Solar interface evaporation desalter

Abstract

The invention relates to a solar interface evaporation desalination device, and belongs to the technical field of seawater desalination. The device comprises a barrel-shaped transparent body and a conical transparent top cover arranged on the transparent body in a sealing and covering mode, a water storage cavity used for storing seawater and a water collecting groove used for collecting fresh water are formed in the transparent body, and an evaporation body used for evaporating the seawater is arranged in the water storage cavity. Water vapor evaporated by the evaporation body is condensed into water on the transparent top cover, the water is drained to the water collecting tank from the inner surface of the transparent top cover, and the evaporation body is a composite photo-thermal hollow fiber membrane, is an efficient photo-thermal absorber for solar interface evaporation and is expected to become a potential candidate material for sustainable seawater desalination. Under the irradiation of sunlight, the evaporation body continuously generates water vapor, the water vapor is gathered in the transparent top cover and then condensed into small water drops, and the small water drops gradually fall into the water collecting tank below from the periphery to the bottom along the inner wall of the transparent top cover.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of seawater desalination, and relates to a solar interfacial evaporation desalination device. BACKGROUND

[0002] The development of the high-efficiency solar interfacial evaporation desalination device has important strategic significance for promoting sustainable development and energy saving and emission reduction. In a long-term continuous evaporation process, the interfacial evaporation system under an open system is studied more at present, and the low solar light absorption rate, high relative humidity and low evaporation rate in a closed system cause low freshwater collection rate, which is an important problem existing universally, and the heat and mass transfer mechanism of the corresponding closed system is also less discussed. SUMMARY

[0003] The application aims at the above problems existing in the prior art and provides a solar interfacial evaporation desalination device with good evaporation performance under a closed condition.

[0004] The object of the application can be achieved by the following technical scheme.

[0005] The solar interfacial evaporation desalination device comprises a transparent barrel-shaped body and a transparent conical top cover provided on the transparent body, a water storage cavity for storing seawater and a water collecting tank for collecting freshwater are arranged in the transparent body, an evaporation body for evaporating seawater is arranged in the water storage cavity, water vapor evaporated by the evaporation body is condensed into water on the transparent top cover, and the water is guided to the water collecting tank by the inner surface of the transparent top cover.

[0006] Under the irradiation of sunlight, the evaporation body continuously generates water vapor which is gathered in the transparent top cover and then condensed into small water droplets. Since the transparent top cover is conical, the small water droplets are beneficial to gradually falling into the water collecting tank from all around and downward along the inner wall of the transparent top cover.

[0007] In the above solar interfacial evaporation desalination device, a support layer is floated on the liquid surface of seawater in the water storage cavity, the evaporation body is strip-shaped and arranged on the support layer, the lower end of the evaporation body is inserted into seawater, and the upper end of the evaporation body is extended out of the upper surface of the support layer.

[0008] The support layer is plate-shaped and made of foam material, and is floated on the surface of seawater. A plurality of evaporation bodies are arranged on the support layer, the plurality of evaporation bodies are distributed in an annular array along the center line of the support layer, and the part of each evaporation body extended out of the upper surface of the support layer extends radially outward along the support layer.

[0009] In the above solar interfacial evaporation desalination device, an air extraction pipe is connected to the transparent top cover, a water collecting container immersed in an ice-water mixture is connected to the other end of the air extraction pipe, and a fan is arranged on the air extraction pipe.

[0010] The evaporation and condensation processes are separated by the exhaust pipe and the fan, which not only reduces the light loss caused by the water mist gathering on the transparent roof, but also keeps the evaporation space dry, which helps to speed up the evaporation process. The water collection container is immersed in an ice-water mixture and regularly releases a certain amount of ice into the external container. The low temperature greatly accelerates the condensation of hot steam and makes the fresh water collection process more convenient.

[0011] In the above-mentioned solar interface evaporation desalination device, the evaporation body is a composite photo-thermal hollow fiber membrane, and the preparation method of the composite photo-thermal hollow fiber membrane comprises the following steps:

[0012] S1, hollow fiber membrane pretreatment: take the hollow fiber membrane and close both ends, then immerse it in ethanol for 4-6h, wash it with water and dry it for standby; take the dried membrane and make it into a bundle-shaped membrane assembly with both ends closed--PSF HFMs assembly for subsequent processing, the PSF HFMs assembly is composed of at least one membrane; the both ends of the hollow fiber membrane are closed with waterproof glue, and the waterproof glue is selected from epoxy glue and polyurethane glue;

[0013] S2, preparation of PSF@PDA / TiO2 HFMs: immerse the pretreated PSF HFMs assembly in the immersion liquid for 5-7h to obtain PSF@PDA / TiO2 HFMs; the immersion liquid is obtained by mixing dopamine DA, ammonium persulfate APS, titanium dioxide TiO2 and 3-aminopropyl triethoxysilane APTES in 8-12mM tris-HCl buffer solution with pH value of 8-9, and the proportion of each component is: 0.15-0.25g DA, 0.05-0.07g APS, 0.15-0.25g TiO2 and 0.4-0.6mL APTES aqueous solution with concentration of 0.04-0.06mol / L are added into every 100-200ml tris-HCl buffer solution;

[0014] S3, preparation of PSF@PDA / TiO2-Ag HFMs: prepare PSF@PDA / TiO2 HFMs and immerse them in 0.05-0.15mol / L Ag + solution under ultraviolet light for 30-60min ultraviolet reduction reaction, active ion Ag + generates metal Ag nanoparticles under ultraviolet light and loads them on the membrane surface to obtain PSF@PDA / TiO2-Ag HFMs; the Ag + is AgNO3 solution, AgSO4 solution and AgCl solution;

[0015] S4, preparation of PSF@PDA / TiO2-Ag / Ppy HFMs:

[0016] PSF@PDA / TiO2-Ag HFMs were placed in an APS aqueous solution and reacted at a low temperature of 2℃~8℃ for 1~2 hours. After wiping off the surface liquid, the surface of polypyrrole (Ppy) was polymerized 1~3 times using chemical vapor deposition. After the reaction was completed, the surface residue was washed with deionized water and dried to obtain PSF@PDA / TiO2-Ag / Ppy HFMs. The concentration of the APS aqueous solution was prepared according to the following ratio: 2~3g APS dissolved in 80~100ml of deionized water.

[0017] In the aforementioned solar interface evaporation desalination device, the PSF HFMs module is formed by sealing both ends of several hollow fiber membrane filaments with waterproof adhesive and bonding the ends of multiple filaments together; the PSF HFMs module is composed of 2-100, 2-80, or 5-60 hollow fiber membrane filaments; the length of the hollow fiber membrane filaments is 5-50 cm, the average pore size of the hollow fiber membrane ranges from 0.01 to 2.0 μm, the porosity ranges from 20-80%, the membrane thickness ranges from 50 to 500 μm, and the inner and outer diameters of the hollow fibers range from 0.1-2.0 mm and 0.25-3.5 mm, respectively; the hollow fiber membrane is a polysulfone hollow fiber membrane;

[0018] In step S4, 30–60 μl of py is used for chemical vapor deposition for each Ppy surface polymerization reaction.

[0019] In the above-mentioned solar interface evaporation desalination device, the impregnation solution in step S2 is prepared as follows: 0.1211 gtris is dissolved in 100 ml of water, and then the pH is adjusted to 8.5 with 20% HCl to obtain a 10 mM tris-HCl buffer solution; 0.2 g DA, 0.06 g APS, 0.2 g TiO2, and 0.5 mL of APTES aqueous solution with a concentration of 0.05 mol / L are weighed and added to the previously prepared tris-HCl buffer solution and uniformly dispersed to prepare the impregnation solution.

[0020] In the aforementioned solar interface evaporation desalination device, steps S3 and S4 are specifically as follows:

[0021] S3. Preparation of PSF@PDA / TiO2-Ag HFMs: PSF@PDA / TiO2 HFMs were placed in a 0.1 mol / L AgNO3 solution and subjected to a UV reduction reaction under a UV lamp for 30 min to obtain the active ion Ag. + PSF@PDA / TiO2-Ag HFMs were prepared by generating metallic Ag nanoparticles under ultraviolet light irradiation and loading them onto the film surface.

[0022] S4. Preparation of PSF@PDA / TiO2-Ag / Ppy HFMs: The concentration of the APS aqueous solution is prepared according to the following ratio: Dissolve 2-2.5g of APS in 80-100ml of deionized water. Place the PSF@PDA / TiO2-Ag HFMs in the APS aqueous solution and react at a low temperature of 2℃-8℃ for 0.7-1.2h. After wiping off the residual liquid on the surface, prepare a petri dish and a large beaker. Fix one end of the membrane module in the petri dish. Drop 35-50μl of py into the beaker. Invert the petri dish onto the large beaker, allowing the membrane module to be inserted into the beaker and suspended in the beaker. Then dry in a vacuum drying oven at 50-70℃ for 1-2h to complete the first polypyrrole (Ppy) vapor phase chemical deposition. Repeat the step of dropping py into the beaker for vapor phase chemical deposition 1-3 times. After the Ppy surface polymerization reaction is completed, wash off the surface residue with deionized water and dry to obtain PSF@PDA / TiO2-Ag / Ppy. HFMs.

[0023] Compared with existing technologies, this solar interface evaporation desalination device has the following advantages:

[0024] The transparent top cover is conical, which facilitates the gradual flow of condensed water droplets down the inner wall of the cover into the water collection tank below. A novel supported titanium dioxide / silver composite photothermal hollow fiber membrane material (PSF@PDA / TiO2-Ag / Ppy HFMs) with a hydrophilic inner surface and a hydrophobic outer surface (Janus structure) was prepared through steps including polydopamine and nano-titanium dioxide deposition polymerization, ultraviolet light reduction of silver ions, and polypyrrole chemical deposition. This material is a highly efficient photothermal absorber for solar interfacial evaporation, exhibiting an average solar light absorption rate of up to 95.4% in the 200-2500 nm wavelength range and a rapid response to solar heat. It also possesses excellent photothermal evaporation and long-term salt resistance, achieving an evaporation rate of 2.72 kg·m³ under one day of sunlight. -2 ·h -1 With an evaporation efficiency of 181%, the actual seawater (Beihai, Guangxi) was maintained at 2.45–2.63 kg·m³ over a 120-hour experimental period. -2 ·h -1 Its high evaporation rate; its evaporation rate is greatly increased under accelerated airflow conditions, with a wind speed of 3 m / s under one sun. -1 The evaporation rate at that time was 5.09 kg·m³. -2 ·h -1 The evaporation rate is 1.87 times that under windless conditions. PSF@PDA / TiO2-Ag / Ppy HFMs show promise as a potential candidate material for sustainable seawater desalination. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the desalination device provided in Example 1.

[0026] Figure 2 This is a schematic diagram of the desalination device provided in Example 2.

[0027] Figure 3 This is a schematic diagram of the desalination device provided in Example 3.

[0028] Figure 4 The following are the water contact angles of the photothermal hollow fiber membrane before and after modification: (a) water contact angle of the inner surface (b) water contact angle of the outer surface (c) siphon height (d) porosity.

[0029] Figure 5 Here are SEM images of the inner and outer surfaces and cross-sections of PSF@PDA / TiO2-Ag / Ppy HFMs: (a) inner surface (b) outer surface (cd) cross-section.

[0030] Figure 6 The images show (a) FTIR spectra and (b) XPS spectra of PSF@PDA / TiO2-Ag / Ppy HFMs.

[0031] Figure 7 Here are the fine energy spectra of PSF@PDA / TiO2-Ag / Ppy HFMs: (a) C 1s energy spectrum (b) N 1s energy spectrum (c) Ti 2p energy spectrum (d) Ag 3d energy spectrum.

[0032] Figure 8 These are the UV-vis spectra of PSF HFMs and PSF@PDA / TiO2-Ag / Ppy HFMs.

[0033] Figure 9 This is an infrared thermal imaging change diagram of PSF@PDA / TiO2-Ag / Ppy HFMs under one day of sunlight.

[0034] Figure 10 It refers to the temperature changes of pure water and two types of composite photothermal hollow fiber membranes.

[0035] Figure 11 These are (a) a temperature and humidity curve and (b) a photograph showing the operation of the interface evaporation desalination unit.

[0036] Figure 12 The evaporation rate and efficiency of PSF@PDA / TiO2-Ag / Ppy HFMs in open / closed systems.

[0037] Figure 13 The external environment and evaporation rate are (a) and (b) respectively, during a 14-day operation of the PSF@PDA / TiO2-Ag / Ppy HFMs desalination unit.

[0038] Figure 14 These are the concentrations of four salt ions before and after the desalination of Beihai seawater.

[0039] In the diagram, 1 is the transparent body; 11 is the water storage chamber; 12 is the water collection tank; 2 is the transparent top cover; 3 is the evaporator; 4 is the support layer; 5 is the exhaust pipe; 6 is the water collection container; and 7 is the fan. Detailed Implementation

[0040] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0041] Example 1

[0042] like Figure 1 The solar interface evaporation desalination device shown includes a cylindrical transparent body 1 and a conical transparent top cover 2 sealed on the transparent body 1. The top cover 2 is wider at the bottom than at the top, and both are made of glass with a thickness of 3mm. The lower end of the transparent body 1 is sealed, and the upper end is open. The upper end of the transparent body 1 and the lower end of the transparent top cover 2 are detachably and sealed together, and the two are concentrically arranged. Figure 1 As shown, a cylindrical water container is coaxially arranged inside the transparent body 1. The interior of the water container is a water storage chamber 11. An evaporator 3 for evaporating seawater is provided in the water storage chamber 11. A water collection tank 12 is formed between the water container and the inner wall of the transparent body 1, surrounding the water container. The water vapor evaporated by the evaporator 3 condenses into water on the transparent top cover 2 and is guided to the water collection tank 12 from the inner surface of the transparent top cover 2.

[0043] To facilitate the installation of evaporator 3, such as Figure 1 As shown, a support layer 4 floats on the surface of seawater within the water storage chamber 11. Several strip-shaped evaporators 3 are threaded onto the support layer 4, with their lower ends extending into the seawater and their upper ends protruding from the upper surface of the support layer 4. The support layer 4 is plate-shaped and made of foam material, floating on the seawater surface. Several evaporators 3 are arranged in a ring array along the centerline of the support layer 4, with the portion of each evaporator 3 extending radially outward from the upper surface of the support layer 4.

[0044] Under sunlight, the evaporator 3 continuously generates water vapor that accumulates inside the transparent top cover 2, where it condenses into small water droplets. Since the transparent top cover 2 is cone-shaped, it is advantageous for the small water droplets to fall gradually from all sides down the inner wall of the transparent top cover 2 into the water collection tank 12 below.

[0045] Evaporator 3 is a composite photothermal hollow fiber membrane, which is prepared using the method described in Example 4.

[0046] Example 2

[0047] Experiments revealed that the evaporation rate and efficiency in the closed system were significantly lower than in the open system. The main reasons are as follows: ① Due to the limited light transmittance of the glass plate in the closed system, the amount of sunlight absorbed by the evaporating material is reduced, resulting in light loss; ② After water vapor evaporates, it condenses into water mist on the top glass plate. When a large amount of water mist accumulates on the top conical glass plate, it forms a water film, leading to severe light loss; ③ As the amount of water vapor in the desalination unit increases and water droplets condense and fall, a high humidity environment is generated in the closed space, which greatly inhibits the water evaporation process. Furthermore, direct sunlight and the exothermic process of water vapor condensation both raise the temperature inside the desalination unit, which is detrimental to the condensation process, posing a significant challenge to freshwater collection. Therefore, the closed system in Example 1 needs to be optimized to achieve better evaporation and desalination efficiency.

[0048] In solar-driven seawater desalination systems, whether condensed water vapor can smoothly enter the freshwater collection area is a concern. The lack of active components like fans to assist in cooling the water vapor delays condensation, thus affecting freshwater collection efficiency. Considering that the evaporation and condensation processes occur in the same enclosed space and would constrain each other, a small exhaust fan 7 is added to divide the entire system into two parts.

[0049] like Figure 2 As shown, the transparent body 1 and transparent top cover 2 in the original sealed device remain unchanged. After the seawater evaporates, it will still turn into water vapor and accumulate at the top. By adding an exhaust pipe 5 and a fan 7, the hot steam above the transparent body 1 is extracted to a water collection container 6 (large beaker) immersed in an ice-water mixture container for condensation and collection.

[0050] Separating the evaporation and condensation processes not only reduces light loss caused by water mist accumulating on the transparent top cover 2, but also keeps the evaporation space dry, which helps the evaporation process proceed quickly. The water collection container 6 is immersed in an ice-water mixture, and an appropriate amount of ice is periodically added to the outer container. The low temperature conditions greatly accelerate the condensation of hot steam and make the freshwater collection process more convenient.

[0051] Example 3

[0052] The structural principle of this embodiment is basically the same as that of Embodiment 1, except that, as Figure 3 As shown, the entire inner cavity of the transparent body 1 is a water storage cavity 11. An annular water-blocking edge is provided on the inner wall of the transparent body 1 above the seawater surface, and an annularly extending water collection trough 12 is formed on the inner side of the water-blocking edge.

[0053] Example 4

[0054] Preparation and characterization of PSF@PDA / TiO2-Ag / Ppy HFMs

[0055] The materials or reagents in the examples and their abbreviations are as follows:

[0056] Polysulfone hollow fiber membranes (PSF HFMs), anhydrous ethanol (AA), ammonium persulfate (APS), titanium dioxide (TiO2), hydrochloric acid (HCl), dopamine (DA), tris(hydroxymethyl)aminomethane (tris), 3-aminopropyltriethoxysilane (APTES, CAS No.: 919-30-2), pyrrole (py, CAS No.: 109-97-7).

[0057] Polysulfone hollow fiber membrane: 8k hollow fiber membrane, average pore size 1μm, porosity 60%, outer diameter 0.55mm, inner diameter 0.3mm, membrane thickness 100μm, purchased from Jiangsu Julan Nanotechnology Co., Ltd.

[0058] I. Preparation of PSF@PDA / TiO2-Ag / Ppy HFMs

[0059] Follow these steps:

[0060] S1. Hollow Fiber Membrane Pretreatment: Take a polysulfone hollow fiber membrane bundle, seal both ends (to prevent anhydrous ethanol from entering the hollow fiber membrane), and immerse it in anhydrous ethanol solution for 4 hours to improve the activity of the hollow fiber membrane and facilitate the stability of the coating material in subsequent experiments. Wash it repeatedly with deionized water until there is no odor on the sample surface. Finally, place the sample in a clean tray, dry and store it, and then cut it into membrane filaments of about 15 cm in length. Take 40 filaments, seal both ends of the membrane filaments with epoxy resin AB glue (to prevent the modification liquid from entering the hollow fiber membrane), and stick the ends of the membrane filaments together to form a bundled membrane module (PSFHFMs module). Let it dry for later use.

[0061] S2. Preparation of PSF@PDA / TiO2 HFMs: Dissolve 0.1211g tris in 100ml of water, then adjust the pH to 8.5 with 20% HCl to obtain a 10mM tris-HCl buffer solution; weigh 0.2g DA, 0.06g APS, 0.2g TiO2, and 0.5mL of 0.05mol / L APTES aqueous solution and add them to the previously prepared tris-HCl buffer solution to prepare an impregnation solution. Place the pretreated PSF HFMs component from step S1 into the impregnation solution and fully impregnate and polymerize for 6h to obtain PSF@PDA / TiO2 HFMs. Remove and wipe away any residual liquid.

[0062] S3. Preparation of PSF@PDA / TiO2-Ag HFMs: PSF@PDA / TiO2 HFMs were placed in a 0.1 mol / L AgNO3 solution and subjected to UV photoreduction reaction for 30 min under a UV lamp to obtain the active ion Ag. + PSF@PDA / TiO2-Ag HFMs were prepared by generating metallic Ag nanoparticles under ultraviolet light irradiation and loading them onto the film surface.

[0063] S4. Preparation of PSF@PDA / TiO2-Ag / Ppy HFMs:

[0064] 2.28 g of APS was dissolved in 90 ml of deionized water. PSF@PDA / TiO2-Ag HFMs were placed in the solution and reacted at a low temperature of 2℃~8℃ for 1 h. After wiping off any surface residue, a petri dish and a large beaker were prepared. One end of the membrane module was fixed in the petri dish. 40 μl of pyrrole (99% purity) was added to the beaker. The petri dish was inverted onto the large beaker, allowing the membrane module to be inserted into the beaker and suspended. The membrane was then dried in a vacuum drying oven at 60℃ for 1 h, completing the first polypyrrole (Ppy) vapor phase chemical deposition. After the first Ppy vapor phase chemical deposition, another 40 μl of pyrrole was added to the beaker, and the membrane was dried in a vacuum drying oven at 60℃ for 1 h, completing the second Ppy vapor phase chemical deposition. This process was repeated for the third Ppy vapor phase chemical deposition. After three consecutive Ppy surface polymerization reactions, the surface residue was washed off with deionized water and dried to obtain PSF@PDA / TiO2-Ag / Ppy HFMs. In this step, the role of APS is to improve the adhesion of the hollow fiber membrane surface, preparing it for better deposition of pyrrole in the next step.

[0065] II. Characterization and Analysis of Surface Wettability and Microstructure

[0066] Considering the significant impact of surface wettability on the water absorption and seawater evaporation performance of the prepared composite photothermal hollow fiber membrane, the water contact angles of the inner and outer surfaces of PSF HFMs and PSF@PDA / TiO2-Ag / Ppy HFMs samples were measured, with each sample tested three times at different locations on the membrane surface. Since some samples exhibit hydrophilicity and can rapidly absorb 0.5 μL of test water droplets, the contact angles from 0 to 100 ms were recorded, and the average and standard deviation of the three measurements were calculated. Because the Janus structure, with a hydrophilic inner surface and a hydrophobic outer surface, facilitates salt precipitation during seawater evaporation without affecting siphon water supply and sunlight absorption, thus reducing salt clogging of the membrane pores, the n-times Ppy polymerization method was used to construct the photothermal hollow fiber membrane PSF@PDA / TiO2-Ag / Ppy with a Janus structure. n HFMs were used to improve their evaporation and salt resistance properties. This was based on the results of wettability characterization (Figure 4 ab) It was found that after three Ppy deposition polymerizations, the photothermal modified film PSF@PDA / TiO2-Ag / Ppy 3 The instantaneous water contact angles of the inner and outer surfaces of the HFMs are 57.8° and 95.0°, respectively, exhibiting a Janus structure. For simplicity, PSF@PDA / TiO2-Ag / Ppy is used in all examples. 3 HFMs are denoted as PSF@PDA / TiO2-Ag / Ppy HFMs.

[0067] Depend on Figure 4 As can be seen, the inner surfaces of both PSF HFMs and PSF@PDA / TiO2-Ag / Ppy HFMs exhibit hydrophilicity, with instantaneous average contact angles of 31.2° and 57.8°, respectively. After 100 ms, the average contact angles decrease to 0° and 12.7°, respectively. During water supply, the inner surface of the membrane becomes wet and forms a strong binding force with water molecules, exhibiting stronger hydrophilicity during evaporation. This facilitates the rapid diffusion and transfer of water through the gradient pores within the membrane to the outer surface for photothermal evaporation. Figure 4 As shown in b, the average contact angles of the outer surfaces of PSF HFMs and PSF@PDA / TiO2-Ag / Ppy HFMs changed from 32.3° and 95.0° to 0° and 94.4° within 0-100 ms, indicating that the outer surface of PSF@PDA / TiO2-Ag / Ppy HFMs exhibits hydrophobicity. The difference in wettability between the inner and outer surfaces of the membrane facilitates salt diffusion, reduces salt deposition on the inner surface of the membrane, and thus improves the lifespan and photothermal conversion efficiency of the photothermal material. Figure 4 As shown in c, the siphon water supply height of PSF HFMs is 9.4 cm. Due to the multiple deposition of the hydrophobic photothermal layer Ppy, the siphon height of the composite photothermal film will inevitably decrease, but the siphon height of PSF@PDA / TiO2-Ag / PpyHFMs is still 8.0 cm, exhibiting good capillary water absorption capacity. In summary, PSF@PDA / TiO2-Ag / Ppy HFMs is a good composite membrane material with a Janus salt-resistant structure.

[0068] The surface microstructure of the composite photothermal hollow fiber membrane PSF@PDA / TiO2-Ag / Ppy HFMs was characterized by SEM, and the results are as follows: Figure 5 As shown in the scanning electron microscope images, the photothermal coating on the outer surface has almost no effect on the porosity of the inner surface of PSF@PDA / TiO2-Ag / Ppy HFMs, which still exhibit a very rich porous surface morphology. Figure 5a) Porosity is crucial for both capillary action and evaporation rate of water. Measurements show that the porosity of PSF@PDA / TiO2-Ag / Ppy HFMs is approximately 55.2%. Figure 4 d) Its interconnected pore structure facilitates the outward diffusion of water vapor, thereby improving evaporation efficiency. The photothermal modified coating forms a relatively uniform rough morphology on the outer surface of the film through disordered arrangement. Figure 5 b) can increase the optical path of incident light after multiple reflections and refractions, thereby improving light absorption efficiency. Figure 5 cd is a cross-sectional SEM image of PSF@PDA / TiO2-Ag / Ppy HFMs, whose porous, sponge-like structure provides a good guarantee for the rapid escape of water vapor during evaporation.

[0069] III. Characterization and Analysis of Surface Chemical Composition and Photothermal Properties

[0070] The chemical structure and elemental composition of PSF@PDA / TiO2-Ag / Ppy HFMs were characterized by FTIR and XPS, and the results are as follows: Figure 6 and Figure 7 As shown. Figure 6 The FTIR spectra of a show the chemical composition of PSF HFMs and PSF@PDA / TiO2-Ag / Ppy HFMs, 2914 cm⁻¹. -1 -CH, 1149cm -1 and 1239cm -1 -CH2 at 1486cm -1 The -CH3 groups at these locations are characteristic peaks of PSF HFMs. Introducing the photothermal modified coating weakens these characteristic peaks and introduces a peak at 575 cm⁻¹. -1 965cm -1 1205cm -1 1410cm -1 and 3230cm -1 No new characteristic peaks such as -NH2, C-OH, C-Si, CN, and NH were observed at the site. Characteristic peaks of PDA and Ppy were observed in the composite photothermal hollow fiber membrane, indicating that these two photothermal materials were successfully incorporated into PSF@PDA / TiO2-Ag / Ppy HFMs. XPS characterization was further performed to confirm the successful introduction of TiO2 and Ag. Figure 6 b and Figure 7 ad). In Figure 6 In b, compared to PSF HFMs, the O1s, N1s, and Si 2p contents of PSF@PDA / TiO2-Ag / Ppy HFMs are significantly increased. Figure 7The C 1s peak energy spectrum in a consists of CC / C=C (284.47 eV), CN (285.59 eV), C-OH (286.30 eV), C=O (288.69 eV), C-Si (283.45 eV), and π-π (291.00 eV) groups. Figure 7 The N1s peak energy spectrum in b consists of two peaks: NH (399.68 eV) and -NH2 (401.08 eV), which further proves the successful fixation of PDA and Ppy. Figure 6 In the PSF@PDA / TiO2-Ag / Ppy HFMs in b, two elements, Ti 2p and Ag 3d, were observed. Figure 7 The Ti 2p peak and Ag 3d peak of cd both prove that TiO2 and Ag have been successfully attached to the surface, while a small amount of Ag + The residue is due to Ag during the UV photoreduction modification process. + Not completely restored to Ag 0 The impact is minimal. The XPS and FTIR test results of the above PSF@PDA / CS-MWCNTs / Ppy HFMs both demonstrate the successful preparation of the composite photothermal hollow fiber membrane material.

[0071] To verify the solar thermal conversion capability of PSF@PDA / TiO2-Ag / Ppy HFMs, its light absorption performance in the wavelength range of 200-2500 nm was tested using a UV-Vis-NIR spectrometer. Figure 8 As shown, the transmittance and reflectance of blank PSF HFMs are significantly higher than those of composite photothermal hollow fiber membranes. The average light absorption rate in the 200-2500 nm wavelength range is only 53.4%, while the average solar absorption rate of PSF@PDA / TiO2-Ag / Ppy HFMs is as high as 95.4%, exhibiting a full-band absorption range of 200-2500 nm. The superior solar absorption capacity of PSF@PDA / TiO2-Ag / Ppy HFMs ensures efficient photothermal conversion in evaporation experiments.

[0072] The photothermal film module containing pure water and PSF@PDA / TiO2-Ag / Ppy HFMs was continuously tested under simulated sunlight switching conditions. Infrared images of temperature changes were obtained as follows: Figure 9 As shown, the temperature change curve is as follows: Figure 10 As shown. By Figure 9 It can be seen that PSF@PDA / TiO2-Ag / Ppy HFMs have obvious light and heat collection capabilities, and can concentrate heat at the interface for water evaporation. Figure 10When simulated sunlight was turned on, the surface temperature of the photothermal material rapidly increased. Under one minute of solar radiation, the surface temperature of PSF@PDA / TiO2-Ag / Ppy HFMs rose rapidly from 25℃ to 36.1℃. After 10 minutes, the temperature continued to rise slowly, and after 30 minutes, the average surface temperature of the photothermal material was 48℃, showing better photothermal conversion performance than PSF@PDA / CS-MWCNTs / PpyHFMs in Chapter 3. When the simulated sunlight source was turned off, the temperature of the composite photothermal hollow fiber membrane also dropped rapidly, indicating its rapid response to solar heat. These results show that the concentration of solar radiation heat in PSF@PDA / TiO2-Ag / PpyHFMs is significantly higher than that in pure water and PSF@PDA / CS-MWCNTs / Ppy HFMs, reducing unnecessary heat loss, improving energy utilization efficiency, and thus promoting the efficient generation of solar vapor. It has good solar thermal conversion capabilities and can serve as a highly efficient solar absorber for interfacial solar evaporation.

[0073] Example 5

[0074] Test results of solar interface evaporation desalination unit

[0075] The solar intensity of natural sunlight on a sunny day is approximately 0.8–1.2 kW·m. -2 The experiment used seawater from Beihai Lake as the experimental subject, and selected the 6 hours with the strongest sunlight (10:00-16:00) under natural sunlight. Figure 11 As shown in (b), the top conical glass plate rapidly fogged up within 20 minutes, and the water mist gradually increased over time, eventually turning into water droplets that fell. Temperature and humidity changes inside the desalination unit were measured using a temperature and humidity sensor probe during the 6-hour evaporation process. Figure 11 a) The temperature gradually increased from an initial 28℃, then remained relatively constant at 42–43.5℃ after 3 hours. The initial humidity was 45%. As the evaporation process progressed, water vapor increased significantly in the enclosed space, and the humidity rapidly increased to 70% within 30 minutes. After 1 hour, the rate of humidity increase gradually slowed down, eventually stabilizing between 85–90%. After 6 hours of evaporation, the PSF@PDA / TiO2-Ag / PpyHFMs interfacial evaporative desalination unit achieved 1.23 kg·m³ of moisture. -2 ·h -1 The average evaporation rate was 6.12 kg·m³. -2 Fresh water. This study confirmed that PSF@PDA / TiO2-Ag / Ppy HFMs can achieve good evaporation performance even in a closed system under natural light.

[0076] Strictly speaking, the saturation humidity in a closed system is 100%. During a photothermal evaporation experiment in a self-made interfacial evaporator desalination unit, the humidity... Figure 11 (a) It is known that the saturation humidity is approximately 90%, which is because the self-made desalination device has not yet reached a completely sealed condition, but the sealing performance is already quite good. To compare the evaporation efficiency of PSF@PDA / TiO2-Ag / Ppy HFMs in an open system (laboratory humidity approximately 50%) and a closed system (the self-made interfacial evaporation desalination device is considered to be under completely closed conditions, with a saturation humidity of approximately 100%), solar interfacial evaporation experiments were conducted under solar irradiance of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0, respectively. Figure 11 The evaporation rates and efficiencies of PSF@PDA / TiO2-Ag / Ppy HFMs in open and closed systems under different illumination conditions are demonstrated. Figure 11 It can be seen that under one solar irradiation, the evaporation efficiency of PSF@PDA / TiO2-Ag / Ppy HFMs in the open system is approximately 181%, while the evaporation efficiency in the closed system is only about 86%. This indicates that humidity conditions have a significant impact on solar interface evaporation. Furthermore, in the open system, the evaporation efficiency of PSF@PDA / TiO2-Ag / Ppy HFMs gradually decreases with increasing light intensity, and the evaporation rate also increases slowly. This is because water evaporates faster under high light intensity, while the water supply capacity of the composite photothermal film material is limited, unable to quickly provide enough water for photothermal evaporation. In the closed system, the humidity is very high, the evaporation rate of PSF@PDA / TiO2-Ag / Ppy HFMs increases relatively slowly, and the evaporation efficiency changes less with increasing light intensity.

[0077] To further evaluate the performance of the optimized PSF@PDA / TiO2-Ag / Ppy HFMs solar desalination device in practical applications under natural light, such as... Figure 13 As shown, seawater from Beihai, Guangxi, was used as the experimental subject. The desalination experiment was conducted during the 6 hours of strongest daily average sunlight (10:00-16:00), and the data was continuously monitored for 14 days, recording daily average temperature, humidity, light intensity, and evaporation. Figure 13 (a) It can be seen that the average temperature and humidity over 14 days were 29.3°C and 47.8%, respectively, and the average light intensity was 0.81 kW·m². -2 Simulated light (1kW·m²) was used in the laboratory. -2During laboratory experiments, the temperature and humidity are typically controlled at 25°C and 50-60%. For evaporation experiments, the average temperature and humidity under natural light over 14 days are slightly better than laboratory conditions, but the light intensity is lower and less stable than simulated light. Due to weather conditions, the sunlight intensity is weaker from day 5 to day 7, but the PSF@PDA / TiO2-Ag / Ppy HFMs solar desalination device can still successfully evaporate seawater and produce condensate. Figure 13 (b) The inset shows the change in seawater evaporation on the first and last days of the experiment. The two curves almost overlap. After optimization of the desalination unit, the average seawater evaporation rate under outdoor conditions for 14 days was 1.48 kg·m³. -2 ·h -1 Furthermore, the daily rate of evaporation remained relatively stable, indicating that, apart from weather influences, the photothermal material itself exhibits good long-term stability. No solar collectors were used during the experiment; the condensate collected was a product of natural sunlight incident on the interfacial evaporation desalination unit. Photothermal evaporation was carried out for 6 hours daily, and a total of 112.56 kg·m³ was collected over 14 days. -2 The freshwater yielded 1.34 kg·m³. -2 ·h -1 The average freshwater collection rate confirms the practicality of the PSF@PDA / TiO2-Ag / Ppy HFMs interfacial evaporative desalination device under natural light.

[0078] The effective evaporation of seawater by the PSF@PDA / TiO2-Ag / Ppy HFMs interfacial evaporator under natural sunlight has been proven. However, for seawater desalination applications, the condensate collected water sample should have low salinity to meet drinking water requirements. Therefore, ICP equipment was used to analyze four typical cations (Na+, Na+, and TiO2) in the seawater sample. + K + Mg 2+ and Ca 2+ The concentrations before and after desalination were measured, and the experimental results are as follows: Figure 14 shown. Na + K + Mg 2+ and Ca 2+ The concentrations of the four salt ions were 11255, 863, 952, and 895 mg·L, respectively. -1 The levels decreased to 9.25, 1.32, 0.96, and 1.15 mg·L⁻¹. -1 The removal rates were all above 99%. Compared with the initial water sample, the concentrations of major salt ions in the seawater met the standards for safe drinking water, which confirms the high efficiency of PSF@PDA / TiO2-Ag / Ppy HFMs in desalination and its great potential in practical applications in drinking water production.

[0079] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A solar-powered interfacial evaporation desalination device, characterized in that, It includes a cylindrical transparent body (1) and a conical transparent top cover (2) sealed on the transparent body (1). The transparent body (1) is provided with a water storage chamber (11) for storing seawater and a water collection tank (12) for collecting fresh water. The water storage chamber (11) is provided with an evaporator (3) for evaporating seawater. The water vapor evaporated by the evaporator (3) condenses into water on the transparent top cover (2) and is guided to the water collection tank (12) from the inner surface of the transparent top cover (2).

2. The solar interface evaporation desalination device according to claim 1, characterized in that, A support layer (4) floats on the surface of the seawater in the water storage cavity (11). The evaporator (3) is strip-shaped and passes through the support layer (4). The lower end of the evaporator (3) extends into the seawater, and its upper end extends out of the upper surface of the support layer (4).

3. The solar interface evaporation desalination device according to claim 1 or 2, characterized in that, The transparent top cover (2) is connected to an air extraction pipe (5), and the other end of the air extraction pipe (5) is connected to a water collection container (6) immersed in an ice-water mixture. A fan (7) is provided on the air extraction pipe (5).

4. The solar interface evaporation desalination device according to claim 1 or 2, characterized in that, The evaporator (3) is a composite photothermal hollow fiber membrane, and the preparation method of the composite photothermal hollow fiber membrane includes the following steps: S1. Hollow fiber membrane pretreatment: After sealing both ends of the hollow fiber membrane filaments, soak them in ethanol for 4-6 hours, wash them with water, and dry them for later use; take the dried membrane filaments to form bundled membrane modules with sealed ends - PSF HFMs modules for subsequent processing. The PSF HFMs module is composed of at least one membrane filament; seal both ends of the hollow fiber membrane filaments with waterproof adhesive, which is selected from epoxy adhesive and polyurethane adhesive. S2. Preparation of PSF@PDA / TiO2HFMs: The pretreated PSF HFMs components from step S1 are immersed in an impregnation solution for 5-7 hours to obtain PSF@PDA / TiO2 HFMs. The impregnation solution is prepared by mixing dopamine (DA), ammonium persulfate (APS), titanium dioxide (TiO2), and 3-aminopropyltriethoxysilane (APTES) in an 8-12 mM tris-HCl buffer solution with a pH of 8-9. The proportions of each component are as follows: 0.15-0.25 g DA, 0.05-0.07 g APS, 0.15-0.25 g TiO2, and 0.4-0.6 mL of 0.04-0.06 mol / L APTES aqueous solution are added to every 100-200 mL of tris-HCl buffer solution. S3. Preparation of PSF@PDA / TiO2-Ag HFMs: PSF@PDA / TiO2 HFMs were prepared by placing them in a 0.05–0.15 mol / L Ag solution. + The solution under UV light reduction reaction for 30–60 min yields active Ag ions. + PSF@PDA / TiO2-Ag HFMs were prepared by generating metallic Ag nanoparticles under ultraviolet light irradiation and loading them onto the film surface; the Ag... + The solutions are AgNO3, AgSO4, and AgCl. S4. Preparation of PSF@PDA / TiO2-Ag / Ppy HFMs: PSF@PDA / TiO2-Ag HFMs were placed in an APS aqueous solution and reacted at a low temperature of 2℃~8℃ for 1~2 hours. After wiping off the surface liquid, the surface of polypyrrole (Ppy) was polymerized 1~3 times using chemical vapor deposition. After the reaction was completed, the surface residue was washed with deionized water and dried to obtain PSF@PDA / TiO2-Ag / Ppy HFMs. The concentration of the APS aqueous solution was prepared according to the following ratio: 2~3g APS dissolved in 80~100ml of deionized water.

5. The solar interface evaporation desalination device according to claim 4, characterized in that, The PSF HFMs module is formed by sealing both ends of several hollow fiber membrane filaments with waterproof adhesive and bonding the ends of multiple filaments together; the PSF HFMs module is composed of 2-100, 2-80, or 5-60 hollow fiber membrane filaments; the length of the hollow fiber membrane filaments is 5-50 cm, the average pore size of the hollow fiber membrane ranges from 0.01 to 2.0 μm, the porosity ranges from 20-80%, the membrane thickness ranges from 50 to 500 μm, and the inner and outer diameters of the hollow fibers range from 0.1-2.0 mm and 0.25-3.5 mm, respectively; the hollow fiber membrane is a polysulfone hollow fiber membrane; In step S4, 30–60 μl of py is used for chemical vapor deposition for each Ppy surface polymerization reaction.

6. The solar interface evaporation desalination device according to claim 4, characterized in that, The impregnation solution in step S2 is prepared as follows: 0.1211g of tris is dissolved in 100ml of water, and then the pH is adjusted to 8.5 with 20% HCl to obtain a 10mM tris-HCl buffer solution; 0.2g of DA, 0.06g of APS, 0.2g of TiO2, and 0.5mL of APTES aqueous solution with a concentration of 0.05mol / L are weighed and added to the previously prepared tris-HCl buffer solution and dispersed evenly to obtain the impregnation solution.

7. The solar interface evaporation desalination device according to claim 4, characterized in that, Steps S3 and S4 are as follows: S3. Preparation of PSF@PDA / TiO2-Ag HFMs: PSF@PDA / TiO2HFMs were placed in 0.1 mol / L AgNO3 solution and subjected to UV photoreduction reaction under a UV lamp for 30 min to obtain the active ion Ag. + PSF@PDA / TiO2-Ag HFMs were prepared by generating metallic Ag nanoparticles under ultraviolet light irradiation and loading them onto the film surface. S4. Preparation of PSF@PDA / TiO2-Ag / Ppy HFMs: The concentration of the APS aqueous solution is prepared according to the following ratio: Dissolve 2-2.5g of APS in 80-100ml of deionized water. Place the PSF@PDA / TiO2-Ag HFMs in the APS aqueous solution and react at a low temperature of 2℃-8℃ for 0.7-1.2h. After wiping off the residual liquid on the surface, prepare a petri dish and a large beaker. Fix one end of the membrane module in the petri dish. Drop 35-50μl of py into the beaker. Invert the petri dish onto the large beaker, allowing the membrane module to be inserted into the beaker and suspended in the beaker. Then dry in a vacuum drying oven at 50-70℃ for 1-2h to complete the first polypyrrole (Ppy) vapor phase chemical deposition. Repeat the step of dropping py into the beaker for vapor phase chemical deposition 1-3 times. After the Ppy surface polymerization reaction is completed, wash off the surface residue with deionized water and dry to obtain PSF@PDA / TiO2-Ag / Ppy. HFMs.

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