Preparation method of a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove roots and biomimetic three-dimensional trapezoidal frustum interface evaporator

Abstract

This invention provides a method for preparing a biomimetic three-dimensional trapezoidal frustum-shaped interface evaporator inspired by mangrove root systems, as well as the biomimetic three-dimensional trapezoidal frustum-shaped interface evaporator itself. The evaporator uses melamine foam as a porous framework, waterborne polyurethane as a binder, and reduced graphene oxide as a photothermal layer, and is fabricated through biomimetic structural design and composite processes. The evaporator features a trapezoidal frustum-shaped geometry that is narrower at the top and wider at the bottom. During solar-driven interface evaporation, it spontaneously forms and couples temperature gradients, salt concentration gradients, the Marangoni effect, and a gravitational field, inducing directional transport and reflux dilution of high-salt fluids. This fundamentally inhibits salt crystallization at the evaporation interface, achieving efficient, stable, and long-term solar-driven seawater desalination. This invention also relates to the application of this evaporator in seawater desalination, providing a new solution for efficient, stable, and scalable solar-driven interface evaporation technology.

Description

Technical Field

[0001] This invention relates to the field of solar interface evaporation technology, and more particularly to a method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems, and the biomimetic three-dimensional trapezoidal frustum interface evaporator. Background Technology

[0002] Freshwater scarcity is a major global challenge. Solar-driven interfacial evaporation (SDIE) technology, due to its low-carbon and sustainable characteristics, has become a promising solution for seawater desalination. However, salt crystallization at the evaporation interface severely limits the long-term stable operation of this technology. Currently, researchers have proposed various strategies to address the salt crystallization problem. For example, constructing Janus structures with asymmetric wetting properties to achieve directional salt removal, or designing three-dimensional evaporators to alleviate salt accumulation by expanding the evaporation surface and lateral convection. However, existing methods often focus on a single salt resistance mechanism, or sacrifice water transport efficiency or structural stability while improving salt tolerance, and the stability of long-term operation at extremely high salinity remains a challenge.

[0003] In adapting to high-salt environments, mangrove root systems have developed a gradient-driven, structure-guided dynamic salt management mechanism, which provides biomimetic inspiration for designing novel salt-resistant solar evaporators. Inspired by this, this invention aims to develop a novel solar interfacial evaporator with a simple structure, strong salt resistance, and the ability to physically suppress interfacial salt accumulation. Summary of the Invention

[0004] To address the shortcomings of existing solar evaporators, such as easy salt accumulation and insufficient long-term stability in high-salinity waters, this invention provides a method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove roots, as well as the biomimetic three-dimensional trapezoidal frustum interface evaporator itself. This invention primarily utilizes the synergistic effect of the biomimetic three-dimensional trapezoidal frustum structure design and the reduced graphene oxide / waterborne polyurethane / melamine sponge composite photothermal material. This spontaneously forms and couples temperature gradients, salt concentration gradients, the Marangoni effect, and a gravitational field during solar-driven interface evaporation, inducing directional transport and reflux dilution of high-salinity fluids. This fundamentally inhibits salt crystallization at the evaporation interface, achieving efficient, stable, and long-term solar-driven seawater desalination.

[0005] The technical means employed in this invention are as follows:

[0006] A method for fabricating a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems includes: S1. Graphene oxide is dispersed in deionized water, and after ultrasonic treatment, acetic acid is added as a reducing agent. The reaction is carried out in a high-temperature water bath. After the reaction is completed, the precipitate is separated by centrifugation, and the precipitate is collected and repeatedly washed with deionized water until neutral. The precipitate is dried to obtain reduced graphene oxide powder. The obtained reduced graphene oxide powder is then redispersed in deionized water to prepare a reduced graphene oxide dispersion. S2. Cut the melamine sponge into a pre-designed three-dimensional trapezoidal frustum structure, and after cleaning and drying, immerse it in an aqueous polyurethane solution. After full adsorption, remove and dry to obtain WPU@MF. S3. Immerse the WPU@MF in the reduced graphene oxide dispersion, and after full adsorption, remove and dry it to finally obtain the biomimetic three-dimensional trapezoidal frustum interface evaporator rGO / WPU@MF loaded with a reduced graphene oxide photothermal layer.

[0007] Further, step S1 includes: S11. Graphene oxide powder is dispersed in deionized water and ultrasonically treated under ice bath conditions to obtain a uniform graphene oxide dispersion. In this embodiment, the concentration of the graphene oxide dispersion is 2 mg / mL. S12. Add acetic acid to the graphene oxide dispersion and stir the mixture in a water bath at 90°C to 100°C. In this embodiment, the volume concentration of acetic acid is 36% and the reaction time is 6 h. S13. Centrifuge the reacted mixture, discard the supernatant, and collect the precipitate; in this embodiment, the centrifugation conditions are 10000 rpm and 5 min.

[0008] S14. Wash the precipitate repeatedly with deionized water and centrifuge until the pH of the supernatant is close to neutral. S15. The washed precipitate is dried at 50℃~70℃ to obtain reduced graphene oxide powder. S16. The reduced graphene oxide powder is redispersed in deionized water to prepare a reduced graphene oxide dispersion.

[0009] Further, step S2 includes: S21. Cut the block-shaped melamine sponge into a three-dimensional trapezoidal frustum structure with a geometric configuration that is narrow at the top and wide at the bottom; S22. The cut three-dimensional trapezoidal truncated melamine sponge is cleaned with deionized water and ethanol in sequence to remove surface impurities. S23. Dry the cleaned three-dimensional trapezoidal truncated melamine sponge. S24. Prepare an aqueous polyurethane solution, and immerse the dried three-dimensional trapezoidal truncated melamine sponge in the prepared aqueous polyurethane solution to allow the three-dimensional trapezoidal truncated melamine sponge to fully absorb the solution. S25. The impregnated three-dimensional trapezoidal truncated melamine sponge is taken out and dried to obtain WPU-modified melamine sponge composite material WPU@MF.

[0010] Furthermore, the upper base of the three-dimensional trapezoidal frustum structure has dimensions of 1 cm × 2 cm, the lower base has dimensions of 1.5 cm × 3 cm, and the height has 1.7 cm.

[0011] Further, step S3 includes: S31. The WPU@MF is completely immersed in the reduced graphene oxide dispersion, and the immersion process is controlled to ensure that the reduced graphene oxide is uniformly loaded on the three-dimensional porous framework surface of the WPU@MF. S32. The treated composite material is taken out from the reduced graphene oxide dispersion and dried and cured to obtain a biomimetic three-dimensional trapezoidal frustum interface evaporator rGO / WPU@MF with melamine sponge as the skeleton, waterborne polyurethane as the adhesive layer and reduced graphene oxide as the photothermal layer.

[0012] Furthermore, the impregnation time is sufficient to allow WPU@MF to fully adsorb the reduced graphene oxide dispersion, and the drying temperature is 60°C.

[0013] This invention also provides a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove roots, prepared by the above method. The biomimetic three-dimensional trapezoidal frustum interface evaporator uses melamine sponge as a porous framework, waterborne polyurethane as a binder, and reduced graphene oxide as a photothermal layer. It has a trapezoidal frustum geometry that is narrow at the top and wide at the bottom. It is used to spontaneously form and couple temperature gradient, salt concentration gradient, Marangoni effect and gravitational field during solar-driven interface evaporation, inducing directional transport and reflux dilution of high-salt fluid.

[0014] Furthermore, the biomimetic three-dimensional trapezoidal truncated interface evaporator is applied in solar-driven seawater desalination or high-salt wastewater treatment. The biomimetic three-dimensional trapezoidal truncated interface evaporator floats on the surface of the water body to be treated, so that the bottom of the biomimetic three-dimensional trapezoidal truncated interface evaporator contacts the water body to form a capillary water transport channel, and the top of the biomimetic three-dimensional trapezoidal truncated interface evaporator receives light to carry out interface evaporation. The steam generated by evaporation is condensed and collected to obtain fresh water.

[0015] Furthermore, the intensity of the illumination is 0.5~1.5. .

[0016] Compared with the prior art, the present invention has the following advantages: 1. The preparation method provided by the present invention uses reduced graphene oxide as a photothermal layer, which has a wide spectrum of high absorption rate and excellent photothermal conversion efficiency, and can effectively localize solar energy at the evaporation interface; a high porosity, three-dimensionally connected melamine sponge is selected as a supporting skeleton, and waterborne polyurethane is used as a binder to enhance structural stability and ensure the firm loading of reduced graphene oxide. This composite structure provides efficient capillary water transport channels and steam escape paths.

[0017] 2. The biomimetic three-dimensional trapezoidal frustum interface evaporator provided by the present invention achieves spontaneous coupling of temperature gradient, salt concentration gradient, Marangoni effect and gravitational field through the coordinated design of trapezoidal frustum geometry with narrow upper part and wide lower part and porous skeleton. It drives high salt fluid to flow back to the main water body along the side wall of trapezoidal frustum, realizing real-time self-removal of salt at the evaporation interface.

[0018] 3. The biomimetic three-dimensional trapezoidal frustum interface evaporator provided by this invention can achieve a pure water evaporation rate of 2.457 under one solar radiation intensity. It can operate stably for more than 40 hours in brine with up to 20 wt% NaCl, maintaining a stable evaporation rate and exhibiting no salt crystallization on the surface, demonstrating excellent salt resistance and long-term operational stability.

[0019] 4. The preparation method provided by this invention is mainly based on impregnation and drying processes. The steps are simple, the raw material cost is relatively low, and it has the potential for large-scale production.

[0020] In summary, by applying the technical solution of this invention, the problems of salt accumulation and insufficient long-term stability of existing solar evaporators in high-salinity water bodies are solved by the biomimetic three-dimensional trapezoidal truncated pyramid structure design and the synergistic effect of the composite photothermal material. Therefore, the technical solution of this invention solves the problems of salt accumulation and insufficient long-term stability of existing solar evaporators in high-salinity water bodies.

[0021] Based on the above reasons, this invention can be widely applied in fields such as seawater desalination, high-salinity wastewater treatment, and solar-driven water purification. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the biomimetic design concept of the present invention and a simplified process diagram of the preparation of the rGO / WPU@MF evaporator.

[0024] Figure 2 This is a microscopic morphology characterization diagram of the material.

[0025] Figure 3 The diagram shows the structure and physicochemical properties of the material.

[0026] Figure 4 This is a diagram characterizing the physical properties of the evaporator.

[0027] Figure 5 This is a graph showing the performance of solar interface evaporation.

[0028] Figure 6 This is a test diagram for salt resistance and seawater desalination applications. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product or device.

[0031] Example 1: Preparation of Evaporator and Materials like Figure 1 As shown, this invention provides a method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems. This section details the preparation process of reduced graphene oxide (rGO) and the final three-dimensional trapezoidal frustum structure solar steam generator, with the following steps: First, the core photothermal material rGO was prepared using the acetic acid reduction method. 400 mg of graphene oxide (GO) powder was dispersed in 200 mL of deionized water and sonicated in an ice bath for 45 minutes to obtain a uniform GO dispersion with a concentration of 2 mg / mL. 40 mL of 36% acetic acid was added to this dispersion, and the mixture was stirred in a 95°C water bath for 6 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 5 minutes, and the supernatant was discarded. The collected precipitate was repeatedly washed with deionized water and centrifuged until the pH of the supernatant was close to neutral. Finally, the precipitate was dried in a 60°C oven to obtain reduced graphene oxide (rGO) powder.

[0032] Next, the integrated evaporator is fabricated, including: (1) Substrate pretreatment: Block melamine sponge (MF) was cut into a three-dimensional trapezoidal frustum structure with an upper base of 1 cm × 2 cm, a lower base of 1.5 cm × 3 cm, and a height of 1.7 cm. It was ultrasonically cleaned sequentially with deionized water and anhydrous ethanol to remove surface impurities, and then thoroughly dried in a 60℃ oven. SEM characterization ( Figure 2 (e)- Figure 2 (g) shows that the original MF has a three-dimensional interconnected mesh-like macroporous structure with uniform pore size distribution and a smooth skeleton surface.

[0033] (2) Preparation of WPU@MF: Prepare an aqueous polyurethane (WPU) solution with a mass concentration of 10 wt%. Completely immerse the dried trapezoidal MF from step (1) in the WPU solution to ensure full adsorption. After removal, dry in a 60℃ oven for 6 hours to obtain the WPU-modified MF composite material, denoted as WPU@MF. SEM image ( Figure 2 (h)- Figure 2 (j) shows that after WPU modification, a smooth and continuous polymer film is formed on the surface of the MF skeleton, which perfectly preserves the three-dimensional interconnected porous structure.

[0034] (3) Preparation of rGO / WPU@MF: The rGO powder obtained in Example 1 was redispersed in deionized water to prepare an rGO dispersion with a concentration of 4 mg / mL. The WPU@MF obtained in step (2) was completely immersed in the rGO dispersion to ensure uniform rGO adhesion. After removal, it was dried in an oven at 60°C for 6 hours to finally obtain a composite evaporator loaded with an rGO photothermal layer, denoted as rGO / WPU@MF.

[0035] Example 2: System Characterization of Materials and Evaporator Structure and Performance The prepared rGO and rGO / WPU@MF composites were comprehensively characterized in terms of structure, chemical properties and physical properties to verify their successful preparation and elucidate the underlying reasons for their high performance.

[0036] First, the microstructure and structural characteristics of the core photothermal material rGO were systematically characterized. For example... Figure 2 As shown in (a) and (b), scanning electron microscopy (SEM) images reveal that rGO is composed of a large number of stacked nanosheets, exhibiting a loose and porous layered structure. High-magnification SEM images clearly show that the nanosheets have typical wrinkled and rolled structures, with cross-linking between the layers to form an irregular hierarchical porous structure. This structure effectively enables multiple scattering and trapping of light, extending its propagation path and improving light absorption efficiency. Transmission electron microscopy (TEM) further reveals the microstructural characteristics of rGO. Low-magnification TEM ( Figure 2 (c) shows that the rGO sheets have high transparency and slightly curled edges, consistent with the characteristics of few-layer graphene; high-resolution TEM ( Figure 2 (d) Clearly shows the nanoscale wrinkles on the surface of the sheets. This rough structure greatly increases the specific surface area of ​​the material, which not only provides more attachment and evaporation sites for water molecules, but also promotes light absorption and improves photothermal conversion efficiency through the local field enhancement effect. Figure 2 The SEM images clearly show the morphological evolution of the material: the original MF has a smooth surface and a three-dimensional interconnected network of macroporous structures. Figure 2 (e)-2(g)); After WPU modification, the skeleton surface is covered with a continuous and smooth polymer film, but the porous structure is well preserved. Figure 2 (h)- Figure 2 (j)); After finally loading rGO, it can be seen that the rGO nanosheets are uniformly attached to the surface of the framework, forming a rough composite photothermal interface (j) Figure 2 (k)- Figure 2 (m)). Energy-dispersive X-ray spectroscopy (EDS) surface scanning analysis ( Figure 2 (n)- Figure 2 (p) further confirmed the uniform distribution of C, N, and O elements in the composite material, indicating that rGO and WPU@MF achieved good composite.

[0037] Secondly, various spectroscopic techniques were used to analyze the chemical structure and composition of the materials. To confirm the successful construction of the composite material and systematically elucidate its structural characteristics, the phase composition, chemical structure, and key physicochemical properties of the materials were characterized. Figure 3 The XRD pattern in (a) reveals the evolution of the material's crystal structure. Pure MF at 27.4 A broad and strong diffraction peak is observed at (2θ), indicating that it has an amorphous porous structure. After the introduction of the WPU adhesive layer, the intensity of this peak weakens, and it decreases to 20.1. The appearance of a broadened diffraction envelope nearby indicates that the WPU has formed a semi-crystalline structure and successfully infiltrated the MF network. After loading rGO, the MF characteristic peaks almost completely disappeared, and at 24.5... The appearance of a new diffraction peak on the rGO (002) crystal plane indicates that rGO has been successfully loaded and that oxygen functional groups were removed during the reduction process, thus restoring the original functional groups. The carbon network forms a disordered layered carbon structure. Figure 3 The FTIR spectrum in (b) further reveals the evolution of the chemical structure. The characteristic peaks of pure MF mainly include 3315. N–H stretching vibration at 1550 / 1460 The triazine ring skeleton and C–N vibration at the location and 815 The triazine ring exhibits outward bending vibration at 1700°C. After WPU loading, the temperature reaches... A characteristic peak for urethane C=O appears at 1530. and 1220 Amide present nearby The presence of C–O–C absorption bands indicates that a covalent interface is formed between MF and WPU via urea bonds. After loading rGO, the spectrum shows a significant change: 3315 The nearby N–H / O–H complex bands are significantly broadened and asymmetrical, indicating that a hydrogen bond network is formed between the oxygen-containing groups of rGO and WPU; 1700 The fine-tuning of the C=O peak shape reflects the superposition contribution of carboxyl groups on the rGO surface; fingerprint region 815 The peak intensity drops sharply, while at 1580 The location corresponds to rGO. The broad absorption band of in-plane vibrations in the carbon framework (C=C) confirms the successful loading, reduction, and coating of the substrate by rGO. These results demonstrate that the material's stability and photothermal transfer are enhanced through a multi-level chemical construction involving covalent anchoring and non-covalent synergy. The evolution of the material's surface chemical state during the modification process was analyzed using XPS. Figure 3 (c) As shown in the full spectrum, the O 1s peak intensity increased after the introduction of WPU into pure MF, indicating that WPU was successfully loaded; after further composite with rGO, the C signal was significantly enhanced, fully presenting the construction process of the ternary system. To further analyze the interfacial chemical state, fine peak separation was performed on the C1s spectrum of rGO / WPU@MF. Figure 3 (d): Aromatics of rGO at 283.7 eV Carbon (C=C), aliphatic carbon in WPU@MF at 284.5 eV, C–O groups from WPU and residual C–O groups in rGO at 286.2 eV, urethane C=O in WPU and carbonyl groups in rGO at 288.0 eV, carboxyl carbon (O–C=O) at the edge of rGO at 289.1 eV, and carbonyl groups appearing at 291.0 eV. The satellite peak directly confirms the existence of extended rGO. Conjugated structure. The evolution of the N 1s spectrum further reveals the interfacial electronic interactions ( Figure 3 (e): WPU@MF shows a nitrogen oxide peak at approximately 403.0 eV, while this peak almost disappears in rGO / WPU@MF, and protonated nitrogen appears at approximately 401.0 eV. The presence of a signal, and the overall shift in binding energy between triazine ring nitrogen and carbamate nitrogen towards lower energies, suggests that the introduction of rGO may have reduced some surface nitrogen oxide species and interacted with their π-electron system. or Interactions increase the electron cloud density of nitrogen atoms. The O 1s spectrum supports this ( Figure 3 (f) The relative content of the C–O component in rGO / WPU@MF decreased to approximately 33.2%, and the C=O peak shifted towards lower energies, indicating an interfacial interaction (such as hydrogen bonding) between the oxygen-containing functional groups on the rGO surface and the C=O / C–O groups in WPU. XPS analysis showed that rGO and WPU@MF interact through oxygen-containing functional groups and... The electronic system forms multiple interfacial interactions, laying a key foundation for optimizing the interfacial structure and properties of composite materials.

[0038] The pore structure of the material is crucial as it serves as both the water transport channel and the steam escape path in the interfacial evaporator. Figure 3 The mercury intrusion porosimetry results (g) show that rGO / WPU@MF possesses an ideal hierarchical porous structure with a porosity of 89.6%, providing ample space for water storage and transport. The pore size distribution exhibits a significant hierarchical characteristic, with a median volumetric pore size of 137.4 mm. This indicates that the interconnected macroporous framework constitutes the main channel for rapid water transport; simultaneously, in the mesoporous (100) -1 ) and micropores ( 10 Pores also exist within this range; these micro- and nano-pores formed by the composite of rGO and WPU can effectively enhance the material's capillary water absorption capacity and surface hydrophilicity. In practical applications, evaporators not only need efficient water delivery capacity but also good mechanical stability. Figure 3 (h) shows the approximately linear stress of rGO / WPU@MF Strain behavior. Under maximum load, the compressive stress is approximately 38.56 kPa, and the Young's modulus is approximately 1.00 mm / m, indicating that the material is soft and has good resilience. The linear characteristics stem from the uniform internal structure, and the good bonding between rGO as a reinforcing material and the WPU@MF matrix enables effective stress transfer and dispersion. Good mechanical properties are attributed to the effective synergy of the three components. The MF framework provides the main support and has deformation recovery capability, the WPU coating layer absorbs and alleviates stress, and the uniformly dispersed rGO nanosheets act as a reinforcing agent, effectively inhibiting the generation and propagation of microcracks, thereby improving the overall strength of the structure. Thermogravimetric analysis (TGA) Figure 3 (i) shows that the thermal decomposition of rGO / WPU@MF in nitrogen can be divided into four stages. Among them: The first stage (room temperature – 200°C) involves a weight loss of approximately 0.8%, primarily due to the evaporation of adsorbed water. The second stage (200–350°C) involves a weight loss of approximately 15%, corresponding to the initial decomposition of the MF framework and the degradation of the WPU soft segments. The third stage (350–500°C) is a rapid weight loss range, with a weight loss of approximately 70%, and the maximum weight loss rate peak is located near 430°C, mainly due to the complete decomposition of the foam framework and the thermal decomposition of the polyurethane hard segments and rGO. The fourth stage (500–800°C) involves a weight loss of approximately 22%, which is a slow carbonization process. The material exhibits good thermal stability, with an initial decomposition temperature of approximately 250°C for a 5% weight loss, and a residual char rate of 3.21% at 800°C. This is mainly due to the barrier effect generated by the dense barrier network formed by the rGO nanosheets, which delays thermal decomposition and promotes the formation of a stable char layer, thereby ensuring that the evaporator maintains structural integrity and performance stability during long-term operation.

[0039] In summary, the structural characterization of the system confirms the successful preparation of the rGO / WPU@MF composite material. This material integrates the rigid porous framework of MF, the elastic hydrophilic properties of WPU, and the photothermal and reinforcing functions of rGO, forming a stable composite system through effective interfacial interactions between the components. Its unique hierarchical porous structure, excellent mechanical elasticity, and thermal stability provide an ideal material platform for constructing efficient, durable, and practically applicable solar interfacial evaporators.

[0040] After confirming the successful construction of the rGO / WPU@MF hybrid evaporator, its physical properties related to interfacial evaporation were further systematically evaluated, and the results are as follows: Figure 4 As shown, a lightweight rGO / WPU@MF evaporator was successfully constructed based on a low-density open-pore framework of pure MF. This evaporator retains its porous structure characteristics, with a packing density of only 0.1027. While maintaining the lightweight nature of the material, it also maintains good structural integrity. Figure 4(a) The water storage and wetting properties of a material directly affect its continuous water supply capacity during the evaporation process. Water retention test results ( Figure 4 (b) shows that the evaporator has a mass of 0.8085 in a dry state. After absorbing water to saturation, its mass increases to 6.2750. The water absorption rate is as high as 676%. Combined with a high porosity of 89.6%, this indicates that a highly interconnected pore network has formed inside the composite material, which can store a large amount of water under capillary action, providing a continuous and sufficient water source for the evaporation interface. Water contact angle test results further demonstrate that the material surface has superhydrophilicity. Figure 4 As shown in (c), the water droplet was completely absorbed within 16 ms after contact with the material. This is due to the introduction of hydrophilic soft segments in the WPU molecular chain and the polar sites provided by the residual oxygen-containing functional groups on the rGO surface. These two factors synergistically enhance the affinity of the material surface for water molecules, allowing water to rapidly wet the surface and penetrate into the material's interior along the three-dimensional interconnected channels. Dynamic water transport test ( Figure 4 (d) indicates that water can be rapidly transported from the bottom to the top of the evaporator within 5 seconds, demonstrating that its internal capillary channels can provide a continuous and stable water supply during evaporation. Furthermore, the composite material exhibits a thermal conductivity of 0.3745 in a wet state. ( Figure 4 (e) has a thermal conductivity lower than that of pure water. This low thermal conductivity mainly stems from the quiescent air layer in the porous framework, which effectively suppresses longitudinal heat conduction, thus facilitating efficient thermal localization at the evaporation interface. As a photothermal evaporator, its ability to capture sunlight directly determines its energy input efficiency. Figure 4 As shown in (f), rGO / WPU@MF exhibits an average absorption rate exceeding 95% in the 250–2500 nm band, which is superior to pure MF and WPU@MF. The characteristic peak at approximately 270 nm is attributed to the C=C bonds in rGO. The transition indicates the successful loading of rGO onto the framework surface. This broad-spectrum absorption characteristic stems not only from the high light absorption capacity of rGO itself, but also from the light-trapping effect generated by the multi-level rough structure jointly constructed by the MF framework, WPU binder, and rGO sheets. This demonstrates that rGO / WPU@MF integrates key characteristics such as lightweight high-porosity structure, rapid water transport, efficient thermal localization, and broad-spectrum strong light absorption, providing a solid material foundation for efficient and stable solar evaporators.

[0041] Example 3: Application of a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove roots in simulated seawater desalination. 1. The MXene / PDA@MF-EF prepared in Example 1 was placed in different simulated water environments (pure water) and subjected to 1 solar (1 Irradiated for 60 minutes under a solar-powered sun for evaporation. Its evaporation performance was tested using a laboratory-based simulated solar experimental device system. During the test, the solar-driven seawater desalination experimental device (built in the laboratory) was used. Figure 5 a). The device consists of several main components: a xenon lamp (simulating sunlight), an electronic balance (recording the mass of water molecules during evaporation), an infrared thermal imager (measuring the surface temperature of the material), and a computer (receiving data from the electronic balance). The evaporation rate and efficiency of rGO / WPU@MF can be obtained from the slope of the mass-time curve. Six evaporation cycle efficiency tests were conducted on rGO / WPU@MF under one sun.

[0042] The interfacial evaporation performance of the rGO / WPU@MF evaporator was systematically evaluated under simulated sunlight conditions. The experimental setup is as follows: Figure 5 As shown in (a), the evaporator floats on the water surface with its top directly exposed to sunlight, simulating the actual solar interface evaporation process. The effect of WPU concentration on the evaporation rate was investigated. Figure 5 As shown in (b) and 5(c), under one solar irradiance, the evaporation mass of the evaporator at different WPU concentrations (8 wt%, 10 wt%, 12 wt%) all showed a linear increasing trend with time, with corresponding evaporation rates of 2.291. 2.457 and 2.029 The 10 wt% WPU sample exhibited the highest evaporation rate, indicating that this concentration was the optimal loading. Too low a WPU concentration may lead to insufficient binding of rGO to the MF framework; too high a concentration may cause pore blockage, affecting water vapor transport. Therefore, subsequent studies were based on this optimized sample (10 wt% WPU). To investigate the evaporator's operational stability, cyclic testing was conducted on the optimized sample. Figure 5 As shown in (d), the evaporation rate remains highly stable without significant decay, indicating that the rGO / WPU@MF evaporator has good cycle stability. Figure 5 (e) and 5(f) tested the evaporation rate as a function of light intensity. The results showed that the evaporation rate continuously increased with increasing light intensity, indicating that the evaporator has good light intensity adaptability. To further explore its efficient evaporation thermal management mechanism, infrared thermal imaging was used to monitor the surface temperature of the evaporator. Figure 5 (g) Under different light intensities, the evaporator surface temperature rose to a steady state within 15–20 minutes, indicating that light can be effectively converted into heat and confined to the top of the evaporator. Figure 5 (h)). Combined with the material's low wet thermal conductivity ( Heat is primarily confined to the evaporation interface region, thereby reducing heat loss and promoting high energy localization. Thanks to the synergistic effect of light absorption, water transport, and heat localization, this three-dimensional trapezoidal truncated pyramid evaporator exhibits stable and efficient interfacial evaporation performance under 1.0 sun conditions.

[0043] II. Salt tolerance experiments were conducted on salt water of different concentrations using a xenon lamp to simulate sunlight. Simulated seawater, and 5wt%, 10wt%, and 20wt% NaCl solutions were used as test seawater concentrations. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Under illumination (light intensity 100) The photothermal evaporation performance of rGO / WPU@MF in salt solutions with different NaCl contents was tested.

[0044] To evaluate the practical application potential of this evaporator in high-salinity seawater desalination, its salt-resistant crystallization characteristics, long-term operational stability, and desalination performance were systematically investigated. The core of its salt-resistant mechanism lies in its biomimetic three-dimensional trapezoidal truncated pyramid structure. Figure 6 (a) This structure employs a trapezoidal geometry on all six sides, effectively coordinating and controlling multiple physical fields such as concentration, temperature, surface tension, and gravity to achieve efficient evaporation and continuous, stable salt removal. The three-dimensional interconnected porous framework ensures stable and efficient water transport, forming the basis for continuous interfacial evaporation. During evaporation, salt ions accumulate at the top interface, forming a high-concentration zone. The gradually increasing width of the trapezoidal sides creates natural diffusion channels, reducing resistance to ion diffusion and driving the high-concentration ions downwards, thus forming a stable concentration diffusion flow. Simultaneously, the temperature and concentration fields of the photothermal conversion process couple, increasing the temperature at the top and upper sides of the evaporator while maintaining a lower temperature at the bottom, creating a stable vertical temperature gradient on the sidewalls. Under the combined effect of high salt and high temperature, the surface tension at the evaporation interface is maximized, triggering the Marangoni effect, causing the surface high-salt fluid to flow downwards along the inclined trapezoidal sidewalls. Under the influence of the trapezoidal geometry and inclined structure, the descending high-salt solution is accelerated back into the water body under gravity and rapidly diluted. Through this synergistic process of ion diffusion, Marangoni effect, and gravitational reflux, the three-dimensional trapezoidal truncated pyramid structure couples multiple physical fields to construct a continuous salt transport cycle. This effectively suppresses salt accumulation and crystallization at the evaporation interface while achieving a synergistic process of evaporation and salt removal.

[0045] This resistance to salt crystallization has been verified experimentally. For example... Figure 6As shown in (b), after placing 0.5 g of NaCl crystals on the surface of the evaporator, the salt crystals completely dissolved within 17 minutes, indicating that the material surface has good hydrophilicity and its porous structure supports rapid capillary transport and ion diffusion. Based on this, the evaporation performance of the evaporator under different salinities was systematically tested. The results show that the evaporation process can proceed stably in simulated seawater, 5 wt%, 10 wt%, and 20 wt% NaCl solutions. Figure 6 (c) corresponds to an evaporation rate of 2.3515. 2.6055 2.5313 and 2.4186 .exist Figure 6 In (d), an increased evaporation rate was observed in 5wt% and 10wt% NaCl solutions, even exceeding that in pure water. This may be attributed to the fact that salt ions can reduce the enthalpy of vaporization of water to some extent, while the efficient salt removal mechanism weakens the obstruction of salt accumulation to light absorption and water transport, allowing the evaporator to fully utilize the thermodynamic advantages brought by the increased salinity. To further evaluate the stability of the evaporator under continuous evaporation conditions at high salinity, Figure 6 (e) indicates that the evaporator performance remained basically stable during continuous evaporation in a 20wt% NaCl solution for 8 hours, with the evaporation rate stabilizing at 2.4%. -2.6 There was no significant attenuation between the two periods, and it was clearly observed that the evaporator surface remained clean throughout, with no salt crystallization. Figure 6 (f) After circulating evaporation in high-concentration brine for 40 hours, the evaporation rate remained stable throughout, without any decrease due to clogging or performance degradation, demonstrating the durability and anti-clogging ability of this biomimetic structure under extreme salinity conditions. Furthermore, the water quality of the evaporator is also a key indicator for evaluating desalination performance. Figure 6 (g) Demonstrates the analysis of water samples after evaporation and condensation using inductively coupled plasma spectroscopy. The results show that the treated water contains... , , , The plasma concentration was significantly lower than that of the original high-salt solution, with an ion rejection rate exceeding 99.9%, indicating that the solar interfacial evaporation is a phase change process where only water molecules vaporize, while salt ions are retained in the liquid phase, and the produced water meets drinking water standards. Figure 6 As shown in (h), the salt removal mechanism and structural design proposed in this study, compared with previously reported methods, exhibit significant advantages in long-term anti-crystallization ability and stability under extreme salinity (e.g., 20 wt%) while maintaining a high evaporation rate. These results demonstrate that the rGO / WPU@MF evaporator has broad application potential in freshwater production.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems, characterized in that, include: S1. Graphene oxide is dispersed in deionized water, and after ultrasonic treatment, acetic acid is added as a reducing agent. The reaction is carried out in a high-temperature water bath. After the reaction is completed, the precipitate is separated by centrifugation, and the precipitate is collected and repeatedly washed with deionized water until neutral. The precipitate is dried to obtain reduced graphene oxide powder. The obtained reduced graphene oxide powder is then redispersed in deionized water to prepare a reduced graphene oxide dispersion. S2. Cut the melamine sponge into a pre-designed three-dimensional trapezoidal frustum structure, and after cleaning and drying, immerse it in an aqueous polyurethane solution. After full adsorption, remove and dry to obtain WPU@MF. S3. Immerse the WPU@MF in the reduced graphene oxide dispersion, and after full adsorption, remove and dry it to finally obtain the biomimetic three-dimensional trapezoidal frustum interface evaporator rGO / WPU@MF loaded with a reduced graphene oxide photothermal layer.

2. The method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems according to claim 1, characterized in that, Step S1 includes: S11. Disperse graphene oxide powder in deionized water and sonicate it under ice bath conditions to obtain a uniform graphene oxide dispersion. S12. Add acetic acid to the graphene oxide dispersion and stir the mixture in a water bath at 90℃~100℃. S13. Centrifuge the mixture after reaction, discard the supernatant, and collect the precipitate; S14. Wash the precipitate repeatedly with deionized water and centrifuge until the pH of the supernatant is close to neutral. S15. The washed precipitate is dried at 50℃~70℃ to obtain reduced graphene oxide powder. S16. The reduced graphene oxide powder is redispersed in deionized water to prepare a reduced graphene oxide dispersion.

3. The method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems according to claim 1, characterized in that, Step S2 includes: S21. Cut the block-shaped melamine sponge into a three-dimensional trapezoidal frustum structure with a geometric configuration that is narrow at the top and wide at the bottom; S22. The cut three-dimensional trapezoidal truncated melamine sponge is cleaned with deionized water and ethanol in sequence to remove surface impurities. S23. Dry the cleaned three-dimensional trapezoidal truncated melamine sponge. S24. Prepare an aqueous polyurethane solution, and immerse the dried three-dimensional trapezoidal truncated melamine sponge in the prepared aqueous polyurethane solution to allow the three-dimensional trapezoidal truncated melamine sponge to fully absorb the solution. S25. The impregnated three-dimensional trapezoidal truncated melamine sponge is taken out and dried to obtain WPU-modified melamine sponge composite material WPU@MF.

4. The method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems according to claim 3, characterized in that, The three-dimensional trapezoidal frustum structure has an upper base dimension of 1 cm × 2 cm, a lower base dimension of 1.5 cm × 3 cm, and a height of 1.7 cm.

5. The method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems according to claim 1, characterized in that, Step S3 includes: S31. The WPU@MF is completely immersed in the reduced graphene oxide dispersion, and the immersion process is controlled to ensure that the reduced graphene oxide is uniformly loaded on the three-dimensional porous framework surface of the WPU@MF. S32. The treated composite material is taken out from the reduced graphene oxide dispersion and dried and cured to obtain a biomimetic three-dimensional trapezoidal frustum interface evaporator rGO / WPU@MF with melamine sponge as the skeleton, waterborne polyurethane as the adhesive layer and reduced graphene oxide as the photothermal layer.

6. The method for preparing a biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems according to claim 5, characterized in that, The impregnation time is sufficient to allow WPU@MF to fully adsorb the reduced graphene oxide dispersion.

7. A biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems, characterized in that, The biomimetic three-dimensional trapezoidal frustum interface evaporator is prepared by the method described in any one of claims 1 to 6. The biomimetic three-dimensional trapezoidal frustum interface evaporator uses melamine sponge as a porous skeleton, waterborne polyurethane as a binder, and reduced graphene oxide as a photothermal layer. It has a trapezoidal frustum geometry that is narrow at the top and wide at the bottom. It is used to spontaneously form and couple temperature gradient, salt concentration gradient, Marangoni effect and gravitational field during solar-driven interface evaporation, and induce directional transport and reflux dilution of high-salt fluid.

8. A biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems according to claim 7, characterized in that, The biomimetic three-dimensional trapezoidal truncated interface evaporator is applied in solar-driven seawater desalination or high-salt wastewater treatment. The biomimetic three-dimensional trapezoidal truncated interface evaporator floats on the surface of the water body to be treated, so that the bottom of the biomimetic three-dimensional trapezoidal truncated interface evaporator contacts the water body to form a capillary water transport channel, and the top of the biomimetic three-dimensional trapezoidal truncated interface evaporator receives light to carry out interface evaporation. The steam generated by evaporation is condensed and collected to obtain fresh water.

9. A biomimetic three-dimensional trapezoidal frustum interface evaporator inspired by mangrove root systems according to claim 8, characterized in that, The intensity of the illumination is 0.5~1.

5. .

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