CN106744736B - A kind of synthetic method of the active porous boron nitride nanosheet for water process - Google Patents

Abstract

A method for synthesizing active porous boron nitride nanosheets for water treatment, heating 0.1 to 10 grams of melamine or dicyandiamide to 300 to 600°C under a protective atmosphere, keeping the temperature for 0.5 to 4 hours, and stopping after the heat preservation is over The gas is introduced and the temperature is lowered to room temperature to obtain a light yellow product; the obtained product is mixed with boric acid at a molar ratio of 1:0.01 to 1:100 and the resulting mixture is heated to 300 to 500°C under a protective atmosphere, and then the protective The gas is passed into the ammonium fluoroborate aqueous solution with a concentration of 0.01-10mmol/L, and then passed into the reaction chamber to continue heating to 600-1000°C, and keep warm for 0.5-4 hours. After the heat preservation is completed, stop the gas flow and lower the temperature. to room temperature, the obtained white product is active porous boron nitride nanosheets, with a specific surface area of up to 817m ² /g, a diameter of 50-300nm, and a thickness of 2-6nm, and has excellent resistance to organic and toxic heavy metal pollutants in aqueous solution. Excellent adsorption capacity, overcome the defects of low adsorption capacity and poor reuse efficiency of commonly used sewage treatment and purification materials.

Description

A kind of synthesis method of active porous boron nitride nanosheets for water treatment

technical field

The invention belongs to the field of inorganic porous materials, in particular to a method for synthesizing active porous boron nitride nanosheets for water treatment.

Background technique

The structure of boron nitride nanosheets is similar to that of graphite. The layer is an infinitely extended hexagonal grid of nitrogen atoms and boron atoms arranged alternately. The layers are arranged alternately in an ABAB... manner, and the boron is ordered and alternated within the layer. There is a strong polar bond with the nitrogen atom. Therefore, the crystal structure has a large interlayer spacing along the C-axis direction, low strength, easy sliding between layers, and has soft lubricating properties. At the same time, hexagonal boron nitride nanosheets have good physical and chemical properties such as good processability, thermal shock and electric shock resistance, high electric field breakdown strength, non-toxic and environmental protection, non-wetting with various metals, and chemical corrosion resistance. , so that hexagonal boron nitride nanosheets are widely used in cosmetics, high temperature, high frequency, high power, optoelectronics and anti-radiation devices, ultraviolet space, wave penetration, high-performance aviation anti-friction, missiles, launch vehicles, return satellites, etc. Military and aerospace fields, as well as polymer composite reinforcement and toughening, improving thermal conductivity of plastics and environmental energy and other fields.

Commonly used boron nitride nanosheet preparation methods include carbothermal reduction, ammonium chloride (urea)-borax method, template method, water (solvent) thermal method, chemical vapor deposition (CVD) method and thermal decomposition method, etc., but these The method has disadvantages such as low yield, high preparation temperature, high cost, or complex process difficult to industrialize, and the obtained boron nitride nanosheets have small specific surface area and poor adsorption capacity, which seriously restricts the application of boron nitride nanosheets in the field of environmental energy. widely used. The boron nitride nanosheets synthesized by these methods are not uniform in size, and the bigger disadvantage is that the synthesis process requires extremely high temperatures, which not only consumes high energy, but also increases the safety hazards of production. Therefore, there is an urgent need for a method with low preparation cost, simple process, low environmental pollution, low energy consumption, and the obtained product has excellent sewage treatment and purification capabilities.

Contents of the invention

The purpose of the present invention is to solve the problems in the prior art and provide a method for preparing active porous boron nitride nanosheets with high yield, mild preparation conditions, low cost and simple process, which has excellent adsorption capacity for pollutants in aqueous solution , and the preparation method is easy to scale up, and can achieve the purpose of mass production.

The technical scheme of the present invention is: a kind of synthetic method of the active porous boron nitride nanosheet used for water treatment, it is characterized in that: (1) melamine or dicyandiamide of 0.1～10 grams are heated to 300 ℃ under protective atmosphere ~600°C, heat preservation for 0.5 to 4 hours, stop the gas supply after the heat preservation is over and lower the temperature to room temperature to obtain a light yellow product; (2) mix the product obtained in (1) with boric acid in nitrogen or argon Heat to 300-500°C under protection, then pass the protective gas into the ammonium fluoroborate aqueous solution, and then pass it into the reaction chamber to continue heating to 600-1000°C, keep it warm for 0.5-4 hours, stop the introduction of gas after the heat preservation is over And the temperature is lowered to room temperature, the obtained white product is active porous boron nitride nanosheets, the specific surface area can reach 817m ² /g, the diameter is 50-300nm, the thickness is 2-6nm, and it has excellent performance on pollutants in aqueous solution. of adsorption capacity.

The protective atmosphere described in the above step (1) is neon, krypton, argon or nitrogen.

When the protective atmosphere in the above step (1) is neon, krypton, argon or nitrogen, the gas flow rate is 50-500 ml/min.

The molar ratio of the pale yellow product to boric acid in the above step (2) is 1:0.01˜1:100.

The concentration of the ammonium fluoroborate aqueous solution in the above step (2) is 0.01˜10 mmol/L.

The protective atmosphere gas flow rate in the above step (2) is 100-300 ml/min.

The beneficial effects of the present invention are:

1. The product obtained by the inventive method is an active porous boron nitride nanosheet with a hexagonal structure, as shown in Figure 1, the wide-angle part (2θ=10～90°) diffraction peak is clear in the powder X-ray diffraction pattern, which is a miscellaneous Layer boron nitride; Fig. 2 and Fig. 3 are the scanning electron microscope picture and the transmission electron micrograph picture of active porous boron nitride nanosheet, have shown respectively that the boron nitride nanosheet shape that this method obtains is uniform, and thickness is only 2～ 6nm, its edge has rich structural defects; Fig. 4 is the adsorption and desorption isotherms of nitrogen under the low temperature of active porous boron nitride nanosheets, showing that the gained active porous boron nitride nanosheets have a high specific surface area; Fig. 5 and Figure 6 show that the active porous boron nitride nanosheets have excellent adsorption capacity and regenerative reuse ability for pollutants in aqueous solution.

2. The obtained boron nitride nanosheets of the present invention have peculiar properties such as light, electricity, magnetism, heat and adsorption, especially characteristics such as high specific surface area, rich structural defects and polarity of B-N bonds, making it an excellent Water purification material, this kind of active porous boron nitride nanosheet has the adsorption capacity of toxic heavy metal pollutants at room temperature up to 0.42 grams per gram, and the adsorption capacity exceeds 70% after repeated use for 10 times, overcoming the commonly used activated carbon that cannot be reused It is widely used in the field of water treatment and purification.

3. The raw material used in the present invention is boric acid, which belongs to industrialized products, is relatively cheap and easy to obtain, and can greatly reduce production costs.

4. The synthesis used in the present invention requires relatively low temperature and simple process, and is suitable for large-scale industrial production.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and specific implementation.

Fig. 1 is the X-ray diffraction spectrogram of active porous boron nitride nanosheet in Example 1.

2 is a scanning electron microscope image of the active porous boron nitride nanosheets in Example 1.

3 is a transmission electron microscope image of the active porous boron nitride nanosheets in Example 1.

Figure 4 is the low-temperature nitrogen adsorption and desorption isotherms of the active porous boron nitride nanosheets in Example 1.

Fig. 5 is the adsorption rate of inorganic pollutants of active porous boron nitride nanosheets in Example 1 at room temperature.

FIG. 6 is a test diagram of the regeneration ability of the active porous boron nitride nanosheets in Example 1. FIG.

Detailed ways

The present invention will be further described below through specific examples, but the examples will not limit the present invention.

Example 1:

(1) Weigh 0.1 g of melamine and heat it to 300°C under the protection of a nitrogen atmosphere with an air flow rate of 50 ml/min, and keep it warm for 0.5 hours. After the heat preservation finishes, stop the feeding of the gas and lower the temperature to room temperature to obtain a light yellow color product; (2) the obtained product is mixed with boric acid in a molar ratio of 1:0.01, and the resulting mixture is heated to 300°C under nitrogen protection, and then the protection gas is passed into the ammonium fluoroborate aqueous solution with a concentration of 0.01mmol/L, and then passed through Put it into the reaction chamber and continue heating to 600°C, and keep it warm for 0.5 hours. After the heat preservation is over, stop the gas flow and lower the temperature to room temperature. The white product obtained is an active porous boron nitride nanosheet, and its specific surface area can reach 817m ² /g, with a diameter of 50-300nm and a thickness of 2-6nm, and has excellent adsorption capacity for organic and inorganic pollutants in aqueous solution.

Through the X-ray diffraction test, the wide-angle diffraction peak in Fig. 1 shows that the product is hexagonal boron nitride, and the diffraction peak is very clear; it can be seen that the product is a sheet structure through the scanning electron microscope (Fig. 2); through the transmission electron microscope ( Fig. 3) find out that the product is a sheet structure; then through low-temperature nitrogen adsorption, desorption isotherm (Fig. 4), it can be calculated that its specific surface area is 817 square meters per gram, and the pore volume is 0.57 cubic meters per gram; The present invention obtains a boron nitride ceramic material with a large number of active adsorption sites, a high specific surface area and a large pore volume. Finally, we tested the water treatment and purification capabilities of activated boron nitride. Figure 5 shows that its adsorption capacity for toxic heavy metal pollutants in aqueous solution at room temperature reaches 0.42 grams per gram; Figure 6 shows that the active boron nitride is reused 10 times, and the adsorption capacity maintains more than 70% of the adsorption capacity, which shows the activity Boron nitride is easy to recycle. This material has broad application prospects in the field of environmental governance.

Example 2:

Through step (1) melamine is changed into dipolycyanamide in the embodiment 1, other each operation is all the same as

Embodiment 1 is identical, obtains product with embodiment 1.

Embodiment 3, 4:

Change the consumption of step (1) melamine or dipolycyanamide into 1g and 10g respectively in embodiment 1, and other operations are all the same as in embodiment 1, and the product obtained is the same as in embodiment 1.

Embodiment 5,6,7:

Change step (1) nitrogen into neon, krypton, argon respectively in the embodiment 1, other each operation is all the same with embodiment 1, obtains the product with embodiment 1.

Embodiment, 8,9:

Change the circulation of protective gas in step (1) in Example 1 to 100, 500 mL per minute respectively, and other operations are the same as in Example 1, and the product obtained is the same as in Example 1.

Embodiment 10, 11:

Change the heating temperature of step (1) in Example 1 to 450, 600°C respectively, and other operations are the same as in Example 1, and the product obtained is the same as in Example 1.

Embodiment 12, 13:

Change the incubation time of step (1) into 2 and 4 hours respectively in embodiment 1, and other operations are all the same as in embodiment 1, and the product obtained is the same as in embodiment 1.

Embodiment 14, 15:

The molar ratios of the light yellow crude product and boric acid in step (2) in Example 1 were changed to 1:1 and 1:100 respectively, and other operations were the same as in Example 1, and the product obtained was the same as in Example 1.

Embodiment 16, 17:

When the gas in step (2) in Example 1 is not passed through the ammonium fluoroborate solution, the heating temperature is changed to 400 and 500° C. respectively, and other operations are the same as in Example 1, and the product obtained is the same as in Example 1.

Embodiment 18, 19:

Change the concentration of the ammonium fluoroborate solution in step (2) into 1mmol/L and 10mmol/L respectively in Example 1, and other operations are the same as in Example 1, and the product obtained is the same as in Example 1.

Embodiment 20, 21:

When the gas in step (2) in Example 1 passes through the ammonium fluoroborate solution, the heating temperature is changed to 800 and 1000° C. respectively, and other operations are the same as in Example 1, and the obtained product is the same as in Example 1.

Embodiment 22, 23:

Change the gas flow of step (2) in Example 1 to 200, 300 mL per minute respectively, and other operations are the same as in Example 1, and the product obtained is the same as in Example 1.

Embodiment 23, 24:

Change the incubation time of step (2) into 2 and 4 hours respectively in embodiment 1, and other operations are all the same as in embodiment 1, and the product obtained is the same as in embodiment 1.

Claims (6)

1. a kind of synthetic method of the active porous boron nitride nano sheet for water treatment, is characterized in that, comprises the steps: Step 1: Heat 0.1 to 10 grams of melamine or dicyandiamide to 300 to 600°C in a protective atmosphere and keep it warm for 0.5 to 4 hours. After the heat preservation is over, stop the gas flow and lower the temperature to room temperature to obtain a light yellow product ; Step 2: Mix the obtained product with boric acid and heat the resulting mixture to 300-500°C under the protection of nitrogen or argon, then pass the protection gas into the aqueous solution containing ammonium fluoroborate; then pass it into the reaction chamber and continue heating to 600-1000°C, keep warm for 0.5-4 hours, stop the gas supply after the warm-keeping is over and lower the temperature to room temperature, the white product obtained is active porous boron nitride nanosheets, with a specific surface area of 817m ² /g and a diameter of 50-300nm, thickness 2-6nm, and has the ability to adsorb pollutants in aqueous solution. 2. The synthesis method according to claim 1, characterized in that: the protective atmosphere is neon, krypton, argon or nitrogen. 3. The synthesis method according to claim 1, characterized in that: when the protective atmosphere is neon, krypton, argon or nitrogen, the gas flow rate is 50-500 ml/min. 4. The synthesis method according to claim 1, characterized in that: the molar ratio of the light yellow product and boric acid contained in the mixture is 1:0.01˜1:100. 5. The synthesis method according to claim 1, characterized in that: the aqueous solution of ammonium fluoroborate is 0.01～10mmol/L. 6. The synthesis method according to claim 1, characterized in that: the protective gas flow rate of feeding an aqueous solution containing ammonium fluoroborate is 100-300 ml/min.