Preparation of cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction and application of cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction in photocatalytic uranyl reduction extraction

Abstract

The invention discloses preparation of a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction and application of the cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction in photocatalytic uranyl reduction extraction. The invention provides the preparation method of the photocatalytic material which is simple in synthesis, high in U (VI) reduction speed and high in reduction efficiency. The preparation method comprises the following steps: compounding a 2D photocatalyst carbon nitride (g-C3N4) with 0D carbon nitride quantum dots (CNQDs) to prepare a g-C3N4 / CNQDs heterojunction mediated by a cyano group; the material has high photocatalytic activity and can be used as a catalyst for reducing U (VI), and the reduction rate of the material is 80.47% and is far higher than the reduction rate of g-C3N4 (39.42%) and CNQDs (1.61%).

Description

Technical Field

[0001] The present invention relates to the preparation of a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction and its photocatalytic uranyl reduction and extraction application. Technical Background

[0002] Uranium is an extremely important raw material in the development of nuclear energy, and its reserves and supply have always been the focus of global attention. As land uranium mines are continuously mined, the available uranium resources are gradually reduced, which poses a serious challenge to the long-term development of nuclear energy. Because rivers continue to wash uranium elements from land into the ocean, the uranium content in seawater can remain relatively stable. In this way, if uranium can be extracted from seawater in an effective way, then in theory, there will be almost inexhaustible uranium resources. Traditional uranium mining produces wastewater containing pollutants, which is harmful to the health of miners and will also have a negative impact on the environment. In comparison, uranium extraction from seawater has certain advantages in terms of environmental protection.

[0003] The photocatalytic method can use sunlight to drive the reduction of U(VI) in an efficient and highly selective manner, which provides a new technical means for the extraction of uranium. The photocatalytic process can generally be carried out at room temperature and pressure, without the need for harsh conditions such as high temperature and high pressure. It can also use renewable energy such as solar energy as a light source, with low energy consumption and little pollution to the environment. In addition, the photocatalytic method is usually highly selective in the extraction of uranium, and even in the presence of interfering ions, uranium can be extracted efficiently. Therefore, there are still many studies dedicated to photocatalytic uranium extraction. Summary of the invention

[0004] Carbon nitride is a very common 2D material, which is generally used as a reducing agent and photocatalyst. However, due to its extremely low luminescence efficiency and low photocatalytic activity, it only has high photocatalytic activity within a specific wavelength range, which makes it less reducible to uranyl. 0D quantum dot materials have extremely high luminescence efficiency. Therefore, in order to solve this problem, carbon nitride quantum dots are innovatively combined with carbon nitride to prepare a cyanide-mediated g-C3N4 / CNQDs heterojunction, thereby improving and broadening the photocatalytic activity of carbon nitride, and realizing the photocatalytic reduction of U(VI) by carbon nitride-carbon nitride quantum dots.

[0005] In order to implement the above steps, the present invention provides the following technical solution, the steps are as follows:

[0006] S1: Preparation of g-C3N4

[0007] Take 10g of urea, grind it thoroughly with an agate mortar, pour it into a crucible, transfer it to a muffle furnace, heat it up at a rate of 5-20℃ / min, and react it at 400-600℃ for 2-4 hours. After cooling to room temperature, take it out and grind it for later use. The obtained product is g-C3N4.

[0008] S2: Preparation of CNQDs

[0009] 1) Heat and stir 1-10 g of trimeramine (MA) in 300-1000 ml of water to dissolve, then add a certain amount of a mixture of potassium chloride (KCl) and sodium chloride (NaCl) (mass ratio = 1:1-1:10), heat and stir to dissolve.

[0010] 2) After the above solution is fully dissolved and mixed, open the lid, continue heating and stirring at 90°C, and evaporate until it becomes viscous.

[0011] 3) The resulting mixture is then calcined in a muffle furnace at 400-600° C. for 1-4 hours at a heating rate of 5-20° C. / min.

[0012] 4) After washing with methanol, the powder was dried in a vacuum oven at 90 °C overnight and then dispersed into a certain volume of deionized water to obtain a CNQDs solution.

[0013] S3: Preparation of CN-CNQDs

[0014] 1) Take a certain amount of g-C3N4 and 10g CNQDs, grind and mix, then transfer to a glass bottle and ultrasonicate until uniform, heat and stir in an oil bath at 100℃ to evaporate excess water.

[0015] 2) The obtained product is transferred into a crucible, placed into a muffle furnace, heated at a rate of 5 to 20°C / min, and maintained at 350°C for 2 to 4 hours.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) The drug used in the present invention is cheap, simple to synthesize, easy to control parameters, and has a high yield;

[0018] 2) Compared with ordinary g-C3N4 and CNQDs, this sample has a higher reduction efficiency for uranium, and can obtain a reduction efficiency of more than 80% after 60 minutes of dark reaction and 90 minutes of light reaction;

[0019] 3) The sample has a certain fluorescence response, and after further research and development, it can be combined with sensors for application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1aThe C / C0 diagram and SEM image of the product prepared in Example 1 of the present invention. Figure 1 XRD patterns of the product prepared in Example 1 of the present invention and g-C3N4.

[0021] Figure 2 FT-IR spectra of the product prepared in Example 1 of the present invention, g-C3N4 and CNQDs.

[0022] Figure 3 This is the EDS graph of the product prepared in Example 1 of the present invention.

[0023] Figure 4 This is a C / C0 comparison chart of the product prepared in Example 1 of the present invention and the product prepared in Comparative Example 1.

[0024] Figure 5 This is a C / C0 comparison chart of the product prepared in Example 1 of the present invention and the product prepared in Comparative Example 2.

[0025] Figure 6 This is a C / C0 comparison chart of the product prepared in Example 1 of the present invention and the product prepared in Comparative Example 3.

[0026] Figure 7 This is a C / C0 comparison chart of the product prepared in Example 1 of the present invention and the product prepared in Comparative Example 4. DETAILED DESCRIPTION

[0027] Example 1

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. Of course, the embodiments described are partial embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0029] S1: Preparation of g-C3N4

[0030] Take 10g of urea, grind it thoroughly with an agate mortar, pour it into a crucible, transfer it to a muffle furnace, heat it up at a rate of 5-20℃ / min, and react it at 400-600℃ for 2-4 hours. After cooling to room temperature, take it out and grind it for later use. The obtained product is g-C3N4.

[0031] S2: Preparation of CNQDs

[0032] 1) Heat and stir 1-10 g of trimeramine (MA) in 300-1000 ml of water to dissolve, then add a certain amount of a mixture of potassium chloride (KCl) and sodium chloride (NaCl) (mass ratio = 1:1-1:10), heat and stir to dissolve.

[0033] 2) After the above solution is fully dissolved and mixed, open the lid, continue heating and stirring at 90°C, and evaporate until it becomes viscous.

[0034] 3) The resulting mixture is then calcined in a constant temperature furnace at 400-600° C. for 1-4 hours at a heating rate of 5-20° C. / min.

[0035] 4) After washing with methanol, the powder was dried in a vacuum oven at 90°C overnight and then dispersed into a certain volume of deionized water to obtain a CNQDs solution.

[0036] S3: Preparation of CN-CNQDs

[0037] 1) Take a certain amount of g-C3N4 and 10g CNQDs, grind and mix, then transfer to a glass bottle and ultrasonicate until uniform, heat and stir in an oil bath at 100℃ to evaporate excess water.

[0038] 2) Then transfer to a crucible, put into a muffle furnace, heat up at a rate of 5 to 20°C / min, and maintain at 350°C for 2 to 4 hours. The prepared product is CN-CNQDs-10-350.

[0039] Figure 1 is the XRD diagram of Example 1 and g-C3N4, Figure 2 The FT-IR images of Example 1, g-C3N4 and CNQDs are shown in Figure 1. From the FT-IR image, it can be seen that cyano groups (-C≡N) appear on CN-CNQDs, indicating that CNQDs and g-C3N4 are successfully composited. Figure 3 This is the EDS image of CN-CNQDs-10-350 prepared in Example 1 after uranium is added. It can be seen from the image that uranium is successfully loaded on the sample.

[0040] Comparative Example 1

[0041] S1: Preparation of g-C3N4

[0042] The preparation method is consistent with that in Example 1.

[0043] Figure 4 The C / C0 diagrams of the reduction of uranium in 0.1 g / L to 5 g / L uranium solutions for Comparative Example 1 and Example 1 are shown. It can be seen that the reduction rate of g-C3N4 is lower than that of CN-CNQDs-10-350 prepared in Example 1, whether in the dark or under light.

[0044] Comparative Example 2

[0045] S1: Preparation of CNQDs

[0046] The method for preparing S2 is consistent with that in Example 1.

[0047] Figure 5 The C / C0 diagram of uranium reduction in 0.1 g / L to 5 g / L uranium solutions of Comparative Example 2 and Example 1, respectively, shows that the reduction rate of CNQDs is much lower than that of CN-CNQDs-10-350 prepared in Example 1, whether in the dark or under light.

[0048] Comparative Example 3

[0049] S1: Preparation of g-C3N4

[0050] The method is consistent with that prepared in Example 1.

[0051] S2: Preparation of CNQDs

[0052] The method is consistent with that prepared in Example 1.

[0053] S3: Preparation of CN-CNQDs-20-350

[0054] The process is basically the same as step S3 in Example 1, characterized in that 5 g of CNQDs are used in step 1), and the obtained sample is named CN-CNQDs-5-350.

[0055] Figure 6 The C / C0 diagrams of the reduction of uranium in 0.1 g / L to 5 g / L uranium solutions of Comparative Example 3 and Example 1 are shown. It can be seen that the reduction rate of CN-CNQDs-5-350 is much lower than that of CN-CNQDs-10-350 prepared in Example 1, whether in the dark or under light.

[0056] Comparative Example 4

[0057] S1: Preparation of g-C3N4

[0058] The method is consistent with that prepared in Example 1.

[0059] S2: Preparation of CNQDs

[0060] The method is consistent with that prepared in Example 1.

[0061] S3: Preparation of CN-CNQDs-10-500

[0062] The process is basically the same as step S3 in Example 1, characterized in that the temperature of the muffle furnace in step 2) is 500° C. The obtained sample is named CN-CNQDs-10-500.

[0063] Figure 7 The C / C0 diagrams of the reduction of uranium in 0.1 g / L to 5 g / L uranium solutions of Comparative Example 4 and Example 1 are shown. It can be seen that the reduction rate of CN-CNQDs-10-500 is much lower than that of CN-CNQDs-10-350 prepared in Example 1, whether in the dark or under light.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0065] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction, characterized in that: The method includes: Take 10g of urea, grind it thoroughly with an agate mortar, pour it into a crucible, transfer it to a muffle furnace, heat it up at a rate of 5-20℃ / min, and react it at 400-600℃ for 2-4 hours. After cooling to room temperature, take it out and grind it for later use to prepare g-C3N4. 1-10g of tripolyamine (MA) is heated and stirred to dissolve in 300-1000ml of water, and then a certain amount of a mixture of potassium chloride (KCl) and sodium chloride (NaCl) is added and heated and stirred to dissolve. After sufficient dissolution and mixing, open the lid, continue heating and stirring at 90°C, and evaporate to a viscous state. The resulting mixture is calcined at 400-600°C for 1-4 hours in a muffle furnace at a heating rate of 5-20°C / min. After washing with methanol, the powder is dried overnight in a vacuum oven at 90°C, and then dispersed in a certain volume of deionized water to obtain a CNQDs solution. Take a certain amount of g-C3N4 and 10g CNQDs and grind and mix them, then transfer them to a glass bottle and ultrasonicate them until they are uniform, heat and stir them in an oil bath at 100℃ to evaporate excess water. Then transfer them to a crucible and put them in a muffle furnace, heating them at a rate of 5-20℃ / min and keeping them at 350℃ for 2-4 hours.

2. The method for preparing a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction according to claim 1, characterized in that: The mass ratio of potassium chloride to sodium chloride is 1:1 to 1:

10.

3. The method for preparing a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction according to claim 1, characterized in that: The calcination time of MA, KCl and NaCl transparent solution in the muffle furnace is 1 to 4 hours.

4. The method for preparing a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction according to claim 1, characterized in that: The calcined CNQDs need to be washed with methanol.

5. The method for preparing a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction according to claim 1, characterized in that: The g-C3N4 / CNQDs solution needs to be ultrasonically dispersed first, then stirred and heated, and then calcined in a muffle furnace.

6. The method for preparing a cyano-mediated 0D / 2D C3N5 / C3N4 heterojunction according to claim 1, characterized in that: When g-C3N4 / CNQDs were calcined in a muffle furnace, the heating rate was 5-20°C / min and 350°C was maintained for 2-4 hours.

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