Bismuth oxide carbonate photocatalyst, and preparation method and application thereof

Abstract

The application provides a bismuth oxide carbonate photocatalyst and a preparation method and application thereof, the bismuth oxide carbonate photocatalyst is prepared through a hydrothermal auxiliary co-precipitation strategy, has high efficient catalytic degradation performance on organic dyes under visible light conditions, and can be suitable for degradation of pollutants in complex water bodies; and the halogen element introduced in the application can obviously enhance the photocatalytic performance of the bismuth oxide carbonate photocatalyst on degradation of organic pollutants, can eliminate the organic pollutants in water bodies at an extremely fast speed, and has a wide applicable prospect in the field of wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials, specifically relating to a bismuth oxycarbonate photocatalyst, its preparation method, and its application. Background Technology

[0002] With the development of the times, many scientists believe that photocatalysis is a technology that can solve energy scarcity and environmental pollution. It is a green and environmentally friendly technology that can directly utilize solar energy. It can be applied in many fields, such as degrading organic pollutants, photocatalytic reduction of CO2, hydrogen desorption from water, and selective organic conversion. Although photocatalysis technology has many advantages, traditional TiO2 photocatalysts can only react to ultraviolet (UV) light. Therefore, in order to develop photocatalysts with higher efficiency and performance for practical applications, creating efficient visible light-driven photocatalysts has become the mainstream research direction both domestically and internationally. In recent years, bismuth-based photocatalysts have become a focus because they not only have good photocatalytic performance in the visible light region but also possess relatively stable chemical properties. Bismuth-based photocatalysts benefit from their suitable electronic band structure, and their morphology is easily tunable. Bi2O2CO3 is a widely studied functional material with unique physicochemical properties, finding wide applications in electrochromic devices, dye-sensitized solar cells, photocatalysis, optical recording devices, sensing, field emission, and high-temperature superconductivity. Summary of the Invention

[0003] This invention aims to provide a bismuth oxycarbonate photocatalyst, its preparation method, and its application. The bismuth oxycarbonate photocatalyst was prepared by a hydrothermal assisted coprecipitation strategy and exhibits high catalytic degradation performance for organic dyes under visible light conditions.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention provides a method for preparing a bismuth oxycarbonate photocatalyst, comprising:

[0006] 1) Dissolve bismuth nitrate pentahydrate in acetic acid to prepare a 0.4 mol / L bismuth nitrate solution, and then dissolve sodium citrate dihydrate in deionized water to prepare a 0.2 mol / L sodium citrate aqueous solution;

[0007] 2) The sodium citrate aqueous solution was slowly added dropwise to the bismuth nitrate solution at a volume ratio of 1:1 to carry out a co-precipitation reaction. After the reaction was completed, the pH of the mixed solution was adjusted to 7.5.

[0008] 3) Transfer the mixture obtained in step 2) to a hydrothermal reactor, seal it, transfer it to a forced-air drying oven and heat it at 180°C for 12 hours. After cooling to room temperature, wash and dry it to obtain bismuth oxycarbonate photocatalyst.

[0009] Preferably, in step 2), the sodium citrate aqueous solution is slowly added dropwise to the bismuth nitrate solution at a rate of 10 mL / h to carry out a co-precipitation reaction for 1 h; and / or in step 3), after cooling to room temperature, the product is washed with a mixture of ethanol and water and then dried in a vacuum oven at 70°C for 12 h.

[0010] The present invention also provides a bismuth oxycarbonate photocatalyst, which is prepared by the above-described method.

[0011] The present invention further provides the application of the above-mentioned bismuth oxycarbonate photocatalyst, comprising: adding the bismuth oxycarbonate photocatalyst to an aqueous solution of an alkaline fluorescent dye, reaching adsorption-desorption equilibrium under dark conditions, and then carrying out a photocatalytic reaction in the wavelength range of sunlight to achieve the removal of the alkaline fluorescent dye.

[0012] Preferably, the amount of the bismuth oxycarbonate photocatalyst added to the aqueous solution of the alkaline fluorescent dye is 0.4 mg / mL.

[0013] Preferably, the basic fluorescent dye is one or more of Rhodamine B, methylene blue, and tetracycline; and / or the aqueous solution of the basic fluorescent dye contains 10 mg / L of basic fluorescent dye; and / or the pH value of the aqueous solution of the basic fluorescent dye is 3-12.

[0014] Preferably, after adding the bismuth oxycarbonate photocatalyst to the aqueous solution of the alkaline fluorescent dye, a halide salt is also added.

[0015] More preferably, the halide salt is selected from any one of sodium chloride, sodium bromide, or sodium iodide.

[0016] More preferably, the molar concentration of the halide salt in the aqueous solution of the basic fluorescent dye is 0.0125 to 0.025 mol / L.

[0017] Preferably, the photocatalytic reaction is carried out at room temperature for at least 15 minutes.

[0018] Natural water bodies have a complex composition, containing many inorganic salt ions. The bismuth oxycarbonate photocatalyst Bi₂O₂CO₃ of this invention more closely resembles the composition of natural water bodies. It not only resists the influence of inorganic anions in the water but is also more suitable for wastewater treatment in complex aquatic environments. Furthermore, the introduction of halide salts significantly improves the photocatalytic degradation performance of Bi₂O₂CO₃ of organic pollutants.

[0019] The beneficial technical effects of this invention include:

[0020] (1) The bismuth oxycarbonate photocatalyst of the present invention is prepared by a hydrothermal-assisted co-precipitation strategy, which has better performance compared with the traditional hydrothermal synthesis method. It is suitable for large-scale industrial production, and the obtained photocatalyst has broad application prospects in the field of wastewater treatment.

[0021] (2) The introduction of halogen elements in this invention significantly enhances the photocatalytic performance of Bi2O2CO3 in degrading organic pollutants, and can eliminate organic pollutants in water at an extremely fast speed.

[0022] (3) The Bi2O2CO3 of the present invention can achieve efficient degradation of organic pollutants and is suitable for pollutant degradation in complex water bodies.

[0023] (4) The Bi2O2CO3 photocatalyst of the present invention has good stability and strong photocatalytic performance. After the introduction of halogen elements, it has excellent cycle performance and stable state. Attached Figure Description

[0024] Figure 1 This is an X-ray diffraction (XRD) pattern of an embodiment of the present invention.

[0025] Figure 2 This is a Fourier transform infrared (FTIR) spectrum of an embodiment of the present invention.

[0026] Figure 3 This is a scanning electron microscope (SEM) image of a test embodiment of the present invention.

[0027] Figure 4 This is an EDS spectrum from an embodiment of the present invention.

[0028] Figure 5 The graphs show the degradation performance of Rhodamine B in the visible light catalytic system of the embodiments and comparative examples 1 and 2 of this invention.

[0029] Figure 6 These are application examples 2, 3, 4, and 5 of this invention, showing the degradation performance of Rhodamine B in a visible light catalytic system.

[0030] Figure 7 This is a graph showing the degradation performance of Rhodamine B in a visible light catalytic system, as described in Example 6 of this invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specifically stated, the numerical values ​​set forth in these embodiments do not limit the scope of the invention. Techniques and methods known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques and methods should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0033] In the following examples, "room temperature" can be 20℃±5℃.

[0034] Example

[0035] Preparation of Bi₂O₂CO₃ by hydrothermal assisted coprecipitation:

[0036] Weigh 8 mmol of bismuth nitrate pentahydrate and dissolve it in 20 mL of acetic acid. Stir the solution on a magnetic stirrer for 30 min at room temperature until it is fully dissolved to obtain a bismuth nitrate solution.

[0037] Weigh 4 mmol of sodium citrate dihydrate and dissolve it in 20 mL of deionized water. Stir the solution on a magnetic stirrer for 30 min at room temperature to ensure complete dissolution and obtain an aqueous solution of sodium citrate.

[0038] A sodium citrate aqueous solution was slowly added dropwise to a bismuth nitrate solution at a rate of 10 mL / h for a co-precipitation reaction for 1 h. After the reaction was complete, the pH of the mixed solution was adjusted to approximately 7.5 by slowly adding NaOH aqueous solution. The resulting mixture was transferred to a hydrothermal reactor, sealed, and then transferred to a forced-air drying oven and heated at 180 °C for 12 h. After cooling to room temperature, the product was washed with a mixture of ethanol and water, and then dried in a vacuum oven at 70 °C for 12 h to obtain bismuth oxycarbonate, denoted as Bi₂O₂CO₃-a.

[0039] The XRD pattern of Bi2O2CO3-a in this embodiment is as follows: Figure 1As shown, Bi₂O₂CO₃ synthesized under hydrothermal assisted coprecipitation exhibits distinct characteristic diffraction peaks. The characteristic peaks of Bi₂O₂CO₃ at 12.95°, 23.90°, 30.30°, 32.73°, 42.31°, 46.96°, and 56.92° correspond one-to-one with the standard diffraction powder card, indicating good crystallinity under hydrothermal assisted coprecipitation. In particular, the sharp diffraction peaks at 30.30° and 56.92° are consistent with the characteristics of Bi₂O₂CO₃.

[0040] Fourier transform infrared (FTIR) spectroscopy was performed on the Bi2O2CO3-a photocatalyst prepared in this embodiment. Figure 2 As shown, Bi2O2CO3-a at 1467 cm⁻¹ -1 1391cm -1 846cm -1 and 550cm -1 Four vibration bands were observed at this location. 1467cm -1 and 1391cm -1 The peak value at that point corresponds to CO3 in Bi2O2CO3. 2- Antisymmetric vibration of the functional group. 846 cm⁻¹ -1 The peak value at that location belongs to CO3. 2- The group experiences out-of-plane bending vibration. 550cm -1 The peak value at that point represents the characteristic tensile vibration of Bi-O.

[0041] The Bi2O2CO3-a photocatalyst prepared in this embodiment was observed using a scanning electron microscope (SEM), and the SEM images are shown below. Figure 3 As shown, Bi2O2CO3-a exhibits a nanoplate shape. Further magnification reveals obvious and uniformly distributed lattice stripes. Combined with the XRD pattern, it can be determined that a Bi2O2CO3 photocatalyst with good crystallinity has been synthesized.

[0042] The EDS spectrum of the Bi2O2CO3-a photocatalyst prepared in this embodiment was observed, as follows: Figure 4 As shown, Bi₂O₂CO₃-a is mainly composed of three elements: bismuth (52.76 wt%), oxygen (29.39 wt%), and carbon (17.85 wt%). XRD and SEM analysis further confirm the synthesis of a Bi₂O₂CO₃ photocatalyst with good crystallinity.

[0043] Comparative Example 1

[0044] Preparation of Bi₂O₂CO₃ by coprecipitation:

[0045] Weigh 8 mmol of bismuth nitrate pentahydrate and dissolve it in 20 mL of acetic acid. Stir the solution on a magnetic stirrer for 30 min at room temperature until it is fully dissolved to obtain a bismuth nitrate solution.

[0046] Weigh 4 mmol of sodium citrate dihydrate and dissolve it in 20 mL of deionized water. Stir the solution on a magnetic stirrer for 30 min at room temperature to ensure complete dissolution and obtain an aqueous solution of sodium citrate.

[0047] A sodium citrate aqueous solution was slowly added dropwise to a bismuth nitrate solution at a rate of 10 mL / h to initiate a coprecipitation reaction for 1 h. After the reaction was complete, the pH of the mixed solution was adjusted to approximately 7.5 by slowly adding NaOH aqueous solution. Stirring was continued for 4 h. Subsequently, the product was washed with a mixture of ethanol and water, and dried in a vacuum oven at 70 °C for 12 h to obtain bismuth oxycarbonate, denoted as Bi₂O₂CO₃- coprecipitate.

[0048] Comparative Example 2

[0049] Preparation of hydrothermal-Bi2O2CO3:

[0050] Weigh 8 mmol of bismuth nitrate pentahydrate and dissolve it in 20 mL of acetic acid. Stir the solution on a magnetic stirrer for 30 min at room temperature until it is fully dissolved to obtain a bismuth nitrate solution.

[0051] Weigh 4 mmol of sodium citrate dihydrate and dissolve it in 20 mL of deionized water. Stir the solution on a magnetic stirrer for 30 min at room temperature to ensure complete dissolution and obtain an aqueous solution of sodium citrate.

[0052] Sodium citrate aqueous solution was directly poured into bismuth nitrate solution, followed by slow dropwise addition of NaOH aqueous solution to adjust the pH of the mixed solution to approximately 7.5. The resulting mixture was transferred to a hydrothermal reactor, sealed, and then transferred to a forced-air drying oven and heated at 180°C for 12 hours. After cooling to room temperature, the product was washed with a mixture of ethanol and water, and then dried in a vacuum oven at 70°C for 12 hours to obtain bismuth oxycarbonate, denoted as Bi₂O₂CO₃-b.

[0053] Application Example 1

[0054] 16 mg of the photocatalytic material prepared in the embodiments of the present invention and Comparative Examples 1 and 2 were added to 40 mL of Rhodamine B aqueous solution. The Rhodamine B content in the aqueous solution was 10 mg / L (CO). The reaction was carried out in the dark for 40 min to reach adsorption-desorption equilibrium. Then, a xenon lamp (300 W, wavelength ≥ 420 nm) was used as the light source, and the photocatalytic reaction was carried out in the sunlight wavelength range for 60 min. During the reaction, 4 mL of the reaction system sample was taken every 20-30 min, centrifuged at 4000 rpm for 3 min, and the degradation efficiency of Rhodamine B was measured and recorded at the maximum absorption wavelength of 554 nm using a UV-Vis spectrophotometer and expressed as C / CO.

[0055] Depend on Figure 5 It can be seen that the photocatalytic performance of Bi₂O₂CO₃ synthesized under the combined effects of coprecipitation and hydrothermal methods is superior to that of Bi₂O₂CO₃ prepared by hydrothermal and coprecipitation methods. This indicates that the addition of the coprecipitation reaction is more conducive to the formation of bismuth oxycarbonate.

[0056] Application Example 2

[0057] Using Bi2O2CO3-a as the photocatalyst in the example, 16 mg of the photocatalyst was added to 40 mL of an aqueous solution of Rhodamine B, with a Rhodamine B content of 10 mg / L (CO). Then, 1 mmol of sodium fluoride was added, and the reaction was carried out in the dark for 40 min to reach adsorption-desorption equilibrium. Then, a xenon lamp (300 W, wavelength ≥ 420 nm) was used as the light source, and the photocatalytic reaction was carried out in the sunlight wavelength range for 60 min. During the reaction, 4 mL of the reaction system sample was taken every 5-10 min, centrifuged at 4000 rpm for 3 min, and the degradation efficiency of Rhodamine B was measured and recorded using a UV-Vis spectrophotometer at the maximum absorption wavelength of 554 nm, expressed as C / CO.

[0058] Application Example 3

[0059] Using Bi2O2CO3-a as the photocatalyst in the example, 16 mg of the photocatalyst was added to 40 mL of an aqueous solution of Rhodamine B, with a Rhodamine B content of 10 mg / L (CO). Then, 1 mmol of sodium chloride was added, and the reaction was carried out in the dark for 40 min to reach adsorption-desorption equilibrium. Then, a xenon lamp (300 W, wavelength ≥ 420 nm) was used as the light source, and the photocatalytic reaction was carried out in the sunlight wavelength range for 60 min. During the reaction, 4 mL of the reaction system sample was taken every 5-10 min, centrifuged at 4000 rpm for 3 min, and the degradation efficiency of Rhodamine B was measured and recorded using a UV-Vis spectrophotometer at the maximum absorption wavelength of 554 nm, expressed as C / CO.

[0060] Application Example 4

[0061] Using Bi2O2CO3-a as the photocatalyst in the example, 16 mg of the photocatalyst was added to 40 mL of an aqueous solution of Rhodamine B, with a Rhodamine B content of 10 mg / L (CO). Then, 1 mmol of sodium bromide was added, and the reaction was carried out in the dark for 40 min to reach adsorption-desorption equilibrium. Then, a xenon lamp (300 W, wavelength ≥ 420 nm) was used as the light source, and the photocatalytic reaction was carried out in the sunlight wavelength range for 60 min. During the reaction, 4 mL of the reaction system sample was taken every 5-10 min, centrifuged at 4000 rpm for 3 min, and the degradation efficiency of Rhodamine B was measured and recorded using a UV-Vis spectrophotometer at the maximum absorption wavelength of 554 nm, expressed as C / CO.

[0062] Application Example 5

[0063] Using Bi2O2CO3-a as the photocatalyst in the example, 16 mg of the photocatalyst was added to 40 mL of an aqueous solution of Rhodamine B, with a Rhodamine B content of 10 mg / L (CO). Then, 1 mmol of sodium iodide was added, and the reaction was carried out in the dark for 40 min to reach adsorption-desorption equilibrium. Then, a xenon lamp (300 W, wavelength ≥ 420 nm) was used as the light source, and the photocatalytic reaction was carried out in the sunlight wavelength range for 60 min. During the reaction, 4 mL of the reaction system sample was taken every 5-10 min, centrifuged at 4000 rpm for 3 min, and the degradation efficiency of Rhodamine B was measured and recorded using a UV-Vis spectrophotometer at the maximum absorption wavelength of 554 nm, expressed as C / CO.

[0064] Depend on Figure 5 It is evident that, except for sodium fluoride, the addition of halide salts significantly improved the photocatalytic performance of Bi₂O₂CO₃, with sodium bromide showing the best improvement. This indicates that the addition of halide salts activates halogen elements into free radicals, significantly reducing the band gap. Combined with... Figure 1 , 2 It is known that adding halide salts does not affect the catalyst itself. Therefore, the effect of sodium bromide concentrations of different mmol / L on performance is further investigated.

[0065] Application Example 6

[0066] Using Bi₂O₂CO₃-a as the photocatalyst in the example, 16 mg of the photocatalyst was added to 40 mL of an aqueous solution of Rhodamine B, with a Rhodamine B content of 10 mg / L (CO). Different concentrations of sodium bromide were added, at amounts of 0.1 mmol, 0.5 mmol, 1 mmol, 5 mmol, and 10 mmol, respectively. The reaction was carried out in the dark for 40 min until adsorption-desorption equilibrium was reached. Then, a xenon lamp (300 W, wavelength ≥ 420 nm) was used as the light source, and the photocatalytic reaction was carried out for 30 min under sunlight. During this period, 4 mL of the reaction system sample was aspirated every 5-10 min, centrifuged at 4000 rpm, and the degradation efficiency of Rhodamine B was measured and recorded using a UV-Vis spectrophotometer at the maximum absorption wavelength of 554 nm, expressed as C / CO. Specific results are shown below. Figure 5 ,Depend on Figure 5 It can be seen that within the range of sodium bromide dosage of 0.5-1 mmol, the photocatalytic performance of Bi2O2CO3 on Rhodamine B gradually increases with the increase of sodium bromide concentration, playing a positive role.

[0067] In summary, the Bi2O2CO3-halogen salt system can efficiently remove organic pollutants through photocatalysis, and within a certain range, increasing the concentration of halide salts will enhance the photocatalytic degradation ability of the system.

[0068] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An application of a bismuth oxycarbonate photocatalyst, comprising: After adding the bismuth oxycarbonate photocatalyst to an aqueous solution of an alkaline fluorescent dye, a halide salt, selected from sodium chloride, sodium bromide, or sodium iodide, is added. After reaching adsorption-desorption equilibrium under dark conditions, a photocatalytic reaction is carried out within the sunlight wavelength range to remove the alkaline fluorescent dye. The preparation method of the bismuth oxycarbonate photocatalyst includes: 1) Dissolve bismuth nitrate pentahydrate in acetic acid to prepare a 0.4 mol / L bismuth nitrate solution, and then dissolve sodium citrate dihydrate in deionized water to prepare a 0.2 mol / L sodium citrate aqueous solution; 2) The sodium citrate aqueous solution was slowly added dropwise to the bismuth nitrate solution at a volume ratio of 1:1 to carry out a co-precipitation reaction. After the reaction was completed, the pH of the mixed solution was adjusted to 7.

5. 3) Transfer the mixture obtained in step 2) to a hydrothermal reactor, seal it, transfer it to a forced-air drying oven and heat it at 180°C for 12 hours. After cooling to room temperature, wash and dry it to obtain bismuth oxycarbonate photocatalyst.

2. The application according to claim 1, characterized in that, In step 2), the sodium citrate aqueous solution is slowly added dropwise to the bismuth nitrate solution at a rate of 10 mL / h to carry out a co-precipitation reaction for 1 h; and / or in step 3), after cooling to room temperature, the product is washed with a mixture of ethanol and water and then dried in a vacuum oven at 70 °C for 12 h.

3. The application according to claim 1, characterized in that, The dosage of the bismuth oxycarbonate photocatalyst in the aqueous solution of the alkaline fluorescent dye is 0.4 mg / mL.

4. The application according to claim 1, characterized in that, The basic fluorescent dye is one or both of Rhodamine B and methylene blue; and / or the aqueous solution of the basic fluorescent dye contains 10 mg / L of basic fluorescent dye; and / or the pH value of the aqueous solution of the basic fluorescent dye is 3-12.

5. The application according to claim 1, characterized in that, The molar concentration of sodium bromide in the aqueous solution of the basic fluorescent dye is 0.0125~0.025 mol / L.

6. The application according to claim 1, characterized in that, The photocatalytic reaction is carried out at room temperature for at least 15 minutes.

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