Cellulose / MXene composite aerogel as well as preparation method and application thereof

Abstract

The invention relates to cellulose / MXene composite aerogel as well as a preparation method and application thereof. The method comprises the following steps: carrying out carboxylation modification on cellulose, dissociating into nanofibers, and preparing into a cellulose aqueous dispersion; the preparation method comprises the following steps: compounding a cellulose aqueous dispersion liquid and a few-layer MXene nanosheet dispersion liquid to form precursor gel; injecting the precursor gel into a mold for freezing; soaking the frozen gel and the mold in an absolute ethyl alcohol / metal ion solution for solvent exchange; after the mixture is in an ice-free state, washing the mixture with water, and drying the mixture under a normal pressure condition to obtain the cellulose / MXene composite aerogel. The technical problem to be solved by the invention is how to provide the cellulose / MXene composite aerogel, so that the cellulose / MXene composite aerogel has excellent porosity, morphology integrity and drying shrinkage rate control level, and can still keep a complete three-dimensional porous skeleton structure in the process of water washing or long-term contact with liquid water. In the interface water evaporation process, good water adsorption, introduction and continuous transportation capacities are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of interfacial solar water evaporation, and in particular relates to a cellulose / MXene composite aerogel and a preparation method and application thereof. Background Art

[0002] Seawater accounts for over 97% of Earth's total water supply. Its vast reserves could potentially meet the growing demand for freshwater after purification. Aerogels, due to their unique structural advantages, are widely used in interfacial solar water evaporation. Cellulose is widely available, renewable, and environmentally friendly, possessing excellent mechanical toughness and a rich array of surface functional groups. MXene, on the other hand, is a type of two-dimensional transition metal carbide / carbonitride obtained by etching a MAX phase, combining high conductivity, large surface area, and a variety of surface-active groups. Combining cellulose and MXene offers complementary advantages at the material level. The high conductivity and excellent photothermal conversion properties of MXene nanosheets lend cellulose-based aerogels greater functionality, making them suitable for interfacial solar water evaporation. Furthermore, the three-dimensional network constructed by cellulose nanofibers effectively prevents the collapse of MXene interlayer stacking. Cellulose nanofibers provide excellent hydrophilic channels and mechanical support at the interface, laying the foundation for sustained water transport and evaporation.

[0003] Regarding the preparation of cellulose / MXene composite aerogels, although existing research has made some progress in supercritical drying and freeze-drying, both have problems such as high equipment costs, long time consumption, or difficulty in large-scale application. Atmospheric pressure drying, although low cost and simple to operate, faces the problem of how to effectively control capillary forces and inhibit skeleton collapse. Some scholars have proposed using a "low-temperature freezing + ethanol solvent exchange" process for atmospheric pressure drying, utilizing the hydrogen bonding and physical nesting relationship between cellulose nanofibers (CNF) and MXene to form an aerogel skeleton with a "brick-and-mud" structure. However, this aerogel skeleton is prone to collapse. To inhibit the collapse of the aerogel skeleton, it is chemically cross-linked or hydrophobically modified after drying to make the overall surface of the material hydrophobic or semi-hydrophobic, thereby improving the stability of the aerogel skeleton in water. However, although this method is effective in maintaining short-term structure, it also blocks the hydrophilic functional groups on the surface of the material, reducing the diffusion rate of water in the pores and the capillary transport capacity, making it difficult to meet the application requirements of maintaining high hydrophilic channels and rapid water transport capacity for a long time; at the same time, this hydrophobic treatment will also affect the continuous performance of the material in subsequent long-term contact with water, and cannot fully meet the requirements for high hydrophilicity and immersion stability. After washing with water or long-term immersion, the material is still prone to structural shrinkage and pore collapse due to capillary forces during the drying process, making it difficult to ensure the continuous structural stability of the material in a high-humidity environment, resulting in its inability to be promoted and applied in fields such as interfacial water evaporation. Summary of the Invention

[0004] The main purpose of the present invention is to provide a cellulose / MXene composite aerogel and its preparation method and application. The technical problem to be solved is how to provide a cellulose / MXene composite aerogel with excellent porosity, morphological integrity and drying shrinkage control level, and to maintain a complete three-dimensional porous skeleton structure during water washing or long-term contact with liquid water; to have good water adsorption, introduction and continuous transport capabilities during interfacial water evaporation, significantly improving evaporation efficiency and process stability; at the same time, the production process is simple and energy consumption is low, making it suitable for promotion to a wider range of practical scenarios.

[0005] The purpose of the present invention and the solution to its technical problems are also achieved by adopting the following technical solutions. According to the present invention, a method for preparing a cellulose battery separator material comprises the following steps:

[0006] S11 carboxylates and modifies cellulose to dissociate into nanofibers, which are then prepared into a cellulose aqueous dispersion; the cellulose aqueous dispersion is compounded with a few-layer MXene nanosheet dispersion to form a precursor gel;

[0007] S12: injecting the precursor gel into a mold and freezing it; immersing the fully frozen gel and the mold together in an 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 a cellulose / MXene composite aerogel.

[0009] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0010] Preferably, in the aforementioned preparation method, the cellulose is selected from coniferous wood pulp and / or broadleaf wood pulp; the carboxylation modification method is selected from any one of TEMPO oxidation, potassium permanganate oxidation and ammonium persulfate oxidation; and the surface carboxyl content of the modified cellulose is 1.0 to 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 to 2.0%, and the solution temperature is -25 to -5°C.

[0013] The objectives of the present invention and the technical problems solved therein are achieved by adopting the following technical solutions: A cellulose / MXene composite aerogel proposed in the present invention comprises cellulose nanofibers and few-layer MXene nanosheets; the modified cellulose nanofibers have carboxyl groups and / or carboxymethyl groups on their surfaces; and the modified cellulose nanofibers, the few-layer MXene nanosheets, and metal ions together form a fiber-sheet network structure.

[0014] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting 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 still maintain a complete three-dimensional porous skeleton structure during water washing or long-term contact with liquid water; the evaporation rate of the cellulose / MXene composite aerogel under 1 times the solar radiation intensity is ≥1.85kg·m -2 ·h -1 , evaporation efficiency ≥89%.

[0016] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions: According to the present invention, an application of the aforementioned cellulose / MXene composite aerogel in the field of interfacial solar water evaporation is proposed.

[0017] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions. According to the present invention, a distributed interface water evaporation device is proposed, which includes:

[0018] Clean water tank, used to receive the returned condensed water;

[0019] A sewage tank is provided in the water purification tank and is used to hold sewage to be purified; the cellulose / MXene composite aerogel as described above is provided in the sewage tank; the cellulose / MXene composite aerogel floats at the gas-liquid interface;

[0020] A condensation hood is arranged above the clean water pool and connected to the clean water pool; the condensation hood and the clean water pool can form a condensed water reflux channel;

[0021] The water outlet is arranged on the water purification pool.

[0022] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0023] Preferably, in the aforementioned distributed interface water evaporation device, the condensation cover is a curved surface structure with a high middle and a low periphery.

[0024] Preferably, in the aforementioned distributed interfacial water evaporation device, the condensation hood and the sewage pool are both telescopic structures.

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

[0026] The cellulose / MXene composite aerogel proposed in the present invention, as well as its preparation method and application, is prepared by carboxylating cellulose, introducing some carboxyl groups or carboxymethyl groups on the cellulose surface, constructing a synergistic network structure of modified cellulose and MXene, and combining solvent exchange with ethanol / metal ion solution at low temperature and a multi-point ion complexation strategy to achieve the preparation of a structurally stable, hydrophilic, water-conductive, and long-term operational MXene / cellulose composite aerogel material under normal pressure and drying conditions. The specific beneficial effects are as follows:

[0027] 1. The cellulose / MXene composite aerogel proposed in the present invention significantly improves the structural retention ability of aerogel materials in aqueous environments. Modified cellulose nanofibers alone cannot maintain their pore structure after drying at normal pressure. However, when combined with MXene and complexed with metal ions at multiple points, they can significantly enhance the aerogel's skeleton strength and anti-capillary force ability, achieving long-term stable operation. The aerogel material prepared by the present invention can still maintain a complete three-dimensional porous skeleton structure during water washing or long-term contact with liquid water, avoiding the problems of such aerogels in the prior art such as collapse and shrinkage after contact with water.

[0028] 2. The cellulose / MXene composite aerogel proposed in this invention achieves efficient interfacial water transport and evaporation without sacrificing the aerogel's hydrophilic properties. The aerogel of this invention does not use hydrophobic blocking agents such as isocyanates to inhibit skeleton collapse, allowing the material surface to retain abundant hydrophilic groups such as carboxyl and hydroxyl groups, ensuring excellent 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 skeleton 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 present invention proposes a method for preparing cellulose / MXene composite aerogels, which can produce low-energy (no energy required for application) and highly conformal aerogel materials at ambient pressure. By optimizing the "freezing-solvent exchange conditions-metal ion complexation" process, the present invention eliminates the need for high-energy freeze-drying or supercritical equipment, achieving stable aerogel formation at ambient pressure. Furthermore, the resulting aerogel material exhibits excellent porosity, morphological integrity, and controlled drying shrinkage. Furthermore, the preparation process is simple and energy-efficient, making it suitable for widespread application in a wider range of practical scenarios.

[0030] 4. The cellulose / MXene composite aerogel proposed in the present invention has long-term operational stability and resistance to salt deposition. It can exhibit good resistance to salt crystallization and water transmission during interfacial water evaporation. After long-term evaporation testing, 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, suitable for a variety of off-grid applications. Through the collaborative design of aerogel materials and devices, the present invention integrates the cellulose / MXene composite aerogel with the structure to construct a distributed interfacial water evaporation device, thereby achieving the functional coupling of "photothermal evaporation - steam escape - condensation reflux - purified water collection". This allows the production of pure water through purification through interfacial solar evaporation materials, without the need for a large electricity supply, making it suitable for deployment in underdeveloped areas.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0034] Figure 2 This is a photo of the aerogel in Example 1 of the present invention;

[0035] Figure 3 This is the test result of the aerogel seawater desalination performance of Example 1 of the present invention;

[0036] Figure 4 This is the test result of the heavy metal treatment performance of the aerogel in Example 1 of the present invention;

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

[0038] Figure 5a The aerogel salt deposition resistance test results of Example 1 of the present invention are photos of the aerogel at the beginning and end of evaporation;

[0039] Figure 6 Photo of aerogel in comparative example 1 of the present invention;

[0040] Figure 7 Photo of aerogel in comparative example 2 of the present invention;

[0041] Figure 8 Photo of aerogel in comparative example 3 of the present invention;

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

[0043] Figure 10 Schematic diagram of the operating process of the distributed interfacial water evaporation device proposed in the present invention. DETAILED DESCRIPTION

[0044] To further illustrate the technical means and effectiveness of the present invention in achieving its intended objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail a cellulose / MXene composite aerogel, its preparation method, and its specific embodiments, structures, features, and effectiveness. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0045] The present invention provides a method for preparing a cellulose / MXene composite aerogel, which comprises the following steps:

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

[0047] The preparation of cellulose aqueous dispersion includes carboxyl modification of cellulose, dissociation into nanofibers and preparation into cellulose aqueous dispersion.

[0048] Cellulose carboxylation modification involves converting some of the hydroxyl groups on the surface of the cellulose molecular chain into carboxyl groups by methods such as TEMPO oxidation, potassium permanganate oxidation, or ammonium persulfate (APS) oxidation. This is known technology and will not be further described in detail in this invention. The present invention preferably uses cellulose selected from softwood pulp and / or hardwood pulp. By regulating the degree of cellulose oxidation, the surface carboxyl content of the cellulose is maintained at 1.0-2.5 mmol / g. This oxidation level provides favorable conditions for the subsequent establishment of multiple complexation sites with metal ions.

[0049] The dissociation into nanofibers is to homogenize the modified cellulose pulp multiple times using a high-pressure homogenizer to dissociate it into nanofibers (CNF); the preferred high-pressure homogenization pressure of the present invention is 80-120 MPa, and nanofibers with a high aspect ratio and good dispersion are obtained through multiple homogenization.

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

[0051] Through moderate oxidation / carboxylation and homogenization treatment in the above steps, the foundation can be laid for subsequent ion complexation and MXene binding, while retaining the hydrophilic properties of cellulose, ensuring that the material has unobstructed water channels during the subsequent interfacial water evaporation conditions.

[0052] Few-layer MXene nanosheets are prepared by low-temperature etching and layered exfoliation process; the preparation of few-layer MXene dispersion is also a prior art, and the present invention is only for illustrative purposes and does not 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, which is stirred at a constant speed to form a uniform active medium; then Ti3AlC2 powder is added to the etching system in batches, and reacted at 35-40°C for 24-36 hours to achieve selective removal of the aluminum layer in the MAX phase. After the reaction is completed, by-products and unreacted products are removed by multi-stage centrifugation combined with dynamic pH monitoring until the pH value of the supernatant is stabilized at 5.5-6.0 to obtain a pure multilayer MXene precipitate; wherein the centrifugal speed is preferably 3000-4000rpm. The precipitate was dispersed in deionized water and subjected to low-temperature ultrasonic treatment under argon protection and ice bath conditions to promote interlayer dissociation. Finally, the precipitate was centrifuged at a speed of 3000-3500 rpm for 60-90 minutes to remove the unpeeled thick flakes and collect the upper colloidal suspension to obtain the few-layer Ti3C2T x The resulting nanosheet dispersion, with its uniform surface charge distribution and excellent stability, can be directly used in the subsequent construction of functional materials. During this step, it is important to ensure that the resulting MXene dispersion exhibits a negative potential in the aqueous phase. This facilitates the subsequent dispersion of the negatively charged carboxyl-bearing cellulose nanofibers and prevents their large-scale aggregation, thus facilitating precise control of the skeleton structure during subsequent coordination and ion complexation.

[0053] The second step is to combine the aqueous cellulose dispersion with the few-layer MXene nanosheet dispersion to form a precursor gel. The nanocellulose suspension and few-layer MXene nanosheets are combined in a specific mass ratio. High-shear dispersion technology is used to achieve uniform bonding of the nanofibers and MXene nanosheets, forming the precursor gel.

[0054] In this step, the carboxyl and carboxymethyl groups on the surface of the modified nanocellulose fibers interact with the hydrophilic groups, such as carboxyl and hydroxyl groups, abundant on the surface of the MXene through hydrogen bonding, electrostatic repulsion, and local coordination to form a preliminary skeleton, which reduces shrinkage during subsequent drying. While ensuring hydrophilicity, this composite step also leverages the two-dimensional sheet properties of MXene and the long fibers of the modified nanocellulose fibers to form a "fiber-sheet" network, laying the foundation for subsequent ion complexation.

[0055] In order to ensure that the "fiber-sheet" network structure formed by the cellulose nanofibers and the two-dimensional sheets of MXene is more stable, the present invention preferably has the following ratio: 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%; 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 are rich in hydrophilic groups such as carboxyl and hydroxyl groups. Through hydrogen bonding, electrostatic repulsion, and local coordination, they form a preliminary skeleton, thereby reducing subsequent drying shrinkage. While maintaining hydrophilicity, this composite utilizes the two-dimensional sheet properties of MXene and the long fiber properties of CNF to form a "fiber-sheet" network, laying the foundation for subsequent ion complexation.

[0057] The third step is to inject the precursor gel into a mold for freezing. The material of the mold can be plastic, metal, silicone, etc., as long as it can adapt to the freezing conditions. The present invention does not impose specific restrictions on this. The mold can be an open mold or a closed mold. The present invention does not impose specific restrictions on this. The freezing is to freeze it below 0°C or in a liquid nitrogen environment to freeze the water and form vertical through or graded channels during the growth of ice crystals. The ice crystals in the freezing process act as a "template" to squeeze out the gel components, forming an artificial directional or random through-pore structure, which provides a good skeleton for subsequent solvent exchange, ion complexation and the final high porosity of the aerogel. Unlike single cellulose or single MXene, this composite system is more likely to form a stable sheet / fibrous collaborative network during the freezing process, reducing the risk of skeleton collapse in the later stage.

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

[0059] The metal ions in this step can be at least one of calcium ions, magnesium ions, aluminum ions and zinc ions. The present invention does not impose specific limitations on this. As long as it can form an electrostatic complex with the cellulose carboxyl group, and can achieve network cross-linking and reinforcement by coordination or adsorption with the charged groups –O / –OH on the surface of MXene, and does not produce an oxidizing effect on MXene, the selected metal ions have a high natural abundance and are environmentally friendly. As can be seen from the above, in the technical solution of the present invention, the metal ions simultaneously undergo a dual complexation reaction with the modified cellulose nanofibers and the surface functional groups of MXene, which is a chemical-physical hybrid cross-linked network with enhanced structural connection through chemical complexation points. The network structure has good stability and can simultaneously improve the material's drying conformal ability, wet structural strength and long-term stability, and is particularly suitable for long-term wet evaporation applications in water environments.

[0060] According to the ratio of cellulose nanofibers and MXene nanosheets in the above technical solution, the present invention preferably has a mass concentration of metal ions in the anhydrous ethanol / metal ion solution of 0.5 to 2.0%, so that the complexation points of the three substances can be basically matched, making the formed skeleton structure more stable.

[0061] The final step is to rinse the aerogel multiple times with clean water after the solvent is exchanged to an ice-free state, and then dry it at room temperature or in an oven at <90°C under normal pressure to solidify the aerogel skeleton and obtain a cellulose / MXene composite aerogel. In this step, normal pressure drying avoids the high energy consumption and equipment complexity of freeze-drying or supercritical drying; and the multi-point complexation network between metal ions-modified cellulose nanofibers-MXene can effectively resist the capillary force of the drying process, thereby maintaining a high porosity and preventing pore collapse; at the same time, there is no need for chemical cross-linking modification or hydrophobic modification, so that it can retain the hydrophilic groups of the material, providing an efficient water transport channel for subsequent scenarios such as interfacial solar evaporation and sewage purification.

[0062] The present invention also proposes a cellulose / MXene composite aerogel prepared according to the above-mentioned 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 evenly distributed and clearly oriented, and no pore wall closure and skeleton collapse are found; after washing with water, the vertical structure can still be maintained, achieving wet structural stability.

[0063] The cellulose / MXene composite aerogel can still maintain a complete three-dimensional porous skeleton 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 ≥1.85kg·m -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] The present invention also proposes a distributed interfacial water evaporation device, which can combine the above-mentioned aerogel with the device to meet the water purification needs, thereby realizing the application of clean water collection and adaptation to off-grid scenarios such as islands and arid areas, as shown in the attached Figure 9 As shown, it includes:

[0066] Clean water tank 3, used to receive refluxed condensed water;

[0067] Sewage pool 2 is provided in the water purification pool and is used to hold the sewage to be purified; the cellulose / MXene composite aerogel as described above is provided in the sewage pool; the cellulose / MXene composite aerogel floats at the gas-liquid interface and can greatly accelerate the evaporation rate of water in the sewage pool;

[0068] A condensation hood 1 is disposed above the clean water pool and connected to the clean water pool; the condensation hood and the clean water pool can form a condensed water reflux channel; water vapor evaporates from the cellulose / MXene composite aerogel under sunlight, and water vapor condenses in the condensation hood; to facilitate the collection and reflux of condensed water, in some embodiments, the condensation hood preferably has a curved surface structure with a high center and a low perimeter; for example, the condensation hood is cylindrical with a semicircular top;

[0069] The water outlet 4 is arranged on the water purification pool.

[0070] The above-mentioned distributed interface water evaporation device is in accordance with the attached Figure 10The operation process shown is for sewage purification. Specifically, various sewage that may need to be treated, such as river water, lake water, sea water, streams, rainwater, and urban sewage, are placed in a sewage pool, and the cellulose / MXene composite aerogel prepared by the present invention is placed in the sewage pool so that it floats at the gas-liquid interface, and the condensation cover is covered on the water purification pool to form a closed space. Then, the assembled distributed interface water evaporation device is placed under the sun. At this time, the water in the sewage will evaporate, condense and reflux, and the purified water can flow back to the water purification pool along the wall of the condensation cover, so that purified water that can be drunk directly can be generated. When purifying water, the water outlet needs to be closed; when water needs to be collected for drinking, the water outlet can be opened to collect water. This makes it possible to drink purified water in some specific scenarios, and does not require energy such as electricity to drive it.

[0071] In order to facilitate the carrying of the distributed interfacial water evaporation device, the present invention preferably designs it as a foldable structure, and preferably the condensation hood and the sewage pool are both telescopic structures; when not in use, the condensation hood and the sewage pool can be folded up and stored in the clean water pool, 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 limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0073] Unless otherwise specified, the materials and reagents mentioned below are commercially available products familiar to those skilled in the art. Unless otherwise specified, the methods described are all well-known methods in the art. Unless otherwise defined, technical or scientific terms used shall have the same meanings as those commonly understood by those skilled in the art.

[0074] Example 1

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

[0076] 1) Preparation of an oxidized nanocellulose dispersion: 5 g of bleached softwood kraft pulp was dispersed in 50 g of deionized water, and 0.08 g of TEMPO reagent, 0.25 g of sodium bromide, and 35 mmol of sodium hypochlorite were added. The mixture was stirred and reacted for 1 hour. During the reaction, the pH was maintained at 10.0 using a 1 mol / L sodium hydroxide solution. The product was then washed with deionized water multiple times until neutral. An appropriate amount of deionized water was added to disperse the product into a 1 wt% dispersion. The product was homogenized six times using a high-pressure homogenizer at 100 MPa to obtain TEMPO-oxidized cellulose nanofibers. The TEMPO-oxidized cellulose nanofibers were prepared into a 1 wt% dispersion and ultrasonically treated in an ice-water bath for 30 min to obtain a uniform dispersion, which was the cellulose aqueous dispersion. The surface carboxyl group / carboxymethyl group ratio was 1.5.

[0077] 2) Preparation of a few-layer MXene nanosheet dispersion: Add 40 mL of HCl solution with a mass concentration of 36% to a polytetrafluoroethylene container, add 2.0 g of LiF, and stir at 350 rpm for 30 minutes to dissolve it to obtain an etching solution. Then gradually add 2.0 g of Ti3AlC2 powder to the etching solution, and then continue stirring at 350 rpm, etch at 35 ° C for 24 hours, and then wash with deionized water several times. The reaction mixture is centrifuged at 3500 rpm for 5 minutes until the pH value of the supernatant is about 6 to obtain a multilayer Ti3C2T x . The 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 to obtain the MXene dispersion. The concentration of the MXene dispersion was adjusted to 1.5 wt%, and sonicated in an ice-water bath for 30 min to obtain a uniform dispersion, which was a few-layer MXene nanosheet dispersion.

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

[0079] 4) The obtained precursor gel was poured into a mold and frozen at -70°C for 1 hour. The sample was then immersed in an ethanol / metal ion bath for 48 hours to completely melt the sample; the ethanol / metal ion bath had a Ca2+ ion mass concentration of 1 wt% and a temperature of -20°C; the sample was washed with water and air-dried 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 performed using conventional methods in the art, as follows:

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

[0083] Figure 2 Shown are photographs of the aerogel prepared in this example, showing its dimensions from different angles. As shown, after multiple rinses with abundant water and drying at atmospheric pressure, the aerogel maintains its intact three-dimensional porous network structure, with no apparent structural collapse. Macroscopically, it exhibits a uniform, deep black surface. This is attributed to the complete integration of the few-layer MXene nanosheets and cellulose nanofibers, which facilitates the material's absorption of sunlight and its conversion into heat energy.

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

[0085] Desalination performance test: real seawater from the Bohai Sea was collected for testing, and the ion concentration of the seawater was measured; the distributed interface evaporation device of the present invention (the cellulose / MXene composite aerogel prepared by the present invention was set in the sewage pool) was used to evaporate and condense the seawater, and the condensed water was collected and the ion concentration of the condensed water was measured; the results of the comparison between the ion concentration of the seawater and the ion concentration of the condensed water are shown in the attached figure. Figure 3 As shown in the figure, compared with the original seawater, the Na + , K + , Mg 2+ and Ca 2+ The concentration of condensed water was significantly reduced by three to four orders of magnitude; and 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 interface evaporation device of the present invention (the cellulose / MXene composite aerogel prepared by the present invention is set in the sewage pool) is used to treat the heavy metal ion Hg 2+ ,Cd 2+ ,Cr 3+ ,Cu 2+ ,Ni 2+ ,Zn 2+ , and Pb2+ The water was purified, and the ion concentration before and after water treatment was compared. Figure 4 As shown in the figure, it can be seen that the overall concentration of heavy metal ions is reduced by 2 to 6 orders of magnitude (ppb), and the removal rate reaches more than 98%, which is comparable to current purification technology.

[0087] Salt deposition resistance test: Figure 5 As shown in the figure, the distributed interfacial evaporation device of the present invention (the cellulose / MXene composite aerogel prepared in the present invention is set in the sewage pool) is used to purify high-concentration salt water. Specifically, a 20wt% NaCl aqueous solution is evaporated under 1 times the solar radiation intensity (hereinafter referred to as 1SUN). After 7 hours of testing, the evaporation rate is still as high as 1.77kg·m -2 ·h -1 The evaporation rate changes with time as shown in the attached Figure 5 As shown in the figure, there is no salt deposition on the surface of the aerogel at the beginning and end of evaporation, as shown in the attached figure. Figure 5a shown.

[0088] Example 2

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

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

[0091] ① Preparation of oxidized nanocellulose dispersion: Disperse 5g of bleached softwood kraft pulp in 50ml of a 1.0wt% dilute sulfuric acid solution. Add 7g of potassium permanganate and react at 600rpm and 60°C for 150min. The product is then washed with deionized water multiple times until neutral, and then dispersed into a 1wt% dispersion with an appropriate amount of deionized water. Homogenize six times using a high-pressure homogenizer at 100mpa to obtain potassium permanganate-oxidized cellulose nanofibers. A 0.8wt% dispersion of the potassium permanganate-oxidized cellulose nanofibers is prepared and ultrasonically treated in an ice-water bath for 30min to obtain a uniform dispersion, which is the cellulose aqueous dispersion; the surface carboxyl / carboxymethyl content is 1.2.

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

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

[0094] 4) Same as Example 1.

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

[0096] Under 1SUN conditions, the aerogel evaporation rate was 1.95kg·m-2·h-1, the efficiency was 89.5%, and the surface temperature was 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 water quality met the WHO drinking water standard; after treating water containing Hg2+, Cd2+, Cr3+, Cu2+, Ni2+, Zn2+, and Pb2+, the concentration of heavy metals decreased by 2–6 orders of magnitude, with a removal rate of ≥97%; under 1SUN conditions, a 20wt% NaCl solution was evaporated for 7h at a rate of 1.70kg·m-2·h-1, and no salt crystals were deposited on the aerogel surface.

[0097] Example 3

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

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

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

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

[0102] 4) Same as Example 1.

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

[0104] Under 1SUN conditions, the aerogel evaporation rate was 2.0kg·m-2·h-1, the efficiency was 92.1%, and the surface temperature was 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 water quality met the WHO drinking water standard; after treating water containing Hg2+, Cd2+, Cr3+, Cu2+, Ni2+, Zn2+, and Pb2+, the concentration of heavy metals decreased by 2–6 orders of magnitude, with a removal rate of ≥98%; under 1SUN conditions, a 20wt% NaCl solution was evaporated for 7h at a rate of 1.72kg·m-2·h-1, and no salt crystals were deposited on the aerogel surface.

[0105] Example 4

[0106] Same as Example 1, except that the concentration of the cellulose aqueous dispersion in step 1) was 1.2%. Test results are as follows: Under 1-Sun conditions, the aerogel evaporation rate was 2.1 kg·m⁻²·h⁻¹, with an efficiency of 92.3% and a surface temperature of 37.1°C. After single-stage 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 treatment of water containing Hg2+, Cd2+, Cr3+, Cu2+, Ni2+, Zn2+, and Pb2+, the concentration of heavy metals decreased by 2–6 orders of magnitude, with a removal efficiency of ≥98%. Under 1-Sun conditions, a 20 wt% NaCl solution was evaporated for 7 hours at a rate of 1.82 kg·m⁻²·h⁻¹, and no salt crystals were observed on the aerogel surface.

[0107] Example 5

[0108] Same as Example 1, except that the concentration of the few-layer MXene nanosheet dispersion in step 1) was 1.2%. Test results are as follows: Under 1-SUN conditions, the aerogel evaporation rate was 1.88 kg·m⁻²·h⁻¹, with an efficiency of 90.32% and a surface temperature of 37.1°C. After single-stage 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 concentration of heavy metals decreased by 2–6 orders of magnitude, with a removal efficiency of ≥98%. Under 1-SUN conditions, a 20 wt% NaCl solution was evaporated for 7 hours at a rate of 1.82 kg·m⁻²·h⁻¹, and no salt crystals were observed on the aerogel surface.

[0109] Example 6

[0110] Same as Example 1, except that the concentration of the few-layer MXene nanosheet dispersion in step 1) was 1.8%. Test results are as follows: Under 1-SUN conditions, the aerogel evaporation rate was 2.19 kg·m⁻²·h⁻¹, with an efficiency of 93.8% and a surface temperature of 37.3°C. After single-stage 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 concentration of heavy metals decreased by 2–6 orders of magnitude, with a removal efficiency of ≥98%. Under 1-SUN conditions, a 20 wt% NaCl solution was evaporated for 7 hours at a rate of 1.86 kg·m⁻²·h⁻¹, and no salt crystals were observed on the aerogel surface.

[0111] Example 7

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

[0113] Example 8

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

[0115] Example 9

[0116] Same as Example 1, except that the Ca2+ ion mass concentration in step 1) is 0.5 wt%. Test results are as follows: Under 1-SUN conditions, the aerogel evaporation rate was 1.9 kg·m-2·h-1, the efficiency was 90.5%, and the surface temperature was 36.5°C. After single 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 concentration of heavy metals decreased by 2–6 orders of magnitude, with a removal rate of ≥98%. Under 1-SUN conditions, a 20 wt% NaCl solution was evaporated for 7 h at a rate of 1.56 kg·m-2·h-1, and no salt crystals were observed on the aerogel surface.

[0117] Example 10

[0118] Same as Example 1, except that the Ca2+ ion mass concentration in step 1) is 2.0 wt%. Test results are as follows: Under 1-SUN conditions, the aerogel evaporation rate is 2.1 kg·m-2·h-1, the efficiency is 93.5%, and the surface temperature is 36.3°C. After single desalination of seawater, the concentrations of Na+, K+, Mg2+, and Ca2+ decreased by 3–4 orders of magnitude, and the water quality met WHO drinking water standards. After treating water containing Hg2+, Cd2+, Cr3+, Cu2+, Ni2+, Zn2+, and Pb2+, the concentration of heavy metals decreased by 2–6 orders of magnitude, with a removal rate of ≥98%. Under 1-SUN conditions, a 20 wt% NaCl solution was evaporated for 7 h at a rate of 1.83 kg·m-2·h-1, and no salt crystals were observed on the aerogel surface.

[0119] Comparative Example 1

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

[0121] 1) Preparation of a mechanical nanocellulose dispersion: 5 g of bleached softwood kraft pulp was dispersed in 50 g of deionized water and homogenized five times using a high-pressure homogenizer at 100 mPa to obtain the mechanical nanocellulose. A 1 wt% dispersion of the mechanical nanocellulose was prepared and ultrasonicated in an ice-water bath for 30 min to obtain a uniform dispersion.

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

[0123] 3) The mechanical nanocellulose dispersion and the few-layer MXene nanosheet dispersion were mixed at a mass ratio of 10:3, and stirred at a high shear rate of 10,000 rpm for 1 h to obtain a mixed dispersion.

[0124] 4) The obtained mixed dispersion was poured into the same mold as in Example 1 and frozen at -70°C for 1 hour. The sample was then immersed in an ethanol / Ca2+ bath (1 wt%, -20°C) for 48 hours to completely melt the sample. The sample was then washed with deionized water and air-dried at room temperature and normal pressure to obtain a black flaky material, as shown in the attached figure. Figure 6 shown.

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

[0126] Comparative Example 2

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

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

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

[0130] 3) Same as Example 1.

[0131] 4) The obtained precursor gel was poured into a mold and frozen at -70°C for 1 hour. The sample was immersed in an ethanol bath for 48 hours to completely melt the sample. The sample was then washed with water and air-dried at room temperature and normal pressure to obtain a partially collapsed material, as shown in the attached figure. Figure 7 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 is that a pure ethanol solution without metal ions is used in the solvent exchange stage. Despite the presence of carboxyl functional groups on the cellulose surface, the aerogel material undergoes significant structural collapse during the drying process due to the lack of coordination crosslinking by metal ions. This phenomenon verifies that metal ion-mediated coordination crosslinking plays a key role in stabilizing the porous structure and reveals the necessity of a synergistic strategy of "functional group modification-ion complexation" to inhibit aerogel drying shrinkage.

[0133] Comparative Example 3

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

[0135] 1) Preparation of a mechanical nanocellulose dispersion: 5 g of bleached softwood kraft pulp was dispersed in 50 g of deionized water and homogenized five times using a high-pressure homogenizer at 100 mPa to obtain the mechanical nanocellulose. A 1 wt% dispersion of the mechanical nanocellulose was prepared and ultrasonicated in an ice-water bath for 30 min to obtain a uniform dispersion.

[0136] 2) Omit this step.

[0137] 3) Omit this step.

[0138] 4) The nanocellulose dispersion was poured into the same mold and frozen at -70°C for 1 hour. The sample was immersed in an ethanol / Ca2+ bath (1 wt%, -20°C) for 48 hours to completely melt the sample. The sample was then washed with deionized water and air-dried at room temperature and normal pressure to obtain a white flaky material, as shown in the attached figure. Figure 8 shown.

[0139] Depend on Figure 8 As shown, the comparative example used the same carboxylated modified cellulose and the same process parameters (including freezing temperature, cross-linking time and drying conditions) as Example 1 during the preparation process, but no few layers of MXene nanosheets were added. Although cellulose itself contains rich carboxyl functional groups and can undergo a certain degree of complexation with metal ions, due to the lack of additional synergistic coordination between MXene nanosheets and cellulose, the three-dimensional skeleton of the aerogel material also underwent obvious structural collapse and shrinkage during the drying process. This comparative experiment clearly verifies the key role of MXene nanosheets in stabilizing the porous structure of aerogels, and further proves the necessity of constructing a "fiber-sheet" synergistic network strategy in the present invention to effectively inhibit the drying shrinkage of aerogels and maintain a high porosity structure.

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

[0141] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiment based on the technical essence of the present invention 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 includes the following steps: S11 carboxylates and modifies cellulose to dissociate into nanofibers, which are then prepared into a cellulose aqueous dispersion; the cellulose aqueous dispersion is compounded with a few-layer MXene nanosheet dispersion to form a precursor gel; S12: injecting the precursor gel into a mold and freezing it; immersing the fully frozen gel and the mold together in an anhydrous ethanol / metal ion solution for solvent exchange; After the S13 solvent was exchanged to an ice-free state, it was rinsed with water and dried under normal pressure to obtain a cellulose / MXene composite aerogel.

2. The preparation method according to claim 1, characterized in that 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 surface carboxyl content of the modified cellulose is 1.0 to 2.5 mmol / g.

3. The preparation method according to claim 1, characterized in that 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.

4. The preparation method according to claim 1, characterized in that 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°C.

5. A cellulose / MXene composite aerogel, characterized in that The invention 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-sheet network structure.

6. The cellulose / MXene composite aerogel according to claim 5, characterized in that The cellulose / MXene composite aerogel is prepared by the preparation method according to any one of claims 1 to 4; the cellulose / MXene composite aerogel can still maintain a complete 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 under 1 times the solar radiation intensity -2 ·h -1 , evaporation efficiency ≥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 includes: Clean water tank, used to receive the returned condensed water; A sewage tank is provided in the water purification tank and is used to hold 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 condensation hood is arranged above the clean water pool and connected to the clean water pool; the condensation hood and the clean water pool can form a condensed water reflux channel; The water outlet is arranged on the water purification pool.

9. The distributed interface water evaporation device according to claim 8, characterized in that: The condensation cover is a curved structure with a high middle and a low periphery.

10. The distributed interface water evaporation device according to claim 8, characterized in that: The condensation hood and the sewage tank are both telescopic structures.

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