Preparation method and application of ZnIn2S4 / Bi5O7I heterojunction photocatalyst

Abstract

The invention provides a preparation method of a ZnIn2S4 / Bi5O7I heterojunction photocatalyst, which comprises the following steps: preparing Bi5O7I, mixing Bi5O7I with ZnSO4. 7H2O and In2S3O12, adding distilled water, carrying out ultrasonic treatment, magnetically stirring, adding thioacetamide, carrying out ultrasonic treatment, magnetically stirring, reacting at 160 DEG C, washing the precipitate with ethanol, washing with deionized water, filtering, and drying to obtain the ZnIn2S4 / Bi5O7I heterojunction photocatalyst. And the ZnIn2S4 / Bi5O7I heterojunction photocatalyst is obtained. The invention also provides an application of degrading the antibiotic metronidazole in water under the irradiation of sunlight. The ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared by the invention can efficiently degrade metronidazole pollutants in water, is beneficial to solving the problem of residues of antibiotic drug metronidazole in water, and provides a green and sustainable solution for the field of water treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysis, and specifically relates to a preparation method and application of a ZnIn2S4 / Bi5O7I heterojunction photocatalyst. Background Art

[0002] Photocatalytic technology produces ·OH, ·O2 under light - Active substances such as ZIS can quickly degrade organic matter and are very promising in the deep treatment of antibiotics in water. ZIS is a common photocatalyst, but its serious internal photogenerated carrier recombination limits its photocatalytic performance. Therefore, it is necessary to develop a new catalyst to improve the carrier separation efficiency of ZIS and effectively improve the degradation efficiency of antibiotics in water. The photocatalytic activity of ZnIn2S4 is limited by the visible light absorption range, and the ultrafast recombination of holes and electrons leads to low separation efficiency of photogenerated electrons and holes; in addition, the photogenerated carrier mobility of ZnIn2S4 is also relatively low. This means that during the photocatalytic process, the generated electrons and holes are transmitted slowly inside the material, which may cause them to be recombinated or lost during migration, further reducing the photocatalytic efficiency. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst and its application in view of the deficiencies of the above-mentioned prior art. The ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared by this method can efficiently degrade metronidazole pollutants in water, help solve the problem of the residue of the antibiotic drug metronidazole in water bodies, and provide a green and sustainable solution for the field of water treatment.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst, the method comprising:

[0005] Preparation of S1 and Bi5O7I:

[0006] Dissolve Bi(NO3)3·5H2O in ethylene glycol and treat with ultrasound to obtain an ethylene glycol solution of Bi(NO3)3;

[0007] Dissolve KI in ethylene glycol and perform ultrasonic treatment to obtain an ethylene glycol solution of KI;

[0008] The ethylene glycol solution of KI is added dropwise to the ethylene glycol solution of Bi(NO3)3, and after stirring, the mixture is reacted at 160°C under a sealed condition for 12 hours, and then the precipitate is washed and dried, and then the temperature is increased from room temperature to 500°C at a heating rate of 3°C / min, and the mixture is calcined at a constant temperature for 2 hours, and then naturally cooled to room temperature to obtain Bi5O7I;

[0009] S2. Combine ZnSO4·7H2O and In2S3O 12 After mixing with the Bi5O7I obtained in S1, distilled water is added, ultrasonic treatment is performed and magnetic stirring is performed, and then thioacetamide is added, ultrasonic treatment is performed and magnetic stirring is performed, and then the reaction is carried out at a temperature of 160°C for 12 hours. After naturally cooling to room temperature, the precipitated material is first washed with ethanol and then with deionized water, filtered, and dried to obtain a ZnIn2S4 / Bi5O7I heterojunction photocatalyst; the atomic molar ratio of Zn to Bi in the ZnIn2S4 / Bi5O7I heterojunction photocatalyst is 1.5%.

[0010] Preferably, the mass ratio of Bi(NO3)3·5H2O and KI in S1 is 1.382:0.501.

[0011] Preferably, the ultrasonic treatment time in S1 is 30 min.

[0012] Preferably, the stirring time in S1 is 2 h.

[0013] Preferably, the ZnSO4·7H2O, In2S3O 12 , and thioacetamide have a molar ratio of 1:1:8.

[0014] Preferably, the ultrasonic treatment time in S2 is 30 min, and the magnetic stirring time is 30 min.

[0015] Preferably, the number of deionized water washing in S2 is 3 times, and the number of ethanol washing is 3 times.

[0016] Preferably, the drying temperature in S2 is 60° C. and the drying time is 6 hours.

[0017] The present invention also provides an application of the ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared by the above preparation method, wherein the ZnIn2S4 / Bi5O7I heterojunction photocatalyst is used to degrade the antibiotic metronidazole in water under sunlight.

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

[0019] The present invention prepares a ZnIn2S4 / Bi5O7I heterojunction. The design of this heterojunction cleverly utilizes the complementarity of the two semiconductor materials in the energy band structure. Through a simple hydrothermal synthesis process, it not only simplifies the preparation process and reduces the cost, but also greatly promotes the effective separation and migration of photogenerated electron-hole pairs inside the material, improves the carrier separation efficiency, and thus significantly improves the efficiency of the photocatalytic reaction. The ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared by the present invention can efficiently degrade antibiotic (metronidazole) pollutants in water, and its degradation efficiency is significantly improved compared to single-component materials (two monomer materials of ZnIn2S4 and Bi5O7I). This material not only helps to solve the problem of antibiotic drugs (metronidazole) residues in water, but also provides a green and sustainable solution for the field of water treatment.

[0020] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the XRD diagram of the ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared in Example 1 of the present invention.

[0022] Figure 2 The SEM images, TEM images, HRTEM images and elemental mapping spectra of the ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared in Example 1 of the present invention are shown in Figures 1 and 2. (ac) SEM images of ZnIn2S4, Bi5O7I and ZnIn2S4 / Bi5O7I; (df) TEM images of ZnIn2S4, Bi5O7I and ZnIn2S4 / Bi5O7I; (gi) HRTEM images of ZnIn2S4, Bi5O7I and ZnIn2S4 / Bi5O7I; (jp) elemental mapping spectrum of ZnIn2S4 / Bi5O7I.

[0023] Figure 3 The photocurrent response, LSV curve and EIS of the ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared in Example 1 of the present invention are shown in FIG.

[0024] Figure 4 This is the energy band structure of the ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared in Example 1 of the present invention.

[0025] Figure 5 The invention relates to a degradation test of metronidazole by using a ZnIn2S4 / Bi5O7I heterojunction photocatalyst synthesized by Bi5O7I and ZnIn2S4 prepared at different calcination temperatures of the present invention.

[0026] Figure 6 The present invention is a test of the degradation of metronidazole by photocatalysts prepared by using different molar ratios of Zn atoms and Bi atoms. DETAILED DESCRIPTION

[0027] Example 1

[0028] The preparation method of the ZIS / Bi5O7I heterojunction photocatalyst of this embodiment is as follows:

[0029] Preparation of S1 and Bi5O7I:

[0030] 1.382 g of Bi(NO3)3·5H2O was dissolved in 25 mL of ethylene glycol and treated with ultrasound for 30 min to obtain an ethylene glycol solution of Bi(NO3)3;

[0031] 0.501 g of KI was dissolved in 25 mL of ethylene glycol and subjected to ultrasonic treatment to obtain an ethylene glycol solution of KI;

[0032] The ethylene glycol solution of KI is added dropwise to the ethylene glycol solution of Bi(NO3)3, stirred for 2 hours, and then reacted in a sealed autoclave at a temperature of 160°C for 12 hours, and then the precipitate is washed and dried, and then heated from room temperature to 500°C at a heating rate of 3°C / min, calcined at a constant temperature for 2 hours, and naturally cooled to room temperature to obtain Bi5O7I;

[0033] S2, 1mmol ZnSO4·7H2O, 1mmol In2S3O 12 , Bi5O7I, and then 50 mL of distilled water was added, and the mixture was ultrasonically treated and magnetically stirred. Then, 8 mmol of thioacetamide was added, and the mixture was ultrasonically treated and magnetically stirred. Then, the mixture was reacted in a Teflon-lined autoclave at 160° C. for 12 hours. After naturally cooling to room temperature, the precipitated material was washed 3 times with ethanol and 3 times with deionized water. After filtering, the precipitated material was dried at 60° C. for 6 hours to obtain a ZnIn2S4 / Bi5O7I heterojunction photocatalyst, which was named ZIS / Bi5O7I 1.5%; the atomic molar ratio of Zn to Bi in the ZnIn2S4 / Bi5O7I heterojunction photocatalyst was 1.5%.

[0034] from Figure 1 It can be seen that ZIS(ZnIn2S4), Bi5O7I and ZnIn2S4(ZIS) / Bi5O7I were successfully synthesized.

[0035] Depend on Figure 2 It can be seen that the SEM image shows that ZnIn2S4 is in the form of petal-shaped microspheres ( Figure 2 a). Bi5O7I is stacked in layers ( Figure 2b). The overall shape of the ZnIn2S4 / Bi5O7I heterojunction is similar to that of ZnIn2S4 ( Figure 2 c), the petal microspheres are kept, but there are flake-like substances Bi5O7I in the gaps. In the HRTEM image of the ZnIn2S4 / Bi5O7I heterojunction, a clear boundary between ZnIn2S4 and Bi5O7I was observed, and the (0012) exposed surface of ZIS and the (201) exposed surface of Bi5O7I were determined based on the lattice fringe spacing ( Figure 2 df). TEM images of ZnIn2S4 / Bi5O7I heterojunction ( Figure 2 gi) observed that the flake Bi5O7I was uniformly wrapped around the outside of ZnIn2S4. The elemental mapping spectrum of the heterojunction confirmed that Bi, I and O were uniformly dispersed on ZnIn2S4 ( Figure 2 jp).

[0036] Depend on Figure 3 It can be seen that from Figure 3 It can be seen from a that the photocurrent response of the ZnIn2S4 / Bi5O7I heterojunction is the best, indicating that the carrier separation efficiency is significantly improved. Figure 3 It can be seen from b that the ZnIn2S4 / Bi5O7I heterojunction can significantly reduce the overpotential. Figure 3 c shows that the transfer resistance of the surface charge of the ZnIn2S4 / Bi5O7I heterojunction is reduced, so the migration speed of the carriers is accelerated. Therefore, the ZnIn2S4 / Bi5O7I heterojunction greatly promotes the effective separation and migration of photogenerated electron-hole pairs inside the material, and improves the photocatalytic performance.

[0037] from Figure 4 From the perspective of energy band structure, ZnIn2S4 / Bi5O7I belongs to Type-II heterojunction. Under illumination, carriers migrate in opposite directions in the two semiconductors (ZnIn2S4 and Bi5O7I), thereby achieving spatial separation of photogenerated electrons and holes. The preparation method of this embodiment cleverly utilizes the complementarity of the energy band structure of the two semiconductor materials. Therefore, the ZnIn2S4 / Bi5O7I heterojunction improves the degradation efficiency of metronidazole.

[0038] This embodiment also conducted experiments to optimize the calcination temperature in step S1 and the atomic molar ratio of Zn and Bi in the ZIS / Bi5O7I heterojunction photocatalyst in step S2.

[0039] (I) An optimization experiment was conducted on the calcination temperature in step S1 of this embodiment, that is, the experimental conditions of the calcination temperature in step S1 were optimized, and the other steps were the same as in Example 1, that is, Bi5O7I at different calcination temperatures (400°C, 450°C, 500°C, 550°C, 600°C) was used to prepare ZnIn2S4 / Bi5O7I heterojunction photocatalysts. The prepared catalysts were named as follows: ZIS / Bi5O7I(400°)1.5%, ZIS / Bi5O7I(450°)1.5%, ZIS / Bi5O7I(500°)1.5% (i.e., the catalyst prepared in this embodiment), ZIS / Bi5O7I(550°)1.5%, ZIS / Bi5O7I(600°)1.5%. Meanwhile, ZnIn2S4(ZIS) and Bi5O7I (Bi5O7I prepared in step S1 of Example 1) were used as controls.

[0040] The preparation method of ZnIn2S4 (ZIS) in the control is:

[0041] 1mmolZnSO4·7H2O and 1mmolIn2S3O 12 After mixing, distilled water was added, ultrasonic treatment was performed and magnetic stirring was performed, and then 8 mmol of thioacetamide was added, ultrasonic treatment was performed and magnetic stirring was performed, and then the reaction was carried out at a temperature of 160°C for 12 hours. After naturally cooling to room temperature, the precipitated material was first washed with ethanol and then with deionized water, filtered, and dried to obtain a ZIS photocatalyst.

[0042] The photocatalytic degradation efficiency of metronidazole in water was evaluated under the irradiation of simulated sunlight, and the degradation rate was quantitatively analyzed by liquid chromatography. The results showed that the photocatalytic degradation efficiency of single ZnIn2S4 and Bi5O7I was low, while the photocatalytic efficiency of ZnIn2S4 / Bi5O7I (500℃) 1.5wt% prepared in this embodiment could reach more than 98%.

[0043] Degradation conditions: 20 mg / L metronidazole solution, catalyst dosage 0.8 g / L, xenon lamp (simulated sunlight) 300W illumination, adsorption 12.5 min, illumination 12.5 min, degradation results are as follows Figure 5 As shown in Table 1, each heterojunction catalyst degrades 20 mg / L to obtain a metronidazole solution. Figure 5 It can be seen that the degradation efficiency of ZIS / Bi5O7I (500℃) 1.5% can reach more than 98%. Therefore, the optimal calcination temperature of Bi5O7I is 500℃.

[0044] Table 1 Degradation test of metronidazole by photocatalysts prepared at different calcination temperatures

[0045]

[0046] (ii) The molar ratio of Zn atoms to Bi atoms in the ZnIn2S4 / Bi5O7I heterojunction photocatalyst in step S2 of this embodiment was optimized, and the other steps were the same as in embodiment 1. That is, catalysts with a molar ratio of Zn atoms to Bi atoms of 0.5%, 1%, 1.5%, 2%, and 2.5% in the ZnIn2S4 / Bi5O7I heterojunction photocatalyst in step S2 were prepared, and the prepared ZnIn2S4 / Bi5O7I heterojunction photocatalysts were named ZIS / Bi5O7I 0.5%, ZIS / Bi5O7I 1%, ZIS / Bi5O7I1.5% (i.e., the catalyst prepared in this embodiment), ZIS / Bi5O7I 2%, and ZIS / Bi5O7I 2.5%.

[0047] The prepared ZnIn2S4 / Bi5O7I heterojunction photocatalysts with different molar ratios of Zn atoms and Bi atoms were used to degrade the antibiotic metronidazole in water under sunlight. The degradation conditions were the same as those in Example 1. ZnIn2S4 (ZIS) and Bi5O7I (Bi5O7I prepared in step S1 of Example 1) were used as controls. The degradation rates were as follows: Figure 6 , as shown in Table 2.

[0048] Table 2 Degradation test of metronidazole by photocatalysts prepared with different molar ratios of Zn atoms and Bi atoms

[0049]

[0050] By adjusting the molar ratio of Zn atoms and Bi atoms (0.5%-2.5%), the optimal ratio of ZnIn2S4 / Bi5O7I heterojunction was determined. The prepared 0.8g / L heterojunction was used to degrade 20mg / L metronidazole solution. It can be seen from the figure that the degradation efficiency of ZnIn2S4 / Bi5O7I is the highest when the ratio of Zn atoms to Bi atoms is 1.5%. Therefore, the catalytic performance of ZnIn2S4 / Bi5O7I1.5% is the best.

[0051] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst, characterized in that: The method is: Preparation of S1 and Bi5O7I: Dissolve Bi(NO3)3·5H2O in ethylene glycol and treat with ultrasound to obtain an ethylene glycol solution of Bi(NO3)3; Dissolve KI in ethylene glycol and perform ultrasonic treatment to obtain an ethylene glycol solution of KI; The ethylene glycol solution of KI is added dropwise to the ethylene glycol solution of Bi(NO3)3, and after stirring, the mixture is reacted at 160°C under sealed conditions for 12 hours, and then the precipitate is washed and dried, and then the temperature is increased from room temperature to 500°C at a heating rate of 3°C / min, and the mixture is calcined at a constant temperature for 2 hours, and then naturally cooled to room temperature to obtain Bi5O7I; S2. Combine ZnSO4·7H2O and In2S3O 12 After mixing with the Bi5O7I obtained in S1, distilled water is added, ultrasonic treatment is performed and magnetic stirring is performed, and then thioacetamide is added, ultrasonic treatment is performed and magnetic stirring is performed, and then the reaction is carried out at a temperature of 160°C for 12 hours. After naturally cooling to room temperature, the precipitated material is first washed with ethanol and then with deionized water, filtered, and dried to obtain a ZnIn2S4 / Bi5O7I heterojunction photocatalyst; the atomic molar ratio of Zn to Bi in the ZnIn2S4 / Bi5O7I heterojunction photocatalyst is 1.5%.

2. The method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst according to claim 1, characterized in that: The mass ratio of Bi(NO3)3·5H2O and KI described in S1 is 1.382:0.

501.

3. The method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst according to claim 1, characterized in that: The ultrasonic treatment time in S1 is 30 min.

4. The method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst according to claim 1, characterized in that: The stirring time in S1 is 2 h.

5. The method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst according to claim 1, characterized in that: S2 ZnSO4·7H2O, In2S3O 12 , and thioacetamide have a molar ratio of 1:1:

8.

6. The method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst according to claim 1, characterized in that: The ultrasonic treatment time in S2 is 30 min, and the magnetic stirring time is 30 min.

7. The method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst according to claim 1, characterized in that: The number of ethanol removal washing in S2 is 3 times, and the number of deionized water washing is 3 times.

8. The method for preparing a ZnIn2S4 / Bi5O7I heterojunction photocatalyst according to claim 1, characterized in that: The drying temperature in S2 is 60°C and the drying time is 6 hours.

9. An application of a ZnIn2S4 / Bi5O7I heterojunction photocatalyst prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The ZnIn2S4 / Bi5O7I heterojunction photocatalyst is used to degrade the antibiotic metronidazole in water under sunlight.

Images