A sandwich structured photocatalyst and a preparation method and application thereof

Abstract

The application provides a sandwich-structured photocatalyst, which is constructed by TiO2 nanosheets and a Co-Fe / MOF with bimetallic activity, the TiO2 nanosheets are covered on the surface of the Co-Fe / MOF to form a layered sandwich structure, and the Co-Fe / MOF is a metal organic framework compound prepared from a precursor of uniform trimellitic acid, cobalt and iron. The precursor of cobalt and iron is stirred and dissolved in an organic solvent, the TiO2 nanosheets are dispersed and immersed in the precursor solution, then the uniform trimellitic acid is added into the immersion liquid to be stirred and ultrasonically dispersed, and then the reaction is carried out in an autoclave by heating, the reaction liquid is centrifuged, washed and vacuum dried to obtain the sandwich-structured photocatalyst TiO2NS@Co-Fe / MOF. The preparation method of the sandwich-structured photocatalyst is simple in reaction system and simple in preparation process, and is suitable for large-scale production. The photocatalyst prepared by the application combines the double functions of the TiO2 nanosheet photocatalysis and the Co-Fe / MOF heterogeneous Fenton interface catalysis, plays a synergistic effect, and can effectively degrade phenolic substances in wastewater.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a sandwich-structured photocatalyst, its preparation method, and its application. Background Technology

[0002] Phenolic wastewater has a wide range of pollution, is highly toxic, stable, and difficult to degrade, posing serious harm to humans, water bodies, fish, and crops. Currently, there are three main methods for phenol removal from wastewater: chemical, physical, and biological methods. Physical methods include extraction, incineration, and adsorption; chemical methods include chemical (photo)oxidation, ultraviolet oxidation, ion exchange, and chemical precipitation; and biological methods include biological filters and activated sludge.

[0003] Photocatalytic oxidation and Fenton oxidation technologies are favored by researchers in the field of environmental protection, especially in the degradation and removal of low-concentration phenol-containing wastewater, due to their advantages such as non-toxicity, low cost, and ease of operation. Both technologies have certain effects in the treatment of phenol-containing wastewater, but each has its limitations. Heterogeneous Fenton oxidation overcomes the disadvantages of homogeneous Fenton oxidation, which requires acidic conditions (pH=3) and produces large amounts of iron sludge due to catalyst loss, and is widely used in the degradation of pollutants in industries such as pesticides, dyes, pharmaceuticals, and cosmetics. However, heterogeneous Fenton oxidation technology has some serious drawbacks, mainly manifested in low catalyst activity, poor stability, slow Fe(II) regeneration kinetics, and high H2O2 consumption. TiO2, the most commonly used catalyst in photocatalysis, also has shortcomings in practical applications. TiO2 has an excessively large band gap, only absorbing ultraviolet light below 380nm, resulting in low solar energy utilization. Furthermore, TiO2 has a high photoelectron-hole recombination rate and a low quantum yield, limiting its photocatalytic performance. Summary of the Invention

[0004] This patented technology provides a sandwich-structured photocatalyst, its preparation method, and its application. This photocatalyst combines photocatalytic oxidation technology with Fenton oxidation technology to obtain a photo-Fenton oxidation system, which can simultaneously solve the problems of low electron density in Fenton oxidation technology and easy recombination of photoelectrons and holes in TiO2 photocatalysis technology, thereby effectively improving catalytic performance.

[0005] This invention provides a method for preparing a sandwich-structured TiO2NS@Co-Fe / MOF photocatalyst by in-situ growth of bimetallic active MOFs on the surface of TiO2 nanosheets. The photocatalyst prepared by this invention combines the dual functions of TiO2 nanosheet photocatalysis and Co-Fe / MOF multiphase Fenton interface catalysis, exerting a synergistic effect and effectively degrading phenolic substances in wastewater.

[0006] To address the problems mentioned in the background art, the present invention provides the following technical solutions:

[0007] A method for preparing a sandwich-structured photocatalyst includes the following steps:

[0008] S1: Add cobalt and iron precursors to an organic solvent and stir until homogeneous to prepare a cobalt and iron precursor solution;

[0009] S2: Add TiO2 nanosheets to the cobalt and iron precursor solution, stir evenly, and obtain the impregnation solution by impregnating the iron and cobalt metal ions on the surface of TiO2 nanosheets.

[0010] S3: Add trimesic acid (TMA) to the impregnation solution, stir and then sonicate to obtain a mixture;

[0011] S4: Place the mixture in a polytetrafluoroethylene high-pressure reactor, heat and react. After the reaction is complete, centrifuge, wash and vacuum dry the reaction solution to obtain a sandwich-structured photocatalyst.

[0012] Furthermore, the organic solvent mentioned in S1 is N,N-dimethylformamide or methanol.

[0013] Furthermore, the precursors of cobalt and iron in S1 include cobalt and iron nitrates and chlorides.

[0014] Furthermore, the molar ratio of the cobalt and iron precursors used in S1 is 1:0.2 to 5.

[0015] Furthermore, the molar ratio of cobalt and iron precursors to TiO2 nanosheets in S2 is 1:5 to 20.

[0016] Furthermore, the molar ratio of the amount of cobalt and iron precursors in S3 to the amount of trimesic acid is 1:1 to 5.

[0017] Furthermore, the reaction conditions in S4 are: reaction temperature 70–120°C, reaction time 8–15 h.

[0018] The present invention also provides a sandwich-structured photocatalyst prepared by the above method. The photocatalyst is constructed from TiO2 nanosheets and bimetallic active Co-Fe / MOF. The TiO2 nanosheets cover the surface of Co-Fe / MOF to form a layered sandwich structure. The Co-Fe / MOF is a metal-organic framework compound prepared from trimesic acid and cobalt and iron precursors.

[0019] The present invention also provides the following technical solution, which applies the above-mentioned sandwich-structured photocatalyst to the photo-Fenton oxidation degradation of phenolic substances in wastewater.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention provides a sandwich-structured photocatalyst, which is constructed from TiO2 nanosheets and bimetallic active Co-Fe / MOF. The TiO2 nanosheets cover the surface of Co-Fe / MOF to form a layered sandwich structure. The Co-Fe / MOF is a metal-organic framework compound prepared from trimesic acid and cobalt and iron precursors.

[0022] This invention also provides a method for preparing a sandwich-structured photocatalyst. The method involves dissolving cobalt and iron precursors in an organic solvent, dispersing and impregnating TiO2 nanosheets in the precursor solution, adding trimellitic acid to the impregnation solution, stirring and ultrasonically dispersing, and then heating the mixture in an autoclave. The reaction solution is then centrifuged, washed, and vacuum dried to obtain the sandwich-structured photocatalyst TiO2NS@Co-Fe / MOF. This method for preparing the sandwich-structured photocatalyst features a simple reaction system, a convenient preparation process, and is suitable for large-scale production.

[0023] The photocatalyst prepared by this invention combines the dual functions of TiO2 nanosheet photocatalysis and Co-Fe / MOF multiphase Fenton interface catalysis, exerting a synergistic effect and effectively degrading phenolic substances in wastewater. Attached Figure Description

[0024] Figure 1 Here is a SEM image of the sandwich-structured photocatalyst in Example 1;

[0025] Figure 2 The EDS spectrum of the sandwich-structured photocatalyst in Example 1;

[0026] Figure 3 This is a comparison chart of the photocatalytic efficiency of TiO2NS@Co-Fe / MOF photocatalyst, TiO2 nanosheets, and Co-Fe / MOF. Detailed Implementation

[0027] To make the technical means, features, and effects of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to specific implementation methods and the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Example 1:

[0029] A method for preparing a sandwich-structured photocatalyst includes the following steps:

[0030] S1: Add 0.24g CoCl2·6H2O and 0.81g FeCl3·6H2O to 100mL DMF, stir well, and prepare a precursor solution of cobalt and iron;

[0031] S2: Add 3.20g of TiO2 nanosheets to the cobalt and iron precursor solution, stir evenly, and disperse iron and cobalt metal ions on the surface of TiO2 nanosheets by impregnation to obtain impregnation solution;

[0032] S3: Add 1.68g of trimesic acid (TMA) to the impregnation solution, stir and then sonicate to obtain a mixture;

[0033] S4: The mixture was placed in a polytetrafluoroethylene high-pressure reactor, heated to 90°C, and reacted for 10 hours. After the reaction was completed, it was cooled, centrifuged and settled, and washed with water, DMF and CH3OH respectively. The resulting solid was dried in a vacuum drying oven at 60°C for 1 hour to obtain a sandwich-structured photocatalyst.

[0034] like Figure 1 The SEM image of the sandwich-structured photocatalyst in Example 1 is shown. As can be seen from the image, the TiO2@Co-Fe / MOF structure prepared in this example has a sheet-like structure with a thickness of about 20 nm and a length of about 60 nm. Compared with TiO2 nanosheets (thickness of about 7-8 nm and length of about 40 nm), its thickness and length have both increased.

[0035] from Figure 1 Preliminary SEM results indicate that after TiO2 and Co-Fe / MOF are combined, TiO2 covers the surface of Co-Fe / MOF, resulting in TiO2@Co-Fe / MOF with a sandwich structure.

[0036] like Figure 2 The EDS (Energy Dispersive Spectroscopy) spectrum of the sandwich-structured photocatalyst in Example 1 is shown. The prepared photocatalyst is composed of C, O, Ti, Fe, and Co. The elemental composition of the catalyst is shown in Table 1. Table 1 shows that the weight percentage of C in the TiO2@Co-Fe / MOF sample is 41.87%, O is 28.26%, Ti is 27.16%, Fe is 2.46%, and Co is 0.26%; the atomic percentage of C is 59.41%, O is 30.11%, Ti is 9.66%, Fe is 0.75%, and Co is 0.07%. The EDS spectrum indicates that TiO2 nanosheets have been successfully composited with Co-Fe / MOF to form the photocatalyst TiO2@Co-Fe / MOF.

[0037] Table 1. Compositional analysis of TiO2@Co-Fe / MOF

[0038]

[0039] The photocatalyst prepared in Example 1 was used for photo-Fenton oxidation degradation of phenol-containing wastewater, wherein the phenol content in the wastewater was 5000 ppm. The specific treatment method was as follows:

[0040] 100g of phenol-containing wastewater was added to a four-necked flask. 1.0g of the photocatalyst prepared in Example 1 was added to the wastewater. The mixture was stirred in the dark for 30 minutes to allow the catalyst to reach adsorption equilibrium. Under ultraviolet-visible light, 3.5g of 30% hydrogen peroxide was added with stirring. The reaction was started and a timer was set. Samples were taken every 10 minutes, and solid impurities were removed by filtration. After quenching with excess tert-butanol, the concentrations of phenolic substances and H2O2 were determined by high-performance liquid chromatography.

[0041] Meanwhile, for comparison, TiO2 nanosheets and Co-Fe / MOF were used as catalysts to perform photo-Fenton degradation oxidation of phenolic wastewater under the same conditions. The photocatalytic efficiency data were plotted in graphs, such as... Figure 3 As shown, the three catalysts continuously degraded phenol-containing wastewater for 60 minutes, resulting in TiO2 nanosheets with a photocatalytic efficiency of 56.8%, Co-Fe / MOF with a photocatalytic efficiency of 60.5%, and TiO2@Co-Fe / MOF with a photocatalytic efficiency of 74.5%.

[0042] The photocatalytic efficiency of TiO2@Co-Fe / MOF is significantly improved compared to the other two materials, which is related to the unique interface structure and bimetallic active electronic structure of the composite material.

[0043] Example 2

[0044] A method for preparing a sandwich-structured photocatalyst includes the following steps:

[0045] S1: Add 1.46g Co(NO3)2·6H2O and 0.40g Fe(NO3)3·9H2O to 100mL DMF, stir well, and prepare a precursor solution of cobalt and iron;

[0046] S2: Add 2.40g of TiO2 nanosheets to the cobalt and iron precursor solution, stir evenly, and disperse iron and cobalt metal ions on the surface of TiO2 nanosheets by impregnation to obtain impregnation solution;

[0047] S3: Add 1.26g of TMA to the impregnation solution, stir and then sonicate to obtain a mixture;

[0048] S4: The mixture was placed in a polytetrafluoroethylene high-pressure reactor, heated to 70°C, and reacted for 15 hours. After the reaction was completed, it was cooled, centrifuged and settled, washed with water, DMF and CH3OH respectively, and the resulting solid was dried in a vacuum drying oven at 60°C for 1 hour to obtain a sandwich-structured photocatalyst.

[0049] The photocatalyst TiO2@Co-Fe / MOF prepared in Example 2 was used for photo-Fenton oxidation degradation of phenol-containing wastewater. Under the same calculation method as in Example 1, the photocatalytic efficiency was 68.8%.

[0050] Example 3

[0051] A method for preparing a sandwich-structured photocatalyst includes the following steps:

[0052] S1: Add 0.29g Co(NO3)2·6H2O and 1.35g FeCl3·6H2O to 100mL DMF, stir well, and prepare a precursor solution of cobalt and iron;

[0053] S2: Add 9.60g of TiO2 nanosheets to the cobalt and iron precursor solution, stir evenly, and disperse iron and cobalt metal ions on the surface of TiO2 nanosheets by impregnation to obtain impregnation solution;

[0054] S3: Add 6.30g of TMA to the impregnation solution, stir and then sonicate to obtain a mixture;

[0055] S4: The mixture was placed in a polytetrafluoroethylene high-pressure reactor, heated to 120°C, and reacted for 8 hours. After the reaction was completed, it was cooled, centrifuged and settled, washed with water, DMF and CH3OH respectively, and the resulting solid was dried in a vacuum drying oven at 60°C for 1 hour to obtain a sandwich-structured photocatalyst.

[0056] The photocatalyst TiO2@Co-Fe / MOF prepared in Example 3 was used for photo-Fenton oxidation degradation of phenol-containing wastewater. Under the same calculation method as in Example 1, the photocatalytic efficiency was 66.9%.

[0057] Example 4

[0058] A method for preparing a sandwich-structured photocatalyst includes the following steps:

[0059] S1: Add 0.72g CoCl2·6H2O and 0.40g Fe(NO3)3·9H2O to 100mL DMF and stir well to prepare a precursor solution of cobalt and iron;

[0060] S2: Add 4.80g of TiO2 nanosheets to the cobalt and iron precursor solution, stir evenly, and disperse iron and cobalt metal ions on the surface of TiO2 nanosheets by impregnation to obtain impregnation solution;

[0061] S3: Add 2.52g of TMA to the impregnation solution, stir and then sonicate to obtain a mixture;

[0062] S4: The mixture was placed in a polytetrafluoroethylene high-pressure reactor, heated to 100℃, and reacted for 9 hours. After the reaction was completed, it was cooled, centrifuged and settled, washed with water, DMF and CH3OH respectively, and the resulting solid was dried in a vacuum drying oven at 60℃ for 1 hour to obtain a sandwich-structured photocatalyst.

[0063] The photocatalyst TiO2@Co-Fe / MOF prepared in Example 4 was used for photo-Fenton oxidation degradation of phenol-containing wastewater. Under the same calculation method as in Example 1, the photocatalytic efficiency was 70.2%.

[0064] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. The application of a sandwich-structured photocatalyst, characterized in that, The sandwich-structured photocatalyst is applied to the photo-Fenton oxidation degradation of phenolic substances in wastewater. The sandwich-structured photocatalyst is constructed from TiO2 nanosheets and bimetallic active Co-Fe / MOF. The TiO2 nanosheets cover the surface of Co-Fe / MOF to form a layered sandwich structure. The Co-Fe / MOF is a metal-organic framework compound prepared from trimesic acid and cobalt and iron precursors. The sandwich-structured photocatalyst was prepared by the following steps: S1: Add cobalt and iron precursors to an organic solvent and stir until homogeneous to prepare a cobalt and iron precursor solution; S2: Add TiO2 nanosheets to the cobalt and iron precursor solution, stir evenly, and obtain the impregnation solution by impregnating the iron and cobalt metal ions on the surface of TiO2 nanosheets. S3: Add pyromellitic acid (TMA) to the impregnation solution, stir and then sonicate to obtain a mixture; S4: Place the mixture in a polytetrafluoroethylene high-pressure reactor, heat and react. After the reaction is complete, centrifuge, wash and vacuum dry the reaction solution to obtain a sandwich-structured photocatalyst.

2. The application of the sandwich-structured photocatalyst as described in claim 1, characterized in that, The organic solvent mentioned in S1 is N,N-dimethylformamide or methanol.

3. The application of the sandwich-structured photocatalyst as described in claim 1, characterized in that, The precursors of cobalt and iron in S1 include cobalt and iron nitrates and chlorides.

4. The application of the sandwich-structured photocatalyst as described in claim 1, characterized in that, The molar ratio of cobalt and iron precursors used in S1 is 1:0.2~5.

5. The application of the sandwich-structured photocatalyst as described in claim 1, characterized in that, The molar ratio of cobalt and iron precursors to TiO2 nanosheets in S2 is 1:5~20.

6. The application of the sandwich-structured photocatalyst as described in claim 1, characterized in that, The molar ratio of cobalt and iron precursors to trimesic acid in S3 is 1:1~5.

7. The application of the sandwich-structured photocatalyst as described in claim 1, characterized in that, The reaction conditions in S4 are: reaction temperature 70~120 ℃, reaction time 8~15 h.

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