Preparation method of bionic evaporator with seawater desalination and solar power generation functions

Abstract

The invention discloses a preparation method of a bionic evaporator with seawater desalination and solar power generation functions, lignin of balsa wood is removed through chemical treatment to retain a natural bimodal porous structure of the balsa wood, and sodium alginate gel crosslinking is utilized to enhance water transmission and anti-pollution performance. And efficient solar energy absorption is realized through bionic surface etching and polypyrrole photo-thermal layer deposition. Meanwhile, the gel evaporator can generate'evaporation potential 'in the process of transmitting the electrolyte solution, and can also generate stable current and voltage in the seawater desalination process; through material innovation and structure optimization, an efficient and low-cost integrated solution is provided for solving the problems of fresh water resource shortage and energy crisis.

Description

Technical Field

[0001] The present invention belongs to the field of solar desalination and energy collection, and specifically relates to a high-efficiency solar evaporator based on a porous structural material of balsa wood (BW), combined with a sodium alginate (SA) gel and a polypyrrole (PPy) photothermal layer, and a preparation method thereof. The evaporator has high-efficiency photothermal conversion, excellent water transmission performance, and resistance to salting out and pollution, and is suitable for large-scale desalination and energy collection. Background Art

[0002] With the continuous growth of the global population and the rapid development of industrialization, the shortage of freshwater resources and the surge in energy demand have become global challenges. Solar-driven interfacial evaporation technology has become one of the effective ways to solve the freshwater and energy crises due to its sustainability, eco-friendliness and cost-effectiveness. At present, the research on solar evaporators mainly focuses on biomimetic structures and functional materials, such as natural substances, organic carbon nanomaterials, hierarchical nanostructured gels, and light-absorbing sponge gels. However, existing solar evaporators still have many problems, such as high cost, complex preparation process, poor scalability, low photothermal conversion efficiency, insufficient water transport capacity, severe surface salting out, contaminant clogging, and poor evaporation stability under harsh environments.

[0003] In recent years, researchers have begun to focus on bio-based materials such as wood, mushrooms, and bamboo, which have natural porous structures and are renewable. However, solar evaporators made from these natural materials have limitations in pretreatment and energy consumption, which greatly restrict their practical applications. In addition, low photothermal conversion efficiency, poor water transmission capacity, severe surface salting out, contaminant clogging, and poor evaporation stability in harsh environments are still serious challenges facing bio-based solar evaporators.

[0004] The present invention provides efficient water transmission channels through the bimodal porous structure of BW, combines the hydrophilic and anti-fouling properties of SA with the photothermal conversion advantages of PPy, and develops a low-cost, easily scalable, and salting-out resistant solar evaporator, which significantly improves the photothermal efficiency and long-term stability. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-efficiency solar evaporator and its preparation method based on a porous structure material of balsa wood (BW), combined with sodium alginate (SA) gel and polypyrrole (Ppy) photothermal layer, to solve the problem that solar evaporators prepared from these natural materials have limitations in pretreatment and energy consumption, which greatly restrict their practical application.

[0006] To solve the above technical problems, the present invention is achieved through the following technical solutions: The present invention is a method for preparing a bionic evaporator with both seawater desalination and solar power generation functions, which specifically includes the following steps: S1. Soak 20 mm × 20 mm × 10 mm balsa wood (BW) blocks in sodium chlorite solution, seal them, and react at 100 °C for 6 h to remove lignin, wash, and air-dry. S2, immersing delignified balsa wood (DBW) in sodium alginate solution, infiltrating under reduced pressure (0.8 MPa) for 10 minutes, and then immersing in calcium chloride solution to cross-link to form sodium alginate gel-coated balsa wood (CDBW); S3, forming a butterfly wing scale structure through blade array processing; S4. Immerse the hydrogel sample with a special surface structure in an ammonium persulfate solution, then place it on an ice surface and add pyrrole monomers to polymerize to form pyrrole.

[0007] Preferably, the concentration is 2 wt %.

[0008] Preferably, the pH is adjusted by glacial acetic acid and maintained at 4.3 to 4.9.

[0009] Preferably, after sealing, the reaction is carried out at 100° C. for 6 hours, the temperature is maintained at 90° C. to 110° C., and the reaction time is controlled to be 5 to 7 hours.

[0010] Preferably, the concentration of sodium alginate is 4% to 6%.

[0011] Preferably, the concentration of calcium chloride is 0.5 mol / L.

[0012] Preferably, the concentration of ammonium persulfate is between 115 mg / mL and 125 mg / mL. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 : SCDBW design schematic and application; Figure 2 : Morphologies of BW and DBW: (a) (b) lateral structure of BW; (c) longitudinal structure of BW; (d) (e) lateral structure of DBW; (f) longitudinal structure of DBW; Figure 3 : Elemental composition diagram of SCDBW: (a) Fourier transform infrared spectrum; (b) photoelectron spectrometer; (c) high-resolution curve of C1s of BW; (d) high-resolution curve of C1s of SCDBW; Figure 4 : Changes in surface wettability: (a) BW; (b) DBW; (c) CDBW; (d) SCDBW; Figure 5Oil-water separation using SCDBW: (a) Contact angles of the evaporator for various oils (b) Rapid detachment of oil droplets from the SCDBW surface (c) Mechanism of SCDBW's anti-oil adhesion (d) Separation flux and total organic carbon (TOC) content of different emulsions using SCDBW (e) Dynamic light scattering (DLS) analysis of kerosene / water emulsions treated with SCDBW, comparing droplet size distribution before and after separation (inset is a photo of the actual object). (f) Schematic diagram of the oil / water emulsion separation mechanism using SCDBW. Figure 6 SCDBW desalination: (a) Schematic diagram of the outdoor desalination water collection device; (b) Changes in light intensity and evaporation rate; (c) Germination after immersion in tap water, purified water, and simulated seawater; (d) Growth; Figure 7 : Schematic diagram of evaporation of SCDBW integrated device and mechanism diagram of thermoelectric module; Figure 8 SCDBW solar evaporation power generation: (a) voltage-time curve generated by the evaporator in simulated seawater and deionized water; (b) photoresponse current diagram. DETAILED DESCRIPTION

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the examples described are part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0015] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. The materials and reagents used in the following examples are all available from conventional commercial channels unless otherwise specified. The present invention will be further described in detail below with reference to the accompanying drawings and examples.

[0016] Example 1 A 20 mm × 20 mm × 10 mm BW was immersed in a 2 wt% sodium chlorite solution (pH 4.6, adjusted with glacial acetic acid), sealed, and reacted at 90°C for 6 hours. Lignification was then removed, washed, and air-dried. The pretreated DBW was immersed in a 5 wt% SA solution and infiltrated under reduced pressure (0.8 MPa) for 15 minutes. It was then immersed in a 500 mM calcium chloride solution for cross-linking to form CDBW. A butterfly wing scale-like structure was formed by blade array treatment. A hydrogel sample with a special surface structure was immersed in a 130 mg / mL ammonium persulfate solution and then placed on ice. Pyrrole monomers were added dropwise to polymerize the Ppy photothermal layer. SCDBW was then washed and dried.

[0017] Example 2 A 20 mm × 20 mm × 10 mm BW was immersed in a 2 wt% sodium chlorite solution (pH 4.6, adjusted with glacial acetic acid), sealed, and reacted at 100°C for 6 hours to remove lignin, then washed and air-dried. The pretreated DBW was immersed in a 5 wt% SA solution and infiltrated under reduced pressure (0.8 MPa) for 8 minutes. It was then immersed in a 500 mM calcium chloride solution for cross-linking to form CDBW. A butterfly wing scale-like structure was formed by blade array treatment. A hydrogel sample with a special surface structure was immersed in a 110 mg / mL ammonium persulfate solution, then placed on ice and dropwisely added with pyrrole monomer to polymerize and form a Ppy photothermal layer. The resulting SCDBW was then washed and dried.

[0018] Example 3 Field emission scanning electron microscopy (FE-SEM) was used to analyze the surface morphology of SCDBW.

[0019] like Figure 2 As shown, the surface morphologies of BW and DBW were observed; Figure 2 In a, it can be observed that the surface of BW presents a bimodal porous structure; the diameter of the small pores is about 19-40 μm, and the diameter of the large pores is about 190 μm. There is no obvious change in the overall pores before and after the removal of lignin; but from Figure 2 It can be seen from bcef that delignification causes many tiny micropores (3-10 μm) to appear on the originally smooth sidewalls. This is because the pit membrane is removed at the same time as the lignin is removed, which means that the longitudinal permeability of water in BW is improved, thereby enhancing the water transmission capacity of the material.

[0020] The chemical composition of SCDBW was analyzed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS).

[0021] like Figure 3 As shown in Figure a, the absorption peaks of lignin were observed at 1462, 1503, and 1593 cm-1, and after treatment with sodium chlorite solution, the peak intensity in the remaining sample decreased significantly, proving the removal of lignin; the absorption peak of SA was also obvious, and the bands at 1417 and 1033 cm-1 belonged to the asymmetric and symmetric stretching vibrations of -COOH and CO, respectively, indicating the successful cross-linking of SA gel; in addition, in the infrared spectrum of SCDBW, the CN stretching vibration peaks belonging to the pyridine ring at 1319 and 1454 cm-1 and the CC stretching vibration peak at 1549 cm-1 can also be observed, confirming the successful growth of Ppy nanosheets on the gel surface.

[0022] from Figure 3 It can also be seen in b that after surface modification, an obvious N element signal peak appears in the spectrum. Figure 3 c is further analyzed, from which three characteristic peaks belonging to CC, CO, and C=O can be fitted. Figure 3 d can be fitted and separated into characteristic peaks at 284.6 eV corresponding to CC, characteristic peaks at 285.1 eV corresponding to CN, characteristic peaks at 286.4 eV corresponding to C-N+, C=N, and characteristic peaks at 288.4 eV corresponding to C=N+; the results obtained by XPS are consistent with those obtained by FT-IR, further proving the existence of Ppy.

[0023] Example 4 The water contact angles (WCA) of BW, DBW, CDBW and SCDBW were measured using a contact angle measuring instrument to study the changes in wettability before and after modification.

[0024] like Figure 4 As shown, it takes 13.55 seconds for a water droplet to fully penetrate BW. After delignification, the water droplet penetration time of DBW is reduced to 1.75 seconds, demonstrating that the removal of lignin significantly enhances the hydrophilicity of BW. After gelation modification, the penetration time is further reduced to 0.4 seconds, indicating that SCDBW possesses superhydrophilicity, a property that plays a crucial role in solar-thermal desalination.

[0025] Example 5 When SCDBW is immersed in water, Figure 5 As shown in a, different oils (such as toluene, kerosene, dichloromethane and chloroform) will deposit on its surface, showing an underwater oil contact angle of about 150°. Figure 5 As shown in Figure 2b, when hexane is sprayed onto the surface of SCDBW, the oil droplets immediately roll off and detach from the surface, indicating that SCDBW has excellent anti-oil performance; this phenomenon is mainly attributed to the strong hydrogen bonding between water molecules and SA, as shown in Figure 2b. Figure 5 As shown in Figure c, a stable hydration layer is formed. SA not only provides strong stability but also enhances the hydrophilicity of the composite layer, improving its hydration capacity. According to the Cassie-Baxter model, this hydration layer acts as a barrier, preventing oil droplets from adhering to the evaporator surface.

[0026] The special wettability of SCDBW enables it to separate oil-in-water emulsions; its separation ability is tested by using typical oil-in-water emulsions (kerosene / water, dichloromethane / water, chloroform / water and toluene / water); Figure 5As shown in Figure d, the permeation fluxes of SCDBW for the above emulsions were 268.74, 267.28, 264.41, and 261.59 L·m⁻²·h⁻¹, respectively, with total organic carbon (TOC) contents of 24.6, 39.7, 27.4, and 12.9 ppm, respectively. Separation efficiencies were 99.76%, 96.26%, 96.62%, and 99.87%, respectively. The differences in separation flux and efficiency are primarily due to differences in oil viscosity and density. SCDBW's superior emulsion separation ability is attributed to its enhanced surface roughness and abundant water transport channels.

[0027] Taking kerosene / water emulsion as an example, the droplet size distribution after separation is reduced from 955–3580 nm to 6.9–12.9 nm. Figure 5 As shown in the inset of e, the filtrate becomes transparent and the white emulsion before separation is almost invisible; Figure 5 Figure f shows the separation mechanism of oil-in-water emulsions. The water-prewetted SCDBW first intercepts and deforms the oil droplets through screening and demulsification, and then the oil droplets aggregate into large droplets. When the buoyancy exceeds the gravity, the aggregated oil droplets float to the water surface to form an oil layer, while clean water passes through the SCDBW, thus achieving efficient separation.

[0028] Example 6 like Figure 6 As shown in a, during a sunny day, the prepared SCDBW was placed in a homemade evaporation device to collect fresh water under natural light. At the same time, the changes in evaporation rate and solar illumination intensity during the entire solar-driven water evaporation process were recorded. The evaporation rate of SCDBW for simulated seawater in an outdoor environment can reach up to 1.322 kg m-2 h-1, indicating that it has great application prospects and development space in real life.

[0029] The collected freshwater was also evaluated for its non-toxicity through a rice seed germination test; Figure 6 c, Figure 6 As shown in Figure d, the rice treated with tap water and desalinated water gradually grew green shoots, while the rice treated with 3.5 wt% simulated seawater did not germinate after 7 days of growth, which confirmed the non-toxicity and biosafety of desalinated water.

[0030] Example 7 The upper and lower surfaces of the SCDBW evaporator were connected to foam copper electrodes, and the voltage and current generated by evaporation under the irradiation of one sunlight intensity were measured using an electrochemical workstation; Figure 8As shown in Figure a, when SCDBW evaporates simulated seawater, it can quickly generate a voltage of 60 mV and remain stable for the next 5 hours; while when evaporating deionized water, the voltage can only reach 20 mV; this shows that the greater the electrolyte concentration in the solution, the greater the evaporation voltage generated; and evaporation power generation is also affected by the strength of the solution electrolyte. The stronger the electrolysis ability and the more charged the solution, the better the evaporation power generation effect will be. Figure 8 As shown in Figure b, the stability of the SCDBW evaporator's evaporation power generation was tested with a cycle of 600 s. After three cycles, the photoresponse current generated was still maintained at 0.1 mA without much attenuation; this shows that the SCDBW evaporator has excellent stability and photoresponse.

Claims

1. A method for preparing a bionic evaporator with both seawater desalination and solar power generation functions, characterized in that: The specific steps include: S1. Soak 20 mm × 20 mm × 10 mm balsa wood (BW) blocks in sodium chlorite solution, seal them, and react at 100 °C for 6 h to remove lignin, wash, and air-dry. S2, immersing delignified balsa wood (DBW) in sodium alginate solution, infiltrating under reduced pressure (0.8 MPa) for 10 minutes, and then immersing in calcium chloride solution to cross-link to form sodium alginate gel-coated balsa wood (CDBW); S3, forming a butterfly wing scale structure through blade array processing; S4. Immerse the hydrogel sample with a special surface structure in ammonium persulfate solution, then place it on ice and add pyrrole monomer to form a pyrrole photothermal layer. After washing and drying, the balsa wood (SCDBW) coated with sodium alginate and polymerized pyrrole on the surface is obtained.

2. The method for preparing a bionic evaporator with both seawater desalination and solar power generation functions according to claim 1, characterized in that: Its concentration is 2wt%.

3. The method for preparing the bionic evaporator with both seawater desalination and solar power generation functions according to claim 1, characterized in that: Its pH needs to be adjusted with glacial acetic acid and maintained at 4.3-4.

9.

4. The method for preparing a bionic evaporator with both seawater desalination and solar power generation functions according to claim 1, characterized in that: After sealing, react at 100°C for 6 hours, maintain the temperature at 90°C to 110°C, and control the reaction time to 5 to 7 hours.

5. The method for preparing a bionic evaporator with both seawater desalination and solar power generation functions according to claim 1, characterized in that: The concentration of sodium alginate is between 4% and 6%.

6. The method for preparing a bionic evaporator with both seawater desalination and solar power generation functions according to claim 1, characterized in that: The concentration of calcium chloride is 0.5 mol / L.

7. The method for preparing a bionic evaporator with both seawater desalination and solar power generation functions according to claim 1, characterized in that: The concentration of ammonium persulfate is between 115 mg / mL and 125 mg / mL.

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