A microbial slow-release porous composite material for sewage treatment, preparation method and use thereof

Abstract

The present invention provides a microbial slow-release porous composite material for sewage treatment, a preparation method, and uses thereof, comprising: dripping an organic ligand solution into a precursor solution composed of a nanocellulose solution and a cobalt source solution; mixing the reaction solution with polyvinyl alcohol, injecting the mixture into a mold, and performing directional freezing to obtain an aerogel matrix; hydrophobic modification of the aerogel matrix to obtain a modified aerogel matrix; mixing a microbial suspension with sodium alginate, and then high-pressure homogenization to obtain a gel precursor emulsion; dripping the mixture into a calcium chloride solution for gelation to obtain gel particles, which are then cross-linked with glutaraldehyde and dried to obtain slow-release capsule particles; dispersing the slow-release capsule particles in deionized water to obtain a dispersion; and immersing the modified aerogel matrix in the dispersion. The aerogel matrix with a multi-level pore structure is composited with a slow-release capsule with a pH-responsive mechanism to achieve physical adsorption, chemical catalysis, and biodegradation for sewage treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment and relates to a microbial slow-release porous composite material for sewage treatment, a preparation method and use thereof. Background Art

[0002] Against the backdrop of global water shortages and increasing water pollution, innovation in wastewater treatment technology has become a core issue in the environmental field. While traditional wastewater treatment methods such as physical filtration, chemical precipitation, and activated sludge have achieved some success in pollutant removal, they still face bottlenecks such as high sludge production, significant risks of secondary pollution, and limited treatment efficiency. For example, the activated sludge method relies on microbial metabolism to degrade organic matter, but microorganisms are easily lost with the effluent, requiring frequent replenishment and struggling to adapt to complex water quality fluctuations. The biofilm method, however, is limited by the specific surface area of ​​the carrier and the stability of microbial attachment, making it difficult to continuously improve treatment efficiency. In recent years, immobilized microbial technology has significantly reduced replenishment frequency by immobilizing functional bacteria within porous carriers. However, these carriers, often made of traditional porous media such as activated carbon and zeolite, suffer from a monotonous pore structure, limited adsorption capacity, and low microbial loading efficiency. Furthermore, they rely on aeration equipment to maintain microbial release, resulting in high operating costs. Furthermore, existing slow-release materials, such as ion-adsorbing carriers or embedded gels, generally suffer from insufficient mechanical strength and poor recyclability, making them difficult to meet the requirements of long-term stable operation.

[0003] With increasing environmental protection requirements, the wastewater treatment industry is in urgent need of novel materials that combine efficient pollutant removal, environmental friendliness, and economic viability. Porous materials, owing to their high specific surface area and tunable pore structure, have become a research hotspot. For example, metal-organic frameworks (MOFs) and biochar composites have shown promise in adsorbing heavy metals and organic pollutants. However, their synthesis processes are complex and costly, and they lack mechanisms for synergistic interactions with microorganisms. Furthermore, while microbial sustained-release technologies can enhance treatment efficacy by extending the active lifespan of bacterial communities, existing approaches often focus on immobilizing a single bacterial species, underutilizing the synergistic effects of complex bacterial co-metabolism. Furthermore, the sustained-release rate struggles to adapt to dynamic water quality fluctuations, resulting in significant fluctuations in pollutant removal efficiency. Furthermore, the inhibition of microbial activity under extreme water conditions (e.g., high salinity and high pH) and the stability of the carrier structure remain key challenges hindering the large-scale application of this technology. Against this backdrop, the development of composite functional materials that combine a controllable pore structure, efficient microbial sustained-release capabilities, and environmental adaptability has significant scientific and engineering value for overcoming the performance bottlenecks of existing wastewater treatment technologies. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a microbial slow-release porous composite material for sewage treatment, its preparation method and use, and to compound an aerogel matrix with a multi-level pore structure with a slow-release capsule with a pH response mechanism to achieve physical adsorption, chemical catalysis and biodegradation in sewage treatment.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a microbial slow-release porous composite material for sewage treatment, the preparation method comprising:

[0007] (I) dropping an organic ligand solution into a precursor solution consisting of a nanocellulose solution and a cobalt source solution to obtain a reaction solution; mixing the reaction solution with polyvinyl alcohol and injecting the mixture into a mold for directionally freezing to obtain an aerogel matrix; and hydrophobically modifying the aerogel matrix to obtain a modified aerogel matrix;

[0008] (II) mixing the microbial suspension with sodium alginate and homogenizing under high pressure to obtain a gel precursor emulsion; dropping the emulsion into a calcium chloride solution for gelation to obtain gel particles, which are then cross-linked with glutaraldehyde and dried to obtain sustained-release capsule particles;

[0009] (III) dispersing the sustained-release capsule particles in deionized water to obtain a dispersion; immersing the modified aerogel matrix in the dispersion, taking it out and drying it to obtain the microbial sustained-release porous composite material.

[0010] The present invention combines an aerogel matrix with a multi-level pore structure with a sustained-release capsule with a pH response mechanism to achieve physical adsorption, chemical catalysis and biodegradation in sewage treatment. The vertical through-holes of the modified aerogel matrix provide high-speed channels for pollutant enrichment and mass transfer. The Co of the surface-loaded ZIF-67 2+ The nodes provide Lewis acid sites, which specifically bind to sulfur-, phosphorus-, or nitrogen-containing pollutants through coordination, enhancing the adsorption selectivity for polar or structurally specific pollutants. A gradient cross-linking process was used to prepare the double-layered sustained-release capsule particles. The outer shell maintains structural integrity under water impact, while the inner core retains active space for microbial colonization and metabolism.

[0011] The present invention uses nanocellulose as a biomass skeleton material, and utilizes the abundant hydroxyl functional groups on its surface to coordinate with cobalt ions. When the cobalt nitrate solution is mixed with the nanocellulose, the cobalt ions are preferentially adsorbed around the oxygen-containing groups of the cellulose molecular chain, forming a uniform metal ion distribution network. The subsequently introduced 2-methylimidazole organic ligand undergoes a self-assembly reaction with the cobalt ions to generate a metal organic framework material ZIF-67 in the gaps of the nanocellulose network. The excess organic ligand not only ensures that the reaction proceeds completely, but also inhibits excessive crystal growth through the steric effect, eventually forming regular dodecahedral crystals. These ZIF-67 crystals are tightly combined with the nanocellulose network through hydrogen bonding, which not only retains the three-dimensional pore structure of the aerogel matrix, but also gives it catalytic active sites, which can quickly capture heavy metal ions (such as Pb 2+ 、Cd 2 + ), organic dye molecules and oil pollutants; at the same time, its Lewis acid sites (Co 2+ Nodes) can also bind to specific pollutants (such as sulfur- or nitrogen-containing compounds) through coordination, enhancing selective adsorption.

[0012] During the preparation of sustained-release capsule particles, sodium alginate molecular chains entangle with the microbial suspension to form a primary protective network. The carboxylic acid groups on the alginate molecular chains interact with calcium ions through an "egg-box" crosslinking mechanism to form a three-dimensional gel structure. This three-dimensional gel structure not only maintains the metabolic activity of the microorganisms but also acts as a physical barrier to reduce mechanical damage to the microorganisms from the external environment. The present invention uses high-pressure homogenization to disperse the gel precursor solution into uniformly sized submicron emulsion droplets. The resulting sustained-release capsule particles (1-5 μm) are aligned with the 50-200 μm vertical pores of the modified aerogel matrix. Capillary forces and surface wettability ensure uniform filling and stable loading of the sustained-release capsule particles within the modified aerogel matrix. During the gelation stage, high-speed stirring of the calcium chloride solution effectively inhibits secondary aggregation between the gel particles, ensuring the independent dispersion of the individual gel particles and the uniform size of the resulting sustained-release capsule particles. The secondary cross-linking of glutaraldehyde solution constructs a covalent bond network through the condensation reaction of aldehyde groups and sodium alginate hydroxyl groups. The calcium ion chelation and glutaraldehyde covalent cross-linking process are used to optimize the gel network structural characteristics, forming sustained-release capsule particles with a shell-core structure with a dense outer layer and a loose inner layer. This asymmetric structure can achieve pH-responsive release in sewage environment - when the environmental pH fluctuation causes partial dissociation of the outer layer of calcium alginate, the inner cross-linked network can still maintain structural stability, so that the microbial release rate is dynamically matched with the pollutant load.

[0013] As a preferred technical solution of the present invention, in step (I), the organic ligand solution consists of 2-methylimidazole and methanol.

[0014] In some optional examples, the concentration of 2-methylimidazole in the organic ligand solution is 0.9~1 mol / L, for example, it can be 0.9mol / L, 0.91mol / L, 0.92mol / L, 0.93mol / L, 0.94mol / L, 0.95mol / L, 0.96mol / L, 0.97mol / L, 0.98mol / L, 0.99mol / L or 1mol / L, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0015] In some optional examples, the mass fraction of the nanocellulose solution is 1~2wt%, for example, it can be 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt% or 2.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] In some optional examples, the cobalt source solution consists of cobalt nitrate and deionized water.

[0017] In some optional examples, the concentration of cobalt nitrate in the cobalt source solution is 0.15~0.25 mol / L, for example, it can be 0.15 mol / L, 0.16 mol / L, 0.17 mol / L, 0.18 mol / L, 0.19 mol / L, 0.2 mol / L, 0.21 mol / L, 0.22 mol / L, 0.23 mol / L, 0.24 mol / L or 0.25 mol / L, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0018] In some optional examples, the volume ratio of the nanocellulose solution to the cobalt source solution is (2~3):1, for example, it can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0:1, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0019] The present invention specifically limits the volume ratio of the nanocellulose solution to the cobalt source solution to (2-3):1. Within this range, the hydroxyl groups on the nanocellulose chains can form a moderate coordination effect with the cobalt ions, ensuring that sufficient metal ions are anchored on the surface of the nanocellulose network while preventing excessive cobalt salt from destroying the hydrogen bond cross-linking structure of the nanocellulose. This allows the subsequently added 2-methylimidazole organic ligand to be evenly distributed in the gaps of the cellulose network and combine with the cobalt ions to form ZIF-67 crystals of uniform size, thereby constructing a stable multi-level pore structure for the aerogel matrix.

[0020] When the amount of nanocellulose solution added is too low, the concentration of cobalt ions is too high, causing the coordination reaction to be concentrated in a local area. The ZIF-67 crystals overgrow to form large agglomerates, which not only block the pores of the aerogel matrix and reduce its porosity, but also weaken the mechanical strength of the nanocellulose network. At the same time, the free cobalt ions that have not completely reacted will crystallize and precipitate during the directional freezing process, destroying the regularity of the pore structure of the aerogel matrix.

[0021] When the amount of nanocellulose solution added is too high, the excess nanocellulose chains hinder the uniform distribution of cobalt ions due to the steric hindrance effect, resulting in insufficient nucleation sites for ZIF-67 crystals. The final ZIF-67 crystals have poor dispersion and reduced density of catalytic active sites. At the same time, the dense network formed by excessive cross-linking of nanocellulose will compress the pore space, causing the specific surface area of ​​the aerogel matrix to drop significantly.

[0022] It should be noted that the present invention does not make specific requirements or special limitations on the dripping speed of the organic ligand solution. Exemplarily, the dripping speed of the organic ligand solution is 1.5~2.5mL / min, for example, it can be 1.5mL / min, 1.6mL / min, 1.7mL / min, 1.8mL / min, 1.9mL / min, 2.0mL / min, 2.1mL / min, 2.2mL / min, 2.3mL / min, 2.4mL / min or 2.5mL / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] In some optional examples, the molar ratio of 2-methylimidazole in the organic ligand solution to cobalt ions in the cobalt source solution is (5~6):1, for example, it can be 5.0:1, 5.1:1, 5.2:1, 5.3:1, 5.4:1, 5.5:1, 5.6:1, 5.7:1, 5.8:1, 5.9:1 or 6.0:1, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0024] In some optional examples, the organic ligand solution is dropped into the precursor solution under stirring and heating conditions.

[0025] In some optional examples, the heating temperature when the organic ligand solution is dripped is 60~70℃, for example, it can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃ or 70℃, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0026] In some optional examples, after all the organic ligand solution is dropped, mixing and stirring are continued under heating conditions for 4 to 5 hours to obtain the reaction solution, for example, it can be 4.0h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5.0h, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] As a preferred technical solution of the present invention, in step (I), the amount of polyvinyl alcohol added is 7-9wt% of the mass of the reaction solution, for example, it can be 7.0wt%, 7.2wt%, 7.4wt%, 7.6wt%, 7.8wt%, 8.0wt%, 8.2wt%, 8.4wt%, 8.6wt%, 8.8wt% or 9.0wt%, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0028] In some optional examples, the mixing and stirring time of the reaction solution and the polyvinyl alcohol is 2 to 4 hours, for example, it can be 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In some optional examples, the directional freezing process includes:

[0030] The temperature is lowered to a first freezing temperature at a first cooling rate and kept warm, and then the temperature is further lowered to a second freezing temperature at a second cooling rate and kept warm.

[0031] In the present invention, the first cooling stage is a rapid cooling to -15-20°C at a rate of -1-2°C / min, which promotes the formation of a large number of tiny ice crystal nuclei in the solution. During the insulation process, the ice crystals initially extend and grow along the temperature gradient, forming an initial pore framework with a diameter of about 50-150μm. The second cooling stage is a slow cooling to -30-40°C at a rate of -0.5-1°C / min. At this time, the viscosity of the solution increases significantly, inducing the formation of a secondary microporous structure on the walls of the formed initial pores. During the insulation process, the solvent molecules in the residual unfrozen liquid phase are fully crystallized, avoiding the stress concentration caused by rapid deep cooling, and ultimately forming a multi-level pore structure with vertically arranged through-pores and wall micropores interwoven. This multi-level pore structure directly affects the wastewater treatment effect of the material. The through-pore large-diameter channels greatly increase the pollutant adsorption rate, and the secondary microporous structure generated on the walls of the large-pore channels provides a high-density anchoring point for the loading of ZIF-67 crystals.

[0032] In some optional examples, the first cooling rate is -1~-2℃ / min, for example, it can be -1℃ / min, -1.1℃ / min, -1.2℃ / min, -1.3℃ / min, -1.4℃ / min, -1.5℃ / min, -1.6℃ / min, -1.7℃ / min, -1.8℃ / min, -1.9℃ / min or -2℃ / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In some optional examples, the first freezing temperature is -15~-20℃, for example, it can be -15℃, -15.5℃, -16℃, -16.5℃, -17℃, -17.5℃, -18℃, -18.5℃, -19℃, -19.5℃ or -20℃, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] In some optional examples, the insulation time at the first freezing temperature is 0.5~1.5h, for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h or 1.5h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In some optional examples, the second cooling rate is -0.5~-1℃ / min, for example, it can be -0.5℃ / min, -0.55℃ / min, -0.6℃ / min, -0.65℃ / min, -0.7℃ / min, -0.75℃ / min, -0.8℃ / min, -0.85℃ / min, -0.9℃ / min, -0.95℃ / min or -1℃ / min, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0036] In some optional examples, the second freezing temperature is -30~-40℃, for example, it can be -30℃, -31℃, -32℃, -33℃, -34℃, -35℃, -36℃, -37℃, -38℃, -39℃ or -40℃, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In some optional examples, the insulation time at the second freezing temperature is 3 to 4 hours, for example, it can be 3.0 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours or 4.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] As a preferred technical solution of the present invention, in step (I), the hydrophobic modification treatment includes:

[0039] The aerogel matrix is ​​immersed in a silane coupling agent solution and shaken and heated, and then the aerogel matrix is ​​taken out, washed and dried to obtain the modified aerogel matrix.

[0040] During the modification process, the silanol groups generated by the hydrolysis of the silane coupling agent undergo a condensation reaction with the hydroxyl groups on the surface of the aerogel matrix, forming a dense Si-O-Si covalent bond network. The directional arrangement of the long-chain alkyl groups enables the surface contact angle of the modified aerogel matrix to reach above 145°. On the one hand, this chemical modification imparts superhydrophobic properties to the aerogel matrix, effectively blocking the penetration of water molecules and preventing the hydrolysis of ZIF-67 crystals in an aqueous environment, which leads to the dissolution of cobalt ions. This allows the modified aerogel matrix to maintain structural integrity over a wide range of pH values ​​from 3 to 11. On the other hand, the silane layer grafted onto the surface of the aerogel matrix can also strengthen the node connections of the cellulose fibers through intermolecular forces, significantly improving the anti-swelling ability of the modified aerogel matrix in an aqueous environment.

[0041] In some optional examples, the silane coupling agent solution consists of a silane coupling agent and an ethanol aqueous solution.

[0042] In some optional examples, the mass fraction of the silane coupling agent in the silane coupling agent solution is 1.8-2.2 wt%, for example, 1.8 wt%, 1.85 wt%, 1.9 wt%, 1.95 wt%, 2.0 wt%, 2.05 wt%, 2.1 wt%, 2.15 wt% or 2.2 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] In some optional examples, the heating temperature of the aerogel matrix when immersed in the silane coupling agent solution is 35~45°C, for example, it can be 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C or 45°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0044] In some optional examples, the immersion time of the aerogel matrix in the silane coupling agent solution is 12 to 24 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] It should be noted that after the aerogel matrix is ​​soaked, it is taken out, washed with anhydrous ethanol, and then vacuum dried. The present invention does not make specific requirements or special limitations on the temperature and time of vacuum drying. For example, the vacuum drying temperature is 45-55 ° C, for example, it can be 45 ° C, 46 ° C, 47 ° C, 48 ° C, 49 ° C, 50 ° C, 51 ° C, 52 ° C, 53 ° C, 54 ° C or 55 ° C; the vacuum drying time is 10-12 h, for example, it can be 10 h, 10.2 h, 10.4 h, 10.6 h, 10.8 h, 11 h, 11.2 h, 11.4 h, 11.6 h, 11.8 h or 12 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] As a preferred technical solution of the present invention, in step (II), the microbial suspension is prepared by the following method:

[0047] Bacillus subtilis is inoculated into LB liquid culture medium and shaken to obtain a Bacillus subtilis bacterial liquid; the supernatant is then removed by centrifugation, and the precipitated bacteria at the bottom are collected and washed; the washed bacteria are resuspended in a pre-cooled buffer solution and mixed evenly to obtain the microbial suspension.

[0048] It should be noted that the culture process of Bacillus subtilis has been disclosed in the prior art. The present invention does not impose specific requirements or special limitations on the process parameters involved. For example:

[0049] The inoculum amount of Bacillus subtilis in LB liquid culture medium is 0.2-0.4 g / 100 mL of LB liquid culture medium, for example, 0.2 g / 100 mL, 0.22 g / 100 mL, 0.24 g / 100 mL, 0.26 g / 100 mL, 0.28 g / 100 mL, 0.3 g / 100 mL, 0.32 g / 100 mL, 0.34 g / 100 mL, 0.36 g / 100 mL, 0.38 g / 100 mL or 0.4 g / 100 mL.

[0050] The temperature of the shaking culture is 35-37°C, for example, 35°C, 35.2°C, 35.4°C, 35.6°C, 35.8°C, 36°C, 36.2°C, 36.4°C, 36.6°C, 36.8°C or 37°C.

[0051] The shaking speed of the shaking culture is 180-200 rpm, for example, it can be 180 rpm, 182 rpm, 184 rpm, 186 rpm, 188 rpm, 190 rpm, 192 rpm, 194 rpm, 196 rpm, 198 rpm or 200 rpm.

[0052] The shaking culture time is 12 to 24 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours.

[0053] The centrifugation temperature of the Bacillus subtilis culture liquid is 4-6°C, for example, 4.0°C, 4.2°C, 4.4°C, 4.6°C, 4.8°C, 5.0°C, 5.2°C, 5.4°C, 5.6°C, 5.8°C or 6.0°C.

[0054] The centrifugal speed of the Bacillus subtilis culture liquid is 4000-6000 rpm, for example, it can be 4000 rpm, 4200 rpm, 4400 rpm, 4600 rpm, 4800 rpm, 5000 rpm, 5200 rpm, 5400 rpm, 5600 rpm, 5800 rpm or 6000 rpm.

[0055] The centrifugation time of the Bacillus subtilis culture liquid is 5 to 10 min, for example, 5.0 min, 5.5 min, 6.0 min, 6.5 min, 7.0 min, 7.5 min, 8.0 min, 8.5 min, 9.0 min, 9.5 min or 10.0 min.

[0056] In some optional examples, the pre-cooling temperature of the buffer solution is 4~6°C, for example, it can be 4.0°C, 4.2°C, 4.4°C, 4.6°C, 4.8°C, 5.0°C, 5.2°C, 5.4°C, 5.6°C, 5.8°C or 6.0°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0057] In some optional examples, the buffer consists of trehalose, polyethylene glycol 6000 and deionized water.

[0058] In some optional examples, the mass fraction of trehalose in the buffer is 5~10wt%, for example, it can be 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt% or 10.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] In some optional examples, the mass fraction of polyethylene glycol 6000 in the buffer solution is 1~2wt%, for example, it can be 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt% or 2.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] In some optional examples, the ratio of the bacteria to the buffer is 1g:(5~10)mL, for example, it can be 1g:5.0mL, 1g:5.5mL, 1g:6.0mL, 1g:6.5mL, 1g:7.0mL, 1g:7.5mL, 1g:8.0mL, 1g:8.5mL, 1g:9.0mL, 1g:9.5mL or 1g:10.0mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] As a preferred technical solution of the present invention, in step (II), the volume ratio of the microbial suspension to the sodium alginate solution when mixed is 1:(2-3), for example, it can be 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9 or 1:3.0, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0062] The present invention specifically limits the volume ratio of the microbial suspension to the sodium alginate solution to 1:(2-3) when mixed. When the volume ratio is within this range, the integrity of the gel shell is ensured while maintaining the mass transfer pathways required for microbial metabolism. In the mixed system, the sodium alginate molecular chains, through the directional arrangement of carboxylic acid groups, chelate with calcium ions to form a three-dimensional network structure with a moderate cross-linking density, which facilitates the penetration of nutrients and the diffusion of metabolites.

[0063] If the amount of sodium alginate solution added exceeds the upper limit of the range specified in the present invention, the entanglement of the high-concentration sodium alginate molecular chains hinders the uniform penetration of calcium ions. The gel shell quickly forms a dense cross-linked layer, while the inner core area presents a loose flocculated structure due to insufficient calcium ion concentration. This non-uniform solidification leads to an imbalance in the mechanical strength distribution of the sustained-release capsule particles. The outer shell is hard and brittle and easily broken, while the inner core cannot effectively restrain microorganisms due to its loose structure.

[0064] If the amount of sodium alginate solution added falls below the lower limit of the range specified in this invention, the gel network crosslink density is insufficient, and the sparse molecular chain spacing causes the sustained-release capsule particles to expand excessively during the swelling process. Repeated swelling-contraction cycles can lead to structural fatigue crack propagation. Furthermore, the weak three-dimensional network cannot effectively block external hydraulic shear, leading to explosive microbial proliferation in the early stages of wastewater treatment, completely eliminating the sustained-release effect.

[0065] In some optional examples, the mass fraction of the sodium alginate solution is 2~4wt%, for example, it can be 2.0wt%, 2.2wt%, 2.4wt%, 2.6wt%, 2.8wt%, 3.0wt%, 3.2wt%, 3.4wt%, 3.6wt%, 3.8wt% or 4.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] In some optional examples, the pressure of the high-pressure homogenization is 150~200 MPa, for example, it can be 150 MPa, 155 MPa, 160 MPa, 165 MPa, 170 MPa, 175 MPa, 180 MPa, 185 MPa, 190 MPa, 195 MPa or 200 MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0067] In some optional examples, the number of high-pressure homogenization is 5 to 7 times, for example, 5 times, 6 times or 7 times, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] It should be noted that, preferably, before the gel precursor emulsion is dripped into the calcium chloride solution, the calcium chloride solution is stirred. For example, the stirring speed is 700-800 rpm, for example, it can be 700 rpm, 710 rpm, 720 rpm, 730 rpm, 740 rpm, 750 rpm, 760 rpm, 770 rpm, 780 rpm, 790 rpm or 800 rpm. The present invention does not make specific requirements or special restrictions on the dripping speed of the gel precursor emulsion into the calcium chloride solution. For example, the dripping speed is 0.3-0.5 mL / min, for example, it can be 0.3 mL / min, 0.32 mL / min, 0.34 mL / min, 0.36 mL / min, 0.38 mL / min, 0.4 mL / min, 0.42 mL / min, 0.44 mL / min, 0.46 mL / min, 0.48 mL / min or 0.5 mL / min.

[0069] In some optional examples, the mass fraction of the calcium chloride solution is 2~5wt%, for example, it can be 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt% or 5.0wt%, but is not limited to the enumerated values, and other unlisted values ​​within the numerical range are also applicable.

[0070] The present invention particularly limits the mass fraction of the calcium chloride solution to 2-5wt%. When the mass fraction of the calcium chloride solution is lower than 2wt%, the cross-linking sites between the sodium alginate molecular chains cannot be fully saturated, and the formed gel network presents a loose flocculent structure, which is prone to deformation and collapse during the secondary cross-linking stage of glutaraldehyde. Under the action of hydraulic pressure, the shell will rupture and the core will disintegrate.

[0071] When the mass fraction of calcium chloride solution exceeds 5wt%, the rapid cross-linking caused by high concentration of calcium ions will destroy the ordered assembly of sodium alginate molecular chains. Excessive calcium ions instantly form a dense cross-linked layer on the surface of the emulsion droplets, seriously hindering the diffusion of calcium ions inward, causing the capsule to present a non-uniform structure of "hardened shell and liquid core". This structure will produce stress cracks during the drying process due to the difference in shrinkage rate between the shell and the core, significantly reducing the mechanical stability of the material.

[0072] As a preferred technical solution of the present invention, in step (II), the glutaraldehyde cross-linking operation step includes: taking out the gel particles and immersing them in a glutaraldehyde solution, and cross-linking in the dark to obtain microcapsule particles.

[0073] In some optional examples, the mass fraction of the glutaraldehyde solution is 1~2wt%, for example, it can be 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt% or 2.0wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0074] The present invention specifically limits the mass fraction of the glutaraldehyde solution to 1-2wt%. Within the concentration range defined in the present invention, the glutaraldehyde molecules cross-link with the hydroxyl groups and carboxylic acid groups of sodium alginate and the amino groups on the surface of microbial cells through their dialdehyde groups. While strengthening the mechanical strength of the sustained-release capsule particles, the cells can also be fixed in position through covalent bonding, forming a dense protective layer on the outer layer and maintaining a moderate swelling space in the inner layer, thereby reserving material exchange channels for microbial metabolic activities.

[0075] When the mass fraction of the glutaraldehyde solution is less than 1wt%, the aldehyde group supply is insufficient, the cross-linking reaction is limited, and the density of the connection points between the sodium alginate molecular chains is significantly reduced. The insufficiently cross-linked gel network exhibits a loose flocculent structure, which is prone to structural collapse during the sewage treatment process. Furthermore, low concentrations of glutaraldehyde have a weak fixation effect on microbial cells. The internal stress generated by the migration of free bacteria within the sustained-release capsule particles accelerates structural destruction, causing most microorganisms to be released early in the sewage treatment process, thus losing the sustained-release effect.

[0076] When the mass fraction of the glutaraldehyde solution exceeds 2wt%, excessive cross-linking caused by the high concentration of aldehyde groups will destroy the gel network. Excessive glutaraldehyde molecules form a dense cross-linked layer on the surface of the gel particles, severely hindering the penetration and diffusion of subsequent reaction reagents. This leads to a large difference in cross-link density between the inner and outer layers. During the drying process, uneven shrinkage stress causes microcracks, significantly weakening the mechanical strength of the material. Furthermore, high concentrations of glutaraldehyde can penetrate cell membranes and irreversibly cross-link with intracellular enzymes, destroying the metabolically active sites of microorganisms and inactivating a large number of functional bacterial communities.

[0077] In some optional examples, the immersion time of the gel particles in the glutaraldehyde solution is 2 to 4 hours, for example, it can be 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0078] It should be noted that the gel particles are taken out and dried after being cross-linked in the glutaraldehyde solution. The present invention does not make specific requirements and special limitations on the drying temperature and drying time. Exemplarily, the drying temperature of the gel particles is 30~40°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, and the drying time of the gel particles is 12~24h, for example, it can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0079] As a preferred technical solution of the present invention, in step (III), the mass fraction of the sustained-release capsule particles in the dispersion is 5 to 10 wt%, for example, it can be 5.0 wt%, 5.5 wt%, 6.0 wt%, 6.5 wt%, 7.0 wt%, 7.5 wt%, 8.0 wt%, 8.5 wt%, 9.0 wt%, 9.5 wt% or 10.0 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0080] In some optional examples, the impregnation process includes:

[0081] The modified aerogel matrix and the dispersion are added to a reactor, the modified aerogel matrix is ​​completely immersed in the dispersion, the reactor is evacuated, and then restored to normal pressure, and the dispersion is stirred under normal pressure; then the evacuation is continued; and the evacuation and restoration of the reactor to normal pressure are repeated 5 to 8 times.

[0082] In some optional examples, the mass ratio of the modified aerogel matrix to the sustained-release capsule particles in the dispersion is 1:(1-2), for example, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0083] The present invention specifically limits the mass ratio of the modified aerogel matrix to the sustained-release capsule particles in the dispersion to 1:(1-2). Within the mass ratio range defined by the present invention, the sustained-release capsule particles can be fully embedded in the inner walls of the vertically arranged micron-sized pores of the modified aerogel matrix, forming a stable bond with the surface chemical bonding through capillary adsorption. This structure not only retains the material transport capability of the through-pores of the modified aerogel matrix, but also restricts the movement of the sustained-release capsule particles.

[0084] When the amount of sustained-release capsule particles added is lower than the lower limit of the range defined in the present invention, a large number of pores in the modified aerogel matrix are left vacant due to the low loading amount of the sustained-release capsule particles. These unused micron-sized pores become secondary adsorption sites for pollutants in the sewage environment.

[0085] When the amount of sustained-release capsule particles added exceeds the upper limit of the range specified in this invention, the excess particles accumulate within the pores of the modified aerogel matrix, hindering the diffusion and penetration of microorganisms and metabolites. Furthermore, excessive accumulation of sustained-release capsule particles can cause the modified aerogel matrix to undergo plastic deformation under sustained compressive strain, leading to excessive stress concentration in localized areas. This can cause microcrack propagation under long-term hydraulic erosion, shortening the material's fatigue life.

[0086] In some optional examples, the reactor is evacuated to -85~-95kPa, for example, it can be -85kPa, -86kPa, -87kPa, -88kPa, -89kPa, -90kPa, -91kPa, -92kPa, -93kPa, -94kPa or -95kPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0087] In some optional examples, the reactor maintains vacuum for 20 to 30 minutes, for example, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes or 30 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0088] In some optional examples, at the normal pressure stage, the dispersion is stirred for 10 to 15 minutes, for example, 10 minutes, 10.5 minutes, 11 minutes, 11.5 minutes, 12 minutes, 12.5 minutes, 13 minutes, 13.5 minutes, 14 minutes, 14.5 minutes or 15 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0089] It should be noted that after the impregnation is completed, the impregnated modified aerogel matrix is ​​taken out and dried. The present invention does not make specific requirements and special limitations on the drying temperature and time. For example, the drying temperature is 50-60 ° C, for example, it can be 50 ° C, 51 ° C, 52 ° C, 53 ° C, 54 ° C, 55 ° C, 56 ° C, 57 ° C, 58 ° C, 59 ° C or 60 ° C, and the drying time is 12-24 h, for example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h or 24 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0090] In a second aspect, the present invention provides a microbial slow-release porous composite material for sewage treatment, which is prepared by the preparation method described in the first aspect.

[0091] In a third aspect, the present invention provides a use of the microbial slow-release porous composite material for sewage treatment according to the second aspect, wherein the microbial slow-release porous composite material is used for sewage treatment.

[0092] Compared with the prior art, the present invention has the following beneficial effects:

[0093] The present invention combines an aerogel matrix with a multi-level pore structure with a sustained-release capsule with a pH response mechanism to achieve physical adsorption, chemical catalysis and biodegradation in sewage treatment. The vertical through-holes of the modified aerogel matrix provide high-speed channels for pollutant enrichment and mass transfer. The Co of the surface-loaded ZIF-67 2+ The nodes provide Lewis acid sites, which specifically bind to sulfur-, phosphorus-, or nitrogen-containing pollutants through coordination, enhancing the adsorption selectivity for polar or structurally specific pollutants. A gradient cross-linking process was used to prepare the double-layered sustained-release capsule particles. The outer shell maintains structural integrity under water impact, while the inner core retains active space for microbial colonization and metabolism. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 A flow chart of the preparation process of the microbial sustained-release porous composite material provided in Examples 1-15 of the present invention;

[0095] Figure 2 The infrared spectra of nanocellulose, ZIF-67 and the aerogel matrix prepared in Example 1 of the present invention are shown;

[0096] Figure 3 XRD spectra of nanocellulose, ZIF-67 and the aerogel matrix prepared in Example 1 of the present invention;

[0097] Figure 4Graphs showing the water contact angle and oil contact angle of the modified aerogel matrix prepared in Example 1 of the present invention;

[0098] Figure 5 This is a swelling ratio curve of the sustained-release capsule particles prepared in Example 1 of the present invention at different pH values;

[0099] Figure 6 This is a scanning electron microscope image of the sustained-release capsule particles prepared in Example 1 of the present invention;

[0100] Figure 7 This is a cumulative release rate curve of the microbial sustained-release porous composite material prepared in Example 1 of the present invention under different pH environments. DETAILED DESCRIPTION

[0101] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0102] Example 1

[0103] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0104] (1) Cobalt nitrate was dispersed in deionized water and mixed to obtain a cobalt source solution with a concentration of 0.15 mol / L. A nanocellulose solution with a mass fraction of 1 wt% and the cobalt source solution were mixed at a volume ratio of 3:1 to obtain a precursor solution. 2-Methylimidazole was dispersed in methanol and mixed to obtain an organic ligand solution with a concentration of 0.9 mol / L. Under stirring and heating conditions at 60°C, the organic ligand solution was dropped into the precursor solution at a rate of 1.5 mL / min. The molar ratio of 2-methylimidazole to cobalt ions was 5:1. After all the organic ligand solution was dropped, the obtained mixture was stirred at 60°C for 5 h to obtain a reaction solution.

[0105] The reaction solution was mixed and stirred with polyvinyl alcohol (PVA) for 2 h, with the amount of PVA added being 7 wt % of the mass of the reaction solution. The mixed solution was then injected into a mold for directional freezing. First, the temperature was lowered to -15°C at a cooling rate of -1°C / min and kept at that temperature for 1.5 h. Subsequently, the temperature was further lowered to -30°C at a cooling rate of -0.5°C / min and kept at that temperature for 4 h to obtain an aerogel matrix.

[0106] Silane coupling agent KH550 was added to an ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 9:1), and the mixture was uniformly mixed to obtain a silane coupling agent solution with a mass fraction of 1.8 wt%. An aerogel matrix was immersed in the silane coupling agent solution and shaken at 35°C for 24 hours. The aerogel matrix was then removed, washed with ethanol, and vacuum dried at 45°C for 12 hours to obtain a modified aerogel matrix.

[0107] (2) Bacillus subtilis was inoculated into LB liquid culture medium at an inoculum amount of 0.2 g / 100 mL of LB liquid culture medium, and then cultured at an ambient temperature of 35°C and an oscillation speed of 180 rpm for 24 h to obtain a Bacillus subtilis bacterial solution; the Bacillus subtilis bacterial solution was centrifuged at 4°C and a speed of 4000 rpm for 10 min, the supernatant was removed after centrifugation, and the precipitated bacteria at the bottom were collected for washing; trehalose, polyethylene glycol 6000 and deionized water were mixed to obtain a buffer solution, the mass fraction of trehalose in the buffer solution was 5 wt%, and the mass fraction of polyethylene glycol 6000 was 1 wt%; the buffer solution was precooled to 4°C, and then the washed bacteria were resuspended in the precooled buffer solution, the ratio of bacteria to buffer solution was 1 g:5 mL, and the microbial suspension was obtained after mixing evenly;

[0108] A microbial suspension was mixed with a 2 wt % sodium alginate solution at a volume ratio of 1:2, and the mixture was uniformly mixed to obtain a gel precursor solution. The gel precursor solution was subjected to high-pressure homogenization at 150 MPa for 7 times to obtain a gel precursor emulsion. A calcium chloride solution was stirred at a high speed of 700 rpm, and the gel precursor emulsion was dripped into the stirred 2 wt % calcium chloride solution at a dripping rate of 0.3 mL / min to obtain gel particles. The gel particles were taken out and immersed in a 1 wt % glutaraldehyde solution, and cross-linked in the dark for 4 h to obtain microcapsule particles. The microcapsule particles were taken out and vacuum dried at 30° C. for 24 h to obtain sustained-release capsule particles.

[0109] (3) The sustained-release capsule particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the sustained-release capsule particles in the dispersion is 5 wt %. The modified aerogel matrix and the dispersion obtained in step (1) are added to a reactor, wherein the mass ratio of the modified aerogel matrix to the sustained-release capsule particles is 1:1, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion. The reactor is evacuated to -85 kPa and maintained for 30 min. Subsequently, nitrogen is introduced into the reactor to restore the pressure to normal, and the dispersion is stirred for 10 min. Subsequently, the reactor is further evacuated to -85 kPa and maintained for 30 min. The reactor is repeatedly evacuated and restored to normal pressure 8 times, and then taken out and vacuum-dried at 50° C. for 24 h to obtain the microbial sustained-release porous composite material.

[0110] Figure 2 The infrared spectra of nanocellulose, ZIF-67 and the aerogel matrix prepared in this embodiment are shown in FIG. As can be seen from the figure, in the infrared spectrum of nanocellulose, 3460 cm -1 and 1735cm -1 The characteristic peaks at 422 cm-1 are attributed to the CH stretching of cellulose hydroxyl groups and the C=O stretching vibration of carboxyl groups. -1 The absorption band at 1382 cm is attributed to the Co-N stretching vibration of ZIF-67. -1 、1417cm -1 and 1453cm -1 The vibration peak at 689 cm is attributed to the CN bond stretching vibration of 2-methylimidazole. -1 、753cm -1 and 1306cm -1 The characteristic peak at is attributed to the bending vibration of 2-methylimidazole. The above results indicate that ZIF-67 nanoparticles are successfully loaded on the aerogel matrix.

[0111] Figure 3 Figure 2 shows the XRD spectra of nanocellulose, ZIF-67, and the aerogel matrix prepared in this example. As can be seen from the figure, the main diffraction peaks at 7.4°, 10.4°, 12.7°, 18.1°, and 26.7° (2θ) correspond to the (011), (002), (112), (222), and (134) crystal planes of ZIF-67, respectively. Furthermore, in the XRD spectrum of the aerogel matrix, the weak characteristic peak at 22.6° is attributed to the (002) crystal plane of nanocellulose. These results indicate that ZIF-67 was successfully loaded onto the aerogel matrix.

[0112] Figure 4The water contact angle and oil contact angle test curves of the modified aerogel matrix prepared in this example are shown. As can be seen from the figure, with the extension of the test time, the surface water contact angle of the modified aerogel matrix decreases slightly, but its average value is 145°, which is still a super hydrophobic surface; similarly, with the extension of the test time, the surface oil contact angle of the modified aerogel matrix also decreases slightly, but its average value is 10°, which is a super oleophilic surface, indicating that the modified aerogel matrix obtained after modification with the silane coupling agent has hydrophobic and oleophilic properties.

[0113] Figure 5 The following graph shows the swelling ratio of the sustained-release capsule particles prepared in this example at different pH values. As can be seen from the graph, the swelling ratio of the sustained-release capsule particles first increases and then decreases with increasing pH in water. The swelling ratio in an aqueous environment with a pH of 4 is less than 1, while in an aqueous environment with a pH of 6, the swelling ratio can reach as high as 20. This is because, in the low pH range (pH < 5), the carboxylic acid groups (-COOH) of sodium alginate are largely protonated, forming intramolecular and intermolecular hydrogen bonds. The presence of hydrogen bonds enhances the interactions between polymer chains, resulting in a compact gel network, reduced porosity, and suppressed swelling ratio. Furthermore, the covalent network formed by glutaraldehyde crosslinking is highly stable under acidic conditions, further limiting the swelling space of the gel. In the intermediate pH range (pH = 5-7), as the pH increases, the carboxylic acid groups gradually deprotonate (-COO⁻), generating electrostatic repulsion. The repulsion between the negatively charged carboxylate ions causes the polymer chains to stretch, expanding the network pores and increasing water permeability. The swelling ratio rises rapidly, reaching a peak around pH = 6. At this point, the carboxylic acid groups are highly ionized, and electrostatic repulsion dominates network expansion, while the cross-linked structure remains intact, creating an optimal balance between swelling and mechanical strength. In the high pH range (pH > 7), excess OH⁻ reacts with sodium alginate to hydrolyze the polysaccharide chains, disrupting the gel network integrity. Despite the complete ionization of the carboxylic acid groups, the network collapses, reducing swelling capacity. Therefore, the sustained-release capsule particles prepared by the present invention exhibit a network contraction due to hydrogen bonding at low pH, while structural disruption and charge shielding dominate at high pH. At intermediate pH, optimal swelling performance is achieved due to maximized electrostatic repulsion. This characteristic endows the sustained-release capsule particles with pH-responsive release, enabling them to adapt to the dynamically changing pollutant loads encountered in wastewater treatment.

[0114] Figure 6 This is a scanning electron microscope image of the sustained-release capsule particles prepared in this example. It can be seen from the figure that the sustained-release capsule particles have a regular shape and a uniform particle size spherical structure. The particle size distribution is mainly concentrated in the range of 1 to 5 μm, with an average particle size of 2.5 μm.

[0115] Figure 7This is a cumulative release rate curve of the microbial slow-release porous composite material prepared in this embodiment under different pH environments. It can be seen from the figure that the microbial slow-release porous composite material prepared in this embodiment has an excellent slow-release effect and can stably release microorganisms within 10 days. At the same time, the slow-release effect of the microbial slow-release porous composite material is different in different pH environments. It triggers rapid release in high-load sewage (pH=6) (degrading 68.9% of COD in 5 days), avoiding pollutant accumulation, and maintains long-term release in conventional sewage (pH=7.4) (continuous effect for 10 days), reducing the frequency of bacterial replenishment.

[0116] Example 2

[0117] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0118] (1) Cobalt nitrate was dispersed in deionized water and mixed to obtain a cobalt source solution with a concentration of 0.18 mol / L. A nanocellulose solution with a mass fraction of 1.2 wt% and the cobalt source solution were mixed at a volume ratio of 2.8:1 to obtain a precursor solution. 2-Methylimidazole was dispersed in methanol and mixed to obtain an organic ligand solution with a concentration of 0.92 mol / L. Under stirring and heating conditions at 62°C, the organic ligand solution was dropped into the precursor solution at a rate of 1.8 mL / min. The molar ratio of 2-methylimidazole to cobalt ions was 5.2:1. After all the organic ligand solution was dropped, the obtained mixture was stirred at 62°C for 4.8 h to obtain a reaction solution.

[0119] The reaction solution was mixed and stirred with polyvinyl alcohol (7.5 wt % of the mass of the reaction solution) for 2.5 h. The mixed solution was injected into a mold for directional freezing. First, the temperature was cooled to -16°C at a cooling rate of -1.2°C / min and kept at that temperature for 1.2 h. Then, the temperature was further cooled to -32°C at a cooling rate of -0.6°C / min and kept at that temperature for 3.8 h to obtain an aerogel matrix.

[0120] Silane coupling agent KH550 was added to an ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 9:1), and the mixture was uniformly mixed to obtain a silane coupling agent solution with a mass fraction of 1.9 wt%. An aerogel matrix was immersed in the silane coupling agent solution and shaken at 38°C for 21 hours. The aerogel matrix was then removed, washed with ethanol, and vacuum dried at 48°C for 11.5 hours to obtain a modified aerogel matrix.

[0121] (2) Bacillus subtilis was inoculated into LB liquid culture medium at an inoculum amount of 0.25 g / 100 mL of LB liquid culture medium, and then cultured at an ambient temperature of 35.5°C and an oscillation speed of 185 rpm for 21 h to obtain a Bacillus subtilis bacterial solution; the Bacillus subtilis bacterial solution was centrifuged at 4.5°C and a speed of 4500 rpm for 8 min, the supernatant was removed after centrifugation, and the precipitated bacteria at the bottom were collected and washed; trehalose, polyethylene glycol 6000 and deionized water were mixed to obtain a buffer solution, the mass fraction of trehalose in the buffer solution was 6 wt%, and the mass fraction of polyethylene glycol 6000 was 1.2 wt%; the buffer solution was precooled to 4.5°C, and then the washed bacteria were resuspended in the precooled buffer solution, the ratio of bacteria to buffer solution was 1 g:6 mL, and the microbial suspension was obtained after mixing evenly;

[0122] A microbial suspension was mixed with a sodium alginate solution having a mass fraction of 2.5 wt %, with a volume ratio of the microbial suspension to the sodium alginate solution being 1:2.2. After uniform mixing, a gel precursor solution was obtained, and the gel precursor solution was subjected to high-pressure homogenization at 160 MPa for 6 times to obtain a gel precursor emulsion; a calcium chloride solution was stirred at a high speed of 720 rpm, and the gel precursor emulsion was dripped into the stirred calcium chloride solution having a mass fraction of 3 wt % at a dripping rate of 0.35 mL / min to obtain gel particles; the gel particles were taken out and immersed in a glutaraldehyde solution having a mass fraction of 1.2 wt %, and cross-linked in the dark for 3.5 h to obtain microcapsule particles; the microcapsule particles were taken out and vacuum dried at 32° C. for 21 h to obtain sustained-release capsule particles;

[0123] (3) The sustained-release capsule particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the sustained-release capsule particles in the dispersion is 6 wt %. The modified aerogel matrix and the dispersion obtained in step (1) are added to a reactor, wherein the mass ratio of the modified aerogel matrix to the sustained-release capsule particles is 1:1.2, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion. The reactor is evacuated to -88 kPa and maintained for 28 min. Subsequently, nitrogen is introduced into the reactor to restore the pressure to normal, and the dispersion is stirred for 12 min. Subsequently, the reactor is further evacuated to -88 kPa and maintained for 28 min. The reactor is repeatedly evacuated and restored to normal pressure 7 times, and then taken out and vacuum-dried at 52 ° C for 21 h to obtain the microbial sustained-release porous composite material.

[0124] Example 3

[0125] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0126] (1) Cobalt nitrate was dispersed in deionized water and mixed to obtain a cobalt source solution with a concentration of 0.2 mol / L. A nanocellulose solution with a mass fraction of 1.5 wt% and the cobalt source solution were mixed at a volume ratio of 2.5:1 to obtain a precursor solution. 2-Methylimidazole was dispersed in methanol and mixed to obtain an organic ligand solution with a concentration of 0.95 mol / L. Under stirring and heating conditions at 65°C, the organic ligand solution was dropped into the precursor solution at a rate of 2 mL / min. The molar ratio of 2-methylimidazole to cobalt ions was 5.5:1. After all the organic ligand solution was dropped, the obtained mixture was stirred at 65°C for 4.5 h to obtain a reaction solution.

[0127] The reaction solution was mixed and stirred with polyvinyl alcohol (PVA) for 3 h, with the amount of PVA added being 8 wt % of the mass of the reaction solution. The mixed solution was then injected into a mold for directional freezing. First, the temperature was cooled to -17°C at a cooling rate of -1.5°C / min and kept at that temperature for 1 h, and then the temperature was further cooled to -35°C at a cooling rate of -0.7°C / min and kept at that temperature for 3.5 h, thereby obtaining an aerogel matrix.

[0128] Silane coupling agent KH550 was added to an ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 9:1), and the mixture was uniformly mixed to obtain a silane coupling agent solution with a mass fraction of 2 wt%. An aerogel matrix was immersed in the silane coupling agent solution and shaken at 40°C for 18 hours. The aerogel matrix was then removed, washed with ethanol, and vacuum dried at 50°C for 11 hours to obtain a modified aerogel matrix.

[0129] (2) Bacillus subtilis was inoculated into LB liquid culture medium at an inoculum amount of 0.3 g / 100 mL of LB liquid culture medium, and then cultured at an ambient temperature of 36°C and an oscillation speed of 190 rpm for 18 h to obtain a Bacillus subtilis bacterial solution; the Bacillus subtilis bacterial solution was centrifuged at 5°C and a speed of 5000 rpm for 7 min, the supernatant was removed after centrifugation, and the precipitated bacteria at the bottom were collected for washing; trehalose, polyethylene glycol 6000 and deionized water were mixed to obtain a buffer solution, the mass fraction of trehalose in the buffer solution was 7 wt%, and the mass fraction of polyethylene glycol 6000 was 1.5 wt%; the buffer solution was precooled to 5°C, and then the washed bacteria were resuspended in the precooled buffer solution, the ratio of bacteria to buffer solution was 1 g:7 mL, and the microbial suspension was obtained after mixing evenly;

[0130] A microbial suspension was mixed with a 3 wt % sodium alginate solution at a volume ratio of 1:2.5, and the mixture was uniformly mixed to obtain a gel precursor solution. The gel precursor solution was subjected to high-pressure homogenization at 180 MPa for 6 times to obtain a gel precursor emulsion. A calcium chloride solution was stirred at a high speed of 750 rpm, and the gel precursor emulsion was dripped into the stirred 3 wt % calcium chloride solution at a dripping rate of 0.4 mL / min to obtain gel particles. The gel particles were taken out and immersed in a 1.5 wt % glutaraldehyde solution, and cross-linked in the dark for 3 h to obtain microcapsule particles. The microcapsule particles were taken out and vacuum dried at 35° C. for 18 h to obtain sustained-release capsule particles.

[0131] (3) The sustained-release capsule particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the sustained-release capsule particles in the dispersion is 7 wt %. The modified aerogel matrix and the dispersion obtained in step (1) are added to a reactor, wherein the mass ratio of the modified aerogel matrix to the sustained-release capsule particles is 1:1.5, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion. The reactor is evacuated to -90 kPa and maintained for 25 min. Subsequently, nitrogen is introduced into the reactor to restore the pressure to normal, and the dispersion is stirred for 13 min. Subsequently, the reactor is further evacuated to -90 kPa and maintained for 25 min. The reactor is repeatedly evacuated and restored to normal pressure 7 times, and then taken out and vacuum-dried at 55° C. for 18 h to obtain the microbial sustained-release porous composite material.

[0132] Example 4

[0133] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0134] (1) Cobalt nitrate was dispersed in deionized water and mixed to obtain a cobalt source solution with a concentration of 0.22 mol / L. A nanocellulose solution with a mass fraction of 1.8 wt% and the cobalt source solution were mixed at a volume ratio of 2.2:1 to obtain a precursor solution. 2-Methylimidazole was dispersed in methanol and mixed to obtain an organic ligand solution with a concentration of 0.98 mol / L. Under stirring and heating conditions at 68°C, the organic ligand solution was dropped into the precursor solution at a rate of 2.2 mL / min. The molar ratio of 2-methylimidazole to cobalt ions was 5.8:1. After all the organic ligand solution was dropped, the obtained mixture was stirred at 68°C for 4.2 h to obtain a reaction solution.

[0135] The reaction solution was mixed and stirred with polyvinyl alcohol (PVA) for 3.5 h, with the amount of PVA added being 8.5 wt % of the mass of the reaction solution. The mixed solution was injected into a mold for directional freezing. First, the temperature was cooled to -18°C at a cooling rate of -1.8°C / min and kept at that temperature for 0.8 h. Then, the temperature was further cooled to -38°C at a cooling rate of -0.8°C / min and kept at that temperature for 3.2 h to obtain an aerogel matrix.

[0136] Silane coupling agent KH550 was added to an ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 9:1), and the mixture was uniformly mixed to obtain a silane coupling agent solution with a mass fraction of 2.1 wt%. An aerogel matrix was immersed in the silane coupling agent solution and shaken at 42°C for 15 hours. The aerogel matrix was then removed, washed with ethanol, and vacuum dried at 52°C for 10.5 hours to obtain a modified aerogel matrix.

[0137] (2) Bacillus subtilis was inoculated into LB liquid culture medium at an inoculum amount of 0.35 g / 100 mL of LB liquid culture medium, and then cultured at an ambient temperature of 36.5°C and an oscillation speed of 195 rpm for 15 h to obtain a Bacillus subtilis bacterial solution; the Bacillus subtilis bacterial solution was centrifuged at 5.5°C and a speed of 5500 rpm for 6 min, the supernatant was removed after centrifugation, and the precipitated bacteria at the bottom were collected and washed; trehalose, polyethylene glycol 6000 and deionized water were mixed to obtain a buffer solution, the mass fraction of trehalose in the buffer solution was 8 wt%, and the mass fraction of polyethylene glycol 6000 was 1.8 wt%; the buffer solution was precooled to 5.5°C, and then the washed bacteria were resuspended in the precooled buffer solution, the ratio of bacteria to buffer solution was 1 g:8 mL, and the microbial suspension was obtained after mixing evenly;

[0138] A microbial suspension was mixed with a sodium alginate solution having a mass fraction of 3.5 wt %, with a volume ratio of the microbial suspension to the sodium alginate solution being 1:2.8. After uniform mixing, a gel precursor solution was obtained, and the gel precursor solution was subjected to high-pressure homogenization at 190 MPa for 5 times to obtain a gel precursor emulsion; a calcium chloride solution was stirred at a high speed of 780 rpm, and the gel precursor emulsion was dropped into the stirred calcium chloride solution having a mass fraction of 4 wt % at a dropping rate of 0.45 mL / min to obtain gel particles; the gel particles were taken out and immersed in a glutaraldehyde solution having a mass fraction of 1.8 wt %, and cross-linked in the dark for 2.5 h to obtain microcapsule particles; the microcapsule particles were taken out and vacuum dried at 38° C. for 15 h to obtain sustained-release capsule particles;

[0139] (3) The sustained-release capsule particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the sustained-release capsule particles in the dispersion is 8 wt %. The modified aerogel matrix and the dispersion obtained in step (1) are added to a reactor, wherein the mass ratio of the modified aerogel matrix to the sustained-release capsule particles is 1:1.8, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion. The reactor is evacuated to -92 kPa and maintained for 22 min. Subsequently, nitrogen is introduced into the reactor to restore the pressure to normal, and the dispersion is stirred for 14 min. Subsequently, the reactor is further evacuated to -92 kPa and maintained for 22 min. The reactor is repeatedly evacuated and restored to normal pressure for 6 times, and then taken out and vacuum-dried at 58° C. for 15 h to obtain the microbial sustained-release porous composite material.

[0140] Example 5

[0141] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0142] (1) Cobalt nitrate was dispersed in deionized water and mixed to obtain a cobalt source solution with a concentration of 0.25 mol / L. A nanocellulose solution with a mass fraction of 2 wt% and the cobalt source solution were mixed at a volume ratio of 2:1 to obtain a precursor solution. 2-Methylimidazole was dispersed in methanol and mixed to obtain an organic ligand solution with a concentration of 1 mol / L. Under stirring and heating conditions at 70°C, the organic ligand solution was dropped into the precursor solution at a rate of 2.5 mL / min. The molar ratio of 2-methylimidazole to cobalt ions was 6:1. After all the organic ligand solution was dropped, the obtained mixture was stirred for 4 h under heating conditions at 70°C to obtain a reaction solution.

[0143] The reaction solution was mixed and stirred with polyvinyl alcohol (PVA) for 4 h, with the amount of PVA added being 9 wt % of the mass of the reaction solution. The mixed solution was injected into a mold for directional freezing. First, the temperature was cooled to -20°C at a cooling rate of -2°C / min and kept at that temperature for 0.5 h, and then the temperature was further cooled to -40°C at a cooling rate of -1°C / min and kept at that temperature for 3 h, thereby obtaining an aerogel matrix.

[0144] Silane coupling agent KH550 was added to an ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 9:1), and the mixture was uniformly mixed to obtain a silane coupling agent solution with a mass fraction of 2.2 wt%. An aerogel matrix was immersed in the silane coupling agent solution and shaken at 45°C for 12 hours. The aerogel matrix was then removed, washed with ethanol, and vacuum dried at 55°C for 10 hours to obtain a modified aerogel matrix.

[0145] (2) Bacillus subtilis was inoculated into LB liquid culture medium at an inoculum amount of 0.4 g / 100 mL of LB liquid culture medium, and then cultured at an ambient temperature of 37°C and an oscillation speed of 200 rpm for 12 h to obtain a Bacillus subtilis bacterial solution; the Bacillus subtilis bacterial solution was centrifuged at 6°C and a speed of 6000 rpm for 5 min, the supernatant was removed after centrifugation, and the precipitated bacteria at the bottom were collected for washing; trehalose, polyethylene glycol 6000 and deionized water were mixed to obtain a buffer solution, the mass fraction of trehalose in the buffer solution was 10 wt%, and the mass fraction of polyethylene glycol 6000 was 2 wt%; the buffer solution was precooled to 6°C, and then the washed bacteria were resuspended in the precooled buffer solution, the ratio of bacteria to buffer solution was 1 g:10 mL, and the microbial suspension was obtained after mixing evenly;

[0146] A microbial suspension was mixed with a sodium alginate solution having a mass fraction of 4 wt %, with the volume ratio of the microbial suspension to the sodium alginate solution being 1:3. After uniform mixing, a gel precursor solution was obtained. The gel precursor solution was subjected to high-pressure homogenization at 200 MPa for 5 times to obtain a gel precursor emulsion. A calcium chloride solution was stirred at a high speed of 800 rpm, and the gel precursor emulsion was dripped into the stirred calcium chloride solution having a mass fraction of 5 wt % at a dripping rate of 0.5 mL / min to obtain gel particles. The gel particles were taken out and immersed in a glutaraldehyde solution having a mass fraction of 2 wt %, and cross-linked in the dark for 2 h to obtain microcapsule particles. The microcapsule particles were taken out and vacuum dried at 40° C. for 12 h to obtain sustained-release capsule particles.

[0147] (3) The sustained-release capsule particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the sustained-release capsule particles in the dispersion is 10 wt %. The modified aerogel matrix and the dispersion obtained in step (1) are added to a reactor, wherein the mass ratio of the modified aerogel matrix to the sustained-release capsule particles is 1:2, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion. The reactor is evacuated to -95 kPa and maintained for 20 min. Subsequently, nitrogen is introduced into the reactor to restore the pressure to normal, and the dispersion is stirred for 15 min. Subsequently, the reactor is further evacuated to -95 kPa and maintained for 20 min. The reactor is repeatedly evacuated and restored to normal pressure 5 times, and then taken out and vacuum-dried at 60° C. for 12 h to obtain the microbial sustained-release porous composite material.

[0148] Example 6

[0149] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (1), the volume ratio of the nanocellulose solution to the cobalt source solution is adjusted to 1:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0150] Example 7

[0151] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (1), the volume ratio of the nanocellulose solution to the cobalt source solution is adjusted to 4:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0152] Example 8

[0153] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the volume ratio of the microbial suspension and the sodium alginate solution when mixed is adjusted to 1:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0154] Example 9

[0155] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the volume ratio of the microbial suspension and the sodium alginate solution when mixed is adjusted to 1:4, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0156] Example 10

[0157] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the mass fraction of the calcium chloride solution is adjusted to 1 wt %. The other operating steps and process parameters are exactly the same as those in Example 1.

[0158] Example 11

[0159] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the mass fraction of the calcium chloride solution is adjusted to 7 wt %. The other operating steps and process parameters are exactly the same as those in Example 1.

[0160] Example 12

[0161] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the mass fraction of the glutaraldehyde solution is adjusted to 0.1 wt %. The other operating steps and process parameters are exactly the same as those in Example 1.

[0162] Example 13

[0163] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the mass fraction of the glutaraldehyde solution is adjusted to 3 wt %. The other operating steps and process parameters are exactly the same as those in Example 1.

[0164] Example 14

[0165] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (3), the mass ratio of the modified aerogel matrix to the slow-release capsule particles is adjusted to 1:0.5, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0166] Example 15

[0167] This embodiment provides a method for preparing a microbial slow-release porous composite material for sewage treatment. The difference from Example 1 is that in step (3), the mass ratio of the modified aerogel matrix to the slow-release capsule particles is adjusted to 1:3, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0168] The microbial slow-release porous composite material prepared in Examples 1-15 of the present invention is used to treat printing and dyeing wastewater and petrochemical wastewater, specifically comprising:

[0169] The microbial slow-release porous composite material prepared in Examples 1-15 of the present invention was added to printing and dyeing wastewater. The COD value in the printing and dyeing wastewater was 824 mg / L, the NH3-N value was 18.3 mg / L, the suspended matter content was 255 mg / L, and the chromaticity value was 580 times (dilution multiple method). The dosage was 2.5 kg / m 3 After 10 days, the concentrations of various pollutants in the treated printing and dyeing wastewater were tested. The concentrations of various pollutants in the treated printing and dyeing wastewater are shown in Table 1.

[0170] The microbial slow-release porous composite material prepared in Examples 1-15 of the present invention was added to petrochemical wastewater, in which the COD value was 2820 mg / L, the NH3-N value was 58.6 mg / L, the suspended matter content was 236 mg / L, and the petroleum content was 125.3 mg / L. The addition amount was 5 kg / m 3 After 10 days, the concentrations of various pollutants in the treated petrochemical wastewater were tested. The concentrations of various pollutants in the treated petrochemical wastewater are shown in Table 2.

[0171] Table 1

[0172]

[0173] Table 2

[0174]

[0175] The test data in Tables 1 and 2 demonstrate that the effluent quality of Examples 1-5 comprehensively exceeds the national standards for printing and dyeing wastewater (GB 4287-2012, "Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industries") and petrochemical wastewater (GB 31571-2015, "Discharge Standard of Pollutants for Petrochemical Industries"). This technology, through its combination of a multi-stage pore structure and slow-release microorganisms, achieves efficient and stable wastewater treatment performance, making it particularly suitable for the advanced treatment of challenging printing and dyeing wastewater and petrochemical wastewater.

[0176] The test data from Examples 1, 6, and 7 show that the effluent quality of Examples 6 and 7 is inferior to that of Example 1. This is because the insufficient amount of nanocellulose solution in Example 6 caused ZIF-67 crystals to agglomerate, clogging pores and reducing adsorption and catalytic efficiency. The excessive amount of nanocellulose solution in Example 7 affected structural stability, leading to pore collapse and reduced pollutant interception efficiency.

[0177] The test data from Examples 1, 8, and 9 show that the effluent quality of Examples 8 and 9 is inferior to that of Example 1. This is because the amount of sodium alginate solution used in Example 8 was too small, resulting in an unstable gel network structure, excessive microbial release, and poor treatment effectiveness. In Example 9, the amount of sodium alginate solution used was too large, resulting in an overly dense gel network, which hindered mass transfer, reduced microbial activity, and poor treatment effectiveness.

[0178] The test data from Examples 1, 10, and 11 show that the effluent quality of Examples 10 and 11 is inferior to that of Example 1. This is because the mass fraction of the calcium chloride solution in Example 10 is too low, resulting in insufficient crosslinking, which causes the sustained-release capsule particles to break easily, microbial loss, and poor treatment effect. The mass fraction of the calcium chloride solution in Example 11 is too high, resulting in an overly dense gel network, which hinders mass transfer, low microbial activity, and poor treatment effect.

[0179] The test data from Examples 1, 12, and 13 indicate that the effluent quality of Examples 12 and 13 is inferior to that of Example 1. This is because the mass fraction of the glutaraldehyde solution in Example 12 is too low, resulting in insufficient crosslinking, which easily breaks the sustained-release capsule particles, causes microbial loss, and impairs the treatment effect. The mass fraction of the glutaraldehyde solution in Example 13 is too high, resulting in an overly dense gel network, hindering mass transfer, low microbial activity, and poor treatment effect.

[0180] The test data from Examples 1, 14, and 15 show that the effluent quality of Examples 14 and 15 is inferior to that of Example 1. This is because the amount of sustained-release capsule particles used in Example 14 is too small, resulting in insufficient loading and limited treatment capacity. In Example 15, the amount of sustained-release capsule particles used is too large, resulting in clogged pores in the modified aerogel matrix, hindered mass transfer, and reduced treatment efficiency.

[0181] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a microbial slow-release porous composite material for sewage treatment, characterized in that: The preparation method comprises: (I) dropping an organic ligand solution into a precursor solution consisting of a nanocellulose solution and a cobalt source solution to obtain a reaction solution; mixing the reaction solution with polyvinyl alcohol and injecting the mixture into a mold; cooling the mixture to -15--20°C at a cooling rate of -1--2°C / min and keeping the temperature for 0.5-1.5 hours; then cooling the mixture to -30--40°C at a cooling rate of -0.5--1°C / min and keeping the temperature for 3-4 hours to obtain an aerogel matrix; and hydrophobically modifying the aerogel matrix to obtain a modified aerogel matrix; (II) mixing a microbial suspension with a sodium alginate solution in a volume ratio of 1:(2-3) and homogenizing under high pressure to obtain a gel precursor emulsion; dropping the mixture into a calcium chloride solution for gelation to obtain gel particles; then removing the gel particles and immersing them in a 1-2 wt% glutaraldehyde solution; cross-linking in the dark to obtain microcapsule particles; and drying to obtain sustained-release capsule particles; (III) dispersing the sustained-release capsule particles in deionized water to obtain a dispersion; adding the modified aerogel matrix and the dispersion into a reactor, wherein the mass ratio of the modified aerogel matrix to the sustained-release capsule particles in the dispersion is 1:(1-2), and the modified aerogel matrix is ​​completely immersed in the dispersion; the reactor is evacuated, and then restored to normal pressure, and the dispersion is stirred at normal pressure; the reactor is then continuously evacuated; the evacuation and restoration of normal pressure to the reactor are repeated 5-8 times; the reactor is taken out and dried to obtain the microbial sustained-release porous composite material.

2. The preparation method according to claim 1, characterized in that In step (I), the organic ligand solution consists of 2-methylimidazole and methanol; The concentration of 2-methylimidazole in the organic ligand solution is 0.9-1 mol / L; The mass fraction of the nanocellulose solution is 1-2 wt %; The cobalt source solution consists of cobalt nitrate and deionized water; The concentration of cobalt nitrate in the cobalt source solution is 0.15-0.25 mol / L; The volume ratio of the nanocellulose solution to the cobalt source solution is (2-3):1; The molar ratio of 2-methylimidazole in the organic ligand solution to cobalt ions in the cobalt source solution is (5-6):1; Under stirring and heating conditions, dropping the organic ligand solution into the precursor solution; The heating temperature when the organic ligand solution is added dropwise is 60-70°C; After all the organic ligand solution is added dropwise, mixing and stirring are continued under heating conditions for 4 to 5 hours to obtain the reaction solution.

3. The preparation method according to claim 1, characterized in that In step (I), the amount of polyvinyl alcohol added is 7-9 wt % of the mass of the reaction solution; The mixing and stirring time of the reaction solution and the polyvinyl alcohol is 2 to 4 hours.

4. The preparation method according to claim 1, characterized in that In step (I), the hydrophobic modification treatment includes: soaking the aerogel matrix in a silane coupling agent solution and shaking and heating it, then taking out the aerogel matrix, washing and drying it to obtain the modified aerogel matrix; The silane coupling agent solution consists of a silane coupling agent and an ethanol aqueous solution; The mass fraction of the silane coupling agent in the silane coupling agent solution is 1.8-2.2 wt %; The heating temperature of the aerogel matrix when immersed in the silane coupling agent solution is 35-45° C.; The aerogel matrix is ​​immersed in the silane coupling agent solution for 12 to 24 hours.

5. The preparation method according to claim 1, characterized in that In step (II), the microbial suspension is prepared by the following method: Bacillus subtilis was inoculated into LB liquid medium and cultured with shaking to obtain a Bacillus subtilis bacterial solution; the supernatant was then removed by centrifugation, and the precipitated bacteria at the bottom were collected and washed; Resuspending the washed bacteria in a pre-cooled buffer solution and mixing them evenly to obtain the microbial suspension; The pre-cooling temperature of the buffer solution is 4-6°C; The buffer solution consists of trehalose, polyethylene glycol 6000 and deionized water; The mass fraction of trehalose in the buffer solution is 5-10wt%; The mass fraction of polyethylene glycol 6000 in the buffer solution is 1-2 wt %; The ratio of the bacterial cells to the buffer solution is 1 g: (5-10) mL.

6. The preparation method according to claim 1, wherein In step (II), the mass fraction of the sodium alginate solution is 2-4 wt %; The pressure of the high-pressure homogenization is 150~200MPa; The number of times of high pressure homogenization is 5 to 7 times; The mass fraction of the calcium chloride solution is 2-5 wt %.

7. The preparation method according to claim 1, characterized in that In step (II), the gel particles are immersed in the glutaraldehyde solution for 2 to 4 hours.

8. The preparation method according to claim 1, characterized in that In step (III), the mass fraction of the sustained-release capsule particles in the dispersion is 5-10 wt %; The reactor was evacuated to -85~-95kPa; The reactor maintains vacuum for 20 to 30 minutes; At normal pressure, the dispersion is stirred for 10 to 15 minutes.

9. A microbial slow-release porous composite material for sewage treatment prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the microbial slow-release porous composite material for sewage treatment according to claim 9, characterized in that: The microbial slow-release porous composite material is used for sewage treatment.

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