Preparation method and application of magnetic inorganic molecular imprinting photocatalytic material

Abstract

The present application relates to a preparation method of magnetic inorganic molecular imprinting photocatalytic material and its application. The preparation method comprises: preparing ferroferric oxide microspheres as the inner core of the inorganic molecular imprinting photocatalytic material; coating an amorphous titanium dioxide matrix molecular imprinting shell layer on the surface of the inner core, and adding a template molecule in the process to obtain an inorganic molecular imprinting photocatalytic material with a template molecule; converting the amorphous titanium dioxide in the inorganic molecular imprinting photocatalytic material with the template molecule into porous anatase titanium dioxide, in-situ synthesizing silver nanoparticles on the surface of the porous anatase titanium dioxide, removing the template molecule under ultraviolet light irradiation, and thus obtaining a magnetic inorganic molecular imprinting photocatalytic material with a core-shell structure. The magnetic inorganic molecular imprinting photocatalytic material prepared by the present application has good selective adsorption and photocatalytic capacity, high stability and green environmental protection advantages, and has potential application value in selectively removing target pollution molecules in wastewater.

Description

Technical Field

[0001] This invention relates to the fields of material preparation and environmental pollution control technology, specifically to the photodegradation and treatment of organic pollutants in the field of environmental protection, and particularly to a method for preparing magnetic inorganic molecularly imprinted photocatalytic materials and their applications. Background Technology

[0002] With the increasing severity of environmental pollution, the harm of organic pollutants (such as antibiotics) in the aquatic environment to human and ecological health has attracted growing attention. Semiconductor photocatalytic oxidation technology is a novel and modern water treatment technology that has a significant degradation effect on various organic substances and has broad application prospects. Among many semiconductor photocatalysts, titanium dioxide (TiO2) has become the most ideal photocatalyst due to its environmental friendliness, superhydrophilicity, high stability, high catalytic activity, and the availability and low cost of raw materials. However, the photocatalysis of TiO2 is mainly driven by free radical reactions, and the related mechanism is non-selective, resulting in low selectivity of TiO2 photocatalysts. It cannot distinguish between persistently toxic pollutants and low-toxicity pollutants. For example, wastewater may contain both highly toxic but low-content organic pollutants and low-toxicity but high-content organic pollutants. These pollutants will competitively adsorb onto the catalyst surface, leading to low catalytic efficiency for highly toxic organic pollutants. Therefore, there is an urgent need to develop selective photocatalysts.

[0003] Molecular imprinting, a biomimetic recognition technology that mimics antigen-antibody interactions in nature, combined with semiconductor photocatalytic oxidation technology, produces molecularly imprinted photocatalytic materials that specifically recognize target pollutant molecules, enabling efficient treatment of organic pollutants in wastewater. Molecular imprinting technology is a technique for preparing polymers with specific binding sites by memorizing the shape, size, and functional groups of template molecules. The preparation of polymers using this technology mainly involves the following three steps: 1) Template molecules and functional monomers bind to each other through non-covalent or covalent forces to form host-guest complexes; 2) A crosslinking agent is added, and photo- or thermal initiation is performed using an initiator, resulting in a polymer that immobilizes the host-guest complex; 3) The imprinted molecules in the polymer are eluted or dissociated, resulting in imprinted polymers containing stereopores that match the size, shape, and functional groups of the template molecules.

[0004] Organic molecularly imprinted polymers (MIMs) are widely used in the preparation of molecularly imprinted photocatalytic materials due to the diversity of their functional monomers and crosslinking agents. However, in practical applications, MIMs suffer from drawbacks such as poor rigidity and inertness, low binding efficiency, and template molecule residues. Furthermore, the organic reagents used in traditional MIM techniques can pollute the environment, and the preparation process is complex. For example, CN111234295A discloses a molecularly imprinted photocatalytic material, its preparation method, and its application. This method involves mixing template molecules, functional monomers, and porogens for a prepolymerization reaction to obtain a prepolymer; mixing the prepolymer, crosslinking agent, initiator, and bismuth oxybromide (BiOBr) under a protective atmosphere for polymerization to obtain an imprinted polymer; and eluting the imprinted polymer to obtain the molecularly imprinted photocatalytic material. This method involves a complex reaction process, requires a large number of reagents, and each reaction step is time-consuming, resulting in poor practicality. Moreover, photocatalytic degradation further accelerates the aging of MIMs and destroys their imprinted cavities, thereby reducing their selectivity.

[0005] In contrast, TiO2-based inorganic molecularly imprinted materials not only possess high thermal stability, mechanical strength, and chemical inertness, but the imprinted matrix itself can also endow the materials with excellent photocatalytic activity, thus demonstrating superiority in the selective photocatalytic degradation of organic pollutants. However, due to the relatively weak coordination ability between the titanium source material used to synthesize TiO2 and the target molecule, it is difficult to form effective imprinting sites during TiO2 preparation. Therefore, research reports on related inorganic molecularly imprinted photocatalytic materials are very limited, and many issues are still under discussion and research. For example, problems need to be solved in terms of simplifying material preparation, improving the light utilization efficiency of catalytic materials, and recycling and reusing materials. Currently, the publicly reported methods for preparing TiO2 inorganic molecularly imprinted photocatalytic materials mainly include hydrothermal methods, liquid phase deposition methods, and sol-gel methods. Among them, the hydrothermal method requires a high-pressure, high-temperature, and closed reaction environment, while the liquid phase deposition method requires the addition of seed crystals for induced synthesis. Therefore, the sol-gel method, which has simple process and mild conditions, has become a common method for preparing TiO2 inorganic molecularly imprinted materials. However, TiO2 generated by the sol-gel method at room temperature is difficult to form anatase crystal with high catalytic activity. It usually requires high-temperature calcination to achieve crystal transformation, which has the disadvantages of long time consumption and high energy consumption.

[0006] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0007] Molecularly imprinted photocatalytic materials mainly fall into two categories: those based on organic and those based on inorganic imprinted matrices. Organic molecularly imprinted polymer photocatalysts are the most studied, exhibiting good selectivity. Due to the spatial confinement provided by molecular imprinting, degradation byproducts are degraded again before they can leave the adsorbent material and enter the solution, resulting in fewer intermediate byproducts. However, because they utilize organic polymer imprints, prolonged use damages the polymer layer, significantly shortening their lifespan. Therefore, research on inorganic molecularly imprinted photocatalytic materials has become a hot topic. Inorganic molecularly imprinted polymers possess ideal mechanical strength and a large specific surface area, making them suitable for separating mixtures of small molecules. However, conventional preparation methods are complex, time-consuming, and energy-intensive. Furthermore, inorganic molecularly imprinted photocatalytic materials face the challenge of difficult separation and recovery in aqueous solutions.

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing magnetic inorganic molecularly imprinted photocatalytic materials, comprising the following steps:

[0009] Iron oxide (Fe3O4) microspheres were prepared to serve as the core of an inorganic molecularly imprinted photocatalytic material.

[0010] A molecularly imprinted shell based on amorphous TiO2 is coated on the surface of the core, and template molecules are added in the process to obtain inorganic molecularly imprinted photocatalytic materials with template molecules.

[0011] Amorphous TiO2 in an inorganic molecularly imprinted photocatalytic material with template molecules is converted into anatase porous titanium dioxide (mTiO2), and silver nanoparticles (Ag NPs) are synthesized in situ on the surface of anatase mTiO2. The template molecules are removed by ultraviolet light irradiation, thereby obtaining a core-shell structured magnetic inorganic molecularly imprinted photocatalytic material.

[0012] The beneficial effects of this technical solution are as follows: This invention coats the surface of Fe3O4 with a molecularly imprinted shell based on amorphous titanium dioxide using a sol-gel method, and transforms amorphous TiO2 into anatase-type mTiO2 using a microwave-assisted hydrothermal method. Simultaneously, Ag NPs are synthesized in situ on its surface, thereby obtaining an inorganic molecularly imprinted polymer Fe3O4@mTiO2@Ag (labeled MIP in subsequent figures and descriptions) with a core-shell structure. Traditional photocatalysts involve coating the surface of the photocatalyst with a layer of organic molecularly imprinted polymer (currently the subject of much research). However, this method has drawbacks: it requires many reagents, has a long reaction time, and the template molecular imprint is easily retained in the cavities within the polymer layer, making it difficult to wash off. Furthermore, the organic molecularly imprinted polymer bound to the surface of the photocatalyst is itself photodegraded over time, resulting in a short lifespan and inability to be reused multiple times. The method for preparing inorganic molecularly imprinted polymers provided by this technical solution removes most of the template molecules during microwave heating (high template molecule removal rate), avoiding template molecules remaining in the imprint cavity and reducing catalytic efficiency. Magnetic Fe3O4 microspheres serve as the core, allowing for material recovery through magnetic separation. TiO2 serves as the molecularly imprinted shell, which can selectively adsorb and photodegrade the target substance.

[0013] Many semiconductor materials with photocatalytic effects have been reported, such as TiO2, C3N4, ZnO, and Fe2O3. TiO2 has attracted widespread attention due to its non-toxicity, wide availability, low preparation cost, good stability, and excellent redox capabilities. TiO2 has three crystal forms: rutile, anatase, and brookite. Anatase TiO2, with its large specific surface area and abundant oxygen vacancies, more easily traps electrons, facilitating electron-hole separation and thus exhibiting better photocatalytic performance than the other two crystal forms. The traditional method for TiO2 crystal transformation is high-temperature calcination, which is time-consuming and energy-intensive. This application employs a microwave-assisted hydrothermal method to transform amorphous TiO2 with anatase-type mTiO2, offering advantages such as low energy consumption and short reaction time. During the microwave-assisted TiO2 crystal transformation process, the solvent ethanol, due to its reducing power, can convert Ag... + It is reduced to AgNPs (Pal et al., 2009). Furthermore, adding ammonia as a porogen during crystallization can facilitate the formation of [Ag(NH3)2]. + Ions are used to reduce the reduction rate of Ag NPs, thereby obtaining more uniform Ag NPs. Ag NPs on the surface of m TiO2 can effectively reduce the recombination rate of photon-induced electron-hole pairs, thereby enhancing the photocatalytic activity of TiO2 under ultraviolet light.

[0014] According to a preferred embodiment, the reactor pressure for converting amorphous TiO2 with anatase-type mTiO2 using a microwave-assisted hydrothermal method is 20 × 10⁻⁶. 5 Pa to 30×10 5 Pa, more preferably 27 × 10 Pa 5 Pa. The microwave-assisted hydrothermal method for converting amorphous TiO2 with a shell to anatase-type mTiO2 takes 12 to 20 minutes. The inventors unexpectedly discovered that the conversion rate, reaction efficiency, and grain size of the generated anatase-type mTiO2 are related to the reactor pressure, temperature, and reaction time. At 20 × 10⁻⁶ Pa, the reaction time for converting amorphous TiO2 with a shell to anatase-type mTiO2 is 12 to 20 minutes. 5 Pa to 30×10 5 Within the reactor pressure range of Pa, under the same temperature and reaction time conditions, the reaction conversion rate first increases and then decreases with increasing reactor pressure. Within the temperature range of 160℃ to 220℃, under the same reactor pressure and reaction time conditions, the grain size of the generated anatase-type mTiO2 decreases with increasing temperature. Under the same reactor pressure and temperature conditions, the reaction conversion rate first increases and then remains constant with time, while the grain size first increases and then remains constant with reaction time. To ensure the generated catalyst possesses the desired photocatalytic performance, the preferred anatase-type mTiO2 grain size is between 10nm and 15nm, with a conversion rate higher than 85%. Based on the above considerations, the preferred reaction conditions are: reactor pressure 27 × 10⁻⁶ Pa. 5 Pa, reaction temperature 180℃, reaction time 15 minutes.

[0015] According to a preferred embodiment, in the microwave-assisted hydrothermal process for converting amorphous TiO2 with anatase-type mTiO2, a stepped heating method is employed. Specifically, according to an optimal embodiment, the reaction is carried out at a reactor pressure of 27 × 10⁻⁶. 5Under the conditions of Pa, the reaction was carried out at 160℃ for 4 minutes, 180℃ for 10 minutes, and 200℃ for 2 minutes. Through this temperature control method, the anatase-type mTiO2 grain size D50 was approximately 11.6 nm, D10 approximately 10.5 nm, and D90 approximately 12.7 nm, with a conversion rate of approximately 92.7%. Both the particle size distribution and conversion rate were superior to those obtained from other uniformly heated reactions. Furthermore, the inventors unexpectedly discovered that this reaction process also improved the photocatalytic performance of the reaction products. Photocatalytic degradation experiments using norfloxacin (NOR) aqueous solution revealed that the magnetic inorganic molecularly imprinted photocatalytic material prepared by this method through anatase-type mTiO2 conversion reaction achieved a degradation efficiency of 91.2% after 90 minutes of photocatalytic degradation with norfloxacin (NOR) aqueous solution. In contrast, magnetic inorganic molecularly imprinted photocatalytic materials obtained through other reaction methods showed degradation efficiencies of 70.2% to 84.5% after 90 minutes of photocatalytic degradation with norfloxacin (NOR) aqueous solution (data from multiple parallel experiments with different temperatures, reactor pressures, and reaction times were compiled). This indicates that the optimized reaction conditions significantly improved the selective degradation efficiency of the target molecule by the magnetic inorganic molecularly imprinted photocatalytic material. According to a preferred embodiment, Fe3O4 microspheres were prepared using a microwave synthesis method.

[0016] According to a preferred embodiment, a method for preparing Fe3O4 microspheres includes the following steps:

[0017] Sodium citrate was dispersed in ethylene glycol; anhydrous sodium acetate and ferric chloride hexahydrate were added to obtain a mixed solution; the mixed solution was heated by microwave; and the black product in the mixed solution was recovered using a magnet, wherein the black product adsorbed by the magnet was Fe3O4.

[0018] According to a preferred embodiment, a molecularly imprinted shell based on amorphous TiO2 is coated on the surface of Fe3O4 microspheres using a sol-gel method.

[0019] According to a preferred embodiment, amorphous TiO2 is converted into anatase mTiO2 using a microwave-assisted hydrothermal method.

[0020] The beneficial effects of this technical solution are as follows: Traditional hydrothermal methods for converting amorphous TiO2 into anatase mTiO2 require placing the reaction mixture in a reaction vessel and heating it to 160°C for 12 hours. However, this invention, using a microwave-assisted hydrothermal method, only requires placing the reaction mixture in a microwave heating system at 180°C for 15 minutes, significantly shortening the reaction time.

[0021] On the other hand, the amorphous TiO2 generated by the traditional sol-gel method has no photocatalytic activity, and the conventional solution is calcination or hydrothermal treatment, which generally requires more than ten hours at high temperature, resulting in a long reaction time. The liquid phase deposition method requires the addition of anatase TiO2 as a crystal nucleus, so that the molecular imprinted layer of TiO2 grows directly on the crystal nucleus. Although the final anatase has a photocatalytically active imprinted layer, it is necessary to introduce seed crystals.

[0022] Furthermore, the doping of Ag NPs on the TiO2 surface can usually be achieved by chemical reduction, photochemical deposition, electrochemical deposition, etc., which require additional steps or the addition of reducing agents. In the microwave hydrothermal assisted TiO2 crystal transformation process, this invention utilizes the reducing properties of the solvent ethanol to synthesize Ag NPs on the m TiO2 surface without the need for additional reducing agents. This method has the advantages of being faster and more efficient, and the prepared Ag NPs have high monodispersity.

[0023] Therefore, the preparation method provided by the present invention is not only simpler in preparation steps and has lower energy consumption, but also has strong selectivity for catalytic targets.

[0024] According to a preferred embodiment, a method for preparing inorganic molecularly imprinted photocatalytic materials with template molecules includes the following steps:

[0025] Fe3O4 and template molecules are dispersed in a mixed solution of ethanol and acetonitrile; titanate and ammonia are added to the mixed solution; the mixed solution is placed on a magnet to recover the product, wherein the dark gray product adsorbed by the magnet is the inorganic molecularly imprinted photocatalytic material with template molecules.

[0026] Preferably, titanate ester is used as the titanium source for the titanium dioxide imprinted matrix in inorganic molecularly imprinted photocatalytic materials.

[0027] Preferably, tetrabutyl titanate is used as the titanium source for the titanium dioxide imprinted matrix in inorganic molecularly imprinted photocatalytic materials.

[0028] Preferably, ammonia provides the alkaline environment required for the hydrolysis of titanate to generate amorphous TiO2, and acts as a pore-forming agent during the microwave-assisted TiO2 crystal transformation process.

[0029] Preferably, the volume ratio of ethanol to acetonitrile is 3:1.

[0030] Preferably, the template molecule can be norfloxacin (NOR). The inorganic molecularly imprinted photocatalytic material with the template molecule is labeled Fe3O4@TiO2@NOR.

[0031] According to a preferred embodiment, a method for preparing magnetic inorganic molecularly imprinted photocatalytic materials includes the following steps:

[0032] An inorganic molecularly imprinted photocatalytic material with a template molecule was placed in a mixed solution of ethanol and pure water. Ammonia and silver nitrate solution were added to the mixed solution. The mixed solution was heated by microwave. The mixed solution was placed on a magnet to recover the black product. The black product was irradiated with ultraviolet light to remove the template molecule. The magnet was then used to recover and wash the product, thereby obtaining a core-shell structured magnetic inorganic molecularly imprinted photocatalytic material Fe3O4@mTiO2@Ag(MIP).

[0033] Preferably, silver nitrate is used as the source of silver nanoparticles on the surface of the magnetic inorganic molecularly imprinted photocatalytic material.

[0034] Preferably, an ethanol-water solution is used as the solvent in the microwave-assisted hydrothermal method, while ethanol acts as a reducing agent to reduce silver nitrate to generate silver nanoparticles.

[0035] The beneficial effects of this technical solution are as follows: This invention uses the sol-gel method and microwave-assisted hydrothermal method to achieve crystal transformation. The difference between this invention and existing technologies lies in the fact that during the crystal transformation process in the microwave-assisted hydrothermal method, the added silver nitrate can generate silver nanoparticles on the material surface while amorphous TiO2 is converted into anatase. The silver nanoparticles, combined with the titanium dioxide photocatalyst, can enhance photocatalytic activity. No other reducing agents are added in this process; ethanol in the solvent can act as the reducing agent. The entire microwave reaction time is very short, requiring only a dozen minutes, significantly reducing energy consumption compared to calcination and hydrothermal methods.

[0036] Preferably, the magnetic inorganic molecularly imprinted photocatalytic material can specifically adsorb and photocatalytically degrade norfloxacin.

[0037] Preferably, ethylene glycol, anhydrous ethanol, and pure water are used as solvents for preparing magnetic inorganic molecularly imprinted photocatalytic materials.

[0038] According to a preferred embodiment, the preparation method of the corresponding inorganic non-molecularly imprinted photocatalytic material (labeled as NIP in subsequent figures and descriptions) is the same as described above, but without the addition of template molecules.

[0039] Currently used photocatalysts for organic pollutant treatment lack selectivity. Competitive adsorption of different types of pollutants on the catalyst surface leads to reduced catalytic efficiency for removing highly toxic pollutants. The method for preparing magnetic inorganic molecularly imprinted photocatalytic materials provided in this technical solution can improve the selectivity of the catalyst for the catalytic target, significantly increasing catalytic efficiency. The inorganic molecularly imprinted polymer obtained using the method provided in this technical solution exhibits good stability and rigidity, and the template molecules are easily eluted. Furthermore, the inorganic molecularly imprinted polymer of this invention does not suffer structural damage with prolonged illumination time or increased usage, as shown in the results of Example 8.

[0040] Another aspect of the present invention provides the application of magnetic inorganic molecularly imprinted photocatalytic materials, which have pores and binding sites that match the template molecules and can be used for the selective photodegradation of organic pollutants.

[0041] According to a preferred embodiment, the structure of the magnetic inorganic molecularly imprinted photocatalytic material is as follows: Fe3O4 is used as the core, and a molecularly imprinted shell with amorphous titanium dioxide as the matrix is ​​coated on the surface of Fe3O4.

[0042] Preferably, the organic pollutant can be norfloxacin.

[0043] Preferably, the organic pollutant can be a quinolone antibiotic. Attached Figure Description

[0044] Figure 1 (a) is a scanning electron microscope image of Fe3O4@TiO2@NOR microspheres; (b) is a scanning electron microscope image of magnetic inorganic molecularly imprinted photocatalytic material; (c) is a transmission electron microscope image of magnetic inorganic molecularly imprinted photocatalytic material.

[0045] Figure 2 Photoelectron spectroscopy of magnetic inorganic molecularly imprinted photocatalytic materials;

[0046] Figure 3 X-ray diffraction patterns of Fe3O4, Fe3O4@TiO2, Fe3O4@m TiO2 and Fe3O4@m TiO2@Ag (MIP);

[0047] Figure 4 (a) shows the effect of solution pH on the adsorption performance of the magnetic inorganic molecularly imprinted photocatalytic material, and (b) shows the effect of the amount of magnetic inorganic molecularly imprinted photocatalytic material on the adsorption efficiency.

[0048] Figure 5 The results are from the selective adsorption experiments of the prepared materials;

[0049] Figure 6 The figures show the photocatalytic degradation efficiency of the prepared materials for norfloxacin and the corresponding first-order degradation rate curves. (a) shows the relationship between the photocatalytic efficiency of the prepared MIP and NIP materials for norfloxacin and time. (b) shows the photocatalytic efficiency of ln(C0 / C0) for norfloxacin. t The linear relationship between ( ) and UV irradiation time;

[0050] Figure 7 The effects of different scavengers on the photocatalysis of norfloxacin;

[0051] Figure 8 This is the result of the reuse of magnetic inorganic molecularly imprinted photocatalytic materials. Detailed Implementation

[0052] The following is a detailed explanation with reference to the accompanying drawings.

[0053] It should be understood that norfloxacin as a template molecule provided in this invention is merely an example and is not intended to limit the invention.

[0054] This application utilizes a method for preparing magnetic inorganic molecularly imprinted photocatalytic materials to obtain molecularly imprinted polymers with Fe3O4 as the core. A polymer layer is synthesized on the surface of Fe3O4, and the spatial size of the pores and the arrangement of functional groups in the polymer layer are highly compatible with the template molecules. This allows the MIP to possess both specific selectivity for template molecules and the paramagnetism of the magnetic particles themselves, ultimately achieving efficient adsorption and separation of template molecules.

[0055] Example 1

[0056] This embodiment relates to the preparation of magnetic inorganic molecularly imprinted photocatalytic materials, specifically providing a method for preparing such materials. The method includes the following steps:

[0057] (1) Preparation of Fe3O4 microspheres: Weigh 0.8 g of sodium citrate into a three-necked flask containing 140 mL of ethylene glycol, and sonicate for 40 min. Add 7.7 g of anhydrous sodium acetate and 2.7 g of ferric chloride hexahydrate to the solution, and sonicate for 5 min to assist dissolution. Place the above mixed solution in the dark and mechanically stir for 1 h. After stirring, transfer the resulting mixed solution to a microwave digester and react at 200 °C for 2 h at a power of 400 W. After the reaction, place the resulting black mixed solution on a magnet to recover the product. The black product that can be adsorbed by the magnet is Fe3O4. Wash three times each with anhydrous ethanol and ultrapure water. Finally, place the obtained Fe3O4 in a vacuum drying oven and vacuum dry at 50 °C for 6 h for later use.

[0058] (2) Preparation of Fe3O4@TiO2@NOR: Weigh 50 mg of Fe3O4 powder and 20 mg of norfloxacin, disperse them in a mixed solution of 120 mL of ethanol and acetonitrile (3:1, v / v), sonicate for 30 min, add 1 mL of tetrabutyl titanate to the mixed solution, continue stirring for 30 min, then add 0.5 mL of ammonia water and stir for 1.5 h. After stirring, place the resulting dark gray mixed solution on a magnet for recovery. The dark gray product that can be adsorbed by the magnet is the inorganic molecularly imprinted polymer Fe3O4@TiO2@NOR with template molecules. Wash three times each with anhydrous ethanol and ultrapure water. Finally, place the obtained Fe3O4@TiO2@NOR in a vacuum drying oven and vacuum dry at 50 °C for 6 h for later use.

[0059] (3) Preparation of Fe3O4@mTiO2@Ag (MIP): Weigh 10 mg of Fe3O4@TiO2@NOR powder into a mixed solution of 40 mL ethanol and 20 mL pure water. Add 1 mL ammonia and 1.5 mL 0.1 M silver nitrate solution to the mixed solution. After ultrasonic dispersion for 30 min, transfer the resulting mixed solution to a microwave digester and react at 180 °C for 15 min at a power of 400 W. Place the resulting black mixed solution on a magnet and recover the black product using the magnet. Wash three times each with anhydrous ethanol and ultrapure water. Place the black product in a pure water solution and irradiate it with ultraviolet light under a high-pressure mercury lamp for 4 h at a power of 250 W. Recover the black product using a magnet and wash three times with ultrapure water to remove the template molecules. The final product is the magnetic inorganic molecularly imprinted material. Place the obtained MIP in a vacuum drying oven and dry it at 50 °C for 6 h for later use. Meanwhile, except for the absence of norfloxacin, magnetic inorganic non-molecular imprinted materials (NIPs) were prepared using the same method as described above.

[0060] Example 2

[0061] In this embodiment, the surface morphology of Fe3O4, Fe3O4@TiO2@NOR, and Fe3O4@mTiO2@Ag was characterized by scanning electron microscopy (SEM), the elemental composition of Fe3O4@mTiO2@Ag was determined by energy dispersive spectroscopy (EDS), and the crystal structure of Fe3O4, Fe3O4@TiO2, Fe3O4@m TiO2, and Fe3O4@m TiO2@Ag was analyzed by X-ray diffraction (XRD). The material characterization results are as follows.

[0062] Most of the Fe3O4 microspheres synthesized by microwave heating are approximately spherical, with an average particle size of about 200 nm. Figure 1 (a) is a scanning electron microscope image of Fe3O4@TiO2@NOR microspheres. Due to the uneven surface of the TiO2 layer covering material, there is obvious particle accumulation with an average particle size of about 250 nm, indicating that TiO2 was successfully coated on the Fe3O4 surface. Figure 1 (b) is a scanning electron microscope image of Fe3O4@m TiO2@Ag. Figure 1 (c) is a transmission electron microscope (TEM) image of Fe3O4@m TiO2@Ag. The image shows a rough surface with an average particle size of approximately 300 nm. The surface is modified with silver nanoparticles of about 30 nm, indicating successful surface modification with silver nanoparticles. (Electron Spectrum of Fe3O4@m TiO2@Ag) Figure 2 The material contains elements such as O, Ti, Fe, Ag and F, which is consistent with the theoretical elements of magnetic inorganic molecularly imprinted photocatalytic materials. The presence of F indicates that a small amount of the template molecule norfloxacin may also be present in the material.

[0063] Figure 3 These are X-ray diffraction patterns for Fe3O4, Fe3O4@TiO2, Fe3O4@m TiO2, and Fe3O4@m TiO2@Ag. The horizontal axis represents twice the incident X-ray angle (2θ), and the vertical axis represents the intensity of diffraction peaks at different diffraction angles (2θ). Fe3O4 exhibits strong diffraction peaks at 2θ diffraction angles of 30.3°, 35.4°, 43.2°, 57.3°, and 62.5°, which are consistent with the standard diffraction peaks of Fe3O4 (JCPDS card number 85-1436). For Fe3O4@TiO2, its XRD pattern shows no TiO2 diffraction peaks except for a weakened Fe3O4 peak, indicating that an amorphous TiO2 shell coats the Fe3O4 core. Compared with Fe3O4@TiO2, Fe3O4@m TiO2 exhibits strong diffraction peaks at 2θ diffraction angles of 25.2°, 37.8°, 48.0°, 53.8°, 54.8°, 62.6°, 68.6°, and 74.9°. These peaks correspond to the (101), (004), (200), (105), (211), (204), (116), and (215) crystal planes of anatase TiO2 (JCPDS card number 01-075-2545), respectively, indicating that microwave-assisted hydrothermal method can effectively transform amorphous TiO2 into anatase crystal form. Furthermore, the XRD pattern of Fe3O4@mTiO2@Ag (MIP) shows four strong diffraction peaks at 2θ values ​​of 38.1°, 44.4°, 64.4°, and 77.4°, which are consistent with the standard diffraction peaks of Ag (JCPDS card number 00-004-0783). These results further demonstrate the successful preparation of magnetic inorganic molecularly imprinted photocatalytic materials.

[0064] Example 3

[0065] This embodiment involves the optimization of adsorption conditions for the material, and explores the adsorption performance of the prepared magnetic inorganic molecularly imprinted photocatalytic material. Specifically, it studies the effects of solution pH and material dosage on the adsorption efficiency of norfloxacin.

[0066] Effective parameters affecting adsorption efficiency include solution pH and material dosage. Specifically, solution pH values ​​of 3, 5, 7, 9, and 11 are considered optimal; 2 mL of 10 μg / mL material is used. -1 The amounts of adsorbent used in norfloxacin solutions were 0.04, 0.06, 0.08, 0.1, 0.12, and 0.14 mg.

[0067] The method for optimizing the pH of the solution is as follows: Take 0.1 mg of Fe3O4@m TiO2@Ag and place it in 2 mL of 10 μg mL solution under different pH conditions. -1The norfloxacin solution was ultrasonically dispersed and reacted with shaking in the dark for 30 minutes, followed by magnetic separation of the material. The supernatant was collected, and the absorbance of norfloxacin at 277 nm was measured using a UV-Vis spectrophotometer. Figure 4 As shown in Figure a, the adsorption capacities of MIP for norfloxacin at solution pH values ​​of 3, 5, 7, 9, and 11 were 20, 146.2, 156.6, 151, and 18.8 mg / g, respectively. -1 .

[0068] Figure 4 The experimental results of a show that the adsorption efficiency of MIP is low under strong acid and strong base conditions. The pH of the solution has little effect on the adsorption effect and the adsorption efficiency is high in a wide pH range of 5 to 9. The MIP of this application has a wide pH range of applicability.

[0069] Method for optimizing adsorbent dosage: Take different masses of Fe3O4@m TiO2@Ag into 2mL of 10μgmL solution. -1 After being ultrasonically dispersed in a norfloxacin solution and shaken in the dark for 30 minutes, the material was magnetically separated, and the absorbance at the maximum absorption wavelength was measured.

[0070] From the experimental results ( Figure 4 b) It can be seen that as the amount of adsorbent increases from 0.04 mg to 0.14 mg, the adsorption efficiency gradually increases from 35% to 78%, but the adsorption capacity per unit mass gradually decreases from 175 mg / g to 110 mg / g. Taking both factors into consideration, the optimal amount of adsorbent in 2 mL of norfloxacin sample solution is determined to be 0.1 mg.

[0071] Example 4

[0072] This embodiment involves the investigation of selective adsorption of materials, specifically studying the adsorption selectivity of MIP and NIP for norfloxacin, ciprofloxacin, enrofloxacin, ofloxacin, tetracycline, and cephalexin.

[0073] Methods for studying adsorption selectivity: 0.05 mg of the prepared MIP and NIP materials were ultrasonically dispersed in 1 mL of 5 × 10⁻⁵ mol / L water. -5 In different types of antibiotic solutions of M, the materials were magnetically separated after shaking in the dark for 30 minutes, and the absorbance of the supernatant was measured and the corresponding concentration was calculated. Figure 5 The figure shows the selective adsorption results of MIP and NIP for norfloxacin and other different antibiotics. As can be seen from the figure, the adsorption capacities of MIP for norfloxacin, ciprofloxacin, enrofloxacin, ofloxacin, tetracycline, sulfadiazine, and cephalexin are 149.5, 5.2, 19.4, 55.0, 1.1, 30.0, and 2.8 mg g, respectively. -1The adsorption capacities of NIP for norfloxacin, ciprofloxacin, enrofloxacin, ofloxacin, tetracycline, sulfadiazine, and cephalexin were 51.1, 7.7, 10.7, 35.5, 11.6, 27.5, and 2.8 mg g, respectively. -1 The adsorption capacity of MIP for norfloxacin is approximately 2.9 times that of NIP, and the adsorption performance of MIP for norfloxacin is much higher than that for other antibiotics, indicating that MIP has good selectivity and recognition performance for norfloxacin.

[0074] Example 5

[0075] This embodiment relates to the study of the photocatalytic performance of materials.

[0076] In the photocatalysis experiment, a 250W high-pressure mercury lamp was used as the ultraviolet light source. Photocatalysis experimental method: First, 0.5 mg of the prepared MIP was added to 10 mL of a 14 μg mL solution. -1 The sample was placed in a norfloxacin solution and shaken in the dark for 30 minutes to reach adsorption equilibrium. Then the sample was placed under a UV light source, and samples were taken at fixed time intervals (10 minutes) to determine the residual concentration of norfloxacin in the sample.

[0077] Figure 6 The curves show the photocatalytic degradation efficiency of the prepared material for norfloxacin and the corresponding first-order degradation rate. Figure 6 Figure a shows the relationship between the photocatalytic efficiency of the prepared MIP and NIP materials for norfloxacin and time. It can be seen that without a photocatalyst, after 60 min of UV irradiation, the residual amount of norfloxacin in the solution is approximately 91.3%, indicating that norfloxacin is relatively stable under these experimental conditions. In the presence of a photocatalyst, after 30 min of shaking in the dark to allow sufficient adsorption of norfloxacin by the prepared MIP and NIP materials, the residual amounts of norfloxacin in the solution are approximately 39.2% and 90.6%, respectively. This result further demonstrates that the prepared magnetic inorganic molecularly imprinted photocatalyst has good adsorption performance for the target molecule. After 60 min of UV irradiation, the residual amount of norfloxacin in the MIP group solution further decreased to 29.9%, and the residual amount in the NIP group solution decreased to 79.5%. The results show that both MIP and NIP have good photocatalytic performance, and the selective adsorption of MIP can significantly improve the photodegradation efficiency of norfloxacin.

[0078] This embodiment uses a simplified pseudo-first-order kinetic equation derived from the Langmuir-Hinshelwood model to study photocatalytic kinetics. The calculation formula is as follows:

[0079] ln(C0 / C t )=k1t

[0080] C0(μg mL-1 C represents the initial concentration of norfloxacin. t (μg mL -1 ) represents the concentration of norfloxacin at time t (min), and k1 is the photodegradation rate constant (min). -1 ).

[0081] Figure 6 b is ln(C0 / C) t The linear relationship between the photocatalytic rate of norfloxacin and the UV irradiation time is shown in the figure, with the slope representing the photodegradation rate of norfloxacin by the material. The figure also shows that the photodegradation rate of the magnetic inorganic molecularly imprinted photocatalytic material prepared in this invention is 0.00397 min. -1 ) is a non-molecular imprinted material (0.00167 min) -1 2.37 times that of ).

[0082] Example 6

[0083] This embodiment involves the study of the photocatalytic mechanism of materials.

[0084] To further explore the potential photocatalytic mechanism of the material, this embodiment used 4-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPOL) as a superoxide radical (·O2). - ) scavenging agents, isopropanol (IPA) as a hydroxyl radical (·OH) scavenger, formic acid as a hole (h+) scavenger, and AgNO3 as an electron (e) scavenger. - ) Cleaning agent. Figure 7 The effect of different scavengers on the photocatalytic activity of norfloxacin is shown on the graph, with the x-axis representing the type of scavenger and the y-axis representing the photodegradation efficiency. Figure 7 It can be seen that in the blank control group, the photodegradation efficiency of MIP for norfloxacin was approximately 65%, while that of NIP was approximately 22%; in the isopropanol (IPA) treatment group, the photodegradation efficiency of MIP was approximately 65%, while that of NIP was approximately 22%; in the 4-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPOL) treatment group, the photodegradation efficiency of MIP was approximately 65%, while that of NIP was approximately 20%; in the formic acid treatment group, the photodegradation efficiency of MIP was approximately 2%, while that of NIP was close to 0; and in the AgNO3 treatment group, the photodegradation efficiency of MIP was approximately 44%, while that of NIP was approximately 10%.

[0085] Compared with the blank control group, the addition of TEMPOL and IPA had little effect on the degradation efficiency, while the addition of formic acid and AgNO3 significantly inhibited the photodegradation efficiency of the material, indicating that h+ and e are the main active substances in photodegradation. Under ultraviolet or visible light irradiation, electrons are excited from the valence band to the conduction band of titanium dioxide to form electron-hole pairs. The hot electrons generated by Ag NPs loaded on the MIP surface through the local surface plasmon resonance effect have sufficient momentum to overcome the Schottky barrier between TiO2 and Ag NPs and are injected into the conduction band of TiO2, reducing the recombination rate of electron-hole pairs induced by TiO2 photons, thereby further enhancing the photocatalytic activity of TiO2 under ultraviolet light.

[0086] Example 7

[0087] This embodiment involves the reuse of materials. To investigate the stability and reusability of the prepared MIP material, the used MIP material in this embodiment was magnetically separated and recovered, washed three times each with anhydrous ethanol and pure water, and vacuum dried at 50°C for 6 hours in a vacuum drying oven. After precise weighing, it was ultrasonically dispersed in a norfloxacin solution and shaken in the dark for 30 minutes. After irradiation with ultraviolet light for 60 minutes, the residual concentration of norfloxacin in the solution was measured. This process was repeated four times. Figure 8 The graph shows the reuse results of the MIP material, with the horizontal axis representing the number of cycles and the vertical axis representing the degradation efficiency. As can be seen from the graph, the degradation efficiency of MIP after one cycle is approximately 62.8%, after two cycles it is approximately 61.8%, after three cycles it is approximately 61.1%, and after four cycles it is approximately 60.2%. The MIP material retains good adsorption and photodegradation properties even after four cycles of reuse, with no significant decrease in the photodegradation efficiency for norfloxacin, indicating that the material has good stability and reusability.

[0088] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and do not constitute a limitation on the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; terms such as "preferredly," "according to a preferred embodiment," or "optionally" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept. Throughout the text, features introduced by "preferredly" are merely optional and should not be construed as mandatory. Therefore, the applicant reserves the right to abandon or delete relevant preferred features at any time.

Claims

1. A method for preparing a magnetic inorganic molecular imprinting photocatalytic material, characterized in that, The method comprises the following steps: Preparation of Fe3O4 microspheres as the core of inorganic molecular imprinting photocatalytic material; Coating an amorphous TiO2-based molecular imprinting shell on the surface of the core, and adding template molecules in the process to obtain an inorganic molecular imprinting photocatalytic material with template molecules, which comprises dispersing Fe3O4 and template molecules in a mixed solution of ethanol and acetonitrile; adding a titanium ester and ammonia water into the mixed solution; and placing the mixed solution on a magnet to recover the product, wherein the dark gray product adsorbed by the magnet is the inorganic molecular imprinting photocatalytic material with template molecules; Converting the amorphous TiO2 in the inorganic molecular imprinting photocatalytic material with template molecules into anatase porous TiO2, and in-situ synthesizing silver nanoparticles on the surface of the anatase porous TiO2, and removing the template molecules by ultraviolet light irradiation, thereby obtaining a magnetic inorganic molecular imprinting photocatalytic material with core-shell structure, which comprises placing the inorganic molecular imprinting photocatalytic material with template molecules in a mixed solution of ethanol and pure water, adding ammonia water and silver nitrate solution into the mixed solution; microwave heating the mixed solution; placing the mixed solution on a magnet to recover the black product; and irradiating the black product with ultraviolet light to remove the template molecules, and recovering and washing the product by a magnet, thereby obtaining the magnetic inorganic molecular imprinting photocatalytic material with core-shell structure Fe3O4@mTiO2@Ag (MIP); In the method, the amorphous titanium dioxide is converted into anatase porous titanium dioxide by a microwave-assisted hydrothermal method. In the reaction process of converting the amorphous shell layer TiO2 into anatase mTiO2 by the microwave-assisted hydrothermal method, a stepwise heating mode is adopted, and the reaction is carried out at 160 DEG C for 4 minutes, at 180 DEG C for 10 minutes and at 200 DEG C for 2 minutes under the condition that the pressure in the reaction kettle is 27x10 5 Pa.

2. The production method according to claim 1, characterized by, The Fe3O4 microspheres are prepared by a microwave synthesis method.

3. Use of a magnetic inorganic molecularly imprinted photocatalytic material, characterized in that, The magnetic inorganic molecular imprinting photocatalytic material is obtained by the preparation method according to claim 1 or 2, has cavities and binding sites matched with the template molecules, and is used for selective photodegradation of organic pollutants.

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