Preparation method and application of nanocellulose-carbon dot composite film
By covalently grafting carbon dots on the surface of nanocellulose and loading metal oxides, a nanocellulose-carbon dot composite film with efficient adsorption and photocatalytic degradation of heavy metals and organic dyes in water was prepared, which solved the problem of insufficient adsorption and regeneration performance of existing materials, and achieved efficient and recyclable wastewater treatment effect.
Patent Information
- Application Number
- CN202510462638.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2025-07-11
AI Technical Summary
Existing nanocellulose materials have limitations in the adsorption and regeneration properties of pollutants. Traditional composite materials have complex preparation processes and poor environmental compatibility, making it difficult to efficiently remove heavy metals and organic dyes in water.
TEMPO oxidized nanocellulose as the matrix, carbon dots were covalently grafted onto the cellulose surface through EDC/NHS-mediated amidation reaction, and nanocellulose-carbon dot composite films were prepared in combination with casting method, and metal oxide nanoparticles were supported to form a stable composite material.
It realizes the efficient adsorption performance and photocatalytic degradation capability of nanocellulose-carbon dot composite film, has excellent heavy metal and organic dye removal capabilities, and can be easily regenerated, suitable for wastewater treatment.
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Figure CN120289844A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of nanocellulose functional materials, and particularly relates to a preparation method and application of a nanocellulose-carbon dot composite film. Background Art
[0002] With the continuous development of industrialization, the problem of water pollution has become increasingly severe. Pollutions of heavy metals (such as lead (Pb 2+ ), copper (Cu 2+ )) and organic dyes (such as methylene blue (MB), congo red (CR)), due to their high toxicity, bioaccumulation and non-degradability, pose a serious threat to the ecosystem and human health. Traditional sewage treatment technologies such as chemical precipitation, adsorption method and membrane separation, although having certain effects, face three major bottlenecks: insufficient removal rate of low-concentration pollutants; secondary pollution; and selectivity defects. Therefore, the development of new multifunctional materials with both high adsorption performance, selective recognition and recyclability has become a research hotspot.
[0003] Nanocellulose (CNF) is considered an ideal environmentally friendly substrate due to its high specific surface area, modifiable hydroxyl groups, biodegradability and mechanical strength. However, pure CNF materials have limitations in terms of pollutant adsorption and regeneration performance. In recent years, a large number of researchers have explored introducing specific properties into CNF through surface functionalization to enhance its adsorption and regeneration performance.
[0004] Carbon dots (CDs), as a new type of carbon-based nanomaterial, have fluorescence characteristics, high chemical stability and abundant surface functional groups, which can enhance the adsorption performance and optical properties of materials. In recent years, researchers have tried to composite nanocellulose with inorganic nanoparticles (such as CDs) to improve the adsorption efficiency, but such materials often have disadvantages such as complex preparation processes, poor environmental compatibility or low recycling efficiency.
[0005] Therefore, there is an urgent need to develop a nanocellulose-carbon dot composite film material with a simple process, excellent adsorption performance, and green recyclability. Summary of the Invention
[0006] The first technical problem to be solved by the present invention is to provide a preparation method of a nanocellulose-carbon dot composite film, which is simple and can obtain a nanocellulose-carbon dot composite film with stable and excellent performance; the second technical problem to be solved by the present invention is to provide a nanocellulose-carbon dot composite film, which has excellent mechanical properties and thermal stability; the third technical problem to be solved by the present invention is to provide an application of a nanocellulose-carbon dot composite film in adsorbing and removing heavy metal ions and dyes, which can efficiently and rapidly remove heavy metals and dyes and has excellent repeated regeneration ability.
[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows:
[0008] A preparation method of a nanocellulose-carbon dot composite film, using TOCNF as the matrix, adding 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide and carbon dots for amidation reaction under the buffer of acetate solution, and then loading metal oxide nanoparticles, and obtaining the nanocellulose-carbon dot composite film by the casting method.
[0009] Further, the preparation method of the carbon dots is: dissolving citric acid and urea in water for hydrothermal reaction to obtain a carbon dot solution.
[0010] Further, the hydrothermal temperature is 160 °C and the time is 4 h.
[0011] Further, the addition amount of the carbon dots is 0-30 mg.
[0012] Further, the amidation reaction process is: mixing TOCNF with an acetate buffer solution, and sequentially adding 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide and carbon dots for light-shielding reaction.
[0013] Further, the metal oxide nanoparticles are CeO2 nanoparticles.
[0014] Further, the preparation process of the TOCNF is: suspending pulp fibers in water containing TEMPO and NaBr, and dropping NaClO solution for reaction to obtain TOCNF.
[0015] Further, the preparation method of the above-mentioned nanocellulose-carbon dot composite film prepares a nanocellulose-carbon dot composite film.
[0016] Further, the application of the above-mentioned nanocellulose-carbon dot composite film in adsorbing and removing heavy metal ions and adsorbing dyes.
[0017] Further, the heavy metal ions are lead ions and copper ions; the dyes are methylene blue and congo red.
[0018] Compared with the prior art, the present invention has the following advantages:
[0019] (1) The present invention innovatively uses TEMPO-oxidized nanocellulose as the matrix material, and covalently grafts carbon dots (CDs) onto the cellulose surface through EDC / NHS-mediated amidation reaction to construct a nanocellulose-carbon dot composite film with stable chemical bonding; this preparation method not only effectively solves the problem of easy aggregation of carbon dots, but also significantly improves the structural stability of the composite material through chemical bonding, enabling it to have excellent adsorption performance and photocatalytic degradation ability, and can efficiently remove heavy metals and organic dye pollutants in water.
[0020] (2) The present invention introduces carboxyl functional groups into the cellulose molecular chain through TEMPO oxidation. On the one hand, these negatively charged carboxyl groups significantly improve the dispersion stability of nanocellulose in the aqueous phase system through electrostatic repulsion. On the other hand, they provide rich reaction sites for the subsequent covalent grafting of carbon dots mediated by EDC / NHS, realizing strong interfacial binding between nanocellulose and carbon dots.
[0021] (3) The nanocellulose used in the present invention has unique morphological characteristics, with a diameter of about 50 nm and a length reaching the micron level, presenting a highly entangled three-dimensional network structure. This fiber network with a high aspect ratio and high specific surface area provides an ideal carrier platform for carbon dots, forming a hierarchical pore structure, which greatly improves the adsorption capacity and mass transfer efficiency of the material.
[0022] (4) The nanocellulose-carbon dot composite film material prepared by the casting film process in the present invention is rich in active functional groups such as hydroxyl and carboxyl on the surface, and shows specific adsorption ability for heavy metal ions such as Pb 2+ , Cu 2+ and dye molecules such as methylene blue and congo red; secondly, the covalently grafted carbon dots improve the photocatalytic degradation performance of the material, and can achieve efficient degradation of organic pollutants under ultraviolet light irradiation; at the same time, the film can be regenerated by simple physical or chemical methods, showing broad application prospects in the field of sewage treatment. Brief Description of the Drawings
[0023] Figure 1 It is a characterization diagram of the carbon dot solution prepared in Example 1 of this application; among them, (a) is the ultraviolet optical characterization, and (b) is the fluorescence performance characterization diagram;
[0024] Figure 2 It is a morphological characterization diagram of the nanocellulose-carbon dot composite film prepared in Example 3 of this application; among them, (a) is the AFM morphological characterization diagram of carbon dots, and (b) is the SEM morphological characterization diagram of CNF (left) and the SEM morphological characterization diagram of CN2 composite film (right);
[0025] Figure 3 It is the stress-strain curve diagram of the nanocellulose-carbon dot composite film prepared in Examples 2-6 of this application;
[0026] Figure 4 It is the thermogravimetric analysis diagram of the nanocellulose-carbon dot composite film prepared in Examples 2-6 of this application;
[0027] Figure 5 It is the adsorption diagram of the nanocellulose-carbon dot composite film prepared in Examples 2-6 of this application for metal ions; among them, (a) is the adsorption diagram of metal ion Pb(II), and (b) is the adsorption diagram of metal ion Cu(II);
[0028] Figure 6 It is the adsorption diagram of the nanocellulose-carbon dot composite film prepared in Examples 2-6 of this application for dyes; among them, (a) is the adsorption diagram of dye MB, and (b) is the adsorption diagram of dye CR;
[0029] Figure 7 It is the regeneration test diagram of the nanocellulose-carbon dot composite film prepared in this application; among them, (a) is the regeneration test diagram of metal ions for the CN2 composite film in Example 3, and (b) is the regeneration test diagram of dyes for the CN1 composite film in Example 2. Detailed implementation manners
[0030] The following combines specific embodiments to further clarify the present invention. The embodiments are implemented on the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.
[0031] In the following embodiments, TEMPO is 2,2,6,6-tetramethylpiperidine-1-oxyl radical, TOCNF is TEMPO-oxidized cellulose nanofibers, EDC is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and NHS is N-hydroxysuccinimide.
[0032] Example 1
[0033] A preparation method of carbon dots includes the following steps:
[0034] (1) Preparation of carbon dots: Take 15 g of citric acid and 30 g of urea and dissolve them in 200 mL of distilled water. After stirring and dissolving, pour the solution into a reaction kettle lined with 100 mL of p-xylylene, and then place the reaction kettle in an oven at 160 °C for 4 h.
[0035] (2) Purification of carbon dots: After filtering the prepared carbon dots through a 0.22 μm nylon microporous filter membrane, pour the solution into a dialysis bag with MW100 and dialyze it in the dark. The dialysis time is 2 d, and the frequency of changing water is 3 times a day. Finally, a light green carbon dot solution is obtained.
[0036] As Figure 1The figure shows the characterization of the prepared carbon dot solution. From the ultraviolet optical characterization of CD in Figure (a), we can see that the excitation wavelength of CD is 234nm and 332nm, and there is a weak peak at 600nm in the visible light. From the fluorescence performance characterization of CD in Figure (b), we can see that after the CD solution absorbs red light, the solution appears blue-green.
[0037] Example 2
[0038] (1) Preparation of nanocellulose: 5 g of dried pulp fiber was suspended in 500 mL of distilled water containing 0.08 g of TEMPO and 0.5 g of NaBr and stirred for 30 min. Then, NaClO solution (5 mmol NaClO per gram of dry pulp fiber) was added dropwise to the mixture and stirred continuously at room temperature. In addition, 0.5 M NaOH was added using an automatic potentiometric titrator to keep the pH value of the solution at 10 for 4 h. After reaching the preset time, anhydrous ethanol was added to stop the reaction, and an appropriate amount of 0.1 M HCl was added to adjust the pH value to neutral. The mixture was then repeatedly centrifuged and washed with distilled water. The suspension was circulated six times with an ultrasonic homogenizer and then dialyzed in distilled water for 3 days. A transparent water suspension of TOCNF with a concentration of about 1 wt% was obtained.
[0039] (2) Preparation of nanocellulose-carbon dot composite film: Weigh 0.4g of absolutely dry TOCNF in a beaker, add sodium acetate / acetic acid buffer (10mL 1M / L), stir at room temperature for 1h; add 119mg EDC, stir at room temperature for 15min; then add 460mg NHS, and continue stirring at room temperature for 15min. The mixed solution is dialyzed in the dark (MW=10000Da) for 2d, and then dialyzed at high frequency in the dark for 2-3h / time for 1d. Add 5 drops (14μL) of glycerol and 5wt% CeO2 nanoparticles based on the original dispersion and stir well for 4-5h, then ultrasonically treat for 15min to obtain a uniformly dispersed film casting solution, pour it into a tetrafluoroethylene plate, degas at room temperature for 24h, and dry it in an oven at 30℃ to obtain a nanocellulose-carbon dot composite film (CN0).
[0040] Example 3
[0041] Different from Example 2, in step (2), 0.1 g of absolutely dry TOCNF was weighed into a beaker, and sodium acetate / acetic acid buffer solution (10 mL of 1 M / L) was added, and the mixture was stirred at room temperature for 1 h; 119 mg of EDC was added, and the mixture was stirred at room temperature for 15 min; then 460 mg of NHS was added, and stirring was continued at room temperature for 15 min; then 5 mg of CD obtained in Example 1 was added, and stirring was continued at room temperature for 12 h. The mixed solution was dialyzed in the dark (MW = 10000 Da) for 2 d, and then dialyzed in the dark at high frequency for 2 - 3 h each time for 1 d. 5 drops (14 μL) of glycerol and 5 wt% CeO2 nanoparticles based on the original dispersion were added, and the mixture was stirred thoroughly for 4 - 5 h, and then ultrasonically treated for 15 min to obtain a uniformly dispersed film casting solution, which was poured on a polytetrafluoroethylene plate and degassed at room temperature for 24 h, and then dried in an oven at 30 °C to obtain a nanocellulose-carbon dot composite film (CN1).
[0042] Example 4
[0043] Different from Example 3, 10 mg of CD was added, and stirring was continued at room temperature for 12 h to obtain a nanocellulose-carbon dot composite film (CN2).
[0044] Figure 2 (a) is the AFM morphological characterization diagram of carbon dots. It can be seen that the CD has slight aggregation, has good dispersibility, and the average horizontal length is 20 nm. Figure 2 (b) is the SEM morphological characterization diagram of CNF (left) and the SEM morphological characterization diagram of the CN2 composite film (right). It can be seen that the surface of CNF is smooth. After adding CeO2 nanoparticles, particulate matter appears on the surface of the CN2 composite film, and there are also particulate matters inside the cross-section. The particulate matter is CeO2 nanoparticles and is relatively uniformly dispersed.
[0045] Example 5
[0046] Different from Example 3, 20 mg of CD was added, and stirring was continued at room temperature for 12 h to obtain a nanocellulose-carbon dot composite film (CN3).
[0047] Example 6
[0048] Different from Example 3, 30 mg of CD was added, and stirring was continued at room temperature for 12 h to obtain a nanocellulose-carbon dot composite film (CN4).
[0049] Figure 3 From the stress-strain curve diagrams of the nanocellulose-carbon dot composite films prepared in Examples 2 - 6, it can be seen that the mechanical properties of CNF and CN0 - 4 composite films are excellent. With the addition of CeO2, the properties of the composite films decrease. When the amount of CD increases, the properties of the composite films do not improve but rather decrease.
[0050] Figure 4 From the thermogravimetric analysis diagram of the nanocellulose-carbon dot composite films prepared in Examples 2-6, it can be seen that the decomposition of all composite films mainly occurs in three stages, namely (I) 40-145 °C, (II) 145-344 °C, and (III) 344-600 °C. In the range of 40-145 °C (Stage I), the mass loss is about 12%, mainly due to the evaporation of free water in the composite film caused by heat. In the range of 145-344 °C (Stage II), the mass loss is about 81.19%, mainly due to the partial breakage and pyrolysis of the cellulose main chain. In the range of 344-600 °C (Stage III), the weight of the composite film decreases significantly again.
[0051] Example 7
[0052] In this experiment, static adsorption tests were carried out on the prepared composite materials.
[0053] Pb(II) and Cu(II) ion solutions with a concentration of 50 ppm and methylene blue and congo red solutions with a concentration of 50 ppm were respectively prepared with distilled water. The composite film prepared in Example 3 was tested with the above solutions. The specific steps are as follows: Take 10 mg of the composite film of Example 3 and immerse it in a 10 mL thumb bottle containing the above solution (the pH of the heavy metal ions is adjusted to 4.0 with 0.1 M HNO3 and 0.1 M NaOH). Subsequently, place it in an oscillating incubator and oscillate and adsorb for 240 min at 25 °C and 200 rpm for static adsorption. Different from the adsorption of heavy metal ions without additional light, the composite film adsorbs dyes MB and CR under ultraviolet light. Finally, an inductively coupled plasma mass spectrometer and a UV-visible spectrophotometer were used. The composite film prepared in the above example was tested with the solution respectively, and the results are as Figure 5 and Figure 6 shown.
[0054] Figure 5 (a) is the adsorption diagram of metal ion Pb(II), Figure 5 (b) is the adsorption diagram of metal ion Cu(II). The results show that the removal efficiency of CN2 composite film for Pb is 76.3%, and the adsorption capacity is 32.4 mg / g, while the removal efficiency of CN2 composite film for Cu is 37.7%, and the adsorption capacity is 19.5 mg / L. This is because the CN composite film has selectivity for heavy metal Pb.
[0055] Figure 6 (a) is the adsorption diagram of dye MB, Figure 6(b) is the adsorption diagram of dye CR. The results show that the removal rate of dye MB by the CN2 composite film is 92.2%, the removal efficiency of the CN1 composite film for CR dye is 57.2%, the adsorption and removal efficiency of the CNF composite film for MB is 90.7%, and the adsorption and removal efficiency for CR is 12.8%. By comparing the removal efficiency of dyes by the CNF and CN films, it can be seen that the addition of CeO2, CD, and glycerol significantly enhances the adsorption and removal performance of the CN film for cationic dye MB and anionic dye CR.
[0056] From Figure 5 and 6 it can be obtained that the nanocellulose composite film has good adsorption effects on heavy metal ions and dyes. It should be noted that the above adsorption experiments list several representative implementation methods for adsorbing heavy metal ions or dyes. In other implementation methods, the types of heavy metal ions and dyes that can be adsorbed are not limited to the heavy metals and dyes in the above experimental examples.
[0057] Example 8
[0058] In this experiment, the prepared composite materials were tested for regeneration.
[0059] Sodium ethylenediaminetetraacetate with a concentration of 0.1 mol / L was prepared with distilled water. The composite film adsorbed with Pb(Ⅱ) and Cu(Ⅱ) ions was immersed in it and oscillated for 12 h. Then, after washing with distilled water, it was taken out and dried. An aqueous solution of H2O2 with a concentration of 30% was used to oscillate and treat the composite film adsorbed with dyes methylene blue and congo red. Then, after washing with distilled water, it was taken out and dried. The prepared composite films were respectively used for the regeneration performance test, and the obtained results are as Figure 7 shown.
[0060] Figure 7 (a) is the regeneration test diagram of metal ions for the CN2 composite film, Figure 7 (b) is the regeneration test diagram of dyes for the CN1 composite film. The results show that after the CN2 composite film was repeatedly adsorbed with Pb(Ⅱ) and Cu(Ⅱ) four times, the adsorption performance decreased slightly, and it could still maintain 64.8% and 17.3% removal efficiency for Pb(Ⅱ) and Cu(Ⅱ). After three cycles, the CN1 composite film could still maintain 87.1% adsorption and removal efficiency for dye MB, and the removal efficiency for CR decreased significantly to 5.2%. It may be that CR is difficult to be completely removed, resulting in a decrease in the regeneration performance. Overall, the CN film still has excellent regeneration performance for heavy metals Pb(Ⅱ) and Cu(Ⅱ) and dye MB.
[0061] The present invention prepares a nanocellulose-carbon dot composite film by a simple method. The prepared nanocellulose-carbon dot composite film has a rough surface and excellent mechanical properties and thermal stability. It can not only adsorb and remove heavy metals, but also excellently remove dyes. In addition, the nanocellulose-carbon dot composite film still exhibits good removal efficiency after four cycles. Generally speaking, the nanocellulose-carbon dot composite film is a sustainable, economical, efficient, stable and promising adsorption material.
[0062] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.
Claims
1. A preparation method of a nanocellulose-carbon dot composite film, characterized in that, Using TOCNF as the matrix, under the buffering of acetate solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide and carbon dots are added for amidation reaction, and then metal oxide nanoparticles are loaded, and a nanocellulose-carbon dot composite film is prepared by the casting method.
2. The preparation method of the nanocellulose-carbon dot composite film according to claim 1, characterized in that: The preparation method of the carbon dots is as follows: citric acid and urea are dissolved in water for hydrothermal reaction to obtain a carbon dot solution.
3. The preparation method of the nano-cellulose-carbon dot composite film according to claim 2, wherein: The hydrothermal temperature is 160 °C and the time is 4 h.
4. The preparation method of the nanocellulose-carbon dot composite film according to claim 1, characterized in that: The addition amount of the carbon dots is 0-30 mg.
5. The preparation method of the nanocellulose-carbon dot composite film according to claim 1, characterized in that: The amidation reaction process is as follows: TOCNF and acetate buffer solution are mixed, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide and carbon dots are added in sequence for reaction in the dark.
6. The preparation method of the nanocellulose-carbon dot composite film according to claim 1, wherein: The metal oxide nanoparticles are CeO2 nanoparticles.
7. The preparation method of the nano-cellulose-carbon dot composite film according to claim 1, characterized in that: The preparation process of the TOCNF is as follows: pulp fibers are suspended in water containing TEMPO and NaBr, and an NaClO solution is added dropwise for reaction to obtain TOCNF.
8. According to the preparation method of the nanocellulose-carbon dot composite film according to any one of claims 1-7, a nanocellulose-carbon dot composite film is prepared.
9. Application of the nanocellulose-carbon dot composite film according to claim 8 in adsorbing and removing heavy metal ions and adsorbing dyes.
10. The application according to claim 9, wherein: The heavy metal ions are lead ions and copper ions; the dyes are methylene blue and congo red.