A method for preparing Bi2O(OH)2SO4 by in-situ redox reaction at a heterogeneous interface

Abstract

The present invention relates to the field of catalyst preparation, and provides a method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction. Using sodium bismuthate dihydrate, sodium sulfite and sulfuric acid as raw materials and water as a solvent, the raw materials are formulated into a solid-liquid mixture; the solid-liquid mixture is stirred at room temperature and normal pressure, and sodium bismuthate is in-situ converted into Bi2O(OH)2SO4 through the redox reaction between sodium bismuthate dihydrate solid and sulfite ions at the solid-liquid interface. The advantages of the present invention are as follows: in the raw materials for preparation of the present invention, water-insoluble sodium bismuthate dihydrate is both an oxidant and a sacrificial template. The preparation process is simple, easy to control, and can reduce the agglomeration of product particles; at the same time, compared with the existing homogeneous hydrothermal method, the method of the present invention can be carried out at room temperature and normal pressure, with simple process, convenient operation, low requirements for equipment, and is easy for industrial production.

Description

Technical Field

[0001] The present invention relates to the field of catalyst preparation, and particularly to a method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction. Background Art

[0002] Semiconductor photocatalytic technology can utilize solar energy to degrade environmental pollutants or decompose water to produce hydrogen, which is of great significance for alleviating energy shortage and environmental pollution problems. Photocatalysts are one of the core elements of this technology. Bismuth oxyhydroxysulfate Bi2O(OH)2SO4 is a new type of wide-bandgap semiconductor material with a bandgap of about 4.18 eV at room temperature. Recent studies have shown that it is a potential excellent photocatalytic material.

[0003] Currently, the preparation of Bi2O(OH)2SO4 mostly adopts homogeneous hydrothermal methods:

[0004] Teng Fei et al. added a mixed solution of bismuth nitrate and sodium sulfate into a high-pressure reaction kettle, maintained it at 50 - 100 °C for 12 - 24 h, and obtained a flower-like Bi2O(OH)2SO4 photocatalyst after centrifugation and drying (CN 103785425A, publication date: May 14, 2014).

[0005] Teng Fei et al. added a mixed solution of bismuth nitrate and sodium sulfate or sodium sulfite into a high-pressure reaction kettle, maintained it at 110 - 180 °C for 12 - 24 h, and obtained a hexagonal hollow tubular Bi2O(OH)2SO4 photocatalyst after centrifugation and drying (CN 103787413A, publication date: May 14, 2014).

[0006] Pang Lu et al. added a mixed solution of hydrogen peroxide, bismuth nitrate and sodium sulfate into a polytetrafluoroethylene liner, carried out a constant-temperature hydrothermal reaction at 80 - 180 °C for 2 - 24 h, and obtained a nanorod Bi2O(OH)2SO4 catalyst after centrifugation, washing and drying (CN104874409A, publication date: September 2, 2015).

[0007] Zhang Junjun et al. added a mixed solution of bismuth nitrate and sodium dodecyl sulfate into a polytetrafluoroethylene liner, maintained it at 170 °C for 7 h, and obtained Bi2O(OH)2SO4 nanobelts after collecting and drying the product (Large-scale synthesisof self-assembled ultralong cannonite nanobelt film as a visible-lightphotocatalyst, Zhang Junjun et al., RSC Adv., 2015, 5, 8537–8543, 2015).

[0008] Wang Shuang et al. added a mixed solution of bismuth nitrate and sodium sulfate into a high-pressure reactor, kept it at 90°C for 24 hours, and obtained Bi2O(OH)2SO4 after centrifugation, washing and drying (High photocatalytic performance of Bi2O(OH)2SO4: Based on dual anion synergistic effect, Wang Shuang et al., Materials Letters, 2021, 284, 128899, 2021).

[0009] However, although the above homogeneous hydrothermal method can prepare Bi2O(OH)2SO4, the particles produced during the preparation process are easy to agglomerate. It is usually difficult to control the Bi2O(OH)2SO4 product with less aggregation and uniform particle size distribution. At the same time, the reaction temperature is high, and a closed hydrothermal reactor that can withstand pressure is required, which places high requirements on the equipment.

[0010] Therefore, developing a Bi2O(OH)2SO4 preparation method that is easy to control and has simple processes and equipment is still a direction that urgently needs in-depth research in this field. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a method for preparing Bi2O(OH)2SO4 by in-situ redox reaction at a heterogeneous interface. The method has simple process, is easy to control, can reduce the agglomeration of product particles, can be carried out at room temperature and normal pressure, and has low equipment requirements.

[0012] The present invention adopts the following technical solutions to solve the above technical problems:

[0013] A method for preparing Bi2O(OH)2SO4 by in-situ redox reaction at a heterogeneous interface, comprising: using water-insoluble sodium bismuthate dihydrate (NaBiO3·2H2O), water-soluble sodium sulfite (Na2SO3) and sulfuric acid (H2SO4) as raw materials, and using water as a solvent, preparing the raw materials into a solid-liquid mixture; stirring the solid-liquid mixture at room temperature and pressure, and converting the sodium bismuthate in-situ into Bi2O(OH)2SO4 by a redox reaction between sodium bismuthate dihydrate solid and sulfite ions at the solid-liquid interface, and the reaction process is as follows:

[0014] .

[0015] As one of the preferred embodiments of the present invention, the molar ratio of the sodium bismuthate dihydrate, sodium sulfite and sulfuric acid is 1:1:1.

[0016] As one of the preferred embodiments of the present invention, the stirring reaction time of the solid-liquid mixture at room temperature and pressure is 10 to 30 hours.

[0017] As one of the preferred embodiments of the present invention, the room temperature specifically refers to: 20~30°C, such as 20°C, 25°C, 30°C, etc., based on the temperature during preparation; the normal pressure refers to one atmospheric pressure, i.e., 0.1 Mpa.

[0018] As one of the preferred embodiments of the present invention, after converting sodium bismuthate into Bi2O(OH)2SO4, the following steps are further included:

[0019] Centrifuge and separate the obtained product, wash it with distilled water, and dry it under vacuum to obtain the final nano-sized Bi2O(OH)2SO4 powder.

[0020] As one of the preferred embodiments of the present invention, after the distilled water washing operation, it is specifically dried under vacuum at 60°C and a vacuum degree of 0.1 Mpa for 2 h.

[0021] As one of the preferred embodiments of the present invention, in the finally obtained product, the average grain size of Bi2O(OH)2SO4 is 93.5~99.7 nm.

[0022] The advantages of the present invention compared with the prior art are as follows:

[0023] The present invention provides a method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction, using water-insoluble sodium bismuthate dihydrate, water-soluble sodium sulfite, and sulfuric acid as raw materials, and in-situ converting sodium bismuthate into Bi2O(OH)2SO4 through the redox reaction at the solid-liquid interface; among them, the "water-insoluble sodium bismuthate dihydrate" is both an oxidant and a sacrificial template, the preparation process is simple, easy to control, and can reduce the agglomeration of product particles (in-situ conversion and deposition on the solid surface can inhibit the migration of product particles and reduce polymerization and agglomeration); at the same time, compared with the existing homogeneous hydrothermal method, the method of the present invention can be carried out at room temperature and normal pressure, the process is simple, the operation is convenient, the equipment requirements are low, and it is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a transmission electron microscope photograph of the product of Example 1 of the present invention (in the figure, the scale bar length is 500 nm);

[0025] Figure 2 It is an XRD pattern of the products of each example and comparative example of the present invention (referring to the XRD of sodium bismuthate dihydrate and bismuthyl sulfate hydroxide). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following is a detailed description of the embodiments of the present invention. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments. For the reagent products and experimental methods used in the following embodiments and comparative examples, unless otherwise specified, they are all conventional reagents or methods in the art and will not be elaborated.

[0027] Example 1

[0028] A method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction in this example:

[0029] (1) Add 0.01 mol of sodium bismuthate dihydrate, 0.01 mol of sodium sulfite, and 0.01 mol of sulfuric acid to 40 ml of distilled water to obtain a solid-liquid mixture.

[0030] (2) Stir and react the solid-liquid mixture obtained in step (1) at room temperature and normal pressure (25 °C, 0.1 Mpa) for 10 h. Through the redox reaction between sodium bismuthate solid and sulfite ions at the solid-liquid interface, sodium bismuthate is in-situ converted into Bi2O(OH)2SO4. The reaction process is as follows:

[0031] .

[0032] (3) Centrifuge and separate the product obtained in step (2), wash it with distilled water, and vacuum dry it at 60 °C and 0.1 Mpa vacuum for 2 h to obtain nano-sized Bi2O(OH)2SO4 powder.

[0033] The transmission electron microscope photograph of the final product in this example is as Figure 1 shown.

[0034] At the same time, XRD analysis was carried out on the final product of this example ( Figure 2 ): In its XRD pattern, only the characteristic diffraction peaks of Bi2O(OH)2SO4 are present, and there are no diffraction peaks of other phases, indicating that after 10 h of redox reaction, sodium bismuthate is completely converted into Bi2O(OH)2SO4. According to the Scherrer formula, the average grain size of Bi2O(OH)2SO4 in the product is 93.5 nm.

[0035] Example 2

[0036] A method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction in this example:

[0037] (1) Add 0.01 mol of sodium bismuthate dihydrate, 0.01 mol of sodium sulfite, and 0.01 mol of sulfuric acid to 40 ml of distilled water to obtain a solid-liquid mixture.

[0038] (2) Stir and react the solid-liquid mixture obtained in step (1) at room temperature and normal pressure (25 °C, 0.1 Mpa) for 20 h. Through the redox reaction between sodium bismuthate dihydrate solid and sulfite ions at the solid-liquid interface, sodium bismuthate is in-situ converted into Bi2O(OH)2SO4. The reaction process is as follows:

[0039] 。

[0040] (3) Centrifuge and separate the product obtained in step (2), wash it with distilled water, and vacuum dry it at 60 °C and 0.1 Mpa vacuum for 2 h to obtain nano-sized Bi2O(OH)2SO4 powder.

[0041] Perform XRD analysis on the final product of this example ( Figure 2 ): In its XRD pattern, there are only characteristic diffraction peaks of Bi2O(OH)2SO4, and no diffraction peaks of other phases are present, indicating that after 20 h of redox reaction, sodium bismuthate is completely converted into Bi2O(OH)2SO4. Calculated according to the Scherrer formula, the average grain size of Bi2O(OH)2SO4 in the product is 97.3 nm.

[0042] Example 3

[0043] A method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction in this example:

[0044] (1) Add 0.01 mol of sodium bismuthate dihydrate, 0.01 mol of sodium sulfite, and 0.01 mol of sulfuric acid to 40 ml of distilled water to obtain a solid-liquid mixture.

[0045] (2) Stir and react the solid-liquid mixture obtained in step (1) at room temperature and normal pressure (25 °C, 0.1 Mpa) for 30 h. Through the redox reaction between sodium bismuthate dihydrate solid and sulfite ions at the solid-liquid interface, sodium bismuthate is in-situ converted into Bi2O(OH)2SO4. The reaction process is as follows:

[0046] 。

[0047] (3) Centrifuge and separate the product obtained in step (2), wash it with distilled water, and vacuum dry it at 60 °C and 0.1 Mpa vacuum for 2 h to obtain nano-sized Bi2O(OH)2SO4 powder.

[0048] Perform XRD analysis on the final product of this example ( Figure 2): In its XRD pattern, there are only characteristic diffraction peaks of Bi2O(OH)2SO4, and no diffraction peaks of other phases are present, indicating that after 30 h of redox reaction, sodium bismuthate is completely converted into Bi2O(OH)2SO4. Calculated according to the Scherrer formula, the average grain size of Bi2O(OH)2SO4 in the product is 99.7 nm.

[0049] Comparative example

[0050] A method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction in this comparative example is basically the same as that in Example 1, and the main difference is that: "sodium sulfate" is used instead of "sodium sulfite" in Example 1 for the reaction.

[0051] XRD analysis was performed on the product of this comparative example ( Figure 2 ): In its XRD pattern, there are only characteristic diffraction peaks of the raw material "sodium bismuthate dihydrate"; it shows that after 10 h, no chemical reaction occurs to sodium bismuthate.

[0052] Based on the above results, it can be seen that:

[0053] (1) After mixing sodium bismuthate dihydrate, sodium sulfite and sulfuric acid in distilled water according to a molar ratio of 1:1:1 and stirring and reacting at room temperature for 10 h, 20 h, and 30 h respectively, the average grain sizes of the obtained product Bi2O(OH)2SO4 are 93.5 nm, 97.3 nm, and 99.7 nm respectively; it shows that with the extension of the stirring reaction time, the average grain size of Bi2O(OH)2SO4 slightly increases; during the preparation process, the average grain size of the product nano-Bi2O(OH)2SO4 can be controlled by controlling the stirring reaction time;

[0054] (2) The presence of the reducing agent "sodium sulfite" is necessary for the formation of the Bi2O(OH)2SO4 product. When using non-reducing "sodium sulfate" to replace "sodium sulfite" in the present invention, sodium bismuthate is not reduced, and the product is still sodium bismuthate, and the Bi2O(OH)2SO4 product cannot be obtained.

[0055] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing Bi2O(OH)2SO4 by in-situ redox reaction at a heterogeneous interface, characterized in that, Using sodium bismuthate dihydrate, sodium sulfite and sulfuric acid as raw materials and water as a solvent, a solid-liquid mixture is prepared from the raw materials; the solid-liquid mixture is stirred at room temperature and normal pressure, and sodium bismuthate is in-situ converted into Bi2O(OH)2SO4 through the redox reaction between sodium bismuthate solid and sulfite ions at the solid-liquid interface. The reaction process is as follows: 。 2. The method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction according to claim 1, characterized in that, The molar ratio of the sodium bismuthate dihydrate, sodium sulfite and sulfuric acid is 1:1:

1.

3. The method for preparing Bi2O(OH)2SO4 by in-situ redox reaction at the heterogeneous interface according to claim 1, wherein The stirring reaction time of the solid-liquid mixture at room temperature and normal pressure is 10 - 30 h.

4. The method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction according to claim 1, characterized in that, The specific room temperature and normal pressure refer to: 20 - 25 °C and one atmosphere.

5. The method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction according to any one of claims 1 to 4, characterized in that, After converting sodium bismuthate into Bi2O(OH)2SO4, the following steps are further included: The obtained product is centrifuged, washed with distilled water and vacuum dried to obtain the final nano-Bi2O(OH)2SO4 powder.

6. The method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction according to claim 5, characterized in that, After the distilled water washing operation, it is specifically vacuum dried at 60 °C and a vacuum degree of 0.1 Mpa for 2 h.

7. The method for preparing Bi2O(OH)2SO4 by heterogeneous interface in-situ redox reaction according to claim 5, characterized in that, In the finally obtained product, the average grain size of Bi2O(OH)2SO4 is 93.5 - 99.7 nm.

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