A rare earth metal tungstate nanosheet material, a preparation method and application thereof

Abstract

The present application relates to a kind of rare earth metal tungstate nanosheet material and its preparation method and application.Rare earth metal tungstate nanosheet material includes PO4 3‑ LnWO4 Nanosheet, Ln is at least one of lanthanide series rare earth metals.Preparation steps: phosphotungstic acid is dissolved with precursor in solvent, stirring to form solution;Add organic amine ligand, stirring to form transparent solution;The solution is subjected to solvothermal reaction;Centrifugation, ethanol washing and drying, to obtain rare earth metal tungstate nanosheet material.Using solvothermal reaction method, two-dimensional sheet structure material is successfully constructed by nanowire interweaving, with high specific surface area, abundant pore and excellent structural stability, effectively overcome the problem of single structure, insufficient active site of traditional photocatalytic material.Various typical antibiotic pollutants are all shown excellent degradation capacity, break through the limitation that most photocatalytic materials are only effective to single pollutant, realize strong pollutant degradation universality.

Description

Technical Field

[0001] This invention relates to a catalyst nanomaterial, specifically to a rare earth metal tungstate nanosheet material, its preparation method, and its application. Background Technology

[0002] Fluoroquinolones (FQs) are a class of broad-spectrum antibacterial drugs widely used in clinical medicine and animal husbandry. These antibiotics are characterized by high stability and resistance to degradation, leading to persistent accumulation and recalcitrant degradation in natural water bodies, making them a typical emerging environmental pollutant. Traditional biodegradation and conventional chemical oxidation methods have limited removal efficiency for FQs and often suffer from insufficient selectivity and complex products. Therefore, developing a photocatalytic material capable of efficiently and selectively degrading FQs under visible light conditions has significant application value.

[0003] Metal tungstate semiconductors have been widely studied for photocatalytic oxidation, reduction, and degradation of water pollutants due to their excellent chemical stability and redox capabilities. However, traditional bulk tungstates generally suffer from problems such as wide band gaps, weak visible light absorption, rapid recombination of photogenerated carriers, and limited active sites on the material surface, which restrict their practical effectiveness in the efficient photocatalytic degradation of antibiotics. Based on this, current research has begun to explore ways to improve the photoelectric properties of tungstates through miniaturization, ion doping, and interface modulation.

[0004] Among numerous regulatory strategies, polyoxometalates (POMs) are widely used for the controllable preparation of metal tungstates due to their well-defined structures, tunable compositions, and stable provision of polyoxometalate clusters. Polyoxometalates play a dual role in tungstate formation: firstly, they act as a homogeneous tungsten source in hydrolysis and condensation reactions, promoting the directed assembly of metal ions and tungsten-oxygen clusters at the molecular scale, forming tungstate structures with nanoscale or even sub-nanometer characteristics; secondly, their internal heteroatoms (such as PO4)... 3- BO3 3- (e.g.,) can introduce lattices or interfaces during the material construction process to adjust the material's band structure, oxygen defect distribution, and surface electronic states, thereby significantly improving visible light absorption capacity and photogenerated carrier separation efficiency.

[0005] While the aforementioned POM-based construction strategies have driven the development of tungstate photocatalytic materials, some systems still rely on toxic metals such as Cd as central ions. Although these materials enhance visible light response through size effects and interface reconstruction, their metal composition poses environmental risks and fails to meet the safety requirements for water pollution control. Furthermore, the surface chemistry of Cd-based tungstates is more suitable for small molecule catalytic reactions, exhibiting limited selective adsorption and directional reaction capabilities for complex, multifunctional FQs molecules, making it difficult to achieve efficient and controllable photocatalytic degradation.

[0006] In contrast, rare earth element La and similar metals (such as Gd) have advantages such as low toxicity, good chemical stability, strong hard acid properties, and the ability to easily form stable structures with tungsten oxide clusters. 3+ The large ionic radius and unique electronic structure enable the construction of stable metal-oxygen-tungsten networks under the control of POMs, while providing more Lewis acid sites on the material surface, which is beneficial for the adsorption, complexation, and targeted activation of complex antibiotic molecules. Furthermore, La-based tungstates offer greater tunability in terms of light absorption, band structure modulation, and carrier behavior, through interaction with PO42-. 3- The synergistic effect of heteroatoms can induce lattice distortion, enhance interfacial polarization, and improve the efficiency of photogenerated electron-hole separation, thereby improving its photocatalytic performance in the visible light region.

[0007] However, despite the inherent advantages of lanthanides (Ln), currently available technologies lack a material system capable of highly selective photocatalytic degradation of antibiotic pollutants. This system utilizes heteropolyacids as structural and electronic control units, with lanthanides as the central element to construct tungstate nanosheets. Existing metal tungstate materials still exhibit significant shortcomings in visible light response, structural controllability, material safety, and selective degradation capabilities for complex antibiotic molecules, making it difficult to meet the practical application requirements for water pollution control.

[0008] In view of this, this patent develops a novel lanthanide tungstate nanosheet photocatalytic material with a nanoscale structure, using a heteropoly acid (phosphotungstic acid) as the control unit and lanthanide elements (La, Gd, Ce, etc.) of Ln as the central metal, in order to solve the technical bottlenecks of existing technologies in terms of material toxicity, photoresponse range, electronic structure regulation and selective degradation of antibiotics. Summary of the Invention

[0009] To address the problems existing in the above-mentioned technologies, the present invention provides a rare earth metal tungstate nanosheet material, its preparation method, and its application.

[0010] This invention first provides a rare earth metal tungstate nanosheet material, which includes PO4. 3-–LnWO4 nanosheets, wherein Ln is at least one of the lanthanide rare earth metals.

[0011] In a preferred embodiment, the PO4 3- –LnWO4 nanosheets have a two-dimensional sheet-like structure containing PO4 3- Doping with Ln 3+ Doped WO4 2- Basic lattice.

[0012] In the preferred scheme, Ln 3+ It is at least one of the following substances: La 3+ Gd 3+ Ce 3+ Pr 3+ 、Nd 3+ 、Sm 3+ Eu 3 + 、Tb 3+ .

[0013] In the preferred embodiment, through Ln precursor and PW 12 PO4 was prepared 3- –LnWO4 nanosheets; Ln precursor and PW 12 The molar ratio is X:1, where X ranges from 1 to 10, or from 3 to 30, or X is 5, 10, or 20.

[0014] This invention provides a method for preparing rare-earth metal tungstate nanosheets based on heteropolyacid regulation, which includes the following steps:

[0015] Step 1: Add phosphotungstic acid (H3PW) 12 O 40 The rare earth metal salt Ln(CH3COO)3·xH2O is dissolved together with cyclohexane in a mixed nonpolar solvent composed of cyclohexane and long-chain alcohols (such as n-hexanol and n-octanol), wherein the volume ratio of cyclohexane to long-chain alcohol is (1:1) to (4:1). The mixture is stirred continuously at 30-50°C for 30-60 minutes to form a homogeneous suspension. This step utilizes the weak coordination ability of the long-chain alcohol to initiate an initial interaction with the rare earth ions, thereby regulating the subsequent nucleation kinetics. Here, "nucleation kinetics" refers to the regulation of the nanosheet formation rate in step 3 below.

[0016] Step 2: Add a complex organic amine ligand to the system from Step 1. This ligand consists of a main amine (selected from oleylamine or hexadecylamine) and a small amount of auxiliary diamine (such as ethylenediamine, 5%-15% by volume). Under an inert atmosphere (such as nitrogen or argon), stir vigorously at 60-80°C for 1-2 hours until a homogeneous, transparent amber solution is formed. Subsequently, allow the solution to stand at room temperature for 2-4 hours to promote the formation of a more stable metal-organic precursor complex.

[0017] Step 3:

[0018] The aged solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene (PTFE), with the filling level controlled at 60%-75%. A stepwise temperature ramping procedure was used for the reaction.

[0019] First stage: Heat to 140-160°C at a rate of 2-3°C / min and hold for 2-4 hours to achieve slow nucleation;

[0020] Second stage: Continue heating to the target temperature of 180-200°C and maintain the temperature for 12-20 hours to promote anisotropic growth and crystallization of the nanosheet structure.

[0021] The molar ratio of the rare earth metal precursor to phosphotungstic acid, X (Ln:PW), is... 12 The value should be strictly controlled between 5 and 30, with X=10 and 20 being preferred.

[0022] Step 4: After the reaction is complete, allow it to cool naturally to room temperature. The product is collected by centrifugation and purified using an alternating washing method: first, wash twice with a mixed solvent of cyclohexane and acetone (1:1 volume ratio) to thoroughly remove long-chain organic amines and residual organic matter; then wash twice with anhydrous ethanol. The obtained product is dried in a vacuum drying oven at 80°C for 8-12 hours to obtain fluffy, powdery rare-earth metal tungstate nanosheets.

[0023] In the preferred scheme:

[0024] The rare earth metal Ln is selected from at least one of the following elements: La, Gd, Ce, Pr, Nd, Sm, Eu, Tb;

[0025] The mixed nonpolar solvent is cyclohexane and n-hexanol in a volume ratio of 3:1;

[0026] The composite organic amine ligand is a mixture of oleylamine and ethylenediamine, wherein ethylenediamine accounts for 10% of the total volume;

[0027] In step 3, the solvothermal reaction is carried out in two stages: first, the temperature is maintained at 150°C for 3 hours, and then the reaction is carried out at 190°C for 16 hours.

[0028] The molar ratio X is 10.

[0029] This invention also provides an application of rare-earth metal tungstate nanosheets based on heteropolyacid regulation in the photocatalytic degradation of antibiotics or drug-like pollutants containing heterocyclic structures. Drug-like pollutants refer to substances containing heterocyclic structures similar to antibiotics, such as sulfonamides and organic dyes like rhodamine B.

[0030] In a preferred embodiment, the antibiotic includes fluoroquinolone antibiotics; the fluoroquinolone antibiotic is at least one of the following substances: CIP, NOR, OFX, ENR, LOM.

[0031] In the preferred scheme, in CO3 2- Photocatalytic degradation is carried out in the system.

[0032] The technical effects of this invention can be summarized as follows:

[0033] This invention addresses the aforementioned technical problems and solutions by achieving significant technical effects through material structure regulation, multi-element synergistic effects, and photocatalytic behavior optimization, as detailed below:

[0034] (1) Technical effects in material design and structural control:

[0035] This invention successfully constructed a two-dimensional sheet-like structure material formed by interwoven nanowires using a solvothermal reaction method. This structure has high specific surface area, abundant pores, and excellent structural stability, effectively overcoming the problems of simple structure and insufficient active sites in traditional photocatalytic materials.

[0036] By controlling the material composition, highly uniform dispersion of multiple elements such as C, N, O, P, Ln, and W was achieved, and controllable W was formed within the material. 6+ / W 5+ Redox pairs and surface oxygen vacancies. The synergistic effect of these two factors significantly improves the separation efficiency of photogenerated electron-hole pairs, accelerates carrier migration, and effectively solves the technical bottlenecks of easy phase separation and high carrier recombination rate in traditional single-component or multi-component systems.

[0037] (2) Technical effects in terms of performance improvement:

[0038] The material PO4 prepared in this invention 3- –LaWO4 (X=10) achieves a target pollutant degradation efficiency of up to 92% under optimal conditions (catalyst dosage 1.0 g / L), significantly outperforming most existing photocatalytic materials. The material's narrow bandgap (3.84 eV) and strong visible light absorption effectively enhance solar energy utilization efficiency, resulting in superior photocatalytic activity in the visible light region and solving the problems of narrow light absorption range and low degradation rate inherent in traditional materials.

[0039] (3) Technical effects in terms of environmental adaptability and universality of application:

[0040] The materials prepared in this invention exhibit excellent degradation capabilities for a variety of typical antibiotic pollutants (including CIP, NOR, OFX, ENR, LOM, etc.), overcoming the limitation of most photocatalytic materials being effective only for single pollutants and achieving strong universality in pollutant degradation. In the presence of Cl... - SO4 2- NO3 - It can maintain stable catalytic performance in water containing common inorganic anions, including CO3. 2- The presence of [the substance] can even promote the reaction process, effectively avoiding the technical defects of traditional photocatalytic systems that are easily inhibited by anions, leading to a decrease in activity. Therefore, it is more suitable for complex real-world aquatic environments. Compared to some existing photocatalytic technologies that require high temperatures, high pressures, or rely on expensive additives, this invention is simple to operate, operates under mild conditions, and has low operating costs, making it more suitable for large-scale engineering applications.

[0041] (4) Technological effects in terms of social and economic value:

[0042] The successful development of this technology provides an efficient, stable, economical, and environmentally friendly approach for the treatment of antibiotic pollution in aquatic environments. Its superior comprehensive performance not only drives new advancements in photocatalytic material design but also contributes new solutions for improving efficiency and reducing costs in water treatment processes. Based on its reliable performance in complex aquatic systems, this technology has broad application potential in municipal wastewater treatment, medical wastewater purification, and industrial wastewater treatment. The widespread application of this technology will help enhance ecological environment governance capabilities, provide strong support for maintaining water ecological security and public health, and has profound social value. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the synthesis steps of the samples in Examples 1-3 of the present invention; OAm in the figure represents oleylamine;

[0044] Figure 2 The images shown are SEM and TEM images of the sample from Example 1 of this invention.

[0045] Figure 3 The XRD patterns of the samples and standard cards in Examples 1-3 of this invention are shown below.

[0046] Figure 4 The UV-Vis-DRS spectra of samples from Examples 1-3 of this invention;

[0047] Figure 5 XPS spectra of samples from Examples 1-3 of this invention;

[0048] Figure 6 The degradation performance diagrams are for samples from Examples 1-3 of this invention.

[0049] Figure 7 The diagram shows the morphology and degradation performance of Example 4 of the present invention.

[0050] Figure 8 The diagram shows the morphology and degradation performance of Example 5 of the present invention. Detailed Implementation

[0051] Example 1: PO4 3- Preparation of LaWO4 (X=10):

[0052] (1) Weigh 0.5 g of PW 12 Add 24 mL of n-hexane to 0.5486 g of La(CH3COO)3·xH2O and stir for 10 min; Note that the mass of xH2O is not included in the 0.5486 g of La(CH3COO)3·xH2O, and this is also the case in the following examples to maintain the correct conversion of dosage and molar ratio.

[0053] (2) Add 5.7 mL of oleylamine and continue stirring for 10 min;

[0054] (3) The solution was transferred to a reaction vessel and reacted at 180 °C for 12 h using a solvothermal method;

[0055] (4) After cooling, centrifuge at 8000 rpm and wash three times with ethanol;

[0056] (5) Vacuum drying at 60 °C yields PO4. 3- –LaWO4 (X=10) nanosheets.

[0057] Example 2: PO4 3- Preparation of LaWO4 (X=5):

[0058] Same as Example 1, except that the feeding ratio of La(CH3COO)3·xH2O is different, which is 0.27743g.

[0059] Example 3: PO4 3- Preparation of LaWO4 (X=20):

[0060] Same as Example 1, except that the feeding ratio of La(CH3COO)3·xH2O is different, which is 1.0973g.

[0061] Example 4: PO4 3- Preparation of GdWO4 (X=10):

[0062] This embodiment is used to verify the applicability of the method of the present invention to other lanthanide metals (Ln). Same as Example 1, but the amount of Gd(CH3COO)3·xH2O added is adjusted to 0.5805 g. The preparation steps are the same as in Example 1, except that the rare earth precursor is replaced with Gd(CH3COO)3·xH2O, and the amount added is 0.5805 g. All other reaction conditions are completely identical, yielding two-dimensional PO4. 3- –GdWO4 (X = 10) nanosheets.

[0063] Example 5: PO4 3- Preparation of CeWO4 (X=10):

[0064] To further extend this invention to more lanthanide metals (Ln=Ce), the same steps as in Example 1 were used, except that the amount of rare earth precursor was adjusted to 0.5507 g of Ce(CH3COO)2·xH2O, thus PO4 could be prepared. 3- –CeWO4 (X = 10) nanosheets.

[0065] The synthesis methods for other lanthanide metals are the same as in Example 1, except that the rare earth precursor is replaced with the precursor corresponding to the desired lanthanide metal element, which will not be described in detail here; and, according to the required X ratio, the corresponding mass of rare earth precursor is selected.

[0066] Reagents and instruments:

[0067] Reagent: n-hexane (C6H) 14 Anhydrous ethanol (C2H6O) and phosphotungstic acid (H3PW) were purchased from Sinopharm Chemical Reagent Co., Ltd. (China). 12 O 40 -6H2O, PW 12 Lanthanum acetate hydrate (La(CH3COO)3–xH2O), oleylamine (OLA), potassium persulfate (PMS), ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OFX), enrofloxacin (ENR), and lomefloxacin (LOM) were purchased from Aladdin (Shanghai, China). All chemical reagents used in the experiments were analytical grade and had not undergone further purification. Deionized water was used in all experimental procedures.

[0068] Instruments: Scanning electron microscope (SEM, JEOL JSM-7800F), transmission electron microscope (TEM, Talos F200X G2), UV-Vis spectrophotometer (solid-state UV-vis-DRS, Shimadzu UV-2405), X-ray photoelectron spectroscopy (XPS, Thermo Scientific Escalab OXi), xenon lamp light source (PLS-SEX300D).

[0069] Experimental Analysis and Explanation:

[0070] 1. PO4 prepared in Example 1 3- -Analysis was conducted on the synthesis of LaWO4 (X=10) material.

[0071] Figure 1 This provides an overview of i.) PO4 3- - Synthesis route of LaWO4 (X=10). This synthesis process uses a one-step solvothermal method to successfully prepare La-based doped WO3 nanosheets. First, in the nonpolar solvent n-hexane, PW 12 A stable metal-amine complex is formed with the lanthanum acetate precursor under the strong coordination of OLA. This complex not only provides spatial confinement for the hydrolysis-condensation of tungstate ions, but also realizes the La... 3+ Uniform doping at the molecular scale was achieved. Subsequently, OLA, acting as a reducing agent and structure-directing agent, induced partial reduction of tungsten in a high-temperature, high-pressure solvothermal environment, promoting the preferential growth of two-dimensional nanosheet structures along specific crystal planes. Centrifugation and washing processes after the reaction effectively removed unreacted precursors and organic residues. Finally, vacuum drying yielded fully crystallized and uniformly doped PO4. 3- -LaWO4 nanosheet material.

[0072] 2. Regarding the PO4 prepared in Example 1 3- -LaWO4 (X=10) material was characterized.

[0073] Figure 2 These are SEM and TEM images of samples from embodiments of the present invention. Figure 2 Image a is an SEM image of an example of this invention. The sample exhibits a layered stacked structure with relatively uniform layer thickness and certain porosity between the layers. PO4 3- -LaWO4 (X=10) exhibits a balance between aggregation and dispersion, achieving synergistic optimization of light absorption, carrier separation, and reaction site exposure. It enhances light capture and carrier separation efficiency through lamellar aggregation, while retaining sufficient active sites and mass transfer channels through appropriate dispersion, thereby improving photocatalytic degradation performance.

[0074] (2) Transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM):

[0075] TEM Figure 2 (b) shows that the material exhibits a two-dimensional sheet-like aggregate structure composed of interwoven nanowires. The sheets are relatively thin and have a certain degree of porosity, providing a structural basis for the uniform dispersion of multiple components. The uniform elemental distribution achieved through the solvothermal method can avoid the formation of defects caused by phase separation, thereby improving the stability of the material structure.

[0076] like Figure 3 As shown, via PO4 3- X-ray diffraction (XRD) patterns of LaWO4 nanosheets confirm the existence of their crystal structure. From... Figure 3 The given XRD patterns show that different Ln / PW 12 The diffraction peaks of the samples synthesized at scales (X=5, 10, 20) all highly coincided with the peak positions of the standard PDF card (#34-0652, La2W2O9), with (200), (210), (321), and (420) being the main characteristic diffraction peaks of this structure. This result directly indicates that the main crystal structure of the obtained material belongs to the La2W2O9 type tungstate lattice. More importantly, PO4 3- and Ln 3+ The introduction of these substances did not change the basic crystal structure of the material, indicating that they entered WO4 in the form of doping or substitution. 2- It exists within the base lattice, rather than forming an independent impurity phase.

[0077] (3) Ultraviolet-Vis absorption spectrum (solid) UV-Vis-DRS:

[0078] Figure 4 The UV-Vis-DRS spectra of samples from Examples 1-3 of this invention are shown. In the UV-Vis-DRS spectra ( Figure 4 In (a), all samples exhibited strong absorption in the ultraviolet region. PO4 3- -LaWO4 (X=5), PO4 3- -LaWO4 (X=10) and PO4 3- The absorption edges of the LaWO4 (X=20) samples were located at 326 nm, 342 nm, and 367 nm, respectively. With increasing component content, the absorption edges exhibited a red shift, indicating enhanced visible light absorption, which is beneficial for improving the utilization rate of solar energy in photocatalytic degradation reactions. In the optical property characterization of photocatalytic materials, the absorption edge refers to the critical wavelength (λ) at which a sharp increase in absorbance or absorption coefficient occurs in the material's light absorption spectrum (usually ultraviolet-visible diffuse reflectance spectrum, UV-Vis DRS) (i.e., absorption begins to significantly increase). g In simpler terms, it is the "turning point" wavelength at which a material goes from absorbing almost no photons to beginning to strongly absorb them.

[0079] PO4 was calculated using the Tauc plots method. 3- -LaWO4 (X=5), PO4 3- -LaWO4 (X=10) and PO4 3- -Band gap width of LaWO4 (X=20) sample ( Eg () Figure 4 b, where the horizontal axis "hν" represents photon energy, and the vertical axis "αhν" represents the relationship between the absorption coefficient (α) and photon energy (hν), with band gaps of 4.02 eV, 3.84 eV, and 4.17 eV, respectively. PO4 3- -LaWO4 (X=10) has the narrowest band gap, which is beneficial for promoting the excitation of electrons from the valence band to the conduction band under light irradiation, thereby generating more photogenerated electron-hole pairs. Combined with enhanced visible light absorption properties, PO4... 3- -LaWO4 (X=10) exhibits excellent photocatalytic degradation performance.

[0080] (4) X-ray photoelectron spectroscopy (XPS):

[0081] Depend on Figure 5 XPS spectra of samples from Examples 1-3 of this invention. Full spectrum scan ( Figure 5 a) Confirmed that all samples contained C, N, O, P, La, and W elements, consistent with EDS results. (Using PO4) 3- -LaWO4 (X=10) as an example. In the La3d spectrum ( Figure 5 In b), the two peaks at 835.28 eV and 838.88 eV correspond to La3d, respectively. 3 / 2 The two peaks at 852.18 eV and 855.68 eV correspond to La3d. 5 / 2 La mainly consists of La 3+ La exists in the form of [missing information]. Slight shifts in binding energy between different samples indicate that variations in component content can modulate La. 3+ The electronic environment affects its coordination state and chemical reactivity. W4f spectrum ( Figure 5 c) It can be divided into two pairs of peaks, located at 34.68 eV, 36.78 eV and 35.68 eV, 37.78 eV respectively, corresponding to W 5+ and W 6+ Of the three samples, PO4 3- -LaWO4 (X=10) of W 5+ The highest proportion of PO4 provides the catalyst with more sites for photocatalytic degradation. However, it can be calculated that PO4... 3- -LaWO4 (X=10) of W 6+ Peak and W 5+ The energy separation between the peaks was not significantly different, indicating that PO4 3- -LaWO4 (X=10) did not exhibit a phase shift due to different reaction times. O1s spectrum ( Figure 5The peaks of d) can be fitted to lattice oxygen (529.88 eV, 530.78 eV and 530.98 eV) and oxygen defects (531.58 eV, 532.28 eV and 532.38 eV).

[0082] The synthesis method provided by this invention can effectively introduce "very small amounts" of W. 5+ (Typically less than 5%), this is a very sophisticated "defect engineering" strategy. 5+ The presence of these ions, by introducing associated oxygen vacancies, synergistically forms active defect centers, which can effectively capture photogenerated electrons, inhibit charge recombination, and enhance surface adsorption, thus significantly improving the light absorption and catalytic degradation performance of the material.

[0083] It should be noted that the elements "C" and "N" mentioned above are derived from the organic amine ligands added to the precursors in the synthesis. They are adsorbed on the surface of the nanosheets and play a stabilizing role.

[0084] 3. PO4 prepared in Examples 1-3 3- -LaWO4 (X=5), PO4 3- -LaWO4 (X=10) and PO4 3- The degradation performance of the LaWO4 (X=20) material was tested. The specific experimental procedure was as follows: a certain mass of ciprofloxacin (CIP) standard was weighed and dissolved in deionized water to prepare a 10 mg / L ciprofloxacin aqueous solution as the working solution; 50 mg of PO4 prepared in Examples 1-3 was weighed. 3- -LaWO4 (X=5), PO4 3- -LaWO4 (X=10) and PO4 3- -LaWO4 (X=20) material was placed in a 100 mL reactor, and 50 mL of a 10 mg / L CIP aqueous solution was added. The solutions were then magnetically stirred in the dark for 30 min to reach equilibrium, followed by continuous irradiation with a visible light source. Water samples were collected at predetermined time intervals. At each time point, 3 mL of solution was taken, centrifuged to remove adsorbent particles, and the absorbance of the supernatant was measured using a Shimadzu UV-2600 spectrophotometer with a wavelength of 272 nm. The adsorption efficiency of CIP (… E Calculate using the following formula:

[0085] ,

[0086] in, C 0 and C The concentrations of CIP solution before and after degradation are shown below. A 0 and A The absorbance values ​​of CIP before and after degradation are shown below.

[0087] Figure 6 The graphs show the degradation performance of samples from Examples 1-3 of this invention. This invention investigated the degradation performance of Examples 1-3 under different influencing factors, such as... Figure 6 As shown in ac. Catalysts with different La contents (PO4). 3- -LaWO4 (X=5), PO4 3- -LaWO4 (X=10) and PO4 3- The photocatalytic CIP degradation performance of -LaWO4 (X=20) is as follows: Figure 6 As shown in a, PO4 can be found 3- -LaWO4 (X=10) exhibited the best degradation performance, a result consistent with previous characterization findings using SEM, TEM, and UV-Vis-DRS. The catalyst showed excellent degradation performance against various typical pollutants, including ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OFX), enrofloxacin (ENR), and lomefloxacin (LOM). Figure 6 (b) All showed excellent degradation ability. Among them, enrofloxacin (ENR) had the highest degradation performance. Regarding the influence of inorganic anions ( Figure 6 c), CO3 2- This process promotes the photocatalytic degradation of CIP in this invention. This phenomenon may originate from CO3. 2- It interacts with reactive species (such as hydroxyl radicals –OH) generated in the reaction system to produce carbonate radicals (CO3), which have strong oxidizing power and higher stability. –- This free radical can attack pollutant molecules more efficiently; meanwhile, CO3 2- It is possible to enhance the adsorption and charge transfer processes of pollutants by adjusting the pH of the solution and optimizing the surface charge state of the catalyst. - SO4 2- and NO3 - The catalyst had a relatively small impact on degradation efficiency, exhibiting no obvious promoting or inhibiting effect. This indicates that the catalyst has good anti-interference ability in complex aquatic environments containing common inorganic anions, especially in environments containing CO3. 2- Its performance can be improved in water bodies, significantly enhancing its potential for practical water remediation applications.

[0088] Figure 7 PO4 of Example 4 3- – Morphology and degradation performance of GdWO4 (X=10). Figure 7 a shows PO4 3- –GdWO4 (X=10) has a nanosheet structure and exhibits excellent photocatalytic degradation performance on fluoroquinolone antibiotics such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OFX), enrofloxacin (ENR), and lomefloxacin (LOM). Figure 7 (b) The degradation rate exceeds 90%.

[0089] Figure 8 PO4 of Example 5 3- – Morphology and degradation performance of CeWO4 (X=10). Figure 8 a shows PO4 3- –GdWO4 (X=10) has a nanosheet structure, but is slightly aggregated. It also exhibits excellent photocatalytic degradation performance against fluoroquinolone antibiotics such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OFX), enrofloxacin (ENR), and lomefloxacin (LOM). Figure 8 b).

[0090] Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the invention, even when only a single embodiment is described with respect to a particular feature. The feature examples provided in this disclosure are intended to be illustrative and not limiting, unless otherwise stated. In practice, one or more technical features of the dependent claims may be combined with the technical features of the independent claims as needed and where technically feasible, and may be derived from the technical features of the respective independent claims in any suitable manner rather than solely by the specific combinations listed in the claims.

[0091] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A rare earth metal tungstate nanoplatelet material, characterized in that, comprising PO4 3- - LnWO4nanosheets, wherein Ln is at least one of the lanthanide rare earth metals; the PO4 3- - LnWO4nanosheets have a two-dimensional sheet-like structure, comprising PO4 3- doped with Ln 3+ doped WO4 2- lattice; Ln 3+ is at least one of the following: La 3+ , Gd 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Tb 3+ ; the PO4 12 is obtained by a solvothermal reaction of Ln precursors and PW 3- - LnWO4nanosheets; the molar ratio of Ln precursors and PW 12 is X:1, with X ranging from 5 to 30.

2. A method of preparing the rare earth metal tungstate nanoplatelets material of claim 1, characterized in that, Comprising the following steps: Step 1: Dissolve phosphotungstic acid and rare earth metal salt Ln(CH3COO)3·xH2O in a mixed non-polar solvent composed of cyclohexane and long-chain alcohol; continuously stir at 30-50°C for 30-60 minutes to form a uniform suspension; this step utilizes the weak coordination ability of long-chain alcohol to interact with rare earth ions, regulating subsequent nucleation kinetics; Step 2: Add a complex organic amine ligand composed of a main amine and an auxiliary diamine to the system of Step 1 above; under inert atmosphere protection, stir vigorously at 60-80°C for 1-2 hours until a uniform, transparent amber solution is formed; then, let the solution stand at room temperature for 2-4 hours to promote the formation of more stable metal-organic precursor complexes; Step 3: Transfer the aged solution to a polytetrafluoroethylene-lined high-pressure reaction kettle, controlling the filling degree to 60%-75%; use a stepwise heating program for the reaction: First stage: heat to 140-160°C at a rate of 2-3°C / min and hold for 2-4 hours to achieve slow nucleation; Second stage: continue to heat to the target temperature of 180-200°C and hold for 12-20 hours to promote anisotropic growth and crystallization of nanosheet structures; Step 4: After the reaction is completed, naturally cool to room temperature; after the product is collected by centrifugation, use an alternating washing method for purification: first wash twice with a mixed solvent of cyclohexane and acetone to completely remove long-chain organic amine and residual organic matter; then wash twice with anhydrous ethanol; dry the obtained product in a vacuum drying oven to obtain fluffy powder of rare earth metal tungstate nanosheet material.

3. The preparation method of the rare earth metal tungstate nanosheet material according to claim 2, characterized in that, The molar ratio X of the rare earth metal precursor to phosphotungstic acid, i.e. Ln:PW 12 Control between 5-30; In Step 1: the long-chain alcohol is n-hexanol or n-octanol; the volume ratio of cyclohexane to long-chain alcohol is 1:1 to 4:1; In Step 2: the main amine is selected from oleylamine or hexadecylamine; the auxiliary diamine is selected from ethylenediamine; the volume ratio of the auxiliary diamine to the complex organic amine ligand is 5%-15%; In Step 4: the volume ratio of cyclohexane to acetone is 1:1; dry the obtained product in a vacuum drying oven at 80°C for 8-12 hours.

4. The preparation method of the rare earth metal tungstate nanosheet material according to claim 3, characterized in that, The rare earth metal Ln is selected from at least one of the following elements: La, Gd, Ce, Pr, Nd, Tb; The mixed non-polar solvent is cyclohexane and n-hexanol, and the volume ratio of cyclohexane to n-hexanol is 3:1; The complex organic amine ligand is a mixture of oleylamine and ethylenediamine, with ethylenediamine accounting for 10% of the total volume; In Step 3, the solvothermal reaction uses a two-stage program: first hold at 150°C for 3 hours, then react at 190°C for 16 hours; The molar ratio X is 10.

5. Use of the rare earth metal tungstate nanosheet material according to claim 1 in photocatalytic degradation of antibiotic or drug-like pollutant containing heterocyclic structures.

6. Use according to claim 5, characterized in that, The antibiotic includes a fluoroquinolone antibiotic; the fluoroquinolone antibiotic is at least one of CIP, NOR, OFX, ENR, LOM. The antibiotic includes a fluoroquinolone antibiotic; the fluoroquinolone antibiotic is at least one of CIP, NOR, OFX, ENR, LOM.

7. Use according to claim 5, characterized in that, In CO3 2- photocatalytic degradation under the system.

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