CN110694645A - Indium zinc sulfide nanosheet/tubular tin oxide heterojunction and preparation method thereof and application in degradation and removal of water pollutants - Google Patents

Abstract

The invention discloses an indium zinc sulfide nanosheet/tubular tin oxide heterojunction, a preparation method and an application in degrading and removing water pollutants; the tin oxide nanotubes are prepared through an electrostatic spinning technology and a high temperature calcination technology, and are used for oxidation Using tin as the substrate, indium-zinc sulfide nanosheets were uniformly grown on its surface by an oil bath, thereby constructing an indium-zinc sulfide nanosheet/tubular tin oxide heterojunction. Indium zinc sulfide is an important metal sulfide with a band gap width of 2.6-2.7 eV, which is a good semiconductor material. The prepared indium zinc sulfide nanosheet/tubular tin oxide heterojunction has a large ratio. surface area, which can provide more adsorption sites and catalytically active sites, effectively improve the separation efficiency of photogenerated electron-holes, and then improve the activity of photocatalytic reaction, which can be better used for the separation and degradation of photocatalytic water pollutants .

Description

Indium zinc sulfide nanosheet/tubular tin oxide heterojunction and its preparation method and its degradation Application in the removal of water pollutants

technical field

The invention relates to the technical field of inorganic nanocomposite materials, in particular to the preparation of indium zinc sulfide nanosheets/tubular tin oxide heterojunctions and the photocatalytic degradation and removal of water pollutants.

Background technique

Environmental and energy issues are prominent problems in the 21st century, and human beings have been trying various methods to solve these two major problems. Among them, solar energy is currently a research hotspot in controlling environmental pollution. Hexavalent chromium is a common heavy metal pollutant, mainly from factory wastewater. Hexavalent chromium has high toxicity and bioaccumulation, which can cause incalculable harm to human body and environment. Unlike other common heavy metals such as cadmium, chromium exists in solution in two forms: trivalent and hexavalent. Among them, the former is one of the trace elements required by the organism, and its toxicity is far less than the latter. Therefore, the reduction of hexavalent chromium to trivalent chromium by some methods is an effective method to remediate polluted water bodies. Photocatalytic technology is an efficient "green" method to solve environmental and energy problems due to its advantages of mild conditions, high efficiency and low energy consumption, and its core is photocatalytic materials. With the development of nanomaterials and nanotechnology, indium zinc sulfide (Znln ₂ S ₄ ) nanophotocatalytic materials have been favored by researchers. However, there are still some problems in the practical application of nanoscale indium zinc sulfide, such as photogenerated electrons - The recombination rate of holes is too fast, and the photon yield is low; it is easy to agglomerate, which greatly reduces its photocatalytic activity, etc.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of indium zinc sulfide nanosheet/tubular nano tin heterojunction. A simple sol-gel electrospinning technique was used to uniformly adsorb tin ions on the surface of PVP/ _SnCI fibers. Subsequently, the spun film was calcined at high temperature, the organic component PVP was burned off, and SnCl2 was oxidized to tin _oxide . Through these two techniques, not only the hollow tubular tin oxide structure can be obtained, but also the subsequent growth of Znln ₂ S ₄ nanosheets on the SnO ₂ surface can be facilitated. In the invention, SnO ₂ is used as a substrate, and Znln ₂ S ₄ nano-sheets are grown in an oil bath to construct an indium-zinc sulfide nano-sheet/tubular tin oxide heterojunction. As an important metal sulfide, Znln ₂ S ₄ has a band gap width of 2.6-2.7 eV, which is a typical narrow band gap structure and can directly absorb and utilize visible light. Compared with the conventional 2D structure, the _Znln2S4 nanosheets are uniformly fixed _on the tubular _SnO2 nanotubes, which maximizes the exposed area and provides more catalytically active sites, thus effectively enhancing the photogenerated electron-holes. It is a promising photocatalytic material with high separation efficiency.

In order to achieve the above object, the present invention adopts following concrete technical scheme:

The indium zinc sulfide nanosheet/tubular tin oxide heterojunction, the preparation method includes the following steps:

(1) Using PVP and tin salt as raw materials, the composite nanofibers were prepared by electrospinning method;

(2) calcining the composite nanofibers of step (1) at high temperature to prepare SnO ₂ nanotubes;

(3) Zinc salt, indium salt, and sulfide are added to the solution, and then SnO ₂ nanotubes are added to react to obtain indium zinc sulfide nanosheets/tubular tin oxide heterojunctions.

A method for degrading and removing organic pollutants in water, comprising the following steps:

(1) Using PVP and tin salt as raw materials, the composite nanofibers were prepared by electrospinning method;

(2) calcining the composite nanofibers of step (1) at high temperature to prepare SnO ₂ nanotubes;

(3) adding zinc salt, indium salt and sulfide into the solution, and then adding SnO ₂ nanotubes, the reaction obtains indium zinc sulfide nanosheets/tubular tin oxide heterojunction;

(4) The indium zinc sulfide nanosheet/tubular tin oxide heterojunction is placed in water containing pollutants to realize the degradation and removal of pollutants in the water.

In the above technical solution, the tin salt is SnCI ₂ ; the zinc salt, indium salt, and sulfide are respectively zinc chloride, indium chloride, and thioacetamide; and the pollutant is a hexavalent chromium compound.

In the above technical scheme, in step (1), tin salt is added to the mixed solvent, then PVP is added to obtain a spinning solution, and then electrospinning is performed to prepare composite nanofibers; the mixed solvent is N,N`-dimethyl Formamide and absolute ethanol, preferably the volume ratio of N,N`-dimethylformamide and absolute ethanol is 1:1; in the spinning solution, the concentration of tin salt is 0.1g/mL, and the quality of PVP is tin 1 to 1.5 times the salt, preferably 1.2 times. The invention adopts a simple sol-gel electrospinning technology to uniformly adsorb tin ions on the composite nanofiber membrane, which not only can obtain a hollow tubular structure, but also facilitates the uniform growth of indium zinc sulfide nanosheets on the surface of the tubular tin oxide. .

In the above technical solution, in step (2), during high temperature calcination, the heating rate is 1.5～3°C/min, preferably 2°C/min; the temperature is 500～650°C, preferably 600°C; after calcination, the temperature is naturally cooled to room temperature, _SnO2 nanotubes are obtained.

In the above technical solution, in step (3), the molar ratio of zinc salt, indium salt and sulfide is 1:2:4, which are used as zinc source, indium source and sulfur source in sequence. During the reaction, the pH is 2-3, preferably 2.5; the reaction temperature is 70-85° C., preferably 80° C.; the reaction time is 1.5-3 h, preferably 2 h. For example, zinc sulfide, indium sulfide and thioacetamide are sequentially added to a solution with a pH of 2.5, sonicated for 5 minutes, and then SnO ₂ nanotubes are added for the reaction; Washed with water and ethanol, and then vacuum-dried in a drying oven to obtain indium zinc sulfide nanosheets/tubular tin oxide heterojunctions.

In the above technical solution, in step (4), the degradation and removal of pollutants in the water is carried out under illumination, and the illumination is visible illumination.

The invention further discloses the application of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction in degrading and treating pollutants in water. Preferably, the pollutants are hexavalent chromium compounds.

Advantages of the present invention

1. In the preparation method of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction disclosed in the present invention, the electrospinning technology is simple to operate, and tin ions can be uniformly distributed on the nanofiber membrane during the preparation process. The size of the prepared nanowires is small, and the hollow tubular structure can be obtained by calcination. The hollow tubular tin oxide has a larger specific surface area, which can expose more active sites and allow more indium zinc sulfide nanosheets to grow, which is beneficial to the photocatalytic reaction.

2. As an important metal sulfide, indium zinc sulfide has a band gap width of 2.6-2.7 eV, and its typical narrow band gap structure enables it to directly absorb and utilize visible light.

3. The present invention uses tubular tin oxide as a substrate, and indium zinc sulfide nanosheets are grown in an oil bath, thereby constructing an indium zinc sulfide nanosheet/tubular tin oxide heterojunction. The composite material has a larger specific surface area, provides more adsorption sites and catalytically active sites, can effectively improve the separation efficiency of photogenerated electrons and holes, thereby improving the activity of photocatalytic reactions, and is better used for light Catalytic separation and degradation of water pollutants.

Description of drawings

Fig. 1 is the scanning electron microscope image of indium zinc sulfide nanosheet/tubular tin oxide heterojunction;

Figure 2 is a transmission electron microscope image of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction;

Figure 3 is a graph showing the degradation curve of hexavalent chromium by indium zinc sulfide nanosheets/tubular tin oxide heterojunction;

Figure 4 is a graph showing the degradation curves of indium zinc sulfide nanosheets/tubular tin oxide heterojunctions against hexavalent chromium solutions with different initial concentrations;

Figure 5 is a graph showing the degradation curves of indium zinc sulfide nanosheets/tubular tin oxide heterojunctions against hexavalent chromium solutions with different initial pH.

Detailed ways

In order to solve the shortcomings in the practical application of nano-photocatalytic materials, the present invention uses sol-gel electrospinning technology, high temperature calcination technology, oil bath and other methods to construct an indium zinc sulfide nanosheet/tubular tin oxide heterojunction photonics Catalytic composite material, as a semiconductor material, indium zinc _sulfide can directly absorb and utilize visible light, and has a narrow band gap structure. It is a good carrier material for the degradation of hexavalent chromium in water pollutants and achieves excellent technical results.

The preparation method of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction of the present invention is as follows:

(1) Using PVP and tin salt as raw materials, the composite nanofibers were prepared by electrospinning method;

(2) calcining the composite nanofibers of step (1) at high temperature to prepare SnO ₂ nanotubes;

(3) Zinc salt, indium salt, and sulfide are added to the solution, and then SnO ₂ nanotubes are added to react to obtain indium zinc sulfide nanosheets/tubular tin oxide heterojunctions.

Example 1

Use a pipette to pipette 5 mL of absolute ethanol and 5 mL of N,N'-dimethylformamide in turn, stir magnetically for 5 min, then add 1 g SnCl ₂ and stir for 5 min, add 1.2 g PVP while stirring, then Stirring was continued for 12 h to form a homogeneous transparent solution; subsequently, the transparent solution was used for electrospinning. Among them, the precursor solution was fed at a constant rate of 0.2 mm min ^-1 using a syringe, a DC power supply was connected to provide a high voltage of 15 KV, and an aluminum foil was placed 15 cm from the needle tip to collect _SnCI /PVP composite fibers.

The above SnCI ₂ /PVP composite fibers were calcined at high temperature at a temperature of 600°C and a heating rate of 2°C/min (from room temperature to 600°C). SnO ₂ , which are SnO ₂ nanotubes.

Add 1 mol of zinc chloride, 2 mol of indium chloride and 4 mol of thioacetamide to 30 mL of ultrapure water (pH=2.5, adjusted with hydrochloric acid) in turn and sonicated for 10 minutes, then added 100 mg of _SnO nanotube powder, and continued to sonicate for 30 minutes A uniform suspension was obtained; the suspension was transferred to a 100ml single-neck flask, reacted in an oil bath at 80° C. for 2 hours, and after the reaction was completed, it was naturally cooled to room temperature; the obtained solution was washed with ultrapure water and ethanol three times in turn, It was then placed in a vacuum oven at 60° C. for 12 h, and finally an indium zinc sulfide nanosheet/tubular tin oxide (ZIS/SnO ₂ ) heterojunction was obtained, which was ZIS/SnO ₂ -1. Adjust the molar amounts of zinc chloride, indium chloride and thioacetamide to 0.5mol, 1mol, 2mol; 1.5mol, 3mol, 6mol; 2mol, 4mol, 8mol; according to different stoichiometric ratios, the obtained products are named respectively are ZIS/SnO ₂ -0.5, ZIS/SnO ₂ -1.5 and ZIS/SnO ₂ -2.

FIG. 1 is a scanning electron microscope image of the above indium zinc sulfide nanosheet/tubular tin oxide, and FIG. 2 is a transmission electron microscope image of the above indium zinc sulfide nanosheet/tubular tin oxide heterojunction. It can be seen from the above figure that small-sized flakes of indium zinc sulfide are uniformly grown on the surface of tin oxide nanotubes.

Embodiment 2

The indium zinc sulfide nanosheet/tubular tin oxide heterojunction of Example 1 was placed in a simulated wastewater containing hexavalent chromium (using potassium dichromate as a chromium source to obtain a hexavalent chromium solution), and a xenon lamp was used as the light source, and the light was illuminated. For a certain period of time, the change curve of the concentration of hexavalent chromium in the water with the illumination time was measured, so as to evaluate the photocatalytic degradation effect of the composite material on pollutants in the water under visible light.

30 mg of indium zinc sulfide nanosheets/tubular tin oxide heterojunctions prepared above were added to 50 mL of hexavalent chromium sewage with a concentration of 50 ppm. First stir for 1 h under dark conditions to make it reach adsorption equilibrium. Then, the xenon light source was turned on, and the catalyst carried out visible light catalytic degradation of hexavalent chromium in water.

The specific degradation effect of hexavalent chromium was detected by a UV-visible spectrophotometer, and calculated from a working curve of hexavalent chromium concentration-absorbance. The specific steps are as follows: at a certain time interval, draw a certain amount of solution, use a filter head to filter out the catalyst, and obtain hexavalent chromium solutions under different degradation times. The absorbance of the hexavalent chromium solution was measured by adding a color developer, and the degradation efficiency was calculated from the absorbance formula. The initial concentration of hexavalent chromium was recorded as 100%. With the progress of the photocatalytic process, the concentration of hexavalent chromium solution gradually decreased, and the degradation curve of hexavalent chromium was obtained after finishing. 3 is the degradation curve of indium zinc sulfide nanosheet/tubular tin oxide heterojunction composite material to hexavalent chromium in water, and the first 60 minutes is the equilibrium adsorption time.

The comparison test is carried out using the above method:

In Example 1, when the PVP is 2 g and the rest remain unchanged, the obtained indium zinc sulfide nanosheet/tubular tin oxide heterojunction ZIS/SnO ₂ -1 has a degradation rate of 89% of hexavalent chromium at 80 minutes; Using the titanium carbide/indium zinc sulfide composite visible light catalyst prepared in Example 1 of CN110124706A, the degradation rate of hexavalent chromium was 69% at 80 minutes.

Embodiment 3

Testing of the degradation curves of indium zinc sulfide nanosheets/tubular tin oxide heterojunctions when the concentrations of the initial hexavalent chromium solutions are different. Using the test method of Example 2, the degradation efficiency of hexavalent chromium with different initial concentrations was tested, and it decreased as the concentration increased. When the concentration is 10ppm, the degradation rate of 100% can be achieved within 10 minutes, and the effect is very good. When the initial concentration is 20 ppm and 30 ppm, it can reach 100% in 30 and 60 minutes, respectively, indicating that the composite material is more favorable for the photocatalytic degradation of low-concentration hexavalent chromium. FIG. 4 is a graph showing the degradation curve of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction when the concentration of the initial hexavalent chromium solution is different.

Testing of the degradation curves of indium zinc sulfide nanosheets/tubular tin oxide heterojunctions (ZIS/SnO ₂ -1) when the pH of the initial hexavalent chromium solution (concentration of 50 ppm) was different. Using the steps of Example 2, when the pH is acidic, the degradation effect is very good; when the pH is alkaline, the degradation effect is very poor. This conclusion is consistent with other literatures, indicating that acidic conditions are conducive to photocatalytic degradation of hexavalent Chromium, alkaline conditions are not conducive to photocatalytic degradation of hexavalent chromium. FIG. 5 is a graph showing the degradation curve of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction when the pH of the initial hexavalent chromium solution is different.

The invention prepares the tin oxide nanotubes through the electrospinning technology and the high-temperature calcination technology. Using tin oxide as a substrate, indium zinc sulfide nanosheets were uniformly grown on its surface by an oil bath, thereby constructing an indium zinc sulfide nanosheet/tubular tin oxide heterojunction. Indium zinc sulfide is an important metal sulfide with a band gap width of 2.6-2.7 eV, which is a good semiconductor material. The prepared indium zinc sulfide nanosheet/tubular tin oxide heterojunction has a large specific surface area, which can provide more adsorption sites and catalytically active sites, effectively improve the separation efficiency of photogenerated electrons and holes, and further improve the The activity of the photocatalytic reaction can be better used for the separation and degradation of photocatalytic water pollutants.

Claims (10)

1. Indium zinc sulfide nanosheet/tubular tin oxide heterojunction, characterized in that the preparation method of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction comprises the following steps: (1) Using PVP and tin salt as raw materials, the composite nanofibers were prepared by electrospinning method; (2) calcining the composite nanofibers of step (1) at high temperature to prepare SnO ₂ nanotubes; (3) Zinc salt, indium salt, and sulfide are added to the solution, and then SnO ₂ nanotubes are added to react to obtain indium zinc sulfide nanosheets/tubular tin oxide heterojunctions. 2. The indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 1, wherein the tin salt is SnCI ₂ ; the zinc salt, the indium salt and the sulfide are respectively zinc chloride, indium chloride, sulfur Substitute acetamide. 3. The indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 1, is characterized in that, in step (1), tin salt is added in mixed solvent, then PVP is added to obtain spinning solution, and then through Electrospinning to prepare composite nanofibers. 4. The indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 3, wherein the mixed solvent is N,N'-dimethylformamide and dehydrated alcohol; in the spinning solution, the tin salt The concentration of tin is 0.1g/mL, and the mass of PVP is 1 to 1.5 times that of tin salt. 5 . The indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 1 , wherein, in step (2), during high temperature calcination, the heating rate is 1.5～3° C./min, and the temperature is 500～650° C. 6 . . 6 . The indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 1 , wherein in step (3), the molar ratio of zinc salt, indium salt and sulfide is 1:2:4. 7 . 7 . The indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 1 , wherein, in step (3), during the reaction, the pH is 2˜3. 8 . 8 . The indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 1 , wherein, in step (3), the reaction temperature is 70-85° C. and the time is 1.5-3 h. 9 . 9. The application of the indium zinc sulfide nanosheet/tubular tin oxide heterojunction according to claim 1 in degrading and removing pollutants in water. 10. The use according to claim 9, wherein the pollutant is a hexavalent chromium compound.

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