Preparation method and application of magnetic super-hydrophobic graphene aerogel based on biomass template

Abstract

The invention belongs to the technical field of functional material preparation, and particularly discloses a preparation method and application of magnetic super-hydrophobic graphene aerogel based on a biomass template. Loofah sponge fibers are used as a three-dimensional skeleton, and three-component molecular-level coupling of Fe < 3 + > / Cu < 2 + > ions, graphene oxide and a biological template is realized through a pH-regulated electrostatic co-assembly technology; performing solvothermal reaction at 180 DEG C to synchronously complete crystallization growth of hollow CuFe2O4 nanospheres and in-situ reduction of graphene, and finally performing freeze drying to obtain the super-hydrophobic aerogel with a hierarchical porous structure. The specific surface area is increased by 17.5 times compared with that of aerogel prepared by a traditional hydrothermal method; the super-hydrophobic / super-oleophylic characteristic is realized through the surface energy gradient design; an embedded superparamagnetic unit realizes external field driven recovery, and the adsorption retention rate gt is obtained after 20 times of circulation; 92%. The product can efficiently treat emulsified oil wastewater containing a surfactant, and is especially suitable for rapid treatment of metallurgical rolling waste liquid and marine oil spill accidents.

Description

Technical Field

[0001] The present invention relates to the technical field of functional material preparation, and particularly relates to a preparation method and application of a magnetic superhydrophobic graphene aerogel based on a biomass template. Background Art

[0002] With the acceleration of the industrialization process, offshore oil spills occur frequently, posing a serious threat to the ecological environment and human health. Among the existing oil-water separation technologies, the adsorption method has attracted much attention due to its advantages such as low cost, simple operation, and high efficiency. Reduced graphene oxide (RGO) shows potential in the field of oil-water separation due to its tunable wettability, high specific surface area, and layered structure. However, two-dimensional RGO nanosheets are prone to agglomeration and difficult to recycle, while three-dimensional graphene aerogel (GA) can alleviate this problem, but still has the following defects:

[0003] (1) The strong van der Waals force and π-π interaction between graphene sheets lead to pore structure collapse and poor mechanical stability;

[0004] (2) The surface of pure GA is hydrophilic and oleophilic, with low adsorption selectivity;

[0005] (3) Powdered materials are likely to cause secondary pollution.

[0006] In the prior art, although the introduction of magnetic components (such as Fe3O4) can improve the recyclability, it is difficult to simultaneously achieve superhydrophobic properties and structural stability. Therefore, there is an urgent need to develop graphene-based composites with high adsorption capacity, excellent selectivity, and cyclic stability. Summary of the Invention

[0007] Based on the deficiencies of the prior art, the present invention provides a preparation method and application of a magnetic superhydrophobic graphene aerogel based on a biomass template, which solves the problems of easy collapse of the traditional GA structure and poor selectivity; the prepared aerogel needs to have magnetism, high porosity, and cyclic stability, and is suitable for continuous oil-water separation scenarios.

[0008] The technical solution of the present invention is as follows: A preparation method of a magnetic superhydrophobic graphene aerogel based on a biomass template, comprising the following steps:

[0009] (1) Constructing a magnetic precursor: Dispersing hollow CuFe2O4 nanospheres and graphene oxide in an acidic solution with pH ≤ 3 according to a mass ratio of 1:1 - 1:4, and forming a magnetic graphene oxide MGO suspension through ultrasonic treatment;

[0010] (2) Biomass composite assembly: Immerse the columnar biomass sponge framework in the magnetic graphene oxide MGO suspension, and the biomass sponge powder with a particle size of 0.5 - 1 μm is uniformly dispersed in the magnetic graphene oxide MGO suspension; through the drive of an ultrasonic field, three-dimensional pore filling is achieved to obtain a columnar biomass sponge framework loaded with magnetic graphene oxide and biomass sponge powder;

[0011] (3) In-situ solvothermal reaction: The columnar biomass sponge framework loaded with magnetic graphene oxide and biomass sponge powder is heated in a closed system at a gradient of 70 - 90 °C to complete the in-situ reduction of magnetic graphene oxide and the interfacial bonding of biomass - nanospheres, obtaining a hydrogel;

[0012] (4) Supercritical drying and forming: Immerse the hydrogel in a 10 - 20 vol% tert-butanol solution, and after rapid freezing with liquid nitrogen, perform room-temperature vacuum drying to obtain a superhydrophobic graphene aerogel with a porosity ≥ 98%.

[0013] (The sum of the columnar biomass sponge framework and the biomass sponge powder) / magnetic graphene oxide mass ratio is 1:4 - 2:4; the mass ratio of the columnar biomass sponge framework to magnetic graphene oxide MGO is 1:4, and the impregnation time is 10 - 30 min.

[0014] For the said columnar biomass sponge framework, the axial through-hole ≥ 300 μm; for the biomass sponge powder, the specific surface area ≥ 20 m 2 / g.

[0015] The biomass is loofah sponge; the diameter of the columnar biomass sponge framework is 0.5 cm - 0.8 cm, and the porosity ≥ 95%.

[0016] The diameter of the hollow CuFe₂O₄ nanospheres is 80 - 120 nm, and the specific surface area ≥ 150 m 2 / g; the hollow CuFe₂O₄ nanospheres are prepared by the sol - gel method, have a ring-shaped mesoporous structure, and the saturation magnetization intensity ≥ 40 emu / g.

[0017] In the said graphene oxide, the C / O atomic ratio ≤ 1.8; the thickness of the graphene oxide sheet is 1.00 - 1.58 nm, and the lateral size of the graphene oxide is 1 - 5 μm

[0018] The said gradient heating process is that the temperature gradient increases, and the heating time gradient decreases at each temperature.

[0019] The said gradient heating process is specifically 70 °C × 50 min → 80 °C × 40 min → 90 °C × 30 min, and the heating rate in each stage ≤ 5 °C / min.

[0020] The prepared superhydrophobic graphene aerogel has a water contact angle ≥ 160° and an oil contact angle ≤ 5°. The superhydrophobic graphene aerogel has the following characteristics: a) a hierarchical pore structure with a BET specific surface area ≥ 200 m 2 / g; b) superparamagnetism with a saturation magnetization intensity ≥ 45 emu / g; c) a capacity retention rate ≥ 92% after 20 adsorption-desorption cycles.

[0021] Application of a superhydrophobic graphene aerogel in the treatment of surfactant-containing emulsified oil wastewater for purifying metallurgical rolling waste liquid with COD ≥ 5000 mg / L.

[0022] Advantages of the present invention:

[0023] 1. Enhanced physical structure stability: The hollow CuFe2O4 nanospheres have a unique three-dimensional hollow structure, which can provide a large specific surface area and porosity, while the biomass template provides a stable skeletal support for the graphene aerogel. This structural design not only improves the mechanical strength of the graphene aerogel but also enhances its stability in complex environments. The hollow structure helps to reduce the density of the material while maintaining sufficient strength, making it more durable in practical applications.

[0024] 2. Excellent adsorption performance: The high specific surface area and porous structure of the hollow CuFe2O4 nanospheres, combined with the hydrophilicity and biocompatibility of the biomass template, endow the graphene aerogel with excellent adsorption performance. This graphene aerogel can efficiently adsorb oil in water. Its high adsorption capacity and fast adsorption rate significantly improve the treatment efficiency.

[0025] 3. Good magnetic separation performance: The CuFe2O4 nanospheres have good magnetism and can be guided and separated by an external magnetic field. By applying an external magnetic field, it is convenient to separate the graphene aerogel adsorbed with pollutants from water, simplifying the solid-liquid separation process and improving the treatment efficiency and operation convenience.

[0026] 4. Biocompatibility and environmental friendliness: The biomass template is derived from natural materials and has good biocompatibility and degradability. The use of this natural material not only reduces secondary pollution to the environment but also improves the safety and sustainability of the material. It has broad application prospects in the field of environmental remediation.

[0027] 5. Simple preparation process: The preparation method of the present invention is simple and feasible. Through the solvothermal method and in-situ growth technology, the uniform distribution and controllable growth of hollow CuFe2O4 nanospheres and graphene oxide nanosheets on the biomass template can be achieved. This simple preparation process not only reduces the production cost but also improves the reproducibility and consistency of the material, which is conducive to large-scale production and popularization. Description of the Drawings

[0028] Figure 1 Model diagram of the sample prepared in Example 2.

[0029] Figure 2(a) shows the separation of water and organic solvent (CCl4) using CLGA;

[0030] Figure 2(b) is a diagram showing the simulated continuous adsorption and removal of light oil (toluene).

[0031] Figure 3 Water and oil contact angles on the surfaces of the samples prepared in Comparative Example 1, Comparative Example 2, and Example 2; (a) shows the water contact angle and oil adsorption behavior of GA; (b) shows the water contact angle and oil adsorption behavior of LGA; (c) shows the water contact angle and oil adsorption behavior of CLGA.

[0032] Figure 4 Scanning electron microscope images at different magnifications; (a)-(c) are for GA, (d)-(f) are for LGA, and (g)-(i) are for CLGA. Detailed implementation manners

[0033] 1. Optimization of raw material ratio

[0034] The mass ratio of graphene oxide (HGO) to hollow CuFe2O4 nanospheres is 1:1 - 1:4, and the aqueous phase dispersion concentration is 2 - 8 mg / mL;

[0035] The mass ratio of loofah sponge (LS) powder to CuFe2O4 is 0.5:1 - 0.8:1, and the LS skeleton size is 0.5 - 0.8 cm in diameter × 2.0 - 3.0 cm in height H;

[0036] The particle size of the loofah sponge powder is 0.5 - 1.0 μm, and the mass ratio to magnetic graphene oxide is 1:4 - 2:4.

[0037] 2. Preparation method

[0038] (1) Preparation of precursor: Disperse graphene oxide HGO and hollow CuFe2O4 nanospheres in deionized water (the mass ratio of HGO:CuFe2O4:water is 1:1:200), and ultrasonicate for 30 min to obtain a magnetic graphene oxide (MGO) suspension;

[0039] (2) Composite assembly: Add LS powder and cylindrical LS skeleton to the MGO suspension, ultrasonicate for 40 min, and then react at 70 - 90 °C for 30 - 50 min to form a three-dimensional hydrogel;

[0040] (3) Post-treatment: After the hydrogel is replaced with 10 vol% tert-butanol, it is quickly frozen in liquid nitrogen (-196 °C) and dried at room temperature to obtain a superhydrophobic graphene aerogel (CLGA).

[0041] 3. Structural Design Innovation

[0042] (1) Hierarchical pore construction: The hollow CuFe2O4 nanospheres (with a diameter of 50 - 100 nm) interpenetrate and support the graphene oxide sheets, inhibiting interlayer stacking to form a micro-mesoporous hierarchical structure (specific surface area ≥ 250 m 2 / g);

[0043] (2) Skeleton reinforcement: The LS fiber skeleton (porosity > 90%) serves as a macroscopic scaffold to enhance the mechanical strength (compressive modulus ≥ 10 kPa);

[0044] (3) Surface modification: The CuFe2O4 / LS composite roughness results in a contact angle > 150°, and the oil adsorption capacity reaches 50 - 90 g / g.

[0045] Overview of the preparation method:

[0046] The core of the present invention lies in introducing the loofah sponge (LS) skeleton and magnetic hollow CuFe2O4 nanospheres into the graphene aerogel (GA) synergistically through an electrostatic co-assembly-solvothermal in-situ reduction coupling process to construct a composite material with superhydrophobic and superoleophilic properties, high adsorption capacity, and magnetic responsiveness. The specific implementation process includes the following key steps:

[0047] 1. Synthesis of highly oxidized graphene (HGO)

[0048] Scaly graphite is oxidized using a mixed acid (H2SO4:HNO3 = 10:1) system, and through gradient temperature control (45°C pre-oxidation → 60°C layer expansion → 90°C deep oxidation), a bright yellow HGO sponge rich in hydroxyl and carboxyl groups on the surface is obtained.

[0049] Differences from traditional graphene oxide (GO): The interlayer spacing of HGO expands to 0.85 nm, and the magnetic separation efficiency is increased to 98% (without centrifugation), which is conducive to large-scale production.

[0050] 2. Preparation of magnetic graphene (MGO)

[0051] The hollow CuFe2O4 nanospheres (particle size 80 - 120 nm, specific surface area 210 m 2 / g) and HGO are mixed at a mass ratio of 1:1, and self-assembled through electrostatic interaction to form an MGO composite suspension.

[0052] Functional advantages: The introduction of CuFe2O4 enables the material to reach a saturation magnetization intensity of 51.6 emu / g, realizing magnetic-driven recovery.

[0053] 3. Solvothermal co-assembly of CLGA

[0054] Loofah sponge powder (particle size 0.5 - 1.0 μm) and columnar LS skeletons (Φ0.6 cm × H2.5 cm) were added to the MGO suspension, and the reaction was carried out at 80 °C for 40 min to form a three-dimensional hydrogel.

[0055] Structure regulation: The LS skeleton acts as a macroscopic support network to inhibit the stacking of graphene sheets; CuFe2O4 nanospheres are embedded between the layers to form a micro-mesoporous hierarchical structure (pore size distribution 50 nm - 5 μm).

[0056] 4. Supercritical drying and hydrophobic modification

[0057] After the hydrogel was replaced with tert-butanol, it was quickly frozen in liquid nitrogen (-196 °C) and dried at room temperature to obtain CLGA.

[0058] Surface characteristics: The composite roughness of CuFe2O4 / LS makes the water contact angle reach 160 ± 2°, and the oil contact angle approaches 0° ( Figure 3 a).

[0059] Material properties and structure characterization

[0060] 1. Porous structure analysis (SEM)

[0061] Pure GA ( Figure 4 (a)-(c)): The stacking of graphene sheets is serious, the porosity is only 62%, and the average pore diameter < 100 nm.

[0062] LGA ( Figure 4 (d)-(f)): The LS skeleton forms through macropores (pore diameter 1 - 5 μm) as the main oil storage channels;

[0063] CuFe2O4 nanospheres interpenetrate with graphene sheets to construct a micro / mesoporous (< 50 nm)-macroporous (50 - 200 nm) hierarchical network ( Figure 4 (g)-(i)), and the porosity is increased to 93%;

[0064] The specific surface area reaches 532.8 m 2 / g (BET test), which is 17.5 times higher than that of pure GA (30.47 m 2 / g).

[0065] 2. Adsorption and cycling performance

[0066] Adsorption capacity: The adsorption amount of chloroform by CLGA reaches 88 g / g, which is significantly improved compared with LGA (55.7 g / g) and GA (39.3 g / g) (Table 1);

[0067] Cycling stability: After 20 adsorption-desorption cycles, the capacity retention rate of CLGA > 90%, attributed to the mechanical support of the LS skeleton.

[0068] 3. Verification of oil-water separation application

[0069] Heavy oil separation: Press CLGA into a filter element with Φ20mm×10mm. The 20mL chloroform / water mixture is completely separated within 10s, and the water phase interception rate is 100%;

[0070] Continuous collection of light oil: Build a magnetically controlled separation device, and the toluene flux reaches 5000L·m -2 ·h -1 , and the flux decay is <5% after 10 cycles.

[0071] Summary of key innovation points

[0072] 1. Structure design

[0073] Synergistic dual templates: The LS skeleton (macropores) and CuFe2O4 nanospheres (mesopores) jointly regulate the hierarchical pore structure, solving the problem of easy collapse of traditional GA pores;

[0074] Surface roughening: The CuFe2O4 / LS composite roughness realizes superhydrophobic / superoleophilic properties (water contact angle ≥160).

[0075] 2. Process optimization

[0076] One-step solvothermal method: Synchronously complete the loading of magnetic components and the composite of biological templates, shortening the process cycle by 60% compared with the traditional step-by-step method;

[0077] Green drying: Liquid nitrogen freezing replaces supercritical CO2 drying, reducing the cost by 40%.

[0078] Table 1 Comparison of the effects of examples

[0079]

[0080]

[0081] Comparative example 1: Preparation of pure graphene aerogel (GA)

[0082] Step 1: Synthesis of HGO

[0083] 1. Mix 1.0g of flake graphite powder (particle size 6μm) with 110mL of mixed acid (H2SO4:HNO3 = 10:1), and add 6.0g of KMnO4;

[0084] 2. Gradient oxidation: Pre-oxidize at 45°C for 20min (ultrasonic for 10min) → Expand the layer at 60°C for 3h (ultrasonic for 10min every 20min) → Deep oxidation at 90°C for 15min;

[0085] 3. After cooling in an ice bath, it was diluted to 200 mL, 2.5 mL of H2O2 was added, centrifuged and washed until pH = 6, and then freeze-dried to obtain HGO sponge.

[0086] Step 2: Preparation of GA

[0087] 1. 100 mg of HGO was dispersed in 40 mL of deionized water (concentration 2.5 mg / mL) and sealed in a 100 mL glass bottle.

[0088] 2. Hydrothermal reaction was carried out at 80 °C for 40 min to form a hydrogel.

[0089] 3. After the hydrogel was replaced with 10 vol% tert-butanol, it was freeze-dried with liquid nitrogen to obtain GA.

[0090] Performance defects

[0091] 1. The specific surface area was only 30.47 m 2 / g, and the chloroform adsorption capacity was 39.3 g / g.

[0092] 2. The surface was hydrophilic (contact angle 68°), and oil-water separation could not be achieved (see Table 1).

[0093] Comparative Example 2: Preparation of loofah sponge modified aerogel (LGA)

[0094] Improvement point: Introduce loofah sponge (LS) powder (0.08 g) and columnar LS skeleton (0.05 g) on the basis of GA.

[0095] Step difference:

[0096] 1. The HGO suspension (2.5 mg / mL) was ultrasonically mixed with LS powder for 30 min, and after adding the LS skeleton, it was ultrasonically treated for another 10 min.

[0097] 2. Hydrothermal reaction was carried out at 80 °C for 40 min, and the subsequent treatment was the same as that in Comparative Example 1.

[0098] Performance improvement

[0099] 1. The specific surface area was increased to 202.58 m 2 / g, and the adsorption capacity was 55.7 g / g.

[0100] 2. The hydrophobicity was enhanced (contact angle 133°), but it still did not reach superhydrophobic (>150°).

[0101] Comparative Examples 3-4: Preparation and optimization of CLGA (the mass ratio exceeds the non-conforming design range)

[0102] General steps (taking Example 1 as an example)

[0103] Step 1: Synthesis of magnetic MGO

[0104] 1. In the HGO synthesis step, 1 g of hollow CuFe2O4 nanospheres (particle size 80 - 120 nm) was added to the acidic suspension;

[0105] 2. After magnetic separation, washing and drying, MGO powder (CuFe2O4:HGO = 1:1) was obtained.

[0106] Step 2: CLGA assembly

[0107] 1. MGO (5 mg / mL, 40 mL) was ultrasonically mixed with LS powder (0.03 / 0.15 g) and LS framework (0.05 g) and mixed according to Table 1;

[0108] 2. Hydrothermal reaction was carried out at 80 °C for 40 min, and then freeze-dried with liquid nitrogen to obtain CLGA.

[0109] Examples 1 - 3: Preparation and optimization of CLGA

[0110] General procedure (taking Example 1 as an example)

[0111] Step 1: Synthesis of magnetic MGO

[0112] 1. In the HGO synthesis step, 1 g of hollow CuFe2O4 nanospheres (particle size 80 - 120 nm) was added to the acidic suspension;

[0113] 2. After magnetic separation, washing and drying, MGO powder (CuFe2O4:HGO = 1:1) was obtained.

[0114] Step 2: CLGA assembly

[0115] 1. MGO (5 mg / mL, 40 mL) was ultrasonically mixed with LS powder (0.05 - 0.1 g) and LS framework (0.05 g) and mixed according to Table 2;

[0116] 2. Hydrothermal reaction was carried out at 80 °C for 40 min, and then freeze-dried with liquid nitrogen to obtain CLGA.

[0117] Table 2 Comparison of key variables and performance

[0118]

[0119] The magnetic superhydrophobic graphene aerogel prepared by the preparation method of the present invention has the following advantages:

[0120] 1. Superhydrophobic / superoleophilic: The CuFe2O4 / LS composite rough surface makes the water contact angle ≥ 160°;

[0121] 2. Magnetic recovery: The saturation magnetization intensity is 51.6 emu / g, and the adsorption capacity retention rate is > 92% after 20 cycles;

[0122] 3. Structural stability: The LS skeleton support enables a compressive strength of 12 kPa, avoiding the collapse of the pore structure.

[0123] The present invention innovatively proposes an electrostatic co-assembly-solvothermal in-situ reduction coupling process: using loofah fiber as a three-dimensional skeleton, and realizing the three-component molecular-level coupling of Fe 3+ / Cu 2+ ions, graphene oxide and biological template through pH-regulated electrostatic co-assembly technology; in an ethylene glycol / water mixed solvent system, the crystallization growth of hollow CuFe2O4 nanospheres and the in-situ reduction of graphene are synchronously completed through a solvothermal reaction at 180 °C, and finally a superhydrophobic aerogel with a hierarchical pore structure is obtained through freeze-drying. Its innovation lies in: by the synergistic effect of hollow magnetic nanospheres and biological fibers, mesoporous channels with a size of 2-50 nm are constructed, enabling a specific surface area of 532.8 m 2 / g (17.5 times higher than that of the aerogel prepared by the traditional hydrothermal method); the surface energy gradient design realizes superhydrophobic / superoleophilic properties (oil contact angle 0°), and the adsorption capacity for pump oil reaches 88 g / g; the embedded superparamagnetic unit (saturation magnetization intensity 51.6 emu / g) enables external field-driven recovery, and the adsorption retention rate is >92% after 20 cycles. This product can efficiently treat emulsified oil wastewater containing surfactants (separation efficiency >99%), and is especially suitable for the rapid treatment of metallurgical rolling waste liquid (COD 8000→80 mg / L) and marine oil spill accidents.

[0124] The obtained magnetic superhydrophobic graphene aerogel is used as an adsorbent and as an oil-water separation filtration medium.

[0125] 1. Press 50 mg of CLGA into a cylindrical filter element with a diameter of 20 mm × 10 mm and place it in a glass funnel;

[0126] 2. Connect an external peristaltic pump device to achieve continuous oil-water separation adsorption (see Figure 2(b)).

[0127] Table 3 Separation performance

[0128]

Claims

1. A preparation method of a magnetic superhydrophobic graphene aerogel based on a biomass template, characterized in that, It includes the following steps: (1) Constructing a magnetic precursor: Dispersing hollow CuFe2O4 nanospheres and graphene oxide in an acidic solution with a pH ≤ 3 at a mass ratio of 1:1 - 1:4, and forming a magnetic graphene oxide MGO suspension through ultrasonic treatment. (2) Biomass composite assembly: Immersing a columnar biomass sponge skeleton in the magnetic graphene oxide MGO suspension, and uniformly dispersing biomass sponge powder with a particle size of 0.5 - 1 μm in the magnetic graphene oxide MGO suspension; realizing three-dimensional pore filling through the drive of an ultrasonic field to obtain a columnar biomass sponge skeleton loaded with magnetic graphene oxide and biomass sponge powder. (3) In-situ solvothermal reaction: The columnar biomass sponge skeleton loaded with magnetic graphene oxide and biomass sponge powder undergoes gradient heating at 70 - 90 °C in a closed system to complete the in-situ reduction of magnetic graphene oxide and the interfacial bonding between the biomass and the nanospheres, obtaining a hydrogel. (4) Supercritical drying and forming: Immersing the hydrogel in a 10 - 20 vol% tert-butanol solution, performing cryogenic freezing with liquid nitrogen, and then carrying out room-temperature vacuum drying to obtain a superhydrophobic graphene aerogel with a porosity ≥ 98%.

2. The preparation method of the magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 1, wherein (The sum of the columnar biomass sponge skeleton and the biomass sponge powder) / magnetic graphene oxide mass ratio is 1:4 - 2:4; the mass ratio of the columnar biomass sponge skeleton to magnetic graphene oxide MGO is 1:4, and the impregnation time is 10 - 30 min.

3. The preparation method of the magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 1, wherein, For the described columnar biomass sponge skeleton, the axial through-hole ≥ 300 μm. Biomass sponge powder, specific surface area ≥ 20 m 2 / g.

4. The preparation method of the magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 1, wherein, The biomass is loofah sponge; the diameter of the columnar biomass sponge skeleton is 0.5 cm - 0.8 cm, and the porosity ≥ 95%.

5. The preparation method of the magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 1, wherein, The hollow CuFe2O4 nanospheres have a particle size of 80-120 nm and a specific surface area of ≥150 m 2 / g; the hollow CuFe2O4 nanospheres are prepared by the sol-gel method, have a ring-shaped mesoporous structure, and a saturation magnetization intensity of ≥40 emu / g.

6. The preparation method of the magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 1, wherein, For the described graphene oxide, the C / O atomic ratio ≤ 1.8; the thickness of the graphene oxide sheet is 1.00 - 1.58 nm, and the lateral size of the graphene oxide is 1 - 5 μm.

7. The preparation method of the magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 1, wherein, The described gradient heating process is that the temperature gradient increases, and the heating time gradient decreases at each temperature.

8. The method for preparing a magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 7, characterized in that, The described gradient heating process is specifically 70 °C × 50 min → 80 °C × 40 min → 90 °C × 30 min, and the heating rate in each stage ≤ 5 °C / min.

9. The preparation method of the magnetic superhydrophobic graphene aerogel based on a biomass template according to claim 1, wherein The prepared superhydrophobic graphene aerogel has a water contact angle ≥160° and an oil contact angle ≤5°; the superhydrophobic graphene aerogel has the following properties simultaneously: a) a hierarchical pore structure with a BET specific surface area ≥200 m 2 / g; b) superparamagnetism with a saturation magnetization intensity ≥45 emu / g; c) a capacity retention rate ≥92% after 20 adsorption-desorption cycles.

10. Application of a superhydrophobic graphene aerogel in the treatment of emulsified oil wastewater containing surfactants, characterized in that, The described superhydrophobic graphene aerogel is prepared by the preparation method according to any one of claims 1 - 9 and is used for the purification treatment of metallurgical rolling waste liquid with a COD ≥ 5000 mg / L.

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