Preparation and application of titanium dioxide-iron oxyhydroxide composite material

Abstract

The invention discloses a preparation method of a titanium dioxide-iron oxyhydroxide (TiO2 / FeOOH) composite material. According to the composite material, ferric trichloride hexahydrate (FeCl36H2O) is used as a Fe source, P25 is used as a Ti source, TiO2 is treated through oxalic acid under the hydrothermal condition, surface defects of TiO2 are increased, and then the TiO2 / FeOOH composite material is prepared through an impregnation method. The composite material is uniform in particle distribution, and effective separation of photo-induced electron-hole pairs is improved after FeOOH and TiO2 are compounded, so that the composite material has relatively good visible light catalytic performance. Experiments show that when the concentration of FeCl36H2O is 0.05 mmol / L, the removal rate of 10mg / L phenol by the TiO2 / FeOOH composite material is 99.99%, and the photocatalytic performance has an optimal value.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a titanium dioxide - iron oxyhydroxide (TiO2 / FeOOH) composite material, belonging to the technical field of photocatalytic composite materials. Background Art

[0002] Benzene series compounds (such as phenol, toluene, etc.), as important chemical raw materials, are widely used in industries such as building materials and textiles. The low - concentration benzene series compounds in air and industrial wastewater pose a great threat to the health of the general public, which cannot be ignored. Photocatalytic technology uses sunlight to drive photocatalysts to generate active species with strong oxidizing power, gradually degrading refractory organic pollutants into non - toxic and harmless carbon dioxide and water. It has the advantages of mild reaction conditions, long - lasting performance, and complete degradation, and is considered one of the ideal environmental pollution treatment technologies. As a photocatalytic material, TiO2 has the characteristics of non - toxicity, low price, high chemical stability, and light corrosion resistance. In addition, the valence band position of TiO2 is about 2.91 eV, the conduction band position is at - 0.19 eV, and the band gap is 3.2 eV, having a relatively strong oxidation ability compared with most photocatalysts. However, the visible - light response range of TiO2 is below 400 nm, making the visible light accounting for about 43% of the solar energy unable to excite TiO2, which greatly limits the practical application of TiO2. Therefore, constructing a Z - type heterojunction can effectively separate photo - generated electrons - holes and improve the photocatalytic efficiency of TiO2 materials. Iron oxyhydroxide not only has good photoelectrochemical properties but also has stable physical and chemical properties. Especially, β - FeOOH can generate photo - generated carriers under visible light, and its surface contains abundant active sites that can adsorb a large amount of organic pollutants. Combining FeOOH and TiO2 can promote the separation of photo - generated electron - hole pairs and help improve the visible - light photocatalytic performance of the material. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of TiO2 / FeOOH composite material, and by combining FeOOH and TiO2, improve the visible - light photocatalytic performance of TiO2 / FeOOH for degrading organic pollutants in water.

[0004] I. Preparation of TiO2 / FeOOH Composite Material (1) Preparation of TiO2 nanoparticles: Disperse P25 in oxalic acid solution, and obtain oxygen - deficient TiO2 nanoparticles (TiO2NPs) after hydrothermal reaction, washing, and drying; Among them, the hydrothermal reaction temperature is 90 - 110 °C, the time is 10 - 15 h; the concentration of the oxalic acid solution is 1.0 mol / L, and the addition amount of P25 is 1.00 g / 60 mL of oxalic acid solution.

[0005] (2)Preparation of TiO2 / FeOOH composite material: Disperse the TiO2 NPs obtained in step (1) in deionized water, add FeCl3·6H2O, let it stand for reaction, then wash and dry to obtain the TiO2 / FeOOH composite material; Among them, the concentration of FeCl3·6H2O in the reaction system is 0.025 - 2.0 mM, and the mass ratio of FeCl3·6H2O to TiO2 NPs is 1:1.8 - 1:136.4; the standing reaction time is 6 h, and the reaction temperature is room temperature.

[0006] TiO2 / FeOOH composite materials are obtained with the concentration of FeCl3∙6H2O in the reaction system being 0.025 mM, 0.05 mM, 0.5 mM, 1.0 mM, and 2.0 mM, and are named TiO2 / FeOOH-0.025, TiO2 / FeOOH-0.05, TiO2 / FeOOH-0.5, TiO2 / FeOOH-1.0, and TiO2 / FeOOH-2.0 respectively.

[0007] II. Structure and properties of TiO2 / FeOOH composite material 1. X-ray diffraction spectrum (XRD) Use a Philips X pert PRO powder diffractometer. The test conditions are Cu Kα ray, tube voltage of 40 kV, tube current of 100 mA, scanning range of 5 - 80°, and step size of 2° / min.

[0008] It can be seen that Figure 1 when 2θ is 25.28°, 36.93°, 37.79°, 38.50°, 48.05°, 53.83°, 55.01°, 62.69°, 68.80°, 70.27°, 75.05°, they respectively correspond to the (101), (103), (004), (112), (200), (105), (211), (204), (116), (220), (215) crystal planes of anatase; when 2θ is 27.40°, 36.03°, 41.23°, 54.31°, they respectively correspond to the (110), (101), (111), (211) crystal planes of rutile. At the same time, it can be seen that both TiO2 and TiO2 / FeOOH contain anatase and rutile phase TiO2, and with the increase of the dosage of FeCl3∙6H2O, the proportion of rutile phase TiO2 in the TiO2 / FeOOH composite material increases slightly, indicating that FeOOH has a certain influence on the crystal phase formation of TiO2. Due to the low content of FeOOH, there is no obvious FeOOH diffraction peak in the composite material.

[0009] 2. Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy (HR-TEM) Tests The TEM test was carried out using a FEI Talos F200x transmission electron microscope from the United States, with an acceleration voltage of 200 kV. Figure 2 The TEM images of TiO2 and TiO2 / FeOOH are shown. It can be seen that different FeOOH contents do not change the morphology and particle size of the composite material. When the concentration of FeCl3∙6H2O increases from 0.05 mM to 2.0 mM, the FeOOH nanoparticles are still evenly distributed. Since the FeOOH content in TiO2 / FeOOH-0.05 is low, its diffraction peak cannot be observed in the XRD spectrum. However, the lattice fringes of TiO2 can be clearly observed in the high-magnification transmission electron microscope image, with a spacing of 0.355 nm, corresponding to the (101) crystal plane of anatase; the lattice spacing of β-FeOOH is 0.332 nm, corresponding to the (310) crystal plane of β-FeOOH. At the same time, the HR-TEM of TiO2 / FeOOH-2.0 can also observe the lattice fringes of β-FeOOH, with a spacing of 0.189 nm, corresponding to the (440) crystal plane of β-FeOOH, indicating that β-FeOOH has successfully grown on the surface of TiO2, while the lattice fringes of β-FeOOH are not very clear, indicating that the crystallinity of β-FeOOH is not very good.

[0010] Figure 3 and Figure 4 are the Mapping images of TiO2 / FeOOH-0.05 and TiO2 / FeOOH-2.0. In TiO2 / FeOOH-0.05, the O element and Ti are evenly distributed, while the Fe element is not very obvious due to its low content. In TiO2 / FeOOH-2.0, it can be clearly seen that the O, Ti, and Fe elements are evenly distributed. This result is consistent with the TEM result. Therefore, it shows that FeOOH has successfully grown on the surface of TiO2.

[0011] 3. Photoluminescence Spectra (PL) Figure 5 is the photoluminescence (PL) spectrum of TiO2 and TiO2 / FeOOH-0.05 composites when the excitation wavelength (λ ex ) is 360 nm. As can be seen from the figure, TiO2 has an obvious fluorescence emission peak at 423 nm. The fluorescence emission peak of the TiO2 / FeOOH-0.05 composite material is at 435 nm, shifted towards the long-wavelength direction, and the peak intensity of the TiO2 / FeOOH-0.05 composite material is significantly lower than that of the TiO2 material, indicating that an appropriate amount of FeOOH forms a heterojunction with TiO2, promoting the separation of photogenerated electrons and holes, reducing the recombination rate of photogenerated electrons and holes, and improving the photocatalytic activity of the composite material.

[0012] 4. Degradation performance of phenol Figure 6 The visible-light photocatalytic performance of TiO2 / FeOOH composite materials and TiO2 materials prepared under different FeCl3∙6H2O concentrations for phenol is shown. It can be seen from the figure that appropriate amount of FeOOH can promote the visible-light photocatalytic degradation performance of TiO2 for phenol. Among them, the degradation rate of phenol by TiO2 / FeOOH-0.05 composite material reaches 100%, which is higher than that of pure TiO2 (94.77%), and has the best visible-light photocatalytic activity. Continuing to increase the concentration of FeCl3∙6H2O, the removal rates of phenol by the prepared TiO2 / FeOOH-1.0 and TiO2 / FeOOH-2.0 composite materials decrease, indicating that the combination of an appropriate amount of FeOOH and TiO2 material helps to improve the visible-light photocatalytic activity of TiO2.

[0013] In summary, in this invention, ferric chloride hexahydrate (FeCl3∙6H2O) is used as the Fe source, and P25 is used as the Ti source. By treating TiO2 with oxalic acid under hydrothermal conditions to increase the surface defects of TiO2, and then preparing the TiO2 / FeOOH composite material by the impregnation method. The composite material has uniform particle distribution. After the combination of FeOOH and TiO2, the effective separation of photo-generated electron-hole pairs is improved, making the composite material have good visible-light photocatalytic performance. In this composite material, FeOOH is uniformly loaded on the surface of TiO2, significantly enhancing the visible-light absorption and the separation efficiency of photo-generated carriers, and the degradation rate of phenol can reach 100%. The process of this invention is simple and low-cost, and is suitable for the efficient photocatalytic degradation of organic pollutants in industrial wastewater. Description of the drawings

[0014] Figure 1 XRD spectra of TiO2 and TiO2 / FeOOH composite materials.

[0015] Figure 2 TEM and HR-TEM images of TiO2 (Figure a, Figure b), TiO2 / FeOOH-0.05 (Figure c, Figure d) and TiO2 / FeOOH-2.0 (Figure e, Figure f).

[0016] Figure 3 Mapping image of TiO2 / FeOOH-0.05.

[0017] Figure 4 Mapping image of TiO2 / FeOOH-2.0.

[0018] Figure 5 PL spectra of TiO2 and TiO2 / FeOOH.

[0019] Figure 6 The photocatalytic performance of TiO2 and TiO2 / FeOOH composites for phenol. Specific embodiments

[0020] The preparation and properties of the TiO2 / FeOOH composite material of the present invention are further described below through specific examples.

[0021] Example 1 (1) Weigh 1.0000 g of P25, disperse it in 60 mL of 1.0 mol / L oxalic acid solution, stir for 10 min, ultrasonicate for 10 min, transfer the solution to the polytetrafluoroethylene liner of a 100 mL autoclave, and raise the temperature to 100 °C at a heating rate of 2 °C / min for a hydrothermal reaction for 12 h. After the reaction is completed and cooled to room temperature, the obtained product is filtered by suction and washed 3 - 5 times with deionized water until neutral. After drying at 60 °C for 12 h, it is ground to obtain white TiO2 nanoparticles, labeled as TiO2 NPs, and its visible-light photocatalytic degradation rate for a 10 mg / L phenol solution is 94.77%.

[0022] (2) Weigh 150 mg of TiO2 NPs, disperse it in 150 mL of deionized water, stir for 10 min, ultrasonicate for 10 min, add 0.0011 g of FeCl3∙6H2O (the molar concentration of FeCl3∙6H2O in the reaction system is 0.025 mM), keep the temperature at 20 °C, and let it stand for 6 h. After the reaction is completed, it is filtered by suction and washed 3 - 5 times with deionized water. After drying at 60 °C for 12 h, it is ground to obtain light yellow TiO2 / FeOOH nanocomposite material, labeled as TiO2 / FeOOH-0.025, and its visible-light photocatalytic degradation rate for a 10 mg / L phenol solution is 99.95%.

[0023] Example 2 The other conditions are the same as in Example 1, the addition amount of FeCl3∙6H2O is 0.0021 g (the molar concentration of FeCl3∙6H2O in the reaction system is 0.05 mM), and the final product is labeled as TiO2 / FeOOH-0.05, and its visible-light photocatalytic degradation rate for a 10 mg / L phenol solution is 100%.

[0024] Example 3 The other conditions are the same as in Example 1, the addition amount of FeCl3∙6H2O is 0.0203 g (the molar concentration of FeCl3∙6H2O in the reaction system is 0.5 mM), and the final product is labeled as TiO2 / FeOOH-0.5, and its visible-light photocatalytic degradation rate for a 10 mg / L phenol solution is 99.93%.

[0025] Example 4 Other conditions were the same as in Example 1. The addition amount of FeCl3∙6H2O was 0.0407 g (the molar concentration of FeCl3∙6H2O in the reaction system was 1.0 mM), and the final product was labeled as TiO2 / FeOOH-1.0. Its visible-light photocatalytic degradation rate for a 10 mg / L phenol solution was 99.75%.

[0026] Example 5 Other conditions were the same as in Example 1. The addition amount of FeCl3∙6H2O was 0.0813 g (the molar concentration of FeCl3∙6H2O in the reaction system was 2.0 mM), and the final product was labeled as TiO2 / FeOOH-2.0. Its visible-light photocatalytic degradation rate for a 10 mg / L phenol solution was 99.06%.

Claims

1. A preparation method of a titanium dioxide-hydroxy iron oxide composite material, characterized in that, It includes the following steps: (1) Preparation of TiO2 nanoparticles: Titanium dioxide P25 is dispersed in an oxalic acid solution, and after hydrothermal reaction, washing, and drying, oxygen-deficient TiO2 nanoparticles (TiO2 NPs) are obtained; (2) Preparation of TiO2 / FeOOH composite: The TiO2 NPs obtained in step (1) are dispersed in deionized water, FeCl3·6H2O is added, and after static reaction, washing, and drying, a TiO2 / FeOOH composite is obtained.

2. The preparation method of the titanium dioxide-hydroxy iron oxide composite material according to claim 1, characterized in that, In step (1), the hydrothermal reaction temperature is 90 - 110 °C, and the time is 10 - 15 h.

3. The preparation method of the titanium dioxide-hydroxy iron oxide composite material according to claim 1, characterized in that, In step (1), the concentration of the oxalic acid solution is 1.0 mol / L, and the addition amount of titanium dioxide P25 is 1.00 g / 60 mL of oxalic acid solution.

4. The preparation method of the titanium dioxide-hydroxy iron oxide composite material according to claim 1, characterized in that, In step (2), the concentration of FeCl3·6H2O in the reaction system is 0.025 - 2.0 mM, and the mass ratio of FeCl3·6H2O to TiO2 NPs is 1:1.8 - 1:136.

4.

5. The preparation method of the titanium dioxide-hydroxy iron oxide composite material according to claim 1, characterized in that, In step (2), the static reaction time is 6 h, and the reaction temperature is room temperature.

6. Use of the titanium dioxide-hydroxy iron oxide composite prepared by the method according to claim 1 in photocatalytic degradation of organic pollutants.

7. The application according to claim 6, wherein: The organic pollutants include phenol, toluene, or refractory organic substances in industrial wastewater.

8. The application according to claim 6, characterized in that: The degradation rate of the composite to phenol under visible light irradiation is ≥99%.

Images