A type of iron-based hydrogel-coated MBBR suspension filler, its preparation method and application

Abstract

This invention belongs to the field of water treatment and discloses an iron-based hydrogel-coated MBBR suspension packing, its preparation method, and its application. The iron-based hydrogel-coated MBBR suspension packing uses MBBR packing as a carrier, with its surface coated with a dialdehyde cellulose-ε-polylysine composite hydrogel and α-Fe₂O₃ nanosheets. The hydrogel layer adsorbs and enriches antibiotics in the water; α-Fe₂O₃ provides the iron source, forming Fe under Fenton-like conditions. 2+ / Fe 3+ The process involves recycling and catalyzing H2O2 to generate hydroxyl radicals, which oxidize and degrade antibiotics. The composite gel stabilizes the iron component, reduces dissolution, and improves mass transfer and degradation efficiency, significantly enhancing the treatment effect of wastewater treatment plants on pharmaceutical wastewater. By efficiently degrading toxic and harmful antibiotics, it effectively reduces the pollution load of the pharmaceutical industry on the water environment, ensuring the stable compliance of wastewater treatment plants and improving their resilience.

Description

Technical Field

[0001] This invention belongs to the field of water treatment, specifically an iron-based hydrogel-coated MBBR suspension filler, its preparation method, and its application. Background Technology

[0002] The pharmaceutical industry is a vital component of my country's national economy, but it is also a typical high-pollution industry. Pharmaceutical wastewater is characterized by its complex composition, high toxicity, and high content of recalcitrant organic matter, making it difficult to effectively degrade using conventional biological treatment methods. In particular, antibiotic and hormone-based pharmaceutical wastewater contains large amounts of bioinhibitory substances, posing a serious threat to the ecological environment and human health. The presence of pharmaceutical companies among the industrial enterprises connected to the Sanmen coastal wastewater treatment plant means that the connection of this wastewater to the municipal sewer system will significantly impact the stable operation of the coastal plant, especially regarding COD levels, which may pose a risk to maintaining compliance with standards.

[0003] Patent CN121490761A discloses a method for degrading antibiotic pollutants using boron-carbon co-regulated nano-zero-valent iron as an activator. This patent synthesizes carbon-coated nano-zero-valent iron via hydrothermal and carbothermal methods, mixes the obtained FeO@C with crystalline boron, adds it to wastewater containing antibiotic pollutants, and then adds persulfate as an oxidant to degrade the antibiotic pollutants. However, this technology is incompatible with existing biological treatment units, requiring a separate reaction tank, resulting in high investment and land costs. 0 @C particles are small in size and difficult to separate, posing an ecological safety risk of leakage into natural water bodies. Furthermore, it relies on boron addition and transforms into iron sludge after a single use, resulting in significant iron waste. This technology has several problems and cannot be widely used.

[0004] In summary, while iron-based Fenton reaction degradation of antibiotic pollutants has applications in water treatment, it still faces challenges such as complex preparation processes, nano-environmental risks, high resource dependence, and low resource utilization. Therefore, developing a water treatment material with high treatment efficiency, low operating costs, no nanomaterial risks, and no iron sludge generation is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide an iron-based hydrogel-coated MBBR suspension filler. The iron-based hydrogel-coated MBBR suspension filler uses MBBR filler as a carrier, with its surface coated with a dialdehyde cellulose-ε-polylysine composite hydrogel and α-Fe₂O₃ nanosheets. The hydrogel layer adsorbs and enriches antibiotics in water; α-Fe₂O₃ provides the iron source, forming Fe under Fenton-like conditions. 2+ / Fe 3+ The cycle catalyzes the generation of hydroxyl radicals from H2O2, which oxidize and degrade antibiotics; the composite gel stabilizes the iron component, reduces dissolution, and improves mass transfer and degradation efficiency.

[0006] An iron-based hydrogel-coated MBBR suspension filler comprises the following components in parts by weight: 10-25 parts of dialdehyde cellulose, 12-30 parts of ε-polylysine, 8-15 parts of polydopamine, 10-20 parts of α-Fe2O3 porous nanosheets, 3-10 parts of PEG400, and 1-4 parts of hexamethylenetetramine.

[0007] Preferably, the iron-based hydrogel comprises the following components in parts by weight: 15-18 parts of dialdehyde cellulose, 18-22 parts of ε-polylysine, 10-13 parts of polydopamine, 12-16 parts of α-Fe2O3 porous nanosheets, 5-7 parts of PEG400, and 2-3 parts of hexamethylenetetramine.

[0008] Preferably, the iron-based hydrogel coating MBBR suspension filler uses MBBR suspension filler as a substrate, and the iron-based hydrogel includes grafted dialdehyde cellulose compounded with ε-polylysine hydrogel and α-Fe2O3 nanosheet coating.

[0009] Dialdehyde cellulose can serve as the main framework of hydrogels, providing a three-dimensional network structure. The aldehyde groups on the molecules can undergo an aldehyde-amine Schiff base cross-linking reaction with the amino groups of ε-polylysine to form a stable gel network. This gel network exhibits strong hydrophilicity and adsorption capacity, enabling it to adsorb and enrich antibiotics, increase local concentration, and accelerate antibiotic degradation. The network structure enhances the hydrophilicity and biocompatibility of the filler surface, reducing iron loss. ε-polylysine provides the amino group, which reacts with the aldehyde groups of dialdehyde cellulose to jointly construct a Schiff base hydrogel cross-linking network. It also possesses reducing properties, allowing Fe to be released during the reaction. 3+ In-situ reduction to Fe 2+ It promotes Fenton-like reactions; polydopamine can act as an interface enhancer, improving the adhesion between the hydrogel and the MBBR substrate and α-Fe2O3 nanosheets, making the coating layer less prone to detachment during use. Polydopamine has reducing properties, which can continuously enhance the adhesion between the hydrogel and the MBBR substrate and α-Fe2O3 nanosheets. 3+ Reduced to Fe 2 + This process maintains the Fenton-like reaction and provides abundant active sites, enhancing the π–π adsorption and electrostatic adsorption of antibiotics. The α-Fe₂O₃ porous nanosheets serve as an iron source for the Fenton-like reaction, providing Fe... 3+ It is converted to Fe under the reducing action of lysine and polydopamine. 2+ It catalyzes the generation of hydroxyl radicals (·OH) from H2O2, oxidizing and degrading antibiotics. The annealing and sintering process enriches the porous structure, increases the specific surface area, adds active sites, and improves catalytic efficiency, achieving Fe... 2+ / Fe 3+The process involves recycling to reduce iron ion dissolution; PEG400 acts as a plasticizer and dispersant to improve the flexibility of the hydrogel, prevent the coating layer from cracking and falling off, improve the dispersibility of α-Fe2O3 nanosheets, reduce agglomeration, enhance the hydrophilicity of the hydrogel, and improve the contact efficiency between wastewater and catalytic sites; hexamethylenetetramine slowly releases basic groups, promoting a more complete aldehyde-amine crosslinking reaction and making the gel network more uniform and dense.

[0010] Preferably, the molar ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:(1-1.2).

[0011] The aldehyde groups on dialdehyde cellulose undergo a Schiff base cross-linking reaction with the amino groups on ε-polylysine to form covalent cross-links, constructing a three-dimensional hydrogel network. The amino groups have weak reducing properties, which can convert the Fe generated in the Fenton-like reaction into Fe. 3+ Reduced to Fe 2+ To achieve Fe 2+ / Fe 3+ The cycle, with excess amino groups, gives the gel surface a weak positive charge, while most antibiotics are weakly negatively charged and can be protonated. Adsorption is enhanced through electrostatic interactions and hydrogen bonds, resulting in enrichment followed by degradation and improved overall removal efficiency. The cross-linked network physically embeds and anchors α-Fe2O3 nanosheets, reducing iron dissolution and loss.

[0012] Preferably, the iron source in the α-Fe2O3 porous nanosheets is one of Fe(NO3)3·9H2O, FeCl3·6H2O or Fe(C5H7O2)3; the molar ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:(5-11).

[0013] In Fe(NO3)3·9H2O, nitrate ions generate gas during thermal decomposition, which has a pore-forming effect, guiding α-Fe2O3 to grow along specific crystal planes, improving the catalytic efficiency of iron material per unit mass, and reducing the amount of iron used; in FeCl3·6H2O, chloride ions have a weak coordination effect with iron ions, and the iron source has a higher mobility during hydrothermal processes, promoting grain growth, forming larger and more uniform grains, reducing grain boundary defects, and improving the structural stability of the material; Fe(C5H7O2)3 has good solubility in organic solvents and can form a uniform precursor solution with polymers such as PVP.

[0014] This invention discloses a method for preparing iron-based hydrogel-coated MBBR suspension filler, comprising the following steps: S1. Add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed at 200-400 r / min, stir at room temperature for 2-4 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1-1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 30-60 min to obtain iron-based hydrogel precursor solution; S2, soak MBBR suspension filler in ethanol for 30-60 min, wash, dry at 40℃, completely immerse in iron-based hydrogel precursor solution, impregnate and adsorb at room temperature for 1-2 h, place in an oven at 40-60℃ for constant temperature crosslinking and curing for 6-12 h, wash, and vacuum dry at 50℃ to obtain iron-based hydrogel coated MBBR suspension filler.

[0015] Preferably, the preparation steps of α-Fe2O3 porous nanosheets in step S1 are as follows: Iron source and polyvinylpyrrolidone are added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 30-60 min. 1 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 7-9. The mixed solution is transferred to a high-pressure hydrothermal reactor, sealed, and heated to 120-150℃ at a rate of 2℃ / min, and held for 1-1.5 h. The temperature is then further increased to 150-220℃ and reacted for 8-12 h. The precipitate is collected by centrifugation, washed, dried, and transferred to a tube furnace. The temperature is increased to 300-500℃ at a rate of 2℃ / min under air atmosphere and held for 2-4 h. After grinding, α-Fe2O3 porous nanosheets are obtained.

[0016] Through a staged hydrothermal-calcination coupled process, multiple precise controls were achieved on the morphology, crystal facets, and porosity of α-Fe₂O₃ nanosheets. Rapid nucleation at low temperature (120-150℃, held for 1-1.5 hours) using a heating rate of 2℃ / min resulted in a large number of uniform iron alkoxide nanocrystals with narrow nucleus size distribution, leading to uniform particle size in the final product. Further heating to 150-220℃ for 8-12 hours allowed for slow growth, forming highly crystalline α-Fe₂O₃ nanosheets with controllable crystal facets and abundant catalytic active sites. High temperature promoted the transformation of the nuclei into the α-Fe₂O₃ crystal phase. Simultaneously, PVP, acting as a morphology template, selectively adsorbed onto specific crystal facets, forming highly crystalline α-Fe₂O₃ nanosheets with controllable crystal facets and abundant catalytic active sites.

[0017] This invention also discloses an application of iron-based hydrogel-coated MBBR suspended packing. The application of the iron-based hydrogel-coated MBBR suspended packing is as follows: during wastewater treatment, the packing is added to the MBBR reactor with a filling rate of 20%-40%, a small amount of reducing agent is added, H2O2 is added to the system, the pH is controlled at 3-6, and the reaction is carried out at room temperature for 120-180 min to remove antibiotics from the wastewater.

[0018] Preferably, the reducing agent is one or more of ascorbic acid, oxalic acid, sodium citrate, sodium sulfite, and hydroxylamine; the antibiotic includes sulfonamides, quinolones, tetracyclines, and erythromycin antibiotics.

[0019] The reducing agent will reduce the Fe on the catalyst surface 3+ Rapid reduction to Fe 2+ Surface Fe 2+ / Fe 3+ Rapid cycling avoids Fe 3+ Iron loss due to hydrolysis and precipitation; ·OH is a non-selective strong oxidant that can attack the unsaturated bonds, aromatic rings and heteroatom bonds of various antibiotics. The hydrogel adsorbs and enriches antibiotic molecules onto the surface of the catalytic layer, thereby achieving degradation.

[0020] The beneficial effects of this invention are as follows: (1) By integrating the α-Fe2O3 Fenton catalyst layer, the DAC-ε-PL hydrogel adsorption layer and the MBBR biofilm carrier into the same packing material, the synergistic effect of chemical oxidation, physical adsorption enrichment and biodegradation was achieved. (2) DAC-ε-PL Schiff base hydrogel has dynamic covalent bond characteristics. It can self-heal after slight damage under hydraulic shear, thus extending the service life of the filler. (3) The hydroxyl radicals generated by the outer α-Fe2O3 catalysis can not only degrade antibiotic molecules, but also effectively destroy the DNA structure of bacteria, thereby reducing the production and release of antibiotic resistance genes from the source; (4) This invention significantly improves the treatment effect of sewage treatment plants on pharmaceutical wastewater. By efficiently degrading toxic and harmful antibiotics, it effectively reduces the pollution load of the pharmaceutical industry on the water environment, ensures the stable compliance of sewage treatment plants, and enhances the impact resistance of sewage treatment plants. Detailed Implementation

[0021] Example 1:

[0022] This embodiment provides an iron-based hydrogel-coated MBBR suspension filler, specifically comprising the following components in parts by weight: 16 parts of dialdehyde cellulose, 19.2 parts of ε-polylysine, 12 parts of polydopamine, 12 parts of α-Fe2O3 porous nanosheets, 6 parts of PEG400, and 2 parts of hexamethylenetetramine. The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:1.2; The iron source in the α-Fe2O3 porous nanosheets is Fe(NO3)3·9H2O; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:6.

[0023] This embodiment also provides a method for preparing iron-based hydrogel-coated MBBR suspension filler, which specifically includes the following steps: S1, iron source and polyvinylpyrrolidone were added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 50 min. 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 8. The mixed solution was transferred to a high-pressure hydrothermal reactor, sealed, and heated to 140℃ at a rate of 2℃ / min and held for 1 h. The temperature was then increased to 200℃ and reacted for 9 h. The precipitate was collected by centrifugation, washed and dried, and transferred to a tube furnace. The temperature was increased to 400℃ at a rate of 2℃ / min and held for 4 h in an air atmosphere. After grinding, α-Fe2O3 porous nanosheets were obtained. S2, add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed to 400 r / min, stir at room temperature for 3 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 50 min to obtain iron-based hydrogel precursor solution. S3. The MBBR suspension filler was soaked in ethanol for 50 min, washed, dried at 40 °C, completely immersed in the iron-based hydrogel precursor solution, impregnated and adsorbed at room temperature for 2 h, placed in a 50 °C oven for constant temperature crosslinking and curing for 10 h, washed, and vacuum dried at 50 °C to obtain iron-based hydrogel-coated MBBR suspension filler. Example 2:

[0024] This embodiment provides an iron-based hydrogel-coated MBBR suspension filler, specifically comprising the following components in parts by weight: 10 parts of dialdehyde cellulose, 12 parts of ε-polylysine, 8 parts of polydopamine, 10 parts of α-Fe2O3 porous nanosheets, 3 parts of PEG400, and 1 part of hexamethylenetetramine. The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:1.2; The iron source in the α-Fe2O3 porous nanosheets is Fe(NO3)3·9H2O; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:6.

[0025] This embodiment also provides a method for preparing iron-based hydrogel-coated MBBR suspension filler, which specifically includes the following steps: S1, iron source and polyvinylpyrrolidone were added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 50 min. 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 8. The mixed solution was transferred to a high-pressure hydrothermal reactor, sealed, and heated to 140℃ at a rate of 2℃ / min and held for 1 h. The temperature was then increased to 200℃ and reacted for 9 h. The precipitate was collected by centrifugation, washed and dried, and transferred to a tube furnace. The temperature was increased to 400℃ at a rate of 2℃ / min and held for 4 h in an air atmosphere. After grinding, α-Fe2O3 porous nanosheets were obtained. S2, add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed to 400 r / min, stir at room temperature for 3 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 50 min to obtain iron-based hydrogel precursor solution. S3. The MBBR suspension filler was soaked in ethanol for 50 min, washed, dried at 40 °C, completely immersed in the iron-based hydrogel precursor solution, impregnated and adsorbed at room temperature for 2 h, placed in a 50 °C oven for constant temperature crosslinking and curing for 10 h, washed, and vacuum dried at 50 °C to obtain iron-based hydrogel-coated MBBR suspension filler. Example 3:

[0026] This embodiment provides an iron-based hydrogel-coated MBBR suspension filler, specifically comprising the following components in parts by weight: 25 parts of dialdehyde cellulose, 30 parts of ε-polylysine, 15 parts of polydopamine, 20 parts of α-Fe2O3 porous nanosheets, 10 parts of PEG400, and 4 parts of hexamethylenetetramine. The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:1.2; The iron source in the α-Fe2O3 porous nanosheets is Fe(NO3)3·9H2O; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:6.

[0027] This embodiment also provides a method for preparing iron-based hydrogel-coated MBBR suspension filler, which specifically includes the following steps: S1, iron source and polyvinylpyrrolidone were added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 50 min. 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 8. The mixed solution was transferred to a high-pressure hydrothermal reactor, sealed, and heated to 140℃ at a rate of 2℃ / min and held for 1 h. The temperature was then increased to 200℃ and reacted for 9 h. The precipitate was collected by centrifugation, washed and dried, and transferred to a tube furnace. The temperature was increased to 400℃ at a rate of 2℃ / min and held for 4 h in an air atmosphere. After grinding, α-Fe2O3 porous nanosheets were obtained. S2, add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed to 400 r / min, stir at room temperature for 3 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 50 min to obtain iron-based hydrogel precursor solution. S3. The MBBR suspension filler was soaked in ethanol for 50 min, washed, dried at 40 °C, completely immersed in the iron-based hydrogel precursor solution, impregnated and adsorbed at room temperature for 2 h, placed in a 50 °C oven for constant temperature crosslinking and curing for 10 h, washed, and vacuum dried at 50 °C to obtain iron-based hydrogel-coated MBBR suspension filler. Example 4:

[0028] This embodiment provides an iron-based hydrogel-coated MBBR suspension filler, specifically comprising the following components in parts by weight: 16 parts of dialdehyde cellulose, 19.2 parts of ε-polylysine, 12 parts of polydopamine, 12 parts of α-Fe2O3 porous nanosheets, 6 parts of PEG400, and 2 parts of hexamethylenetetramine. The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:1.2; The iron source in the α-Fe2O3 porous nanosheets is FeCl3·6H2O; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:6.

[0029] This embodiment also provides a method for preparing iron-based hydrogel-coated MBBR suspension filler, which specifically includes the following steps: S1, iron source and polyvinylpyrrolidone were added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 50 min. 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 8. The mixed solution was transferred to a high-pressure hydrothermal reactor, sealed, and heated to 140℃ at a rate of 2℃ / min and held for 1 h. The temperature was then increased to 200℃ and reacted for 9 h. The precipitate was collected by centrifugation, washed and dried, and transferred to a tube furnace. The temperature was increased to 400℃ at a rate of 2℃ / min and held for 4 h in an air atmosphere. After grinding, α-Fe2O3 porous nanosheets were obtained. S2, add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed to 400 r / min, stir at room temperature for 3 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 50 min to obtain iron-based hydrogel precursor solution. S3. The MBBR suspension filler was soaked in ethanol for 50 min, washed, dried at 40 °C, completely immersed in the iron-based hydrogel precursor solution, impregnated and adsorbed at room temperature for 2 h, placed in a 50 °C oven for constant temperature crosslinking and curing for 10 h, washed, and vacuum dried at 50 °C to obtain iron-based hydrogel-coated MBBR suspension filler. Example 5:

[0030] This embodiment provides an iron-based hydrogel-coated MBBR suspension filler, specifically comprising the following components in parts by weight: 16 parts of dialdehyde cellulose, 22 parts of ε-polylysine, 12 parts of polydopamine, 12 parts of α-Fe2O3 porous nanosheets, 6 parts of PEG400, and 2 parts of hexamethylenetetramine. The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:1.2; The iron source in the α-Fe2O3 porous nanosheets is Fe(C5H7O2)3; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:6.

[0031] This embodiment also provides a method for preparing iron-based hydrogel-coated MBBR suspension filler, which specifically includes the following steps: S1, iron source and polyvinylpyrrolidone were added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 50 min. 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 8. The mixed solution was transferred to a high-pressure hydrothermal reactor, sealed, and heated to 140℃ at a rate of 2℃ / min and held for 1 h. The temperature was then increased to 200℃ and reacted for 9 h. The precipitate was collected by centrifugation, washed and dried, and transferred to a tube furnace. The temperature was increased to 400℃ at a rate of 2℃ / min and held for 4 h in an air atmosphere. After grinding, α-Fe2O3 porous nanosheets were obtained. S2, add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed to 400 r / min, stir at room temperature for 3 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 50 min to obtain iron-based hydrogel precursor solution. S3. The MBBR suspension filler was soaked in ethanol for 50 min, washed, dried at 40 °C, completely immersed in the iron-based hydrogel precursor solution, impregnated and adsorbed at room temperature for 2 h, placed in a 50 °C oven for constant temperature crosslinking and curing for 10 h, washed, and vacuum dried at 50 °C to obtain iron-based hydrogel-coated MBBR suspension filler. Example 6:

[0032] In wastewater treatment, packing material is added to the MBBR reactor at a filling rate of 30%, ascorbic acid is added, H2O2 is added to the system, the pH is controlled at 4, and the reaction is carried out at room temperature for 150 min to remove antibiotics from the wastewater.

[0033] Comparative Example 1: This comparative example provides an iron-based hydrogel-coated MBBR suspension filler, specifically comprising the following components in parts by weight: 16 parts of dialdehyde cellulose, 22 parts of ε-polylysine, 12 parts of polydopamine, 12 parts of α-Fe2O3 porous nanosheets, 6 parts of PEG400, and 2 parts of hexamethylenetetramine. The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:1.2; The iron source in the α-Fe2O3 porous nanosheets is Fe(NO3)3·9H2O; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:4.

[0034] This comparative example also provides a method for preparing iron-based hydrogel-coated MBBR suspension filler, specifically including the following steps: S1, iron source and polyvinylpyrrolidone were added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 50 min. 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 8. The mixed solution was transferred to a high-pressure hydrothermal reactor, sealed, and heated to 140℃ at a rate of 2℃ / min and held for 1 h. The temperature was then increased to 200℃ and reacted for 9 h. The precipitate was collected by centrifugation, washed and dried, and transferred to a tube furnace. The temperature was increased to 400℃ at a rate of 2℃ / min and held for 4 h in an air atmosphere. After grinding, α-Fe2O3 porous nanosheets were obtained. S2, add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed to 400 r / min, stir at room temperature for 3 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 50 min to obtain iron-based hydrogel precursor solution. S3. The MBBR suspension filler was soaked in ethanol for 50 min, washed, dried at 40 °C, completely immersed in the iron-based hydrogel precursor solution, impregnated and adsorbed at room temperature for 2 h, placed in a 50 °C oven for constant temperature crosslinking and curing for 10 h, washed, and vacuum dried at 50 °C to obtain iron-based hydrogel-coated MBBR suspension filler.

[0035] The difference between this comparative example and Example 1 is that the mass ratio of iron source to polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:4.

[0036] Comparative Example 2: This comparative example provides an iron-based hydrogel-coated MBBR suspension filler, specifically comprising the following components in parts by weight: 16 parts of dialdehyde cellulose, 22 parts of ε-polylysine, 12 parts of polydopamine, 12 parts of α-Fe2O3 porous nanosheets, 6 parts of PEG400, and 2 parts of hexamethylenetetramine. The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:1.2; The iron source in the α-Fe2O3 porous nanosheets is Fe(NO3)3·9H2O; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:8.

[0037] This comparative example also provides a method for preparing iron-based hydrogel-coated MBBR suspension filler, specifically including the following steps: S1, iron source and polyvinylpyrrolidone were added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 50 min. 1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 8. The mixed solution was transferred to a high-pressure hydrothermal reactor, sealed, and heated to 140℃ at a rate of 2℃ / min and held for 1 h. The temperature was then increased to 200℃ and reacted for 9 h. The precipitate was collected by centrifugation, washed and dried, and transferred to a tube furnace. The temperature was increased to 400℃ at a rate of 2℃ / min and held for 4 h in an air atmosphere. After grinding, α-Fe2O3 porous nanosheets were obtained. S2, add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed to 400 r / min, stir at room temperature for 3 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 50 min to obtain iron-based hydrogel precursor solution. S3. The MBBR suspension filler was soaked in ethanol for 50 min, washed, dried at 40 °C, completely immersed in the iron-based hydrogel precursor solution, impregnated and adsorbed at room temperature for 2 h, placed in a 50 °C oven for constant temperature crosslinking and curing for 10 h, washed, and vacuum dried at 50 °C to obtain iron-based hydrogel-coated MBBR suspension filler.

[0038] The difference between this comparative example and Example 1 is that the mass ratio of iron source to polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:8.

[0039] Comparative Example 3: In wastewater treatment, packing material is added to the MBBR reactor at a filling rate of 30%, ascorbic acid is added, H2O2 is added to the system, the pH is controlled at 3, and the reaction is carried out at room temperature for 150 min to remove antibiotics from the wastewater.

[0040] Comparative Example 4: In wastewater treatment, packing material is added to the MBBR reactor at a filling rate of 30%, ascorbic acid is added, H2O2 is added to the system, the pH is controlled at 6, and the reaction is carried out at room temperature for 150 min to remove antibiotics from the wastewater.

[0041] Experimental Example 1: This experimental example is based on the application of the iron-based hydrogel-coated MBBR suspended packing prepared in Examples 1-5 and Comparative Examples 1-2 in wastewater treatment tests according to Example 6. The results are shown in Table 1 below.

[0042] Table 1: Test results of wastewater treatment experiments conducted in Examples 1-5 and Comparative Examples 1-2 based on the application in Example 6. Example 1 achieved a COD removal rate of 96.0% and an average antibiotic removal rate of 96.9%, meeting the Class A emission standard. This formulation demonstrated balanced adsorption-catalysis synergy, with removal rates exceeding 95% for all four types of antibiotics. Example 2 achieved a COD removal rate of 92.0% and an average antibiotic removal rate of 91.1%, failing to meet the Class A emission standard. Insufficient total hydrogel components led to decreased adsorption and enrichment capacity, inadequate iron ion anchoring, and a significantly lower overall treatment effect compared to Example 1. Example 3 achieved a COD removal rate of 96.8% and an average antibiotic removal rate of 96.2%. The dense hydrogel network provided richer adsorption sites and stronger iron fixation capacity, while the α-Fe2O3 catalytic layer played a full role, although the cost was high. Example 4 achieved a COD removal rate of 96.4% and an average antibiotic removal rate of 95.8%. The ferric chloride system was slightly better than ferric nitrate in COD removal and could be considered a better iron source. Example 5 achieved a COD removal rate of 95.0% and an average antibiotic removal rate of 92.9%. Compared to Example 1, the COD removal rate decreased by 1.0%, and the antibiotic removal rate decreased by 4.0%. This indicates that when the ε-PL ratio is too high, the hydrogel cross-linking network becomes excessively dense or amino groups compete for adsorption, which is detrimental to antibiotic adsorption and iron ion cycling.

[0043] Experimental Example 2: This experimental example is a wastewater treatment experiment conducted according to Example 6, Comparative Example 3, and Comparative Example 4 in Example 1. The results are shown in Table 2 below.

[0044] Table 2: Experimental test results of wastewater treatment in Example 1 based on the applications in Example 6, Comparative Example 3, and Comparative Example 4. Example 6: COD removal rate reached 96.0%, BOD5 removal rate 95.3%, and average antibiotic removal rate 96.9%. At pH=4, the ·OH generation rate and H2O2 utilization rate reached the optimal balance, and the Schiff base hydrogel network structure was stable, reaching the optimal balance point. Comparative Example 3: COD removal rate was 93.5%, BOD5 removal rate was 92.2%, and average antibiotic removal rate was 93.8%. Although the ·OH generation rate was faster under strongly acidic conditions, the ineffective decomposition of H2O2 increased, and the Schiff base bond began to hydrolyze at pH=3, resulting in decreased hydrogel network stability. Comparative Example 4: COD removal rate was 89.4%, BOD5 removal rate was 84.4%, and average antibiotic removal rate was 86.0%. The activity of traditional Fenton decreased sharply at pH>5, but the synergistic effect of the α-Fe2O3 heterogeneous Fenton catalyst and ascorbic acid reducing agent was superior to the traditional Fenton system, but the material performance was worse than that of Example 6.

Claims

1. An iron-based hydrogel-coated MBBR suspension filler, characterized in that, The iron-based hydrogel comprises the following components in parts by weight: 10-25 parts of dialdehyde cellulose, 12-30 parts of ε-polylysine, 8-15 parts of polydopamine, 10-20 parts of α-Fe2O3 porous nanosheets, 3-10 parts of PEG400, and 1-4 parts of hexamethylenetetramine.

2. The iron-based hydrogel-coated MBBR suspension filler according to claim 1, characterized in that, The iron-based hydrogel comprises the following components in parts by weight: 15-18 parts of dialdehyde cellulose, 18-22 parts of ε-polylysine, 10-13 parts of polydopamine, 12-16 parts of α-Fe2O3 porous nanosheets, 5-7 parts of PEG400, and 2-3 parts of hexamethylenetetramine.

3. The iron-based hydrogel-coated MBBR suspension filler according to claim 1 or 2, characterized in that, The mass ratio of aldehyde amine in the dialdehyde cellulose to ε-polylysine is 1:(1-1.2).

4. The iron-based hydrogel-coated MBBR suspension filler according to claim 1 or 2, characterized in that, The iron source in the α-Fe2O3 porous nanosheets is one of Fe(NO3)3·9H2O, FeCl3·6H2O or Fe(C5H7O2)3; the mass ratio of the iron source to the polyvinylpyrrolidone monomer in the α-Fe2O3 porous nanosheets is 1:(4-8).

5. The iron-based hydrogel-coated MBBR suspension filler according to claim 1 or 2, characterized in that, The iron-based hydrogel-coated MBBR suspension filler uses MBBR suspension filler as a substrate, and the iron-based hydrogel includes grafted dialdehyde cellulose compounded with ε-polylysine hydrogel and α-Fe2O3 nanosheet coating.

6. A method for preparing the iron-based hydrogel-coated MBBR suspension filler according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add dialdehyde cellulose and ε-polylysine to deionized water, control the stirring speed at 200-400 r / min, stir at room temperature for 2-4 h to fully dissolve, add polydopamine, PEG400 and hexamethylenetetramine in sequence, continue stirring for 1-1.5 h until uniformly dispersed, add α-Fe2O3 porous nanosheets, and ultrasonically disperse for 30-60 min to obtain iron-based hydrogel precursor solution; S2, soak MBBR suspension filler in ethanol for 30-60 min, wash, dry at 40℃, completely immerse in iron-based hydrogel precursor solution, impregnate and adsorb at room temperature for 1-2 h, place in an oven at 40-60℃ for constant temperature crosslinking and curing for 6-12 h, wash, and vacuum dry at 50℃ to obtain iron-based hydrogel coated MBBR suspension filler.

7. The iron-based hydrogel-coated MBBR suspension filler according to claim 6, characterized in that, The preparation steps of α-Fe2O3 porous nanosheets in step S1 are as follows: Iron source and polyvinylpyrrolidone are added to a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 1:1 and stirred for 30-60 min. 1 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 7-9. The mixed solution is transferred to a high-pressure hydrothermal reactor, sealed, and heated to 120-150℃ at a rate of 2℃ / min, and held for 1-1.5 h. The temperature is then further increased to 150-220℃ and reacted for 8-12 h. The precipitate is collected by centrifugation, washed, dried, and transferred to a tube furnace. The furnace is heated to 300-500℃ at a rate of 2℃ / min under air atmosphere and held for 2-4 h. After grinding, α-Fe2O3 porous nanosheets are obtained.

8. An application of the iron-based hydrogel-coated MBBR suspension filler according to any one of claims 1-7, characterized in that, The application of the iron-based hydrogel-coated MBBR suspended packing is as follows: during wastewater treatment, the packing is added to the MBBR reactor at a filling rate of 20%-40%, a small amount of reducing agent is added, H2O2 is added to the system, the pH is controlled at 3-6, and the reaction is carried out at room temperature for 120-180 min to remove antibiotics from the wastewater.

9. The application of the iron-based hydrogel-coated MBBR suspension filler according to claim 8, characterized in that, The reducing agent is one or more of ascorbic acid, oxalic acid, sodium citrate, sodium sulfite, and hydroxylamine.

10. The application of the iron-based hydrogel-coated MBBR suspension filler according to claim 8, characterized in that, The antibiotics include sulfonamides, quinolones, tetracyclines, and erythromycin antibiotics.

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