Core-shell photocatalyst for efficiently degrading pollutants in water and preparation method of core-shell photocatalyst

Abstract

The invention is applicable to the technical field of environmental functional materials and pollution abatement, and provides a core-shell photocatalyst capable of efficiently degrading pollutants in water and a preparation method thereof.The photocatalyst takes TiO particles as a core structure and takes a high-swelling cyclodextrin polymer prepared through esterification cross-linking reaction of cyclodextrin and ethylenediamine tetraacetic acid dianhydride as a shell layer; and forming the core-shell structure composite material. Efficient enrichment and rapid degradation of organic pollutants in water are achieved through the adsorption-catalysis synergistic effect, and the method has the advantages of being environmentally friendly, excellent in performance, good in stability and wide in application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental functional materials and pollution control, and in particular relates to a core-shell photocatalyst for efficiently degrading pollutants in water and a preparation method thereof. Background Art

[0002] Water pollution and water scarcity are among the most serious challenges facing the world in the 21st century. With the rapid development of modern industry and agriculture, a large number of organic pollutants have entered the aquatic environment, including endocrine disruptors, antibiotics, and organic dyes widely used in industries such as textiles, leather, printing, and papermaking. These pollutants often have complex and stable aromatic structures, are difficult to biodegrade, and persist in the environment. In addition, many organic pollutants exhibit significant biotoxicity even at extremely low concentrations, such as bisphenol A (BPA), exposure to which can cause health problems such as tumor development and birth defects. Therefore, the development of efficient and sustainable water treatment technologies to remove various recalcitrant organic pollutants has become an urgent issue.

[0003] Cyclodextrin (CD) is a naturally occurring cyclic oligosaccharide. Its unique hollow geometry allows it to form host-guest complexes with a variety of pollutants, showing promising applications in environmental remediation. In recent years, researchers have synthesized porous CD polymers by hypercrosslinking with rigid crosslinkers (such as tetrafluoroterephthalonitrile). These polymers, due to their high surface area and mesoporous structure, are capable of rapidly removing trace organic pollutants from water (Alsbaiee A et al., Nature, 2016). However, these materials rely heavily on aromatic crosslinkers, many of which are potentially biotoxic, and the design and regulation of their pore structure remain challenging.

[0004] On the other hand, while cyclodextrin polymers (such as EDTA-CDP) constructed with flexible crosslinkers (e.g., carboxylic acids) are environmentally friendly, their synthesis typically requires high reaction temperatures, resulting in low reactivity and yield (Zhao F et al., Environ. Sci. Technol., 2015). Furthermore, EDTA-CDP's non-porous structure, small specific surface area, and slow adsorption rate limit its application in high-end water purification. Conventional adsorbent materials are also limited by their saturated adsorption capacity, resulting in incomplete removal of pollutants. Furthermore, the regeneration process is cumbersome, impacting the recyclability of the materials. Therefore, there is an urgent need to develop new water treatment technologies that can achieve rapid, efficient, and sustainable pollutant removal.

[0005] Photocatalytic technology is considered an important means of achieving sustainable water treatment because it can continuously remove organic pollutants from water without the need for secondary treatment and requires only small amounts of chemical reagents. Among them, titanium dioxide (TiO2) is the most widely used photocatalyst due to its excellent physicochemical stability, low cost, environmental friendliness, and high catalytic activity. However, TiO2 also has significant limitations: its photoresponse range is limited to the ultraviolet region (approximately 5% of the solar spectrum), which greatly restricts the effective use of solar energy; at the same time, the rapid recombination of photogenerated electron-hole pairs further reduces catalytic efficiency. In addition, the hydrophilic surface of TiO2 has a weak adsorption capacity for non-polar organic pollutants (such as pharmaceuticals, personal care products, and endocrine disruptors), hindering the migration of pollutants to catalytic active sites, thereby reducing the utilization of reactive oxygen species (ROS) and resulting in unsatisfactory catalytic degradation results.

[0006] To overcome these challenges, researchers have proposed a variety of modification strategies, including morphology manipulation, noble metal doping, element doping, dye sensitization, and heterostructure construction. Among them, nanomaterials formed by combining macrocyclic compounds such as cyclodextrins with TiO2 are considered a promising solution. These composite materials not only enhance pollutant adsorption but also effectively inhibit electron-hole recombination, significantly improving photocatalytic performance in practical applications.

[0007] Therefore, in view of the above situation, there is an urgent need to develop a core-shell photocatalyst and preparation method for efficiently degrading pollutants in water to overcome the shortcomings in current practical applications. Summary of the Invention

[0008] The purpose of the present invention is to provide a core-shell photocatalyst for efficiently degrading pollutants in water and a preparation method thereof, aiming to solve the problems mentioned in the above background technology.

[0009] The present invention is achieved by providing a core-shell photocatalyst for efficiently degrading pollutants in water. The photocatalyst has TiO2 particles as the core structure and a highly swellable cyclodextrin polymer (His-CDP) prepared by esterification and cross-linking reaction of cyclodextrin and ethylenediaminetetraacetic dianhydride as the shell layer, forming a core-shell structure composite material.

[0010] According to a further technical solution, the shell layer has a mesoporous structure with a pore size of 2-50 nm and a specific surface area of ​​>500 m² / g, and the particle size of the TiO2 particles is at least one of 25 nm, 60 nm, 100 nm or 150 nm.

[0011] In a further technical solution, the cyclodextrin is at least one of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin; and / or the molar ratio of ethylenediaminetetraacetic acid dianhydride to cyclodextrin is 3:1 to 15:1; and / or the mass ratio of cyclodextrin to TiO2 is 5:1 to 1:10; and / or the shell is connected to the TiO2 core structure through an ester bond, and the infrared absorption peaks of the ester bond are located at 1735 cm⁻¹ and 1198 cm⁻¹.

[0012] Another object of the present invention is to provide a method for preparing a core-shell photocatalyst for efficiently degrading pollutants in water, comprising the following steps: TiO2, cyclodextrin and ethylenediaminetetraacetic dianhydride are dissolved and dispersed in an anhydrous solvent, and a catalyst is added dropwise after heating and stirring to carry out an esterification reaction to generate a dark yellow precipitate; the precipitate is filtered, washed to neutrality, and freeze-dried to obtain the core-shell photocatalyst.

[0013] In a further technical solution, the solvent is N,N-dimethylformamide and / or tetrahydrofuran; and / or the catalyst is diethylamine and / or triethylamine, and the molar ratio of ethylenediaminetetraacetic dianhydride to the catalyst is 2:1 to 1:3; and / or the solid-liquid ratio of the cyclodextrin to the solvent is 1:8 to 1:20.

[0014] According to a further technical solution, the esterification reaction temperature is 10-70° C., the reaction time is 1-60 minutes, and the stirring speed is 100-800 rpm.

[0015] A further technical solution comprises the following specific steps: adding TiO2, β-cyclodextrin and EDTAD to DMF, stirring at 500 rpm at 60°C for 10 minutes, adding triethylamine dropwise and continuing stirring for 20 minutes, filtering the precipitate and washing with water and methanol until neutral, and freeze-drying to obtain the core-shell photocatalyst.

[0016] Another object of the present invention is to use a core-shell photocatalyst for efficiently degrading pollutants in water in removing organic pollutants in water. The core-shell photocatalyst enriches organic pollutants near the TiO2 core structure through adsorption-catalytic synergy for photocatalytic degradation. The organic pollutants include at least one of bisphenol A, bisphenol S, ciprofloxacin or organic dyes.

[0017] According to a further technical solution, the adsorption rate of BPA by the core-shell photocatalyst is 0.109-0.1143 g / (mg・min), the photocatalytic degradation rate constant is 0.017-0.025 min⁻¹, and the degradation efficiency remains above 72% after five cycles.

[0018] The present invention provides a core-shell photocatalyst for efficiently degrading pollutants in water and a preparation method thereof, which has the following beneficial effects: This material uses environmentally friendly β-cyclodextrin, ethylenediaminetetraacetic dianhydride (EDTAD) and commercial TiO2 (P25) as raw materials. It constructs a composite material with a "core-shell" structure under mild conditions through a one-step esterification cross-linking method. The preparation process is simple, low-cost, and has prospects for industrial application.

[0019] Its core advantages are: the His-CDP shell has a high specific surface area (>500m² / g) and a mesoporous structure (2–50nm), which can quickly enrich a variety of organic pollutants and transport them to the vicinity of the TiO2 core catalytic site, significantly improving the utilization efficiency of reactive oxygen species (ROS), breaking through the limitation of the TiO2 hydrophilic interface's weak adsorption capacity for hydrophobic pollutants, and achieving efficient capture and in situ degradation of pollutants.

[0020] Experiments show that the adsorption rate, adsorption capacity and degradation rate of His-CDP-TiO2 for BPA are 2.4 times, 5.8 times and 4.4 times that of unmodified TiO2, respectively. It can efficiently degrade a variety of organic pollutants within 180 minutes, showing excellent versatility. The material has good cyclic stability, and its BPA degradation efficiency remains above 72% after five repeated uses.

[0021] As the first bifunctional core-shell material constructed by combining β-cyclodextrin, EDTAD and TiO2, the present invention has significant originality and broad application prospects. It is a new multifunctional photocatalytic material with high adsorption capacity, strong catalytic activity and good stability. It is suitable for industrial wastewater treatment and environmental remediation and has important scientific research value and market promotion potential.

[0022] In summary, the present invention achieves efficient enrichment and rapid degradation of organic pollutants in water through adsorption-catalysis synergistic effects, and has the advantages of being environmentally friendly, excellent performance, good stability and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the preparation principle of a core-shell photocatalyst for efficiently degrading pollutants in water provided by an embodiment of the present invention; Figure 2 The infrared spectra of His-CDP-TiO2 photocatalytic composite material and raw material monomers; Figure 3 This is the X-ray photoelectron spectrum of the His-CDP-TiO2 photocatalytic composite material; Figure 4 This is a scanning electron microscope image of the His-CDP-TiO2 photocatalytic composite material; Figure 5 This is the effect of His-CDP-TiO2 photocatalytic composite material on BPA adsorption at different adsorption times; Figure 6 is the adsorption isotherm of BPA on His-CDP-TiO2 photocatalytic composite material; Figure 7 This is the time-dependent photocatalytic degradation diagram of BPA by His-CDP-TiO2 photocatalytic composite material; Figure 8 This is the pseudo first-order kinetic model diagram of the photocatalytic degradation of BPA by His-CDP-TiO2 photocatalytic composite material; Figure 9 This is the photodegradation efficiency diagram of His-CDP-TiO2 (40%) on different types of organic pollutants; Figure 10 This is the cyclic photodegradation performance diagram of His-CDP-TiO2 (40%) for BPA. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0026] like Figure 1 As shown, a core-shell photocatalyst for efficiently degrading organic pollutants in water provided by an embodiment of the present invention, that is, a photocatalyst for efficiently adsorbing and catalytically degrading organic pollutants in water, wherein the photocatalyst is a core-shell structure composite adsorption material formed by anchoring the highly swellable cyclodextrin polymer to the TiO2 surface to form a shell layer, wherein the shell layer is a highly swellable cyclodextrin polymer obtained by hyper-crosslinking cyclodextrin and ethylenediaminetetraacetic dianhydride through a solvent-induced esterification reaction, and TiO2 (P25) particles are used as a core structure.

[0027] The rigid β-CD provides precise molecular recognition sites and structural stability for His-CDP, while the flexible cross-linked network gives His-CDP water absorption and swelling properties. This "soft-hard" alternating microstructure design enables His-CDP to have a high specific surface area, mesopore size, and abundant active adsorption sites after swelling. It can quickly enrich organic pollutants near the core TiO2, improve the utilization efficiency of reactive oxygen species (ROS) and catalytic degradation performance, and achieve efficient and sustainable "capture and degradation" of target pollutants. At the same time, the β-CD component in the composite material acts as an effective hole scavenger, inhibiting electron-hole recombination and enhancing the catalytic oxidation ability of phenolic pollutants.

[0028] like Figure 1As shown, one embodiment of the present invention also provides a method for preparing a core-shell photocatalyst for efficiently degrading pollutants in water, comprising the following steps: TiO2, cyclodextrin and ethylenediaminetetraacetic dianhydride are dissolved and dispersed in an anhydrous solvent, and after heating and stirring, a catalyst is slowly added dropwise to carry out an esterification reaction, and stirring is continued to obtain a dark yellow precipitate; the obtained precipitate is filtered and repeatedly washed with deionized water and methanol until the filtrate is neutral; the washed product is freeze-dried to obtain a composite material labeled His-CDP-TiO2.

[0029] Wherein, the catalyst is diethylamine and / or triethylamine; the solvent is N,N-dimethylformamide and / or tetrahydrofuran; and / or the particle size of the TiO2 is at least one of 25 nm, 60 nm, 100 nm or 150 nm; and / or the cyclodextrin is at least one of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin.

[0030] The molar ratio of the ethylenediaminetetraacetic acid dianhydride to cyclodextrin is 3:1 to 15:1; and / or the molar ratio of the ethylenediaminetetraacetic acid dianhydride to the catalyst is 2:1 to 1:3; and / or the mass ratio of the cyclodextrin to TiO2 is 5:1 to 1:10; and / or the solid-liquid ratio of the cyclodextrin to the solvent is 1:8 to 1:20 (g / mL).

[0031] The reaction temperature of the esterification reaction is 10-70° C., the reaction time is 1-60 minutes, and the stirring speed is 100-800 rpm.

[0032] like Figure 1-10 As shown, one embodiment of the present invention further provides an application of a core-shell photocatalyst for efficiently degrading pollutants in water in removing organic pollutants in water.

[0033] like Figure 2-10 As shown, in application, the specific preparation method of the His-CDP-TiO2 photocatalytic composite material includes the following steps: Step 1: Preparation of His-CDP-TiO2 photocatalytic composite material A highly swellable cyclodextrin polymer (His-CDP) was coated onto the surface of TiO2 (P25) particles using an anchoring method. The following steps were performed: TiO2, β-cyclodextrin (β-CD), and ethylenediaminetetraacetic dianhydride (EDTAD) were added to a scintillation vial, followed by the addition of anhydrous N,N-dimethylformamide (DMF). The mixture was stirred at 500 rpm on a heated stirrer at 60°C for 10 minutes. An appropriate amount of triethylamine was then slowly added dropwise as a catalyst, and stirring was continued for 20 minutes. A dark yellow precipitate formed in the reaction system. The resulting precipitate was filtered and washed thoroughly with copious amounts of deionized water and then methanol until the filtrate was neutral. Finally, the washed product was freeze-dried in vacuo to obtain the target material, which was labeled His-CDP-TiO2.

[0034] Step 2: Characterization of the structure and morphology of His-CDP-TiO2 photocatalytic composite materials In order to verify the structural characteristics and micromorphology of the His-CDP-TiO2 photocatalytic composite material prepared in the present invention, it was systematically characterized and analyzed by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).

[0035] 1. Infrared spectroscopy (FT-IR) analysis The structures of the raw materials and synthesized products were characterized using a Thermo Fisher Nicoleti S6700 Fourier transform infrared spectrometer in the range of 400–4000 cm⁻¹. Figure 2 Infrared spectra of TiO2, β-cyclodextrin (β-CD), His-CDP, and His-CDP-TiO2 are presented. In the spectrum of His-CDP-TiO2, the absorption peak at 1735 cm⁻¹ corresponds to the stretching vibration of C=O in the ester bond, while the peak at 1198 cm⁻¹ is attributed to the stretching vibration of C–O–C, indicating that the esterification and cross-linking reaction has successfully occurred. Furthermore, peaks for C–H stretching vibration, C–O stretching vibration, and O–C–O antisymmetric stretching vibration appear at 2928 cm⁻¹, 1156 cm⁻¹, and 1025 cm⁻¹, respectively, preserving the basic structural characteristics of cyclodextrin, indicating that it was not destroyed during the reaction. These results confirm that His-CDP is successfully anchored to the TiO2 surface, forming a core-shell composite material with a three-dimensional network structure.

[0036] 2. X-ray Photoelectron Spectroscopy (XPS) Analysis The elemental composition of the His-CDP-TiO2 surface was analyzed using a K-Alpha X-ray photoelectron spectrometer from Thermo Scientific, USA. Figure 3As shown in a, the XPS wide scan spectrum shows that the surface of the material mainly contains C, O, Ti and a small amount of N elements, which further confirms the effective combination of His-CDP and TiO2. In the Ti2p high-resolution spectrum ( Figure 3 b), 458.4eV and 464.1eV correspond to Ti 4 + Ti2p3 / 2 and Ti2p1 / 2 orbitals, the energy difference between the two peaks is 5.7eV, which is consistent with the Ti 4 +, and no other valence titanium species were found, indicating that TiO2 remained stable in the composite material without chemical reduction or oxidation.

[0037] 3. Scanning Electron Microscope (SEM) Analysis The microstructure of His-CDP-TiO2 was observed using a SU8010 field emission scanning electron microscope from Hitachi, Japan. Figure 4 As shown. Pure TiO2 appears as irregularly agglomerated nanoparticles, while His-CDP-TiO2 presents a three-dimensional network structure composed of round particles, indicating that His-CDP is successfully coated on the TiO2 surface and forms an ordered assembly structure. It is worth noting that as the TiO2 content increases from 10% to 40%, the particle size in the composite material decreases significantly from approximately 5μm to 0.5μm. This reduction in particle size helps to increase the specific surface area of ​​the material and the degree of exposure of active sites, thereby improving the contact efficiency with pollutants and promoting the rate of photocatalytic reaction.

[0038] Step 2: Adsorption performance of bisphenol A (BPA) in water by His-CDP-TiO2 photocatalytic composite material 1. Adsorption kinetics study To evaluate the adsorption kinetics of bisphenol A (BPA) in water by His-CDP-TiO2, adsorption experiments were conducted in the dark. The following procedures were performed: 10 mg of His-CDP-TiO2 was added to 20 mL of a BPA solution with an initial concentration of 0.1 mmol / L. The experimental temperature was controlled at 25°C, the initial pH was 6.45, and the stirring rate was 300 rpm. Samples of 1 mL were taken at designated time points (10 s, 30 s, 1 min, 2 min, 5 min, 10 min, 30 min, 60 min, 120 min, and 180 min). The mixture was then filtered through a 0.45 μm polypropylene filter to remove adsorbent particles. The residual BPA concentration in the filtrate was determined using a UV spectrophotometer.

[0039] All experiments were repeated three times and the results were averaged. The removal efficiency of BPA by His-CDP-TiO2 was calculated according to formula (1): (1) Among them, c0 (mmol / L) and c t (mmol / L) represent the initial concentration of BPA and the residual concentration at time t (mmol / L), respectively.

[0040] The adsorption amount qt (mg / g) is calculated according to formula (2): (2) Where V is the volume of the solution (L), Mw (g / mol) is the molar mass of BPA (g / mol), and madsorbent (g) is the mass of the adsorbent (g).

[0041] The pseudo-second-order adsorption kinetic model (Formula 3) was further used to fit the adsorption process: (3) Among them, k obs (g / mg / min) is the pseudo-second-order kinetic rate constant (g / (mg·min)), q t (mg / g) and q e (mg / g) represent the adsorption amount at time t and the equilibrium state (mg / g), respectively.

[0042] Figure 5 The temporal curve of the BPA adsorption capacity of His-CDP-TiO2 is presented. The results show that a pseudo-second-order kinetic model fits the adsorption data well, indicating that the adsorption process is primarily controlled by a chemical adsorption mechanism. Compared with unmodified TiO2 (P25), the His-CDP coating significantly improved the adsorption rate and capacity of BPA on His-CDP-TiO2.

[0043] For example, His-CDP-TiO2 (10%) reached adsorption equilibrium in only about 2 minutes, while TiO2 (P25) required over 60 minutes. The adsorption rate of BPA on His-CDP-TiO2 (10%) was 0.109 g / mg / min, 2.25 times that of TiO2 (P25). Furthermore, the equilibrium adsorption capacity of His-CDP-TiO2 (10%) was 35 mg / g, approximately 7 times that of TiO2 (P25). This indicates that the His-CDP structure not only enhances its affinity for BPA but also provides more active adsorption sites, significantly improving its adsorption performance.

[0044] 2. Adsorption isotherm study To investigate the adsorption capacity and adsorption mechanism of bisphenol A (BPA) on His-CDP-TiO2, an isothermal adsorption experiment was conducted. The following steps were performed: 10 mg of the adsorbent was added to 20 mL of BPA solutions with varying initial concentrations. The reaction was allowed to proceed at 25°C, an initial pH of 6.45, and a stirring rate of 300 rpm for one hour. After reaching adsorption equilibrium, samples were collected and the residual BPA concentration was determined.

[0045] Two classic adsorption isotherm models, the Langmuir model and the Sips model (Langmuir-Freundlich model), were used to fit and analyze the adsorption data.

[0046] The Langmuir isotherm adsorption model is shown in formula (4): (4) The Sips model is a combination of the Langmuir and Freundlich models and is applicable to heterogeneous surface adsorption processes. Its expression is shown in formula (5): (5) Where: q e (mmol / g) adsorption amount at adsorption equilibrium (mmol / g); c e (mmol / L) is the residual concentration of BPA in the solution at adsorption equilibrium (mmol / L); qmax (mmol / g), K L and K S (L / mmol) and n S The maximum adsorption capacity of the adsorbent for BPA, adsorption equilibrium constant and heterogeneity factor were obtained by fitting respectively.

[0047] Figure 6 The adsorption isotherms and model fitting results for BPA on His-CDP-TiO2 are presented. It can be seen that the adsorption data for all samples are more consistent with the Langmuir model, indicating that the adsorption behavior is primarily monolayer adsorption, the adsorption sites are evenly distributed, and the adsorption process is highly selective and saturated.

[0048] Further analysis revealed that the maximum adsorption capacity of His-CDP-TiO2 for BPA decreased with increasing TiO2 content. For example, the maximum adsorption capacities of His-CDP-TiO2 (10%), His-CDP-TiO2 (25%), and His-CDP-TiO2 (40%) were 0.35 mmol / g, 0.30 mmol / g, and 0.26 mmol / g, respectively, significantly higher than that of unmodified TiO2 (P25) (0.056 mmol / g). This indicates that the His-CDP coating effectively improves the material's adsorption capacity for BPA.

[0049] In summary, His-CDP-TiO2 exhibits excellent adsorption properties, with both a high adsorption rate and a large adsorption capacity. This property facilitates the rapid accumulation of BPA near the catalytically active sites of the TiO2 core, thereby increasing the utilization efficiency of reactive oxygen species (ROS) and enhancing the photocatalytic degradation effect, providing a key guarantee for achieving efficient integrated "capture and degradation" of pollutants.

[0050] 3. Study on photocatalytic degradation performance To evaluate the photocatalytic degradation ability of His-CDP-TiO2 for a variety of organic pollutants (including BPA, BPS, CPX, MB, CV, and BBY), a systematic test was conducted under experimental conditions. The specific steps were as follows: 20 mg of the catalyst was added to 40 mL of aqueous solution containing 20 mg / L of each pollutant. The mixture was stirred at 300 rpm under UV light (λ = 365 nm, intensity 300 mW / cm²) and maintained at 25°C. At specific time intervals (1 min, 5 min, 10 min, 30 min, 60 min, 90 min, 120 min, 150 min, and 180 min), 1 mL of the mixture was sampled and filtered through a 0.22 μm polypropylene filter to remove adsorbent particles. The concentrations of the target organic pollutants were determined using high-performance liquid chromatography-mass spectrometry (HPLC-MS), and qualitative and quantitative analysis of BPA photodegradation intermediates and byproducts was performed.

[0051] The photodegradation removal rate of the pollutants by the catalyst was calculated according to formula (1), and the pseudo-first-order kinetic model (formula 6) was used to calculate the photodegradation rate constant k (min⁻¹) of the catalyst for BPA: (6) Among them, k (min -1 ) is the reaction rate constant, c0 (mmol / L) and c t (mmol / L) are the initial concentration of BPA and the residual concentration of BPA in the filtrate at time t, respectively.

[0052] Figure 7 The comparison of the photocatalytic degradation effects of TiO2 (P25) and His-CDP-TiO2 on BPA was demonstrated. The results showed that in the absence of a catalyst, the BPA solution was almost not degraded after 180 minutes of UV irradiation. In contrast, all His-CDP-TiO2 samples showed significantly enhanced degradation efficiency for BPA. The photodegradation efficiency of BPA for His-CDP-TiO2 with three different TiO2 contents exceeded 99% after 180 minutes, while the unmodified TiO2 (P25) only achieved a degradation efficiency of about 65%. The pseudo-first-order kinetic model fits the photocatalytic degradation data of BPA for various catalysts well ( Figure 8The degradation rate of BPA by TiO2 (P25) was 0.0057 min⁻¹, and after His-CDP was coated on its surface, the degradation rate was significantly improved. For example, the degradation rate of BPA by His-CDP-TiO2 (40%) reached 0.025 min⁻¹, which was 4.4 times that of TiO2 (P25). This is consistent with the similar degradation rates of high-performance photocatalysts such as CDP-TiO2 and CD-TiO2 reported in the literature (García-Díaz E et al., Water Research, 2020; Zhang Detal., Environmental Science & Technology, 2018).

[0053] It is worth noting that while increasing the His-CDP content helps increase the adsorption rate of BPA, its effect on the photocatalytic degradation rate shows the opposite trend. As the His-CDP content increases from 10% to 40%, the photocatalytic degradation rate decreases from 0.017 min⁻¹ (His-CDP-TiO2 10%), 0.022 min⁻¹ (His-CDP-TiO2 25%), to 0.025 min⁻¹ (His-CDP-TiO2 40%). This is because while a high His-CDP content promotes the rapid enrichment of BPA, it also blocks more TiO2 photocatalytic active sites, thereby affecting the overall photocatalytic efficiency.

[0054] 4. Research on stability and reusability To evaluate the stability and reusability of the His-CDP-TiO2 photocatalyst in actual water treatment, after completing a complete photocatalytic reaction cycle (180 minutes), the catalyst was recovered by centrifugation and tested for five consecutive cycles under the same experimental conditions to examine the retention of its photocatalytic activity.

[0055] Figure 9 The degradation efficiency of His-CDP-TiO2 (40%) against a variety of organic pollutants was demonstrated, confirming the material's broad applicability in photocatalytic degradation processes. Results showed that within 180 minutes, His-CDP-TiO2 (40%) efficiently removed a variety of organic pollutants, including the endocrine disruptor bisphenol S (BPS) (94% removal efficiency), the antibiotic ciprofloxacin (CPX) (95% removal efficiency), the cationic dyes methylene blue (MB) (97% removal efficiency), crystal violet (CV) (96% removal efficiency), and the disperse dye bismarck brown Y (BBY) (96% removal efficiency). These results demonstrate the versatility of His-CDP-TiO2, effectively addressing organic micropollutants in water with diverse structures, polarities, and molecular weights.

[0056] Figure 10 The degradation performance of His-CDP-TiO2 (40%) for BPA over five consecutive photocatalytic cycles was demonstrated. In the first cycle, the BPA removal efficiency reached 96.28%, followed by 90.24%, 87.17%, 81.09%, and 72.03%. The photocatalytic efficiency slowly decreased with increasing cycles, likely due to minor catalyst loss during the washing process or partial occupation of TiO2 surface active sites by degradation intermediates. Despite this, His-CDP-TiO2 maintained a degradation efficiency exceeding 72% after five cycles, demonstrating excellent stability and good regeneration capability.

[0057] In summary, a composite photocatalytic material, His-CDP-TiO2, with a "core-shell" structure was successfully constructed by anchoring and coating the highly swellable cyclodextrin polymer His-CDP on the TiO2 surface. The His-CDP in the outer layer of this material not only rapidly enriches target organic pollutants near the catalytic sites of the TiO2 core, thereby improving the utilization efficiency of reactive oxygen species (ROS), but also plays a synergistic role in the photocatalytic process: the β-cyclodextrin component acts as an effective hole scavenger, inhibiting electron-hole recombination and enhancing the oxidation capacity of phenolic pollutants. The combined action of these multiple mechanisms gives this material significant advantages in achieving efficient capture and degradation of organic pollutants.

[0058] Example 1: Preparation of His-CDP-TiO2 (10%) and its performance test TiO2 (0.119 g), β-cyclodextrin (0.50 g, 0.44 mmol), ethylenediaminetetraacetic dianhydride (EDTAD, 0.564 g, 2.20 mmol), and N,N-dimethylformamide (DMF, 8 mL) were added to a 20 mL scintillation vial. The vial was then placed on a heated stirrer at 60°C and stirred at 500 rpm for 10 minutes. After the reaction system became homogeneous, 0.5 mL of triethylamine was slowly added dropwise as a catalyst. Stirring was continued for 20 minutes, resulting in a dark yellow precipitate. The product was collected by filtration and washed sequentially with copious amounts of deionized water and methanol until the filtrate was neutral. Finally, the product was freeze-dried in vacuo to obtain the target material, which was labeled His-CDP-TiO2 (10%) based on the theoretical mass ratio of His-CDP to TiO2.

[0059] Adsorption performance test results: The sample reached adsorption equilibrium for bisphenol A (BPA) within 10 minutes, with an equilibrium adsorption capacity of 35 mg / g, an adsorption rate of 0.1090 g / (mg·min), and a maximum adsorption capacity of 86.64 mg / g.

[0060] Photocatalytic performance test results: After 180 minutes of ultraviolet light (λ=365nm) irradiation, the degradation rate of BPA exceeded 99%, and the degradation rate constant was 0.017min⁻¹.

[0061] Example 2: Preparation of His-CDP-TiO2 (25%) and its performance testing TiO2 (0.357 g), β-cyclodextrin (0.50 g, 0.44 mmol), ethylenediaminetetraacetic dianhydride (0.564 g, 2.20 mmol), and DMF (8 mL) were added to a 20 mL scintillation vial. The remaining steps were the same as in Example 1, including heating and stirring (60°C, 500 rpm, 10 min), adding triethylamine (0.5 mL) dropwise, stirring for 20 min, filtering, washing, and vacuum freeze-drying. The resulting sample was labeled His-CDP-TiO2 (25%) based on the mass ratio of His-CDP to TiO2.

[0062] Adsorption performance test results: The sample reached adsorption equilibrium for BPA within 10 minutes, the equilibrium adsorption amount was 30 mg / g, the adsorption rate was 0.0912 g / (mg·min), and the maximum adsorption capacity was 68.40 mg / g.

[0063] Photocatalytic performance test results: After 180 minutes of ultraviolet light irradiation, the degradation rate of BPA exceeded 99%, and the degradation rate constant was 0.022min⁻¹.

[0064] Example 3: Preparation of His-CDP-TiO2 (40%) and its performance testing TiO2 (0.713 g), β-cyclodextrin (0.50 g, 0.44 mmol), ethylenediaminetetraacetic dianhydride (0.564 g, 2.20 mmol), and DMF (8 mL) were added to a 20 mL scintillation vial. Subsequent steps were consistent with Example 1, including heating and stirring (60°C, 500 rpm, 10 min), adding triethylamine (0.5 mL) dropwise, stirring for 20 min, filtering, washing until neutral, and freeze-drying. The resulting sample was labeled His-CDP-TiO2 (40%).

[0065] Adsorption performance test results: The sample reached adsorption equilibrium for BPA within 10 minutes, the equilibrium adsorption amount was 26 mg / g, the adsorption rate was 0.1143 g / (mg·min), and the maximum adsorption capacity was 59.28 mg / g.

[0066] Photocatalytic performance test results: After 180 minutes of ultraviolet light irradiation, the degradation rate of BPA exceeded 99%, and the degradation rate constant was 0.025min⁻¹.

[0067] The above-described embodiments of the present invention provide a core-shell photocatalyst and preparation method for efficiently degrading pollutants in water, aiming to address key technical challenges such as the saturation and regeneration difficulties of traditional adsorbents, as well as the photocatalyst's weak ability to enrich pollutants. The present invention has the following significant advantages: 1) The raw materials used include β-cyclodextrin, ethylenediaminetetraacetic dianhydride (EDTAD), and commercial TiO2 (P25), all of which are green, low-toxic, biodegradable, and environmentally friendly substances that will not cause secondary pollution; 2) It is synthesized under mild conditions using a one-step esterification cross-linking method, which does not require complex equipment or expensive reagents and has good prospects for industrial application; 3) The His-CDP shell rapidly enriches a variety of organic pollutants (such as bisphenol A, BPS, CPX, and dyes) through its high specific surface area (>500 m² / g) and mesoporous structure (2–50 nm), concentrating the pollutants near the TiO2 core, significantly increasing the local concentration and reactive oxygen species (ROS) utilization efficiency, achieving efficient capture and in situ mineralization of pollutants. 4) Traditional TiO2 has a weak adsorption capacity for hydrophobic pollutants (such as BPA), resulting in low photocatalytic efficiency. However, the His-CDP shell effectively overcomes this limitation, significantly improving the ROS attack efficiency; 5) The adsorption rate of BPA on His-CDP-TiO2 was 0.109 g / (mg·min), 2.4 times that of unmodified TiO2; the maximum adsorption capacity reached 0.38 mmol / g, 5.8 times that of TiO2; the photocatalytic degradation rate was 0.025 min⁻¹, 4.4 times that of TiO2; and it could efficiently degrade a variety of organic pollutants within 180 minutes, demonstrating good versatility and adaptability. 6) After five consecutive photocatalytic cycles, the degradation efficiency of BPA remained above 72%, demonstrating good structural stability and reusability; 7) For the first time, β-cyclodextrin, EDTAD and TiO2 were combined to construct a core-shell composite material with dual functions of adsorption and photocatalysis. This has not been reported before and is original and has broad application prospects.

[0068] In summary, the present invention achieves the synergistic effect of efficient enrichment and rapid degradation of pollutants through the rational design of the "core-shell" structure. It is a new multifunctional photocatalytic material with high adsorption capacity, strong catalytic activity, good stability and sustainable application potential. It is suitable for industrial wastewater treatment, environmental remediation and other fields, and has important practical significance and market promotion value.

[0069] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A core-shell photocatalyst for efficiently degrading pollutants in water, characterized in that: The photocatalyst uses TiO2 particles as a core structure and a highly swellable cyclodextrin polymer prepared by esterification and cross-linking reaction of cyclodextrin and ethylenediaminetetraacetic dianhydride as a shell layer to form a core-shell structure composite material.

2. The core-shell photocatalyst for efficiently degrading pollutants in water according to claim 1, characterized in that: The shell layer has a mesoporous structure with a pore size of 2–50 nm and a specific surface area of ​​>500 m² / g; The particle size of the TiO2 particles is at least one of 25 nm, 60 nm, 100 nm or 150 nm.

3. The core-shell photocatalyst for efficiently degrading pollutants in water according to claim 2, characterized in that: The cyclodextrin is at least one of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin; and / or, the molar ratio of ethylenediaminetetraacetic dianhydride to cyclodextrin is 3:1 to 15:1; And / or, the mass ratio of cyclodextrin to TiO2 is 5:1 to 1:10; And / or, the shell layer is connected to the TiO2 core structure through an ester bond, and the infrared absorption peaks of the ester bond are located at 1735 cm⁻¹ and 1198 cm⁻¹.

4. A method for preparing a core-shell photocatalyst for efficiently degrading pollutants in water according to any one of claims 1 to 3, characterized in that: The following steps are involved: TiO2, cyclodextrin and ethylenediaminetetraacetic dianhydride are dissolved and dispersed in an anhydrous solvent, heated and stirred, and then a catalyst is added dropwise to carry out an esterification reaction to generate a dark yellow precipitate; The precipitate is filtered, washed to neutrality, and freeze-dried to obtain the core-shell photocatalyst.

5. The method for preparing a core-shell photocatalyst for efficiently degrading pollutants in water according to claim 4, characterized in that: The solvent is N,N-dimethylformamide and / or tetrahydrofuran; And / or, the catalyst is diethylamine and / or triethylamine, and the molar ratio of ethylenediaminetetraacetic dianhydride to the catalyst is 2:1 to 1:3; And / or, the solid-liquid ratio of the cyclodextrin to the solvent is 1:8 to 1:

20.

6. The method for preparing a core-shell photocatalyst for efficiently degrading pollutants in water according to claim 5, characterized in that: The esterification reaction temperature is 10-70° C., the time is 1-60 minutes, and the stirring speed is 100-800 rpm.

7. The method for preparing a core-shell photocatalyst for efficiently degrading pollutants in water according to claim 6, characterized in that: The specific steps are: TiO2, β-cyclodextrin and EDTAD were added to DMF, stirred at 500 rpm at 60°C for 10 minutes, triethylamine was added dropwise and stirring was continued for 20 minutes, the precipitate was filtered and washed with water and methanol until neutral, and freeze-dried to obtain the core-shell photocatalyst.

8. Use of the core-shell photocatalyst for efficiently degrading pollutants in water according to any one of claims 1 to 3 in removing organic pollutants in water, characterized in that: The core-shell photocatalyst enriches organic pollutants near the TiO2 core structure through adsorption-catalysis synergy for photocatalytic degradation, and the organic pollutants include at least one of bisphenol A, bisphenol S, ciprofloxacin or organic dyes.

9. Use of the core-shell photocatalyst for efficiently degrading pollutants in water according to claim 8 in removing organic pollutants in water, characterized in that: The core-shell photocatalyst has an adsorption rate of BPA of 0.109 to 0.1143 g / (mg·min), a photocatalytic degradation rate constant of 0.017 to 0.025 min⁻¹, and a degradation efficiency of more than 72% after five cycles.

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