing machine, the directional freezing module is immersed in cold ethanol at a uniform speed; Figure 3 This is an optical image of the cross section of the rattan bionic solar-driven evaporator described in Example 1. The spots in the image are pores left after the bubbles are removed; Figure 4 This is an SEM image of the rattan bionic solar-driven evaporator described in Example 1. As can be seen from the figure, the rattan bionic solar-driven evaporator contains pores and a large number of vertical channels, which can significantly improve the evaporation efficiency of the rattan bionic solar-driven evaporator. Figure 5 This is a physical picture of an integrated rattan bionic solar-driven evaporator prepared from the rattan bionic solar-driven evaporator described in Example 1. A corresponding number of rattan bionic solar-driven evaporators can be selected as needed to prepare an integrated rattan bionic solar-driven evaporator to further improve its evaporation efficiency.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a rattan bionic solar-driven evaporator, characterized in that: The steps include: (1) dissolving thermoplastic polyurethane, a black photothermal conversion material, and polyvinyl pyrrolidone in 1,4-dioxane to obtain a mixed solution; the black photothermal conversion material is multi-walled carbon nanotubes; (2) introducing gas into the mixed solution to obtain a gas-containing solution; (3) performing continuous directional freezing on the gas-containing solution, wherein during the directional freezing process, the height of the ice crystals is higher than the freezing liquid surface, and a frozen product is obtained after the freezing is completed; the directional freezing method comprises: loading the gas-containing solution into a freezing module, inserting the freezing module into a refrigerant at a rate of 12 to 60 mm / h; the temperature of the refrigerant is -30 to -40°C; (4) freeze-drying the frozen product to obtain a foam having pores and vertical channels; (5) hydrophilic modification of the foam to obtain the rattan biomimetic solar-driven evaporator; the hydrophilic modification method comprises: immersing the foam in a hydrophilic modification solution to form a hydrophilic coating on the vertical channel wall; The hydrophilic modification solution includes dopamine and polyethyleneimine.

2. The method for preparing the rattan bionic solar-driven evaporator according to claim 1, characterized in that: In step (1), the mass fraction of the thermoplastic polyurethane is 2% to 6%, the mass fraction of the photothermal conversion material is 0.2% to 2%, and the added amount of the polyvinyl pyrrolidone is 10 wt% of the mass of the multi-walled carbon nanotubes.

3. The method for preparing the rattan bionic solar-driven evaporator according to claim 1, characterized in that: In step (2), the gas is at least one of nitrogen, oxygen, and carbon dioxide.

4. A rattan bionic solar-driven evaporator, characterized in that: Prepared by the method according to any one of claims 1 to 3.

5. An integrated solar-driven evaporator, characterized in that: The evaporator is prepared from the rattan bionic solar-driven evaporator as described in claim 4.

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