CN111659411B - Preparation and application of rare earth cerium doped iron molybdate photocatalyst - Google Patents

Abstract

The invention provides a preparation method and application of rare earth cerium doped iron molybdate photocatalyst, which is prepared by mixing Fe (NO)₃)・9H₂Dissolving O in deionized water, adding Ce (NO) at room temperature₃)₃To obtain Fe (NO)₃)・9H₂O and Ce (NO)₃)₃The mixed solution of (1); will be (NH)₄)₆Mo₇O₂₄・4H₂O is dissolved in deionized water and added dropwise to Fe (NO)₃)・9H₂O and Ce (NO)₃)₃Stirring the mixed solution, adding ammonia water to adjust the pH value to 3-4, reacting for 12-13 h at 180-185 ℃, centrifugally washing and drying to obtain the rare earth cerium doped iron molybdate photocatalyst Ce-Fe₂(MoO₄)₃. The cerium-doped iron molybdate prepared by the invention is in a uniform nano spherical structure and has a larger specific surface area; meanwhile, the doping of the rare earth element can effectively reduce the photoproduction electron-hole recombination rate of the photocatalyst, can improve the specific surface area of the photocatalyst to a certain extent, is beneficial to improving the photocatalytic efficiency, and ensures that the Ce-Fe photocatalyst is prepared by adding the rare earth element into the photocatalyst₂(MoO₄)₃Has wide application prospect in the field of photocatalytic dye wastewater treatment.

Description

Preparation and application of a rare earth cerium doped iron molybdate photocatalyst

technical field

The invention relates to a preparation method of a rare earth cerium-doped iron molybdate photocatalyst (Ce-Fe ₂ (MoO ₄ ) ₃ ), in particular to a nano-spherical structure cerium-doped iron molybdate (Ce-Fe ₂ (MoO _{4 )} ) ₃ ) preparation method, the prepared rare earth cerium doped iron molybdate photocatalyst is used for photocatalytic degradation of organic pollutants in dye wastewater, belonging to the field of material preparation and the field of photocatalysis application.

Background technique

Iron molybdate (Fe ₂ (MoO ₄ ) ₃ ) has excellent properties such as response to ultraviolet and visible light, high specific surface energy, selectivity, and strong exposure activity. What is more worthy of attention is that in iron molybdate, molybdate itself has catalytic properties, and iron also has catalytic properties. Therefore, a synergistic catalytic effect can be achieved between the two, making iron molybdate stronger catalytic performance. . Due to the excellent properties of Fe ₂ (MoO ₄ ) ₃ such as catalysis, optics and magnetism, Fe 2 (MoO 4 ) 3 has broad application prospects in the fields of catalysts, magnetic materials and optical fibers.

China is rich in rare earth resources, among which cerium is the most abundant and cheapest element. At the same time, cerium has a unique 4f ¹ , 5d ¹ , 6S ² electronic arrangement structure, so it can be stable in the form of +4 or +3. The existence of different valence states will affect the coordination structure of atoms, and the unique valence state configuration of cerium element is of great help to the improvement of its material properties. The morphology, size, specific surface area and oxygen vacancies of the material together affect its photocatalytic performance, in which oxygen vacancies are related to the electronic structure of cerium ions, and the transition process of cerium ions in different valence states is accompanied by the storage and release of _O2 , the release At the same time, the formation of oxygen vacancies can directly participate in the reaction, so it exhibits redox performance. At the same time, the doping of cerium can effectively reduce the photo-generated electron-hole recombination rate of the photocatalyst, so the doping of cerium into iron molybdate can significantly to enhance its photocatalytic performance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method and application of a rare earth cerium doped iron molybdate photocatalyst.

1. Preparation of rare earth cerium-doped iron molybdate photocatalyst (Ce-Fe ₂ (MoO ₄ ) ₃ )

The preparation method of the rare earth cerium doped iron molybdate photocatalyst of the present invention is that Fe(NO ₃ )·9H ₂ O is dissolved in deionized water, and Ce(NO ₃ ) ₃ is added at room temperature to obtain Fe(NO ₃ )·9H Mixed solution of ₂ O and Ce(NO ₃ ) ₃ ; (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O was dissolved in deionized water and added dropwise to Fe(NO ₃ )·9H ₂ O and Ce( NO ₃ ) ₃ mixed solution, continue stirring for 4~6h in a water bath at 25°C, add ammonia water to adjust the pH to 3~4, react at 180~185°C for 12~13h, wash by centrifugation, and dry at 80~85°C to obtain Rare earth cerium doped iron molybdate photocatalyst Ce-Fe ₂ (MoO ₄ ) ₃ . Among them, the molar ratio of Ce(NO ₃ ) ₃ and Fe(NO ₃ )·9H ₂ O is 0.01~0.06:1; Fe(NO ₃ )·9H ₂ O and (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ The molar ratio of O is 1:0.2~1:0.25.

2. Morphology of rare earth cerium doped iron molybdate (Ce-Fe ₂ (MoO ₄ ) ₃ )

1. Scanning electron microscope analysis

FIG. 1 is a scanning electron microscope image of rare earth cerium-doped iron molybdate (Ce-Fe ₂ (MoO ₄ ) ₃ ) with a Ce doping content of 2% and iron molybdate (Fe ₂ (MoO ₄ ) ₃ ) prepared by the present invention. It can be seen from FIG. 1A that the rare earth cerium doped iron molybdate (Ce-Fe ₂ (MoO ₄ ) ₃ ) is in the form of uniform nanoparticles, with a large specific surface area and a particle size of 110-220 nm. It can be seen from Fig. 1B that iron molybdate (Fe ₂ (MoO ₄ ) ₃ ) is a microflower assembled by nanosheets.

2. XRD analysis

Figure 2 shows pure iron molybdate, rare earth cerium doped iron molybdate (Ce-Fe ₂ (MoO ₄ ) ₃ ): 1%-Ce, rare earth cerium doped iron molybdate (Ce-Fe ₂ (MoO ) prepared by the present invention ₄ ) ₃ ): XRD pattern of 2%-Ce, it can be seen from the figure that all diffraction peaks are consistent with the diffraction peaks of standard card PDF#35-0183, indicating that the sample was successfully synthesized. No additional diffraction peaks appeared after doping rare earth element cerium, which indicated that the crystal structure of Fe ₂ (MoO ₄ ) ₃ did not change after the introduction of rare earth ions. Compared with Fe ₂ (MoO ₄ ) ₃ without rare earth element doping, the XRD peaks of Fe ₂ (MoO ₄ ) ₃ after introducing rare earth element doping are partially shifted, which may be due to the doping of rare earth element ions. The Fe ³⁺ was substituted into the catalyst crystal, resulting in the deformation of Fe ₂ (MoO ₄ ) ₃ lattice.

3. Catalytic performance of rare earth cerium doped iron molybdate (Ce-Fe ₂ (MoO ₄ ) ₃ )

Figure 3 shows the photocatalytic performance of the prepared samples with the ratios of Ce ³⁺ and Fe ³⁺ being 1%, 2%, 4%, and 6%, respectively. Shanghai Lanyi LY-GHX-Xe-300 was used. Type photocatalytic reactor, where the xenon lamp light source is HSX-F300 xenon lamp of Beijing Newbit Technology Co., Ltd., a filter is used at the light source to filter out ultraviolet light (λ<400 nm), the reaction device circulates water at a constant temperature and continuously stirs, respectively. The photocatalytic performance tests were carried out under dark conditions and visible light irradiation. It can be found from the figure that the doping of rare earth cerium element can effectively improve the photocatalytic performance of Fe ₂ (MoO ₄ ) ₃ , and the degradation ability of the catalyst material Ce-Fe ₂ (MoO ₄ ) ₃ to methylene blue is in the order of Ce-2% /Fe ₂ (MoO ₄ ) ₃ >Ce-1%/Fe ₂ (MoO ₄ ) ₃ >Ce-4%/Fe ₂ (MoO ₄ ) ₃ >Ce-6%/Fe ₂ (MoO ₄ ) ₃ >Fe ₂ (MoO ₄ ) ₃ . Among them, Ce-2%/Fe ₂ (MoO ₄ ) ₃ has the strongest photocatalytic performance, and the undoped cerium catalyst material has the weakest photocatalytic performance. After 4 h of photocatalytic reaction, the degradation rate of Ce-2%/Fe ₂ (MoO ₄ ) ₃ to methylene blue solution reached 95.7%, while the degradation rate of undoped cerium catalyst material to methylene blue solution was only 63.29%.

To sum up, the cerium-doped iron molybdate prepared by the present invention has a uniform nano-spherical structure and has a large specific surface area; at the same time, the doping of rare earth elements can effectively reduce the photo-generated electron-hole recombination rate of the photocatalyst, and The specific surface area of the photocatalyst can be increased to a certain extent, which is beneficial to the improvement of the photocatalytic efficiency, which makes the Ce-Fe ₂ (MoO ₄ ) ₃ have broad application prospects in the field of photocatalytic dye wastewater treatment.

Description of drawings

FIG. 1 is a scanning electron microscope image of rare earth cerium doped iron molybdate Ce-Fe ₂ (MoO ₄ ) ₃ : 2%-Ce and iron molybdate.

Fig. 2 is the XRD pattern of the sample prepared by the present invention.

FIG. 3 is a photocatalytic performance diagram of the photocatalytic degradation of methylene blue of the sample prepared in the present invention.

Detailed ways

The preparation and properties of a rare earth cerium-doped iron molybdate (Ce-Fe ₂ (MoO ₄ ) ₃ ) of the present invention will be further described below through specific examples.

Example 1

Dissolve 1.0 mmol Fe(NO ₃ )·9H ₂ O in 20 mL of deionized water, and then add 0.01 mmol Ce(NO ₃ ) ₃ at room temperature to obtain a mixture of Fe(NO ₃ )·9H ₂ O and Ce(NO ₃ ) ₃ mixed solution; 0.22 mmol (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O was dissolved in 20 mL of deionized water, and added dropwise to Fe(NO ₃ )·9H ₂ O and Ce(NO ) under magnetic stirring ₃ ) In the mixed solution of ₃ , keep stirring in a constant temperature water bath at 25°C for 6h, add ammonia water to adjust the pH to 4; finally transfer to a high pressure reaction kettle containing 50mL polytetrafluoroethylene liner, react at 180°C for 12h, and wait for the reaction to end After centrifugation and washing with deionized water three times, centrifugation and washing with absolute ethanol for two times, and then drying at 80 °C, a rare earth cerium-doped iron molybdate Ce-Fe ₂ (MoO ₄ ) ₃ photocatalyst was obtained: 1%-Ce .

Catalytic performance: The above prepared materials were added to the methylene blue solution. After 4 h of photocatalytic reaction, the degradation rate of methylene blue in the solution reached 92.85%.

Example 2

Dissolve 1.0 mmol Fe(NO ₃ )·9H ₂ O in 20 mL of deionized water, and then add 0.02 mmol Ce(NO ₃ ) ₃ at room temperature to obtain a mixture of Fe(NO ₃ )·9H ₂ O and Ce(NO ₃ ) ₃ mixed solution; 0.22 mmol (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O was dissolved in 20 mL of deionized water, and added dropwise to Fe(NO ₃ )·9H ₂ O and Ce(NO ) under magnetic stirring ₃ ) In the mixed solution of ₃ , keep stirring in a constant temperature water bath at 25°C for 6h, add ammonia water to adjust the pH to 4; finally transfer to a high pressure reaction kettle containing 50mL polytetrafluoroethylene liner, react at 180°C for 12h, and wait for the reaction to end After centrifugation and washing with deionized water for three times, centrifugation and washing with absolute ethanol for two times, and then drying at 80° C., the rare earth cerium doped iron molybdate photocatalyst Ce-Fe ₂ (MoO ₄ ) ₃ : 2%-Ce was obtained .

Catalytic performance: The above prepared materials were added to the methylene blue solution. After 4 h of photocatalytic reaction, the degradation rate of methylene blue in the solution reached 95.7%.

Example 3

Dissolve 1.0 mmol Fe(NO ₃ )·9H ₂ O in 20 mL of deionized water, and then add 0.04 mmol Ce(NO ₃ ) ₃ at room temperature to obtain a mixture of Fe(NO ₃ )·9H ₂ O and Ce(NO ₃ ) ₃ Mixed solution; 0.22mmol (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O was dissolved in 20 mL of deionized water, and added dropwise to Fe(NO ₃ )·9H ₂ O and Ce(NO ) under magnetic stirring ₃ ) In the mixed solution of ₃ , keep stirring in a constant temperature water bath at 25°C for 6h, add ammonia water to adjust the pH to 4; finally transfer to a high pressure reaction kettle containing 50mL polytetrafluoroethylene liner, react at 180°C for 12h, and wait for the reaction to end After centrifugation and washing with deionized water for three times, centrifugation and washing with absolute ethanol for two times, and then drying at 80 °C, the rare earth cerium doped iron molybdate photocatalyst Ce-Fe ₂ (MoO ₄ ) ₃ : 4%-Ce was obtained .

Catalytic performance: The above prepared materials were added to the methylene blue solution. After 4 h of photocatalytic reaction, the degradation rate of methylene blue in the solution reached 67.39%.

Example 4

Dissolve 1.0 mmol Fe(NO ₃ )·9H ₂ O in 20 mL of deionized water, and then add 0.06 mmol Ce(NO ₃ ) ₃ at room temperature to obtain a mixture of Fe(NO ₃ )·9H ₂ O and Ce(NO ₃ ) ₃ Mixed solution; 0.22mmol (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O was dissolved in 20 mL of deionized water, and added dropwise to Fe(NO ₃ )·9H ₂ O and Ce(NO ) under magnetic stirring ₃ ) In the mixed solution of ₃ , keep stirring in a constant temperature water bath at 25°C for 6h, add ammonia water to adjust the pH to 4; finally transfer to a high pressure reaction kettle containing 50mL polytetrafluoroethylene liner, react at 180°C for 12h, and wait for the reaction to end After centrifugation and washing with deionized water for three times, centrifugation and washing with absolute ethanol for two times, and then drying at 80 °C, the rare earth cerium doped iron molybdate photocatalyst Ce-Fe ₂ (MoO ₄ ) ₃ : 6%-Ce was obtained .

Catalytic performance: The above prepared materials were added to the methylene blue solution. After 4 h of photocatalytic reaction, the degradation rate of methylene blue in the solution reached 65.65%.

Claims (5)

1. A process for preparing the rare-earth Ce doped iron molybdate photocatalyst includes such steps as adding Fe (NO)₃)・9H₂Dissolving O in deionized water, adding Ce (NO) at room temperature₃)₃To obtain Fe (NO)₃)・9H₂O and Ce (NO)₃)₃The mixed solution of (1); will be (NH)₄)₆Mo₇O₂₄・4H₂O is dissolved in deionized water and added dropwise to Fe (NO)₃)・9H₂O and Ce (NO)₃)₃Stirring the mixed solution, adding ammonia water to adjust the pH value to 3-4, reacting for 12-13 h at 180-185 ℃, centrifugally washing and drying to obtain the rare earth cerium doped iron molybdate photocatalyst Ce-Fe₂(MoO₄)₃(ii) a What is needed isThe above Ce (NO)₃)₃And Fe (NO)₃)・9H₂The molar ratio of O is 0.01-0.02: 1.

2. The method of claim 1, wherein the preparation method comprises the following steps: said Fe (NO)₃)・9H₂O and (NH)₄)₆Mo₇O₂₄・4H₂The molar ratio of O is 1: 0.2-1: 0.25.

3. The method for preparing a rare earth cerium doped iron molybdate photocatalyst as claimed in claim 1, wherein the method comprises the following steps: the stirring is carried out for 4-6 h under a water bath at 25 ℃.

4. The method of claim 1, wherein the preparation method comprises the following steps: the drying temperature is 80-85 ℃.

5. The use of the rare earth cerium doped iron molybdate photocatalyst prepared by the preparation method according to any one of claims 1 to 4 for photocatalytic degradation of organic pollutants in dye wastewater, characterized in that: the organic contaminant is methylene blue.

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