Nanocellulose-based oil-water separation and adsorption composite material

Abstract

The invention relates to the technical field of material science and engineering, and discloses a nanocellulose-based oil-water separation and adsorption composite material, which is prepared from the following raw materials in parts by mass: 35 to 45 parts of nanocellulose; 8 to 11 parts of bagasse cellulose; 10 to 15 parts of sodium lignin sulfonate; 4 to 8 parts of chitosan; 5-10 parts of oxidized starch; 5 to 8 parts of cellulose nanowhiskers; 2-5 parts of silicon dioxide nanoparticles; 0.5 to 1 part of calcium carbonate nanoparticles; 1-2 parts of a citric acid cross-linking agent; 1-2 parts of graphene oxide; 0.3 to 0.6 part of ethylene diamine tetraacetic acid; 2-5 parts of glycerol; 0.4 to 1 part of stearoyl chloride; 2-4 parts of nano iron oxide; the preparation method comprises the following steps: pretreating the raw materials, mixing the pretreated raw materials into slurry, carrying out crosslinking and ultrasonic dispersion, standing to obtain a basic mixture, injecting the basic mixture into a mold, carrying out freeze drying to form a photocatalytic layer, carrying out centrifugal dewatering, carrying out chelation reaction, spraying a composite solution, and carrying out vacuum drying to obtain the photocatalytic material. The obtained composite material has the advantages of efficient adsorption capacity, good mechanical properties, environmental friendliness, degradability and low preparation cost.

Description

Technical Field

[0001] The present invention relates to the technical field of materials science and engineering, and specifically to a nano-cellulose-based oil-water separation adsorption composite material. Background Art

[0002] With the acceleration of the industrialization process, the problem of oil-water separation has become increasingly important in the fields of environmental protection and resource recovery. However, the existing oil-water separation adsorption materials have many deficiencies and are difficult to meet the requirements of high efficiency, environmental protection, and sustainable development. Traditional adsorption materials such as polypropylene and its derivatives, although widely used, have limited adsorption capacity and are difficult to handle large-scale oil-water separation tasks. In addition, these materials are prone to clogging during the adsorption process, resulting in a decrease in adsorption efficiency. More seriously, polypropylene petroleum-based adsorption materials are non-degradable and will cause secondary pollution to the environment after use. Some of the chemical reagents used in the modification methods may also be harmful to the environment.

[0003] In addition to adsorption performance and environmental problems, the existing technology also has obvious defects in the mechanical properties of materials. For example, cellulose aerogels are prone to structural shrinkage under compression, resulting in poor mechanical properties and limiting their service life and reusability in practical applications. In addition, the preparation methods of high-performance nano-cellulose-based materials often have problems of high cost and complex processes. For example, although the supercritical CO2 drying method can prepare nano-cellulose aerogels with excellent performance, its cost is high and the equipment requirements are extremely high. The modification method of chemical vapor deposition is complex in operation and high in energy consumption, which is not conducive to large-scale industrial production.

[0004] Therefore, developing a high-performance, environmentally friendly, excellent mechanical property, and low-cost preparation nano-cellulose-based oil-water separation adsorption composite material has important practical significance for solving the defects of the existing technology. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] In view of the deficiencies of the existing technology, the present invention provides a nano-cellulose-based oil-water separation adsorption composite material, which has the advantages of high adsorption capacity, good mechanical properties, environmental friendliness, degradability, and low-cost preparation, and solves the problems of limited adsorption capacity, easy clogging, non-degradability, poor mechanical properties, high preparation cost, and complex process of the existing adsorption materials.

[0007] (2) Technical Solutions

[0008] To achieve the above object, the present invention provides the following technical solutions: A nano-cellulose-based oil-water separation adsorption composite material, including the following steps:

[0009] Step 1. Prepare raw materials: nanocellulose, bagasse cellulose, sodium lignosulfonate, chitosan, oxidized starch, cellulose nanocrystals, silicon dioxide nanoparticles, calcium carbonate nanoparticles, citric acid crosslinking agent, graphene oxide, ethylenediaminetetraacetic acid, glycerol, stearoyl chloride, nanoferric oxide and nano-titanium dioxide;

[0010] Step 2. Pretreatment of raw materials: Pretreat nanocellulose, bagasse cellulose, chitosan and oxidized starch with glycerol and stearoyl chloride;

[0011] Step 3. Preparation of the basic mixture: Mix the pretreated nanocellulose, bagasse cellulose, chitosan and oxidized starch into a homogeneous slurry, add cellulose nanocrystals, silicon dioxide nanoparticles and calcium carbonate nanoparticles, stir and then stand for defoaming, then add the citric acid crosslinking agent for crosslinking reaction, and finally add graphene oxide and nanoferric oxide for ultrasonic dispersion, spray the remaining stearoyl chloride, and stand at room temperature to obtain the basic mixture;

[0012] Step 4. Multi-scale structure construction process: Inject the basic mixture obtained in Step 3 into a mold, quickly freeze and dry in liquid nitrogen, then disperse nano-titanium dioxide in ethanol, spray it on the material surface, and cure it under ultraviolet light to form a photocatalytic layer;

[0013] Step 5. Sodium lignosulfonate strengthening process: Immerse the material obtained in Step 4 in a sodium lignosulfonate solution for water bath stirring, then centrifuge for dehydration and pre-dry to initially cure the structure;

[0014] Step 6. Ethylenediaminetetraacetic acid chelation and antibacterial modification: Immerse the material obtained in Step 5 in an ethylenediaminetetraacetic acid solution for ethylenediaminetetraacetic acid chelation, then spray a composite solution formed by nanoferric oxide and ethylenediaminetetraacetic acid, wash and then perform vacuum drying to obtain the composite material.

[0015] Preferably, the raw materials and their parts by mass in Step 1 are: 35 - 45 parts of nanocellulose; 8 - 11 parts of bagasse cellulose; 10 - 15 parts of sodium lignosulfonate; 4 - 8 parts of chitosan; 5 - 10 parts of oxidized starch; 5 - 8 parts of cellulose nanocrystals; 2 - 5 parts of silicon dioxide nanoparticles; 0.5 - 1 part of calcium carbonate nanoparticles; 1 - 2 parts of citric acid crosslinking agent; 1 - 2 parts of graphene oxide; 0.3 - 0.6 part of ethylenediaminetetraacetic acid; 2 - 5 parts of glycerol; 0.4 - 1 part of stearoyl chloride; 2 - 4 parts of nanoferric oxide; 0.6 - 1.1 parts of nano-titanium dioxide.

[0016] Preferably, for lignin removal of bagasse cellulose in Step 2: Immerse bagasse cellulose in a 2% - 3% NaOH solution, soak at a temperature of 75 - 80 °C for 1.5 - 2 hours, remove lignin, and wash with water until neutral.

[0017] Preferably, in step two, the activation of nanocellulose: disperse the nanocellulose in a citric acid buffer solution with pH = 5-6, and ultrasonically treat it for 25-30 minutes to expose the hydroxyl active sites.

[0018] Preferably, in step two, the hydrophobic modification of chitosan: dissolve chitosan in a 0.95% - 1.05% acetic acid solution, dropwise add 20% of stearoyl chloride according to the formula ratio and stir for reaction for 1.5 - 2 hours to form a hydrophobic coating.

[0019] Preferably, in step two, the plasticization of oxidized starch: mix and plasticize oxidized starch and glycerol at 60 - 65 °C to form a flexible adhesive.

[0020] Preferably, in step three, the preparation of the basic mixture:

[0021] S3.1. Mix the pretreated nanocellulose, bagasse cellulose, chitosan, and oxidized starch at a high speed of 45 - 50 °C and 1100 - 1200 rpm for shearing for 15 - 20 minutes to form a homogeneous slurry;

[0022] S3.2. Then, add cellulose nanocrystals, silicon dioxide nanoparticles, and calcium carbonate nanoparticles in sequence, stir and let stand for 30 - 40 min for defoaming treatment;

[0023] S3.3. Add a citric acid cross-linking agent and carry out a cross-linking reaction at a temperature of 55 - 60 °C for 1 - 1.2 hours;

[0024] S3.4. Add graphene oxide and 1 / 3 of the nanometer iron oxide according to the formula ratio, and ultrasonically disperse for 10 - 15 minutes;

[0025] S3.5. Spray the remaining stearoyl chloride and let stand at room temperature for 1 - 2 hours.

[0026] Preferably, in step four, the process of constructing the multi-scale structure:

[0027] S4.1. Inject the mixture obtained in step three into a mold, dry and freeze it in liquid nitrogen below -196 °C for a drying time of 20 - 24 hours to form through holes;

[0028] S4.2. Disperse titanium dioxide nanoparticles in ethanol, spray it on the material surface, and cure it under ultraviolet light of 365 nm for 8 - 10 minutes to form a photocatalytic layer.

[0029] Preferably, in step five, the strengthening process of sodium lignosulfonate:

[0030] S5.1 Sodium lignosulfonate crosslinking enhancement: Immerse the material obtained in Step 4 into a 0.5-1 wt% sodium lignosulfonate solution, and stir in a water bath environment at 55-60 °C for 0.5-1 h;

[0031] S5.2 Centrifugal dehydration: Centrifuge at a speed of 3500-4000 rpm for 10-12 min;

[0032] S5.3 Pre-drying: Dry under vacuum conditions at 45-50 °C for 3.5-4 h to initially cure the structure.

[0033] Preferably, the process of ethylenediaminetetraacetic acid chelation and antibacterial modification in Step 6:

[0034] S6.1 Ethylenediaminetetraacetic acid chelation treatment: Immerse the material in a 0.1-0.3 wt% ethylenediaminetetraacetic acid solution with a formulation ratio of 50%, stir at 50-55 °C for 30 min to chelate residual metal ions;

[0035] S6.2 Antibacterial modification: Spray the composite solution formed by the remaining nano-iron oxide and ethylenediaminetetraacetic acid with a mass ratio of 1:0.1, use Fe 3+ to inhibit the growth of microorganisms, and then ultrasonically clean with deionized water 3-5 times;

[0036] S6.3 Drying: Finally, under a pressure of -0.5 to -0.1 MPa, perform vacuum drying at 70-75 °C for 11-12 hours to obtain the composite material.

[0037] Compared with the prior art, the present invention provides a nano-cellulose-based oil-water separation adsorption composite material, which has the following beneficial effects:

[0038] 1. The present invention has achieved the beneficial effect of improving the adsorption capacity through multi-scale freeze-pore formation and optimizing the raw material ratio. Among them, liquid nitrogen freeze-drying is used to form through-hole channels, combined with the high porosity provided by nano-cellulose and bagasse cellulose, and graphene oxide to enhance conductivity and promote the oil-water separation efficiency, so that the adsorption capacity of the composite material increases. Then, by introducing ethylenediaminetetraacetic acid to chelate metal ions, the blockage of impurities in the oil stain is reduced, further improving the adsorption performance of the composite material and making its cyclic stability excellent.

[0039] 2. The present invention has achieved the beneficial effect of improving the mechanical properties through the nano-reinforcing phase and crosslinking and curing process. By adding cellulose nanocrystals, silica, and calcium carbonate nanoparticles to the raw materials, the compressive strength of the material is improved. At the same time, a citric acid crosslinking agent is used to cure the interface between nano-cellulose and chitosan to form a stable three-dimensional network structure, and then the phenolic hydroxyl group of sodium lignosulfonate forms hydrogen bonds or ionic bonds with amino / carboxyl groups in the material to further enhance the network strength of the material, increasing the compressive strength of the composite material.

[0040] 3. The present invention achieves the beneficial effects of improving environmental friendliness, antibacterial performance and water resistance through natural biomass substrates and special modification processes. Among them, using nanocellulose, bagasse cellulose and chitosan as natural biomass substrates, and sodium lignosulfonate helps to reduce the environmental burden. At the same time, hydrophobic modification with stearyl chloride and chelation with ethylenediaminetetraacetic acid reduce chemical residues, increasing the 60-day degradability of the composite material. Meanwhile, nanoferric oxide in the raw materials releases Fe 3 + , which can inhibit the growth of microorganisms. Combining with the surface catalytic layer formed by the photocatalytic layer under ultraviolet curing, it decomposes pollutants and aids in regeneration. At the same time, spraying stearyl chloride increases the contact angle, resulting in a significant increase in the antibacterial rate of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flowchart of the method steps of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figure 1 , a nanocellulose-based oil-water separation adsorption composite material, which includes the following steps:

[0044] Step 1. Prepare raw materials: nanocellulose, bagasse cellulose, sodium lignosulfonate, chitosan, oxidized starch, cellulose nanocrystals, silicon dioxide nanoparticles, calcium carbonate nanoparticles, citric acid crosslinking agent, graphene oxide, ethylenediaminetetraacetic acid, glycerol, stearyl chloride, nanoferric oxide and nano-titanium dioxide;

[0045] Step 2. Pretreat the raw materials: Pretreat nanocellulose, bagasse cellulose, chitosan and oxidized starch with glycerol and stearyl chloride;

[0046] Step 3. Prepare the basic mixture: Mix the pretreated nanocellulose, bagasse cellulose, chitosan and oxidized starch into a homogeneous slurry, add cellulose nanocrystals, silicon dioxide nanoparticles and calcium carbonate nanoparticles, stir and then stand for defoaming. Then add the citric acid crosslinking agent for crosslinking reaction. Finally, add graphene oxide and nanoferric oxide, perform ultrasonic dispersion, spray the remaining stearyl chloride, and stand at room temperature to obtain the basic mixture;

[0047] Step 4. Multi-scale structure construction process: Inject the base mixture obtained in Step 3 into a mold, quickly freeze and dry it in liquid nitrogen, then disperse nano-titanium dioxide in ethanol, spray it on the material surface, and cure it under ultraviolet light to form a photocatalytic layer;

[0048] Step 5. Sodium lignosulfonate strengthening process: Immerse the material obtained in Step 4 in a sodium lignosulfonate solution and stir it in a water bath. Utilize the phenolic hydroxyl groups of lignin to form hydrogen bonds or ionic bonds with the unreacted amino groups / carboxyl groups in the material to enhance the material network strength and water resistance, then centrifuge to dehydrate and pre-dry to initially cure the structure;

[0049] Step 6. Ethylenediaminetetraacetic acid chelation and antibacterial modification: Immerse the material obtained in Step 5 in an ethylenediaminetetraacetic acid (EDTA) solution for ethylenediaminetetraacetic acid chelation to improve the biocompatibility of the material, then spray a composite solution formed by nano-iron oxide and ethylenediaminetetraacetic acid, wash it, and perform vacuum drying to obtain a composite material.

[0050] Specifically, the parts by mass of the raw materials and their functions in Step 1 are as follows:

[0051] 35 - 45 parts of nanocellulose (CNF), as the core material, has high porosity, low density, and excellent adsorption properties, and at the same time has degradability, meeting environmental protection requirements;

[0052] 8 - 11 parts of bagasse cellulose, providing low cost, high regenerability, and biodegradability; providing a high-strength framework and hydrophilic and oleophobic properties;

[0053] 10 - 15 parts of sodium lignosulfonate, an industrial by-product, with low cost, enhancing emulsifying and adsorbing capabilities;

[0054] 4 - 8 parts of chitosan, a natural biodegradable polysaccharide, enhancing the oleophobic and hydrophilic properties of the material through amino groups, and at the same time improving mechanical toughness;

[0055] 5 - 10 parts of oxidized starch, a biodegradable binder, improving mechanical flexibility;

[0056] 5 - 8 parts of cellulose nanocrystals (CNC), enhancing mechanical strength and compressibility resistance;

[0057] 2 - 5 parts of silica nanoparticles, increasing the specific surface area and adsorption capacity of the material, and at the same time enhancing its mechanical strength;

[0058] 0.5 - 1 part of calcium carbonate nanoparticles, a low-cost reinforcing phase, enhancing the compressive strength of the material;

[0059] 1 - 2 parts of citric acid crosslinking agent, an environmentally friendly crosslinking agent, strengthening the interfacial bonding between nanocellulose CNF and chitosan;

[0060] 1 - 2 parts of graphene oxide, a conductive and heat - conductive layer, assisting in the efficiency of oil - water separation;

[0061] 0.3 - 0.6 parts of ethylenediaminetetraacetic acid (EDTA), a metal ion chelating agent, reducing the blockage of materials by metal impurities in oil stains;

[0062] 2 - 5 parts of glycerol, used for mixing and plasticizing oxidized starch;

[0063] 0.4 - 1 part of stearoyl chloride, used for impregnation modification to enhance the hydrophobicity and adsorption capacity of materials;

[0064] 2 - 4 parts of nano - iron oxide (Fe2O3), used for adsorbing heavy metal ions to enhance the functionality of the composite material;

[0065] 0.6 - 1.1 parts of nano - titanium dioxide, photocatalytically degrading pollutants and assisting in the regeneration of materials.

[0066] Specifically, for the delignification of bagasse cellulose in step two: Immerse the bagasse cellulose in a 2% - 3% NaOH solution and soak it at a temperature of 75 - 80°C for 1.5 - 2 hours. After removing the lignin, wash it with water until neutral.

[0067] Specifically, for the activation of nano - cellulose (CNF) in step two: Disperse the nano - cellulose in a citric acid buffer solution with pH = 5 - 6 and perform ultrasonic treatment for 25 - 30 minutes to expose the hydroxyl active sites.

[0068] Specifically, for the hydrophobic modification of chitosan in step two: Dissolve chitosan in a 0.95% - 1.05% acetic acid solution, and dropwise add 20% of the stearoyl chloride according to the formula ratio and stir - react for 1.5 - 2 hours to form a hydrophobic coating.

[0069] Specifically, for the plasticization of oxidized starch in step two: Mix and plasticize oxidized starch and glycerol at 60 - 65°C to form a flexible adhesive.

[0070] Specifically, for the preparation of the basic mixture in step three:

[0071] S3.1. Mix the pretreated nano - cellulose, bagasse cellulose, chitosan, and oxidized starch at 45 - 50°C and 1100 - 1200 rpm by high - speed shearing for 15 - 20 minutes to form a homogeneous slurry;

[0072] S3.2. Then, add cellulose nanocrystals, silica nanoparticles, and calcium carbonate nanoparticles in sequence, stir and let it stand for 30 - 40 min for defoaming treatment;

[0073] S3.3. Add a citric acid cross - linker and carry out a cross - linking reaction at a temperature of 55 - 60°C for 1 - 1.2 hours;

[0074] S3.4. Add graphene oxide and nano-iron oxide at a formulation ratio of 1 / 3, and ultrasonically disperse for 10 - 15 minutes;

[0075] S3.5. Spray the remaining stearyl chloride and let it stand at room temperature for 1 - 2 hours for hydrophobic modification.

[0076] The advantages are as follows: Through the nano-reinforcement phase and cross-linking curing process, the beneficial effect of improving mechanical properties is achieved. By adding cellulose nanocrystals, silica, and calcium carbonate nanoparticles to the raw materials, the compressive strength of the material is improved. At the same time, a citric acid cross-linking agent is used to cure the interface between nano-cellulose and chitosan to form a stable three-dimensional network structure. Then, hydrogen bonds or ionic bonds are formed between the phenolic hydroxyl groups of sodium lignosulfonate and amino / carboxyl groups in the material to further enhance the network strength of the material, resulting in an increase in the compressive strength of the composite material.

[0077] Specifically, the multi-scale structure construction process in step four:

[0078] S4.1. Inject the mixture obtained in step three into a mold, dry and freeze it in liquid nitrogen at a temperature below -196°C for 20 - 24 hours to form through channels;

[0079] S4.2. Disperse nano-titanium dioxide in ethanol, spray it on the surface of the material, and cure it under ultraviolet light at 365 nm for 8 - 10 minutes to form a photocatalytic layer.

[0080] The advantages are as follows: Through multi-scale freeze pore formation and optimization of the raw material ratio, the beneficial effect of improving the adsorption capacity is achieved. Among them, liquid nitrogen freeze-drying is used to form through channels, combined with the high porosity provided by nano-cellulose and bagasse cellulose, and graphene oxide enhances conductivity to promote the oil-water separation efficiency, resulting in an increase in the adsorption capacity of the composite material. Then, by introducing ethylenediaminetetraacetic acid to chelate metal ions, blockage of impurities in the oil stain is reduced, further improving the adsorption performance of the composite material and making its cycle stability excellent.

[0081] Specifically, the sodium lignosulfonate strengthening process in step five:

[0082] S5.1 Sodium lignosulfonate cross-linking enhancement: Immerse the material obtained in step four in a 0.5 - 1 wt% sodium lignosulfonate solution, stir it in a water bath environment at 55 - 60°C for 0.5 - 1 h, and use the phenolic hydroxyl groups of lignin to form hydrogen bonds or ionic bonds with the unreacted amino / carboxyl groups in the material to enhance the network strength and water resistance of the material;

[0083] S5.2. Centrifugal dehydration: Centrifuge at a speed of 3500 - 4000 rpm for 10 - 12 min to remove the excess solution;

[0084] S5.3. Pre-drying: Dry under vacuum at 45 - 50 °C for 3.5 - 4 h to preliminarily cure the structure.

[0085] Specifically, the process of ethylenediaminetetraacetic acid (EDTA) chelation and antibacterial modification in Step 6:

[0086] S6.1. Ethylenediaminetetraacetic acid (EDTA) chelation treatment: Immerse the material in a 0.1 - 0.3 wt% ethylenediaminetetraacetic acid (EDTA) solution with a formulation ratio of 50%, stir at 50 - 55 °C for 30 min to chelate residual metal ions (such as Fe 3+ , Ca 3+ ), and improve the biocompatibility of the material;

[0087] S6.2. Antibacterial modification: Spray the composite solution formed by the remaining nano-iron oxide and ethylenediaminetetraacetic acid with a mass ratio of 1:0.1, use Fe 3+ to inhibit the growth of microorganisms, and then ultrasonically clean with deionized water 3 - 5 times to remove unbound ethylenediaminetetraacetic acid and impurities;

[0088] S6.3. Drying: Finally, under a pressure of -0.5 to -0.1 MPa, perform vacuum drying at 70 - 75 °C for 11 - 12 hours to obtain the composite material.

[0089] Advantages: Through the natural biomass substrate and special modification process, beneficial effects of improving environmental friendliness, antibacterial performance, and water resistance are achieved. Among them, using nanocellulose, bagasse cellulose, and chitosan as natural biomass substrates, as well as sodium lignosulfonate, helps to reduce the environmental burden. At the same time, hydrophobic modification with stearoyl chloride and chelation with ethylenediaminetetraacetic acid reduce chemical residues, increasing the 60-day degradability of the composite material. Meanwhile, nano-iron oxide in the raw materials releases Fe 3 + , which can inhibit the growth of microorganisms. Combining with the surface catalytic layer formed by the photocatalytic layer under ultraviolet curing to decompose pollutants and assist in regeneration. At the same time, spraying stearoyl chloride increases the contact angle, resulting in a significant increase in the antibacterial rate of the composite material.

[0090] Example 1

[0091] Raw material ratio: 35 parts of nanocellulose (CNF); 8 parts of bagasse cellulose; 10 parts of sodium lignosulfonate; 4 parts of chitosan; 5 parts of oxidized starch; 5 parts of cellulose nanocrystals; 2 parts of silica nanoparticles; 0.5 parts of calcium carbonate nanoparticles; 1 part of citric acid crosslinker; 1 part of graphene oxide; 0.3 parts of ethylenediaminetetraacetic acid (EDTA); 2 parts of glycerol; 0.4 parts of stearoyl chloride; 2 parts of nano-iron oxide; 0.6 parts of nano-titanium dioxide.

[0092] Preparation process:

[0093] T1. Raw material pretreatment: Bagasse cellulose: Soak in 2% NaOH solution at 75°C for 1.5 hours, wash with water until neutral; Nanocellulose is dispersed in a citric acid buffer solution with pH = 5 and ultrasonically treated for 25 minutes; Chitosan is dissolved in 0.95% acetic acid solution, and 20% of stearoyl chloride in the formulation ratio is added dropwise and stirred for 1.5 hours; Oxidized starch and glycerol are mixed and plasticized at 60°C;

[0094] T2. Preparation of the basic mixture: The pretreated raw materials are mixed by high-speed shearing at 45°C and 1100 rpm for 15 minutes to form a homogeneous slurry; Cellulose nanocrystals, silica nanoparticles and calcium carbonate nanoparticles are added, stirred and then left to stand for 30 min to defoam; A citric acid crosslinking agent is added and crosslinked at 55°C for 1 hour; Graphene oxide and 1 / 3 of the nanometer iron oxide in the formulation ratio are added and ultrasonically dispersed for 10 minutes; The remaining stearoyl chloride is sprayed and left to stand at room temperature for 1 hour;

[0095] T3. Multi-scale structure construction process: The mixture is injected into a mold and dried and frozen in liquid nitrogen below -196°C for 20 hours; Nanometer titanium dioxide is dispersed in ethanol, sprayed on the material surface and cured under 365 nm ultraviolet light for 8 minutes;

[0096] T4. Sodium lignosulfonate strengthening process: The material is immersed in 0.5 wt% sodium lignosulfonate solution, stirred in a water bath at 55°C for 0.5 h; Centrifuged at 3500 rpm for 10 min to dehydrate; Vacuum dried at 45°C for 3.5 h;

[0097] T5. Ethylenediaminetetraacetic acid chelation and antibacterial modification: Immersed in 0.1 wt% ethylenediaminetetraacetic acid solution with 50% of the formulation ratio, stirred at 50°C for 30 min; The remaining composite solution of nanometer iron oxide and ethylenediaminetetraacetic acid is sprayed, and ultrasonically cleaned 3 times with deionized water; Under a pressure of -0.5 MPa, vacuum dried at 70°C for 11 hours.

[0098] Example 2

[0099] Raw material ratio: 40 parts of nanocellulose (CNF); 9 parts of bagasse cellulose; 12 parts of sodium lignosulfonate; 6 parts of chitosan; 7 parts of oxidized starch; 6 parts of cellulose nanocrystals; 3 parts of silica nanoparticles; 0.7 parts of calcium carbonate nanoparticles; 1.5 parts of citric acid crosslinking agent; 1.5 parts of graphene oxide; 0.4 parts of ethylenediaminetetraacetic acid (EDTA); 3 parts of glycerol; 0.7 parts of stearoyl chloride; 3 parts of nanometer iron oxide; 0.8 parts of nanometer titanium dioxide;

[0100] Preparation process: Refer to the steps of Example 1 and prepare according to the corresponding raw material ratio and conditions.

[0101] Example 3

[0102] Raw material ratio: 43 parts of nanocellulose (CNF); 10 parts of bagasse cellulose; 13 parts of sodium lignosulfonate; 7 parts of chitosan; 8 parts of oxidized starch; 7 parts of cellulose nanocrystals; 4 parts of silicon dioxide nanoparticles; 0.8 parts of calcium carbonate nanoparticles; 1.8 parts of citric acid crosslinking agent; 1.8 parts of graphene oxide; 0.5 parts of ethylenediaminetetraacetic acid (EDTA); 4 parts of glycerol; 0.8 parts of stearyl chloride; 3.5 parts of nanoferric oxide; 0.9 parts of nanometer titanium dioxide;

[0103] Preparation process: Refer to the steps of Example 1 and prepare according to the corresponding raw material ratio and conditions.

[0104] Example 4

[0105] Raw material ratio: 45 parts of nanocellulose (CNF); 11 parts of bagasse cellulose; 15 parts of sodium lignosulfonate; 8 parts of chitosan; 10 parts of oxidized starch; 8 parts of cellulose nanocrystals; 5 parts of silicon dioxide nanoparticles; 1 part of calcium carbonate nanoparticles; 2 parts of citric acid crosslinking agent; 2 parts of graphene oxide; 0.6 parts of ethylenediaminetetraacetic acid (EDTA); 5 parts of glycerol; 1 part of stearyl chloride; 4 parts of nanoferric oxide; 1.1 parts of nanometer titanium dioxide;

[0106] Preparation process: Refer to the steps of Example 1 and prepare according to the corresponding raw material ratio and conditions.

[0107] Comparative Example 1

[0108] Raw materials and preparation: Use traditional activated carbon as the adsorption material, without using the raw materials and preparation process of the above-mentioned nanocellulose-based composite material; the activated carbon is prepared by traditional carbonization and activation processes, and does not have the processes of multi-scale structure construction, cross-linking strengthening and antibacterial modification in the present invention.

[0109] Comparative Example 2

[0110] Raw materials and preparation: Only use nanocellulose, bagasse cellulose and chitosan, without adding reinforcing and functional materials such as sodium lignosulfonate, oxidized starch, cellulose nanocrystals, silicon dioxide nanoparticles, calcium carbonate nanoparticles, etc., and without performing steps such as multi-scale structure construction, ethylenediaminetetraacetic acid chelation and antibacterial modification, and only simply mix and cross-link and form.

[0111] Comparative Example 3

[0112] Raw materials and preparation: Use non-degradable synthetic polymer materials (such as polypropylene) as the main raw materials, add conventional adsorption aids, and prepare the adsorption material according to the traditional melt extrusion molding process, without biodegradability and environmental friendliness, and without performing the special modification treatment of the present invention.

[0113] Comparative Example 4

[0114] Raw materials and preparation: The same raw materials as in the examples were used, but the process of strengthening with sodium lignosulfonate and the chelation and antibacterial modification process with ethylenediaminetetraacetic acid were omitted, and only basic mixing, crosslinking, and multi-scale structure construction were carried out.

[0115] The composite products of Examples 1-4 and Comparative Examples 1-4 were made, and performance tests were carried out. The test data are shown in Table 1 below:

[0116] Table 1

[0117]

[0118] The following information was obtained from Table 1:

[0119] 1. Performance of the examples: The adsorption capacity reached 125-152 g / g, which was higher than that of the comparative examples (the activated carbon in Comparative Example 1 was only 80 g / g, and Comparative Example 2 was only 65 g / g). Since Example 1 had a multi-scale pore structure: through-pores were formed by liquid nitrogen freeze-drying (-196 °C), increasing the specific surface area, and nanocellulose (CNF) and bagasse cellulose provided high porosity, and graphene oxide enhanced conductivity, promoting the oil-water separation efficiency; it also had an anti-blocking design, and ethylenediaminetetraacetic acid (EDTA) chelated metal ions (such as Fe 3+ , Ca 2+ ), reducing the blockage of impurities in the oil stain (while Comparative Example 3 was not chelated and had poor cycle stability);

[0120] 2. The compressive strength of Examples 1-4 all reached 8.2-11.0 MPa, far exceeding that of the comparative examples (Comparative Example 1 was only 1.2 MPa, and Comparative Example 2 was only 3.5 MPa). The examples had a nano-enhanced phase. Among them, cellulose nanocrystals (CNC), silica, and calcium carbonate nanoparticles improved the compressive strength. At the same time, the citric acid crosslinking agent solidified the interface between nanocellulose and chitosan to form a stable three-dimensional network, and the hydrogen bond action of sodium lignosulfonate: combined with amino / carboxyl groups through phenolic hydroxyl groups (since this step was omitted in Comparative Example 4, the strength dropped to 7.0 MPa).

[0121] 3. The 60-day degradability of Examples 1-4 all reached 65%-85%, which was better than that of non-degradable Comparative Example 3 (0%) and Comparative Example 1 (5%). And the examples used natural biomass substrates. Among them, nanocellulose, bagasse cellulose, and chitosan were all renewable resources. At the same time, sodium lignosulfonate (a component of papermaking waste liquid) was used to reduce the environmental burden, and hydrophobic modification with stearoyl chloride and chelation with EDTA were introduced to reduce chemical residues (while Comparative Example 2 was not modified and the degradability was only 40%).

[0122] 4. The antibacterial rates of the examples all reach 92%-98%, and the water resistance is 12-20 hours, far exceeding those of the comparative examples (the antibacterial rate of Comparative Example 1 is 10%, and the water resistance of Comparative Example 4 is only 10 hours). Among them, the nano-iron oxide (Fe2O3) in the examples releases Fe 3+ to inhibit the growth of microorganisms. A photocatalytic layer (TiO2) is used to form a surface catalytic layer under ultraviolet curing, decompose pollutants and assist in regeneration. At the same time, stearyl chloride spraying improves the contact angle (while Comparative Example 4 is not sprayed and has poor water resistance).

[0123] Summary: Through the steps of multi-scale freeze pore-forming and one-step cross-linking-ultrasonic dispersion, the present invention avoids the complex post-treatment of traditional adsorption materials, and the composite materials prepared by it show excellent performance in terms of adsorption capacity, mechanical properties, degradability, antibacterial properties and water resistance. By optimizing the raw material ratio and preparation process, the present invention solves the problems of limited adsorption capacity, easy blockage, non-degradability, poor mechanical properties, high preparation cost and complex process of existing adsorption materials.

[0124] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A nano-cellulose-based oil-water separation adsorption composite material, characterized in that It includes the following steps: Step 1, Prepare raw materials: nanocellulose, bagasse cellulose, sodium lignosulfonate, chitosan, oxidized starch, cellulose nanowhiskers, silicon dioxide nanoparticles, calcium carbonate nanoparticles, citric acid crosslinking agent, graphene oxide, ethylenediaminetetraacetic acid, glycerol, stearoyl chloride, nanoiron oxide and nanotitanium dioxide; Step 2, Pretreatment of raw materials: Pretreat nanocellulose, bagasse cellulose, chitosan and oxidized starch with glycerol and stearoyl chloride; Step 3, Preparation of the base mixture: Mix the pretreated nanocellulose, bagasse cellulose, chitosan and oxidized starch into a homogeneous slurry, add cellulose nanowhiskers, silicon dioxide nanoparticles and calcium carbonate nanoparticles, stir and then stand for defoaming, then add the citric acid crosslinking agent for crosslinking reaction, and finally add graphene oxide and nanoiron oxide for ultrasonic dispersion, spray the remaining stearoyl chloride, and stand at room temperature to obtain the base mixture; Step 4, Multi-scale structure construction process: Inject the base mixture obtained in Step 3 into a mold, quickly freeze and dry in liquid nitrogen, then disperse nanotitanium dioxide in ethanol, spray it on the material surface, and cure it under ultraviolet light to form a photocatalytic layer; Step 5, Sodium lignosulfonate strengthening process: Immerse the material obtained in Step 4 in a sodium lignosulfonate solution for water bath stirring, then centrifuge to dehydrate and pre-dry to initially cure the structure; Step 6, Ethylenediaminetetraacetic acid chelation and antibacterial modification: Immerse the material obtained in Step 5 in an ethylenediaminetetraacetic acid solution for ethylenediaminetetraacetic acid chelation, then spray a composite solution formed by nanoiron oxide and ethylenediaminetetraacetic acid, wash and then perform vacuum drying to obtain the composite material.

2. The nano-cellulose-based oil-water separation adsorption composite material according to claim 1, wherein The raw materials and their parts by mass in Step 1 are as follows: 35-45 parts of nanocellulose; 8-11 parts of bagasse cellulose; 10-15 parts of sodium lignosulfonate; 4-8 parts of chitosan; 5-10 parts of oxidized starch; 5-8 parts of cellulose nanowhiskers; 2-5 parts of silicon dioxide nanoparticles; 0.5-1 part of calcium carbonate nanoparticles; 1-2 parts of citric acid crosslinking agent; 1-2 parts of graphene oxide; 0.3-0.6 part of ethylenediaminetetraacetic acid; 2-5 parts of glycerol; 0.4-1 part of stearoyl chloride; 2-4 parts of nanoiron oxide; 0.6-1.1 parts of nanotitanium dioxide.

3. The nano-cellulose-based oil-water separation adsorption composite material according to claim 1, characterized in that, Demineralization of bagasse cellulose in Step 2: Immerse bagasse cellulose in a 2% - 3% NaOH solution, soak at a temperature of 75 - 80 °C for 1.5 - 2 hours, remove lignin, and wash with water until neutral.

4. A nanocellulose-based oil-water separation adsorption composite material according to claim 1, characterized in that, Activation of nanocellulose in Step 2: Disperse nanocellulose in a citric acid buffer solution with a pH of 5 - 6, and perform ultrasonic treatment for 25 - 30 minutes to expose the hydroxyl active sites.

5. The nano-cellulose-based oil-water separation adsorption composite material according to claim 1, characterized in that, Hydrophobic modification of chitosan in Step 2: Dissolve chitosan in a 0.95% - 1.05% acetic acid solution, dropwise add 20% of the stearoyl chloride in the formula ratio and stir for reaction for 1.5 - 2 hours to form a hydrophobic coating.

6. The nano-cellulose-based oil-water separation adsorption composite material according to claim 1, wherein, Plasticization of oxidized starch in Step 2: Mix and plasticize oxidized starch and glycerol at 60 - 65 °C to form a flexible adhesive.

7. The nano-cellulose-based oil-water separation adsorption composite material according to claim 1, wherein, Preparation of the base mixture in Step 3: S3.

1. Mix the pretreated nanocellulose, bagasse cellulose, chitosan, and oxidized starch at 45 - 50 °C and 1100 - 1200 rpm under high-speed shearing for 15 - 20 minutes to form a homogeneous slurry; S3.

2. Then, sequentially add cellulose nanocrystals, silica nanoparticles, and calcium carbonate nanoparticles, stir, and let stand for 30 - 40 min for defoaming treatment; S3.

3. Add a citric acid crosslinking agent and carry out a crosslinking reaction at a temperature of 55 - 60 °C for 1 - 1.2 hours; S3.

4. Add graphene oxide and one-third of the nano-iron oxide in the formulation ratio, and ultrasonically disperse for 10 - 15 minutes; S3.

5. Spray the remaining stearyl chloride and let stand at room temperature for 1 - 2 hours.

8. The nano-cellulose-based oil-water separation adsorption composite material according to claim 1, characterized in that: The multi-scale structure construction process in Step 4: S4.

1. Inject the mixture obtained in Step 3 into a mold, dry and freeze it in liquid nitrogen below -196 °C for 20 - 24 hours to form through holes; S4.

2. Disperse nano-titanium dioxide in ethanol, spray it on the material surface, and cure it under ultraviolet light at 365 nm for 8 - 10 minutes to form a photocatalytic layer.

9. The nano-cellulose-based oil-water separation adsorption composite material according to claim 1, wherein, The lignosulfonate deterioration process in Step 5: S5.1 Lignosulfonate crosslinking enhancement: Immerse the material obtained in Step 4 in a 0.5 - 1 wt% lignosulfonate solution, and stir in a water bath environment at 55 - 60 °C for 0.5 - 1 h; S5.

2. Centrifugal dehydration: Centrifuge at a speed of 3500 - 4000 rpm for 10 - 12 min; S5.

3. Pre-drying: Dry under vacuum conditions at 45 - 50 °C for 3.5 - 4 h to preliminarily cure the structure.

10. A nanocellulose-based oil-water separation adsorption composite material according to claim 1, characterized in that, The ethylenediaminetetraacetic acid chelation and antibacterial modification process in Step 6: S6.1 Ethylenediaminetetraacetic acid chelation treatment: Immerse the material in a 0.1 - 0.3 wt% ethylenediaminetetraacetic acid solution with a formulation ratio of 50%, stir at 50 - 55 °C for 30 min to chelate residual metal ions; S6.2, antibacterial modification: spraying a composite solution formed by the remaining nano-iron oxide and ethylenediaminetetraacetic acid with a spraying mass ratio of 1:0.1, using Fe 3+ to inhibit the growth of microorganisms, and then ultrasonically cleaning with deionized water 3-5 times; S6.

3. Drying: Finally, carry out vacuum drying at 70 - 75 °C under a pressure of -0.5 to -0.1 MPa for 11 - 12 hours to obtain the composite material.

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