Cellulose / mxene composite aerogel and preparation method and application thereof

Abstract

The present application relates to a kind of cellulose / MXene composite aerogel and its preparation method and application.The method includes the following steps: cellulose is carboxylated modification, dissociates into nanofiber, and then is prepared into cellulose water dispersion;Cellulose water dispersion is combined with few-layer MXene nanosheet dispersion, to form precursor gel;The precursor gel is injected into mold and frozen;The frozen gel is immersed in anhydrous ethanol / metal ion solution together with mold solvent exchange;After ice-free, wash with water, dry under normal pressure, to obtain cellulose / MXene composite aerogel.The technical problem to be solved by the present application is how to provide a kind of cellulose / MXene composite aerogel, so that it has excellent porosity, complete morphology and dry shrinkage rate control level, and can still maintain the complete three-dimensional porous skeleton structure during washing or long-term contact with liquid water;During the interface water evaporation process, it has good water adsorption, import and sustained transport capacity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of interface solar water evaporation, and particularly relates to a cellulose / MXene composite aerogel as well as a preparation method and application thereof. BACKGROUND

[0002] At present, the global water resource shortage problem has become increasingly serious. Climate change, population growth and industrial pollution and other multiple factors superimposed, making the contradiction between supply and demand of water resources increasingly acute. Seawater resources account for more than 97% of the total water on earth, and can meet the growing demand for fresh water after purification due to its huge reserves. Aerogels are widely used in the field of interface solar water evaporation due to their unique structural advantages. Cellulose is widely available, renewable and environmentally friendly, and has good mechanical toughness and rich surface functional groups. MXene is a two-dimensional transition metal carbide / carbon nitride obtained by etching MAX phase, and has high conductivity, large specific surface area and various surface active groups. Combining cellulose and MXene can realize "complementary advantages" at the material level. On the one hand, the high conductivity and excellent light-heat conversion performance of MXene nanosheets can endow cellulose-based aerogels with more functionality, which can be applied to interface solar water evaporation. On the other hand, the three-dimensional network constructed by cellulose nanofibers can effectively prevent the collapse of MXene interlayer stacking, and cellulose nanofibers can provide excellent hydrophilic channels and mechanical support at the interface, laying the foundation for continuous water transport and evaporation.

[0003] For the preparation of cellulose / MXene composite aerogel, although some progress has been made in supercritical drying and freeze drying, there are still problems such as high equipment cost, long time consumption and difficulty in large-scale application. Although normal pressure drying has low cost and simple operation, it still faces the problem of how to effectively control the capillary force and inhibit the collapse of the skeleton. Some scholars propose to use the process of "low temperature freezing + ethanol solvent exchange" for normal pressure drying, and use the hydrogen bond interaction and physical nesting relationship between cellulose nanofiber (CNF) and MXene to form an aerogel skeleton similar to "brick-mud" structure. However, this aerogel skeleton is prone to collapse. In order to inhibit the collapse of the aerogel skeleton, the overall surface of the material is made hydrophobic or semi-hydrophobic after drying through chemical cross-linking or hydrophobic modification, so as to improve the stability of the aerogel skeleton in water. However, although this method is effective in short-term structure maintenance, it also blocks the hydrophilic functional groups on the surface of the material, reducing the diffusion rate and capillary transport capacity of water in the pores, which is difficult to meet the application requirements of long-term maintenance of high hydrophilic channels and rapid water transport capacity. At the same time, this hydrophobic treatment will also affect the sustained performance of the material during subsequent long-term contact with water, and cannot fully meet the demand for high hydrophilicity and soakable stability. After washing with water or long-term soaking, the material is still prone to structure shrinkage and pore collapse during the drying process due to capillary force, which is difficult to guarantee the sustained structural stability of the material in a high humidity environment, resulting in its inability to be widely applied in the field of interface water evaporation. SUMMARY

[0004] The main purpose of the present application is to provide a cellulose / MXene composite aerogel and its preparation method and application, and to solve the technical problem of how to provide a cellulose / MXene composite aerogel with excellent porosity, complete morphology and drying shrinkage control level, which can still maintain a complete three-dimensional porous skeleton structure during washing with water or long-term contact with liquid water. It has good water adsorption, introduction and sustained transport capacity during the process of interface water evaporation, significantly improving the evaporation efficiency and process stability. At the same time, the production process is simple and low in energy consumption, which is suitable for popularization in more extensive practical scenarios.

[0005] The purpose of the present application and the solution to its technical problems are also realized by the following technical solutions. According to the preparation method of a cellulose battery separator material proposed by the present application, the following steps are included:

[0006] S11 carboxymethyl modification of cellulose, dissociation into nanofibers, and preparation into a cellulose water dispersion; compounding the cellulose water dispersion with a few-layer MXene nanosheet dispersion to form a precursor gel;

[0007] S12 inject the precursor gel into a mold and freeze; immerse the fully frozen gel together with the mold in anhydrous ethanol / metal ion solution for solvent exchange;

[0008] After the S13 solvent was exchanged to an ice-free state, it was rinsed with water and dried under normal pressure to obtain cellulose / MXene composite aerogel.

[0009] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0010] Preferably, in the aforementioned preparation method, the cellulose is selected from softwood pulp and / or hardwood pulp; the carboxylation modification method is selected from any one of TEMPO oxidation, potassium permanganate oxidation and ammonium persulfate oxidation; and the carboxyl content on the surface of the modified cellulose is 1.0~2.5 mmol / g.

[0011] Preferably, in the aforementioned preparation method, the mass concentration of the cellulose aqueous dispersion is 0.8~1.2%; the mass concentration of the few-layer MXene nanosheet dispersion is 1.2~1.8%; and the composite mass ratio of the cellulose aqueous dispersion to the few-layer MXene nanosheet dispersion is 2.5~5:1.

[0012] Preferably, in the aforementioned preparation method, the mass concentration of metal ions in the anhydrous ethanol / metal ion solution is 0.5~2.0%, and the solution temperature is -25~-5 ℃.

[0013] The objective of this invention and the technical problem it solves are achieved by the following technical solution. A cellulose / MXene composite aerogel according to this invention comprises cellulose nanofibers and few-layer MXene nanosheets; the surface of the modified cellulose nanofibers includes carboxyl groups and / or carboxymethyl groups; the modified cellulose nanofibers, the few-layer MXene nanosheets, and metal ions together form a fiber-sheet network structure.

[0014] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0015] Preferably, the aforementioned cellulose / MXene composite aerogel is prepared according to the aforementioned preparation method; the cellulose / MXene composite aerogel can maintain an intact three-dimensional porous framework structure during water washing or long-term contact with liquid water; under 1 times the solar radiation intensity, the evaporation rate of the cellulose / MXene composite aerogel is ≥1.85 kg•m-2•h-1, and the evaporation efficiency is ≥89%.

[0016] The objective of this invention and the technical problem it solves are achieved through the following technical solution: An application of the aforementioned cellulose / MXene composite aerogel in the field of interfacial solar water evaporation, according to this invention.

[0017] The objective of this invention and the technical problem it solves are achieved by the following technical solution. A distributed interfacial water evaporation device according to this invention comprises:

[0018] A water purification tank is used to receive the returned condensate.

[0019] A wastewater tank is located within the water purification tank and is used to hold wastewater to be purified; the wastewater tank contains the aforementioned cellulose / MXene composite aerogel; the cellulose / MXene composite aerogel floats at the gas-liquid interface;

[0020] A condenser hood is installed above the water purification tank and connected to the water purification tank; the condenser hood and the water purification tank can form a condensate return channel;

[0021] The water outlet is located on the water purification tank.

[0022] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0023] Preferably, in the aforementioned distributed interface water evaporation device, the condenser shroud has an arc-shaped structure that is higher in the middle and lower at the periphery.

[0024] Preferably, in the aforementioned distributed interface water evaporation device, both the condenser hood and the wastewater tank are telescopic structures.

[0025] By employing the above technical solution, the cellulose / MXene composite aerogel, its preparation method, and its application proposed in this invention have at least the following advantages:

[0026] This invention proposes a cellulose / MXene composite aerogel, its preparation method, and its applications. By carboxylating cellulose to introduce carboxyl or carboxymethyl groups onto the cellulose surface, a synergistic network structure of modified cellulose and MXene is constructed. Combined with a low-temperature solvent exchange and multi-point ion complexation strategy with ethanol / metal ion solution, a structurally stable, hydrophilic, and hydroconductive MXene / cellulose composite aerogel material capable of long-term operation can be prepared under ambient pressure and drying conditions. Specific beneficial effects are as follows:

[0027] 1. The cellulose / MXene composite aerogel proposed in this invention significantly improves the structural retention ability of aerogel materials in an aqueous environment. Modified cellulose nanofibers alone cannot maintain their porous structure after drying at normal pressure. However, when combined with MXene and complexed with metal ions at multiple points, it significantly enhances the skeletal strength and capillary resistance of the aerogel, achieving long-term stable operation. The aerogel material prepared by this invention maintains its complete three-dimensional porous skeletal structure even during water washing or long-term contact with liquid water, avoiding the collapse and shrinkage problems of this type of aerogel in the prior art after contact with water.

[0028] 2. The cellulose / MXene composite aerogel proposed in this invention can achieve efficient interfacial water transport and evaporation without sacrificing the hydrophilic properties of the aerogel. The aerogel of this invention does not use hydrophobic blocking agents such as isocyanates to inhibit framework collapse, thus retaining abundant hydrophilic groups such as carboxyl and hydroxyl groups on the material surface. This ensures good water adsorption, introduction, and continuous transport capabilities during interfacial water evaporation. Compared to existing MXene / cellulose aerogels that require hydrophobic modification with hydrophobic blocking agents such as isocyanates to inhibit framework collapse, the aerogel material of this invention is more suitable for continuously operating evaporation systems, significantly improving evaporation efficiency and process stability.

[0029] 3. The method for preparing cellulose / MXene composite aerogel proposed in this invention can produce this low-energy-consumption (no energy-driven operation required for application) and highly conformable aerogel material under normal pressure. This invention optimizes the "freezing-solvent exchange conditions-metal ion complexation" process, eliminating the need for energy-intensive freeze-drying or supercritical equipment, and achieving stable aerogel structure formation at normal pressure. Furthermore, the obtained aerogel material exhibits excellent porosity, morphological integrity, and controlled drying shrinkage. Simultaneously, the preparation process is simple and energy-efficient, making it suitable for wider application in practical scenarios.

[0030] 4. The cellulose / MXene composite aerogel proposed in this invention has long-term operational stability and salt deposition resistance. It exhibits good salt crystallization resistance and water transport capacity during the evaporation of interfacial water. After long-term evaporation tests, the surface of the aerogel material can still maintain structural integrity and functional stability, avoiding the problems of pore blockage and performance degradation caused by salt accumulation.

[0031] 5. The cellulose / MXene composite aerogel proposed in this invention can be integrated into a distributed interfacial water evaporation device, adaptable to various off-grid application scenarios. This invention, through the synergistic design of aerogel materials and devices, integrates the cellulose / MXene composite aerogel with the structure to construct a distributed interfacial water evaporation device, thereby achieving functional coupling of "photothermal evaporation - steam escape - condensation reflux - purified water collection." This allows for the production of pure water through purification using interfacial solar evaporation materials, eliminating the need for large-scale electricity supply and making it suitable for promotion in underdeveloped areas.

[0032] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0033] Figure 1This is a morphology-SEM image of the aerogel in Example 1 of the present invention;

[0034] Figure 2 This is a photograph of the aerogel from Embodiment 1 of the present invention;

[0035] Figure 3 These are the test results of the aerogel seawater desalination performance of Example 1 of the present invention;

[0036] Figure 4 These are the test results of the heavy metal treatment performance of the aerogel in Example 1 of this invention;

[0037] Figure 5 This is the result of the aerogel salt deposition resistance test in Example 1 of the present invention - change in evaporation rate;

[0038] Figure 5a These are photographs of the aerogel at the beginning and end of evaporation, showing the results of the salt deposition resistance test of the aerogel in Example 1 of this invention.

[0039] Figure 6 Comparative Example 1: Aerogel photograph;

[0040] Figure 7 Comparative Example 2: Aerogel photograph;

[0041] Figure 8 Comparative Example 3: Aerogel photograph;

[0042] Figure 9 A schematic diagram of the distributed interface water evaporation device proposed in this invention;

[0043] Figure 10 A schematic diagram of the operation process of the distributed interface water evaporation device proposed in this invention. Detailed Implementation

[0044] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, provides a detailed description of the specific implementation methods, structures, features, and effects of a cellulose / MXene composite aerogel, its preparation method, and its applications based on the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0045] This invention proposes a method for preparing cellulose / MXene composite aerogel, which includes the following steps:

[0046] The first step is to prepare an aqueous dispersion of cellulose and few-layer MXene nanosheets. The specific steps are as follows:

[0047] The preparation of cellulose aqueous dispersions includes cellulose carboxylation modification, dissociation into nanofibers, and formulation into cellulose aqueous dispersions.

[0048] Cellulose carboxylation modification involves carboxylating wood pulp through methods such as TEMPO oxidation, potassium permanganate oxidation, or ammonium persulfate (APS) oxidation, converting some hydroxyl groups on the surface of the cellulose molecular chain into carboxyl groups. This is existing technology and will not be elaborated upon in this invention. Preferably, the cellulose in this invention is selected from softwood pulp and / or hardwood pulp. By controlling the degree of oxidation of cellulose, the surface carboxyl group content of cellulose is maintained at 1.0-2.5 mmol / g. At this oxidation level, favorable conditions are provided for the subsequent establishment of multiple complexation sites between cellulose and metal ions.

[0049] The dissociation into nanofibers is achieved by repeatedly homogenizing the modified cellulose slurry using a high-pressure homogenizer to dissociate it into nanofibers (CNF). In this invention, the pressure of high-pressure homogenization is preferably 80-120 MPa. Through multiple homogenizations, nanofibers with a high aspect ratio and good dispersibility are obtained.

[0050] The cellulose aqueous dispersion is prepared by ultrasonically dispersing the modified nanofibers with carboxyl or carboxymethyl groups on their surface to obtain a uniform aqueous dispersion. Preferably, the mass concentration of the aqueous dispersion is 0.5-2%; this range is set to ensure stability at room temperature without significant sedimentation.

[0051] The appropriate oxidation / carboxylation and homogenization processes described above lay the foundation for subsequent ion complexation and MXene binding, while preserving the hydrophilic properties of cellulose to ensure unobstructed water channels in the material during subsequent interfacial water evaporation.

[0052] Few-layer MXene nanosheets were prepared using a low-temperature etching and layer-by-layer exfoliation process. The preparation of the few-layer MXene dispersion is also an existing technology; this invention is merely illustrative and not intended to limit the scope of the invention. In some specific embodiments, the specific process is as follows: First, lithium fluoride and hydrochloric acid are added to a corrosion-resistant container to prepare an in-situ hydrofluoric acid etching solution. This solution is stirred at a constant speed to form a uniform active medium. Then, Ti3AlC2 powder is added to the etching system in batches, and the reaction is carried out at 35-40℃ for 24-36 hours to achieve selective removal of the aluminum layer in the MAX phase. After the reaction, by-products and unreacted substances are removed through multi-stage centrifugation combined with dynamic pH monitoring until the pH of the supernatant stabilizes at 5.5-6.0, obtaining a pure multilayer MXene precipitate. The preferred centrifugation speed is 3000-4000 rpm. The precipitate was dispersed in deionized water and subjected to low-temperature ultrasonic treatment under argon protection and an ice bath to promote interlayer dissociation. Finally, it was centrifuged at 3000-3500 rpm for 60-90 minutes to remove unpeeled thick flakes and collect the upper colloidal suspension to obtain the few-layer Ti3C2T. x The nanosheet dispersion exhibits uniform surface charge distribution and excellent stability, making it suitable for direct use in the construction of subsequent functional materials. In this step, it is crucial to ensure that the obtained MXene dispersion possesses a negative potential in the aqueous phase. This facilitates the simultaneous dispersion with similarly negatively charged carboxyl-containing cellulose nanofibers and prevents large-scale aggregation, thereby enabling precise control of the framework structure during subsequent coordination and ion complexation processes.

[0053] The second step involves combining an aqueous cellulose dispersion with a few-layer MXene nanosheet dispersion to form a precursor gel. This combination is achieved by mixing the nanocellulose suspension and the few-layer MXene nanosheets at a specific mass ratio, using a high-shear dispersion technique to uniformly combine the nanofibers and MXene nanosheets, thus forming the precursor gel.

[0054] In this step, the carboxyl and carboxymethyl groups on the surface of the modified nanocellulose fibers, along with the hydrophilic groups such as carboxyl and hydroxyl groups abundant on the surface of MXene, can form a preliminary skeleton through hydrogen bonding, electrostatic repulsion, and local coordination, thus reducing shrinkage during subsequent drying. This composite step, while ensuring hydrophilicity, also utilizes the two-dimensional lamellar properties of MXene to form a "fiber-lamellae" network with the long fiber characteristics of the modified nanocellulose fibers, laying the foundation for subsequent ion complexation.

[0055] To ensure a more stable "fiber-sheet" network structure formed by cellulose nanofibers and MXene two-dimensional sheets, the preferred formulation of the two is as follows: the mass concentration of the cellulose aqueous dispersion is 0.8~1.2%; the mass concentration of the few-layer MXene nanosheet dispersion is 1.2~1.8%; and the composite mass ratio of the cellulose aqueous dispersion to the few-layer MXene nanosheet dispersion is 2.5~5:1.

[0056] Cellulose nanofibers and MXene, with their surfaces rich in hydrophilic groups such as carboxyl and hydroxyl groups, can form a preliminary framework through hydrogen bonding, electrostatic repulsion, and local coordination, thereby reducing subsequent drying shrinkage. This composite, while maintaining hydrophilicity, utilizes the two-dimensional lamellar properties of MXene and the long fiber characteristics of CNF to form a "fiber-lamellae" network, laying the foundation for subsequent ion complexation.

[0057] The third step is to inject the precursor gel into a mold for freezing. The mold can be made of plastic, metal, silicone, etc., as long as it can withstand freezing conditions; this invention does not impose specific limitations on this. The mold can be an open mold or a closed mold; this invention does not impose specific limitations on this. Freezing involves freezing it below 0°C or in a liquid nitrogen environment, causing the water to freeze and forming vertically interconnected or hierarchical channels during ice crystal growth. The ice crystals during freezing act as "templates," displacing the gel components and forming artificially oriented or random through-pore structures, providing a good framework for subsequent solvent exchange, ion complexation, and the high porosity of the final aerogel. Unlike single cellulose or single MXene, this composite system more easily forms a stable sheet-like / fibrous synergistic network during freezing, reducing the risk of later framework collapse.

[0058] The fourth step involves immersing the fully frozen gel, along with the mold, in an anhydrous ethanol / metal ion solution for solvent exchange. This allows the ice crystals to melt layer by layer and exchange solvent with the ethanol solution. Solvent replacement at low temperatures slows down the ice melting rate and prevents the skeleton from collapsing rapidly. According to the system configuration of this invention, the preferred solvent replacement temperature is -25 to -5 °C. Metal ions can form electrostatic complexes with cellulose carboxyl groups, enhancing the mechanical strength of the skeleton, and can also adhere to or coordinate with the charged groups –O / –OH of MXene. After ethanol replaces water, it reduces the surface tension during the drying process, making atmospheric pressure drying feasible. In this step, the network skeleton initially formed by MXene and modified cellulose nanofibers is further reinforced by cross-linking with metal ions, thereby mitigating subsequent capillary damage.

[0059] In this step, the metal ion can be at least one of calcium ions, magnesium ions, aluminum ions, and zinc ions. This invention does not specifically limit this, as long as it can form an electrostatic complex with the carboxyl groups of cellulose, and can achieve network cross-linking and reinforcement through coordination or adsorption with charged groups –O / –OH on the MXene surface, and does not cause oxidation of MXene, the selected metal ion has high natural abundance and is environmentally friendly. As can be seen from the above, in the technical solution of this invention, the metal ions undergo a dual complexation reaction with the modified cellulose nanofibers and the functional groups on the MXene surface. It enhances the structural connection through chemical complexation sites and is a chemical-physical hybrid cross-linking network. This network structure has good stability and can simultaneously improve the material's drying shape retention, wet structural strength, and long-term stability, making it particularly suitable for long-term wet evaporation applications in aquatic environments.

[0060] Based on the ratio of cellulose nanofibers and MXene nanosheets in the above technical solution, the present invention preferably uses an anhydrous ethanol / metal ion solution with a metal ion mass concentration of 0.5-2.0%, which can make the complexation points of the three substances basically matched, and make the formed skeleton structure more stable.

[0061] The final step involves multiple rinsings with water after solvent exchange to an ice-free state, followed by atmospheric drying at room temperature or in an oven at <90°C under normal pressure to solidify the aerogel framework, resulting in a cellulose / MXene composite aerogel. In this step, atmospheric drying avoids the high energy consumption and equipment complexity of freeze-drying or supercritical drying. The multi-point complex network between metal ions, modified cellulose nanofibers, and MXene effectively resists capillary forces during drying, maintaining high porosity and preventing pore collapse. Furthermore, no chemical cross-linking or hydrophobic modification is required, allowing the material to retain its hydrophilic groups and providing efficient water transport channels for subsequent applications such as interfacial solar evaporation and wastewater purification.

[0062] This invention also proposes a cellulose / MXene composite aerogel prepared according to the above preparation method, which includes cellulose nanofibers and few-layer MXene nanosheets; the surface of the modified cellulose nanofibers includes carboxyl groups and / or carboxymethyl groups; the modified cellulose nanofibers, the few-layer MXene nanosheets, and metal ions together form a fiber-sheet network structure; the three-dimensional mesh pores of the network structure are uniformly distributed and clearly oriented, and no pore wall closure or framework collapse was found; it can still maintain a vertical structure after water washing, achieving wet structural stability.

[0063] The cellulose / MXene composite aerogel maintains its intact three-dimensional porous framework structure during water washing or prolonged contact with liquid water; under 1 times the solar radiation intensity, the evaporation rate of the cellulose / MXene composite aerogel is ≥1.85 kg·m³. -2·h -1 Evaporation efficiency ≥89%.

[0064] The present invention also proposes an application of the aforementioned cellulose / MXene composite aerogel in the field of interfacial solar water evaporation.

[0065] This invention also proposes a distributed interfacial water evaporation device, which can combine the above-mentioned aerogel with the device to meet water purification needs, thereby realizing the application of water collection and adapting to off-grid scenarios such as islands and arid regions, as shown in the attached figure. Figure 9 As shown, it includes:

[0066] Water purification tank 3 is used to receive the returned condensate;

[0067] Wastewater tank 2 is located inside the water purification tank and is used to hold wastewater to be purified; the wastewater tank contains cellulose / MXene composite aerogel as described above; the cellulose / MXene composite aerogel floats at the gas-liquid interface and can greatly accelerate the evaporation rate of water in the wastewater tank;

[0068] A condenser hood 1 is disposed above the water purification tank and connected to the water purification tank; the condenser hood and the water purification tank can form a condensate return channel; water evaporates from the cellulose / MXene composite aerogel under sunlight, and the water vapor condenses in the condenser hood; to facilitate the collection and return of condensate, in some embodiments, the condenser hood is preferably an arc-shaped structure with a high center and low periphery; for example, the condenser hood is cylindrical with a semi-circular top;

[0069] Water outlet 4 is located on the water purification tank.

[0070] The above-mentioned distributed interface water evaporation device is in accordance with the attached... Figure 10 The illustrated workflow involves wastewater purification. Specifically, various types of wastewater, such as river water, lake water, seawater, stream water, rainwater, and urban sewage, that may require treatment are placed in a wastewater tank. The cellulose / MXene composite aerogel prepared according to this invention is then placed in the wastewater tank, allowing it to float at the gas-liquid interface. A condenser cover is placed over the purification tank, creating a closed space. The assembled distributed interface water evaporation device is then placed under sunlight. During this process, the water in the wastewater evaporates, condenses, and flows back, allowing the purified water to flow back into the purification tank along the condenser cover wall. This produces purified water that is safe to drink directly. The outlet must be closed during water purification; when water is needed, it is opened to collect it. This allows for the consumption of purified water in specific scenarios without requiring electricity or other energy sources.

[0071] To facilitate the portability of the distributed interface water evaporation device, the present invention preferably designs it as a foldable structure, and preferably both the condenser cover and the wastewater tank are telescopic structures; when not in use, the condenser cover and the wastewater tank can be folded up and stored in the water purification tank, thereby making it more convenient to use.

[0072] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0073] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0074] Example 1

[0075] This embodiment prepares a cellulose / MXene composite aerogel, specifically including the following steps:

[0076] 1) Preparation of oxidized cellulose nanofiber dispersion: 5g of bleached coniferous sulfate pulp was dispersed in 50g of deionized water. 0.08g of TEMPO reagent, 0.25g of sodium bromide, and 35mmol of sodium hypochlorite were added. The mixture was stirred for 1 hour, maintaining the pH at 10.0 using 1mol / L sodium hydroxide solution. The product was then washed repeatedly with deionized water until neutral. An appropriate amount of deionized water was added to disperse the product into a 1wt% dispersion. The dispersion was homogenized 6 times at 100MPa using a high-pressure homogenizer to obtain TEMPO oxidized cellulose nanofibers. A 1wt% dispersion of the TEMPO oxidized cellulose nanofibers was prepared and ultrasonically treated in an ice-water bath for 30 minutes to obtain a homogeneous dispersion, which is the cellulose aqueous dispersion; its surface carboxyl / carboxymethyl content was 1.5%.

[0077] 2) Preparation of few-layer MXene nanosheet dispersion: 40 mL of 36% HCl solution was added to a polytetrafluoroethylene (PTFE) container, followed by 2.0 g of LiF. The mixture was stirred at 350 rpm for 30 minutes at room temperature to dissolve the MXene nanosheets, yielding an etching solution. Then, 2.0 g of Ti3AlC2 powder was gradually added to the etching solution, and the mixture was continuously stirred at 350 rpm. Etching was carried out at 35°C for 24 hours, followed by repeated washing with deionized water. The reaction mixture was centrifuged at 3500 rpm for 5 minutes until the pH of the supernatant was approximately 6, yielding multilayer Ti3C2T nanosheets. xThe resulting precipitate was redispersed in deionized water and sonicated in an ice bath under an argon flow for 1 hour. The sonicated solution was then centrifuged at 3500 rpm for 1 hour. The supernatant was collected, which was the MXene dispersion. The concentration of the MXene dispersion was adjusted to 1.5 wt%, and the solution was sonicated in an ice-water bath for 30 minutes to obtain a homogeneous dispersion, which was the few-layer MXene nanosheet dispersion.

[0078] 3) The above cellulose aqueous dispersion and few-layer MXene nanosheet dispersion were mixed at a mass ratio of 10:3 and stirred at a high-speed shearing condition of 10,000 rpm for 1 h to obtain the precursor gel.

[0079] 4) Pour the obtained precursor gel into a mold and freeze it at -70℃ for 1 hour. Then immerse the sample in an ethanol / metal ion bath for 48 hours to allow the sample to completely melt. The Ca²⁺ ion concentration in the ethanol / metal ion bath is 1 wt%, and the temperature is -20℃. Wash with water and air dry at room temperature and normal pressure to obtain a cellulose / MXene composite aerogel with a three-dimensional porous structure.

[0080] 5) Performance Testing

[0081] Unless otherwise specified, all tests were conducted using conventional methods in the field, as detailed below:

[0082] The microstructure of the aerogel was observed and analyzed using scanning electron microscopy (SEM), such as... Figure 1 As shown, due to the multi-point complexation between metal ions and modified cellulose nanofibers and MXene nanosheets, the resulting aerogel has a fluffy network structure with a good porous microstructure.

[0083] Figure 2 The images show photographs of the aerogel prepared in this embodiment from different angles. As can be seen from the figures, after being rinsed multiple times with a large amount of water and dried at normal pressure, the aerogel still maintains a complete three-dimensional porous network structure, and no obvious structural collapse was observed. Macroscopically, it exhibits a uniform dark black surface feature, which is attributed to the full integration of few-layer MXene nanosheets and cellulose nanofibers, which is beneficial for the material to absorb sunlight and convert it into heat energy.

[0084] Evaporation performance test: The aerogel prepared in this embodiment was used as the interfacial water evaporation photothermal material for water evaporation rate testing. The results showed that under 1 times the solar radiation intensity, its evaporation rate was 2.04 kg·m³. -2 ·h -1 The evaporation efficiency can reach 91.5%, and the maximum surface temperature can reach 36.8℃.

[0085] Seawater desalination performance test: Real seawater from the Bohai Sea was collected for testing, and the ion concentration of the seawater was measured; the seawater was also evaporated and condensed using the distributed interfacial evaporation device of this invention (a wastewater tank containing the cellulose / MXene composite aerogel prepared according to this invention) and the condensate was collected, and the ion concentration of the condensate was measured; the comparison results of the ion concentration of seawater and ion concentration of condensate are attached. Figure 3 As shown, compared to the original seawater, the Na+ in the condensate after one desalination treatment is significantly higher. + K + Mg 2+ and Ca 2+ The concentration of the substance was reduced by three to four orders of magnitude; moreover, the water quality of the desalinated condensate was significantly better than the drinking water standards set by the World Health Organization.

[0086] Heavy metal treatment performance test: The distributed interfacial evaporation device of this invention (with the cellulose / MXene composite aerogel prepared in this invention installed in the sewage tank) was used to treat heavy metal ions containing Hg. 2+ Cd 2+ , Cr 3+ Cu 2+ Ni 2+ Zn 2+ and Pb 2+ The water underwent purification treatment. The ion concentration before and after treatment is compared to that shown in the attached figure. Figure 4 As shown in the figure, the overall concentration of heavy metal ions was reduced by 2 to 6 orders of magnitude (ppb), and the removal rate reached over 98%, which is comparable to current purification technologies.

[0087] Salt deposition resistance test: such as Figure 5 As shown, the distributed interfacial evaporation device of this invention (containing the cellulose / MXene composite aerogel prepared according to this invention in the wastewater tank) was used to purify high-concentration brine. Specifically, a 20 wt% NaCl aqueous solution was evaporated under 1 times the solar radiation intensity (hereinafter referred to as 1 SUN). After 7 hours of testing, the evaporation rate was still as high as 1.77 kg·m³. -2 ·h -1 The evaporation rate changes over time as shown in the attached figure. Figure 5 As shown in the attached figure; no salt deposition was observed on the surface of the aerogel at the beginning and end of evaporation. Figure 5a As shown.

[0088] Example 2

[0089] This embodiment prepares a cellulose / MXene composite aerogel, specifically including the following steps:

[0090] 1) Preparation of cellulose-based composite photothermal materials:

[0091] ① Preparation of oxidized cellulose nanofiber dispersion: 5g of bleached coniferous sulfate pulp was dispersed in 50ml of a 1.0 wt% dilute sulfuric acid solution. 7g of potassium permanganate was added, and the mixture was reacted at 600rpm and 60℃ for 150min. The product was then washed repeatedly with deionized water until neutral. An appropriate amount of deionized water was added to disperse it into a 1 wt% dispersion. The dispersion was homogenized 6 times using a high-pressure homogenizer at 100MPa to obtain potassium permanganate oxidized cellulose nanofibers. A 0.8 wt% dispersion of the potassium permanganate oxidized cellulose nanofibers was prepared and ultrasonically treated in an ice-water bath for 30min to obtain a homogeneous dispersion, which is the cellulose aqueous dispersion; its surface carboxyl / carboxymethyl content was 1.2%.

[0092] 2) Preparation of few-layer MXene nanosheet dispersion: Same as in Example 1.

[0093] 3) The above cellulose aqueous dispersion and few-layer MXene nanosheet dispersion were mixed at a mass ratio of 10:2 and stirred at a high-speed shearing condition of 10,000 rpm for 1 h to obtain the precursor gel.

[0094] 4) Same as Example 1.

[0095] 5) The test results are as follows:

[0096] Under 1 SUN conditions, the aerogel evaporation rate was 1.95 kg·m⁻²·h⁻¹, with an efficiency of 89.5% and a surface temperature of 34.9℃. After one-time desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the produced water quality met WHO drinking water standards. After treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥97%. Under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.70 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0097] Example 3

[0098] This embodiment prepares a cellulose / MXene composite aerogel, specifically including the following steps:

[0099] 1) Preparation of oxidized cellulose nanofiber dispersion: 5g of bleached coniferous sulfate pulp was dispersed in 500ml of ammonium persulfate solution (1mol / L) and reacted at 600rpm and 60℃ for 90min. After the reaction, deionized water was added until the pH reached 4. The mixture was then homogenized four times using a high-pressure homogenizer at 100mPa to obtain ammonium persulfate oxidized cellulose nanofibers. A 1wt% dispersion of the ammonium persulfate oxidized cellulose nanofibers was prepared and ultrasonically treated in an ice-water bath for 30min to obtain a homogeneous dispersion, which is the cellulose aqueous dispersion; its surface carboxyl / carboxymethyl content was 1.4.

[0100] 2) Preparation of few-layer MXene nanosheet dispersion: Same as in Example 1.

[0101] 3) The above cellulose aqueous dispersion and few-layer MXene nanosheet dispersion were mixed at a mass ratio of 10:4 and stirred at a high-speed shearing condition of 10,000 rpm for 1 h to obtain the precursor gel.

[0102] 4) Same as Example 1.

[0103] 5) The test results are as follows:

[0104] Under 1 SUN conditions, the aerogel evaporation rate was 2.0 kg·m⁻²·h⁻¹, with an efficiency of 92.1% and a surface temperature of 37.5℃. After one-time desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the produced water quality met WHO drinking water standards. After treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥98%. Under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.72 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0105] Example 4

[0106] Same as Example 1. The difference is that the concentration of the cellulose aqueous dispersion in step 1) is 1.2%. The test results are as follows: Under 1 SUN conditions, the aerogel evaporation rate is 2.1 kg·m⁻²·h⁻¹, the efficiency is 92.3%, and the surface temperature is 37.1 ℃; after one desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the quality of the produced water meets the WHO drinking water standards; after treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, and the removal rate was ≥98%; under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.82 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0107] Example 5

[0108] Same as Example 1. The difference is that the concentration of the few-layer MXene nanosheet dispersion in step 1) is 1.2%. The test results are as follows: Under 1 SUN conditions, the aerogel evaporation rate is 1.88 kg·m⁻²·h⁻¹, with an efficiency of 90.32% and a surface temperature of 37.1℃; after one desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the quality of the produced water met the WHO drinking water standards; after treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥98%; under 1 SUN conditions, the evaporation rate of 20 wt% NaCl solution for 7 h was 1.82 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0109] Example 6

[0110] Same as Example 1. The difference is that the concentration of the few-layer MXene nanosheet dispersion in step 1) is 1.8%. The test results are as follows: Under 1 SUN conditions, the aerogel evaporation rate is 2.19 kg·m⁻²·h⁻¹, with an efficiency of 93.8% and a surface temperature of 37.3 ℃; after one desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the quality of the produced water met the WHO drinking water standards; after treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥98%; under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.86 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0111] Example 7

[0112] Same as Example 1. The difference is that in step 1), the ethanol / metal ion bath uses Zn ions. 2+ The test results are as follows: Under 1 SUN conditions, the aerogel evaporation rate was 1.98 kg·m⁻²·h⁻¹, with an efficiency of 90.4% and a surface temperature of 36.3 ℃; after one desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the quality of the produced water met the WHO drinking water standards; after treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥97%; under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.66 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0113] Example 8

[0114] Same as Example 1. The difference is that in step 1), the ethanol / metal ion bath uses Al ions. 3+ The test results are as follows: Under 1 SUN conditions, the aerogel evaporation rate was 1.97 kg·m⁻²·h⁻¹, with an efficiency of 91.2% and a surface temperature of 36.7 ℃; after one desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the quality of the produced water met the WHO drinking water standards; after treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥98%; under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.68 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0115] Example 9

[0116] Same as Example 1. The difference is that the Ca²⁺ ion concentration in step 1) is 0.5 wt%. The test results are as follows: Under 1 SUN conditions, the aerogel evaporation rate is 1.9 kg·m⁻²·h⁻¹, with an efficiency of 90.5% and a surface temperature of 36.5 ℃; after one desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the quality of the produced water met the WHO drinking water standards; after treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥98%; under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.56 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0117] Example 10

[0118] Same as Example 1. The difference is that the Ca²⁺ ion concentration in step 1) is 2.0 wt%. The test results are as follows: Under 1 SUN conditions, the aerogel evaporation rate is 2.1 kg·m⁻²·h⁻¹, with an efficiency of 93.5% and a surface temperature of 36.3 ℃; after one desalination of seawater, the concentrations of Na⁺, K⁺, Mg²⁺, and Ca²⁺ decreased by 3–4 orders of magnitude, and the quality of the produced water met the WHO drinking water standards; after treating water containing Hg²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Pb²⁺, the heavy metal concentration decreased by 2–6 orders of magnitude, with a removal rate ≥98%; under 1 SUN conditions, evaporation of 20 wt% NaCl solution for 7 h was achieved at a rate of 1.83 kg·m⁻²·h⁻¹, and no salt crystal deposition was observed on the aerogel surface.

[0119] Comparative Example 1

[0120] This comparative example prepares an aerogel, specifically including the following steps:

[0121] 1) Preparation of mechanically produced nanocellulose dispersion: 5g of bleached coniferous sulfate pulp was dispersed in 50g of deionized water and homogenized 5 times using a high-pressure homogenizer at 100m Pa to obtain mechanically produced nanocellulose. A 1wt% dispersion of the mechanically produced nanocellulose was prepared and ultrasonically treated in an ice-water bath for 30min to obtain a homogeneous dispersion.

[0122] 2) Preparation of few-layer MXene nanosheet dispersion: Same as in Example 1.

[0123] 3) The above mechanically prepared nanocellulose dispersion and the few-layer MXene nanosheet dispersion were mixed at a mass ratio of 10:3 and stirred at a high-speed shearing condition of 10,000 rpm for 1 h to obtain a mixed dispersion.

[0124] 4) Pour the obtained mixed dispersion into the same mold as in Example 1, freeze at -70°C for 1 hour, then immerse the sample in an ethanol / Ca²⁺ bath (1 wt%, -20°C) for 48 hours to allow the sample to completely melt. After washing with deionized water, air dry at room temperature and normal pressure to obtain a black sheet material, as shown in the attached figure. Figure 6 As shown.

[0125] Depend on Figure 6 As shown, although the comparative example used the same process parameters as Example 1 (including freezing temperature, crosslinking agent concentration, and drying conditions), the aerogel could not form an oriented porous structure because its cellulose was not modified by carboxylation or carboxymethylation. This phenomenon is attributed to the lack of active functional groups, such as -COOH / -COO⁻, on the surface of the unmodified cellulose, which can bind to metal ions. This leads to the failure of its crosslinking network construction, and consequently, during the atmospheric pressure drying process, due to the lack of ionic bonding to stabilize the three-dimensional framework, the nanocellulose network collapses irreversibly due to capillary stress, forming only a sheet-like structure.

[0126] Comparative Example 2

[0127] This comparative example prepares an aerogel, specifically including the following steps:

[0128] 1) Preparation of oxidized nanocellulose dispersion: Same as in Example 1.

[0129] 2) Preparation of MXene dispersion: Same as in Example 1.

[0130] 3) Same as Example 1.

[0131] 4) Pour the obtained precursor gel into a mold, freeze at -70℃ for 1 hour, then immerse the sample in an ethanol bath for 48 hours to allow it to completely thaw. Wash with water and air dry at room temperature and normal pressure to obtain partially collapsed material, as shown in the attached figure. Figure 7 As shown.

[0132] As attached Figure 7 As shown, this comparative example uses carboxylated modified cellulose and maintains the same process parameters as the example (including freezing temperature, crosslinking time, and drying conditions). The key difference lies in the use of a metal ion-free pure ethanol solution during the solvent exchange stage. Although carboxyl functional groups exist on the cellulose surface, the aerogel material undergoes significant structural collapse during drying due to the lack of coordination crosslinking by metal ions. This phenomenon verifies that metal ion-mediated coordination crosslinking plays a crucial role in stabilizing the porous structure and reveals the necessity of the synergistic strategy of "functional group modification-ion complexation" in suppressing aerogel drying shrinkage.

[0133] Comparative Example 3

[0134] This comparative example prepares an aerogel, specifically including the following steps:

[0135] 1) Preparation of mechanically produced nanocellulose dispersion: 5g of bleached coniferous sulfate pulp was dispersed in 50g of deionized water and homogenized 5 times using a high-pressure homogenizer at 100m Pa to obtain mechanically produced nanocellulose. A 1wt% dispersion of the mechanically produced nanocellulose was prepared and ultrasonically treated in an ice-water bath for 30min to obtain a homogeneous dispersion.

[0136] 2) This step can be omitted.

[0137] 3) This step can be omitted.

[0138] 4) Pour the above-mentioned nanocellulose dispersion into the same mold, freeze at -70°C for 1 hour, then immerse the sample in an ethanol / Ca²⁺ bath (1 wt%, -20°C) for 48 hours to allow the sample to completely melt. Afterward, wash with deionized water and air-dry at room temperature and normal pressure to obtain a white flake material, as shown in the attached image. Figure 8 As shown.

[0139] Depend on Figure 8As shown, this comparative example used the same carboxylated modified cellulose and the same process parameters (including freezing temperature, crosslinking time, and drying conditions) as Example 1, but without the addition of few-layer MXene nanosheets. Although cellulose itself contains abundant carboxyl functional groups and can undergo a certain degree of complexation with metal ions, the lack of additional synergistic coordination between MXene nanosheets and cellulose resulted in significant structural collapse and shrinkage of the three-dimensional framework of the aerogel material during drying. This comparative experiment clearly verifies the key role of MXene nanosheets in stabilizing the porous structure of aerogels, further demonstrating the necessity of constructing a "fiber-sheet" synergistic network strategy in this invention for effectively suppressing aerogel drying shrinkage and maintaining a high-porosity structure.

[0140] The technical features in the claims and / or specification of this invention can be combined, and the combination is not limited to the combinations obtained through reference in the claims. Technical solutions obtained by combining the technical features in the claims and / or specification are also within the scope of protection of this invention.

[0141] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a cellulose / MXene composite aerogel, characterized in that, It comprises the following steps: S11 carboxylate modification of cellulose, dissociation into nanofibers, and preparation into a cellulose water dispersion; compounding the cellulose water dispersion with a few-layer MXene nanosheet dispersion to form a precursor gel; S12 injecting the precursor gel into a mold and freezing; immersing the fully frozen gel together with the mold in anhydrous ethanol / metal ion solution for solvent exchange; S13 after solvent exchange to ice-free state, washing with water, drying under normal pressure to obtain cellulose / MXene composite aerogel.

2. The production method according to claim 1, characterized by, The cellulose is selected from softwood pulp and / or hardwood pulp; the method of carboxylate modification is selected from any one of TEMPO oxidation, potassium permanganate oxidation and ammonium persulfate oxidation; the carboxyl content of the modified cellulose is 1.0-2.5 mmol / g.

3. The preparation method according to claim 1, characterized in that, The mass concentration of the cellulose water dispersion is 0.8-1.2%; the mass concentration of the few-layer MXene nanosheet dispersion is 1.2-1.8%; the composite mass ratio of the cellulose water dispersion to the few-layer MXene nanosheet dispersion is 2.5-5:

1.

4. The method of claim 1, wherein, The mass concentration of metal ions in the anhydrous ethanol / metal ion solution is 0.5-2.0%, and the solution temperature is -25 to -5 ℃.

5. A cellulose / MXene composite aerogel, characterized in that, It comprises modified cellulose nanofibers and few-layer MXene nanosheets; the surface of the modified cellulose nanofibers comprises carboxyl groups and / or carboxymethyl groups; the modified cellulose nanofibers, the few-layer MXene nanosheets and metal ions together form a fiber-sheetwork structure.

6. The cellulose / MXene composite aerogel according to claim 5, wherein, It is prepared according to the preparation method of any one of claims 1 to 4; the cellulose / MXene composite aerogel can maintain an intact three-dimensional porous skeleton structure during water washing or long-term contact with liquid water; the evaporation rate of the cellulose / MXene composite aerogel is ≥1.85 kg·m -2 ·h -1 under 1-fold solar radiation intensity, and the evaporation efficiency is ≥89%.

7. Use of the cellulose / MXene composite aerogel according to claim 5 or 6 in the field of interfacial solar water evaporation.

8. A distributed interface water evaporation device, characterized in that, It comprises: A clean water pool for receiving backflow condensate water; A sewage pool arranged in the clean water pool for containing sewage to be purified; The sewage pool is provided with the cellulose / MXene composite aerogel according to claim 5 or 6; the cellulose / MXene composite aerogel floats at the gas-liquid interface; A condensing cover arranged above the clean water pool and connected with the clean water pool; the condensing cover and the clean water pool can form a condensate water backflow channel; A water outlet arranged on the clean water pool.

9. The distributed interface water evaporation apparatus of claim 8, wherein, The condensing cover is an arc surface structure with a middle high and a periphery low.

10. The distributed interface water evaporation apparatus of claim 8, wherein, The condensing cover and the sewage pool are both telescopic structures.

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