In—NH.SUB.2./g-C.SUB.3.N.SUB.4 .nanocomposite with visible-light photocatalytic activity and preparation and application thereof

Abstract

The present invention provides an In—NH.sub.2/g-C.sub.3N.sub.4 nanocomposites with visible-light photocatalytic activity and application thereof, which can effectively remove organic pollutants (such as tetracycline) in water. First, the graphite phase carbonitride carbon (g-C.sub.3N.sub.4) was obtained by thermal condensation, and g-C.sub.3N.sub.4 nanosheet was prepared by thermal oxidative etching. Then, acicular MIL-68(In)—NH.sub.2 (In—NH.sub.2) was grown in situ on the surface of g-C.sub.3N.sub.4 nanosheet by solvothermal method. The In—NH.sub.2/g-C.sub.3N.sub.4 nanocomposites with high visible-light photocatalytic activity were obtained. The CNNS firstly was prepared in the present invention, which is beneficial to the needle-like In—NH.sub.2 growing on the surface of CNNS and having close interfacial contact with each other, forming a heterojunction, promoting the separation of photogenerated electrons and holes pairs, and enhancing visible-light photocatalytic degradation of organic pollutants. The nanocomposites show high structural stability and reusability, which has great potential in the field of water remediation.

Claims

1. A method of preparing In—NH.sub.2/g-C.sub.3N.sub.4 nanocomposites with visible-light photocatalytic activity comprises the following steps: obtaining a g-C.sub.3N.sub.4 nanosheet by oxidation etching of a g-C.sub.3N.sub.4 powder in air; and obtaining the In—NH.sub.2/g-C.sub.3N.sub.4 nanocomposites by in-situ growth of In—NH.sub.2 on the surface of the g-C.sub.3N.sub.4 nanosheet by a solvothermal method.

2. The method according to claim 1, wherein the temperature of the oxidation etching is 300 to 500° C. and the time of oxidation etching is 2 to 5 hours, and the temperature rising rate of the oxidation etching is 2 to 10° C./min.

3. The method according to claim 1, wherein the g-C.sub.3N.sub.4 nanosheet is dispersed in a solvent, an indium salt is added, an amino compound is added, a reaction is carried out at 80 to 150° C. for 2 to 10 hours, and the In—NH.sub.2 is grown in situ on the surface of the g-C.sub.3N.sub.4 nanosheet.

4. The method according to claim 3, wherein the molar ratio of the indium salt to the amino compound is 1:(0.1 to 0.5); the mass ratio of the g-C.sub.3N.sub.4 nanosheet to the indium salt is 1:(10 to 15).

5. The method according to claim 3, wherein the solvent is dimethyl sulfoxide, N, N-dimethylformamide or N, N-dimethyl acetamide; the indium salt is indium nitrate or indium trichloride.

6. The method according to claim 1, further comprising: calcining urea at 550° C. for 4 hours in air, cooling to room temperature, and grounding to obtain the g-C.sub.3N.sub.4 powder.

7. A method for preparing In—NH.sub.2, comprising: dissolving an indium salt in a solvent, adding an amino compound, and then reacting at 80 to 150° C. for 2 to 10 hours, and finally, obtaining the In—NH.sub.2.

8. The method according to claim 7, wherein a molar ratio of the indium salt to the amino compound is 1:(0.1 to 0.5); and the solvent is dimethyl sulfoxide, N, N-dimethylformamide or N, N-dimethylacetamide; the indium salt is indium nitrate or indium trichloride.

9. The In—NH.sub.2/g-C.sub.3N.sub.4 nanocomposites with visible-light photocatalytic activity prepared according to claim 1 and used for photocatalytic degradation of organic pollutants in water.

10. The In—NH.sub.2 prepared according to claim 7 and used for photocatalytic degradation of organic pollutants in water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a transmission electron micrograph image of g-C.sub.3N.sub.4 nanosheet in the example 1;

(2) FIG. 2 is a transmission electron micrograph image of needle-like In—NH.sub.2 in the example 2;

(3) FIG. 3 is a flow chart for the preparing process of as-synthesized In—NH.sub.2/g-C.sub.3N.sub.4 nanocomposites in the example 3;

(4) FIG. 4 is a transmission electron micrograph image of as-synthesized In—NH.sub.2/g-C.sub.3N.sub.4 in the example 3;

(5) FIG. 5 is N.sub.2 adsorption-desorption isotherm of as-synthesized In—NH.sub.2/g-C.sub.3N.sub.4 in the example 3.

EXAMPLES

(6) Examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

Example 1

Synthesis of g-C.SUB.3.N.SUB.4 .Nanosheet

(7) The g-C.sub.3N.sub.4 nanosheet was prepared by a process of thermal condensation and oxidative etching. 30 g of urea was added to the alumina crucible, capped, and placed in a tube furnace. The tube furnace was heated to 550° C. at a rate of 2.5° C./min in air and calcined for 4 hours. After cooling to room temperature, the obtained yellow product was ground into a powder and placed in an open crucible, and heated at 500° C. at a rate of 2.5° C./min for 2 hours. Thereafter, the obtained g-C.sub.3N.sub.4 nanosheet was washed several times with deionized water and dried in a vacuum oven at 100° C. for 12 hours. As can be seen from FIG. 1, the as-synthesized g-C.sub.3N.sub.4 nanosheet is a lamellar material.

Example 2

Synthesis of Needle-Shaped In—NH.SUB.2

(8) 1.5 mmol of indium nitrate and 0.5 mmol of 2-aminoterephthalic acid were dissolved in 10 mL of N,N-dimethylformamide with sonication at room temperature. After stirring for 1 hour, the above mixture was transferred to a 25 mL tetrafluoroethylene inner liner, sealed in a stainless steel autoclave, and reacted at 150° C. for 10 hours. After cooling to room temperature, the product was washed three times with N,N-dimethylformamide and absolute ethanol, respectively. Then, the suspension was centrifuged, and dried in a vacuum oven at 100° C. for 12 hours to give a pale yellow powder. As can be seen from FIG. 2, the as-synthesized In—NH.sub.2 is a needle-like material.

Example 3

Synthesis of In—NH.SUB.2./g-C.SUB.3.N.SUB.4 .Nanocomposites

(9) The synthetic route of In—NH.sub.2/g-C.sub.3N.sub.4 is shown in FIG. 3. 50 mg of g-C.sub.3N.sub.4 nanosheet (Example 1) was ultrasonically dispersed in 10 mL of N,N-dimethylformamide. After 30 minutes of sonication, 1.5 mmol of indium nitrate was added. After stirring for 60 minutes, 0.5 mmol of 2-aminoterephthalic acid was added and stirred for 30 minutes. Thereafter, the mixture was transferred to a 25 mL tetrafluoroethylene liner, sealed in a stainless steel autoclave, and reacted at 125° C. for 5 hours. The product was collected by centrifugation and washed several times with N,N-dimethylformamide and absolute ethanol, respectively. The final product was placed in a vacuum oven and dried at 100° C. for 12 hours. As can be seen from FIG. 4, the needle-like In—NH.sub.2 grows in situ on the surface of the g-C.sub.3N.sub.4 nanosheet with close interfacial contact with each other. The nitrogen adsorption-desorption isotherm of In—NH.sub.2/g-C.sub.3N.sub.4 is shown in FIG. 5, and is classified as a type I isotherm based on the International Union of Pure and Applied Chemistry (IUPAC). The material was mainly micropores with a specific surface area of 281 m.sup.2 g.sup.−1, the average pore size was 5.359 nm, and the total pore volume was 0.313 cm.sup.3 g.sup.−1.

Example 4

Synthesis of In—NH.SUB.2./g-C.SUB.3.N.SUB.4 .Nanocomposites

(10) 25 mg of g-C.sub.3N.sub.4 nanosheet (Example 1) was ultrasonically dispersed in 10 mL of N,N-dimethylformamide. After 30 minutes of sonication, 1.5 mmol of indium nitrate was added. After stirring for 60 minutes, 0.5 mmol of 2-aminoterephthalic acid was added and stirred for 30 minutes. Thereafter, the mixture was transferred to a 25 mL tetrafluoroethylene liner, sealed in a stainless steel autoclave, and reacted at 125° C. for 5 hours. The product was collected by centrifugation and washed several times with N,N-dimethylformamide and absolute ethanol. The final product was placed in a vacuum oven and dried at 100° C. for 12 hours.

Example 5

Synthesis of In—NH.SUB.2./g-C.SUB.3.N.SUB.4 .Nanocomposites

(11) 100 mg of g-C.sub.3N.sub.4 nanosheet (Example 1) was ultrasonically dispersed in 10 mL of N,N-dimethylformamide. After 30 minutes of sonication, 1.5 mmol of indium nitrate was added. After stirring for 60 minutes, 0.5 mmol of 2-aminoterephthalic acid was added and stirred for 30 minutes. Thereafter, the mixture was transferred to a 25 mL tetrafluoroethylene liner, sealed in a stainless steel autoclave, and reacted at 125° C. for 5 hours. The product was collected by centrifugation and washed several times with N,N-dimethylformamide and absolute ethanol. The final product was placed in a vacuum oven and dried at 100° C. for 12 hours.

Example 6

Experiment of Visible-Light Photocatalytic Degradation of Tetracycline Over g-C.SUB.3.N.SUB.4 .Nanosheet

(12) The photoreactor is a PCX50A Discover multi-channel photocatalytic reaction system (Beijing Perfectlight Science and Technology Co., Ltd.), and LED lamps (420≤λ≤800 nm, 5 W, ≈50 mW/cm.sup.2) were used as visible-light sources. 50 mL of 50 mg/L aqueous solution of tetracycline was added to a 60 mL cylindrical quartz tube, and 25 mg of the photocatalyst g-C.sub.3N.sub.4 nanosheet obtained in the above Example 1 was dispersed therein, and magnetically stirred (500 rpm). Prior to irradiation, the suspension was kept in the dark for 1 hour to achieve an adsorption-desorption equilibrium where the tetracycline removal rate was about 3%. Then, turn on the LED light. Next, 3 mL of the sample was withdrawn at regular intervals (30 min) and filtered through a 0.22 μm syringe filter to remove the solid catalyst. Finally, the concentration of remaining tetracycline after degradation was measured by a UV-vis spectrometer with a maximum absorption wavelength of 357 nm. After 150 minutes of illumination, the tetracycline removal rate was 30%.

Example 7

Experiment of Visible-Light Photocatalytic Degradation of Tetracycline Over In—NH.SUB.2

(13) 50 mL of 50 mg/L aqueous solution of tetracycline was added to a 60 mL cylindrical quartz tube, and 25 mg of the photocatalyst In—NH.sub.2 obtained in the above Example 2 was dispersed therein, and magnetically stirred (500 rpm). Prior to irradiation, the suspension was kept in the dark for 1 hour to achieve an adsorption-desorption equilibrium where the tetracycline removal rate was about 29%. Then, turn on the LED light. Next, 3 mL of the sample was withdrawn at regular intervals (30 min) and filtered through a 0.22 μm syringe filter to remove the solid catalyst. Finally, the concentration of remaining tetracycline after degradation was measured by a UV-vis spectrometer with a maximum absorption wavelength of 357 nm. After 150 minutes of illumination, the tetracycline removal rate was 58%.

Example 8

Experiment of Visible-Light Photocatalytic Degradation of Tetracycline Over In—NH.SUB.2./g-C.SUB.3.N.SUB.4

(14) 50 mL of 50 mg/L aqueous solution of tetracycline was added to a 60 mL cylindrical quartz tube, and 25 mg of the photocatalyst In—NH.sub.2/g-C.sub.3N.sub.4 obtained in the above Example 3 was dispersed therein, and magnetically stirred (500 rpm). Prior to irradiation, the suspension was kept in the dark for 1 hour to achieve an adsorption-desorption equilibrium where the tetracycline removal rate was about 43%. Then, turn on the LED light. Next, 3 mL of the sample was withdrawn at regular intervals (30 min) and filtered through a 0.22 μm syringe filter to remove the solid catalyst. Finally, the concentration of remaining tetracycline after degradation was measured by a UV-vis spectrometer with a maximum absorption wavelength of 357 nm. After 150 minutes of illumination, the tetracycline removal rate was 71%.

Example 9

Experiment of Visible-Light Photocatalytic Degradation of Tetracycline Over In—NH.SUB.2./g-C.SUB.3.N.SUB.4

(15) 50 mL of 50 mg/L aqueous solution of tetracycline was added to a 60 mL cylindrical quartz tube, and 25 mg of the photocatalyst In—NH.sub.2/g-C.sub.3N.sub.4 obtained in the above Example 4 was dispersed therein, and magnetically stirred (500 rpm). Prior to irradiation, the suspension was kept in the dark for 1 hour to achieve an adsorption-desorption equilibrium where the tetracycline removal rate was about 38%. Then, turn on the LED light. Next, 3 mL of the sample was withdrawn at regular intervals (30 min) and filtered through a 0.22 μm syringe filter to remove the solid catalyst. Finally, the concentration of remaining tetracycline after degradation was measured by a UV-vis spectrometer with a maximum absorption wavelength of 357 nm. After 150 minutes of illumination, the tetracycline removal rate was 61%.

Example 10

Experiment of Visible-Light Photocatalytic Degradation of Tetracycline Over In—NH.SUB.2./g-C.SUB.3.N.SUB.4

(16) 50 mL of 50 mg/L aqueous solution of tetracycline was added to a 60 mL cylindrical quartz tube, and 25 mg of the photocatalyst In—NH.sub.2/g-C.sub.3N.sub.4 obtained in the above Example 5 was dispersed therein, and magnetically stirred (500 rpm). Prior to irradiation, the suspension was kept in the dark for 1 hour to achieve an adsorption-desorption equilibrium where the tetracycline removal rate was about 39%. Then, turn on the LED light. Next, 3 mL of the sample was withdrawn at regular intervals (30 min) and filtered through a 0.22 μm syringe filter to remove the solid catalyst. Finally, the concentration of remaining tetracycline after degradation was measured by a UV-vis spectrometer with a maximum absorption wavelength of 357 nm. After 150 minutes of illumination, the tetracycline removal rate was 63%.

Example 11

Cyclic Experiment of Visible-Light Photocatalytic Degradation of Tetracycline Over In—NH.SUB.2./g-C.SUB.3.N.SUB.4

(17) The In—NH.sub.2/g-C.sub.3N.sub.4 composite material recovered after 150 minutes of illumination in the above Example 8 was washed successively with deionized water and absolute ethanol, dried, placed in a fresh 50 mL 50 mg/L tetracycline solution. The mixture was illuminated with LED lamp for 150 minutes. Next, 3 mL of the sample was withdrawn at regular intervals (30 min) and filtered through a 0.22 μm syringe filter to remove the solid catalyst. The concentration of remaining TC after degradation was measured by a UV-vis spectrometer with a maximum absorption wavelength of 357 nm. This process was repeated three times, and the In—NH.sub.2/g-C.sub.3N.sub.4 composite material always maintained good photocatalytic performance. After irradiation for 150 minutes, the removal efficiency of tetracycline in the aqueous solution was 71%, 70%, and 70%, respectively.