A photo-oxidation-driven self-healing, self-supporting, floating multiphase reaction system, its construction method, and its application.

Abstract

This invention discloses a photo-oxidation-driven self-healing, self-supporting, floating multiphase reaction system, its construction method, and its application. Specifically, a self-supporting framework based on a bacterial cellulose (BC) and chitosan (CS) crosslinked network is constructed, and heterojunction catalytic components are loaded via in-situ chemical deposition to achieve Fe... x O y In-situ confined anchoring of the multiphase reaction matrix of -CeO2 active sites. This invention covers a dual application paradigm from wastewater treatment (large-scale deployment) to high-purity water purification (modular filter membrane), greatly reducing energy consumption and operation and maintenance costs in wastewater treatment and high-purity water purification, and has significant industrial application value.

Description

Technical Field

[0001] This invention belongs to the technical fields of wastewater treatment, water purification and functional materials, and provides a photo-oxidation driven self-healing self-supporting floating multiphase reaction system, its construction method and application. Background Technology

[0002] With the acceleration of urbanization, the composition of urban sewage (including domestic sewage, medical wastewater, and industrial runoff) is becoming increasingly complex, containing large amounts of organic matter, pathogens, antibiotics, and endocrine disruptors. Taking the Chongqing Caiyun Lake sewage treatment demonstration project as an example, despite preliminary physicochemical treatment and tiered wetland natural purification, the aquatic ecosystem still faces the threat of persistent pollutants, and fish in the lake are not recommended for consumption due to bioaccumulation. This situation indicates that relying on the traditional "sewage treatment plant + natural purification" model is insufficient to completely solve the problem of persistent organic pollutant residues, and there is an urgent need to develop more efficient deep purification technologies.

[0003] Chlorinated organic compounds, among the first persistent organic pollutants listed in the Stockholm Convention, have become a major challenge in water treatment due to their high toxicity, environmental persistence, and strong bioaccumulation. Because the carbon-chlorine (C-Cl) bond has extremely high bond energy, it exhibits strong chemical inertness in traditional biodegradation or conventional chemical oxidation processes, making it difficult to degrade into harmless small molecules.

[0004] Currently, the main methods for treating such pollutants include solvent extraction, physical adsorption, and advanced oxidation processes (AOPs): Solvent extraction: complex process, high solvent cost, and prone to secondary biotoxicity; Physical adsorption: can only achieve spatial transfer of pollutants, limited by adsorption capacity and difficult to achieve complete mineralization of pollutants; Advanced oxidation processes (AOPs): although they can convert large molecules into small molecules, they often face problems such as slow free radical generation rate and difficulty in overcoming kinetic bottlenecks when treating highly stable chlorinated pollutants.

[0005] Although photocatalytic-assisted advanced oxidation technology is considered the most promising solution due to its advantages such as high efficiency, low energy consumption, and environmental friendliness, its engineering application in open water areas (such as Caiyun Lake) is still limited by the following bottlenecks: 1. Powder recycling problem: Traditional photocatalysts are mostly in the form of nanoparticles, which are difficult to recycle after application. This not only causes the loss of active components, but may also generate potential nanomaterial pollution. 2. Light transmittance limitation: Turbidity in water can lead to light attenuation, reducing the light energy utilization rate of the catalyst; 3. Lack of functional regeneration: During operation, the catalyst is easily encapsulated by organic matter and deactivated (membrane fouling). Conventional high-temperature sintering regeneration has low energy efficiency and will damage the structure of the support.

[0006] In conclusion, developing a novel multiphase reaction system that combines high catalytic activity, self-supporting structure, self-floating properties, and in-situ regeneration capabilities is of significant practical importance. Inspired by the phytoplankton frames in Chongqing Caiyun Lake National Wetland Park, constructing a three-dimensional network using biomass materials and confining and anchoring highly efficient catalytic sites is not only crucial for achieving the complete degradation of chlorinated organic compounds but also a core pathway for transforming wastewater treatment from a "resource-intensive" model to a "green and sustainable paradigm."

[0007] Membrane fouling is a well-known and persistent problem in the water purification industry. Although existing water purification systems incorporate physical backwashing or chemical cleaning processes, these methods are largely ineffective against large organic molecules that have penetrated the membrane pores. Physical backwashing can only remove the loose surface layer and is powerless against deep-seated fouling within the pores; chemical cleaning involves strong acids, strong alkalis, or oxidizing agents (such as sodium hypochlorite), which are not only complex to operate and generate secondary pollutants, but also cause chemical damage to the delicate structure of the filter membrane itself, accelerating its aging and failure. To restore membrane flux, some industrial solutions attempt to use high-temperature sintering or strong oxidizing solvent treatment, but these methods are extremely energy-intensive. For biomass-based or flexible polymer filter membranes, high-temperature environments can directly lead to framework carbonization or collapse. This "consuming more energy for regeneration" model severely limits the engineering implementation of regenerable filter membranes.

[0008] Therefore, developing a membrane filter system with "in-situ, green, and non-destructive" regeneration capabilities is of significant engineering importance. By introducing a photo-oxidation driven paradigm, and utilizing the strong oxidizing free radicals generated by photocatalytically assisted advanced oxidation (PC-AOPs), pollutants accumulated within the membrane can be directly mineralized and removed at room temperature and pressure. This approach transforms the membrane filter from a "disposable consumable" into a "recyclable functional unit," significantly reducing the operating costs of water purification systems and achieving true energy self-sufficiency and resource conservation in water treatment by extending membrane lifespan. Summary of the Invention

[0009] In view of this, the purpose of this invention is to provide a photo-oxidation driven self-healing self-supporting floating multiphase reaction system, its construction method and application, which aims to solve the problems of difficult recovery, easy loss, high regeneration energy consumption and difficulty in morphological integration faced by traditional powder catalysts in water treatment.

[0010] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for constructing a photo-oxidation-driven self-healing, self-supporting, floating multiphase reaction system, the specific steps of which are as follows: S1. First, bacterial cellulose (BC) and chitosan (CS) are used as raw materials to prepare BC emulsion and CS solution respectively. Then, the BC emulsion and CS solution are mixed evenly to obtain BC-CS emulsion. S2. Then, dissolve the water-soluble iron salt and aqueous cerium salt in deionized water to obtain the corresponding aqueous solutions. Next, add these aqueous solutions to the BC-CS emulsion, stir thoroughly, add ammonia solution dropwise, and stir vigorously to obtain a mixed solution. S3. Finally, glutaraldehyde solution was slowly added dropwise to the mixed solution, and the mixture was stirred until a gel was formed. After post-treatment, the heterostructure @BC-CS aerogel was obtained. The heterostructure @BC-CS aerogel is selected from: Fe-CeO2@BC-CS aerogel, Fe-Fe2O3-CeO2@BC-CS aerogel, Fe3O4-CeO2@BC-CS aerogel or Fe2O3-CeO2@BC-CS aerogel.

[0011] Preferably, in step S1, the preparation method of the BC emulsion is as follows: First, the bacterial cellulose (BC) is washed and transferred to a 0.05M ammonia solution, stirred for 1 hour, and the solid is collected by suction filtration; then, the solid is added to the first part of deionized water, and the pH value of the solution is adjusted to neutral with 1% dilute acetic acid to obtain a sheet-like transparent gel; finally, the sheet-like transparent gel is removed from the water, crushed using a juicer, a portion is dried to determine the solid content, and the remaining crushed gel is added to the second part of deionized water to prepare a BC emulsion with a solid content of 2 wt%, thus obtaining the BC emulsion.

[0012] More preferably, the mass ratio of BC, ammonia solution, and the first part of deionized water is 1:100:100, and the concentration of the ammonia solution is 0.05M.

[0013] Preferably, in step S1, the CS solution is prepared by dissolving chitosan CS in dilute acetic acid solution by stirring to obtain the CS solution.

[0014] Preferably, in step S1, the volume ratio of BC emulsion to CS solution is 7:3, the solid content of BC emulsion is 2 wt%, and the mass concentration of CS solution is 2%.

[0015] Preferably, in steps S2 and S3, the water-soluble iron salt and water-soluble cerium salt are FeCl3·6H2O, FeCl2·4H2O, and Ce(NO3)3·6H2O, respectively. The ratio of deionized water, BC-CS emulsion, ammonia solution, and glutaraldehyde solution is 702.5 mg: 257.5 mg: 611.4 mg: 10 mL: 150 mL: 5 mL: 1 mL, wherein the mass concentration of the ammonia solution is 25% and the mass concentration of the glutaraldehyde solution is 2.5%. The corresponding product is Fe3O4-CeO2@BC-CS aerogel.

[0016] Further preferred post-treatment methods are liquid nitrogen quick-freezing and vacuum freeze-drying. The liquid nitrogen quick-freezing time is 5–10 minutes, and the specific process conditions for vacuum freeze-drying are: vacuum degree 10 Pa and cold trap temperature -50℃. Liquid nitrogen quick-freezing is a pre-freezing stage, the purpose of which is to quickly freeze and form solids, while vacuum drying is a sublimation stage, where water evaporates and pores are left.

[0017] Preferably, in steps S2 and S3, the water-soluble iron salt and water-soluble cerium salt are FeCl3·6H2O and Ce(NO3)3·6H2O, respectively, and the ratio of deionized water, BC-CS emulsion, ammonia solution, and glutaraldehyde solution is 702.5 mg: 611.4 mg: 10 mL: 150 mL: 5 mL: 1 mL, wherein the mass concentration of the ammonia solution is 25% and the mass concentration of the glutaraldehyde solution is 2.5%; the corresponding product is Fe2O3-CeO2@BC-CS aerogel.

[0018] Further preferred post-treatment methods are liquid nitrogen quick-freezing and vacuum freeze-drying. The liquid nitrogen quick-freezing time is 5 to 10 minutes, and the specific process conditions for vacuum freeze-drying are: vacuum degree 10 Pa and cold trap temperature -50℃.

[0019] Preferably, in steps S2 and S3, the water-soluble iron salt and water-soluble cerium salt are FeCl3·6H2O and Ce(NO3)3·6H2O, respectively, which are dissolved in deionized water to obtain a 1mM FeCl3 solution and a 2mM Ce(NO3)3 solution; the preparation method of the mixed solution is as follows: the FeCl3 solution is added to the BC-CS emulsion, stirred thoroughly, 1.5M NaBH4 solution is added dropwise for reduction, then Ce(NO3)3 solution is added, stirring is continued, 0.01M KOH solution is added dropwise, and stirring is vigorous to obtain the product; the corresponding product is Fe-Fe2O3-CeO2@BC-CS aerogel.

[0020] More preferably, the ratio of FeCl3 solution, Ce(NO3)3 solution, BC-CS emulsion, NaBH4 solution, KOH solution, and glutaraldehyde solution is 20mL:10mL:10mL:100μL:10mL:1mL, wherein the mass concentration of glutaraldehyde solution is 2.5%.

[0021] A further preferred post-processing method is liquid nitrogen quick-freezing, vacuum freeze-drying, and calcination. The liquid nitrogen quick-freezing time is 5–10 minutes. The vacuum freeze-drying process conditions are: vacuum degree 10 Pa, cold trap temperature -50°C. The calcination process conditions are: calcination at 250°C for 2 hours under an inert atmosphere. Biomass typically begins to coke at 250°C, which in this invention forms a "carbon / metal composite structure," enhancing conductivity and stability.

[0022] The present invention also provides a photo-oxidation-driven self-healing, self-supporting, floating multiphase reaction system, which is obtained by the aforementioned construction method.

[0023] The present invention also provides the application of the aforementioned photo-oxidation driven self-healing self-supporting floating multiphase reaction system in wastewater treatment.

[0024] Preferably, the aforementioned photo-oxidation-driven self-healing, self-supporting, floating multiphase reaction system is used in the degradation of organic pollutants in wastewater.

[0025] Preferably, the organic pollutant is methylene blue and 4-chlorophenol.

[0026] The beneficial effects of this invention are: This invention provides a photo-oxidation-driven self-healing, self-supporting, floating multiphase reaction system, its construction method, and its application. Specifically, a flexible self-supporting framework based on a bacterial cellulose (BC) and chitosan (CS) crosslinked network is constructed, and heterojunction catalytic components are loaded via in-situ chemical deposition to achieve Fe... x O y In-situ confined anchoring of the multiphase reaction matrix of (Fe-Fe2O3, Fe3O4 or Fe2O3)-CeO2 active sites.

[0027] This invention has the following advantages: 1. High stability: This invention uses bacterial cellulose (BC) and chitosan (CS) as raw materials. Under the cross-linking effect of glutaraldehyde, a BC-CS composite gel with a chemically cross-linked structure is formed through the condensation reaction of aldehyde groups and amino groups, thereby improving the mechanical strength and water resistance of the resulting self-supporting structure.

[0028] This invention introduces metal precursors simultaneously during the gelation process, achieving spatially confined distribution of active sites. Specifically, iron salts (FeCl3, FeCl2) and cerium salts (Ce(NO3)3) are added to the BC-CS emulsion in a predetermined ratio. The abundant hydroxyl and amino groups on the surfaces of BC and CS are used to electrostatically adsorb and complex metal ions. The pH of the system is adjusted to induce in-situ nucleation of metal ions on the surface of biomass fibers, forming Fe... x O y -CeO2 heterostructure.

[0029] To meet the demand for high performance, this invention further introduces a strong reducing agent (NaBH4) to reduce the iron in situ to generate nano-zero valent iron, which is then calcined by programmed temperature rise (250°C, inert atmosphere) to form a Fe-Fe2O3-CeO2 composite system with a high electron transfer rate.

[0030] Therefore, this invention employs an in-situ synthesis method to firmly embed heterojunctions into a 3D network, preventing the detachment of nanocatalysts and the leaching of active species, thus ensuring the structural stability and environmental safety of the catalytic system.

[0031] 2. Low energy consumption: This invention utilizes the coupling effect of photocatalytic assisted advanced oxidation (PC-AOPs) to generate strong oxidizing free radicals in situ under photo-assisted conditions, thoroughly mineralizing deposited contaminants inside and on the surface of the matrix, and removing organic impurities attached to the skeletal pores in situ, thereby achieving performance steady-state maintenance and regeneration that is not dependent on thermal treatment.

[0032] This invention eliminates the need for high-temperature sintering required for traditional catalyst regeneration, and can restore more than 90% of flux and activity by using ultraviolet light.

[0033] 3. Wide applicability: This invention utilizes liquid nitrogen rapid freezing combined with vacuum freeze-drying technology to form an aerogel with a highly developed three-dimensional interpenetrating macroporous structure, i.e., an apparent density of less than 30–50 mg / cm³. 3 A self-supporting floating reaction matrix.

[0034] Macroscopic buoyancy: Relying on the ultralight properties of the BC-CS skeleton, the matrix floats stably at the gas-liquid-solid three-phase interface, supporting physical retrieval.

[0035] Microscopic magnetic attraction: In addition to macroscopic suspension, Fe3O4-CeO2@BC-CS aerogel with in-situ generated magnetic Fe3O4 components also supports precise capture driven by an external magnetic field.

[0036] Therefore, this invention utilizes intrinsic low density to achieve interface self-floating to support macroscopic physical salvage, and coordinates with internal magnetic lattice to achieve microscopic directional capture, thus solving the problem of full-scale recovery in open water and confined spaces.

[0037] This invention can be used as a floating purification unit in open water or integrated into a water purification device as a filter membrane with self-purification function.

[0038] 4. Environmentally friendly: This invention uses a pure biomass substrate (BC / CS), which has excellent biodegradability and ecological compatibility.

[0039] In summary, this invention covers a dual application paradigm from wastewater treatment (large-scale deployment) to high-purity water purification (modular filter membrane), which greatly reduces the energy consumption and operation and maintenance costs of wastewater treatment and high-purity water purification, and has significant industrial application value.

[0040] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 Flowchart of the construction method of this invention; Figure 2 Schematic diagram of the microstructure of BC-CS aerogel and Fe3O4-CeO2@BC-CS aerogel; Figure 3 The schematic diagram of material recycling of the present invention includes: A: the mass of the prepared aerogel (diameter 2 cm, height 1 cm), with the density calculated as the average value; B: flotation experiments of Fe-Fe2O3-CeO2@BC-CS aerogel (Ⅰ), Fe3O4-CeO2@BC-CS aerogel (Ⅲ), and Fe2O3-CeO2@BC-CS aerogel (Ⅱ); C: magnetic attraction experiments of Fe-Fe2O3-CeO2@BC-CS aerogel, Fe3O4-CeO2@BC-CS aerogel, and Fe2O3-CeO2@BC-CS aerogel; D: demonstration experiment using the prepared aerogel as an integrated filter membrane. Figure 4 Schematic diagram of photo-oxidation-driven in-situ self-healing of Fe3O4-CeO2@BC-CS aerogel; Figure 5Comparison of photocatalytic degradation performance of Fe-Fe2O3-CeO2@BC-CS (A), Fe3O4-CeO2@BC-CS (B) and Fe2O3-CeO2@BC-CS (C) using UV-vis analysis (sampling at 5-minute intervals from 0 to 30 min). Figure 6 Comparison of methylene blue degradation after Fe3O4-CeO2@BC-CS recycling; Figure 7 XRD (A) and SEM (B) images of Fe3O4-CeO2@BC-CS aerogel; Figure 8 XRD (A) and XPS (B) images of Fe-Fe2O3-CeO2@BC-CS aerogel; Figure 9 Pure BC aerogel is fragile; Figure 10 BC:CS = 3:7, exhibiting excellent mechanical stability; Figure 11 The effect of different BC:CS ratios on material properties during the preparation of Fe2O3-CeO2@BC-CS aerogel; where the left side shows BC:CS = 5:5 and the right side shows BC:CS = 7:3. Figure 12 The effect of crosslinking agent concentration, where A represents upright placement and B represents inverted placement; Figure 13 A comparison of nano-cerium dioxide, nano-ferric oxide, and nano-cerium dioxide-nano-ferric oxide composite materials; Figure 14 Comparison of the buoyancy of materials: on the left, aerogels with a high proportion of active ingredients settle, while those with a high proportion of active ingredients float. Figure 15 Photocatalytic degradation of 4-chlorophenol using Fe3O4-CeO2@BC-CS. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its content.

[0043] Reference Implementation Preparation of BC-CS emulsion Preparation of BC emulsion: First, the bacterial cellulose (BC) is washed and transferred to a 0.05M ammonia solution, stirred for 1 hour, and the solid is collected by suction filtration. Then, the solid is added to the first part of deionized water, and the pH of the solution is adjusted to neutral with 1% dilute acetic acid to obtain a sheet-like transparent gel. Finally, the sheet-like transparent gel is removed from the water, crushed using a juicer, and a portion is dried to determine the solid content. The remaining crushed gel is then added to the second part of deionized water to prepare a BC emulsion with a solid content of 2%, which is the BC emulsion mentioned above.

[0044] The mass ratio of BC, ammonia solution, and deionized water in the first part is 1:100:100, and the concentration of the ammonia solution is 0.05M.

[0045] Preparation of CS solution: Dissolve chitosan (CS) powder in a 1% (w / w) dilute acetic acid solution to obtain a 2% (w / w) CS solution.

[0046] Take 30 mL of the prepared CS solution and 70 mL of BC emulsion, and add them to a 250 mL beaker. Mix thoroughly with magnetic stirring to obtain the BC-CS emulsion.

[0047] Example 1

[0048] Preparation of Fe3O4-CeO2@BC-CS aerogel 702.5 mg FeCl3·6H2O, 257.5 mg FeCl2·4H2O, and 611.4 mg Ce(NO3)3·6H2O were dissolved in 10 mL of deionized water, respectively, and then added to 150 mL of BC-CS emulsion. Under mechanical stirring, the metal ions were fully adsorbed onto BC and CS. Then, 5 mL of 25% ammonia solution was added dropwise, and vigorous stirring continued for 1 hour. Finally, 1 mL of 2.5% glutaraldehyde (GA) solution was slowly added dropwise to the mixture, and stirring was accelerated until a gel formed. The gel was then rapidly frozen in liquid nitrogen and freeze-dried under vacuum to obtain Fe3O4-CeO2@BC-CS aerogel. Figure 7 ).

[0049] Example 2

[0050] Preparation of Fe2O3-CeO2@BC-CS aerogel Dissolve 702.5 mg FeCl3·6H2O and 611.4 mg Ce(NO3)3·6H2O separately in 10 mL of deionized water, then add them to 150 mL of BC-CS emulsion. Under mechanical stirring, allow the metal ions to fully adsorb onto BC and CS. Then, add 5 mL of 25% ammonia water dropwise, and continue vigorous stirring for 1 hour. Next, slowly add 1 mL of 2.5% glutaraldehyde (GA) solution to the mixture, continuing to accelerate stirring until a gel forms. Quickly freeze in liquid nitrogen and freeze-dry under vacuum to obtain Fe2O3-CeO2@BC-CS aerogel.

[0051] Example 3

[0052] Preparation of Fe-Fe2O3-CeO2@BC-CS aerogel Prepare 20 mL of 1 mM FeCl3 solution and add it to the BC-CS emulsion. Stir vigorously to allow for complete adsorption, then add 100 µL of 1.5 M NaBH4 for reduction. Next, add 10 mL of 2 mM Ce(NO3)3 solution and continue stirring for 30 minutes. Add 10 mL of 0.01 M KOH solution dropwise, then slowly add 1 mL of 2.5% glutaraldehyde (GA) solution to the mixture, continuing to stir rapidly until a gel forms. Quickly freeze in liquid nitrogen, freeze-dry under vacuum, and calcine at 250 °C in an inert atmosphere for 2 hours to obtain Fe-Fe2O3-CeO2@BC-CS aerogel. Figure 1 , Figure 8 ) Comparative Example 1 Preparation of BC aerogel Weigh a certain amount of bacterial cellulose (BC), wash it with deionized water to remove impurities, transfer it to a 0.05 M ammonia solution and stir for 1 hour, then filter it; add the solid product back into deionized water and adjust the pH of the solution to neutral with dilute acetic acid; crush the resulting sheet-like transparent gel with a juicer to obtain BC emulsion.

[0053] 100 mL of BC emulsion was poured into polytetrafluoroethylene (PTFE) molds of different sizes, and then these molds were placed in a foam box. Subsequently, 500 mL of liquid nitrogen was added to the foam box to rapidly freeze the BC in the PTFE molds. Then, they were transferred to a freeze dryer for further freeze-drying to obtain BC aerogel.

[0054] BC aerogel has the following problems: Structural limitations: Although BC has extremely high crystallinity and mechanical strength, its fibers are mainly bonded by hydrogen bonds. In humid environments or under strong compression, the fibers are prone to displacement, resulting in poor resilience and easy structural collapse.

[0055] Limited functionality: BC itself is chemically inert and has few surface-active groups (mainly hydroxyl groups), resulting in limited metal adsorption capacity.

[0056] Brittleness issue: Dried pure BC aerogel is brittle and lacks toughness. Figure 9 ) Comparative Example 2 Preparation of CS aerogel Chitosan (CS) powder was dissolved in dilute acetic acid solution to obtain a 2% CS solution.

[0057] Take 30 ml of the prepared CS solution and slowly add 1 ml of 2.5% glutaraldehyde (GA) solution, continuing to stir rapidly until a gel forms. Quick freezing with liquid nitrogen and vacuum freeze-drying failed to achieve gelation.

[0058] CS aerogel has the following problems: Extremely low mechanical strength: CS is an amorphous or low-crystallinity polymer with good film-forming properties but poor ability to form a "skeleton". Pure CS aerogel is usually very soft and brittle, and will turn into powder under slight pressure, making it difficult to use as a structural material independently.

[0059] Poor water resistance: Chitosan is highly soluble in acidic environments and readily swells or even partially dissolves in pure water. Without cross-linking, it will rapidly disintegrate in water treatment or biomedical applications.

[0060] Pore ​​size is difficult to control: Pure CS is difficult to form a continuous and stable nanonetwork during the freezing process, and is prone to forming large sheet structures.

[0061] Comparative Example 3 Preparation of BC-CS aerogel Weigh a certain amount of bacterial cellulose (BC), wash it with deionized water to remove impurities, transfer it to a 0.05 M ammonia solution and stir for 1 hour, then filter it; add the solid product back into deionized water and adjust the pH of the solution to neutral with dilute acetic acid; crush the resulting sheet-like transparent gel with a juicer to obtain BC emulsion.

[0062] Chitosan (CS) powder was dissolved in dilute acetic acid solution to obtain a 2% CS solution.

[0063] Take 30 mL of the prepared CS solution and 70 mL of the BC emulsion, and add them to a 250 mL beaker. Mix thoroughly with magnetic stirring. Slowly add 1 mL of 2.5% glutaraldehyde (GA) solution to the mixture, and continue stirring until a gel forms. Quickly freeze in liquid nitrogen and freeze-dry under vacuum to obtain BC-CS aerogel. A comparison of its microstructure with Fe3O4-CeO2@BC-CS aerogel can be found in [link to table]. Figure 2 .

[0064] BC and CS ratio screening: The volume ratio of BC emulsion to CS solution is 9:1, and the resulting BC-CS aerogel is fragile.

[0065] A BC-CS aerogel with a volume ratio of 7:3 to BC emulsion and CS solution exhibits good mechanical stability. Figure 10 ) The BC-CS aerogel with a volume ratio of 5:5 exhibits excellent mechanical stability.

[0066] Two BC-CS aerogels with good mechanical stability were further composited with Fe2O3-CeO2 to obtain Fe2O3-CeO2@BC-CS aerogel. After stirring in water for 24 hours, the Fe2O3-CeO2@BC-CS aerogel with a volume ratio of BC emulsion to CS solution of 5:5 dispersed. Figure 11 This is because CS itself will cause severe swelling and structural collapse.

[0067] Table 1 summarizes the performance comparison of the three aerogels obtained in Comparative Examples 1 to 3.

[0068] Table 1. Comparison of different aerogels Comparative Examples 1-3 lead to the conclusion that BC-CS cross-linked composites have an advantage of "1+1>2", as detailed below: 1. Forming a "reinforced concrete" structure On a physical level: BC nanofibers act as "steel bars" to provide a rigid framework, while CS acts like "cement" to wrap and fill the gaps between the fibers.

[0069] At the chemical level, glutaraldehyde (GA) acts as a bridge between the two. The aldehyde group of GA forms covalent bonds (such as Schiff base bonds) with the amino group of CS and the hydroxyl group of BC (or between CS chains). This three-dimensional cross-linked network greatly improves the compressive strength and shape stability of the aerogel.

[0070] 2. Excellent water resistance and chemical stability Through cross-linking, CS changes from "easily swollen" to "non-swollen". The composite aerogel can maintain its shape in solution and will not easily fall apart, which expands its application range (such as wastewater treatment).

[0071] 3. Enhanced functional activity CS introduces a large number of amino groups (-NH2). These groups endow the aerogel with strong adsorption properties, enabling it to efficiently chelate metal ions, facilitating subsequent in-situ anchoring of metal ions and the preparation of Fe. x O y-CeO2@BC-CS provides a rich set of functional groups.

[0072] 4. Precise control of microstructure BC limits the excessive expansion of CS, while the introduction of CS modulates the pore size distribution of BC. Under liquid nitrogen quick-freezing process, this composite system can form a more uniform hierarchical porous structure, which not only has low density but also huge specific surface area.

[0073] Comparative Example 4 Screening of glutaraldehyde solution dosage Maintain the volume ratio of BC emulsion to CS solution at 7:3, and vary the amount or concentration of GA added.

[0074] Group 1: No GA added (physical mixing, as a negative control, to prove that without cross-linking, it will disintegrate); Group 2: relative to the total volume, 1 mmol / L GA, reaction time 6 hours, no gel formed; Group 3: relative to total volume, 2.5 mmol / L GA, gelation time 30 minutes; Group 4: relative to the total volume, 5 mmol / L GA, gelation time 5 minutes (glutaraldehyde is biotoxic and should be used in the smallest possible amount to achieve the purpose of cross-linking).

[0075] Test indicators: gel time (gel speed), water resistance (whether it falls apart when soaked in water), and microstructure (SEM observation of the degree of cross-linking).

[0076] Expected results: Too little GA will result in incomplete cross-linking and unstable structure; too much GA will cause the aerogel to become brittle, turn yellow, and become toxic.

[0077] See results Figure 12 .

[0078] Comparative Example 5 Freezing conditions screening This invention uses liquid nitrogen for quick freezing, which is significantly different from ordinary refrigerator freezing and ultra-low temperature freezers.

[0079] Experimental Design: Process 1: Rapid freezing with liquid nitrogen at -196℃, completed in 5-10 minutes. The extreme supercooling leads to instantaneous nucleation, forming extremely fine and uniform ice crystals. These crystals have small, evenly distributed pores, exhibiting a honeycomb structure and high strength. They also have a large specific surface area and a density of 32 mg / cm³. 3 .

[0080] Process 2: Freezing at -20℃ in a conventional refrigerator, taking approximately 5 hours; extremely slow cooling allows ample time for ice crystals to grow, forming large, irregular crystals. The pores are huge and uneven, the framework is prone to collapse, and the specific surface area is low. Density: 65 mg / cm³3 .

[0081] Process 3: -80℃ ultra-low temperature freezing, requiring more than 2 hours, demanding specific equipment, and not easily industrialized. Specific surface area is between that of the -20℃ process and the liquid nitrogen process. Density: 43 mg / cm³ 3 .

[0082] To ensure better buoyancy of the catalyst, low density and structural stability are important. Considering practical application value, liquid nitrogen quick-freezing is preferable.

[0083] Comparative Example 6 Heterojunction screening Fe3O4-CeO2@BC-CS aerogel, Fe2O3-CeO2@BC-CS aerogel, and Fe-Fe2O3-CeO2@BC-CS aerogel were prepared according to the methods in Examples 1 to 3, respectively.

[0084] Commercially available nano-Fe3O4, nano-CeO2 (purchased from Aladdin), and MnO2 were used in the following experiments. Nano-Fe3O4 (single iron group), nano-CeO2 (single cerium group), and nano-MnO2-nano-CeO2 composite material (replacement group, replacing Fe3O4 with equimolar MnO2) were tested. Results showed that the single iron group had a slow degradation rate, indicating that Ce can accelerate the iron cycle; the single cerium group degraded extremely slowly, indicating that Fe is the main active site; when using manganese dioxide, commonly used in Fenton oxidation, to replace iron(III) oxide, the MnO2-CeO2 replacement group performed worse than the nano-Fe3O4-nano-CeO2 composite material, indicating that Fe had the best redox potential match. Catalytic testing experiment: 50 mg of catalyst and 50 mg of PMS were added to 100 ml of 30 ppm methylene blue solution. The reaction was carried out under light irradiation for 10 minutes, and UV-vis was measured to calculate the degradation rate. Figure 13 ) in conclusion: Fe-Ce heterojunctions exhibit significant catalytic synergistic effects.

[0085] 1. Heterojunction effect: The activity of single components is much lower than that of composite components, which confirms that a type II heterojunction is formed between Fe3O4 and CeO2, which accelerates the separation of photogenerated carriers.

[0086] 2. Electron shuttle mechanism: The introduction of Ce ions constructs Ce... 3+ / Ce 4+ The redox pair, acting as an "electron shuttle," promotes the oxidation of Fe. 3+ To Fe 2+ The regeneration of iron solves the bottleneck of slow iron cycling in the Fenton reaction.

[0087] Comparative Example 7 Floatability and stability screening The BC-CS framework and the specific Fe-Ce loading achieved a density balance, which ensured natural light contact without sinking to the bottom and causing catalytic dead zones.

[0088] Following the method in Example 2, Fe2O3-CeO2@BC-CS aerogel was obtained, which can float.

[0089] In Example 2, the dosage was adjusted so that the material would sink to the bottom if the dosage exceeded 100 mmol FeCl3·6H2O and 100 mmol Ce(NO3)3·6H2O.

[0090] See details Figure 14 .

[0091] Figure 3 The schematic diagram of material recycling of the present invention includes: A: the mass of the prepared aerogel (diameter 2 cm, height 1 cm), with the density calculated as the average value; B: flotation experiment of Fe-Fe2O3-CeO2@BC-CS aerogel, Fe3O4-CeO2@BC-CS aerogel, and Fe2O3-CeO2@BC-CS aerogel; C: magnetic attraction experiment of Fe-Fe2O3-CeO2@BC-CS aerogel, Fe3O4-CeO2@BC-CS aerogel, and Fe2O3-CeO2@BC-CS aerogel; D: demonstration experiment of using the prepared aerogel as an integrated filter membrane.

[0092] Catalytic performance evaluation Methylene blue was used as a simulated pollutant in this experiment. 100 mg of the prepared aerogel was added to 200 mL of a 200 ppm methylene blue solution, followed by 20 mmol / L persulfate (PMS) for degradation. For the photocatalytic experiment, a 300 W light source was placed 30 cm above the reaction flask. 1.5 mL of solution was taken at regular intervals, and the concentration of remaining methylene blue was measured using UV-vis, or the color change was directly observed to evaluate the ability of the designed catalyst to degrade the pollutant. A comparison of the photocatalytic degradation performance of methylene blue by Fe-Fe2O3-CeO2@BC-CS aerogel, Fe3O4-CeO2@BC-CS aerogel, and Fe2O3-CeO2@BC-CS aerogel is shown in [link to relevant documentation]. Figure 5 It is evident that catalysts containing low-valent iron exhibit better photo-assisted Fenton catalysis performance, with the performance order being: Fe-Fe2O3-CeO2@BC-CS aerogel > Fe3O4-CeO2@BC-CS aerogel > Fe2O3-CeO2@BC-CS aerogel.

[0093] Figure 6Comparison of the pollutant degradation capabilities of Fe3O4-CeO2@BC-CS aerogels after repeated use. After each use, press... Figure 4 As shown, photo-oxidation-driven in-situ self-repair was performed, and the material was then reused without further processing, maintaining good catalytic performance. When the material's surface active sites become carbonized or contaminated due to long-term degradation of organic dyes or 4-chlorophenol, the surface active sites can be cleaned in situ by irradiating the material with ultraviolet light for 10 minutes in a solution containing 20 mM PMS. This allows the free radicals generated by PC-AOPs to remove the contaminants in situ, restoring the degradation rate of organic pollutants to 90% of its initial state.

[0094] Further degradation experiments were conducted on 4-chlorophenol. The concentration of 4-chlorophenol was prepared at 20 mg / L, the concentration of PMS was 20 mg / L, and the catalyst concentration was 500 mg / L. The degradation effect was evaluated by liquid chromatography. The results are shown below. Figure 15 .

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for constructing a self-supported floating type multiphase reaction system driven by photooxidation for self-repairing, characterized in that, The specific steps are as follows: S1. First, bacterial cellulose (BC) and chitosan (CS) are used as raw materials to prepare BC emulsion and CS solution respectively. Then, the BC emulsion and CS solution are mixed evenly to obtain BC-CS emulsion. S2. Then, dissolve the water-soluble iron salt and aqueous cerium salt in deionized water to obtain the corresponding aqueous solutions. Next, add these aqueous solutions to the BC-CS emulsion, stir thoroughly, add ammonia solution dropwise, and stir vigorously to obtain a mixed solution. S3. Finally, glutaraldehyde solution was slowly added dropwise to the mixed solution, and the mixture was stirred until a gel was formed. After post-treatment, the heterostructure @BC-CS aerogel was obtained. The heterostructure @BC-CS aerogel is selected from: Fe-CeO2@BC-CS aerogel, Fe-Fe2O3-CeO2@BC-CS aerogel, Fe3O4-CeO2@BC-CS aerogel or Fe2O3-CeO2@BC-CS aerogel.

2. The construction method according to claim 1, characterized in that, In step S1, the preparation method of BC emulsion is as follows: First, the bacterial cellulose BC is washed and transferred to a 0.05M ammonia solution, stirred for 1 hour, and the solid is collected by suction filtration; then the solid is added to the first part of deionized water, and the pH value of the solution is adjusted to neutral with 1% dilute acetic acid to obtain a sheet-like transparent gel; finally, the sheet-like transparent gel is removed from the water, crushed using a juicer, a portion is dried to determine the solid content, and the remaining crushed gel is added to the second part of deionized water to prepare a BC emulsion with a solid content of 2 wt%, thus obtaining the BC emulsion.

3. The construction method of claim 1, wherein, In step S1, the CS solution is prepared by stirring chitosan CS in a dilute acetic acid solution to obtain the CS solution.

4. The construction method of claim 1, wherein, In step S1, the volume ratio of BC emulsion to CS solution is 7:3, the solid content of BC emulsion is 2 wt%, and the mass concentration of CS solution is 2%.

5. The construction method according to claim 1, characterized in that, In steps S2 and S3, the water-soluble iron salt and water-soluble cerium salt are FeCl3·6H2O, FeCl2·4H2O, and Ce(NO3)3·6H2O. The ratio of FeCl3·6H2O, FeCl2·4H2O, Ce(NO3)3·6H2O, deionized water, BC-CS emulsion, ammonia solution, and glutaraldehyde solution is 702.5 mg: 257.5 mg: 611.4 mg: 10 mL: 150 mL: 5 mL: 1 mL, wherein the mass concentration of the ammonia solution is 25% and the mass concentration of the glutaraldehyde solution is 2.5%; the corresponding product is Fe3O4-CeO2@BC-CS aerogel.

6. The construction method according to claim 1, characterized in that, In steps S2 and S3, the water-soluble iron salt and water-soluble cerium salt are FeCl3·6H2O and Ce(NO3)3·6H2O, respectively. The ratio of FeCl3·6H2O, Ce(NO3)3·6H2O, deionized water, BC-CS emulsion, ammonia solution, and glutaraldehyde solution is 702.5 mg: 611.4 mg: 10 mL: 150 mL: 5 mL: 1 mL, wherein the mass concentration of the ammonia solution is 25% and the mass concentration of the glutaraldehyde solution is 2.5%. The corresponding product is Fe2O3-CeO2@BC-CS aerogel.

7. The construction method according to claim 1, characterized in that, In steps S2 and S3, the water-soluble iron salt and water-soluble cerium salt are FeCl3·6H2O and Ce(NO3)3·6H2O, respectively, which are dissolved in deionized water to obtain a 1mM FeCl3 solution and a 2mM Ce(NO3)3 solution. The mixed solution is prepared by adding the FeCl3 solution to the BC-CS emulsion, stirring thoroughly, adding 1.5M NaBH4 solution for reduction, then adding Ce(NO3)3 solution, continuing to stir, adding 0.01M KOH solution, and stirring vigorously to obtain the product. The corresponding product is Fe-Fe2O3-CeO2@BC-CS aerogel.

8. A photo-oxidation-driven self-healing, self-supporting, floating multiphase reaction system, characterized in that, It is obtained by the construction method described in any one of claims 1 to 7.

9. The application of the photo-oxidation driven self-healing self-supporting floating multiphase reaction system as described in claim 8 in wastewater treatment.

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