Magnetic particle loaded porous composite material for sewage treatment as well as preparation method and application thereof

Abstract

The invention provides a magnetic particle loaded porous composite material for sewage treatment and a preparation method and application thereof, and the preparation method comprises the following steps: dropwise adding an organic ligand solution into a precursor solution composed of a nanocellulose solution and a cobalt source solution to obtain a reaction solution; mixing the reaction solution with polyvinyl alcohol, injecting the mixture into a mold, and performing directional freezing to obtain an aerogel matrix; carrying out hydrophobic modification on the aerogel matrix to obtain a modified aerogel matrix; dropwise adding an ammonia water solution into the iron source solution for reaction, and performing magnetic separation, washing and drying after the reaction to obtain magnetic particles; performing chitosan modification on the magnetic particles to obtain modified magnetic particles; dispersing the modified magnetic particles in deionized water to obtain dispersion liquid; and dipping the modified aerogel matrix in the dispersion liquid, taking out and drying. The prepared magnetic particle loaded porous composite material can synchronously adsorb heavy metal ions and organic pollutants and catalytically degrade refractory substances, and efficient recovery and regeneration are achieved through an external magnetic field.

Description

Technical Field

[0001] The present 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 thereof, and uses thereof. Background Art

[0002] With the acceleration of the industrialization and urbanization processes, the problem of water environmental pollution has become increasingly severe. In particular, there is an 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 method have limitations such as low efficiency, high cost, and easy generation of secondary pollution. Adsorption method has become a research hotspot due to its simple operation and wide applicability. However, although conventional adsorption materials such as activated carbon and silica gel porous materials have certain adsorption capacities, they generally have problems such as limited adsorption capacity and difficult regeneration, and it is difficult to efficiently separate and recover them after adsorption, resulting in material loss and potential environmental risks.

[0003] In recent years, magnetic composite materials have received attention due to their characteristics of rapid solid-liquid separation by applying 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 prior art, attempts to combine magnetic particles with porous materials mostly use stepwise loading or chemical cross-linking methods, which have problems such as complex preparation processes, poor structural stability of materials, and easy shedding of magnetic components. In addition, most composite materials have insufficient co-adsorption ability for complex pollutants and are difficult to efficiently remove multiple pollutants simultaneously. For example, some materials cannot effectively degrade organic pollutants after adsorbing heavy metals, resulting in limited actual application scenarios. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a magnetic particle-loaded porous composite material for sewage treatment, a preparation method thereof, and uses thereof. The magnetic particle-loaded porous composite material prepared by the present invention has both a high specific surface area, strong mechanical properties, and rapid separation ability, can simultaneously adsorb heavy metal ions, organic pollutants, and catalytically degrade refractory substances, and realizes efficient recovery and regeneration through an external magnetic field.

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

[0006] In the first aspect, a preparation method of a magnetic particle-loaded porous composite material for sewage treatment, the preparation method comprising:

[0007] (I) Drop an organic ligand solution into a precursor solution composed of a nanocellulose solution and a cobalt source solution to obtain a reaction solution; mix the reaction solution with polyvinyl alcohol and then inject it into a mold for directional freezing to obtain an aerogel matrix; perform hydrophobic modification on the aerogel matrix to obtain a modified aerogel matrix;

[0008] (II) Drop an ammonia aqueous solution into the iron source solution for reaction. After the reaction, magnetic particles are obtained through magnetic separation, washing, and drying. The magnetic particles are modified with chitosan to obtain modified magnetic particles;

[0009] (III) Disperse the modified magnetic particles in deionized water to obtain a dispersion. Immerse the modified aerogel matrix in the dispersion, take it out and dry it to obtain the magnetic particle-loaded porous composite material.

[0010] The present invention provides a preparation method of 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 and loaded with magnetic particles modified by chitosan. The magnetic particle-loaded porous composite material prepared by the present invention has both a high specific surface area, strong mechanical properties, and fast separation ability, can simultaneously adsorb heavy metal ions, organic pollutants, and catalytically degrade refractory substances, and realizes efficient recovery and regeneration through an external magnetic field.

[0011] In the present invention, nanocellulose is used as a biomass skeleton material, and its surface-rich hydroxyl functional groups coordinate with cobalt ions. When cobalt nitrate solution is mixed with nanocellulose, cobalt ions are preferentially adsorbed around the oxygen-containing groups of the cellulose molecular chain, forming a uniform metal ion distribution network. Subsequently, the introduced 2-methylimidazole organic ligand undergoes a self-assembly reaction with cobalt ions, generating metal-organic framework material ZIF-67 in the nanocellulose network gaps. The excessive organic ligand not only ensures the complete progress of the reaction but also inhibits the overgrowth of crystals through steric hindrance effects, finally forming regular dodecahedral crystals. These ZIF-67 crystals are tightly bound to the nanocellulose network through hydrogen bonding, not only retaining the three-dimensional pore structure of the aerogel matrix but also endowing it with catalytic active sites, capable of rapidly capturing heavy metal ions (such as Pb 2+ 、Cd 2 + )、organic dye molecules, and oil pollutants in wastewater; at the same time, its Lewis acidic 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 the modified magnetic particles, first, the coprecipitation method is adopted to promote the reaction of Fe 3+ with Fe 2+Synchronously hydrolyze to generate Fe(OH)3 and Fe(OH)2 colloids, and form spinel-structured Fe3O4 nanoparticles through dehydration and oxidation reactions. The co-precipitation method adopted in the present invention does not require high-temperature calcination, 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 flexible chitosan wraps on the surface of the magnetic particles, constructing a dynamic buffer layer. Its abundant 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 adsorption capacity of the material 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, forming modified magnetic particles with both mechanical strength and flexibility, enabling them to maintain structural integrity under dynamic water flow impact and complex hydraulic conditions, and solving the technical problems of easy sedimentation and difficult recovery of traditional magnetic particles.

[0013] The modified aerogel matrix uses nanocellulose as the framework, constructs vertically penetrating micron-sized pores through a directional freezing process, and combines with the dodecahedral crystal structure of ZIF-67 to form a mesoporous network with a high specific surface area. Its hydrophobic modification layer endows the composite material with selective adsorption ability, enabling hydrophobic pollutants to preferentially adhere to the pore wall surface. The modified magnetic particles have Fe3O4 as the core and form a core-shell structure through chitosan modification. Under acidic conditions, the Fe on the surface of the Fe3O4 inner core 3+ is reduced to Fe 2+ , and then reacts with hydrogen peroxide (H2O2) to generate hydroxyl radicals (·OH), oxidizing and decomposing the refractory organic matter adsorbed in the pores of the aerogel matrix into small molecule substances. Different from traditional photocatalysis that relies on ultraviolet light, the Fenton-like reaction can be carried out at normal temperature and pressure and is activated by a chemical reagent (H2O2), avoiding the dependence on light sources in photocatalysis and being 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 bond interactions with the modified aerogel matrix, enhancing the capture efficiency of pollutants with opposite charges, endowing the composite material with high adsorption capacity and catalytic active sites, and enabling rapid capture of heavy metal ions and activation of 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 is composed of 2-methylimidazole and methanol.

[0015] In some alternative examples, the concentration of 2-methylimidazole in the organic ligand solution is 0.9 to 1 mol / L. For example, it can be 0.9 mol / L, 0.91 mol / L, 0.92 mol / L, 0.93 mol / L, 0.94 mol / L, 0.95 mol / L, 0.96 mol / L, 0.97 mol / L, 0.98 mol / L, 0.99 mol / L or 1 mol / L. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] In some alternative examples, the mass fraction of the nanocellulose solution is 1 to 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%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] In some alternative examples, the cobalt source solution is composed of cobalt nitrate and deionized water.

[0018] In some alternative examples, the concentration of cobalt nitrate in the cobalt source solution is 0.15 to 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] In some alternative examples, the volume ratio of the nanocellulose solution to the cobalt source solution is (2 to 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally 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 framework, the dosage of nanocellulose directly affects the crosslinking density of the fiber network and the coordination efficiency of 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 an appropriate coordination interaction with cobalt ions, ensuring that sufficient metal ions are anchored on the surface of the nanocellulose network while avoiding the destruction of the hydrogen bond crosslinking structure of nanocellulose by excessive cobalt salts. This enables the subsequent addition of 2-methylimidazole organic ligands to be evenly distributed in the cellulose network gaps and combine with cobalt ions to generate ZIF-67 crystals with uniform sizes, constructing a stable hierarchical pore structure for the aerogel matrix.

[0021] When the addition amount of the nanocellulose solution is too low, the concentration of cobalt ions is too high, causing the coordination reaction to concentrate in local areas. The ZIF-67 crystals grow excessively to form large-size aggregates, 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 unreacted free cobalt ions will crystallize out during the directional freezing process, destroying the regularity of the pore structure of the aerogel matrix.

[0022] When the addition amount of the nanocellulose solution is too high, the excessive nanocellulose chains hinder the uniform distribution of cobalt ions due to steric hindrance effects, resulting in insufficient nucleation sites for ZIF-67 crystals. The finally formed ZIF-67 crystals have poor dispersibility and a reduced density of catalytic active sites. At the same time, the dense network formed by excessive crosslinking of nanocellulose will compress the pore space, significantly decreasing the specific surface area of the aerogel matrix.

[0023] It should be noted that the present invention does not make specific requirements or special limitations on the dropping rate of the organic ligand solution. Exemplarily, the dropping rate of the organic ligand solution is 1.5-2.5 mL / min, for example, it can be 1.5 mL / min, 1.6 mL / min, 1.7 mL / min, 1.8 mL / min, 1.9 mL / min, 2.0 mL / min, 2.1 mL / min, 2.2 mL / min, 2.3 mL / min, 2.4 mL / min, or 2.5 mL / min, but it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0024] In some alternative 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 it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

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

[0026] In some alternative examples, the heating temperature when the organic ligand solution is dropped is 60 - 70 °C, for example, it can be 60 °C, 61 °C, 62 °C, 63 °C, 64 °C, 65 °C, 66 °C, 67 °C, 68 °C, 69 °C or 70 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0027] In some alternative examples, after the organic ligand solution is completely dropped, stirring and mixing are continued under heating conditions for 4 - 5 h to obtain the reaction solution, for example, it can be 4.0 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h or 5.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] As a preferred technical solution of the present invention, in step (Ⅰ), the addition amount of the polyvinyl alcohol is 7 - 9 wt% of the mass of the reaction solution, for example, it can be 7.0 wt%, 7.2 wt%, 7.4 wt%, 7.6 wt%, 7.8 wt%, 8.0 wt%, 8.2 wt%, 8.4 wt%, 8.6 wt%, 8.8 wt% or 9.0 wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] In some alternative examples, the stirring and mixing time of the reaction solution and the polyvinyl alcohol is 2 - 4 h, for example, it can be 2.0 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3.0 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h or 4.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

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

[0031] Cooling to a first freezing temperature at a first cooling rate and holding, and then continuing to cool to a second freezing temperature at a second cooling rate and holding.

[0032] In the present invention, in the first cooling stage, the temperature is rapidly decreased to -15~-20°C at a rate of -1~-2°C / min, promoting the formation of a large number of tiny ice crystal nuclei in the solution. During the heat preservation process, the ice crystals initially extend and grow along the temperature gradient direction to form an initial pore framework with a diameter of about 50~150μm. In the second cooling stage, the temperature is slowly decreased to -30~-40°C at a rate of -0.5~-1°C / min. At this time, the solution viscosity increases significantly, inducing the generation of secondary microporous structures on the wall surface of the formed initial pores. During the heat preservation process, the solvent molecules in the remaining unfrozen liquid phase are fully crystallized, avoiding stress concentration caused by rapid deep cooling, and finally forming a hierarchical pore structure in which vertically arranged through pores are intertwined with wall surface micropores. This hierarchical pore structure directly affects the sewage treatment effect of the material. The through large-diameter channels greatly improve the pollutant adsorption rate, and the secondary microporous structures generated on the wall surface of the large-diameter channels provide high-density anchoring sites for the loading of ZIF-67 crystals.

[0033] In some optional examples, the first cooling rate is -1~-2°C / min. For example, it can be -1°C / min, -1.1°C / min, -1.2°C / min, -1.3°C / min, -1.4°C / min, -1.5°C / min, -1.6°C / min, -1.7°C / min, -1.8°C / min, -1.9°C / min or -2°C / min, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0034] In some optional examples, the first freezing temperature is -15~-20°C. For example, it can be -15°C, -15.5°C, -16°C, -16.5°C, -17°C, -17.5°C, -18°C, -18.5°C, -19°C, -19.5°C or -20°C, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0035] In some optional examples, the heat preservation 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 it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0036] In some alternative examples, the second cooling rate is -0.5 to -1 °C / min. For example, it can be -0.5 °C / min, -0.55 °C / min, -0.6 °C / min, -0.65 °C / min, -0.7 °C / min, -0.75 °C / min, -0.8 °C / min, -0.85 °C / min, -0.9 °C / min, -0.95 °C / min or -1 °C / min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] In some alternative examples, the second freezing temperature is -30 to -40 °C. For example, it can be -30 °C, -31 °C, -32 °C, -33 °C, -34 °C, -35 °C, -36 °C, -37 °C, -38 °C, -39 °C or -40 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0038] In some alternative examples, the heat preservation time at the second freezing temperature is 3 to 4 h. For example, it can be 3.0 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h or 4.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

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

[0040] Soak the aerogel matrix in a silane coupling agent solution, oscillate and heat it, then take out the aerogel matrix, wash and dry it 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 to form a dense Si-O-Si covalent bond network. The directional arrangement of the long-chain alkyl groups makes the surface contact angle of the modified aerogel matrix reach more than 145°. On the one hand, this chemical modification endows the aerogel matrix with superhydrophobic properties, which can effectively block the penetration of water molecules and prevent the hydrolysis reaction of ZIF-67 crystals in the water environment, resulting in the dissolution of cobalt ions, so that the modified aerogel matrix maintains its structural integrity within a wide range of pH = 3 to 11. On the other hand, the silane layer grafted on the surface of the aerogel matrix can also reinforce the node connection of cellulose fibers through intermolecular forces, significantly improving the anti-swelling ability of the modified aerogel matrix in the aqueous phase environment.

[0042] The modified aerogel matrix exhibits excellent hydrophobic and oleophilic 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 pores forms an oleophilic environment due to surface energy differences, further enhancing the enrichment ability for refractory pollutants such as benzene series and polycyclic aromatic hydrocarbons.

[0043] In some alternative examples, the silane coupling agent solution is composed of a silane coupling agent and an ethanol aqueous solution.

[0044] In some alternative examples, the mass fraction of the silane coupling agent in the silane coupling agent solution is 1.8 - 2.2 wt%, for example, it can be 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 unlisted values within this numerical range are equally applicable.

[0045] In some alternative examples, the heating temperature when the aerogel matrix is soaked 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 equally applicable.

[0046] In some alternative examples, the soaking time of the aerogel matrix in the silane coupling agent solution is 12 - 24 h, for example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h or 24 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0047] It should be noted that after the soaking of the aerogel matrix is completed, it is taken out, washed with absolute ethanol, and then vacuum dried. The present invention does not make specific requirements and special limitations on the temperature and time of vacuum drying. Exemplarily, the temperature of vacuum drying 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 time of vacuum drying 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 unlisted values within this numerical range are equally applicable.

[0048] As a preferred technical solution of the present invention, in step (II), the iron source solution is composed 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0050] The present invention particularly defines the molar ratio of ferric chloride to ferrous chloride as (1.9~2.1):1. When the molar ratio of Fe 3+ to Fe 2+ is within the range defined by the present invention, it can maximize the homogeneous nucleation and directional growth of Fe3O4. Fe 3+ and Fe 2+ form a stable spinel structure through synergistic effects, ensuring that the magnetic particles have high crystallinity and uniform pore distribution. An appropriate amount of Fe 3+ can not only maintain the stability of the redox potential of the reaction system, prevent Fe 2+ from being oxidized, but also prevent the generation of impurity phases caused by excessive Fe 3+ , enabling the generated magnetic particles to have both excellent magnetic responsiveness and high catalytic activity.

[0051] When the addition amount of ferric chloride exceeds the upper limit of the range defined by the present invention, excessive Fe 3+ will precipitate in the form of iron oxyhydroxide or amorphous iron oxide, forming impurity phases, resulting in the surface of the magnetic particles being covered with inert substances, reducing their saturation magnetization intensity and catalytic active site density. In addition, excessive Fe 3+ will change the acid-base environment of the reaction system, thereby causing local pH fluctuations, promoting the oxidation of Fe 2+ to Fe 3+ , resulting in the aggregation of magnetic particles. This will not only reduce the specific surface area of the material, but also hinder the uniform coating of chitosan, weakening the dispersion stability of the magnetic particles.

[0052] When the addition amount of ferrous chloride exceeds the upper limit of the range defined by the present invention, excessive Fe 2+ will cause the formation path of Fe3O4 to be blocked, and then generate FeO with weak magnetism or other metastable iron oxides, resulting in a significant decrease in the saturation magnetization intensity of the magnetic particles and reducing the separation efficiency of the composite material under an external magnetic field. At the same time, the enrichment of Fe 2+ will enhance the reducibility of the system, thereby triggering side reactions, destroying the subsequent surface coating of chitosan, and further affecting its adsorption capacity for pollutants. In addition, Fe 2+Excess will also lead to abnormal particle morphology, forming cubic or spherical structures instead of the ideal octahedral crystal form, resulting in a reduction in the number of exposed active sites and a decrease in catalytic degradation performance.

[0053] In some alternative examples, the total mass fraction of ferric chloride and ferrous chloride in the iron source solution is 2 - 4 wt%, for example, it can be 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 not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

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

[0055] In some alternative examples, the heating temperature when the ammonia aqueous solution is dropped 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, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

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

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

[0058] In some alternative 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, it can be 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. Other unlisted values within this numerical range are equally applicable.

[0059] In some alternative examples, after all of the aqueous ammonia solution has been added dropwise, mixing and stirring are continued under heating conditions for 30 to 60 minutes. For example, it can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0060] It should be noted that magnetic particles are obtained after magnetic separation, washing, and drying after the reaction. The present invention does not make specific requirements or special limitations on the drying temperature and time. Exemplarily, the drying temperature is 50 to 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 to 12 hours. For example, it can be 6.0 hours, 6.5 hours, 7.0 hours, 7.5 hours, 8.0 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours, or 12.0 hours, but is not limited to the listed values. Other unlisted values within this numerical range are equally 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 an acetic acid solution to obtain a chitosan solution, and 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, and then magnetic separation, washing, and drying are carried out 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. Other unlisted values within this numerical range are equally applicable.

[0064] In some optional examples, the concentration of chitosan in the chitosan solution is 1 to 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0065] The present invention specifically limits the concentration of chitosan in the chitosan solution to 1 to 2 mg / mL. As a natural polymer, chitosan is rich in amino and hydroxyl functional groups on its molecular chain. These groups form a stable coating layer through coordination with the surface of magnetic particles. When the chitosan concentration is within the range defined by the present invention, chitosan molecules in the solution can be evenly adsorbed on the surface of magnetic particles to form a dense but not overly piled coating layer. The appropriate coating can not only effectively prevent the aggregation of magnetic particles in the water environment but also maintain their dispersion stability in complex water bodies through the electrostatic repulsion of 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 magnetic particles, and the magnetic particles are prone to aggregation, resulting in a decrease in their dispersibility in water and easy occurrence of aggregation phenomena. The aggregated magnetic particles will not only reduce the contact area between the material and pollutants but also weaken their adsorption capacity due to the reduction of the surface area. In addition, the incomplete coating of chitosan will cause partial exposure of magnetic particles, which will then trigger an oxidation reaction, leading to the dissolution of Fe 3+ dissolution, which not only affects the structural stability of the material but also poses a risk of secondary pollution due to the release of iron ions.

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

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

[0069] It should be noted that after adding magnetic particles to the chitosan solution, ultrasonic dispersion is required. The present invention does not make specific requirements and special limitations on the power and time of ultrasonic dispersion. Exemplarily, 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 it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0070] In some optional examples, the volume ratio of the mixed solution to 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 it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0071] The present invention specifically limits the volume ratio of the mixed solution to glutaraldehyde to 100:(1 - 2). Glutaraldehyde, as a cross - linker, forms a three - dimensional network structure by undergoing a condensation reaction with amino and hydroxyl groups in chitosan molecules, 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 dosage of glutaraldehyde can not only ensure the sufficient cross - linking of chitosan molecular chains to form a dense protective layer, but also avoid the shielding of functional groups and the increase of mass transfer resistance caused by excessive cross - linking.

[0072] When the addition amount of glutaraldehyde is lower than the lower limit of the range defined by the present invention, the cross - linking reaction is insufficient, the connection between chitosan molecules is loose, and it is difficult to form a stable protective layer of a three - dimensional network structure, resulting in more pores and defects in the coating layer on the surface of magnetic particles, significantly reducing its dispersion stability. In addition, the uncross - linked chitosan molecules also have insufficient adsorption capacity, making it difficult to effectively capture pollutants, and pollutants are likely to accumulate on the material surface, hindering the progress of subsequent catalytic reactions.

[0073] When the addition amount of glutaraldehyde exceeds the upper limit of the range defined in the present invention, it will cause excessive cross-linking. Excessive glutaraldehyde molecules will form a dense cross-linking network with the amino and hydroxyl groups of chitosan, resulting in an overly dense chitosan coating layer, significantly reducing the number of active sites of the active functional groups on the surface of the modified magnetic particles. In addition, this dense structure will reduce the electrostatic adsorption ability of the modified magnetic particles to heavy metal ions and the π-π interaction with organic pollutants, inhibiting the efficiency of the Fenton-like reaction.

[0074] In some alternative examples, the time of the cross-linking reaction is 3 to 4 h. For example, it can be 3.0 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h or 4.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0075] In some alternative examples, the heating temperature of the cross-linking reaction is 50 to 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, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0076] It should be noted that after the cross-linking reaction, the modified magnetic particles are obtained through magnetic separation, washing and drying. The present invention does not make specific requirements and special limitations on the drying temperature and time. Exemplarily, the drying temperature is 50 to 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 to 12 h. For example, it can be 8.0 h, 8.5 h, 9.0 h, 9.5 h, 10.0 h, 10.5 h, 11.0 h, 11.5 h or 12.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally 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 liquid is 1 to 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 unlisted values within this numerical range are equally applicable.

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

[0079] Add the modified aerogel matrix and the dispersion liquid into a reaction kettle, fully immerse the modified aerogel matrix in the dispersion liquid, evacuate the reaction kettle, and then restore it to normal pressure. Stir the dispersion liquid under normal pressure; then continue to evacuate; repeat the evacuation and restoration to normal pressure for the reaction kettle 3 to 5 times.

[0080] The negative pressure - normal pressure alternating impregnation process adopted in the present invention realizes the deep penetration and uniform loading of modified magnetic particles in the multi - level pores of the modified aerogel matrix. In the first evacuation stage, the gas in the pores of the modified aerogel matrix is discharged, and a stable low - pressure environment is formed inside, which promotes the dispersion liquid to gradually infiltrate the main pores in the modified aerogel matrix under capillary action. In the negative pressure holding stage, the dispersion liquid can overcome the wetting resistance of the micro - nano pores inside the modified aerogel matrix and penetrate to the deep layer of the modified aerogel matrix. When nitrogen is introduced to restore normal pressure, the external air pressure increases, which promotes the secondary distribution of the dispersion liquid in the pores of the modified aerogel matrix, and the modified magnetic particles gradually settle on the pore wall surface under the action of gravity and van der Waals force. Stir the dispersion liquid in the normal pressure stage to break the particle aggregates in the dispersion liquid.

[0081] In some optional examples, the mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion liquid 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 it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0082] The present invention specifically limits the mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion liquid to 1:(0.5 - 0.7). The modified aerogel matrix, as a porous framework, its three - dimensional network structure provides the physical space for pollutant adsorption and the mass transfer channel for catalytic reactions. The modified magnetic particles undergo a Fenton - like reaction under the activation of H2O2, generating a large number of hydroxyl radicals to degrade organic pollutants. The appropriate loading of the modified magnetic particles can be evenly embedded in the pore wall of the modified aerogel matrix, which not only retains the rapid adsorption capacity of the modified aerogel matrix for pollutants but also achieves a dynamic balance of adsorption - degradation through catalytic degradation.

[0083] When the addition amount of the modified magnetic particles is lower than the lower limit of the range defined in the present invention, the catalytic degradation ability of the obtained composite material is significantly reduced. The number of hydroxyl radicals generated through the Fenton - like reaction is small, and the organic pollutants adsorbed on the surface of the modified aerogel matrix cannot be decomposed in time, which is likely to cause secondary release of pollutants due to adsorption saturation. In addition, the magnetic responsiveness of the modified magnetic particles at low loading levels is difficult to fully exert, the separation and recovery efficiency is reduced, and the process complexity and operation cost are increased.

[0084] When the addition amount of the modified magnetic particles exceeds the upper limit of the range defined in the present invention, the excessive modified magnetic particles will block 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 lead to a decrease in the catalytic degradation reaction efficiency due to the increase in mass transfer resistance.

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

[0086] In some alternative examples, the reaction kettle maintains the vacuum for 20~30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0087] In some alternative examples, in the atmospheric pressure stage, the dispersion liquid is stirred for 30~40 min, for example, it can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min or 40 min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0088] It should be noted that after the impregnation is completed, the impregnated modified aerogel matrix is taken out for drying. The present invention does not make specific requirements and 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 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 unlisted values within this numerical range are equally applicable.

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

[0091] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0092] The present invention provides a preparation method of 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, and magnetic particles modified by chitosan are loaded. The magnetic particle-loaded porous composite material prepared by the present invention has both a high specific surface area, strong mechanical properties and rapid separation ability, can simultaneously adsorb heavy metal ions and organic pollutants and catalytically degrade refractory substances, and realizes efficient recovery and regeneration through an external magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0094] Figure 2 is an infrared spectrogram of nanocellulose, ZIF-67 and the aerogel matrix prepared in Example 1 of the present invention;

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

[0096] Figure 4 is a test curve graph of the water contact angle and oil contact angle of the modified aerogel matrix prepared in Example 1 of the present invention;

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

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

[0099] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and their accompanying drawings. The embodiments recorded herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary, and should not be construed as a limitation on the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of the present application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments recorded herein.

[0100] Example 1

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

[0102] (1) Disperse cobalt nitrate in deionized water. After mixing evenly, a cobalt source solution with a concentration of 0.15 mol / L is obtained. Mix a nano-cellulose solution with a mass fraction of 1 wt% and the cobalt source solution in a volume ratio of 3:1 to obtain a precursor solution. Disperse 2-methylimidazole in methanol. After mixing evenly, an organic ligand solution with a concentration of 0.9 mol / L is obtained. Under stirring and heating conditions at 60 °C, the organic ligand solution is dropped into the precursor solution at a rate of 1.5 mL / min. The molar ratio of 2-methylimidazole to cobalt ions is 5:1. After all the organic ligand solution is dropped, continue to stir the obtained mixture at 60 °C for 5 h to obtain a reaction solution;

[0103] Mix the reaction solution and polyvinyl alcohol and stir for 2 h. The addition amount of polyvinyl alcohol is 7 wt% of the mass of the reaction solution. Inject the mixed solution into a mold for directional freezing. First, cool down at a cooling rate of -1 °C / min to -15 °C and keep it warm for 1.5 h. Subsequently, continue to cool down at a cooling rate of -0.5 °C / min to -30 °C and keep it warm for 4 h to obtain an aerogel matrix;

[0104] Add the silane coupling agent KH550 to an ethanol aqueous solution (the volume ratio of absolute ethanol to deionized water in the ethanol aqueous solution is 9:1). After mixing evenly, a silane coupling agent solution with a mass fraction of 1.8 wt% is obtained. Immerse the aerogel matrix in the silane coupling agent solution and oscillate at 35 °C for 24 h. Subsequently, take out the aerogel matrix, wash it with ethanol, and then place it in a vacuum dryer at 45 °C for 12 h to obtain a modified aerogel matrix;

[0105] (2) Dissolve ferric chloride and ferrous chloride in deionized water. The molar ratio of ferric chloride to ferrous chloride is 1.9:1. After mixing evenly, an iron source solution is obtained. The total mass fraction of ferric chloride and ferrous chloride in the iron source solution is 2 wt%. Under the conditions of water bath heating and stirring at 50 °C, dropwise add an ammonia water solution with a mass fraction of 25 wt% to the iron source solution at a dropping rate of 1 mL / min until the pH value of the obtained mixed solution is 9. Subsequently, continue to mix and stir at 50 °C in a water bath for 60 min. After magnetic separation, washing, and vacuum drying, magnetic particles are obtained. Among them, the temperature of vacuum drying is 50 °C, and the time of vacuum drying is 12 h;

[0106] Chitosan was dissolved in a 1 wt% acetic acid solution, and after mixing evenly, a chitosan solution was obtained. The concentration of chitosan in the chitosan solution was 1 mg / mL; magnetic particles were added to the chitosan solution, and the ratio of magnetic particles to the chitosan solution was 1 g:40 mL. Ultrasonic dispersion was carried out at an ultrasonic power of 200 W for 40 min to obtain a mixed solution; glutaraldehyde was added to the mixed solution, and the volume ratio of the mixed solution to glutaraldehyde was 100:1. Mixing and stirring were carried out at 50 °C for 4 h to carry out a cross-linking reaction. After the reaction was completed, magnetic separation, washing, and vacuum drying were carried out to obtain modified magnetic particles, where the temperature of vacuum drying was 50 °C and the time of vacuum drying was 12 h;

[0107] (3)The modified magnetic particles obtained in step (2) were dispersed in deionized water, and after mixing evenly, a dispersion was obtained. The mass fraction of the modified magnetic particles in the dispersion was 1 wt%; the modified aerogel matrix obtained in step (1) and the dispersion were added to a reaction kettle, and the mass ratio of the modified aerogel matrix to the modified magnetic particles was 1:0.5, ensuring that the modified aerogel matrix was completely immersed in the dispersion. The reaction kettle was evacuated to -80 kPa and maintained for 30 min; then nitrogen was introduced into the reaction kettle to return to normal pressure, and the dispersion was stirred for 30 min; then the reaction kettle was evacuated to -80 kPa again and maintained for 30 min; the reaction kettle was evacuated and returned to normal pressure 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 is the infrared spectrum of nanocellulose, ZIF-67, and the aerogel matrix prepared in this example. It can be seen from the figure that in the infrared spectrum of nanocellulose, the characteristic peaks at 3460 cm -1 and 1735 cm -1 are attributed to the C-H stretching of cellulose hydroxyl and the C=O stretching vibration of carboxyl, respectively. In the infrared spectrum of the aerogel matrix obtained after in-situ growth of ZIF-67 nanoparticles, the absorption band appearing at 422 cm -1 is attributed to the Co-N stretching vibration of ZIF-67, and the vibration peaks at 1382 cm -1 , 1417 cm -1 and 1453 cm -1 are attributed to the C-N bond stretching vibration of 2-methylimidazole. The characteristic peaks at 689 cm -1 , 753 cm -1 and 1306 cm -1 are 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 3XRD patterns of nanocellulose, ZIF-67 and the aerogel matrix prepared in this example. It can be seen from the figure that the main diffraction peaks at 2θ = 7.4°, 10.4°, 12.7°, 18.1° and 26.7° correspond to the (011), (002), (112), (222) and (134) crystal planes of ZIF-67, respectively. In addition, in the XRD pattern of the aerogel matrix, the weak characteristic peak at 22.6° belongs to the (002) crystal plane of nanocellulose. The above results indicate that ZIF-67 is successfully loaded on the aerogel matrix.

[0110] Figure 4 Test curve graphs of the water contact angle and oil contact angle of the modified aerogel matrix prepared in this example. It can be seen from the figure that as the test time prolongs, the surface water contact angle of the modified aerogel matrix slightly decreases, but its average value is 145°, still belonging to a superhydrophobic surface; similarly, as the test time prolongs, the surface oil contact angle of the modified aerogel matrix also slightly decreases, but its average value is 10°, belonging to a superhydrophilic surface, which indicates that the modified aerogel matrix obtained after modification with a silane coupling agent has hydrophobic and oleophilic properties.

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

[0112] Figure 6 The transmission electron microscope image of the modified magnetic particles prepared in this example shows that the particle size of the magnetic particles is about 10 nm and they are spherical, but the particles tend to agglomerate to form more aggregates. The modified magnetic particles obtained after chitosan coating and glutaraldehyde cross-linking are also approximately spherical, with a particle size of about 10-20 nm, and their dispersibility in water medium is significantly better than that of 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 comprises the following steps:

[0115] (1) Dispersing cobalt nitrate in deionized water, mixing evenly to obtain a cobalt source solution with a concentration of 0.18 mol / L, and mixing a nanocellulose solution with a mass fraction of 1.2 wt% and the cobalt source solution evenly in a volume ratio of 2.8:1 to obtain a precursor solution; dispersing 2-methylimidazole in methanol, mixing evenly to obtain an organic ligand solution with a concentration of 0.92 mol / L, and dripping the organic ligand solution into the precursor solution at a rate of 1.8 mL / min under stirring and heating conditions at 62° C., wherein the molar ratio of 2-methylimidazole to cobalt ions is 5.2:1. After all the organic ligand solution is dripped, the obtained mixed solution is continuously stirred under heating conditions at 62° C. for 4.8 h to obtain a reaction solution;

[0116] The reaction solution and polyvinyl alcohol were mixed and stirred for 2.5 hours, and the amount of polyvinyl alcohol added was 7.5wt% of the mass of the reaction solution. 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 warm for 1.2 hours, and then the temperature was further cooled to -32°C at a cooling rate of -0.6°C / min and kept warm for 3.8 hours to obtain an aerogel matrix.

[0117] The silane coupling agent KH550 was added to the ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 9:1), and the mixture was evenly mixed to obtain a silane coupling agent solution with a mass fraction of 1.9wt%; the aerogel matrix was immersed in the silane coupling agent solution, and was shaken at 38°C for 21h, and then the aerogel matrix was taken out, washed with ethanol, and then vacuum dried at 48°C for 11.5h to obtain a modified aerogel matrix;

[0118] (2) Dissolve ferric chloride and ferrous chloride in deionized water. The molar ratio of ferric chloride to ferrous chloride is 1.95:1. After mixing evenly, an iron source solution is obtained. The total mass fraction of ferric chloride and ferrous chloride in the iron source solution is 2.5 wt%. Under the conditions of water bath heating and stirring at 52 °C, a 26 wt% ammonia water solution is added dropwise to the iron source solution at a dropping rate of 2 mL / min until the pH value of the obtained mixed solution is 9.2. Subsequently, continue to mix and stir at 52 °C in a water bath for 50 min. After magnetic separation, washing, and vacuum drying, magnetic particles are obtained. Among them, the temperature of vacuum drying is 52 °C, and the time of vacuum drying is 10 h;

[0119] Dissolve chitosan in a 1.5 wt% acetic acid solution. After mixing evenly, a chitosan solution is obtained. The concentration of chitosan in the chitosan solution is 1.2 mg / mL. Add the magnetic particles to the chitosan solution. The ratio of magnetic particles to chitosan solution is 1 g:42 mL. Perform ultrasonic dispersion for 38 min at an ultrasonic power of 220 W to obtain a mixed solution. Add glutaraldehyde to the mixed solution. The volume ratio of the mixed solution to glutaraldehyde is 100:1.2. Perform mixing and stirring at 52 °C for 3.8 h to carry out a cross-linking reaction. After the reaction is completed, perform magnetic separation, washing, and vacuum drying to obtain modified magnetic particles. Among them, the temperature of vacuum drying is 52 °C, and the time of vacuum drying is 11 h;

[0120] (3) Disperse the modified magnetic particles obtained in step (2) in deionized water. After mixing evenly, a dispersion is obtained. The mass fraction of the modified magnetic particles in the dispersion is 1.2 wt%. Add the modified aerogel matrix obtained in step (1) and the dispersion to a reaction kettle. 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. Vacuum the reaction kettle to -82 kPa and maintain it for 28 min. Subsequently, introduce nitrogen into the reaction kettle to restore it to normal pressure, and stir the dispersion for 32 min. Subsequently, continue to vacuum the reaction kettle to -82 kPa and maintain it for 28 min. Repeat the process of vacuuming and restoring normal pressure on the reaction kettle 4 times, and then take it out and perform vacuum drying at 52 °C for 11.5 h to obtain the magnetic particle-loaded porous composite material.

[0121] Example 3

[0122] This example provides a preparation method of a magnetic particle-loaded porous composite material for sewage treatment, as Figure 1 shown. The specific preparation method includes the following steps:

[0123] (1) Disperse cobalt nitrate in deionized water. After mixing evenly, a cobalt source solution with a concentration of 0.2 mol / L is obtained. Mix the nanocellulose solution with a mass fraction of 1.5 wt% and the cobalt source solution according to a volume ratio of 2.5:1 to obtain a precursor solution. Disperse 2-methylimidazole in methanol. After mixing evenly, an organic ligand solution with a concentration of 0.95 mol / L is obtained. Under stirring and heating at 65 °C, the organic ligand solution is dropped into the precursor solution at a rate of 2 mL / min. The molar ratio of 2-methylimidazole to cobalt ions is 5.5:1. After all the organic ligand solution is dropped, continue to stir the obtained mixture at 65 °C for 4.5 h to obtain a reaction solution;

[0124] Mix the reaction solution and polyvinyl alcohol and stir for 3 h. The addition amount of polyvinyl alcohol is 8 wt% of the mass of the reaction solution. Inject the mixed solution into a mold for directional freezing. First, cool down to -17 °C at a cooling rate of -1.5 °C / min and keep warm for 1 h. Then, continue to cool down to -35 °C at a cooling rate of -0.7 °C / min and keep warm for 3.5 h to obtain an aerogel matrix;

[0125] Add the silane coupling agent KH550 to an ethanol aqueous solution (the volume ratio of absolute ethanol to deionized water in the ethanol aqueous solution is 9:1). After mixing evenly, a silane coupling agent solution with a mass fraction of 2 wt% is obtained. Immerse the aerogel matrix in the silane coupling agent solution and oscillate at 40 °C for 18 h. Then take out the aerogel matrix, wash it with ethanol, and place it in a vacuum dryer at 50 °C for 11 h to obtain a modified aerogel matrix;

[0126] (2) Dissolve ferric chloride and ferrous chloride in deionized water. The molar ratio of ferric chloride to ferrous chloride is 2:1. After mixing evenly, an iron source solution is obtained. The total mass fraction of ferric chloride and ferrous chloride in the iron source solution is 3 wt%. Under the conditions of water bath heating at 55 °C and stirring, drop the ammonia water solution with a mass fraction of 27 wt% into the iron source solution at a dropping rate of 3 mL / min until the pH value of the obtained mixed solution is 9.5. Then continue to mix and stir at 55 °C under the condition of water bath heating for 40 min. After magnetic separation, washing, and vacuum drying, magnetic particles are obtained. Among them, the temperature of vacuum drying is 55 °C and the time of vacuum drying is 9 h;

[0127] Chitosan was dissolved in a 2 wt% acetic acid solution, and after mixing evenly, a chitosan solution was obtained. The concentration of chitosan in the chitosan solution was 1.5 mg / mL; magnetic particles were added to the chitosan solution, and the ratio of magnetic particles to the chitosan solution was 1 g:45 mL. Ultrasonic dispersion was carried out at an ultrasonic power of 250 W for 35 min to obtain a mixed solution; glutaraldehyde was added to the mixed solution, and the volume ratio of the mixed solution to glutaraldehyde was 100:1.5. Mixing and stirring were carried out at 55 °C for 3.5 h to carry out a cross-linking reaction. After the reaction ended, magnetic separation, washing, and vacuum drying were carried out to obtain modified magnetic particles. Among them, the temperature of vacuum drying was 55 °C, and the time of vacuum drying was 10 h;

[0128] (3)The modified magnetic particles obtained in step (2) were dispersed in deionized water, and after mixing evenly, a dispersion was obtained. The mass fraction of the modified magnetic particles in the dispersion was 1.5 wt%; the modified aerogel matrix obtained in step (1) and the dispersion were added to a reaction kettle. The mass ratio of the modified aerogel matrix to the modified magnetic particles was 1:0.6, ensuring that the modified aerogel matrix was completely immersed in the dispersion. The reaction kettle was evacuated to -85 kPa and maintained for 25 min; then nitrogen was introduced into the reaction kettle to return to normal pressure, and the dispersion was stirred for 35 min; then the reaction kettle was evacuated to -85 kPa again and maintained for 25 min; the reaction kettle was evacuated and returned 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 example provides a preparation method of a magnetic particle-loaded porous composite material for sewage treatment, as Figure 1 shown. The specific preparation method includes the following steps:

[0131] (1)Cobalt nitrate was dispersed in deionized water, and after mixing evenly, a cobalt source solution with a concentration of 0.22 mol / L was obtained. A nanocellulose solution with a mass fraction of 1.8 wt% and the cobalt source solution were mixed evenly according to a volume ratio of 2.2:1 to obtain a precursor solution; 2-methylimidazole was dispersed in methanol, and after mixing evenly, an organic ligand solution with a concentration of 0.98 mol / L was obtained. 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 mixed solution was continuously stirred at 68 °C for 4.2 h to obtain a reaction solution;

[0132] The reaction solution was mixed with polyvinyl alcohol and stirred for 3.5 h. The addition amount of polyvinyl alcohol was 8.5 wt% of the mass of the reaction solution. The mixed solution was poured into a mold for directional freezing. First, it was cooled to -18°C at a cooling rate of -1.8°C / min and held for 0.8 h. Subsequently, it was further cooled to -38°C at a cooling rate of -0.8°C / min and held for 3.2 h to obtain an aerogel matrix.

[0133] The silane coupling agent KH550 was added to an ethanol aqueous solution (the volume ratio of absolute ethanol to deionized water in the ethanol aqueous solution was 9:1). After mixing evenly, a silane coupling agent solution with a mass fraction of 2.1 wt% was obtained. The aerogel matrix was immersed in the silane coupling agent solution and oscillated at 42°C for 15 h. Subsequently, the aerogel matrix was taken out, washed with ethanol, and placed in a vacuum dryer at 52°C for 10.5 h to obtain a modified aerogel matrix.

[0134] (2) Ferric chloride and ferrous chloride were dissolved in deionized water. The molar ratio of ferric chloride to ferrous chloride was 2.05:1. After mixing evenly, an iron source solution was obtained. The total mass fraction of ferric chloride and ferrous chloride in the iron source solution was 3.5 wt%. Under the conditions of water bath heating and stirring at 58°C, an aqueous ammonia solution with a mass fraction of 27 wt% was added dropwise to the iron source solution at a dropping rate of 4 mL / min until the pH value of the obtained mixed solution was 9.8. Subsequently, it was continuously mixed and stirred at 58°C under the condition of water bath heating for 40 min. After magnetic separation, washing, and vacuum drying, magnetic particles were obtained. Among them, the temperature of vacuum drying was 58°C, and the time of vacuum drying was 8 h.

[0135] Chitosan was dissolved in a 2.5 wt% acetic acid solution. After mixing evenly, a chitosan solution was obtained. The concentration of chitosan in the chitosan solution was 1.8 mg / mL. The magnetic particles were added to the chitosan solution. The ratio of magnetic particles to chitosan solution was 1 g:48 mL. Ultrasonic dispersion was carried out at an ultrasonic power of 280 W for 32 min to obtain a mixed solution. Glutaraldehyde was added to the mixed solution. The volume ratio of the mixed solution to glutaraldehyde was 100:1.8. Mixing and stirring were carried out at 58°C for 3.2 h to carry out a crosslinking reaction. After the reaction ended, magnetic separation, washing, and vacuum drying were carried out to obtain modified magnetic particles. Among them, the temperature of vacuum drying was 58°C, and the time of vacuum drying was 9 h.

[0136] (3) Disperse the modified magnetic particles obtained in step (2) in deionized water. After mixing evenly, a dispersion liquid is obtained, and the mass fraction of the modified magnetic particles in the dispersion liquid is 1.8 wt%. Add the modified aerogel matrix obtained in step (1) and the dispersion liquid into a reaction kettle. 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 liquid. Vacuum the reaction kettle to -88 kPa and maintain it for 22 min. Subsequently, introduce nitrogen into the reaction kettle to restore it to normal pressure, and stir the dispersion liquid for 38 min. Then continue to vacuum the reaction kettle to -88 kPa and maintain it for 22 min. Repeat the operations of vacuuming and restoring to normal pressure for the reaction kettle three times, and then take it out and vacuum dry it at 58 °C for 10.5 h to obtain the magnetic particle-loaded porous composite material.

[0137] Example 5

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

[0139] (1) Disperse cobalt nitrate in deionized water. After mixing evenly, a cobalt source solution with a concentration of 0.25 mol / L is obtained. Mix a nanocellulose solution with a mass fraction of 2 wt% and the cobalt source solution evenly according to a volume ratio of 2:1 to obtain a precursor solution. Disperse 2-methylimidazole in methanol. After mixing evenly, an organic ligand solution with a concentration of 1 mol / L is obtained. Under the conditions of stirring and heating at 70 °C, drop the organic ligand solution into the precursor solution at a rate of 2.5 mL / min. The molar ratio of 2-methylimidazole to cobalt ions is 6:1. After all the organic ligand solution is dropped, continue to stir the obtained mixed solution at 70 °C for 4 h to obtain a reaction solution;

[0140] Mix the reaction solution and polyvinyl alcohol and stir for 4 h. The addition amount of polyvinyl alcohol is 9 wt% of the mass of the reaction solution. Inject the mixed solution into a mold for directional freezing. First, cool it at a cooling rate of -2 °C / min to -20 °C and keep it warm for 0.5 h. Then continue to cool it at a cooling rate of -1 °C / min to -40 °C and keep it warm for 3 h to obtain an aerogel matrix;

[0141] Add the silane coupling agent KH550 to an ethanol aqueous solution (the volume ratio of absolute ethanol to deionized water in the ethanol aqueous solution is 9:1). After mixing evenly, a silane coupling agent solution with a mass fraction of 2.2 wt% is obtained. Immerse the aerogel matrix in the silane coupling agent solution and oscillate it at 45 °C for 12 h. Then take out the aerogel matrix, wash it with ethanol, and place it in a vacuum dryer at 55 °C for 10 h to obtain a modified aerogel matrix;

[0142] (2) Dissolve ferric chloride and ferrous chloride in deionized water. The molar ratio of ferric chloride to ferrous chloride is 2.1:1. After mixing evenly, an iron source solution is obtained. The total mass fraction of ferric chloride and ferrous chloride in the iron source solution is 4 wt%. Under the conditions of water bath heating at 60 °C and stirring, a 28 wt% ammonia water solution is added dropwise to the iron source solution at a dropping rate of 5 mL / min until the pH value of the obtained mixed solution is 10. Subsequently, continue to mix and stir for 30 min under the condition of water bath heating at 60 °C. After magnetic separation, washing, and vacuum drying, magnetic particles are obtained. Among them, the temperature of vacuum drying is 60 °C, and the time of vacuum drying is 6 h;

[0143] Dissolve chitosan in a 3 wt% acetic acid solution. After mixing evenly, a chitosan solution is obtained. The concentration of chitosan in the chitosan solution is 2 mg / mL. Add the magnetic particles to the chitosan solution. The ratio of magnetic particles to chitosan solution is 1 g:50 mL. Perform ultrasonic dispersion for 30 min at an ultrasonic power of 300 W to obtain a mixed solution. Add glutaraldehyde to the mixed solution. The volume ratio of the mixed solution to glutaraldehyde is 100:2. Perform mixing and stirring at 60 °C for 3 h to carry out a cross-linking reaction. After the reaction is completed, perform magnetic separation, washing, and vacuum drying to obtain modified magnetic particles. Among them, the temperature of vacuum drying is 60 °C, and the time of vacuum drying is 8 h;

[0144] (3) Disperse the modified magnetic particles obtained in step (2) in deionized water. After mixing evenly, a dispersion liquid is obtained. The mass fraction of the modified magnetic particles in the dispersion liquid is 2 wt%. Add the modified aerogel matrix obtained in step (1) and the dispersion liquid to the reaction kettle. 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 liquid. Vacuum the reaction kettle to -90 kPa and maintain it for 20 min. Subsequently, introduce nitrogen into the reaction kettle to restore to normal pressure, and stir the dispersion liquid for 40 min. Subsequently, continue to vacuum the reaction kettle to -90 kPa and maintain it for 20 min. Repeat the process of vacuuming and restoring to normal pressure for the reaction kettle 3 times, and then take it out and perform vacuum drying at 60 °C for 10 h to obtain the magnetic particle-loaded porous composite material.

[0145] Example 6

[0146] This example provides a preparation method of 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 other operation 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 Embodiment 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 operation steps and process parameters are exactly the same as those in Embodiment 1.

[0149] Embodiment 8

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

[0151] Embodiment 9

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

[0153] Embodiment 10

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

[0155] Embodiment 11

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

[0157] Embodiment 12

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

[0159] Embodiment 13

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

[0161] Embodiment 14

[0162] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Embodiment 1 is that in step (3), the mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion liquid is adjusted to 1:0.2, and the other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0163] Embodiment 15

[0164] This embodiment provides a method for preparing a magnetic particle-loaded porous composite material for sewage treatment. The difference from Embodiment 1 is that in step (3), the mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion liquid is adjusted to 1:1, and the other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0165] The magnetic particle-loaded porous composite materials prepared by using Embodiments 1-15 of the present invention are used to treat printing and dyeing wastewater and petrochemical wastewater, specifically including:

[0166] The magnetic particle-loaded porous composite materials prepared by using Embodiments 1-15 of the present invention are put into the printing and dyeing wastewater. The COD value in the printing and dyeing wastewater is 824 mg / L, the NH3-N value is 18.3 mg / L, the suspended solid content is 255 mg / L, the chromaticity value is 580 times (dilution multiple method), and the dosage of the composite material is 2.5 kg / m 3 , and at the same time, 30 wt% hydrogen peroxide is added to the printing and dyeing wastewater. The addition amount of hydrogen peroxide is 2 kg per ton of printing and dyeing wastewater. After 10 days, the concentrations of various pollutants in the treated printing and dyeing wastewater are tested, and the concentrations of various pollutants in the treated printing and dyeing wastewater are shown in Table 1.

[0167] The magnetic particle-loaded porous composite materials prepared by using Embodiments 1-15 of the present invention are put into the petrochemical wastewater. The COD value in the petrochemical wastewater is 2820 mg / L, the NH3-N value is 58.6 mg / L, the suspended solid content is 236 mg / L, the petroleum content is 125.3 mg / L, and the dosage of the composite material is 5 kg / m 3 , and at the same time, 30 wt% hydrogen peroxide is added to the petrochemical wastewater. The addition amount of hydrogen peroxide is 5 kg per ton of petrochemical wastewater. After 10 days, the concentrations of various pollutants in the treated petrochemical wastewater are tested, and the concentrations of various pollutants in the treated petrochemical wastewater are shown in Table 2.

[0168] Table 1

[0169]

[0170] Table 2

[0171]

[0172] It can be seen from the test data provided in Table 1 and Table 2 that the effluent water quality of Examples 1-5 is comprehensively better than the national standard requirements of printing and dyeing wastewater (GB4287-2012 "Discharge Standard of Water Pollutants for the Textile Dyeing and Finishing Industry") and petrochemical wastewater (GB31571-2015 "Discharge Standard of Pollutants for the Petrochemical Industry"). This technology combines a multi-level pore structure with the magnetic response of magnetic particles to achieve efficient and stable sewage treatment performance, especially suitable for the advanced treatment of high-difficulty printing and dyeing wastewater and petrochemical wastewater.

[0173] It can be seen from the test data of Example 1, Example 6 and Example 7 that the effluent water quality of Example 6 and Example 7 is inferior to that of Example 1. This is because the dosage of the nanocellulose solution in Example 6 is too small, resulting in the aggregation of ZIF-67 crystals, blocking the pores and reducing the adsorption efficiency. In Example 7, the dosage of the nanocellulose solution is too large, affecting the structural stability, resulting in pore collapse and a decrease in the interception efficiency of pollutants.

[0174] It can be seen from the test data of Example 1, Example 8 and Example 9 that the effluent water quality of Example 8 and Example 9 is inferior to that of Example 1. This is because the dosage of ferric chloride in Example 8 is too small, reducing the efficiency of the Fenton-like reaction, insufficient oxidation of refractory organic matter, and a decrease in the degradation efficiency of pollutants. In Example 9, the dosage of ferric chloride is too large, generating by-products, interfering with the adsorption equilibrium, damaging the pore structure, and a decrease in 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 water 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 dispersion of the modified magnetic particles and low utilization rate of catalytic active sites, and a decrease in the degradation efficiency of pollutants; in Example 11, the concentration of chitosan in the chitosan solution is too high, resulting in an overly thick surface coating layer of the modified magnetic particles, hindering mass transfer and a decrease in 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 water quality of Example 12 and Example 13 is inferior to that of Example 1. This is because the dosage of glutaraldehyde in Example 12 is too low, and the modified magnetic particles are easily lost, resulting in a decline in long-term operation performance; in Example 13, the dosage of glutaraldehyde is too high, resulting in an overly dense cross-linked network, pore blockage, a decrease in adsorption kinetic performance, and a decrease in the interception efficiency of pollutants.

[0177] It can be seen from the test data of Example 1, Example 14 and Example 15 that the effluent water quality of Example 14 and Example 15 is inferior to that of Example 1. This is because the dosage of the modified magnetic particles in Example 14 is too low, the catalytic reaction is incomplete, there are residues of refractory organic substances, and the degradation efficiency of pollutants is reduced; the dosage of the 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 description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a magnetic particle-loaded porous composite material for sewage treatment, characterized in that The preparation method includes: (I) Drop the organic ligand solution into the precursor solution composed of the nanocellulose solution and the cobalt source solution to obtain a reaction solution; mix the reaction solution with polyvinyl alcohol and then inject it into a mold for directional freezing to obtain an aerogel matrix; perform hydrophobic modification on the aerogel matrix to obtain a modified aerogel matrix; (II) Drop the ammonia water solution into the iron source solution for reaction, and after the reaction, perform magnetic separation, washing, and drying to obtain magnetic particles; perform chitosan modification on the magnetic particles to obtain modified magnetic particles; (III) Disperse the modified magnetic particles in deionized water to obtain a dispersion; immerse the modified aerogel matrix in the dispersion, take it out and dry it to obtain the magnetic particle-loaded porous composite material.

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

3. The preparation method according to claim 1, characterized in that, In step (I), the addition amount of polyvinyl alcohol is 7 - 9 wt% of the mass of the reaction solution; The mixing and stirring time of the reaction solution and polyvinyl alcohol is 2 - 4 h; The directional freezing process includes: Cool down to the first freezing temperature at the first cooling rate and keep warm, and then continue to cool down to the second freezing temperature at the second cooling rate and keep warm; The first cooling rate is -1 - 2 °C / min; The first freezing temperature is -15 - 20 °C; The heat preservation time at the first freezing temperature is 0.5 - 1.5 h; The second cooling rate is -0.5 - 1 °C / min; The second freezing temperature is -30 - 40 °C; The heat preservation time at the second freezing temperature is 3 - 4 h.

4. The preparation method according to claim 1, characterized in that, In step (I), the hydrophobic modification treatment includes: Immerse the aerogel matrix in the silane coupling agent solution, oscillate and heat it, then take out the aerogel matrix, wash and dry it to obtain the modified aerogel matrix; The silane coupling agent solution is composed 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 when the aerogel matrix is immersed in the silane coupling agent solution is 35 - 45 °C; The immersion time of the aerogel matrix in the silane coupling agent solution is 12 - 24 h.

5. The preparation method according to claim 1, characterized in that, In step (II), the iron source solution is composed 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, the ammonia water solution is dropped into the iron source solution; The heating temperature when the ammonia water solution is dropped is 50 - 60 °C; The mass fraction of the ammonia water solution is 25 - 28 wt%; The ammonia water solution is dropped into the iron source solution until the pH value of the obtained mixed solution is 9 - 10; After all the ammonia water solution is dropped, continue to mix and stir for 30 - 60 min under heating conditions.

6. The preparation method according to claim 1, wherein In step (II), the modification method of the magnetic particles includes: Dissolve chitosan in acetic acid solution to obtain a chitosan solution, add the magnetic particles into the chitosan solution and disperse them by ultrasonic wave to obtain a mixed solution; add glutaraldehyde to the mixed solution for cross-linking reaction, and then obtain the modified magnetic particles through magnetic separation, washing and drying.

7. The preparation method according to claim 6, characterized in that, 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 glutaraldehyde is 100:(1 - 2); The time of the cross-linking reaction is 3 - 4 h; The heating temperature of the cross-linking reaction is 50 - 60 °C.

8. The preparation method according to claim 1, characterized in that, In step (III), the mass fraction of the modified magnetic particles in the dispersion liquid is 1 - 2 wt%; The impregnation process includes: Add the modified aerogel matrix and the dispersion liquid into a reaction kettle, completely immerse the modified aerogel matrix in the dispersion liquid, evacuate the reaction kettle, and then restore it to normal pressure, and stir the dispersion liquid under normal pressure; then continue to evacuate; repeat the evacuation and restoration to normal pressure of the reaction kettle for 3 - 5 times; The mass ratio of the modified aerogel matrix to the modified magnetic particles in the dispersion liquid is 1:(0.5 - 0.7); The reaction kettle is evacuated to -80 - -90 kPa; The time for the reaction kettle to maintain vacuum is 20 - 30 min; In the normal pressure stage, stir the dispersion liquid for 30 - 40 min.

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

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

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