S-doped Bi5O7I catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of water treatment, and particularly relates to an S-doped Bi5O7I catalyst and a preparation method and application thereof.The preparation method comprises the steps that bismuth salt and alkali metal salt of iodine are dissolved in ethylene glycol respectively and then mixed to be uniform; adding a sulfur source, uniformly mixing, and carrying out hydrothermal reaction; collecting a product, washing and drying to obtain a precursor; and calcining the precursor to obtain the S-doped Bi5O7I catalyst. The S-doped Bi5O7I catalyst can remove antibiotics in water under photocatalysis, and has the advantages of being simple, effective, easy to implement, high in safety, free of secondary pollution and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and in particular relates to an S-doped Bi5O7I catalyst and a preparation method and application thereof. Background Art

[0002] Antibiotics have potent inhibitory and antimicrobial properties, playing a vital role in healthcare, animal husbandry, and other fields. Their widespread global use has led to their persistent presence and accumulation in aquatic environments, triggering multiple environmental problems. The accumulation of antibiotics in water bodies can not only disrupt the growth and population structure of aquatic organisms, disrupting ecosystem balance, but also, because conventional water treatment processes have limited removal capacity for many antibiotics, continued exposure can enhance antibiotic resistance in environmental microorganisms, posing a complex threat to ecological health and potentially human safety.

[0003] In order to effectively eliminate antibiotic pollution in water bodies and reduce its environmental risks, researchers have explored a variety of treatment technologies such as filtration, adsorption, advanced oxidation, biodegradation, and photocatalytic degradation. Among them, photocatalytic degradation is an effective and environmentally friendly method for harmless treatment of pollutants. However, this technology also has obvious shortcomings, such as easy recombination of photogenerated carriers, weak light absorption capacity, low light energy utilization, insufficient reaction kinetics, etc., which limit its promotion and application in actual environmental governance. In order to improve the performance of photocatalysts and expand the application scenarios of the technology, many methods have been used to modify photocatalysts, such as defect introduction, morphology optimization, and heterogeneous structure construction. Summary of the Invention

[0004] To address the problems of existing photocatalysts, such as easy recombination of photogenerated carriers, weak light absorption, low light energy utilization, and insufficient reaction kinetics, the present invention provides a S-doped Bi5O7I catalyst with high catalytic efficiency, high stability, and environmental friendliness. The technical solution is as follows: A method for preparing a S-doped Bi5O7I catalyst comprises the following steps: dissolving a bismuth salt and an alkali metal salt of iodine in ethylene glycol respectively, and then mixing them evenly; adding a sulfur source, mixing them evenly, and then performing a hydrothermal reaction; collecting the product, washing it, and drying it to obtain a precursor; and calcining the precursor to obtain the S-doped Bi5O7I catalyst.

[0005] Furthermore, the molar ratio of the bismuth salt to the alkali metal salt of iodine is 1:0.8-1.2; and the molar ratio of S in Bi5O7I is 0.1%-9%.

[0006] Furthermore, the bismuth salt is bismuth nitrate; the alkali metal salt of iodine is potassium iodide or sodium iodide; and the sulfur source is thiourea.

[0007] Further, the following steps are included: a. Dissolve a bismuth salt in an ethylene glycol solution to obtain solution A; dissolve an alkali metal salt of iodine in an ethylene glycol solution to obtain solution B; b. Slowly add solution A to solution B and mix thoroughly to form a uniform mixed solution. Add a sulfur source to the mixed solution, mix thoroughly, and then hydrothermally react at 150-180°C for 8-16 hours. After the reaction is complete, collect the precipitate, wash thoroughly, and dry to obtain the precursor. c. Calcinate the dried precursor at 400-500°C for 1.5-3 hours to obtain the S-doped Bi5O7I catalytic material.

[0008] Furthermore, the concentration of bismuth nitrate in the solution A is 0.01-1 mmol / mL; the concentration of potassium iodide in the solution B is 0.1-1 mmol / mL.

[0009] Furthermore, step b is hydrothermally reacted at 160° C. for 12 h; and step c is calcined at 450° C. for 2 h.

[0010] Furthermore, the heating rate of the calcination in step c is 2-8°C / min.

[0011] The S-doped Bi5O7I catalyst prepared by the above method has a light absorption edge greater than 400nm.

[0012] Furthermore, under visible light catalysis for 120 min, the degradation rate of norfloxacin was greater than 50%.

[0013] Application of the S-doped Bi5O7I catalyst prepared by the above method in treating antibiotic-containing wastewater.

[0014] Figure 9 The mechanism of catalytic degradation of antibiotics in water under visible light using the catalyst of the present invention is demonstrated. The S doping of the present invention reduces the band gap of Bi5O7I from 3.11 eV to 3.02 eV, significantly improves the light absorption performance, and improves the separation and transfer efficiency of photogenerated carriers. When Bi5O7I / S is excited by visible light, the photogenerated electrons (e ‒ ) from VB to CB, and then migrate to SO VS state, hindering the direct recombination of electrons and holes, while photogenerated holes (h + ) remains in VB. The photogenerated carriers migrate to the catalyst surface and participate in the photocatalytic reaction. ‒ Reduce O2 into ROS, + Convert H2O adsorbed on the catalyst surface into ·OH. + , ROS and ·OH, and then oxidatively degraded into small molecular compounds, and finally degraded into CO2 and H2O.

[0015] By adopting the above scheme, the method of the present invention has the following advantages: 1. This invention innovatively constructs S-doped Bi5O7I photocatalytic materials, regulates the band gap structure of Bi5O7I, and regulates the separation and transfer efficiency of photogenerated carriers, thereby improving the generation efficiency of reactive oxygen species (ROS) and achieving effective degradation of antibiotics, providing new ideas and technical methods for the removal of antibiotics in water.

[0016] 2. The method of the present invention dopes sulfur into Bi5O7I, resulting in a stable structure and no interface issues. This solves the problems of poor heterojunction structure stability, easy separation, and poor recycling capacity. The carrier concentration is more adjustable.

[0017] 3. The process of the present invention is simple and easy to operate, the reaction conditions are easy to achieve, the safety is high, there is no excessive addition of non-product elements, the product has high purity and few impurities, there is no secondary pollution, and the application prospect is broad.

[0018] 4. The introduction of sulfur into the S-doped Bi5O7I of the present invention increases the light absorption range of Bi5O7I, reduces the band gap, significantly improves the light absorption performance, and improves the separation and transfer efficiency of photogenerated carriers. It can effectively degrade antibiotics in water under visible light irradiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the X-ray diffraction pattern (XRD) of Examples 1 to 4 and Comparative Example 1; Figure 2 is a comparison chart of the UV-visible diffuse reflectance spectra (DRS) of Bi5O7I / S-5% in Example 1 and Bi5O7I in Comparative Example 1; Figure 3 is a scanning electron microscope (SEM) image of Example 1; Figure 4 is a transmission electron microscope (TEM) image of Example 1; Figure 5 is an energy dispersive X-ray spectroscopy (EDX) diagram of Example 1; Figure 6 1 is a graph showing the effect of photocatalytic degradation of norfloxacin in water in Examples 1 to 4 and Comparative Examples 1 and 2; Figure 7 This is a graph showing the degradation of norfloxacin after adding a free radical scavenger during the visible light catalytic degradation of norfloxacin in water in Example 1; Figure 8 This is a comparison chart of the cycle experiment of visible light catalytic degradation of norfloxacin in water in Example 1; Figure 9 This is a diagram showing the mechanism of utilizing visible light to catalyze the degradation of antibiotics in water according to Example 1. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] Example 1: (1) 4 mmol Bi(NO3)·5H2O was ultrasonically dissolved in 40 mL of ethylene glycol solution, and the solution was named solution A; 4 mmol KI was dissolved in 20 mL of ethylene glycol solution, and the solution was named solution B; (2) Solution A was slowly added dropwise to solution B, and after stirring for 30 min, 0.2 mmol of thiourea was added as a sulfur source to the mixed solution. The mixture was stirred for 30 min and kept at 160 °C for 12 h. The product was collected by filtration, washed with anhydrous ethanol and ultrapure water, and dried at 60 °C for 10 h to obtain a S-doped Bi5O7I precursor. (3) The dried precursor was placed in a muffle furnace and calcined at 450 °C for 2 h at a heating rate of 5 °C / min to obtain S-doped Bi5O7I catalytic material, named Bi5O7I / S-5%.

[0022] Figure 3 and Figure 4 The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Example 1 show that the S-doped Bi5O7I prepared by the method of the present invention has a nano-spherical structure.

[0023] Figure 5 This is the energy dispersive X-ray spectrum (EDX) diagram of Example 1. It can be seen from the EDX diagram that Example 1 contains Bi, O, I and S elements, indicating that the Bi5O7I / S photocatalyst was successfully prepared and S was successfully doped into Bi5O7I.

[0024] Example 2: The difference from Example 1 is that: 0.004 mmol thiourea was added as a sulfur source into the mixed solution, and the solution was named Bi5O7I / S-0.1%.

[0025] Example 3: The difference from Example 1 is that: 0.04 mmol thiourea was added as a sulfur source into the mixed solution, and the solution was named Bi5O7I / S-1%.

[0026] Example 4: The difference from Example 1 is that: 0.32 mmol of thiourea was added as a sulfur source into the mixed solution, and the solution was named Bi5O7I / S-8%.

[0027] Comparative Example 1: The difference from Example 1 is: 4 mmol Bi(NO₃)·5H₂O and 4 mmol KI were uniformly dispersed in 60 mL of ethylene glycol solution. After thorough stirring for 60 minutes, the mixture was transferred to a 100 mL reactor and heated to 160°C for 12 hours. The solid material was collected by centrifugation, washed with anhydrous ethanol and ultrapure water, and dried at 60°C for 10 hours. Finally, the dried solid material was calcined in a muffle furnace at 450°C for 2 hours to obtain the Bi₅OₐI catalyst.

[0028] Comparative Example 2: The difference from Example 1 is: 0.4 mmol thiourea was added as a sulfur source into the mixed solution and named Bi5O7I / S-10%.

[0029] Example sample performance test: X-ray diffraction: Figure 1 The XRD patterns of the catalysts (Bi5O7I, Bi5O7I / S-0.1%, Bi5O7I / S-1%, Bi5O7I / S-5% and Bi5O7I / S-8%) of Examples 1 to 4 and Comparative Example 1 are shown in FIG. Figure 1 The diffraction peaks of the Bi5O7I sample are consistent with those of its standard card (JCPDS: 40-0548), and it has six typical crystal planes, namely (200), (312), (004), (204), (024), and (224). The XRD spectra of Bi5O7I / S-0.1%, Bi5O7I / S-1%, Bi5O7I / S-5%, and Bi5O7I / S-8% are similar to those of Bi5O7I.

[0030] UV-Vis diffuse reflectance: Figure 2 The UV-Vis DRS graphs of Example 1 and Comparative Example 1 show that the light absorption edge of Bi5O7I is 399 nm, while that of Bi5O7I / S-5% is 411 nm. The absorption edge of Bi5O7I / S-5% shows a slight red shift, and the light absorption performance of S-doped Bi5O7I is higher than that of Bi5O7I, indicating that the introduction of S element can effectively improve the light absorption performance and light utilization efficiency of Bi5O7I.

[0031] Testing for visible light photocatalytic degradation of NOR in water: 20 mg of each catalyst sample from each example and comparative example was uniformly dispersed in a 50 mL, 10 mg / L NOR solution. Each mixture was reacted in the dark at 30°C and 500 rpm for 30 minutes to achieve adsorption-desorption equilibrium. The mixed solution was then subjected to a photocatalytic reaction under a xenon lamp (λ > 420 nm). The reaction system temperature was 30°C, the illumination time was 120 minutes, and the solution was stirred at 500 rpm.

[0032] Figure 6 This is a comparison chart of the visible light photocatalytic degradation effect of NOR in water by various photocatalytic materials. Figure 6 As can be seen, compared to pure Bi5O7I, the Bi5O7I / S photocatalytic material significantly improves NOR degradation. Bi5O7I / S-5% exhibits the highest photocatalytic activity, achieving a NOR degradation rate of 95.55%. Comparative Example 2, with a 10% sulfur doping level, exhibits lower catalytic activity than Comparative Example 1, demonstrating that sulfur doping must be maintained within an appropriate range to enhance catalytic performance, while excessive sulfur doping is detrimental to NOR degradation.

[0033] Free radical generation during NOR degradation: 20 mg of Example 1 was evenly dispersed in a NOR solution (50 mL, 10 mg / L). The mixture was placed at 30°C and 500 rpm for 30 min in the dark to achieve adsorption-desorption equilibrium. 0.1 mmol / L disodium ethylenediaminetetraacetic acid (EDTA-2Na-h + ), 0.1 mmol / L silver nitrate (AgNO3-e ‒ ), 0.1 mmol / L tryptophan (TRP- 1 O2), 0.1 mmol / L benzoquinone (BQ-·O2 − ) and 0.5 mmol / L isopropyl alcohol (IPA-OH), and then the mixed solutions were placed under a xenon lamp (λ>420 nm) for photocatalytic reaction. The temperature of the reaction system was 30 ℃, the illumination time was 120 min, and the solution stirring rate was 500 rpm.

[0034] Figure 7 The degradation efficiency of NOR after adding the capture agent in the process of visible light catalytic degradation of NOR in water in Example 1 can be seen from the figure. Compared with the control group without the capture agent, the degradation rate of NOR after adding the capture agent decreased to varying degrees, indicating that the active species (h⁺, e⁻, 1O2, ·O2⁻ and ·OH) all participated in the degradation reaction of NOR. Among them, h⁺ and ·O2⁻ contributed most significantly to the degradation of NOR, followed by ·OH and 1 O2, while the effect of e⁻ is relatively weak. This result indicates that photogenerated holes (h⁺) and superoxide radicals (·O2⁻) are the key active species in the photocatalytic degradation of NOR.

[0035] Stability testing of visible light photocatalytic degradation of NOR in water: 20 mg of Example 1 was uniformly dispersed in a 50 mL NOR solution (10 mg / L). The mixture was incubated in the dark at 30°C and 500 rpm for 30 minutes to achieve adsorption-desorption equilibrium. The mixed solution was then subjected to photocatalytic reaction under a xenon lamp (λ > 420 nm) at 30°C, 120 minutes of illumination, and 500 rpm of stirring. 50 mL of the 10 mg / L NOR solution was added, and the degradation experiment was repeated four times. The degradation efficiency of the Bi5O7I / S photocatalyst against the antibiotic was measured each time.

[0036] Figure 8 This is a comparison chart of the Bi5O7I / S photocatalytic degradation of NOR cycle experiment in water in Example 1. Figure 8 It can be seen that after four cycles of experiments, the degradation efficiency of Bi5O7I / S photocatalyst for antibiotics only dropped from 99.5% to 86.4%, still showing a good degradation effect, indicating that Bi5O7I / S photocatalyst has good stability.

[0037] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a S-doped Bi5O7I catalyst, characterized in that: The method comprises the following steps: dissolving a bismuth salt and an alkali metal salt of iodine in ethylene glycol respectively, and then mixing them evenly; adding a sulfur source, mixing them evenly, and then performing a hydrothermal reaction; The product is collected, washed, and dried to obtain a precursor; the precursor is calcined to obtain a S-doped Bi5O7I catalyst.

2. The method for preparing the S-doped Bi5O7I catalyst according to claim 1, characterized in that: The molar ratio of the bismuth salt to the alkali metal salt of iodine is 1:0.8-1.2; the molar ratio of S in Bi5O7I is 0.1%-9%.

3. The method for preparing the S-doped Bi5O7I catalyst according to claim 1, characterized in that: The bismuth salt is bismuth nitrate; the alkali metal salt of iodine is potassium iodide or sodium iodide; and the sulfur source is thiourea.

4. The method for preparing the S-doped Bi5O7I catalyst according to claim 1, characterized in that: The following steps are involved: a. Dissolve a bismuth salt in an ethylene glycol solution to obtain solution A; dissolve an alkali metal salt of iodine in an ethylene glycol solution to obtain solution B; b. Slowly add solution A to solution B and mix thoroughly to form a uniform mixed solution. Add a sulfur source to the mixed solution, mix thoroughly, and then hydrothermally react at 150-180°C for 8-16 hours. After the reaction is complete, collect the precipitate, wash thoroughly, and dry to obtain the precursor. c. Calcinate the dried precursor at 400-500°C for 1.5-3 hours to obtain the S-doped Bi5O7I catalytic material.

5. The method for preparing the S-doped Bi5O7I catalyst according to claim 4, characterized in that: The concentration of bismuth nitrate in the solution A is 0.01-1 mmol / mL; the concentration of potassium iodide in the solution B is 0.1-1 mmol / mL.

6. The method for preparing the S-doped Bi5O7I catalyst according to claim 4, characterized in that: Step b: hydrothermal reaction at 160° C. for 12 h; step c: calcination at 450° C. for 2 h.

7. The method for preparing the S-doped Bi5O7I catalyst according to claim 4, characterized in that: The heating rate of the calcination in step c is 2-8°C / min.

8. A S-doped Bi5O7I catalyst prepared by the method according to any one of claims 1 to 7, characterized in that The light absorption edge is greater than 400nm.

9. The S-doped Bi5O7I catalyst according to claim 8, characterized in that Under visible light catalysis for 120 minutes, the degradation rate of norfloxacin was greater than 50%.

10. Use of the S-doped Bi5O7I catalyst prepared by the method according to claim 8 in treating antibiotic-containing wastewater.

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