A surface-modified PVDF / oxide composite particle, its preparation method and application

Abstract

This invention relates to a surface-modified PVDF / oxide composite particle, its preparation method, and its application. The method includes the following steps: PVDF, nano-oxide powder, and an organic solvent are mixed uniformly, and after standing and degassing, a blended slurry is obtained; wherein the nano-oxide powder includes one or more of nano-titanium dioxide powder and nano-silica powder; the blended slurry is dropped into water to form microspheres, and the organic solvent is removed to obtain PVDF / oxide microspheres; the PVDF / oxide microspheres are placed in a mixed solution for co-deposition modification, followed by solid-liquid separation, water washing, and drying to obtain surface-modified PVDF / oxide composite particles. The PVDF / oxide composite particles of this invention possess advantages such as being environmentally friendly, having excellent adsorption effects, and being easy to recycle, thus showing promising prospects for industrial application.

Description

Technical Field

[0001] This invention relates to a surface-modified PVDF / oxide composite particle, its preparation method and application, and more particularly to a surface-modified PVDF / oxide composite particle with polyphenol chitosan copolymer, its preparation method and application. Background Technology

[0002] Rare earth elements, composed of 15 lanthanide metals and scandium and yttrium, totaling 17 elements, are known as "industrial vitamins" and are widely used in permanent magnets, medical devices, new energy, and optoelectronic devices. Advanced rare earth materials are also key supporting materials in aerospace equipment, marine engineering equipment, biomedicine and high-performance medical devices, advanced rail transit equipment, energy-saving and new energy vehicles, electronic information, and national defense. Rare earth resources, as a globally recognized strategic mineral, are non-renewable. According to statistics from the U.S. Geological Survey (USGS) in 2021, the global total reserves of rare earth resources are 120 million tons (in oxides), but less than 4% of rare earth ores in nature are suitable for industrial production.

[0003] Therefore, recovering rare earth resources from rare earth mining, processing, and waste products is of great significance. Secondary rare earth resources are typically recovered using relatively clean and efficient hydrometallurgical methods, such as hydrometallurgical recovery of waste rare earth phosphors and hydrometallurgical leaching of rare earth tailings. Traditional precipitation filtration and evaporation crystallization methods consume large amounts of reagents and energy, resulting in low efficiency and high costs, making them uneconomical. Organic solvent extraction methods also have certain requirements on the initial concentration of rare earth ions and have poor selectivity for interfering ions, while also generating large amounts of organic waste liquid. Adsorption methods, due to their advantages of short reaction time, large adsorption capacity, and reduced use of organic matter, show considerable potential for adsorbing rare earth ions from solution.

[0004] Chitosan (CS) is a non-toxic, biodegradable polysaccharide obtained by deacetylation of chitin. Its structure contains abundant amino and hydroxyl groups, which can chelate with metal ions in solution, making it suitable for heavy metal adsorption and purification. However, chitosan's low density, tendency to float, and weak mechanical strength make it difficult to use alone, and it is usually prepared into composite materials.

[0005] Polyvinylidene fluoride (PVDF) is used as an ion exchange membrane material due to its excellent properties such as anti-aging, chemical resistance, UV radiation resistance and low density. However, its surface has good hydrophobicity and usually needs to be modified to be hydrophilic. After modification, it may have an adverse effect on the efficiency, mechanical properties and lifespan of PVDF membrane.

[0006] Chinese invention patent application CN110368908A discloses a polyphenol-modified chitosan adsorbent, its preparation method, and its application in germanium recovery. The preparation method includes the following steps: After washing and drying crab shells, they are soaked in hydrochloric acid solution with continuous stirring for 10-15 hours. The crab shells are then washed until neutral, and sodium hydroxide solution is added. The mixture is heated to 80-100℃ and reacted for 2-6 hours. After washing with water until neutral, 1% KMnO4 and NaHSO3 solutions are added for rinsing, and the mixture is dried to obtain a white solid, chitosan. The dried chitosan is then taken and added to sodium hydroxide solution, reacting at 80-120℃ for 5-10 hours to obtain a white chitosan solid. Polyphenols and the chitosan solid are placed in a three-necked flask, and methanol is added. The mixture is stirred continuously until dissolved, and stirred at 20-50℃ for 12-24 hours. After washing and drying, the polyphenol-modified chitosan adsorbent is obtained. The polyphenol-modified chitosan adsorbent prepared by this invention can effectively adsorb germanium ions, but the resulting adsorbent is difficult to maintain a fixed morphology, which increases the difficulty of adsorbent recovery in practical applications, and even increases the possibility of adsorbent residue in water bodies, polluting the water bodies; moreover, chitosan can dissolve in solution under acidic / weakly acidic atmosphere, making it difficult to recover the adsorbent. Summary of the Invention

[0007] To address the shortcomings of existing technologies, one objective of this invention is to provide a green and environmentally friendly surface-modified PVDF (polyvinylidene fluoride) / oxide composite particle with excellent adsorption effect and easy recycling and reuse, as well as a method for its preparation; another objective of this invention is to provide applications of surface-modified PVDF / oxide composite particles.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0009] A method for preparing surface-modified PVDF / oxide composite particles includes the following steps:

[0010] S1. Mix PVDF, nano-oxide powder and organic solvent evenly, let stand and degas to obtain a blended slurry;

[0011] Among them, nano oxide powder includes one or more of nano titanium dioxide powder and nano silicon dioxide powder;

[0012] S2. The blended slurry is dropped into water to form microspheres. After the organic solvent is removed, PVDF / oxide microspheres are obtained.

[0013] S3. After immersing the PVDF / oxide microspheres in the mixed solution, the solid and liquid are separated, washed with water, and dried to obtain surface-modified PVDF / oxide composite particles.

[0014] The preparation method of the mixture includes the following steps: adding chitosan, polyphenolic organic matter and laccase to a buffer solution with a pH of 4-5.5, mixing evenly, and then obtaining the mixture.

[0015] Thus, by first blending PVDF and nano-oxides and allowing the mixture to stand and degas (to prevent air bubbles from accumulating on the surface of the droplets and breaking, which would lead to uneven particle size), hydrophilic microspheres are prepared. This facilitates the subsequent co-deposition and modification of polyphenolic organic matter and chitosan onto the surface of the PVDF / oxide microspheres. During deposition, chitosan and polyphenolic organic matter are co-deposited and modified onto the surface of the PVDF / oxide microspheres under laccase catalysis. This helps the co-deposited material to stably "adhere" to the surface of the PVDF / oxide microspheres, giving the PVDF / oxide composite particles both good adsorption effect and recycling performance. Moreover, the main raw materials are green and environmentally friendly, which has good economic benefits and promising prospects for industrial application.

[0016] Preferably, the polyphenolic organic compounds include one or more of dopamine, tannic acid, and gallic acid.

[0017] Furthermore, in S1, the PVDF content in the blended slurry is 5-12 wt%, the nano-oxide powder content is 1-5 wt%, and the organic solvent content is 77-94 wt%. Controlling the PVDF content helps in successful pellet formation. When the PVDF content is too high, the viscosity of the mixed slurry is too high, making pellet formation difficult and resulting in a "tailing" appearance during dripping. When the PVDF content is too low, the viscosity of the mixed liquid is too low, making it difficult to achieve uniform dripping and obtain microspheres with uniform particle size. Controlling the amount of nano-oxide powder added ensures that the PVDF / oxide microspheres have good hydrophilicity, meeting the needs of subsequent co-deposition, and also imparts good physical properties to the PVDF / oxide microspheres. If no powder is added or the amount added is too small, the microspheres have poor hydrophilicity and low mechanical properties, limiting their subsequent recycling. If the added content is too high, the cost is likely to be high.

[0018] Preferably, the PVDF content in the blended slurry is 7-10 wt%, the nano-oxide powder content is 2-3 wt%, and the organic solvent content is 81-91 wt%.

[0019] Preferably, the blended slurry also contains PEG, with the PEG content being 4-6 wt%.

[0020] Further, the relative molecular weight of the PEG is 1000-5000, preferably 1000-3000.

[0021] Optionally, the relative molecular weight of PVDF is 300,000 to 700,000, further, the relative molecular weight of PVDF is 400,000 to 600,000, and even further, it is 450,000 to 550,000.

[0022] Preferably, the particle size of the nano-oxide powder is 1-100 nm, more preferably 5-50 nm, and even more preferably 10-30 nm.

[0023] Further, in S1, the organic solvent is DMAc.

[0024] Further, in S1, PVDF, nano-oxide powder and organic solvent are stirred at 65-75°C for 4-6 hours, and then allowed to stand to remove air, to obtain a blended slurry; preferably, the standing time is 4-18 hours.

[0025] Further, in S2, the blended slurry is dripped into water using a pipette or syringe to form microspheres; preferably, the method for removing organic solvents includes the following steps: soaking the microspheres in water for 4-10 hours, changing the water every 1-3 hours during this period.

[0026] Further, in step S3, the PVDF / oxide microspheres are placed in a mixed solution and stirred for 0.5-3 hours, followed by solid-liquid separation, water washing, and drying to obtain surface-modified PVDF / oxide composite particles; preferably, the water washing is performed multiple times; preferably, the drying method is vacuum drying.

[0027] Further, in S3, the mass ratio of PVDF / oxide microspheres, chitosan, polyphenolic organic matter and laccase is 400-600:800-1200:800-1200:5-15; preferably 450-550:900-1100:900-1100:8-12.

[0028] Further, in S3, the preparation method of the mixture includes the following steps: dissolving chitosan in a buffer solution with a pH of 4-5.5, then adding gallic acid and laccase, and stirring evenly to obtain the mixture; preferably, the buffer solution is a NaAc-HAc buffer solution.

[0029] Optionally, the particle size of the PVDF / oxide composite particles is 1.5-3.5 mm.

[0030] Based on the same inventive concept, the present invention also provides a surface-modified PVDF / oxide composite particle, which is prepared by the preparation method described above.

[0031] Based on the same inventive concept, the present invention also provides the application of the surface-modified PVDF / oxide composite particles as described above, wherein the surface-modified PVDF / oxide composite particles are used as adsorbent materials to adsorb rare earth ions from solution.

[0032] Preferably, in application, the surface-modified PVDF / oxide composite particles are mixed with the solution to be adsorbed, and then stirred.

[0033] This invention uses PVDF, which has advantages such as low density, acid and alkali resistance, and aging resistance, as the matrix material. To facilitate the subsequent co-deposition modification of polyphenolic organic compounds and chitosan on the surface of the microspheres, an inorganic nano-oxide co-doping method is used to improve its hydrophilicity. Simultaneously, considering the subsequent recovery (recycling) and stability (lifespan) of the PVDF / oxide composite particles, spherical PVDF / oxide microspheres are prepared based on the phase inversion method by controlling the raw material ratio, serving as the matrix material.

[0034] This invention enables the preparation of PVDF / oxide composite particles co-deposited with chitosan and polyphenolic organic compounds. On the surface of hydrophilic PVDF / oxide microspheres, polyphenolic organic compounds, under weakly acidic conditions, can be converted into quinone compounds through trace amounts of laccase catalysis. These compounds can then undergo Michael addition or Schiff base reactions with the amino groups on the chitosan surface to achieve co-precipitation modification. The modified microsphere material contains abundant hydroxyl and amino groups, which can chelate with rare earth ions to achieve adsorption.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. This invention employs a nano-oxide co-doping method to prepare hydrophilic PVDF / oxide microspheres as the matrix material for subsequent co-deposition by adjusting the amount of PVDF. This avoids the drawback of reduced water permeability after modification of traditional PVDF membrane materials. Furthermore, the spherical PVDF / TiO2 has a larger specific surface area that can be used for modification. The resulting PVDF / oxide composite particles also have greater application flexibility in terms of particle size. For example, they can be used to form packing columns or directly added to the solution to be treated.

[0037] 2. Chitosan, rich in hydroxyl and amino groups, is a natural and green adsorbent for rare earth metal ions. However, it is soluble in acidic environments, making post-adsorption recovery difficult. This invention addresses this issue by co-depositing chitosan and polyphenolic organic compounds onto the surface of PVDF / oxide microspheres under laccase catalysis. This stabilizes the chitosan, solving the recycling problem. Simultaneously, the carboxyl or hydroxyl functional groups in the polyphenolic organic compounds promote adsorption.

[0038] 3. The PVDF / oxide composite particles of the present invention have uniform particle size, stable chemical properties, and abundant functional groups such as carboxyl, amino, and hydroxyl groups on their surface. They can effectively recover rare earth ions from rare earth solutions and have broad application prospects.

[0039] 4. The PVDF / oxide composite particles of this invention are easy to recover. After adsorption treatment, the PVDF / oxide composite particles can be recovered through simple solid-liquid separation methods, such as filtration, and then further processed using H... + The competitive adsorption can achieve the desorption of rare earth ions, thus realizing the recycling and regeneration of PVDF / oxide composite particles, which has good recycling value.

[0040] 5. Compared with traditional PVDF films or PVDF inorganic doped films, the PVDF / oxide composite particles of the present invention have the advantage of good stability and are more convenient and flexible in application.

[0041] 6. The PVDF / oxide composite particles of the present invention have regular geometry, stable properties, can be recycled and reused, have high adsorption efficiency, and the main raw materials are green and environmentally friendly and will not cause secondary pollution. They can efficiently and greenly recover rare earth resources from rare earth solutions.

[0042] In summary, the PVDF / oxide composite particles prepared by this invention have the advantages of being environmentally friendly, having excellent adsorption effect, and being easy to recycle. Attached Figure Description

[0043] Figure 1 This is a flowchart illustrating the preparation process of the CS / GA-PVDF / TiO2 composite particles in Example 1 of the present invention.

[0044] Figure 2 This is a schematic diagram illustrating the synthesis principle of the CS / GA-PVDF / TiO2 composite particles in Example 1 of the present invention.

[0045] Figure 3 This is a digital photograph of the PVDF / TiO2 microspheres synthesized in Example 1 of the present invention.

[0046] Figure 4 Figure 1 shows the contact angle of pure PVDF microspheres (top) and PVDF / TiO2 microspheres (bottom) prepared in Example 1 of this invention.

[0047] Among them, without the addition of nano-TiO2 blend modification, PVDF microspheres exhibited good hydrophobicity, with the contact angle of PVDF microspheres with water decreasing only from the initial 90.59° to 86.61° in 144s; while after the addition of nano-TiO2 blend modification, the contact angle of PVDF / TiO2 microspheres with water decreased from the initial 42.68° to 24.93° within 36 seconds, exhibiting good hydrophilicity.

[0048] Figure 5 This is a digital photograph of the CS / GA-PVDF / TiO2 composite particles synthesized in Example 1 of the present invention.

[0049] Figure 6 The infrared spectra of the CS / GA-PVDF / TiO2 composite particles synthesized in Example 1 of this invention before and after adsorption are shown.

[0050] Among them, at 1540cm -1 and 1074cm -1 These correspond to the peak positions of the amide bond (CN) and epoxy group (COC), respectively, demonstrating that chitosan and gallic acid were successfully co-deposited and modified on the surface of PVDF / TiO2 microspheres. The fact that the peak positions did not change before and after adsorption indicates the relative stability of the adsorbent material. However, -COO - The position of the symmetric stretching vibration peak changed from 1408 cm⁻¹ before adsorption. -1 dropped to 1386cm -1 The bending vibration peak position of amino group (-NH2) changed from 1643 cm⁻¹ before adsorption. -1 dropped to 1596cm -1 The position of the hydroxyl (C-OH) stretching vibration peak changed from 1184 cm⁻¹ before adsorption. -1 Dropped to 1165cm -1 And within 3100–3600cm -1 The peak intensity of the range decreased significantly after adsorption, indicating that the adsorption process mainly involved chelation between amino, carboxyl, and hydroxyl groups and rare earth ions.

[0051] Figure 7 The results are SEM-EDS of the CS / GA-PVDF / TiO2 composite particles synthesized in Example 1 of this invention.

[0052] Figure 8 This is a digital photograph of the CS / GA-PVDF / TiO2 composite particles synthesized in Comparative Example 3 of this invention.

[0053] Figure 9 This is a digital photograph of the experimental phenomenon observed in Comparative Example 4, where the mixed slurry was dropped into deionized water using a pipette. Detailed Implementation

[0054] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0055] Unless otherwise specified, the raw materials used in the following specific examples are all commercially available products and are analytical grade reagents.

[0056] Example 1

[0057] The preparation process of the CS / GA-PVDF / TiO2 composite particles in this embodiment includes the following steps:

[0058] (1) PEG (relative molecular weight 1000-3000), nano-TiO2 powder (particle size 10-25 nm), and PVDF (relative molecular weight 400,000-600,000) were added sequentially to DMAc solvent. After stirring in a 70℃ water bath for 4 hours, the mixture was allowed to stand for 12 hours to obtain a homogeneous slurry. The slurry was then pipetted into deionized water and soaked for 6 hours (the water was changed every 2 hours during this period) to obtain PVDF / TiO2 microspheres (see [link to product description]). Figure 3 The microspheres are white in appearance and have a relatively uniform particle size, mainly concentrated in the range of 2 to 3 mm.

[0059] The mixed slurry contains 9 wt% PVDF, 3 wt% TiO2 powder, 6 wt% PEG, and 82 wt% DMAc.

[0060] (2) Dissolve 1000 mg chitosan in 200 ml of NaAc-Hac buffer solution (pH = 5.0), then add 1000 mg gallic acid and 10 mg laccase and stir until homogeneous to obtain a mixture; then add 500 mg PVDF / TiO2 microspheres to the mixture, stir for 1 h, filter, rinse with plenty of deionized water, and vacuum dry to obtain CS / GA-PVDF / TiO2 composite particles (see...). Figure 5 (It has a light yellow appearance) and is ready for use.

[0061] See Figure 7 The CS / GA-PVDF / TiO2 composite particles obtained in this embodiment have a relatively regular shape, appearing spherical when viewed up close. The overall characteristic elements, such as F and Ti, are relatively evenly distributed, and the surface is relatively rough with obvious wrinkles, which provides a larger surface area for adsorption.

[0062] A 100 mg / L neodymium solution (based on neodymium ion concentration) was prepared using neodymium nitrate hexahydrate Nd(NO3)3·6H2O. 100 mg of CS / GA-PVDF / TiO2 composite particles were placed in 100 ml of the neodymium solution and stirred for 5 h. A sample was then taken to determine the Nd ion concentration in the solution. The adsorption capacity was calculated using equation (1). (Note: C0 is the initial concentration in the solution, C...) t (where V is the rare earth concentration in the solution after adsorption, V is the solution volume, and m is the mass of adsorbent added.)

[0063]

[0064] Calculations show that the adsorption capacity of the CS / GA-PVDF / TiO2 composite particles for rare earth neodymium is 65.8 mg / g, indicating a good adsorption effect.

[0065] Comparative Example 1

[0066] Repeat Example 1, except that nano-TiO2 is not added in step (1).

[0067] Calculations showed that the final adsorption capacity of the CS / GA-PVDF composite particles for rare earth neodymium was 2.1 mg / g, indicating poor adsorption performance. A possible reason is that PVDF has hydrophobic properties, making it difficult for gallic acid to adhere to the surface for co-deposition modification, and the color change after modification was not significant.

[0068] Comparative Example 2

[0069] Repeat Example 1, except that in step (2), chitosan is not added and gallic acid is added at a rate of 2000 mg.

[0070] Calculations showed that the adsorption capacity of GA-PVDF / TiO2 composite particles for rare earth neodymium was 17.3 mg / g, indicating poor adsorption performance. This suggests that gallic acid also has a certain adsorption capacity for rare earth ions, but chitosan plays a major role in the adsorption process of rare earth ions.

[0071] Comparative Example 3

[0072] Repeat Example 1, except that laccase is not added in step (2).

[0073] See Figure 8 The resulting CS / GA-PVDF / TiO2 composite particles were dark gray, which may be due to the low degree of polymerization caused by the absence of laccase, resulting in a dark gray surface color with no obvious color change. However, the product with added laccase showed a clear color reaction, indicating that laccase is important for co-deposition modification.

[0074] Calculations showed that the adsorption capacity of the CS / GA-PVDF / TiO2 composite particles without laccase was only 13.0 mg / g for rare earth neodymium, which was low. This was mainly due to the insufficient amount of chitosan on its surface, which could not provide more adsorption sites for rare earth ions.

[0075] Comparative Example 4

[0076] Example 1 was repeated, except that the content of PVDF in the mixed slurry was 4 wt%, the content of TiO2 powder was 3 wt%, the content of PEG was 6 wt%, and the content of DMAc was 87 wt%.

[0077] Under these conditions, the mixed slurry has excessive fluidity, making it difficult to form uniform spheres when dropped into the solution. Due to its poor viscosity, phenomena such as "elongation" and "stringing" will occur in the solution. See [link to relevant documentation]. Figure 9 During the experiment, it was found that the viscosity of the mixed slurry was low, making it difficult to control its free dripping.

[0078] Comparative Example 5

[0079] The CS / GA-PVDF / TiO2 composite particles after neodymium adsorption in Example 1 were eluted with 0.1 mol / L HCl, dried, and then added to a freshly prepared rare earth solution (same as in Example 1) for recycling tests. The results showed that after 3 cycles, the adsorption capacity of CS / GA-PVDF / TiO2 for neodymium still exceeded 60 mg / g, and after 5 cycles, the adsorption capacity of CS / GA-PVDF / TiO2 for neodymium still exceeded 55 mg / g, indicating that the adsorbent material can be easily recovered and recycled.

[0080] As can be seen, in the CS / GA-PVDF / TiO2 composite particles obtained by co-deposition modification in this invention, chitosan is more firmly fixed on the surface of the microspheres, thus enabling the possibility of recycling.

[0081] Example 2

[0082] Example 1 was repeated, except that the content of PVDF in the mixed slurry was 5 wt%, the content of TiO2 powder was 3 wt%, the content of PEG was 6 wt%, and the content of DMAc was 86 wt%.

[0083] During the experiment, it was observed that the slurry with good fluidity could drop and form spheres effectively. Calculations showed that the CS / GA-PVDF / TiO2 composite particles adsorbed 63.2 mg / g of rare earth neodymium ions, indicating good adsorption performance.

[0084] Example 3

[0085] Example 1 was repeated, except that the content of PVDF in the mixed slurry was 12 wt%, the content of TiO2 powder was 3 wt%, the content of PEG was 6 wt%, and the content of DMAc was 79 wt%.

[0086] During the experiment, it was observed that the slurry with good fluidity could drop and form spheres effectively. Calculations showed that the CS / GA-PVDF / TiO2 composite particles adsorbed 60.7 mg / g of rare earth neodymium ions, indicating good adsorption performance.

[0087] Comparative Example 5

[0088] Example 1 was repeated, except that the content of PVDF in the mixed slurry was 13 wt%, the content of TiO2 powder was 3 wt%, the content of PEG was 6 wt%, and the content of DMAc was 78 wt%.

[0089] During the experiment, it was found that the viscosity of the mixed slurry was high, making it difficult to achieve free flow and pelletizing.

[0090] Comparative Example 6

[0091] Example 1 was repeated, except that the content of PVDF in the mixed slurry was 9 wt%, the content of TiO2 powder was 0.5 wt%, the content of PEG was 6 wt%, and the content of DMAc was 84.5 wt%.

[0092] During the experiment, it was found that the microspheres had poor hydrophilicity, resulting in poor co-deposition modification effect of chitosan and gallic acid. The adsorption capacity of the particles for rare earth neodymium ions was calculated to be 21.5 mg / g, which is a general adsorption effect. The reason may be that the poor hydrophilicity of the microsphere surface restricts the polymerization of gallic acid on the surface.

[0093] Comparative Example 7

[0094] Example 1 was repeated, except that the content of PVDF in the mixed slurry was 9 wt%, the content of TiO2 powder was 1 wt%, the content of PEG was 6 wt%, and the content of DMAc was 84 wt%.

[0095] The experiment revealed that the slurry had good fluidity, allowing it to drip and form microspheres that exhibited a certain degree of hydrophilicity. Calculations showed that the CS / GA-PVDF / TiO2 composite particles adsorbed 61.4 mg / g of rare earth neodymium ions, demonstrating excellent adsorption performance.

[0096] It is evident that by controlling the amount of nano-titanium dioxide added, the hydrophilicity of the resulting microspheres can be effectively adjusted, and CS / GA-PVDF / TiO2 composite particles with good adsorption capacity can be obtained; however, considering factors such as cost, the amount of nano-titanium dioxide added should not be too high.

[0097] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

Claims

1. A method for preparing surface-modified PVDF / oxide composite particles, characterized in that, Includes the following steps: S1. Mix PVDF, nano-oxide powder and organic solvent evenly, let stand and degas to obtain a blended slurry; The nano-oxide powder includes one or more of nano-titanium dioxide powder and nano-silica powder; the PVDF content in the blended slurry is 5-12 wt%, the nano-oxide powder content is 1-5 wt%, and the organic solvent content is 77-94 wt%. S2. The blended slurry is dropped into water to form microspheres. After the organic solvent is removed, PVDF / oxide microspheres are obtained. S3. After immersing the PVDF / oxide microspheres in the mixed solution, the solid and liquid are separated, washed with water, and dried to obtain surface-modified PVDF / oxide composite particles. The preparation method of the mixture includes the following steps: adding chitosan, polyphenolic organic matter and laccase to a buffer solution with a pH of 4-5.5, mixing evenly, and then obtaining the mixture.

2. The preparation method according to claim 1, characterized in that, In S1, the PVDF content in the blended slurry is 7-10 wt%, the nano-oxide powder content is 2-3 wt%, and the organic solvent content is 81-91 wt%.

3. The preparation method according to claim 1, characterized in that, In S1, the blended slurry also contains PEG, with a PEG content of 4-6 wt%.

4. The preparation method according to claim 3, characterized in that, The relative molecular weight of the PEG is 1000-5000.

5. The preparation method according to claim 1, characterized in that, In S1, the relative molecular weight of PVDF is 300,000 to 700,000.

6. The preparation method according to claim 1, characterized in that, In S1, the particle size of the nano-oxide powder is 1-100 nm.

7. The preparation method according to claim 6, characterized in that, In S1, the particle size of the nano-oxide powder is 5-50 nm.

8. The preparation method according to claim 7, characterized in that, In S1, the particle size of the nano-oxide powder is 10-30 nm.

9. The preparation method according to claim 1, characterized in that, In S1, the organic solvent is DMAc.

10. The preparation method according to claim 1, characterized in that, In S1, PVDF, nano-oxide powder and organic solvent are stirred at 65-75℃ for 4-6 hours, then allowed to stand and degas to obtain a blended slurry.

11. The preparation method according to claim 10, characterized in that, The settling time is 4-18 hours.

12. The preparation method according to claim 1, characterized in that, In S2, the blended slurry is dripped into water using a pipette or syringe to form microspheres.

13. The preparation method according to claim 1, characterized in that, In S2, the method for removing organic solvents includes the following steps: soaking the microspheres in water for 4-10 hours, changing the water every 1-3 hours during this period.

14. The preparation method according to claim 1, characterized in that, In step S3, the PVDF / oxide microspheres are placed in a mixed solution and stirred for 0.5-3 hours. Then, solid-liquid separation, water washing, and drying are performed to obtain surface-modified PVDF / oxide composite particles.

15. The preparation method according to claim 14, characterized in that, The washing process involves multiple rinses.

16. The preparation method according to claim 14, characterized in that, The drying method is vacuum drying.

17. The preparation method according to claim 1, characterized in that, In S3, the mass ratio of PVDF / oxide microspheres, chitosan, polyphenolic organic matter and laccase is 400-600: 800-1200: 800-1200: 5-15.

18. The preparation method according to claim 17, characterized in that, The mass ratio of PVDF / oxide microspheres, chitosan, polyphenolic organic matter and laccase is 450-550: 900-1100: 900-1100: 8-12.

19. The preparation method according to claim 1, characterized in that, In S3, the preparation method of the mixture includes the following steps: dissolve chitosan in a buffer solution with a pH of 4-5.5, then add polyphenolic organic matter and laccase, and stir evenly to obtain the mixture.

20. The preparation method according to claim 19, characterized in that, The buffer solution is a NaAc-HAc buffer solution.

21. The preparation method according to claim 1, characterized in that, The polyphenolic organic compounds include one or more of dopamine, tannic acid, and gallic acid.

22. A surface-modified PVDF / oxide composite particle, characterized in that, It is prepared by the preparation method according to any one of claims 1-21.

23. The application of the surface-modified PVDF / oxide composite particles as described in claim 22, characterized in that, The surface-modified PVDF / oxide composite particles are used as adsorbent materials to adsorb rare earth ions from the solution.

24. The application of the surface-modified PVDF / oxide composite particles according to claim 23, characterized in that, In application, simply mix the surface-modified PVDF / oxide composite particles with the solution to be adsorbed and stir.

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