Preparation method and application of ultra-efficient nitrate-based free radical activation catalyst

Abstract

The invention relates to a preparation method and application of an ultra-efficient nitrate-based free radical activation catalyst, and the preparation method comprises the following steps: S1, dissolving bismuth nitrate Bi (NO3) 3.5 H2O and polyvinylpyrrolidone (PVP) in a mannitol solution; s2, adding potassium bromide into the solution in the step S1, and performing ultrasonic treatment to form a white suspension; s3, transferring the suspension into a high-pressure reaction kettle for hydrothermal reaction; and S4, after the reaction is completed, cooling, centrifugally collecting precipitates, washing, and carrying out vacuum freeze drying to obtain the bismuth oxybromide BixOBr nanosheet catalyst. According to the application of the super-efficient nitrate-based free radical activation catalyst in degradation of organic pollutants, the bismuth oxybromide BixOBr nanosheet catalyst is added into a water body containing nitrate, the nitrate is activated to generate free radicals by utilizing the piezoelectric effect induced by photoinduced deformation of the photocatalyst under the condition that an external electric field and an oxidizing agent are not needed, and the degradation efficiency of the nitrate-based free radical activation catalyst is improved. Therefore, organic pollutants are degraded.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental functional materials, and particularly to a preparation method of a super-efficient nitrate-based free radical activation catalyst and its application in catalytic degradation of organic pollutants. Background Art

[0002] With the increasing global attention to environmental pollution and energy consumption problems, photocatalysis / piezoelectrocatalysis technology, as a green and sustainable catalytic method, has attracted extensive attention in solving environmental problems. Piezoelectrocatalysis technology has shown great potential in environmental governance. The photo-induced deformation phenomenon refers to the deformation of the material structure under light illumination, which triggers its piezoelectric effect, and photo-piezoelectrocatalysis utilizes this effect to activate chemical reactions. In the field of pollutant degradation, photocatalysis technology has been widely studied, especially in the treatment of organic pollutants, such as the degradation of organophosphorus flame retardants. These chemical substances pose a serious threat to the ecological environment and human health due to their toxicity and persistence. Therefore, the development of efficient photo / piezoelectrocatalytic materials for activating nitrate to generate free radicals and then degrading organic pollutants has become an important direction in environmental remediation research.

[0003] Currently, traditional photocatalytic methods face challenges of low catalytic efficiency and slow reaction rate when treating organophosphorus pollutants. Photoelectricity can cause the deformation of materials, thereby enhancing the piezoelectric effect of the materials, improving their electron transfer ability, and promoting the occurrence of reactions. During the nitrate activation process, the light-induced deformation effect can effectively promote the generation of highly active free radicals from nitrate, and these free radicals can react with organic substances to achieve their degradation. Such reactions are usually carried out under mild conditions, which can not only improve the catalytic efficiency but also reduce by-products and environmental pollution during the reaction process, and it is an ideal green catalytic technology.

[0004] However, although the photo-voltage-piezoelectricity synergistic catalysis technology shows excellent application prospects, there are still certain technical bottlenecks. First, the selection and design of photocatalytic materials are crucial. The materials must have good photo-induced deformation characteristics and high-efficiency photocatalytic performance. Currently, researchers have designed some nanomaterials and composite materials, such as doped elements or modified photocatalysts, to enhance the photo-induced deformation effect and catalytic activity of the materials. Secondly, the free radical generation mechanism and degradation pathway in the reaction system still need to be further studied to achieve more efficient pollutant degradation. In addition, how to improve the stability and reusability of photocatalytic materials in practical applications is also an important topic in current research.

[0005] It should be noted that the information disclosed in the above background art section is only used for understanding the background of the present application, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] The main object of the present invention is to overcome the defects existing in the above-mentioned background technology, and to provide a preparation method and application of a super-efficient nitrate-based radical activation catalyst.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A preparation method of a super-efficient nitrate-based radical activation catalyst, comprising the following steps: S1: Dissolve bismuth nitrate Bi(NO3)3·5H2O and polyvinylpyrrolidone PVP in a mannitol solution; S2: Add potassium bromide KBr to the solution in step S1, and perform ultrasonic treatment to form a white suspension; S3: Transfer the suspension to a high-pressure reaction kettle for hydrothermal reaction; S4: After the reaction is completed, cool, centrifuge to collect the precipitate, wash, and vacuum freeze-dry to obtain a bismuth oxybromide Bi x OBr nanosheet catalyst.

[0008] Further, in step S1, according to the following ratio: the dosage of bismuth nitrate is within 50 mg, the molecular weight of PVP is 10,000, the dosage is within 5 g, the concentration of the mannitol solution is within 0.2 M, and the volume is within 100 mL.

[0009] Further, in step S1, magnetic stirring is performed for a time within 60 minutes.

[0010] Further, in step S2, the dosage of potassium bromide is within 1000 mg, and the ultrasonic treatment time is within 60 minutes.

[0011] Further, in step S3, the temperature of the hydrothermal reaction is within 200°C, and the reaction time is within 3 hours.

[0012] Further, in step S4, the vacuum freeze-drying time is within 50 hours.

[0013] Further, in step S4, washing is performed with water and ethanol in sequence. The specific method of ethanol washing is: add ethanol to the precipitate, and remove the supernatant after centrifugal separation.

[0014] An application of the super-efficient nitrate-based radical activation catalyst in degrading organic pollutants, adding the bismuth oxybromide Bi x OBr nanosheet catalyst to a water body containing nitrate, and using the piezoelectric effect induced by its photoinduced deformation to activate nitrate to generate free radicals without the need for an external electric field and oxidant, thereby degrading organic pollutants.

[0015] Further, 10 - 100 mg of Bix The OBr nanocatalyst is added to a 200 mL solution containing nitrate and organic pollutants; the nitrate is potassium nitrate with a concentration of 0 - 100 mg / L; the organic pollutant is tributyl phosphate with a concentration of 0 - 100 mg / L.

[0016] Furthermore, the illumination wavelength of the light source is in the range of 200 - 800 nm, and the illumination intensity is 0 - 200 mW / cm 2 , and mechanical perturbation treatment is carried out, for example, stirring is performed at a speed within 1000 r / min.

[0017] The present invention has the following beneficial effects: The present invention provides a preparation method and application of a super-efficient nitrate-based radical activation catalyst. By innovatively preparing bismuth oxybromide (Bi x OBr) nanomaterials with both photoinduced deformation effect and piezoelectric effect, it successfully solves the technical bottlenecks such as low catalytic efficiency and slow reaction rate existing in traditional photocatalytic technologies when treating organophosphorus pollutants. The main advantages of the present invention are as follows: The prepared Bi x OBr nanosheet catalyst can achieve the piezoelectric-photocatalytic dual-driving effect under light irradiation and mechanical stirring conditions. Through the piezoelectric effect induced by photoinduced deformation, nitrate in water is synergistically activated to efficiently generate hydroxyl radicals and reactive nitrogen species, and the efficient degradation of organic pollutants can be achieved under mild conditions without the addition of an external electric field and oxidant. It is particularly suitable for the treatment of industrial wastewater containing coexisting nitrate and organic pollutants. The catalyst prepared by the present invention has the characteristics of cheap and easily available raw materials, simple synthesis process, good chemical stability, and recyclability. The degradation efficiency of the typical organophosphorus flame retardant tributyl phosphate (TnBP) can reach more than 99.9%. It not only realizes additive-free and harmless operation in the sewage treatment process, avoids secondary pollution, but also can recycle inorganic nitrogen and organic matter, providing a green, efficient, and economically feasible new solution for the advanced treatment of industrial wastewater, and has significant environmental benefits and application prospects.

[0018] Other beneficial effects in the embodiments of the present invention will be further described below. Detailed Embodiments

[0019] The following gives a detailed description of the embodiments of the present invention. It should be emphasized that the following description is merely exemplary and not intended to limit the scope of the present invention and its applications.

[0020] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0021] Aiming at the deficiency of weak piezoelectric effect in existing piezophotocatalysis, the present invention provides a preparation method of a Bi x OBr nanocatalyst that simultaneously utilizes the photovoltaic and piezoelectric effects and its application in degrading organic pollutants. The photoinduced deformation of this catalyst can enhance its piezoelectric effect, which is beneficial to enhancing the piezoelectric activation of nitrate to produce free radicals.

[0022] The embodiments of the present invention provide a preparation method of an ultra-high-efficiency nitrate-based free radical activation catalyst, including the following steps: Step S1: Dissolve bismuth nitrate Bi(NO3)3·5H2O and polyvinylpyrrolidone PVP in a mannitol solution; Step S2: Add potassium bromide KBr to the solution in Step S1 and perform ultrasonic treatment to form a white suspension; Step S3: Transfer the suspension to a high-pressure reaction kettle for hydrothermal reaction; Step S4: After the reaction is completed, cool, centrifuge to collect the precipitate, wash, and vacuum freeze-dry to obtain the bismuth oxybromide Bi x OBr nanosheet catalyst. It can be understood that the specific value of x in the present invention is not limited on the premise of satisfying the photoinduced deformation-induced piezoelectric effect of the catalyst, and preferably x = 1 or 2.

[0023] The specific embodiments of the present invention are further described below.

[0024] In some embodiments, the bismuth oxybromide (Bi x OBr) nanocatalyst is obtained by combining metal elements and inorganic elements, and its preparation method includes the following steps: Step S1: Dissolve 0 - 50 mg of Bi(NO3)3·5H2O and 0 - 5 g of PVP (molecular weight 10000) in sequence in 60 mL of 0 - 0.2 M mannitol solution, and magnetically stir for 0 - 60 minutes.

[0025] Step S2: Add 0 - 1000 mg of KBr to the above solution and perform ultrasonic treatment for 0 - 60 minutes.

[0026] Step S3: Transfer the obtained white suspension to a 100 mL polytetrafluoroethylene (PTFE) autoclave and perform hydrothermal treatment at 0 - 200°C for 0 - 3 hours.

[0027] Step S4: After cooling to room temperature, centrifuge to collect the white precipitate and wash it several times with water and ethanol. Finally, obtain Bi x OBr nanosheets by vacuum freeze-drying for 0 - 50 h.

[0028] The specific operation method of ethanol washing in Step S4 is to add ethanol to the solution, then place it in a centrifuge for centrifugal separation, and remove the supernatant.

[0029] In some embodiments, for the application of a bismuth oxybromide (Bi x OBr) nanocatalyst, weigh 10 - 100 mg of the Bi x OBr nanocatalyst and put it into a container, add it to a mixed solution of 200 mL of tributyl phosphate (0 - 100 mg / L) and potassium nitrate (0 - 50 mg / L), and place the mixed solution under a light source for irradiation and stirring to test the performance. Activate nitrate to produce free radicals through the photovoltaic and piezoelectric effects, and achieve the efficient removal of organic pollutants with the help of active free radicals. The light wavelength of the light source is 200 - 800 nm, and its intensity is 0 - 200 mW / cm 2 , and the stirring speed is 0 - 1000 r / min.

[0030] In some embodiments, the Bi x OBr nanocatalyst has a photoinduced deformation and piezoelectric effect, and the preparation method includes the following steps: Dissolve 10 mg of Bi(NO3)3·5H2O and 1 g of PVP (molecular weight 10000) in 60 mL of 0.075 M mannitol solution in sequence, and magnetically stir for 30 minutes.

[0031] Add 500 mg of KBr to the above solution and ultrasonically treat for 30 minutes.

[0032] Transfer the obtained white suspension to a 100 mL polytetrafluoroethylene (PTFE) autoclave and perform hydrothermal treatment at 160°C for 2 hours.

[0033] After cooling to room temperature, centrifuge to collect the white precipitate and wash it several times with water and ethanol. Finally, obtain BiOBr nanosheets with photoinduced deformation effect and piezoelectric effect by vacuum freeze-drying for 48 h.

[0034] Dissolve 20 mg of Bi(NO3)3·5H2O and 1 g of PVP (molecular weight 10000) in 60 mL of 0.075 M mannitol solution in sequence, and magnetically stir for 30 minutes.

[0035] Add 500 mg of KBr to the above solution and ultrasonically treat for 30 minutes.

[0036] Transfer the obtained white suspension to a 100 mL polytetrafluoroethylene (PTFE) autoclave and perform hydrothermal treatment at 160 °C for 2 hours.

[0037] After cooling to room temperature, centrifuge to collect the white precipitate and wash it several times with water and ethanol. Finally, obtain Bi2OBr nanosheets with photo-deformation effect and piezoelectric effect through vacuum freeze-drying for 48 h.

[0038] Dissolve 40 mg of Bi(NO3)3·5H2O and 1 g of PVP (molecular weight 10,000) successively in 60 mL of 0.075 M mannitol solution and stir magnetically for 30 minutes.

[0039] Add 500 mg of KBr to the above solution and sonicate for 30 minutes.

[0040] Transfer the obtained white suspension to a 100 mL polytetrafluoroethylene (PTFE) autoclave and perform hydrothermal treatment at 160 °C for 2 hours.

[0041] After cooling to room temperature, centrifuge to collect the white precipitate and wash it several times with water and ethanol. Finally, obtain BiOBr nanosheets with optoelectronic and piezoelectric effects through vacuum freeze-drying for 48 h.

[0042] An application of a Bi x OBr catalyst utilizing optoelectronic and piezoelectric effects to activate nitrate to produce free radicals for degrading organic pollutants.

[0043] An application of a Bi x OBr catalyst with photo-deformation and piezoelectric effects to activate nitrate to produce free radicals for degrading organic pollutants. Weigh 10 - 50 mg of the Bi x OBr nanocatalyst and put it into a container, add it to a mixed solution of 200 mL of tributyl phosphate (0 - 100 mg / L) and potassium nitrate (0 - 100 mg / L), irradiate the mixed solution under a light source and stir it, with the stirring speed of 0 - 1000 r / min.

[0044] The Bi x OBr nanocatalyst prepared by the present invention and its application in activating nitrate to degrade organic pollutants have the following advantages: good chemical stability, designability, recyclability, etc. Moreover, the raw materials are cheap, easily available, green and environmentally friendly, and the synthesis process is simple. And during the degradation process, free radicals can be generated to realize organic pollutants without introducing other oxidants. The Bi xThe OBr material can achieve the piezoelectric-photocatalytic dual-driving effect under light irradiation and stirring, with the degradation efficiency of pollutants reaching over 99.9%. It has the advantages of not requiring an external electric field and oxidant, mild reaction conditions, and stable catalytic activity. This invention is particularly suitable for the deep treatment and resource utilization of industrial wastewater containing coexisting nitrate and organic pollutants.

[0045] In the following examples, the test methods are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0046] In the following examples, the Bi x OBr catalyst was prepared as follows: 3 mg of Bi(NO3)3·5H2O and 0.8 g of PVP (molecular weight 10,000) were successively dissolved in 50 mL of 0.075 M mannitol solution, and magnetically stirred for 10 minutes. 500 mg of KBr was added to the above solution, and ultrasonicated for 30 minutes. The obtained white suspension was transferred to a 100 mL polytetrafluoroethylene (PTFE) autoclave and hydrothermally treated at 160°C for 1 hour. After cooling to room temperature, the white precipitate was collected by centrifugation and washed several times with water and ethanol. Finally, Bi x OBr nanosheets were obtained by vacuum freeze-drying for 48 h.

[0047] Experimental Example 1 20 mg of Bi x OBr nanocatalyst was weighed and placed in 200 mL of a mixed aqueous solution containing 10 mg / L of the organophosphorus flame retardant tributyl phosphate (TnBP) and 30 mg / L of potassium nitrate (KNO3). The reaction system was irradiated under a light source with a wavelength of 200 - 800 nm, the light intensity was 60 mW / cm 2 ², and continuously mechanically stirred at a speed of 600 r / min. After the reaction was completed, through analysis and determination, the removal rate of the organophosphorus flame retardant TnBP reached 90.3%.

[0048] Experimental Example 2 The same experimental conditions as in Experimental Example 1 were adopted, except that the initial concentration of the organophosphorus flame retardant tributyl phosphate (TnBP) was increased to 50 mg / L. After the reaction was completed, through analysis and determination, the removal rate of the organophosphorus flame retardant TnBP reached 95.6%.

[0049] Experimental Example 3 The same experimental conditions as in Experimental Example 1 were adopted, except that the initial concentration of the organophosphorus flame retardant tributyl phosphate (TnBP) was increased to 100 mg / L. After the reaction was completed, through analysis and determination, the removal rate of the organophosphorus flame retardant TnBP reached 99.9%.

[0050] The nano-structure of the optoelectronic enhanced photo-piezoelectric Bi x OBr catalyst prepared by the present invention has a high photo-induced deformation efficiency and a good piezoelectric effect. By using the photo-piezoelectric photocatalytic process of bismuth oxybromide nano-materials to activate nitrate to generate free radicals for degrading organic pollutants, it has the advantages of low preparation cost, mild operating conditions, no three wastes discharge, and environmental friendliness. The present invention not only realizes the additive-free, harmless, stable and resourceful treatment of sewage, solves the problems of low efficiency and easy secondary pollution of traditional sludge treatment methods, but also improves the efficiency of sewage treatment, and at the same time respectively resourcefully utilizes inorganic nitrogen and organic matter, making up for the deficiencies of the prior art and bringing a new solution to the field of sewage treatment.

[0051] The Bi x OBr nano-catalyst prepared by the present invention and its application in activating nitrate to degrade organic pollutants have the following advantages: good chemical stability, designability and recyclability, etc., and also have the advantages of cheap and easily available raw materials, green environmental protection, and simple synthesis process. And no other oxidant needs to be introduced during the degradation process to generate free radicals to realize organic pollutants.

[0052] The Bi x OBr material prepared by the present invention can achieve the dual-drive effect of piezo-photocatalysis under light irradiation and stirring, and the degradation efficiency of pollutants reaches more than 99.9%. It has the advantages of no need for external electric field and oxidant, mild reaction conditions, and stable catalytic activity. The present invention is particularly suitable for the deep treatment and resource utilization of industrial wastewater containing coexisting nitrate and organic pollutants.

[0053] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several alternatives or modifications can be made to these described embodiments, and these alternative or modified forms should all be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description with reference to terms such as "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. Without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the scope of protection of the patent application.

Claims

1. A preparation method of a super-efficient nitrate-based free radical activation catalyst, characterized in that, It includes the following steps: S1: Dissolve bismuth nitrate Bi(NO3)3·5H2O and polyvinylpyrrolidone PVP in a mannitol solution; S2: Add potassium bromide KBr to the solution in step S1 and perform ultrasonic treatment to form a white suspension; S3: Transfer the suspension to a high-pressure reaction kettle for hydrothermal reaction; S4: After the reaction is completed, cool it, centrifuge to collect the precipitate, wash it, and freeze-dry it under vacuum to obtain the bismuth oxybromide Bi x OBr nanosheet catalyst.

2. The preparation method according to claim 1, characterized in that: In step S1, according to the following ratio: the dosage of bismuth nitrate is within 50 mg, the molecular weight of PVP is 10000, the dosage is within 5 g, the concentration of the mannitol solution is within 0.2 M, and the volume is within 100 mL.

3. The preparation method according to claim 1, wherein: In step S1, perform magnetic stirring for a time within 60 minutes.

4. The preparation method according to claim 1, characterized in that: In step S2, the dosage of potassium bromide is within 1000 mg, and the ultrasonic treatment time is within 60 minutes.

5. The preparation method according to claim 1, characterized in that: In step S3, the temperature of the hydrothermal reaction is within 200 °C, and the reaction time is within 3 hours.

6. The preparation method according to claim 1, characterized in that: In step S4, the vacuum freeze-drying time is within 50 hours.

7. The preparation method according to claim 1, wherein: In step S4, wash with water and ethanol in sequence. The specific method of ethanol washing is: add ethanol to the precipitate, and remove the supernatant after centrifugation.

8. Use of the ultra-high efficiency nitrate radical activation catalyst according to any one of claims 1 to 7 in degrading organic pollutants, characterized in that: Add the bismuth oxybromide Bi x OBr nanosheet catalyst to the water body containing nitrate, and utilize the piezoelectric effect induced by its photoinduced deformation to activate nitrate to generate free radicals without the need for an external electric field and oxidant, thereby degrading organic pollutants.

9. The application according to claim 8, characterized in that: Add 10 - 100 mg of Bi x OBr nanocatalyst to 200 mL of a solution containing nitrate and organic pollutants; the nitrate is potassium nitrate with a concentration of 0 - 100 mg / L; the organic pollutant is tributyl phosphate with a concentration of 0 - 100 mg / L.

10. The application according to claim 9, wherein: The illumination wavelength of the light source is in the range of 200 - 800 nm, and the illumination intensity is 0 - 200 mW / cm 2 , and mechanical perturbation treatment is carried out.