A magnetic particle-loaded porous composite material for sewage treatment, and its preparation method and use

Abstract

The present invention provides a magnetic particle-loaded porous composite material for sewage treatment, a preparation method thereof, and uses thereof, comprising: dripping 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; hydrophobically modifying the aerogel matrix to obtain a modified aerogel matrix; dripping an ammonia solution into an iron source solution for reaction, magnetically separating, washing, and drying the reaction to obtain magnetic particles; modifying the magnetic particles with chitosan to obtain modified magnetic particles; dispersing the modified magnetic particles in deionized water to obtain a dispersion; immersing the modified aerogel matrix in the dispersion and removing it for drying. The magnetic particle-loaded porous composite material prepared by the present invention can simultaneously adsorb heavy metal ions and organic pollutants and catalytically degrade refractory substances, and can be efficiently recovered and regenerated by applying an external magnetic field.

Description

Technical Field

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

[0002] With the acceleration of industrialization and urbanization, water pollution is becoming increasingly serious, especially the urgent need to treat heavy metal ions, organic pollutants, and refractory substances in industrial wastewater. Traditional sewage treatment technologies such as chemical precipitation and activated sludge methods have limitations such as low efficiency, high cost, and easy secondary pollution. Adsorption methods have become a research hotspot due to their ease of operation and wide applicability. However, although conventional adsorption materials such as activated carbon, silica gel and other porous materials have certain adsorption capabilities, they generally have problems such as limited adsorption capacity and difficulty in regeneration. In addition, it is difficult to efficiently separate and recover after adsorption, resulting in material loss and potential environmental risks.

[0003] In recent years, magnetic composite materials have attracted attention due to their ability to achieve rapid solid-liquid separation through an external magnetic field. However, the low specific surface area and insufficient surface active sites of single magnetic materials limit their adsorption performance. In the existing technology, attempts to combine magnetic particles with porous materials mostly use step-by-step loading or chemical cross-linking methods, which have problems such as complex preparation process, poor material structure stability, and easy shedding of magnetic components. In addition, most composite materials have insufficient synergistic adsorption capacity for complex pollutants, making it difficult to remove multiple pollutants simultaneously and efficiently. For example, some materials cannot effectively degrade organic pollutants after adsorbing heavy metals, resulting in limited practical application scenarios. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a magnetic particle-loaded porous composite material for sewage treatment, its preparation method and use. The magnetic particle-loaded porous composite material prepared by the present invention has a high specific surface area, strong mechanical properties and rapid separation ability, can simultaneously adsorb heavy metal ions and organic pollutants and catalytically degrade difficult-to-degrade substances, and achieve efficient recovery and regeneration through an external magnetic field.

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

[0006] In a first aspect, a method for preparing a magnetic particle-loaded porous composite material for sewage treatment is provided, the 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) dropping an ammonia solution into an iron source solution to react, and obtaining magnetic particles after magnetic separation, washing, and drying; and modifying the magnetic particles with chitosan to obtain modified magnetic particles;

[0009] (III) dispersing the modified magnetic 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 magnetic particle-loaded porous composite material.

[0010] This invention provides a method for preparing a magnetic particle-loaded porous composite material. Through the synergistic effect of nanocellulose and metal-organic framework materials, an aerogel matrix with a hierarchical pore structure is constructed, upon which chitosan-modified magnetic particles are loaded. The resulting magnetic particle-loaded porous composite material exhibits a high specific surface area, strong mechanical properties, and rapid separation capabilities. It can simultaneously adsorb heavy metal ions and organic pollutants, catalytically degrade refractory substances, and achieve efficient recovery and regeneration through an external magnetic field.

[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] In the process of preparing modified magnetic particles, first, the co-precipitation method is used to promote the Fe 3+ with Fe 2+Fe(OH)3 and Fe(OH)2 colloids are generated by simultaneous hydrolysis, and spinel-structured Fe3O4 nanoparticles are formed through dehydration and oxidation reactions. The co-precipitation method adopted by the present invention does not require high-temperature calcination, thus avoiding magnetic decay and structural collapse. The generated Fe3O4 magnetic particles have both superparamagnetism and high catalytic activity. Subsequently, chitosan is used to coat and modify the magnetic particles. The flexibility of chitosan is wrapped around the surface of the magnetic particles to construct a dynamic buffer layer. Its rich amino and hydroxyl functional groups can not only inhibit the aggregation of magnetic particles through electrostatic repulsion and steric hindrance effects, but also form multiple interactions with pollutant molecules through coordination, significantly improving the material's adsorption capacity for heavy metal ions and organic pollutants. Finally, glutaraldehyde is used for cross-linking. The three-dimensional network structure formed by glutaraldehyde cross-linking firmly binds the dispersed magnetic particles to form modified magnetic particles with both mechanical strength and flexibility, so that they can still maintain structural integrity under dynamic water flow impact and complex hydraulic conditions, solving the technical problems of traditional magnetic particles being easy to settle and difficult to recover.

[0013] The modified aerogel matrix uses nanocellulose as the skeleton, and a directional freezing process is used to construct vertically penetrating micron-scale pores. Combined with the dodecahedral crystal structure of ZIF-67, a mesoporous network with a high specific surface area is formed. Its hydrophobic modification layer gives the composite material selective adsorption ability, allowing hydrophobic pollutants to preferentially adhere to the pore wall surface. The modified magnetic particles use Fe3O4 as the core and are modified with chitosan to form a core-shell structure. Under acidic conditions, the Fe3O4 core is 3+ Reduced to Fe 2+ , which then reacts with hydrogen peroxide (H2O2) to generate hydroxyl radicals (·OH), which oxidize and decompose the refractory organic matter adsorbed within the pores of the aerogel matrix into small molecules. Unlike traditional photocatalysis that relies on ultraviolet light, the Fenton-like reaction can be carried out at room temperature and pressure. Activated by chemical reagents (H2O2), it avoids the dependence of photocatalysis on light sources and is more suitable for practical applications in complex water environments. In addition, the chitosan on the surface of the modified magnetic particles is rich in amino and hydroxyl groups, which can form electrostatic attraction and hydrogen bonding with the modified aerogel matrix, enhancing the capture efficiency of oppositely charged pollutants. This gives the composite material efficient adsorption capacity and catalytic active sites, which can quickly capture heavy metal ions and activate the Fenton-like reaction to degrade organic matter.

[0014] As a preferred technical solution of the present invention, in step (I), the organic ligand solution consists of 2-methylimidazole and methanol.

[0015] 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.

[0016] 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.

[0017] In some optional examples, the cobalt source solution consists of cobalt nitrate and deionized water.

[0018] 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.

[0019] 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.

[0020] The present invention specifically limits the volume ratio of the nanocellulose solution to the cobalt source solution to (2-3):1. As the core component of the aerogel skeleton, the amount of nanocellulose used directly affects the cross-linking density of the fiber network and the coordination efficiency of the cobalt ions. When the volume ratio of the nanocellulose solution to the cobalt source solution is within the range defined by the present invention, 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 salts from destroying the hydrogen-bonded cross-linked structure of the nanocellulose. This allows the subsequently added 2-methylimidazole organic ligand to be evenly distributed in the gaps of the cellulose network, combining with the cobalt ions to form uniformly sized ZIF-67 crystals, thereby constructing a stable multi-level pore structure for the aerogel matrix.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] In some optional examples, the organic ligand solution is dropped into the precursor solution under stirring and heating conditions.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] In some optional examples, the directional freezing process includes:

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] As a preferred technical solution of the present invention, in step (I), the hydrophobic modification treatment includes:

[0040] 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.

[0041] During the hydrophobic 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.

[0042] The modified aerogel matrix exhibits excellent hydrophobic and lipophilic properties in sewage treatment. The low surface energy effect of the hydrophobic surface preferentially captures oil droplets and hydrophobic organic pollutants. At the same time, the ZIF-67 mesoporous structure in the vertical channels forms a lipophilic environment due to the surface energy difference, further enhancing the enrichment ability of difficult-to-degrade pollutants such as benzene series and polycyclic aromatic hydrocarbons.

[0043] In some optional examples, the silane coupling agent solution consists of a silane coupling agent and an ethanol aqueous solution.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] As a preferred technical solution of the present invention, in step (II), the iron source solution consists of ferric chloride, ferrous chloride and deionized water.

[0049] As a preferred technical solution of the present invention, the molar ratio of ferric chloride to ferrous chloride is (1.9-2.1):1, for example, it can be 1.9:1, 1.92:1, 1.94:1, 1.96:1, 1.98:1, 2:1, 2.02:1, 2.04:1, 2.06:1, 2.08:1 or 2.1:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] The present invention specifically limits the molar ratio of ferric chloride to ferrous chloride to (1.9-2.1):1. 3+ with Fe 2+ When the molar ratio of Fe3O4 is within the range defined in the present invention, the homogeneous nucleation and directional growth of Fe3O4 can be promoted to the maximum extent. 3+ with Fe 2+ The synergistic effect forms a stable spinel structure, ensuring that the magnetic particles have high crystallinity and uniform pore distribution. 3+ It can maintain the redox potential of the reaction system stable and avoid Fe 2+ Being oxidized, it can also prevent Fe 3+ The excessive amount of the heterogeneous phase generates magnetic particles with both excellent magnetic responsiveness and high catalytic activity.

[0051] When the amount of ferric chloride added exceeds the upper limit of the range defined in the present invention, the excess Fe 3+ It will precipitate in the form of iron oxyhydroxide or amorphous iron oxide to form a mixed phase, resulting in the surface of the magnetic particles being covered with inert substances, reducing their saturation magnetization and catalytic active site density. 3+ It will change the acid-base environment of the reaction system, thereby causing local pH fluctuations and promoting Fe 2+ Oxidized to Fe 3+ , causing the magnetic particles to agglomerate, which not only reduces the specific surface area of ​​the material, but also hinders the uniform coating of chitosan and weakens the dispersion stability of the magnetic particles.

[0052] When the amount of ferrous chloride added exceeds the upper limit of the range defined in the present invention, Fe 2+ Excessive Fe3O4 will block the generation path of Fe3O4, and then generate FeO or other metastable iron oxides with weaker magnetism, which will significantly reduce the saturation magnetization of magnetic particles and reduce the separation efficiency of composite materials under external magnetic field. 2+ The enrichment of Fe will enhance the reducibility of the system, thereby triggering side reactions, destroying the subsequent chitosan surface coating, and thus affecting its adsorption capacity for pollutants. 2+Excessive addition will also lead to abnormal particle morphology, forming a cubic or spherical structure instead of the ideal octahedral crystal form, resulting in a reduction in the number of exposed active sites and reduced catalytic degradation performance.

[0053] In some optional examples, the total mass fraction of ferric chloride and ferrous chloride in the iron source solution is 2-4 wt%, for example, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt% or 4.0 wt%, but is not limited to the enumerated values, and other unlisted values ​​within the numerical range are also applicable.

[0054] In some optional examples, the aqueous ammonia solution is dripped into the iron source solution under stirring and heating conditions.

[0055] In some optional examples, the heating temperature when the ammonia solution is dripped is 50~60℃, for example, it can be 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃ or 60℃, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0056] In some optional examples, the mass fraction of the ammonia solution is 25~28wt%, for example, it can be 25wt%, 25.2wt%, 25.4wt%, 25.6wt%, 25.8wt%, 26wt%, 26.2wt%, 26.4wt%, 26.6wt%, 26.8wt%, 27wt%, 27.2wt%, 27.4wt%, 27.6wt%, 27.8wt% or 28wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] It should be noted that the present invention does not make specific requirements and special limitations on the dripping speed of the ammonia solution. Exemplarily, the dripping speed of the ammonia solution is 1~5mL / min, for example, it can be 1.0mL / min, 1.5mL / min, 2.0mL / min, 2.5mL / min, 3.0mL / min, 3.5mL / min, 4.0mL / min, 4.5mL / min or 5.0mL / min, but it is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0058] In some optional examples, an aqueous ammonia solution is added dropwise to the iron source solution until the pH value of the resulting mixed solution is 9 to 10, for example, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9 or 10, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0059] In some optional examples, after all the ammonia solution is added dropwise, mixing and stirring are continued under heating conditions for 30 to 60 minutes, for example, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] It should be noted that after the reaction, magnetic particles are obtained after magnetic separation, washing and drying. The present invention does not make specific requirements or special limitations on the drying temperature and time. Exemplarily, 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 6-12h, for example, it can be 6.0h, 6.5h, 7.0h, 7.5h, 8.0h, 8.5h, 9.0h, 9.5h, 10.0h, 10.5h, 11.0h, 11.5h or 12.0h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] As a preferred technical solution of the present invention, in step (II), the method for modifying the magnetic particles includes:

[0062] Chitosan is dissolved in acetic acid solution to obtain a chitosan solution, the magnetic particles are added to the chitosan solution and ultrasonically dispersed to obtain a mixed solution; glutaraldehyde is added to the mixed solution for cross-linking reaction, followed by magnetic separation, washing and drying to obtain the modified magnetic particles.

[0063] As a preferred technical solution of the present invention, the mass fraction of acetic acid in the acetic acid solution is 1 to 3 wt%, for example, it can be 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt% or 3.0 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0064] In some optional examples, the concentration of chitosan in the chitosan solution is 1-2 mg / mL, for example, it can be 1.0 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.3 mg / mL, 1.4 mg / mL, 1.5 mg / mL, 1.6 mg / mL, 1.7 mg / mL, 1.8 mg / mL, 1.9 mg / mL or 2.0 mg / mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0065] The present invention specifically limits the chitosan concentration in the chitosan solution to 1-2 mg / mL. Chitosan, a natural polymer, is rich in amino and hydroxyl functional groups on its molecular chain. These groups form a stable coating by coordinating with the surface of the magnetic particles. When the chitosan concentration is within the specified range, the chitosan molecules in the solution can be evenly adsorbed on the surface of the magnetic particles, forming a dense but not excessively accumulated coating. This moderate coating effectively prevents the aggregation of the magnetic particles in an aqueous environment and maintains their dispersion stability in complex water bodies through the electrostatic repulsion of the amino groups.

[0066] When the concentration of chitosan is lower than 1 mg / mL, a complete coating layer cannot be formed on the surface of the magnetic particles. The magnetic particles are prone to agglomeration, resulting in reduced dispersibility in water and easy clustering. The agglomerated magnetic particles not only reduce the contact area between the material and the pollutants, but also weaken their adsorption capacity due to the reduced surface area. In addition, incomplete chitosan coating will cause some areas of the magnetic particles to be exposed, which will trigger oxidation reactions and cause Fe 3+ Dissolution not only affects the structural stability of the material, but also creates the risk of secondary pollution due to the release of iron ions.

[0067] When the concentration of chitosan exceeds 2 mg / mL, the excess chitosan molecules will form a dense and thick coating on the surface of the magnetic particles. Although this will enhance the mechanical strength of the magnetic particles to a certain extent, the excessively thick coating will significantly reduce the specific surface area of ​​the magnetic particles, resulting in a reduction in the effective exposure area of ​​active adsorption sites and catalytic active sites, thereby affecting the adsorption rate of pollutants and the catalytic degradation efficiency of the magnetic particles.

[0068] In some optional examples, the ratio of the magnetic particles to the chitosan solution is 1g:(40~50)mL, for example, it can be 1g:40mL, 1g:41mL, 1g:42mL, 1g:43mL, 1g:44mL, 1g:45mL, 1g:46mL, 1g:47mL, 1g:48mL, 1g:49mL or 1g:50mL, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0069] It should be noted that after the magnetic particles are added to the chitosan solution, ultrasonic dispersion is required. The present invention does not make specific requirements or special limitations on the power and time of ultrasonic dispersion. For example, the ultrasonic power of ultrasonic dispersion is 200~300W, for example, it can be 200W, 210W, 220W, 230W, 240W, 250W, 260W, 270W, 280W, 290W or 300W, and the ultrasonic time of ultrasonic dispersion is 30~40min, for example, it can be 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min or 40min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0070] In some optional examples, the volume ratio of the mixed solution to the glutaraldehyde is 100:(1-2), for example, it can be 100:1.0, 100:1.1, 100:1.2, 100:1.3, 100:1.4, 100:1.5, 100:1.6, 100:1.7, 100:1.8, 100:1.9 or 100:2.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] The present invention specifically limits the volume ratio of the mixed solution to glutaraldehyde to 100:(1-2). Glutaraldehyde, acting as a crosslinking agent, undergoes a condensation reaction with amino and hydroxyl groups in chitosan molecules to form a three-dimensional network structure, thereby enhancing the mechanical strength and dispersion stability of the modified magnetic particles. When the volume ratio of the mixed solution to glutaraldehyde is within the range defined by the present invention, the amount of glutaraldehyde used ensures sufficient crosslinking of the chitosan molecular chains to form a dense protective layer, while also preventing the blocking of functional groups and increased mass transfer resistance caused by excessive crosslinking.

[0072] When the amount of glutaraldehyde added is below the lower limit of the range specified in the present invention, the cross-linking reaction is incomplete, the connections between the chitosan molecules become loose, and it is difficult to form a stable three-dimensional network structure protective layer. This leads to the presence of numerous pores and defects in the surface coating of the magnetic particles, significantly reducing their dispersion stability. Furthermore, due to insufficient adsorption capacity, the incompletely cross-linked chitosan molecules are difficult to effectively capture pollutants, and pollutants are prone to accumulation on the material surface, hindering the subsequent catalytic reaction.

[0073] When the amount of glutaraldehyde added exceeds the upper limit of the range specified in this invention, excessive cross-linking occurs. Excessive glutaraldehyde molecules form a dense cross-linked network with the amino and hydroxyl groups of chitosan, resulting in an overly dense chitosan coating. This significantly reduces the number of active sites of the surface active functional groups of the modified magnetic particles. Furthermore, this dense structure reduces the modified magnetic particles' electrostatic adsorption capacity for heavy metal ions and π-π interactions with organic pollutants, inhibiting the efficiency of Fenton-like reactions.

[0074] In some optional examples, the cross-linking reaction time 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.

[0075] In some optional embodiments, the heating temperature of the cross-linking reaction is 50~60℃, for example, it can be 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃ or 60℃, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0076] It should be noted that after the cross-linking reaction is completed, the modified magnetic particles are obtained after magnetic separation, washing and drying. 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 8-12h, for example, it can be 8.0h, 8.5h, 9.0h, 9.5h, 10.0h, 10.5h, 11.0h, 11.5h or 12.0h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0077] As a preferred technical solution of the present invention, in step (III), the mass fraction of the modified magnetic particles in the dispersion is 1-2 wt%, for example, it can be 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt% or 2.0 wt%, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0078] In some optional examples, the impregnation process includes:

[0079] 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 3 to 5 times.

[0080] The negative pressure-normal pressure alternating impregnation process adopted by the present invention realizes the deep penetration and uniform loading of the modified magnetic particles in the multi-level pores of the modified aerogel matrix. In the first vacuum stage, the gas in the pores of the modified aerogel matrix is ​​discharged, and a stable low-pressure environment is formed inside, which prompts the dispersion to gradually infiltrate the main pores in the modified aerogel matrix under capillary action. In the negative pressure holding stage, the dispersion can overcome the wetting resistance of the micro-nano pores inside the modified aerogel matrix and penetrate into the deep layers of the modified aerogel matrix. When nitrogen is introduced to restore normal pressure, the increase in external air pressure prompts the dispersion to be redistributed in the pores of the modified aerogel matrix, and the modified magnetic particles gradually settle to the pore wall under the action of gravity and van der Waals forces. The dispersion is stirred in the normal pressure stage to break up the particle agglomerates in the dispersion.

[0081] In some optional examples, the mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion is 1:(0.5~0.7), for example, it can be 1:0.5, 1:0.52, 1:0.54, 1:0.56, 1:0.58, 1:0.6, 1:0.62, 1:0.64, 1:0.66, 1:0.68 or 1:0.7, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0082] The present invention specifically limits the mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion to 1:(0.5-0.7). The modified aerogel matrix acts as a porous framework, and its three-dimensional network structure provides physical space for pollutant adsorption and mass transfer channels for catalytic reactions. Activated by H2O2, the modified magnetic particles undergo a Fenton-like reaction, generating a large number of hydroxyl radicals that degrade organic pollutants. The appropriate loading of modified magnetic particles allows them to be evenly embedded in the pore walls of the modified aerogel matrix, preserving the modified aerogel matrix's rapid adsorption capacity for pollutants while achieving a dynamic balance between adsorption and degradation through catalytic degradation.

[0083] When the amount of modified magnetic particles added is below the lower limit of the range defined by the present invention, the catalytic degradation ability of the resulting composite material is significantly reduced, the number of hydroxyl radicals generated through the Fenton-like reaction is small, and organic pollutants adsorbed on the surface of the modified aerogel matrix cannot be decomposed in a timely manner, which can easily lead to secondary release of pollutants due to adsorption saturation. In addition, the magnetic responsiveness of the modified magnetic particles at low loadings is difficult to fully utilize, reducing separation and recovery efficiency, increasing process complexity and operating costs.

[0084] When the amount of modified magnetic particles added exceeds the upper limit of the range defined in the present invention, the excess modified magnetic particles will clog the vertical pores of the modified aerogel matrix, hindering the diffusion and contact of pollutants in the sewage, which will not only reduce the adsorption rate of the composite material, but also reduce the efficiency of the catalytic degradation reaction due to the increase in mass transfer resistance.

[0085] In some optional examples, the reactor is evacuated to -80~-90kPa, for example, it can be -80kPa, -81kPa, -82kPa, -83kPa, -84kPa, -85kPa, -86kPa, -87kPa, -88kPa, -89kPa or -90kPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0086] 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.

[0087] In some optional examples, at the normal pressure stage, the dispersion is stirred for 30 to 40 minutes, for example, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes or 40 minutes, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0088] 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 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.

[0089] In a second aspect, the present invention provides a magnetic particle-loaded porous composite material for sewage treatment, which is prepared by the preparation method described in the first aspect.

[0090] In a third aspect, the present invention provides a use of the magnetic particle-loaded porous composite material for sewage treatment as described in the second aspect, wherein the magnetic particle-loaded porous composite material is used for sewage treatment.

[0091] Compared with the prior art, the present invention has the following beneficial effects:

[0092] This invention provides a method for preparing a magnetic particle-loaded porous composite material. Through the synergistic effect of nanocellulose and metal-organic framework materials, an aerogel matrix with a hierarchical pore structure is constructed, upon which chitosan-modified magnetic particles are loaded. The resulting magnetic particle-loaded porous composite material exhibits a high specific surface area, strong mechanical properties, and rapid separation capabilities. It can simultaneously adsorb heavy metal ions and organic pollutants, catalytically degrade refractory substances, and achieve efficient recovery and regeneration through an external magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 Flow chart of the preparation process of the magnetic particle-loaded porous composite material provided in Examples 1-15 of the present invention;

[0094] Figure 2 The infrared spectra of nanocellulose, ZIF-67 and the aerogel matrix prepared in Example 1 of the present invention are shown;

[0095] Figure 3 XRD spectra of nanocellulose, ZIF-67 and the aerogel matrix prepared in Example 1 of the present invention;

[0096] Figure 4 Graphs showing the water contact angle and oil contact angle of the modified aerogel matrix prepared in Example 1 of the present invention;

[0097] Figure 5 This is an infrared spectrum of the magnetic particles and modified magnetic particles prepared in Example 1 of the present invention;

[0098] Figure 6 This is a transmission electron micrograph of the modified magnetic particles prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0099] 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.

[0100] Example 1

[0101] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0102] (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.

[0103] 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.

[0104] 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.

[0105] (2) Ferric chloride and ferrous chloride were dissolved in deionized water with a molar ratio of ferric chloride to ferrous chloride of 1.9:1, and mixed evenly to obtain an iron source solution, wherein the total mass fraction of ferric chloride and ferrous chloride in the iron source solution was 2 wt %; under the conditions of heating and stirring in a water bath at 50°C, a 25 wt % ammonia aqueous solution was added dropwise to the iron source solution at a rate of 1 mL / min until the pH value of the obtained mixed solution reached 9, and then the mixture was heated in a water bath at 50°C for 60 min, and magnetic particles were obtained after magnetic separation, washing and vacuum drying, wherein the vacuum drying temperature was 50°C and the vacuum drying time was 12 h;

[0106] Chitosan was dissolved in a 1 wt % acetic acid solution and mixed uniformly to obtain a chitosan solution, wherein the concentration of chitosan in the chitosan solution was 1 mg / mL; magnetic particles were added to the chitosan solution at a ratio of 1 g of magnetic particles to the chitosan solution of 1 g:40 mL, and ultrasonic dispersion was performed at an ultrasonic power of 200 W for 40 minutes to obtain a mixed solution; glutaraldehyde was added to the mixed solution at a volume ratio of the mixed solution to glutaraldehyde of 100:1, and the mixture was stirred at 50° C. for 4 hours to cause a cross-linking reaction. After the reaction, magnetic separation, washing, and vacuum drying were performed to obtain modified magnetic particles, wherein the vacuum drying temperature was 50° C. and the vacuum drying time was 12 hours;

[0107] (3) The modified magnetic particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the modified magnetic particles in the dispersion is 1 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 modified magnetic particles is 1:0.5, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion, and the reactor is evacuated to -80 kPa and maintained for 30 min; nitrogen is then introduced into the reactor to restore to normal pressure, and the dispersion is stirred for 30 min; the reactor is then evacuated to -80 kPa and maintained for 30 min; the reactor is repeatedly evacuated and restored to normal pressure for 5 times, and then taken out and vacuum dried at 50° C. for 12 h to obtain the magnetic particle-loaded porous composite material.

[0108] 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.

[0109] Figure 3Figure 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. In addition, 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 on the aerogel matrix.

[0110] Figure 4 The 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 hydrophilic surface, indicating that the modified aerogel matrix obtained after modification with the silane coupling agent has hydrophobic and lipophilic properties.

[0111] Figure 5 The infrared spectra of the magnetic particles and modified magnetic particles prepared in this example are shown in the figure. As can be seen from the figure, in the infrared curve of the magnetic particles, 3449 cm -1 The characteristic peak at 1626 cm is attributed to the antisymmetric stretching vibration of hydroxyl (-OH). -1 The characteristic peak at 586 cm is attributed to the bending vibration of hydroxyl (-OH). -1 The characteristic peak at 3420 cm is attributed to the stretching vibration of Fe-O bond. -1 The characteristic peak at 2927 cm is attributed to the stretching vibration of -NH (amino group). -1 The characteristic peak at 1630 cm is attributed to the CH stretching vibration of the aliphatic methylene (-CH2-) or methyl (-CH3) in the chitosan molecular chain. -1 The characteristic peak at 1150 cm is attributed to the stretching vibration of C=O in the amide group (-NH-CO-) of chitosan. -1 The characteristic peak at 1070 cm is attributed to the stretching vibration of CO in the Schiff base structure (C=N) generated by the glutaraldehyde cross-linking reaction. -1 The characteristic peak at 1022 cm is attributed to the stretching vibration of the incompletely coordinated hydroxyl groups (-OH) on the Fe3O4 surface or the residual hydroxyl groups of chitosan. -1 The characteristic peak at 586 cm is attributed to the stretching vibration of the Schiff base structure (C=N) generated by the reaction of the primary amine (-NH2) of chitosan with glutaraldehyde, indicating a successful cross-linking reaction. -1The characteristic peak at is attributed to the Fe-O stretching vibration.

[0112] Figure 6 The following is a transmission electron micrograph of the modified magnetic particles prepared in this example. As can be seen from the figure, the magnetic particles are spherical with a particle size of approximately 10 nm, but the particles tend to agglomerate, forming a large number of aggregates. The modified magnetic particles obtained after chitosan coating and glutaraldehyde cross-linking are also approximately spherical with a particle size of approximately 10-20 nm. Their dispersibility in aqueous media is significantly better than that of the magnetic particles.

[0113] Example 2

[0114] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0115] (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.

[0116] 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.

[0117] 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.

[0118] (2) Ferric chloride and ferrous chloride were dissolved in deionized water with a molar ratio of ferric chloride to ferrous chloride of 1.95:1, and mixed evenly to obtain an iron source solution, wherein the total mass fraction of ferric chloride and ferrous chloride in the iron source solution was 2.5 wt %; under the conditions of heating and stirring in a water bath at 52°C, a 26 wt % ammonia aqueous solution was added dropwise to the iron source solution at a rate of 2 mL / min until the pH value of the obtained mixed solution reached 9.2, and then the mixture was continued to be heated in a water bath at 52°C for 50 min, and magnetic particles were obtained after magnetic separation, washing and vacuum drying, wherein the vacuum drying temperature was 52°C and the vacuum drying time was 10 h;

[0119] Chitosan was dissolved in a 1.5 wt % acetic acid solution and mixed uniformly to obtain a chitosan solution, wherein the concentration of chitosan in the chitosan solution was 1.2 mg / mL; magnetic particles were added to the chitosan solution at a ratio of 1 g of magnetic particles to the chitosan solution of 1 g:42 mL, and ultrasonic dispersion was performed at an ultrasonic power of 220 W for 38 minutes to obtain a mixed solution; glutaraldehyde was added to the mixed solution at a volume ratio of the mixed solution to glutaraldehyde of 100:1.2, and the mixture was stirred at 52° C. for 3.8 hours to cause a cross-linking reaction. After the reaction, magnetic separation, washing, and vacuum drying were performed to obtain modified magnetic particles, wherein the vacuum drying temperature was 52° C. and the vacuum drying time was 11 hours;

[0120] (3) The modified magnetic particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the modified magnetic particles in the dispersion is 1.2 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 modified magnetic particles is 1:0.55, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion, and the reactor is evacuated to -82 kPa and maintained for 28 minutes; nitrogen is then introduced into the reactor to restore to normal pressure, and the dispersion is stirred for 32 minutes; the reactor is then evacuated to -82 kPa and maintained for 28 minutes; the reactor is repeatedly evacuated and restored to normal pressure 4 times, and then taken out and vacuum dried at 52°C for 11.5 hours to obtain the magnetic particle-loaded porous composite material.

[0121] Example 3

[0122] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0123] (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.

[0124] 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.

[0125] 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.

[0126] (2) Ferric chloride and ferrous chloride were dissolved in deionized water with a molar ratio of ferric chloride to ferrous chloride of 2:1, and mixed evenly to obtain an iron source solution, wherein the total mass fraction of ferric chloride and ferrous chloride in the iron source solution was 3 wt %; under the conditions of heating and stirring in a water bath at 55°C, a 27 wt % ammonia aqueous solution was added dropwise to the iron source solution at a rate of 3 mL / min until the pH value of the obtained mixed solution reached 9.5, and then the mixture was continued to be heated in a water bath at 55°C for 40 min, and magnetic particles were obtained after magnetic separation, washing and vacuum drying, wherein the vacuum drying temperature was 55°C and the vacuum drying time was 9 h;

[0127] Chitosan was dissolved in a 2 wt % acetic acid solution and mixed uniformly to obtain a chitosan solution, wherein the concentration of chitosan in the chitosan solution was 1.5 mg / mL; magnetic particles were added to the chitosan solution at a ratio of 1 g of magnetic particles to the chitosan solution of 1 g:45 mL, and ultrasonic dispersion was performed at an ultrasonic power of 250 W for 35 minutes to obtain a mixed solution; glutaraldehyde was added to the mixed solution at a volume ratio of the mixed solution to glutaraldehyde of 100:1.5, and the mixture was stirred at 55° C. for 3.5 hours to cause a cross-linking reaction. After the reaction, magnetic separation, washing, and vacuum drying were performed to obtain modified magnetic particles, wherein the vacuum drying temperature was 55° C. and the vacuum drying time was 10 hours;

[0128] (3) The modified magnetic particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the modified magnetic particles in the dispersion is 1.5 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 modified magnetic particles is 1:0.6, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion, and the reactor is evacuated to -85 kPa and maintained for 25 min; nitrogen is then introduced into the reactor to restore to normal pressure, and the dispersion is stirred for 35 min; the reactor is then evacuated to -85 kPa and maintained for 25 min; the reactor is repeatedly evacuated and restored to normal pressure 4 times, and then taken out and vacuum dried at 55 ° C for 11 h to obtain the magnetic particle-loaded porous composite material.

[0129] Example 4

[0130] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0131] (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.

[0132] 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.

[0133] 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.

[0134] (2) Ferric chloride and ferrous chloride were dissolved in deionized water with a molar ratio of ferric chloride to ferrous chloride of 2.05:1, and mixed evenly to obtain an iron source solution, wherein the total mass fraction of ferric chloride and ferrous chloride in the iron source solution was 3.5 wt %; under the conditions of heating and stirring in a water bath at 58°C, a 27 wt % ammonia aqueous solution was added dropwise to the iron source solution at a rate of 4 mL / min until the pH value of the obtained mixed solution reached 9.8, and then the mixture was heated in a water bath at 58°C for 40 min, and magnetic particles were obtained after magnetic separation, washing and vacuum drying, wherein the vacuum drying temperature was 58°C and the vacuum drying time was 8 h;

[0135] Chitosan was dissolved in a 2.5 wt % acetic acid solution and mixed uniformly to obtain a chitosan solution, wherein the concentration of chitosan in the chitosan solution was 1.8 mg / mL; magnetic particles were added to the chitosan solution at a ratio of 1 g of magnetic particles to the chitosan solution of 1 g:48 mL, and ultrasonic dispersion was performed at an ultrasonic power of 280 W for 32 minutes to obtain a mixed solution; glutaraldehyde was added to the mixed solution at a volume ratio of the mixed solution to glutaraldehyde of 100:1.8, and the mixture was stirred at 58° C. for 3.2 hours to cause a cross-linking reaction. After the reaction, magnetic separation, washing, and vacuum drying were performed to obtain modified magnetic particles, wherein the vacuum drying temperature was 58° C. and the vacuum drying time was 9 hours;

[0136] (3) The modified magnetic particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the modified magnetic particles in the dispersion is 1.8 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 modified magnetic particles is 1:0.65, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion, and the reactor is evacuated to -88 kPa and maintained for 22 min; nitrogen is then introduced into the reactor to restore to normal pressure, and the dispersion is stirred for 38 min; the reactor is then evacuated to -88 kPa and maintained for 22 min; the reactor is repeatedly evacuated and restored to normal pressure three times, and then taken out and vacuum dried at 58 ° C for 10.5 h to obtain the magnetic particle-loaded porous composite material.

[0137] Example 5

[0138] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment, such as Figure 1 As shown, the preparation method specifically includes the following steps:

[0139] (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.

[0140] 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.

[0141] 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.

[0142] (2) Ferric chloride and ferrous chloride were dissolved in deionized water with a molar ratio of ferric chloride to ferrous chloride of 2.1:1, and mixed evenly to obtain an iron source solution, wherein the total mass fraction of ferric chloride and ferrous chloride in the iron source solution was 4 wt %. Under the conditions of heating and stirring in a water bath at 60°C, a 28 wt % ammonia aqueous solution was added dropwise to the iron source solution at a rate of 5 mL / min until the pH value of the obtained mixed solution reached 10. The mixture was then heated in a water bath at 60°C for 30 min, and magnetic particles were obtained after magnetic separation, washing and vacuum drying, wherein the vacuum drying temperature was 60°C and the vacuum drying time was 6 h.

[0143] Chitosan was dissolved in a 3 wt % acetic acid solution and mixed uniformly to obtain a chitosan solution, wherein the concentration of chitosan in the chitosan solution was 2 mg / mL; magnetic particles were added to the chitosan solution at a ratio of 1 g of magnetic particles to the chitosan solution of 50 mL, and ultrasonic dispersion was performed at an ultrasonic power of 300 W for 30 minutes to obtain a mixed solution; glutaraldehyde was added to the mixed solution at a volume ratio of the mixed solution to glutaraldehyde of 100:2, and the mixture was stirred at 60° C. for 3 hours to cause a cross-linking reaction. After the reaction, magnetic separation, washing, and vacuum drying were performed to obtain modified magnetic particles, wherein the vacuum drying temperature was 60° C. and the vacuum drying time was 8 hours;

[0144] (3) The modified magnetic particles obtained in step (2) are dispersed in deionized water and mixed evenly to obtain a dispersion, wherein the mass fraction of the modified magnetic particles in the dispersion is 2 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 modified magnetic particles is 1:0.7, ensuring that the modified aerogel matrix is ​​completely immersed in the dispersion, and the reactor is evacuated to -90 kPa and maintained for 20 min; nitrogen is then introduced into the reactor to restore to normal pressure, and the dispersion is stirred for 40 min; the reactor is then evacuated to -90 kPa and maintained for 20 min; the reactor is repeatedly evacuated and restored to normal pressure three times, and then taken out and vacuum dried at 60° C. for 10 h to obtain the magnetic particle-loaded porous composite material.

[0145] Example 6

[0146] This embodiment provides a method for preparing a magnetic particle-loaded 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.

[0147] Example 7

[0148] This embodiment provides a method for preparing a magnetic particle-loaded 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.

[0149] Example 8

[0150] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the molar ratio of ferric chloride to ferrous chloride is adjusted to 1.5:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0151] Example 9

[0152] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the molar ratio of ferric chloride to ferrous chloride is adjusted to 2.5:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0153] Example 10

[0154] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the concentration of chitosan in the chitosan solution is adjusted to 0.5 mg / mL, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0155] Example 11

[0156] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the concentration of chitosan in the chitosan solution is adjusted to 2.5 mg / mL, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0157] Example 12

[0158] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the volume ratio of the mixed solution to glutaraldehyde is adjusted to 100:0.5, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0159] Example 13

[0160] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Example 1 is that in step (2), the volume ratio of the mixed solution to glutaraldehyde is adjusted to 100:2.5, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0161] Example 14

[0162] This embodiment provides a method for preparing a magnetic particle-loaded 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 modified magnetic particles in the dispersion is adjusted to 1:0.2, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0163] Example 15

[0164] This embodiment provides a method for preparing a magnetic particle-loaded 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 modified magnetic particles in the dispersion is adjusted to 1:1, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0165] The magnetic particle-loaded 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:

[0166] The magnetic particle-loaded 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 solids content was 255 mg / L, and the chromaticity value was 580 times (dilution multiple method). The dosage of the composite material was 2.5 kg / m 3 At the same time, 30wt% hydrogen peroxide was added to the printing and dyeing wastewater, and the amount of hydrogen peroxide added was 2kg / ton of printing and dyeing wastewater. 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.

[0167] The magnetic particle-loaded porous composite material prepared in Examples 1-15 of the present invention was added to petrochemical wastewater. The COD value in the petrochemical wastewater 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 of the composite material was 5 kg / m 3 At the same time, 30wt% hydrogen peroxide was added to the petrochemical wastewater, and the amount of hydrogen peroxide added was 5kg / ton of petrochemical wastewater. 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.

[0168] Table 1

[0169]

[0170] Table 2

[0171]

[0172] The test data provided in Tables 1 and 2 demonstrate that the effluent quality of Examples 1-5 comprehensively exceeds the national standards for printing and dyeing wastewater (GB4287-2012, "Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industries") and petrochemical wastewater (GB31571-2015, "Discharge Standard of Pollutants for Petrochemical Industries"). This technology, by combining a multi-level pore structure with the magnetic response of magnetic particles, achieves efficient and stable wastewater treatment performance, making it particularly suitable for the advanced treatment of challenging printing and dyeing wastewater and petrochemical wastewater.

[0173] 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 amount of nanocellulose solution used in Example 6 is too small, causing ZIF-67 crystals to agglomerate and block pores, reducing adsorption efficiency. In Example 7, the amount of nanocellulose solution used is too large, affecting structural stability and causing pore collapse, resulting in reduced pollutant interception efficiency.

[0174] The test data of 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 ferric chloride added in Example 8 is too small, which reduces the efficiency of the Fenton-like reaction, insufficient oxidation of difficult-to-degrade organic matter, and reduced pollutant degradation efficiency. In Example 9, the amount of ferric chloride added is too large, which generates byproducts, interferes with the adsorption equilibrium, damages the pore structure, and reduces the interception efficiency of pollutants.

[0175] It can be seen from the test data of Example 1, Example 10 and Example 11 that the effluent quality of Example 10 and Example 11 is inferior to that of Example 1. This is because the concentration of chitosan in the chitosan solution in Example 10 is too low, resulting in poor dispersibility of the modified magnetic particles, low utilization of catalytic active sites, and reduced degradation efficiency of pollutants; the concentration of chitosan in the chitosan solution in Example 11 is too high, resulting in an excessively thick surface coating layer of the modified magnetic particles, which hinders mass transfer and reduces the oil-water separation efficiency.

[0176] It can be seen from the test data of Example 1, Example 12 and Example 13 that the effluent quality of Example 12 and Example 13 is inferior to that of Example 1. This is because the amount of glutaraldehyde added in Example 12 is too low, the modified magnetic particles are easily lost, and the long-term operation performance decays; the amount of glutaraldehyde added in Example 13 is too high, resulting in an overly dense cross-linked network, pore clogging, reduced adsorption kinetics, and decreased interception efficiency of pollutants.

[0177] It can be seen from the test data of Example 1, Example 14 and Example 15 that the effluent quality of Example 14 and Example 15 is inferior to that of Example 1. This is because the dosage of modified magnetic particles in Example 14 is too low, the catalytic reaction is incomplete, difficult-to-degrade organic matter remains, and the degradation efficiency of pollutants is reduced; the dosage of modified magnetic particles in Example 15 is too high, resulting in an excessive pore loading of the modified aerogel matrix, an increase in mass transfer resistance, and adsorption saturation.

[0178] 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 magnetic particle-loaded porous composite material for sewage treatment, characterized in that: The preparation method comprises: (I) under stirring and heating conditions, dropping an organic ligand solution into a precursor solution consisting of a nanocellulose solution and a cobalt source solution, and after all the organic ligand solution is dropped, continuing to mix and stir under heating conditions for 4 to 5 hours to obtain a reaction solution, wherein the organic ligand solution is composed of 2-methylimidazole and methanol, the volume ratio of the nanocellulose solution to the cobalt source solution is (2 to 3):1, and the heating temperature during the dropwise addition of the organic ligand solution is 60 to 70°C; mixing the reaction solution with polyvinyl alcohol and injecting it into a mold for directionally freezing to obtain an aerogel matrix; and hydrophobically modifying the aerogel matrix to obtain a modified aerogel matrix; The directional freezing process includes: cooling to a first freezing temperature at a first cooling rate and keeping the temperature, and then continuing to cool to a second freezing temperature at a second cooling rate and keeping the temperature; The first cooling rate is -1~-2℃ / min, the first freezing temperature is -15~-20℃, and the holding time at the first freezing temperature is 0.5~1.5h. The second cooling rate is -0.5~-1℃ / min, the second freezing temperature is -30~-40℃, and the holding time at the second freezing temperature is 3~4h. (II) dropping an ammonia solution into an iron source solution to react, and obtaining magnetic particles after magnetic separation, washing, and drying; and modifying the magnetic particles with chitosan to obtain modified magnetic particles; The modification method of magnetic particles comprises: dissolving chitosan in an acetic acid solution to obtain a chitosan solution, adding magnetic particles to the chitosan solution and ultrasonically dispersing the mixture to obtain a mixed solution; adding glutaraldehyde to the mixed solution to carry out a cross-linking reaction, and then magnetically separating, washing, and drying to obtain modified magnetic particles; (III) dispersing the modified magnetic particles in deionized water to obtain a dispersion; immersing the modified aerogel matrix in the dispersion, removing the matrix and drying the matrix to obtain the magnetic particle-loaded porous composite material; The impregnation process includes: The modified aerogel matrix and the dispersion are added to a reactor, with the mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion being 1:(0.5-0.7). The modified aerogel matrix is ​​completely immersed in the dispersion. The reactor is evacuated and then restored to normal pressure. The dispersion is stirred at normal pressure, and then the evacuation is continued. The evacuation and restoration of the reactor to normal pressure are repeated 3-5 times.

2. The preparation method according to claim 1, wherein In step (I), 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 molar ratio of 2-methylimidazole in the organic ligand solution to cobalt ions in the cobalt source solution is (5-6):

1.

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 iron source solution consists of ferric chloride, ferrous chloride and deionized water; The molar ratio of ferric chloride to ferrous chloride is (1.9-2.1):1; The total mass fraction of ferric chloride and ferrous chloride in the iron source solution is 2-4 wt %; Under stirring and heating conditions, dripping the ammonia solution into the iron source solution; The heating temperature when the ammonia solution is added dropwise is 50-60°C; The mass fraction of the ammonia solution is 25-28 wt %; Adding an aqueous ammonia solution dropwise to the iron source solution until the pH value of the resulting mixed solution is 9-10; After all the ammonia solution is added dropwise, continue mixing and stirring under heating conditions for 30 to 60 minutes.

6. The preparation method according to claim 1, characterized in that In step (II), the mass fraction of acetic acid in the acetic acid solution is 1-3 wt %; The concentration of chitosan in the chitosan solution is 1-2 mg / mL; The ratio of the magnetic particles to the chitosan solution is 1 g: (40-50) mL; The volume ratio of the mixed solution to the glutaraldehyde is 100:(1-2); The cross-linking reaction time is 3 to 4 hours; The heating temperature of the cross-linking reaction is 50-60°C.

7. The preparation method according to claim 1, characterized in that In step (III), the mass fraction of the modified magnetic particles in the dispersion is 1-2 wt %; The reactor was evacuated to -80~-90kPa; The reactor maintains vacuum for 20 to 30 minutes; At normal pressure, the dispersion is stirred for 30 to 40 minutes.

8. A magnetic particle-loaded porous composite material for sewage treatment prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the magnetic particle-loaded porous composite material for sewage treatment according to claim 8, characterized in that: The magnetic particle-loaded porous composite material is used for sewage treatment.

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