G-C3N4-based adsorbent and synthesis method thereof

Abstract

The invention belongs to the technical field of printing and dyeing wastewater treatment, and particularly relates to a g-C3N4-based adsorbent and a synthesis method thereof.The method comprises the steps that urea is put into a drying oven to be dried, dried urea is obtained, lauryl sodium sulfate is added into the dried urea, mixing and grinding are conducted, a mixture is obtained, then the mixture is transferred into a crucible to be calcined, and a calcined product is obtained; and cooling the calcined product to room temperature, washing and drying to obtain the g-C3N4-based adsorbent. According to the preparation method, the lauryl sodium sulfate is added firstly and then calcined, so that the electronegativity of the product is effectively improved, the electrostatic adsorption capacity to cationic methylene blue is remarkably improved, and the adsorption rate is finally improved.

Description

Technical Field

[0001] The invention belongs to the technical field of printing and dyeing wastewater treatment, and specifically relates to a g-C3N4-based adsorbent and a synthesis method thereof. Background Art

[0002] With the increasing awareness of environmental protection and increasingly stringent environmental regulations, the development of efficient, low-cost, and environmentally friendly adsorbents has become an urgent need to solve the problem of water pollution. Although a variety of materials have been developed for the adsorption of dyes such as methylene blue, further improving the adsorption performance and exploring more green and environmentally friendly materials and their applications remain important research directions in the field of environmental science and technology. In the process of exploring green and environmentally friendly adsorbents, g-C3N4, as an emerging two-dimensional material, has attracted much attention due to its unique physicochemical properties (such as high specific surface area, good stability, tunable electronic structure, etc.). The performance of g-C3N4-based adsorbents can be further optimized through different synthesis methods and modification strategies.

[0003] At present, the synthesis methods of g-C3N4 include hydrothermal method, calcination method, impregnation method and in-situ deposition method. The invention patent with application number CN202311292768.6 discloses a simple preparation method and application of modified carbon nitride, which places the original carbon nitride in ultrapure water and applies light source illumination to change the structure of carbon nitride and increase the hydroxyl-OH functional group, thereby obtaining a modified carbon nitride (GCN) with a negative charge on the surface, while the band gap is reduced, and the separation efficiency of photogenerated carriers is greatly improved, which effectively improves the effect of photocatalytic degradation of methylene blue. However, the prior art still has the problem that g-C3N4 directly used as a dye adsorbent has a poor adsorption effect on methylene blue. Summary of the invention

[0004] The purpose of the present invention is to provide a g-C3N4-based adsorbent and a method for synthesizing the same, which improves the adsorption effect of g-C3N4 on methylene blue by increasing the electronegativity of g-C3N4.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for synthesizing a g-C3N4-based adsorbent, the method comprising:

[0007] Putting urea into an oven for drying to obtain dry urea;

[0008] adding sodium lauryl sulfate to dry urea, mixing and grinding to obtain a mixture;

[0009] The mixture is transferred into a crucible for calcination to obtain a calcined product;

[0010] The calcined product was cooled to room temperature, washed, and oven-dried to obtain a g-C3N4-based adsorbent.

[0011] The mass ratio of the urea to sodium dodecyl sulfate is 100:0.5-3.

[0012] The calcination temperature is 450-550° C., and the calcination time is 1.5-3 hours.

[0013] The temperature of the oven-dried urea is 50-80° C., and the drying time of the oven-dried urea is at least 0.5 h.

[0014] The calcination is carried out in a muffle furnace, and the heating rate of the muffle furnace is 2-10° C. / min.

[0015] The temperature of the oven drying the calcined product is 50-80° C., and the drying time is 6-12 hours.

[0016] The grinding time is 10-30 min.

[0017] In a second aspect, the present invention provides a g-C3N4-based adsorbent, which is prepared according to the aforementioned synthesis method.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The synthesis method of the g-C3N4-based adsorbent of the present invention comprises the following steps: firstly putting urea into an oven for drying to obtain dry urea, then adding sodium dodecyl sulfate to the dry urea, mixing and grinding to obtain a mixture, then transferring the mixture into a crucible for calcination to obtain a calcined product, and then cooling the calcined product to room temperature, washing, and drying in an oven to obtain the g-C3N4-based adsorbent; the method effectively improves the electronegativity of the product by first adding sodium dodecyl sulfate and then calcining, thereby significantly improving the electrostatic adsorption capacity for cationic methylene blue, and finally improving the adsorption rate for cationic methylene blue. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The adsorption rates of Examples 1-3 and Comparative Example 1 for methylene blue.

[0021] Figure 2 These are the XRD diagrams of Example 2 and Comparative Example 1.

[0022] Figure 3 The zeta potential of Example 2 and Comparative Example 1.

[0023] Figure 4 is the Zeta potential of Comparative Examples 2-4.

[0024] Figure 5It is the adsorption rate of comparative example 2-4 for methylene blue. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with specific implementations and drawings.

[0026] A method for synthesizing a g-C3N4-based adsorbent, the method comprising:

[0027] Putting urea into an oven for drying to obtain dry urea;

[0028] adding sodium lauryl sulfate to dry urea, mixing and grinding to obtain a mixture;

[0029] The mixture is transferred into a crucible for calcination to obtain a calcined product;

[0030] The calcined product was cooled to room temperature, washed, and oven-dried to obtain a g-C3N4-based adsorbent.

[0031] The mass ratio of the urea to sodium dodecyl sulfate is 100:0.5-3.

[0032] The calcination temperature is 450-550° C., and the calcination time is 1.5-3 hours.

[0033] The temperature of the oven-dried urea is 50-80° C., and the drying time of the oven-dried urea is at least 0.5 h.

[0034] The calcination is carried out in a muffle furnace, and the heating rate of the muffle furnace is 2-10° C. / min.

[0035] The temperature of the oven drying the calcined product is 50-80° C., and the drying time is 6-12 hours.

[0036] The grinding time is 10-30 min.

[0037] A g-C3N4-based adsorbent is prepared according to the aforementioned synthesis method.

[0038] Embodiment 1:

[0039] A method for synthesizing a g-C3N4-based adsorbent is carried out in the following steps:

[0040] S1. Place 20 g of urea in an oven at 60° C. and bake for 30 min to obtain dry urea;

[0041] S2, add 0.1g sodium dodecyl sulfate (SDS) to dry urea, mix and grind for 10min to obtain a mixture; the mass ratio of urea to SDS is 100:0.5;

[0042] S3, transferring the mixture into a crucible, placing it in a muffle furnace, and heating the temperature to 550° C. at a rate of 10° C. / min for calcining for 2 h to obtain a calcined product;

[0043] S4. The calcined product was cooled to room temperature, washed with pure water and ethanol alternately for 3 times, and placed in an oven for drying at 55°C for 6 h to obtain a g-C3N4-based adsorbent.

[0044] Embodiment 2:

[0045] The difference from Example 1 is that:

[0046] S1. Place 20 g of urea in an oven at 80° C. and bake for 30 min to obtain dry urea;

[0047] S2, adding 0.4 g SDS to the dry urea, mixing and grinding for 20 min to obtain a mixture; the mass ratio of urea to SDS is 100:2;

[0048] S3, transferring the mixture into a crucible, placing it in a muffle furnace, and heating the temperature to 550° C. at a rate of 10° C. / min for calcining for 2 h to obtain a calcined product;

[0049] S4. The calcined product was cooled to room temperature, washed with pure water and ethanol alternately for 3 times, and placed in an oven for drying at 55°C for 12 h to obtain a g-C3N4-based adsorbent.

[0050] Embodiment 3:

[0051] The difference from Example 1 is that:

[0052] S1. Place 20 g of urea in an oven at 50° C. and bake for 40 min to obtain dry urea;

[0053] S2, adding 0.6 g SDS to the dry urea, mixing and grinding for 30 min to obtain a mixture; the mass ratio of urea to SDS is 100:3;

[0054] S3, transferring the mixture into a crucible, placing it in a muffle furnace, and heating the temperature to 550° C. at a rate of 10° C. / min for calcining for 2 h to obtain a calcined product;

[0055] S4. The calcined product was cooled to room temperature, washed with pure water and ethanol alternately for 3 times, and placed in an oven and dried at 55°C for 10 h to obtain a g-C3N4-based adsorbent.

[0056] Comparative Example 1:

[0057] S1. Place 20 g of urea in an oven at 60° C. and bake for 10 min to obtain dry urea;

[0058] S2, transferring the dried urea into a crucible, placing the crucible into a muffle furnace, and heating the temperature to 550° C. at a rate of 10° C. / min for calcining for 2 h to obtain a calcined product;

[0059] S3. The calcined product was cooled to room temperature, washed with pure water and ethanol alternately for 3 times, and placed in an oven for drying at 55°C for 6 h to obtain a g-C3N4-based adsorbent.

[0060] Comparative Example 2:

[0061] S1. Put 20g of urea into an oven and dry it for 10min to obtain dry urea;

[0062] S2, transferring the dried urea into a crucible, placing the crucible into a muffle furnace, and heating the temperature to 550° C. at a rate of 10° C. / min for calcining for 2 h to obtain a calcined product;

[0063] S3, the calcined product was cooled to room temperature, washed with pure water and ethanol alternately for 3 times, and then placed in an oven for 6 hours to obtain the original g-C3N4;

[0064] S4, add 20mL pure water to the original g-C3N4, then add SDS, the weight ratio of g-C3N4:SDS is 1:0.5; first stir at 300rpm for 10min, then ultrasonicate at 40KHZ, 30℃, 60% ultrasonic power for 1h;

[0065] S5. Wash with pure water and ethanol alternately for 3 times, put it in an oven and bake it at 55°C for 6 h to obtain the final product.

[0066] Comparative Example 3:

[0067] The difference from Comparative Example 2 is that:

[0068] The weight ratio of g-C3N4:SDS is 1:1.

[0069] Comparative Example 4:

[0070] The difference from Comparative Example 2 is that:

[0071] The weight ratio of g-C3N4:SDS is 1:2.

[0072] Performance Test:

[0073] (1) 20 mg of the samples prepared in Examples 1-3 and Comparative Example 1 were placed in 50 mL of a 20 mg / L methylene blue dye solution, stirred at 25°C for 3 h, and then centrifuged to obtain the supernatant. The supernatant was tested using an ultraviolet-visible spectrophotometer at a wavelength of 664 nm, and the adsorption rate was calculated based on the test results. The calculation results are shown in FIG. Figure 1 As shown, from Figure 1It can be seen that compared with the comparative example 1 without adding SDS, the samples prepared in Examples 1-3 have a higher adsorption rate for methylene blue dye, and the adsorption rate of Example 2 is the highest, which is 92.5%. The following analysis will continue with Example 2 as an example.

[0074] (2) X-ray diffraction analysis was performed on the samples obtained in Example 2 and Comparative Example 1. The XRD patterns obtained were as follows: Figure 2 As shown, it can be seen that g-C3N4 in Example 2 and Comparative Example 1 were successfully synthesized. Figure 2 Two characteristic peaks of g-C3N4 are shown. The 27.6° diffraction peak corresponds to the (002) crystal plane of g-C3N4, which is formed by the interlayer stacking of aromatic fragments. The 13.2° diffraction peak corresponds to the (100) crystal plane of g-C3N4, which is formed by the periodic arrangement of the basic structural units triazine within the layer. The 27.6° diffraction peak of Example 2 is broader and weaker than the 27.6° diffraction peak of Comparative Example 1, indicating that the interlayer stacking is reduced.

[0075] (3) The samples obtained in Example 2 and Comparative Example 1 were tested for Zeta potential. The test results are as follows: Figure 3 As shown, from Figure 3 It can be seen that the zeta potential of comparative example 1 is -33.7 mV, and the zeta potential of example 2 is -39.7 mV, and the zeta potential of example 2 is more negative. This may be because SDS can release a large amount of heat at high temperature, causing thermal stripping of g-C3N4. During the thermal stripping process, hydrogen bonds are broken and part of the amine groups are removed, resulting in enhanced electronegativity. Enhanced electronegativity is more conducive to the electrostatic adsorption of the cationic dye methylene blue, thereby improving the adsorption rate.

[0076] At the same time, the samples obtained in Comparative Examples 2-4 were tested for Zeta potential. Figure 4 As shown, it can be seen that the Zeta potential of Comparative Examples 2-4 is higher than that of Examples 1-3, and even higher than that of Comparative Example 1 without SDS. 20 mg of the sample prepared in Comparative Examples 2-4 was placed in 50 mL of 20 mg / L methylene blue dye solution, stirred at 25°C for 3 hours, centrifuged to obtain the supernatant, and tested under a UV-visible spectrophotometer at a test wavelength of 664 nm; the test results are shown in FIG. Figure 5 As shown, it can be seen that the adsorption rates of comparative examples 2-4 for methylene blue dye are relatively poor, being only 4.6%, 4.4% and 4.2%.

Claims

1. A method for synthesizing a g-C3N4-based adsorbent, characterized in that: The synthesis method comprises: Putting urea into an oven for drying to obtain dry urea; adding sodium lauryl sulfate to dry urea, mixing and grinding to obtain a mixture; The mixture is transferred into a crucible for calcination to obtain a calcined product; The calcined product was cooled to room temperature, washed, and oven-dried to obtain a g-C3N4-based adsorbent.

2. The method for synthesizing a g-C3N4-based adsorbent according to claim 1, characterized in that: The mass ratio of the urea to sodium dodecyl sulfate is 100:0.5-3.

3. The method for synthesizing a g-C3N4-based adsorbent according to claim 1, characterized in that: The calcination temperature is 450-550° C., and the calcination time is 1.5-3 hours.

4. The method for synthesizing a g-C3N4-based adsorbent according to claim 3, characterized in that: The calcination is carried out in a muffle furnace, and the heating rate of the muffle furnace is 2-10° C. / min.

5. The method for synthesizing a g-C3N4-based adsorbent according to claim 1, characterized in that: The temperature of the oven-dried urea is 50-80° C., and the drying time of the oven-dried urea is at least 0.5 h.

6. The method for synthesizing a g-C3N4-based adsorbent according to claim 1, characterized in that: The temperature of the oven drying the calcined product is 50-80° C., and the drying time is 6-12 hours.

7. The method for synthesizing a g-C3N4-based adsorbent according to claim 1, characterized in that: The grinding time is 10-30 min.

8. A g-C3N4-based adsorbent, characterized in that: The g-C3N4-based adsorbent is prepared according to the synthesis method described in any one of claims 1-7.

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