Bi2WO6 / g-C3N4 heterojunction photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a Bi2WO6 / g-C3N4 heterojunction photocatalyst as well as a preparation method and application of the Bi2WO6 / g-C3N4 heterojunction photocatalyst. The Bi2WO6 / g-C3N4 heterojunction photocatalyst is prepared from Bi2WO6 particles and a g-C3N4 nanosheet, and a Z type heterojunction is formed between the Bi2WO6 particles and the g-C3N4 nanosheet. According to the Bi2WO6 / g-C3N4 (BCN) photocatalyst, through collaborative optimization of a heterojunction structure and surface engineering, the visible light absorption range is widened, the charge separation efficiency is improved, and active sites are enriched, the catalyst has rich surface hydroxyl groups and oxygen vacancies and a hierarchical mesoporous structure, the adsorption capacity on ZEN is enhanced, and the photocatalytic activity of the photocatalyst is improved. Separation and transfer of photon-generated carriers are promoted, and catalytic reaction kinetics is improved; compared with single g-C3N4 or Bi2WO6, the degradation rates of ZEN are respectively increased by 2.51 times and 12.57 times, and the degradation efficiency reaches 99.4%.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst technology, specifically to a Bi2WO6 / g-C3N4 heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] Mycotoxin contamination in food and the environment poses a significant global threat to food safety, ecological integrity, and human health, urgently requiring close attention. Among these harmful fungal metabolites, zearalenone (ZEN) is a potent mycotoxin primarily biosynthesized by Fusarium species via the polyketide pathway, exhibiting widespread and persistent contamination characteristics. ZEN is routinely detected in various grains, animal feed, and derivative foods. The International Agency for Research on Cancer (IARC) classifies it as a Group 3 carcinogen, and over 120 countries worldwide have established stringent maximum residue limits (MRLs) for ZEN in various agricultural products (1-200 μg / kg). A critical issue is that during the wet processing of contaminated grains, ZEN can seep into the water and accumulate in the process water, posing a serious threat to aquatic ecosystems.

[0003] Furthermore, the resorcinol lactone structure of ZEN gives it definite reproductive toxicity, causing adverse effects such as endocrine disruption, teratogenicity, and potential carcinogenicity in mammals. Given these multifaceted health and environmental hazards, developing efficient and environmentally friendly ZEN removal technologies has become an urgent research priority. To address the pervasive threat of ZEN pollution, researchers have explored various traditional detoxification strategies, encompassing physical, biological, and chemical methods.

[0004] Physical methods (such as adsorption and irradiation) offer the advantage of rapid processing, but they typically suffer from limitations such as poor removal selectivity, potential nutrient loss from food matrices, and reliance on specialized equipment. Biological methods, utilizing microorganisms or enzymes for degradation, are environmentally friendly, but they also face challenges such as slow reaction kinetics, demanding operating parameters, and difficulties in maintaining microbial stability for large-scale applications.

[0005] While chemical treatments (such as ozone oxidation and alkaline hydrolysis) may be effective, they often pose safety hazards, have high operating costs, and can lead to a decline in the quality of treated products. Crucially, despite the advantages of these traditional methods, none simultaneously achieve the two core objectives of practical ZEN removal: high efficiency and environmental friendliness. This critical gap has driven the exploration of advanced technologies, among which semiconductor-based photocatalysis has emerged as a highly attractive alternative.

[0006] Photocatalysis using solar energy offers advantages such as room-temperature operation, low energy input, and complete mineralization of organic pollutants without secondary pollution. Although this technology has been successfully applied to the degradation of mycotoxins such as aflatoxin B1 (AFB1), patulin (PAT), and deoxynivalenol (DON), research on the photocatalytic degradation of ZEN is still insufficient, highlighting its potential and demand for catalyst development under visible light. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a Bi2WO6 / g-C3N4 heterojunction photocatalyst that can achieve efficient degradation of zearalenone in food and the environment.

[0008] This invention is achieved through the following technical solution: A Bi2WO6 / g-C3N4 heterojunction photocatalyst comprises: Bi2WO6 particles and g-C3N4 nanosheets, wherein a Z-shaped heterojunction is formed between the Bi2WO6 particles and the g-C3N4 nanosheets.

[0009] The present invention also provides a preparation method, comprising the following steps: (1) Urea was calcined once under a nitrogen atmosphere, cooled and ground into powder; the resulting powder was calcined a second time under a nitrogen atmosphere, cooled and g-C3N4 nanomaterials were obtained. (2) Dissolve Bi(NO3)3・5H2O and Na2WO4・2H2O in ethylene glycol in proportion and stir to form a first solution; heat the first solution to carry out a hydrothermal reaction, cool and centrifuge to collect the precipitate, wash and vacuum dry to obtain Bi2WO6; (3) Bi2WO6 and g-C3N4 nanomaterials were dispersed in anhydrous ethanol in a certain proportion, and after ultrasonic treatment, they were stirred. The product was separated by centrifugation, washed, vacuum dried and ground to obtain Bi2WO6 / g-C3N4 heterojunction photocatalyst.

[0010] Furthermore, in step (1), the heating rate of the first calcination is 4-6℃ / min, the calcination temperature is 530-570℃, and the holding time is 3-5h; the heating rate of the second calcination is 4-6℃ / min, the calcination temperature is 480-520℃, and the holding time is 3-5h.

[0011] Furthermore, in step (2), the molar mass ratio of Bi(NO3)3・5H2O to Na2WO4・2H2O is (1.8-2.2):1; the stirring time is 25-35 min; the hydrothermal reaction temperature is 170-190℃, and the reaction time is 10-14 h; the washing is performed by washing with deionized water and ethanol 2-4 times each; the drying temperature is 55-65℃, and the drying time is 6-10 h.

[0012] Furthermore, in step (3), the mass ratio of Bi2WO6 to g-C3N4 nanomaterial is (1.8-2.2):(6.5-7.5); the ultrasonic treatment frequency is 35-45kHz, the power is 280-320W, and the treatment time is 1.5-2.5h; the stirring treatment time is 10-14h; the washing is done by washing with deionized water and anhydrous ethanol 2-4 times each; the drying temperature is 55-65℃, and the drying time is 10-14h.

[0013] Furthermore, in step (1), the heating rate of the first calcination is 5℃ / min, the calcination temperature is 550℃, and the holding time is 4h; the heating rate of the second calcination is 5℃ / min, the calcination temperature is 500℃, and the holding time is 4h.

[0014] Furthermore, in step (2), the molar mass ratio of Bi(NO3)3・5H2O to Na2WO4・2H2O is 2:1, the stirring time is 30 min, the solvothermal reaction temperature is 180℃ and the reaction time is 12 h, the washing is 3 times each, and the drying temperature is 60℃ and the time is 8 h.

[0015] Furthermore, in step (3), the mass ratio of Bi2WO6 to g-C3N4 nanomaterials is 2:7, the ultrasonic frequency is 40kHz, the power is 300W, the time is 2h, the stirring time is 12h, the washing is performed 3 times, and the drying temperature is 60℃ for 12h. This invention also provides the application of Bi2WO6 / g-C3N4 heterojunction photocatalyst in the degradation of zearalenone in zearalenone.

[0016] The beneficial effects of this invention are as follows: 1. The BCN photocatalyst in this invention achieves broadened visible light absorption range, improved charge separation efficiency, and enriched active sites through synergistic optimization of heterojunction structure and surface engineering. The catalyst has abundant surface hydroxyl groups and oxygen vacancies, as well as a hierarchical mesoporous structure, which not only enhances the adsorption capacity for ZEN, but also promotes the separation and transfer of photogenerated charge carriers, thereby improving the catalytic reaction kinetics. Compared with single g-C3N4 or Bi2WO6, the ZEN degradation rate is increased by 2.51 times and 12.57 times, respectively, with a degradation efficiency of 99.4%.

[0017] 2. The catalyst in this invention degrades zearalenone using •O2. - and h + As the main active substance, it converts ZEN into a low-toxicity ortho-quinone derivative through a lactone ring cleavage pathway, completely eliminating its endocrine-disrupting activity and demonstrating a significant detoxification effect.

[0018] 3. The preparation method of this invention is simple and controllable, with low cost, requiring no complex equipment, and the catalyst has good stability and can be reused. The application process is mild and has no secondary pollution, making it suitable for large-scale promotion and application. It has important value in the fields of food safety and environmental protection. Attached Figure Description

[0019] Figure 1 The images show the morphology and elemental characterization of the components in this invention (A is the SEM image of g-C3N4 nanosheets, B is the SEM image of Bi2WO6 nanoparticles, C is the SEM image of the BCN composite material, D is the TEM image of g-C3N4 nanosheets, E is the TEM image of Bi2WO6 nanoparticles, F is the TEM image of the BCN composite material, G is the HAADF-STEM image of the BCN composite material, and H and L are the distribution spectra of Bi, W, O, C, and N elements in the BCN composite material, respectively). Figure 2 The XPS analysis diagrams of the photocatalysts in this invention are shown below (A is the full XPS spectrum of g-C3N4, Bi2WO6 and BCN, B is the high-resolution C1s spectrum, C is the high-resolution N1s spectrum, D is the high-resolution Bi4f spectrum, E is the high-resolution W4f spectrum, and F is the high-resolution O1s spectrum). Figure 3 The diagram shows the structure and surface properties of the photocatalyst in this invention (A is the XRD pattern, B is the FT-IR spectrum, C is the nitrogen adsorption-desorption isotherm, and D is the EPR spectrum). Figure 4 The following are the photocatalytic degradation performance figures of ZEN in this invention: (A is a comparison of degradation efficiency of different catalysts, B is the HPLC chromatogram of ZEN degradation by BCN, C is the degradation kinetic curve, D is the effect of catalyst dosage on degradation efficiency, E is the effect of initial pH on degradation efficiency, and F is the cycle stability curve of BCN). Figure 5 This is a graph showing the analysis of active species in this invention (A represents the effect of the trapping agent on ZEN degradation, B represents the degradation rate constant in the presence of different trapping agents, and C represents the DMPO trapping of O2). - (EPR signal diagram) Figure 6 The following are the photoelectric performance diagrams of the photocatalyst in this invention (A is the UV-VisDRS spectrum, B is the Tauc plot, C is the PL spectrum, D is the EIS Nyquist plot, and E is the transient photocurrent response curve). Figure 7 The following diagram illustrates the degradation mechanism and toxicity assessment of ZEN in this invention: (A is the optimized molecular structure of ZEN, B is the electrostatic potential surface diagram of ZEN, C is a schematic diagram of the degradation pathway of ZEN, D is the developmental toxicity of ZEN and its degradation products, and E is the 96h-LC-weighted image of ZEN and its degradation products on blackhead carp).50 F represents the 48h-IGC of ZEN and its degradation products against Tetrahymena piriformis. 50 ); Figure 8 This is a high-resolution transmission electron microscope (HRTEM) image of the photocatalyst in this invention; Figure 9 This is the X-ray energy spectrum (EDS) of the photocatalyst in this invention. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] Example 1: A method for preparing a Bi2WO6 / g-C3N4 heterojunction photocatalyst, comprising the following steps: (1) Preparation of ultrathin g-C3N4 nanosheets: 10g of urea was placed in a covered alumina crucible and placed in a tube furnace. Nitrogen gas was introduced (flow rate 50mL / min), and the temperature was raised to 530℃ at 4℃ / min and held for 3h. After cooling, the powder was ground into powder. The powder was placed in the tube furnace again and calcined at 480℃ at 4℃ / min under a nitrogen atmosphere for 3h. After cooling, ultrathin g-C3N4 nanosheets were obtained.

[0022] (2) Preparation of surface hydroxylated oxygen-rich vacancy Bi2WO6: Weigh 1.8 mmol Bi(NO3)3・5H2O and 1 mmol Na2WO4・2H2O, add 60 mL ethylene glycol, stir vigorously for 25 min until completely dissolved; transfer the solution to a 100 mL polytetrafluoroethylene-lined autoclave, heat at 170 °C for 10 h, cool and centrifuge to collect the precipitate, wash twice with deionized water and ethanol, and vacuum dry at 55 °C for 6 h to obtain surface hydroxylated oxygen-rich vacancy Bi2WO6.

[0023] (3) Preparation of Bi2WO6 / g-C3N4 heterojunction: 18mg Bi2WO6 and 65mg ultrathin g-C3N4 nanosheets were dispersed in 40mL anhydrous ethanol, ultrasonically treated at 35kHz and 280W for 1.5h, and then magnetically stirred for 10h; the product was separated by centrifugation, washed and vacuum dried at 55℃ for 10h, and then ground to obtain BCN photocatalyst.

[0024] The catalyst element has a mesoporous structure with a pore size of 2-45 nm and a band gap energy of 2.70 eV.

[0025] Example 2: A method for preparing a Bi2WO6 / g-C3N4 heterojunction photocatalyst, comprising the following steps: (1) Preparation of ultrathin g-C3N4 nanosheets: 10g of urea was placed in a covered alumina crucible and placed in a tube furnace. Nitrogen gas was introduced (flow rate 50mL / min), and the temperature was raised to 550℃ at 5℃ / min and held for 4h. After cooling, the powder was ground into powder. The powder was placed in the tube furnace again and calcined at 500℃ at 5℃ / min under a nitrogen atmosphere for 4h. After cooling, ultrathin g-C3N4 nanosheets were obtained.

[0026] (2) Preparation of surface hydroxylated oxygen-rich vacancy Bi2WO6: Weigh 2 mmol Bi(NO3)3・5H2O and 1 mmol Na2WO4・2H2O, add 60 mL ethylene glycol, stir vigorously for 30 min until completely dissolved; transfer the solution to a 100 mL polytetrafluoroethylene-lined autoclave, heat at 180 °C for 12 h, cool and centrifuge to collect the precipitate, wash with deionized water and ethanol 3 times each, and vacuum dry at 60 °C for 8 h to obtain surface hydroxylated oxygen-rich vacancy Bi2WO6.

[0027] (3) Preparation of Bi2WO6 / g-C3N4 heterojunction: 20mg Bi2WO6 and 70mg ultrathin g-C3N4 nanosheets were dispersed in 40mL anhydrous ethanol and ultrasonically treated at 40kHz and 300W for 2h, followed by magnetic stirring for 12h; the product was separated by centrifugation, washed and vacuum dried at 60℃ for 12h, and then ground to obtain BCN photocatalyst.

[0028] The catalyst has a mesoporous structure with a pore size of 3-48 nm and a band gap energy of 2.65 eV.

[0029] Example 3: A method for preparing a Bi2WO6 / g-C3N4 heterojunction photocatalyst, comprising the following steps: (1) Preparation of ultrathin g-C3N4 nanosheets: 10g of urea was placed in a covered alumina crucible and placed in a tube furnace. Nitrogen gas was introduced (flow rate 50mL / min), and the temperature was raised to 570℃ at 6℃ / min and held for 5h. After cooling, the powder was ground into powder. The powder was placed in the tube furnace again and calcined at 520℃ at 6℃ / min under a nitrogen atmosphere for 5h. After cooling, ultrathin g-C3N4 nanosheets were obtained.

[0030] (2) Preparation of surface hydroxylated oxygen-rich Bi2WO6: Weigh 2.2 mmol Bi(NO3)3・5H2O and 1 mmol Na2WO4・2H2O, add 60 mL ethylene glycol, and stir vigorously for 35 min until completely dissolved; transfer the solution to a 100 mL polytetrafluoroethylene-lined autoclave, heat at 190 °C for 14 h, cool and centrifuge to collect the precipitate, wash with deionized water and ethanol 4 times each, and vacuum dry at 65 °C for 10 h to obtain surface hydroxylated oxygen-rich Bi2WO6.

[0031] (3) Preparation of Bi2WO6 / g-C3N4 heterojunction: 22mg Bi2WO6 and 75mg ultrathin g-C3N4 nanosheets were dispersed in 40mL anhydrous ethanol and ultrasonically treated at 45kHz and 320W for 2.5h, followed by magnetic stirring for 14h; the product was separated by centrifugation, washed and vacuum dried at 65℃ for 14h, and then ground to obtain BCN photocatalyst.

[0032] The catalyst has a mesoporous structure with a pore size of 5-50 nm and a band gap energy of 2.60 eV.

[0033] Example 4: Structural characterization of the photocatalyst, taking the Bi2WO6 / g-C3N4 heterojunction photocatalyst prepared in Example 2 as an example: Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed distinct morphological features: such as Figure 1 A and Figure 1 As shown in Figure D, pure g-C3N4 exhibits a typical layered structure, with interconnected nanosheets forming a three-dimensional porous network, which is beneficial for increasing specific surface area and exposing abundant active sites. In contrast, as... Figure 1 B and Figure 1 As shown in Figure E, pure Bi₂WO₆ exhibits a uniform and densely distributed particle morphology, indicating its high crystallinity. TEM and high-resolution transmission electron microscopy (HRTEM) analyses confirmed that two-dimensional g-C₃N₄ nanosheets and Bi₂WO₆ nanoparticles successfully formed a heterojunction structure in the BCN composite material. Figure 1 C and Figure 1 As shown in Figure F, the TEM image reveals the coexistence of layered g-C3N4 structures and dispersed Bi2WO6 nanoparticles, indicating spontaneous assembly during the formation of the composite material. Figure 8 As shown, further HRTEM characterization clearly reveals a close-contact heterojunction structure between crystalline Bi₂WO₆ and amorphous g-C₃N₄. At the heterojunction boundary, lattice fringes with an interlayer spacing of 0.326 nm are clearly distinguishable, perfectly corresponding to the (014) crystal plane of monoclinic Bi₂WO₆. This close interfacial contact facilitates efficient transfer of photogenerated carriers and synergistic catalytic effects between the heterojunctions. Figure 1 GL and Figure 9 As shown, energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of C, N, Bi, O, and W elements in BCN, with C having the highest mass fraction (62.0%), followed by N (20.4%), Bi and O both at 6.6%, and W at 4.5%. This elemental composition and distribution clearly indicate that g-C3N4 serves as the structural framework, with Bi2WO6 successfully composited on its surface, forming a BCN heterojunction composite material.

[0034] X-ray photoelectron spectroscopy (XPS) analysis provides direct evidence of surface elemental composition and chemical state. For example... Figure 2 As shown in Figure A, pure g-C3N4 exhibits significant C1s and N1s peaks, pure Bi2WO6 shows obvious Bi4f, O1s, and W4f peaks, and the spectrum of the BCN composite material contains all these characteristic peaks, with no impurity peaks detected, confirming successful composite material formation without elemental loss or impurity introduction. High-resolution spectroscopy elucidates the chemical state: as... Figure 2 As shown in Figure B, the C1s spectrum of g-C3N4 has a main peak at 288.2 eV, attributed to the NC=N bond in the triazine ring; the shoulder peaks at 284.8 eV and 286.5 eV correspond to the C=C bond and possibly the C=O bond caused by slight surface oxidation or oxygen adsorption. Figure 2 As shown in Figure C, its N1s spectrum has a main peak at 398.8 eV (N=CN), and the peaks at 401.2 eV and 403.5 eV are attributed to NH and possibly NO bonds, further indicating the presence of slightly oxidized or adsorbed oxygen-containing groups on the surface. The C1s and N1s spectra of BCN are similar to those of pure g-C3N4, but the peak intensities change, indicating that Bi2WO6 partially covers or modifies the surface of g-C3N4, but does not change its basic chemical structure. Figure 2 As shown in D, the Bi4f spectrum of pure Bi2WO6 shows Bi... 3+ Characteristic double peaks, such as Figure 2 As shown in E, the W4f spectrum shows W6 + The twin peaks, such as Figure 2 As shown in Figure F, the O1s spectrum has a main peak at 530-532 eV, which is attributed to lattice oxygen (O²⁻). - It is worth noting that the Bi4f and W4f peaks in BCN are slightly shifted compared to pure Bi2WO6, while the O1s intensity changes, indicating that there is interfacial charge redistribution or chemical bonding at the heterojunction.

[0035] like Figure 3 As shown in Figure A, the X-ray diffraction (XRD) pattern elucidates the crystal structure. Pure g-C3N4 exhibits a broad peak near 27.5°, corresponding to the (002) crystal plane, reflecting its layered stacked structure based on triazine rings, with small crystallite size or some disorder. Pure Bi2WO6 shows multiple sharp diffraction peaks, matching the standard card (JCPDS No. 39-0256), confirming its high crystallinity and good phase purity. The XRD pattern of the BCN composite clearly contains the characteristic (002) peak of g-C3N4 and all the major peaks of Bi2WO6, verifying the preservation of the crystal structures of the two phases and the successful construction of the heterojunction. The changes in peak intensity and full width at half maximum (FWHM) in the composite indicate that changes in crystallite size or slight lattice distortion may have occurred during the composite process. Figure 3As shown in Figure B, Fourier transform infrared spectroscopy (FTIR) further confirmed the chemical composition and structural characteristics. Characteristic peaks of pure g-C3N4 include: 3400-3200 cm⁻¹. -1 (NH stretching vibration), 1650cm -1 (C=N stretching vibration), 1400-1300cm -1 (CN stretching vibration) and 810cm -1 (Triazine ring out-of-plane bending vibration). Characteristic peaks of pure Bi₂WO₆ include: 3500–3300 cm⁻¹. -1 (OH stretching vibration), 1650cm -1 (OH bending vibration) and 800-1100cm -1 (WO stretching vibration) (Yuan et al., 2020). The FTIR spectrum of BCN retained all the characteristic peaks of g-C3N4 (NH, C=N, CN, triazine ring) and the main peaks of Bi2WO6 (OH, WO), indicating that the core chemical structures of the two components remained intact during the recombination process, providing a functional group basis for the synergistic catalytic effect within the heterojunction. Figure 3 As shown in Figure C, the nitrogen adsorption-desorption isotherm evaluated the pore structure characteristics. The BCN composite exhibits a typical Type IV isotherm and a significant hysteresis loop, indicating a stable mesoporous structure. The pore size distribution curve shows that the main pore sizes are concentrated in the 2-50 nm mesoporous range. This optimized porous structure originates from the synergistic assembly of g-C3N4 sheets and Bi2WO6 particles, which significantly increases the specific surface area, facilitating reactant adsorption and promoting the efficient separation and transport of photogenerated carriers. Furthermore, as shown in Figure C... Figure 3 As shown in Figure D, a distinct Lorentz-type signal was detected in the electron paramagnetic resonance (EPR) spectrum at g=2.002, clearly confirming the presence of oxygen vacancies (OVs) in the BCN composite material. These defects can serve as active sites, significantly enhancing the separation of photogenerated charges, which is crucial for improving photocatalytic activity.

[0036] In summary, these multi-technical characterization techniques confirm the successful fabrication of a structurally stable BCN heterojunction. This material integrates a layered porous framework of g-C3N4 with a crystalline Bi2WO6 phase, forming a tightly bound interface with oxygen vacancies and an optimized mesoporous structure. This structure synergistically combines the advantages of both components, laying a solid foundation for efficient visible light-driven ZEN degradation.

[0037] Example 5: Performance test of photocatalyst for ZEN degradation The degradation efficiency of ZEN under visible light was evaluated through batch experiments. A typical experimental procedure was as follows: 5 mg of photocatalyst was dispersed in 50 mL of ZEN aqueous solution (initial concentration: 2 μg / mL). Before irradiation, the suspension was magnetically stirred (500 rpm; IKAC-MAGHS7, Germany) in the dark for 30 minutes and kept at a constant temperature (25±1℃) to establish adsorption-desorption equilibrium. Subsequently, the suspension was irradiated with a 300W xenon lamp (CEL-HXF300, Beijing Zhongjiao Jinyuan Technology Co., Ltd.) equipped with a 420 nm cutoff filter (ensuring λ>420 nm) to initiate the reaction. During irradiation (0-40 minutes), 2 mL of sample was periodically taken every 10 minutes and immediately centrifuged at 12,000 rpm for 5 minutes to remove catalyst particles. The concentration of ZEN in the supernatant was quantified using high-performance liquid chromatography (HPLC, Thermo Fisher Scientific, USA) equipped with a C18 column and a fluorescence detector (FLD, excitation wavelength: 274 nm, emission wavelength: 440 nm). The degradation efficiency (η, %) is calculated using the following formula: η(%) = [(C0 - C t ) / C0]×100%, where C0 and C t The ZEN concentrations are shown at equilibrium (t=0 min) and at time t, respectively. To assess reusability, the catalyst was recovered by centrifugation after each degradation cycle (40 min), ultrasonically washed three times with ultrapure water (10 min each time), dried under vacuum at 60 °C for 12 h, and then used for the next cycle. A total of 5 consecutive degradation cycles were performed.

[0038] This example evaluates the photocatalytic degradation activity of different catalysts for ZEN under visible light. For example... Figure 4 As shown in Figure A, the self-degradation of ZEN under visible light is negligible without a catalyst. With the introduction of a photocatalyst, the degradation efficiency gradually increases with irradiation time. Notably, significant differences in activity appear after 20 minutes, with the degradation efficiency ranking as follows: BCN > g-C3N4 > Bi2WO6. After 40 minutes of irradiation, the degradation efficiency of BCN reaches 99.4%, g-C3N4 is 82.4%, and Bi2WO6 is 26.8%, clearly demonstrating the superior performance of the BCN heterojunction. Figure 4 As shown in Figure B, the liquid chromatography chromatogram further demonstrates the time-dependent decrease in the ZEN peak intensity under BCN photocatalysis, confirming its highly efficient degradation ability. Figure 4 As shown in Figure C, kinetic analysis indicates that the degradation process of all catalysts follows pseudo-first-order kinetics. As expected, the BCN composite material exhibits the highest reaction rate constant (k = 0.1043 min⁻¹). -1The photocatalytic activity was 2.51 times and 12.57 times that of pure g-C3N4 and Bi2WO6, respectively. This significant enhancement in photocatalytic activity is mainly attributed to the efficient interfacial charge separation facilitated by the tight heterojunction structure (confirmed by TEM / XPS) and the abundant active sites (including oxygen vacancies confirmed by EPR and optimized porous structure revealed by BET analysis), which synergistically promoted light absorption and ZEN activation. Key reaction parameters were optimized to achieve the best degradation efficiency of ZEN by BCN. Figure 4 As shown in Figure D, the effect of catalyst concentration indicates that increasing the BCN dose from 0.05 mg / mL to 0.2 mg / mL significantly improved the degradation rate within the same irradiation time. This is attributed to the increased availability of active sites and photogenerated carriers. However, further increasing the concentration to 0.4 mg / mL did not significantly improve the activity. This saturation effect may be due to enhanced light scattering and shielding at higher catalyst concentrations, reducing light transmittance and effective photon absorption. Therefore, a BCN concentration of 0.2 mg / mL was chosen as the optimal condition. Figure 4 As shown in Figure E, pH optimization revealed relatively low degradation efficiency (approximately 80%) under acidic conditions (pH 4–6), likely due to unfavorable electrostatic interactions between the catalyst surface and ZEN molecules. The efficiency sharply increased to 97.5% at pH 7, indicating optimal activity under near-neutral conditions, favorable for adsorption and reaction kinetics. While efficiency decreased slightly under alkaline conditions (pH 8–9) (still remaining at approximately 90%), it remained at a high level, demonstrating BCN's robustness over a wide pH range. Therefore, BCN exhibits the highest photocatalytic activity for ZEN degradation under near-neutral to weakly alkaline conditions. Furthermore, as… Figure 4 As shown in Figure F, BCN exhibits excellent reusability and stability. The catalyst maintained stable degradation performance throughout four consecutive cycles, with nearly identical degradation curves and efficiencies. Even after the fifth cycle, although a slight decrease in efficiency was observed (primarily attributed to minor mass loss during catalyst recovery and reuse), the activity remained at a high level. This confirms the good structural stability and practical reusability of the BCN photocatalyst.

[0039] The above results demonstrate that the BCN heterojunction composite photocatalyst exhibits excellent activity in visible light-driven ZEN degradation, while also possessing excellent reusability and stability. Furthermore, as shown in Table 1, compared to previously reported ZEN photodegradation catalysts, the BCN composite material prepared in Example 2 exhibits superior performance, achieving a faster degradation rate constant (0.1043 min⁻¹). -1 The high efficiency (99.4%) and enhanced photocatalytic activity under visible light highlight BCN's superior photocatalytic capabilities. These properties make BCN a promising material for the efficient photocatalytic degradation and detoxification of ZEN in relevant environments.

[0040] Photocatalyst type Dosage ZEN concentration Irradiation type Irradiation time <![CDATA[Rate constant / min -1 > Removal efficiency References <![CDATA[g-C3N4]]> 5mg / mL 0.5 μg / mL Ultraviolet light 70 minutes - 96% Comparative Example 1 WCN-AP7 0.5 mg / mL 2.5 μg / mL Visible light 60 minutes 0.0371 89.5% Comparative Example 2 BWO-U 0.4 mg / mL 2.0 μg / mL Visible light 90 minutes 0.0406 98% Comparative Example 3 <![CDATA[TiO2 / GCN]]> 0.75 mg / mL 10 μg / mL Ultraviolet light 25 minutes - 97.7% Comparative Example 4 BCN 0.2 mg / mL 2.0 μg / mL Visible light 40 minutes 0.1043 99.4% This invention Reactive oxygen species (ROS) play a crucial role in the photocatalytic degradation of organic pollutants. To elucidate the main ROS in the degradation of ZEN by BCN, EDTA (h) was used. + (capture agent), K2Cr2O7 (e - (Scavenger), isopropanol (IPA, ·OH scavenger), and benzoquinone (BQ, ·O2 scavenger) - Free radical capture experiments were conducted using a scavenging agent. Figure 5 As shown in A and 5B, the degradation rate decreased by 33% and 40%, respectively, when •OH and e- were captured. It is noteworthy that quenching h… + and O2 - This resulted in significantly higher inhibition rates, at 78% and 85%, respectively. These results clearly indicate that although h + e - •OH and •O2 - Both participate in the photocatalytic process, but h + and O2 - It is the main active species and contributes most significantly to ZEN degradation in the BCN system. ESR analysis using 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) as a spin trap further confirmed this finding. Figure 5 C). Under visible light irradiation, all catalysts produced detectable DMPO-·O2. - The adduct signal, in which the BCN composite exhibits the strongest characteristic peak intensity, confirms that it possesses superior O2 content compared to pure g-C3N4 or Bi2WO6 under the same conditions. - Generation capability.

[0041] The enhanced ROS generation by BCN should stem from its optimized light absorption and carrier dynamics. For example... Figure 6 As shown in Figure A, the UV-Vis diffuse reflectance spectrum reveals a significant red shift in the absorption edge (approximately 500 nm) of BCN compared to g-C3N4 (approximately 450 nm) and Bi2WO6 (approximately 400 nm), indicating a significant enhancement in its visible light absorption and utilization capabilities. Figure 6 As shown in Figure B, Tauc plot analysis determined the bandgap energies: Bi₂WO₆ (2.78 eV), g-C₃N₄ (2.72 eV), and BCN (2.65 eV). The narrowest bandgap allows BCN to utilize photons of longer wavelengths, thereby generating more photogenerated electron-hole pairs for ROS synthesis. Theoretically, •O₂ - The formation of O2 requires photoinduced electrons to overcome the activation energy barrier. The enhanced visible light absorption and suitable bandgap arrangement of BCN facilitate efficient carrier utilization, thereby promoting the formation of O2. -The generation of ROS. To understand the ROS generation advantage of BCN, its charge separation efficiency was further evaluated. For example... Figure 6 As shown in Figure C, photoluminescence (PL) spectroscopy reveals that pure g-C3N4 exhibits the highest emission intensity, indicating severe charge recombination. The PL intensity of BCN is significantly quenched, suggesting that efficient suppression of electron-hole recombination is achieved through the formation of a tight Bi2WO6 / g-C3N4 heterojunction. Figure 6 As shown in Figure D, the electrochemical impedance spectroscopy further reveals that BCN has the smallest Nyquist semicircle, reflecting its lowest charge transfer resistance and the easiest migration of photogenerated carriers to the surface. Similarly, the transient photocurrent response indicates that BCN exhibits the strongest and fastest photocurrent response, such as... Figure 6 As shown in Figure E, it is confirmed that it possesses superior charge separation and transfer efficiency under visible light irradiation. These properties collectively promote the survival of photogenerated electrons, which are used for O2. - The reduction of (O2+e) - →・O2 - ).

[0042] In summary, the superior photocatalytic activity of BCN for ZEN stems from the synergistic advantages of its structural and electronic properties. The heterojunction structure broadens the visible light absorption range, narrows the band gap, and accelerates charge separation, thereby enabling the efficient generation of •O2. - As the primary ROS, the tight interface between g-C3N4 and Bi2WO6 facilitates rapid electron transfer to adsorbed O2, while the retained porous structure and oxygen vacancies enhance ROS stability and substrate accessibility. This mechanism ensures rapid and selective mineralization of ZEN under visible light, highlighting the potential of BCN in practical mycotoxin removal and detoxification applications.

[0043] like Figure 7 As shown in Figure C, the stepwise degradation mechanism of ZEN was explained by HPLC-TOF-MS / MS analysis, and a multi-pathway process triggered by ROS attack was revealed—(1) Initial dehydrogenation: ZEN undergoes a hydrogen abstraction reaction to form a metastable intermediate P1 (C 18 H 19 O3, m / z=283.13), characterized by the formation of conjugated double bonds. (2) Epoxidation and lactone ring opening: •O2 - Mediated double bond epoxidation and h + Catalytic hydrolysis and cleavage of the lactone ring occur simultaneously, generating the intermediate P2 (C 18 H 23 O4, m / z=303.6) and P3 (C 18 H 23O4, m / z=291.15). These products participate in reversible aldol-like condensation cycles. (3) Decarboxylation and rearrangement: P1 undergoes decarboxylation to generate P4 (C4) with an adjacent carbonyl-carboxyl system. 11 H9O4, m / z = 205.049). P4 undergoes decarboxylation and rearrangement to form P5 (C). 12 H 15 O3, m / z=207.10). (4) Aromatic ring cleavage: The methoxy-substituted benzene ring (C-OCH3) in P5 becomes a free radical attack (mainly •O2). - The target of the fungal toxin is to induce demethylation and ring breakage, ultimately generating the ortho-quinone derivative P6 (C8H5O4, m / z=165.02). The quinone structure in P6 disrupts the estrogen receptor binding capacity, effectively eliminating the endocrine-disrupting activity of the fungal toxin.

[0044] like Figure 7 As shown in DF, the toxicity assessment using the TEST model highlights the ecological benefits of ZEN mineralization. For the blackhead catfish (Pimephales promelas), the 96-hour median lethal concentration (LC50) of ZEN is... 50 The concentration was 12.3 mg / L. All degradation intermediates showed significantly reduced acute toxicity, with P6 showing the lowest LC50. 50 The highest concentration (67.73 mg / L) indicates the lowest environmental risk. The 48-hour median inhibitory concentration (IC50) of *Tetrahymenapyriformis* was [not specified]. 50 The values ​​showed that P2 (214.3 mg / L), P4 (37.17 mg / L), P5 (164.15 mg / L), and P6 (164.15 mg / L) were all higher than the parent compound (8.7 mg / L), confirming a significant detoxification effect. It is noteworthy that P3 retained part of the conjugated diene structure, resulting in a smaller reduction in toxicity (IGC). 50 =14.2 mg / L); its ecological transformation still needs further research.

[0045] BCN heterojunctions achieve efficient degradation and detoxification of ZEN under visible light through a well-defined multi-step pathway, which involves photogenerated carriers and ROS (primarily •O2). - The process is initiated by targeted bond breaking (particularly the C27-O34 ester bond). A synergistic effect within the heterojunction ensures high ROS flux, transforming the highly toxic parent molecule into intermediates with significantly reduced acute toxicity, particularly the final product, the ortho-quinone derivative P6. This study provides a fundamental mechanistic understanding and strong evidence supporting the efficiency and practical feasibility of BCN for the simultaneous removal and detoxification of ZEN. Future work will investigate the long-term ecological effects of the intermediates and their transformation in complex matrices.

[0046] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A Bi2WO6 / g-C3N4 heterojunction photocatalyst, characterized in that: include: Bi2WO6 particles and g-C3N4 nanosheets, wherein a Z-shaped heterojunction is formed between the Bi2WO6 particles and the g-C3N4 nanosheets.

2. A method for preparing the Bi2WO6 / g-C3N4 heterojunction photocatalyst according to claim 1, characterized in that, Includes the following steps: (1) Urea was calcined once under a nitrogen atmosphere, cooled and ground into powder; the resulting powder was calcined a second time under a nitrogen atmosphere, cooled and g-C3N4 nanomaterials were obtained. (2) Dissolve Bi(NO3)3・5H2O and Na2WO4・2H2O in ethylene glycol in proportion and stir to form the first solution; The first solution was heated to carry out a hydrothermal reaction. After cooling, the precipitate was collected by centrifugation, washed, and vacuum dried to obtain Bi2WO6. (3) Bi2WO6 and g-C3N4 nanomaterials were dispersed in anhydrous ethanol in a certain proportion, and then subjected to ultrasonic treatment and stirring treatment. The product was separated by centrifugation, washed, vacuum dried and ground to obtain Bi2WO6 / g-C3N4 heterojunction photocatalyst.

3. The preparation method according to claim 2, characterized in that: In step (1), the heating rate of the first calcination is 4-6℃ / min, the calcination temperature is 530-570℃, and the holding time is 3-5h; the heating rate of the second calcination is 4-6℃ / min, the calcination temperature is 480-520℃, and the holding time is 3-5h.

4. The preparation method according to claim 2, characterized in that: In step (2), the molar mass ratio of Bi(NO3)3・5H2O to Na2WO4・2H2O is (1.8-2.2):1; the stirring time is 25-35 min; the hydrothermal reaction temperature is 170-190℃ and the reaction time is 10-14 h; the washing is performed by washing with deionized water and ethanol 2-4 times each; the drying temperature is 55-65℃ and the drying time is 6-10 h.

5. The preparation method according to claim 2, characterized in that: In step (3), the mass ratio of Bi2WO6 to g-C3N4 nanomaterial is (1.8-2.2):(6.5-7.5); the ultrasonic treatment frequency is 35-45kHz, the power is 280-320W, and the treatment time is 1.5-2.5h; the stirring treatment time is 10-14h; the washing is done by washing with deionized water and anhydrous ethanol 2-4 times each; the drying temperature is 55-65℃, and the drying time is 10-14h.

6. The preparation method according to claim 2, characterized in that: In step (1), the heating rate of the first calcination is 5℃ / min, the calcination temperature is 550℃, and the holding time is 4h; the heating rate of the second calcination is 5℃ / min, the calcination temperature is 500℃, and the holding time is 4h.

7. The preparation method according to claim 2, characterized in that: In step (2), the molar mass ratio of Bi(NO3)3・5H2O to Na2WO4・2H2O is 2:1, the stirring time is 30 min, the solvothermal reaction temperature is 180℃ and the reaction time is 12 h, the washing is 3 times each, and the drying temperature is 60℃ and the time is 8 h.

8. The preparation method according to claim 2, characterized in that: In step (3), the mass ratio of Bi2WO6 to g-C3N4 nanomaterials is 2:7, the ultrasonic frequency is 40kHz, the power is 300W, the time is 2h, the stirring time is 12h, the washing is 3 times each, and the drying temperature is 60℃ for 12h.

9. The application of the Bi2WO6 / g-C3N4 heterojunction photocatalyst according to claim 1 in the degradation of zearalenone.

Images