Fe3O4 / TiO2 photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a Fe3O4 / TiO2 photocatalyst as well as a preparation method and application thereof, and the preparation method of the Fe3O4 / TiO2 photocatalyst comprises the following steps: dissolving an iron source and sodium citrate in water, adding an alcoholic solution in which a titanium source is dissolved, uniformly stirring and mixing, adjusting the pH value to 8-10, performing solvothermal reaction in a reaction kettle, and separating to obtain the Fe3O4 / TiO2 photocatalyst. The photocatalyst TiO2 and the magnetic iron oxide Fe3O4 are compounded, so that organic pollutants which are difficult to degrade can be thoroughly oxidized into CO2, H2O and other small molecules which are harmless to the environment, and the photocatalyst is convenient to recycle and can be recycled for multiple times.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic nanomaterials, and particularly relates to an Fe 3 O 4 / TiO 2 photocatalyst and its preparation method and application. Background Technique

[0003] Photocatalysis technology is a green technology with important application prospects in the fields of energy and environment. Photocatalytic materials have become the focus of research in the degradation of organic dyes. Compared with traditional methods for treating organic dyes, photocatalytic materials have greater advantages in treating organic dyes. Photocatalytic materials convert solar energy into chemical energy or electrical energy, so they are cleaner and pollution-free in terms of energy selection. Moreover, as a renewable resource, making full use of solar energy can effectively alleviate the energy crisis. When photocatalytic materials are used to treat organic dyes, organic pollutants can be completely oxidized into pollution-free H 2 O and CO 2 , which can also avoid secondary pollution during the treatment process.

[0004] As an important photocatalytic material, nano-TiO 2 has the advantages of non-toxic and pollution-free, gas sensitivity and humidity sensitivity, good dielectric effect, photoelectric conversion, photochromism, high catalytic activity, strong oxidizing property, good stability, etc., and has been widely used in various fields such as photocatalytic degradation of organic pollutants, photocatalytic solar cells, photocatalytic water splitting for hydrogen production, dielectric materials, and self-cleaning materials. However, there is a common problem in the treatment of organic dyes in water by catalysts at present, that is, after treating organic pollutants in water, how to recycle the used catalyst. The conventional recycling method is to achieve separation and recycling through centrifugation, but there are many problems in actual operation, such as the relatively large energy consumption required for the centrifugation process. In addition, when the centrifugation speed is not large enough, incomplete separation will occur, which will cause secondary pollution.

[0005] Therefore, it is very necessary to find a new separation method, and magnetic recycling is a good choice because when the catalyst has magnetism, the catalyst can be easily separated by simply applying a strong magnetic field from the outside. This recycling method is more efficient, fast and pollution-free. Summary of the Invention

[0006] Based on the above technical problems, the present invention proposes an Fe 3 O 4 / TiO 2 photocatalyst and its preparation method and application. By combining the photocatalyst TiO 2 with the magnetic iron oxide Fe 3 O4 The composite can not only completely oxidize refractory organic pollutants into small molecules harmless to the environment such as CO 2 and H 2 O, but also be conveniently recycled and reused multiple times.

[0007] A preparation method of an Fe 3 O 4 / TiO 2 photocatalyst proposed by the present invention includes: dissolving an iron source and sodium citrate in water, adding an alcohol solution containing a titanium source, stirring and mixing evenly, adjusting the pH to 8-10, and then carrying out a solvothermal reaction. After separation, the Fe 3 O 4 / TiO 2 photocatalyst is obtained.

[0008] In the present invention, the titanium source is dissolved in alcohol and then added to an aqueous solution containing the dissolved iron source, and the Fe 3 O 4 / TiO 2 photocatalyst is prepared by a solvothermal reaction; compared with the Fe 3 O 4 / TiO 2 photocatalyst prepared by a hydrothermal method, its particles are spherical, TiO 2 is coated on the surface of the Fe 3 O 4 sphere, with uniform distribution, large specific surface area, close combination, and the best catalytic activity and magnetic properties.

[0009] Preferably, the iron source is at least one of ferric chloride, ferric sulfate or ferric nitrate, and the titanium source is at least one of tetrabutyl titanate or tetraisopropyl titanate.

[0010] Preferably, the molar ratio of the iron source to the titanium source is 1:0.1-0.15; the molar ratio of the iron source to sodium citrate is 1:2-3.

[0011] Preferably, the alcohol is at least one of methanol, ethanol or isopropanol, and the pH is adjusted using ammonia water.

[0012] Preferably, the temperature of the solvothermal reaction is 160-200 °C and the time is 16-32 h.

[0013] Preferably, it further includes grafting polyvinylpyridine on the surface of the Fe 3 O 4 / TiO 2 photocatalyst.

[0014] Preferably, the grafting of polyvinylpyridine on the surface of the Fe 3 O 4 / TiO2 The grafting of polyvinylpyridine on the surface of the photocatalyst specifically includes:

[0015] The Fe 3 O 4 / TiO 2 After the surface of the photocatalyst is modified with dopamine, it is condensed with 2-bromo isobutyryl bromide, and then surface-initiated atom transfer radical polymerization reaction is carried out with vinylpyridine, that is, grafting of polyvinylpyridine on the surface of Fe 3 O 4 / TiO 2 photocatalyst is realized.

[0016] In the present invention, by grafting polyvinylpyridine on the surface of Fe 3 O 4 / TiO 2 photocatalyst, on the one hand, the pyridine group contains imino group, which can form affinity adsorption with dyes. Therefore, the above-mentioned Fe 3 O 4 / TiO 2 photocatalyst after grafting polyvinylpyridine can further improve the adsorption and catalytic degradation performance of organic dyes; on the other hand, the hydrophilic property of the pyridine group also makes the Fe 3 O 4 / TiO 2 photocatalyst have better dispersibility, and can prevent the Fe 3 O 4 / TiO 2 photocatalyst from agglomerating due to its extremely high surface activity, ensuring the catalytic activity.

[0017] The present invention also proposes a Fe 3 O 4 / TiO 2 photocatalyst, which is prepared by the above preparation method.

[0018] The present invention also proposes an application of the above-mentioned Fe 3 O 4 / TiO 2 photocatalyst in the degradation of dyes by photocatalytic synergistic Fenton reaction.

[0019] Preferably, the dye is methyl orange, malachite green, rhodamine B or methylene blue.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The present invention uses the solvothermal method to coat TiO 2 on the surface of Fe 3 O 4 sphere, and obtains a Fe 3 O4 / TiO 2 photocatalyst, so that the powder TiO can be maintained 2 with high catalytic activity and the purpose of recycling can be achieved. Description of the Drawings

[0022] Figure 1 SEM image of the Fe 3 O 4 / TiO 2 photocatalyst described in Example 1;

[0023] Figure 2 EDS line scan image of the Fe 3 O 4 / TiO 2 photocatalyst described in Example 1;

[0024] Figure 3 UV-Vis absorption spectra of the Fe 3 O 4 / TiO 2 photocatalyst described in Example 1 and pure TiO 2 ;

[0025] Figure 4 Photocatalytic degradation efficiency diagram of the Fe 3 O 4 / TiO 2 photocatalyst added to the methylene blue dye solution: (a) is the UV-Vis curve, (b) is the degradation curve;

[0026] Figure 5 Photocatalytic degradation efficiency diagram of the Fe 3 O 4 / TiO 2 photocatalyst synergistically with Fenton catalysis added to the methylene blue dye solution: (a) is the UV-Vis curve, (b) is the degradation curve;

[0027] Figure 6 Photocatalytic degradation efficiency diagram of the Fe 3 O 4 / TiO 2 photocatalyst synergistically with Fenton catalysis added to the methyl orange dye solution: (a) is the UV-Vis curve, (b) is the degradation curve;

[0028] Figure 7 For the Fe described in Example 1 3 O 4 / TiO 2Photocatalytic degradation efficiency diagram of the photocatalyst synergistic Fenton catalysis added to the malachite green dye solution: (a) is the UV-Vis curve, and (b) is the degradation curve;

[0029] Figure 8 For Fe described in Example 1 3 O 4 / TiO 2 Photocatalytic degradation efficiency diagram of the photocatalyst synergistic Fenton catalysis added to the rhodamine B dye solution: (a) is the UV-Vis curve, and (b) is the degradation curve. Detailed implementation manners

[0030] Next, the present invention will be described in detail with specific examples for the technical solutions, but it should be clearly stated that these examples are for illustrative purposes only and are not construed as limiting the scope of the present invention.

[0031] Example 1

[0032] A preparation method of an Fe 3 O 4 / TiO 2 photocatalyst, comprising:

[0033] Dissolve 1.42 g of FeCl 3 ·6H 2 O and 3.0 g of sodium citrate in 50 mL of distilled water, add 10 mL of anhydrous ethanol solution containing 200 μL of tetrabutyl titanate and stir well. After adjusting the pH to 9 - 10 with ammonia water, pour it into a reaction kettle, place it in an oven at 180 °C for 24 h. After that, the obtained product is washed three times with deionized water and ethanol under the magnetic field force, and then centrifuged to obtain the Fe 3 O 4 / TiO 2 photocatalyst.

[0034] Figure 1 For the Fe described in Example 1 3 O 4 / TiO 2 SEM diagram of the photocatalyst, referring to Figure 1 It can be seen that the Fe 3 O 4 / TiO 2 photocatalyst is spherical, with a smooth surface, a large specific surface area, a large contact area with organic substances, and a layer of fine white TiO 2 particles uniformly coated on the surface of the Fe 3 O 4 spherical particles.

[0035] Figure 2 For the Fe described in Example 1 3 O4 / TiO 2 EDS line scan of the photocatalyst, refer to Figure 2 It can be seen that the red curve is the particle size distribution curve of O element, the blue curve is the particle size distribution curve of Fe element, and the green curve is the particle size distribution curve of Ti element.

[0036] Figure 3 For Fe described in Example 1 3 O 4 / TiO 2 UV-visible absorption spectra of the photocatalyst and pure TiO 2 , refer to Figure 3 It can be seen that TiO 2 has no obvious absorption of visible light, but Fe 3 O 4 / TiO 2 photocatalyst has good absorption in both ultraviolet and visible light ranges. It can be seen that Fe 3 O 4 / TiO 2 in the photocatalyst, the doping of Fe 3 O 4 will partially penetrate into the interior of the TiO 3+ lattice, narrowing the bandgap position of TiO 2 , effectively expanding the light response range of TiO 2 , making the light absorption edge band of the Fe 2 O 3 / TiO 4 photocatalyst have an obvious red shift compared with TiO 2 , greatly improving the catalytic efficiency of TiO 2 in the ultraviolet and visible light ranges. 2

[0037] Example 2

[0038] A preparation method of an Fe 3 O 4 / TiO 2 photocatalyst, including:

[0039] Dissolve 1.59 g of FeCl 3 ·6H 2 O and 4.5 g of sodium citrate in 50 mL of distilled water, add 10 mL of anhydrous ethanol solution dissolved with 200 μL of tetrabutyl titanate and stir well. After adjusting the pH to 9 - 10 with ammonia water, pour it into a reaction kettle, place it in an oven at 200 °C for reaction for 16 h. After that, the obtained product is washed three times with deionized water and ethanol under magnetic force, and then centrifuged to obtain the Fe 3 O 4 / TiO 2Photocatalyst

[0040] Example 3

[0041] A kind of Fe 3 O 4 / TiO 2 Preparation method of photocatalyst, comprising:

[0042] Dissolve 1.06 g of FeCl 3 ·6H 2 O and 2.0 g of sodium citrate in 50 mL of distilled water, add 10 mL of anhydrous ethanol solution dissolved with 200 μL of tetrabutyl titanate and stir well. Adjust the pH to 9 - 10 with ammonia water, then pour it into a reaction kettle, place it in an oven at 160 °C and react for 32 h. The obtained product is washed repeatedly with deionized water and ethanol under the magnetic field force. After centrifugation, Fe 3 O 4 / TiO 2 Photocatalyst

[0043] Example 4

[0044] A kind of Fe 3 O 4 / TiO 2 Preparation method of photocatalyst, comprising:

[0045] Dissolve 1.42 g of FeCl 3 ·6H 2 O and 3.0 g of sodium citrate in 50 mL of distilled water, add 10 mL of anhydrous ethanol solution dissolved with 200 μL of tetrabutyl titanate and stir well. Adjust the pH to 9 - 10 with ammonia water, then pour it into a reaction kettle, place it in an oven at 180 °C and react for 24 h. After that, the obtained product is washed three times repeatedly with deionized water and ethanol under the magnetic field force, and then centrifuged. Add the obtained Fe 3 O 4 / TiO 2 Composite into dopamine Tirs solution with a concentration of 2 g / L and pH of 8.5 (obtained by adding dopamine hydrochloride to tris(hydroxymethyl)aminomethane buffer solution and stirring to dissolve), stir and mix for 6 h, filter, dry, and then add the obtained dopamine-modified Fe 3 O 4 / TiO 2 Composite into N, N-dimethylformamide, then add triethylamine and stir to mix evenly. Then add N, N-dimethylformamide solution dissolved with 2-bromoisobutyryl bromide. The mass ratio of Fe 3 O 4 / TiO 2 Composite, triethylamine and 2-bromoisobutyryl bromide is 1:3:0.3. Stir and react for 24 h, then centrifuge and filter. The obtained modified Fe 3 O4 / TiO 2 The complex is added to a mixed solvent of methanol and N,N-dimethylformamide with a volume ratio of 1:1, and then vinylpyridine, cuprous chloride, and pentamethyldiethylenetriamine are added. Fe 3 O 4 / TiO 2 The mass ratio of the complex, vinylpyridine, cuprous chloride, and pentamethyldiethylenetriamine is 1:0.5:0.01:0.1. Stir and react for 12 h under nitrogen protection. After centrifugation and filtration, wash with alcohol and dry to obtain the Fe 3 O 4 / TiO 2 photocatalyst.

[0046] Comparative Example 1

[0047] A method for preparing a Fe 3 O 4 / TiO 2 photocatalyst, comprising:

[0048] Dissolve 1.42 g of FeCl 3 ·6H 2 O and 3.0 g of sodium citrate in 50 mL of distilled water, add 2 g of titanyl sulfate and stir well. Adjust the pH to 9 - 10 with ammonia water, then pour it into a reaction kettle and place it in an oven at 180 °C for 24 h. After the obtained product is washed three times with deionized water and ethanol under magnetic force, centrifuge to obtain the Fe 3 O 4 / TiO 2 photocatalyst.

[0049] Comparative Example 2

[0050] A method for preparing a Fe 3 O 4 / TiO 2 photocatalyst, comprising:

[0051] Dissolve 1.42 g of FeCl 3 ·6H 2 O and 3.0 g of sodium citrate in 50 mL of distilled water, add 200 μL of tetrabutyl titanate and stir well. Then add 0.1 g of V C , adjust the pH to 9 - 10 with ammonia water, pour it into a reaction kettle and place it in an oven at 180 °C for 24 h. After the obtained product is washed with deionized water and ethanol under magnetic force and centrifuged three times, the Fe 3 O 4 / TiO 2 photocatalyst is obtained.

[0052] For the Fe obtained from the above examples and comparative examples3 O 4 / TiO 2 The photocatalyst is used for catalytic degradation of dye pollutants. The specific method is as follows:

[0053] Mix 30 mL of 10 mg / L methylene blue dye solution with water at a volume ratio of 2:5, add 0.03 g of the Fe 3 O 4 / TiO 2 photocatalyst. After placing it in the dark environment for 20 min, under the illumination of a xenon lamp (350 W), use a constant temperature stirrer to stir rapidly. Take a solution every 20 min, centrifuge and take the supernatant, observe the color change, and use a UV-visible spectrophotometer to test the absorbance-wavelength curve of the supernatant. The results are as Figure 4 shown.

[0054] Figure 4 For the photocatalytic degradation efficiency diagram of the Fe 3 O 4 / TiO 2 photocatalyst added to the methylene blue dye solution, referring to Figure 4 it can be seen that the absorbance of the Fe 3 O 4 / TiO 2 photocatalyst described in Example 1 at the maximum absorption wavelength of methylene blue is the same when degrading for 10 min and 30 min using a xenon light source. After degrading for 60 min, the absorbance of the dye solution at the maximum absorption wavelength of methylene blue hardly changes, and the concentration hardly decreases, indicating that the photocatalytic degradation efficiency of the pure photocatalyst for methylene blue dye solution is extremely low, the time required is long, and the degradation is incomplete.

[0055] Mix 30 mL of 10 mg / L methylene blue, methyl orange, malachite green, and rhodamine B dye solutions with water at a volume ratio of 1:1 respectively, add 2 mL of H 2 O 2 solution (30 wt%) and 0.02 g of the Fe 3 O 4 / TiO 2 photocatalyst. After placing it in the dark environment for 20 min, under the illumination of a xenon lamp (350 W), use a constant temperature stirrer to stir rapidly. Take a solution every 20 min, centrifuge and take the supernatant, observe the color change, and use a UV-visible spectrophotometer to test the absorbance-wavelength curve of the supernatant. The results are as Figures 5-8 shown.

[0056] Figure 5 For the Fe 3 O 4 / TiO 2Photocatalytic degradation efficiency diagram of methylene blue dye solution with the synergistic Fenton catalysis of photocatalyst, refer to Figure 5 It can be seen that at 20 min, the absorbance of the dye solution at the maximum absorption wavelength of methylene blue decreased significantly. From 20 min to 120 min, the degradation rate of methylene blue decreased significantly and became slower and slower. At 20 min, the concentration of the dye solution had decreased to half, but due to the slower and slower degradation rate, the concentration decrease also became slower and slower.

[0057] Figure 6 For the Fe 3 O 4 / TiO 2 Photocatalytic degradation efficiency diagram of methyl orange dye solution with the synergistic Fenton catalysis of photocatalyst, refer to Figure 6 It can be seen that at 20 min, the absorbance of the dye solution at the maximum absorption wavelength of methyl orange decreased significantly. At 40 min, the absorption peak at the maximum absorption wavelength of methyl orange was about to disappear. After 60 min of degradation, the absorbance-wavelength curve of the dye solution was close to horizontal. At 20 min, the concentration of the dye solution had decreased by half, and at 60 min, the concentration of the dye solution decreased close to 0.

[0058] Figure 7 For the Fe 3 O 4 / TiO 2 Photocatalytic degradation efficiency diagram of malachite green dye solution with the synergistic Fenton catalysis of photocatalyst, refer to Figure 7 It can be seen that at 20 min, the absorption peak of the dye solution at the maximum absorption wavelength of malachite green was hardly visible. At 40 min and 60 min, the absorption peaks at the maximum absorption wavelength of malachite green had disappeared. At 20 min, the concentration of the dye solution had decreased to the concentration of methyl orange after 60 min of degradation, and at 40 min, the concentration of the dye solution had decreased to the lowest.

[0059] Figure 8 For the Fe 3 O 4 / TiO 2 Photocatalytic degradation efficiency diagram of rhodamine B dye solution with the synergistic Fenton catalysis of photocatalyst, refer to Figure 8 It can be seen that at 20 min, the absorbance of the dye solution at the maximum absorption wavelength of rhodamine B was already extremely low. From 20 min to 160 min, the degradation rate of rhodamine B decreased significantly and finally dropped to 0. At 20 min, the degradation rate of the dye solution was extremely fast, similar to the concentration of malachite green after 20 min of degradation, but the dye solution was not completely degraded until 160 min.

[0060] As can be seen from the above, the Fe 3 O4 / TiO 2 The photocatalyst is used for Fenton catalysis, with high degradation efficiency and short time consumption. Especially for methyl orange and malachite green dye solutions, the degradation is completed in less than 40 minutes. For relatively stable methylene blue and rhodamine B dye solutions, the degradation is basically completed at 120 minutes, and the concentration of the dye solution after degradation basically tends to 0.

[0061] Referring to the above experimental conditions, 30 mL of 10 mg / L methylene blue, methyl orange, malachite green, and rhodamine B dye solutions are respectively mixed with water at a volume ratio of 1:1, and 2 mL of H 2 O 2 solution (30 wt%) and 0.02 g of the Fe 3 O 4 / TiO 2 photocatalyst described in the examples or comparative examples are added. After being placed in the dark for 20 minutes, under the illumination of a xenon lamp (350 W), a constant temperature stirrer is used for rapid stirring. A solution is taken once after 160 minutes, the supernatant is taken after centrifugation, and its absorbance is measured. The degradation rate is calculated based on the change in absorbance before and after the reaction. The results are shown in Table 1 below:

[0062] Table 1 Catalytic activity of the Fe 3 O 4 / TiO 2 photocatalyst described in the examples and comparative examples

[0063]

[0064] As can be seen from Table 1 above, the Fe 3 O 4 / TiO 2 photocatalyst obtained by the solvothermal method of the present invention has excellent performance and has a good degradation effect on organic dyes in dye wastewater.

[0065] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a Fe3O4 / TiO2 photocatalyst, characterized in that: include: The iron source and sodium citrate are dissolved in water, an alcohol solution containing a titanium source is added, the pH is adjusted to 8-10 after stirring and mixing, and then a solvent thermal reaction is carried out. After separation, the Fe3O4 / TiO2 photocatalyst is obtained.

2. The method for preparing the Fe3O4 / TiO2 photocatalyst according to claim 1, characterized in that: The iron source is at least one of ferric chloride, ferric sulfate or ferric nitrate, and the titanium source is at least one of tetrabutyl titanate or tetraisopropyl titanate.

3. The method for preparing the Fe3O4 / TiO2 photocatalyst according to claim 1 or 2, characterized in that: The molar ratio of the iron source to the titanium source is 1:0.1-0.15; the molar ratio of the iron source to sodium citrate is 1:2-3.

4. The method for preparing the Fe3O4 / TiO2 photocatalyst according to any one of claims 1 to 3, characterized in that: The alcohol is at least one of methanol, ethanol or isopropanol, and the pH adjustment is performed using aqueous ammonia.

5. The method for preparing the Fe3O4 / TiO2 photocatalyst according to any one of claims 1 to 4, characterized in that: The solvent thermal reaction temperature is 160-200° C. and the time is 16-32 hours.

6. The method for preparing the Fe3O4 / TiO2 photocatalyst according to any one of claims 1 to 5, characterized in that: The method also includes grafting polyvinyl pyridine onto the surface of the Fe3O4 / TiO2 photocatalyst.

7. The method for preparing the Fe3O4 / TiO2 photocatalyst according to claim 6, characterized in that: The grafting of polyvinyl pyridine onto the surface of the Fe3O4 / TiO2 photocatalyst specifically comprises: After the Fe3O4 / TiO2 photocatalyst surface is modified with dopamine, it is condensed with 2-bromoisobutyryl bromide and then subjected to surface initiated atom transfer radical polymerization reaction with vinylpyridine, thereby achieving grafting of polyvinylpyridine on the Fe3O4 / TiO2 photocatalyst surface.

8. A Fe3O4 / TiO2 photocatalyst, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the Fe3O4 / TiO2 photocatalyst according to claim 8 in photocatalytic synergistic Fenton-like reaction to degrade dyes.

10. The use of the Fe3O4 / TiO2 photocatalyst in catalytic degradation of dye wastewater according to claim 9, characterized in that: The dye is methyl orange, malachite green, rhodamine B or methylene blue.

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