CN104998674A - Silicate clay-carbon nitride composite material of multilevel structure and preparation method of silicate clay-carbon nitride composite material - Google Patents

Abstract

The invention belongs to the field of inorganic non-metal matrix composite materials. It is a silicate clay-carbon nitride composite material with a multi-level structure. The silicate clay is used as a nucleus, and carbon nitride is loaded on the surface of the silicate clay to form a multi-level structure. Structured carbon nitride nanosheets. Its preparation method is as follows: (1) Evenly disperse the silicate clay into the formaldehyde solution, adjust the pH value of the system under stirring, then add melamine to obtain a mixed dispersion liquid, continue to stir and keep warm for reaction; use acidic solution to adjust the pH value of the system to be acidic, continue Constant temperature reaction, adjusting the pH value of the system with an alkaline solution to obtain a composite solution; (2) drying the above composite solution, and then performing a pyrolysis reaction under a nitrogen atmosphere to obtain a silicate clay/carbon nitride composite material . The carbon and nitrogen elements in the resin can nucleate in its silicate clay and grow into carbon nitride nanosheets with a multi-level structure in situ, thereby effectively preventing the agglomeration and folding of carbon nitride nanosheets and improving the composite material. specific surface area.

Description

A kind of silicate clay-carbon nitride composite material with multi-level structure and preparation method thereof

technical field

The invention belongs to the field of inorganic non-metal matrix composite materials, and in particular relates to a preparation method of a silicate clay/carbon nitride composite material with a multi-level structure.

Background technique

Graphite carbon nitride (gC ₃ N ₄ ) is a new type of non-metallic photocatalytic material with visible light response. Oxygen, photocatalytic organic selective synthesis, photocatalytic degradation of organic pollutants and other fields. However, gC ₃ N ₄ has disadvantages such as small specific surface area and poor dispersion in water, which restrict its photocatalytic performance. Therefore, the problem is often solved by changing the microstructure of gC ₃ N ₄ , such as designing porous structures, preparing nanorods and nano-thin layers, etc., but the above methods still have certain defects. The synthesis of porous gC ₃ N ₄ requires steps such as adding and then removing the template, while the preparation of gC ₃ N ₄ nano-thin layers often adopts the solvent stripping method; these methods make the production process of gC ₃ N ₄ relatively complicated and costly. Time consumption, cost increase. Chinese patent CN 103539090B synthesized a highly oriented carbon nitride nanorod array with uniform shape and size. However, this method requires a high-temperature hydrothermal process and is not suitable for large-scale production. Therefore, how to adopt a relatively simple method to prepare carbon nitride materials with high specific surface area and excellent dispersion performance is a key technical problem to be solved.

Contents of the invention

The present invention overcomes the disadvantages of the complex preparation process of graphite phase silicon nitride in the prior art, and provides a silicate clay-carbon nitride composite material with a multi-level structure and a preparation method thereof. The method has the advantages of simplicity, low cost, etc. Features, suitable for large-scale production, the carbon nitride composite material has both high specific surface area and excellent dispersion performance.

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is a silicate clay-carbon nitride composite material with a multi-level structure. The silicate clay with a one-dimensional nanostructure is used as a nucleus, and the carbon nitride is loaded Hierarchical carbon nitride nanosheets formed on the surface of silicate clay.

Preferably, the silicate clay is one of attapulgite, halloysite or sepiolite.

The preparation method of above-mentioned silicate clay-carbon nitride composite material, the steps are as follows:

(1) Evenly disperse the silicate clay into the formaldehyde solution, adjust the pH of the system to 8.5-10.0 under stirring, then add melamine to obtain a mixed dispersion, raise the temperature of the system to 80-90°C, continue to stir and keep warm for 30-60 Minutes; use an acidic solution to adjust the pH of the system to 4.0-5.8, and continue the constant temperature reaction. When the mixed solution drops into the deionized water and appears white mist and is not easy to disperse, immediately adjust the pH of the system to 7.5-9.0 with an alkaline solution , making silicate clay/melamine-formaldehyde resin composite liquid;

(2) Dry the silicate clay/melamine-formaldehyde resin composite solution prepared in step (1) at a temperature of 80°C to 100°C, and then place it under a nitrogen atmosphere at a temperature of 450°C to 650°C The pyrolysis reaction is carried out for 4 to 10 hours, and the silicate clay/carbon nitride composite material is obtained.

Preferably, the mass percent concentration of the formaldehyde solution is 37%-40%.

Preferably, the mass ratio of formaldehyde to melamine is 0.30-1:1, and the mass ratio of the mass of silicate clay to the total mass of formaldehyde and melamine in the mixed solution is 0.1-0.3:1.

Further, the alkaline solution is one of sodium hydroxide solution, potassium hydroxide solution or ammonia solution, and the mass percent concentration of the alkaline solution is 10%-25%.

Further, the acidic solution is one of formic acid solution, acetic acid solution or ammonium chloride solution, and the mass percent concentration of the acidic solution is 5-15%.

Beneficial effects of the present invention:

1. In the present invention, the silicate clay with one-dimensional nanostructure is used as the nucleus, and the "in-situ polymerization-pyrolysis" method is used to polymerize melamine-formaldehyde resin in situ on the surface of the silicate clay, and then through the pyrolysis reaction. The advantage of preparing silicate clay/carbon nitride composite materials is that the "skeleton" effect of the one-dimensional nanostructured silicate clay is fully utilized, and the carbon and nitrogen elements in the resin can nucleate on the surface, in situ The growth of carbon nitride nanosheets with a multi-level structure effectively prevents the agglomeration and folding of the carbon nitride nanosheets and increases the specific surface area of the composite material.

2. During the pyrolysis reaction process for preparing silicate clay/carbon nitride composites, lattice ions (such as Fe, Mn, etc.) in silicate clay minerals can effectively dope carbon nitride, thereby enabling Reduce the band gap of carbon nitride materials and improve their photocatalytic performance.

Description of drawings

1 is a transmission electron microscope (TEM) photo of the attapulgite/carbon nitride composite material prepared according to Example 5.

Detailed ways

Below in conjunction with embodiment, the present invention will be further described, but the scope to be protected by the present invention is not limited to the scope involved in embodiment:

Example 1

1. Evenly disperse 2.4 kg of attapulgite into 5.0 kg of formaldehyde solution with a concentration of 37% by mass, and adjust the pH value of the system to 8.5 with a sodium hydroxide solution with a concentration of 10% by mass while stirring, and then add 6.2 kg of melamine to obtain a mixed dispersion, heat the system to 80°C, continue to stir and keep warm for 60 minutes, adjust the pH of the system to 5.8 with a formic acid solution with a concentration of 5% by mass, and continue the constant temperature reaction. When the deionized water appears white mist and is not easy to disperse, the pH value of the system is adjusted to 7.5 with a sodium hydroxide solution with a concentration of 10% by mass immediately to obtain a composite solution of attapulgite/melamine-formaldehyde resin;

2. Dry the attapulgite/melamine-formaldehyde resin composite liquid prepared in step 1 at a temperature of 100°C, and then place it under a nitrogen atmosphere at a temperature of 450°C for 10 hours of pyrolysis reaction. That is, the attapulgite/carbon nitride composite material is obtained.

Example 2

1. Evenly disperse 1.2 kilograms of halloysite into 15.0 kilograms of formaldehyde solution with a concentration of 40% by mass, and adjust the pH value of the system to 10.0 with a potassium hydroxide solution with a concentration of 25% by mass while stirring, and then add 6.0 kilograms of melamine is obtained mixed dispersion liquid, and system is heated up to 90 ℃, continues to stir and keep warm reaction for 30 minutes, is 4.0 with the ammonium chloride solution adjustment system pH value that mass percent concentration is 15%, continues constant temperature reaction, when mixed droplet When entering deionized water and appearing as white mist and not easy to disperse, immediately adjust the pH value of the system to 9.0 with a potassium hydroxide solution with a concentration of 25% by mass to obtain a halloysite/melamine-formaldehyde resin composite liquid;

2. Dry the halloysite/melamine-formaldehyde resin composite solution prepared in step 1 at a temperature of 80° C., and then place it under a nitrogen atmosphere at a temperature of 650° C. for 4 hours for pyrolysis. That is, the halloysite/carbon nitride composite material is obtained.

Example 3

1. Evenly disperse 1.5 kg of sepiolite into 7.5 kg of formaldehyde solution with a concentration of 38% by mass, and adjust the pH value of the system to 9.5 with ammonia solution with a concentration of 17.5% by mass while stirring, and then add 4.8 kg Melamine is obtained mixed dispersion liquid, and system is heated up to 85 ℃, continues to stir and keep warm reaction for 45 minutes, adjust system pH value to be 5.0 with the acetic acid solution that mass percent concentration is 10%, continue constant temperature reaction, when mixed liquid drops into deionized water When the white mist appears and is not easy to disperse, the pH value of the system is adjusted to 8.5 with an ammonia solution with a concentration of 17.5% by mass immediately to obtain a sepiolite/melamine-formaldehyde resin composite liquid;

2. Dry the sepiolite/melamine-formaldehyde resin composite solution prepared in step 1 at a temperature of 90°C, and then place it under a nitrogen atmosphere at a temperature of 550°C for 7 hours of pyrolysis reaction. That is, the sepiolite/carbon nitride composite material is obtained.

Example 4

1. Evenly disperse 0.95 kg of halloysite into 5.0 kg of formaldehyde solution with a concentration of 39% by mass, and adjust the pH value of the system to 9.0 with a potassium hydroxide solution with a concentration of 15% by mass while stirring, and then add 4.3 kg of melamine to obtain a mixed dispersion, the temperature of the system was raised to 83 ° C, continued stirring and heat preservation reaction for 50 minutes, adjusted the pH value of the system to 4.5 with 10% acetic acid solution by mass percent concentration, continued constant temperature reaction, when the mixed solution dropped into When the deionized water appears as white mist and is not easy to disperse, the pH value of the system is adjusted to 8.0 with a potassium hydroxide solution with a mass percentage concentration of 15% immediately to obtain a halloysite/melamine-formaldehyde resin composite liquid;

2. Dry the halloysite/melamine-formaldehyde resin composite solution prepared in step 1 at a temperature of 95° C., and then place it under a nitrogen atmosphere at a temperature of 500° C. for 8 hours for pyrolysis. That is, the halloysite/carbon nitride composite material is obtained.

Example 5

1. Evenly disperse 1.0 kg of attapulgite into 5.0 kg of formaldehyde solution with a concentration of 37% by mass, and adjust the pH value of the system to 9.5 with a sodium hydroxide solution with a concentration of 10% by mass while stirring, and then add 2.2 kg of melamine to obtain a mixed dispersion, the temperature of the system was raised to 85°C, and the reaction was continued with stirring and heat preservation for 55 minutes, and the pH value of the system was adjusted to 4.8 with a formic acid solution with a mass percentage concentration of 5%, and the constant temperature reaction was continued. When the deionized water appears as white mist and is not easy to disperse, the pH value of the system is adjusted to 8.5 with a sodium hydroxide solution with a concentration of 10% by mass immediately to obtain a composite solution of attapulgite/melamine-formaldehyde resin;

2. Dry the attapulgite/melamine-formaldehyde resin composite solution prepared in step 1 at a temperature of 85°C, and then place it under a nitrogen atmosphere at a temperature of 600°C for 6 hours of pyrolysis reaction. That is, the attapulgite/carbon nitride composite material is obtained. It can be seen from Figure 1 that carbon nitride with a lamellar structure and a particle size of about 50 nm grows on the surface of attapulgite rod crystals, thus forming a multi-level structure of attapulgite/carbon nitride composite material.

Comparative example 1

Comparing Example 5, its technical process is to prepare melamine-formaldehyde resin first, and then carry out pyrolysis reaction after physically mixing with attapulgite to obtain attapulgite/carbon nitride composite material. The specific operation steps are as follows:

1. While stirring, add dropwise a 10% sodium hydroxide solution to a 5.0 kg mass percent concentration of 37% formaldehyde solution to adjust the pH of the system to 9.5, then add 2.2 kilograms of melamine to obtain a mixed dispersion solution, raise the temperature of the system to 85°C, continue to stir and keep warm for 55 minutes, adjust the pH value of the system to 4.8 with a formic acid solution with a mass percent concentration of 5%, and continue the constant temperature reaction. When the mixed solution is dropped into deionized water, it will appear white mist And when it is not easy to disperse, the pH value of the system is adjusted to 8.5 with a sodium hydroxide solution with a mass percentage concentration of 10% immediately to obtain a melamine-formaldehyde resin;

2. Mix 1 kg of attapulgite with the melamine-formaldehyde resin prepared in step 1, and carry out the pyrolysis reaction at a temperature of 600°C under a nitrogen atmosphere for 6 hours to obtain attapulgite/nitridation carbon composites. The specific surface area of the composite material prepared in Example 5 can reach 80.0m ² /g, and the specific surface area of the composite material prepared in Comparative Example 1 can reach 41.6m ² /g.

Claims (7)

1. A silicate clay-carbon nitride composite material with a multi-level structure, characterized in that: the silicate clay with a one-dimensional nanostructure is a nucleus, and carbon nitride is loaded on the surface of the silicate clay to form a multi-level Structured carbon nitride nanosheets. 2. The multi-level silicate clay-carbon nitride composite material according to claim 1, characterized in that: the silicate clay is one of attapulgite, halloysite or sepiolite kind. 3. the preparation method of silicate clay-carbon nitride composite material according to claim 1 or 2, is characterized in that, step is as follows: (1) Evenly disperse the silicate clay into the formaldehyde solution, adjust the pH of the system to 8.5-10.0 under stirring, then add melamine to obtain a mixed dispersion, raise the temperature of the system to 80-90°C, continue to stir and keep warm for 30-60 Minutes; use an acidic solution to adjust the pH of the system to 4.0-5.8, and continue the constant temperature reaction. When the mixed solution drops into the deionized water and appears white mist and is not easy to disperse, immediately adjust the pH of the system to 7.5-9.0 with an alkaline solution , making silicate clay/melamine-formaldehyde resin composite liquid; (2) Dry the silicate clay/melamine-formaldehyde resin composite solution prepared in step (1) at a temperature of 80°C to 100°C, and then place it under a nitrogen atmosphere at a temperature of 450°C to 650°C The pyrolysis reaction is carried out for 4 to 10 hours, and the silicate clay/carbon nitride composite material is obtained. 4. The preparation method of silicate clay-carbon nitride composite material according to claim 3, characterized in that: the mass percent concentration of the formaldehyde solution is 37%-40%. 5. The preparation method of silicate clay-carbon nitride composite material according to claim 3, characterized in that: the mass ratio of formaldehyde to melamine is 0.30 to 1:1, and the mass of silicate clay and the mixed solution The total mass ratio of formaldehyde and melamine in the mixture is 0.1-0.3:1. 6. the preparation method of silicate clay-carbon nitride composite material according to claim 3 is characterized in that: described alkaline solution is a kind of in sodium hydroxide solution, potassium hydroxide solution or ammonia solution , the mass percent concentration of the alkaline solution is 10% to 25%. 7. the preparation method of silicate clay-carbon nitride composite material according to claim 3 is characterized in that: described acidic solution is a kind of in formic acid solution, acetic acid solution or ammonium chloride solution, acidic solution The mass percent concentration is 5-15%.