Downward evaporation portable photo-thermal drinking water purifier and manufacturing method and application thereof

Abstract

The application discloses a portable downward evaporation photothermal drinking water purifier and a manufacturing method and application thereof. The purifier is composed of a purifier core accessory, a water storage cup to be treated and a clean water collecting cup. The core accessory comprises a heat insulation protective layer, a photothermal conversion layer, a water supply channel, a water-proof air-permeable layer and a porous condensation layer. The heat insulation protective layer is a high-transparency anti-fog plate, the high-efficiency photothermal material is deposited on the upper surface of the water supply channel as the photothermal conversion layer, the water supply channel supplies water through capillary force, the water-proof air-permeable layer composed of a hydrophobic air-permeable film and a rigid mesh sheet is tightly attached to the lower surface of the photothermal conversion layer, and the porous condensation layer is below the water-proof air-permeable layer. The downward evaporation design avoids the loss of incident light caused by the condensation of steam above the photothermal material, and the condensation heat is used to heat the water to be treated. The purifier operates under solar radiation, and can complete efficient light steam conversion and convenient drinking water condensation collection without other energy supply, and can be used to solve the problems of lack of fresh water and sewage treatment.

Description

Technical Field

[0001] This invention relates to the field of solar thermal evaporation and seawater desalination devices, and in particular to a portable solar thermal water purifier for solar thermal evaporation seawater desalination, its manufacturing method, and its application. Background Technology

[0002] Freshwater scarcity has become an increasingly serious global problem, with more than one-third of the world's population facing water shortages. Industrial and domestic wastewater discharge exacerbates groundwater pollution, leaving many island and reef areas facing a situation of having access to water but no water.

[0003] Interfacial localized solar water evaporation technology utilizes photothermal conversion materials to absorb incident sunlight and efficiently convert it into heat, heating the liquid water at the interface to produce water vapor. In today's world of scarce freshwater and energy resources, this process has broad application prospects in large-scale power generation, seawater desalination, wastewater treatment, medical disinfection, and distillation separation due to its advantages such as low cost, no secondary pollution, and no consumption of fossil fuels other than solar energy. Compared to commercial freshwater production methods such as multi-stage flash evaporation and reverse osmosis, which have high requirements for infrastructure, energy consumption, and centralized installation, high-efficiency interfacial localized solar thermal water purifiers have lower facility requirements and operating costs. Therefore, exploring and developing simple-to-configure, independently operating high-efficiency solar thermal water purifiers is highly attractive.

[0004] Improving the energy conversion efficiency and water collection capacity of solar thermal water purifiers is a research hotspot. Previous researchers have used interfacial solar local heating and novel solar thermal material designs to improve solar energy absorption and energy conversion efficiency, and achieved higher water collection rates and performance stability by suppressing heat loss and implementing effective anti-salt accumulation strategies. The literature *Energy & Environmental Science*, 13(2020) 3, 830-839, reports a solar-driven multi-stage membrane evaporation device that achieves a breakthrough in photo-vapor conversion efficiency by recovering and reusing the enthalpy of vaporization, using the heat released from each stage of steam condensation for the next stage of water evaporation. However, most current research and design of solar thermal water purifiers focuses on improving the solar thermal water evaporation capacity through localized thermal evaporation and multi-stage evaporation designs, without exploring corresponding device design strategies from a holistic perspective of light absorption, heat management, water transport, and condensate layer design. Summary of the Invention

[0005] The main objective of this invention is to provide a portable solar thermal drinking water purifier that is easy to prepare and can operate independently. This solar thermal water purifier can be used in scenarios such as seawater desalination and sewage treatment. By using the solar thermal water purifier, clean drinking water can be obtained solely through solar photovoltaic steam conversion without consuming any fossil energy or electrical energy.

[0006] The technical solution adopted in this invention is as follows:

[0007] A portable photothermal drinking water purifier with downward evaporation technology comprises three components. The first part is the core component of the photothermal water purifier, where the three photothermal water treatment stages—full-spectrum solar radiation absorption, solar photovoltaic vapor conversion, and vapor condensation—and the recovery and release of latent heat occur within this structure. The process of the photothermal material absorbing sunlight and converting it into heat to heat liquid water and generate steam occurs at the interface between the photothermal material and water, belonging to interfacial photothermal evaporation technology. The steam generated at the photothermal material interface further diffuses and condenses downwards from the photothermal material; therefore, the purifier is a downward evaporation type photothermal water purifier. The second part is a cylindrical cup for storing the water to be treated, continuously supplying water for the photothermal evaporation process in the first part. The third part is a cup for collecting the clean water obtained from the condensation of steam in the first part. The cup is made of one or more of acrylic, polypropylene, and polycarbonate. The first part of the cup is supported on the side wall of the second part's opening by a wide, outwardly projecting edge at the top, but it is not permanently sealed. The first part is nested within the second part of the cup body, with a certain gap between the side walls of the first and second parts. A small opening on one side of the bottom surface of the first part of the water purifier connects to a thin tube, the other end of which connects to an opening on one side of the bottom surface of the second part. Both ends of the thin tube are completely sealed at the openings. At the center of the bottom of the first part of the water purifier, there is also an opening with a diameter of 5-20 mm. A sleeve is fixedly connected to the opening, the inside of which is used to insert a water-absorbing fiber supply channel, and the outside is the condensation zone of the photothermal water purifier. Therefore, this tube separates the water source to be treated from the condensate. The second and third parts of the photothermal water purifier cup body are sealed using one or more of the following methods: threads, snaps, and clamps. This allows for easy assembly or disassembly and ensures the excellent sealing performance of the photothermal water purifier.

[0008] The first part of the photothermal water purifier integrates the main component structures, including a heat insulation layer, a photothermal conversion layer, a breathable and waterproof layer, a porous condensation layer, and a water supply channel.

[0009] The heat insulation layer is made of one of the following materials: acrylic sheet, aerogel sheet, and glass sheet, with a thickness of 1-6 mm. Choosing a material with high light transmittance and low thermal conductivity reduces the loss of solar radiation reaching the photothermal material and also provides insulation, suppressing heat dissipation from the photothermal conversion layer. Furthermore, the heat insulation layer also seals and protects the internal structure of the photothermal water purifier. To prevent steam condensation and surface fogging on the inner surface of the heat insulation layer during use, a commercial hydrophilic coating of nano-silica and titanium dioxide is applied to the inner surface of the heat insulation layer to prevent light loss during sunlight penetration into the photothermal material due to water droplet accumulation.

[0010] The photothermal conversion layer is composed of hollow multi-shell photothermal material deposited on capillary fiber material. The capillary fiber material is one or more of degreased cotton, absorbent paper, and cellulose membrane. The loading of the photothermal material on the surface of the photothermal conversion layer is 1-20 mg·cm⁻¹. -2 The photothermal conversion layer of the photothermal water purifier is closely attached to the lower surface of the heat insulation protective layer, and the interfacial solar photovoltaic vapor conversion process takes place in this layer. The assembly steps of the photothermal conversion material and the water supply channel include: First, cutting water-absorbing fiber sheets with a thickness of 3-20 mm, peeling the water-absorbing fiber sheets into upper and lower layers, avoiding the central part of the fiber sheet during peeling, so that the water-absorbing fibers in the central area remain connected as a whole, gathering the peeled lower layer of water-absorbing fibers towards the center to form a vertical column and fixing it, and making the upper layer of water-absorbing fiber sheet into one of the following shapes: lotus leaf, umbrella, and mushroom, to obtain the water supply channel; then, the photothermal material with a hollow multi-shell structure is uniformly dispersed in a dispersant by ultrasound, and the resulting suspension is deposited on the horizontal upper surface of the water supply channel to form a uniform light absorber layer, so that the photothermal material is in close contact with the upper surface of the water-absorbing fiber sheet of the water supply, to obtain the photothermal conversion layer.

[0011] The stem portion of the water supply channel, passing through the sleeve in the center of the first part of the cup, is completely immersed in the water source to be treated. Water is continuously supplied to the horizontal surface of the water supply channel, which is tightly connected to it, through capillary force. The upper horizontal water supply channel, coated with photothermal material, is supported by the cup on the surface of the photothermal water purifier and does not directly contact the water stored in the second part below. The water supply channel ensures a sufficient water supply while reducing heat loss through conduction to the water to be treated.

[0012] The breathable and waterproof layer consists of a hydrophobic and breathable membrane and a rigid mesh. The hydrophobic and breathable membrane is either a polytetrafluoroethylene (PTFE) membrane or a polyvinylidene fluoride (PVDF) membrane. The breathable but waterproof membrane is located on the lower surface of the upper horizontal water supply channel, preventing the treated water in the water supply channel from seeping downwards and contaminating the clean water generated in the lower condensation layer, while ensuring that steam can diffuse downwards unimpeded. The rigid mesh, located on the lower surface of the hydrophobic and breathable membrane, can be used to create a millimeter-level space between the photothermal conversion layer and the condensation layer as an interlayer air gap. This interlayer air gap helps reduce heat dissipation caused by direct contact between the photothermal conversion layer and the condensation layer, preventing further temperature increases in the condensation layer.

[0013] The porous condensation layer utilizes a porous metal material with high thermal conductivity, specifically one or more of foamed aluminum, foamed copper, and foamed nickel. Compared to traditional straight-tube, serpentine, finned, and harp-type steam condensation layers, porous metal is not only easier to process, but also, within the same volume, has a specific surface area several times that of a planar structure, significantly increasing the contact area between the condensing material and the steam. Secondly, the three-dimensional topology of porous metal is more conducive to the aggregation of surface condensate droplets, which are then removed from the porous metal under gravity. Finally, porous metal materials have various porosities and thicknesses, allowing the condensation rate to be influenced by adjusting the porosity. In summary, a porous metal with a pore density of 10-100 ppi, a thickness of 20-100 mm, and a central cylindrical opening was chosen as the condensation layer for the solar thermal water purifier.

[0014] Furthermore, hydrophilic modification is achieved by coating the porous metal surface with nano-silica particles: First, the cut commercial porous metal is immersed in deionized water and anhydrous ethanol in sequence and ultrasonicated for 5-30 min respectively to make the porous metal surface clean and free of stains; then the porous metal is immersed in a mixed solution of 5-50 mL deionized water, 0.5-10 mL ammonia water and 10-200 mL anhydrous ethanol; separately, 1-10 mL of tetraethyl orthosilicate is diluted in 10-200 mL anhydrous ethanol, and the diluted tetraethyl orthosilicate solution is slowly dripped into the above solution containing the porous metal. After stirring at room temperature for 0.5-24 h, the porous metal is taken out, the surface of the porous metal is rinsed with ethanol to remove the residual liquid, and then dried with nitrogen.

[0015] This invention discloses a method for obtaining drinking water through photothermal steam distillation: Water to be treated is added to a cup, and the surface of the photothermal conversion layer is irradiated. The stem of the water supply channel is immersed in the water. First, capillary action drives the water to rise to the horizontal interface of the photothermal conversion layer. The photothermal material converts the absorbed solar energy into heat energy, which is transferred downwards to the liquid water at the interface, causing it to evaporate and generate steam. Driven by temperature and pressure gradients, the steam passes downwards from the photothermal conversion layer through a hydrophobic and breathable membrane and air gaps, diffusing downwards to the porous condensation layer, where it condenses and releases heat to obtain clean water. The latent heat released by condensation preheats the water to be treated in the capillary core of the water supply channel stem and the water stored in the second part of the water purifier, thereby improving the photothermal steam conversion efficiency. Since the first part of the water purifier, where the condensation layer is located, is completely immersed in the water, the water cools the condensation layer, creating a large temperature and vapor pressure gradient between the photothermal conversion layer and the condensation layer. Therefore, the steam generated by the photothermal conversion layer can diffuse downwards to the condensation layer with a stable steam flux. Finally, the clean water collected through the photo-vapor conversion and condensation process flows into the third section of the water purifier through a conduit extending from the bottom of the first section, preventing secondary pollution of the clean water by the external environment. Meanwhile, the easy-to-disassemble feature of the third section allows for convenient and immediate access to the collected clean water.

[0016] The present invention has the following beneficial effects:

[0017] 1. In traditional photothermal water purifiers, steam condenses on the inner wall of the transparent cover above the photothermal material. The condensed droplets cause light reflection and scattering, which adversely affects the light absorption rate of the photothermal material. In this invention, evaporation and steam diffusion occur on the back side of the photothermal conversion layer. Therefore, the condensation of steam will not affect the light capture of the photothermal material in the water purifier.

[0018] 2. The condensation layer is designed to be positioned below the water surface of the water to be treated stored in the second part of the water purifier. Therefore, the latent heat released during the condensation process is recovered and used to preheat the water to be treated stored in the second part of the water purifier, which is beneficial to improving the system's photo-steam conversion efficiency.

[0019] 3. The water supply channel is designed in one of the following shapes: lotus leaf, mushroom, and umbrella. This type of water supply channel can provide water to the photothermal conversion layer to meet the evaporation rate, while reducing the contact area between the photothermal evaporation layer and the water to be treated stored in the second part of the water purifier below. This greatly limits the unnecessary dissipation of heat from the photothermal conversion layer to the water to be treated.

[0020] 4. All components of the solar thermal water purifier are made of inexpensive and readily available materials, and each part is structurally independent, ensuring that each part is easy to disassemble and replace. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the portable photothermal drinking water purifier with downward evaporation according to the present invention. In the figure, 1 is the first part of the photothermal water purifier, 2 is the cup for storing the water source to be treated, and 3 is the cup for collecting the clean water.

[0022] Figure 2 yes Figure 1 A schematic diagram of the AA cross section, in which 11. heat insulation layer, 12. photothermal conversion layer, 13. breathable and waterproof layer, 14. porous condensation layer, 15. water supply channel;

[0023] Figure 3 This is a schematic diagram of the working principle of the portable photothermal drinking water purifier with downward evaporation according to the present invention. In the diagram, B represents the direction of heat transfer, and C represents the direction of steam transfer.

[0024] Figure 4 This is a graph showing the change in water collection rate of a photothermal drinking water purifier before and after different structural optimizations.

[0025] Figure 5 Changes in the water collection rate of a gapless photothermal drinking water purifier during long-term seawater desalination.

[0026] Figure 6 Changes in the water collection rate of a photothermal drinking water purifier with an air gap during long-term seawater desalination.

[0027] Figure 7 The water evaporation rate of different photothermal conversion materials;

[0028] Figure 8 This is a comparison chart of ion concentrations in the condensate obtained from seawater desalination using seawater and solar thermal drinking water purifiers. Detailed Implementation

[0029] To make the description of the objectives, technical solutions, and advantages of this invention clearer and more complete, the invention will be further described in detail with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only used to illustrate the technical concept and structural features of this invention and do not constitute a limitation on the scope of protection of this invention. Example 1

[0030] like Figure 1 and Figure 2 As shown, the portable photothermal water purifier with downward evaporation is divided into three parts. The first part 1 contains the core component structure of the photothermal water purifier, including a heat insulation layer 11, a photothermal conversion layer 12, a breathable and waterproof layer 13, a porous condensation layer 14, and a water supply channel 15.

[0031] The first part 1 and the second part 2 are nested together in an acrylic cup body. The second part 2 and the third part 3 are connected by threads. The water to be treated is added into the second part 2 cup body through the central sleeve of the first part 1, and the water level approaches the mouth of the cup body.

[0032] A copper foam with a pore density of 10 ppi and a thickness of 40 mm is placed in the first part 1 cup body, and the copper foam is nested outside the sleeve in the center of the cup body; the mesh sheet is horizontally placed on the narrow step cut out at the mouth of the first part 1 cup.

[0033] Cut a 10 mm thick degreased cotton sheet and peel it into two layers (the upper layer is about 6 mm thick and the lower layer is about 4 mm thick). Avoid the central area of ​​the fiber sheet when peeling, so that the degreased cotton in the central area remains connected. Gather the peeled lower layer of degreased cotton towards the center to form a vertical column and fix it, so that the degreased cotton sheet forms a lotus leaf-shaped structure, thus obtaining the water supply channel 15.

[0034] Hollow multi-shell structured photothermal material is uniformly dispersed in a dispersant using ultrasound. The suspension of the material is then deposited onto the horizontal upper surface of the water supply channel 15 composed of degreased cotton, forming a uniform light-absorbing layer. This ensures close contact between the photothermal material and the upper surface of the degreased cotton sheet used for water supply. The deposition amount of the photothermal material is 10 mg·cm³. -2 A photothermal conversion layer 12 was prepared.

[0035] A hole is made in the center of the polytetrafluoroethylene membrane so that the vertical stem of the water supply channel passes through this hole. The membrane is placed on the lower surface of the horizontal area of ​​the water supply channel 15 to prevent the water to be treated from flowing down from the edge of the degreased cotton sheet and contaminating the porous condensation layer 14. The stem of the water supply channel is inserted downward into the water to be treated through the central sleeve of the first part 1 cup body until the polytetrafluoroethylene membrane comes into contact with the upper surface of the placed rigid mesh sheet to form a breathable and waterproof layer 13.

[0036] After washing and drying a 3 mm thick acrylic sheet with deionized water, immerse it in a saturated sodium hydroxide ethanol solution and sonicate it for 20 minutes. Then remove it, rinse off the residual alkali solution on the surface with deionized water, and blow it dry with nitrogen to remove oil, dust and water marks. Use a scraper to evenly apply a hydrophilic coating agent of nano-silica and nano-titanium dioxide to the surface of the acrylic sheet, let it air dry naturally, and then scrape and dry it again to obtain a hydrophilic and anti-fogging heat insulation protective layer 11.

[0037] A highly transparent and hydrophilic acrylic sheet is tightly covered on the upper surface of the photothermal conversion layer 12, which is deposited with hollow multi-shell material, to seal the photothermal water purifier and complete the assembly of the heat insulation protection layer 11. Example 2

[0038] The first part 1 and the second part 2 are nested together as polycarbonate cups. The second part 2 and the third part 2 are connected by a snap fastener. The water to be treated is added into the second part 2 cup through the central sleeve of the first part 1, and the water level approaches the mouth of the cup.

[0039] A nickel foam with a pore density of 100 ppi and a thickness of 100 mm is placed in the first part 1 cup body, and the nickel foam is nested outside the sleeve in the center of the cup body; the mesh sheet is horizontally placed on the narrow step cut out at the mouth of the first part 1 cup.

[0040] Cut a 20 mm thick absorbent fiber sheet and peel it into two layers (the upper layer is about 15 mm thick and the lower layer is about 5 mm thick). Avoid the central area of ​​the fiber sheet during peeling, so that the absorbent fibers in the central area remain connected. Gather the peeled lower absorbent fibers towards the center to form a vertical column and fix it. Bend the upper absorbent fibers and make the entire absorbent fiber sheet into a mushroom-shaped structure to obtain the water supply channel 15.

[0041] Hollow multi-shell photothermal material is uniformly dispersed in a dispersant using ultrasound. The suspension of the material is then deposited onto the horizontal upper surface of the water supply channel 15 composed of absorbent fibers, forming a uniform light-absorbing layer. This ensures close contact between the photothermal material and the upper surface of the absorbent fiber sheet used for water supply. The deposition amount of the photothermal material is 20 mg·cm³. -2 A photothermal conversion layer 12 was prepared.

[0042] A hole is made in the center of the polyvinylidene fluoride membrane so that the vertical stem of the water supply channel passes through this hole. The membrane is placed on the lower surface of the horizontal area of ​​the water supply channel 15 to prevent the water to be treated from flowing down from the edge of the absorbent fiber sheet and contaminating the porous condensation layer 14. The stem of the water supply channel is inserted downward into the water to be treated through the central sleeve of the first part 1 cup body until the polyvinylidene fluoride membrane comes into contact with the upper surface of the placed rigid mesh sheet to form a breathable and waterproof layer 13.

[0043] After washing and drying a 1 mm thick glass slide with deionized water, immerse it in a saturated sodium hydroxide ethanol solution and sonicate it for 20 minutes. Then remove it, rinse off the residual alkali solution on the surface with deionized water, and blow it dry with nitrogen to remove oil, dust and water marks. Use a scraper to evenly apply a hydrophilic coating agent of nano-silica and nano-titanium dioxide to the surface of the glass slide, let it air dry naturally, and then scrape and dry it again to obtain a hydrophilic and anti-fogging heat insulation protective layer 11.

[0044] A highly transparent, hydrophilic glass sheet is tightly covered on the upper surface of the photothermal conversion layer 12, on which hollow multi-shell material is deposited, thus sealing the photothermal water purifier and completing the assembly of the heat insulation protection layer 11. Example 3

[0045] The first part 1 and the second part 2 are nested together as polypropylene cups. The second part 2 and the third part 3 are connected by clamps. The water to be treated is added into the second part 2 cup through the central sleeve of the first part 1, and the water level approaches the mouth of the cup.

[0046] Aluminum foam with a pore density of 40 ppi and a thickness of 20 mm is placed in the first part 1 cup body, and the aluminum foam is nested outside the sleeve in the center of the cup body; the mesh sheet is horizontally placed on the narrow step cut out at the mouth of the first part 1 cup.

[0047] Cut a 3 mm thick absorbent fiber sheet and peel it into two layers (the upper layer is about 2 mm thick and the lower layer is about 1 mm thick). Avoid the central area of ​​the fiber sheet during peeling, so that the absorbent fibers in the central area remain connected. Gather the peeled lower absorbent fibers towards the center to form a vertical column and fix it. Bend the upper absorbent fibers downward so that the entire absorbent fiber sheet is made into an umbrella-shaped structure, thus obtaining the water supply channel 15.

[0048] Hollow multi-shell structured photothermal material is uniformly dispersed in a dispersant using ultrasound. The suspension of the material is then deposited onto the horizontal upper surface of the water supply channel 15 composed of absorbent fibers, forming a uniform light-absorbing layer. This ensures close contact between the photothermal material and the upper surface of the absorbent fiber sheet used for water supply. The deposition amount of the photothermal material is 1 mg·cm³. -2 A photothermal conversion layer 12 was prepared.

[0049] A hole is made in the center of the polytetrafluoroethylene membrane so that the vertical stem of the water supply channel passes through this hole. The membrane is placed on the lower surface of the horizontal area of ​​the water supply channel 15 to prevent the water to be treated from flowing down from the edge of the absorbent fiber sheet and contaminating the porous condensation layer 14. The stem of the water supply channel is inserted downward into the water to be treated through the central sleeve of the first part 1 cup body until the polytetrafluoroethylene membrane comes into contact with the upper surface of the placed rigid mesh sheet to form a breathable and waterproof layer 13.

[0050] After washing and drying the 6 mm thick aerogel sheet with deionized water, it was immersed in a saturated sodium hydroxide ethanol solution and sonicated for 20 min. After removing it, the surface was rinsed with deionized water to remove the residual alkali solution and then dried with nitrogen gas to remove oil, dust and water marks. The nano-silica and nano-titanium dioxide hydrophilic coating agent was evenly applied to the surface of the aerogel sheet with a scraper and allowed to air dry naturally. The coating was then applied and dried again to obtain a hydrophilic and anti-fogging heat insulation protective layer 11.

[0051] A highly permeable and hydrophilic aerogel sheet is tightly covered on the upper surface of the photothermal conversion layer 12, which is deposited with hollow multi-shell material, thus sealing the photothermal water purifier and completing the assembly of the heat insulation protection layer 11. Example 4

[0052] To optimize the water collection rate of the solar thermal water purifier, this embodiment optimizes the hydrophilicity and hydrophobicity of the porous condensation layer 14 of the solar thermal water purifier based on Embodiment 1. Two pieces of porous copper foam of the same size were selected. One piece of porous copper foam was coated with nano-silica particles for hydrophilic treatment, while the other piece of copper foam was not treated.

[0053] The method for hydrophilic treatment of the surface of foamed copper is as follows: hydrophilic modification is achieved by coating the surface of porous foamed copper with nano-silica particles. First, the cut commercial foamed copper is immersed in deionized water and anhydrous ethanol in sequence and ultrasonicated for 15 min each to make the surface of the foamed copper clean and free of stains. Then, the foamed copper is immersed in a mixed solution of 30 mL deionized water, 2 mL ammonia water and 200 mL anhydrous ethanol. 5 mL of tetraethyl orthosilicate is diluted with 100 mL of anhydrous ethanol and slowly dripped into the above solution containing the foamed copper. After stirring at room temperature for 3 h, the foamed copper is taken out, rinsed with ethanol to remove the residual liquid on the surface of the foamed copper and dried with nitrogen.

[0054] The untreated commercial foamed copper surface exhibited a water contact angle of 101.8°, demonstrating hydrophobicity. The contact angle of the hydrophilic treated foamed copper was 27.1°, indicating a significant improvement in the hydrophilicity of the porous condensation layer 14. Furthermore, due to the corrosion resistance, oxidation resistance, and chemical stability of silica, using silica-coated foamed copper as the porous condensation layer 14 prevents oxidation of the foamed copper in high-temperature and humid environments, thereby eliminating contamination of condensate caused by corrosion.

[0055] Hydrophilic and non-hydrophilic treated copper foams were assembled into a photothermal water purifier as described in Example 1, and water collection rate tests were performed separately. The photothermal material deposited in the photothermal conversion layer of the photothermal water purifier was a three-shell Fe3O4 / C hollow multi-shell material. The water collection rate test conditions were: an irradiance of 1 kW·m² provided by a solar light source simulator. -2 The light intensity was calibrated using a light intensity meter. The photothermal water purifier was placed under the light source and irradiated. After the photothermal water purifier reached a stable state, the timing test was started. After a period of time, the amount of clean water collected in the third cup of this stage was recorded using a balance to evaluate the water collection rate of the photothermal water purifier.

[0056] like Figure 4 As shown, when untreated hydrophobic copper foam is used as the porous condensation layer 14, the water collection rate of the solar thermal water purifier is 1.13 kg·m³. -2 ·h -1 When the porous condensation layer of copper foam with a hydrophilic surface treatment is used, the water collection rate of the solar thermal water purifier is 1.58 kg·m³. -2 ·h -1 The water collection performance of solar thermal water purifiers has been significantly improved. Example 5

[0057] This embodiment optimizes the porosity of the porous condenser layer 14 in the photothermal water purifier of Example 1. Two common pore densities, 20 ppi and 40 ppi, were selected as the porous condenser layers 14 of the photothermal water purifier, respectively. After surface hydrophilic treatment, the water collection rates of the photothermal water purifiers were tested and compared under the same conditions.

[0058] The photothermal materials in the photothermal water purifier all adopt a three-shell Fe3O4 / C hollow multi-shell material, with a power output of 1 kW·m -2 The photothermal water collection rate was tested under solar radiation. After the photothermal water purifier reached a stable state, the mass change of the clean water collected in the third cup was recorded using a balance, and the test time was also recorded.

[0059] like Figure 4 As shown, with a copper foam pore density of 20 ppi, the water collection rate of the photothermal water purifier is 1.76 kg·m³. -2 ·h -1 At 40 ppi, the corresponding water collection rate of the solar thermal water purifier is 1.43 kg·m³. -2 ·h -1 20 ppi of foamed copper showed better condensation performance. Example 6

[0060] To optimize the water collection rate of the photothermal water purifier, this embodiment optimizes the air gap structure between the photothermal conversion layer 12 and the porous condensation layer 14 based on Embodiment 1. A non-toxic, odorless, high-temperature resistant, corrosion-resistant, and highly resilient high-density polyethylene and polypropylene mesh is used as a rigid frame to create an air gap between the photothermal conversion layer 12 and the porous condensation layer 14. The mesh thickness is 3 mm. All photothermal materials in the photothermal water purifier are three-shell Fe3O4 / C hollow multi-shell materials, achieving a 1 kW·m... -2 The photothermal water collection rate was tested under solar radiation. After the photothermal water purifier reached a stable state, the mass change of the clean water collected in the third cup was recorded using a balance, and the test time was also recorded.

[0061] When there is no air gap between the photothermal conversion layer 12 and the porous condensation layer 14, the steady-state water collection rate of the photothermal water purifier is 1.57 kg·m³. -2 ·h -1 When air gaps are created using mesh panels, the steady-state water collection rate of the solar thermal water purifier is 1.78 kg·m³. -2 ·h -1 .

[0062] Figure 5 and Figure 6This study tested the stability of the water collection rate during long-term seawater desalination using two photothermal water purifiers: one without interlayer air gaps and one with interlayer air gaps. The photothermal water purifiers underwent seawater desalination testing for 8 hours daily for 10 days, and the steady-state water collection rate was recorded daily. The results showed that the water collection rate of both photothermal water purifiers did not decrease during long-term seawater desalination, and the water collection rate of the photothermal water purifier with interlayer air gaps remained stable at 1.8 kg·m³. -2 ·h -1 Around 1.55 kg·m³, the water collection rate of the photothermal water purifier, which has no interlayer air gaps, remains stable. -2 ·h -1 Both have good performance stability and service life. Example 7

[0063] In this embodiment, the photothermal conversion materials of Example 1 were optimized. Fe3O4 / C hollow multi-shell material with excellent photothermal performance and amorphous Ta2O5 / C hollow multi-shell material with strong environmental resistance and high water evaporation rate were selected as the photothermal conversion materials for the photothermal water purifier.

[0064] like Figure 7 As shown, the three-shell Fe3O4 / C hollow multi-shell material at 1 kW·m -2 The photothermal evaporation rate under solar irradiation is 3.58 kg·m³. -2 ·h -1 Amorphous two-shell Ta₂O₅ / C hollow multi-shell structure at 1 kW·m -2 It exhibited a remarkable photothermal evaporation rate of 3.97 kg·m³ under solar irradiation. -2 ·h -1 .

[0065] At 1 kW·m -2 The water collection rate of a solar thermal water purifier was tested under solar irradiation. For example... Figure 4 As shown, the water collection rate of the amorphous Ta2O5 / C hollow multi-shell material photothermal water purifier is 1.9 kg·m. -2 ·h -1 This is higher than the 1.78 kg·m³ of Fe3O4 / C hollow multi-shell material photothermal water purifier. -2 ·h -1 .

[0066] like Figure 8As shown, the concentrations of all ions in the clean water obtained after seawater desalination by the photothermal water purifier meet the drinking water standards stipulated by the World Health Organization. This indicates that the portable photothermal drinking water purifier designed in this invention, which is simple to configure, operates independently, and whose components are easy to disassemble and assemble, has high-performance seawater desalination capabilities and has practical application value for wastewater treatment and drinking water access in coastal or remote areas.

Claims

1. A portable photothermal drinking water purifier with downward evaporation, characterized in that, The photothermal drinking water purifier is divided into three parts. The first part (1) is the core component of the photothermal drinking water purifier, and the photothermal evaporation water purification process occurs inside the first part (1). The second part (2) is a cup for storing the water source to be treated, which continuously supplies water for the photothermal evaporation process of the first part (1). The third part (3) is a cup for collecting the clean water obtained by the condensation of the steam of the first part (1). The core component (1) of the photothermal drinking water purifier includes a heat insulation layer (11), a photothermal conversion layer (12), a breathable and waterproof layer (13), a porous condensation layer (14), and a water supply channel (15). The cup body of the photothermal drinking water purifier is made of one or more of acrylic, polypropylene and polycarbonate. The first part (1) is supported on the side wall of the cup mouth of the second part (2) by a wide outer edge protruding outward in the horizontal direction at the top, so that the first part (1) is nested in the cup body of the second part (2), and there is a gap between the side wall of the first part (1) and the side wall of the second part (2). The first part (1) of the photothermal drinking water purifier has an opening on one side of the bottom surface and a thin tube is connected to it. The other end of the thin tube is connected to the opening on one side of the bottom surface of the second part (2). The connection between the two ends of the thin tube and the opening is completely sealed. The first part (1) of the photothermal drinking water purifier has an opening at the center of the bottom. A sleeve is fixedly connected to the opening. The sleeve is used to insert a water supply channel composed of water-absorbing fibers. The outside of the sleeve is the porous condensation layer (14) of the photothermal drinking water purifier. The water supply channel (15) is composed of one or more capillary fiber materials selected from degreased cotton, absorbent paper and cellulose membrane. The water supply channel is one of lotus leaf shape, umbrella shape and mushroom shape. The stem of the water supply channel passes through the sleeve in the center of the first part (1) and is immersed in the water source to be treated. The photothermal conversion layer (12) is formed by uniformly depositing a photothermal material with a hollow multi-shell structure on the horizontal upper surface of the water supply channel; The method for manufacturing the photothermal conversion layer (12) and the water supply channel (15) includes the following steps: Step 1) Cut a water-absorbing fiber sheet with a thickness of 3-20 mm, peel the water-absorbing fiber sheet into upper and lower layers, avoiding the center part of the fiber sheet when peeling, so that the water-absorbing fibers in the center area remain connected as a whole, gather the peeled lower layer of water-absorbing fibers towards the center to form a vertical column and fix it, and make the upper layer of water-absorbing fiber sheet into one of the following shapes: lotus leaf, umbrella, and mushroom, to obtain the water supply channel (15). Step 2) The photothermal material with a hollow multi-shell structure is uniformly dispersed in a dispersant by ultrasound. The resulting suspension is deposited on the horizontal upper surface of the water supply channel composed of the water-absorbing fibers to form a uniform light absorber layer, so that the photothermal material is in close contact with the upper surface of the water-absorbing fiber sheet for water supply, and a photothermal conversion layer (12) is obtained.

2. A portable photothermal drinking water purifier with downward evaporation according to claim 1, characterized in that, The second part (2) and the third part (3) of the cup body of the solar thermal drinking water purifier are connected by one or more of the following methods: threads, snaps and clamps.

3. A portable photothermal drinking water purifier with downward evaporation according to claim 1, characterized in that, The heat insulation protective layer (11) is located at the top of the photothermal drinking water purifier. Its material is one of acrylic sheet, aerogel sheet and glass sheet with high light transmittance. The surface of the heat insulation protective layer (11) is treated with hydrophilic anti-fogging.

4. A portable photothermal drinking water purifier with downward evaporation according to claim 1, characterized in that, The breathable and waterproof layer (13) is composed of a hydrophobic and breathable membrane and a rigid mesh sheet. The hydrophobic and breathable membrane is either a polytetrafluoroethylene membrane or a polyvinylidene fluoride membrane.

5. A portable photothermal drinking water purifier with downward evaporation according to claim 1, characterized in that, The porous condensation layer (14) is made of a porous metal material with high thermal conductivity. The porous metal is one or more of aluminum foam, copper foam and nickel foam. The surface of the porous metal is coated with hydrophilic nanoparticles for hydrophilic modification treatment.

6. The application of the portable photothermal drinking water purifier with downward evaporation as described in any one of claims 1-5 in photothermal seawater desalination, characterized in that, Using capillary force, the water to be treated is driven to rise through the water supply channel to the interface of the horizontal photothermal conversion layer (12). The photothermal material converts the absorbed solar energy into heat energy and transfers it to the liquid water at the interface, causing it to evaporate and generate steam. Driven by the temperature gradient and pressure gradient, the steam diffuses downward from the photothermal conversion layer (12) through the breathable waterproof layer (13) to the porous condensation layer (14). The condensation releases heat to obtain clean water. The latent heat released by the condensation preheats the water to be treated in the capillary water absorption core at the stem of the water supply channel (15) and the water to be treated stored in the second part (2) of the photothermal drinking water purifier. The clean water flows into the clean water collection cup of the third part (3) of the photothermal drinking water purifier through the opening on one side of the bottom surface of the first part (1) of the photothermal drinking water purifier and the thin tube connected thereto.

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