A BiOCl / Bi2WO6 heterojunction adsorption photocatalyst and a preparation method and application thereof

Abstract

A BiOCl / Bi2WO6 heterojunction adsorption photocatalyst, its preparation method, and its application are disclosed, relating to the fields of semiconductor photocatalytic materials and water treatment technology. The catalyst comprises BiOCl and Bi2WO6 with oxygen-vacancy-rich and highly exposed (110) crystal faces, forming a tight heterojunction interface. In preparation, ethylene glycol, thiourea, and glacial acetic acid are first used to regulate the nucleation and crystal face growth of BiOCl, resulting in BiOCl with highly exposed (110) crystal faces and rich in oxygen vacancies. Then, Bi2WO6 is prepared and ultrasonically combined with the oxygen-vacancy-rich and highly exposed (110) crystal facet BiOCl to obtain the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst. This material enhances pollutant adsorption and enrichment and surface oxygen activation through the (110) crystal facet and oxygen vacancies, and promotes photogenerated charge separation and migration through the heterojunction, thereby achieving efficient adsorption-photocatalytic synergistic degradation of organic pollutants.

Description

Technical Field

[0001] This invention relates to the field of semiconductor photocatalytic materials and water treatment technology, and in particular to a BiOCl / Bi2WO6 heterojunction adsorption photocatalyst, its preparation method and application. Background Technology

[0002] With industrialization and population growth, dyes, aromatic organic compounds, and other recalcitrant micropollutants pose a persistent environmental risk when they enter water bodies. Semiconductor photocatalysis technology can generate photogenerated electrons and holes under light conditions and further induce redox reactions, thus possessing the potential for green, low-energy, and sustainable treatment of pollutants.

[0003] Bismuth-based halide oxides such as BiOCl possess a layered crystal structure and a built-in electric field, which facilitates the separation of photogenerated carriers. The relatively negative conduction band position of BiOCl promotes molecular oxygen activation and the generation of superoxide radicals. However, traditional BiOCl still suffers from insufficient visible light absorption, rapid carrier recombination, and insufficient adsorption and enrichment capacity for low-concentration pollutants, limiting its application in practical wastewater treatment.

[0004] In existing technologies, methods such as constructing heterojunctions, elemental doping, noble metal modification, or defect modulation can improve photocatalytic performance. However, a single strategy often cannot simultaneously address issues such as pollutant surface enrichment, light absorption range, interfacial charge migration, and reactive oxygen generation efficiency. Especially when the concentration of micropollutants is low, the driving force for pollutant migration from the water body to the catalyst surface is insufficient, leading to a decrease in adsorption and in-situ catalytic degradation efficiency.

[0005] Therefore, there is an urgent need to develop a bismuth-based composite photocatalyst that combines high adsorption and enrichment capacity, efficient interfacial charge transfer capacity, and strong molecular oxygen activation capacity to achieve rapid, economical, stable, and sustainable degradation of organic pollutants. Summary of the Invention

[0006] The purpose of this invention is to provide a BiOCl / Bi2WO6 heterojunction adsorption photocatalyst with high exposure of oxygen-rich vacancy (110) crystal plane, its preparation method and application, so as to solve the problems of insufficient adsorption capacity of existing BiOCl-based photocatalysts for pollutants, fast recombination of photogenerated carriers, low efficiency of active oxygen generation and limited degradation efficiency of organic pollutants.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a BiOCl / Bi2WO6 heterojunction adsorption photocatalyst, comprising BiOCl and Bi2WO6; wherein the BiOCl has oxygen-rich vacancies and highly exposed (110) crystal planes, and a heterojunction contact interface is formed between the BiOCl and the Bi2WO6.

[0009] The BiOCl with oxygen-rich vacancies and highly exposed (110) crystal planes is denoted as O. V -(110) BiOCl, the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst is denoted as O V -(110) BiOCl / Bi2WO6.

[0010] Furthermore, the Bi2WO6 and the BiOCl (i.e., O) V The mass ratio of -(110) BiOCl) is 1:(5-20), preferably 1:(8-12), and more preferably 1:10.

[0011] Furthermore, the BiOCl (i.e. O) V -(110) BiOCl) has a structure characterized by high exposure of the (110) crystal plane, and its peak intensity ratio (abbreviated as I) of the (110) crystal plane to the (101) crystal plane is high. (110) / I (101) The peak intensity ratio (abbreviated as I) of the (110) crystal plane to the (102) crystal plane is 1.0 to 2.0. (110) / I (102) The value ranges from 1.5 to 3.0.

[0012] For example, in X-ray diffraction peaks (i.e., in X-ray diffraction (XRD) patterns), O V -(110) BiOCl of I (110) / I (101) It is 1.46, O V -(110) BiOCl of I (110) / I (102) It is 2.38.

[0013] Among them, O V -(110) BiOCl of I (110) / I (101) and I (110) / I (102) Both are higher than BiOCl without crystal plane manipulation (its I (110) / I (101) and I (110) / I (102) (They are 0.44 and 0.39 respectively).

[0014] Furthermore, the BiOCl (i.e. O)V -(110) BiOCl) has oxygen-rich vacancies, and its oxygen vacancy characteristic signal intensity is higher than that of BiOCl without crystal plane modulation, but lower than that of the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst (i.e., O). V -(110)BiOCl / Bi2WO6).

[0015] Specifically, in electron paramagnetic resonance (EPR) testing, the intensity order of the characteristic signal of oxygen vacancies near g=2.003 is: O V -(110) BiOCl / Bi2WO6 > O V -(110) BiOCl > BiOCl (BiOCl without crystal plane modulation).

[0016] Secondly, the present invention provides a method for preparing the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst, comprising the following steps:

[0017] S1. In the presence of a crystal plane modifier, BiOCl (i.e., O) with oxygen-rich vacancies and highly exposed (110) crystal planes was prepared by liquid-phase synthesis. V -(110) BiOCl);

[0018] S2. Bi2WO6 was prepared by hydrothermal method;

[0019] S3. Disperse, dry, and grind the BiOCl from step S1 and the Bi2WO6 from step S2 to obtain the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst (i.e., O). V -(110) BiOCl / Bi2WO6).

[0020] In step S1, the crystal plane regulator includes ethylene glycol, thiourea (i.e., thiourea solution), and glacial acetic acid (i.e., glacial acetic acid aqueous solution). This invention utilizes ethylene glycol, thiourea, and glacial acetic acid to jointly regulate the nucleation and crystal growth of BiOCl, increasing the exposure ratio of the (110) crystal plane of BiOCl and introducing abundant oxygen vacancies, thereby enhancing the adsorption and enrichment capacity of organic pollutants on the catalyst surface.

[0021] In step S3, the dispersion treatment specifically involves dispersing in a dispersion medium. The dispersion medium is selected from at least one of ethanol, water, an aqueous ethanol solution, methanol, and isopropanol; the dispersion and compounding method includes at least one of ultrasonic dispersion, mechanical stirring, and ball milling dispersion; the dispersion and compounding time is 60–180 min (e.g., 60 min). For example, the dispersion medium is ethanol, and the dispersion and compounding method is ultrasonic dispersion.

[0022] Further, step S1 includes: dispersing bismuth salt in ethylene glycol, adding thiourea to form a bismuth-containing complex system, adding chloride salt to generate a BiOCl precursor, then adding glacial acetic acid aqueous solution to carry out a crystal facet control reaction, followed by separation (e.g., solid-liquid separation), washing, and drying to obtain BiOCl (i.e., O) with oxygen-rich vacancies and highly exposed (110) crystal faces. V -(110) BiOCl).

[0023] Further, in step S1, the bismuth salt is selected from at least one of Bi(NO3)3·5H2O or BiCl3, the chloride salt is selected from at least one of KCl or NaCl, and the molar ratio of the bismuth salt to the chloride salt is 1:1.

[0024] For example, in step S1, the bismuth salt is Bi(NO3)3·5H2O, and the chloride salt is KCl.

[0025] Further, in step S1, the concentration of the thiourea is 0.5–2 mol / L (e.g., 1 mol / L).

[0026] Further, in step S1, the volume fraction of the glacial acetic acid aqueous solution is 1% to 5% (e.g., 2%).

[0027] Furthermore, in step S1, the temperature of the crystal plane control reaction is room temperature to 80°C (e.g., room temperature), the time is 0.5 to 6 h (e.g., 1 h), and the drying temperature is 60 to 120°C (e.g., 60°C).

[0028] Further, in step S1, each 5 mM bismuth salt corresponds to 5 mM chloride salt, 50 mL ethylene glycol, 20 mL thiourea, and 50 mL glacial acetic acid aqueous solution.

[0029] Further, step S2 includes: mixing tungstate and bismuth salt, reacting them hydrothermally, washing and drying to obtain Bi2WO6.

[0030] Further, in step S2, the bismuth salt is selected from at least one of Bi(NO3)3·5H2O or BiCl3, and the tungstate is selected from at least one of WCl6 or Na2WO4·2H2O.

[0031] For example, in step S2, the bismuth salt is Bi(NO3)3·5H2O, and the tungstate is Na2WO4·2H2O.

[0032] Further, in step S2, the molar ratio of the tungstate to the bismuth salt is 1:2.

[0033] Furthermore, in step S2, the hydrothermal reaction temperature is 120–200°C (e.g., 160°C), and the hydrothermal reaction time is 6–24 h (e.g., 18 h).

[0034] Further, in step S3, the mass ratio of BiOCl in step S1 to Bi2WO6 in step S2 is 0.1:0.01. For example, the BiOCl in step S1 is 0.1 g and the Bi2WO6 in step S2 is 0.01 g.

[0035] Thirdly, the present invention provides an application of the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst in the removal of organic pollutants in water, wherein the organic pollutants include cationic dyes, and the cationic dyes include Rhodamine B.

[0036] Furthermore, the application preferably includes the steps of first adsorbing and enriching in the dark state, and then carrying out photocatalytic degradation under simulated sunlight or visible light.

[0037] Further, the amount of the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst added is: 0.5 grams of the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst (i.e., O2WO6) added per 100 mL of wastewater (i.e., the water body containing organic pollutants mentioned above). V -(110) BiOCl / Bi2WO6).

[0038] Furthermore, the organic pollutant is Rhodamine B, with an initial concentration of 10 mg / L.

[0039] Furthermore, the dark adsorption time is 0–60 min, and the photocatalytic reaction time is 10–60 min.

[0040] In addition, the organic pollutants also include organic dyes, methylene blue, methyl orange, aromatic organic compounds or any combination thereof.

[0041] On the other hand, the present invention also provides a method for removing Rhodamine B, comprising: adding the above-mentioned photocatalyst to a photocatalytic degradation system to remove Rhodamine B from organic wastewater. The photocatalytic degradation system includes a reactor, a light source, a stirring or circulation unit, and the above-mentioned photocatalyst; the photocatalyst is disposed within the reactor for adsorption, enrichment, and photocatalytic degradation of water containing organic pollutants (i.e., the aforementioned organic wastewater) under illumination.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. This invention improves the adsorption and enrichment capacity of organic pollutants on the catalyst surface by controlling the crystal plane and introducing oxygen vacancies, especially by using ethylene glycol, thiourea and glacial acetic acid to jointly regulate the nucleation and crystal growth of BiOCl, so that the (110) crystal plane of BiOCl is highly exposed and rich in oxygen vacancies.

[0044] 2. The present invention uses Bi2WO6 containing the same bismuth element and BiOCl to construct a tight heterojunction, which is beneficial to the formation of interfacial charge transfer driving force, suppressing electron-hole recombination, and retaining strong redox ability.

[0045] 3. In this invention, the (110) high-exposed crystal plane and oxygen-rich vacancies of BiOCl are conducive to the activation of surface adsorbed oxygen, and promote the generation of active oxygen species such as superoxide radicals under light conditions, so that the organic pollutants enriched on the catalyst surface are rapidly oxidized and degraded.

[0046] 4. This invention achieves synergy between adsorption enrichment and photocatalytic degradation, enabling efficient removal of organic pollutants such as Rhodamine B within a short irradiation time.

[0047] 5. The material system of the present invention does not depend on precious metals, the preparation process is simple, the raw materials are readily available, and it has the potential for application in the purification of organic wastewater and the treatment of advanced oxidation water. Attached Figure Description

[0048] Figure 1 BiOCl, O V -(110) BiOCl, Bi2WO6 and O V -(110) XRD pattern of BiOCl / Bi2WO6 sample.

[0049] Figure 2 BiOCl, O V -(110) BiOCl, Bi2WO6 and O V -(110) TEM and HRTEM images of BiOCl / Bi2WO6 samples; where (a) and (b) are TEM and HRTEM images of BiOCl, and (c) and (d) are O V -(110) TEM and HRTEM images of BiOCl, (e) and (f) are TEM and HRTEM images of Bi2WO6, and (g) and (h) are O V -(110) TEM and HRTEM images of BiOCl / Bi2WO6;

[0050] Figure 3 BiOCl, O V -(110) BiOCl and O V-(110) EPR spectrum of BiOCl / Bi2WO6;

[0051] Figure 4 BiOCl, O V -(110) BiOCl, Bi2WO6 and O V -(110) Experimental results of dark adsorption and photocatalysis of Rhodamine B by BiOCl / Bi2WO6 sample; where (a) is the dark adsorption-time curve; (b) is the pseudo-first-order kinetic model; (c) is the pseudo-second-order kinetic model; (d) is the intraparticle diffusion model;

[0052] Figure 5 For O V -(110) BiOCl / Bi2WO6、O V -(110) Results of photocatalytic degradation and dark adsorption performance of BiOCl, BiOCl and Bi2WO6 samples for RhB; where (a) is the degradation rate of RhB by each sample; (b) is the first-order kinetics of RhB degradation by each sample; (c) is the O V -(110) Adsorption of RhB solution by BiOCl / Bi2WO6 sample in the dark; (d) is O V -(110) UV-Vis spectrum of photocatalysis of RhB solution by BiOCl / Bi2WO6 sample. Detailed Implementation

[0053] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0054] It should be noted that, for ease of distinction and understanding, BiOCl without crystal plane manipulation is denoted as "BiOCl", while BiOCl with oxygen-rich vacancies and high exposure of the (110) crystal plane (i.e., BiOCl with crystal plane manipulation) is denoted as "O". V -(110) BiOCl", the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst with high exposure of oxygen-rich vacancies on the (110) crystal plane is denoted as "O". V -(110) BiOCl / Bi2WO6".

[0055] In summary, this invention provides a BiOCl / Bi2WO6 heterojunction adsorption photocatalyst with high exposure of oxygen-rich vacancy (110) crystal planes, its preparation method, and its application. This catalyst (i.e., O...) V -(110) BiOCl / Bi2WO6) includes O V-(110)BiOCl and Bi2WO6 form a tight heterojunction interface. During preparation, ethylene glycol, thiourea, and glacial acetic acid are used to regulate the nucleation and crystal plane growth of BiOCl, resulting in BiOCl with highly exposed (110) crystal planes and rich in oxygen vacancies (i.e., O2WO6). V -(110) BiOCl); then prepare Bi2WO6, and combine it with O V -(110) BiOCl ultrasonic composite to obtain O V -(110) BiOCl / Bi2WO6. This material enhances pollutant adsorption and enrichment and surface oxygen activation through the (110) crystal facet and oxygen vacancies, and promotes photogenerated charge separation and migration through heterojunction, thereby achieving efficient adsorption-photocatalytic synergistic degradation of organic pollutants.

[0056] The following specific examples will provide further explanation.

[0057] Example 1: O V -(110) Preparation of BiOCl photocatalyst

[0058] Weigh 5 mM Bi(NO3)3·5H2O and disperse it uniformly in 50 mL of ethylene glycol, stirring at room temperature. Then, add 20 mL of 1 mol / L thiourea solution dropwise to the system, resulting in a yellow suspension. Next, add 5 mM KCl, and a large amount of precipitate forms as the reaction proceeds. Then, slowly add 50 mL of 2% (v / v) glacial acetic acid aqueous solution, stirring continuously for 1 h to complete the reaction. After the reaction is complete, collect the product by centrifugation and wash thoroughly with deionized water and anhydrous ethanol until the supernatant is colorless and transparent and the system is nearly neutral. Dry the obtained solid in a 60°C oven overnight, collect and grind it to obtain the regulated BiOCl (i.e., O2O3). V -(110) BiOCl).

[0059] Example 2: Preparation of BiOCl photocatalyst

[0060] Compared to Example 1, this embodiment uses the same bismuth salt and chloride salt system to prepare unregulated BiOCl, except that deionized water is used instead of ethylene glycol and thiourea solution is not added, while other conditions remain unchanged.

[0061] Example 3: Preparation of Bi2WO6 photocatalyst

[0062] 2 mM Na₂WO₄·2H₂O was dissolved in 20 mL of deionized water; separately, 4 mM Bi(NO₃)₃·5H₂O was dissolved in 20 mL of 0.5 mol / L nitric acid solution, and both solutions were stirred for at least 30 min. The two solutions were then mixed, and the resulting mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor and hydrothermally reacted at 160 °C for 18 h. After the reaction, the product was washed three times and vacuum dried overnight to obtain Bi₂WO₆.

[0063] Example 4: O V -(110) Preparation of BiOCl / Bi2WO6 photocatalyst

[0064] Weigh 0.01 g of Bi2WO6 obtained in Example 3 and 0.1 g of O obtained in Example 1. V -(110) BiOCl was added to 20 mL of ethanol and ultrasonically dispersed for 60 min to allow the two sheet-like components to fully contact and form a composite system. The dispersion was then dried, and the resulting solid was ground uniformly to obtain O. V -(110) BiOCl / Bi2WO6 heterojunction adsorption photocatalyst.

[0065] Analysis example 1:

[0066] I. The photocatalytic materials in Examples 1 to 4 were characterized using X-ray diffraction (XRD), see [reference]. Figure 1 As shown.

[0067] Figure 1 O is shown V -(110) BiOCl / Bi2WO6、O V -(110) X-ray diffraction (XRD) patterns of BiOCl, Bi2WO6 and BiOCl samples.

[0068] X-ray diffraction (XRD) pattern Figure 1 This revealed the structural features of these samples. BiOCl and O V The characteristic peaks of (110) BiOCl at 12°, 25.9°, 32.5°, and 33.4° correspond to the (001), (101), (110), and (102) crystal planes of BiOCl (JCPDS 06–0249; marked with “▽”), respectively, and no obvious impurity peaks were detected. It is noteworthy that, compared to pristine BiOCl, O V -(110) The (110) crystal plane of BiOCl is more exposed, while the relative intensity of the (101) and (102) crystal planes is reduced. The growth direction of BiOCl can be determined by the intensity ratio of the (110) / (101) and (110) / (102) crystal planes. As shown in Table 1, OV -(110) I of BiOCl sample (110) / I (101) Value and I (110) / I (102) The values ​​are higher than the JCPDS standard values ​​(0.75, 0.79), indicating that the crystal has good orientation along the (110) crystal plane. The diffraction peaks of Bi2WO6 can be matched with those of orthorhombic Bi2WO6 (JCPDS 39–0256; indicated by "•"), corresponding to the (131), (060), (202), (133), (262), (114), (333), (204) and (462) crystal planes, appearing at 28.3°, 32.9°, 47.1°, 55.9°, 58.6°, 71.7°, 76.0°, 78.5° and 87.5°. V -(110) In the BiOCl / Bi2WO6 composite material, O appears V The characteristic peaks of BiOCl (-(110) and Bi2WO6 also appeared, indicating that O was successfully constructed. V -(110) BiOCl / Bi2WO6 heterojunction structure.

[0069] Table 1. Crystallographic plane ratios calculated based on XRD.

[0070]

[0071] II. The photocatalytic materials in Examples 1 to 4 were characterized by TEM. See [link to TEM description]. Figure 2 As shown.

[0072] Figure 2 The following images are shown: (a) TEM image of BiOCl, (b) HRTEM image, and O V -(110) TEM image of BiOCl (c), HRTEM image of Bi2WO6 (e), TEM image of Bi2WO6 (f), HRTEM image of BiOCl, O V -(110) (g) TEM image and (h) HRTEM image of BiOCl / Bi2WO6.

[0073] The microstructure of the photocatalyst was further analyzed using transmission electron microscopy (TEM). Figure 2 As shown in (a) and (b), the TEM images ( Figure 2 (a) shows that the original BiOCl exhibits a self-assembled spherical structure. High-resolution TEM image ( Figure 2 (b) reveals that BiOCl has ordered lattice stripes with a spacing of 0.267 nm, corresponding to the (102) crystal plane, indicating that it has high crystallinity and an ordered crystal structure. Figure 2 (c) shows O V -(110) Typical TEM image of BiOCl, showing O V -(110) The nanosheets of BiOCl are smaller than those of BiOCl and change from a sheet-like structure to an irregular elliptical shape. High-resolution TEM image ( Figure 2 (d) shows O V -(110) BiOCl has ordered lattice fringes with interplanar spacings of 0.275 nm and 0.267 nm, corresponding to the (110) and (102) crystal planes, respectively, indicating that O V -(110) BiOCl has a higher degree of exposure of the (110) crystal plane. Figure 2 Images (e) and (f) show the distinct rectangular plate-like nanosheet morphology of Bi₂WO₆ with a plane spacing of 0.315 nm, corresponding to the (131) crystal plane. V -(110) Transmission electron microscopy images of the BiOCl / Bi2WO6 heterostructure further clearly show a stacked surface contact structure, with irregular elliptical sheets tightly attached to the surface of rectangular plate-like nanosheets. Figure 2 (g), (h)). Figure 2 Image (h) shows a high-resolution transmission electron microscopy image of the heterostructure interface, where the 0.275 nm interplanar spacing in the elliptical sheets corresponds to the (110) plane of BiOCl, while the 0.315 nm interplanar spacing in the rectangular plate-like nanosheets corresponds to the (131) plane of Bi2WO6. This indicates the successful formation of O V -(110) BiOCl / Bi2WO6 heterostructure.

[0074] III. The photocatalytic materials from Examples 1 to 4 were characterized using EPR. (See [link]) Figure 3 As shown.

[0075] Figure 3 BiOCl and O were shown V -(110) BiOCl and O V -(110) Electron paramagnetic resonance (EPR) spectrum of BiOCl / Bi2WO6.

[0076] To verify oxygen vacancies (O V The presence of O was confirmed by electron paramagnetic resonance (EPR) testing. V .like Figure 3 As shown, three distinct symmetrical EPR signal peaks appeared at g = 2.003, which are consistent with O. V The characteristic signals are consistent. It is worth noting that the intensity order of the characteristic signals of different photocatalysts is: O V-(110) BiOCl / Bi2WO6>O V -(110) BiOCl>BiOCl, indicating O V -(110) BiOCl / Bi2WO6 has higher O V content.

[0077] Analysis example 2:

[0078] The photocatalytic materials from Examples 1 to 4 were used as test materials for dark adsorption and photocatalysis experiments of Rhodamine B, as detailed below:

[0079] The photocatalytic experiment was conducted in a water-cooled quartz tube under illumination (xenon lamp, 350 W). The photocatalyst (50 mg) was added to an RhB solution (100 mL, concentration 10 mg / L) and uniformly dispersed. The well-dispersed suspension was then stirred in the dark for 60 minutes to reach adsorption-desorption equilibrium. During illumination, 1.5 mL of solution was drawn from the quartz tube every 10 minutes. The extract was then centrifuged twice, and the supernatant was collected to determine the absorption intensity of RhB. The removal rate of RhB was calculated using Equation 1 by comparing the intensity of the absorption peak at 554 nm.

[0080] Removal efficiency (%) = (C0 - C) t ) / C0 × 100% (1)

[0081] Where C0 is the concentration of RhB at the beginning of illumination, C t The concentration of the RhB solution at time t (minutes).

[0082] The experimental results are as follows:

[0083] Figure 4 BiOCl and O were shown V -(110) BiOCl, Bi2WO6 and O V -(110) The results of dark adsorption and photocatalysis experiments of BiOCl / Bi2WO6 samples for Rhodamine B are shown in the figure: (a) is the curve of dark adsorption amount changing with time; (b) is the fitting of the pseudo-first-order kinetic model; (c) is the fitting of the pseudo-second-order kinetic model; (d) is the fitting of the particle diffusion model.

[0084] The efficient adsorption of micropollutants on the catalyst surface is of great significance for their subsequent photocatalytic degradation. Figure 4Figure (a) shows the dark adsorption-time curve (including error bars) of the synthesized photocatalyst for Rhodamine B (RhB). In the initial 10 minutes, RhB is rapidly adsorbed, attributed to the abundant adsorption sites on the material surface and the large concentration difference of RhB between the catalyst surface and the bulk solution. As the number of adsorption sites and the concentration difference decrease, the adsorption rate gradually decreases, reaching equilibrium at 30 minutes. Compared to BiOCl, O V -(110) BiOCl exhibits superior adsorption performance, which may be related to the increase in surface active sites and improved pore structure due to appropriate composition. The adsorption process of the catalyst was fitted using pseudo-first-order kinetic (PFO) and pseudo-second-order kinetic (PSO) models. Figure 4 As shown in (b) and (c), the goodness of fit of PSO is significantly higher than that of PFO, indicating that the adsorption rate of Rhodamine B (RhB) by the catalyst is mainly controlled by chemical action, and there may be electron sharing and transfer between the pollutant and the adsorbent. Figure 4 Based on the intraparticle diffusion fitting results in (d), the adsorption process consists of three stages: external diffusion, boundary layer diffusion, and surface adsorption. The slope decreases (k... p This indicates that in this RhB microcontamination system, external diffusion and boundary layer diffusion are the main rate-controlling steps. Compared with BiOCl, O V -(110) BiOCl still exhibits a higher diffusion rate, proving that abundant functional groups and porous structures play an important role in improving adsorption performance.

[0085] Figure 5 O is shown V -(110) BiOCl / Bi2WO6、O V -(110) Degradation curves (a) and kinetic fitting diagram (b) of Rhodamine B (RhB) by BiOCl, BiOCl and Bi2WO6; under dark conditions (c) and visible light irradiation (d), the reaction of Rhodamine B solution with O V -(110) UV-Vis absorption spectrum of BiOCl / Bi2WO6 contact.

[0086] Based on its high adsorption performance, the degradation effect on RhB was further investigated. Figure 5 (a) shows the photodegradation rate-time curves (with error bars) of the synthesized photocatalyst for RhB. Due to its narrow photoresponse range, Bi₂WO₆ exhibits the lowest degradation rate; while O₂... V -(110) BiOCl exhibits stronger photocatalytic activity due to its high adsorption capacity for RhB. O V -(110) After BiOCl combines with Bi2WO6, O V-(110) The photocatalytic performance of BiOCl / Bi2WO6 is significantly improved, reaching up to 100%. However, compared with O V Compared to BiOCl, O (110) V -(110) The adsorption performance of BiOCl / Bi2WO6 for RhB is only slightly improved. This may be due to the interaction between Bi2WO6 and O. V -(110) The heterojunction formed between BiOCl atoms prolongs the lifetime of photogenerated carriers. The photocatalytic reaction kinetics were analyzed using a first-order kinetic model. Figure 5 (b)). O V The apparent constant k of the BiOCl / Bi2WO6 system is 0.14629 min. -1 , respectively approximately O V -(110) BiOCl(0.0501 min -1 BiOCl (0.00374 min) -1 ) and Bi2WO6 (0.00176 min) -1 The adsorption and photocatalysis effects were 2.91 times, 39.1 times, and 83.1 times greater than those observed in O2O. These results indicate that adsorption and photocatalysis significantly influence each other in O2O. V -(110) It can have a good synergistic effect in the BiOCl / Bi2WO6 system.

[0087] To verify the adsorption and photocatalytic degradation process, the UV-Vis spectrum of the RhB solution was also recorded, such as... Figure 5 As shown in (c), under dark conditions, the intensity of the UV-Vis spectrum drops sharply within the first 10 minutes, then gradually stabilizes. Meanwhile, the maximum absorption wavelength (λmax = 554 nm) remains unchanged, and the curves are almost parallel. This indicates that under dark conditions, O V The removal of RhB by BiOCl / Bi2WO6 (110) is mainly attributed to adsorption. Subsequently, with the initiation of visible light irradiation, the absorption peak decreased again over time. More importantly, a significant blue shift was observed in the maximum absorption wavelength of RhB, indicating that the photocatalytic reaction had occurred, accompanied by the formation of some byproducts, such as... Figure 5 As shown in (d). However, the absorbance intensity of all RhB absorption peaks gradually decreases and no other peaks appear, indicating that RhB has been absorbed by O. V -(110) BiOCl / Bi2WO6 is completely degraded.

[0088] The embodiments described above are merely preferred embodiments of the present invention and are not exhaustive examples of all possible implementations of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A BiOCl / Bi2WO6 heterojunction adsorption photocatalyst, characterized in that, It includes BiOCl and Bi2WO6; the BiOCl has oxygen-rich vacancies and highly exposed (110) crystal planes, and forms a heterojunction contact interface with the Bi2WO6.

2. The BiOCl / Bi2WO6 heterojunction adsorption photocatalyst according to claim 1, characterized in that, The mass ratio of Bi2WO6 to BiOCl is 1:(5-20).

3. The BiOCl / Bi2WO6 heterojunction adsorption photocatalyst according to claim 1, characterized in that, The BiOCl has a structure with a high exposure of the (110) crystal plane, and the peak intensity ratio of the (110) crystal plane to the (101) crystal plane is 1.0 to 2.0, and the peak intensity ratio of the (110) crystal plane to the (102) crystal plane is 1.5 to 3.

0.

4. The BiOCl / Bi2WO6 heterojunction adsorption photocatalyst according to claim 1, characterized in that, The BiOCl has oxygen-rich vacancies, and the intensity of its oxygen vacancy characteristic signal is higher than that of BiOCl without crystal plane modulation, but lower than that of the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst.

5. The method for preparing the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. BiOCl with oxygen-rich vacancies and highly exposed (110) crystal planes was prepared by liquid-phase synthesis in the presence of a crystal plane modifier. S2. Bi2WO6 was prepared by hydrothermal method; S3. Disperse, dry and grind the BiOCl from step S1 and the Bi2WO6 from step S2 to obtain the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst.

6. The preparation method according to claim 5, characterized in that, Step S1 includes: dispersing bismuth salt in ethylene glycol, adding thiourea to form a bismuth-containing complex system, adding chloride salt to generate BiOCl precursor, then adding glacial acetic acid aqueous solution to carry out crystal facet regulation reaction, and after separation, washing and drying, obtaining BiOCl with oxygen-rich vacancies and highly exposed (110) crystal facets.

7. The preparation method according to claim 6, characterized in that, In step S1, the bismuth salt is selected from at least one of Bi(NO3)3·5H2O or BiCl3, the chloride salt is selected from at least one of KCl or NaCl, and the molar ratio of the bismuth salt to the chloride salt is 1:

1. The concentration of thiourea is 0.5–2 mol / L, the volume fraction of the glacial acetic acid aqueous solution is 1%–5%, the temperature for crystal facet control reaction is room temperature to 80°C, the time is 0.5–6 h, and the drying temperature is 60–120°C.

8. The preparation method according to claim 5, characterized in that, Step S2 includes: mixing tungstate and bismuth salt, reacting them hydrothermally, washing and drying to obtain Bi2WO6.

9. The preparation method according to claim 8, characterized in that, In step S2, the bismuth salt is selected from at least one of Bi(NO3)3·5H2O or BiCl3, the tungstate is selected from at least one of WCl6 or Na2WO4·2H2O, the molar ratio of the tungstate to the bismuth salt is 1:2, the hydrothermal reaction temperature is 120-200℃, and the hydrothermal reaction time is 6-24 h.

10. The application of the BiOCl / Bi2WO6 heterojunction adsorption photocatalyst according to any one of claims 1 to 4 in the removal of organic pollutants in water, characterized in that, The organic pollutant includes cationic dyes, and the cationic dyes include Rhodamine B.

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