HETEROJUNCTION COMPOSITE MATERIAL CONSISTING OF ONE-DIMENSIONAL IN2O3 HOLLOW NANOTUBE AND TWO-DIMENSIONAL ZNFE2O4 NANOSHEET, AND APPLICATION THEREOF IN WATER POLLUTANT REMOVAL

Abstract

A heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets and its application are disclosed. When using this material for catalytic reactions, the hollow cavity and two-dimensional nanosheets of hollow nanomaterials can not only reduce the migration distance to accelerate the electron-hole separation, but also provide a large surface area and rich active sites to promote pollution adsorption and surface catalysis. At the same time, multiple light scattering or reflection in the hollow cavity of the hollow nanomaterials can increase light absorption and utilization. In addition, the heterojunction photocatalyst constructed by growing two-dimensional semiconductor nanosheets on a tubular substrate can promote the effective separation of photogenerated electrons and photogenerated holes, thereby improving the catalytic efficiency. In terms of catalytic performance, In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4 shows effective degradation of tetracycline, and due to its ferromagnetism, it shows convenient and good separation effect and has good recycling performance.

Claims

1. A method of preparing a heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets, comprising the following steps: 1) using an indium salt as raw material to prepare an In template by a solvent-thermal method; 2) calcining the In template under air atmosphere to obtain In.sub.2O.sub.3; 3) using an electrodeposition method to load zinc-iron bimetallic hydroxide nanosheets on the surface of In.sub.2O.sub.3 to obtain an In.sub.2O.sub.3 supported zinc-iron bimetallic hydroxide composite material; then calcining the In.sub.2O.sub.3 supported zinc-iron bimetallic hydroxide composite material at high temperature in air to obtain a heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets.

2. The method according to claim 1, wherein in step (1), dissolving indium salt and terephthalic acid in a solvent to obtain a mixed solution; then the mixed solution is refluxed to obtain an In template.

3. The method according to claim 2, wherein said indium salt is In(NO.sub.3).sub.3.4.5H.sub.2O and the solvent is DMF; the heating temperature of the reflux reaction is 110 to 130 C., and the time is 25 to 35 min; the dosage ratio of indium salt, terephthalic acid and solvent is 30 mg:30 mg:30 mL.

4. The method according to claim 1, wherein in step (2), dispersing the In template in ethanol and Nafion solution to obtain a coating liquid; then coating the coating liquid on the surface of an ITO glass, drying and calcining in an air atmosphere to prepare In.sub.2O.sub.3.

5. The method according to claim 1, wherein in step (2), the calcination is first incubating at 120 C. for 2 h, then raising the temperature to 500 to 550 C. with the heating rate of 2 to 5 C./min, and calcining for 2 hours.

6. The method according to claim 1, wherein in step (3), the electrodeposition method uses a three-electrode system, and the electrolyte solution is obtained by dissolving zinc nitrate hexahydrate and ferric nitrate nonahydrate in water, the electrodeposition time is 400 s to 600 s; the high temperature calcination is carried out at 450 to 500 C. for 1012 h, and the heating rate is 2 to 5 C./min.

7. The method according to claim 6, wherein in the three-electrode system, a platinum wire electrode serves as a counter electrode and a calomel electrode serves as a reference electrode; the molar ratio of zinc nitrate hexahydrate and ferric nitrate nonahydrate is 1:2.

8. The heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets prepared according to the method of claim 1.

9. (canceled)

10. (canceled)

11. A method of removing a water pollutant, comprising: providing the heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets of claim 8; and contacting polluted water with the heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets to remove the water pollutant.

12. The method of claim 11, wherein the water pollutant is an antibiotic.

13. The method of claim 11, wherein contacting water with the heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets is carried out under light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is the TEM image of In template.

[0032] FIG. 2 is the TEM image of In.sub.2O.sub.3.

[0033] FIG. 3 is the TEM image of In.sub.2O.sub.3@ZnFe.sub.2O.sub.4-500.

[0034] FIG. 4 is the Tetracycline photodegradation curve for In.sub.2O.sub.3@ZnFe.sub.2O.sub.4-500.

[0035] FIG. 5 shows the recycling performance of In.sub.2O.sub.3@ZnFe.sub.2O.sub.4-500 towards tetracycline photodegradation.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

[0036] Synthesis of In template through solvothermal method comprising following steps: 30 mg of In(NO.sub.3).sub.3.4.5H.sub.2O and 30 mg of terephthalic acid are dissolved in 30 ml of N,N-Dimethylformamide (DMF) and stirred for 2 min to obtain a colorless and transparent solution. Then, the resultant solution is refluxed at 120 C. for 30 min. After cooling to room temperature, pumping filtrate with 0.22 m microporous filter membrane to obtain a white product, washed with ethanol three times and dried at 60 C. in a blast drying oven for 2 h to obtain the In template. As can be seen in FIG. 1, the TEM image shows that the In template exhibited solid structure, with about 3.1 m in length and about 650 nm in diameter.

Embodiment 2

[0037] Preparation of one-dimensional hollow nanotube In.sub.2O.sub.3: First, weigh 20 mg of the In template obtained in Embodiment 1 and disperse it in 200 l of absolute ethanol and 10 l of Nafion solution, disperse it uniformly by ultrasound for 20 min, then apply it to the surface of the ITO glass and dry it. It is placed in a muffle furnace and kept at 120 C. for 2 h in an air atmosphere, then heated to 500 C. at a heating rate of 5 C./min and calcined for 2 h to obtain one-dimensional hollow nanotube In.sub.2O.sub.3 and its transmission electron microscope shown in Figure. 2, the obtained In.sub.2O.sub.3 has a hollow structure, and is attached to ITO glass (In.sub.2O.sub.3/ITO). If not holding at 120 C. for 2 hours, directly calcining at 500 C. for 2 hours, the obtained In.sub.2O.sub.3/ITO is used in Embodiment 4, and the heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets prepared according to Embodiment 4 is used with the method of Embodiment 6, and after 120 minutes of illumination, the removal rate of tetracycline in the aqueous solution reached 71%.

[0038] As a comparison, the preparation of pure In.sub.2O.sub.3 hollow nanotube does not need to be attached to the ITO glass. The specific operation is as follows: Weigh 200 mg of the In template in Embodiment 1 and place it in a muffle furnace, and insulate at 120 C. under an air atmosphere for 2 h, then heated to 500 C. and calcined for 2 h, the heating rate is 5 C./min, to obtain pure In.sub.2O.sub.3 hollow nanotube, and the transmission electron microscopy diagram is similar to FIG. 2.

Embodiment 3

[0039] Preparation of one-dimensional hollow nanotube and two-dimensional nanosheet heterojunction composites (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-400 s): Weigh 2.23 g zinc nitrate hexahydrate and 6.05 g ferric nitrate nonahydrate in 100 ml of deionized water and mix them, the solution is an electrolyte solution, using a three-electrode system (ITO glass with In.sub.2O.sub.3 attached to the surface obtained in Embodiment 2 as a working electrode, a platinum wire electrode as a counter electrode, and a calomel electrode as a reference electrode). Electrodeposition in the electrochemical workstation CHI660E Deposite at 1 V (vs.SCE) voltage for 400 s, wash with deionized water 3 times after the deposition to obtain In.sub.2O.sub.3 supported zinc-iron bimetal hydroxide composite material (In.sub.2O.sub.3 @ ZnFe-LDH-400 s). Drying at room temperature for 12 h; after drying, the above product is placed in a muffle furnace and calcined at 450 C. (heating rate of 5 C./min) under an air atmosphere for 10 h to obtain one-dimensional indium oxide hollow nanotube/two-dimensional zinc ferrite nanosheet heterojunction composite material (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-400 s), the resulting composite only forms a thin shell sheath on the surface of In.sub.2O.sub.3.

Embodiment 4

[0040] Preparation of one-dimensional hollow nanotube and two-dimensional nanosheet heterojunction composites (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s): Weigh 2.23 g zinc nitrate hexahydrate and 6.05 g ferric nitrate nonahydrate and dissolve them in 100 ml deionized water. The mixed solution is an electrolyte solution, using a three-electrode system (ITO glass with In.sub.2O.sub.3 attached to the surface obtained in Embodiment 2 as a working electrode, a platinum wire electrode as a counter electrode, and a calomel electrode as a reference electrode). Carry out electrodeposition in the electrochemical workstation CHI660E, deposite at 1V (vs.SCE) voltage for 500 s, wash with deionized water 3 times after the reaction, to obtain In.sub.2O.sub.3 supported zinc-iron bimetallic hydroxide composite material (In.sub.2O.sub.3 @ ZnFe-LDH-500 s), dried at room temperature for 12 h. After drying, put the above product in a muffle furnace and calcinate at 450 C. (heating rate is 5 C./min) under air atmosphere for 10 h to obtain a heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s). The transmission electron micrograph is shown in FIG. 3. The resulting composite is a relatively regular nanosheet formed on the surface of In.sub.2O.sub.3. Dry In.sub.2O.sub.3 @ ZnFe-LDH-500 s is unstable and cannot be used as a water treatment catalyst.

[0041] For the purpose of comparison, the preparation method of pure ZnFe.sub.2O.sub.4 nanosheets is: first, a zinc-iron bimetal hydroxide (ZnFe-LDH) nanosheet is prepared by hydrothermal reaction; then, the above zinc-iron bimetal hydroxide (ZnFe-LDH) nanosheet is placed in a muffle furnace and calcined at 450 C. in air atmosphere (heating rate is 5 C./min) for 10 h to obtain two-dimensional zinc ferrite nanosheets.

Embodiment 5

[0042] Preparation of one-dimensional hollow nanotube and two-dimensional nanosheet heterojunction composites (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-600 s): Weigh 2.23 g of zinc nitrate hexahydrate and 6.05 g of ferric nitrate nonahydrate in 100 ml of deionized water, the mixed solution is an electrolyte solution. Using a three-electrode system (ITO glass with In.sub.2O.sub.3 attached to the surface obtained in Embodiment 2 as a working electrode, a platinum wire electrode as a counter electrode, and a calomel electrode as a reference electrode). Carry out electrodeposition in the electrochemical workstation CHI660E, deposite at 1V (vs.SCE) voltage for 600 s, wash with deionized water 3 times after the reaction to obtain In.sub.2O.sub.3 supported zinc iron bimetal hydroxide composite material (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-600 s), dry at room temperature for 12 h, After drying, the above product is placed in a muffle furnace and calcined at 450 C. (heating rate of 5 C./min) under an air atmosphere for 10 h to obtain a heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-600 s). The resulting composite is almost completely covered by ZnFe.sub.2O.sub.4 nanosheets.

Embodiment 6

[0043] The heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s) degradation experiment of tetracycline: Weigh 50 mg of the photocatalyst In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s obtained in Embodiment 4, place it in 100 mL of tetracycline aqueous solution with a concentration of 10 mg/L. Stir for half an hour in the dark to achieve adsorption-desorption equilibrium. After equilibration, the catalyst is irradiated with a 300 W xenon lamp, and 5 mL is sampled every half hour, using a UV spectrophotometer, and referring to the standard curve, to obtain the residual concentration of tetracycline in the corresponding water sample. FIG. 4 is a graph showing the relationship between the absorbance of residual tetracycline and time. It can be seen from the figure that under the condition of adding In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s and applying light, the removal rate of tetracycline in the aqueous solution reaches more than 95% after 120 minutes of light; in the same way, In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-400 s, In.sub.2O.sub.3 @ZnFe.sub.2O.sub.4-600 s, ZnFe.sub.2O.sub.4, pure In.sub.2O.sub.3 hollow nanotubes are exposed to light for 120 minutes, and the removal rates of tetracycline in the aqueous solution reached 85%, 88%, 25%, and 43%, respectively.

Embodiment 7

[0044] The heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s) cyclic degradation experiment of tetracycline: due to the heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s) is ferromagnetic, so after degrading 10 ppm of tetracycline for 120 minutes, a magnet can be used to effectively separate the catalyst. After that, the catalyst obtained by the above separation is dried in a 60 C. oven for 12 hours, and then placed again in 100 mL of a tetracycline aqueous solution with a concentration of 10 mg/L. Stir for half an hour in the dark to achieve adsorption-desorption equilibrium. After equilibration, the catalyst is irradiated with a 300 W xenon lamp, and 5 mL is sampled every half hour, using a UV spectrophotometer, and referring to the standard curve, to obtain the residual concentration of tetracycline in the corresponding water sample. After three cycles, the relationship between residual tetracycline absorbance and time is shown in FIG. 5. As can be seen from the figure, its catalytic performance is basically stable, and it still maintains good catalytic performance, which shows that In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4-500 s has good stability, and in the process of circulation, only using a magnet will separate the compound. It is very convenient to separate the material from the solution, which provides convenience for practical use.

[0045] In summary, using the above two materials to construct a heterojunction composite material consisting of one-dimensional In.sub.2O.sub.3 hollow nanotube and two-dimensional ZnFe.sub.2O.sub.4 nanosheets with visible light response, this design is not only conducive to the separation and migration of photo-generated carriers, it also improves the adsorption of pollutant molecules, and also exposes abundant surface catalytic active sites. In the present invention, the In template is first used to obtain one-dimensional hollow indium oxide (In.sub.2O.sub.3) nanotube by calcination in the air, and then the one-dimensional hollow In.sub.2O.sub.3 nanotube are used as the carrier to obtain one-dimensional hollow nanotube/two-dimensional nanosheet heterojunction composite material (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4) by the method of electrodeposition followed by calcination. Using the above composite material as a photocatalyst, the tetracycline is catalytically degraded under visible light irradiation. The one-dimensional hollow nanotube and two-dimensional nanosheet heterojunction composite materials (In.sub.2O.sub.3 @ ZnFe.sub.2O.sub.4) invented by the present invention can efficiently purify tetracycline and other organic pollutants in water through photocatalytic methods.