Lignin intercalation two-dimensional nano material as well as preparation method and application thereof

Abstract

The invention discloses a lignin intercalation two-dimensional nano material as well as a preparation method and application thereof, and relates to the technical field of macromolecules. The preparation method of the lignin intercalation two-dimensional nano material comprises the following steps: adding biomass powder into a deep eutectic solvent for reaction, and centrifuging after the reaction is completed to obtain an upper lignin extracting solution; adding the upper-layer lignin extracting solution into the two-dimensional nanosheet dispersion liquid, stirring, and centrifugally washing after the stirring reaction is completed to obtain a precipitate; and freeze-drying the precipitate to obtain the lignin intercalation two-dimensional nano material. According to the method, the lignin and the two-dimensional nano-material are compounded through static electricity, hydrogen bonds and pi-pi interaction by utilizing the hydroxyl and aromatic structure of the lignin, and in addition, the hydroxyl functional group of the lignin and the active group on the surface of the two-dimensional nano-sheet can jointly adsorb lead ions.

Description

Technical Field

[0001] The present invention relates to the field of polymer technology, and in particular to a lignin intercalated two-dimensional nanomaterial, a preparation method thereof, and an application thereof. Background Art

[0002] Heavy metal ions present in water are highly toxic, highly mobile, and non-biodegradable. Water contamination caused by lead ions can lead to a variety of diseases, including diarrhea and cancer, posing a serious threat to human health. Two-dimensional (2D) nanosheets have attracted considerable attention due to their favorable layered structure and have been developed for lead ion removal. However, due to the high surface energy of 2D nanosheets, aggregation and stacking inevitably occur during the preparation and adsorption processes. This results in a small interlayer spacing and specific surface area of ​​the 2D nanosheets, poor dispersion, and a reduction in adsorption sites and a weakened adsorption effect.

[0003] Lignin, the second largest biomass resource in nature, is a natural aromatic polymer derived from plants. Often considered a waste product in the papermaking industry, it offers the advantages of low cost and biodegradability. Lignin's hydroxyl and aromatic structures make it suitable for complexing with two-dimensional nanosheets. Furthermore, lignin itself is a three-dimensional, cross-linked, rigid macromolecule containing benzene rings, offering strong deformation resistance and the ability to absorb and disperse external forces. Lignin can stabilize the two-dimensional nanosheets through intercalation, maintaining a well-dispersed state and enhancing their mechanical strength. Furthermore, lignin is rich in oxygen-containing functional groups (-OH, -COOH, and -OCH3), enabling it to adsorb lead ions through electrostatic attraction, ion exchange, or complexation. However, its inherent structure and properties limit its adsorption capacity and efficiency. Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, embodiments of the present invention provide a lignin-intercalated two-dimensional nanomaterial, a preparation method thereof, and an application thereof.

[0006] In a first aspect, the present invention provides a method for preparing a lignin-intercalated two-dimensional nanomaterial, comprising the following steps: (1) Adding biomass powder to a low eutectic solvent for reaction, and centrifuging after the reaction to obtain the upper lignin extract; (2) adding the upper lignin extract to the two-dimensional nanosheet dispersion and stirring, and after the stirring reaction is completed, centrifuging and washing to obtain a precipitate; (3) Freeze-drying the precipitate to obtain lignin-intercalated two-dimensional nanomaterials.

[0007] Further, the two-dimensional nanosheet dispersion liquid is obtained by dispersing the tungsten disulfide nanosheet into deionized water, and the lignin intercalated two-dimensional nanomaterial is a lignin intercalated tungsten disulfide nanomaterial.

[0008] Further, the mass ratio of lignin to tungsten disulfide in the lignin intercalated tungsten disulfide nanomaterial is 1.5:1-1:1.5.

[0009] Further, the two-dimensional nanosheet dispersion liquid is obtained by dispersing the graphene oxide nanosheet into deionized water, and the lignin intercalated two-dimensional nanomaterial is a lignin intercalated graphene oxide nanomaterial.

[0010] Further, the mass ratio of lignin to graphene oxide in the lignin intercalated graphene oxide nanomaterial is 1:1.5-1:3.

[0011] Further, the preparation method of the graphene oxide nanosheet comprises: (a) reacting graphite powder, phosphorus pentoxide, potassium persulfate and sulfuric acid, and then adding ultrapure water after cooling to room temperature to obtain a mixture; (b) adding sulfuric acid to the mixture of step (a) after washing and drying, and then adding potassium permanganate while stirring to react; (c) adding ultrapure water and hydrogen peroxide while stirring in step (b), and then centrifuging and washing to obtain a precipitate; (d) ultrasonic treatment and centrifugation of the precipitate to obtain a graphene oxide dispersion liquid; (e) filtering the graphene oxide dispersion liquid and drying to obtain graphene oxide nanosheet.

[0012] Further, the biomass powder comprises one or more of walnut shell powder, wheat straw powder, corn straw powder and sorghum straw powder.

[0013] Further, the deep eutectic solvent comprises one of a mixture of choline chloride and oxalic acid dihydrate, a mixture of choline chloride and lactic acid, and a mixture of choline chloride and formic acid.

[0014] Further, the reaction temperature in step (1) is 110-130°C, and the reaction time is 1-2h.

[0015] Further, the stirring speed in step (2) is 800-1100rpm, and the reaction time is 3-5h.

[0016] In a second aspect, the present application provides a lignin intercalated two-dimensional nanomaterial prepared by the method of the first aspect.

[0017] In a third aspect, the application provides an application of the lignin intercalated two-dimensional nanomaterial prepared by the method of the first aspect or the lignin intercalated two-dimensional nanomaterial of the second aspect in treatment of lead contaminated water, which is used for adsorbing lead ions in the lead contaminated water.

[0018] Compared with the prior art, the application has the following beneficial effects: The lignin intercalated two-dimensional nanosheet of the application greatly reduces the stacking and agglomeration of the two-dimensional nanosheet, avoids the adverse effects of the stacking and agglomeration of the two-dimensional nanosheet on the performance development of the two-dimensional nanosheet, enhances the stability and dispersion of the nanosheet, and improves the interlayer spacing and specific surface area of the nanosheet.

[0019] The application utilizes the hydroxyl and aromatic structure of lignin to realize the compounding of lignin and two-dimensional nanomaterial through electrostatic, hydrogen bonding and pi-pi interaction, and in addition, the hydroxyl functional group of lignin and the active group on the surface of the two-dimensional nanosheet can jointly realize the adsorption of lead ions.

[0020] Lignin itself is a three-dimensional cross-linked rigid macromolecule containing benzene rings, has strong anti-deformation ability, and can directly bear and disperse external force, so the lignin intercalated two-dimensional nanomaterial obtained by the application can not only improve the mechanical strength of the nanosheet, but also enhance the adsorption of lead ions, and has excellent lead ion wastewater treatment capacity. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and / or additional aspects and advantages of the application will become apparent and be readily understood from the following description, taken in conjunction with the drawings, in which: Figure 1 A flow chart of the preparation method of the lignin intercalated two-dimensional nanomaterial of the application; Figure 2 A schematic diagram of the mixture of choline chloride and oxalic acid dihydrate as a eutectic solvent of the application; Figure 3 A schematic diagram of the lignin extraction solution of Example 1 of the application; Figure 4 A schematic diagram of the tungsten disulfide dispersion solution of Example 1 of the application; Figure 5 A schematic diagram of the graphene oxide dispersion solution of Example 4 of the application; Figure 6 A schematic diagram of the unit lead ion adsorption amount of the materials of Examples 1-3 and Comparative Examples 1, 2, 4, 5; Figure 7 A schematic diagram of the unit lead ion adsorption amount of the materials of Examples 4-6 and Comparative Examples 1, 3, 6, 7; Figure 8 A SEM image of tungsten disulfide as received; Figure 9 This is the SEM image of tungsten disulfide nanosheets obtained by ball milling, where: Figure 9 (b) in the Figure 9 (a) Enlarged view of the boxed portion; Figure 10 This is the SEM image of the lignin / tungsten disulfide material prepared in Example 1, wherein: Figure 10 (b) in the Figure 10 (a) Enlarged view of the boxed portion; Figure 11 This is the SEM image of the graphene oxide prepared in Example 4; Figure 12 This is the SEM image of the lignin / graphene oxide material prepared in Example 4, wherein: Figure 12 (b) in the Figure 12 Enlarged view of the boxed portion in (a). DETAILED DESCRIPTION

[0022] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0023] The following describes the lignin intercalated two-dimensional nanomaterial proposed by the present invention, its preparation method and application with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the preparation method of the lignin intercalated two-dimensional nanomaterial of the present invention comprises the following steps: (1) Adding biomass powder to a low eutectic solvent for reaction, and centrifuging after the reaction to obtain the upper lignin extract; (2) adding the upper lignin extract to the two-dimensional nanosheet dispersion and stirring, and after the stirring reaction is completed, centrifuging and washing to obtain a precipitate; (3) The precipitate is freeze-dried to obtain lignin-intercalated two-dimensional nanomaterials.

[0025] Among them, step (1) is the extraction process of lignin, wherein biomass powder is added to a low eutectic solvent for reaction, and after the reaction is completed, the upper liquid is obtained by centrifugation to obtain a lignin extract.

[0026] The present invention utilizes the hydroxyl and aromatic structures of lignin to achieve the composite of lignin and two-dimensional nanomaterials through electrostatics, hydrogen bonds and π-π interactions. In addition, the hydroxyl functional groups of lignin and the active groups on the surface of the two-dimensional nanosheets can jointly achieve the adsorption of lead ions.

[0027] In some embodiments, the biomass powder is obtained by crushing the biomass and passing the biomass through an 80-mesh sieve, wherein the biomass powder comprises one of walnut shell powder, wheat straw powder, corn straw powder, and sorghum straw powder.

[0028] In some embodiments, the deep eutectic solvent comprises one of a mixture of choline chloride and oxalic acid dihydrate, a mixture of choline chloride and lactic acid, and a mixture of choline chloride and formic acid. The present application can achieve the pretreatment of biomass powder and the green and environmentally friendly extraction of lignin by using the deep eutectic solvent to extract lignin.

[0029] When the mixture of choline chloride and oxalic acid dihydrate is used as the deep eutectic solvent, the choline chloride and the oxalic acid dihydrate are mixed in a molar ratio of 1:1, and are placed in a water bath at 80°C for heating and stirring until clear and transparent, to obtain a deep eutectic solvent solution, as shown in FIG. 1. Figure 2 As shown in FIG. 1, the obtained deep eutectic solvent remains uniform and transparent after standing at room temperature for 24 hours, without obvious precipitation, indicating that the deep eutectic solvent is successfully prepared.

[0030] In some embodiments, the reaction temperature of the biomass powder and the deep eutectic solvent is 110-130°C, and the reaction time is 1-2h. It can be understood that the reaction temperature of the biomass powder and the deep eutectic solvent can be 110°C, 120°C, 130°C, or a value within a range formed by any two of the values, and the reaction time can be 1h, 1.5h, 2h, or a value within a range formed by any two of the values.

[0031] The reaction temperature of the biomass powder and the deep eutectic solvent within a suitable range not only allows the deep eutectic solvent to maintain a stable structure and good penetration and dissolution capacity, effectively destroys the internal binding force of the biomass, and promotes the efficient reaction, but also avoids the side reactions such as pyrolysis of components, and ensures the product quality and reaction economy. When the reaction temperature is too high, on the one hand, the hydrogen bond network of the deep eutectic solvent is destroyed, which loses the stable eutectic structure and the original dissolution performance; on the other hand, the cellulose and hemicellulose in the biomass may be pyrolyzed and carbonized, which not only reduces the quality and yield of the target product (lignin), but also may produce by-products to pollute the system. When the reaction temperature is too low, the kinetic energy of the deep eutectic solvent molecules is insufficient, which is difficult to break through the hydrogen bond, van der Waals force, and other interactions between the cellulose, hemicellulose, and lignin in the biomass, and cannot effectively penetrate the inside of the biomass powder, resulting in that the target reactions such as lignin dissolution and component separation are difficult to occur, and the efficiency is extremely low.

[0032] In some embodiments, after the lignin extraction solution is obtained, the precipitate is obtained by vacuum filtration, and the concentration of lignin in the lignin extraction solution is tested according to the amount of the precipitate.

[0033] Step (2) is a reaction process of lignin and two-dimensional nanosheets, that is, the lignin extraction solution obtained in step (1) is added to the prepared two-dimensional nanosheet dispersion solution, and the mixture is fully reacted under stirring, and then the precipitate is obtained by centrifugal washing.

[0034] In step (2), the stirring speed of the stirring reaction is 800-1100 rpm, and the reaction time is 3-5 h. It can be understood that the stirring speed can be 800 rpm, 900 rpm, 1000 rpm, 1100 rpm or any value within the range formed by two arbitrary values. The reaction time can be 3 h, 4 h, 5 h or any value within the range formed by two arbitrary values.

[0035] In some embodiments, the process of obtaining the precipitate by centrifugal washing in step (2) is to centrifuge the solution after the reaction is completed, first wash it to neutral with ultrapure water, then wash it with tert-butyl alcohol, and finally obtain the precipitate.

[0036] In some embodiments, the two-dimensional nanosheet dispersion solution is obtained by dispersing two-dimensional nanosheets in deionized water, wherein the two-dimensional nanosheets include one of tungsten disulfide nanosheets and graphene oxide nanosheets. It can be understood that the two-dimensional nanosheets can also be other suitable materials.

[0037] When the two-dimensional nanosheets are tungsten disulfide nanosheets, the two-dimensional nanosheet dispersion solution is obtained by dispersing the tungsten disulfide nanosheets in deionized water, wherein the tungsten disulfide nanosheets are obtained by ball milling the original tungsten disulfide. The original tungsten disulfide is in a bulk structure, and the tungsten disulfide nanosheets are obtained by ball milling. The purpose of ball milling is to mechanically exfoliate the bulk tungsten disulfide to few-layer or single-layer sheets. The exfoliated sample is easy to disperse in deionized water and react with other substances.

[0038] When the two-dimensional nanosheets are graphene oxide nanosheets, the two-dimensional nanosheet dispersion solution is obtained by dispersing the graphene oxide nanosheets in deionized water.

[0039] In some embodiments, the method for preparing graphene oxide nanosheets includes: (a) reacting graphite powder, phosphorus pentoxide, potassium persulfate and sulfuric acid, and then adding ultrapure water after cooling to room temperature to obtain a mixture; (b) adding sulfuric acid to the mixture of step (a) and adding potassium permanganate while stirring to react; (c) adding ultrapure water and hydrogen peroxide while stirring to step (b), and then centrifuging and washing to obtain a precipitate; (d) ultrasonic treatment and centrifugation of the precipitate to obtain a graphene oxide dispersion solution; (e) filtering the graphene oxide dispersion solution and drying to obtain graphene oxide nanosheets.

[0040] In some embodiments, the sulfuric acid is concentrated sulfuric acid with a mass concentration of 95% to 98%, the reaction temperature in step (a) is 75 to 80°C, and the reaction time is 4 to 5 hours. In step (b), the addition of potassium permanganate is performed in an ice water bath, and then the temperature is raised to a reaction temperature of 30 to 40°C, and the reaction is performed for 2 to 3 hours. In step (c), the ice water bath is used, and the hydrogen peroxide is added to remove the unreacted potassium permanganate oxidant. The centrifugal washing process is first washed with hydrochloric acid with a mass concentration of 10%, and then washed with ultrapure water. In step (d), the ultrasonic treatment is used to make the precipitate fully dispersed, and the centrifugation is used to remove the large particle precipitate that is not uniformly dispersed.

[0041] Step (3) is a process of freeze-drying the precipitate obtained in step (2). The freeze-drying is performed in a low-temperature and low-humidity environment to remove water / solvent, while the original properties of the material are maximally retained, so as to facilitate subsequent processing and application. In some embodiments, the freeze-drying is performed at a temperature of -60 to -65°C for 24 to 48 hours.

[0042] When the two-dimensional nanosheet is a graphene oxide nanosheet, the lignin intercalated two-dimensional nanomaterial prepared is a lignin intercalated graphene oxide nanomaterial.

[0043] In some embodiments, the mass ratio of lignin to graphene oxide in the lignin intercalated graphene oxide nanomaterial is 1.5:1 to 1:1.5. It can be understood that the mass ratio of lignin to graphene oxide in the lignin intercalated graphene oxide nanomaterial can be 1.5:1, 1:1, 1:1.5, or a value within a range formed by any two values.

[0044] When the content of graphene oxide is too high, the graphene oxide is prone to agglomeration, the internal sites of the agglomerates are wrapped, the exposed effective adsorption sites are reduced, the adsorption capacity is not increased but decreased, the dispersion of lignin on graphene oxide is destroyed, the stability of the material in the solution is reduced, and the adsorption of Pb² + is not sufficient, and the adsorption capacity of the composite adsorbent for Pb² + is reduced, and it is difficult to achieve the ideal adsorption effect. +

[0045] When the two-dimensional nanosheet is a graphene oxide nanosheet, the lignin intercalated two-dimensional nanomaterial prepared is a lignin intercalated graphene oxide nanomaterial. In some embodiments, the mass ratio of lignin to graphene oxide in the lignin intercalated graphene oxide nanomaterial is 1:1.5 to 1:3. It can be understood that the mass ratio of lignin to graphene oxide in the lignin intercalated graphene oxide nanomaterial can be 1:1.5, 1:2, 1:3, or a value within a range formed by any two values. ​

[0046] When the content of graphene oxide (GO) is too high, there is a strong van der Waals force between the GO sheets. If the content is too high, lignin will not be able to fully disperse the GO and it will agglomerate, which will reduce the exposed effective adsorption sites and cause the adsorption capacity to decrease instead of increase. In addition, the preparation cost of GO is higher than that of lignin, and excessive use will increase the cost. Moreover, the agglomerated GO may reduce the stability of the composite material in the solution, which is similar to Pb² + Insufficient contact. When the content of graphene oxide is too low, the hydroxyl, carboxyl and other oxygen-containing groups on the GO surface are the adsorbents of Pb² + The key sites of Pb² + The adsorption capacity of GO will decrease significantly, making it difficult to remove lead ions efficiently. The GO layer structure can increase the porosity and specific surface area of ​​the material. When the content is low, it cannot effectively optimize the dense structure of lignin itself, resulting in Pb² + The mass transfer inside the material is slow, and the adsorption rate is slow; GO's specific adsorption capacity for heavy metal ions (such as binding Pb² through coordination and electrostatic effects) + ) is weaker than lignin, and a low proportion will make the composite adsorbent less sensitive to Pb² + The preferential adsorption capacity of ions is reduced and is easily interfered by other ions.

[0047] The lignin-intercalated two-dimensional nanomaterial of the present invention is used to adsorb lead ions from lead-contaminated water. Due to its steric hindrance and electrostatic repulsion, lignin acts as an intercalating agent, addressing the problem of two-dimensional nanosheets easily agglomerating and accumulating in water. Lignin is rich in oxygen-containing functional groups, which can synergistically adsorb with the two-dimensional nanosheets, acting as an adsorbent to improve the adsorption efficiency of lead ions. Therefore, the lignin-intercalated two-dimensional nanomaterial of the present invention can improve the adsorption efficiency of lead ions.

[0048] The present invention is described in detail below with reference to the embodiments.

[0049] Example 1 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the low eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 h. After the reaction was completed, the upper liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract, such as Figure 3 As shown. Studies have shown that most of the DES extract is lignin, and a small part is other substances and impurities. Lignin contains color-developing groups, which will change the color of the original transparent DES solution. Figure 3The lignin extraction was successful. A portion of the lignin-rich DES solution (deep eutectic solvent solution) was taken and vacuum filtered to obtain a precipitate. The lignin concentration was then constant, and the precipitate was measured to be 12.0 mg / mL.

[0050] (3) The original tungsten disulfide was ball-milled to obtain tungsten disulfide nanosheets, and 120 mg of tungsten disulfide nanosheets were dispersed in 100 mL of deionized water to obtain a 1.2 mg / mL tungsten disulfide dispersion, as shown in FIG. Figure 4 As shown. The original tungsten disulfide is black, and after successful exfoliation and dispersion in water, it becomes dark green. Figure 4 It can be seen that tungsten disulfide is successfully dispersed in deionized water. The volume of tungsten disulfide is not considered in the measurement.

[0051] (4) Add 10 mL of lignin extract to the tungsten disulfide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0052] (5) The precipitate was freeze-dried at -60°C for 48 h to obtain lignin-intercalated tungsten disulfide nanomaterials, i.e., lignin / tungsten disulfide materials.

[0053] Example 2 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0054] (3) The original tungsten disulfide was ball-milled to obtain tungsten disulfide nanosheets, and 120 mg of tungsten disulfide was dispersed in 100 mL of deionized water and ball-milled to obtain a 1.2 mg / mL tungsten disulfide dispersion. The volume of tungsten disulfide was not considered during the measurement.

[0055] (4) Add 15 mL of lignin extract to the tungsten disulfide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0056] (5) The precipitate was freeze-dried at -60°C for 48 h to obtain lignin-intercalated tungsten disulfide nanomaterials, i.e., lignin / tungsten disulfide materials.

[0057] Example 3 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0058] (3) The original tungsten disulfide was ball-milled to obtain tungsten disulfide nanosheets, and 180 mg of tungsten disulfide was dispersed in 100 mL of deionized water and ball-milled to obtain a 1.8 mg / mL tungsten disulfide dispersion. The volume of tungsten disulfide was not considered during the measurement.

[0059] (4) Add 10 mL of lignin extract to the tungsten disulfide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0060] (5) The precipitate was freeze-dried at -60°C for 48 h to obtain lignin-intercalated tungsten disulfide nanomaterials, i.e., lignin / tungsten disulfide materials.

[0061] Example 4 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0062] (3) 1 g of graphite powder, 1.5 g of phosphorus pentoxide, 1.5 g of potassium persulfate and 36 mL of sulfuric acid were reacted in an 80 °C water bath for 4.5 h, cooled to room temperature, added with 1 L of ultrapure water, and allowed to stand for 12 h; after standing, the mixture was washed with ultrapure water, dried, added with 120 mL of sulfuric acid, and stirred in an ice-water bath while adding 5 g of potassium permanganate, heated to 35 °C and allowed to react for 2 h; 1 L of ultrapure water and 10 mL of hydrogen peroxide were added in an ice-water bath; the mixture was first washed with 10% hydrochloric acid and then centrifuged with ultrapure water to obtain a precipitate; the precipitate was dispersed in deionized water by ultrasonication for 1 h, and centrifuged at 5000 rpm to obtain a graphene oxide dispersion; the graphene oxide dispersion was filtered and dried to obtain graphene oxide nanosheets.

[0063] (4) 240 mg of the graphene oxide prepared in step (3) was dispersed in 100 mL of deionized water to obtain a 2.4 mg / mL graphene oxide dispersion, as shown in FIG. Figure 5 As shown, from Figure 5 It can be seen that graphene oxide is successfully dispersed in deionized water. The volume of graphene oxide is not considered in the measurement.

[0064] (5) Add 10 mL of lignin extract to the graphene oxide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0065] (6) The precipitate was freeze-dried at -60 °C for 48 h to obtain lignin-intercalated graphene oxide nanomaterials, i.e., lignin / graphene oxide materials.

[0066] Example 5 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0067] (3) 1 g of graphite powder, 1.5 g of phosphorus pentoxide, 1.5 g of potassium persulfate and 36 mL of sulfuric acid were reacted in an 80 °C water bath for 4.5 h, cooled to room temperature, added with 1 L of ultrapure water, and allowed to stand for 12 h; after standing, the mixture was washed with ultrapure water, dried, and added with 120 mL of sulfuric acid. While stirring in an ice-water bath, 5 g of potassium permanganate was added, and the mixture was heated to 35 °C and allowed to react for 2 h; 1 L of ultrapure water and 10 mL of hydrogen peroxide were added in an ice-water bath; the mixture was first washed with 10% hydrochloric acid and then centrifuged with ultrapure water to obtain a precipitate; the precipitate was ultrasonically dispersed in deionized water, and centrifuged to obtain a graphene oxide dispersion; the graphene oxide dispersion was filtered and dried to obtain graphene oxide nanosheets.

[0068] (4) 180 mg of the graphene oxide prepared in step (3) was dispersed in 100 mL of deionized water to obtain a 1.8 mg / mL graphene oxide dispersion, wherein the volume of the graphene oxide was not taken into account during the measurement.

[0069] (5) Add 10 mL of lignin extract to the graphene oxide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0070] (6) The precipitate was freeze-dried at -60 °C for 48 h to obtain lignin-intercalated graphene oxide nanomaterials, i.e., lignin / graphene oxide materials.

[0071] Example 6 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0072] (3) 1 g of graphite powder, 1.5 g of phosphorus pentoxide, 1.5 g of potassium persulfate and 36 mL of sulfuric acid were reacted in an 80 °C water bath for 4.5 h, cooled to room temperature, added with 1 L of ultrapure water, and allowed to stand for 12 h; after standing, the mixture was washed with ultrapure water, dried, and added with 120 mL of sulfuric acid. While stirring in an ice-water bath, 5 g of potassium permanganate was added, and the mixture was heated to 35 °C and allowed to react for 2 h; 1 L of ultrapure water and 10 mL of hydrogen peroxide were added in an ice-water bath; the mixture was first washed with 10% hydrochloric acid and then centrifuged with ultrapure water to obtain a precipitate; the precipitate was ultrasonically dispersed in deionized water, and centrifuged to obtain a graphene oxide dispersion; the graphene oxide dispersion was filtered and dried to obtain graphene oxide nanosheets.

[0073] (4) 360 mg of the graphene oxide prepared in step (3) was dispersed in 100 mL of deionized water to obtain a 3.6 mg / mL graphene oxide dispersion, wherein the volume of the graphene oxide was not taken into account during the measurement.

[0074] (5) Add 10 mL of lignin extract to the graphene oxide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0075] (6) The precipitate was freeze-dried at -60 °C for 48 h to obtain lignin-intercalated graphene oxide nanomaterials, i.e., lignin / graphene oxide materials.

[0076] Comparative Example 1 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0077] (3) Add 10 mL of lignin extract to 100 mL of ultrapure water and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0078] (4) Freeze-dry the precipitate at -60°C for 48 h to obtain lignin.

[0079] Comparative Example 2 The original tungsten disulfide was ball-milled to obtain tungsten disulfide nanosheets, which were then used alone in subsequent experiments.

[0080] Comparative Example 3 The graphene oxide prepared in step (3) of Example 4 was used alone in subsequent experiments.

[0081] Comparative Example 4 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0082] (3) The original tungsten disulfide was ball-milled to obtain tungsten disulfide nanosheets, and 60 mg of tungsten disulfide was dispersed in 100 mL of deionized water and ball-milled to obtain a 0.6 mg / mL tungsten disulfide dispersion. The volume of tungsten disulfide was not considered during the measurement.

[0083] (4) Add 10 mL of lignin extract to the tungsten disulfide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0084] (5) The precipitate was freeze-dried at -60°C for 48 h to obtain lignin-intercalated tungsten disulfide nanomaterials, i.e., lignin / tungsten disulfide materials.

[0085] Comparative Example 5 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0086] (3) The original tungsten disulfide was ball-milled to obtain tungsten disulfide nanosheets, and 240 mg of tungsten disulfide was dispersed in 100 mL of deionized water and ball-milled to obtain a 2.4 mg / mL tungsten disulfide dispersion. The volume of tungsten disulfide was not considered during the measurement.

[0087] (4) Add 10 mL of lignin extract to the tungsten disulfide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0088] (5) The precipitate was freeze-dried at -60°C for 48 h to obtain lignin-intercalated tungsten disulfide nanomaterials, i.e., lignin / tungsten disulfide materials.

[0089] Comparative Example 6 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0090] (3) 1 g of graphite powder, 1.5 g of phosphorus pentoxide, 1.5 g of potassium persulfate and 36 mL of sulfuric acid were reacted in an 80 °C water bath for 4.5 h, cooled to room temperature, added with 1 L of ultrapure water, and allowed to stand for 12 h; after standing, the mixture was washed with ultrapure water, dried, and added with 120 mL of sulfuric acid. While stirring in an ice-water bath, 5 g of potassium permanganate was added, and the mixture was heated to 35 °C and allowed to react for 2 h; 1 L of ultrapure water and 10 mL of hydrogen peroxide were added in an ice-water bath; the mixture was first washed with 10% hydrochloric acid and then centrifuged with ultrapure water to obtain a precipitate; the precipitate was ultrasonically dispersed in deionized water, and centrifuged to obtain a graphene oxide dispersion; the graphene oxide dispersion was filtered and dried to obtain graphene oxide nanosheets.

[0091] (4) Disperse 120 mg of the graphene oxide prepared in step (3) in 100 mL of deionized water to obtain a 1.2 mg / mL graphene oxide dispersion, wherein the volume of the graphene oxide is not taken into account during measurement.

[0092] (5) Add 10 mL of lignin extract to the graphene oxide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0093] (6) The precipitate was freeze-dried at -60 °C for 48 h to obtain lignin-intercalated graphene oxide nanomaterials, i.e., lignin / graphene oxide materials.

[0094] Comparative Example 7 (1) Choline chloride and oxalic acid dihydrate were mixed in a molar ratio of 1:1, and heated and stirred in a water bath at 80°C until the mixture became clear and transparent to obtain a deep eutectic solvent solution; (2) The walnut shells were crushed and passed through an 80-mesh molecular sieve to obtain walnut shell powder. 10 g of the walnut shell powder was added to 100 mL of the deep eutectic solvent solution obtained in step (1). The reaction was carried out at a reaction temperature of 120°C for 1 hour. After the reaction was completed, the supernatant liquid was centrifuged to obtain a lignin-rich DES solution, i.e., a lignin extract. A portion of the lignin-rich DES solution was taken and vacuum filtered to obtain a precipitate. The lignin concentration was constant to a constant volume. Based on the amount of the precipitate, the lignin concentration was measured to be 12.0 mg / mL.

[0095] (3) 1 g of graphite powder, 1.5 g of phosphorus pentoxide, 1.5 g of potassium persulfate and 36 mL of sulfuric acid were reacted in an 80 °C water bath for 4.5 h, cooled to room temperature, added with 1 L of ultrapure water, and allowed to stand for 12 h; after standing, the mixture was washed with ultrapure water, dried, and added with 120 mL of sulfuric acid. While stirring in an ice-water bath, 5 g of potassium permanganate was added, and the mixture was heated to 35 °C and allowed to react for 2 h; 1 L of ultrapure water and 10 mL of hydrogen peroxide were added in an ice-water bath; the mixture was first washed with 10% hydrochloric acid and then centrifuged with ultrapure water to obtain a precipitate; the precipitate was ultrasonically dispersed in deionized water, and centrifuged to obtain a graphene oxide dispersion; the graphene oxide dispersion was filtered and dried to obtain graphene oxide nanosheets.

[0096] (4) 480 mg of the graphene oxide prepared in step (3) was dispersed in 100 mL of deionized water to obtain a 4.8 mg / mL graphene oxide dispersion, wherein the volume of the graphene oxide was not taken into account during the measurement.

[0097] (5) Add 10 mL of lignin extract to the graphene oxide dispersion and stir at a stirring speed of 1000 rpm for 4 h. After the reaction is completed, centrifuge and wash. First wash with ultrapure water until neutral, and then wash with tert-butanol to obtain a precipitate.

[0098] (6) The precipitate was freeze-dried at -60 °C for 48 h to obtain lignin-intercalated graphene oxide nanomaterials, i.e., lignin / graphene oxide materials.

[0099] Test Example 1 A 100 mg / L lead nitrate solution was prepared, and 1 mg of each of the materials from Examples 1 to 6 and Comparative Examples 1 to 7 was added to 10 mL of the lead nitrate solution. The mixture was placed on a shaker at 120 rpm and 25°C for 24 hours. The mixture was then filtered and separated using a nylon syringe filter (pore size 0.22 μm). The residual lead ion concentration was quantitatively determined by flame atomic absorption spectrometry, and the unit lead ion adsorption capacity of each material was calculated. The test results are shown in Figure 2. Figure 6 and Figure 7 shown.

[0100] Among them, the lead ion adsorption capacity is the difference between the initial lead ion amount and the residual lead ion amount. The lead ion adsorption capacity per unit material refers to the adsorption capacity of 1 mg of adsorbent. Calculated, where q e is the unit lead ion adsorption capacity, unit is mg / g; C0 is the Pb 2+ The initial concentration of Pb in the solution is in mg / L; Ce is the initial concentration of Pb in the solution, ... 2+ The equilibrium concentration of , in mg / L; V is the volume of the solution, in L; m is the mass of the adsorbent used, in g.

[0101] according to Figure 6 It can be seen that in the range of 1.5:1~1:1.5, the adsorption capacity of lignin / tungsten disulfide is better than that of lignin and tungsten disulfide alone. When the ratio of lignin to tungsten disulfide is 2:1 and 1:2, the adsorption capacity of lignin / tungsten disulfide is weak. This is because when the content of tungsten disulfide is too high, tungsten disulfide is prone to agglomeration, and the internal sites of the agglomerates are wrapped, which reduces the exposed effective adsorption sites, resulting in a decrease in adsorption capacity instead of an increase, destroying the dispersing effect of lignin on tungsten disulfide and reducing the stability of the material in the solution. + Insufficient contact. When the content of tungsten disulfide is too low, the specific adsorption sites provided by tungsten disulfide (such as S atoms and Pb² + The coordination effect of the composite adsorbent is insufficient for Pb² + The adsorption capacity will decrease and it will be difficult to achieve the ideal adsorption effect.

[0102] according to Figure 7It can be seen that in the range of 1:1.5~1:3, the adsorption capacity of lignin / graphene oxide is better than that of lignin and graphene oxide alone. When the ratio of lignin to graphene oxide is 1:1 and 1:4, the adsorption capacity of lignin / graphene oxide is weak. This is because when the content of graphene oxide is too high, there is a strong van der Waals force between the graphene oxide sheets. If the content is too high, the lignin cannot fully disperse the graphene oxide and it will agglomerate, which will reduce the exposed effective adsorption sites and cause the adsorption capacity to decrease instead of increase. In addition, excessive graphene oxide will increase the cost, and the agglomerated graphene oxide may reduce the stability of the composite material in the solution, which is similar to Pb² + Insufficient contact. When the content of graphene oxide is too low, the hydroxyl, carboxyl and other oxygen-containing groups on the surface of graphene oxide are the adsorbents of Pb² + The key sites of Pb² + The adsorption capacity of lignin will decrease significantly, making it difficult to remove lead ions efficiently. The sheet structure of graphene oxide can increase the porosity and specific surface area of ​​the material. When the content is low, it cannot effectively optimize the dense structure of lignin itself, resulting in Pb² + The mass transfer inside the material is slow, and the adsorption rate is slow; the specific adsorption capacity of graphene oxide for heavy metal ions (such as binding Pb² through coordination and electrostatic interaction) + ) is weaker than lignin, and a low proportion will make the composite adsorbent less sensitive to Pb² + The preferential adsorption capacity of ions is reduced and is easily interfered by other ions.

[0103] Test Example 2 SEM tests were performed on the original tungsten disulfide sample and the tungsten disulfide nanosheets obtained after ball milling. The test results are as follows: Figure 8 and Figure 9 As shown, Figure 9 (b) in the Figure 9 The enlarged view of the box part (a) in the figure. Figure 8 and Figure 9 It can be seen that the original bulk tungsten disulfide exhibits a typical accordion-like layered stacking structure. Mechanical exfoliation successfully reduces the bulk size, which can be evidenced by the increase in the number of edge flakes and the thinning of interlayer cracks observed in the exfoliated samples. However, the obtained tungsten disulfide nanosheets still retain obvious lateral stacking, forming interconnected layered aggregates.

[0104] The lignin / tungsten disulfide material prepared in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 10 As shown, Figure 10 (b) in the Figure 10 The enlarged view of the box part (a) in the figure. Figure 10It can be seen that lignin and WS2 (tungsten disulfide) nanosheets form a uniform structure. The SEM image of the composite material clearly shows that lignin is uniformly distributed on the surface of WS2 nanosheets. The intercalation of lignin significantly enhances the dispersion and stabilization of the detached WS2 nanosheets.

[0105] Test Example 3 The graphene oxide prepared in Example 4 was subjected to SEM testing, and the test results are as follows: Figure 11 As shown. Figure 11 It can be seen that due to the interaction of oxygen-containing groups, the obtained graphene oxide nanosheets have a smooth surface and wrinkled edges, but are accompanied by varying degrees of stacking.

[0106] The lignin / graphene oxide material prepared in Example 4 was subjected to SEM testing, and the test results are as follows: Figure 12 As shown, Figure 12 (b) in the Figure 12 The enlarged view of the box part (a) in the figure. Figure 12 It can be seen that after lignin is intercalated into GO nanosheets, lignin is evenly aggregated on the surface of the nanosheets, effectively promoting the dispersion of GO nanosheets.

[0107] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms may be directed to different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are mutually inconsistent.

[0108] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0109] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a lignin intercalated two-dimensional nanomaterial, characterized in that: The following steps are involved: (1) Adding biomass powder to a low eutectic solvent for reaction, and centrifuging after the reaction to obtain the upper lignin extract; (2) adding the upper lignin extract to the two-dimensional nanosheet dispersion and stirring, and after the stirring reaction is completed, centrifuging and washing to obtain a precipitate; (3) Freeze-drying the precipitate to obtain lignin-intercalated two-dimensional nanomaterials.

2. The method for preparing the lignin intercalated two-dimensional nanomaterial according to claim 1, wherein: The two-dimensional nanosheet dispersion is obtained by dispersing tungsten disulfide nanosheets in deionized water, and the lignin-intercalated two-dimensional nanomaterial is a lignin-intercalated tungsten disulfide nanomaterial.

3. The method for preparing the lignin intercalated two-dimensional nanomaterial according to claim 2, wherein: The mass ratio of lignin to tungsten disulfide in the lignin intercalated tungsten disulfide nanomaterial is 1.5:1 to 1:1.

5.

4. The method for preparing the lignin intercalated two-dimensional nanomaterial according to claim 1, wherein: The two-dimensional nanosheet dispersion is obtained by dispersing graphene oxide nanosheets in deionized water, and the lignin intercalated two-dimensional nanomaterial is a lignin intercalated graphene oxide nanomaterial.

5. The method for preparing the lignin intercalated two-dimensional nanomaterial according to claim 4, characterized in that: The mass ratio of lignin to graphene oxide in the lignin-intercalated graphene oxide nanomaterial is 1:1.5-1:

3.

6. The method for preparing the lignin intercalated two-dimensional nanomaterial according to claim 4, wherein: The preparation method of the graphene oxide nanosheets comprises: (a) reacting graphite powder, phosphorus pentoxide, potassium persulfate, and sulfuric acid, cooling to room temperature, adding ultrapure water, and allowing to stand to obtain a mixture; (b) washing and drying the mixture of step (a), adding sulfuric acid, and adding potassium permanganate while stirring to react; (c) adding ultrapure water and hydrogen peroxide to the product in step (b) while stirring, and centrifuging and washing to obtain a precipitate; (d) ultrasonically treating the precipitate and centrifuging it to obtain a graphene oxide dispersion; (e) The graphene oxide dispersion is filtered and dried to obtain graphene oxide nanosheets.

7. The method for preparing the lignin intercalated two-dimensional nanomaterial according to claim 1, wherein: The biomass powder includes one or more of walnut shell powder, wheat straw powder, corn straw powder and sorghum straw powder; And / or, the deep eutectic solvent comprises one of a mixture of choline chloride and oxalic acid dihydrate, a mixture of choline chloride and lactic acid, and a mixture of choline chloride and formic acid.

8. The method for preparing the lignin intercalated two-dimensional nanomaterial according to claim 1, wherein: In the step (1), the reaction temperature of adding the biomass powder to the deep eutectic solvent is 110-130° C. and the reaction time is 1-2 h; And / or, the stirring speed of the stirring reaction in step (2) is 800-1100 rpm, and the reaction time is 3-5 h.

9. A lignin intercalated two-dimensional nanomaterial, characterized in that: The lignin-intercalated two-dimensional nanomaterial is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the lignin intercalated two-dimensional nanomaterial prepared by the preparation method of any one of claims 1 to 8 or the lignin intercalated two-dimensional nanomaterial according to claim 9 in the treatment of lead-contaminated water.

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