Self-repairing hydrogel photo-thermal evaporation material as well as preparation method and application thereof

Abstract

The invention provides a self-repairing hydrogel photo-thermal evaporation material as well as a preparation method and application thereof. Spongy hydrogel which has self-repairing capability and can be used for seawater desalination is successfully prepared by a free radical polymerization method. Hydrophilic and hydrophobic effects and reversible interaction of hydrogen bonds and the like of the whole system are regulated and controlled through design of chemical components, meanwhile, certain pore channels are formed in hydrophilic and hydrophobic areas in the polymerization process in microphase separation of deionized water, and the pore channels provide transmission channels for water transportation; more importantly, the ordered distribution of the hydrophilic and hydrophobic regions is beneficial to the directional arrangement of water molecules, and weakens the formation of hydrogen bonds which are useless for the self-repairing performance in the water-containing environment, thereby promoting the repairing capability of the water-containing environment. The hydrophilic and hydrophobic effects are introduced into a polymer skeleton, so that the external acting force can be effectively dissipated, and the impact resistance and compressive strength of the spongy hydrogel are further enhanced.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel technology, and relates to sponge-like hydrogels that can be used for seawater desalination. In particular, it relates to a self-healing hydrogel photothermal evaporation material with self-healing capabilities that can be used for seawater desalination, as well as its preparation method and application. Background Technology

[0002] In recent years, solar-driven interface evaporation technology has attracted much attention due to its direct use of solar energy, low energy consumption, and simple system structure. This technology places photothermal materials at the gas-liquid interface to achieve localized thermal conversion of solar energy, avoiding the inefficiency of traditional bulk heating and significantly improving evaporation efficiency.

[0003] Photothermal evaporation materials, as the core of this technology, need to possess high-efficiency photothermal conversion capabilities, excellent water transport performance, and a stable structure. Currently, researchers have developed various photothermal evaporation materials based on hydrogels, porous carbon materials, and polymer foams. Among them, sponge-like hydrogels, due to their porous structure and hydrophilicity, can achieve rapid water transport and evaporation. Furthermore, some materials have further improved photothermal efficiency by introducing photothermal components (such as polypyrrole, metal particles, and carbon materials). However, existing materials are susceptible to mechanical damage or chemical corrosion during long-term use, leading to performance degradation and limiting their practical applications.

[0004] Existing sponge-like hydrogel photothermal evaporation materials still have the following key problems: (1) Existing methods for preparing sponge-like hydrogels are complex and often require the addition of pore-forming agents, pore-forming substances (templates), or special treatments such as directional freezing to obtain water transport channels.

[0005] (2) Insufficient mechanical stability. Traditional hydrogel photothermal evaporation materials are prone to structural damage under repeated compression, stretching or external impact, which leads to blockage of water transmission channels or decline in photothermal performance, affecting the integrity of water transmission channels.

[0006] (3) It has almost no self-healing properties. Once existing materials are damaged (such as cracks, perforations, etc.), they cannot repair themselves and need to be repaired or replaced manually, which increases maintenance costs.

[0007] (4) Poor durability in harsh environments and poor resistance to salt deposition. Salt deposition is easily formed in high-concentration salt water, which leads to a significant decrease in evaporation efficiency. In addition, photothermal components are prone to detachment or degradation in high-temperature, high-salt or extreme pH environments, which also leads to a decrease in evaporation efficiency. These problems seriously restrict the large-scale application of photothermal evaporation materials.

[0008] Therefore, developing a hydrogel material that combines efficient photothermal conversion, stable porous structure, and self-healing properties is of great value. Summary of the Invention

[0009] To address the key defects of existing sponge-like hydrogel photothermal evaporation materials, this invention provides a self-healing hydrogel photothermal evaporation material, its preparation method, and its application.

[0010] First, this invention provides a method for preparing a self-healing hydrogel photothermal evaporation material. This invention successfully prepares a sponge-like hydrogel with self-healing capabilities for seawater desalination through free radical polymerization. The chemical composition is designed to regulate the reversible interactions such as hydrophilic-hydrophobic relationships and hydrogen bonds throughout the system. During polymerization, the hydrophilic and hydrophobic regions separate in the microphase of deionized water, forming pores that provide transport channels for water. More importantly, the orderly distribution of the hydrophilic and hydrophobic regions facilitates the directional alignment of water molecules, reducing the formation of hydrogen bonds that are detrimental to self-healing performance in aqueous environments, thereby promoting its repair capabilities in such environments. Introducing this hydrophilic-hydrophobic interaction into the polymer backbone effectively dissipates external forces, thereby enhancing the impact resistance and compressive strength of the sponge-like hydrogel.

[0011] Secondly, the present invention provides a self-healing hydrogel photothermal evaporation material prepared by the above method.

[0012] Finally, this invention provides the application of the above-mentioned self-healing hydrogel photothermal evaporation material, wherein the water evaporation rate of the self-healing hydrogel photothermal evaporation material of this invention can reach 1.4 kg m³ / s under 1 sun. -2 h -1 After complete cutting and thermal repair, the material's mechanical strength can be restored to 80 kPa, and the evaporation performance remains stable, reaching 98% of the original performance. This excellent self-healing ability not only greatly extends the service life of solar evaporators, but also allows for easy shape reconstruction to adapt to different application needs, which is of positive significance for promoting the practical application of solar water purification technology.

[0013] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for preparing a self-healing hydrogel photothermal evaporation material, the method comprising the following steps: 1) Hydrophilic treatment of carbon nanomaterials; 2) Dissolve the hydrophilic carbon nanomaterials, FeCl3·6H2O and N,N'-methylenebisacrylamide obtained in step 1) in deionized water and sonicate to obtain a dispersion; 3) Add methyl acrylate, acrylic acid and initiator solution to the dispersion obtained in step 2). After mixing thoroughly, transfer the reaction solution to the mold. The reaction is completed and polymerization is completed to obtain a self-healing hydrogel photothermal evaporation material.

[0014] In this technical solution, methyl acrylate is used as a hydrophobic monomer and acrylic acid is used as a hydrophilic monomer. By adjusting the ratio of hydrophilic monomer (acrylic acid) and hydrophobic monomer, a porous gel material with a certain degree of hydrophilic and hydrophobic phase separation is prepared in an aqueous solution. The resulting polymer can bind water around the polymer, and a self-healing hydrogel photothermal evaporation material can be prepared without post-processing.

[0015] Ferric chloride plays a catalytic role, forming a redox system with potassium persulfate to accelerate the generation of free radicals. Acrylic acid, acting as a reactant monomer, also adjusts the pH of the system, accelerating the heterogeneous activation of the system. Although the reaction can occur without ferric chloride, the reaction time will be longer. The reaction system of this invention is a heterogeneous system. This invention does not require the use of surfactants; only when acrylic acid (AA) and methyl acrylate (MA) are in the appropriate molar ratio can a relatively uniform network be prepared, exhibiting a sponge-like porous structure with macroscopic phase separation characteristics, and demonstrating excellent photothermal evaporation performance and outstanding thermo-induced self-healing ability.

[0016] As a preferred embodiment of the present invention, step 1) specifically involves: mixing carbon nanomaterials, concentrated nitric acid and concentrated sulfuric acid, heating and refluxing at 135 ℃-145 ℃, centrifuging at 9000 rpm-10000 rpm, discarding the supernatant, redispersing the precipitate, centrifuging to neutrality, filtering, and freeze-drying to obtain hydrophilic carbon nanomaterials.

[0017] In a preferred embodiment of the present invention, the carbon nanomaterial is prepared in a ratio of concentrated nitric acid to concentrated sulfuric acid of 1g:50mL:150mL.

[0018] In a preferred embodiment of the present invention, the carbon nanomaterial is a multi-walled carbon nanotube.

[0019] As a preferred embodiment of the present invention, in step 2), the mass ratio of the hydrophilic treated carbon nanomaterial, FeCl3·6H2O and N,N'-methylenebisacrylamide is 45-55:90-95:20-30.

[0020] In a preferred embodiment of the present invention, the molar ratio of methyl acrylate to acrylic acid is 0.1-0.4:1.

[0021] As a preferred embodiment of the present invention, the initiator solution is a 2wt% potassium persulfate solution.

[0022] As a preferred embodiment of the present invention, in step 3), the polymerization reaction temperature is 55-65℃ and the reaction time is 1.5-3h.

[0023] A second aspect of the present invention provides a self-healing hydrogel photothermal evaporation material prepared by the above-described preparation method.

[0024] The third aspect of this invention provides the application of the above-mentioned self-healing hydrogel photothermal evaporation material in the field of seawater desalination.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention introduces hydrophilic and hydrophobic interactions into the hydrogel network, giving the hydrogel a porous structure and self-healing properties in environments containing a small amount of water.

[0026] 2) This invention prepares a sponge-like photothermal evaporation hydrogel with self-healing properties in a one-pot process using free radical polymerization, achieving a long-term stable evaporation rate under high salt concentration and self-healing in the presence of water, thereby improving the mechanical strength and service life of the material.

[0027] 3) The preparation method of the present invention is simple and efficient. It can simultaneously achieve the formation of water transport channels and self-healing properties in hydrogel through simple free radical polymerization, without the need for other complicated preparation and post-processing processes.

[0028] 4) The water evaporation rate of the self-healing hydrogel photothermal evaporation material of the present invention can reach 1.4 kg / m³ under 1 sun. -2 h -1 After complete severance and thermal repair, the material's mechanical strength can be restored to 80 kPa, and its evaporation performance remains stable, reaching 98% of its original performance. This superior self-healing capability not only significantly extends the lifespan of the solar evaporator but also allows for easy shape reconstruction to adapt to different application needs. The flexible geometric designability of the self-healing hydrogel photothermal evaporation material provides an effective way to further improve its performance through structural optimization, demonstrating its promising application prospects in the field of seawater desalination. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application 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 only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of the preparation process of the present invention.

[0031] Figure 2 This describes the microstructure of the self-healing hydrogel photothermal evaporation material of this invention.

[0032] Figure 3 This invention relates to the mechanical properties and light absorption properties of the self-healing hydrogel photothermal evaporation material.

[0033] Figure 4 This invention relates to the photothermal evaporation performance of the self-healing hydrogel photothermal evaporation material.

[0034] Figure 5 The present invention relates to the self-healing hydrogel photothermal evaporation material and its evaporation performance and salt resistance to salt water of different concentrations.

[0035] Figure 6 This invention relates to the purification performance of the self-healing hydrogel photothermal evaporation material.

[0036] Figure 7 This invention relates to the self-healing properties of the self-healing hydrogel photothermal evaporation material. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] See Figure 1 This invention provides a method for preparing a self-healing hydrogel photothermal evaporation material, the method comprising the following steps: 1) Hydrophilic treatment of multi-walled carbon nanotubes; 2) Dissolve the hydrophilic treated multi-walled carbon nanotubes, FeCl3·6H2O and N,N'-methylenebisacrylamide obtained in step 1) in deionized water and sonicate to obtain a dispersion. 3) Add methyl acrylate, acrylic acid and initiator solution to the dispersion obtained in step 2). After mixing thoroughly, transfer the reaction solution to the mold. The reaction is completed and polymerization is completed to obtain a self-healing hydrogel photothermal evaporation material.

[0039] Example 1

[0040] The preparation method of the self-healing hydrogel photothermal evaporation material provided in this embodiment includes the following steps: 1) Hydrophilic treatment of multi-walled carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) were mixed with 50 mL of concentrated nitric acid and 150 mL of concentrated sulfuric acid in a three-necked flask and heated under reflux at 140 °C for 4 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes, and the supernatant was discarded. The resulting precipitate was redispersed with deionized water and the centrifugation was repeated until the dispersion was neutral. The neutral MWCNTs were filtered to remove excess water and then freeze-dried to obtain hydrophilicated multi-walled carbon nanotubes (H-MWCNTs).

[0041] 2) Dissolve 50 mg of hydrophilized multi-walled carbon nanotubes (H-MWCNTs), 94 mg of FeCl3·6H2O and 25 mg of N,N'-methylenebisacrylamide (MBAA) in 15 mL of deionized water and sonicate for 30 minutes to obtain a uniform dispersion.

[0042] 3) Add methyl acrylate and acrylic acid in a molar ratio of 0.1:1 to the dispersion obtained in step 2). Then add 5 mL of 2 wt% potassium persulfate (KPS) solution as an initiator. After thorough mixing, transfer the reaction solution to a mold and react at 60°C for 2 hours to complete the polymerization, obtaining a self-healing hydrogel photothermal evaporation material (named CMA-1).

[0043] Example 2

[0044] The preparation method of the self-healing hydrogel photothermal evaporation material provided in this embodiment includes the following steps: 1) Hydrophilic treatment of multi-walled carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) were mixed with 50 mL of concentrated nitric acid and 150 mL of concentrated sulfuric acid in a three-necked flask and heated under reflux at 140 °C for 4 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes, and the supernatant was discarded. The resulting precipitate was redispersed with deionized water and the centrifugation was repeated until the dispersion was neutral. The neutral MWCNTs were filtered to remove excess water and then freeze-dried to obtain hydrophilicated multi-walled carbon nanotubes (H-MWCNTs).

[0045] 2) Dissolve 50 mg of hydrophilized multi-walled carbon nanotubes (H-MWCNTs), 94 mg of FeCl3·6H2O and 25 mg of N,N'-methylenebisacrylamide (MBAA) in 15 mL of deionized water and sonicate for 30 minutes to obtain a uniform dispersion.

[0046] 3) Add methyl acrylate and acrylic acid in a molar ratio of 0.2:1 to the dispersion obtained in step 2). Then add 5 mL of 2 wt% potassium persulfate (KPS) solution as an initiator. After thorough mixing, transfer the reaction solution to a mold and react at 60°C for 2 hours to complete the polymerization, obtaining a self-healing hydrogel photothermal evaporation material (named CMA-2).

[0047] Example 3

[0048] The preparation method of the self-healing hydrogel photothermal evaporation material provided in this embodiment includes the following steps: 1) Hydrophilic treatment of multi-walled carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) were mixed with 50 mL of concentrated nitric acid and 150 mL of concentrated sulfuric acid in a three-necked flask and heated under reflux at 140 °C for 4 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes, and the supernatant was discarded. The resulting precipitate was redispersed with deionized water and the centrifugation was repeated until the dispersion was neutral. The neutral MWCNTs were filtered to remove excess water and then freeze-dried to obtain hydrophilicated multi-walled carbon nanotubes (H-MWCNTs).

[0049] 2) Dissolve 50 mg of hydrophilized multi-walled carbon nanotubes (H-MWCNTs), 94 mg of FeCl3·6H2O and 25 mg of N,N'-methylenebisacrylamide (MBAA) in 15 mL of deionized water and sonicate for 30 minutes to obtain a uniform dispersion.

[0050] 3) Add methyl acrylate and acrylic acid in a molar ratio of 0.3:1 to the dispersion obtained in step 2). Then add 5 mL of 2 wt% potassium persulfate (KPS) solution as an initiator. After mixing thoroughly, transfer the reaction solution to a mold and react at 60°C for 2 hours to complete the polymerization, and obtain a self-healing hydrogel photothermal evaporation material (named CMA-3).

[0051] Example 4

[0052] The preparation method of the self-healing hydrogel photothermal evaporation material provided in this embodiment includes the following steps: 1) Hydrophilic treatment of multi-walled carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) were mixed with 50 mL of concentrated nitric acid and 150 mL of concentrated sulfuric acid in a three-necked flask and heated under reflux at 140 °C for 4 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes, and the supernatant was discarded. The resulting precipitate was redispersed with deionized water and the centrifugation was repeated until the dispersion was neutral. The neutral MWCNTs were filtered to remove excess water and then freeze-dried to obtain hydrophilicated multi-walled carbon nanotubes (H-MWCNTs).

[0053] 2) Dissolve 50 mg of hydrophilized multi-walled carbon nanotubes (H-MWCNTs), 94 mg of FeCl3·6H2O and 25 mg of N,N'-methylenebisacrylamide (MBAA) in 15 mL of deionized water and sonicate for 30 minutes to obtain a uniform dispersion.

[0054] 3) Add methyl acrylate and acrylic acid in a molar ratio of 0.4:1 to the dispersion obtained in step 2). Then add 5 mL of 2 wt% potassium persulfate (KPS) solution as an initiator. After thorough mixing, transfer the reaction solution to a mold and react at 60°C for 2 hours to complete the polymerization, obtaining a self-healing hydrogel photothermal evaporation material (named CMA-4).

[0055] Comparative Example The preparation method of the self-healing hydrogel photothermal evaporation material provided in this comparative example includes the following steps: 1) Hydrophilic treatment of multi-walled carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) were mixed with 50 mL of concentrated nitric acid and 150 mL of concentrated sulfuric acid in a three-necked flask and heated under reflux at 140 °C for 4 hours. After the reaction, the mixture was centrifuged at 10,000 rpm for 10 minutes, and the supernatant was discarded. The resulting precipitate was redispersed with deionized water and the centrifugation was repeated until the dispersion was neutral. The neutral MWCNTs were filtered to remove excess water and then freeze-dried to obtain hydrophilicated multi-walled carbon nanotubes (H-MWCNTs).

[0056] 2) Dissolve 50 mg of hydrophilized multi-walled carbon nanotubes (H-MWCNTs), 94 mg of FeCl3·6H2O and 25 mg of N,N'-methylenebisacrylamide (MBAA) in 15 mL of deionized water and sonicate for 30 minutes to obtain a uniform dispersion.

[0057] 3) Add acrylic acid to the dispersion obtained in step 2). Then add 5 mL of 2 wt% potassium persulfate (KPS) solution as an initiator. After mixing thoroughly, transfer the reaction solution to a mold and react at 60 °C for 2 hours to complete the polymerization and obtain a hydrogel (named CMA-0).

[0058] The self-healing hydrogel photothermal evaporation materials prepared in Examples 1-4 and the hydrogel obtained in Comparative Example 1 were characterized by their photothermal evaporation performance, salt resistance, purification performance and self-healing performance.

[0059] Material characterization The surface morphology of the freeze-dried samples was observed using a field emission scanning electron microscope (ZEISS Gemini SEM500); the mechanical properties were tested using a SANA (Superconducting Electron Testing Machine). The optical absorption properties of the materials were tested using a UV-Vis-NIR spectrophotometer (Shimadzu UV 3600).

[0060] Photothermal evaporation performance During indoor testing, a layer of polyethylene foam (25 mm radius) was wrapped around the hydrogel (10 mm radius) as a buoyancy and insulation layer, and the hydrogel was floated in a 100 mL glass beaker containing 100 g of deionized water. A xenon lamp (HX-F300) was used to simulate the solar spectrum, and an SM206-SOLAR solar radiometer was used to monitor and calibrate the light intensity. The surface temperature of the evaporator was simultaneously acquired via thermocouples and an infrared thermal imager (Testo 875 i) to obtain its spatial distribution. The mass change of moisture was continuously recorded using a JJ324BC high-precision digital balance. The temperature was 25 °C, and the humidity was kept constant at approximately 30–40%.

[0061] The evaporation rate is calculated using formula (1). ): (1); Where dm / dt represents the mass of water evaporated from the surface of the hydrogel during the evaporation process per unit time, and S is the projected area of ​​the light-absorbing surface of the sample when it is irradiated by light.

[0062] The evaporation efficiency of the corresponding CMA is calculated according to formula (2): (2); in, Indicates the evaporation rate. Optical concentration, P 0 Solar radiation intensity (unit: 1 kW·m) -2 ). h v It is the enthalpy change of water at the corresponding evaporation temperature. According to... h v =2501.6−2.275× T -0.00186× T 2 Calculations show that T It is the temperature of the evaporation surface (°C).

[0063] Salt resistance Evaporator samples were immersed in NaCl solutions of different concentrations (3.5 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%) for 12 hours to reach adsorption equilibrium, followed by indoor photothermal evaporation experiments. Salt resistance was evaluated by monitoring the stability of the evaporation rate and observing salt crystallization on the evaporation surface. To further investigate long-term stability and resistance to salt precipitation, continuous evaporation experiments for 10 hours and alternating cycles of high (20 wt%) and low (3.5 wt%) salinity were conducted.

[0064] Purification performance To evaluate the purification effects on acidic and alkaline liquids, simulated seawater, and dye wastewater (MG, MO, CV), a custom-designed condenser was used to collect the condensate produced during evaporation. A pH meter was used to monitor changes in the solution's pH value before and after evaporation, and inductively coupled plasma mass spectrometry (ICP-MS) was used to quantitatively analyze the residual concentration of metal ions in the solution. Changes in dye concentration were assessed by measuring the absorbance at characteristic absorption wavelengths using a UV-Vis spectrophotometer (UV-4802S).

[0065] Repair performance To evaluate the self-healing ability of the hydrogel, a strip sample (5 cm × 1 cm × 0.1 cm) was cut in half, the cut surfaces were tightly sealed together, and then placed in a sealed bag and heated in an oven at 80 ℃ for 4 hours. The repaired sample was cooled to room temperature, and its surface morphology, mechanical properties, and photothermal evaporation properties were then characterized. Mechanical properties were tested using a SANA (Superconducting Nanoscale Testing Machine) at a tensile rate of 5 mm / min.

[0066] result: Material characterization results: See Figure 2 Hydrogels with low methyl acrylate (MA) content Figure 2 (a) and Figure 2 (b) The structure was dense, and no obvious pores were observed; as the MA content increased, a porous structure gradually appeared in the sample. Figure 2 (c) Figure 2 (d) and Figure 2 (d1)), and a uniformly distributed porous network is formed in CMA-4 ( Figure 2 (e) and Figure 2 (e1)). Further observation revealed that the pore structure in CMA-3 has fewer through holes ( Figure 2 (d2)), while CMA-4 is mainly based on through-hole structure ( Figure 2 (e2)).

[0067] Due to the change in phase separation scale regulated by MA content, low-MA-content self-healing hydrogel photothermal evaporation materials exhibit an inhomogeneous structure with a loose outer layer and a dense inner layer after freeze-drying, while high-MA-content self-healing hydrogel photothermal evaporation materials show a uniform white porous morphology overall. This difference in macroscopic morphology confirms the difference in their internal phase separation behavior: under low MA conditions, hydrophobic components locally aggregate to form a microphase separation structure, confining water molecules within a nanoscale region and inhibiting the nucleation and growth of ice crystals. When the MA content increases to a certain level, macroscopic phase separation occurs in the system, forming continuous and interconnected aqueous channels, providing a pathway for freeze-drying of water, and ultimately obtaining an interconnected porous structure.

[0068] The un-lyophilized hydrogel was observed using environmental scanning electron microscopy (ESEM). Figure 2 (f) and Figure 2 (g) The results showed that CMA-4 maintained a clear porous structure in the wet state, while CMA-3 had no obvious pores.

[0069] See Figure 3 (a) With increasing MA content, the compressive strength of the self-healing hydrogel photothermal evaporation material is significantly improved. Hydrophobic groups in MA form hydrophobic microdomains through intermolecular association, which serve as reversible and dynamic physical crosslinking points, effectively enhancing the crosslinking density of the polymer network. Since the hydrophobic force is lower than that of covalent bonds, under external compressive load, these hydrophobic crosslinked regions preferentially dissociate and recombine as "sacrificial bonds," continuously dissipating energy through a reversible fracture mechanism, thereby delaying the occurrence of macroscopic failure and significantly improving the mechanical toughness and compressive strength of the material.

[0070] See Figure 3 (b) With the increase of MA addition, the elastic modulus and loss modulus both increase significantly, especially CMA-4. CMA-4 exhibits excellent mechanical properties, can withstand multiple compressions, and maintains structural integrity under static compression load of 500 g weight and complex deformations such as bending and torsion, indicating that it has good potential application reliability.

[0071] See Figure 3 (c) With the introduction of only 0.2 wt% H-MWCNTs, CMA-0.4 exhibits broad-spectrum and efficient absorption characteristics in the solar spectrum range of 250-2500 nm, with an absorption rate of over 97% across the entire band.

[0072] Results of photothermal evaporation performance: See Figure 4 (a) The evaporation performance of all CMA self-healing hydrogel photothermal evaporation materials is significantly better than that of pure water, and shows a clear two-stage improvement with increasing MA content: the characteristic from CMA-0 to CMA-3 stages, the evaporation rate from 1.04 kgm -2 h -1 Steady growth to 1.27 kg m -2 h -1 A significant jump occurs at CMA-4, with a rate reaching 1.40 kg m. -2 h -1 .

[0073] like Figure 4 As shown in (b), CMA-4 exhibits excellent and stable evaporation performance under different light intensities, while CMA-3, with weaker water transport capacity, shows significant performance degradation under varying light conditions. Figure 4(c)).

[0074] Salt tolerance results: like Figure 5 As shown in (a), the evaporation curves at different salinities have similar shapes, with the main differences being in the slope and the steady-state evaporation rate. When the salt concentration increases from 3.5 wt% to 20 wt%, the evaporation rate increases from 1.42 kg·m³ / h. -2 ·h -1 It decreased slightly to 1.30 kg·m -2 ·h -1 The decrease was only 0.12 kg·m -2 ·h -1 ( Figure 5 (b) An evaporation experiment was conducted on CMA-4 for 10 hours. The results showed that its evaporation rate remained stable at approximately 1.40 kg·m³. -2 ·h -1 No significant attenuation was observed. Figure 5 (c) and no salt crystals were observed on the surface after evaporation. Figure 5 (d) This indicates that CMA-4 hydrogel has excellent salt resistance.

[0075] Due to the material's inherent hydrophilic porous structure and its effective ion transport capabilities, this structure enhances liquid-phase mass transfer by establishing a concentration gradient, thereby giving the material surface salt-dissolving properties. Figure 5 (f)). For example Figure 5 As shown in (e), when approximately 0.5 g of NaCl solid was sprinkled on the surface of CMA-4 and floated on the surface of 3.5 wt% brine, the salt was completely dissolved within 30 min, further verifying this property.

[0076] Therefore, the sponge-like porous structure endows CMA-4 hydrogel with excellent salt-dissolving properties in different salinity ranges, enabling it to continuously desalinate and exhibiting good durability and structural stability.

[0077] Purification performance results: like Figure 6 As shown in (a), CMA maintains a good evaporation rate in both acidic and alkaline wastewater. Figure 6 As shown in (b), the pH values ​​of strongly acidic and strongly alkaline solutions significantly tended towards neutral after evaporation and purification. Inductively coupled plasma atomic emission spectrometry (ICP) was used to analyze the concentration changes of Na⁺, K⁺, Mg²⁺, and Ca²⁺ ions in actual seawater before and after evaporation. Figure 6 (c) The results showed that the concentrations of all ions were significantly reduced, and the resulting freshwater fully met the drinking water standards set by the World Health Organization (WHO). This reflects the wastewater purification capabilities of CMA under harsh conditions.

[0078] Self-healing performance test results: like Figure 7 As shown in (a), the mechanical repair efficiency of the hydrogel decreased from approximately 90% to approximately 50% after the introduction of MA. After thermal repair, the CMA-4 hydrogel still maintained a mechanical strength of 70 to 90 kPa, sufficient to withstand certain deformation without cracking. Figure 7 (b) More importantly, after five consecutive repair-break cycles, the strength of the same sample remained stable at around 80 kPa. Figure 6 (c) Therefore, even with a slight reduction in repair efficiency, the mechanical strength retained by the material after repair is fully sufficient to meet the operational requirements of the photothermal evaporator. Furthermore, as... Figure 7 (d) and Figure 7 As shown in (e), after repair at 60℃ for 4 h, the CMA-4 hydrogel still exhibits a macroscopically interconnected porous structure, and the evaporation rate does not decrease after repair. Therefore, CMA-4 can not only achieve structural repair but also evaporation rate repair, with a repair efficiency as high as 98%. Figure 7 (f)).

[0079] As can be seen, the water evaporation rate of the self-healing hydrogel photothermal evaporation material of the present invention can reach 1.4 kgm³ under 1 sun. -2 h -1 After complete severance and thermal repair, the material's mechanical strength can be restored to 80 kPa, and its evaporation performance remains stable, reaching 98% of its original performance. This superior self-healing capability not only significantly extends the lifespan of the solar evaporator but also allows for easy shape reconstruction to adapt to different application needs. The flexible geometric designability of the self-healing hydrogel photothermal evaporation material provides an effective way to further improve its performance through structural optimization, demonstrating its promising application prospects in the field of seawater desalination.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a self-healing hydrogel photothermal evaporation material, characterized in that, The preparation method includes the following steps: 1) Hydrophilic treatment of carbon nanomaterials; 2) Dissolve the hydrophilic carbon nanomaterials, FeCl3·6H2O and N,N'-methylenebisacrylamide obtained in step 1) in deionized water and sonicate to obtain a dispersion; 3) Add methyl acrylate, acrylic acid and initiator solution to the dispersion obtained in step 2). After mixing thoroughly, transfer the reaction solution to the mold. The reaction is completed and polymerization is completed to obtain a self-healing hydrogel photothermal evaporation material.

2. The method for preparing a self-healing hydrogel photothermal evaporation material according to claim 1, characterized in that, Step 1) Specifically, carbon nanomaterials, concentrated nitric acid and concentrated sulfuric acid are mixed and heated under reflux at 135 ℃-145 ℃. The mixture is centrifuged at 9000-10000 rpm, the supernatant is discarded, the precipitate is redispersed, centrifuged and washed until neutral, filtered, and freeze-dried to obtain hydrophilic carbon nanomaterials.

3. The method for preparing a self-healing hydrogel photothermal evaporation material according to claim 2, characterized in that, The carbon nanomaterials are prepared in a ratio of concentrated nitric acid to concentrated sulfuric acid of 1g:50mL:150mL.

4. The method for preparing a self-healing hydrogel photothermal evaporation material according to claim 1 or 2, characterized in that, The carbon nanomaterial is a multi-walled carbon nanotube.

5. The method for preparing a self-healing hydrogel photothermal evaporation material according to claim 1, characterized in that, In step 2), the mass ratio of hydrophilic treated carbon nanomaterials, FeCl3·6H2O, and N,N'-methylenebisacrylamide is 45-55:90-95:20-30.

6. The method for preparing a self-healing hydrogel photothermal evaporation material according to claim 1, characterized in that, The molar ratio of methyl acrylate to acrylic acid is 0.1-0.4:

1.

7. The method for preparing a self-healing hydrogel photothermal evaporation material according to claim 1, characterized in that, The initiator solution is a 2 wt% potassium persulfate solution.

8. The method for preparing a self-healing hydrogel photothermal evaporation material according to claim 1, characterized in that, In step 3), the polymerization temperature is 55-65℃ and the reaction time is 1.5 h-3 h.

9. A self-healing hydrogel photothermal evaporation material, characterized in that, The self-healing hydrogel photothermal evaporation material is prepared by the preparation method described in any one of claims 1-8.

10. An application of the self-healing hydrogel photothermal evaporation material as described in claim 9, characterized in that, Application of the self-healing hydrogel photothermal evaporation material in the field of seawater desalination.

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