A photocatalytic adsorption particle for sewage treatment and a preparation method and application thereof

Abstract

The application discloses a kind of photocatalytic adsorption particles for sewage treatment and its preparation method and application, belong to photocatalytic material technical field. By in-situ solvothermal complex method, double Z type heterojunction photocatalyst is constructed, energy band structure is optimized, and photocatalytic degradation capacity is improved;With polysaccharide such as konjac glucomannan as matrix, its dispersibility and porosity are improved by acid modification and ultrasonic treatment, graphene oxide is introduced to enhance performance, three-dimensional multi-stage pore structure is formed by physical foaming and microwave irradiation, and surface functionalization is carried out with β-cyclodextrin, and selective adsorption capacity is enhanced. The obtained particles have dual functions of adsorption and photocatalysis, adsorb antibiotics pollutants quickly, photocatalysis further degrades them into small molecule harmless products, and both of them realize efficient removal and complete mineralization. The particle material can be regenerated, environment-friendly, and can be naturally degraded after use, avoiding secondary pollution, and showing broad application prospect in the field of wastewater organic pollutant degradation.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, and specifically relates to a photocatalytic adsorption particle for wastewater treatment, its preparation method, and its application. Background Technology

[0002] In recent years, the problem of persistent organic pollutants in water bodies has become increasingly serious, posing a continuous and severe threat to ecosystem stability and human health. The persistent presence of persistent organic pollutants such as tetracyclines, quinolones, and sulfonamides in the environment not only easily leads to the spread of antibiotic resistance but also results in the accumulation of ecotoxicity, posing numerous potential harms to the ecological environment and human health. While traditional water treatment technologies (such as activated carbon adsorption, membrane separation, and single photocatalysis) can remove pollutants to some extent, they still have significant shortcomings in terms of treatment efficiency, target selectivity, sustainability, and material recyclability. In particular, the non-degradability and limited lifespan of these materials severely restrict their long-term application and environmental benefits. Therefore, there is an urgent need to develop new green, efficient, and recyclable treatment materials.

[0003] Currently, methods for removing recalcitrant organic pollutants mainly fall into three categories: physical adsorption, chemical oxidation, and biodegradation. Physical adsorption technologies, such as activated carbon, zeolite, graphene, and polymeric adsorbents, can rapidly remove some pollutants, but their selectivity is poor, and the regeneration process often relies on high-temperature calcination or strong acid / alkali elution, which can easily cause structural damage and secondary pollution to the adsorbent. Chemical oxidation technologies, such as ozone oxidation, Fenton reaction, and single-semiconductor photocatalysis, can achieve deep degradation of pollutants, but they generally suffer from harsh reaction conditions, high oxidant consumption, or easy recombination of photogenerated carriers, resulting in limited energy efficiency and stability. Biodegradation utilizes microbial metabolism to decompose pollutants; the process is mild and environmentally friendly, but the degradation rate for structurally stable molecules with strong antibacterial activity, such as tetracyclines and quinolones, is extremely low, and microbial activity is easily inhibited in complex aquatic environments.

[0004] To address the above issues, researchers have attempted to combine polysaccharide-based materials with inorganic photocatalysts to achieve a synergistic effect of adsorption and photocatalytic degradation. However, existing research mainly focuses on non-degradable petroleum-based polymers (such as polyacrylate and polyacrylamide) composite semiconductors, or simply using natural polysaccharides as coating layers to load photocatalytic particles. These technical solutions still have several limitations: (1) The polymer body is non-degradable or has an excessively long degradation cycle, and the residues after treatment are prone to forming new secondary pollution, which is difficult to meet the needs of green and sustainable development; (2) The photocatalytic systems used are mostly single semiconductor structures with insufficient band matching, and photogenerated electrons and holes recombine rapidly at the bulk phase or interface, resulting in a significant decrease in visible light utilization and quantum efficiency; (3) The structure of composite particles is mostly single-pore size or low specific surface area morphology, lacking a hierarchical pore system, which limits mass transfer and diffusion, making it difficult for pollutant molecules to quickly enter the reaction sites; (4) The surface chemical functional sites are limited, lacking molecular recognition ability for specific pollutants (especially polar and macromolecular antibiotics), resulting in low selective adsorption efficiency, making it difficult to achieve efficient and targeted pollutant removal in complex aquatic environments.

[0005] Konjac glucomannan (KGM), an abundant natural polysaccharide, possesses excellent hydrophilicity, biocompatibility, and biodegradability, and has been widely used in environmental remediation. However, single KGM-based materials exhibit limited adsorption capacity, insufficient selectivity for target molecules, and lack of photocatalytic activity when removing recalcitrant organic pollutants, resulting in insufficient selectivity and removal efficiency for complex organic pollutants. Existing KGM-based composite materials mostly employ simple mixing or coating methods, resulting in weak interfacial bonding and poor photocatalyst dispersion, failing to meet the requirements for efficient treatment of recalcitrant organic pollutants. Z-type heterojunction photocatalysts, due to their unique band structure, can effectively promote the spatial separation of photogenerated electrons and holes, significantly improving visible light response and pollutant degradation rates, demonstrating great potential in photocatalytic degradation of pollutants. Based on this, organically combining Z-type heterojunction photocatalysts with KGM to construct biodegradable composite particles with both high-efficiency adsorption and photocatalytic degradation capabilities has become an important development direction for green water treatment technology.

[0006] In summary, there is an urgent need for a novel composite adsorption-photocatalytic particle that simultaneously possesses a biodegradable polysaccharide framework, a highly efficient Z-shaped heterojunction photocatalytic system, a hierarchical pore structure, and a functionalized surface. This particle, while ensuring the material's environmental friendliness, can achieve rapid capture and efficient photodegradation of recalcitrant antibiotics and other organic pollutants. Summary of the Invention

[0007] To address the shortcomings of traditional water treatment technologies and existing composite technologies, there is a need for novel composite particles that combine a biodegradable polysaccharide framework and a highly efficient Z-shaped heterojunction photocatalytic system to achieve the current state of technology for the rapid capture and efficient photodegradation of recalcitrant organic pollutants. This invention aims to provide a photocatalytic adsorption particle for wastewater treatment, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] This invention provides a method for preparing photocatalytic adsorption particles for wastewater treatment, comprising the following steps:

[0010] Step 1: BiOCl nanosheets are mixed and dissolved with graphitic carbon nitride, and an in-situ solvothermal reaction is carried out to obtain a double Z-type heterojunction photocatalyst.

[0011] Step 2: Dissolve konjac glucomannan, add cross-linking agent, graphene oxide dispersion and nonionic surfactant, stir evenly to obtain polysaccharide matrix solution;

[0012] Step 3: Add the double Z-type heterojunction photocatalyst to the polysaccharide matrix solution, disperse it ultrasonically, and stir to obtain the double Z-type heterojunction photo-matrix precursor solution;

[0013] Step 4: Place the double Z-type heterojunction optical-matrix precursor liquid in a reaction vessel, introduce nitrogen gas, and react to obtain a precursor solution with a multi-level porous structure.

[0014] Step 5: Place the precursor solution with a multi-level porous structure in a microwave reactor for solidification reaction to obtain multi-level porous particles.

[0015] Step 6: Impregnate the multi-level porous particles, adjust the pH value, react, filter, and dry to finally obtain photocatalytic adsorption particles.

[0016] In step 1, the BiOCl nanosheets are obtained by reacting bismuth salt and chloride with dilute nitric acid as solvent and allowing the reaction to proceed at room temperature for 6-10 hours. The graphitic carbon nitride (g-C3N4) is specifically prepared by calcining melamine or urea. The calcination is carried out at 300 ℃~350 ℃ for 1 h~2 h, followed by heating to 500 ℃~550 ℃ and holding for 3 h~5 h.

[0017] Preferably, the bismuth salt is any one of bismuth nitrate, bismuth acetate, and bismuth chloride, and the chloride is potassium chloride or sodium chloride.

[0018] Preferably, the solvent used is a mixture of water and ethylene glycol.

[0019] Preferably, the g-C3N4 microparticles are specifically prepared by calcining melamine, wherein the calcination is carried out at 350 °C for 2 h, followed by heating to 550 °C and holding for 4 h.

[0020] In step 1, the BiOCl nanosheets and graphitic carbon nitride are reacted in a mass ratio of 1~3:1~3, the in-situ solvothermal reaction temperature is 120℃~160℃, and the reaction time is 6 h~12 h.

[0021] In step 2, the mass ratio of konjac glucomannan to crosslinking agent, graphene oxide, and nonionic surfactant is 100:(5-30):(5-25):(1-8). The nonionic surfactant is any one of cocamidopropyl betaine, nonylphenol polyoxyethylene ether, Tween-20, and Tween-80. The crosslinking agent is any one of citric acid, sodium alginate, phytocyanin, and sodium tripolyphosphate.

[0022] Preferably, the nonionic surfactant is cocamidopropyl betaine to improve the dispersion and loading uniformity of the catalyst; the crosslinking agent organic acid enables the konjac glucomannan matrix chain to fully unfold, increasing the binding sites of the photocatalyst and the crosslinking agent, while the graphene oxide is used to achieve rapid electron transfer, synergistically improving the stability and photocatalytic efficiency of the system.

[0023] In step 3, the ultrasonic dispersion is first performed at 200 W to 400 W for 10 to 20 minutes, followed by stirring at 200 rpm to 400 rpm for 20 to 40 minutes. This allows the broken photocatalyst to be uniformly dispersed under shear force and convection, and gradually embedded into the konjac glucomannan matrix. This avoids secondary agglomeration of the photocatalyst, promotes the interfacial bonding between the catalyst and the konjac glucomannan matrix, enables the composite particles to form a stable spatial network structure, and ensures its long-term stability and durability in complex aquatic environments.

[0024] In step 4, the nitrogen gas pressure is 0.05 MPa to 0.20 MPa, the gas introduction time is 3 min to 10 min, and the temperature is 25 ℃ to 45 ℃; in step 5, the curing reaction power is 400 W to 800 W, and the time is 2 min to 5 min.

[0025] By adjusting the gas flow rate, the amount of non-surfactant, and the temperature gradient, the pore size distribution can be precisely controlled, forming a multi-level porous structure combining macropores, mesopores, and micropores. This results in macropores with a diameter range of 50 μm to 200 μm, mesopores with a diameter range of 2 nm to 50 nm, and micropores with a diameter less than 2 nm. Microwave radiation heating rapidly induces the esterification-ionic synergistic crosslinking reaction between citric acid and konjac glucomannan, and heating is immediately terminated to lock the pore structure, simultaneously forming a stable three-dimensional crosslinked network. This achieves a balance between high porosity and good mechanical strength in the particles.

[0026] In step 6, the impregnation solution is a mixed solution containing β-cyclodextrin and ethylenediamine, the impregnation temperature is 25 ℃~40 ℃, the pH value is adjusted to 8~9, and the reaction is carried out at room temperature for 10 h~14 h.

[0027] Preferably, the mixed solution contains 0.5% to 5.0% by mass of β-cyclodextrin and 0.5% to 1.0% by mass of ethylenediamine.

[0028] This invention provides photocatalytic adsorption particles for wastewater treatment, which are prepared by the above-described method.

[0029] This invention provides the application of the above-mentioned photocatalytic adsorption particles for wastewater treatment in the degradation of organic pollutants in wastewater.

[0030] The organic pollutant is any one or a combination of tetracycline antibiotics, quinolone antibiotics, sulfonamide antibiotics, and macrolide antibiotics.

[0031] Compared with the prior art, the present invention achieves the following technical effects:

[0032] The present invention provides a method for preparing photocatalytic adsorption particles for wastewater treatment. This method constructs a double-Z heterojunction photocatalyst via an in-situ solvothermal composite method, optimizing the band structure to promote spatial separation of photogenerated electrons and holes, reducing carrier recombination, and ensuring tight interfacial bonding between the two phases, forming a stable electron migration path. This enhances photocatalytic degradation capability. Compared with traditional single photocatalysts, this double-Z structure effectively avoids rapid recombination of photogenerated electrons and holes, significantly improving the separation efficiency and migration rate of photogenerated carriers, thereby greatly improving photocatalytic degradation efficiency and providing the composite particles with sustained and efficient photocatalytic activity. The polysaccharide matrix solution uses konjac glucomannan as a biodegradable polysaccharide to provide an environmentally friendly framework to avoid secondary degradation. For secondary pollution, cross-linking agents enhance network structure stability, graphene oxide improves electron transport and mechanical properties, and nonionic surfactants ensure uniform dispersion of components and prevent agglomeration. A double-Z heterojunction photocatalyst is added to a polysaccharide matrix solution and ultrasonically dispersed and stirred to obtain a uniform precursor solution, ensuring good distribution of the photocatalyst in the matrix to maintain high photocatalytic activity. After purging the precursor solution with nitrogen, a microwave irradiation reaction is performed. The nitrogen environment prevents oxidation interference, and microwave irradiation rapidly induces cross-linking and solidification to form multi-level porous particles. The hierarchical pore structure optimizes mass transfer, diffusion, and adsorption capacity. The multi-level porous particles are impregnated and the pH value is adjusted to enhance the selective adsorption capacity for specific pollutants through surface functionalization, achieving targeted capture of pollutants. The various technical features work closely together: the double-Z heterojunction provides a highly efficient photocatalytic core, the polysaccharide matrix ensures material degradability, the porous structure improves mass transfer efficiency, and surface functionalization enhances selectivity, jointly achieving a synergistic effect of adsorption and photocatalysis to rapidly enrich and completely degrade recalcitrant organic pollutants.

[0033] Furthermore, KGM was pretreated using a synergistic approach of acid modification and ultrasonic treatment. Acid hydrolysis partially reduced the entanglement of molecular chains, promoted the formation of crystalline regions, and improved the reactivity of molecular chains. Simultaneously, the ultrasonic cavitation effect generated microjets and shock waves in the system, disrupting the particle aggregation state, refining the particles, and introducing a porous structure, thereby improving the dispersibility and porosity of KGM. This modification method not only improved the solution homogeneity of the matrix but also enhanced the structural stability of the subsequent cross-linking network, laying the foundation for the molding and functional realization of composite particles.

[0034] Furthermore, graphene oxide and cocamidopropyl betaine were introduced into the matrix solution. Graphene oxide acts as an electron bridge, accelerating the migration of photogenerated electrons at different phase interfaces. Through hydrogen bonding and electrostatic interactions, it forms a stable bond with the KGM molecular chains, enhancing the mechanical properties and anti-collapse ability of the network. Nonionic surfactants significantly improve the dispersibility of photocatalytic particles in the KGM matrix, preventing aggregation and ensuring the uniformity and photocatalytic efficiency of the composite system. A physical foaming method was employed, with precise nitrogen gas introduction and controlled reaction temperature to achieve controlled gas evolution in the solution, inducing the formation of a three-dimensional hierarchical pore structure combining macropores, mesopores, and micropores. Macropores provide rapid mass transfer channels, mesopores enhance pollutant diffusion and photogenerated carrier migration, and micropores provide a large specific surface area for adsorbing small molecule pollutants. The synergistic effect of these three components not only enhances the reaction interface but also effectively improves pollutant capture capacity and reaction rate, balancing adsorption capacity and mass transfer efficiency. Microwave radiation is used as a heating method, leveraging its penetrating heating and rapid bulk phase temperature rise characteristics to uniformly and efficiently induce esterification and ionic cross-linking reactions between citric acid and KGM molecular chains, thereby rapidly locking the pore structure and solidifying it. Compared with traditional heating methods, microwave radiation avoids local overheating and pore structure collapse, ensuring that the resulting multi-level porous particles have a uniform structure, stable pores, and good mechanical properties.

[0035] Further surface functionalization of the particles using β-cyclodextrin leverages its molecular cavity for spatial recognition of antibiotic molecules such as tetracyclines, while the introduction of amino groups enhances surface hydrophilicity and selective adsorption capacity. This functionalization design not only achieves selective enrichment of target pollutants but also improves the overall material's specific removal capability, providing a new approach for the efficient treatment of complex pollutants in water bodies. By rationally controlling the proportions of each component and cross-linking conditions in the composite system, the resulting particles maintain good mechanical strength and structural stability under conditions of high temperature, salinity variations, or long-term use, preventing the material's lifespan from being affected by pore structure collapse or excessive matrix degradation, thus ensuring stable and durable performance in complex environments.

[0036] The photocatalytic adsorption particles prepared in this invention possess both adsorption and photocatalytic functions. The adsorption process rapidly enriches antibiotic pollutants in water, while photocatalysis further degrades them into harmless small-molecule products. The two processes are spatially coupled and temporally synergistic, achieving highly efficient removal and complete mineralization of pollutants, demonstrating superior comprehensive performance compared to single adsorption or single photocatalytic materials. The KGM used, as well as the controllable synthesis components such as BiOCl, g-C3N4, and graphene oxide, all exhibit good renewability and environmental friendliness. The resulting composite particle material not only possesses excellent biodegradability, allowing for natural degradation after use and avoiding secondary pollution, but also balances high efficiency and sustainability, showcasing broad application prospects.

[0037] The application provided by this invention utilizes photocatalytic adsorption particles for the degradation of organic pollutants in wastewater. The double-Z heterojunction photocatalyst within these particles exhibits a synergistic effect with the polysaccharide matrix. Under illumination, the photocatalyst generates active substances with strong oxidizing capabilities, capable of oxidizing and decomposing antibiotic molecules. The polysaccharide matrix, through adsorption, enriches the antibiotics around the photocatalyst, increasing the contact opportunities between the photocatalyst and pollutants, thereby improving the photocatalytic degradation efficiency. Simultaneously, the hierarchical porous structure provides channels for mass transport, facilitating the reaction and further enhancing the overall removal efficiency. In the process of antibiotic degradation, these photocatalytic adsorption particles primarily decompose or remove antibiotics through physicochemical processes such as photocatalytic oxidation and adsorption. The final products are typically inorganic substances, such as carbon dioxide, water, and simple inorganic salts, without generating secondary pollution, meeting environmental protection requirements. They possess advantages such as high efficiency, anti-interference, stability, and environmental friendliness, demonstrating significant application potential and promotional value in the field of wastewater treatment. Attached Figure Description

[0038] Figure 1 EDS energy spectrum of BiOCl prepared in Example 1 of this invention.

[0039] Figure 2 Infrared spectrum of BiOCl prepared in Example 1 of this invention.

[0040] Figure 3 Infrared spectrum of BiOCl / KGM-based photocatalytic adsorption particles prepared in Example 1 of this invention.

[0041] Figure 4 The absorbance change curve of the photocatalytic adsorption particles prepared in Example 1 of this invention adsorbing tetracycline antibiotics.

[0042] Figure 5 A photograph of the photocatalytic adsorption particles prepared in Example 1 of this invention in a wet state.

[0043] Figure 6 Scanning electron microscope (SEM) images of the photocatalytic adsorption particles prepared in the dry state in Example 1 of this invention, wherein A is a SEM image of the photocatalytic adsorption particles at a lower magnification (100×) and B is a SEM image of the photocatalytic adsorption particles at a higher magnification (400×). Detailed Implementation

[0044] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0045] Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products. In this invention, unless otherwise specified, all experimental materials used are commercially available commodities well-known to those skilled in the art.

[0046] Example 1

[0047] This embodiment provides a photocatalytic adsorption particle composed of a dual Z-type heterojunction photocatalyst and a polysaccharide matrix. The specific preparation process is as follows:

[0048] (1) Preparation of photocatalysts

[0049] Weigh 1.0 g of Bi(NO3)3·5H2O and dissolve it in 50 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; then slowly add 20 mL of KCl solution (0.2 mol / L), stir for 2 h, let stand for 6 h, wash the precipitate after the reaction, and dry to obtain BiOCl nanosheet powder.

[0050] 5.0 g of melamine was weighed and placed in a porcelain boat, and then calcined in a muffle furnace in two stages. First, the temperature was raised to 350 °C and held for 2 h, and then raised to 550 °C and held for 4 h to obtain g-C3N4 microparticle powder.

[0051] BiOCl nanosheets and g-C3N4 microparticles were mixed at a mass ratio of 3:1. The mixture was added to a mixed solvent system (ethylene glycol and water in a volume ratio of 1:1). The reaction system was placed at 150℃ for in-situ solvothermal reaction for 8 hours, so that BiOCl was uniformly crystallized and deposited on the surface of g-C3N4 to form a stable double Z-type heterojunction photocatalyst powder.

[0052] (2) Preparation of polysaccharide matrix solution

[0053] Weigh 2.0 g of konjac glucomannan (KGM) and add it to 100 mL of deionized water. Stir and dissolve at 60 °C. Add 0.5 g of citric acid (as a natural cross-linking agent), 20 mL of graphene oxide (concentration 1 mg / mL) and 0.2 g of cocamidopropyl betaine to the solution and stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0054] (3) Photocatalyst and matrix composite

[0055] 0.5 g of double Z-type heterojunction catalyst powder was added to 50 mL of the above polysaccharide matrix solution, and ultrasonicated (300 W, 15 min). Then, mechanical stirring was continued at 300 rpm for 20 min to obtain a homogeneous double Z-type heterojunction photo-matrix precursor solution.

[0056] (4) Preparation of precursor solutions with hierarchical porous structures

[0057] The double Z-type heterojunction optical-matrix precursor solution was placed in a constant temperature reactor and aerated at 35 ℃ and 0.150 MPa nitrogen pressure for 6 min to form a precursor solution with a multi-level pore structure of macropore-mesopore-micropore synergy.

[0058] (5) Preparation of multi-level porous particles

[0059] The precursor solution with a multi-level porous structure was transferred into a reaction vessel and placed in a microwave reactor. It was irradiated with 400 W microwave power for 5 min. Rapid microwave heating induced esterification and ionic cross-linking reactions between citric acid and KGM. The precursor solidified and locked the pore structure to obtain multi-level porous particles.

[0060] (6) Surface functionalization modification

[0061] The obtained multi-porous particles were placed in a mixture containing 5% β-cyclodextrin solution and 1% ethylenediamine solution, the pH was adjusted to 8.5, and the reaction was carried out at room temperature for 12 h. After the reaction was completed, the particles were washed and dried to obtain photocatalytic adsorption particles with cyclodextrin cavities and amino functional groups on the surface.

[0062] The performance of the photocatalytic adsorption particles prepared in this embodiment was tested: Microscopic observation revealed that the particles were regular near-spherical in shape, with a particle size ranging from 1.5 to 2.0 mm and a relatively smooth surface. This regular spherical structure facilitates the flow and dispersion of the particles in practical applications, increasing the contact area with pollutants. Using tetracycline as the target pollutant, the absorbance of its characteristic absorption peak at a wavelength of 280 nm was measured at certain time intervals. The change in absorbance reflected the change in tetracycline concentration, thereby calculating the removal rate. Within 0 to 25 hours, the absorbance gradually decreased, indicating that tetracycline was continuously adsorbed or degraded by the photocatalytic adsorption particles. The removal rate reached 92% within 25 hours, demonstrating that the photocatalytic adsorption particles have a good removal effect on tetracycline.

[0063] See appendix Figure 1 Table 1 shows the elemental analysis of the photocatalytic adsorption particles. The particles contain major elements such as C, O, N, Bi, and Cl. C and O are derived from KGM and surface functionalized components, N is derived from g-C3N4 and amino modification, and Bi and Cl correspond to BiOCl. The quantitative elemental analysis in Table 1 shows that the proportion of Bi and Cl is basically consistent with the theoretical feed ratio, and the elemental distribution is uniform, indicating that BiOCl has been successfully loaded and uniformly dispersed in the polysaccharide matrix. This indicates that the double Z-type heterojunction photocatalyst components are tightly bound to the polysaccharide matrix, ensuring the stability of the subsequent photocatalytic reaction and facilitating its continuous progress.

[0064] Table 1: Relative content of major elements in KGM microspheres loaded with BiOCl by in-situ synthesis

[0065]

[0066] See appendix Figures 2-3 Fourier transform infrared spectroscopy was performed on the synthesized BiOCl powder and the KGM-based photocatalytic adsorption particles loaded with BiOCl to analyze their structural characteristics. Figure 2 It can be seen that the synthesized BiOCl powder exhibits typical Bi-O and Bi-Cl lattice vibration characteristic peaks in the Fourier transform infrared spectrum, verifying the structural integrity and purity of the prepared inorganic phase, indicating that the prepared BiOCl has the expected crystal structure. (From the attached...) Figure 3As can be seen, the BiOCl-loaded KGM-based photocatalytic adsorbent particles exhibit shifts and intensity changes in absorption peaks in the FT-IR spectrum compared to pure KGM. This indicates the existence of hydrogen bonds, electrostatic interactions, or coordination interactions between the BiOCl and KGM molecular chains, thereby enhancing interfacial bonding and stability. This allows the photocatalyst to be better immobilized on the polysaccharide matrix, which is beneficial for the photocatalytic reaction. The attached figure does not separately show the peak shape changes of β-cyclodextrin and graphene oxide, but their binding mechanism with KGM is similar to that of the BiOCl-KGM system, both enhancing the stability of the composite network through functional group interactions.

[0067] See appendix Figure 4 Using tetracycline as the target pollutant, the change of its characteristic absorption peak at a wavelength of 280 nm over time was detected to analyze the removal efficiency of tetracycline under the synergistic effect of adsorption-photocatalysis. (From the attached...) Figure 4 It can be seen that under the synergistic effect of adsorption and photocatalysis, the absorbance decreased significantly over time, and the removal rate exceeded 90% after 25 hours, indicating that the photocatalytic adsorption particles have a significant removal effect on antibiotics under the dual effects of adsorption and photocatalysis. Adsorption can rapidly enrich tetracycline on the particle surface, while photocatalysis can further degrade the adsorbed tetracycline into harmless substances. The two work synergistically to greatly improve the removal efficiency of tetracycline.

[0068] See appendix Figure 5 By observing the photocatalytic adsorption particles in a humid state, it was found that they maintained a spherical shape, were relatively uniform in morphology, were plump, and had good elasticity. These favorable morphological characteristics allow the photocatalytic adsorption particles to better adapt to different environmental conditions and maintain stable performance in practical applications.

[0069] See appendix Figure 6 Scanning electron microscopy was used to examine the microstructure of the photocatalytic adsorption particles. Figure 6 As can be seen, the photocatalytic adsorption particles are generally regular spheres with some irregular protrusions, presumably BiOCl distributed on the substrate surface. This indicates that the photocatalyst was successfully loaded and its active sites were exposed, which is beneficial to the photocatalytic reaction. Simultaneously, the particles exhibit a connected pore structure, forming a multi-level pore network. This network facilitates the rapid diffusion of pollutants into the particle interior, increases the reaction interface, and thus enhances the adsorption-photocatalytic performance, enabling the particles to remove pollutants more efficiently.

[0070] In summary, this invention successfully prepared a photocatalytic adsorption particle composed of a double Z-shaped heterojunction photocatalyst and a polysaccharide matrix. This particle exhibits a regular spherical morphology, good elemental distribution, stable structure, and a multi-level porous network. Performance testing results show that the particle has a significant removal effect on tetracycline under the synergistic effect of adsorption and photocatalysis, achieving a removal rate of over 92% within 25 hours. Simultaneously, the particle maintains good morphology and elasticity under wet conditions, and its internal multi-level porous structure facilitates the diffusion and reaction of pollutants, providing a solid foundation for practical applications.

[0071] Example 2

[0072] This embodiment provides a photocatalytic adsorption particle composed of a dual Z-type heterojunction photocatalyst and a polysaccharide matrix. The specific preparation process is as follows:

[0073] (1) Preparation of photocatalysts

[0074] Weigh 1.2 g of Bi(NO3)3·5H2O and dissolve it in 60 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; slowly add 20 mL of KCl solution (0.3 mol / L), stir for 1.5 h, let stand for 10 h, wash the precipitate and dry it after the reaction is complete to obtain BiOCl nanosheet powder.

[0075] Weigh 0.4 g of melamine and place it in a porcelain boat. Then, perform a two-stage calcination in a muffle furnace. First, raise the temperature to 300℃ and hold for 1.5 h, then raise it to 520℃ and hold for 3.5 h to obtain g-C3N4 microparticle powder.

[0076] BiOCl nanosheets and g-C3N4 microparticles were mixed at a mass ratio of 2:1 and added to a mixed solvent of ethylene glycol and water at a volume ratio of 2:1. The mixture was subjected to an in-situ solvothermal composite reaction at 140℃ for 6 hours. The BiOCl produced by the reaction crystallized and deposited uniformly on the surface of g-C3N4, forming a stable double Z-type heterojunction photocatalyst powder.

[0077] (2) Preparation of polysaccharide matrix solution

[0078] Weigh 1.5g of KGM and add it to 80mL of deionized water. Stir and dissolve at 50℃. Add 0.3g of citric acid (as a natural cross-linking agent), 10mL of graphene oxide (concentration 1mg / mL), and 0.15g of Tween-20 to the solution and stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0079] (3) Photocatalyst and matrix composite

[0080] 0.3 g of double Z-type heterojunction catalyst powder was added to 40 mL of the above polysaccharide matrix solution, and ultrasonicated (300 W, 10 min). Then, mechanical stirring was continued at 250 rpm for 15 min to obtain a uniform double Z-type heterojunction photo-matrix precursor solution.

[0081] (4) Preparation of precursor solutions with hierarchical porous structures

[0082] The double Z-type heterojunction optical-matrix precursor solution was placed in a constant temperature reactor and aerated at 30℃ and 0.200MPa nitrogen pressure for 4 min to form a precursor solution with a multi-level pore structure of macropore-mesopore-micropore synergy.

[0083] (5) Preparation of multi-level porous particles

[0084] The precursor solution with a multi-level porous structure was transferred into a reaction vessel and placed in a microwave reactor. It was then irradiated with 300W microwave power for 4 minutes and rapidly heated by microwaves. This process solidified the precursor and locked the pore structure, resulting in multi-level porous particles.

[0085] (6) Surface functionalization modification

[0086] The obtained multi-porous particles were placed in a mixture containing 3% β-cyclodextrin solution and 1% ethylenediamine solution, the pH was adjusted to 8.0, and the reaction was carried out at room temperature for 10 h. After the reaction was completed, the particles were washed and dried to obtain photocatalytic adsorption particles with cyclodextrin cavities and amino functional groups on the surface.

[0087] Performance tests were conducted on the photocatalytic adsorption particles prepared in this embodiment. Microscopic observation showed that the particles were generally regular and nearly spherical, with a particle size of 1.3-1.8 mm and a relatively dense and smooth surface, which is beneficial for the particle's mobility and uniform dispersion in water. Using tetracycline as the target pollutant, the absorbance of its characteristic absorption peak at 280 nm was measured at specified time intervals. The results showed that the absorbance gradually decreased over time, indicating that tetracycline was continuously removed under adsorption and photocatalysis. During the reaction process from 0 to 20 hours, the tetracycline concentration decreased significantly, and the removal rate reached 88% at 20 hours, indicating that the particles obtained in this embodiment possess a stable adsorption-photocatalytic synergistic degradation capability.

[0088] Example 3

[0089] This embodiment provides a photocatalytic adsorption particle composed of a dual Z-type heterojunction photocatalyst and a polysaccharide matrix. The specific preparation process is as follows:

[0090] (1) Preparation of photocatalysts

[0091] 1.0 g of Bi(NO3)3·5H2O was weighed and dissolved in 50 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; 20 mL of KCl solution (0.3 mol / L) was slowly added, stirred for 2 h, and allowed to stand for 10 h. After the reaction was completed, the precipitate was washed and dried to obtain BiOCl nanosheet powder.

[0092] 5.0g of urea was weighed and placed in a porcelain boat, and then calcined in a muffle furnace in two stages. The temperature was first raised to 340℃ and held for 2 hours, and then raised to 500℃ and held for 4 hours to obtain g-C3N4 microparticle powder.

[0093] BiOCl nanosheets and g-C3N4 microparticles were mixed at a mass ratio of 2:1 and added to a mixed solvent of ethylene glycol and water at a volume ratio of 2:1. The mixture was subjected to an in-situ solvothermal composite reaction at 160℃ for 12 h. The BiOCl produced by the reaction was uniformly crystallized and deposited on the surface of g-C3N4 to form a stable double Z-type heterojunction photocatalyst powder.

[0094] (2) Preparation of polysaccharide matrix solution

[0095] Weigh 1.5g of KGM and add it to 80mL of deionized water. Stir and dissolve at 50℃. Add 0.3g of citric acid (as a natural cross-linking agent), 10mL of graphene oxide (concentration 1mg / mL), and 0.15g of Tween-20 to the solution and stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0096] (3) Photocatalyst and matrix composite

[0097] 0.3 g of double Z-type heterojunction catalyst powder was added to 40 mL of the above polysaccharide matrix solution, and ultrasonicated (300 W, 10 min). Then, mechanical stirring was continued at 250 rpm for 15 min to obtain a uniform double Z-type heterojunction photo-matrix precursor solution.

[0098] (4) Preparation of precursor solutions with hierarchical porous structures

[0099] The double Z-type heterojunction optical-matrix precursor solution was placed in a constant temperature reactor and aerated at 30℃ and 0.20 MPa nitrogen pressure for 10 min to form a precursor solution with a multi-level pore structure of macropore-mesopore-micropore synergy.

[0100] (5) Preparation of multi-level porous particles

[0101] The precursor solution with a multi-level porous structure was transferred into a reaction vessel and placed in a microwave reactor. It was then irradiated with 300W microwave power for 4 minutes and rapidly heated by microwaves. This process solidified the precursor and locked the pore structure, resulting in multi-level porous particles.

[0102] (6) Surface functionalization modification

[0103] The obtained multi-porous particles were placed in a mixture containing 3% β-cyclodextrin solution and 1% ethylenediamine solution, the pH was adjusted to 8.0, and the reaction was carried out at room temperature for 10 h. After the reaction was completed, the particles were washed and dried to obtain photocatalytic adsorption particles with cyclodextrin cavities and amino functional groups on the surface.

[0104] Performance tests were conducted on the photocatalytic adsorption particles prepared in this embodiment. Microscopic observation showed that the particles were generally regular and nearly spherical, with a particle size of 1.3-1.8 mm and a relatively dense and smooth surface, which is beneficial for the particle's mobility and uniform dispersion in water. Using tetracycline as the target pollutant, the absorbance of its characteristic absorption peak at 280 nm was measured at specified time intervals. The results showed that the absorbance gradually decreased over time, indicating that tetracycline was continuously removed under adsorption and photocatalysis. During the reaction process from 0 to 20 hours, the tetracycline concentration decreased significantly, and the removal rate reached 88% at 20 hours, indicating that the particles obtained in this embodiment possess a stable adsorption-photocatalytic synergistic degradation capability.

[0105] Example 4

[0106] This embodiment provides a photocatalytic adsorption particle composed of a dual Z-type heterojunction photocatalyst and a polysaccharide matrix. The specific preparation process is as follows:

[0107] (1) Preparation of photocatalysts

[0108] Weigh 0.8 g of Bi(NO3)3·5H2O and dissolve it in 40 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; slowly add 25 mL of NaCl solution (0.1 mol / L), stir for 3 h, let stand for 8 h, wash the precipitate and dry it after the reaction is complete to obtain BiOCl nanosheet powder.

[0109] 0.6 g of melamine was weighed and placed in a porcelain boat, and then calcined in a muffle furnace in two stages. The temperature was first raised to 340 °C and held for 2 h, and then raised to 540 °C and held for 4 h to obtain g-C3N4 microparticle powder.

[0110] BiOCl nanosheets and g-C3N4 microparticles were mixed at a mass ratio of 1:1 and added to a mixed solvent of ethylene glycol and water at a volume ratio of 3:1. The mixture was subjected to an in-situ solvothermal composite reaction at 160℃ for 10 h. The resulting BiOCl formed a stable double Z-type heterojunction photocatalyst powder.

[0111] (2) Preparation of polysaccharide matrix solution

[0112] Weigh 2.5 g of KGM and add it to 120 mL of deionized water. Stir and dissolve at 70 °C. Add 0.8 g of sodium alginate (as a natural cross-linking agent), 30 mL of graphene oxide (concentration 1 mg / mL), and 0.25 g of Tween-80 to the solution. Stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0113] (3) Photocatalyst and matrix composite

[0114] 0.8 g of double Z-type heterojunction catalyst powder was added to 60 mL of the above polysaccharide matrix solution, and ultrasonicated (350 W, 20 min). Then, mechanical stirring was continued at 400 rpm for 25 min to obtain a uniform double Z-type heterojunction photo-matrix precursor solution.

[0115] (4) Preparation of precursor solutions with hierarchical porous structures

[0116] The double Z-type heterojunction optical-matrix precursor solution was placed in a constant temperature reactor and aerated at 40℃ and 0.180MPa nitrogen pressure for 8 minutes to form a precursor solution with a multi-level pore structure of macropore-mesopore-micropore synergy.

[0117] (5) Preparation of multi-level porous particles

[0118] The precursor solution with a multi-level porous structure was transferred into a reaction vessel and placed in a microwave reactor. It was irradiated with 450W microwave power for 6 minutes to solidify the precursor and lock the pore structure, thus obtaining multi-level porous particles.

[0119] (6) Surface functionalization modification

[0120] The obtained multi-porous particles were placed in a mixture containing 6% β-cyclodextrin solution and 2% ethylenediamine solution, the pH was adjusted to 9.0, and the reaction was carried out at room temperature for 8 hours. After the reaction was completed, the particles were washed and dried to obtain photocatalytic adsorption particles with cyclodextrin cavities and amino functional groups on the surface.

[0121] Performance tests were conducted on the photocatalytic adsorption particles prepared in this embodiment. Microscopic analysis showed that the particles had a relatively uniform spherical structure with a particle size distribution of 1.6-2.2 mm. A small number of protrusions were present on the particle surface, presumably due to the exposed BiOCl loading, which is beneficial for improving the utilization efficiency of the photocatalytic active sites. Using tetracycline as the target pollutant, the absorbance at 280 nm was tested over time. The results showed a rapid decrease in absorbance, indicating that the adsorption and photocatalytic processes continued. After 20 hours of reaction, the tetracycline removal rate reached 84%, indicating that the particles obtained in this embodiment possess a stable adsorption-photocatalytic synergistic degradation capability.

[0122] Example 5

[0123] Based on Examples 1-4, this embodiment uses the photocatalytic adsorption particles prepared in Example 1 to verify their removal effect on quinolone antibiotics. The specific experimental results are as follows:

[0124] Prepare 100 mL of ciprofloxacin (CIP) aqueous solution with a concentration of 50 mg / L. Add 0.1 g of the photocatalytic adsorption particles prepared in Example 1 to the prepared ciprofloxacin aqueous solution. Mix the particles evenly with magnetic stirring and irradiate them under visible light with λ > 420 nm. Continuously monitor the concentration change of the ciprofloxacin aqueous solution to evaluate the removal effect of the composite particles.

[0125] The results showed that the synergistic removal rate of ciprofloxacin through adsorption and photocatalysis exceeded 85% within 25 hours, indicating that the photocatalytic adsorption particles exhibited a significant effect in removing ciprofloxacin. Further analysis revealed that the concentration of ciprofloxacin decreased significantly within the first 5 hours, then gradually stabilized. In summary, the results of this embodiment demonstrate that photocatalytic adsorption particles also possess excellent efficacy in the removal of quinolone antibiotics, providing strong experimental evidence for their application in environmental remediation.

[0126] Example 6

[0127] This embodiment, based on Examples 1-4, uses the photocatalytic adsorption particles prepared in Example 1 to verify their removal effect on sulfonamide antibiotics. The removal effect is also compared with that of a single photocatalyst and unmodified polysaccharide particles. Specific experimental results are as follows:

[0128] 100 mL of a 50 mg / L sulfamethoxazole (SMX) aqueous solution was prepared. 0.1 g of the photocatalytic adsorption particles prepared in Example 1 was added to the prepared sulfamethoxazole aqueous solution and magnetically stirred until homogeneous. The mixture was then irradiated under visible light (λ > 420 nm) to simulate natural light conditions, stimulating the photocatalyst to generate active substances. The concentration change of the sulfamethoxazole aqueous solution was continuously monitored using high-performance liquid chromatography (HPLC) to evaluate the removal effect of the composite particles. A control group, a single photocatalyst control group (compared to the photocatalyst of the composite particles in Example 1), and an unmodified polysaccharide particle control were also included. The control group (the polysaccharide base of the composite particles in Example 1) was used as a reference sample. At different time points after the start of the experiment (e.g., 0h, 1h, 3h, 5h, 10h, 15h, 20h, 25h), a certain volume (e.g., 5mL) of solution was pipetted from the mixture of each experimental group and the control group. After appropriate filtration, the solution was injected into a high-performance liquid chromatograph (HPLC) to determine the concentration of sulfamethoxazole in the solution. Based on the sulfamethoxazole concentration data determined by the HPLC, the sulfamethoxazole removal rate of each experimental group and the control group at different time points was calculated according to the following formula: Removal rate (%) = (C0 - C t) / C0×100% Where C0 is the initial concentration of sulfamethoxazole at the start of the experiment (50 mg / L), C t The concentration of sulfamethoxazole at time t during the experiment.

[0129] The results showed that within 25 hours, the photocatalytic adsorption particles of this invention achieved a removal rate of 80% for sulfamethoxazole, which was 25-30 percentage points higher than that of single photocatalysts or unmodified polysaccharide particles. This indicates that the photocatalytic adsorption particles of this invention combine the adsorption effect of polysaccharide particles with the photocatalytic degradation effect of photocatalysts. The synergistic effect of the two significantly improves the removal capacity of sulfonamide antibiotics, demonstrating its potential value in the field of environmental remediation.

[0130] Example 7

[0131] This embodiment, based on Examples 1-4, uses the photocatalytic adsorption particles prepared in Example 1 to verify their removal effect on macrolide antibiotics. The removal effect is also compared with that of a single photocatalyst and unmodified polysaccharide particles. Specific experimental results are as follows:

[0132] 100 mL of 40 mg / L erythromycin (ERY, a macrolide antibiotic) aqueous solution was prepared. 0.1 g of the photocatalytic adsorption particles from Example 1 was added to the prepared macrolide antibiotic aqueous solution. The mixture was magnetically stirred until homogeneous and then irradiated under visible light (λ > 420 nm) to simulate natural light conditions, thereby exciting the photocatalyst to produce active substances. The concentration change of the macrolide antibiotic aqueous solution was continuously monitored using high performance liquid chromatography (HPLC) to evaluate the removal effect of the composite particles.

[0133] The results showed that the photocatalytic adsorption particles of the present invention could remove 75% of erythromycin within 25 hours, exhibiting a significant adsorption-photocatalytic synergistic effect, indicating that the photocatalytic adsorption particles of the present invention also have application potential in the treatment of macrolide antibiotics.

[0134] Example 8

[0135] Based on Examples 1-4, this embodiment uses the photocatalytic adsorption particles prepared in Example 1 to verify their practical application performance in complex water bodies (simulated wastewater containing multiple antibiotics). It examines their removal efficiency for different types of antibiotics and their total organic carbon (TOC) removal capacity, evaluates their anti-interference ability and practical application potential, and the specific experimental results are as follows:

[0136] Preparation of simulated wastewater: Weigh 2 mg of tetracycline (TC), 1.5 mg of ciprofloxacin (CIP), 1.5 mg of sulfamethoxazole (SMX), and 1 mg of erythromycin (ERY), place them in a small beaker, add an appropriate amount of deionized water to dissolve them, and then transfer them to a 100 mL volumetric flask. Dilute to the mark with deionized water to prepare 100 mL of simulated wastewater containing 20 mg / L tetracycline, 15 mg / L ciprofloxacin, 15 mg / L sulfamethoxazole, and 10 mg / L erythromycin. Add 0.1 g of the photocatalytic adsorption particles prepared in Example 1 to the prepared simulated wastewater. Place the mixture on a magnetic stirrer, turn on the magnetic stirring function, and simultaneously irradiate the mixture with a visible light source with a wavelength greater than 420 nm to begin the adsorption-photocatalysis experiment. Within 25 hours of the start of the experiment, at regular intervals (e.g., 1 hour, 3 hours, 5 hours, 10 hours, 15 hours, 20 hours, and 25 hours), a certain volume (e.g., 5 mL) of solution was pipetted from the mixed system, filtered appropriately, and then injected into a high-performance liquid chromatograph (HPLC) to determine the concentrations of tetracycline, ciprofloxacin, sulfamethoxazole, and erythromycin. The total organic carbon (TOC) content was determined using a total organic carbon analyzer. Based on the HPLC concentration data of each antibiotic, the removal rate (%) was calculated using the formula: Removal rate (%) = (C0... C t ) / C0×100% (where C0 is the initial concentration of each antibiotic, C t Calculate the removal rate of each antibiotic at different time points (where t is the concentration of each antibiotic).

[0137] The results showed that in complex water bodies containing multiple antibiotics, the photocatalytic adsorption particles of this invention exhibited a certain removal effect on various antibiotics within 25 hours, with tetracycline removal rates of approximately 90%, ciprofloxacin approximately 85%, sulfamethoxazole approximately 80%, and erythromycin approximately 75%; the total organic carbon (TOC) removal rate was approximately 70%. These results demonstrate that the photocatalytic adsorption particles maintain high efficiency in multi-component antibiotic coexistence systems, exhibiting good anti-interference capabilities and practical application potential.

[0138] Comparative Example 1 (using only BiOCl, without constructing a double Z-shaped heterojunction)

[0139] Comparative Example 1 provides a photocatalytic adsorption particle based on Example 1, and the specific preparation process is as follows:

[0140] (1) Preparation of photocatalysts

[0141] Weigh 1.0 g of Bi(NO3)3·5H2O and dissolve it in 50 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; then slowly add 50 mL of KCl solution (0.2 mol / L), stir for 2 h, let stand for 6 h, wash the precipitate after the reaction, and dry to obtain BiOCl nanosheet powder.

[0142] (2) Preparation of polysaccharide matrix solution

[0143] Weigh 2.0g of KGM and add it to 100mL of deionized water. Stir and dissolve at 60℃. Add 0.5g of citric acid (as a natural cross-linking agent), 20mL of graphene oxide (concentration 1mg / mL), and 0.2g of cocamidopropyl betaine to the solution. Stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0144] (3) Photocatalyst and matrix composite

[0145] Add 0.5 g of BiOCl nanosheet powder to 50 mL of the above polysaccharide matrix solution, sonicate (300 W, 15 min), and continue mechanical stirring at 300 rpm for 20 min to obtain a uniform photocatalyst-matrix precursor solution.

[0146] (4) Preparation of precursor solutions with hierarchical porous structures

[0147] The precursor solution was placed in a constant temperature reactor and aerated at 35°C and 0.150 MPa nitrogen pressure for 6 minutes to form a precursor solution with a multi-level pore structure of macropores, mesopores and micropores.

[0148] (5) Preparation of multi-level porous particles

[0149] The precursor solution with a multi-level porous structure was transferred into a reaction vessel and placed in a microwave reactor. It was irradiated with 400W microwave power for 5 minutes. Rapid microwave heating induced esterification and ionic cross-linking reactions between citric acid and KGM. The precursor solidified and locked the pore structure to obtain multi-level porous particles.

[0150] (6) Surface functionalization modification

[0151] The obtained multi-porous particles were placed in a mixture containing 5% β-cyclodextrin solution and 1% ethylenediamine solution, the pH was adjusted to 8.5, and the reaction was carried out at room temperature for 12 hours. After the reaction was completed, the particles were washed and dried to obtain photocatalytic adsorption particles with cyclodextrin cavities and amino functional groups on the surface.

[0152] Comparative Example 1, based on Example 1, omitted step 1, and did not construct a double Z-shaped heterojunction. The same BiOCl preparation process as in Example 1 was used, but the double Z-shaped heterojunction was not constructed. Preparation of the polysaccharide matrix solution: same as in Example 1; Photocatalyst and matrix composite: BiOCl was directly loaded into the KGM matrix. Subsequent steps: same as in Example 1.

[0153] Microscopic observation revealed that the photocatalytic adsorption particles prepared in Comparative Example 1 had a particle size distribution of 1.2-2.8 mm and a relatively rough and uneven surface. Using tetracycline as the target pollutant, the concentration of tetracycline in the solution was measured at different time points under the same experimental conditions, and the removal rate was calculated. The photocatalytic adsorption particles prepared in Comparative Example 1 achieved a removal rate of 40% within 26 hours, with a relatively slow decline in the curve. Compared to the approximately 90% tetracycline removal rate achieved by the photocatalytic adsorption particles in Example 1 within 25 hours, the removal effect of this comparative example was significantly worse. This is because the single BiOCl photocatalyst is prone to electron-hole recombination. Electrons and holes recombine before fully participating in the photocatalytic reaction, releasing energy, resulting in a reduction in the number of active species used to degrade tetracycline and a decrease in catalytic efficiency. Furthermore, although the polysaccharide matrix has a certain adsorption capacity, adsorption alone is insufficient for the rapid and effective removal of tetracycline, resulting in a low overall removal rate and a slow reaction rate. This fully demonstrates that the construction of double Z-shaped heterojunctions can effectively improve the performance of photocatalysts, reduce electron-hole recombination, enhance the ability of photocatalytic degradation of antibiotics, and also have a certain positive impact on particle morphology.

[0154] Comparative Example 2 (foaming without nitrogen gas)

[0155] Comparative Example 2 provides a photocatalytic adsorption particle based on Example 1, and the specific preparation process is as follows:

[0156] (1) Preparation of photocatalysts

[0157] Weigh 1.0 g of Bi(NO3)3·5H2O and dissolve it in 50 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; then slowly add 20 mL of KCl solution (0.2 mol / L), stir for 2 h, let stand for 6 h, wash the precipitate after the reaction, and dry to obtain BiOCl nanosheet powder.

[0158] 5.0 g of melamine was weighed and placed in a porcelain boat, and then calcined in a muffle furnace in two stages. First, the temperature was raised to 350 °C and held for 2 h, and then raised to 550 °C and held for 4 h to obtain g-C3N4 microparticle powder.

[0159] BiOCl nanosheets and g-C3N4 microparticles were mixed at a mass ratio of 3:1. The mixture was added to a mixed solvent system (ethylene glycol and water in a volume ratio of 1:1). The reaction system was placed at 150 °C for in-situ solvothermal composite reaction for 8 h, so that BiOCl was uniformly crystallized and deposited on the surface of g-C3N4 to form a stable double Z-type heterojunction photocatalyst powder.

[0160] (2) Preparation of polysaccharide matrix solution

[0161] Weigh 2.0g of konjac glucomannan (KGM) and add it to 100mL of deionized water. Stir and dissolve at 60℃. Add 0.5g of citric acid (as a natural cross-linking agent), 20mL of graphene oxide (concentration 1mg / mL) and 0.2g of cocamidopropyl betaine to the solution and stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0162] (3) Photocatalyst and matrix composite

[0163] Add 0.5 g of double Z-type heterojunction catalyst powder to 50 mL of the above polysaccharide matrix solution, sonicate (300 W, 15 min), and continue mechanical stirring at 300 rpm for 20 min to obtain a uniform double Z-type heterojunction photo-matrix precursor solution.

[0164] (4) Preparation of precursor solutions with hierarchical porous structures

[0165] The double Z-type heterojunction optical-matrix precursor solution was placed in a constant temperature reactor and reacted at 35 °C for 6 min to form a precursor solution with a multi-level porous structure.

[0166] (5) Preparation of multi-level porous particles

[0167] The precursor solution with a multi-level porous structure was transferred into a reaction vessel and placed in a microwave reactor. It was irradiated with 400W microwave power for 5 minutes. Rapid microwave heating induced esterification and ionic cross-linking reactions between citric acid and KGM. The precursor solidified and locked the pore structure to obtain multi-level porous particles.

[0168] (6) Surface functionalization modification

[0169] The obtained multi-porous particles were placed in a mixture containing 5% β-cyclodextrin solution and 1% ethylenediamine solution, the pH was adjusted to 8.5, and the reaction was carried out at room temperature for 12 hours. After the reaction was completed, the particles were washed and dried to obtain photocatalytic adsorption particles with cyclodextrin cavities and amino functional groups on the surface.

[0170] Comparative Example 2 omits step four, and nitrogen foaming is not performed. Other steps are the same as in Example 1.

[0171] Performance testing was conducted on the photocatalytic adsorption particles prepared in Comparative Example 2. Microscopic observation revealed irregular particle morphology with a particle size distribution of 1.0-3.5 mm. Using tetracycline as the target pollutant, the absorbance of its characteristic absorption peak at 280 nm was measured at specific time intervals. Changes in absorbance reflected changes in tetracycline concentration, and the removal rate was calculated. After 25 hours, the removal rate of the photocatalytic adsorption particles prepared in Comparative Example 2 was approximately 55%. Analysis: The lack of a macroporous-mesoporous-microporous structure reduced the specific surface area, limiting diffusion and mass transfer, thus decreasing adsorption efficiency.

[0172] Comparative Example 3 (without surface functionalization modification)

[0173] Comparative Example 3, based on Example 1, provides a photocatalytic adsorption particle, the specific preparation process of which is as follows:

[0174] (1) Preparation of photocatalysts

[0175] Weigh 1.0 g of Bi(NO3)3·5H2O and dissolve it in 50 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; then slowly add 20 mL of KCl solution (0.2 mol / L), stir for 2 h, let stand for 6 h, wash the precipitate after the reaction, and dry to obtain BiOCl nanosheet powder.

[0176] 5.0 g of melamine was weighed and placed in a porcelain boat, and then calcined in a muffle furnace in two stages. First, the temperature was raised to 350 °C and held for 2 h, and then raised to 550 °C and held for 4 h to obtain g-C3N4 microparticle powder.

[0177] BiOCl nanosheets and g-C3N4 microparticles were mixed at a mass ratio of 3:1. The mixture was added to a mixed solvent system (ethylene glycol and water in a volume ratio of 1:1). The reaction system was placed at 150 °C for in-situ solvothermal reaction for 8 h, so that BiOCl was uniformly crystallized and deposited on the surface of g-C3N4 to form a stable double Z-type heterojunction photocatalyst powder.

[0178] (2) Preparation of polysaccharide matrix solution

[0179] Weigh 2.0g of KGM and add it to 100mL of deionized water. Stir and dissolve at 60℃. Add 0.5g of citric acid (as a natural cross-linking agent), 20mL of graphene oxide (concentration 1mg / mL), and 0.2g of cocamidopropyl betaine to the solution and stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0180] (3) Photocatalyst and matrix composite

[0181] Add 0.5g of double Z-type heterojunction catalyst powder to 50mL of the above polysaccharide matrix solution, sonicate (300W, 15min), and continue mechanical stirring at 300rpm for 20min to obtain a uniform double Z-type heterojunction photo-matrix precursor solution.

[0182] (4) Preparation of precursor solutions with hierarchical porous structures

[0183] The double Z-type heterojunction optical-matrix precursor solution was placed in a constant temperature reactor and aerated at 35°C and 0.150 MPa nitrogen pressure for 6 min to form a precursor solution with a multi-level pore structure of macropore-mesopore-micropore synergy.

[0184] (5) Preparation of multi-level porous particles

[0185] The precursor solution with a multi-level porous structure was transferred into a reaction vessel and placed in a microwave reactor. It was irradiated with 400W microwave power for 5 minutes. Rapid microwave heating induced esterification and ionic cross-linking reactions between citric acid and KGM. The precursor solidified and locked the pore structure to obtain photocatalytic adsorption particles.

[0186] Comparative Example 3 is based on Example 1, but step six, β-cyclodextrin amino functionalization modification, is omitted. The tetracycline adsorption performance is tested directly using basic porous particles. The rest is the same as in Example 1.

[0187] Performance tests were conducted on the photocatalytic adsorption particles prepared in Comparative Example 3: Microscopic observation revealed that the particles were regularly spherical with smooth surfaces and lacked functional groups. Tetracycline adsorption performance: the removal rate was less than 50% after 25 hours, and the selectivity was poor. Analysis: The lack of β-cyclodextrin molecular cavities and amino sites, coupled with the absence of spatial recognition sites and hydrophilicity regulation, limited the adsorption performance.

[0188] Comparative Example 4 (Traditional Water Bath Heating)

[0189] Comparative Example 4 provides a photocatalytic adsorption particle based on Example 1, and the specific preparation process is as follows:

[0190] (1) Preparation of photocatalysts

[0191] Weigh 1.0 g of Bi(NO3)3·5H2O and dissolve it in 50 mL of dilute nitric acid (0.1 mol / L) to obtain a homogeneous and clear solution; then slowly add 20 mL of KCl solution (0.2 mol / L), stir for 2 h, let stand for 6 h, wash the precipitate after the reaction, and dry to obtain BiOCl nanosheet powder.

[0192] 5.0 g of melamine was weighed and placed in a porcelain boat, and then calcined in a muffle furnace in two stages. First, the temperature was raised to 350 °C and held for 2 h, and then raised to 550 °C and held for 4 h to obtain g-C3N4 microparticle powder.

[0193] BiOCl nanosheets and g-C3N4 microparticles were mixed at a mass ratio of 3:1. The mixture was added to a mixed solvent system (ethylene glycol and water in a volume ratio of 1:1). The reaction system was placed at 150 °C for in-situ solvothermal composite reaction for 8 h, so that BiOCl was uniformly crystallized and deposited on the surface of g-C3N4 to form a stable double Z-type heterojunction photocatalyst powder.

[0194] (2) Preparation of polysaccharide matrix solution

[0195] Weigh 2.0 g of KGM and add it to 100 mL of deionized water. Stir and dissolve at 60 °C. Add 0.5 g of citric acid (as a natural cross-linking agent), 20 mL of graphene oxide (concentration 1 mg / mL), and 0.2 g of cocamidopropyl betaine to the solution and stir until homogeneous to obtain a uniform polysaccharide matrix solution.

[0196] (3) Photocatalyst and matrix composite

[0197] 0.5 g of double Z-type heterojunction catalyst powder was added to 50 mL of the above polysaccharide matrix solution, and ultrasonicated (300 W, 15 min). Then, mechanical stirring was continued at 300 rpm for 20 min to obtain a uniform double Z-type heterojunction photo-matrix precursor solution.

[0198] (4) Preparation of precursor solutions with hierarchical porous structures

[0199] The double Z-type heterojunction optical-matrix precursor solution was placed in a constant temperature reactor and aerated at 35°C and 0.150 MPa nitrogen pressure for 6 min to form a precursor solution with a multi-level pore structure of macropore-mesopore-micropore synergy.

[0200] (5) Preparation of multi-level porous particles

[0201] The precursor solution with a multi-level porous structure was transferred into a reaction vessel, placed in a water bath, and reacted at 90°C for 6 hours to obtain multi-level porous particles.

[0202] (6) Surface functionalization modification

[0203] The obtained porous particles were placed in a mixture containing 5% β-cyclodextrin solution and 1% ethylenediamine solution, the pH was adjusted to 8.5, and the reaction was carried out at room temperature for 12 hours. After the reaction was completed, the particles were washed and dried to obtain photocatalytic adsorption particles with cyclodextrin cavities and amino functional groups on the surface.

[0204] Comparative Example 4 was modified from Example 1 by using traditional water bath heating (90℃ / 6h) for crosslinking molding. The water bath temperature was 90℃ throughout the process, lasting for 6 hours. The remaining steps were the same as in Example 1.

[0205] Performance tests were conducted on the photocatalytic adsorption particles prepared in Comparative Example 4. Microscopic observation revealed surface collapse, indistinct pore structure, and a significantly reduced specific surface area. Tetracycline adsorption performance: the removal rate was nearly 58% after 25 hours, with a slow decline in the adsorption curve. Analysis: Conventional heating methods resulted in uneven cross-linking, difficulty in stabilizing and locking the pore structure, poor dispersion of the photocatalyst components, and a significant decrease in performance.

[0206] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing photocatalytic adsorption particles for wastewater treatment, characterized in that, Includes the following steps: Step 1: BiOCl nanosheets and graphitic carbon nitride are mixed and dissolved at a mass ratio of 1~3:1~3, and the mixture is subjected to in-situ solvothermal reaction at 120℃~160℃ for 6 h~12 h to obtain a heterojunction photocatalyst. Step 2: Dissolve konjac glucomannan, add citric acid, graphene oxide dispersion and nonionic surfactant, stir evenly to obtain polysaccharide matrix solution, wherein the mass ratio of konjac glucomannan to citric acid, graphene oxide and nonionic surfactant is 100:(5-30):(5-25):(1-8); Step 3: Add the heterojunction photocatalyst to the polysaccharide matrix solution, first ultrasonically disperse it at 200 W ~ 400 W for 10 min ~ 20 min, then stir at 200 rpm ~ 400 rpm for 20 min ~ 40 min to obtain the heterojunction photo-matrix precursor solution; Step 4: Place the heterojunction optical-matrix precursor solution in a reactor and introduce nitrogen gas at 25 ℃~45 ℃ to obtain a precursor solution with a multi-level porous structure; the nitrogen gas pressure is 0.05 MPa~0.20 MPa and the introduction time is 3 min~10 min. Step 5: Place the precursor solution with a multi-level porous structure in a microwave reactor and solidify it for 2 min to 5 min at a power of 400 W to 800 W to obtain multi-level porous particles. Step 6: The multi-level porous particles are immersed in a mixed solution containing β-cyclodextrin and ethylenediamine at 25 ℃ to 40 ℃. The pH is adjusted to 8 to 9 and the reaction is carried out at room temperature for 10 h to 14 h. After filtration and drying, the photocatalytic adsorption particles are finally obtained.

2. The method for preparing photocatalytic adsorption particles for wastewater treatment according to claim 1, characterized in that, In step 1, the BiOCl nanosheets are obtained by reacting bismuth salt and chloride with dilute nitric acid as solvent and allowing the reaction to proceed at room temperature for 6 to 10 hours. The graphitic carbon nitride is specifically prepared by calcining melamine or urea. The calcination is carried out at 300°C to 350°C for 1 to 2 hours, followed by heating to 500°C to 550°C and holding for 3 to 5 hours.

3. A photocatalytic adsorption particle for wastewater treatment, characterized in that, It is prepared by the preparation method described in claim 1.

4. The application of the photocatalytic adsorption particles for wastewater treatment as described in claim 3 in the degradation of organic pollutants in wastewater.

5. The application according to claim 4, characterized in that, The organic pollutant is any one or a mixture of tetracycline antibiotics, quinolone antibiotics, sulfonamide antibiotics, and macrolide antibiotics.

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