Zwitterionic modified titanium dioxide and preparation method thereof

Abstract

The invention discloses zwitter-ion modified titanium dioxide and a preparation method thereof. The titanium dioxide comprises a titanium dioxide matrix and a coating layer located on the surface of the titanium dioxide matrix, the coating layer comprises a Zn < 2 + >-amino acid type zwitter-ion complex film layer, and the Zn < 2 + >-amino acid type zwitter-ion complex film layer is generated in situ through amino acid type zwitter-ions and a Zn source; the amino acid type zwitterions are selected from at least one compound meeting the following structural general formula: R '-CO-NR-CH (X)-COO-M < + >; wherein R'is an alkyl chain of C8-C18. The modified titanium dioxide provided by the invention still has relatively good dispersion stability and antibacterial property under relatively high humidity and relatively wide pH range, the covering power of the titanium dioxide is further improved due to the improvement of the dispersion stability, and the problem of collaborative optimization of the titanium dioxide in the aspects of dispersion stability, covering power and antibacterial property in the prior art is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of titanium dioxide preparation technology, specifically relating to a zwitterionic modified titanium dioxide and its preparation method. This modified titanium dioxide can significantly improve the dispersion stability, optical hiding power, and antibacterial properties of coatings, and is suitable for use in architectural coatings, industrial anti-corrosion coatings, marine coatings, and medical antibacterial coatings. Background Technology

[0002] Traditional titanium dioxide (TiO2) is prone to agglomeration in coating applications due to its high surface energy, resulting in sedimentation and uneven gloss of the coating film after a storage period of ≤3 months. Existing silane coupling agent modifications (such as KH-570) can improve dispersibility, but they are sensitive to humidity (>60% failure) and are only applicable to a narrow pH range. Titanium dioxide's hiding power depends on its high refractive index (2.71 for rutile), but conventional inorganic coatings (such as SiO2 / Al2O3) reduce the refractive index to ≤2.65, resulting in a 10-15% loss of hiding power. Ordinary TiO2 requires UV excitation to exhibit antibacterial properties, while commonly used Ag loading modification not only increases costs by more than 30% but also presents metal ion migration issues. Although the betaine-type zwitterionic modification used in patent CN110845032A improves dispersibility, its quaternary ammonium structure is easily degraded at pH>9 and has an antibacterial rate of <70% against Gram-negative bacteria. Existing technologies have failed to effectively solve the synergistic optimization problem of titanium dioxide in terms of dispersion stability, hiding power, and antibacterial properties. Summary of the Invention

[0003] The purpose of this invention is to provide a zwitterionic modified titanium dioxide and its preparation method to overcome the shortcomings of the prior art.

[0004] The objective of this invention is achieved through the following technical solution: The first aspect of this application provides a zwitterionic modified titanium dioxide, the titanium dioxide comprising a titanium dioxide matrix and a coating layer located on the surface of the titanium dioxide matrix; The coating layer includes Zn 2+ -Amino acid-type zwitterionic complex film layer, wherein Zn 2+ -The amino acid zwitterionic complex membrane is generated in situ using amino acid zwitterionic and Zn sources; The amino acid-type zwitterion is selected from at least one compound that satisfies the following general structural formula: R'–CO–NR–CH(X)–COO - M + ; Where: R' is C8~C 18 alkyl chain.

[0005] Preferably, the titanium dioxide matrix is ​​anatase titanium dioxide or rutile titanium dioxide with a particle size of 200~300nm.

[0006] Preferably, X is selected from H, CH3, or CH2CH2COOH; M is selected from Na. + K + NH4 + or TEA + R is selected from H or CH3.

[0007] Preferably, the coating layer further includes layers located on the Zn 2+ - An inorganic coating layer inside the membrane of an amino acid-type zwitterionic complex.

[0008] Preferably, the zinc source is at least one selected from zinc nitrate, zinc chloride, zinc sulfate, or zinc acetate.

[0009] Preferably, the amount of zinc source, calculated as zinc ions, is 0.1% to 1% of the mass of the titanium dioxide matrix; The amount of the amino acid-type zwitterion used is 0.1-2% of the mass of the titanium dioxide matrix.

[0010] The second aspect of this application provides a method for preparing zwitterionic modified titanium dioxide as described above, comprising the following steps: S1. Unmodified titanium dioxide is dispersed in a pH buffer solution containing carboxylate groups and pretreated to expose the Ti-OH sites on the surface. S2. An amino acid-type zwitterion is added to react with the titanium dioxide to form a Ti-OOC- coordination bond; S3. Add a zinc source and perform a complexation reaction with amino acid zwitterionic residues to obtain Zn. 2+ -Amino acid type zwitterionic complex membrane layer.

[0011] Preferably, the pH buffer solution in step S1 is selected from at least one of citric acid buffer solution, tartaric acid buffer solution, oxalic acid buffer solution, EDTA buffer solution or acetate buffer solution; the concentration of the buffer in the pH buffer solution is 0.01~0.1 mol / L; The pH of the pH buffer solution is 5.5~6.5; the pretreatment is ultrasonication at 50~70℃ for 0.5~1.5h, with an ultrasonic power of 200~400W.

[0012] Preferably, the reaction temperature in step S2 is 50~70℃, and the reaction time is 2~5h.

[0013] Preferably, the reaction temperature in step S3 is 50~70℃, and the reaction time is 1~3h.

[0014] The modified titanium dioxide provided in this application still exhibits good dispersion stability and antibacterial properties under high humidity and a wide pH range. The improved dispersion stability further enhances the hiding power of the titanium dioxide, effectively solving the problem of synergistic optimization of dispersion stability, hiding power and antibacterial properties of titanium dioxide in the prior art. Detailed Implementation

[0015] This application provides a zwitterionic modified titanium dioxide, comprising a titanium dioxide matrix and a coating layer located on the surface of the titanium dioxide matrix.

[0016] The coating layer includes Zn 2+ -Amino acid-type zwitterionic complex film layer, this Zn 2+ -The amino acid zwitterionic complex membrane is generated in situ using amino acid zwitterionic and Zn sources; Amino acid zwitterions are selected from at least one compound that satisfies the following general structural formula: R'–CO–NR–CH(X)–COO - M + ; Where: R' is C8~C 18 alkyl chain.

[0017] This amino acid-type zwitterion links a hydrophobic long-chain alkyl group (R') to the amino group of a natural amino acid via an amide bond. The long-chain alkyl group (R') can be straight-chain or branched. NR–CH(X)–COO - Derived from natural amino acids, such as glycine, sarcosine, glutamic acid, and alanine. Therefore, preferably, X is selected from H, CH3, or CH2CH2COOH, etc., and R is selected from H or CH3, etc.; M + Cations that can be selected from conventional zwitterions, such as Na + K + NH4 + or TEA + wait.

[0018] The titanium dioxide of this application is obtained by composite modification with amino acid-type zwitterions and a Zn source. The carboxyl group in the α-amino acid-type zwitterion used in this application can react with the titanium dioxide matrix Ti. 4+It forms a strong Ti-OOC coordination bond with a bond energy >200 kJ / mol, which is higher than the Si-O-Ti bond energy of silane coupling agents (approximately 150 kJ / mol). This results in a more stable structure and greater resistance to hydrolysis. It can firmly bind amino acid-type zwitterions to the titanium dioxide matrix surface, preventing their detachment. Even under high humidity, the amino acid-type zwitterions can fully exert their effect, improving the product's storage stability. The pH-responsive characteristics of the amino acid-type zwitterions allow it to form a dynamic charge buffer layer on the TiO2 surface: in acidic environments, -NH3... + -NH2 + Protonation inhibits particle flocculation in alkaline environments. Ionization generates electrostatic repulsion, effectively preventing titanium dioxide agglomeration over a wide pH range and improving its dispersion stability. Furthermore, the long alkyl chains (C8-C18) in the amino acid-type zwitterion prevent particle approach through steric hindrance, enhancing compatibility with coating resins and improving the stability of titanium dioxide in coating resins.

[0019] In addition to amino acid zwitterions, this application also utilizes a zinc source to form a structurally stable chelate with the amino acid zwitterion in situ (the bond energy between the zinc ion and the carboxyl group is relatively strong). It tends to complex with carboxyl groups to form structurally stable complexes, thus ensuring that Zn ions are also stably bound to the titanium dioxide matrix surface. Compared to directly using Zn ions for inorganic coating, this effectively prevents Zn ion migration. 2+ -Amino acid-based zwitterionic chelates can achieve sustained-release antibacterial effects. The positive charge on the surface of the chelate (-NH3) + -NH2 + It can disrupt the bacterial cell membrane potential and the lipid solubility of zwitterionic fatty chains (fatty chains can forcefully insert into the bacterial cell membrane through hydrophobic interactions, disrupting the ordered structure of the lipid bilayer, and ultimately destroying the membrane integrity by forming channels or causing membrane disintegration, causing leakage of cell contents, thereby leading to rapid bacterial death). The coordinated action of these three bactericidal mechanisms significantly improves the bactericidal performance, and it has broad-spectrum bactericidal performance against common Gram-positive and Gram-negative bacteria.

[0020] Furthermore, the pH buffering capacity (pKa 3.5~9.0) of amino acid-type zwitterions ensures the stability of the modified titanium dioxide application system over a wide pH range (3~11). The hydrophobic effect of long-chain alkyl groups (C8~C18) effectively inhibits water penetration, improving the coating's weather resistance. The hydrophobic / hydrophilic segment ratio (1~3:1) in the molecule optimizes the interfacial bonding with different resin matrices. The structural integration of antibacterial components and dispersants avoids performance attrition in traditional compounding processes. Zn is complexed using the carboxyl groups on the surface of amino acid-type zwitterions. 2+ It reduces costs by more than 50% compared to nano-silver, and the complex achieves Zn2+ Slow-release oxidation improves the antibacterial durability of modified titanium dioxide. Furthermore, Zn... 2+ Compared to other metal ions such as copper ions, they do not have an adverse effect on the hue of titanium dioxide.

[0021] Therefore, the modified titanium dioxide provided in this application still exhibits good dispersion stability and antibacterial properties under high humidity and a wide pH range. The improved dispersion stability further enhances the hiding power of titanium dioxide, effectively solving the problem of synergistic optimization of dispersion stability, hiding power and antibacterial properties of titanium dioxide in the prior art.

[0022] Preferably, the titanium dioxide matrix can be anatase titanium dioxide or rutile titanium dioxide. Furthermore, the selected titanium dioxide matrix has a particle size of 200~300nm to prevent large particles from causing uneven coating and affecting the modification effect.

[0023] More preferably, the amino acid-type zwitterion is selected from at least one of sodium stearoyl glutamate (potassium), sodium cocoyl glutamate (potassium), sodium cocoyl methyl alanine (potassium), sodium cocoyl glycinate (potassium), sodium lauroyl sarcosinate (potassium), sodium lauroyl alanine (potassium), etc. This compound has high compatibility with the coating matrix, and is inexpensive and easy to obtain.

[0024] The zinc source is selected from one of zinc nitrate, zinc chloride, zinc sulfate, or zinc acetate.

[0025] Preferably, the amount of zinc source, calculated as zinc ions, is 0.1-1% of the mass of the titanium dioxide matrix; the amount of amino acid-type zwitterions is 0.1-2% of the mass of the titanium dioxide matrix. Within this range, zinc ions and amino acid-type zwitterions can fully complex, while effectively exerting their respective functions without wasting resources.

[0026] Preferably, to enhance the performance of titanium dioxide, the coating layer further includes a layer located on Zn. 2+ - Inorganic coating layers inside the membrane of amino acid-type zwitterionic complexes, such as silicon-aluminum coating layers, single aluminum coating layers, etc.

[0027] This application also provides a method for preparing zwitterionic modified titanium dioxide as described above, comprising the following steps: S1. Unmodified titanium dioxide is dispersed in a pH buffer solution containing carboxyl groups and pretreated to expose the Ti-OH sites on the surface so that it can fully combine and react with the carboxyl groups in the amino acid zwitterions. The buffer (carboxylate ions) in the pH buffer solution can undergo a coordination reaction with the titanium (Ti) ions on the outermost layer of the TiO2 surface. This reaction breaks the original Ti-O-Ti or Ti-OH bonds, thereby creating new, more reactive Ti sites. At the same time, the pH buffer solution can maintain the reaction system within a stable pH range, which is more conducive to the reaction.

[0028] S2. An amino acid-type zwitterion is added and reacts with the titanium dioxide matrix. The carboxyl group in the amino acid-type zwitterion reacts with Ti. 4+ Its function is to form Ti-OOC-coordinate bonds; S3. Add a zinc source to induce a complexation reaction with amino acid zwitterionic residues. The amino acid residues react with Zn. 2+ The chelate formed yields Zn 2+ -Amino acid type zwitterionic complex membrane layer.

[0029] This application first adds amino acid-type zwitterions to the titanium dioxide slurry. The amino acid-type zwitterions contain carboxyl groups to form bridges, which can chelate the zinc ions added later.

[0030] Preferably, the pH buffer solution is selected from at least one of citric acid buffer solution, tartaric acid buffer solution, oxalic acid buffer solution, EDTA buffer solution or acetic acid buffer solution. Of course, other buffer solutions with the same function can also be used.

[0031] As will be understood by those skilled in the art, buffer solutions generally contain an acid and its conjugate base, such as a citric acid buffer solution containing citric acid and sodium citrate.

[0032] Preferably, the concentration of the buffer in the pH buffer solution is 0.01~0.1 mol / L.

[0033] Preferably, the pH of the pH buffer solution in step S1 is 5.5-6.5; the pretreatment involves sonication at 50-70°C for 0.5-1.5 hours with an ultrasonic power of 200-400W. Ultrasound can further break down the soft aggregates formed between titanium dioxide particles by van der Waals forces, thus exposing the sites.

[0034] Preferably, the concentration of titanium dioxide in the pH buffer solution in step S1 is 200~300g / L.

[0035] As those skilled in the art will understand, high temperature can promote the reaction, and sufficient reaction time can also ensure a complete reaction. Preferably, the reaction temperature in step S2 is 50~70℃, and the reaction time is 2~5h. The reaction temperature in step S3 is 50~70℃, and the reaction time is 1~3h.

[0036] In step S3, the zinc source is preferably added slowly in an aqueous solution with a concentration of 0.05~0.2mol / L; the addition rate is preferably 0.2~0.8mL / min, so as to fully complex the zinc source with the zwitterions.

[0037] As those skilled in the art will understand, after the formation of the complex in step S3, the process further includes a solid-liquid separation step (which may be performed by centrifugation, pressure filtration, etc.) to remove unreacted salts, as well as a washing and drying step.

[0038] The preferred washing solution is an aqueous solution of ethanol, with a volume ratio of ethanol to water of 1:3, which can effectively wash away both inorganic salts and organic substances.

[0039] Vacuum drying is preferred for drying, with a temperature of 70~90℃.

[0040] The titanium dioxide materials obtained in the various examples and comparative examples were used to establish a conventional high-gloss latex paint system for performance evaluation. The high-gloss latex paint system included 24 parts deionized water, 0.4 parts dispersant, 0.2 parts wetting agent, 0.2 parts defoamer, 4 parts film-forming agent, 0.2 parts cellulose, 18 parts titanium dioxide, 2 parts thickener, and 60 parts styrene-acrylic emulsion. The above components were stirred at 1500 r / min for 30 min until they were mixed evenly.

[0041] The latex paint systems corresponding to each embodiment and comparative example were tested and evaluated. The dispersion stability of titanium dioxide was tested, and the latex paint systems corresponding to each embodiment and comparative example were evaluated. Stability was tested using the 7-day sedimentation rate, and the percentage increase in centrifugal sedimentation rate of each modified titanium dioxide compared to the unmodified titanium dioxide was calculated. The 60° reflectance of the modified and unmodified titanium dioxide (titanium dioxide) in each embodiment or comparative example was measured using a gloss meter as gloss, and the percentage increase in gloss of each modified titanium dioxide compared to the unmodified titanium dioxide was calculated. The hiding power (comparative ratio) of the modified titanium dioxide formulated into latex paint panels in each embodiment or comparative example was measured using a colorimeter. Simultaneously, the contrast ratio of the unmodified titanium dioxide (titanium dioxide) was measured to be 0.92.

[0042] Example 1 The preparation steps of zwitterionic modified titanium dioxide are as follows: S1. Surface activation: Rutile TiO2 was dispersed in a citrate-sodium citrate buffer solution (0.05 mol / L) at pH 6.0, with a titanium dioxide concentration of 200 g / L. The solution was ultrasonically treated at 60 °C for 1 h (300 W) to expose the Ti-OH sites on the surface. S2. Zwitterion modification: Sodium cocoyl glutamate was added at a mass fraction of 0.5% of TiO2, and the reaction was carried out at 60℃ for 4 hours to form Ti-OOC- coordination bonds; S3. Antibacterial functionalization: Add 0.5% Zn(NO3)2 solution dropwise at a rate of 0.5 mL / min, age at 60℃ for 2 h, and then centrifuge; S4. Post-treatment: Wash the solid phase three times with ethanol / water (volume ratio 1:3) and dry it under vacuum at 80℃ to obtain the modified product.

[0043] Results: The dispersion stability (centrifugal sedimentation rate) of the waterborne coating was 80% higher than that of unmodified TiO2 (unmodified TiO2 in Examples 1-3 and Comparative Examples 1-6 refers to titanium dioxide that has not undergone zwitterionic modification, consistent with rutile TiO2 in step S1, with a sedimentation rate of 60%), the 60° gloss was increased by 5%, the hiding power (comparative ratio) reached 0.93 (0.92 for unmodified titanium dioxide), and the antibacterial rate against Gram-positive Escherichia coli reached 97.8%.

[0044] Example 2 The preparation steps of zwitterionic modified titanium dioxide are as follows: S1. Surface activation: Rutile TiO2 was dispersed in a citrate-sodium citrate buffer solution at pH 6.0 (0.05 mol / L citrate-sodium citrate concentration), with a titanium dioxide concentration of 200 g / L in the buffer solution. The solution was ultrasonically treated at 60 °C for 1 h (300 W power) to expose the Ti-OH sites on the surface. S2. Zwitterion modification: Add sodium stearoyl glutamate at 1% of the mass fraction of TiO2, react at 60℃ for 4h to form Ti-OOC- coordination bonds; S3. Antibacterial functionalization: Add 1% Zn(NO3)2 solution at a rate of 0.5 mL / min, age at 60℃ for 2 h, and then centrifuge; S4. Post-treatment: Wash the solid phase three times with ethanol / water (volume ratio 1:3) and dry it under vacuum at 80℃ to obtain the modified product.

[0045] Results: The dispersion stability (centrifugal sedimentation rate) of the waterborne coating was improved by 90% compared with that of the unmodified TiO2, the 60° gloss was improved by 15%, the hiding power (contrast ratio) reached 0.94 (0.92 for the unmodified coating), and the antibacterial rate against Gram-positive bacteria Escherichia coli reached 98.5%.

[0046] Example 3 The preparation steps of zwitterionic modified titanium dioxide are as follows: S1. Surface activation: TiO2 was dispersed in an acetate-sodium acetate buffer solution at pH 6.0 (acetic acid-sodium acetate concentration of 0.1 mol / L), with a titanium dioxide concentration of 200 g / L in the buffer solution. The solution was ultrasonically treated at 60 °C for 1 h (power 300 W) to expose the Ti-OH sites on the surface. S2. Zwitterion modification: Sodium cocoyl methyl alanine was added at a concentration of 0.5% of TiO2 mass fraction, and the reaction was carried out at 60℃ for 4 hours to form Ti-OOC- coordination bonds; S3. Antibacterial functionalization: Add 0.5% Zn(NO3)2 solution dropwise at a rate of 0.5 mL / min, age at 60℃ for 2 h, and then centrifuge; S4. Post-treatment: Wash the solid phase three times with ethanol / water (volume ratio 1:3) and dry it under vacuum at 80℃ to obtain the modified product.

[0047] Results: The dispersion stability (centrifugal sedimentation rate) of the waterborne coating was improved by 85% compared with that of the unmodified TiO2, the 60° gloss was improved by 10%, the hiding power (contrast ratio) reached 0.95 (0.92 for the unmodified coating), and the antibacterial rate against Gram-positive bacteria Escherichia coli reached 96.7%.

[0048] Comparative Example 1 Modification was performed using 0.5% aminopropyltriethoxysilane. When aminopropyltriethoxysilane was added during the powdering of titanium dioxide, significant sedimentation occurred after 7 days of storage, with a sedimentation rate of 20%. The 60° gloss decreased by 10%, and the hiding power (contrast ratio) was 0.85 (0.92 for unmodified). It had no significant bactericidal effect on Gram-positive bacteria Escherichia coli, with a bactericidal rate of 23.5%.

[0049] Comparative Example 2 Modification with 0.5% polyethylene glycol (PEG) was performed. PEG was added during the preparation of titanium dioxide powder. After 7 days of storage, significant sedimentation occurred with a sedimentation rate of 18%. The 60° gloss decreased by 5%, and the hiding power (contrast ratio) was 0.82 (0.92 for unmodified). It had no significant bactericidal effect on Gram-positive bacteria Escherichia coli, with a bactericidal rate of 21.6%.

[0050] Comparative Example 3 Modification with 0.5% trimethylolpropane, added during the powdering of titanium dioxide, improved the dispersion stability (centrifugal sedimentation rate) of waterborne coatings by 70% compared to unmodified TiO2, increased the 60° gloss by 5%, and the hiding power (contrast ratio) was 0.90 (0.92 for unmodified). It had no significant bactericidal effect on Gram-positive bacteria Escherichia coli, with a bactericidal rate of only 25.7%.

[0051] Comparative Example 4 Modification was performed using 0.5% sodium stearate, which was added during the powdering of titanium dioxide. After 7 days of storage, significant sedimentation occurred, with a sedimentation rate of 30%. The 60° gloss decreased by 15%, and the hiding power (contrast ratio) was 0.81 (0.92 for unmodified). It had no significant bactericidal effect on Gram-positive bacteria Escherichia coli, with a bactericidal rate of 35.9%.

[0052] Comparative Example 5 Compared to Example 3, only Zn ions were modified, i.e. step 2 was omitted, and everything else was the same as in Example 3.

[0053] The dispersion stability of the water-based coating is poor. Significant sedimentation occurs after 7 days of storage, with a sedimentation rate of 30%. The 60° gloss decreases by 25%, and the hiding power (contrast ratio) is 0.91 (0.92 for unmodified). It has a significant bactericidal effect on Gram-positive bacteria Escherichia coli, with a bactericidal rate of 85.8%, but this is significantly lower than that of Example 3.

[0054] Comparative Example 6 Compared with Example 3, step 3 is omitted, Zn ions are not modified, and everything else is the same as in Example 3.

[0055] The dispersion stability (centrifugal sedimentation rate) of the waterborne coating was improved by 70% compared with that of the unmodified TiO2, the 60° gloss was not significantly reduced, the hiding power (contrast ratio) was 0.91 (0.92 for the unmodified), and there was no significant bactericidal effect on Gram-positive bacteria Escherichia coli, with a bactericidal rate of 39.8%.

[0056] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A zwitterionic modified titanium dioxide, characterized in that, The titanium dioxide comprises a titanium dioxide matrix and a coating layer located on the surface of the titanium dioxide matrix; The coating layer includes Zn 2+ -Amino acid-type zwitterionic complex film layer, wherein Zn 2+ -The amino acid zwitterionic complex membrane is generated in situ using amino acid zwitterionic and Zn sources; The amino acid-type zwitterion is selected from at least one compound that satisfies the following general structural formula: R'–CO–NR–CH(X)–COO - M + ; Where: R' is C8~C 18 alkyl chain.

2. The zwitterionic modified titanium dioxide as described in claim 1, characterized in that, The titanium dioxide matrix is ​​anatase titanium dioxide or rutile titanium dioxide, with a particle size of 200~300nm.

3. The zwitterionic modified titanium dioxide as described in claim 1, characterized in that, X is selected from H, CH3, or CH2CH2COOH; M is selected from Na. + K + NH4 + or TEA + R is selected from H or CH3.

4. The zwitterionic modified titanium dioxide as described in claim 1, characterized in that, The coating layer also includes the Zn 2+ - An inorganic coating layer inside the membrane of an amino acid-type zwitterionic complex.

5. The zwitterionic modified titanium dioxide as described in claim 1, characterized in that, The zinc source is at least one selected from zinc nitrate, zinc chloride, zinc sulfate, or zinc acetate.

6. The zwitterionic modified titanium dioxide as described in claim 1, characterized in that, The amount of zinc source used, calculated as zinc ions, is 0.1% to 1% of the mass of the titanium dioxide matrix; The amount of the amino acid-type zwitterion used is 0.1-2% of the mass of the titanium dioxide matrix.

7. A method for preparing zwitterionic modified titanium dioxide as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Unmodified titanium dioxide is dispersed in a pH buffer solution containing carboxylate groups and pretreated to expose the Ti-OH sites on the surface. S2. An amino acid-type zwitterion is added to react with the titanium dioxide to form a Ti-OOC- coordination bond; S3. Add a zinc source and perform a complexation reaction with amino acid zwitterionic residues to obtain Zn. 2+ -Amino acid type zwitterionic complex membrane.

8. The method for preparing zwitterionic modified titanium dioxide as described in claim 7, characterized in that, The pH buffer solution in step S1 is selected from at least one of citric acid buffer solution, tartaric acid buffer solution, oxalic acid buffer solution, EDTA buffer solution or acetate buffer solution; the concentration of the buffer in the pH buffer solution is 0.01~0.1 mol / L; The pH of the pH buffer solution is 5.5~6.5; the pretreatment is ultrasonication at 50~70℃ for 0.5~1.5h, with an ultrasonic power of 200~400W.

9. The method for preparing zwitterionic modified titanium dioxide as described in claim 7, characterized in that, The reaction temperature in step S2 is 50~70℃, and the reaction time is 2~5h.

10. The method for preparing zwitterionic modified titanium dioxide as described in claim 7, characterized in that, The reaction temperature in step S3 is 50~70℃, and the reaction time is 1~3h.