CN103922296B - A kind of spherical boron nitride and application thereof - Google Patents

Abstract

The invention relates to spherical boron nitride and its application. Spherical boron nitride was prepared from template, boric acid and urea. The method comprises the following steps: dissolving the template agent, nitrogen source and boron source in water until the solution is clear; heating the clear solution in a hydrothermal reaction kettle to prepare a precursor; calcining the precursor under an air atmosphere; under a protective atmosphere, High-temperature pyrolysis; the obtained product is soaked and washed repeatedly with water and ethanol to obtain spherical boron nitride with a high surface area. The spherical boron nitride synthesized by the invention has a large specific surface area, strong ability to adsorb organic pollutants, simple preparation process, cheap raw materials, no special catalyst and other additives, and the method is green and environment-friendly.

Description

A kind of spherical boron nitride and its application

technical field

The invention relates to a spherical boron nitride material with high adsorption activity, which belongs to the science of inorganic non-metallic materials.

Background technique

As an important inorganic non-metallic material, boron nitride has a series of excellent performance characteristics such as good mechanical properties, high thermal conductivity, stable chemical properties, and strong oxidation resistance. Materials, catalyst supports, environmental protection and other fields have potential application value.

At present, industrially produced boron nitride powders are produced in batches from simple raw materials such as boric acid and urea or melamine through metallurgical pyrolysis reactions. The surface area is very low. But even so, boron nitride powder still has many uses, such as being used in the manufacture of high temperature resistant crucibles, insulators, release agents, lubricants, etc. At present, many new high specific surface, high porosity non-oxide inorganic ceramic solid powder materials (such as porous silicon nitride, boron nitride, gallium nitride, etc.) have attracted the attention of researchers. These materials are used as catalyst supports, Sensors, gas adsorbents, membrane materials and other aspects have good application prospects. So far, although boron nitride materials have obvious advantages in many applications, there is no simple and easy method to prepare high-purity special-type boron nitride products with high yield.

Contents of the invention

In view of the above problems, the present invention provides a spherical boron nitride with cheap preparation raw materials, simple preparation process, environmental protection and high adsorption capacity for organic pollutants.

The technical scheme adopted in the present invention is: a kind of spherical boron nitride, and its preparation method comprises the following steps:

1) dissolving the template agent, nitrogen source and boron source in water under magnetic stirring to obtain a colorless and transparent solution; wherein,

The template agent is glucose, MCM-15 molecular sieve or Y-molecular sieve; the preferred template agent is glucose;

The nitrogen source is urea, melamine, biuret, ammonium chloride or ammonium nitrate; preferably, the nitrogen source is urea;

The boron source is preferably boric acid;

Preferably, the molar ratio of template agent, nitrogen source and boron source is 1.0-8.5:1:1.

2) Put the colorless transparent solution into a stainless steel reaction kettle, place the reaction kettle in a constant temperature oven, react at 180°C-220°C for 24-110h, cool down to room temperature naturally, filter, wash with water and ethanol in turn, and dry Obtain solid A afterward;

3) Put solid A in a high-temperature furnace, raise the temperature to 450-900° C. at a rate of 1-6° C. per minute under air atmosphere, and keep it at 450-900° C. for 2-12 hours to obtain solid B;

4) Put the solid B in a closed container, raise the temperature to 900-1700° C. at a rate of 1-6° C. per minute under protective gas, and keep the temperature at 900-1700° C. for 1-14 hours to obtain solid C; The protective gas mentioned above is ammonia or nitrogen. Preferably, the protective gas is nitrogen.

5) Immerse the solid C with hydrochloric acid aqueous solution for 1-48 hours, ultrasonicate, stir, then filter, wash the precipitate with water and ethanol, and then dry at 50-150°C for 3-24 hours to obtain the target product spherical boron nitride .

The spherical boron nitride prepared by the present invention has the characteristics of large specific surface area, controllable appearance size, cheap raw materials, simple operation, low reaction temperature, low requirements on equipment, and reduced production cost. The specific surface area of boron powder is relatively small, and the preparation process is complicated, the reaction temperature is high, the requirements for equipment are high, and the production cost is relatively high.

The spherical boron nitride of the invention has high adsorption capacity for organic pollutants. The method is as follows: add the above-mentioned spherical boron nitride into the waste water containing organic pollutants, adjust the concentration of organic pollutants to 5-15mg/L, pH to 6.5-7.5, and let stand.

The spherical boron nitride of the present invention will also be widely used in hydrogen storage, catalyst carrier and the like.

The beneficial effect of the present invention is: the present invention synthesizes and prepares the reaction precursor by the hydrothermal method under the control of the template, and the formed boron nitride has a spherical basic appearance through the control of the template, and then the calcination method is used to remove the boron nitride in the precursor. The template is then pyrolyzed at high temperature under protective gas, and then soaked to obtain spherical boron nitride. And the size of the spherical shape can be controlled differently according to the amount of template agent used, and its size ranges from about 0.2 μm to 1.5 μm. The invention has cheap raw materials, wide sources and simple process, and can obtain spherical boron nitride at relatively low temperature. The prepared spherical boron nitride has large specific surface area, high porosity, high adsorption capacity for organic pollutants, can be reused, and has broad application prospects in the fields of water treatment, purification and clean energy. The adsorption of the spherical boron nitride of the present invention to organic pollutants presents a rapid adsorption with an adsorption rate of up to 88% within 10s, has a high adsorption capacity for organic dyes, and can be reused, and can be used in hydrogen storage materials and catalysts. It also has broad application prospects in carrier and water treatment.

Description of drawings

Fig. 1 is the infrared spectrum of the spherical boron nitride prepared in embodiment 1.

Fig. 2 is the X-ray powder diffraction spectrum of spherical boron nitride prepared in Example 1.

3 is a scanning electron microscope of spherical boron nitride prepared in Example 1.

Fig. 4 is the nitrogen nitrogen adsorption-desorption isotherm of the spherical boron nitride prepared in Example 1.

Fig. 5 is the relationship between the adsorption time and the removal rate of spherical boron nitride to methylene blue in Example 16.

Fig. 6 is the infrared spectrogram of the adsorption and desorption of spherical boron nitride to methylene blue in Example 16.

Fig. 7 is the adsorption situation of spherical boron nitride recycled 5 times in embodiment 16.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific examples.

Embodiment 1 spherical boron nitride

(1) Preparation method

1) Dissolve glucose, urea and boric acid in a molar ratio of 1:1:1 in water with the assistance of magnetic stirring to obtain a colorless and transparent solution;

2) Put the colorless and transparent solution into a 100ml stainless steel hydrothermal reaction kettle, put the reaction kettle into a constant temperature oven, and keep it warm at 180°C for 24 hours; naturally cool down to room temperature, filter the product, and wash it with water and ethanol several times in sequence , dried to give a brown solid;

3) Put the brown solid in a high-temperature furnace, raise the temperature to 450°C at a rate of 1°C per minute under air atmosphere, and keep it at this temperature for 2 hours to obtain a light yellow solid;

4) Put the light yellow solid in a container, under the protection of nitrogen, raise the temperature to 900°C at a rate of 1°C per minute, and keep it at this temperature for 2 hours to obtain a white solid;

5) Immerse the white solid with hydrochloric acid aqueous solution with a volume ratio of 1:1 for 1 hour, ultrasonicate, stir, and then filter, and wash the precipitate with water and ethanol several times; keep it at 50°C for 3 hours, and the product is spherical boron nitride.

(2) Product verification

1) The infrared spectrum of the prepared spherical boron nitride is shown in Figure 1, as can be seen from Figure 1, the product has obvious absorption peaks near the wavenumbers of 1384cm ^-1 and 786cm ^-1 , wherein the corresponding absorption peak at 1384cm ^-1 It is produced by the in-plane stretching vibration of the BN bond, and the absorption peak at 786cm ^-1 is formed by the out-of-plane bending vibration of the BNB bond. These absorption peaks are the characteristic absorption peaks of boron nitride.

2) The X-ray powder diffraction pattern of the prepared spherical boron nitride is shown in Figure 2. There are diffraction peaks at 2θ=26.70°, 43.8°, and 55.1°, which are similar to those of boron nitride (002), (101), (004) corresponding to the facet index.

3) The scanning electron microscope and adsorption curves of the prepared spherical boron nitride are shown in Figures 3 and 4. From Figure 3, it can be seen that the prepared boron nitride is uniform spherical with a diameter of about 0.2-0.8 μm. The control, the product is basically spherical. Calculated from Figure 4, it can be seen that the specific surface area of the product reaches 176.78m ² /g, which is superior to some boron nitride materials reported so far, such as active porous boron nitride (50m ² /g), boron nitride (168m ² /g) , nano-boron nitride (26.8m ² /g), etc., can be used as good adsorbent and catalyst carrier.

Embodiment 2 spherical boron nitride

The preparation method is the same as in Example 1, except that the molar ratio of glucose, urea and boric acid is changed. The results are shown in Table 1.

Table 1

Glucose: Urea: Boric acid 2:1:1 4:1:1 6:1:1 8:1:1 8.5:1:1 Morphology of spherical boron nitride 0.2-0.8μm 0.3-1.0μm 0.4-1.3μm 0.6-1.4μm 0.6-1.5μm

It can be seen from Table 1 that the size of the sphere can be controlled by changing the amount of glucose to meet different needs.

Example 3 spherical boron nitride

The preparation method is the same as in Example 1, except that the urea in step 1) is changed to melamine, biuret, ammonium chloride or ammonium nitrate respectively, and the results are shown in Table 2.

Table 2

nitrogen source Melamine biuret ammonium chloride ammonium nitrate Morphology of spherical boron nitride 0.2-1.5μm 0.6-1.5μm 0.5-1.3μm 0.6-1.2μm

Example 4 spherical boron nitride

The preparation method is the same as in Example 1, except that the glucose in step 1) is changed to MCM-41 molecular sieve or Y-molecular sieve respectively, and the results are shown in Table 3.

table 3

Templating agent MCM-41 molecular sieve Y-molecular sieve Morphology of spherical boron nitride 0.4-0.9μm (0.3)-(1.2)μm

Example 5 spherical boron nitride

The preparation method is the same as that of Example 1, the difference being that the heat preservation time in step 2) is changed, and the results are shown in Table 4.

Table 4

Example 6 Spherical boron nitride

The preparation method is the same as in Example 1, except that the protective gas in step 4) is changed from nitrogen to ammonia, and the results are shown in Table 5.

table 5

Protective gas Ammonia Morphology of spherical boron nitride 0.5-1.7μm

Example 7 Spherical boron nitride

The preparation method is the same as in Example 1, except that the temperature in step 2) is changed, and the results are shown in Table 6.

Table 6

Embodiment 8 spherical boron nitride

The preparation method is the same as in Example 1, except that the temperature in step 3) is changed, and the results are shown in Table 7.

Table 7

Embodiment 9 spherical boron nitride

The preparation method is the same as in Example 1, except that the heating rate is changed, and the results are shown in Table 8.

Table 8

Step 3 heating rate 2 3 4 5 6 Step 4 heating rate 2 3 4 5 6 Morphology of spherical boron nitride 0.2-1.3μm 0.2-1.5μm 0.2-1.1μm 0.2-1.2μm 0.2-1.2μm

Embodiment 10 spherical boron nitride

The preparation method is the same as that of Example 1, except that the heat preservation time of step 3) is changed, and the results are shown in Table 9.

Table 9

Embodiment 11 spherical boron nitride

The preparation method is the same as in Example 1, except that the temperature in 4) is changed, and the results are shown in Table 10.

Table 10

Embodiment 12 spherical boron nitride

The preparation method is the same as that of Example 1, except that the heat preservation time of step 4) is changed, and the results are shown in Table 11.

Table 11

Embodiment 13 spherical boron nitride

The preparation method is the same as in Example 1, except that the soaking time in step 5) is changed, and the results are shown in Table 3.

table 3

Embodiment 14 spherical boron nitride

The preparation method is the same as in Example 1, except that the drying temperature in step 5) is changed, and the results are shown in Table 13.

Table 13

Drying temperature (℃) 60 80 100 130 150 Morphology of spherical boron nitride 0.2-1.5μm 0.2-1.3μm 0.2-1.3μm 0.2-1.4μm 0.2-1.4μm

Embodiment 15 spherical boron nitride

The preparation method is the same as in Example 1, except that the drying time in step 5) is changed, and the results are shown in Table 14.

Table 14

Embodiment 16 application experiment

1) The method is as follows: the spherical boron nitride prepared in Example 1 is added to the solution containing the organic pollutant methylene blue, the pH of the solution is adjusted to be neutral, and 2 mg of the boron nitride prepared in Example 1 is added in 20ml, 10mg/L of the methylene blue solution. Spherical boron nitride, static adsorption.

2) The influence of adsorption time on the adsorption rate is shown in Figure 5. From Figure 5, it can be seen that when the adsorption time is 10s, the adsorption rate can reach 88.64%, and the adsorption time reaches equilibrium after 20 minutes, and the adsorption rate is about 94.8% .

3) The infrared spectrum of the adsorption and desorption of spherical boron nitride to methylene blue is shown in Figure 6. As shown in Figure 6, in the infrared spectrum of the sample after adsorption, comparatively speaking, there is an obvious absorption peak of methylene blue, but after high temperature desorption treatment, only the characteristic peak of boron nitride remains.

4) Spherical boron nitride is adsorbed, then calcined and then adsorbed. The adsorption data of 5 cycles are shown in Figure 7. The equilibrium time of each adsorption is 30 minutes, and the adsorbed boron nitride is repeatedly used as an adsorbent after simple high-temperature calcination treatment. It can be seen from Figure 7 that after recycling 5 times, the adsorption rate can still be close to 90%, and the repeatability is good.

Claims (8)

1. a spherical boron nitride is characterized in that the preparation method comprises the steps: 1) The template agent, nitrogen source and boron source are dissolved in water under magnetic stirring to obtain a colorless and transparent solution; wherein, the template agent is glucose, MCM-15 molecular sieve or Y-molecular sieve; the nitrogen source is Urea, melamine, biuret, ammonium chloride or ammonium nitrate; the boron source is boric acid; the molar ratio of template agent, nitrogen source and boron source is 1.0-8.5:1:1; 2) Put the colorless transparent solution into a stainless steel reaction kettle, place the reaction kettle in a constant temperature oven, react at 180°C-220°C for 24-110h, cool down to room temperature naturally, filter, and wash the precipitate with water and ethanol in sequence, Solid A was obtained after drying; 3) Put solid A in a high-temperature furnace, raise the temperature to 450-900° C. at a rate of 1-6° C. per minute under air atmosphere, and keep it at 450-900° C. for 2-12 hours to obtain solid B; 4) Put solid B in a closed container, raise the temperature to 900-1700° C. at a rate of 1-6° C. per minute under protective gas, and keep warm at 900-1700° C. for 1-14 hours to obtain solid C; 5) Immerse the solid C with hydrochloric acid aqueous solution for 1-24 hours, ultrasonicate, stir, then filter, wash the precipitate with water and ethanol, and then dry at 50-150°C for 3-24 hours to obtain the target product spherical boron nitride . 2. The spherical boron nitride according to claim 1, characterized in that: the template agent is glucose. 3. The spherical boron nitride according to claim 1, characterized in that: the nitrogen source is urea. 4. The spherical boron nitride according to claim 1, characterized in that: the protective gas is ammonia or nitrogen. 5. The spherical boron nitride as claimed in claim 4, characterized in that: the protective gas is nitrogen. 6. The application of spherical boron nitride as claimed in claim 1 in adsorbing organic pollutants. 7. The application according to claim 6, characterized in that the method is as follows: adding the spherical boron nitride according to claim 1 to the wastewater containing organic pollutants, adjusting the concentration of organic pollutants to 5-15mg/L, The pH is 6.5-7.5, let stand for adsorption. 8. The application of spherical boron nitride according to claim 1 in hydrogen storage material, catalyst carrier and water treatment.