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

Abstract

The invention belongs to the technical field of new materials, and particularly relates to a preparation method and application of a photocatalytic composite fabric with an oxidation-reduction reversible characteristic. Comprising the following steps: synthesizing an oxidation-reduction reversible cross-linking agent molecule with a high-activity central site, preparing an oxide semiconductor nanoparticle doped composite coating, and preparing a photocatalytic composite fabric. A high-strength coating can be constructed on the surface of the fabric through a simple spraying method, and the photocatalytic composite fabric is obtained. Compared with the photocatalytic fabric prepared by the traditional cross-linking agent, the photocatalytic fabric has the advantages of good organic pollutant degradation effect, high reaction rate, long service life and easiness in large-scale preparation, and has wide application prospects in the field of degradation of organic pollutants by fabrics.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials, and in particular relates to a cross-linking agent and photocatalytic composite fabric with oxidation-reduction reversible characteristics and application thereof in degrading organic pollutants. Background Art

[0002] Organic pollutants such as polycyclic aromatic compounds, dyes, and pesticides are extremely harmful to the ecosystem because of their long-term presence in the environment. Photocatalytic degradation of semiconductor nanoparticles such as titanium dioxide is an effective method for pollutant treatment. Compared with commonly used precipitation methods, physical adsorption methods, ion exchange methods, etc., it has the advantages of ease of use, low cost, and continuous operation. However, there are some limitations when using powdered semiconductor nanoparticles directly in water. For example, titanium dioxide will clump and cannot be evenly dispersed in water; it will settle in water, resulting in a significant weakening of the catalytic effect; the post-processing process is more cumbersome and difficult to separate and recycle. Combining titanium dioxide with fabrics can effectively solve the above problems. It can not only improve the photocatalytic efficiency, but also can be quickly separated and recycled, making it convenient to control the photocatalytic reaction.

[0003] Crosslinking agents are the key to preparing photocatalytic composite fabrics. On the one hand, the fastness of the nanoparticle coating on the fiber must be guaranteed to meet the service life requirements, and on the other hand, its photocatalytic activity must not be affected as much as possible. These are all issues that need to be weighed in practical applications. At present, commonly used crosslinking agents can be divided into inorganic crosslinking agents and organic crosslinking agents. A significant advantage of inorganic crosslinking agents is that they are not easily degraded by ultraviolet rays, which can fully guarantee their service life. For example, the document Progress in Organic Coatings, 2017, (113): 15-24 reported an inorganic crosslinking agent prepared by hydrolyzing tetraethyl orthosilicate and methyltrimethoxysilane under acidic conditions. The results showed that the crosslinking agent has excellent anti-photodegradation properties. However, the composite fabric prepared using inorganic crosslinking agents has poor flexibility, and the coating formed on the surface of the fabric is hard and brittle, and there is a risk of falling off the fiber. In contrast, composite fabrics prepared using organic crosslinking agents such as polyester, polyurethane, and polyamide have the advantage of good flexibility. For example, the document ACS Applied Materials & Interfaces, 2013, 5(9): 3697-3703 reported that titanium dioxide was loaded onto cotton fabric using 2-hydroxyethyl acrylate as a crosslinking agent, and the prepared composite fabric showed good catalytic effect. However, the organic crosslinking agent is easily degraded under continuous irradiation of ultraviolet rays, which leads to coating failure. Therefore, it is urgent to develop new crosslinking agents to solve the above problems in order to improve the photocatalytic efficiency of composite fabrics.

[0004] Combining the characteristics of the above two types of crosslinkers to prepare a new type of organic-inorganic hybrid crosslinker is expected to obtain high-performance photocatalytic composite fabrics. The inorganic part of the crosslinker is used to achieve high-strength bonding between particles and fabrics, and the organic part is used to achieve the flexibility of the composite fabric, achieving a long and efficient service life. In addition, if the redox active center can be introduced through the organic part of the molecule, the photocatalytic activity of semiconductor nanoparticles can also be improved through its sensitization effect, resulting in a high-efficiency photocatalytic composite fabric with redox reversible characteristics. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for synthesizing an organic-inorganic hybrid crosslinking agent with oxidation-reduction reversible properties, and uses the method to prepare a highly efficient photocatalytic composite fabric.

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

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

[0008] 1) dissolving p-phenylenediamine and 3-glycidyloxypropyltrimethoxysilane in methanol, performing reflux reaction, and then removing the methanol solvent by rotary evaporation to obtain a crosslinking agent precursor;

[0009] 2) adding the crosslinking agent precursor to a mixed solvent of formic acid, water and ethanol, stirring the mixture, and obtaining a crosslinking agent having redox reversible properties;

[0010] 3) The cross-linking agent is mixed with the oxide semiconductor nanoparticles, and after mechanical stirring and ultrasonic treatment, the mixture is coated on the surface of the fabric, and after drying, a photocatalytic composite fabric with oxidation-reduction reversible characteristics is obtained.

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

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

[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, in step 2), the stirring time is 72 hours and the stirring temperature is 25°C.

[0015] Furthermore, in the above preparation method, in 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 cross-linking agent to the oxide semiconductor nanoparticles is 1:1-4.

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

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

[0019] Application of the photocatalytic composite fabric with oxidation-reduction reversible properties prepared by any of the preparation methods described above in the degradation of organic pollutants.

[0020] The invention has the following beneficial effects: the inorganic component with silanol as the crosslinking agent can form a Si-O-Si crosslinking network through intermolecular dehydration condensation, and can also condense with the hydroxyl groups on the surface of the nanoparticles, so that the nanoparticles can be fixed on the surface of the fabric with the minimum dosage. The organic component with p-phenylenediamine can provide an oxidation-reduction active center for the fabric, and play a role in photosensitizing the nanoparticles. The combined effect of the two components ensures the high efficiency photocatalytic activity and long service life of the composite fabric. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The infrared spectra of the cross-linking agent precursor, PDA and GPTMS in Example 1.

[0022] Figure 2 is the UV-visible absorption spectrum of the cross-linking agent in Example 1.

[0023] Figure 3 This is the cyclic voltammetry curve of the cross-linking agent in Example 1.

[0024] Figure 4 Optical image of titanium dioxide doped nylon photocatalytic composite fabric with redox reversible crosslinker.

[0025] Figure 5A This is a scanning electron microscope image of titanium dioxide doped oxidation-reduction reversible crosslinker nylon photocatalytic composite fabric before washing.

[0026] Figure 5B This is a scanning electron microscope image of titanium dioxide doped redox reversible crosslinker nylon photocatalytic composite fabric after washing for 2 hours.

[0027] Figure 6 This is a graph showing the concentration changes of titanium dioxide-doped nylon photocatalytic composite fabric with oxidation-reduction reversible crosslinking agent after four consecutive photocatalytic degradations of methylene blue.

[0028] Figure 7 This is a comparison chart of the concentration changes of titanium dioxide doped redox reversible cross-linker nylon photocatalytic composite fabric and control fabric for photocatalytic degradation of methylene blue. DETAILED DESCRIPTION

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

[0030] Example 1 Synthesis of a cross-linking agent with redox reversible properties

[0031] 1) PDA (18.49 mmol, 2.0060 g) was dissolved in 50 mL of anhydrous methanol by ultrasonic bath, and then 3-glycidyloxypropyltrimethoxysilane (GPTMS) (73.96 mmol, 17.4800 g) was added, and after being uniformly dissolved, the mixture was refluxed at 100° C. for 48 h. Methanol was then removed by rotary evaporation to obtain a brown-yellow viscous liquid.

[0032] 2) Add 120 mL of anhydrous ethanol, sonicate in a water bath until completely dissolved, then drop 12 g of 0.1 mol·L -1 The formic acid aqueous solution was then stirred at room temperature for 72 hours to fully hydrolyze it, and 1.00 g of the cross-linking agent was taken out for drying, and the solid content of the cross-linking agent was found to be 12.9%.

[0033] By infrared spectroscopy before and after the reaction ( Figure 1 ), it can be clearly seen that there is no characteristic peak of epoxy group in the crosslinking agent precursor, proving that the ring-opening addition reaction is fully carried out. Figure 2 The UV-visible absorption spectrum shows two obvious absorption peaks at wavelengths of 580 and 620 nm. This phenomenon should be attributed to the loss of electrons from the molecular center, which produces a free radical cation, effectively combining the benzene ring and the two nitrogen atoms. Figure 3 The cyclic voltammetry curve showed two obvious oxidation peaks at 0.9V and 1.1V, proving that the molecule can achieve electronic transition 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 19.00g, then weigh 1.00g of P25 titanium dioxide and add it to the solution, treat it with ultrasound for about 1min in a water bath to make it evenly mixed, and then use an ultrasonic cell crusher in an ice water bath to treat the dispersed system with a tip ultrasound for 30min at a power of 350W, during which it is cycled in a 3-second on, 3-second off mode. According to the above method, a photocatalytic coating with a mass ratio of crosslinking agent molecules to P25 titanium dioxide of 1:1 and a mass fraction of P25 titanium dioxide of 5wt% is prepared.

[0036] Similarly, keeping the mass of 1.00g P25 titanium dioxide unchanged, 3.87g, 2.56g, and 1.94g of the cross-linking agent were weighed respectively, and deionized water was added to 19.00g respectively to prepare photocatalytic coatings with a mass ratio of cross-linking agent molecules to P25 titanium dioxide of 1:2, 1:3, and 1:4, and a mass fraction of P25 titanium dioxide of 5wt%.

[0037] Example 3 Preparation of reversible oxidation-reduction titanium dioxide / nylon photocatalytic composite fabric

[0038] First, the nylon mesh is cut into 23cm×24cm specifications (the metal frame supporting the fabric is 23cm×24cm), then soaked in anhydrous ethanol for cleaning to remove surface impurities, then thoroughly dried and accurately weighed. Next, the nylon mesh is firmly fixed to the metal frame with a clamp, ensuring that the center of the nylon mesh is taut so that the coating can be evenly distributed. When ready, take 1.00g of the photocatalytic coating that has been accurately weighed and use a spray gun to evenly spray the front of the nylon mesh at a pressure of 0.3MPa until all the coating in the spray gun is used up.

[0039] The infrared lamp was turned on to dry the sprayed nylon mesh. After the drying process, the mesh was weighed again. Next, the back of the nylon mesh was sprayed according to the same spraying operation procedure as the front. The two sides of the nylon mesh were sprayed alternately until the P25 titanium dioxide adhesion on the nylon mesh was 0.06g (the adhesion per unit area was 3.32×10 -2 mg cm -2 The sprayed composite fabric was placed in an oven at 90°C and dried for 72 hours to allow the crosslinking agent to fully crosslink and solidify, thereby obtaining a titanium dioxide-doped nylon photocatalytic composite fabric with an oxidation-reduction reversible crosslinking agent.

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

[0041] Example 4 Photocatalytic degradation of methylene blue by composite fabric

[0042] First, place a strip composite fabric sample with a diameter of 60mm and a width of 20mm in deionized water with a depth of about 5mm. Place a UV curing lamp with a power of 100W and a wavelength of 365nm on the sample, and the bulb is about 60mm away from the liquid surface. Turn on the UV lamp and irradiate for 15 minutes. After the irradiation is completed, irradiate the other side for another 15 minutes. The purpose of this pre-treatment method for the composite fabric is that through ultraviolet irradiation, the oxidation-reduction active sites of the crosslinker in the composite fabric will lose electrons, and the lost electrons will directly enter the conduction band of titanium dioxide, promoting the photocatalytic process of titanium dioxide. At the same time, the presence of deionized water provides a suitable environment for electron conversion, which helps titanium dioxide capture electrons.

[0043] Then, add 30 mL of 10 mg·L -1 methylene blue solution, put in a magnetic stirrer and a plastic stand with holes, and place the treated composite fabric in the center of the plastic stand. Use a plastic ring with an inner diameter of 55mm to fix the fabric, ensuring that the fabric is in a flat state so that it can evenly receive ultraviolet light. At this time, the fabric is immersed in the liquid surface by about 2mm. Put the device in an ice water bath and start the magnetic stirring device to promote the circulation of the solution. In order to avoid the fabric adsorbing dyes and affecting the test results, wait for 15 minutes for the fabric to absorb dyes to reach equilibrium, and then measure the absorbance of the methylene blue solution. Then turn on the ultraviolet lamp, record the absorbance change of the solution every 15 minutes, and continue to record the maximum absorbance value. The entire illumination process lasts for 2 hours. Figure 6 It shows that even if the composite fabric is used continuously for four times, it can still maintain good catalytic activity, which indicates that the composite fabric has a long service life.

[0044] Comparative Example 1

[0045] GPTMS (42 mmol, 10.0100 g) was dissolved in 25 mL of anhydrous ethanol by ultrasonication in a water bath, and then 15 g of 0.1 mol·L was slowly added dropwise after stirring and heating to 60 °C. -1The formic acid solution was stirred for 5 hours to fully hydrolyze. According to the methods of Examples 2 and 3, comparative crosslinking agents and comparative photocatalytic composite fabrics were prepared, and according to the method of Example 4 (without pretreatment), methylene blue was photocatalytically degraded. Figure 7 It shows that titanium dioxide doped redox reversible crosslinker nylon photocatalytic composite fabric has a faster reaction rate when photocatalytically degrading methylene blue compared with the control composite fabric.

Claims

1. A method for preparing a photocatalytic composite fabric with oxidation-reduction reversible properties, characterized in that: The steps include: 1) dissolving p-phenylenediamine and 3-glycidyloxypropyltrimethoxysilane in methanol, performing reflux reaction, and then removing the methanol solvent by rotary evaporation to obtain a crosslinking agent precursor; 2) adding the crosslinking agent precursor to a mixed solvent of formic acid, water and ethanol, stirring the mixture, and obtaining a crosslinking agent having redox reversible properties; 3) The cross-linking agent is mixed with the oxide semiconductor nanoparticles, and after mechanical stirring and ultrasonic treatment, the mixture is coated on the surface of the fabric, and after drying, a photocatalytic composite fabric with oxidation-reduction reversible characteristics is obtained.

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

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 hours and the stirring temperature is 25°C.

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, ZnO, CdS, ZnS, PbS, and PbSe.

7. The preparation method according to claim 1, characterized in that: In step 3), the mass ratio of the cross-linking agent to the 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, nylon, and non-woven fabrics.

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. Use of the photocatalytic composite fabric with oxidation-reduction reversible properties prepared by the preparation method according to any one of claims 1 to 9 in degrading organic pollutants.

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