CN102350353A - A kind of preparation method of Fe3O4/C/TiO2 composite photocatalyst - Google Patents

Abstract

The invention relates to a preparation method of an Fe3O4/C/TiO2 composite photocatalyst, which comprises the following steps: (1) dissolving titanium alkoxide in absolute lower alcohol to prepare a titanium alkoxide absolute alcohol solution; (2) adding Fe3O4/C nano powder into the titanium alkoxide absolute alcohol solution, carrying out ultrasonic dispersion and stirring to obtain a uniform mixture; and (3) putting the mixture into a closed container which previously contains distilled water (the mixture does not directly contact the distilled water), heating to 70-200 DEG C, keeping the temperature for 1-96 hours, cooling to room temperature, washing the powder and drying to obtain the Fe3O4/C/TiO2 composite photocatalyst. The preparation method provided by the invention is simple, and has the advantage of lower cost; and the composite photocatalyst maintains the characteristic of high catalytic activity of titanium dioxide nano crystal grains, and can be magnetically recycled, thereby providing a solution for separating and recycling nano crystal titanium dioxide.

Description

A kind of preparation method of Fe3O4/C/TiO2 composite photocatalyst

technical field

The invention belongs to the field of preparation of _TiO2 composite photocatalyst, in particular to a preparation method of _Fe3O4 /C/ _TiO2 composite _{photocatalyst} .

Background technique

Nano-titanium dioxide is a common photocatalyst, which has attracted widespread attention because of its good chemical stability, high oxidation activity, non-toxicity to the human body, low cost, and wide application range. However, there are two main factors restricting the application of nano-titanium dioxide in sewage treatment: one is that titanium dioxide with high catalytic activity and strong oxidation ability often requires ultraviolet light excitation; the other is that nanocrystalline photocatalysts have high activity but high recycling costs. Photocatalysts with thin films and multi-level structures can solve the problem of difficult recycling, but the photocatalytic efficiency is not high. Thin films usually immobilize photocatalysts such as nano-titanium dioxide on inert supports such as glass by physical or chemical methods, but this type of photocatalyst has a small solid-liquid contact area, resulting in low photocatalytic activity. The particle size of nano-titanium dioxide with multi-level structure is often larger than 10 μm. Due to the scattering and absorption of light on the surface, the interior of the particle is a region that is difficult to be irradiated by light, and its light-harvesting efficiency needs to be improved. At present, photocatalysts with high activity and easy recovery still need further research.

Recently, magnetic materials have been introduced into photocatalysts to prepare magnetic photocatalysts with a core/shell structure. This not only retains the high photocatalytic activity of the nanocrystals, but also utilizes the characteristics of magnetic cores that are easy to achieve magnetic separation and recovery. Xuan et al. (J.Phys.Chem.C, 2009, 113, 553.) prepared hollow microspheres of Fe ₃ O ₄ /TiO ₂ using poly(styrene-acrylic acid) as a template. The experiments showed good photodegradation and magnetic recovery performance. Because the photocorrosion of TiO ₂ will cause damage to the magnetic core Fe ₃ O ₄ (J.Phys.Chem.B, 2000, 104, 4387.), it is not conducive to the long-term application of magnetic photocatalysts. Song et al. (J.Am.Ceram.Soc., 2007, 90, 4015.) used the sol-gel method to prepare a core/shell structure photocatalyst with magnetic Fe ₃ O ₄ as the magnetic core. corrosion, a layer of SiO ₂ is coated between the titanium dioxide photocatalyst and the magnetic core.

Contents of the invention

The technical problem to be solved by the present invention is to provide a preparation method of Fe ₃ O ₄ /C/TiO ₂ composite photocatalyst, which is simple, relatively low in cost, and does not require high equipment; The characteristics of high catalytic activity of titanium dioxide nanocrystals are recognized. In most photocatalytic reactions, the photocatalytic activity is similar to that of nano-titanium dioxide prepared by gas-phase method, and it also has the advantages of magnetic recovery. It provides a good solution for the separation and recovery of nanocrystalline titanium dioxide. found a solution.

A kind of _Fe3O4 /C/ _TiO2 composite photocatalyst preparation method of the present _invention comprises:

(1) dissolving titanium alkoxide in anhydrous lower alcohol to make a titanium alkoxide anhydrous alcohol solution with a concentration of 0.001 to 0.12mL/mL;

(2) Add Fe ₃ O ₄ /C nanopowder into the above-mentioned titanium alkoxide anhydrous alcohol solution, and after ultrasonic dispersion and stirring, a uniform mixture is obtained, wherein the concentration of Fe ₃ O ₄ /C is 0.5-100.0 mg/ mL;

(3) Put the above mixture into a closed container filled with distilled water in advance. The mixture is not in direct contact with distilled water, then heated to 70-200°C, kept for 1-96 hours, then cooled to room temperature, and finally the obtained powder After washing and drying, the Fe ₃ O ₄ /C/TiO ₂ composite photocatalyst is obtained.

The titanium alkoxide in the step (1) is one or more of tetraethyl titanate, tetraisopropyl titanate and tetrabutyl titanate.

The lower alcohol in the step (1) is one or more of methanol, ethanol, n-propanol and isopropanol.

The Fe ₃ O ₄ /C nano-powder in the step (2) is obtained by modifying the Fe ₃ O ₄ microspheres with carbon, and then recovering in a magnetic field, washing with water, washing with alcohol, and drying.

The above-mentioned Fe ₃ O ₄ microspheres are prepared by solvothermal method, and the specific operation method is: add 1.35g FeCl ₃ ·6H ₂ O, 3.6g anhydrous sodium acetate, 1g polyethylene glycol, 0.5g polyvinylpyrrolidone Put it into 50mL ethylene glycol solution, after being ultrasonically stirred, put it in a reaction kettle, and react at 200°C for 10 hours to obtain Fe ₃ O ₄ microspheres.

The ratio of the distilled water in the step (3) to the amount of titanium element in the titanium alkoxide is 20-3000.

The Fe ₃ O ₄ /C/TiO ₂ composite photocatalyst obtained in the step (3) has a core/shell structure, wherein the core is Fe ₃ O ₄ microspheres, the transition layer is a C layer, and the shell layer is a well-crystalline Anatase titanium dioxide nanocrystals with a grain size of 5-20nm.

Now make some specific restrictions on the relevant process parameters of the reaction:

(1) The amount of water: the water is at the bottom of the airtight container and does not directly contact with the titanium alkoxide. When heated, the water starts to evaporate, and finally the titanium alkoxide is completely hydrolyzed. In the actual reaction, the ratio of water to titanium species is between 20 and 3000.

(2) Concentration of Fe ₃ O ₄ /C: The concentration of Fe ₃ O ₄ /C in the alcohol solution is between 0.5 mg/mL and 100.0 mg/mL.

(3) Concentration of titanium alkoxide: the concentration of titanium alkoxide in lower alcohol is in the range of 0.001mL/mL to 0.120mL/mL, and the thickness of anatase titanium dioxide coating can be changed by changing the concentration of titanium alkoxide .

The thickness of the anatase titanium dioxide coating layer is determined by the amount of added titanium alkoxide (0.010mL-1.500mL). Depending on the amount of titanium alkoxide, a titanium dioxide layer with a thickness of several nanometers to hundreds of nanometers can be formed.

The present invention mainly provides a method for preparing a Fe ₃ O ₄ /C/TiO ₂ magnetically recyclable composite photocatalyst with a core/shell structure, which can be used to prepare nucleation/ Shell-structured magnetically recyclable composite photocatalysts. The composite photocatalyst prepared by the present invention not only retains the characteristics of high catalytic activity of titanium dioxide nanocrystal grains, but also has photocatalytic activity similar to that of nano titanium dioxide prepared by gas phase method in most photocatalytic reactions, and has the advantage of being magnetically recyclable , providing a solution for the separation and recovery of nanocrystalline titanium dioxide.

The preparation method of a Fe ₃ O ₄ /C/TiO ₂ composite photocatalyst of _the present invention uses Fe ₃ O ₄ /C microspheres _as a carrier to promote the hydrolysis of titanium alkoxide by water vapor. An anatase phase titanium dioxide layer was formed on the surface of the microspheres. This _composite photocatalyst has a core-shell structure, the core is _Fe3O4 microspheres, the transition layer is C layer, and the shell layer is crystalline titanium dioxide, which can improve the recovery characteristics of titanium dioxide when used as a photocatalyst.

Beneficial effect

(1) The preparation method of the present invention is simple, the cost is relatively low, the requirements for equipment are not high, and large-scale production is possible;

(2) The magnetic photocatalyst of the present invention retains the high characteristics of the photocatalytic activity of titanium dioxide nanocrystal grains, and the shell layer titanium dioxide is an anatase phase, and its crystal grains are 5～20nm, which is relevant to the temperature of vapor phase treatment;

(3) The magnetic photocatalyst prepared by the present invention maintains the magnetic properties of its core, so that it can be recovered by a magnetic field.

Description of drawings

Fig. 1 (a) is the transmission electron _micrograph of the _Fe3O4 particles prepared by solvothermal method, (b) is the transmission electron micrograph of the _Fe3O4 /C/ _{TiO2 composite} photocatalyst prepared in Example 1; (c ) The high-resolution electron micrograph of the selected area in Figure 1(b), in which the lattice fringes of anatase titanium dioxide can be clearly observed, indicating that titanium dioxide has good crystallinity, and the crystals of the anatase (101) plane The lattice spacing is 0.35 nm, and the grain size of anatase titanium dioxide is about 10 nm; (d) The energy spectrum results of the selected area in Fig. 1(b);

Figure 2 is the magnetic hysteresis loop diagram of Fe ₃ O ₄ particles, Fe ₃ O ₄ /C microspheres and the Fe ₃ O ₄ /C/TiO ₂ composite photocatalyst prepared in Example 1 and the magnetic recovery photo of the magnetic photocatalyst ;

Fig. 3 is the efficiency diagram _of the photodegradation methylene blue of _Fe3O4 /C/ _TiO2 composite photocatalyst prepared in example 1 and its long-term cycle efficiency diagram;

Fig. 4 is the X-ray diffraction results of the Fe ₃ O ₄ particles prepared by the solvothermal method and the Fe ₃ O ₄ /C/TiO ₂ composite photocatalyst prepared in Example 2.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

Add 0.20 mL of butyl titanate into 8 mL of absolute ethanol, stir for 2 minutes, add 0.1 g of pre-prepared Fe ₃ O ₄ /C microspheres into lower alcohol, ultrasonically disperse and stir for 3 minutes each. Pour the absolute alcohol solution containing Fe ₃ O ₄ /C microspheres into the crucible, and then put it on the upper part of the sealable container. The bottom of the sealable container is prefilled with 3 mL of distilled water. After sealing the container, put it into an oven, start heating to 150°C, the heating rate is 10-20°C/min, and keep it warm for 10 hours after the temperature reaches the set temperature. After the heat preservation is over, cool down to room temperature naturally, open the airtight container, take out the crucible, pour out the powder, wash with distilled water and absolute alcohol for 3 times, and dry in vacuum at 60°C for 8 hours.

Figure 1(a) shows the transmission electron micrograph of Fe ₃ O ₄ particles prepared by solvothermal method, (b) transmission electron micrograph of Fe ₃ O ₄ /C/TiO ₂ composite photocatalyst, (c) Figure 1( High-resolution SEM image of the selected area in b). The lattice fringes of anatase titanium dioxide can be clearly observed in the figure, indicating that titanium dioxide has good crystallinity, the lattice spacing of the anatase (101) plane is 0.35nm, and the grain size of anatase titanium dioxide is about 10nm. (d) Spectroscopy results for the selected region in Fig. 1(b).

Example 2

Add 0.20 mL of butyl titanate into 8 mL of absolute ethanol, stir for 2 minutes, add 0.1 g of pre-prepared Fe ₃ O ₄ /C microspheres into lower alcohol, ultrasonically disperse and stir for 3 minutes each. Pour the absolute alcohol solution containing Fe ₃ O ₄ /C microspheres into the crucible, and then put it on the upper part of the sealable container. The bottom of the sealable container is prefilled with 3 mL of distilled water. After sealing the container, put it into an oven, start heating to 200°C, the heating rate is 10-20°C/min, and keep it warm for 10 hours after the temperature reaches the set temperature. Cool down to room temperature naturally after the heat preservation, open the airtight container, take out the crucible, pour out the powder, wash with distilled water and absolute alcohol three times respectively, and dry in vacuum at 60°C for 8 hours.

Example 3

Add 0.10 mL of butyl titanate into 8 mL of absolute ethanol, stir for 2 minutes, add 0.03 g of pre-prepared Fe ₃ O ₄ /C microspheres into lower alcohol, ultrasonically disperse and stir for 10 minutes each. Pour the absolute alcohol solution containing Fe ₃ O ₄ /C microspheres into the crucible, and then put it on the upper part of the sealable container. The bottom of the sealable container is prefilled with 20 mL of distilled water. After sealing the container, put it into an oven, start heating to 200°C, the heating rate is 20-30°C/min, and keep it warm for 8 hours after the temperature reaches the set temperature. Cool down to room temperature naturally after the heat preservation, open the airtight container, take out the crucible, pour out the powder, wash with distilled water and absolute alcohol three times respectively, and dry in vacuum at 90°C for 24 hours.

Example 4

Add 0.05 mL of butyl titanate to 8 mL of absolute ethanol, stir for 2 minutes, add 0.5 g of pre-prepared Fe ₃ O ₄ /C microspheres to lower alcohol, ultrasonically disperse and stir for 20 minutes each. Pour the absolute alcohol solution containing Fe ₃ O ₄ /C microspheres into the crucible, and then put it on the upper part of the sealable container. The bottom of the sealable container is prefilled with 20 mL of distilled water. After sealing the container, put it into an oven, start heating to 200°C, the heating rate is 20-30°C/min, and keep it warm for 18 hours after the temperature reaches the set temperature. Cool down to room temperature naturally after heat preservation, open the airtight container, take out the crucible, pour out the powder, wash with distilled water and absolute alcohol three times respectively, and vacuum dry at 90°C for 48 hours.

Wherein the Fe ₃ O ₄ /C nanopowder is obtained by modifying Fe ₃ O ₄ microspheres with carbon, and then recovering by magnetic field, washing with water, washing with alcohol, and drying. The Fe ₃ O ₄ microspheres are Prepared by solvothermal method, the specific operation method is: add 1.35g FeCl ₃ 6H ₂ O, 3.6g anhydrous sodium acetate, 1g polyethylene glycol, 0.5g polyvinylpyrrolidone into 50mL ethylene glycol solution, After ultrasonication and stirring, place it in a reaction kettle and react at 200°C for 10 hours to obtain Fe ₃ O ₄ microspheres.

Claims (7)

1. Fe ₃O ₄/ C/TiO ₂The preparation method of composite photo-catalyst comprises:

(1) the titanium alkoxide is dissolved in the anhydrous lower alcohol, processing concentration is the titanium alkoxide anhydrous alcohol solution of 0.001～0.12mL/mL;

(2) with Fe ₃O ₄/ C nano-powder adds in the above-mentioned titanium alkoxide anhydrous alcohol solution, through ultrasonic dispersion and stirring, obtains uniform mixture, wherein Fe ₃O ₄The concentration of/C is 0.5～100.0mg/mL;

(3) said mixture is put into the closed container that fills distilled water in advance, said mixture does not directly contact with distilled water, is heated to 70～200 ℃ then, is incubated 1～96 hour, and cool to room temperature with the washing of gained powder, drying, promptly gets Fe at last again ₃O ₄/ C/TiO ₂Composite photo-catalyst.

2. a kind of Fe according to claim 1 ₃O ₄/ C/TiO ₂The preparation method of composite photo-catalyst is characterized in that: the titanium alkoxide in the said step (1) is one or more in tetraethyl titanate, tetraisopropyl titanate, the butyl titanate.

3. a kind of Fe according to claim 1 ₃O ₄/ C/TiO ₂The preparation method of composite photo-catalyst is characterized in that: the lower alcohol in the said step (1) is one or more in methyl alcohol, ethanol, normal propyl alcohol, the isopropyl alcohol.

4. a kind of Fe according to claim 1 ₃O ₄/ C/TiO ₂The preparation method of composite photo-catalyst is characterized in that: the Fe in the said step (2) ₃O ₄/ C nano-powder is through with Fe ₃O ₄Microballoon obtains after magnetic field recovery, washing, alcohol are washed, dried after carbon is modified again.

5. a kind of Fe according to claim 4 ₃O ₄/ C/TiO ₂The preparation method of composite photo-catalyst is characterized in that: described Fe ₃O ₄Microballoon is for what prepare through solvent thermal process, and concrete operation method is: with 1.35gFeCl ₃6H ₂O, 3.6g anhydrous sodium acetate, 1g polyethylene glycol, 0.5g polyvinylpyrrolidone join in the 50mL ethylene glycol solution, through ultrasonic, stir after, place agitated reactor, after 10 hours, promptly get Fe 200 ℃ of reactions ₃O ₄Microballoon.

6. a kind of Fe according to claim 1 ₃O ₄/ C/TiO ₂The preparation method of composite photo-catalyst is characterized in that: the ratio of the amount of substance of titanium elements is 20～3000 in the distilled water in the said step (3) and the titanium alkoxide.

7. a kind of Fe according to claim 1 ₃O ₄/ C/TiO ₂The preparation method of composite photo-catalyst is characterized in that: the Fe that obtains in the said step (3) ₃O ₄/ C/TiO ₂Composite photo-catalyst is a core/shell structure, and its center is Fe ₃O ₄Microballoon, transition zone are the C layer, and shell is that anatase titania is nanocrystalline, and crystallite dimension is 5～20nm.

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