Salt-repellent evaporator based on thermal field driving and preparation method of salt-repellent evaporator

Abstract

The invention relates to a salt repellent evaporator based on thermal field driving and a preparation method thereof, and belongs to the technical field of electro-thermal conversion. The preparation method comprises the following steps: S1, sequentially wrapping a heating wire and a second hydrophilic fiber on the surface of a first hydrophilic fiber to obtain a composite fiber yarn; and S2, the composite fiber yarn is sewn on a fabric base material to construct a thermal field area, then the thermal field area is sequentially immersed into a binder solution and a photothermal material solution for photothermal loading, and the salt-repellent evaporator based on thermal field driving is obtained after drying. By constructing an electric heating thermal field, circulation of salt particles can be driven under the condition that the evaporation rate is increased, and therefore efficient, salt-repellent and durable seawater desalination is achieved for sustainable clean water production.

Description

Technical Field

[0001] The invention belongs to the technical field of electrothermal conversion, and in particular relates to a salt-rejecting evaporator driven by a thermal field and a preparation method thereof. Background Art

[0002] Researchers have paid extensive attention to photothermal interfacial evaporation technology, which has achieved a reduction in heat loss and significantly improved water evaporation efficiency, but most have not solved or ignored the negative impact of salt crystallization on evaporation equipment during the evaporation process. Since evaporation is a concentration process, a large amount of salt deposition will be produced during the desalination process, resulting in decreased evaporation performance and equipment damage. The common salt rejection strategy is achieved by optimizing the circulation channel and increasing water affinity to promote brine supply. However, increasing the brine supply may impair evaporation efficiency because most of the energy input is used to heat large amounts of water. Therefore, simultaneously obtaining efficient water evaporation and long-term desalination is a bottleneck for clean water collection.

[0003] In the past few years, there has been a surge of interest in developing efficient solar evaporators to break the evaporation rate limit. The main design principles lie in reducing the energy demand for water evaporation and introducing additional energy sources (such as electricity, wind power, and cold evaporation). Conventional solar evaporators have a single radiation input and exhibit uniform surface heating and vertical thermal gradients, which can be attributed to the strong photothermal conversion of the photothermal conversion material and the large heat consumption of water. Weak ion circulation caused only by inherent capillary forces and hydrophilic functional groups may lead to severe salt deposition, which will limit the effective operation during high salinity or long desalination. Marangoni flow driven by surface tension gradients caused by salt concentration and heat flow gradients plays an important role in the salt rejection process. During the evaporation process, the intensity and distribution of the thermal field inherently induce water / ion migration, resulting in salinity fluctuations and Marangoni flow. Weak ion circulation in the evaporator can hardly offset the blockage of salt particles; on the contrary, evaporators with strong thermal fields may cause directional Marangoni flow due to rapid vapor dissipation and strong compensating flow, leading to intensified salt crystallization. In comparison, the thermal field evaporator with active heat integration presents three-dimensional and omnidirectional thermal gradients, which can accelerate water evaporation, enhance Marangoni flow, and promote ion circulation. Therefore, desalination can be achieved through a fine thermal field structure and moderate Marangoni circulation.

[0004] Invention patent CN 115652497 A discloses a method for preparing photothermal fabrics based on solar water evaporation interface regulation. In this method, hydrophilic cotton thread and polyaniline polymer loaded cotton thread are woven as warp and weft respectively according to the staggered rule, and the interface pattern and interface water channel are regulated and woven by weaving to obtain photothermal fabrics, which have the advantages of uniform photothermal load, high photothermal conversion efficiency, and high evaporation efficiency. However, the complex production process, difficulty in efficient mass production and high cost of this achievement limit its industrial application.

[0005] Invention patent CN 117917381 A discloses a highly efficient anti-salt and anti-evaporation photothermal material for high-concentration salt water. The method is to form a dense MOF nanolayer on the surface of the fabric through a hydrothermal reaction, followed by carbonization; using the special structure of MOF, the evaporation enthalpy of water is reduced, and the utilization rate of solar energy is improved; using the high water absorption characteristics of MOF, the convection and diffusion of salt water on the surface of the photothermal material are enhanced, avoiding salt blockage. However, this method will bring about a large heat loss while rejecting salt, thereby reducing the evaporation rate, and ultimately cannot achieve the purpose of efficiently treating concentrated salt water.

[0006] Invention patent CN118724131A discloses an electrothermal-assisted solar interface evaporation system, which consists of a solar interface evaporation composite material and device. It improves the evaporation efficiency through electrothermal-photothermal synergy, and can be used for all-weather bitter salt water desalination, and still has a high evaporation rate at night. However, the system does not show salt rejection performance, and the long-term operation stability will be damaged in a high-concentration salt water environment, resulting in a significant decrease in the evaporation rate.

[0007] Therefore, it is urgent to develop an electrically assisted solar interfacial evaporation system with salt rejection performance. Summary of the invention

[0008] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the additional energy supplied to increase the rate of emission will cause salt accumulation due to the limited water supply capacity of the conventional device in the prior art. The one-way restricted salt ion flow limits the ion circulation between the evaporation device and the salt water, which aggravates the nucleation and accumulation of salt particles on the surface of the evaporation device.

[0009] To solve the above technical problems, the present invention provides a thermal field driven salt-rejecting evaporator and a preparation method thereof. Firstly, a composite fiber yarn (CEY) with excellent mechanical strength, flexibility and sewability is prepared by winding hydrophilic fibers on the surface of an electric heating wire. Then, the composite fiber yarn (CEY) is sewn into different patterns on the surface of a fabric substrate to construct an electrothermal field. Finally, a photothermal material is loaded on the fabric to prepare a salt-rejecting evaporator with an electrothermal and photothermal conversion energy gradient, namely, a composite fabric (TGF).

[0010] The first object of the present invention is to provide a method for preparing a salt rejection evaporator based on thermal field drive, comprising the following steps:

[0011] S1, sequentially wrapping the heating wire and the second hydrophilic fiber on the surface of the first hydrophilic fiber to obtain a composite fiber yarn;

[0012] S2. Sewing the composite fiber yarn described in S1 onto a fabric substrate to construct a thermal field area, and then immersing them in a binder solution and a photothermal material solution in turn for photothermal loading, and obtaining the thermal field-driven salt-rejecting evaporator after drying.

[0013] In one embodiment of the present invention, in S1, the first hydrophilic fiber and the second hydrophilic fiber are independently selected from one or more of cotton, tencel, viscose and wool.

[0014] In one embodiment of the present invention, in S1, the heating wire is selected from one or more of a nickel-chrome alloy, a titanium alloy and an iron-aluminum alloy.

[0015] In one embodiment of the present invention, in S2, before sewing, the composite fiber yarn is further subjected to passivation treatment; the passivation solution used in the passivation treatment is selected from one or more of chromate passivation solution, chromium-free passivation solution, nitric acid passivation solution and sulfuric acid passivation solution.

[0016] In one embodiment of the present invention, in S2, the fabric substrate is selected from one or more of cotton fabric, tencel fabric, viscose fabric and wool fabric.

[0017] In one embodiment of the present invention, in S2, the pattern of the thermal field area is selected from one or more of a triangle, a square, a pentagon, a hexagon and a circle.

[0018] In one embodiment of the present invention, in S2, the circumference of the pattern is 7 cm-13 cm; and / or the diameter of the pattern is 1 cm-5 cm.

[0019] In one embodiment of the present invention, in S2, the binder is selected from one or more of polydopamine, polyethylene glycol and polyethyleneimine, and the concentration of the binder solution is 0.1 wt%-0.5 wt%.

[0020] In one embodiment of the present invention, in S2, the photothermal material is selected from one or more of carbon nanotubes, carbon black, graphene and polypyrrole, and the concentration of the photothermal material solution is 0.2wt%-0.6wt%.

[0021] In one embodiment of the present invention, in S2, the immersion time in the binder solution and the photothermal material solution is independently 0.5 h-1.5 h.

[0022] The second object of the present invention is to provide a salt rejection evaporator based on thermal field drive prepared by the method described.

[0023] The technical solution of the present invention has the following advantages over the prior art:

[0024] (1) The preparation method described in the present invention prepares a thermal gradient salt-rejecting evaporator with vertical photothermal transfer and horizontal photothermal transfer. The salt-rejecting evaporator with integrated electrothermal thermal field presents a three-dimensional and omnidirectional thermal gradient, which can accelerate water evaporation, enhance Marangoni flow, and promote ion circulation. Therefore, desalination can be achieved through a fine thermal field structure and a moderate Marangoni cycle. By adjusting the electrothermal thermal field, patterns of different shapes (different thermal field distributions) of the same circumference (same resistance) of triangles, squares, pentagons, hexagons and circles are constructed to optimize thermal field conversion. For materials of the same resistance, when the same voltage is supplied, the optimal utilization of energy conversion can be achieved by optimizing the electrothermal thermal field distribution. Water continuously absorbs heat and evaporates during phase change and surface heat transfer. When direct current is applied, due to Joule heat and surface cooling effects, the composite fiber yarn generates a large amount of heat and diffuses from the central thermal field area to the surrounding area through water.

[0025] (2) The thermal field-driven salt-rejecting evaporator described in the present invention realizes the improvement of energy conversion efficiency by constructing the pattern and size of the thermal field. Due to the combination of the electrothermal thermal field and the photothermal thermal field, a Marangoni flow with a wide circulation capacity is jointly driven. The salt-rejecting evaporator constructed with multiple thermal fields exhibits a strong salt concentration gradient and temperature gradient-induced Marangoni flow due to the heat transfer between different media and the rapid evaporation on the surface. The water flow circulation composed of Marangoni flow, evaporative dissipation, capillary wicking and compensation flow can realize an effective salt ion dilution cycle.

[0026] (3) The thermal field driven salt rejection evaporator described in the present invention can drive the circulation of salt particles while accelerating the evaporation rate by constructing an electrothermal thermal field, thereby achieving efficient and salt-rejecting and durable seawater desalination for sustainable clean water production.

[0027] (4) The thermal field area distribution in the thermal field-driven salt-rejecting evaporator described in the present invention is moderate, and the electric heat source in the middle area allows heat transfer inward and outward. The rapid evaporation in the thermal field area allows the Marangoni flow, multiple compensation flows, and capillary water supply flows to circulate with each other. Therefore, due to the balanced Marangoni flow, multiple water flows stably drive ion circulation under mutual disturbance, thereby ensuring strong salt resistance. The thermal field-driven salt-rejecting evaporator drives abundant water flow circulation under the premise of additional heat supply, optimizing and realizing rapid and efficient evaporation and salt rejection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 Schematic diagram of the preparation process of the composite fabric of the present invention;

[0030] Figure 2 Schematic diagram of thermal field areas with different patterns of the present invention;

[0031] Figure 3 It is a schematic diagram of circular thermal field areas of different diameters of the present invention;

[0032] Figure 4 The test result of the fracture pressure of the test example 1 of the present invention;

[0033] Figure 5 The test result of the solar light absorption rate of the test example 2 of the present invention;

[0034] Figure 6 The test results of the water supply flux of Test Example 2 of the present invention;

[0035] Figure 7 The test results of water evaporation performance of Test Example 4 of the present invention;

[0036] Figure 8 The test results of the seawater desalination performance of Test Example 5 of the present invention;

[0037] Fig. 9 Schematic diagram of the salt rejection mechanism of TGF-C with circular thermal field areas of different diameters according to the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0039] In the present invention, unless otherwise explained, technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs.

[0040] In the present invention, unless otherwise stated, the term "and / or" used in the present invention includes any and all combinations of one or more of the associated listed items.

[0041] In the present invention, unless otherwise stated, the experimental methods used in the embodiments of the present invention are conventional methods unless otherwise stated, and the materials, reagents, etc. used are all commercially available unless otherwise stated.

[0042] In the present invention, unless otherwise specified, the fiber materials used in the examples of the present invention were ultrasonically treated in anhydrous ethanol for 4 hours to remove impurities and contaminants inside or on the fiber surface.

[0043] In the present invention, unless otherwise specified, the size of the cotton cloth substrate used in the examples of the present invention was set to 5 cm×5 cm.

[0044] In the present invention, unless otherwise specified, the mass ratio of polydopamine to Tris in the polydopamine / Tris dispersion used in the examples of the present invention is 1:6.

[0045] Example 1

[0046] Reference Figure 1 As shown, the thermal field driven salt rejection evaporator and the preparation method thereof of this embodiment specifically include the following steps:

[0047] S1. Preparation of composite fiber yarn: The Tencel fiber is guided and fed by a tension controller and a positive roller, and the nickel-chrome alloy heating wire is wrapped on the Tencel fiber on the upper section of the hollow core shaft, and then the double-layer yarn is further wrapped with the outer Tencel fiber; the yarn is then wound on a straight tube and further anti-rusted with a chromium-free passivation liquid to obtain a composite fiber yarn (CEY) with a core-shell structure.

[0048] S2. Through software modeling, modulation programming and automatic sewing machine sewing, composite fiber yarn (CEY) was sewn into different patterns on a cotton substrate to construct a thermal field area, and then the fabric was immersed in a polydopamine / Tris dispersion with a concentration of 0.3wt% and a carbon nanotube (CNT) dispersion with a concentration of 0.4wt% for 1h each for photothermal loading, and dried in an oven to obtain a salt-rejecting evaporator with electrothermal and photothermal conversion energy gradients, namely a composite fabric (TGF);

[0049] The perimeter of the pattern is set to 9.5 cm, and the shapes of the patterns are adjusted to be regular triangles, squares, pentagons, hexagons, and circles. Figure 2 ) to obtain composite fabrics; they were named TGF-T, TGF-S, TGF-P, TGF-H and TGF-C respectively.

[0050] Set the shape of the pattern to a circle, and adjust the diameter of the circle to 2cm, 3cm, and 4.4cm ( Figure 3 ) to obtain composite fabrics; they were named TGF-C1, TGF-C2 and TGF-C3 respectively.

[0051] Comparative Example 1

[0052] The method is basically the same as Example 1, except that the composite fiber yarn (CEY) is not sewn together. The obtained composite fabric is named TGF-C0.

[0053] Test Example 1

[0054] Based on Example 1, referring to the standard of FZ / T 01114-2012, the breaking pressure of Tencel fiber, nickel alloy heating wire and composite fiber yarn (CEY) was tested, and the results are as follows: Figure 4 As shown. Figure 4 It can be seen that compared with Tencel fiber and nickel-coated alloy heating wire, the elongation at break and breaking strength of composite fiber yarn (CEY) have been significantly improved, and excellent mechanical strength is essential for long-term operation. Wrapping Tencel fiber on the surface of nickel-coated alloy heating wire significantly improves the mechanical properties. The friction resistance between the wrapped composite fiber yarn (CEY) is increased, the sliding resistance is increased, and the core-shell structure reduces the unevenness between the fibers, producing a thread with excellent mechanical strength, flexibility and sewing ability. Therefore, the mechanical strength of the composite fiber yarn (CEY) is significantly improved after gradual processing.

[0055] Test Example 2

[0056] Based on Example 1, referring to the standard of JJG178-2007, the solar absorption rate of the original cotton cloth and the composite fabric (TGF-C2) was tested, and the results are as follows: Figure 5 As shown. Figure 5 It can be seen that the full spectrum solar energy absorption rate of the original cotton cloth is about 33%. After the photothermal particle loading, the solar radiation utilization rate of the composite fabric (TGF) is significantly improved to about 89%.

[0057] The water flux of the original cotton cloth and the composite fabric (TGF) was calculated based on the saturated water absorption mass per unit area. Figure 6 As shown. Figure 6 It can be seen that the water flux of the original cotton cloth and the composite fabric (TGF) is about 3.9 kg / m 2 and 3.8kg / m 2 , the water supply performance of the composite fabric (TGF) remained stable after loading the photothermal material, with only a slight difference in moisture flux (±2%).

[0058] The improvement of photothermal performance is attributed to the excitation and relaxation of the π band by thermalization caused by electron-electron and electron-phonon scattering. Due to the presence of abundant hydrophilic groups such as -OH, -COOH and interconnected fiber channels, the hydrophilicity and water supply capacity of the composite fabric remain highly competitive, which is crucial for the continuous water supply and ion circulation of seawater desalination devices. In short, the photothermal conversion performance of the composite fabric after loading with photothermal materials is significantly improved, while still maintaining a strong water supply capacity.

[0059] Test Example 3

[0060] Based on Example 1, the energy utilization effect of electrothermal conversion of TGF-T, TGF-S, TGF-P, TGF-H and TGF-C was tested, and the surface temperature of the sample was read using a thermocouple. After the 2V DC voltage was supplied and operated stably for 1h, 100 points on the sample surface were uniformly selected for temperature measurement using a thermocouple. The measurement results show that the surface average temperature of TGF-T with a triangular thermal field is 36.2°C, and the standard deviation of the temperature distribution range is 9.1°C; the surface average temperature of TGF-S with a square thermal field is 36.9°C, and the standard deviation of the temperature distribution range is 8.9°C; the surface average temperature of TGF-P with a pentagonal thermal field is 37.3°C, and the standard deviation of the temperature distribution range is 8.2°C; the surface average temperature of TGF-H with a hexagonal thermal field is 37.8°C, and the standard deviation of the temperature distribution range is 7.8°C; the surface average temperature of TGF-C with a circular thermal field is 38.5°C, and the standard deviation of the temperature distribution range is 7.2°C. From the temperature measurement results, it can be seen that the TGF-C with a circular thermal field with the largest thermal field area has a higher average temperature, smaller thermal fluctuations, and more uniform energy distribution.

[0061] The electrothermal evaporation performance of TGF-T, TGF-S, TGF-P, TGF-H and TGF-C was tested. The evaporation rate obtained by the test is the change in evaporation mass per unit area and per unit hour. The calculated energy utilization efficiency is the ratio of evaporation energy consumption to electrothermal energy supply. Under a 2V DC voltage input, the electrothermal efficiency of TGF-T with a triangular thermal field is 19%, and the evaporation rate is 0.64kg·m -2 ·h -1 The electrothermal efficiency of TGF-S with a square thermal field is 26%, and the evaporation rate is 0.68 kg·m -2 ·h -1 The electrothermal efficiency of TGF-P with a pentagonal thermal field is 29%, and the evaporation rate is 0.73 kg·m -2 ·h -1 The electrothermal efficiency of TGF-H with a hexagonal thermal field is 32%, and the evaporation rate is 0.75 kg·m -2 ·h -1 The electrothermal efficiency of TGF-C with a circular thermal field is 37%, and the evaporation rate is 0.81 kg·m -2 ·h -1 According to the isoperimetric theorem, among closed geometric shapes with the same perimeter, the circular area is the largest. Therefore, the TGF-C with a circular thermal field with the largest thermal field area can spread heat energy more evenly throughout the evaporator, and has better electrothermal conversion efficiency and electrothermal driven water evaporation performance.

[0062] Test Example 4

[0063] Based on Example 1 and Comparative Example 1, the water evaporation performance of TGF-C0, TGF-C1, TGF-C2 and TGF-C3 was tested. The evaporation rate obtained by the test is the change in evaporation mass per unit area and per unit hour. The calculated energy utilization efficiency is the ratio of evaporation energy consumption to photothermal / electrical thermal energy supply. The results are as follows: Figure 7 As shown. Figure 7 It can be seen that under 1 sun light intensity and 2 V DC voltage, the TGF-C sample heats up rapidly and drives water evaporation. The water evaporation rates of TGF-C0, TGF-C1, TGF-C2, and TGF-C3 are 1.1 kg·m -2 ·h -1 , 2.6kg·m -2 ·h -1 , 2.4kg·m -2 ·h -1 , 2.1kg·m -2 ·h -1 . TGF-C0 has a weak evaporation rate due to the lack of electrothermal field construction, and the energy supply basically comes from photothermal conversion. According to Joule's law and the law of resistance, a large thermal field area with a longer resistance wire presents higher resistance and weaker electrothermal conversion. As the length of the thermal field heating wire CEY increases, the resistance of TGF-C1, TGF-C2, and TGF-C3 increases, so their electrothermal conversion efficiency gradually decreases, thereby weakening the electrothermal conversion performance.

[0064] Test Example 5

[0065] Based on Example 1 and Comparative Example 1, the desalination performance of TGF-C0, TGF-C1, TGF-C2 and TGF-C3 was tested. The simulated seawater used NaCl as the simulated ratio. The evaporation rate obtained by the test was the change in evaporation mass per unit area and per unit hour. The calculated energy utilization efficiency was the ratio of evaporation energy consumption to photothermal / electrical thermal energy supply. The long-term high-concentration salt water (10wt%) desalination rate of TGF-C was recorded. The results are as follows: Figure 8 As shown. Figure 8 It can be seen that the initial and final rates of TGF-C0 are 0.74 kg·m -2 ·h -1 and 0.39 kg·m -2 ·h -1 The rate attenuation reached 48%; the initial and final rates of TGF-C1 were 1.8 kg·m -2 ·h -1 and 1.3 kg·m -2 ·h -1 The rate attenuation reached 28%; the initial and final rates of TGF-C2 were 1.7 kg·m -2·h -1 and 1.6 kg·m -2 ·h -1 The rate decay was only 6%; the initial and final rates of TGF-C3 were 1.6 kg·m -2 ·h -1 and 1.2 kg·m -2 ·h -1 , the rate attenuation reached 25%. Overall, TGF-C2 exhibited a stable desalination rate due to the abundant interconnected fiber channels and sufficient ion circulation. The salt ions in TGF-C2 experienced a stable non-oriented free circulation, and the sufficient and strong ion circulation enabled efficient and salt-tolerant desalination. Due to the lack of Marangoni flow circulation, TGF-C0 had obvious salt particle deposition; TGF-C1 had a concentrated Marangoni flow circulation but aggravated salt crystallization; TGF-C3 had a weak edge Marangoni flow circulation and could not effectively alleviate the crystallization of salt particles. The attenuation of other TGF-Cs can be attributed to the considerable solar reflection caused by the white salt particles accumulated on the surface, which limited the energy supply for photothermal conversion, and the internally deposited salt particles blocked the water supply channel and the steam dispersion path. Therefore, the optimized thermal field structure can significantly improve the salt tolerance in the long-term high-salinity desalination process. Due to the efficient, adaptable and durable desalination capacity, the all-weather freshwater condensation collection capacity of TGF-C2 reached about 6.3kg·m -2 , with good practical water purification capabilities. After 15 days of high-concentration seawater desalination operation, its condensate treatment performance remains stable and efficient, which is crucial for stable operation in complex real-world environments.

[0066] In the desalination process, salt blockage occurs mainly because the weak ion circulation rate cannot offset the nucleation rate of salt particles. Therefore, asymmetric evaporation, Marangoni cycle, compensation flow, etc. should be regulated to build a strong ion circulation. The salt rejection mechanism of TGF-C with circular electrothermal thermal field areas of different diameters of the present invention is as follows Fig. 9As shown, TGF-C1 with concentrated thermal field distribution evaporates rapidly in the central area, and strong Marangoni flow and evaporation compensation flow converge to the central thermal field, while the outward diffusing Marangoni flow is relatively weak. Therefore, after long-term seawater desalination, salt particles will accumulate in the central thermal field of TGF-C1. Similarly, the Marangoni flow that appears in TGF-C3 with a wide thermal field distribution promotes the circulation of ions, but the edge thermal field only allows a weak circulation flow, which is still not enough to suppress the formation of salt particles. In contrast, TGF-C2 with a medium thermal field distribution has strong ion circulation performance. The heat source in the middle area allows heat transfer inward and outward. Accelerated evaporation in the thermal field area allows compensation flow to converge from all directions. Therefore, due to the balanced Marangoni flow, multiple water flows circulate under mutual disturbance, which makes the ion circulation sufficient, thereby ensuring strong salt resistance.

[0067] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing a salt rejection evaporator based on thermal field drive, characterized in that: The following steps are involved: S1, sequentially wrapping the heating wire and the second hydrophilic fiber on the surface of the first hydrophilic fiber to obtain a composite fiber yarn; S2. Sewing the composite fiber yarn described in S1 onto a fabric substrate to construct a thermal field area, and then immersing them in a binder solution and a photothermal material solution in turn for photothermal loading, and obtaining the thermal field-driven salt-rejecting evaporator after drying.

2. The method for preparing a salt-rejecting evaporator driven by a thermal field according to claim 1, characterized in that: In S1, the first hydrophilic fiber and the second hydrophilic fiber are independently selected from one or more of cotton, tencel, viscose and wool.

3. The method for preparing a salt-rejecting evaporator driven by a thermal field according to claim 1, characterized in that: In S1, the heating wire is selected from one or more of a nickel-chrome alloy, a titanium alloy and an iron-aluminum alloy.

4. The method for preparing a salt-rejecting evaporator driven by a thermal field according to claim 1, characterized in that: In S2, before sewing, the composite fiber yarn is passivated; the passivation solution used in the passivation treatment is selected from one or more of chromate passivation solution, chromium-free passivation solution, nitric acid passivation solution and sulfuric acid passivation solution.

5. The method for preparing a salt-rejecting evaporator driven by a thermal field according to claim 1, characterized in that: In S2, the pattern of the thermal field area is selected from one or more of a triangle, a square, a pentagon, a hexagon and a circle.

6. The method for preparing a salt-rejecting evaporator based on thermal field drive according to claim 1, characterized in that: In S2, the circumference of the pattern is 7 cm-13 cm; and / or the diameter of the pattern is 1 cm-5 cm.

7. The method for preparing a salt rejection evaporator based on thermal field drive according to claim 1, characterized in that: In S2, the binder is selected from one or more of polydopamine, polyethylene glycol and polyethyleneimine, and the concentration of the binder solution is 0.1wt%-0.5wt%.

8. The method for preparing a salt-rejecting evaporator driven by a thermal field according to claim 1, characterized in that: In S2, the photothermal material is selected from one or more of carbon nanotubes, carbon black, graphene and polypyrrole, and the concentration of the photothermal material solution is 0.2wt%-0.6wt%.

9. The method for preparing a salt-rejecting evaporator driven by a thermal field according to claim 1, characterized in that: In S2, the immersion time in the binder solution and the photothermal material solution is independently 0.5 h to 1.5 h.

10. A salt rejection evaporator based on thermal field drive prepared by the method according to any one of claims 1 to 9.

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