Rare earth / bimetal synergistically enhanced composite photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a preparation method and application of a rare earth / bimetal synergistically enhanced composite photocatalyst, the rare earth / bimetal synergistically enhanced composite photocatalyst comprises a defect type titanium dioxide TiO2-x carrier rich in oxygen vacancies, copper-nickel bimetal nanoparticles are loaded on the TiO2-x carrier, and rare earth elements are doped on the TiO2-x carrier; the rare earth element is at least one or any combination of ytterbium, erbium, neodymium, cerium and dysprosium, and the doping amount of the rare earth element is 0.1-1%; the molar ratio of copper to nickel is 1: (0.9-1.1); the molar ratio of the sum of the molar weights of copper and nickel to TiO2-x is 2: (6-7). According to the invention, three mechanisms of defect engineering, bimetallic plasmon effect and rare earth element modification are synergistically combined, so that the prepared catalyst has full-spectrum response capability and efficient photo-generated charge separation efficiency, and shows excellent degradation performance on antibiotic pollutants such as norfloxacin under visible light and near-infrared light; and the preparation method is simple and low in cost, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a rare earth / bimetallic synergistic enhanced composite photocatalyst, belonging to the field of environmental catalytic material preparation technology. Background Technology

[0002] Antibiotics, such as norfloxacin, are persistent organic pollutants that accumulate in water bodies, posing a serious threat to ecological balance and human health. Semiconductor photocatalysis, especially technology based on titanium dioxide (TiO2), shows great potential for treating such pollutants due to its environmental friendliness and chemical stability. However, commercial TiO2 materials (such as P25) face two main bottlenecks: first, their wide band gap limits their photoresponse range to the ultraviolet region, which accounts for about 5% of the solar spectrum, resulting in low solar energy utilization; second, the extremely fast recombination rate of photogenerated electron-hole pairs severely restricts their quantum efficiency and overall catalytic performance.

[0003] To this end, researchers explored various modification strategies. For example, oxygen vacancies (O2) were introduced into the TiO2 lattice through high-temperature reduction treatment. v ) and Ti 3+ Defective titanium dioxide (TiO2) is formed. 2-x This can effectively reduce the band gap and extend light absorption into the visible light region. Furthermore, by loading inexpensive non-noble metal nanoparticles such as copper-nickel (CuNi), the surface plasmon resonance (SPR) effect can be utilized to enhance visible light capture capabilities, and Ni acts as an electron trap to promote the effective separation of photogenerated charges. However, approximately 45% of the energy in the near-infrared (NIR) region of the solar spectrum remains unutilized.

[0004] Although current modification strategies have made some progress, most studies are still limited to single or two-mechanism combinations, lacking a general technical solution that can systematically integrate the advantages of defect engineering, SPR effect, and rare earth element modification (including upconversion and charge trapping). Therefore, developing a composite photocatalyst with simple preparation process, controllable cost, and high efficiency response across the entire spectrum is of great significance for promoting the practical application of photocatalysis technology in environmental remediation. Summary of the Invention

[0005] The main objective of this invention is to provide a rare earth / bimetallic synergistic enhanced full-spectrum responsive composite photocatalyst, aiming to solve a series of technical problems of existing TiO2 photocatalysts, such as narrow spectral response range, low visible light utilization, easy recombination of photogenerated carriers, and high cost of noble metal modification.

[0006] Another objective of this invention is to provide a method for preparing the above-mentioned composite photocatalyst, which is simple in process, cost-controllable, and suitable for large-scale production.

[0007] Another object of the present invention is to provide the application of the above-mentioned composite photocatalyst in the photocatalytic degradation of persistent organic pollutants such as antibiotics in water.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A rare-earth / bimetallic synergistically enhanced composite photocatalyst comprising oxygen-vacancy-rich defective titanium dioxide (TiO2). 2-x support, TiO 2-x The carrier is loaded with copper-nickel bimetallic nanoparticles and doped with rare earth elements; the rare earth elements are at least one or any combination of ytterbium (Yb), erbium (Er), neodymium (Nd), cerium (Ce), and dysprosium (Dy), with a molar doping amount of 0.1-1%; the molar ratio of copper to nickel is 1:(0.9~1.1); the sum of the molar amounts of copper and nickel is 1:(0.9~1.1). 2-x The molar ratio is 2:(6~7).

[0010] The molar doping amount of the above rare earth elements is 0.1-1%. That is, the molar amount of rare earth elements is 0.1-1% of the molar amount of TiO2.

[0011] The aforementioned rare-earth / bimetallic synergistic enhanced composite photocatalyst exhibits strong absorption across the entire visible light region. It also demonstrates extremely high separation efficiency of photogenerated charges.

[0012] The above-mentioned defective titanium dioxide (TiO) 2-x The carrier is formed by introducing oxygen vacancy defects into the titanium dioxide lattice. These oxygen vacancy defects can reduce the band gap of titanium dioxide, thereby extending the photoresponse range into the visible light region. In the copper-nickel bimetallic nanoparticles, copper nanoparticles can generate surface plasmon resonance (SPR) to enhance visible light absorption and generate high-energy hot electrons; nickel nanoparticles act as electron traps to promote the capture and transfer of photogenerated electrons, thereby synergistically improving the separation efficiency of photogenerated electron-hole pairs. The rare earth elements emit light through upconversion luminescence mechanisms (such as Yb). 3+ / Er 3+ or Yb 3+ / Nd 3+ The system converts near-infrared light, which the catalyst cannot directly utilize, into absorbable visible light, or acts as a charge trapping center (such as Ce). 3+ or Dy 3+ ), further suppressing the recombination of photogenerated loads, thereby reacting with TiO2 2-x The support and CuNi nanoparticles produce a synergistic enhancement effect.

[0013] The inventors discovered through experiments that the effects of doping with different rare earth elements vary significantly. Furthermore, more doping is not necessarily better; the optimal dosage differs considerably for different rare earth elements or combinations. This application offers the following preferred solutions:

[0014] As one specific preferred option: the mass ratio of rare earth elements ytterbium (Yb) and erbium (Er) is 1:(8~10), preferably a mixture of 9:1; the molar doping amount of rare earth elements is 0.5%, at which point the catalyst has the highest degradation activity under visible light (>400 nm); when the pH value is 5±0.5, norfloxacin is completely degraded within 90 min.

[0015] This application considers a degradation rate of ≥99.9999% as complete degradation (100%).

[0016] As another specific preferred option, the rare earth elements are a mixture of ytterbium (Yb) and neodymium (Nd) in a mass ratio of (0.5~1.5):1, more preferably 1:1, with a molar doping amount of 0.1%. It was found that the degradation effect is optimal under weakly alkaline conditions (pH=9±0.5), and the degradation rate of norfloxacin can reach 89% in 2 hours. This option requires a small amount of rare earth doping.

[0017] As another specific preferred option: the rare earth element is dysprosium (Dy), and different Dy values... 3+ All doped samples exhibited light absorption in the UV-Vis region. The fluorescence intensity reached its lowest value at a dysprosium molar doping concentration of 1%, indicating optimal charge separation efficiency at this concentration. The degradation effect was most ideal at pH 7 ± 0.5, achieving an 89% norfloxacin degradation rate after 2 hours. As another specific preferred option, using cerium (Ce) as the rare earth element, the catalyst with a cerium molar doping concentration of 0.25% was confirmed to have the best performance, achieving an 85% norfloxacin degradation rate at pH 7-9 after 2 hours.

[0018] The above Yb 3+ / Er 3+ Yb 3+ / Nd 3+ It possesses unique upconversion luminescence properties, capable of converting low-energy near-infrared photons into high-energy visible photons, which are then absorbed by the TiO2 matrix, enabling indirect utilization of near-infrared light. 3+ Dy 3+ Due to its abundant f-orbital energy levels, it can serve as an efficient charge trapping center, further suppressing the recombination of photogenerated loads.

[0019] A method for preparing a rare-earth / bimetallic synergistic enhanced composite photocatalyst includes the following steps: S1: mixing and ball-milling a titanium dioxide precursor, copper salt, nickel salt, and reducing agent, followed by solid-state thermal treatment under an inert or reducing atmosphere, washing, and drying to prepare defect-type titanium dioxide CuNi / TiO supported on copper-nickel nanoparticles. 2-x Composite material; the molar ratio of copper salt to nickel salt is 1:(0.9~1.1); the mass of CuNi is 24~25wt% of the mass of TiO2; S2: the CuNi / TiO2 obtained in step S1 is... 2-x The composite material is mixed with a solution containing the target rare earth element, and then subjected to heat treatment or drying treatment to introduce rare earth ions into the composite material, thereby obtaining the rare earth / bimetallic synergistic reinforced composite photocatalyst; the rare earth element is selected from at least one or a combination of ytterbium (Yb), erbium (Er), neodymium (Nd), cerium (Ce), and dysprosium (Dy); the molar amount of the rare earth element is 0.1-1% of the molar amount of TiO2.

[0020] In S1 above, inert atmosphere heat treatment induces oxygen vacancies (VO) in the TiO2 lattice, while the loading of copper-nickel alloy nanoparticles (CuNi NPs) optimizes the charge separation efficiency of TiO2 through electron redistribution. These combined effects of multiple regulatory mechanisms in S2 significantly enhance the catalytic performance.

[0021] In order to balance product performance and cost, in step S1, the copper salt is copper chloride (CuCl2), the nickel salt is nickel chloride (NiCl2), the titanium dioxide powder is P25 type titanium dioxide, and the sodium borohydride (NaBH4).

[0022] In step S1 above, the heat treatment is carried out in a tube furnace at a temperature of 350~500℃ for 1~2 hours.

[0023] The mixing in S2 above is a solution impregnation method.

[0024] To ensure the performance of the obtained catalyst, in step S2 above, the heat treatment or drying treatment is low-temperature calcination or vacuum drying; the low-temperature calcination temperature is 250℃ to 350℃, and the time is 1-3h; the vacuum drying temperature is 40-80℃, the vacuum degree is 133 Pa, and the time is 4-12h.

[0025] The above-mentioned rare earth / bimetallic synergistic enhanced composite photocatalyst is used for photocatalytic degradation of organic pollutants in water; the organic pollutants are antibiotic pollutants, and the photocatalytic degradation is carried out under the irradiation of a light source containing visible light and / or near-infrared light.

[0026] The aforementioned rare earth / bimetallic synergistic enhanced composite photocatalyst can be used to degrade norfloxacin under visible and / or near-infrared light irradiation.

[0027] The above-mentioned rare earth / bimetallic synergistic enhanced composite photocatalyst can be recycled. After the reaction is completed, the solid is collected by centrifugation, washed with deionized water and anhydrous ethanol, and dried at 60°C for 4 hours before it can be used for the next catalysis.

[0028] This invention combines three mechanisms—defect engineering, bimetallic plasmon effect, and rare earth element modification (such as upconversion or charge trapping)—to prepare a catalyst with full-spectrum response and high photogenerated charge separation efficiency. It exhibits excellent degradation performance of antibiotic pollutants such as norfloxacin under visible and near-infrared light. Moreover, the preparation method is simple and low-cost, and has broad application prospects.

[0029] This application refers to doping amount, specifically molar doping amount. All other percentages, unless otherwise specified, are mass percentages.

[0030] Any techniques not mentioned in this invention are based on existing technologies.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) Full-spectrum high-efficiency photocatalytic activity: By introducing oxygen vacancies, CuNi bimetallic nanoparticles and rare earth elements, the full spectrum of ultraviolet-visible-near-infrared light is utilized in a synergistic manner. In particular, the rare earth upconversion mechanism effectively utilizes near-infrared light, and the SPR effect of Cu and the electron trapping ability of Ni significantly improve the separation efficiency of photogenerated electron-hole pairs in the visible light region, thus exhibiting a high-efficiency degradation ability for antibiotics such as norfloxacin in the full spectrum.

[0033] (2) Low cost: The use of Cu and Ni, which are abundant and inexpensive, to replace precious metals significantly reduces the preparation cost of catalysts, which is conducive to large-scale application.

[0034] (3) Simple preparation method: It adopts mature industrial technologies such as ball milling, heat treatment, and impregnation. The process is simple, the conditions are mild, and it is easy to operate and scale up production.

[0035] (4) High stability and reusability: The prepared composite photocatalyst still maintains high catalytic activity after multiple cycles of use, showing good chemical stability and reusability.

[0036] (5) Environmentally friendly: The photocatalytic process is carried out at normal temperature and pressure, which can effectively mineralize organic pollutants into harmless small molecules such as CO2 and H2O, reducing the generation of secondary pollution. Attached Figure Description

[0037] Figure 1 XRD comparison spectra of the series of composite photocatalysts prepared in Example 1;

[0038] Figure 2 For Yb 3+ Er 3+ FT-IR spectra of a series of composite materials;

[0039] Figure 3 For Yb 3+ Er 3+ UV-Vis diffuse reflectance spectra of a series of composite materials;

[0040] Figure 4 For Yb 3+ Er 3+ Photoluminescence spectra of a series of composite materials;

[0041] Figure 5 For Yb 3+ Er 3+ NOR degradation efficiency of a series of composite materials;

[0042] Figure 6 Yb under the influence of pH 3+ Er 3+ -CuNi / TiO 2-x NOR degradation efficiency of composite materials;

[0043] Figure 7 For Dy 3+ FT-IR spectra of a series of composite materials;

[0044] Figure 8 For Dy 3+ UV-Vis diffuse reflectance spectra of a series of composite materials;

[0045] Figure 9 For Dy 3+ Photoluminescence spectra of a series of composite materials;

[0046] Figure 10 For Dy 3+ NOR degradation efficiency of a series of composite materials;

[0047] Figure 11 Dy under the influence of pH 3+ -CuNi / TiO 2-x NOR degradation efficiency of composite materials;

[0048] Figure 12 For Yb 3+ ,Nd 3+ FT-IR spectra of a series of composite materials;

[0049] Figure 13 For Yb 3+ ,Nd 3+ UV-Vis diffuse reflectance spectra of a series of composite materials;

[0050] Figure 14 For Yb 3+ , Nd 3+ Photoluminescence spectra of a series of composite materials;

[0051] Figure 15 For Yb 3+ , Nd 3+ NOR degradation efficiency of a series of composite materials;

[0052] Figure 16 Yb under the influence of pH 3+ ,Nd 3+ -CuNi / TiO 2-x NOR degradation efficiency of composite materials;

[0053] Figure 17 For Ce 3+ FT-IR spectra of a series of composite materials;

[0054] Figure 18 For Ce 3+ UV-Vis diffuse reflectance spectra of a series of composite materials;

[0055] Figure 19 For Ce 3+ Photoluminescence spectra of a series of composite materials;

[0056] Figure 20 For Ce 3+ NOR degradation efficiency of a series of composite materials;

[0057] Figure 21 Ce under the influence of pH 3+ -CuNi / TiO 2-x NOR degradation efficiency of composite materials;

[0058] Figure 22 For Yb 3+ / Er 3+ -CuNi / TiO 2-x The response capability of composite photocatalysts to near-infrared light;

[0059] Figure 23 CuNi / TiO 2-x The degradation effect of composite materials on NOR;

[0060] Figure 24 For Yb 3+ -CuNi / TiO 2-xThe degradation effect of composite materials on NOR;

[0061] Figure 25 For Er 3+ -CuNi / TiO 2-x The degradation effect of composite materials on NOR;

[0062] Figure 26 For Yb 3+ / Er 3+ -CuNi / TiO 2-x The reusability of composite photocatalysts; Detailed Implementation

[0063] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0064] Unless otherwise specified, all cases were conducted at room temperature (15~25℃).

[0065] The general preparation method in each case is as follows:

[0066] S1: CuNi / TiO 2-x Preparation of intermediates: 5 g of P25 type TiO2, 0.01 mol CuCl2, 0.01 mol NiCl2, and 6 g of NaBH4 were weighed and ball-milled in a jar until the particle size was approximately 10-100 nm. The mixture was then heated to 500°C at a heating rate of 5°C / min under a N2 atmosphere and calcined at 500°C for 2 hours. After natural cooling to room temperature, the mixture was washed successively with anhydrous ethanol and deionized water to remove excess impurities and unreacted raw materials. The final product was vacuum dried at 60°C for 4 hours to obtain CuNi / TiO2. 2-x powder. S2: Introduction of rare earth elements:

[0067] Preparation of rare earth solution: Weigh 0.6 g of rare earth oxide, add 5 mL of concentrated nitric acid (15 mol / L HNO3) to dissolve it completely, and then make up to 10 mL with deionized water to obtain a rare earth ion stock solution with a predetermined molar concentration of about 0.32 mol / L.

[0068] Mixing and sonication: Weigh 3.8 g of the CuNi / TiO2 prepared in step S1. 2-xThe composite material powder was placed in a centrifuge tube. Based on the target rare earth element doping ratios (0.1%, 0.25%, 0.5%, 0.75%, 1%), 0.2 mL, 0.5 mL, 1 mL, 1.5 mL, and 2 mL of the aforementioned rare earth ion stock solution were respectively added to CuNi / TiO₂ using a pipette. 2-x Deionized water was then added to the composite powder until the material was completely submerged. The mixture was then placed in an ultrasonic cleaner and ultrasonically vibrated for 30 minutes to ensure that the rare earth ions were uniformly mixed with the matrix material.

[0069] Heat treatment and post-treatment: The ultrasonically treated mixture was transferred to a tube furnace, protected with nitrogen, and heated to 300℃ at a heating rate of 5℃ / min, and held at this temperature for 2 hours. After the sample cooled naturally to room temperature in the furnace, it was removed and washed five times alternately with deionized water and anhydrous ethanol (three times with deionized water and twice with anhydrous ethanol) to remove residual impurity ions from the surface. Finally, the washed sample was dried and ground (to a particle size of approximately 10-100 nm) to obtain rare earth ion / CuNi-TiO with different doping concentrations. 2-x Composite photocatalyst.

[0070] Example 1: Yb 3+ / Er 3+ -CuNi / TiO 2-x Preparation and performance characterization of composite photocatalysts

[0071] (1) Preparation method

[0072] S1: CuNi / TiO 2-x Preparation of intermediates:

[0073] Weigh 5 g of P25 type TiO2, 0.01 mol CuCl2, 0.01 mol NiCl2, and 6 g of NaBH4, and ball mill them thoroughly in a ball mill jar until the particle size is approximately 10-100 nm. Then, heat the mixture to 500°C under a N2 atmosphere at a heating rate of 5°C / min, and calcine it at 500°C for 2 hours. After naturally cooling to room temperature, wash the mixture successively with anhydrous ethanol and deionized water to remove excess impurities and unreacted raw materials. Finally, vacuum dry at 60°C for 4 hours to obtain CuNi / TiO2. 2-x powder.

[0074] S2:Yb 3+ Er 3+ Introduction of:

[0075] 1. Preparation of rare earth solution: Weigh 0.6 g Yb₂O₃, add 5 mL concentrated nitric acid (15 mol / L HNO₃) to dissolve it completely, then dilute to 10 mL with deionized water to obtain a Yb solution with a predetermined molar concentration of approximately 0.32 mol / L. 3+ Stock solution; Er2 with a molar concentration of approximately 0.32 mol / L was prepared using the same method. 3+ Stock solution.

[0076] 2. Mixing and sonication: Weigh 3.8 g of the CuNi / TiO2 prepared in step S1. 2-x The composite material powder was placed in centrifuge tubes. Based on the target rare earth element doping ratios (0.1%, 0.25%, 0.5%, 0.75%, 1%), 0.2 mL, 0.5 mL, 1 mL, 1.5 mL, and 2 mL of the two rare earth stock solutions were pipetted, respectively. Yb 3+ :Er 3+ The stock liquid volume ratio is 1:9, and CuNi / TiO is added. 2-x Add the rare earth ions to the composite powder. Then add deionized water until the material is completely submerged. Place the mixture in an ultrasonic cleaner and ultrasonically vibrate (300W) for 30 minutes to ensure that the rare earth ions are uniformly mixed with the matrix material.

[0077] 3. Heat Treatment and Post-treatment: The ultrasonically treated mixture was transferred to a tube furnace, protected with nitrogen, and heated to 300℃ at a heating rate of 5℃ / min, and held at this temperature for 2 hours. After the sample cooled naturally to room temperature in the furnace, it was removed and washed five times alternately with deionized water and anhydrous ethanol to remove residual impurity ions from the surface. Finally, the washed sample was dried and ground to obtain Yb with different doping concentrations. 3+ / Er 3+ -CuNi-TiO 2-x Composite photocatalyst.

[0078] (2) Performance characterization and degradation effect

[0079] As attached Figure 1 As shown in the XRD comparison pattern, TiO2 -x The sample's spectra show characteristic diffraction peaks of anatase and rutile titanium dioxide, indicating that the material has a mixed-crystal structure dominated by the anatase phase. The weak diffraction peak observed at approximately 19.8° is attributed to the Magnéli phase reduced titanium dioxide (TinO₂). 2n-1 Furthermore, the main diffraction peaks of both the anatase and rutile phases showed a slight leftward shift (towards a lower angle), indicating a slight increase in lattice spacing, which is consistent with TiO2. -xThe presence of oxygen vacancies and the resulting lattice distortion are consistent. After the introduction of copper (Cu) and nickel (Ni), CuNi / TiO2... -x A new diffraction peak appeared at 44.48° in the sample's spectra, corresponding to the CuNi alloy phase. For Yb... 3+ Er 3+ -CuNi / TiO2 -x The composite material not only retains all the characteristic diffraction peaks of the TiO2 matrix and CuNi alloy, but also shows two weak diffraction peaks near 2θ of 27°~29°, which confirms that ytterbium (Yb) and erbium (Er) have been successfully doped into the composite material.

[0080] As attached Figure 2 As shown, Fourier transform infrared spectroscopy (FT-IR) reveals that the material exhibits high light intensity in the 500-800 cm⁻¹ range. -1 The presence of vibrational absorption peaks at the Ti-O-Ti bond indicates that the recombination process did not disrupt the basic framework structure of TiO2. In the figure, 0.1%, 0.25%, 0.5%, 0.75%, and 1% represent the total doping amount of rare earth elements. In this example, it represents the total doping amount of ytterbium and erbium. For example, 1% indicates that the total doping amount of ytterbium and erbium is 1%.

[0081] As attached Figure 3 As shown, the UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) indicates that, compared with unmodified TiO2, the light absorption boundary of the catalyst in this embodiment is significantly red-shifted, exhibiting strong absorption throughout the visible light region.

[0082] As attached Figure 4 As shown, the photoluminescence (PL) spectrum reveals that the fluorescence emission intensity of the catalyst in this embodiment is significantly quenched, indicating that the separation efficiency of photogenerated charges is extremely high.

[0083] Application Test 1:

[0084] The photocatalytic degradation performance of the prepared composite photocatalyst was evaluated using norfloxacin (NOR) as the target pollutant. The specific test procedure is as follows:

[0085] Solution preparation and catalyst addition:

[0086] Accurately weigh 10 mg of the prepared photocatalyst powder and disperse it in 50 mL of norfloxacin aqueous solution with an initial concentration of 10 mg / L.

[0087] Dark reaction adsorption:

[0088] The above suspension was placed in a photochemical reactor and magnetically stirred for 30 min under light-protected conditions to allow the catalyst and pollutants to reach adsorption-desorption equilibrium.

[0089] Photocatalytic reaction:

[0090] The photocatalytic degradation reaction was initiated by turning on the light source. A 300 W xenon lamp was used as the light source, equipped with a 400 nm cutoff filter to remove ultraviolet light (obtaining visible light). The distance between the light source and the liquid surface was maintained at 10 cm. During the reaction, the temperature of the reaction system was maintained at 25 ± 2 ℃ through a circulating water condensation system, and continuous stirring was maintained.

[0091] Sampling and testing:

[0092] After the light exposure begins, 2 mL of suspension is taken from the reaction system at fixed intervals, and the photocatalyst particles are removed using a 0.22 μm aqueous filter. The absorbance at the maximum absorption wavelength of norfloxacin, 273 nm, is then measured using a UV-Vis spectrophotometer.

[0093] Data processing:

[0094] Based on the change in absorbance, according to the formula

[0095] D=

[0096] In the formula, C0 and C t (mg·L) -1 ) represent the concentrations of the target pollutant at the initial time and time t (minutes), respectively.

[0097] As attached Figure 5 As shown, by changing the total amount of rare earth doping, it was found that the catalyst exhibited the highest degradation activity under visible light (>400 nm) at a doping amount of 0.5%, demonstrating the optimization of the upconversion process (this process did not involve the addition of any pH adjuster).

[0098] Application Test 2:

[0099] pH selection test: Except for the initial pH value of the reaction solution, all other experimental conditions (including catalyst dosage, initial concentration of norfloxacin, type of light source, reaction temperature and sampling detection method, etc.) are completely consistent with the above "Photocatalytic degradation performance test method (application test 1)".

[0100] The specific adjustment process is as follows:

[0101] Before the dark reaction adsorption, 0.1 mol / L hydrochloric acid (HCl) aqueous solution and 0.1 mol / L sodium hydroxide (NaOH) aqueous solution were used as adjusting agents. By adding these acid and alkaline solutions dropwise and monitoring in real time with a precision pH meter, the initial pH value of the norfloxacin reaction solution was adjusted to preset gradient values ​​(e.g., pH = 3, 5, 7, 9, 11). After the pH value stabilized, subsequent photocatalytic degradation experiments were carried out according to the aforementioned standard procedure.

[0102] As attached Figure 6 As shown, the effect of initial pH on degradation was investigated using a catalyst with the best effect at a doping concentration of 0.5%. It was found that at pH=5, the degradation rate reached its optimum due to the strongest electrostatic attraction between the catalyst surface (pI=4.77) and norfloxacin molecules (pKa≈6.3).

[0103] Application Test 3:

[0104] As attached Figure 22 As shown, to further verify the Yb prepared by this invention 3+ / Er 3+ -CuNi / TiO2- x The responsiveness of the composite photocatalyst to near-infrared light and the effectiveness of its upconversion mechanism were further investigated by conducting photocatalytic activity tests under monochromatic near-infrared light.

[0105] Test method:

[0106] The light source of the photocatalytic reaction system was replaced with a near-infrared laser with a wavelength of 980 nm (power density set at 1.5 W / cm²). 2 The remaining test conditions (including catalyst dosage of 10 mg, norfloxacin solution concentration of 10 mg / L, volume of 50 mL, reaction temperature of 25±2℃, etc.) are consistent with the above "Photocatalytic Degradation Performance Test Method (Application Test 1)".

[0107] Test results:

[0108] Experimental results show that the composite photocatalyst prepared in Example 1 still exhibits significant photocatalytic activity under irradiation with 980 nm near-infrared light alone. After 2 hours of photoreaction, the degradation rate of norfloxacin reached 46%, confirming the effective utilization of near-infrared light energy by this material.

[0109] Application Test 4:

[0110] Cyclic stability and reusability performance testing

[0111] To evaluate the stability and reusability of the prepared composite photocatalyst, this invention selects Yb with the optimal photocatalytic activity.3+ / Er 3+ -CuNi / TiO 2-x The sample underwent five cycles of degradation experiments.

[0112] The specific testing steps are as follows:

[0113] First round of reactions:

[0114] Following the aforementioned "Photocatalytic Degradation Performance Test Method," 10 mg of catalyst was dispersed in 50 mL of norfloxacin solution with an initial concentration of 10 mg / L. The pH was adjusted to 5, and the degradation reaction was carried out under visible light irradiation for 2 h. After the reaction, samples were taken to determine the remaining concentration of norfloxacin and the first-round degradation rate was calculated.

[0115] Catalyst recovery and regeneration:

[0116] After the reaction was complete, the reaction solution was allowed to stand and precipitate, and the supernatant was discarded. The catalyst precipitate at the bottom was transferred to a centrifuge tube and centrifuged at 10,000 r / min for 5 min to collect the solid. Subsequently, the precipitate was washed three times with deionized water and anhydrous ethanol, respectively, to remove the organic intermediates adsorbed on the surface. The washed catalyst was then dried in a vacuum drying oven at 60℃ for 4 hours to obtain the regenerated photocatalyst powder.

[0117] Loop testing:

[0118] The recovered and regenerated catalyst powder was then added back into a freshly prepared 50 mL solution of 10 mg / L norfloxacin, and the photocatalytic reaction process was repeated. This process was repeated for a total of 5 cycles.

[0119] Test results:

[0120] The experimental results are attached. Figure 26 As shown, after five consecutive cycles, the degradation rate of norfloxacin by this composite photocatalyst did not show a significant decrease. Specifically, the degradation rate was 100% in the first cycle, and remained above 90% after the fifth cycle. This indicates that the material has excellent chemical stability and resistance to photocorrosion, making it suitable for long-term repeated use in practical water treatment applications.

[0121] Comparative Example 1

[0122] This comparative example aims to examine the photocatalytic performance of intermediate materials without rare earth elements, in order to verify the necessity of introducing rare earth elements.

[0123] Catalyst preparation:

[0124] The CuNi / TiO2 prepared in step S1 of the "General Preparation Method" without rare earth doping is directly selected. 2-x Powder is used as a photocatalyst.

[0125] The photocatalytic performance was tested using the same photocatalytic degradation test method as in Example 1, with the pH controlled at 5.

[0126] The experimental results are shown in Figure 23. After 2 hours of photocatalytic reaction, CuNi / TiO2- x The catalyst achieved a final degradation rate of 56% for norfloxacin.

[0127] Compared with the test results of Example 1, under the same pH=5 conditions, the degradation efficiency of Comparative Example 1 without rare earth doping was significantly lower than that of the composite catalyst with 0.5% doping in Example 1 (which achieved a degradation rate of nearly 100%). This result indicates that although the CuNi bimetallic support and TiO2-x defect structure provide some photocatalytic activity, the lack of rare earth ions (Yb) is a significant factor. 3+ / Er 3+ The introduction of rare earth ions prevents the material from utilizing low-energy photons through upconversion mechanisms, and the lack of rare earth ions as charge trapping centers to suppress electron-hole recombination limits the overall photocatalytic performance.

[0128] Comparative Example 2

[0129] This comparative example aims to examine the single rare earth element (Yb). 3+ The effect of doping on photocatalytic performance was investigated to verify the importance of the synergistic effect of bimetallic ions in this invention.

[0130] Catalyst preparation:

[0131] Compared with Example 1, the only difference in this comparative example is the way rare earth ions are introduced in step S2.

[0132] The specific operation was as follows: only ytterbium nitrate was added when preparing the impregnation solution, without adding erbium nitrate. The molar fraction of Yb³⁺ doping relative to TiO₂ was controlled to be 0.5%. All other preparation steps (including the preparation of the S1 intermediate, ultrasonic dispersion parameters, heat treatment temperature and time, etc.) were performed exactly as described in Example 1, ultimately yielding single-doped Yb. 3+ -CuNi / TiO 2-x Composite photocatalyst.

[0133] Photocatalytic performance test:

[0134] The reaction was carried out under the same test conditions as in Example 1, at pH 5 and under the same light source.

[0135] Experimental results are as follows Figure 24 As shown, after 2 hours of photocatalytic reaction, this single-doped Yb 3+ The final degradation rate of norfloxacin in the sample was only 50%. The inventors believe this is because, in the upconversion luminescence system, Yb... 3+ Typically acting as a "sensitizer," it is responsible for absorbing energy and must be combined with Er, which acts as an "activator." 3+ Only then can a complete energy transfer channel be constructed, thereby converting low-energy light into high-energy light. Without Er... 3+ Yb alone 3+ The inability to achieve effective upconversion results in performance inferior to undoped samples. This fully demonstrates the significant advancement of the present invention's technique of using a specific ratio of dual-ion co-doping.

[0136] Comparative Example 3

[0137] This comparative example aims to examine another single rare earth element (Er). 3+ The influence of doping on photocatalytic performance was investigated, further verifying the synergistic enhancement mechanism of the dual-ion co-doped system.

[0138] Catalyst preparation:

[0139] Compared with Example 1, the only difference in this comparative example is the way rare earth ions are introduced in step S2.

[0140] The specific procedure is as follows: when preparing the impregnation solution, only erbium nitrate is added, and ytterbium nitrate is not added. Control Er 3+ The doping amount relative to the molar fraction of TiO2 was 0.5%. All other preparation steps were strictly performed according to Example 1, ultimately yielding a single-doped Er... 3+ -CuNi / TiO 2-x Composite photocatalyst.

[0141] Photocatalytic performance test:

[0142] The standard test method was the same as in Example 1. The reaction was carried out at pH 5 and under the same light source.

[0143] like Figure 25 As shown, experimental results indicate that, within the same reaction time (2 h), this single-doped Er 3+ The catalyst resulted in a degradation rate of 68% for norfloxacin, which was significantly lower than that of the dual-doped composite material.

[0144] Example 2: Dy 3+ -CuNi / TiO 2-x Preparation and performance characterization of composite photocatalysts

[0145] (1) Preparation method

[0146] In addition to introducing only Dy in step S2 3+ The ions were identical to those in Example 1, and a series of Dy doping amounts with different doping levels were prepared. 3+ -CuNi / TiO 2-x Composite photocatalyst.

[0147] (2) Performance characterization and degradation effect

[0148] As attached Figure 7 As shown, the infrared spectrum is in the range of 400-800 cm⁻¹. -1 The broad peaks that appear between them are characteristic absorption peaks of Ti-O-Ti.

[0149] As attached Figure 8 As shown, UV-Vis DRS spectra reveal different Dy values. 3+ The doped samples all exhibited light absorption in the ultraviolet-visible region.

[0150] As attached Figure 9 As shown, the PL spectrum indicates that in Dy 3+ When the doping concentration is 1%, the fluorescence intensity of the material reaches its lowest value, indicating that the charge separation efficiency is optimal at this concentration. Performance testing was conducted using the same method as in Example 1, as shown in the attached figure. Figure 10 As shown, by comparing different Dy 3+ The catalyst activity was determined by doping amount, confirming that a 1% doping amount of catalyst was the most effective in degrading norfloxacin, with a degradation rate of 88% in 2 hours (no pH adjuster was added during this process).

[0151] As attached Figure 11 As shown, the effect of initial pH was investigated using the catalyst with the best effect of 1% doping. It was found that the degradation effect was most ideal under neutral conditions (pH=7), with a degradation rate of up to 89%.

[0152] Example 3: Yb 3+ / Nd 3+ -CuNi / TiO2- x Preparation and performance characterization of composite photocatalysts

[0153] (1) Preparation method

[0154] In addition to introducing Yb at a mass ratio of 1:1 in step S2 3+ Dy 3+ The ions were identical to those in Example 1, and a series of Yb³⁺ / Nd³⁺-CuNi / TiO₂- ions with different total doping amounts were prepared. x Composite photocatalyst.

[0155] (2) Performance characterization and degradation effect

[0156] As attached Figure 12 As shown, FT-IR spectroscopy confirmed that the TiO2 framework structure of the material remained stable after rare earth doping.

[0157] As attached Figure 13 As shown, UV-Vis DRS spectroscopy reveals that all of these catalysts exhibit excellent visible light absorption performance.

[0158] As attached Figure 14 As shown in the PL spectrum, the fluorescence quenching effect is most significant at a total rare earth doping concentration of 0.5%, indicating that photogenerated charge recombination is effectively suppressed. Performance testing was conducted using the same method as in Example 1, as shown in the attached figure. Figure 15 As shown, by comparing the catalyst activities with different doping amounts, it was confirmed that the catalyst with a low doping amount of 0.1% had the best activity, and the degradation rate reached 86% in 2 hours (no pH adjuster was added in this process).

[0159] As attached Figure 16 As shown, the effect of initial pH value was investigated on the catalyst with the best performance in the pre-test, which had a doping concentration of 0.1%. It was found that the degradation effect was optimal under weakly alkaline conditions (pH=9).

[0160] Example 4: Ce³⁺-CuNi / TiO2- x Preparation and performance characterization of composite photocatalysts

[0161] (1) Preparation method

[0162] In addition to introducing only Dy in step S2 3+ The ions were identical to those in Example 1, and a series of Ce³⁺-CuNi / TiO₂ with different doping levels were prepared. 2-x Composite photocatalyst.

[0163] (2) Performance characterization and degradation effect

[0164] As attached Figure 17 As shown, the FT-IR spectrum indicates that the introduction of Ce³⁺ did not alter the fundamental vibrational modes of the Ti-O-Ti material, and the structure remained intact.

[0165] As attached Figure 18 As shown, the UV-Vis DRS spectrum indicates that this series of materials has a high absorption intensity in the visible light region.

[0166] As attached Figure 19As shown in the PL spectrum, the fluorescence intensity was lowest at a Ce³⁺ doping concentration of 0.75%, indicating that this concentration is most favorable for charge separation. Performance testing was conducted using the same method as in Example 1, as shown in the attached figure. Figure 20 As shown, by comparing the catalyst activities with different doping amounts, it was confirmed that the catalyst with a doping amount of 0.25% had the best performance, and the degradation rate could reach 81% in 2 hours (no pH adjuster was added in this process).

[0167] As attached Figure 21 As shown, the effect of initial pH value was investigated using the catalyst with the best performance in the pre-test at a doping concentration of 0.25%. The test process was completely consistent with the pH test method in Example 1. It was found that a high degradation rate of about 85% could be obtained under both neutral (pH=7) and weakly alkaline (pH=9) conditions, showing a wide pH applicable range.

Claims

1. A composite photocatalyst of rare earth / bimetallic synergistic enhancement, characterized in that: Defective titanium dioxide TiO comprising oxygen-vacancy-rich defects 2-x Support, TiO 2-x The support is loaded with copper-nickel bimetallic nanoparticles and simultaneously doped with rare earth elements; the rare earth elements are at least one of ytterbium, erbium, neodymium, cerium, dysprosium or any combination thereof, the doping amount of the rare earth elements is 0.1-1%; the molar ratio of copper to nickel is 1:(0.9-1.1); and the molar ratio of the sum of the molar amounts of copper and nickel to TiO2-x is 2:(6-7).

2. The rare earth / bimetal synergistically enhanced composite photocatalyst according to claim 1, characterized in that: The rare earth element is a mixture of ytterbium and erbium with a mass ratio of 1: (8-10), and the doping amount of the rare earth element is 0.45-0.55%; when the pH value is 5±0.5, the norfloxacin is completely degraded within 90 min.

3. The rare earth / bimetal synergistically enhanced composite photocatalyst according to claim 1, characterized in that: The rare earth element is a mixture of ytterbium and neodymium with a mass ratio of (0.5-1.5):1, and the doping amount of the rare earth element is 0.08-0.12%; when the pH value is 9±0.5, the norfloxacin degradation rate reaches 89% within 2h.

4. The rare earth / bimetal synergistically enhanced composite photocatalyst according to claim 1, characterized in that: The rare earth element is dysprosium, and the doping amount of dysprosium is 1%; when the pH value is 7±0.5, the norfloxacin degradation rate reaches 89% within 2h.

5. The rare earth / bimetal synergistically enhanced composite photocatalyst according to claim 1, characterized in that: The rare earth element is cerium, and the doping amount of cerium is 0.25%; when the pH value is 7-9, the norfloxacin degradation rate reaches 85% within 2h.

6. A method for preparing a rare earth / bimetal synergistically enhanced composite photocatalyst, characterized in that, The method comprises the following steps: S1: mixing ball-milling titanium dioxide precursor, copper salt, nickel salt and reducing agent, then solid-phase heat treatment under inert atmosphere or reducing atmosphere, washing, drying, to prepare copper-nickel nanoparticle loaded defective titanium dioxide CuNi / TiO 2-x Composite material; the molar ratio of copper salt and nickel salt is 1: (0.9~1.1); the mass of CuNi is 24~25wt% of the mass of TiO2. S2: The CuNi / TiO obtained in step S1 2-x The composite material is mixed with a solution containing the target rare earth element, and then subjected to heat treatment or drying treatment to introduce rare earth ions into the composite material to obtain the rare earth / bimetallic synergistic enhanced composite photocatalyst; the rare earth element is selected from at least one or a combination of ytterbium, erbium, neodymium, cerium, and dysprosium; the molar amount of the rare earth element is 0.1-1% of the molar amount of TiO2.

7. The production method according to claim 6, wherein In step S1, the copper salt is copper chloride, the nickel salt is nickel chloride, the titanium dioxide powder is P25 type titanium dioxide, and the reducing agent is sodium borohydride.

8. The production method according to claim 6 or 7, characterized by, In step S1, the heat treatment is carried out in a tube furnace, the heat treatment temperature is 350-500℃, and the time is 1-2h. In step S2, the heat treatment or drying treatment is low-temperature calcination or vacuum drying; the low-temperature calcination temperature is 250-350℃, and the time is 1-3h; the vacuum drying temperature is 40-80℃, the vacuum degree is 133 Pa, and the time is 4-12h.

9. Use of the rare earth / bimetal synergistically enhanced composite photocatalyst according to any one of claims 1-5, characterized in that: The photocatalyst is used for photocatalytic degradation of organic pollutants in water; the organic pollutants are antibiotic pollutants, and the photocatalytic degradation is carried out under irradiation of a light source containing visible light and / or near-infrared light.

10. Use according to claim 9, characterized in that: Norfloxacin is degraded under irradiation of visible light and / or near-infrared light.

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