Preparation method and application of cellulose nanocrystal composite imprinted aerogel
By aminating modification on cellulose nanocrystals, and cross-linking with aldehyde-modified sodium alginate, then introducing citric acid and heat cross-linking, combined with ion blotting technology, a composite blot aerogel material with efficient and selective adsorption of neodymium ions was prepared, solving the problem of insufficient efficiency and selectivity of traditional adsorbents in neodymium recovery.
Patent Information
- Application Number
- CN202510544188.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2025-06-06
AI Technical Summary
Traditional adsorbents have problems with poor adsorption efficiency and poor selective separation ability in rare earth element recovery, especially in the recycling of neodymium elements.
Using sol-gel technology and freeze-drying technology, a composite blot aerogel material with cellulose nanocrystals as the substrate crosslinked sodium alginate and citric acid was prepared, and surface modification was performed through ion blotting technology to form a material with specific adsorption sites for neodymium ions.
It realizes efficient recovery of neodymium ions in water, improves adsorption capacity and selective adsorption performance, and solves the shortcomings of traditional adsorbents in neodymium recovery.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of environmental material preparation and separation, and specifically relates to a method for preparing imprinted aerogel by using a sol-gel method and a freeze-drying method, using cellulose nanocrystals as a substrate to cross-link sodium alginate and citric acid, and coupling ion imprinting technology for selectively separating neodymium ions. Background Art
[0002] As the "strategic fulcrum" of modern industrial technological innovation, rare earth elements (REEs) have become increasingly prominent in the fields of clean energy, electronic information, national defense science and technology, etc. Among them, neodymium (Nd) has become the core material driving the green energy transformation by virtue of its irreplaceable nature in NdFeB permanent magnets. High-performance permanent magnets in global wind turbines, new energy vehicle motors and consumer electronic devices rely on Nd, driving its demand year by year. The problems that follow include the increase in the annual production of discarded magnets and the high loss rate of rare earth elements. However, the geopolitically dominated rare earth supply chain pattern, the environmental cost of primary mineral mining, and the industrialization bottleneck of NdFeB magnet recycling technology are exacerbating the global challenge of sustainable utilization of Nd. Therefore, in order to supplement the high-consumption rare earth elements, efficient recovery of rare earth elements can not only alleviate the shortage of strategic resources and reduce the carbon footprint of the industrial chain, but also promote industrial transformation and improve environmental quality.
[0003] At present, wet recovery is the mainstream recovery method for rare earth elements. Commonly used wet recovery methods include solvent extraction, ion exchange, and chemical precipitation. These methods often show low extraction capacity for rare earths with low concentrations. Adsorption, on the contrary, has the advantages of convenient operation, high recovery efficiency and minimal environmental pollution, and can well enrich rare earths in solution. The separation efficiency and process economy of adsorption are directly determined by the performance of the adsorption material. Although traditional adsorbents (such as activated carbon and resin) have certain adsorption capacity, they generally face bottlenecks such as high cost, poor regeneration and secondary pollution risks. Cellulose, as the most abundant natural polymer in nature, has degradability, high hydroxyl density and cost advantages, providing an ideal substrate for the development of green adsorbents. More importantly, mechanical grinding or chemical acid hydrolysis can obtain cellulose nanocrystals from cellulose, and the construction of three-dimensional porous aerogel-type adsorbents through self-assembly has become a frontier direction to break through the limitations of traditional materials. Its high specific surface area, adjustable hierarchical pore structure and active hydroxyl groups that are easy to modify help to improve the adsorption capacity and mass transfer rate, and can also achieve material regeneration through freeze drying. This strategy provides an innovative path for rare earth recycling that is both efficient and sustainable. However, pure cellulose aerogel has problems with poor adsorption efficiency and poor selective separation ability in the process of rare earth adsorption.
[0004] Therefore, functional modification of the active hydroxyl groups rich in cellulose nanocrystals and grafting of other functional monomers can help solve the above problems. Many studies have shown that sodium alginate and citric acid are reliable rare earth recovery materials with excellent adsorption efficiency. Sodium alginate (SA) is a natural hydrophilic colloidal polysaccharide with a large number of free carboxyl groups and hydroxyl groups distributed on its skeleton. When sodium alginate encounters metal ions, it can form gel particles, which makes it easier for sodium alginate to separate rare earth ions. In addition, sodium alginate has the advantages of good stability, biodegradability and non-toxicity, and also has a certain cross-linking ability. However, some scholars use simple physical mixing methods to construct materials using sodium alginate, which can easily lead to problems such as poor adsorption effect and poor material stability. This stability is limited because the hydrogen bond or ionic bond energy of physical cross-linking is extremely low. Considering the complex reality of the use environment of the adsorbent, designing a method to form covalent cross-links between modified cellulose and sodium alginate can significantly enhance its mechanical properties and structural stability. Summary of the invention
[0005] The present invention aims to provide a preparation method and application of cellulose nanocrystal composite imprinted aerogel. The present invention uses cellulose nanocrystals (CNCs) as a substrate, sodium alginate (SA) and citric acid (CA) as crosslinking agents and as functional monomers to prepare cellulose / sodium alginate / citric acid composite imprinted aerogel materials, and uses ion imprinting technology to modify the surface to prepare adsorption sites with specificity for Nd(III), thereby solving the problem that traditional adsorbents cannot selectively adsorb Nd(III).
[0006] The technical solution adopted by the present invention is: The invention provides a cellulose nanocrystal composite imprinted aerogel. The sol-gel technology is used to make amino-modified cellulose nanocrystals and aldehyde-modified sodium alginate undergo Schiff base cross-linking, which significantly enhances the entanglement and rigidity of the two structures, so that they can maintain their spatial structure after freeze-drying. Then, citric acid is introduced by thermal cross-linking technology, and rare earth element vacancies are introduced by ion imprinting technology to modify the surface, so as to prepare a cellulose / sodium alginate / citric acid composite imprinted aerogel material for adsorbing and separating rare earth elements.
[0007] More specifically, the present invention provides a method for preparing the above-mentioned cellulose nanocrystal composite imprinted aerogel, comprising the following steps: (1) Providing amino-modified cellulose nanocrystal hydrosol and aldehyde-modified sodium alginate; (2) uniformly mixing the amino-modified cellulose nanocrystal hydrosol and the aldehyde-modified sodium alginate to form a hydrogel by cross-linking reaction; (3) Adding citric acid solution to the hydrogel obtained in step (2), and then adding rare earth metal salt, incubating in a water bath at 45°C to form a sol, and freeze-drying to form an aerogel; heating the aerogel at 140°C for 10 minutes to cross-link the citric acid, and then eluting to remove the rare earth metal element, and freeze-drying to obtain cellulose nanocrystal cross-linked sodium alginate and citric acid composite imprinted aerogel (CNC-ISC).
[0008] As one of the preferred solutions of the above technical solution, the preparation method of the amino-modified cellulose nanocrystal hydrosol is as follows: S10. Preparation of cellulose nanocrystals (CNCs): A certain amount of medical cotton wool was dissolved in a mixed solution of sulfuric acid / deionized water with a volume ratio of 1:1. After continuous magnetic stirring in an oil bath at 45 °C for 3 hours, it was poured into a beaker containing ice water and allowed to stand for 12 hours. The upper transparent solution was removed, and the lower suspension was centrifuged at 10,000 rpm for 10 minutes, three times. Finally, it was dialyzed and purified to pH > 2.4 to obtain a white suspension. The concentration of the white suspension was adjusted to 4.0 wt% in a rotary evaporator to obtain CNCs.
[0009] S11. Preparation of amino-modified cellulose nanocrystals: Take a certain mass of lithium chloride and dissolve it in a flask containing CNCs and N,N-dimethylacetamide. Add a certain volume of triethylamine and p-toluenesulfonyl chloride, and carry out p-toluenesulfonyl chlorination reaction at 8 °C for 24 hours. After the reaction is completed, heat it to 100 °C, and add ethylenediamine dropwise for 3 hours of nucleophilic substitution reaction. Among them, the mass ratio of CNCs, lithium chloride, and p-toluenesulfonyl chloride is: 1 g: 0.16 g: 0.17 g; and the solid-liquid ratio of CNCs to N,N-dimethylacetamide, triethylamine, and ethylenediamine is 1 g: 3.2 mL: 0.24~0.25 mL: 0.18~0.19 mL, respectively. Let it stand and precipitate in 300 mL of water, remove the supernatant, and centrifuge to obtain the precipitate. Wash it alternately with isopropanol and water for 4 times, disperse it in 100 mL of water, and dry it appropriately to obtain an amino-modified cellulose nanocrystal hydrosol.
[0010] As one of the preferred schemes of the above technical scheme, the preparation method of the aldehyde-modified sodium alginate is as follows: a certain mass of sodium alginate is added to a flask containing LiCl, a certain volume of deionized water and a certain mass of sodium periodate and heated in a water bath at 75°C for 3 hours. The mass ratio of sodium alginate, lithium chloride and sodium periodate is 1 g: 2.1~2.2 g: 0.6~0.7 g. The solid-liquid ratio of sodium alginate and deionized water is 1 g: 63.131 mL. It is worth noting that the flask is covered with aluminum foil to prevent photoinduced decomposition of periodate. The product is filtered and washed 4 times with deionized water to remove iodine-containing compounds.
[0011] As one of the preferred solutions of the above technical solution, the mass ratio of CNCs to sodium alginate is 1 g: (0.06 g ~0.20 g).
[0012] As one of the preferred solutions of the above technical solution, the concentration of the citric acid solution is 4 wt % and the solvent is water.
[0013] As one of the preferred solutions of the above technical solution, the rare earth metal salt is Nd(NO 3 ) 3 ·5H 2 O.
[0014] As one of the preferred solutions of the above technical solution, CNCs, citric acid and Nd(NO 3 ) 3 ·5H 2 The mass ratio of O is 1 g: (0.01~0.04) g: 0.008~0.01 g.
[0015] As one of the preferred solutions of the above technical solution, the eluting solution is composed of glacial acetic acid and water in a volume ratio of 1:9.
[0016] As one of the preferred solutions of the above technical solution, the freeze-drying temperature is -80~-90°C and the time is 48 hours.
[0017] The present invention adopts sol-gel technology and freeze-drying technology to prepare composite imprinted aerogel with cellulose nanocrystals as the base, cross-linked sodium alginate and citric acid, and realizes efficient recovery of Nd(III) in water, and has excellent adsorption capacity and selective adsorption performance for Nd(III).
[0018] The technical principles and beneficial effects of the present invention are as follows: The present invention improves the mechanical properties and anti-interference ability of aerogel by aminated modification of active hydroxyl groups on cellulose nanocrystals and crosslinking with aldehyde-modified sodium alginate by Schiff base to form a more stable covalent bond. At the same time, more functional groups are introduced by thermal crosslinking of citric acid to improve the adsorption capacity of Nd(III), and then the selectivity of aerogel is enhanced by combining ion imprinting technology.
[0019] Citric acid (CA) contains three carboxyl structures and has a strong coordination effect with rare earth ions. The coordination stability of rare earth elements with citric acid in solution is good. It is introduced into aerogel materials through ion imprinting technology to form a memory cavity of the target rare earth ion, also called an imprinting site, which has selective adsorption capacity for the target rare earth ion. At the same time, this selective adsorption capacity also comes from the interaction between the functional monomers or functional groups on the surface of the aerogel and Nd(Ⅲ) during the adsorption process. It provides new insights for the selective recovery of Nd(Ⅲ) in water.
[0020] The introduction of sodium alginate and citric acid provides abundant groups for aerogels, provides connection sites for the immobilization of ion-imprinted polymers, and improves the adsorption kinetics of the materials. The introduction of ion imprinting technology can effectively solve the problem that ordinary adsorbents cannot selectively adsorb Nd(III), and provides a new method for the recovery and adsorption of Nd(III). BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 SEM images of CNC (a), CNC-SA (b), CNC-NISC (c) and CNC-ISC (d) aerogels prepared in the present invention; Figure 2 FT-IR images of CNC (a), CNC-SA (b), CNC-NISC (c) and CNC-ISC (d) aerogels prepared in the present invention; Figure 3 X-ray photoelectron spectra of CNC-NISC and CNC-ISC prepared in Example 1 and Comparative Example 1 before and after adsorption; Figure 4 The effects of the prepared CNC (a), CNC-SA (b), CNC-NISC (c) and CNC-ISC (d) on the adsorption value of neodymium ions and the imprinting factor IF at different pH values; Figure 5 The regeneration characteristics of CNC-SA, CNC-NISC and CNC-ISC prepared in the present invention after five adsorption and desorption cycles. DETAILED DESCRIPTION
[0022] The present invention will be further described below in conjunction with specific implementation examples. Example 1
[0023] A method for preparing a composite imprinted aerogel of cellulose nanocrystal cross-linked sodium alginate and citric acid comprises the following steps: (1) Preparation of cellulose nanocrystals (CNCs): A certain amount of medical cotton wool was dissolved in a 1:1 sulfuric acid / deionized water mixed solution. After continuous magnetic stirring in an oil bath at 45 °C for 3 hours, it was poured into a beaker containing ice water and allowed to stand for 12 hours. The upper transparent solution was removed, and the lower suspension was centrifuged at 10,000 rpm for 10 minutes, three times. Finally, it was dialyzed and purified to pH > 2.4 to obtain a white suspension. The concentration of the white suspension was adjusted to 4.0 wt% in a rotary evaporator to obtain CNCs.
[0024] (2) Preparation of amino-modified cellulose nanocrystals: Take 2 g of LiCl and dissolve it in a flask containing 12.5 g of CNCs and 40 mL of N,N-dimethylacetamide. Add 3.1 mL of triethylamine and 2.12 g of p-toluenesulfonyl chloride, and carry out p-toluenesulfonyl chlorination reaction at 8 °C for 24 hours. After the reaction is completed, heat it to 100 °C and add 2.342 mL of ethylenediamine for 3 hours of nucleophilic substitution reaction. Let it stand in 300 mL of water to precipitate, remove the supernatant, and centrifuge to obtain the precipitate. Wash it alternately with isopropanol and water for 4 times, disperse it in 100 mL of water, and dry it appropriately to obtain an amino-modified cellulose nanocrystal hydrosol.
[0025] (3) Preparation of aldehyde-modified sodium alginate: 1.584 g of SA was added to a flask containing 3.376 g of LiCl, 100 mL of deionized water, and 1.064 g of sodium periodate and heated in a water bath at 75 °C for 3 h. It is worth noting that the flask was covered with aluminum foil to prevent the photoinduced decomposition of periodate. The product was filtered and washed with deionized water 4 times to remove iodine-containing compounds.
[0026] (4) Preparation of amino-modified cellulose nanocrystals cross-linked with aldehyde-modified sodium alginate (CNC-SA): The amino-modified CNCs in (2) and the aldehyde-modified sodium alginate in (3) were mixed and reacted at 37 °C for 1 hour to obtain a hydrogel.
[0027] (5) Preparation of cellulose nanocrystal cross-linked sodium alginate and citric acid composite imprinted aerogel (CNC-ISC): 0.296 g of citric acid was added to 7.114 mL of water to make a 4 wt% solution of citric acid, which was then added to the cellulose cross-linked sodium alginate hydrogel solution in (4). Then, 0.1 g of Nd(NO 3 ) 3 ·5H 2O, 45 ℃ water bath to form sol. After freeze drying to form aerogel, it was heated at 140 ℃ for 10 minutes to cross-link citric acid. It was soaked in an eluent with a volume ratio of glacial acetic acid to water of 1:9 for 24 hours to remove neodymium ions, and freeze dried again to obtain aerogel, named CNC-ISC. Comparative Example 1
[0028] A method for preparing a cellulose nanocrystal cross-linked sodium alginate and citric acid composite aerogel (CNC-ISC), which is different from Example 1 in that: Nd (NO 3 ) 3 ·5H 2 O, the prepared aerogel was named CNC-NISC. Comparative Example 2
[0029] The difference between this example and Example 1 is that the citric acid and imprinting molecule cross-linking step is not performed, and in step (4), the amino-modified CNCs and the aldehyde-modified sodium alginate are mixed, reacted at 37° C. for 1 hour, and freeze-dried to prepare an aerogel, which is recorded as CNC-SA. Comparative Example 3
[0030] The difference between this example and Example 1 is that the CNCs were not subjected to amino modification and subsequent cross-linking steps such as sodium alginate, citric acid and imprinted molecule cross-linking. Instead, a small amount of CNCs were taken and freeze-dried to directly prepare pure cellulose nanocrystal aerogel, named CNC. Example 2
[0031] The same steps as in Example 1 are carried out: (1) Same as Example 1; (2) Same as Example 1; (3) Preparation of aldehyde-modified sodium alginate: 0.792 g of sodium alginate was added to a flask containing 1.688 g of LiCl, 50 mL of deionized water, and 0.532 g of sodium periodate and heated in a water bath at 75 °C for 3 h. It is worth noting that the flask was covered with aluminum foil to prevent the photo-induced decomposition of periodate. The product was filtered and washed with deionized water 4 times to remove iodine-containing compounds.
[0032] (4) Preparation of amino-modified cellulose nanocrystals cross-linked with aldehyde-modified sodium alginate: The amino-modified CNCs in (2) and the aldehyde-modified sodium alginate in (3) were mixed and reacted at 37 °C for 1 hour.
[0033] (5) Preparation of cellulose nanocrystal cross-linked sodium alginate and citric acid composite imprinted aerogel: 0.148 g of citric acid was added to 3.557 mL of water to make a 4 wt% solution of citric acid, which was then added to the mixed solution of cellulose cross-linked sodium alginate that was not freeze-dried in (4), and then 0.1 g of Nd(NO 3 ) 3 ·5H 2 O, 45 ℃ water bath to form sol. After freeze drying to form aerogel, it was heated at 140 ℃ for 10 minutes to cross-link citric acid. It was soaked in an eluent with a volume ratio of glacial acetic acid to water of 1:9 for 24 hours to remove neodymium ions, and freeze dried again to obtain aerogel, named CNC-ISC-2. Example 3
[0034] The same steps as in Example 1 are carried out: (1) Same as Example 1; (2) Same as Example 1; (3) Preparation of aldehyde-modified sodium alginate: 2.376 g of sodium alginate was added to a flask containing 5.064 g of LiCl, 150 mL of deionized water, and 1.596 g of sodium periodate and heated in a water bath at 75 °C for 3 h. It is worth noting that the flask was covered with aluminum foil to prevent the photo-induced decomposition of periodate. The product was filtered and washed with deionized water 4 times to remove iodine-containing compounds.
[0035] (4) Preparation of amino-modified cellulose nanocrystals cross-linked with aldehyde-modified sodium alginate: The amino-modified CNCs in (2) and the aldehyde-modified sodium alginate in (3) were mixed and reacted at 37 °C for 1 hour.
[0036] (5) Preparation of cellulose nanocrystal cross-linked sodium alginate and citric acid composite imprinted aerogel (CNC-ISC): 0.444 g of citric acid was added to 10.671 mL of water to make a 4 wt% solution of citric acid, which was then added to the mixed solution of cellulose cross-linked sodium alginate that was not freeze-dried in (4), and then 0.1 g of Nd(NO 3 ) 3 ·5H 2 O, 45 ℃ water bath to form sol. After freeze drying to form aerogel, it was heated at 140 ℃ for 10 minutes to cross-link citric acid. It was soaked in an eluent with a volume ratio of glacial acetic acid to water of 1:9 for 24 hours to remove neodymium ions, and freeze dried again to obtain aerogel, named CNC-ISC-3.
[0037] Figure 1SEM images of CNC (a), CNC-SA (b), CNC-NISC (c) and CNC-ISC (d) prepared by the present invention; it can be seen from the figure that the introduction of sodium alginate and citric acid makes the width of the fiber bundle thicker, which not only improves the mechanical properties but also prevents the damage of the adsorption site. At the same time, the three-dimensional layered structure and pores are retained.
[0038] Figure 2 FT-IR images of CNC (a), CNC-SA (b), CNC-NISC (c) and CNC-ISC (d) prepared by the present invention; As can be seen from the figure, the related groups of sodium alginate and citric acid appeared inside CNC-NISC and CNC-ISC, indicating that sodium alginate and citric acid were successfully introduced into CNCs. Moreover, the imprinting technology did not significantly change the groups on the surface of CNC-ISC.
[0039] Figure 3 Figure 1 is the X-ray photoelectron energy spectrum of CNC-NISC and CNC-ISC prepared in Example 1 and Comparative Example 1 before and after adsorption of Nd(III); it can be seen from the figure that after adsorption, CNC-NISC and CNC-ISC show the binding energy peak spectrum of carboxylate OC=O at 288.19 eV and 287.99 eV, respectively, indicating that -COO- on the surface of the material participates in the coordination of Nd(III), and this coordination often forms a complex to retain Nd(III) in the pores of the aerogel; the C=N and -NH- binding energies of CNC-NISC are reduced to 399.53 eV and 401.53 eV, respectively, and those of CNC-ISC are reduced to 399.49 eV and 401.64 eV, respectively. The slight shift in binding energy may be caused by the attraction of nitrogen-containing groups such as C=N and -NH- to Nd(III); the C=O binding energies of CNC-NISC and CNC-ISC are increased to 532.19 eV and 533.63 eV, respectively. eV and 531.91 eV, indicating that -COO- donates a lone electron pair to the 4d orbital of Nd(III), resulting in a decrease in its electron cloud density; CNC-NISC and CNC-ISC form new peaks at lower binding energies of 531.40 eV and 530.94 eV, respectively, which are attributed to the metal coordination of -COO⁻ with Nd(III); CNC-NISC and CNC-ISC show correlation peaks of the corresponding binding energies of Nd 4d 5 / 2 and Nd 4d 3 / 2, indicating that Nd(Ⅲ) is successfully adsorbed on the surfaces of CNC-NISC and CNC-ISC. It is worth noting that the total spectrum shows that no peak of Nd 4d binding energy is detected before the adsorption of CNC-ISC material, indicating that the acid washing process we used is effective. After adsorption, CNC-NISC and CNC-ISC show correlation peaks of Nd 4d, proving that Nd(Ⅲ) is adsorbed on the aerogel.
[0040] Figure 4 The effects of the adsorption values of neodymium ions and the imprinting factor IF of CNC (a), CNC-SA (b), CNC-NISC (c) and CNC-ISC (d) prepared by the present invention at different pH values are shown in the figure. As can be seen from the figure, CNC-ISC has a better adsorption effect on Nd(III), and the imprinting factor is 1.107 at pH = 5.0.
[0041] Figure 5 The regeneration characteristics of CNC-SA, CNC-NISC and CNC-ISC after five cycles of adsorption and desorption; it can be seen that the adsorption capacity of Nd(Ⅲ) by CNC-SA, CNC-NISC and CNC-ISC decreased to 72.52%, 77.31% and 81.60% of the initial adsorption capacity after five cycles, respectively. By comparison, the repeated adsorption performance of Nd(Ⅲ) by imprinted material CNC-ISC is better than that of non-imprinted material CNC-NISC.
[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing cellulose nanocrystal composite imprinted aerogel, characterized in that: The steps include: (1) Providing amino-modified cellulose nanocrystal hydrosol and aldehyde-modified sodium alginate; (2) uniformly mixing the amino-modified cellulose nanocrystal hydrosol and the aldehyde-modified sodium alginate to form a hydrogel by cross-linking reaction; (3) Adding citric acid solution to the hydrogel obtained in step (2), and then adding rare earth metal salt, bathing in water to form a sol, and freeze-drying to form an aerogel; thermally cross-linking the aerogel, eluting to remove the rare earth element, and freeze-drying to obtain a cellulose nanocrystal cross-linked sodium alginate and citric acid composite imprinted aerogel.
2. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The preparation method of the amino-modified cellulose nanocrystal hydrosol is as follows: S10, put the absorbent cotton into the sulfuric acid solution, stir it continuously with magnetic force at 45℃ for 3 hours, then pour it into a beaker containing ice water and let it stand for more than 12 hours; The upper transparent solution was removed, and the lower suspension was centrifuged at 10,000 rpm for 10 minutes, three times; finally, it was dialyzed and purified to pH>2.4 to obtain a white suspension; the white suspension was concentrated by rotary evaporation and the concentration was adjusted to 4.0 wt%, thereby obtaining a cellulose nanocrystal suspension; S11. Evenly mix cellulose nanocrystal suspension, lithium chloride, N,N-dimethylacetamide, triethylamine and p-toluenesulfonyl chloride, react at 8 ℃ for 24 hours, heat to 100 ℃ after the reaction, add ethylenediamine dropwise and react for 3 hours; after the reaction, let stand in 300 mL of water for precipitation, remove the supernatant, centrifuge to obtain the precipitate, wash and disperse in 100 mL of water to obtain amino cellulose nanocrystal hydrosol; wherein the mass ratio of cellulose nanocrystals, lithium chloride and p-toluenesulfonyl chloride in the cellulose nanocrystal suspension is 1:0.16:0.17, and the solid-liquid ratio of cellulose nanocrystals to N,N-dimethylacetamide, triethylamine and ethylenediamine in the cellulose nanocrystal suspension is 1 g:3.2 mL:0.24~0.25 mL:0.18~0.19 mL.
3. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The preparation method of the formaldehyded sodium alginate is as follows: sodium alginate and sodium periodate are added to an aqueous solution of LiCl, heated in a water bath at 75°C for 3 hours, filtered and washed after the reaction is completed, and the sodium alginate is obtained; wherein the mass ratio of sodium alginate, lithium chloride and sodium periodate is 1:2.1-2.2:0.6-0.
7.
4. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The mass ratio of cellulose nanocrystals to sodium alginate is 1:0.06-0.20; the cross-linking reaction is carried out at 37°C for 1 hour.
5. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The mass concentration of the citric acid solution in step (3) is 4 wt %, and the solvent is water; the mass ratio of cellulose nanocrystals, citric acid and rare earth metal salt is 1:0.01~0.04:0.008~0.01; and the water bath temperature for forming a sol-like state is 45°C.
6. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The rare earth metal salt is Nd(NO3)3·5H2O.
7. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The thermal crosslinking is carried out by heating the reaction at 140° C. for 10 minutes.
8. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The eluent used for elution is composed of glacial acetic acid and water in a volume ratio of 1:
9.
9. The method for preparing the cellulose nanocrystal composite imprinted aerogel according to claim 1, characterized in that: The freeze drying temperature is -80 to -90°C, and the freeze drying time is 48 hours.
10. Use of the cellulose nanocrystal composite imprinted aerogel according to claim 1 in selective adsorption, separation and recovery of Nd(III) in water.