MoO3 / TiO2 heterojunction material with photocatalytic memory effect and application of MoO3 / TiO2 heterojunction material in degradation of quinolone antibiotics

Abstract

The invention discloses a MoO3 / TiO2 heterojunction material with a photocatalytic memory effect and application of the MoO3 / TiO2 heterojunction material in degradation of quinolone antibiotics, and belongs to the technical field of inorganic non-metallic material preparation, solar energy utilization and environmental protection. A molybdenum source precursor solution and a titanium source precursor solution are adopted to react, polyvinylpyrrolidone is used for modifying the surface of the material, the MoO3 / TiO2 heterojunction material is obtained, and the material can generate photochromic and photocatalytic memory effects under the pre-illumination effect. The memory effect provides continuous driving force for the catalytic reaction, and the activity of the material in the dark-state catalytic process is remarkably enhanced. The MoO3 / TiO2 heterojunction material disclosed by the invention shows excellent catalytic degradation performance in practical application, and particularly shows extremely high catalytic efficiency in the aspect of water pollution control.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic non-metallic material preparation, solar energy utilization and environmental protection, and in particular to a MoO3 / TiO2 heterojunction material with a photocatalytic memory effect and application thereof in degradation of quinolone antibiotics. BACKGROUND

[0002] In recent years, the accumulation of emerging organic pollutants such as antibiotics in water environment and their characteristics of being difficult to degrade have attracted widespread attention. Traditional physical and chemical adsorption, chemical oxidation and biological treatment have obvious limitations in selectivity, thoroughness and secondary pollution control. Photocatalysis is considered as an important environmental catalytic path because it can utilize light energy to drive redox and achieve deep mineralization under mild conditions. Since Fujishima and Honda observed the phenomenon of photo-induced decomposition of water on a titanium dioxide (TiO2) electrode in 1972, photocatalysis research has gradually moved from basic photochemistry, surface science and semiconductor physics to the application level of environmental governance and energy conversion. Materials such as TiO2 and ZnO have shown potential in the degradation of organic pollutants, removal of heavy metals and air purification. The mechanism relies on the redox reaction of the electron-hole pairs generated by band gap excitation on the surface. However, the existing systems generally face the problems of mainly responding to ultraviolet light, insufficient utilization of visible light, rapid recombination of photo-generated carriers in the bulk / surface, hindered interfacial transport and poor cycling stability in complex water bodies, especially when facing mixed antibiotic pollutants with stable structure and high concentration. The selective regulation and complete mineralization of intermediates are still insufficient.

[0003] In view of the above problems, the prior art improves light absorption, suppresses recombination and optimizes charge migration through doping, surface modification, morphology control, composite with carbon materials and construction of heterojunction (such as Type-II, Z-scheme, S-scheme). Among them, the S-type heterojunction can realize spatial separation while retaining strong oxidation / reduction ability due to the energy band directional mismatch and built-in electric field, and is considered to have the advantages of reaction activity and selectivity; defect engineering (such as introduction and regulation of oxygen vacancies) also helps to build trap levels, enhance carrier trapping and affect the interface reaction path. Although these strategies have improved the performance to some extent, the energy band alignment, interface dipole and charge channel of different material combinations still depend on the specific system and interface quality; the generation, spatial distribution and lifetime of defects are difficult to accurately control; the computable- verifiable closed-loop evidence chain of charge and intermediate evolution in the whole process of “pre-illumination-dark state-illumination again” is still missing, which limits the designability and sustainability in real complex substrate scenarios.

[0004] Molybdenum trioxide (MoO3) is valued for its layered structure formed by stacking of molybdenum-oxygen octahedra and its photochromic properties. The high specific surface area and abundant adsorption sites brought by the nanotube / porous morphology of MoO3 are beneficial to promoting the interface reaction kinetics and providing a geometric basis for constructing high-quality heterojunction interfaces. Previous studies have shown that a "photocatalytic memory behavior" can occur in the MoO3 system, which means that after pre-illumination, the material can still maintain a certain catalytic activity under dark conditions, and after re-illumination, it can quickly recover and enhance. This is believed to be related to photo-generated defects (such as oxygen vacancies), trap states, and local structure reconstruction. However, single-phase MoO3 still has deficiencies in visible light absorption intensity, charge directional migration, and defect stability, and its potential needs to be further released through the construction of S-type heterojunctions with typical semiconductors (such as TiO2) and defect engineering coupling.

[0005] Under this background, in order to meet the needs of deep mineralization and durable operation of complex mixed pollution systems such as quinolone antibiotics (such as ciprofloxacin CIP, norfloxacin NOR), it is urgent to establish a methodology centered on interface regulation and defect induction: on the one hand, by controlling the crystallographic matching and interface tight coupling of MoO3 / TiO2, a stable built-in electric field and directional charge migration channel are formed to suppress body / surface recombination; on the other hand, by introducing and maintaining controllable oxygen vacancies and other defects, the carrier capture and directional migration ability is improved, and the material is given sustained activity under dark conditions after pre-illumination and rapid recovery upon re-illumination. Systematic verification of structure, defect state and charge behavior is carried out by XRD, XPS, HRTEM, EPR, steady / unsteady state PL and other multi-spectral and microscopic characterizations, and the mineralization degree and cycle stability are evaluated by total organic carbon (TOC) and other indicators, which can provide an implementable technical path for constructing S-type MoO3 / TiO2 heterojunction materials with "photocatalytic memory behavior", thereby responding to the demand for high selectivity and persistent photocatalytic materials in complex pollutant scenarios. SUMMARY

[0006] The purpose of the present application is to provide a MoO3 / TiO2 heterojunction material with photocatalytic memory effect and its application in quinolone antibiotic degradation. The MoO3 / TiO2 heterojunction material prepared by solution thermal polymerization has the characteristics of inorganic semiconductor material, can generate photo-generated charges under light conditions, and can produce photocatalytic memory effect and sustained long-acting photochromism, realizing photocatalytic adsorption and degradation of quinolone antibiotic pollutants by the MoO3 / TiO2 heterojunction material, and the mineralization rate of quinolone antibiotics reaching nearly ninety percent.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows: The application discloses a MoO3 / TiO2 heterojunction material with a photocatalytic memory effect, which is composed of molybdenum trioxide nanotubes and titanium dioxide nanoparticles, wherein the molybdenum trioxide nanotubes are assembled by pure-phase molybdenum trioxide crystals, and the inner diameter and wall thickness of the nanotubes are nanoscale; the titanium dioxide nanoparticles are composed of titanium dioxide crystals and have a nanoparticle-like morphology.

[0008] Further, the MoO3 / TiO2 heterojunction material is a powder formed by attaching titanium dioxide particles to the surface of the molybdenum trioxide nanotubes.

[0009] Further, the molybdenum trioxide crystals are orthorhombic crystals with a space group of Pbnm and have a layered structure stacked by molybdenum-oxygen octahedrons; the titanium dioxide crystals are anatase-type tetragonal crystals belonging to the I41 / amd space group.

[0010] Further, the MoO3 / TiO2 heterojunction material has the characteristics of a wide-bandgap semiconductor photocatalytic material and has a peculiar photocatalytic memory effect, that is, after being irradiated for a certain time, the material can still continuously exhibit a color change and has super strong optical performance and catalytic degradation performance.

[0011] Further, the preparation method of the MoO3 / TiO2 heterojunction material comprises the following steps: taking ammonium heptamolybdate and tetrabutyl titanate as raw materials to prepare a molybdenum source precursor solution and a titanium source precursor solution respectively, mixing the two solutions, taking polyvinylpyrrolidone as a surfactant, and obtaining the MoO3 / TiO2 heterojunction material by using a solution thermal polymerization method. (1) tetrabutyl titanate is added into anhydrous ethanol to obtain a titanium source precursor solution; ammonium heptamolybdate is dissolved in deionized water, and concentrated hydrochloric acid is added to obtain a molybdenum source precursor solution; polyvinylpyrrolidone is dissolved in anhydrous ethanol to obtain a polyvinylpyrrolidone solution; (2) the titanium source precursor solution and the molybdenum source precursor solution obtained in step (1) are mixed in a certain proportion to obtain a mixed solution A, the mixed solution A is mixed with the polyvinylpyrrolidone solution in a certain proportion and is uniformly stirred to obtain a MoO3 / TiO2 heterojunction precursor solution; (3) the MoO3 / TiO2 heterojunction precursor solution is transferred into a stainless steel hydrothermal reaction kettle with a polytetrafluoroethylene lining, and hydrothermal reaction is carried out at a certain temperature; after the reaction, the lower solid material is separated by centrifugation, and then is sequentially subjected to washing and drying treatment; (4) the sample obtained after the drying treatment in step (3) is calcined in a muffle furnace, and the MoO3 / TiO2 heterojunction material is obtained.

[0012] Further, in step (1), the concentration of the titanium source precursor solution is 0.15-0.25 mol / L, the concentration of the ammonium heptamolybdate solution is 0.1-0.2 mol / L, and the concentration of the polyvinylpyrrolidone solution is 0.08-0.12 mol / L; the pH value of the molybdenum source precursor solution is adjusted to 1-3 by using concentrated hydrochloric acid, and the concentration of the concentrated hydrochloric acid is 12 mol / L.

[0013] Further, in step (2), when preparing the mixed solution A, the volume ratio of the titanium source precursor solution to the molybdenum source precursor solution is 1:(1-2); when preparing the molybdenum trioxide / titanium dioxide heterojunction precursor solution, the volume ratio of the mixed solution A to the polyvinylpyrrolidone solution is (5-10):1.

[0014] Further, in step (3), the temperature of the hydrothermal reaction is 140-200℃, and the hydrothermal reaction time is 12-20 hours; the washing treatment is to sequentially wash the collected lower substances with deionized water and ethanol, and each is washed alternately for three times; the drying treatment is to dry in a constant-temperature vacuum drying box at 60℃ for 12-18 hours.

[0015] Further, in step (4), the temperature of the calcination treatment is 300-500℃, and the calcination treatment time is 4-6 hours.

[0016] Further, the MoO3 / TiO2 heterojunction material is applied to photocatalytic degradation of quinolone antibiotic pollutants in water environment, and the application process is as follows: the MoO3 / TiO2 heterojunction material is pre-irradiated (300W full light lamp) for more than 20 minutes, and then added into the water containing quinolone antibiotic pollutants to perform photocatalytic adsorption and degradation of the pollutants under light irradiation or in dark environment.

[0017] Further, the quinolone antibiotic pollutants are one or both of ciprofloxacin and norfloxacin; after pre-irradiation, the dark-state (in the dark environment without light irradiation) catalytic degradation performance of the material on the quinolone antibiotic pollutants in water is greatly enhanced, the degradation rate of ciprofloxacin (80ppm) reaches 48.58%, the degradation rate of norfloxacin (80ppm) reaches 36.84%, and the degradation rate of ciprofloxacin / norfloxacin mixed solution (80ppm) reaches 30.19%; the photocatalytic degradation performance of the material on the quinolone antibiotic pollutants is also greatly enhanced, the degradation rate of ciprofloxacin (80ppm) reaches 90.53%, the degradation rate of norfloxacin (80ppm) reaches 86.4%, the degradation rate of ciprofloxacin / norfloxacin mixed solution (80ppm) reaches 89.07%, and the mineralization rate of ciprofloxacin / norfloxacin mixed solution (80ppm) reaches 86.37%.

[0018] The advantages of the present application are: 1. The present application uses tetrabutyl titanate, ammonium heptamolybdate, polyvinylpyrrolidone (PVP) and concentrated hydrochloric acid as raw materials, which are all easily available in the laboratory; the whole process uses water / ethanol as the solvent system, does not introduce heavy metals or toxic ligands, and the by-products are easy to dispose, meeting the green preparation requirements and compliance use needs of environmental purification materials.

[0019] 2. The present application realizes uniform compounding of Ti / Mo sources and blending with polyvinylpyrrolidone (PVP) in the precursor stage, and grows by hydrothermal method, to obtain a close contact interface in situ after calcination, reducing the interface defects caused by secondary physical compounding; the energy band mismatch and built-in electric field of MoO3 / TiO2 are beneficial to the spatial separation and directional migration of electrons and holes, reducing the bulk / surface recombination, and improving the actual quantum efficiency and stability.

[0020] 3. The PVP in the present application acts as a soft template / surfactant, assisting nucleation growth and local coordination coating, to obtain nanoparticles and tubular assemblies with high specific surface area and reasonable pore structure; by adjusting the PVP concentration and mixing ratio, the grain size, interface roughness and secondary agglomeration degree can be finely adjusted, thereby simultaneously increasing the adsorption and photocatalysis.

[0021] 4. In the MoO3 / TiO2 heterojunction material of the present application, the tubular structure of MoO3 provides abundant adsorption sites, and TiO2 contributes a stable reactive surface, which realizes the integration of "enrichment-activation-mineralization" under the coupling of a close heterojunction; the MoO3 / TiO2 heterojunction material shows higher reaction selectivity and deeper mineralization degree (quantified and evaluated by TOC testing index) for mixed pollutants such as ciprofloxacin (CIP), norfloxacin (NOR) and other quinolones, and has better anti-interference and cycle performance than conventional single-phase materials.

[0022] 5. The MoO3 / TiO2 heterojunction material of the present application has a significant and persistent photochromic behavior under room temperature light conditions, which is attributed to its unique photocatalytic memory effect. The photochromic change of the MoO3 / TiO2 heterojunction material changes its internal electronic structure, which leads to better separation of photo-generated carriers and subsequent beneficial effects on its catalytic performance. After photochromism, the performance of the MoO3 / TiO2 heterojunction material in photocatalytic degradation of quinolone antibiotics is enhanced, especially for ciprofloxacin and norfloxacin. For the degradation and mineralization rate of a mixed ciprofloxacin / norfloxacin pollutant solution (80 ppm), the rate even reaches 86.37%, and the MoO3 / TiO2 heterojunction material has good cycle stability and reusability.

[0023] 6. The MoO3 / TiO2 heterojunction material of the present application is used in the following way: first, pre-illumination (300W full light lamp, more than 20 minutes), then added to the water containing quinolone antibiotic pollutants for catalytic adsorption and degradation of pollutants. The heterojunction material shows enhanced photocatalytic degradation performance after pre-illumination, in addition, the material shows a photocatalytic memory effect in the dark environment after pre-illumination, and still has good degradation ability for the pollutant solution. It can be applied to catalytic adsorption and degradation of quinolone antibiotic pollutants in water in dark environment and under light conditions. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 X-ray diffraction peak pattern of the MoO3 / TiO2 heterojunction material prepared in Example 1.

[0025] Figure 2 Microscopic morphology of the MoO3 / TiO2 heterojunction material prepared in Example 1 under transmission electron microscope.

[0026] Figure 3 High-resolution morphology of the MoO3 / TiO2 heterojunction material prepared in Example 1 under transmission electron microscope.

[0027] Figure 4 X-ray photoelectron spectroscopy of Mo element 3d peak, Ti element 2p peak and O element 1s peak of the MoO3 / TiO2 heterojunction material prepared in Example 1; wherein: (a) Mo element 3d peak; (b) Ti element 2p peak; (c) O element 1s peak.

[0028] Figure 5 MoO3 / TiO2 heterojunction material prepared in Example 1; wherein: (a) MoO3 / TiO2 heterojunction material prepared in Example 1; (b) MoO3 / TiO2 heterojunction material prepared in Example 1; (c) MoO3 / TiO2 heterojunction material prepared in Example 1.

[0029] Figure 6 Effect comparison chart of MoO3 / TiO2 heterojunction material prepared in Example 1 after pre-illumination in the dark for catalytic degradation of quinolone antibiotics (80ppm); wherein: (a) ciprofloxacin; (b) norfloxacin; (c) ciprofloxacin / norfloxacin mixed solution; (d) cyclic stability for degradation of mixed solution.

[0030] Figure 7The photocatalytic degradation effect comparison chart of quinolone antibiotics (80 ppm) under light source after pre-illumination of MoO3 / TiO2 heterojunction material prepared in Example 1; wherein: (a) ciprofloxacin; (b) norfloxacin; (c) mixed solution of ciprofloxacin / norfloxacin; (d) cyclic stability of degradation of the mixed solution.

[0031] Figure 8 The mass spectrum spectrum of MoO3 / TiO2 heterojunction material prepared in Example 1 under different times of photocatalytic degradation of ciprofloxacin / norfloxacin mixed pollutant solution (80 ppm) under ultra-high performance liquid chromatography-mass spectrometry, wherein: (a) original solution; (b) solution after photocatalytic degradation.

[0032] Figure 9 The TC-IC content chart of MoO3 / TiO2 heterojunction material prepared in Example 1 under different times of photocatalytic degradation of ciprofloxacin / norfloxacin mixed pollutants under total organic carbon analyzer.

[0033] Figure 10 The reaction path of MoO3 / TiO2 heterojunction material prepared in Example 1 for photocatalytic mineralization of ciprofloxacin.

[0034] Figure 11 The reaction path of MoO3 / TiO2 heterojunction material prepared in Example 1 for photocatalytic mineralization of norfloxacin. DETAILED DESCRIPTION

[0035] The application will be further described below in combination with the drawings and examples.

[0036] The MoO3 / TiO2 heterojunction material with photocatalytic memory effect prepared in the application is realized by interface regulation and defect engineering means, which realizes high order of crystal structure, tight coupling of interface, and formation of strong built-in electric field and S-type energy band arrangement on energy band structure, effectively promotes the spatial separation and directional migration of photo-generated carriers. Compared with traditional photocatalysts, the material in the application shows high mineralization ability of quinolone pollutants (such as ciprofloxacin, norfloxacin, etc.) under light conditions, and still maintains the sustained degradation performance under non-light conditions after pre-illumination excitation, showing a significant photocatalytic memory effect. The effect is derived from the synergistic effect of oxygen vacancy defects and S-type heterostructure, which can quickly recover and enhance the catalytic activity under the condition of re-illumination, thereby significantly improving the cyclic stability and application durability of the material. The material in the application has broad application prospects in the field of environmental governance such as antibiotic wastewater treatment.

[0037] The application provides a MoO3 / TiO2 heterojunction material with a photocatalytic memory effect, which is a nanometer powder formed by titanium dioxide particles adhering to the surface of molybdenum trioxide nanotubes, and is an inorganic semiconductor material with a three-dimensional skeleton and a nanotube / particle composite structure.

[0038] The MoO3 / TiO2 heterojunction material has the characteristics of a wide-bandgap semiconductor material, and due to the existence of molybdenum-oxygen octahedral layer-by-layer stacking of molybdenum trioxide and the tubular structure of molybdenum trioxide being much larger than the titanium dioxide nanoparticles, it is a three-dimensional structure.

[0039] The MoO3 / TiO2 heterojunction material has a unique photocatalytic memory effect, that is, after a certain period of light irradiation, it can still exhibit a sustained discoloration phenomenon and has super strong optical performance and catalytic degradation performance, realizing photocatalytic adsorption and degradation of quinolone antibiotic pollutants in water, and even for a mixed pollutant solution of ciprofloxacin / norfloxacin (80 ppm), the mineralization rate can reach nearly ninety percent.

[0040] The preparation method of the MoO3 / TiO2 heterojunction material is that a molybdenum source aqueous solution composed of ammonium heptamolybdate is reacted with a titanium source ethanol solution composed of tetrabutyl titanate, and the surface is modified with a polyvinylpyrrolidone ethanol solution, and the MoO3 / TiO2 heterojunction material is obtained by using a solution thermal polymerization method.

[0041] In the following examples, the concentration of the concentrated hydrochloric acid used is 12 mol / L. Example 1

[0042] This example is the preparation of the MoO3 / TiO2 heterojunction material with a photocatalytic memory effect, which is prepared by using a solution thermal polymerization method, that is, a molybdenum source aqueous solution composed of ammonium heptamolybdate is reacted with a titanium source ethanol solution composed of tetrabutyl titanate, and the surface is modified with a polyvinylpyrrolidone ethanol solution, and the specific process is as follows: A certain amount of tetrabutyl titanate is added to a beaker containing anhydrous ethanol, the cup opening is sealed with a plastic wrap, and stirring is performed on a magnetic stirrer for 20 minutes, and then ultrasonic treatment is performed in an ultrasonic machine for 10 minutes to obtain a titanium source precursor solution with a concentration of 0.2 mol / L.

[0043] A certain amount of ammonium heptamolybdate was weighed and added to a beaker containing deionized water. The mouth of the beaker was sealed with plastic wrap, and the mixture was stirred on a magnetic stirrer for 20 minutes and then treated with ultrasonic waves for 10 minutes to obtain a 0.2 mol / L ammonium heptamolybdate solution. Concentrated hydrochloric acid with a concentration of 12 mol / L was slowly added to the solution until the pH value of the solution was 2. The solution was then continuously stirred on a magnetic stirrer for 20 minutes to obtain a molybdenum source precursor solution.

[0044] A certain amount of polyvinylpyrrolidone was added to anhydrous ethanol, and the mixture was stirred on a magnetic stirrer for 20 minutes to obtain a 0.1 mol / L polyvinylpyrrolidone solution in anhydrous ethanol.

[0045] The titanium source precursor solution obtained in step (1) and the molybdenum source precursor solution obtained in step (2) were mixed in a volume ratio of 1:1 and stirred on a magnetic stirrer for 10 minutes to obtain a mixed solution. The mixed solution and the polyvinylpyrrolidone solution in anhydrous ethanol obtained in step (3) were mixed in a volume ratio of 8:1 and stirred on a magnetic stirrer for 20 minutes to obtain a heterojunction precursor solution.

[0046] (5) The heterojunction precursor solution was transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene, and hydrothermal reaction was performed at 180°C for 15 hours in a temperature-controlled drying box. After the reaction, the lower layer material was separated and collected from the final solution using a centrifugal method, and the collected material was washed with deionized water and ethanol, respectively, and the washing was alternated for three times. After washing, the obtained material was dried in a constant temperature vacuum drying box at 60°C for 15 hours.

[0047] (6) The sample dried completely in step (5) was calcined in a muffle furnace at 400°C for 6 hours to obtain the MoO3 / TiO2 heterojunction material.

[0048] Figure 1 The XRD diffraction peak pattern of the MoO3 / TiO2 heterojunction material prepared in this example and the standard PDF card can be compared, and it can be found that the diffraction peak pattern of the synthesized MoO3 / TiO2 heterojunction material has no impurity peak and basically coincides with the standard sample, which is a pure phase of orthorhombic molybdenum trioxide and anatase titanium dioxide composite, corresponding to PDF #01-074-7911 and PDF #01-070-6826, respectively. Figure 2 The micro-morphology pattern of the MoO3 / TiO2 heterojunction material prepared in this example under a transmission electron microscope can clearly show the tubular morphology characteristics of molybdenum trioxide and the titanium dioxide nanoparticles embedded on it. Figure 3The image shown is a high-resolution transmission electron microscope image of the MoO3 / TiO2 heterojunction material prepared in this embodiment. It shows that the inner diameter of the molybdenum trioxide tube, the wall thickness, and the titanium dioxide nanoparticles are all at the nanoscale. Furthermore, the lattice fringes correspond to the crystal planes of molybdenum trioxide and titanium dioxide, respectively, which further proves the successful preparation of the MoO3 / TiO2 heterojunction material.

[0049] Figure 4 This is a fine X-ray photoelectron spectroscopy (XPS) spectrum of the MoO3 / TiO2 heterojunction material prepared in this embodiment. Figure 4 The characteristic peaks of Mo, Ti, and O can be seen in the image. Mo's 3... d 3 / 2 and 3 d 5 / 2 Orbital peaks and Ti 2p 1 / 2 and 2p 3 / 2 The orbital peaks are clearly visible, and each peak area perfectly matches its energy limit. Figure 1 This once again demonstrates the successful preparation of the MoO3 / TiO2 heterojunction material, and the obtained sample is the expected product.

[0050] The crystal structure model of the MoO3 / TiO2 heterojunction material is established as follows: Figure 5 It is composed of molybdenum trioxide ( Figure 5 (a) and titanium dioxide ( Figure 5 (b) is combined at the interface. Figure 5 (c) perfectly matches the heterogeneous structure. Example 2:

[0051] This embodiment describes the application of the MoO3 / TiO2 heterojunction material prepared in Example 1 in the catalytic degradation of quinolone antibiotic pollutants under dark conditions after pre-light irradiation. The process is as follows: 1. Take 20 mg of the MoO3 / TiO2 heterojunction material powder obtained in Example 1 and add it to a beaker containing 100 mL of a quinolone antibiotic (ciprofloxacin, norfloxacin, or ciprofloxacin / norfloxacin) solution with a concentration of 80 ppm. Stir the resulting suspension in the dark for 20 minutes to reach adsorption-desorption equilibrium. Then continue stirring and timing, and take 4 mL of solution from the beaker at intervals of 10 min, for a total of 80 min.

[0052] 2. After 80 minutes of adsorption and degradation, 4 mL of the mixed solution taken at different time points were centrifuged and filtered. The supernatant was taken and the concentration of the remaining pollutants in the supernatant was measured. At the same time, the concentration of pollutants in the solution without pre-illumination and without the addition of catalyst was compared. Figure 6The effect comparison chart of MoO3 / TiO2 heterojunction material with memory effect in catalytic degradation of quinolone antibiotic pollutants in darkness is given, and from the chart, it can be seen that the MoO3 / TiO2 heterojunction material has good adsorption performance and photocatalytic memory effect. After pre-illumination, it still can show good catalytic ability even in dark environment.

[0053] 3. 20 mg of MoO3 / TiO2 heterojunction material powder obtained in Example 1 was added to a beaker containing 100 mL of quinolone antibiotic (ciprofloxacin or norfloxacin or ciprofloxacin / norfloxacin) solution with a concentration of 80 ppm, and the obtained suspension was stirred in darkness for 20 minutes to achieve adsorption-desorption equilibrium. Then it was placed under a 300 W xenon lamp light source with a full wavelength filter, and continued to be stirred and timed, and 4 mL of solution was taken from the beaker every interval of time. The sampling interval time was 10 min, and the total photocatalytic experiment was 60 min.

[0054] 4. After 60 minutes of photocatalytic degradation, the 4 mL mixed solutions taken at different time periods were centrifuged and filtered respectively, the supernatant was taken, and then the remaining pollutant concentration in the supernatant was measured, and compared with the pollutant concentration of the solution without illumination and without the addition of MoO3 / TiO2 heterojunction material. Figure 7 The effect comparison chart of MoO3 / TiO2 heterojunction material with memory effect in photocatalytic degradation of quinolone antibiotic pollutants after pre-illumination is given, and it can be clearly seen that in addition to the enhanced catalytic ability in dark environment, the MoO3 / TiO2 heterojunction material shows stronger photocatalytic performance after re-illumination. After the MoO3 / TiO2 heterojunction material produces photocatalytic memory effect, the degradation rate of the MoO3 / TiO2 heterojunction material to ciprofloxacin (80 ppm) and norfloxacin (80 ppm) pollutant solution and ciprofloxacin / norfloxacin (80 ppm) mixed pollutant solution is greater than 80%, and the photocatalytic degradation ability is very considerable. Example 3:

[0055] In this embodiment, the MoO3 / TiO2 heterojunction material prepared in Example 1 is used for photocatalytic mineralization of quinolone antibiotic pollutants, and the process is as follows: The samples taken at different times in the process of photocatalytic ciprofloxacin / norfloxacin mixed pollutant solution (80 ppm) in Example 2 were centrifuged and filtered with a filter membrane with a pore size of 0.22 microns, the filtrate was placed in a suitable capacity bottle, and was tested under a ultra-high performance liquid chromatograph-mass spectrometer, and the mineralization effect of the MoO3 / TiO2 heterojunction material on ciprofloxacin / norfloxacin mixed pollutants at different time periods was analyzed. Figure 8The mass spectrum of the MoO3 / TiO2 heterojunction material prepared in Example 1 after pre-illumination to produce a photocatalytic memory effect and photocatalytic degradation of a mixture of ciprofloxacin and norfloxacin at different times under ultra-high performance liquid chromatography-mass spectrometry is shown in Figures 1 and 2. Figure 8 As can be seen from the comparison of (a) and (b), after 60 min of photocatalytic degradation, the mixed ciprofloxacin / norfloxacin pollutants are almost degraded into small molecular products. Figure 9 The TC-IC content diagram of the MoO3 / TiO2 heterojunction material prepared in Example 1 at different times under total organic carbon analysis after photocatalytic degradation of a mixture of ciprofloxacin and norfloxacin can clearly show that after 60 min of photocatalytic degradation, the mineralization rate of the mixed pollutants is as high as 86.37%, proving the excellent quinolone pollutant mineralization ability of the material after the photocatalytic memory effect. Figure 10 and Figure 11 The possible reaction paths of the MoO3 / TiO2 heterojunction material prepared in Example 1 for photocatalytic mineralization of ciprofloxacin and norfloxacin are shown in Figures 3 and 4. According to the mass spectrum results, the specific degradation and mineralization reaction paths of ciprofloxacin and norfloxacin can be deduced, which are completely consistent with the results of liquid chromatography-mass spectrometry testing and are consistent with the reports of other ciprofloxacin and norfloxacin degradation and mineralization related literatures. It can be seen that the MoO3 / TiO2 heterojunction material with a photocatalytic memory effect can almost completely degrade and mineralize quinolone antibiotic pollutants.

[0056] The results of the example show that the MoO3 / TiO2 heterojunction material with a photocatalytic memory effect synthesized by the present application has a three-dimensional complex structure, and has good adsorption and photocatalytic properties. Under the synergistic effect of adsorption and photocatalysis, the catalytic and degradation performance of the material is further improved. After the photocatalytic memory effect, the dark-state catalytic and photocatalytic properties are further enhanced.

[0057] In summary, the MoO3 / TiO2 heterojunction material of the present application has a unique three-dimensional structure, which is generated by reacting an ammonium heptamolybdate-based molybdenum source precursor solution and a tetrabutyl titanate-based titanium source precursor solution, and the surface of the material is modified with polyvinylpyrrolidone to optimize its performance. The MoO3 / TiO2 heterojunction material of the present application can produce photochromism and photocatalytic memory effect under the action of pre-illumination. The memory effect provides a sustained driving force for the catalytic reaction, significantly enhancing the activity of the material in the dark-state catalytic process. The MoO3 / TiO2 heterojunction material of the present application exhibits excellent catalytic degradation performance in practical applications, especially in water pollution control, showing extremely high catalytic efficiency. The MoO3 / TiO2 heterojunction material can effectively adsorb and degrade quinolone antibiotic pollutants in water. In a ciprofloxacin / norfloxacin mixed pollutant system, the MoO3 / TiO2 heterojunction material of the present application can achieve a mineralization rate of 86.37%, indicating that it has a significant effect in environmental pollution control.

[0058] The above examples are for reference only, and inorganic semiconductor photocatalytic materials, methods for preparing the same, and photocatalytic applications thereof that are similar to or extended from the present patent based on the ideas of the present patent are all within the scope of protection of the present patent.

Claims

1. A MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect, characterized in that: The material is a composite of molybdenum trioxide nanotubes and titanium dioxide particles, wherein: the molybdenum trioxide nanotubes are assembled from pure-phase molybdenum trioxide crystals, and the inner diameter and wall thickness of the tubes are both nanoscale sizes; the titanium dioxide particles are particles with nanoscale sizes composed of titanium dioxide crystals. 2.The MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect according to claim 1, characterized in that: The molybdenum trioxide crystals are orthorhombic, with a space group of Pbnm, and have a layered structure stacked by molybdenum-oxygen octahedrons; the titanium dioxide crystals are tetragonal anatase, belonging to the space group I41 / amd. 3.The MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect according to claim 1 or 2, characterized in that: The MoO3 / TiO2 heterojunction material is a powder formed by the attachment of titanium dioxide particles to the surface of molybdenum trioxide nanotubes; the MoO3 / TiO2 heterojunction material has the characteristics of a wide-bandgap semiconductor photocatalytic material, and has a unique photocatalytic memory effect, that is, after a certain period of light exposure, it can still exhibit a color change and has super strong optical and catalytic degradation properties. 4.The MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect according to claim 1 or 2, characterized in that: The preparation method of the MoO3 / TiO2 heterojunction material is to mix a titanium source precursor solution and a molybdenum source precursor solution in a certain proportion, use polyvinylpyrrolidone as a surfactant, and use a solution thermal polymerization method to obtain the MoO3 / TiO2 heterojunction material; the preparation method specifically includes the following steps: (1) adding tetrabutyl titanate into anhydrous ethanol to obtain a titanium source precursor solution; dissolving ammonium heptamolybdate in deionized water, and then adding concentrated hydrochloric acid to obtain a molybdenum source precursor solution; dissolving polyvinylpyrrolidone in anhydrous ethanol to obtain a polyvinylpyrrolidone solution; (2) mixing the titanium source precursor solution and the molybdenum source precursor solution obtained in step (1) in a certain proportion to obtain a mixed solution A, and then mixing the mixed solution A and the polyvinylpyrrolidone solution in a certain proportion and stirring uniformly to obtain a molybdenum trioxide / titanium dioxide heterojunction precursor solution; (3) transferring the molybdenum trioxide / titanium dioxide heterojunction precursor solution obtained in step (2) to a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner, and performing a reaction at a certain temperature; after the reaction, the obtained material is centrifuged to separate the lower solid material, and then sequentially subjected to washing and drying treatments; (4) placing the sample obtained after the drying treatment in step (3) in a muffle furnace for calcination treatment to obtain the molybdenum trioxide / titanium dioxide heterojunction material (MoO3 / TiO2 heterojunction material). 5.The MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect according to claim 4, characterized in that: In step (1), the concentration of tetrabutyl titanate in the titanium source precursor solution is 0.15-0.25 mol / L, the concentration of ammonium heptamolybdate in the ammonium heptamolybdate solution is 0.1-0.2 mol / L, and the concentration of polyvinylpyrrolidone in the polyvinylpyrrolidone solution is 0.08-0.12 mol / L; the pH value of the molybdenum source precursor solution is adjusted to 1-3 by using concentrated hydrochloric acid, and the concentration of the concentrated hydrochloric acid is 12 mol / L. 6.The MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect according to claim 4, characterized in that: In step (2), when preparing the mixed solution A, the volume ratio of the titanium source precursor solution to the molybdenum source precursor solution is 1:(1-2); when preparing the molybdenum trioxide / titanium dioxide heterojunction precursor solution, the volume ratio of the mixed solution A to the polyvinylpyrrolidone solution is (5-10):

1. 7.The MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect according to claim 4, characterized in that: In step (3), the temperature of the hydrothermal reaction is 140-200 DEG C, and the hydrothermal reaction time is 12-20 hours. The washing treatment is to wash the collected lower solid material with deionized water and ethanol in turn, and each is washed for three times alternately; the drying treatment is to dry in a constant temperature vacuum drying box at 60 DEG C for 12-18 hours. 8.The MoO 3 / TiO 2 heterojunction material with photocatalytic memory effect according to claim 4, characterized in that: In step (4), the temperature of the calcination treatment is 300-500 DEG C, and the calcination treatment time is 4-6 hours.

9. The application of MoO3 / TiO2 heterojunction material with photocatalytic memory effect in the degradation of quinolone antibiotics according to claim 1, characterized in that: The MoO3 / TiO2 heterojunction material is applied to photocatalytic degradation of quinolone antibiotic pollutants in water environment, and the application process is as follows: the MoO3 / TiO2 heterojunction material is pre-irradiated (300W full light lamp) for more than 20 minutes, and then added into water containing quinolone antibiotic pollutants to carry out pollutant catalytic adsorption and degradation under light or no light.

10. The application of MoO3 / TiO2 heterojunction material with photocatalytic memory effect in the degradation of quinolone antibiotics according to claim 9, characterized in that: The quinolone antibiotic pollutants are one or both of ciprofloxacin and norfloxacin; after pre-irradiation, the material has greatly enhanced dark state (in the dark environment without light) catalytic degradation performance on quinolone antibiotic pollutants in water, and the degradation rate of ciprofloxacin (80ppm) reaches 48.58%, the degradation rate of norfloxacin (80ppm) reaches 36.84%, and the degradation rate of ciprofloxacin / norfloxacin mixed solution (80ppm) reaches 30.19%; the material also has greatly enhanced photocatalytic degradation performance on quinolone antibiotic pollutants, and the degradation rate of ciprofloxacin (80ppm) reaches 90.53%, the degradation rate of norfloxacin (80ppm) reaches 86.4%, the degradation rate of ciprofloxacin / norfloxacin mixed solution (80ppm) reaches 89.07%, and the mineralization rate of ciprofloxacin / norfloxacin mixed solution (80ppm) reaches 86.37%.

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