A method for preparing and applying a C3N4 / CDs / molecular sieve composite material.

Abstract

The application relates to a preparation method and application of a C3N4 / CDs / molecular sieve composite material, and the preparation steps comprise the following steps: dissolving carbon nitride precursors and carbon dot precursors in deionized water to obtain a precursor solution, adding ground molecular sieves, stirring, and obtaining a dispersion liquid; filtering the stirred dispersion liquid, taking filter residues, placing the filter residues into a crucible, heating in a muffle furnace, and naturally cooling to room temperature for a period of time, so as to obtain the C3N4 / CDs / molecular sieve composite material. The method is simple and low in cost, and the obtained composite material has quite excellent adsorption performance.

Description

Technical Field

[0001] This invention relates to the field of composite materials, specifically to a method for preparing and applying a C3N4 / CDs / molecular sieve composite material. Background Technology

[0002] Water pollution is becoming increasingly serious. Pollutants in water, such as dyes, heavy metals, and pharmaceuticals, are highly stable, difficult to degrade, and bioaccumulate. To change this situation, effective treatment of dye wastewater is necessary. In recent years, researchers have proposed a variety of methods, among which adsorption methods are widely used in wastewater treatment due to their simplicity, low cost, and high efficiency.

[0003] Molecular sieves are a class of microporous crystals with regular channel structures. Ion exchange alters the distribution of cations on the surface of molecular sieves, resulting in molecular sieves with different pore sizes. Sodium-A type molecular sieves are three-dimensional framework compounds composed of silicon-oxygen and aluminum-oxygen tetrahedra, belonging to the cubic crystal system, and possess high ion exchange capacity. Silicon-oxygen and aluminum-oxygen tetrahedra are interconnected by oxygen bridges, forming multi-ring structures. These multi-ring structures are further interconnected by oxygen bridges, forming cavities with a three-dimensional structure. They exhibit good physical strength (crushing resistance ≥100.0 N / sphere with a diameter of 3mm–5mm). Due to their good stability and large specific surface area, molecular sieves are commonly used as adsorbents and carriers. Carbon nanodots (CDs) are promising nanomaterials with advantages such as extremely small size (less than 10 nm) and numerous oxygen-containing functional groups on their surface; they hold great potential in drug delivery, biolabeling, and optoelectronic devices. Carbon nitride (C3N4) is a novel two-dimensional graphite-like layered material with excellent thermal stability, chemical stability, and optical properties, and is commonly used in photocatalysis. It provides abundant binding sites and is often combined with other materials to create novel materials.

[0004] Incorporating carbon nanodots and carbon nitride into molecular sieves can effectively enhance their adsorption capacity. However, due to the excellent water solubility of carbon nanodots, they cannot be prepared by conventional methods, and no researchers have yet found using this method to combine these three materials and apply them to dye wastewater treatment. Summary of the Invention

[0005] This invention provides a method for preparing C3N4 / CDs / molecular sieve composite materials, which is simple to prepare, low in cost, and produces composite materials with stable structure and good adsorption performance.

[0006] The solution of this invention to the above-mentioned technical problems is as follows: A method for preparing a C3N4 / CDs / molecular sieve composite material, comprising the following steps:

[0007] 1) Take carbon nitride precursor and carbon dot precursor, add them to deionized water to obtain precursor solution, then add ground molecular sieve and stir to obtain dispersion.

[0008] 2) Filter the stirred dispersion, put the filter residue into a crucible and heat it in a muffle furnace, keep it at that temperature for a period of time, and let it cool naturally to room temperature to obtain the C3N4 / CDs / molecular sieve composite material.

[0009] Preferably, in step 1), the carbon nitride precursor is one or a mixture of two of urea and dicyandiamine; the carbon dot precursor is one or a mixture of two of citric acid and ethylenediamine.

[0010] Preferably, in step 1), the carbon nitride precursor is urea; and the carbon dot precursor is a mixture of citric acid.

[0011] Preferably, in step 1), the concentration of carbon nitride precursor in the precursor solution is 0.02-1 g / mL; and the concentration of carbon dot precursor is 0.002-0.03 g / mL.

[0012] Preferably, in step 1), the concentration of carbon nitride precursor in the precursor solution is 1 g / mL; the concentration of carbon dot precursor is 0.03 g / mL.

[0013] Preferably, in step 1), the concentration of the molecular sieve in the dispersion is 0.01-0.06 g / mL. Preferably, in step 1), the concentration of the molecular sieve in the dispersion is 0.04 g / mL. The molecular sieve can be sodium-A type molecular sieve, 13X molecular sieve, ZSM-5 molecular sieve, or 5A molecular sieve.

[0014] Preferably, in step 1), the stirring speed is 100-500 r / min and the stirring time is 0.5-3 h. More preferably, in step 1), the stirring speed is 100 r / min and the stirring time is 2 h.

[0015] Preferably, in step 2), the heating temperature is 550℃, the holding time is 2 hours, and the heating rate is 1-10℃ / min.

[0016] Preferably, in step 2), the C3N4 / CDs / molecular sieve composite material contains 1-4 wt% C3N4 and 20-30 wt% CDs.

[0017] The application of the C3N4 / CDs / molecular sieve composite material prepared by the method described above in the preparation of adsorbents.

[0018] The beneficial effects of this invention are: the preparation method of the C3N4 / CDs / molecular sieve composite material provided by this invention is simple, and the raw materials are inexpensive and readily available. Compared with single-doped C3N4 or CDs molecular sieve materials, the carbon nitride material after carbon doping has an increased specific surface area and better adsorption performance.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0021] Figure 1 SEM images of the C3N4 / CDs / molecular sieve composite material in Example 1; a and b are SEM images of sodium-A type molecular sieve at different magnifications; c and d are SEM images of the C3N4 / CDs / molecular sieve composite material at different magnifications.

[0022] Figure 2 The image shows the EDS energy spectrum of the C3N4 / CDs / molecular sieve composite material in Example 1.

[0023] Figure 3 The image shows the infrared spectrum of the C3N4 / CDs / molecular sieve composite material in Example 1. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1

[0026] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a sieve size between 100 and 200 mesh. 50 g of urea and 1.5 g of citric acid were dissolved in 50 mL of deionized water and stirred for 30 min to obtain a urea-citric acid mixed solution. 2 g of molecular sieve powder was added to the mixed solution, and the mixture was stirred at 100 r / min for 2 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting C3N4 / CDs / sodium-A type molecular sieve composite material was obtained.

[0027] Adsorption performance test: 1. At room temperature, 0.4g of the above composite material was added to a 250mL wide-mouth bottle containing 100mL of 100mg / L methylene blue solution, and the mixture was stirred at 200r / min for 1h to adsorb. The adsorption rate was 99.6%.

[0028] 2. At room temperature, 0.1 g of the above composite material was added to a 250 mL wide-mouth bottle containing 100 mL of 100 mg / L methylene blue solution, and the mixture was stirred at 200 r / min for 1 h for adsorption. The adsorption rate was 44%.

[0029] 3. At room temperature, 0.1g of the above composite material was added to a 100mL wide-mouth bottle containing 100mL of methylene blue solution with a concentration of 50mg / L, and the mixture was stirred at a rate of 200r / min for 1h to adsorb the material. The adsorption rate was 70%.

[0030] Adsorption experiments under three different conditions showed that the adsorbent mass was positively correlated with the adsorption efficiency; the concentration of the solution to be treated was positively correlated with the adsorption efficiency, while the adsorption efficiency was negatively correlated.

[0031] Morphology testing: SEM images of the C3N4 / CDs / sodium-A type molecular sieve composite material and ordinary sodium-A type molecular sieve are shown below. Figure 1 As shown, the surface of the molecular sieve is relatively smooth. After being doped with C3N4 and CDs, clusters and bumps appear on the surface of the material.

[0032] EDS test: Results are as follows Figure 2 As shown, the calculated carbon dot content is 22.3wt%-25.5wt%, and the carbon nitride content is 1.4wt%-3.6wt%.

[0033] Infrared characterization: Results are as follows Figure 3 As shown, the functional groups corresponding to carbon dots and carbon nitride can be observed.

[0034] Comparative Example 1

[0035] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a mesh size between 100 and 200 mesh. 50 g of urea was dissolved in 50 mL of deionized water and stirred for 30 min to obtain a urea solution. 2 g of molecular sieve powder was added to the solution, and the mixture was stirred at 100 r / min for 2 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting C3N4 / sodium-A type molecular sieve composite material was obtained.

[0036] Adsorption performance test: At room temperature, 0.4 g of the composite material was added to a 250 mL wide-mouth bottle containing 100 mL of methylene blue solution with a concentration of 100 mg / L, and the mixture was stirred at a rate of 200 r / min for 1 h for adsorption. The adsorption rate was 24.3%.

[0037] Comparative Example 2

[0038] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a sieve size between 100 and 200 mesh. 1.5 g of citric acid was dissolved in 50 mL of deionized water and stirred for 30 min to obtain a citric acid solution. 2 g of molecular sieve powder was added to the solution, and the mixture was stirred at 100 r / min for 2 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting product was a CDs / sodium-A type molecular sieve composite material.

[0039] Adsorption performance test: At room temperature, 0.4 g of the composite material was added to a 250 mL wide-mouth bottle containing 100 mL of methylene blue solution with a concentration of 100 mg / L, and the mixture was stirred at a rate of 200 r / min for 1 h for adsorption. The adsorption rate was 44.2%.

[0040] By comparing Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that, compared with single carbon-doped nanodots or carbon nitride doping in molecular sieves, the co-incorporation of both materials into molecular sieves can effectively improve their adsorption capacity.

[0041] Example 2

[0042] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a mesh size between 100 and 200 mesh. 50 g of urea and 1.5 g of citric acid were dissolved in 50 mL of deionized water and stirred for 30 min to obtain a urea-citric acid mixed solution. 2 g of molecular sieve powder was immersed in the mixed solution and stirred at 100 r / min for 0.5 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting C3N4 / CDs / sodium-A type molecular sieve composite material was obtained.

[0043] Adsorption performance test: At room temperature, 0.1g of the above composite material was added to a 100mL wide-mouth bottle containing 100mL of methylene blue solution with a concentration of 50mg / L, and the mixture was stirred at a rate of 200r / min for 1h to adsorb the material. The adsorption rate was 53%.

[0044] Example 3

[0045] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a mesh size between 100 and 200 mesh. 50 g of urea and 1.5 g of citric acid were dissolved in 50 mL of deionized water and stirred for 30 min to obtain a urea-citric acid mixed solution. 2 g of molecular sieve powder was immersed in the mixed solution and stirred at 100 r / min for 1 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting C3N4 / CDs / sodium-A type molecular sieve composite material was obtained.

[0046] Adsorption performance test: At room temperature, 0.1g of the composite material was added to a 100mL wide-mouth bottle containing 100mL of 50mg / L methylene blue solution, and the mixture was stirred at 200r / min for 1h to adsorb the adsorption. The adsorption rate was 64%.

[0047] Example 4

[0048] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a mesh size between 100 and 200 mesh. 50 g of urea and 1.5 g of citric acid were dissolved in 50 mL of deionized water and stirred for 30 min to obtain a urea-citric acid mixed solution. 2 g of molecular sieve powder was immersed in the mixed solution and stirred at 100 r / min for 3 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting C3N4 / CDs / sodium-A type molecular sieve composite material was obtained.

[0049] Adsorption performance test: At room temperature, 0.1g of the composite material was added to a 100mL wide-mouth bottle containing 100mL of methylene blue solution with a concentration of 50mg / L, and the mixture was stirred at a rate of 200r / min for 1h to adsorb the material. The adsorption rate was 70%.

[0050] The variable in Examples 1-4 was the impregnation time of the molecular sieve powder in the urea-citric acid mixed solution. It can be seen that in the impregnation time range of 0.5-2 hours, the adsorption performance of the product is positively correlated with the impregnation time. When the impregnation time exceeds 2 hours, the adsorption performance of the product does not change significantly. The impregnation process is the process of molecular sieve adsorbing precursors. In the first two hours, with the increase of impregnation time, the amount of precursors adsorbed by the molecular sieve also increases, resulting in an increase in carbon nitride dots on the final composite material and improved adsorption effect. After two hours, the molecular sieve reaches equilibrium in adsorbing precursors, and the adsorption amount does not increase with time. The content of carbon nitride / carbon dots in the composite material remains essentially unchanged, and the performance remains essentially unchanged.

[0051] Example 5

[0052] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a mesh size between 100 and 200 mesh. 50 g of urea and 1.5 g of citric acid were dissolved in 50 mL of deionized water and stirred for 30 min to obtain a urea-citric acid mixed solution. 1 g of molecular sieve powder was immersed in the mixed solution and stirred at 100 r / min for 2 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting C3N4 / CDs / sodium-A type molecular sieve composite material was obtained.

[0053] Adsorption performance test: At room temperature, 0.1g of the composite material was added to a 100mL wide-mouth bottle containing 100mL of methylene blue solution with a concentration of 50mg / L, and the mixture was stirred at a rate of 200r / min for 1h to adsorb the material. The adsorption rate was 70%.

[0054] Example 6

[0055] A certain mass of spherical sodium-A type molecular sieve was ground and sieved to obtain powder with a mesh size between 100 and 200 mesh. 50 g of urea and 1.5 g of citric acid were dissolved in 50 mL of deionized water and stirred for 30 min to obtain a urea-citric acid mixed solution. 3 g of molecular sieve powder was immersed in the mixed solution and stirred at 100 r / min for 2 h, followed by filtration. The filter residue was placed in a crucible and heated in a muffle furnace. The temperature was increased to 550 °C at a rate of 2 °C / min, held for 2 h, and then allowed to cool naturally to room temperature. The resulting C3N4 / CDs / sodium-A type molecular sieve composite material was obtained.

[0056] Adsorption performance test: At room temperature, 0.1g of the composite material was added to a 100mL wide-mouth bottle containing 100mL of methylene blue solution with a concentration of 50mg / L, and the mixture was stirred at a rate of 200r / min for 1h to adsorb the material. The adsorption rate was 49%.

[0057] In Examples 1, 5, and 6, the variable was the mass of the molecular sieve powder. When the mass of the molecular sieve powder was 1-2g, the adsorption efficiency was basically the same. When the mass of the molecular sieve powder increased to 3g, the adsorption efficiency decreased. Under the same impregnation conditions, when the mass of the molecular sieve increased to a certain extent, the amount of adsorption precursor per unit mass of molecular sieve decreased, resulting in a decrease in the content of carbon nitride and carbon dots in the final composite material. Carbon dots and carbon nitride are beneficial for adsorption, and as their content decreases, the adsorption rate decreases.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a C3N4 / CDs / molecular sieve composite material for preparing an adsorbent, characterized in that, Includes the following steps: 1) Take carbon nitride precursor and carbon dot precursor, add them to deionized water to obtain precursor solution, then add ground molecular sieve, stir at 100-500 r / min for 0.5-3 h to obtain dispersion; in dispersion, the concentration of molecular sieve is 0.01-0.06 g / mL. The molecular sieve is a sodium-A type molecular sieve; 2) Filter the stirred dispersion, place the filter residue in a crucible and heat it in a muffle furnace for a period of time, then allow it to cool naturally to room temperature to obtain a C3N4 / CDs / molecular sieve composite material, wherein the C3N4 content is 1-4wt% and the CDs content is 20-30wt%. The carbon nitride precursor is one or a mixture of two of urea and dicyandiamine; the carbon dot precursor is one or a mixture of two of citric acid and ethylenediamine.

2. The method according to claim 1, characterized in that, In step 1), the carbon nitride precursor is urea; the carbon dot precursor is citric acid.

3. The method according to claim 1, characterized in that, In step 1), the concentration of carbon nitride precursor in the precursor solution is 0.02-1 g / mL; the concentration of carbon dot precursor is 0.002-0.03 g / mL.

4. The method according to claim 3, characterized in that, In step 1), the concentration of carbon nitride precursor in the precursor solution is 1 g / mL, and the concentration of carbon dot precursor is 0.03 g / mL.

5. The method according to claim 1, characterized in that, In step 2), the heating temperature is 550℃, the holding time is 2h, and the heating rate is 1-10℃ / min.

6. The application of the C3N4 / CDs / molecular sieve composite material prepared by any one of the methods described in claims 1-5 in the preparation of adsorbents.

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