CN102995120A - A kind of nano TiO2 single crystal material, its preparation method and application - Google Patents

Abstract

The invention relates to a nanometer _TiO2 single crystal material, its preparation method and application, and belongs to the field of inorganic nanometer material preparation. The invention prepares the anatase type nano _TiO2 single crystal particles with uniform particle size distribution through the combination of precipitation and hydrothermal method under the condition of relatively low temperature, and the diameter is about 30nm. The invention has simple preparation process and low energy consumption, and the obtained titanium dioxide material has uniform appearance and high purity, and has good performance of photocatalytic degradation of organic matter.

Description

A kind of nano TiO2 single crystal material, its preparation method and application

technical field

The present invention relates to a nano _TiO2 single crystal material, its preparation method and application, and belongs to the field of inorganic nano material preparation, in particular to a nano _TiO2 single crystal material with highly uniform particle size and its preparation method, and its photocatalytic field usage.

Background technique

As an important semiconductor oxide, TiO ₂ has been widely used in pigments, coatings, inks, cosmetics, environmental pollution control and other fields due to its excellent physical and chemical properties since the 1960s. In particular, its excellent photocatalytic and photoelectric properties have enabled _TiO2 to be widely used in emerging industries such as photocatalysis and solar cells. These applications of TiO ₂ are closely related to its own morphology, size, crystal structure and so on. There are three common crystal forms of TiO ₂ : brookite, anatase and rutile, among which anatase TiO ₂ shows excellent performance in photocatalysis and solar cells. The small size of _TiO2 has a larger specific surface area, and the high specific surface area helps to improve the light absorption and refractive index, which is beneficial to the adsorption of reactants on the surface, so that _TiO2 has higher photocatalytic activity. In order to ensure the stable performance of TiO ₂ in continuous research and application, the synthesized TiO ₂ material should have a crystal structure, and the particle size should be uniform; at the same time, nano-TiO ₂ with uniform particle size distribution is very important in the field of metering and standardization. application. Therefore, it is of great significance to prepare anatase crystal nano- _TiO2 materials with uniform particle size.

CN 101318128A discloses a preparation method of high photocatalytic activity nano- _TiO2 with anatase structure, comprising the following steps: (1) Weighing titanium metal organic compound or inorganic salt of titanium and dissolving it in glacial acetic acid to make a mixed solution, mixing the solution in absolute ethanol to obtain solution 1; (2) select two or three templates and dissolve them in absolute ethanol to obtain solution 2; (3) mix solution 1 and solution 2, add distilled water, stir, Obtain a clear solution, let it stand for 2 to 5 days, form a gel, and dry; (4) calcinate the dried product to remove the template agent, and obtain nano-TiO ₂ with anatase structure and high photocatalytic activity. The anatase prepared by the method of the invention The high photocatalytic activity nano TiO ₂ with ore structure has a particle size smaller than P-25, a specific surface area larger than P-25, and a higher photocatalytic activity than P-25. It can be widely used in photocatalysis, sensitized solar cells and other fields.

CN 1312223A relates to a production method of nano TiO ₂ , which is to select metal salts soluble in water or organic solvents to dissolve them, mix uniformly in ion or molecular state, and then select a suitable precipitant or use evaporation, crystallization, Sublimation, hydrolysis and other processes, the metal ions are uniformly precipitated or crystallized, and then dehydrated or decomposed to obtain a powder.

At present, the preparation methods of nano-TiO ₂ materials include gas phase method and liquid phase method. Among them, the gas phase method is used in a small range due to large energy consumption, high cost and complicated process, while the liquid phase method is widely used due to the advantages of relatively low energy consumption and cost, good uniformity and simple equipment required. Commonly used liquid phase methods include chemical precipitation method, sol-gel method, water/alcoholic thermal method and microemulsion method, among which chemical precipitation method is a commonly used method. However, the _TiO2 prepared by the precipitation method is amorphous and has little photocatalytic activity. To obtain crystalline _TiO2 material, high temperature heat treatment is required. With the increase of heat treatment temperature, the hard agglomeration of nano-TiO ₂ particles will occur, and the specific surface area will decrease significantly. Therefore, it is of great significance to prepare nano-TiO ₂ crystal materials at low temperature. The invention combines chemical precipitation and hydrothermal synthesis to prepare anatase-type nano _TiO2 material with uniform particle size distribution under low temperature conditions.

Contents of the invention

The object of the present invention is to provide a kind of anatase type nano TiO ₂ material with uniform particle size distribution and its preparation method and application.

For reaching this purpose, the present invention adopts following technical scheme:

One of object of the present invention is to provide a kind of nanometer _TiO2 The preparation method of single crystal material, described method comprises the following steps:

(1) Add TiCl ₄ dropwise to the ammonia solution until the system is neutral or weakly alkaline to obtain an emulsion;

(2) Separating the solid-liquid of the emulsion in step (1) to obtain a precipitate, and then washing the precipitate to neutrality;

(3) Disperse the precipitate in step (2) in ethanol, water or a mixed system of ethanol and water, and place it in a reaction kettle for reaction;

(4) After the reaction is completed, the obtained white emulsion is separated from solid to liquid, washed to obtain a precipitate, and freeze-dried to obtain a nano-TiO ₂ single crystal material with uniform particle size distribution.

The concentration of TiCl ₄ in the step (1) of the present invention is 0.05-0.5 mol/L. If the concentration is too small, the amount of precipitation obtained in step (2) will be relatively small and the dropwise addition will take time. If the concentration is too high, the pH of the system will change too quickly and the precipitation will be uneven. The _{concentration} of TiCl in the present invention can be selected from 0.051~0.49mol/L, 0.08~0.4mol/L, 0.11~0.34mol/L, 0.16~0.3mol/L, 0.23~0.28mol/L, etc. In the present invention, preferably 0.1-0.2 mol/L, more preferably 0.2 mol/L.

The concentration of the ammonia solution of the present invention is 0.12~0.8mol/L, such as 0.14~0.78mol/L, 0.3~0.6mol/L, 0.33~0.57mol/L, 0.37~0.51mol/L, 0.43mol/L, etc. , more preferably 0.2~0.5mol/L, most preferably 0.5mol/L.

In the step (1) of the present invention, TiCl ₄ is added dropwise to the ammonia solution until the system is neutral or weakly alkaline, for example, the pH value is 7.02~9.5, 7.4~9, 8~8.5, etc., preferably dropped into the system The pH value is 7.2-9.0, more preferably the pH value is 8.0.

In the step (2) of the present invention, the precipitate is washed to neutrality with deionized water. Other methods capable of washing the precipitate to neutrality can also be selected from the prior art by those skilled in the art.

The volume ratio of ethanol to water in step (3) of the present invention is 10:0~0:10, wherein 10:0 means all ethanol, and 0:10 means all water, both of which can be used to implement the present invention. The volume ratio is preferably 10:0~1:1, such as 9.9:0.1, 9.2:0.8, 8.5:1.5, 7.6:2.4, 7:3, 6.2:3.8, 5.5:4.5, etc., more preferably 9:1.

The reaction time in the step (3) of the present invention is 2 to 18 hours. If the reaction time is too short, the product cannot be obtained; if it is too long, the product particles will agglomerate and the dispersibility will be relatively poor. For example, 2.01~17.8h, 3~15h, 3.8~14h, 5~12.3h, 7.5~11h, 9h, etc., more preferably 3~15h, most preferably 7.5h.

The reaction temperature in the step (3) of the present invention is 110-180°C. If the reaction temperature is too low, it is necessary to prolong the reaction time to obtain the product and the crystallinity of the product is poor; if the reaction temperature is too high, the product is easy to agglomerate, and energy consumption is unsafe. For example, 112~178°C, 120~168°C, 124~163°C, 130~157°C, 137~150°C, 146°C, etc., more preferably 120~150°C, most preferably 150°C.

In the step (4) of the present invention, the precipitate is washed with ethanol and deionized water.

The freeze-drying temperature in the step (4) of the present invention is -85~-40°C, such as -84~-41°C, -81~-43°C, -75~-48°C, -67~-55°C, -62~-59°C, etc., more preferably -75~-50°C, most preferably -60°C.

The solid-liquid separation described in step (2) and step (4) of the present invention includes filtration, centrifugal separation, sedimentation, gravity sedimentation or centrifugal sedimentation; preferably centrifugal separation. Those skilled in the art can know and select the way of solid-liquid separation from the prior art, which can realize the separation of the solid state and the liquid state of the corresponding system without changing its inherent properties.

A kind of nanometer TiO The preparation method of _single crystal material, described method is optimized, comprises the following steps:

(1) Add 0.1~0.2mol/L TiCl ₄ dropwise to 0.2~0.5mol/L ammonia solution until the pH of the system is 8.0 to obtain a white emulsion;

(2) Centrifuge the emulsion in step (1) to obtain a precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in ethanol, water or a mixed system of ethanol and water, place it in a reaction kettle, and react at 120~150°C for 3~15h;

(4) After the reaction is completed, centrifuge the obtained white emulsion, wash the obtained precipitate with ethanol and deionized water, and freeze-dry it at -75~-50°C to obtain nano- _TiO2 monolayers with uniform particle size distribution. crystal material.

The second object of the present invention is to provide a nano- _TiO2 single crystal material obtained by the method as described above, the particle size distribution of the material is uniform, the average particle diameter is about 30nm, and the relative standard deviation is less than 9%. The average particle size may be 29nm, 30nm, 32nm, etc. Those skilled in the art can know the particle size range of the nanomaterial of the present invention according to the relative standard deviation. The specific surface area is 70~80m ² /g.

_The third object of the present invention is to provide an application of the nano TiO ₂ single crystal material, which is used as a photocatalyst.

Compared with the prior art solutions, the present invention has the following beneficial effects:

The _TiO2 particles obtained by the method of the present invention have regular morphology, good crystallinity, uniform size, good dispersibility, high product purity, and high photocatalytic activity. The preparation method is simple to operate, environmentally friendly, and the reaction conditions are mild. , low energy consumption, easy to popularize and use.

Description of drawings

Fig. 1 is the TiO that the present invention makes The transmission electron microscope figure of _single crystal material;

Fig. ₂ is the TiO that the present invention makes The scanning electron microscope figure of single crystal material;

Fig. 3 is the TiO that the present invention makes _{The XRD} figure of single crystal material;

Fig. 4 is a comparison chart of the photocatalytic effect of degrading methylene blue between the _TiO2 single crystal material prepared by the present invention and the commercial nano _-TiO2 material.

The present invention will be further described in detail below. However, the following examples are only simple examples of the present invention, and do not represent or limit the protection scope of the present invention, and the protection scope of the present invention shall be determined by the claims.

Detailed ways

For better illustrating the present invention, facilitate understanding technical scheme of the present invention, typical but non-limiting embodiment of the present invention is as follows:

Example 1

(1) Add 0.2mol/L TiCl ₄ dropwise to 100mL 0.5mol/L ammonia solution until the pH of the system is 8.0 to obtain a white emulsion;

(2) Centrifuge the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in 50mL of ethanol (that is, the volume ratio of ethanol to water is 10:0), put it in a reaction kettle, and react at 150°C for 5h;

(4) After the reaction, the obtained white emulsion was centrifuged, the precipitate was washed and freeze-dried at -65°C to obtain an anatase nano-TiO ₂ single crystal material with uniform particle size distribution.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 32nm, the specific surface area is 72m ² /g, and the relative standard deviation is 8%.

Example 2

(1) Add 0.2mol/L TiCl ₄ dropwise to 100mL 0.5mol/L ammonia solution until the pH of the system is 8.0 to obtain a white emulsion;

(2) Centrifuge the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in a system with a volume ratio of 50mL of ethanol to water of 9:1, place in a reaction kettle, and react at 150°C for 5h;

(4) After the reaction, the obtained white emulsion was centrifuged, the precipitate was washed and freeze-dried at -75°C to obtain an anatase nano-TiO ₂ single crystal material with uniform particle size distribution.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 30nm, the specific surface area is 76m ² /g, and the relative standard deviation is 7%.

Example 3

(1) Add 0.2mol/L TiCl ₄ dropwise to 100mL 0.5mol/L ammonia solution until the pH of the system is 8.0 to obtain a white emulsion;

(2) Centrifuge the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in 50mL of ethanol (that is, the volume ratio of ethanol to water is 10:0), put it in a reaction kettle, and react at 150°C for 15h;

(4) After the reaction, the obtained white emulsion was centrifuged, the precipitate was washed and freeze-dried at -50°C to obtain anatase nano-TiO ₂ single crystal material with uniform particle size distribution.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 32nm, the specific surface area is 71m ² /g, and the relative standard deviation is 9%.

Example 4

(1) Add 0.2mol/L TiCl ₄ dropwise to 100mL 0.2mol/L ammonia solution until the pH of the system is 8.0 to obtain a white emulsion;

(2) Centrifuge the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in 50mL of ethanol (that is, the volume ratio of ethanol to water is 10:0), put it in a reaction kettle, and react at 120°C for 7.5h;

(4) After the reaction, the obtained white emulsion was centrifuged, the precipitate was washed and freeze-dried at -65°C to obtain an anatase nano-TiO ₂ single crystal material with uniform particle size distribution.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 30nm, the specific surface area is 75m ² /g, and the relative standard deviation is 7%.

Example 5

(1) Add 0.1mol/L TiCl ₄ dropwise to 100mL 0.2mol/L ammonia solution until the pH of the system is 8.0 to obtain a white emulsion;

(2) Centrifuge the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in 50mL of ethanol (that is, the volume ratio of ethanol to water is 10:0), put it in a reaction kettle, and react at 150°C for 7.5h;

(4) After the reaction, the obtained white emulsion was centrifuged, the precipitate was washed and freeze-dried at -60°C to obtain an anatase nano-TiO ₂ single crystal material with uniform particle size distribution.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 29nm, the specific surface area is 78m ² /g, and the relative standard deviation is 8%.

Example 6

(1) Add 0.05mol/L TiCl ₄ dropwise to 100mL 0.8mol/L ammonia solution until the pH of the system is 9.5 to obtain a white emulsion;

(2) Centrifuge the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in a system with a volume ratio of 50mL of ethanol to water of 1:1, put it in a reaction kettle, and react at 120°C for 5h;

(4) After the reaction is completed, the obtained white emulsion is centrifuged, and the precipitate is washed with ethanol and deionized water and freeze-dried at -68°C to obtain anatase nano- _TiO2 single crystal with uniform particle size distribution Material.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 31 nm, the specific surface area is 74 m ² /g, and the relative standard deviation is 7%.

Example 7

(1) Add 0.5mol/L TiCl ₄ dropwise to 100mL 0.12mol/L ammonia solution until the pH of the system is 9.0 to obtain a white emulsion;

(2) Centrifuge and filter the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in 50mL of water (that is, the volume ratio of ethanol to water is 0:10), place it in a reaction kettle, and react at 180°C for 2 hours;

(4) After the reaction, the obtained white emulsion was centrifugally filtered, and the precipitate was washed and freeze-dried at -40°C to obtain an anatase nano-TiO ₂ single crystal material with uniform particle size distribution.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 30nm, the specific surface area is 75m ² /g, and the relative standard deviation is 8%.

Example 8

(1) Add 0.15mol/L TiCl ₄ dropwise to 100mL 0.3mol/L ammonia solution until the pH of the system is 7.2 to obtain a white emulsion;

(2) Gravity sedimentation of the white emulsion in step (1) to obtain a white precipitate, and then wash the precipitate with deionized water until neutral;

(3) Disperse the precipitate in step (2) in a system with a volume ratio of 50mL of ethanol and water of 7:3, place it in a reaction kettle, and react at 110°C for 18h;

(4) After the reaction is completed, the obtained white emulsion is gravity settled to obtain a precipitate, which is washed with ethanol and deionized water and freeze-dried at -85°C to obtain anatase nano-TiO with uniform particle size distribution. ₂ single crystal material.

The TiO ₂ single crystal material prepared in this example contains a large number of nanoparticles with regular shape, uniform size and good dispersion. The particle size of the particles is 28nm, the specific surface area is 80m ² /g, and the relative standard deviation is 5%.

Example 9

Example 6 is a comparison of the photocatalytic effect of the TiO ₂ single crystal material (A) prepared by the present invention as a catalyst and the commercial TiO ₂ (B) catalyst with an average particle size of 30nm when degrading the dye methylene blue. Add 0.01 g of the catalyst to 100 mL of methylene blue solution containing 10 mg/L, and stir for 1 h under dark conditions, so that the catalyst and the dye reach an adsorption-desorption equilibrium. The reactor was irradiated from the outside with a high-pressure xenon lamp with an emission wavelength of 365 nm. During the illumination process, samples were taken every 15 minutes, centrifuged at 8000r/min for 5 minutes, and the supernatant liquid was taken for testing in a UV-Vis spectrophotometer. The concentration of the methylene blue solution corresponds to the absorbance at 665 nm. The results show that the activity of the _TiO2 material prepared by the invention to catalyze the degradation of methylene blue is higher than that of the commercial _TiO2 catalyst.

The applicant declares that the present invention illustrates the preparation method of the present invention through the above examples, but the present invention is not limited to the above steps, that is, it does not mean that the present invention must rely on the above steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of the selected raw materials in the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. a nanometer _TiO2The preparation method of single crystal material is characterized in that, described method comprises the following steps: (1) Add TiCl ₄ dropwise to the ammonia solution until the system is neutral or weakly alkaline to obtain an emulsion; (2) Separating the solid-liquid of the emulsion in step (1) to obtain a precipitate, and then washing the precipitate to neutrality; (3) Disperse the precipitate in step (2) in ethanol, water or a mixed system of ethanol and water, and place it in a reaction kettle for reaction; (4) After the reaction is completed, the obtained white emulsion is separated from solid to liquid, washed to obtain a precipitate, and freeze-dried to obtain a nano-TiO ₂ single crystal material with uniform particle size distribution. 2. The method according to claim 1, wherein the concentration of TiCl in step (1) is 0.05-0.5 _mol /L, preferably 0.1-0.2 mol/L, more preferably 0.2 mol/L; Preferably, the concentration of the aqueous ammonia solution is 0.12-0.8mol/L, more preferably 0.2-0.5mol/L, most preferably 0.5mol/L; Preferably, in step (1), TiCl ₄ is added dropwise to the ammonia solution until the pH of the system is 7.2-9.0, more preferably 8.0. 3. The method according to claim 1 or 2, characterized in that, in the step (2), the precipitate is washed to neutrality with deionized water. 4. The method according to any one of claims 1-3, wherein the volume ratio of ethanol to water in the step (3) is 10:0~0:10, preferably 10:0~1:1 , further preferably 9:1; Preferably, the reaction time in the step (3) is 2~18h, more preferably 3~15h, most preferably 7.5h; Preferably, the reaction temperature in the step (3) is 110-180°C, more preferably 120-150°C, most preferably 150°C. 5. The method according to any one of claims 1-4, characterized in that, in the step (4), the precipitate is washed with ethanol and deionized water. 6. The method according to any one of claims 1-5, characterized in that the freeze-drying temperature in the step (4) is -85~-40°C, more preferably -75~-50°C, most preferably- 60°C. 7. The method according to any one of claims 1-6, the solid-liquid separation in step (2) and step (4) includes centrifugal separation, sedimentation, gravity sedimentation or centrifugal sedimentation, preferably centrifugal separation. 8. The method according to any one of claims 1-7, characterized in that the method comprises the following steps: (1) Add 0.1~0.2mol/L TiCl ₄ dropwise to 0.2~0.5mol/L ammonia solution until the pH of the system is 8.0 to obtain a white emulsion; (2) Centrifuge the white emulsion in step (1) to obtain a precipitate, and then wash the precipitate with deionized water until neutral; (3) Disperse the precipitate in step (2) in ethanol, water or a mixed system of ethanol and water, place it in a reaction kettle, and react at 120~150°C for 3~15h; (4) After the reaction is completed, centrifuge the obtained white emulsion, wash the obtained precipitate with ethanol and deionized water, and freeze-dry it at -75~-50°C to obtain nano- _TiO2 monolayers with uniform particle size distribution. crystal material. 9. A nano- _TiO2 single crystal material obtained by the method according to any one of claims 1-8, characterized in that the material has a uniform particle size distribution, an average particle size of about 30nm, and a relative standard deviation of ≤9%. 10. A nanometer _TiO2 single crystal material as claimed in claim 9, characterized in that the nanometer _TiO2 single crystal material is used as a photocatalyst.

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