Preparation method and application of photocatalytic composite fabric with oxidation-reduction reversible characteristics

Abstract

The application belongs to the technical field of new materials, and particularly relates to a preparation method and application of a photocatalytic composite fabric with oxidation-reduction reversible characteristics. The method comprises synthesis of an oxidation-reduction reversible crosslinking agent molecule with a high active center site, preparation of an oxide semiconductor nanoparticle doped composite coating, and preparation of the photocatalytic composite fabric. The photocatalytic composite fabric can be obtained by constructing a coating with high strength on the surface of the fabric through a simple spraying method. Compared with a photocatalytic fabric prepared by using a traditional crosslinking agent, the photocatalytic fabric has good degradation effect on organic pollutants, fast reaction rate, long service life, and is easy to be prepared on a large scale, and has a wide application prospect in the field of fabric degradation of organic pollutants.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a crosslinking agent and photocatalytic composite fabric with reversible oxidation-reduction properties and its application in the degradation of organic pollutants. Background Technology

[0002] Organic pollutants such as polycyclic aromatic hydrocarbons, dyes, and pesticides pose a significant threat to ecosystems due to their long-term presence in the environment. Photocatalytic degradation using semiconductor nanoparticles such as titanium dioxide is an effective method for pollutant treatment, offering advantages over commonly used methods like precipitation, physical adsorption, and ion exchange, including ease of use, low cost, and continuous operation. However, the direct use of powdered semiconductor nanoparticles in water presents limitations. For example, titanium dioxide tends to clump and cannot be uniformly dispersed in water; it also settles, significantly weakening the catalytic effect; and the post-treatment process is cumbersome, making separation and recovery difficult. Combining titanium dioxide with fabrics effectively solves these problems. It not only improves photocatalytic efficiency but also allows for rapid separation and recovery, facilitating the control of the photocatalytic reaction.

[0003] Crosslinking agents are crucial for the preparation of photocatalytic composite fabrics. On the one hand, it's essential to ensure the strength of the nanoparticle coating on the fibers to meet service life requirements; on the other hand, it's crucial to minimize any impact on photocatalytic activity. These are issues that require careful consideration in practical applications. Currently, commonly used crosslinking agents can be divided into inorganic and organic crosslinking agents. A significant advantage of inorganic crosslinking agents is their resistance to UV degradation, ensuring a longer service life. For example, the literature Progress in Organic Coatings, 2017, (113): 15-24 reports an inorganic crosslinking agent prepared by hydrolyzing tetraethyl orthosilicate and methyltrimethoxysilane under acidic conditions, demonstrating excellent resistance to photodegradation. However, composite fabrics prepared using inorganic crosslinking agents exhibit poor flexibility, and the coating formed on the fabric surface is hard and brittle, posing a risk of detachment from the fibers. In contrast, composite fabrics prepared using organic crosslinking agents such as polyester, polyurethane, and polyamide have the advantage of good flexibility. For example, the literature ACS Applied Materials & Interfaces, 2013, 5(9): 3697-3703 reported the use of ethyl 2-hydroxyacrylate as a crosslinking agent to load titanium dioxide onto cotton fabrics, and the resulting composite fabrics showed good catalytic effects. However, organic crosslinking agents are easily degraded under continuous ultraviolet irradiation, leading to coating failure. Therefore, it is urgent to develop novel crosslinking agents to solve the above problems and improve the photocatalytic efficiency of composite fabrics.

[0004] Combining the characteristics of the two types of crosslinking agents mentioned above to prepare novel organic-inorganic hybrid crosslinking agents holds promise for obtaining high-performance photocatalytic composite fabrics. The inorganic portion of the crosslinking agent achieves a high-strength bond between particles and fabric, while its organic portion provides flexibility to the composite fabric, resulting in a long and efficient service life. Furthermore, if redox active centers can be introduced through the organic portion of the molecule, their sensitization effect can enhance the photocatalytic activity of semiconductor nanoparticles, leading to highly efficient photocatalytic composite fabrics with reversible redox properties. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for synthesizing an organic-inorganic hybrid crosslinking agent with reversible oxidation-reduction properties, and uses this method to prepare a highly efficient photocatalytic composite fabric.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a photocatalytic composite fabric with reversible oxidation-reduction properties includes the following steps:

[0008] 1) P-phenylenediamine and 3-glycidyloxypropyltrimethoxysilane were dissolved in methanol, refluxed, and then the methanol solvent was removed by rotary evaporation to obtain the crosslinking agent precursor.

[0009] 2) The crosslinking agent precursor is added to a mixed solvent of formic acid, water and ethanol, and stirred to obtain a crosslinking agent with reversible redox properties;

[0010] 3) The crosslinking agent is blended with oxide semiconductor nanoparticles, mechanically stirred and ultrasonically treated, and then coated onto the surface of the fabric. After drying, a photocatalytic composite fabric with redox reversible properties is obtained.

[0011] Furthermore, in the above preparation method, in step 1), the molar ratio of p-phenylenediamine and 3-glycidyloxypropyltrimethoxysilane is 1:4.

[0012] Furthermore, in the above preparation method, in step 1), the reflux reaction temperature is 100℃ and the reaction time is 48h.

[0013] Furthermore, in the above preparation method, in step 2), the mass ratio of formic acid, water, and ethanol is 1:217:1745.

[0014] Furthermore, in the above preparation method, step 2), the stirring time is 72 hours and the stirring temperature is 25°C.

[0015] Furthermore, in the above preparation method, step 3), the oxide semiconductor nanoparticles include, but are not limited to, nano-TiO2, ZnO, CdS, ZnS, PbS, and PbSe.

[0016] Furthermore, in the above preparation method, in step 3), the mass ratio of the crosslinking agent to the oxide semiconductor nanoparticles is 1:1-4.

[0017] Furthermore, in the above preparation method, step 3), the fabric includes, but is not limited to, cotton, linen, silk, wool, polyester, nylon, and nonwoven fabric.

[0018] Furthermore, in the above preparation method, step 3), the coating method includes, but is not limited to, spraying, dipping, and scraping.

[0019] Application of photocatalytic composite fabrics with redox reversible properties prepared by any of the above methods in the degradation of organic pollutants.

[0020] The beneficial effects of this invention are as follows: the inorganic component, using silanol groups as a crosslinking agent, can form a Si-O-Si crosslinking network through intermolecular dehydration condensation, and can also condense with hydroxyl groups on the surface of nanoparticles, thus fixing nanoparticles to the fabric surface with minimal dosage. The organic component, p-phenylenediamine, provides redox active centers for the fabric, thereby photosensitizing the nanoparticles. The combined effect of these two components ensures the high efficiency of photocatalytic activity and the long service life of the composite fabric. Attached Figure Description

[0021] Figure 1 The images show the infrared spectra of the crosslinking agent precursor, PDA, and GPTMS in Example 1.

[0022] Figure 2 The image shows the UV-Vis absorption spectrum of the crosslinking agent in Example 1.

[0023] Figure 3 The image shows the cyclic voltammetry curve of the crosslinking agent in Example 1.

[0024] Figure 4 Optical image of a nylon photocatalytic composite fabric doped with titanium dioxide and an oxidation-reduction reversible crosslinking agent.

[0025] Figure 5A Scanning electron microscope (SEM) image of a nylon photocatalytic composite fabric doped with titanium dioxide and an oxidation-reduction reversible crosslinking agent before washing.

[0026] Figure 5B Scanning electron microscope (SEM) image of a nylon photocatalytic composite fabric doped with titanium dioxide and an oxidation-reduction reversible crosslinking agent after washing for 2 hours.

[0027] Figure 6 The graph shows the concentration changes of titanium dioxide-doped nylon photocatalytic composite fabric in four consecutive photocatalytic degradations of methylene blue.

[0028] Figure 7 A comparison of the concentration changes of titanium dioxide-doped nylon photocatalytic composite fabric and control fabric in the photocatalytic degradation of methylene blue. Detailed Implementation

[0029] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0030] Example 1: Synthesis of a crosslinking agent with reversible redox properties

[0031] 1) p-Phenylenediamine (PDA) (18.49 mmol, 2.0060 g) was dissolved in 50 mL of anhydrous methanol by ultrasonication in a water bath. Then, 3-glycidyloxypropyltrimethoxysilane (GPTMS) (73.96 mmol, 17.4800 g) was added. After homogeneous dissolution, the solution was refluxed at 100 °C for 48 h. The methanol was then removed by rotary evaporation to obtain a brownish-yellow viscous liquid.

[0032] 2) Add 120 mL of anhydrous ethanol, sonicate in a water bath until completely dissolved, then add 12 g of 0.1 mol·L⁻¹ dropwise. -1 Formic acid aqueous solution was prepared and then stirred at room temperature for 72 hours to allow for complete hydrolysis. 1.00 g of crosslinking agent was dried, and the solid content of the crosslinking agent was found to be 12.9%.

[0033] Infrared spectra before and after the reaction ( Figure 1 The comparison clearly shows that the characteristic peaks of epoxy groups are absent in the crosslinking agent precursor, proving that the ring-opening addition reaction proceeded fully. Figure 2 The UV-Vis absorption spectrum reveals two distinct absorption peaks at wavelengths of 580 and 620 nm. This phenomenon is attributed to the loss of electrons at the molecular center, resulting in the formation of a free radical cation that effectively binds the benzene ring and the two nitrogen atoms together. Figure 3 The cyclic voltammetry curves showed two distinct oxidation peaks at 0.9 V and 1.1 V, proving that the molecule can achieve electronic transitions and has good redox reversible properties.

[0034] Example 2: Preparation of Titanium Dioxide-Doped Oxidation-Reduction Reversible Photocatalytic Coating

[0035] Weigh 7.75g of the crosslinking agent prepared in Example 1, add deionized water to a final volume of 19.00g, then weigh 1.00g of P25 titanium dioxide and add it to the solution. Sonicate the mixture in a water bath for approximately 1 minute to ensure uniform mixing. Then, in an ice-water bath, use an ultrasonic cell disruptor at 350W to perform high-precision ultrasonic treatment on the dispersion for 30 minutes, cycling the process with a 3-second on-off cycle. A photocatalytic coating with a crosslinking agent to P25 titanium dioxide mass ratio of 1:1 and a P25 titanium dioxide mass fraction of 5wt% was prepared according to the above method.

[0036] Similarly, keeping the mass of 1.00g of P25 titanium dioxide constant, weigh 3.87g, 2.56g, and 1.94g of crosslinking agent respectively, and then add deionized water to 19.00g respectively to prepare photocatalytic coatings with a crosslinking agent molecule to P25 titanium dioxide mass ratio of 1:2, 1:3, and 1:4, and a P25 titanium dioxide mass fraction of 5wt%.

[0037] Example 3: Preparation of Oxidation-Reduction Reversible Titanium Dioxide / Nylon Photocatalytic Composite Fabric

[0038] First, cut the nylon mesh fabric into 23cm x 24cm pieces (the metal frame supporting the fabric should also be 23cm x 24cm). Then, soak it in anhydrous ethanol to remove surface impurities, followed by thorough drying and precise weighing. Next, use clips to securely fix the nylon mesh fabric to the metal frame, ensuring the center of the fabric is taut for even coating distribution. Once ready, take 1.00g of accurately weighed photocatalytic coating and, under 0.3MPa pressure, evenly spray it onto the front of the nylon mesh fabric using a spray gun until all the coating in the spray gun is used up.

[0039] Infrared lamps were turned on to dry the sprayed nylon mesh. After drying, the mesh was weighed again. Next, the same spraying procedure as for the front side was followed to spray the back side of the nylon mesh. The spraying process was repeated on both sides of the nylon mesh until the P25 titanium dioxide coating on the nylon mesh reached 0.06g (3.32×10⁻⁶ g / cm²). -2 mg·cm -2 The coated composite fabric was placed in an oven at 90°C and dried for 72 hours to allow the crosslinking agent to fully crosslink and cure, resulting in a titanium dioxide-doped nylon photocatalytic composite fabric with a reversible oxidation-reduction crosslinking agent.

[0040] Figure 4Optical images of a nylon photocatalytic composite fabric doped with titanium dioxide and an oxidation-reduction reversible crosslinking agent. The composite fabric was then cut into 3cm × 6cm pieces and placed in a 200mL beaker containing 140mL of deionized water. The mixture was stirred at 300rpm for 2 hours, and the adhesion strength of the P25 titanium dioxide was tested. Figure 5A and Figure 5B It can be seen that P25 titanium dioxide is evenly adhered to the fabric surface before and after washing.

[0041] Example 4: Photocatalytic Degradation of Methylene Blue by Composite Fabric

[0042] First, a strip of composite fabric sample with a diameter of 60 mm and a width of 20 mm was placed in deionized water to a depth of approximately 5 mm. A 100W UV curing lamp with a wavelength of 365 nm was placed above the sample, with the bulb approximately 60 mm above the liquid surface. The UV lamp was turned on and irradiated for 15 minutes. After irradiation, the other side was irradiated for another 15 minutes. The purpose of this pretreatment method for the composite fabric is that, through UV irradiation, the redox active sites of the crosslinking agent in the composite fabric lose electrons. These lost electrons directly enter the conduction band of titanium dioxide, promoting the photocatalytic process of titanium dioxide. Simultaneously, the presence of deionized water provides a suitable environment for electron conversion, facilitating the capture of electrons by titanium dioxide.

[0043] Then add 30 mL of 10 mg·L⁻¹ to a 60 mm diameter plastic container. -1 A methylene blue solution was prepared, and a magnetic stir bar and a perforated plastic holder were placed inside. The pre-treated composite fabric was then placed in the center of the plastic holder. A plastic ring with an inner diameter of 55 mm was used to fix the fabric in place, ensuring it was flat to receive UV light evenly. At this point, the fabric was immersed in the liquid for approximately 2 mm. The device was then placed in an ice-water bath, and the magnetic stir bar was turned on to promote solution circulation. To avoid the fabric adsorbing dye and affecting the test results, the fabric was allowed to reach dye adsorption equilibrium for 15 minutes. At this point, the absorbance of the methylene blue solution was measured. Subsequently, the UV lamp was turned on, and the absorbance change of the solution was recorded every 15 minutes, continuously recording the maximum absorbance value. The entire illumination process lasted for 2 hours. Figure 6 The results showed that the composite fabric maintained good catalytic activity even after four consecutive uses, indicating that the composite fabric has a long service life.

[0044] Comparative Example 1

[0045] GPTMS (42 mmol, 10.0100 g) was sonicated in a water bath and dissolved in 25 mL of anhydrous ethanol. After stirring and heating to 60 °C, 15 g of 0.1 mol·L⁻¹ was slowly added dropwise. -1The formic acid solution was stirred for another 5 hours to ensure complete hydrolysis. A comparative crosslinking agent and a comparative photocatalytic composite fabric were prepared according to the methods of Examples 2 and 3, and then subjected to photocatalytic degradation of methylene blue according to the method of Example 4 (no pretreatment required). Figure 7 This indicates that the titanium dioxide-doped nylon photocatalytic composite fabric, compared to the control composite fabric, exhibits a faster reaction rate in the photocatalytic degradation of methylene blue.

Claims

1. A method for preparing a photocatalytic composite fabric with reversible redox properties, characterized in that, Includes the following steps: 1) P-phenylenediamine and 3-glycidyloxypropyltrimethoxysilane were dissolved in methanol, refluxed, and then the methanol solvent was removed by rotary evaporation to obtain the crosslinking agent precursor. 2) The crosslinking agent precursor is added to a mixed solvent of formic acid, water and ethanol, and stirred to obtain a crosslinking agent with reversible redox properties; 3) The crosslinking agent is blended with oxide semiconductor nanoparticles, mechanically stirred and ultrasonically treated, and then coated onto the surface of the fabric. After drying, a photocatalytic composite fabric with reversible oxidation-reduction properties is obtained.

2. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of p-phenylenediamine and 3-glycidyloxypropyltrimethoxysilane is 1:

4.

3. The preparation method according to claim 1, characterized in that, In step 1), the reflux reaction temperature is 100°C and the reaction time is 48 h.

4. The preparation method according to claim 1, characterized in that, In step 2), the mass ratio of formic acid, water, and ethanol is 1:217:1745.

5. The preparation method according to claim 1, characterized in that, In step 2), the stirring time is 72 h and the stirring temperature is 25 ℃.

6. The preparation method according to claim 1, characterized in that, In step 3), the oxide semiconductor nanoparticles include, but are not limited to, nano-TiO2 and ZnO.

7. The preparation method according to claim 1, characterized in that, In step 3), the mass ratio of crosslinking agent to oxide semiconductor nanoparticles is 1:1-4.

8. The preparation method according to claim 1, characterized in that, In step 3), the fabric includes, but is not limited to, cotton, linen, silk, wool, polyester, and nylon.

9. The preparation method according to claim 1, characterized in that, In step 3), the coating method includes, but is not limited to, spraying, dipping, and scraping.

10. The application of the photocatalytic composite fabric with redox reversible properties prepared by the preparation method according to any one of claims 1-9 in the degradation of organic pollutants.

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