Nanocellulose MOF composite aerogel and preparation method and application thereof

Abstract

This invention discloses a nanocellulose MOF composite aerogel, its preparation method, and its application, belonging to the field of biomass materials technology. HKUST-1 was synthesized using copper nitrate trihydrate, 1,3,5-benzenetricarboxylic acid, and ethanol as raw materials via a hydrothermal method at 120°C for 10 hours. Then, CuS@HKUST-1 was synthesized using thioacetyl, ethanol, and HKUST-1 as raw materials via local in-situ vulcanization at 50°C for 1 hour. Stearic acid (SA) was grafted onto the synthesized CuS@HKUST-1 and then incorporated into a three-dimensional network structure composed of lignin cellulose nanofibers (LCNF), polyvinyl alcohol (PVA), and carboxymethyl chitosan (CMCS). Using glutaraldehyde and glycerol as crosslinking agents, the mixture was freeze-dried and hydrophobically modified with methyltrimethoxysilane (MTMS) to obtain the nanocellulose MOF composite aerogel. The composite aerogel of this invention features low cost, simple fabrication, photothermal effect, and excellent oil-water separation performance.

Description

Technical Field

[0001] This invention belongs to the field of biomass materials technology, specifically relating to a nanocellulose MOF composite aerogel, its preparation method, and its application. Background Technology

[0002] Due to the indiscriminate discharge of industrial wastewater and the serious damage caused to the ecological environment and human living environment by offshore oil spills, oil-water separation is an urgent problem to be solved.

[0003] Nanocellulose, as a biodegradable cellulose nanoparticle, has broad application prospects. It not only possesses the excellent properties of cellulose but also exhibits good mechanical strength, structural flexibility, high specific surface area, high aspect ratio, high purity, and good adsorption properties. Furthermore, the surface of nanocellulose is rich in active groups, exhibiting tunable self-assembly behavior, and can be chemically modified to prepare nanocellulose functional materials with unique performance advantages. In recent years, nanocellulose has demonstrated unique advantages and development in fields such as biomedicine, catalytic oxidation, purification, and reinforcing agents. For example, nanocellulose extracted from biomass can be used as a reinforcing agent to improve the mechanical strength of composite materials, for removing medical antibiotic wastewater, as a skin-friendly material to accelerate wound healing, and can also be used to develop special functional materials such as oil-water separation agents. Meanwhile, porous aerogel materials prepared using nanocellulose combine the various advantages of nanocellulose with the lightweight and porous characteristics of aerogels. They can overcome the shortcomings of traditional aerogels and effectively solve the problem of high-value-added utilization of nanocellulose, and have received much attention in recent years, with their application in the field of oil-water separation being one of the research hotspots. Furthermore, cellulose's greatest advantage lies in its renewable nature and abundant raw material sources. Soheil Bahraminia used crystalline cellulose extracted from waste paper, nano-TiO2, nano-SiO2, and vinyltrimethoxysilane as raw materials to prepare a superhydrophobic nanocellulose aerogel using a simple dip-coating method. This aerogel exhibits a water contact angle of 163.39°, demonstrating superhydrophobicity, and displays an adsorption capacity of 28.5–31.5 g / g for various oil pollutants and organic solvents, while also showing good removal efficiency for some emulsion oil droplets.

[0004] Although nanocellulose aerogels have made some progress in oil-water separation, they still face several challenges. Fan prepared a Cg-PEI aerogel with a cross-linked network by combining oxidized NFC (ONC), polyethyleneimine (PEI), and ethylene glycol diglyceride ether (EGDE). This aerogel can reach adsorption equilibrium for some low-viscosity crude oils, such as n-hexane, chloroform, and carbon tetrachloride, within 5 seconds. However, for some high-viscosity crude oils, due to the slower diffusion rate, it takes 60 minutes to reach adsorption equilibrium. Traditional nanocellulose aerogels are mainly suitable for adsorption of low-viscosity oils (<100 mPa•s) and are not applicable to high-viscosity crude oils (10³ - 10⁻¹⁰ mPa•s) in practical applications. 5 High-viscosity oils (mPa•s) adsorption, due to their poor fluidity, can clog the pore structure of aerogels, severely hindering their diffusion into the absorbent's internal pores via capillary forces. Since approximately 40% of global oil reserves are heavy crude oil, there is an urgent need to improve the performance of nanocellulose aerogels to effectively remove high-viscosity crude oil. Crude oil viscosity decreases with increasing temperature, making it easier for aerogel materials to adsorb it; therefore, the development of advanced porous materials with self-heating capabilities is crucial for cleaning up heavy crude oil. In recent years, various strategies for directly or indirectly heating porous absorbent materials have been proposed, including solar thermal, electrothermal, and magnetothermal technologies. Due to the abundance and cleanliness of solar energy, solar thermal absorbent materials have made significant progress. To date, various photothermal conversion materials based on carbon, semiconductors, MXene, and polymers have been used to enhance porous absorbents to achieve solar-assisted crude oil leak repair. Chen prepared an environmentally friendly, multifunctional bacterial cellulose / MXene aerogel (P-SBC / MXene aerogel) that can achieve rapid oil recovery. The P-SBC / MXene aerogel exhibits excellent photothermal and electrothermal capabilities, with a surface temperature of 1.0 kW / m². 2 Under sunlight, the temperature can quickly reach 93°C, and at 3.0 V, it can quickly reach 124°C. The heat generated can reduce the viscosity of crude oil, enabling rapid adsorption. Although the heat generated by graphene and MXene can effectively reduce the viscosity of crude oil and increase the adsorption capacity of the aerogel, the complexity of the pretreatment process, the harshness of the preparation conditions, and the high cost of these materials limit their application in the field of oil-water separation.

[0005] Metal-organic frameworks (MOFs) are highly crystalline porous entities constructed using metals or metal clusters as basic units, linked to organic ligands via coordination bonds. MOF materials possess tunable composition, diverse structures, extremely high specific surface area, and excellent thermochemical stability, making them promising for applications in catalysis, gas storage, and adsorption separation. However, the fact that MOFs exist in a difficult-to-form powder form limits their recyclability and reusability in practical applications. Combining the synthesis of MOF nanoparticles with renewable biopolymers is a promising technology that can endow composite materials with superior structure and function, thereby expanding their application range. Summary of the Invention

[0006] To address the above problems, this invention provides a nanocellulose MOF composite aerogel, its preparation method, and its applications. This preparation method is characterized by low cost and simple preparation, and the prepared composite aerogel exhibits photothermal effects, reusability, high separation efficiency, and a three-dimensional porous structure. This invention solves the problems of high cost, complex preparation, and low or no adsorption efficiency for high-viscosity crude oil in current aerogel production methods.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing a nanocellulose MOF composite aerogel includes the following steps: (1) Copper nitrate solution was added to 1,3,5-benzenetricarboxylic acid ethanol solution. After stirring and mixing evenly, it was transferred to a hydrothermal reactor. A certain amount of N,N-dimethylformamide was added, and the mixture was stirred at 80-85 °C for 15-20 h. After the reaction was completed, it was centrifuged and dried to obtain HKUST-1. (2) Add HKUST-1 from step (1) to a thioacetamide ethanol solution and react at 45-50 °C for 1-2 h. After the reaction is complete, centrifuge and dry to obtain CuS@HKUST-1. (3) Add CuS@HKUST-1 from step (2) to stearic acid ethanol solution, stir the reaction at room temperature for 18-20 h, and after the reaction is completed, centrifuge and dry to obtain CuS@HKUST-1 / SA; (4) Add a certain amount of lignin nanocellulose (LCNF), polyvinyl alcohol (PVA) and carboxymethyl chitosan (CMCS) to the container in sequence, stir and mix evenly, then disperse CuS@HKUST-1 / SA in step (3) with ethanol, then add it to the container, stir evenly, then add glutaraldehyde for crosslinking, freeze dry, and you can get LCNF / CMCS / PVA / CuS@HKUST-1 / SA aerogel; (5) Methyltrimethoxysilane (MTMS) is added to the LCNF / CMCS / PVA / CuS@HKUST-1 / SA aerogel in step (4) for hydrophobic modification. The aerogel is placed in a 70-75 ℃ oven for 6-8 h to obtain nanocellulose MOF composite aerogel, denoted as: LCNF / CMCS / PVA / CuS@HKUST-1 / SA-MTMS.

[0009] Furthermore, in step (1), the copper nitrate solution is obtained by adding copper nitrate hexahydrate to water and stirring evenly at a mass-to-volume ratio of 1:10-12; the 1,3,5-benzenetricarboxylic acid ethanol solution is obtained by adding 1,3,5-benzenetricarboxylic acid to ethanol and stirring evenly at a mass-to-volume ratio of 1:30-44; the volume ratio of copper nitrate solution to 1,3,5-benzenetricarboxylic acid ethanol solution is 1:1; and the volume ratio of copper nitrate solution to N,N-dimethylformamide is 7.5-10:1.

[0010] Furthermore, in step (1), the stirring is carried out using magnetic stirring at a speed of 500-1000 rpm / min; the centrifugation speed is 8000-10000 rpm / min for 5-10 min; and the drying is carried out using vacuum drying at 60-65℃ for 12-24 h.

[0011] Furthermore, in step (3), the mass-to-volume ratio of CuS@HKUST-1 to stearic acid ethanol solution is 1:200-250.

[0012] Furthermore, in step (3), the stearic acid ethanol solution is prepared by mixing stearic acid and ethanol at a mass-to-volume ratio of 1:20-25 and stirring at 40-50℃ until completely dissolved. The centrifugation speed is 8000-10000 rpm / min and the time is 5-10 min. The drying is carried out under vacuum at 60-65℃ for 12-24 h.

[0013] Furthermore, in step (4), the mass ratio of lignin nanocellulose, polyvinyl alcohol, and carboxymethyl chitosan is 1.2-2:1:1.

[0014] Furthermore, in step (4), the amount of CuS@HKUST-1 / SA added is 16% of the total mass of lignin nanocellulose, polyvinyl alcohol and carboxymethyl chitosan; the amount of glutaraldehyde added is 0.1% of the total mass of lignin nanocellulose, polyvinyl alcohol, carboxymethyl chitosan and CuS@HKUST-1 / SA.

[0015] Furthermore, in step (4), the freeze-drying process involves pre-freezing at -20°C for 2-3 hours before freezing, followed by freeze-drying at -50°C for 36-48 hours.

[0016] Furthermore, the mass-to-volume ratio of LCNF / CMCS / PVA / CuS@HKUST-1 / SA aerogel to methyltrimethoxysilane is 1:4-5; the volume ratio of hydrophobically modified methyltrimethoxysilane to water is 1:1.

[0017] The nanocellulose MOF composite aerogel prepared by the method of the present invention can be applied to oil-water separation.

[0018] The working principle of this invention is as follows: This invention prepares a porous photothermal aerogel with CuS@HKUST-1 / SA loaded on an LCNF / CMCS / PVA composite matrix and modified with MTMS hydrophobically. This aerogel relies on LCNF, CMCS, and PVA to construct a hydrogen-bonded, cross-linked, enhanced three-dimensional porous framework, providing ample adsorption channels to improve the physical adsorption capacity and permeation mass transfer efficiency of crude oil. The composite CuS@HKUST-1 / SA provides photothermal functional units, achieving efficient photothermal conversion through the plasma resonance effect (LSPR) of CuS. The photothermal heating effect can significantly reduce crude oil viscosity, accelerate the wetting, diffusion, and adsorption enrichment of crude oil within the porous channels, and greatly improve crude oil adsorption efficiency. MTMS silane grafting endows the material surface with low surface energy superhydrophobic and oleophilic properties, enabling selective and directional adsorption of crude oil in oil-water systems, preventing water intrusion into the pores, and synergistically combining the porous framework adsorption effect, photothermal viscosity reduction enhancement, and hydrophobic selective separation effect. Ultimately, it achieves rapid, high-capacity, and selective adsorption and separation of crude oil, especially high-viscosity heavy crude oil, in oil-containing aqueous phases.

[0019] The beneficial effects of this invention are: (1) This invention uses biodegradable lignin nanocellulose (LCNF), polyvinyl alcohol (PVA), and carboxymethyl chitosan (CMCS) as a substrate to prepare aerogels, providing a low-cost, simple-to-prepare, photothermal effect-efficient nanocellulose MOF composite aerogel material that can effectively absorb high-viscosity crude oil. It not only avoids environmental pollution but is also low-cost, eco-friendly, and in line with the sustainable development strategy.

[0020] (2) The present invention cleverly integrates MOF material into the three-dimensional network structure of LCNF / PVA / CMCS, which solves the problem of MOF material being difficult to recycle. At the same time, the added MOF material can also add photothermal properties to the aerogel.

[0021] (3) The nanocellulose MOF composite aerogel of the present invention can achieve underwater hydrophobic / oleophilic wettability, and the adsorption capacity for various low viscosity oils can reach 51 g / g. At the same time, it has excellent reusability. After 20 cycles of adsorption-extrusion of carbon tetrachloride, it can still maintain a high adsorption rate. It has a high adsorption capacity (41.01 g / g) for high viscosity oils (butter). After 10 cycles of adsorption-extrusion, it can still maintain an adsorption capacity of 38.01 g / g, which shows that it has excellent reusability. Attached Figure Description

[0022] Figure 1 The image shows a scanning electron microscope (SEM) image of the HKUST-1 material prepared in Example 1 at a scale bar of 10 μm.

[0023] Figure 2 The image shows a scanning electron microscope (SEM) image of the CuS@HKUST-1 material prepared in Example 1 at a scale bar of 5 μm.

[0024] Figure 3 Scanning electron microscope image of the nanocellulose MOF composite aerogel prepared in Example 1 at a scale bar of 1 mm.

[0025] Figure 4 This is a graph showing the temperature changes of nanocellulose MOF composite aerogel under different light conditions.

[0026] Figure 5 This is an adsorption diagram of different oils on nanocellulose MOF composite aerogels.

[0027] Figure 6 This is an adsorption cycle diagram of nanocellulose MOF composite aerogel.

[0028] Figure 7 This is a graph showing the adsorption capacity of high-viscosity oil (butter) for nanocellulose MOF composite aerogel.

[0029] Figure 8 Adsorption cycle diagram of high-viscosity oil (butter) for nanocellulose MOF composite aerogel Detailed Implementation The invention will be described in detail below with reference to specific embodiments.

[0030] Example 1 A method for preparing a nanocellulose MOF composite aerogel includes the following steps: (1) Preparation of HKUST-1 material 2.577 g of copper nitrate hexahydrate was dissolved in 30 ml of deionized water to obtain a copper nitrate solution. 1.500 g of 1,3,5-benzenetricarboxylic acid was added to 30 ml of anhydrous ethanol and magnetically stirred for 30 min at room temperature until homogeneous, yielding a 1,3,5-benzenetricarboxylic acid ethanol solution. The copper nitrate solution was added dropwise to the 1,3,5-benzenetricarboxylic acid ethanol solution, and magnetic stirring was continued for another 30 min at room temperature until thoroughly mixed. After homogeneity, the solution was transferred to a 100 ml high-pressure reactor, and 4 ml of N,N-dimethylformamide was added. The reaction was carried out at 80 ℃ for 20 h. After the reaction was complete, the mixture was removed, cooled to room temperature, centrifuged at 8000 rpm / min for 5 min, and washed several times with methanol until the supernatant was colorless to remove excess unreacted copper nitrate hexahydrate. Finally, the obtained blue solid was collected and dried overnight in a vacuum drying oven at 60 ℃ to obtain the HKUST-1 material.

[0031] (2) Preparation of CuS@HKUST-1 material Add 200 ml of ethanol to a 250 ml beaker, then weigh 0.500 g of thioacetamide and add it to the ethanol. Dissolve the thioacetamide completely in a constant temperature water bath at 50 ℃ to obtain a thioacetamide ethanol solution.

[0032] Weigh 0.200g of HKUST-1 material and add it to a thioacetamide ethanol solution. React at 50 °C for 1 h. After the reaction is complete, remove the beaker, allow it to cool to room temperature, centrifuge at 8000 rpm / min for 5 min, and wash alternately with ethanol and methanol. Finally, collect the obtained dark green solid and dry it overnight in a 60 °C drying oven to obtain CuS@HKUST-1 material. Drying is performed under vacuum at 60 °C for 6-8 h, followed by drying in a 120 °C vacuum drying oven for 12 h.

[0033] (3) Preparation of CuS@HKUST-1 / SA material To prepare a 150 mM stearic acid-ethanol solution: Weigh 80 ml of ethanol and add it to a 100 ml beaker. Then weigh 4.2672 g of stearic acid and add it to the ethanol solution. Place the beaker in a 40°C constant temperature water bath and stir until completely dissolved and without obvious turbidity or precipitate. After the solution cools to room temperature, transfer it to a 100 ml volumetric flask. Wash the beaker 2-3 times with a small amount of anhydrous ethanol, transferring all the washings into the volumetric flask. Add anhydrous ethanol to 1-2 cm below the graduation mark, then use a dropper to add the solution dropwise until the meniscus is tangent to the graduation mark. Tighten the stopper and invert the flask 10-15 times to mix.

[0034] 20 ml of a prepared 150 mM stearic acid-ethanol solution was added to a 50 ml beaker. Then, 0.2 g of CuS@HKUST-1 was weighed and added to the stearic acid-ethanol solution. The mixture was magnetically stirred at room temperature for 20 h. After the reaction was complete, the mixture was centrifuged at 8000 rpm for 5 min and washed several times with anhydrous ethanol to remove unreacted stearic acid. Finally, the solid was collected and dried overnight in a vacuum drying oven at 60 ℃ to obtain the CuS@HKUST-1 / SA material.

[0035] (4) Preparation of LCNF / CMCS / PVA / CuS@HKUST-1 / SA aerogel: Weigh out 20g of 0.6% LCNF, 5g of 2% PVA, and 5g of 2% CMCS sequentially and add them to a beaker. Stir magnetically at room temperature until homogeneous to form an LCNF / PVA / CMCS mixed gel. Then weigh out 0.048g of CuS@HKUST-1 / SA into a 10ml beaker, disperse it thoroughly with a small amount of ethanol, and then add it dropwise to the LCNF / PVA / CMCS mixed gel. Stir magnetically for 30 min until homogeneous. After homogeneity, add 50ul of 25% glutaraldehyde and allow it to crosslink completely for 1-2 min. Defoam the mixture using ultrasonication, transfer it to a mold, pre-freeze at -20℃ for 2-4 h, then transfer it to -50℃ and freeze overnight. Finally, freeze-dry using a lyophilizer for 48 h to obtain LCNF / CMCS / PVA / CuS@HKUST-1 / SA-16% aerogel.

[0036] (5) Preparation of nanocellulose MOF composite aerogel: The obtained LCNF / CMCS / PVA / CuS@HKUST-1 / SA-16% aerogel was transferred entirely to a 1000 ml beaker. 3 ml of methyltrimethoxysilane and 3 ml of deionized water were placed in separate 10 ml sample vials, which were then placed open inside the 1000 ml beaker. The 1000 ml beaker was then sealed and placed in a 75 ℃ forced-air oven for 6 h. After the reaction was complete, the nanocellulose MOF composite aerogel was obtained, denoted as: LCNF / CMCS / PVA / CuS@HKUST-1-16% / SA-MTMS aerogel.

[0037] In the above LCNF / CMCS / PVA / CuS@HKUST-1-16% / SA-MTMS, the 16% in CuS@HKUST-1 / SA-16% means the percentage of CuS@HKUST-1 / SA in the total mass of LCNF, CMCS, and PVA.

[0038] Example 2 Steps (1)-(3) are the same as in Example 1, and CuS@HKUST-1 / SA material is prepared.

[0039] (4) Weigh 20g of 0.6% LCNF, 5g of 2% PVA, and 5g of 2% CMCS in sequence and add them to a beaker. Stir magnetically at room temperature to mix them evenly. Then weigh 0.0256g of CuS@HKUST-1 / SA into a 10ml beaker and disperse it fully with a small amount of ethanol. Then add it dropwise to the LCNF / PVA / CMCS mixed gel and stir magnetically for 30min to mix it evenly. After mixing evenly, add 50ul of 25% glutaraldehyde and crosslink it fully for 1~2min. Then defoam it by sonication and transfer it to a mold. Pre-freeze it in a -20℃ freezer for 2h, then transfer it to a -50℃ freezer and freeze it overnight. Finally, freeze-dry it for 48h using a freeze dryer to obtain LCNF / CMCS / PVA / CuS@HKUST-1 / SA-8% aerogel.

[0040] (5) Transfer all of the obtained LCNF / CMCS / PVA / CuS@HKUST-1 / SA-8% aerogel to a 1000 ml beaker. Take 3 ml of methyltrimethoxysilane and 3 ml of deionized water and place them in 10 ml sample vials respectively. Place the vials open in the 1000 ml beaker, then seal the 1000 ml beaker and place it in a 75 ℃ forced-air oven for 6 h. After the reaction is complete, the nanocellulose MOF composite aerogel can be obtained, denoted as: LCNF / CMCS / PVA / CuS@HKUST-1-8% / SA-MTMS aerogel.

[0041] Example 3 Steps (1)-(3) are the same as in Example 1, and CuS@HKUST-1 / SA material is prepared.

[0042] (4) Weigh 20g of 0.6% LCNF, 5g of 2% PVA, and 5g of 2% CMCS in sequence and add them to a beaker. Stir magnetically at room temperature to mix them evenly. Then weigh 0.075g of CuS@HKUST-1 / SA into a 10ml beaker and disperse it fully with a small amount of ethanol. Then add it dropwise to the LCNF / PVA / CMCS mixed gel and stir magnetically for 30min to mix it evenly. After mixing evenly, add 50ul of 25% glutaraldehyde and crosslink it fully for 1~2min. Then defoam it by sonication and transfer it to a mold. Pre-freeze it in a -20℃ freezer for 2h and then transfer it to a -50℃ freezer to freeze overnight. Finally, freeze-dry it for 48h using a freeze dryer to obtain LCNF / CMCS / PVA / CuS@HKUST-1 / SA-24% aerogel.

[0043] (5) Transfer all of the obtained LCNF / CMCS / PVA / CuS@HKUST-1 / SA-24% aerogel to a 1000 ml beaker. Take 3 ml of methyltrimethoxysilane and 3 ml of deionized water and place them in 10 ml sample vials respectively. Place the vials open in the 1000 ml beaker, then seal the 1000 ml beaker and place it in a 75 ℃ forced-air oven for 6 h. After the reaction is complete, the nanocellulose MOF composite aerogel can be obtained, denoted as: LCNF / CMCS / PVA / CuS@HKUST-1 / SA-24%-MTMS aerogel.

[0044] Comparative Example 1 Preparation of LCNF / CMCS / PVA aerogel: 20g of 0.6% LCNF, 5g of 2% PVA, and 5g of 2% CMCS were weighed sequentially and added to a beaker. The mixture was magnetically stirred at room temperature until homogeneous. After stirring for 30 min, 50 μL of 25% glutaraldehyde was added, and the mixture was allowed to crosslink completely for 1-2 min. The mixture was then defoamed by ultrasonication, transferred to a mold, pre-frozen at -20℃ for 2 h, then transferred to -50℃ and frozen overnight. Finally, the aerogel was freeze-dried for 48 h to obtain the LCNF / CMCS / PVA aerogel.

[0045] Material performance testing: (1) Material scanning electron microscopy The HKUST-1 material, CuS@HKUST-1 material, and nanocellulose MOF composite aerogel prepared in Example 1 were subjected to electron microscopy scanning. The results are as follows: Figure 1-3 As shown.

[0046] Figure 1 Scanning electron microscope image of HKUST-1 material prepared in Example 1 at a scale bar of 10 μm; Figure 2 The scanning electron microscope image of the CuS@HKUST-1 material prepared in Example 1 at a scale bar of 5 μm; Figure 3 The image shows a scanning electron microscope image of the nanocellulose MOF composite aerogel prepared in Example 1 with a scale bar of 1 mm.

[0047] Depend on Figure 1 It can be seen that HKUST-1 exhibits a typical octahedral crystal morphology with a smooth surface and clear edges, which is the characteristic crystal form of HKUST-1. Figure 2 It can be seen that CuS@HKUST-1 retains the octahedral framework of HKUST-1, but the surface becomes rough, with wrinkles and granular protrusions (the uneven structure of the surface can be seen in the magnified image), indicating that CuS has been successfully loaded onto the surface of HKUST-1. Figure 3 It can be seen that the nanocellulose MOF composite aerogel exhibits a dense three-dimensional network porous structure with uniform pores and an intact overall structure.

[0048] (2) Photothermal performance testing of materials The photothermal properties of the hydrophobically modified nanocellulose MOF composite aerogel prepared according to this invention were tested. Specifically, a xenon lamp was used to simulate sunlight. The sample, connected to a thermocouple, was placed at the center of the light intensity. Temperature was monitored and recorded using an SMRF-T multi-channel temperature monitoring system, with each cycle lasting 4 minutes. Simultaneously, the light intensity of the xenon lamp was changed to simulate variations in sunlight intensity, and the temperature changes of the aerogel were monitored and recorded. The results are as follows: Figure 4 As shown.

[0049] Depend on Figure 4 It can be seen that as the light intensity increases from 80mW to 170mW, the photothermal temperature of the aerogel also increases continuously. The steady-state temperature increases linearly with power, indicating that the material does not exhibit light saturation within the tested power range, and the photothermal conversion efficiency remains stable. This demonstrates that the added CuS@HKUST-1 / SA endows the aerogel with excellent photothermal properties. The aerogel prepared in this invention can achieve its own temperature increase through the photothermal effect, thereby reducing crude oil viscosity, improving crude oil flowability, and promoting its efficient adsorption, significantly increasing the crude oil adsorption capacity, and ultimately achieving more efficient oil-water separation.

[0050] (3) Adsorption experiments of materials on different oils The composite aerogel prepared according to this invention was subjected to adsorption tests on different oils (carbon tetrachloride, dimethicone, edible oil, liquid paraffin, cyclohexane, n-hexane, and pump oil). The specific procedure was as follows: First, the composite aerogel was initially weighed and recorded as m0; then, it was completely immersed in the oil solution to be adsorbed and allowed to stand until adsorption equilibrium was reached. After removal, the residual oil phase on the surface was wiped off with filter paper, and the aerogel was weighed again and recorded as m1. The adsorption was then calculated using the formula Q = (m1 / m0) * m1 / m0. The adsorption capacity of the aerogel is calculated using m0) / m0, and the adsorption capacity is obtained. Figure 5 .

[0051] pass Figure 5 It can be seen that the adsorption range of LCNF / CMCS / PVA / CuS@HKUST-1-16% / SA-MTMS aerogel is 25~51g / g, and the overall adsorption performance is better. Among them, the adsorption capacity for carbon tetrachloride reaches 51g / g.

[0052] After adsorption, the saturated aerogel was desorbed by extrusion and regenerated by washing with ethanol to remove residual oil from the pores. After the ethanol had fully evaporated, the regenerated aerogel was used for the next round of adsorption tests. The "adsorption-desorption-regeneration" steps were repeated for 20 cycles to obtain the desired aerogel. Figure 6 .Depend on Figure 6 It is known that the composite aerogel of the present invention can still maintain more than 20g / g after 20 CCl4 adsorption cycles, and has excellent reusability. Figure 7 The adsorption capacity of nanocellulose MOF composite aerogel for butter was demonstrated. It was found that LCNF / CMCS / PVA / CuS@HKUST-1-16% / SA-MTMS possesses a high adsorption capacity, and that... Figure 8 It can be seen that LCNF / CMCS / PVA / CuS@HKUST-1-16% / SA-MTMS can still maintain a high adsorption capacity (38g / g) after 10 adsorption-extrusion cycles.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a nanocellulose MOF composite aerogel, characterized in that: The method includes the following steps: (1) Copper nitrate solution was added to 1,3,5-benzenetricarboxylic acid ethanol solution. After stirring and mixing evenly, it was transferred to a hydrothermal reactor. A certain amount of N,N-dimethylformamide was added, and the mixture was stirred at 80-85 °C for 15-20 h. After the reaction was completed, it was centrifuged and dried to obtain HKUST-1. (2) Add HKUST-1 from step (1) to a thioacetamide ethanol solution and react at 45-50 °C for 1-2 h. After the reaction is complete, centrifuge and dry to obtain CuS@HKUST-1. (3) Add CuS@HKUST-1 from step (2) to stearic acid ethanol solution, stir the reaction at room temperature for 18-20 h, and after the reaction is completed, centrifuge and dry to obtain CuS@HKUST-1 / SA; (4) Add a certain amount of lignin nanocellulose, polyvinyl alcohol and carboxymethyl chitosan to the container in sequence, stir and mix evenly, then disperse CuS@HKUST-1 / SA in step (3) with ethanol, then add it to the container, stir evenly, then add glutaraldehyde for cross-linking, freeze dry, and you can get LCNF / CMCS / PVA / CuS@HKUST-1 / SA aerogel. (5) Add methyltrimethoxysilane and water to the LCNF / CMCS / PVA / CuS@HKUST-1 / SA aerogel in step (4) for hydrophobic modification, and place it in 70-75 ℃ for 6-8 h to obtain nanocellulose MOF composite aerogel.

2. The method for preparing nanocellulose MOF composite aerogel as described in claim 1, characterized in that: In step (1), the volume ratio of copper nitrate solution to 1,3,5-benzenetricarboxylic acid ethanol solution is 1:1; the volume ratio of copper nitrate solution to N,N-dimethylformamide is 7.5-10:1; magnetic stirring is used for all stirring, with a speed of 500-1000 rpm / min; centrifugation is performed at a speed of 8000-10000 rpm / min for 5-10 min; and vacuum drying is performed at 60-65℃ for 12-24 h.

3. The method for preparing nanocellulose MOF composite aerogel as described in claim 1, characterized in that: In step (2), the thioacetamide ethanol solution is obtained by stirring and dissolving thioacetamide ethanol at a mass ratio of 1:400-450 to ethanol until homogeneous; the mass ratio of thioacetamide to HKUST-1 is 5-6:2; the centrifugation speed is 8000-10000 rpm / min and the time is 5-10 min; the drying is carried out by vacuum drying at 60℃ for 6-8 h, and then placed in a vacuum drying oven at 120℃ for 12 h.

4. The method for preparing nanocellulose MOF composite aerogel as described in claim 1, characterized in that: In step (3), the mass-to-volume ratio of CuS@HKUST-1 to stearic acid ethanol solution is 1:200-250.

5. The method for preparing nanocellulose MOF composite aerogel as described in claim 1, characterized in that: In step (3), the stearic acid ethanol solution is prepared by mixing stearic acid and ethanol at a mass-to-volume ratio of 1:20-25 and stirring at 40-50℃ until completely dissolved. The centrifugation speed is 8000-10000 rpm / min and the time is 5-10 min. The drying is carried out under vacuum at 60-65℃ for 12-24 h.

6. The method for preparing nanocellulose MOF composite aerogel as described in claim 1, characterized in that: In step (4), the mass ratio of lignin nanocellulose, polyvinyl alcohol, and carboxymethyl chitosan is 1.2-2:1:

1.

7. The method for preparing nanocellulose MOF composite aerogel as described in claim 1, characterized in that: In step (4), the amount of CuS@HKUST-1 / SA added is 16% of the total mass of lignin nanocellulose, polyvinyl alcohol and carboxymethyl chitosan; the amount of glutaraldehyde added is 0.1% of the total mass of lignin nanocellulose, polyvinyl alcohol, carboxymethyl chitosan and CuS@HKUST-1 / SA.

8. The method for preparing nanocellulose MOF composite aerogel as described in claim 1, characterized in that: In step (4), the mass-to-volume ratio of LCNF / CMCS / PVA / CuS@HKUST-1 / SA aerogel to methyltrimethoxysilane is 1:4-5; the volume ratio of hydrophobically modified methyltrimethoxysilane to water is 1:

1.

9. The nanocellulose MOF composite aerogel prepared by any one of the preparation methods described in claims 1-8.

10. The application of the nanocellulose MOF composite aerogel as described in claim 9, characterized in that: Its application in oil-water separation.

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