Carbon nitride composite material as well as preparation method and application thereof

Abstract

The invention relates to a carbon nitride composite material and a preparation method and application thereof, and the preparation method comprises the following steps: (1) dissolving sodium alginate and carbon black in water, adding polyacrylic acid, stirring and reacting for a certain time to obtain a mixture; and (2) adding a CN precursor into the mixture in the step (1) while heating and stirring, heating to a gel state, and roasting at high temperature to obtain the carbon nitride composite material. According to the catalyst prepared by the method, the specific surface area of the carbon nitride material is increased, and the structural integrity and crystallinity of the carbon nitride material are prevented from being damaged.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection functional materials, and particularly relates to a carbon nitride composite material, a preparation method thereof and an application thereof. Background Art

[0002] As a new type of photocatalytic material, carbon nitride materials have attracted much attention in recent years and can be used as catalyst carriers in different catalytic systems. However, traditional preparation methods usually use CN precursors such as urea or melamine for calcination to prepare crystalline phase C3N4 samples, and the specific surface area of the prepared C3N4 is relatively low, which limits its application.

[0003] The literature "Activity and mechanism of g-C3N4 photocatalytic degradation of 2,4-DCP" (Wu Bin et al., Environmental Chemistry, 2017) used melamine as a raw material and synthesized a graphite-like carbon nitride (g-C3N4) photocatalyst by a thermal condensation reaction under high temperature conditions. The results showed that the prepared g-C3N4 had a lamellar structure and a specific surface area of 15.3 m 2 ·g -1 . Under visible light (λ>420 nm) irradiation, 2,4-dichlorophenol, an organic small molecule pollutant, was degraded by g-C3N4. After reacting for 250 min with a dosage of 0.67 g·L -1 , the mineralization rate of 2,4-DCP reached 60%; the degradation efficiency of 2,4-DCP was the highest under weakly acidic conditions (pH = 5.4); through capture experiments and electron spin resonance (ESR) experiments, it was shown that superoxide radicals (O 2 · - ) were the main active species in the process of g-C3N4 photocatalytic degradation of 2,4-DCP. However, the specific surface area of the g-C3N4 prepared by this method was only 15.3 m 2 ·g -1 , which was relatively low.

[0004] CN111841599A discloses a preparation method of a carbon quantum dot-doped carbon nitride composite nanomaterial with photocatalytic antibacterial properties, comprising the following steps: loading a CQDs precursor (precursor of carbon quantum dots) into crucible A, and then loading a CN precursor (precursor of carbon nitride) into crucible B; loading crucible B into crucible A (crucibles A and B are of different sizes, and crucible A is larger than crucible B), covering crucible A, and putting it into a muffle furnace for heating treatment at a temperature of 570-650 °C to obtain the carbon quantum dot-doped carbon nitride composite nanomaterial with photocatalytic antibacterial properties (CQDs\CN composite photocatalytic antibacterial material). The CQDs precursor is one or more of ammonium citrate, EDTA, EDTA, and melamine; the CN precursor is one or more of urea, melamine, dicyandiamide, and thiourea. In the preparation process of this method, ammonia gas is generated by the decomposition of ammonium citrate, which has an etching effect on CN, increasing the specific surface area of the prepared carbon quantum dot-doped carbon nitride composite nanomaterial, and it is difficult to stably control the preparation process. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a carbon nitride composite material, its preparation method and application. The catalyst prepared by the method of the present invention improves the specific surface area of the carbon nitride material and avoids the destruction of the structural integrity and crystallinity of the carbon nitride material.

[0006] The first aspect of the present invention provides a preparation method of a carbon nitride composite material, comprising the following steps:

[0007] (1) Dissolve sodium alginate and carbon black in water, add polyacrylic acid, and stir and react for a certain time to obtain a mixture;

[0008] (2) Add the CN precursor to the mixture obtained in step (1) under heating and stirring, heat to a gel state, and obtain the carbon nitride composite material through high-temperature calcination.

[0009] In the present invention, in step (1), the mass ratio of sodium alginate to water is 0.5-2.5:100, preferably 0.5-1.0:100.

[0010] In the present invention, in step (1), the mass ratio of sodium alginate to carbon black is 1:0.03-0.1, preferably 1:0.03-0.06.

[0011] In the present invention, in step (1), the molar ratio of polyacrylic acid to sodium alginate is 1:0.5-2, preferably 1:1-1.2.

[0012] In the present invention, the stirring in step (1) can be carried out by using conventional magnetic and electric stirring equipment, the stirring rate is 500-1500 rpm, and the stirring time is 1-5 h.

[0013] In the present invention, further preferably, a certain amount of EDTA is added simultaneously in step (1), and the addition amount is 0.1%-0.5% of the mass of sodium alginate.

[0014] In the present invention, for step (2), the heating is carried out by any one of water bath heating, heating with a magnetic stirrer with heating function, heating with an electric hot plate, etc. The heating temperature is 30-60°C, and the stirring rate is 500-1500 rpm.

[0015] In the present invention, the CN precursor in step (2) is selected from at least one of melamine, dicyandiamide, monocyanamide, urea, thiourea, ammonium bisulfate, etc.

[0016] In the present invention, the CN precursor in step (2) is added according to the mass ratio of 10-30:1 to carbon black.

[0017] In the present invention, in step (2), it is heated to a gel state and then subjected to high-temperature roasting. The roasting temperature is 400-500°C, and the roasting time is 2-10 h. The roasting can be carried out using a conventional roasting device such as a muffle furnace.

[0018] In the second aspect of the present invention, a carbon nitride composite material is provided, which is prepared by the method of the present invention described above. The specific surface area of the prepared carbon nitride composite material is 50 m 2 / g or more.

[0019] In the third aspect of the present invention, an application of the prepared carbon nitride composite material is provided, that is, it is used as a photocatalyst, having good photocatalytic effect, especially suitable for the photocatalytic degradation of rhodamine B reaction. This benefits from the preparation method of the present invention, which improves the specific surface area while keeping the catalyst in good crystallinity, and thus shows better photocatalytic performance.

[0020] In the application of the present invention, specifically, the carbon nitride composite material is dispersed into the water body containing rhodamine B, and the usage amount of the composite material is 0.1-5.0 g / mL.

[0021] In the application of the present invention, the temperature of the photocatalytic degradation is 10-40°C, and the pH is 2-6.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) In the present invention, a mixed solution of sodium alginate, carbon black, and polyacrylic acid is first prepared, then a CN precursor is added under heating and stirring to obtain a gel, and then amorphous carbon is doped into the crystalline phase C3N4 by roasting. Through the synergistic effect of each component, the specific surface area of the carbon nitride composite material is increased. Compared with the carbon nitride material prepared by the traditional method, the specific surface area is increased by more than 50%, which is beneficial to mass transfer and diffusion and improves the photocatalytic effect.

[0024] (2) The preparation method of the present invention overcomes the damage to the structural integrity of the carbon nitride material caused by the introduction of amorphous carbon, and while increasing the specific surface area, it avoids the destruction of the crystal form of carbon nitride. Detailed implementation manners

[0025] The technical solutions and effects of the present invention will be further described below through examples. The examples are implemented on the premise of the technical solutions of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0026] In the following examples, the experimental methods are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples can all be obtained from biochemical reagent stores unless otherwise specified. The water used is all deionized water.

[0027] Example 1

[0028] Weigh 2.5 g of sodium alginate and 0.125 g of carbon black and dissolve them in 500 mL of distilled water. Add polyacrylic acid according to the molar ratio of polyacrylic acid to sodium alginate of 1:1, with a stirring rate of 500 rpm, and stir magnetically for 3 h to obtain a mixed solution. Under the conditions of heating and stirring, the heating temperature is 45 °C and the stirring rate is 500 rpm. Slowly add 2.5 g of melamine powder, and continue heating until it gels, then stop heating and transfer it to a muffle furnace for calcination at 500 °C for 5 hours to obtain a carbon nitride composite material. After testing, the specific surface area of the prepared composite material is 65.3 m 2 / g.

[0029] Example 2

[0030] Weigh 5.0 g of sodium alginate and 0.2 g of carbon black and dissolve them in 500 mL of distilled water. Add polyacrylic acid according to the molar ratio of polyacrylic acid to sodium alginate of 1:1.2, stir magnetically for 4 h, with a stirring rate of 500 rpm, to obtain a mixed solution; heat and stir on a magnetic stirrer, with a heating temperature of 35 °C and a stirring rate of 500 rpm. Slowly add 5.0 g of melamine powder, and continue heating until it gels, then stop heating and transfer it to a muffle furnace for calcination at 450 °C for 7 hours to obtain a carbon nitride composite material. After testing, the specific surface area of the prepared composite material is 61.7 m 2 / g.

[0031] Example 3

[0032] Weigh 7.5 g of sodium alginate and 0.75 g of carbon black, dissolve them in 500 mL of distilled water, add polyacrylic acid according to the molar ratio of polyacrylic acid to sodium alginate of 1:1.1, stir magnetically for 2 h at a stirring rate of 500 rpm to obtain a mixed solution; heat and stir on a magnetic stirrer at a heating temperature of 60 °C and a stirring rate of 500 rpm. Add 7.5 g of melamine powder, continue heating until gelation, then stop heating, transfer to a muffle furnace and calcine at 400 °C for 10 hours to obtain a carbon nitride composite material. After testing, the specific surface area of the prepared composite material is 55.9 m 2 / g.

[0033] Example 4

[0034] Same as Example 1, except that: the CN precursor uses urea, and finally a carbon nitride composite material is obtained. After testing, the specific surface area of the prepared composite material is 62.2 m 2 / g.

[0035] Example 5

[0036] Same as Example 1, except that: the CN precursor uses cyanamide, and finally a carbon nitride composite material is obtained. After testing, the specific surface area of the prepared composite material is 58.4 m 2 / g.

[0037] Example 6

[0038] Same as Example 1, except that: in step (1), EDTA is added simultaneously, and the addition amount is 0.2% of the mass of sodium alginate. After testing, the specific surface area of the prepared composite material is 68.2 m 2 / g.

[0039] Comparative Example 1

[0040] Same as Example 1, except that: sodium alginate, carbon black, polyacrylic acid, and melamine are mixed and heated together, and finally a composite material is obtained. After analysis, the specific surface area of the prepared composite material is 48.2 m 2 / g.

[0041] Comparative Example 2

[0042] Same as Example 1, except that: sodium alginate is not used, and finally a composite material is obtained. After analysis, the specific surface area of the prepared composite material is 40.6 m 2 / g.

[0043] Comparative Example 3

[0044] Same as Example 1, except that: polyacrylic acid is not used, and finally a composite material is obtained. After analysis, the specific surface area of the prepared composite material is 31.7 m 2 / g.

[0045] Comparative Example 4

[0046] Same as Example 1, except that carbon black was not used, and the composite material was finally obtained. After analysis, the specific surface area of the prepared composite material was 18.6 m 2 / g.

[0047] Test Example

[0048] The degradation performance of the carbon nitride composite materials prepared in the examples and comparative examples was tested. The selected model pollutant was Rhodamine B, the reaction solution was 100 mL, the concentration was 10 mg / L, and the xenon lamp light source was turned on. The dosage of the carbon nitride composite material was 200 g. Samples were taken and tested on a spectrophotometer to detect the remaining concentration of Rhodamine B, calculate the removal rate, and the evaluation performance is shown in Table 1.

[0049] Table 1

[0050]

[0051]

[0052] From the above test results, it can be seen that the specific surface area of the catalyst prepared by the present invention is significantly improved, and it has good pollutant removal effect. The effect of the catalyst prepared without adopting the complete technical solution of the present invention is significantly reduced.

Claims

1. A method for preparing a carbon nitride composite material, characterized in that it comprises the following steps: (1) Dissolve sodium alginate and carbon black in water, add polyacrylic acid, and stir and react for a certain time to obtain a mixture; (2) Add a CN precursor to the mixture in step (1) under heating and stirring, heat to a gel state, and perform high-temperature calcination to obtain a carbon nitride composite material.

2. The method according to claim 1, characterized in that: In step (1), the mass ratio of sodium alginate to water is 0.5 - 2.5:100, preferably 0.5 - 1.0:

100.

3. The method according to claim 1, characterized in that: In step (1), the mass ratio of sodium alginate to carbon black is 1:0.03 - 0.1, preferably 1:0.03 - 0.

06.

4. The method according to claim 1, characterized in that: In step (1), the molar ratio of polyacrylic acid to sodium alginate is 1:0.5 - 2, preferably 1:1 - 1.

2.

5. The method according to claim 1, characterized in that: In step (1), the stirring rate is 500 - 1500 rpm, and the stirring time is 1 - 5 h.

6. The method according to claim 1, characterized in that: In step (1), a certain amount of EDTA is added simultaneously, and the addition amount is 0.1% - 0.5% of the mass of sodium alginate.

7. The method according to claim 1, characterized in that: In step (2), the heating temperature is 30 - 60 °C, and the stirring rate is 500 - 1500 rpm.

8. The method according to claim 1, characterized in that: The CN precursor in step (2) is selected from at least one of melamine, dicyandiamide, monocyanamide, urea, thiourea, or ammonium bisulfate.

9. The method according to claim 1, characterized in that: The CN precursor in step (2) is added according to a mass ratio of 10 - 30:1 to carbon black.

10. The method according to claim 1, characterized in that: In step (2), heat to a gel state and perform high-temperature calcination. The calcination temperature is 400 - 500 °C, and the calcination time is 2 - 10 h.

11. A carbon nitride composite material, characterized in that it is prepared by the method described in any one of claims 1 - 10.

12. The application of the carbon nitride composite material prepared by the method described in any one of claims 1 - 10 or the carbon nitride composite material described in claim 11, characterized in that: It is used as a photocatalyst, especially suitable for the photocatalytic degradation of rhodamine B reaction.

13. The application according to claim 12, characterized in that: Disperse the carbon nitride composite material into the water body containing rhodamine B for photocatalyst degradation, and the usage amount of the carbon nitride composite material is 0.1 - 5.0 g / mL.

14. The application according to claim 12 or 13, characterized in that: The temperature of photocatalytic degradation is 10 - 40 °C, and the pH is 2 - 6.

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