Preparation method of dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material and ultraviolet shielding application of dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material
By preparing a two-dimensional nanosheet composite material of dealkalized lignin/cerium-doped hydroxyapatite, the problems of photocatalytic activity of inorganic nanoparticles and instability of organic materials were solved, achieving efficient ultraviolet shielding and biocompatibility, with a sun protection index of 9.2-9.5.
Patent Information
- Application Number
- CN202511529978.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-24
- Publication Date
- 2026-01-27
AI Technical Summary
Existing inorganic UV-resistant nanoparticles suffer from photocatalytic activity and biocompatibility issues, while chemical organic materials are unstable and environmentally harmful, making it difficult to prepare highly efficient UV-shielding materials.
A method for preparing a two-dimensional nanosheet composite material of dealkalized lignin and cerium-doped hydroxyapatite was adopted. Through steps such as ultrasonication, stirring, and microwave hydrothermal reaction, a two-dimensional sheet structure with hydrogen bonds was formed, which enhances the ultraviolet absorption capacity.
It achieves highly efficient UV shielding, while also possessing good biocompatibility and safety, and boasts an excellent sun protection factor.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of ultraviolet shielding materials technology, specifically to a method for preparing a dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material and its application. Background Technology
[0002] As ozone depletes, the Earth's surface receives more ultraviolet radiation, causing serious damage to the biosphere. Generally, ultraviolet radiation from sunlight can be divided into three parts: UVA (320-400 nm), UVB (280-320 nm), and UVC (200-280 nm). UVA and UVB can cause various skin diseases and even cancer, and can also affect plant growth and accelerate the aging of polymer materials.
[0003] As a type of optical functional material, UV-blocking materials are of great significance to social development and human life. UV-blocking materials are generally divided into two main categories based on their protective mechanisms: inorganic materials (forming a protective barrier to reflect UV rays away from human skin) and organic materials (absorbing UV rays). Inorganic materials mainly include titanium dioxide (TiO2) and zinc oxide (ZnO), which are chemically inert and photostable, and do not decompose over time under light exposure. However, the photocatalytic activity of inorganic nanoparticles may generate reactive free radicals, which can cause damage at the cellular level. Organic materials are aromatic compounds, such as avobenzone, oxybenzone, enshurizol, and octocrylene. Their aromatic structures, conjugated with carbonyl groups, can absorb high-intensity UV radiation. However, organic components are usually small in size and unstable, easily excited by UV light and generating free radicals, leading to skin damage and premature aging. Simultaneously, organic materials can seep into the ocean, creating a dangerous aquatic environment for small organisms and coral reefs.
[0004] Alkali-free lignin, as an abundant renewable resource, possesses excellent UV absorption and antioxidant properties due to its aromatic framework and phenolic hydroxyl groups. The UV absorption and shielding performance of alkali-free lignin is mainly related to its chromophores (phenols and ketones), with conjugation effects and the type of substituents significantly influencing UV absorption. Furthermore, the structure of alkali-free lignin contains many chromophores with π bonds and unbonded electron groups associated with them, which enhances its UV absorption capacity and intensity. The technical challenge in using alkali-free lignin lies in the fact that its UV shielding efficiency cannot match that of commercially available shielding agents, and its nano-sizing process is prone to aggregation, limiting its performance. Meanwhile, hydroxyapatite (HAp), a major component of human bone, exhibits high biocompatibility and non-toxicity. Studies have shown that iron doping modification can significantly alter the UV absorption of HAP samples (Journal of Inorganic Materials, 2025, 40: 05). To date, there have been no reports on constructing two-dimensional composite materials with metal-doped HAP and dealkalized lignin, particularly on preparing composite materials with specific morphologies (such as two-dimensional nanosheets) by combining metal-doped HAP and dealkalized lignin to achieve UV shielding performance. Summary of the Invention
[0005] To address the hazards of organic UV-shielding materials to the human body and the environment, as well as the limitations of inorganic UV-resistant nanoparticles in photocatalytic activity, inherent cytotoxicity, and lack of biocompatibility, this invention proposes a method for preparing a dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material.
[0006] To achieve the objectives of this invention, the following technical solution is adopted: A method for preparing an alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material includes the following steps: (1) The dealkalized lignin and deionized water were mixed evenly by stirring (mass ratio of 1:10~30). The mixture was ultrasonicated in an ultrasonic reactor at 200~300 W power for 10~40 min to obtain a dealkalized lignin nanosheet mixture. The precipitate obtained after centrifugation was freeze-dried to obtain the dealkalized lignin nanosheet structure.
[0007] (2) Mix cerium nitrate and deionized water evenly by stirring. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder and water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.01~0.2 and the molar ratio of (Ce+Ca) / P is 1.5~2. Mix the three solutions and stir in a water bath at 30℃~60℃ for 30 min.
[0008] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.1 g / mL to 0.45 g / mL. The resulting suspension is stirred in a water bath at 25℃ to 50℃ for 0.5 to 1 hour. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 80 to 110℃ and 0.2 to 1 MPa for 60 to 90 minutes. After centrifugation, the mixture is washed with deionized water, centrifuged again, and then freeze-dried to obtain the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material.
[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves a wide bandwidth for UV absorption by doping hydroxyapatite, which is used in human skeletal structures, with metals, thus combining the good biocompatibility of hydroxyapatite with excellent UV shielding performance. Alkali-doped lignin nanosheets are mixed with hydroxyapatite, using pre-prepared alkali-doped lignin nanosheets as templates. Through template action, large sheet-like hydroxyapatite nanosheets are generated in situ on the surface of the alkali-doped lignin nanosheets. On one hand, the groups on the surface of hydroxyapatite form hydrogen bonds with the abundant functional groups on the surface of alkali-doped lignin, preventing aggregation between the alkali-doped lignin nanosheets and forming a two-dimensional sheet-like structure with an ultra-high specific surface area. This greatly increases the interaction interface with UV light, thereby improving UV shielding efficiency; thus fully utilizing the UV shielding performance of the alkali-doped lignin / cerium-doped hydroxyapatite nanosheet composite material.
[0010] This invention significantly reduces the band gap of HAp by cerium ion doping, broadening and enhancing its absorption bandwidth in the UVA-UVB band. Ultimately, the synergistic effect of dealkalized lignin and cerium-doped HAp results in an excellent sun protection index for the composite material and improves its overall safety. Attached Figure Description
[0011] Figure 1 The XRD patterns of hydroxyapatite and cerium-doped hydroxyapatite prepared in Example 3 are shown. Figure 2 Solid-state ultraviolet absorption spectra of the dealkalized lignin, hydroxyapatite, cerium-doped hydroxyapatite, dealkalized lignin / cerium-doped hydroxyapatite and zinc-doped hydroxyapatite structural samples prepared in Example 3. Figure 3 Ultraviolet transmittance curves of dealkalized lignin, hydroxyapatite, cerium-doped hydroxyapatite, dealkalized lignin / cerium-doped hydroxyapatite prepared in Example 3, and zinc-doped hydroxyapatite prepared in Comparative Example 3. Figure 4 TEM images of a) pristine hydroxyapatite and b) flaky dealkalized lignin prepared in Example 3, c) flaky hydroxyapatite, and d) cerium-doped hydroxyapatite; Figure 5 The SPF value of the example sample; Figure 6 Band gap calculations were performed for pure hydroxyapatite and the cerium-doped hydroxyapatite material prepared in Example 3. Detailed Implementation
[0012] Example 1
[0013] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:20), and sonicate the mixture in an ultrasonic vessel at 300 W power for 20 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0014] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.1 and the molar ratio of (Ce+Ca) / P is 1.7. Mix the three solutions and stir in a water bath at 45°C for 30 min.
[0015] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.3 g / mL. The resulting suspension is stirred in a water bath at 35°C for 0.5 hours. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 100°C and 0.8 MPa for 80 minutes. After centrifugation, washing with deionized water, and centrifugation, the mixture is freeze-dried to obtain the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material.
[0016] X-ray powder diffraction (XRD) was performed on the alkali-reduced lignin / cerium-doped hydroxyapatite composite material prepared in this embodiment. Its morphology and structure were observed under a transmission electron microscope (TEM), and its ultraviolet shielding effect was tested using a UV-Vis instrument. The XRD patterns are shown below. Figure 1 As shown: Cerium-doped hydroxyapatite material exhibits multiple diffraction peaks, which are hydroxyapatite diffraction peaks; TEM images of dealkalized lignin, cerium-doped hydroxyapatite, and dealkalized lignin / cerium-doped hydroxyapatite lamellar structures are shown below. Figure 4 As shown in the figures, a) and b) represent the original hydroxyapatite and plate-like dealkalized lignin structures prepared in Example 3. As can be seen from the figures, the prepared cerium-doped hydroxyapatite and dealkalized lignin are presented in a plate-like manner, providing a larger interface area, reducing agglomeration, and simultaneously improving ultraviolet shielding capability.
[0017] The SPF numerical spectrum of the alkali-free lignin / cerium-doped hydroxyapatite composite material is as follows: Figure 5As shown, according to the Colita standard, 100 mg of powder and 900 mg of glycerin were mixed evenly in an agate mortar to prepare a simulated sunscreen agent with a mass ratio of 1:9. 32.5 mg of the sample was weighed onto a PMMA test plate (5×5 cm) using an analytical balance and spread evenly with a finger wearing a finger cot. The SPF of the sample was then tested using an SPF meter. A higher SPF indicates better UV protection; in this example, the value was 9.2.
[0018] Example 2
[0019] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:10), and sonicate the mixture in an ultrasonic vessel at 200 W power for 40 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0020] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.2 and the molar ratio of (Ce+Ca) / P is 1.5. Mix the three solutions and stir in a 60℃ water bath for 30 min.
[0021] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.1 g / mL. The resulting suspension is stirred in a water bath at 40°C for 1 hour. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 80°C and 0.2 MPa for 70 min. After centrifugation, washing with deionized water, centrifugation, and freeze-drying, the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
[0022] The SPF test of the alkali-degraded lignin / cerium-doped hydroxyapatite composite material is as shown in Example 1. Figure 5 As shown, the value in this embodiment is 9.1.
[0023] Example 3
[0024] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:10), and sonicate the mixture in an ultrasonic vessel at 250 W power for 30 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0025] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.1 and the molar ratio of (Ce+Ca) / P is 1.67. Mix the three solutions and stir in a 50℃ water bath for 30 min.
[0026] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.2 g / mL. The resulting suspension is stirred in a 50°C water bath for 1 hour. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 90°C and 0.6 MPa for 90 min. After centrifugation, washing with deionized water, centrifugation, and freeze-drying, the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
[0027] The SPF test of the alkali-free lignin / cerium-doped hydroxyapatite composite material is as shown in Example 1, and the value in this example is 9.5.
[0028] Example 4
[0029] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:20), and sonicate the mixture in an ultrasonic vessel at 225 W power for 10 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0030] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.01 and the molar ratio of (Ce+Ca) / P is 1.8. Mix the three solutions and stir in a 30°C water bath for 30 min.
[0031] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.3 g / mL. The resulting suspension is stirred in a water bath at 25°C for 0.5 hours. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 110°C and 0.4 MPa for 70 min. After centrifugation, washing with deionized water, centrifugation, and freeze-drying, the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
[0032] The SPF test of the alkali-free lignin / cerium-doped hydroxyapatite composite material is as shown in Example 1, and the value in this example is 9.1.
[0033] Example 5
[0034] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:30), and sonicate the mixture in an ultrasonic vessel at 250 W power for 25 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0035] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride with water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.1 and the molar ratio of (Ce+Ca) / P is 2. Mix the three solutions and stir in a water bath at 40°C for 30 min.
[0036] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.45 g / mL. The resulting suspension is stirred in a water bath at 30°C for 0.5 hours. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 80°C and 1.0 MPa for 60 min. After centrifugation, washing with deionized water, and centrifugation, the mixture is freeze-dried to obtain the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material.
[0037] The SPF test of the alkali-free lignin / cerium-doped hydroxyapatite composite material is as shown in Example 1, and the value in this example is 8.9.
[0038] Comparative Example 1
[0039] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:20), and sonicate the mixture in an ultrasonic vessel at 300 W power for 20 min to obtain a mixture of dealkalized lignin nanosheets. After centrifugation, the precipitate is dried in an oven to obtain the dealkalized lignin structure.
[0040] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.1 and the molar ratio of (Ce+Ca) / P is 1.7. Mix the three solutions and stir in a water bath at 45°C for 30 min.
[0041] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.3 g / mL. The resulting suspension is stirred in a water bath at 35°C for 0.5 hours. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 100°C and 0.8 MPa for 80 minutes. After centrifugation, washing with deionized water, centrifugation, and freeze-drying, the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
[0042] Unfreeze-dried alkali-reduced lignin does not form a uniform lamellar structure and does not have good UV shielding ability. The SPF test of the alkali-reduced lignin / cerium-doped hydroxyapatite composite material is as shown in Example 1, and the value in this example is 2.6.
[0043] Comparative Example 2
[0044] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:10), and sonicate the mixture in an ultrasonic vessel at 200 W power for 40 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0045] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of sodium dihydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.2 and the molar ratio of (Ce+Ca) / P is 1.5. Mix the three solutions and stir in a 60℃ water bath for 30 min.
[0046] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.1 g / mL. The resulting suspension is stirred in a 40°C water bath for 1 hour. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 80°C and 0.2 MPa for 70 min. After centrifugation, washing with deionized water, centrifugation, and freeze-drying, the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
[0047] In this comparative example, acidic sodium dihydrogen phosphate was used to synthesize hydroxyapatite, resulting in cerium-doped hydroxyapatite with poor UV shielding ability. The SPF test of the alkali-degraded lignin / cerium-doped hydroxyapatite composite material is as shown in Example 1, with a value of 2.7 in this example.
[0048] Comparative Example 3
[0049] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:10), and sonicate the mixture in an ultrasonic vessel at 250 W power for 30 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0050] (2) Mix an appropriate amount of zinc chloride with deionized water by stirring until homogeneous. Mix calcium chloride with water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Zn / (Zn+Ca) is 0.1 and the molar ratio of (Zn+Ca) / P is 1.67. Mix the three solutions and stir in a 50℃ water bath for 30 min.
[0051] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.2 g / mL. The resulting suspension is stirred in a 50°C water bath for 1 hour. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 90°C and 0.6 MPa for 90 min. After centrifugation, washing with deionized water, centrifugation, and freeze-drying, the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
[0052] In this comparative example, cerium doping was replaced with zinc doping hydroxyapatite. Figure 2 It can be seen that its solid ultraviolet absorption curve is not as good as that of cerium doping, so its ultraviolet shielding effect is poor. The SPF test of the dealkalized lignin / zinc doped hydroxyapatite composite material is as in Example 1, and the value in this example is 2.9.
[0053] Comparative Example 4
[0054] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:20), and sonicate the mixture in an ultrasonic vessel at 225 W power for 10 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0055] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.01 and the molar ratio of (Ce+Ca) / P is 1.8. Mix the three solutions and stir in a 30°C water bath for 30 min.
[0056] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.3 g / mL. The resulting suspension is stirred in a water bath at 25°C for 0.5 hours. The mixture is then transferred to a conventional hydrothermal reactor and reacted at 110°C for 70 minutes. After centrifugation, the mixture is washed with deionized water, centrifuged again, and then freeze-dried to obtain the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material.
[0057] In this comparative experiment, cerium-doped hydroxyapatite was synthesized using conventional hydrothermal methods, resulting in incomplete reaction between cerium and hydroxyapatite, thus leading to poor UV shielding capabilities. The SPF test results for the alkali-reduced lignin / cerium-doped hydroxyapatite composite material are as shown in Example 1, with a value of 2.6 in this example.
[0058] Comparative Example 5
[0059] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:30), and sonicate the mixture in an ultrasonic vessel at 250 W power for 25 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0060] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring until homogeneous. Mix calcium chloride with water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.1 and the molar ratio of (Ce+Ca) / P is 2. Mix the three solutions and stir in a water bath at 40°C for 30 min.
[0061] (3) The powder obtained in step (1) and the mixture in step (2) are mixed evenly at a solid-liquid ratio of 0.45 g / mL. The resulting suspension is stirred in a water bath at 30°C for 0.5 hours. The mixture is then transferred to a microwave hydrothermal reactor and reacted at 80°C and 1.0 MPa for 60 min. After centrifugation, washing with deionized water, centrifugation, and oven drying, the dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
[0062] The composite material in this comparative example was dried in an oven, which caused some of the dealkalized lignin to carbonize, resulting in poor UV shielding. The SPF test of the dealkalized lignin / cerium-doped hydroxyapatite composite material was as shown in Example 1, with a value of 2.8 in this example.
[0063] Comparative Example 6
[0064] (1) Mix an appropriate amount of dealkalized lignin with deionized water by stirring (mass ratio 1:10), and sonicate the mixture in an ultrasonic vessel at 250 W power for 30 min to obtain a dealkalized lignin nanosheet mixture. After centrifugation, the precipitate obtained is freeze-dried to obtain a dealkalized lignin nanosheet structure.
[0065] (2) Mix an appropriate amount of cerium nitrate with deionized water by stirring. Mix calcium chloride and water to prepare a solution. Mix an appropriate amount of disodium hydrogen phosphate powder with water to prepare a solution. Ensure that the molar ratio of Ce / (Ce+Ca) is 0.1 and the molar ratio of (Ce+Ca) / P is 1.67. Mix the three solutions and stir in a water bath at 50°C for 30 min. Transfer the mixture to a microwave hydrothermal reactor and react at 90°C and 0.6 MPa for 90 min. After centrifugation, wash with deionized water, and freeze-dry after centrifugation to obtain cerium-doped hydroxyapatite two-dimensional nanosheet composite material.
[0066] (3) The powder obtained in step (1) and the powder in step (2) are mixed evenly at a mass ratio of 0.2 and then physically ground and mixed in an agate mortar to obtain a dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material.
[0067] The SPF test of the alkali-free lignin / cerium-doped hydroxyapatite composite material is as shown in Example 1, and the value in this example is only 2.2.
[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material, characterized in that, Includes the following steps: (1) Alkali-free lignin was mixed with deionized water, subjected to ultrasonic treatment, and then separated by centrifugation and freeze-dried to obtain alkali-free lignin nanosheets; (2) Dissolve the calcium source, cerium source and phosphorus source in deionized water to prepare a precursor mixture; wherein the molar ratio of Ce / (Ce+Ca) is 0.01~0.2 and the molar ratio of (Ce+Ca) / P is 1.5~2; (3) The dealkali-free lignin nanosheets obtained in step (1) are mixed with the precursor mixture obtained in step (2). After stirring, the mixed suspension is microwave-reacted in a microwave hydrothermal reactor. Finally, after centrifugation, washing and freeze-drying, the dealkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material is obtained.
2. The method for preparing the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material according to claim 1, characterized in that: In step (1), the ultrasonic treatment is performed at a power of 200~300 W for 10~40 min.
3. The method for preparing the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material according to claim 1, characterized in that: The calcium source mentioned in step (2) is calcium chloride, the cerium source is cerium nitrate, and the phosphorus source is disodium hydrogen phosphate.
4. The method for preparing the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material according to claim 3, characterized in that: In step (2), the molar ratio of Ce / (Ce+Ca) is 0.1~0.2; the molar ratio of (Ce+Ca) / P is 1.67~1.
8.
5. The method for preparing the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material according to claim 1, characterized in that: In step (3), the temperature of the microwave hydrothermal reaction is 80~110℃, the pressure is 0.2~1 MPa, and the reaction time is 60~90 min.
6. The method for preparing the alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material according to claim 1, characterized in that: The dealkalized lignin nanosheets obtained in step (1) and the precursor mixture obtained in step (2) were mixed at a solid-liquid ratio of 0.1 g / mL to 0.45 g / mL.
7. A dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material, characterized in that, The composite material is prepared by the method described in any one of claims 1-6.
8. An ultraviolet shielding composition, characterized in that, The alkali-free lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material described in claim 7 is used as an effective component for ultraviolet shielding.
9. The application of the dealkalized lignin / cerium-doped hydroxyapatite two-dimensional nanosheet composite material according to claim 7 in the preparation of ultraviolet shielding products.