Method for preparing iron-doped rutile titanium dioxide

A kind of preparation method of iron-doped rutile titanium dioxideTechnical field

[0001] The present invention relates to a method for preparing iron-doped rutile titanium dioxide with different contents at a lower temperature, and its application in the fields of photocatalysis, sewage treatment and air purification, and solar cells.

Background technique

[0002] Titanium dioxide, as a highly efficient, non-toxic, physicochemical and optically stable photocatalytic material, has been used in water splitting hydrogen production, photovoltaic cells, photoreduction of carbon dioxide to produce fuels, and the degradation of organic pollutants in the environment. A certain degree of progress has attracted widespread attention. However, due to the wider band gap of titanium dioxide (3. OeV-3. 2eV), so only ultraviolet light can be used, but ultraviolet light only accounts for 3%-5% of sunlight energy. In addition, titanium dioxide itself has a low specific surface area and poor adsorption performance, while titanium dioxide can only undergo photocatalytic degradation reactions of organic pollutants adsorbed on its surface, so the photocatalytic efficiency is not high. In order to improve its adsorption performance, most of the literature uses the method of combining titanium dioxide with strong adsorption materials (such as apatite, activated carbon, graphene, etc.) to form a composite material to improve its adsorption performance. Currently, anion and cation doping has been proven to effectively improve the responsiveness of the titanium dioxide photocatalyst to visible light. The radius of iron ions is similar to that of titanium ions, so it is easier to enter the titanium dioxide crystal lattice to form a solid solution or replace the titanium ions in the crystal lattice. After iron ion doping, a new doping energy level will be formed, so it can enhance its absorption of visible light. In addition, some documents show that iron has a variety of valence states, which can be combined with electrons and holes respectively, thereby inhibiting the recombination of electron-hole pairs, improving light quantum efficiency, and enhancing photocatalytic activity under visible light. It is generally believed that rutile titanium dioxide has poor photocatalytic activity due to its low carrier mobility, photogenerated electron-hole pair recombination too fast. The traditional method to synthesize rutile titanium dioxide requires long-term roasting at high temperature (not lower than 750°C), but high-temperature roasting will promote the reduction of the specific surface area of titanium dioxide grains, thereby reducing the photocatalytic activity. Different content iron doped rutile dioxide synthesized by this method Titanium reduces the synthesis temperature, has excellent adsorption performance and visible light activity, similar results have not been reported in the literature.

Summary of the invention

[0003] The object of the present invention is to provide a method for preparing iron-doped rutile titanium dioxide with high visible light photocatalytic activity at a lower temperature. In the present invention, an appropriate amount of tin is introduced into the system as a crystal phase regulator and a crystal phase stabilizer, and rutile titanium dioxide can be obtained at a relatively low temperature. On this basis, a series of iron doping with different contents is carried out at the same time. The titanium dioxide photocatalyst prepared after doping can not only keep the rutile type unchanged, but also has good reactivity in the reaction of visible light photocatalytic degradation of methylene blue.

[0004] The present invention provides a method for preparing an iron-doped rutile-type titanium dioxide photocatalytic material with high visible light photocatalytic activity at a lower temperature, and the specific steps are:

[0005] 1) Take a certain amount of titanium precursor, mix it with different amounts of iron salt and tin salt, and heat it in a water bath to

30° C-100° C;

[0006] 2) Add an appropriate amount of a certain concentration of hydrogen peroxide solution to the mixed solution, and stir, mix evenly, and keep it in a 30° C-100° C water bath for 0.5-4 hours;

[0007] 3) Put the obtained gel in an oven above 60°C for drying;

[0008] 4) Grind the dried powder and burn it at 450-600°M for 2-8h.

[0009] The titanium precursor is one or more of tetraisopropyl titanate, tetrabutyl titanate, titanium tetrachloride, and titanium sulfate, and the iron salt is ferric nitrate, which is chlorinated One or more of iron, iron sulfate, and iron acetylacetonate, and the tin salt is one or more of tin tetrachloride, stannous chloride, and stannous oxalate.

[0010] The prepared titanium dioxide has strong adsorption performance and visible light catalytic activity in the photocatalytic reaction of visible light photocatalytic degradation of organic pollutants.

[0011] The present invention has the following advantages:

[0012] The operation process is simple, the reaction conditions are mild, and the energy consumption is low, and the prepared iron-doped rutile titanium dioxide has good adsorption performance and photocatalytic activity in the visible light photocatalytic reaction.

Description of the drawings

[0013] FIG. 1 is the XRD spectra of Examples 1 to 5. From the spectra, it can be found that the introduction of an appropriate amount of tin as a crystal phase regulator and a crystal phase stabilizer is calcined at 500 ° C to obtain pure rutile titanium dioxide After a series of iron doping at the same time, the prepared titanium dioxide photocatalyst is still pure rutile, but the peak shape is slightly broadened, indicating that iron doping does not change the crystalline phase composition of titanium dioxide, but reduces the grain size.

[0014] FIG. 2 is Example 1~Example 5 and commercial P-25Ti0₂The solid ultraviolet-visible diffuse reflectance absorption spectrum can be found from the figure, which is similar to the commercial P-25Ti0₂In comparison, tin doping can improve the visible light absorption performance of titanium dioxide samples to a certain extent, while iron doping can significantly increase the visible light absorption of titanium dioxide, and the higher the iron content, the stronger the visible light absorption.

[0015] FIG. 3 is an ultraviolet-visible diffuse reflectance absorption spectrum of the photocatalytic degradation process of Example 3. Methylene blue has a characteristic absorption at 664nm, and the absorbance is directly proportional to the concentration, so the concentration of methylene blue can be determined based on the absorbance. The dark reaction for 30min indicates the concentration when the adsorption equilibrium is reached. With the prolongation of light time, the absorbance of methylene blue at 664nm gradually decreased, indicating that methylene blue was gradually degraded.

[0016] FIG. 4 is an evaluation spectrum of the adsorption performance and visible light photocatalytic performance of Examples 1 to 5 and commercial P-25 titanium monoxide (Degussa). It can be seen from the figure that compared with P-25 titanium dioxide, the adsorption performance and photocatalytic performance of the prepared iron-doped rutile titanium dioxide photocatalyst have been greatly improved. .

Detailed ways

[0017] The method for evaluating the adsorption performance of titanium dioxide provided by the present invention is as follows:

[0018] Evaluation of adsorption performance: the photocatalyst prepared with 50ml110ppm methylene blue solution and 0.050g was added to the quartz reactor, stirred in a dark box for half an hour, at which time the adsorption equilibrium was reached, sampled 2ml, centrifuged to take the supernatant , Use an ultraviolet-visible spectrophotometer to measure its absorbance.

[0019] The present invention provides dioxide Evaluation adsorption properties of titanium as follows:

[0020] Photocatalytic performance evaluation: 50ml10ppm methylene blue solution and 0.050g prepared photocatalyst were added to the quartz reactor, stirred in a dark box for half an hour, and then turned on the 300W magic emanation lamp pair equipped with a λ 2 420nm filter The reaction vessel was irradiated with a reaction time of 60 minutes. The lights were turned off every 15 minutes to sample 2ml, and the supernatant was collected by centrifugation. The supernatant was measured with an ultraviolet-visible spectrophotometer to determine the degradation degree of the methylene blue solution.

Example 1

[0022] In a 1L beaker was added 2ml isopropyl titanate, 0.0280g stannous oxalate, and then slowly added 30ml mass fraction of 30%. 2. Stir for half an hour in a constant temperature water bath at 50°C. After that, the gel was placed in an oven at 120°C to dry.

Grind the dried dry glue into powder, and burn it in a muffle furnace at 500°M for 4h. And the obtained powder was subjected to XRD, adsorption performance and photocatalytic performance measurement.

Example 2

[0024] Add 2ml of isopropyl titanate, 0.0280g of stannous oxalate, and 0.0024g of iron acetylacetonate to a 1L beaker, and then slowly add 30ml of a 30% mass fraction. 2. Stir for half an hour in a constant temperature water bath at 50°C, then put the gel in an oven at 120°C to dry. Grind the dried dry glue into powder, and burn it in a muffle furnace at 500°M for 4h. And the obtained powder was subjected to XRD, adsorption performance and photocatalytic performance measurement.

Example 3

[0026] Add 2ml isopropyl titanate, 0.0280g stannous oxalate, 0.0119g iron acetylacetonate in a 1L beaker, and then slowly add 30ml with a mass fraction of 30%. 2. Stir in a constant temperature water bath at 50°C for half an hour, then put the gel in an oven at 120°C to dry. Grind the dried dry glue into powder, and burn it in a muffle furnace at 500°M for 4h. And the obtained powder was subjected to XRD, adsorption performance and photocatalytic performance measurement.

Example 4

[0028] Add 2ml isopropyl titanate, 0.0280g stannous oxalate, 0.0238g iron acetylacetonate in a 1L beaker, and then slowly add 30ml with a mass fraction of 30%. 2. Stir in a constant temperature water bath at 50°C for half an hour, then put the gel in an oven at 120°C to dry. Grind the dried dry glue into powder, and burn it in a muffle furnace at 500°M for 4h. And the obtained powder was subjected to XRD, adsorption performance and photocatalytic performance measurement.

Example 5

[0030] Add 2ml isopropyl titanate, 0.0280g stannous oxalate, 0.0714g iron acetylacetonate in a 1L beaker, and then slowly add 30ml with a mass fraction of 30%. 2. Stir in a constant temperature water bath at 50°C for half an hour, then put the gel in an oven at 120°C to dry. Grind the dried dry glue into powder, and burn it in a muffle furnace at 500°M for 4h. And the obtained powder was subjected to XRD, adsorption performance and photocatalytic performance measurement.

<td rowspan="2">[0031]</td><td colspan="3">Table 1</td>

<td>sample</td><td>Specific surface area</td><td>Grain size</td>

<td></td><td>(%)</td><td></td><td>(nm ,)</td>

<td></td><td>Example 1</td><td>36 1</td><td>33</td>

<td>[0032]</td><td>Example 2</td><td>52.8</td><td>34</td>

<td></td><td>Example 3</td><td>52 6</td><td>32</td>

<td></td><td>Example 4</td><td>50.2</td><td>30</td>

<td></td><td>Example 5</td><td>52.1</td><td>28</td>

<td>[0033]</td><td colspan="3">Table 1 is the specific surface area and crystal grain size of Example 1~Example 5. It is found that the dioxygen prepared after iron doping</td>

The specific surface area of titanium oxide is significantly increased. The crystal grain size of titanium dioxide is calculated according to the Scherer equation, and its range is 28-34nm.

[0034] Table 2

[0035]

<td rowspan="2">sample</td><td colspan="2">Degradation rate(%)</td><td rowspan="2">Reaction rate constant k</td>

<td>Adsorption</td><td>Visible light irradiation lh</td>

<td>P-25TiO₂</td><td>3.4</td><td>8.78</td><td>0.00093</td>

<td>Example 1</td><td>24.6</td><td>40.4</td><td>0.00396</td>

<td>Example 2</td><td>24.6</td><td>46 3</td><td>0.00558</td>

<td>Example 3</td><td>30.1</td><td>59.5</td><td>0.00897</td>

<td>Example 4</td><td>22.9</td><td>41.2</td><td>0.00473</td>

<td>Example 5</td><td>16.0</td><td>25.0</td><td>0.00177</td>

[0036] Table 2 shows the degradation rate and reaction rate constant of the photocatalytic degradation of methylene blue. The results show that after tin doping, the adsorption performance and photocatalytic activity have been greatly improved, and after different iron doping, the adsorption performance and photocatalytic activity both show a trend of first increasing and then decreasing. Among them, Example 3 is the best doping content, the adsorption performance is more than 8 times that of P-25 titanium dioxide, and the photocatalytic reaction activity is more than 9 times that of P-25 titanium dioxide.