A Yb-BiOI / Ce-MgAl-LDH composite photocatalyst, its preparation method, and its application.

Abstract

This invention discloses a Yb-BiOI / Ce-MgAl-LDH composite photocatalyst, its preparation method, and its application, belonging to the field of environmental functional materials and photocatalysis technology. The purpose of this invention is to provide a Yb-BiOI / Ce-MgAl-LDH composite photocatalyst with high catalytic activity, good stability, and reusability, its preparation method, and its application in the efficient degradation of tetracycline antibiotics. This invention prepares a Yb-BiOI / Ce-MgAl-LDH heterojunction composite catalyst with a three-dimensional flower-like interwoven morphology via a hydrothermal method. Under visible light and H2O2 coexistence conditions, this catalyst not only promotes photogenerated carriers (e-carriers) through the built-in electric field at the heterojunction interface, but also… ‑ / h + Effective separation of Ce, while utilizing Ce 3+ / Ce 4+ Redox pairs with Yb 3+ Doping-induced active sites synergistically catalyze the decomposition of H2O2, continuously generating high concentrations of hydroxyl radicals (·OH); photogenerated electrons can accelerate the valence state cycle of rare earth ions, while Fenton-like reactions promote charge separation. The deep coupling of the two produces a significant synergistic enhancement effect, achieving rapid and deep degradation of antibiotics.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and photocatalysis technology. Specifically, it relates to a method for preparing a ytterbium-doped bismuth iodide-oxygenated and cerium-doped magnesium-aluminum layered bimetallic hydroxide composite photocatalyst (Yb-BiOI / Ce-MgAl-LDH), and its application in the degradation of tetracycline antibiotics by activating hydrogen peroxide under visible light. Background Technology

[0002] Tetracycline antibiotics are widely used in the treatment of human diseases and in livestock farming for growth promotion and disease prevention due to their broad-spectrum antibacterial activity and low production cost. However, these antibiotics have low metabolic rates in organisms, and large quantities are excreted into environmental water bodies in their original or active metabolite forms. Because traditional wastewater treatment processes have limited removal efficiency for antibiotic-related micropollutants, tetracycline antibiotics are frequently detected in the aquatic environment, posing a potential threat to aquatic ecosystems. More seriously, residual sub-inhibitory concentrations of antibiotics in water bodies can continuously induce bacteria to produce antibiotic resistance genes (ARGs), which then spread throughout the microbial community through horizontal gene transfer, weakening the effectiveness of clinical antibiotic treatments and posing a significant challenge to global public health security.

[0003] Advanced oxidation processes (AOPs) based on semiconductor photocatalytic oxidation technology are considered one of the most promising green technologies for treating antibiotic pollution in water bodies because they can utilize sunlight to generate highly oxidizing active species and achieve non-selective mineralization of organic pollutants. Among many photocatalytic materials, bismuth oxyiodide (BiOI) has attracted much attention due to its unique layered crystal structure, suitable band gap (approximately 1.7–1.9 eV), and excellent visible light response performance. Meanwhile, layered bimetallic hydroxides (LDHs) are often used as catalyst supports or directly as photocatalytic active components because of their tunable layer metal composition, large specific surface area, good hydration and dispersibility, and good adsorption and enrichment capabilities.

[0004] To overcome the bottlenecks of high photogenerated carrier recombination rate, insufficient oxidation capacity, and low visible light utilization efficiency of pure-phase BiOI materials, researchers have conducted extensive modification work. Existing technologies mainly follow two directions: one is to regulate the semiconductor band structure through metal ion doping, such as the use of rare earth elements (Yb, Er, La, etc.) to dope BiOI, as reported in published literature, to introduce impurity energy levels and expand the photoresponse range; the other is to construct heterojunction composite systems, such as combining wide-bandgap semiconductors like CeO2, TiO2, and g-C3N4 with LDH, utilizing the built-in electric field at the interface to promote charge spatial separation. These strategies have improved the photocatalytic activity of single materials to some extent and exhibited enhanced degradation performance for target pollutants such as tetracycline and oxytetracycline under simulated illumination conditions.

[0005] However, existing technical solutions still have the following shortcomings that urgently need to be overcome:

[0006] Limited modification strategies limit the improvement of charge separation efficiency. Existing studies mostly employ single modification methods, relying solely on heterostructure construction or elemental doping, failing to effectively couple band structure control, interface engineering, and active site design. Single modification strategies have limited effects on improving the spatial separation and interface migration speed of photogenerated electron-hole pairs, and the recombination loss problem of photogenerated carriers remains unresolved.

[0007] Insufficient oxidation capacity hinders deep mineralization. While most reported BiOI-based or LDH-based composite photocatalysts exhibit visible light response, their relatively positive conduction band bottom potential and weak photogenerated electron reduction capabilities make it difficult to effectively activate dissolved oxygen to generate superoxide radicals. Furthermore, the catalyst surface lacks efficient activation... The active center of the hydroxyl radical (·OH) results in a low yield of highly oxidizing hydroxyl radicals. This makes it difficult for the system to achieve complete ring-opening mineralization of stubborn pollutants with stable molecular structures and well-developed conjugated systems, such as tetracycline, and the degradation products may still retain ecotoxicity.

[0008] Low functional integration and lack of Fenton-like synergistic mechanisms. Existing technologies lack systematic consideration of catalytic function integration. Most composite systems focus only on improving photogenerated charge separation efficiency, neglecting the simultaneous introduction of Fenton-like active metal sites (such as variable-valence metals like Fe, Co, and Mn) into the catalyst structure. The synergistic effect of photocatalysis and Fenton-like oxidation is not fully realized, resulting in low oxidant utilization efficiency and low total organic carbon (TOC) removal rates.

[0009] The preparation process is lengthy and the structural reproducibility is poor. The synthesis of some existing composite materials requires multiple independent processes (such as the LDH support co-precipitation method combined with the BiOI solvothermal method), which is complex, energy-intensive, and makes it difficult to achieve precise control over component distribution, interfacial contact state, and microstructure between different batches. This not only restricts the in-depth analysis of the structure-property relationship of the materials, but also hinders the transformation of this type of photocatalytic technology from laboratory research to practical water treatment engineering applications.

[0010] In summary, there is an urgent need to develop a novel composite photocatalyst that, through integrated structural design, simultaneously achieves rare-earth doping bandgap modulation, in-situ construction of heterojunction interfaces, and integration of Fenton-like catalytic active centers to synergistically enhance visible light absorption, charge separation, oxidation activation, and operational stability. The construction method of this composite system must also possess the characteristics of simple process, mild conditions, and good batch reproducibility to meet the needs of efficient, green, and low-cost treatment of tetracycline antibiotics and their resistance genes in complex aquatic environments. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a Yb-BiOI / Ce-MgAl-LDH composite photocatalyst with high catalytic activity, good stability, and reusability, along with its preparation method and application in the efficient degradation of tetracycline antibiotics. This invention provides a composite photocatalyst with a specific component ratio, wherein the mass ratio of Yb-BiOI to Ce-MgAl-LDH is 3:1, and relates to the preparation method and application of this catalyst, aiming to systematically overcome the defects existing in the prior art.

[0012] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0013] The purpose of this invention is to provide a method for preparing a Yb-BiOI / Ce-MgAl-LDH composite photocatalyst, comprising the following steps:

[0014] Step 1, Preparation of Ce-MgAl-LDH: A urea-ammonium fluoride-assisted hydrothermal method was used, with magnesium salts, aluminum salts, and cerium salts as precursors. After hydrothermal reaction, washing, and drying, three-dimensional flower-like Ce-MgAl-LDH was obtained, wherein cerium was present as Ce. 3+ and Ce 4+ Mixed valence states exist;

[0015] Step 2, Preparation of Yb-BiOI: Yb-BiOI was obtained by solvothermal method using bismuth nitrate pentahydrate, potassium iodide and ytterbium nitrate as precursors, after hydrothermal reaction in ethylene glycol solvent, washing and drying.

[0016] Step 3, Preparation of Yb-BiOI / Ce-MgAl-LDH composite catalyst: The Ce-MgAl-LDH obtained in Step 1 and the Yb-BiOI obtained in Step 2 are mixed at a mass ratio of 1:3, dispersed in water, and subjected to a secondary hydrothermal composite reaction after ultrasonic dispersion. After the reaction, the mixture is washed and dried to obtain the Yb-BiOI / Ce-MgAl-LDH composite photocatalyst.

[0017] Further specifying, in step 1, the molar ratio of Mg, Al, and Ce is controlled to be (5.5-6.5):(1.7-2.1):(0.08-0.12).

[0018] Further specifying, in step 1, the temperature of the hydrothermal reaction is 100-140℃, and the time is 12-36 hours.

[0019] To further specify, in step 1, the magnesium salt is magnesium nitrate.

[0020] To further specify, in step 1, the aluminum salt is aluminum nitrate.

[0021] To further specify, in step 1, the cerium salt is cerium nitrate.

[0022] Further specifying, in step 2, the temperature of the hydrothermal reaction is 120-160℃, and the time is 6-12 hours.

[0023] Further specifying, in step 2, the amount of ytterbium nitrate added is 2-6% molar percentage relative to bismuth nitrate pentahydrate.

[0024] Further specifying, in step 3, the temperature of the hydrothermal reaction is 80-120℃, and the time is 4-8 hours.

[0025] Further specifying, in step 3, the mass ratio of Yb-BiOI to Ce-MgAl-LDH is 3:1.

[0026] Another object of the present invention is to provide a Yb-BiOI / Ce-MgAl-LDH composite photocatalyst prepared by any of the methods described above.

[0027] Further specifying, the catalyst is a three-dimensional composite structure formed by the cross-stacking of Yb-BiOI nanosheets and Ce-MgAl-LDH nanosheets; its specific surface area is 18-21 m². 2 / g, with an average pore size of 15-18 nm.

[0028] Furthermore, the application of the Yb-BiOI / Ce-MgAl-LDH composite photocatalyst of the present invention is provided, specifically its application in the synergistic degradation of tetracycline antibiotics in water by hydrogen peroxide under visible light. The specific method of this application involves adding the composite photocatalyst and hydrogen peroxide (H2O2) to polluted water containing tetracycline antibiotics, and then carrying out a catalytic oxidation reaction under visible light irradiation.

[0029] Further specifying, the tetracycline antibiotics include at least one of tetracycline, tetracycline hydrochloride, oxytetracycline, ofloxacin, and doxycycline.

[0030] Further specified, the dosage of the composite photocatalyst is 0.1-1.0 g / L, the dosage of hydrogen peroxide is 0.1-10 mM, and the initial concentration of tetracycline antibiotics is 5-50 mg / L.

[0031] Further specifying, the application is carried out in water with a pH of 3-11, the reaction is carried out at room temperature, and the wavelength of the visible light source used is greater than or equal to 420 nm.

[0032] This invention achieves controllable preparation of the morphology, crystal phase, and interfaces of composite materials from single components through a full-process hydrothermal method and precise stoichiometry control, ensuring high specific surface area, tight heterojunction, and excellent batch repeatability. Oxidation capacity and charge separation efficiency are simultaneously and significantly improved. This is achieved not only by improving charge separation through heterojunction but also by introducing Ce / Yb dual active centers, opening up a new pathway for efficiently generating highly oxidizing ·OH, fundamentally enhancing the system's oxidative degradation capability.

[0033] This invention precisely controls the material composition at the atomic scale. Specifically, it synthesizes Ce-MgAl-LDH using a molar ratio of Mg:Al:Ce = 6:1.9:0.1, prepares BiOI doped with mixed valence states of Yb, and then composites the two at an optimal mass ratio of Yb-BiOI:Ce-MgAl-LDH = 3:1. Simultaneously, all core materials are prepared using a unified, controllable hydrothermal process. Ce-MgAl-LDH is specifically synthesized using a urea-ammonium fluoride-assisted hydrothermal method to ensure uniform morphology and a tight interface. Based on this, this invention, for the first time, synergistically constructs a dual enhancement mechanism: on the one hand, the built-in electric field at the heterojunction interface drives the efficient separation of photogenerated charges; on the other hand, Yb... 3+ The doping of Ce promoted Ce 3+ / Ce 4+ The efficiency of the redox cycle enhances the process of the Fenton-like reaction. These two processes are deeply coupled and mutually reinforcing, forming a significant synergistic effect and constituting the core mechanism for achieving rapid and deep degradation of pollutants.

[0034] Compared to existing technologies, the improvements of this invention are specifically reflected in the following four aspects:

[0035] Existing technologies for doping layered bimetallic hydroxides (LDHs) primarily focus on common metallic elements, and the determination of doping amounts and composite ratios generally lacks in-depth design and systematic optimization based on structure-property relationships. This invention first precisely controls the material composition at the atomic scale: the molar ratio of Mg, Al, and Ce in Ce-MgAl-LDH is determined to be 6:1.9:0.1. This ratio ensures that cerium is incorporated into the LDH layers in a low-concentration but functionally effective manner, and the introduction of Ce... 3+ / Ce 4+Simultaneously, the redox pair induces significant lattice expansion (manifested as an increase in the (003) interplanar spacing) and avoids damage to the main layered structure of LDH due to excessive doping. Crucially, this invention, through a series of experiments, verified and determined that the optimal composite mass ratio of Yb-BiOI to Ce-MgAl-LDH is 3:1, which is the optimized ratio to maximize photocatalytic performance. This atomically precise component design ensures that all functional units—including the adsorption and support functions of LDH, the redox activity of Ce / Yb dual rare earth elements, and the photosensitivity of BiOI—coexist in optimal condition and work synergistically, laying a solid foundation for the subsequent construction of a highly efficient photocatalytic system.

[0036] Existing technologies often employ a combination of multiple synthesis methods, resulting in inconsistent process routes and limited controllability and reproducibility. This invention uses a precisely controllable hydrothermal method for all core preparation steps, achieving a high degree of process consistency and uniformity. Specifically: ① Ce-MgAl-LDH is synthesized using a urea-ammonium fluoride-assisted hydrothermal method, which facilitates the formation of uniform and stable three-dimensional flower-like nanostructures. Urea decomposition provides a uniform alkaline environment, while ammonium fluoride plays a morphology-guiding role, synergistically achieving effective cerium doping and controllable construction of specific nanostructures. ② Yb-BiOI is also prepared independently using a hydrothermal method. ③ The final composite process also employs a hydrothermal method, in-situ composites the two precursor materials at a Yb-BiOI:Ce-MgAl-LDH mass ratio of 3:1. The unified high-temperature, high-pressure hydrothermal synthesis environment of this invention significantly promotes chemical bonding and structural reorganization of the two-phase nanosheets at the interface, rather than simple physical mixing. This process promotes the formation of a tighter and more stable heterojunction interface, a key prerequisite for achieving efficient interfacial charge transfer. Meanwhile, this preparation route has outstanding advantages such as good reproducibility, high product crystallinity, and strong morphological controllability.

[0037] The most fundamental mechanistic difference between this invention and existing technologies lies in the construction of the synergistic mechanism. Existing technological improvements often rely on a single mechanism (such as type I or type II heterojunctions). This invention, through the aforementioned precise synthesis and composite process, simultaneously constructs two highly coupled functional mechanisms: First, X-ray photoelectron spectroscopy (XPS) characterization confirms that, due to the matched energy level structures of Yb-BiOI and Ce-MgAl-LDH and their tight contact at the interface, electron transfer occurs from Yb-BiOI to Ce-MgAl-LDH at the interface, thereby forming a strong built-in electric field. This electric field acts as an "electron pump," driving photogenerated electrons (electrons) under illumination. - ) and holes (h + Firstly, it enables efficient spatial separation in the opposite direction. Secondly, it successfully introduced rare earth elements (Ce). 3+ / Ce 4+ With doped Yb 3+The photogenerated electrons, together with H2O2 in the reaction system, construct a highly efficient heterogeneous Fenton-like reaction cycle. These two mechanisms are not isolated but deeply coupled and synergistically enhanced. Specifically, after being separated under the drive of the built-in electric field, photogenerated electrons can be reacted by Ce... 4+ The active center captures and reduces to Ce 3+ This significantly promotes the production of cerium ions (Ce). 3+ / Ce 4+ The redox pair cycle. This valence state cycle continuously consumes photogenerated electrons, providing an efficient pathway for carrier migration, thereby effectively suppressing electron-hole recombination and further improving the overall charge separation efficiency. Meanwhile, Yb 3+ The introduction of this technology enhances the aforementioned catalytic process synergistically from multiple dimensions by modulating the material's band structure, promoting photogenerated carrier separation, and providing active sites for interfacial reactions. This coupling mechanism enables photogenerated carriers to induce active species (such as...) The generation efficiency of both ) and Fenton-like reaction-induced active species (such as ·OH) was exponentially improved, showing a synergistic enhancement effect, ultimately achieving ultra-fast and deep mineralization degradation of target pollutants.

[0038] Under the condition of a Yb-BiOI:Ce-MgAl-LDH mass ratio of 3:1, the material obtained by hydrothermal composite exhibits a three-dimensional interwoven floral structure, with significantly optimized specific surface area and pore structure, and enhanced surface hydrophilicity. The above-mentioned excellent physicochemical properties and the aforementioned dual catalytic mechanism mutually enhance each other, jointly endowing the composite material with excellent photocatalytic degradation performance, broad substrate adaptability, and excellent cycling stability.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] Highly efficient "photocatalysis-Fenton-like" synergistic effect: The Yb-BiOI / Ce-MgAl-LDH composite catalyst prepared in this invention, under the coexistence of visible light and H2O2, not only efficiently separates photogenerated charges (e) through the built-in electric field of the heterojunction, but also... - and h + ), while using Ce 3+ / Ce 4+ Redox pairs with Yb 3+ Doping regulates oxygen vacancies, synergistically promoting the decomposition of H2O2 to generate a large amount of ·OH. Photogenerated electrons accelerate the valence cycle of rare earth ions, while Fenton-like reactions promote charge separation. The deep coupling of these two factors produces a significant synergistic enhancement effect, enabling rapid and deep degradation of antibiotics.

[0041] Excellent photocatalytic performance: Under optimized conditions (catalyst 5 mg, TC-HCl 10 mg / L, H2O2 200 μL, pH 8.24, visible light irradiation), the catalyst achieved a 100% degradation rate of tetracycline hydrochloride (TC-HCl) within 20 minutes, which is much higher than that of single-component catalysts or other composite materials.

[0042] Due to the deep synergy of the "built-in electric field" and "dual rare earth cycle" dual mechanisms, the efficiency, rate and mineralization degree of this patented catalyst in activating H2O2 to degrade tetracycline under visible light significantly surpass those of single-component, simple complex or catalysts with only a single mechanism.

[0043] Good broad spectrum and environmental adaptability: This catalyst shows high efficiency in the degradation of various antibiotics such as oxytetracycline (OTC), ofloxacin (OFL), and doxycycline (DOCX) (removal rate >75%), and can maintain high activity in actual water samples containing different inorganic anions or humic acids and in a wide pH range, showing good potential for practical application.

[0044] Excellent structural stability and recyclability: After five cycles, the catalyst maintains a degradation rate of over 80% for TC-HCl, and its crystal structure and surface chemical state remain largely unchanged before and after the reaction, indicating good chemical stability and reusability. The composite interface formed by the hydrothermal method exhibits strong chemical bonding, and the catalyst demonstrates good structural stability and activity retention under cyclic use and different water quality conditions. It also shows broad-spectrum degradation effects on various antibiotics, exhibiting enhanced stability and applicability. The preparation process demonstrates continuity and scalability potential.

[0045] Controllable and repeatable preparation process: All core steps employ the hydrothermal method. By precisely controlling parameters such as precursor ratio, reaction temperature, and time, controllable preparation of material morphology, crystal phase, and composite interface is achieved. The process is consistent and highly repeatable, which is beneficial for large-scale production. The use of the mature hydrothermal method throughout provides a clear route and well-defined parameters, avoiding the instability caused by mixing multiple processes and facilitating future large-scale production.

[0046] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0047] Figure 1 The image shows a scanning electron microscope (SEM) image of the Yb-BiOI / Ce-MgAl-LDH composite catalyst prepared in Example 1.

[0048] Figure 2The image shows a transmission electron microscope (TEM) image of the Yb-BiOI / Ce-MgAl-LDH composite catalyst prepared in Example 1.

[0049] Figure 3 This is a high-resolution transmission electron microscope (HRTEM) image of the Yb-BiOI / Ce-MgAl-LDH composite catalyst prepared in Example 1.

[0050] Figure 4 Comparison of X-ray diffraction (XRD) spectra of Ce-MgAl-LDH, Yb-BiOI, and Yb-BiOI / Ce-MgAl-LDH prepared in Example 1.

[0051] Figure 5 The image shows a comparison of the X-ray photoelectron spectroscopy (XPS) spectra of the Yb-BiOI / Ce-MgAl-LDH composite catalyst prepared in Example 1 and the comparative Ce-MgAl-LDH.

[0052] Figure 6 The performance curves of the Yb-BiOI / Ce-MgAl-LDH / H2O2 / Vis system in Experiment 1 for degrading tetracycline hydrochloride (TC-HCl) and the comparison diagram of different systems are shown.

[0053] Figure 7 The graph shows the degradation effect of different coexisting anions on TC-HCl in Experiment 2.

[0054] Figure 8 The graph shows the effect of different pH values ​​on the degradation of TC-HCl in Experiment 3.

[0055] Figure 9 The graph shows the degradation effect of the Yb-BiOI / Ce-MgAl-LDH / H2O2 / Vis system on different antibiotics in Experiment 4.

[0056] Figure 10 The graph shows the stability test results of the Yb-BiOI / Ce-MgAl-LDH catalyst after five cycles in Experiment 5.

[0057] Figure 11 The figure shows the effect of different free radical scavengers on the degradation of TC-HCl in the Yb-BiOI / Ce-MgAl-LDH / H2O2 / Vis system in Experiment 6. Detailed Implementation

[0058] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0059] Example 1: Preparation of Yb-BiOI / Ce-MgAl-LDH composite photocatalyst

[0060] (1) Preparation of Ce-MgAl-LDH: 1.282 g Mg(NO3)2·6H2O (Mg source, 5 mmol), 0.703 g Al(NO3)3·9H2O (Al source, 1.875 mmol) and 0.043 g Ce(NO3)3·6H2O (Ce source, 0.1 mmol) were weighed and dissolved in 40 mL of deionized water. 1.8 g urea and 0.148 g NH4F were also weighed and dissolved in 40 mL of deionized water. The two solutions were mixed and magnetically stirred for 30 min, then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and reacted at 120 °C for 24 h. After natural cooling, the product was centrifuged, washed three times each with deionized water and ethanol, dried under vacuum at 60 °C for 12 h, and ground to obtain a pale yellow Ce-MgAl-LDH powder.

[0061] (2) Preparation of Yb-BiOI: Weigh 0.970 g Bi(NO3)3·5H2O (2 mmol) and 0.332 g KI (2 mmol) and dissolve them in 40 mL ethylene glycol. Stir for 30 min until clear. Add 0.039 g Yb(NO3)3·5H2O (0.09 mmol) and continue stirring for 30 min. Transfer the solution to a 50 mL autoclave and react at 140 °C for 8 h. After natural cooling, centrifuge the product, wash it three times each with deionized water and ethanol, and dry it under vacuum at 60 °C for 12 h to obtain orange-red powder Yb-BiOI.

[0062] (3) Preparation of Yb-BiOI / Ce-MgAl-LDH: Accurately weigh 0.150 g Yb-BiOI and 0.050 g Ce-MgAl-LDH, add 50 mL of deionized water, and ultrasonically disperse for 40 min. Transfer the suspension to a 50 mL autoclave and react at 100 °C for 6 h. After natural cooling, collect the product by centrifugation, wash, and dry at 60 °C for 12 h to obtain the final composite catalyst Yb-BiOI / Ce-MgAl-LDH.

[0063] The morphology of the obtained sample is as follows Figure 1-3 As shown, the XRD pattern is as follows Figure 4 As shown, XPS analysis is as follows Figure 5 As shown, this demonstrates the successful composite material and the formation of heterostructures.

[0064] The catalyst is composed of Yb-BiOI nanosheets and Ce-MgAl-LDH nanosheets that are intersected and stacked to form a unique three-dimensional cluster composite morphology. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) show that there is a tight heterojunction interface between the two phases, where the 0.29 nm lattice stripe corresponds to the (102) crystal plane of Yb-BiOI and the 0.36 nm lattice stripe corresponds to the (006) crystal plane of Ce-MgAl-LDH.

[0065] X-ray diffraction (XRD) patterns show that the (012), (110) and (113) diffraction peaks of Ce-MgAl-LDH shift to lower angles after recombination, indicating that the interplanar spacing increases due to strong interfacial interactions.

[0066] X-ray photoelectron spectroscopy (XPS) analysis confirmed that the characteristic peak binding energies of Ce, Mg, and Al elements in the complex exhibit a redshift compared to Ce-MgAl-LDH alone. This indicates that electrons are transferred from Yb-BiOI to Ce-MgAl-LDH, creating a built-in electric field at the interface that promotes charge separation.

[0067] Nitrogen adsorption-desorption tests showed that the composite catalyst possesses a type IV isotherm and an H3 type hysteresis loop, with a specific surface area of ​​approximately 19.267 m². 2 / g, with an average pore size of approximately 16.197 nm and a pore volume of approximately 0.100 cm³. 3 / g, the abundant mesoporous structure is conducive to the adsorption and mass transfer of reactants.

[0068] The following experiments were used to verify the effectiveness of the invention.

[0069] Experiment 1: Performance test of Yb-BiOI / Ce-MgAl-LDH in degrading tetracycline hydrochloride (TC-HCl)

[0070] 50 mL of a 10 mg / L TC-HCl aqueous solution was placed in a 100 mL beaker, along with 5 mg of the Yb-BiOI / Ce-MgAl-LDH catalyst prepared in Example 1, and then 200 μL of a 30 wt% H₂O₂ solution. The pH was adjusted to 8.24 using dilute NaOH or HCl solution. Irradiation was performed using a 300 W xenon lamp (equipped with a 420 nm cutoff filter) as the visible light source under magnetic stirring. At regular intervals, 2 mL samples were taken and immediately filtered through a 0.22 μm filter to remove the catalyst. The remaining concentration of TC-HCl was measured at 357 nm using a UV-Vis spectrophotometer, and the degradation rate was calculated. Comparative experiments were also conducted, including a blank control (light irradiation only), H₂O₂ only, and catalyst only. The results are as follows: Figure 6As shown, the Yb-BiOI / Ce-MgAl-LDH / H2O2 / Vis system exhibited the highest degradation efficiency, reaching 100% degradation rate in 20 min, confirming a significant synergistic effect.

[0071] Experiment 2: To evaluate the applicability of the Yb-BiOI / Ce-MgAl-LDH / H2O2 / Vis system in real-world complex aquatic environments, the effects of different coexisting anions on the degradation efficiency of TC-HCl were investigated. In the anion interference experiment, SO42- concentration gradients of different concentrations were introduced into a 10 mg / L TC-HCl solution. 2 NO3, CO3 2 ⁻、Cl ⁻ And humic acid (HA) was degraded under the conditions of 5 mg catalyst, 200 μL H2O2, and visible light irradiation. The results are as follows: Figure 7 As shown, all substances exhibit concentration-dependent inhibitory effects. Among them, HA exhibits the strongest inhibition due to its simultaneous competitive active site, free radical quenching, and light shielding effects, indicating that dissolved organic matter and some anions in actual water bodies are key limiting factors affecting the effectiveness of the technology.

[0072] Experiment 3: To evaluate the applicability of the Yb-BiOI / Ce-MgAl-LDH / H2O2 / Vis system in real-world complex aquatic environments, the effect of initial solution pH on the degradation efficiency of TC-HCl was investigated. Experiments were conducted by adjusting the initial solution pH to the range of 3.23 to 11.21. As shown in Figure 8, the system exhibited the best catalytic activity under weakly alkaline conditions (pH=8.24). Under strong acid conditions (pH=3.23), degradation was significantly inhibited due to the protonation of H2O2 and the electrostatic repulsion between the catalyst and pollutants. Under strong alkaline conditions (pH=11.21), the efficiency decreased slightly due to the ineffective decomposition of H2O2, confirming that a weakly alkaline environment is most conducive to the efficient operation of this catalytic system.

[0073] Experiment 4: Broad-spectrum degradation performance of Yb-BiOI / Ce-MgAl-LDH against different antibiotics

[0074] The experimental method was the same as in Experiment 1, using 10 mg / L of oxytetracycline (OTC), ofloxacin (OFL), doxycycline (DOCX), and rhodamine B (RhB) as target pollutants, respectively, and degradation experiments were conducted under the same conditions. The results are as follows: Figure 9 As shown, the system exhibits high removal rates (>75%) for OTC, OFL, and DOCX within 20 min, with OTC being almost completely removed within 10 min, indicating that the catalyst has a broad-spectrum degradation capability for various antibiotics.

[0075] Experiment 5: Cyclic stability test of Yb-BiOI / Ce-MgAl-LDH catalyst

[0076] The degradation conditions were the same as in Experiment 1 (target pollutant TC-HCl) for each cycle. After each reaction, the reaction solution was centrifuged to recover the catalyst, washed three times each with deionized water and ethanol, dried at 60°C, and used as the catalyst for the next cycle. This process was repeated five times. The results are as follows: Figure 10 As shown, after five cycles, the degradation rate of TC-HCl can still be maintained above 80%, indicating that the catalyst has good stability and reusability.

[0077] Experiment 6: Identification of active species during degradation (free radical quenching experiment)

[0078] The experimental conditions were the same as in Experiment 1. 10 mmol / L of tert-butanol (TBA, as a ·OH scavenger) and p-benzoquinone (p-BQ, as a ·OH scavenger) were added to the reaction system, respectively. (scavenger), furfuryl alcohol (FFA, as) (capture agent) and disodium ethylenediaminetetraacetate (EDTA-2Na, as h) + (Capture agent). The changes in the degradation rate of TC-HCl after the addition of different capture agents were observed and compared. Results are as follows: Figure 11 As shown, the addition of FFA and EDTA-2Na had the most significant inhibitory effect on degradation, indicating that... and h + It is the main active species in the degradation process, ·OH and It also participated in the reaction, confirming the synergistic mechanism of multiple active species.

[0079] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A method for preparing a Yb-BiOI / Ce-MgAl-LDH composite photocatalyst, characterized in that, Comprising the following steps: Step 1, dissolving magnesium salt, aluminum salt and cerium salt in deionized water to obtain solution A, dissolving urea and ammonium fluoride in deionized water to obtain solution B, mixing solution A and B uniformly, carrying out hydrothermal reaction, after the reaction is completed, natural cooling, centrifugation, repeated washing with deionized water and anhydrous ethanol in turn, drying, grinding, to obtain Ce-MgAl-LDH; Step 2, dissolving bismuth nitrate pentahydrate and potassium iodide in ethylene glycol, magnetic stirring until completely dissolved, then adding ytterbium nitrate, continue stirring until uniform, solvothermal reaction, after the reaction is completed, natural cooling, centrifugation, repeated washing with deionized water and anhydrous ethanol in turn, drying, to obtain Yb-BiOI; Step 3, dispersing Yb-BiOI prepared in step 2 and Ce-MgAl-LDH prepared in step 1 in deionized water, ultrasonic dispersion until uniform, hydrothermal reaction, after the reaction is completed, natural cooling, centrifugation, washing, drying, finally obtaining Yb-BiOI / Ce-MgAl-LDH composite photocatalyst.

2. The method of claim 1, wherein, In step 1, the molar ratio of Mg, Al and Ce is (5.5-6.5):(1.7-2.1):(0.08-0.12), the magnesium salt is magnesium nitrate, the aluminum salt is aluminum nitrate, and the cerium salt is cerium nitrate, and the hydrothermal reaction is carried out at 100-140℃.

3. The method of claim 1, wherein, In step 2, the solvothermal reaction is carried out at 120-160℃, and the addition amount of ytterbium nitrate is 2%-6% relative to the molar percentage of bismuth nitrate pentahydrate.

4. The method of claim 1, wherein, In step 3, the mass ratio of Yb-BiOI and Ce-MgAl-LDH is 3:1, and the hydrothermal reaction is carried out at 80-120℃.

5. A Yb-BiOI / Ce-MgAl-LDH composite photocatalyst prepared by the method of any one of claims 1-4.

6. The photocatalyst according to claim 5, wherein It is a three-dimensional composite structure formed by the mutual cross-stacking of Yb-BiOI nanosheets and Ce-MgAl-LDH nanosheets; its specific surface area is 18-21 m² / g, and the average pore size is 15-18 nm.

7. The use of the Yb-BiOI / Ce-MgAl-LDH composite photocatalyst of claim 5 or 6 in the degradation of tetracycline antibiotics in water under visible light in cooperation with hydrogen peroxide.

8. Use according to claim 7, characterized in that, The tetracycline antibiotics include at least one of tetracycline, tetracycline hydrochloride, terramycin, ofloxacin and doxycycline.

9. Use according to claim 7, characterized in that, The dosage of the photocatalyst is 0.1-1.0 g / L, the dosage of hydrogen peroxide is 0.1-10 mM, and the initial concentration of tetracycline antibiotics is 5-50 mg / L.

10. Use according to claim 7, characterized in that, It is carried out in a water body with a pH value of 3-11, and the wavelength of the visible light source is ≥420 nm.

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